EUROPEAN COMMISSION
DIRECTORATE-GENERAL JRC
JOINT RESEARCH CENTRE
Institute for Prospective Technological Studies (IPTS)
Sustainable Production and Consumption Unit
European IPPC Bureau
26 November 2010
Analysis of the questionnaires received
on the performance of central waste water treatment plants for the
review of the Common Waste Water and Waste Gas
Treatment/Management Systems in the Chemical Sector BREF
INTRODUCTION
This document has been prepared as a reference for the review of the Common Waste Water
and Waste Gas Treatment/Management Systems in the Chemical Sector (CWW) BREF by a
subgroup of the CWW technical working group (TWG). The list of the members of the CWW
TWG that participated in the work of this subgroup is given in the Annexes (see Section 4.1).
This document presents the results of the analysis made by the ad hoc CWW TWG subgroup of
the questionnaires received regarding the performance of European central waste water
treatment plants (WWTPs). The CWW TWG subgroup held two meetings in Paris (on 11–
12 January 2010 and on 24–25 June 2010) to discuss the data from the questionnaires and this
document presents the result of the discussions held together with some background information
researched by the European IPPC Bureau. For information, the mandate of the CWW TWG
subgroup can be found in Section 4.2.
This document notably takes into account many updates on the data initially provided in the
questionnaires. It also takes into account information from the 'Comparative analysis of the first
series of chemical BREFs' (dated December 2007) as well as the BAT conclusions reached in
the first series of chemical BREFs.
Furthermore, information contained in the 'Statistical analysis of monitoring data from waste
water effluents of the chemical industry' – input of the German delegation to the TWG BREF
CWW dated 24 March 2010 has also been taken into account in the elaboration of this
document.
The document is organised into three sections. Section 1 provides some background information
on the questionnaires received. Section 2 analyses the performance data reported for some key
parameters. The performances reported are put into perspective by comparing them with the
BATAEL conclusions reached in the elaboration of the first series of chemical BREFs.
Section 3 discusses the variability of the monitoring results.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
1
TABLE OF CONTENTS
INTRODUCTION ...................................................................................................................................... 1
TABLE OF CONTENTS ........................................................................................................................... 3
1 BACKGROUND ON THE QUESTIONNAIRES RECEIVED ........................................................ 4
1.1 General ........................................................................................................................................... 4
1.2 Representativity of the questionnaires ............................................................................................ 5
1.3 Quality of the questionnaires .......................................................................................................... 6
1.4 Characteristics of the central waste water treatment plants ............................................................ 8
1.4.1
General .................................................................................................................................. 8
1.4.2
Type of discharge and type of receiving waters .................................................................... 8
1.4.3
Main characteristics of the waste water influents treated ...................................................... 9
1.4.4
Main unit processes at the central WWTPs ......................................................................... 11
2 ANALYSES OF KEY PARAMETERS ............................................................................................ 13
2.1 General ......................................................................................................................................... 13
2.2 Sum parameters ............................................................................................................................ 15
2.2.1
COD, TOC, and BOD5 ........................................................................................................ 15
2.2.1.1
COD ....................................................................................................................... 15
2.2.1.2
TOC........................................................................................................................ 22
2.2.1.3
BOD5 ...................................................................................................................... 25
2.2.2
TSS ...................................................................................................................................... 30
2.2.3
AOX .................................................................................................................................... 35
2.3 Metals ........................................................................................................................................... 41
2.3.1
General ................................................................................................................................ 41
2.3.2
Cadmium (Cd) ..................................................................................................................... 46
2.3.3
Chromium total (Total-Cr)................................................................................................... 48
2.3.4
Chromium VI (Cr VI) .......................................................................................................... 50
2.3.5
Copper (Cu) ......................................................................................................................... 52
2.3.6
Mercury (Hg) ....................................................................................................................... 55
2.3.7
Nickel (Ni) ........................................................................................................................... 58
2.3.8
Lead (Pb) ............................................................................................................................. 61
2.3.9
Zinc (Zn) .............................................................................................................................. 63
2.4 Other parameters ........................................................................................................................... 67
2.4.1
Nitrogen compounds ............................................................................................................ 67
2.4.1.1
General ................................................................................................................... 67
2.4.1.2
Total nitrogen (Total-N) ......................................................................................... 67
2.4.1.3
Ammonia (as NH4-N)............................................................................................. 75
2.4.1.4
Nitrite (as NO2-N) .................................................................................................. 79
2.4.1.5
Nitrate (as NO3-N) ................................................................................................. 81
2.4.2
Phosphorus compounds ....................................................................................................... 84
2.4.2.1
General ................................................................................................................... 84
2.4.2.2
Total phosphorus (Total-P) .................................................................................... 85
2.4.2.3
Phosphate (as PO4-P) ............................................................................................. 89
2.4.3
Phenols ................................................................................................................................ 90
2.4.4
Chlorides .............................................................................................................................. 93
2.4.5
Sulphates .............................................................................................................................. 97
2.4.6
Cyanides (free) .................................................................................................................. 100
2.4.7
Toxicity.............................................................................................................................. 103
2.4.7.1
General ................................................................................................................. 103
2.4.7.2
Fish or fish egg toxicity........................................................................................ 104
2.4.7.3
Daphnia toxicity ................................................................................................... 106
2.4.7.4
Algae toxicity ....................................................................................................... 107
2.4.7.5
Bacterial luminescence toxicity ........................................................................... 108
3 DISCUSSION CONCERNING THE VARIABILITY OF MONITORING RESULTS ............ 110
SR/EIPPCB/BP CWW TWG subgroup
November 2010
3
1 Background on the questionnaires received
1.1
General
A total of 70 questionnaires on the performances of European central waste water treatment
plants (WWTPs) have been received by the European IPPC Bureau as of 25 March 2010. Most
of them have been submitted using the Word template agreed upon at the kick-off meeting of
June 2008. An overview of these questionnaires is given in Table 1.1.
Organisation/Member State
that submitted questionnaires
Austria
Belgium
CEFIC
DE 4
FR 1
IT 1
NL 1
SE 1
UK 10
Number of questionnaires
received as of 25/03/2010
1
7
Questionnaire codes
68
49, 50, 51, 52, 53, 54, 55
18
17, 18, 19, 20 (1), 21, 22, 23 (1),
24, 25, 26, 27, 28, 29, 30 (2), 31,
32, 33, 34
Czech Republic
France
(as Member State)
France
(direct submission by operators)
3
61, 62, 63
3
35, 60, 64
5
38, 39 (2), 40, 41, 57
Germany
19
Italy
Portugal
Spain
United Kingdom
(direct submission by operator)
Total received:
5
2
6
01, 02, 03, 041, 042, 05, 06, 07,
08, 09, 10, 11, 12, 13, 14, 15,
16, 36, 56
42 (1), 45, 46, 58, 69 (3)
43, 44
37, 47, 48, 65 (4), 66 (4), 67 (4)
1
59 (2)
70

Taken into account for the
analysis in this document:
63

20, 23 and 42 have been
removed (1)
30, 39, 55 and 59 have been
removed (2)
(1) Removed for the analysis because: 23 was the same as 01; 20 was the same as 02; 42 is considered outside of
the scope of the CWW BREF.
(2) Removed for the analysis because: 30 has no information on the chemical production carried out; 39 does not
treat waste waters coming chemical production; 55 has no information on emissions; 59 is the same as 32 and
information on 32 is more complete.
(3) Submitted on 12/02/2010.
(4) Main treatment process is oxidation with H2O2.
Table 1.1:
Overview of the questionnaires received for the review of the CWW BREF on the
performance of central WWTPs
1.2
Confidentiality of questionnaires
Only a few questionnaires received by the EIPPCB were initially submitted in confidentiality.
After discussions with the submitters, the latter removed the claim for confidentiality on the
whole questionnaires. However, some data (few) in some of the questionnaires were claimed as
confidential (generally the cost information) and was treated as such by the EIPPCB.
Consequently, confidentiality is not considered a major issue for questionnaires in the review of
the CWW BREF contrary to other BREFs.
4
November 2010SR/EIPPCB/Analysis questionnaires CWW
CEFIC indicated that cost data are considered very sensitive in regard to antitrust issues. It
considers that a WWTP, as basic infrastructure facilities, determines the competiveness of
production.
1.3
Representativity of the questionnaires
The questionnaires have the characteristics listed below:

Relatively large number of questionnaires received (i.e. 70, of which 63 were taken for
analysis, see Table 1.1).
Questionnaires arise from 11 different Member States (AT, BE, CZ, DE, ES, FR, IT, NL,
PT, SE, UK).
Questionnaires cover direct (88 %) and indirect (12 %) discharges to receiving waters.
Questionnaires reflect treatment of waste waters originating from IPPC installations from
the organic sector (57 %), the inorganic sector (7 %) and both sectors (36 %).
Questionnaires reflect different sizes of WWTPs, from relatively small WWTPs treating
less than 10000 m3/yr (i.e. #38, #66, and #05) to large WWTPs treating volumes of waste
waters above 20000000 m3/yr (i.e. #10 treating 24455000 m3/yr and #02 treating
120000000 m3/yr). This is shown in Figure 1.1. (WWTPs #02 and #10 are outside of the
graph scale and are not shown in the figure). It can be noted that the waste water
treatment capacity was not considered suitable for analysis/comparison because there is
no common definition/understanding of waste water treatment capacity in the industry.
The different sizes of WWTPs are also reflected in the annual influent load of COD
reported, ranging from approximately 100 t/y – 24382 t/y (see Figure 1.2).
Questionnaire #02 did not report COD in the influent, however it reported 50115 t/y TOC
in the influent which is equivalent to about 145000 t/y COD. This means that the
questionnaires cover WWTPs treating influent load of COD ranging from approximately
100 t/y – 145000 t/y.





Average amount of waste water treated per year
Average waste water treated
Capacity of treatment
20000
19000
14
18000
17000
16000
22
15000
11
13000
49
12000
45
11000
10000
43
69
03
9000
041
35
8000
7000
46
63
WW treated (1000 m3 /yr)
14000
5000
4000
3000
2000
1000
0
0
38
66
05
65
32
58
52
62
41
60
24
33
29
31
34
51
67
08
40
47
19
53
25
28
56
27
61
26
37
36
09
68
17
01
18
57
12
21
48
07
13
54
50
06
042
15
16
64
44
6000
10
20
30
40
50
60
Central WWTPs
Figure 1.1:
Average volume of waste water treated per year in the central WWTPs reported
CEFIC indicated that for Germany, the questionnaires submitted are representative of rather
medium and large central WWTPs treating waste waters coming from medium-size chemical
SR/EIPPCB/BP CWW TWG subgroup
November 2010
5
production sites. Questionnaires do not represent the situation of indirect discharge very well
(only nine questionnaires reflect the situation of central WWTPs that discharge indirectly to
receiving waters, i.e. #09, #24, #31, #38, #56, #48, #65, #66, #68).
COD loads treated in the Central WWTPs
Annual influent COD load (t/y)
30000
25000
20000
15000
49 28
68
22 63
10000
5000
44 06
67 17
35 29 69 18 54
24
19
40 41
62 65 33 042 60 08 61
25
50 64
01 21
041 57 45
0
0
Figure 1.2:
1.4
WWTPs
33
Minimum, average, and maximum influent COD loads treated in the central
WWTPs reported
Quality of the questionnaires
The quality of the questionnaires improved significantly with the work of the TWG subgroup
who collected important information that was missing (i.e. not initially reported in the
questionnaires submitted), in particular concerning:



the type of recipient waters (i.e. Questionnaires numbers #041, #042, #05, #06, #07, #08,
#09, #10, #11, #12, #13, #14, #15, #16, #43)
the amount of waste water treated per year (i.e. Questionnaires numbers #06, #07, #20,
#27, #31, #43, #54)
the treatment steps/unit operations and processes (i.e. Questionnaires numbers #05, #06,
#08, #24, #25, #28, #29, #40, #41, #63).
Also, the TWG subgroup made numerous corrections and clarifications on a number of
individual data in the compiled Excel list of questionnaires. This process of
correction/clarification was very time consuming and was carried out mainly in the period
January to November 2010.
The EIPPCB proposed a rating of the individual questionnaires according to the completeness
of the information provided. The following specific criteria have been used:
A: very complete set of data submitted using the agreed upon template:
i.e. #01, #02, #17, #21, #22, #24, #27, #28, #29, #34, #35, #36, #41, #43, #44, #46, #49,
#50, #54, #56, #57, #58, #61, #62, #65, #67, #68, #69.
6
November 2010SR/EIPPCB/Analysis questionnaires CWW
B: fairly complete set of data submitted using the agreed upon template:
i.e. #03, #25, #33, #38, #40, #45, #53, #63, #64.
C: set of data may not always be sufficient (background information is limited):
#041, #042, #05, #06, #07, #08, #09, #10, #11, #12, #13, #14, #15, #16, #18, #19, #26,
#32, #37, #47, #51, #52, #60, #66.
D: fairly incomplete set of data: i.e. #48.
E: very incomplete set of data: i.e., #31.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
7
1.5
Characteristics of the central waste water treatment plants
1.5.1
General
The WWTPs treat waste waters coming from one or several installations under the scope of the
vertical chemical BREFs.
1.5.2
Type of discharge and type of receiving waters
Effluents from central WWTPs are discharged to the following receiving waters:

Direct releases (54 central WWTPs):
◦
◦
◦
◦
◦

river (i.e. #01, #02, #03, #041, #042, #05, #06, #07, #08, #10, #11, #12, #13, #14,
#15, #16, #17, #18, #19, #21, #22, #26, #32, #35, #36, #41, #45, #49, #50, #51,
#52, #53, #54, #56, #57, #60, #61, #62, #63, #67)
lake (i.e. #64)
canal (i.e. #27, #40)
sea (i.e. #29, #33, #34, #37, #43, #44, #47, #48, #69)
estuary (i.e. #25, #28).
Indirect releases (9 central WWTPs):
◦
◦
biological WWTP for further treatment (i.e. #09, #24, #38, #46, #58, #65, #66,
#68), sometimes together with municipal waste water (i.e. #65) or in a municipal
WWTP (i.e. #09, #24, #38, #58, #66, #68)
settling lagoon (#31).
The repartition of central WWTPs according to the type of discharge (direct/indirect) and the
type of receiving waters are shown in Figure 1.3 and Figure 1.4 respectively.
Type of discharge
Direct releases
Indirect releases
Indirect releases: 9
installations (14 %)
Direct releases: 54
installations (86 %)
Figure 1.3:
8
Type of discharge from central WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
Receiving water
River
Canal
Sea
River: 40 install. (63 %)
Estuary
Lake
Settling lagoon
Municipal WWTP
Municipal WWTP:
8 install. (13 %)
Canal: 2 install. (3 %)
Settling lagoon:
1 install. (2 %)
Lake: 1 install. (2 %)
Figure 1.4:
1.5.3
Estuary: 2 install. (3 %)
Sea: 9 install. (14 %)
Repartition of central WWTPs according to the receiving water
Main characteristics of the waste water influents treated
Central WWTPs have been put in one of the three following groups depending on the origin of
the waste waters:



Central WWTPs treating waste waters originating from IPPC installations of organic
sectors (i.e. LVOC, OFC, POL) (36 WWTPs or 57 %):
o Direct discharges: #01, #06, #07, #08, #11, #12, #13, #14, #15, #16, #18, #19,
#25, #26, #28, #29, #33, #34, #36, #37, #40, #41, #47, #48, #51, #52, #53, #54,
#57, #60, #62, #64;
o Indirect discharges: #09, #24, #65, #66;
Central WWTPs treating waste waters originating from IPPC installations of inorganic
sectors (i.e. LVIC-S, LVIC-AAF, SIC, CAK) (5 WWTPs or 8 %):
o Direct discharges: #042, #05, #32, #56;
o Indirect discharges: #31;
Central WWTPs treating waste waters originating from IPPC installations of both
organic and inorganic sectors (22 WWTPs or 35 %):
o Direct discharges: #02, #03, #041, #10, #17, #21, #22, #27, #35, #43, #44, #45,
#49, #50, #61, #63, #67, #69;
o Indirect discharges: #38, #46, #58, #68.
The repartition of central WWTPs according to the main characteristics of the waste water
influents treated is shown in Figure 1.5.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
9
Type of discharge and main characteristics of the effluent treated
Direct ─ mainly
organic: 32 (51 %)
Direct ─ both organic
and inorganic: 18 (29 %)
Direct ─ mainly organic
Direct ─ both organic and
inorganic
Direct ─ mainly inorganic
Indirect ─ mainly organic
Indirect ─ mainly
inorganic: 1 (2 %)
Indirect ─ both organic
and inorganic: 4 (6 %)
Figure 1.5:
10
Direct ─ mainly
inorganic: 4 (6 %)
Indirect ─ both organic and
inorganic
Indirect ─ mainly inorganic
Indirect ─ mainly
organic: 4 (6 %)
Repartition of central WWTPs according to the main characteristics of the waste
water influents treated
November 2010SR/EIPPCB/Analysis questionnaires CWW
1.5.4
Main unit processes at the central WWTPs
In order to compare emission levels from the various installations, the techniques used were
grouped. Central waste water treatment is always a combination of individual treatment steps.
For example, the most commonly used activated sludge process is generally preceeded and
followed by a solids removal step. The activated sludge process may be combined with
simultaneous nitrification/denitrification and/or phosphorus removal depending on the
composition of the waste water. The heterogeneous combinations and, in addition, the different
denominations used in the questionnaires for the same technique made it difficult to group
installations.
Complete-mixed activated sludge was identified as the main final unit process for waste waters
with organic substances and direct discharges. In the EIPPCB analysis of the questionnaires, it
was assumed that unit processes denominated ''biological treatment'' or similar could be put into
the same category unless more specific information was given.
The installations using complete-mix activated sludge process were then further categorised
according to:




flat tanks, tower biology, or membrane bioreactor
solids removal techniques
central pretreatment steps, e.g. anaerobic step, additional activated sludge process,
physico-chemical treatments
occurrence of simultaneous nitrogen and/or phosphorus removal.
The main unit processes used at the central WWTPs are:

Physico-chemical treatments only (14 central WWTPs):
◦
◦
◦
◦
◦
◦
◦

Physico-chemical and biological treatment or only biological treatment (49 central
WWTPs):
◦
◦
◦
◦
◦
1
ad hoc chemical treatments (i.e. #05)
neutralisation (for 54% of the plants)
precipitation/flocculation followed by a solids removal step (e.g. sedimentation,
filtration, or flotation) (i.e. #042, #27, #31, #32, #56); #27 with stripping as
pretreatment
oil-water separation and flotation (i.e. #26, #35, #46)
oxidation with H2O2 (i.e. #65, #66, #67)
decantation + sedimentation + ultrafiltration + stripping (i.e. #38)
skimming and sedimentation (i.e. #53).
Complete-mixed activated sludge (CMAS) flat tank (i.e. Questionnaires numbers
#01, #02, #03, #041, #06, #09, #10, #11, #12, #17, #18, #19, #22, #24, #25, #28,
#37, #40, #43, #44, #47, #48, #49, #50, #51, #52, #54, #57, #58, #60, #61, #62,
#63, #64, #68)
CMAS tower biology (i.e. #07, #13, #14, #15, #16, #21, #45, #57)
Complete-mixed activated sludge membrane bioreactor (i.e. #08, #21, #36, #411,
#69)
Fixed-bed reactor (i.e. #29)
Expanded bed process (i.e. #33, #34).
Only part of the effluent is treated by a membrane bioreactor
SR/EIPPCB/BP CWW TWG subgroup
November 2010
11
With respect to solids (TSS) removal step, the following techniques are applied at central
WWTPs:

sedimentation (i.e. #02, #03, #041, #06, #07, #09, #12, #13, #14, #15, #16, #17, #18, #19,
#22, #24, #25, #28, #37, #40, #43, #44, #47, #48, #49, #52, #54, #57, #62, #63, #68)
ultrafiltration, including membrane bioreactor (i.e. #08, #21, #36, #412, #69)
sand filtration (i.e. #01, #34, #45, #61)
reverse osmosis (i.e. #58) has an effect on TSS removal. However it is not designed for
this purpose
flotation (i.e. #10, #11, #21, #29, #33, #50, #51, #60, #64).




Depending on the organic load of the influent, a variety of central pretreatment processes are
used, including:

additional activated sludge processes (i.e. #01, #041, #08, #09, #10, #14, #33, #41, #61,
#63);
trickling filter (i.e. #07, #57)
anaerobic pretreatment (i.e. #16, #29)
oxidation (i.e. #18, #58)
fixed-bed reactor (i.e. #24)
oil-water separation (i.e. #45)
stripping (i.e. #55).






Several of the installations apply simultaneous nitrogen and/or phosphorous removal (Note: For
some installations nitrogen and/or phosphorus removal were not explicitly mentioned but could
be derived from the influent and effluent data):

biological nitrogen removal via nitrification/denitrification (i.e. #01, #02, #03, #041, #06,
#07, #08, #09, #10, #11, #12, #14, #16, #21, #22, #34, #36, #37, #40, #41, #45, #49, #50,
#52, #57, #60, #61, #63, #69)
phosphorus removal, either biologically and/or via precipitation (i.e. #01, #02, #03, #041,
#06, #07, #10, #12, #14, #16, #57, #63).

It can be noted that the complete-mixed activated sludge system is used (in combination
with other techniques) in 49 central WWTPs, i.e. more than half of the central WWTPs
covered by the questionnaires.
2
Only part of the effluent is treated by a membrane bioreactor
12
November 2010SR/EIPPCB/Analysis questionnaires CWW
2 Analyses of key parameters
2.1
General
The following sections discuss the reported performance of central WWTPs over a number of
parameters and review the BAT Associated Emission Levels (AELs) conclusions achieved in
the first series of chemical BREFs. In order to help the discussion on the performances achieved
and to make the link to the techniques used, a number of graphs have been made.
The following symbols have been used in these graphs:
Symbol Type of discharge
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Influent
Influent
Influent
Influent
Influent
Influent
Average values
Type of waste water (WW) treated
Direct discharge from central WWTP treating organic WW
Direct discharge from central WWTP treating organic and inorganic WW
Direct discharge from central WWTP treating inorganic WW
Indirect discharge from central WWTP treating organic WW
Indirect discharge from central WWTP treating organic and inorganic WW
Indirect discharge from central WWTP treating inorganic WW
Direct discharge from central WWTP treating organic WW
Direct discharge from central WWTP treating organic and inorganic WW
Direct discharge from central WWTP treating inorganic WW
Indirect discharge from central WWTP treating organic WW
Indirect discharge from central WWTP treating organic and inorganic WW
Indirect discharge from central WWTP treating inorganic WW
Maximum values
80th percentile
90th percentile
Average values determined without removing abnormal discharges
Highest monthly averages (i.e. smoothed out)
No information ─ probably real maximum (i.e. outliers not removed)
Outliers removed
Predefined maximum value
Real maximum (i.e. outliers not removed)
Legend
Also, the following abbreviations have been used in the graphs for the techniques reported:
Abbreviatio
n
Adsorp.
Abbreviation
Definition
Strip.
Neut.
Stripping
Mechanical treatment (screen, grit
chambers)
Balancing of flows and loads
Central incineration of WW
containing recalcitrant TOC
Neutralisation
P precip.
Phosphorus removal by precipitation
Pond./lag.
Prec./coag./floc.
OWS
Sed.1
Lag.
Flot.
Precipitation/coagulation/flocculation
Oil-water separation
(Primary) sedimentation
Lagoon
Flotation
Biofilt.
Memb. Bior.
Anaerob.
Nitri./deni.
OHP
CMAS_FT
Complete-mixed activated sludge flat
tank
CMAS_MBR
CMAS_TB
Complete-mixed activated sludge
tower biology
Meca.
Bal.
Inciner.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
Definition
Adsorption
Coag./floc.
Coagulation/flocculation
Sed.2
Final sedimentation
Filtr.
Filtration
RO
Reverse osmosis (RO)
Polishing
pond/sedimentation lagoon
Biofilters
Membrane bioreactor
Anaerobic treatment
Nitrification/denitrification
Oxidation with H2O2
Complete-mixed activated
sludge membrane
bioreactor
13
Concentrations given in the graphs showing both influent and effluent emissions are average
values, generally averages of 24-hour daily composite samples.
Abatement efficiencies in the graphs have been calculated based on average values (generally
averages of 24-hour daily composite samples) on concentration and load data, both coinciding
in the majority of cases.
For each parameter analysed, concentrations in the effluent of the set of central WWTPs are
presented in a table so as to display the minimum (over the set of central WWTPs), the
maximum, as well as the 10th, 25th, 50th, 75th and 90th percentiles. Percentiles were estimated
taking the total number of data for a given parameter, multiplying it by the respective
percentage (i.e. 10 %, 25 %, 50 %, 75 %, and 90 %) and rounding it to an integer.
14
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.2
2.2.1
Sum parameters
COD, TOC, and BOD5
Substances which have an unfavourable influence on the oxygen balance are included in the
indicative list of substances to be taken into account for fixing emission limit values in
Annex III of the IPPC Directive.
2.2.1.1
COD
Background information on COD
Chemical oxygen demand (COD) is commonly used to indirectly measure the amount of
organic compounds in water by measuring the mass of oxygen needed for their total oxidation
to carbon dioxide. The most widespread COD monitoring methods use dichromate as an
oxidising agent. COD has to be considered in relation to total suspended solids (TSS) since TSS
removal efficiency affects performance achieved with respect to COD (see Section 2.2.2).
Care has to be taken when converting COD to TOC or vice versa using ratios; these ratios need
to be well established for each case. Theoretical COD/TOC ratios of organic substances range
from 0.67 (oxalic acid) to 5.33 (methane). For those central WWTPs which reported both COD
and TOC data (only 8 WWTPs out of 63), COD/TOC ratios range from 2.23 to 7.01 for the
influent (median 3.15) and from 1.73 to 5.54 for the effluent (median 3.17). One central
WWTPs reported ratios outside the theoretical range: #44 with COD/TOC ratio of 7.01 for the
influent. For WWTP #042, this could be caused by the high concentrations of inorganic
substances.
For economic and environmental reason, COD was replaced to some extent by TOC in
Germany. To understand the consequences of this, the German national environmental agency
(UBA) published a study in 1999 which compared the COD/TOC ratios for different industrial
sectors. For the chemical industry, 1053 samples of 38 effluents were analyzed. The average
COD/TOC ratio was 2.98, the 10th percentile was 2.39, and the 90th percentile was 4.02. The
average did not change much (2.91+/-0.4) when the values <10th percentile and >90th
percentile were not taken into account. Since the biological treatment is mainly an oxidative
process, the COD/TOC ratio in the effluent is rather expected to be low. On the other hand,
inorganic substances that contribute to the COD may be formed in the process or pass it without
oxidation (esp. ammonia; maybe TSS), and oxidized material (CO2) is removed from the
process. The quoted results show that in the end most effluents are expected to be in the range
2.5 – 3.5 in terms of COD/TOC ratio.
Germany considers that COD concentrations are not standalone parameters for evaluating BAT.
The abatement efficiency is generally a more pertinent parameter than the concentration in the
effluent. Because of the strong dependency of the COD abatement efficiency on the production
mix and the pretreatment techniques used, there should additionally be comments on this data,
especially if COD concentration is relatively high and/or abatement efficiency is relatively low
(see BREF OFC).
Overview of central WWTP performance on COD
Figure 2.1 presents the COD concentration in the influent and effluent of central biological
WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
15
Figure 2.1:
COD concentration in the influent and effluent of central biologial WWTPs
It can be noted that WWTPs showing either relatively high BOD5 and/or TSS values in the
effluent (i.e. #24, #28, #29, #37, #44, #57, #68) or WWTPs treating only waste waters coming
from OFC plants (i.e. #06, #41, #19) tend to have higher COD emissions.
Figure 2.2 presents the specific waste sludge in central WWTPs using complete-mixed activated
sludge (CMAS) systems.
16
November 2010SR/EIPPCB/Analysis questionnaires CWW
Specific waste sludge in central WWTPs using complete-mixed
activated (CMAS) systems
Sludge (t dry solids) per t of COD abated
12
11
19
10
9
8
7
6
61
5
4
60
3
2
1
49
25
44
24
01
50
28
57
54
40
62
17
64
22
69
0
0
Figure 2.2:
18
WWTPs
Specific waste sludge in central WWTPs using complete-mixed activated sludge
systems
Figure 2.3 presents the specific energy consumption of central WWTPs using (CMAS) systems.
It can be noted that installations #08, #21, #36, #41 and #69 use membrane bioreactors, which
explains higher specific energy consumption.
Energy (in KWh) per kg of COD abated
Specific energy consumption of central WWTPs using
complete-mixed activated sludge (CMAS) systems
36
041
34
32
30
28
26
24
22
69
20
18
16
14
61
12
10
8
41
08
60
6
4
19
2
49
18
28
63
44
01
68
17
57
21
40
25
45
36
0
0
Figure 2.3:
WWTPs
21
Specific energy consumption of central WWTPs using complete-mixed activated
sludge systems
SR/EIPPCB/BP CWW TWG subgroup
November 2010
17
Number of plants reporting data
51 out of the 63 WWTPs reported COD concentration values in the effluent (or 81 %) and 42
(or 82 %) of these reported COD values in the influent. 39 WWTPs reported COD loads in the
effluent and 33 WWTPs in the influent.
Peaks of emissions
At 7 WWTPs (i.e. #25 1041 mg/l; #24, 1217 mg/l; #38, 1650 mg/l; #68, 1900 mg/l; #29,
2100 mg/l; #65, 6461 mg/l and #28, 8106 mg/l), average effluent COD is above 1000 mg/l. It
can be noted that WWTPs #24, #38 and #65 are indirect dischargers and that WWTPs #38 and
#65 are physico-chemical WWTPs.
Averaging periods used for reporting emissions
Most of the averaging periods reported are yearly averages (often of 24-hour daily composite
samples).
Techniques reported to minimise/reduce COD discharge
The following pretreatment operations (carried out at the installation(s) from which the waste
waters originate) have been reported in the questionnaires:







stripping
distillation
adsorption
extraction
chemical oxidation
biological treatment
filtration.
Treatment operations carried out in the central WWTPs are summarised in Section 1.5.4.
BAT-AELs for COD in the existing series of chemical BREFs
BAT-AELs for COD in the existing series of chemical BREFs are given in Table 2.1.
18
November 2010SR/EIPPCB/Analysis questionnaires CWW
BREF
(year
adopted)
Abatement
efficiency
(%)
Emission
levels
(mg/l)
76 – 96 ( )
30 –
250 (2)
1
CWW
Load
levels
For final waste water discharge into
surface water without dilution with
rainwater and/or uncontaminated cooling
water
Free oil/hydrocarbons discharged into a
receiving water
For waste water emissions for the whole
LVOC sector. The LVOC BREF also
defines BAT-AELs for the illustrative
processes
(2003)
30 –
125 (3)
30 –
125 (4)
LVOC
(2002)
OFC
(2005)
>95 (5)
Remarks
12 –
250 (6)
After treatment in a biological WWTP
19 – 30 g/t
prod.
30 g/t
prod.
50 –
480 g/t
prod.
150 –
200 g/t
prod.
3000 –
5000 g/t
prod.
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
LVIC-S
(2006)
LVICAAF
No BAT-AELs
(2006)
SIC (2006)
Refineries
(2003)
30 –
125 (7)
3–
70 (8) g/t
cop
(1) Low performance rates for low contaminant concentrations. For a better comparability of strategies with or
without central biological WWTP, COD-performance is based on the raw contaminant load, i.e. the load
before treatment and recycling/recovery procedures.
(2) Averaging period not indicated.
(3) Monthly average.
(4) Averaging period not indicated. The lower end of this range is determined by values of 30 – 45 mg/l for
lower olefin effluents.
(5) Combination of pretreatment and biological treatment.
(6) Yearly average.
(7) Monthly average. One Member State claims that the upper level of the concentration should be 75 and the
upper value for the load should be 45 because a standard biotreater reduces the COD content by 90-97 %.
As a consequence, 75 is easy to achieve in a well designed and operated biox. cop: crude oil or feedstocks
processed.
(8) Yearly average.
Table 2.1:
BAT-AELs for COD in the existing (adopted) series of chemical BREFs
Reported achieved performance
The COD concentrations in the effluent and the abatement efficiencies of central WWTPs are
given in Table 2.2.
The abatement efficiency in load versus the concentration in the effluent for COD at central
biological WWTPs is given in Figure 2.4.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
19
Abatement efficiency in load versus
concentration in effluent for COD
Average abatement efficiency on load (%)
100
95
90
85
80
80
70
60
50
40
30
20
10
0
Figure 2.4:
Parameter
COD average
(mg/l)
COD
abatement
based on
concentrations
(%) (6)
COD
abatement
based on
loads (%) (12)
0
100
400 400
200
300
Effluent average concentration (mg/l)
9000
Abatement efficiency in load versus the concentration in the effluent for COD at
central biological WWTPs
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
9 (1)
28 (2)
52 (3)
105 (4)
295 (5)
1217
8106
44
60
82 (7)
89 (8)
95 (9)
98 (10)
99 (11)
44
52
73 (13)
88
92 (15)
95 (16)
98 (17)
(1) #13 (DE) yearly average of 2h samples taken daily, abatement efficiency of 98 %.
(2) #08 (DE) yearly average, abatement efficiency of 95 %.
(3) #11 (DE) average based on 22 measurements.
(4) #49 (BE) yearly average of 24-hour composite samples, abatement efficiency of 80 – 95 %.
(5) #41 (FR); yearly averages of 24-hour composite samples, abatement efficiency of 89.6 %.
(6) 42 values are summarised in this row.
(7) #15 (DE), effluent average COD 148 mg/l.
(8) #19 (CEFIC), effluent average 161 mg/l.
(9) #40 (FR), effluent average 50 mg/l.
(10) #52 (BE), effluent average 67 mg/l.
(11) #58 (IT), effluent average 16 mg/l.
(12) 31 values are summarised in this row.
(13) #68 (AT), effluent average COD 1900 mg/l.
(15) #33 (CEFIC), effluent average COD 39 mg/l.
(16) #08 (DE), effluent average COD 28 mg/l.
(17) #01 (DE), effluent average COD 82 mg/l.
Table 2.2:
20
COD concentrations in the effluent and abatement efficiencies of central WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
It should be noted that good performers also include plants discharging indirectly to the
receiving water (e.g. #58 with 16 mg/l as a yearly average and #093 with 57 mg/l as yearly
average). Abatement efficiencies reported are in the range of 44 – 98 % on load. For the 50th
percentile of central WWTPs and higher, abatement efficiencies on load are in the range of 88 –
98 %. Efficiencies reported for load and concentrations match in the vast majority of cases. It
can be noted that several installations achieve abatement efficiencies higher than 90% with
average effluent concentrations below 100 mg/l (see Figure 2.4).
Fluctuations of emissions around the average (in concentration)
Maximum COD values reported (often 24-hour composite samples) vary around the average by
approximately a factor of 2 to 10 or more, but more generally by between 2 and 4.
Changes of production or events such as shutdowns at the level of the individual chemical
production plants can explain variations in COD emissions.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), COD is considered not quantifiable below 7 mg O2/l. Two international
standards for measuring COD exist. ISO 6060 (1989) is applicable to water with a value
between 30 mg/l and 700 mg/l. The chloride contents must not exceed 1000 mg/l. If the value
exceeds 700 mg/l, the water sample is diluted. For greatest accuracy, it is preferable that the
value of the sample is in the range of 300 mg/l to 600 mg/l. ISO 15705 (2002) uses the sealed
tube method which is applicable up to a COD value of 1000 mg/l and a chloride concentration
not exceeding 1000 mg/l. The method has a detection limit of 6 mg/l for photometric detection
at 600 nm, and 15 mg/l for titrimetric detection. In addition, sealed tube tests for a COD range
of 5 – 60 mg/l are commercially available. According to industry, sealed tube tests (called ultralow range, e.g. from HACH) being sensitive to chlorides lead to inaccurate results for waste
waters with high chloride content. Industry therefore considers more appropriate to use TOC
measurements.
The TWG subgroup considers that the limit of detection (LOD) of COD is around 50 mg O2/l
when high concentrations of sulphite are present.
Parameters that affect performance
High removal of the total organic loads depends mainly on the removal of the refractory organic
fraction of this total load as well as on the optimum operation of the biological part of the
treatment system to remove the biodegradable part.
Relevant refractory organic loading needs adequate pretreatment. The OFC BREF indicates that
refractory organic loading is not relevant if the waste water stream shows a bioeliminability of
greater than about 80 – 90 %. In cases with lower bioeliminability, the refractory organic
loading is not relevant if it is lower than the range of about 7.5 – 40 kg TOC per batch or per
day.
Once the refractory organic loading has been taken care of before the biological treatment, a
number of parameters have to be kept under control to ensure the highest efficiency of the
biological treatment (in terms of abatement/removal of pollutants, energy efficiency, production
of sludge, odour nuisance, etc.). These parameters are, for the most part, specific to each type of
biological treatment process used (suspended growth or fixed film processes) and to the
technology chosen for the treatment process (e.g. trickling filter, sequencing batch reactor,
membrane bioreactor). However, as a rule of thumb, smooth operation, especially with limited
variations of loads and characteristics of the influent waste water, is generally desirable,
especially for activated sludge processes. One should also bear in mind that (seasonal) ambient
temperatures as well as the waste water temperature affect the biological treatment.
3
WWTP #09 used to discharge effluents directly to the receiving water
SR/EIPPCB/BP CWW TWG subgroup
November 2010
21
It should be noted that biological treatment takes time (days to weeks) to recover from upset
conditions (sudden variations in the flow and load). In extreme conditions the whole population
of bacteria/microorganisms has to be replaced. Fixed biomass could be less sensitive.
In petroleum refineries, for example, excessive amounts of spent caustic (used to abate SOX
emissions) can quickly overwhelm a waste water treatment system due to the normally high
chemical oxygen demand (COD) of the spent caustic. Another issue can be a significant
increase in ammonia and sulphide loads that result from upsets in the operation of sour-water
strippers. These loads can, in turn, upset a biological treatment system if it is not designed to
handle ammonia and sulphide.
Restrictions on water usage or high water recycling can explain relatively high concentration of
COD (and of pollutants in general) even if high abatement efficiency are achieved.
Relation between performance and techniques used, as reported in the questionnaires
There are no clear performance trend associated with the use of certain techniques or
combinations of techniques. A large panel of techniques allow for achieving COD discharges
below the 50th percentile for COD (i.e. 105 mg/l as a yearly average of 24-hour composite
samples).
Regardless of the type of treatment system selected, one of the keys to effective biological
treatment is to develop and maintain an acclimated, healthy biomass, sufficient in quantity to
handle maximum flows and the organic loads to be treated.
2.2.1.2
TOC
Background information on TOC
Total organic carbon (TOC) analysis is used to directly measure the amount of organic
compounds in water. The most widespread methods use a combustion chamber to completely
oxidise the organic substances to carbon dioxide which is then measured by spectrometry.
Inorganic carbon is not included in the TOC. Identifying changes in the normal/expected TOC
concentrations can be a good indicator of potential threats to a waste water treatment system.
Various online TOC analysers exist. There is a trend to replace COD by TOC for economic and
ecological reasons.
Overview of central WWTP performance on TOC
Figure 2.5 presents the TOC concentration in the influent and effluent of central biological
WWTPs.
22
November 2010SR/EIPPCB/Analysis questionnaires CWW
TOC concentration in the influent and effluent of central biological WWTPs
500
400
Number of central WWTPs
06
CMAS_TB+Anaerob.+Sed.2
36
CMAS_FT+Sed.2
47
Inciner.+CMAS_FT+Sed.2
17
CMAS_MBR+Filt.
48
CMAS_FT
51
CMAS_FT+Sed.2
OWS+CMAS_FT+Sed.2
44
041
CMAS_FT+Sed.2
50
10
CMAS_FT+Flot.
01
49
16
37
CMAS_FT
02
CMAS_FT+Sed.2+Flot.
54
07
CMAS_FT+Sed.2
11
CMAS_FT+CMAS_TB
CMAS_FT+Sed.2
09
CMAS_FT+Sed.2+Flot.
CMAS_FT+Sed.2+Flot.
CMAS_FT+Sed.2+Pond/lag.
22
CMAS_FT+Filt.
0
08
CMAS_FT+Sed.2
0
34
CMAS_FT+Sed.2
69
CMAS_MBR
100
Exp.-bed+Flot.+Adsorp.+Filt.
influent 150-550
200
CMAS_FT+Sed.2
300
CMAS_FT+CMAS_MBR+Filt.
TOC (mg/l)
25
24
Overview of average values
(mg/l)
Maximum
339
90th percentile
133
75th percentile
60
50th percentile
39
25th percentile
18
10th percentile
12
Minimum
4
Figure 2.5:
TOC concentration in the influent and effluent of central biological WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 28 reported TOC concentration values in the effluent (or 44 %) and only
about half of these reported TOC values in the influent.
Peaks of emissions
At one WWTP, the TOC in the effluent is above 200 mg/l (i.e. #25, TOC of 339 mg/l).
Averaging periods used for reporting emissions
The vast majority of averaging periods reported are yearly averages (e.g. of 24-hour daily
composite samples, of weekly samples, of bi-monthly samples, of samples taken four times per
year).
Techniques reported to minimise/reduce TOC discharge
The techniques are the same as those indicated under the COD section (see Section 2.2.1.1).
BAT-AELs for TOC in the existing series of chemical BREFs
No BAT-AELs for TOC are given in the series of chemical BREFs.
Reported achieved performance
The TOC concentrations in the effluent and the abatement efficiencies of central WWTPs are
given in Table 2.3.
The abatement efficiency in load versus the concentration in the effluent for TOC is given in
Figure 2.6.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
23
Abatement efficiency in load versus
concentration in effluent for TOC
Average abatement efficiency on load (%)
100
95
90
85
80
80
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90 100 100
200
300
400
Effluent average concentration (mg/l)
Figure 2.6:
Parameter
TOC average
(mg/l)
TOC
abatement
based on
concentrations
(%) (6)
TOC
abatement
based on
loads (%) (7)
Abatement efficiency in load versus the concentration in the effluent for TOC
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
3 (1)
6 (2)
13 (3)
35 (4)
59 (5)
158
339
39.2
73.4
84.8
93.4
94.7
96.5
97.0
39.1
78.3
80.3
92.8
94.7
96.9
97.3
(1) #042 (DE) yearly average, abatement efficiency of 80 %.
(2) #56 (DE), yearly averages of of 24-hour composite samples.
(3) #22 (CEFIC) based on qualified samples taken daily, abatement efficiency of 93.4 %.
(4) #49 (BE) yearly average of 24-hour composite samples, abatement efficiency of 80 – 95 %.
(5) #17 (CEFIC) averaging period not indicated.
(6) 17 figures are summarised in this row.
(7) 13 figures are summarised in this row.
Table 2.3:
TOC concentrations in the effluent and abatement efficiencies of central WWTPs
Abatement efficiencies on loads reported are in the range 39.1 – 97.3 %. For the 50th percentile
of central WWTPs and higher, abatement efficiencies are in the range of 93 – 97 %, similar to
COD abatement efficiencies.
Fluctuations of emissions around the average (in concentration)
Maximum TOC values reported vary around the average by a factor 1.1 to 4.3 or more, but
more generally by between 2 and 3.
24
November 2010SR/EIPPCB/Analysis questionnaires CWW
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), TOC is considered not quantifiable below 10 mg/l. The international
standards for measuring TOC are EN 1484 (1997) and ISO 8245 (1999). Both standards are
guidelines to measure TOC by oxidation via combustion, addition of an appropriate oxidant,
UV-radiation, or any other high-energy radiation. The carbon dioxide formed is determined
either directly or after reduction while the final determination of carbon dioxide is carried out by
a number of different procedures, for example: infrared spectrophotometry, titration, thermal
conductivity, conductometry, coulometry, use of carbon dioxide-sensitive sensors and flame
ionisation detection. Inorganic carbon is removed by acidification and purging, or is determined
separately. EN 1484 gives an application range of 0.3 mg/l to 1000 mg/l while the lower value
is only applicable in special cases, for example drinking water, measured with instruments
capable of measuring these low levels.
Parameters that affect performance
See discussion under the COD parameter (see Section 2.2.1.1).
Relation between performance and techniques used as reported in the questionnaires
See discussion under the COD parameter (see Section 2.2.1.1).
2.2.1.3
BOD5
Background information on BOD5
BOD5 measures the amount of dissolved oxygen required or consumed in five days at a constant
temperature for the microbiological decomposition (oxidation) of organic material in water
The concentration in the effluent is generally a more pertinent parameter than the abatement
efficiency.
CEFIC indicated that BOD5 is not a parameter that is used much in Germany to monitor
industrial discharges of waste water. COD and TOC are preferred because they are considered
more reliable and because they are faster to determine. CEFIC also indicated that BOD5 is not
an accurate parameter to describe the efficiency of biological treatment because:



The monitoring method used is not very accurate considering reproducibility and
methodology dependence (dilution method versus respirometer for example);
The analytical result depends on local conditions of the laboratory, such as the used
inoculum for the test;
BOD measurement does not allow any prediction on the performance within the WWTP.
It only provides an indication whether the waste water is easily degradable to a certain
rate.
Germany said that the BOD5 data it delivered (i.e. 90 percentile values) reflects the variations of
the biological WWTPs.
For most of the BOD values given in the German questionnaires, BOD5 has been monitored
weekly.
The ratio BOD5/COD in the raw effluent cannot be used as an operative parameter for the waste
water treatment, but gives a rough indication of biodegradability. As a rule of thumb,
BOD/COD ratios before treatment of <0.2 indicate relatively undegradable organic substances,
ratios between 0.2 and 0.4 indicate moderately to highly degradable organic substances, and
ratios of >0.4 indicate highly degradable organic substances (see revised CWW BREF Draft 1,
Section 3.2.3.4.3). BOD5/COD ratios in the influents and effluents of CWWs are shown in
Table 2.4. The OFC BREF indicates that the Zahn-Wellens test provides more useful
information than is possible from the BOD/TOC ratio (see Section 4.3.1.3 of the OFC BREF).
SR/EIPPCB/BP CWW TWG subgroup
November 2010
25
Parameter
BOD5/COD
ratios in
influent (1)
BOD5/COD
ratios in
effluent (2)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.00 (2)
0.22
0.33
0.45
0.53
0.58
0.81
0.00 (2)
0.03
0.05
0.10
0.18
0.29
0.44
(1) There are 30 values summarised in this row.
(2) Installation #65. Possibly a data error because an influent of BOD5 at 2 mg/l and an effluent of BOD5 at 1 mg/l
seem to be low figures.
(2) 39 values are summarised in this row.
Table 2.4
BOD5/COD ratios in the influents and effluents of CWWs.
As can be seen from Table 2.4, more than 90 % of the WWTPs surveyed treat waste waters with
BOD5/COD ratios >0.2. i.e. waste waters with presumably moderately to highly degradable
organic substances. In the effluents, the BOD5/COD ratios are mostly <0.2 indicating waste
waters with relatively undegradable substances.
Overview of central WWTP performance on BOD5
Figure 2.7 presents the BOD5 concentration in the influent and effluent of central biological
WWTPs.
26
November 2010SR/EIPPCB/Analysis questionnaires CWW
BOD5 concentration in the influent and effluent of central WWTPs (detail)
Figure 2.7:
CMAS_FT
CMAS_FT
OWS+CMAS_FT+Sed.2
CMAS_MBR+Sed.2
CMAS_TB+Anaerob.+Sed.2
16
41
CMAS_FT+CMAS_TB+Sed.2
50
63
57
14
15
52
CMAS_FT
61
CMAS_FT
45
OWS+CMAS_FT+Flot.
041
CMAS_FT+Sed.2
49
CMAS_FT+Filt.+Pond/lag.
OWS+CMAS_TB+Sed.2+Filt.
07
62
43
24
40
64
CMAS_TB+Sed.2
06
19
CMAS_TB+Sed.2
60
CMAS_FT
12
Inciner.+CMAS_FT+Sed.2
CMAS_FT+Sed.2
54
CMAS_FT+Sed.2
22
CMAS_FT+CMAS_TB
01
CMAS_FT+Filt.
13
03
CMAS_FT+Sed.2
0
08
CMAS_MBR
0
CMAS_TB+Sed.2
10
CMAS_FT+Sed.2
20
CMAS_FT+Flot.
30
CMAS_FT+Sed.2+Pond/lag.
BOD5 (mg/l)
40
CMAS_FT+Sed.2+Flot.
CMAS_FT+Sed.2+Pond/lag.
50
28
Number of central WWTPs
BOD5 concentration in the influent and effluent of central biological WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 42 reported BOD5 concentration values in the effluent (or 67 %) and 34
WWTPs reported BOD5 values in the influent.
Peaks of emissions
At eight WWTP, average BOD5 in the effluent is above 50 mg/l (i.e. #44, 58 mg/l; #46,
72.9 mg/l; #29, 150 mg/l; #37, 269 mg/l; #68, 270 mg/l; #38, 300 mg/l; #65, 1133 mgl/l; #28,
2931 mg/l, direct discharge to estuary). It can be noted that WWTPs #46, #24, #68, #38, and
#65 are indirect dischargers and that WWTPs #46, #38 and #65 are physico-chemical WWTPs.
Averaging periods used for reporting emissions
The vast majority of averaging periods reported are yearly averages (e.g. of 24-hour daily
composite samples, of weekly samples, of bi-monthly samples, of samples taken four times per
year).
Techniques reported to minimise/reduce BOD5 discharge
The techniques used to remove COD (see Section 2.2.1.1) may remove (part of the) BOD too;
on the other hand, pretreatment of COD may in certain cases raise BOD (conversion of nondegradable to biodegradable matter e.g. by partial oxydation). The only technique which is a
priori dedicated to remove BOD is biological treatment (removal of C).
BAT-AELs for BOD5 in the existing series of chemical BREFs
The BAT-AELs for BOD5 in the existing (adopted) series of chemical BREFs are given in
Table 2.5.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
27
BREF
(year
adopted)
Abat.
efficiency
(%)
Emission
levels
(mg/l)
CWW
2 – 20 (1)
(2003)
<20 (2)
LVOC
<20 (3)
(2002)
OFC (2005)
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
LVIC-S
>99
Load
levels
Remarks
Free oil/hydrocarbons discharged into a
receiving water
After central biological treatment
After central biological treatment. The
LVOC BREF also defines BAT-AELs
for the illustrative processes
After treatment in a biological WWTP
1 – 18 (4)
(2006)
LVIC-AAF
(2006)
SIC (2006)
Refineries
2 – 20 (5)
0.5 – 11 (6) g/t cop
(2003)
(1) BOD5: monthly average.
(2) In general. Averaging period not indicated. In the case of activated sludge, a typical application is a low-loaded
biological stage with a daily COD load of ≤0.25 kg/kg sludge.
(3) BOD: daily average. A typical design for this treatment plant is a lowly loaded biological treatment plant, which
in the case of an activated sludge plant is a COD load of ≤ 0.25 kg COD/kg sludge (as dry solids) per day.
(4) Yearly average.
(5) Monthly average.
(6) Yearly average.
Table 2.5:
BAT AELs for BOD5 in the existing (adopted) series of chemical BREFs
Reported achieved performance
The BOD5 concentrations in the effluent and the abatement efficiencies of central WWTPs are
given in Table 2.6.
The abatement efficiency in load versus the concentration in the effluent for BOD5 at central
biological WWTPs is given in Figure 2.8.
28
November 2010SR/EIPPCB/Analysis questionnaires CWW
Abatement efficiency in load versus
concentration in effluent for BOD5
Average abatement efficiency on load (%)
100
98
96
94
92
90
90
45
0
Figure 2.8:
Parameter
BOD5 average
(mg/l)
BOD5
abatement
based on
concentrations
(%) (6)
BOD5
abatement
based on
loads (%) (7)
10
0
50 50
40
20
30
Effluent average concentration (mg/l)
3000
Abatement efficiency in load versus the concentration in the effluent for BOD 5 at
central biological WWTPs
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
1 (1)
1.5 (1 bis)
2.5 (2)
5 (3)
7.5 (4)
26.9 (5)
150
2931
51.1
68.6
94.5
97.6
98.9
99.6
99.9
51.1
65.3
91.0
97.7
98.6
99.5
99.9
(1) #08 (DE) yearly average, abatement efficiency of 99.7 %.
(1 bis) #53 (BE) 24-hour composite samples (in proportion to the volume of discharged waste water).
(2) #03 (DE) quarter average of 14 samples (one sample/week), abatement efficiency of 99 %.
(3) #60 (FR) yearly average of 24-hour composite samples, abatement efficiency of 98.7 %.
(4) #52 (BE) yearly average, abatement efficiency of 99.7 %.
(5) #63 (CZ) yearly average of 24-hour composite samples, abatement efficiency of 96.3 %..
(6) 34 figures are summarised in this row.
(7) 26 figures are summarised in this row.
Table 2.6:
BOD5 concentrations in the effluent and abatement efficiencies of central WWTPs
Abatement efficiencies reported are in the range 51.1 – 99.9 %. For the 50th percentile of
central WWTPs and higher, abatement efficiencies are generally >97.5 %. Efficiencies reported
for load and concentrations match in the vast majority of the cases.
Fluctuations of emissions around the average (in concentration)
Maximum BOD5 values reported vary around the average by approximately a factor of 2 to 8 or
more, but more generally by between 2.5 and 5.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
29
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), BOD5 is considered not quantifiable below 3 mg O2/l. Four international
standards for measuring BOD exist. EN 1899-1 (1998) and ISO 5815-1 (2003) specify a BOD
determination of waters by dilution and seeding with suppression of nitrification by
allylthiourea. They are applicable to all waters having biochemical oxygen demands greater
than or equal to 3 mg/l of oxygen (the limit of determination) and not exceeding 6000 mg/l of
oxygen. EN 1899-2 (1998) and ISO 5815-2 (2003) specify a BOD determination of waters of
undiluted samples. They are applicable to BOD values greater than or equal to 0.5 mg/l of
oxygen (the limit of determination) and not exceeding 6 mg/l of oxygen.
Parameters that affect performance
See discussion on biological treatment under the COD parameter (see Section 2.2.1.1).
Since BOD<COD, monitoring of BOD is not essential when COD/TOC is low.
Relation between performance and techniques used as reported in the questionnaires
See discussion under the COD parameter (see Section 2.2.1.1). Germany considers that it can be
expected that BOD concentration in the effluent/performance is less dependent on the variation
of the production than COD/TOC, and can be controlled by the proper handling of the final
treatment alone.
2.2.2
TSS
Background information on TSS
Materials in suspension are included in the indicative list of substances to be taken into account
for fixing emission limit values in Annex III of the IPPC Directive.
There are some reasons to link the analysis of TSS with those of COD/TOC, phosphorus and
BOD5. If BOD/COD/TOC removal functions poorly, TSS emissions may be affected.
Conversely, high TSS values can correlate with/cause high concentrations of other parameters,
namely BOD, COD/TOC, total phosphorus, total nitrogen, and metals.
It is possible to have higher TSS values in the effluent than in the influent (e.g. #68, where the
excess sludge is removed in a downstream municipal WWTP), which is due to the presence of
biomass. Therefore, it does not make sense to calculate abatement efficiencies for the whole
central WWTP, which are heterogeneous combinations of different unit processes.
The concentration in the effluent is generally a more pertinent parameter than the abatement
efficiency.
Overview of central WWTP performance on TSS
Figure 2.9 presents the TSS concentration in the influent and effluent of central biological
WWTPs. Figure 2.10 presents the TSS concentration in the influent and effluent of central
physico-chemical WWTPs.
30
November 2010SR/EIPPCB/Analysis questionnaires CWW
TSS concentration in the influent and effluent of central biological WWTPs (detail)
51
29
Figure 2.9:
Meca.+Flot.+Filt.
0
CMAS_MBR
0
61
21
33
54
19
43
Sed.2+Flot.
50
44
Air_flot.
Sed.1+Sed.2
Meca.+Sed.2
Sed.2+Pond/lag.
62
49
60
influent 20-430
Flot.
64
Meca.+OWS+Sed.1+Sed.2
OWS+Air_flot.+Flot.
41
041
Meca.
40
09
Sed.2
07
45
37
Sed.1
03
02
Sed.1+Sed.2
01
08
Filt.+Pond/lag.
34
Sed.1+Filt.
10
Sed.1+Sed.2
20
Sed.2+CMAS_MBR
Sed.1
30
Air+flot.
40
Sed.1+Sed.2
50
OWS+Sed.1+Sed.2+Filt.
60
Sed.1+Flot.
TSS (mg/l)
70
Meca.+OWS+Sed.1+Sed.2
17
Sed.2
80
Sed.2
48
90
Flot.
100
29
Number of central WWTPs
TSS concentration in the influent and effluent of central biological WWTPs
It is to be noted that there is only one TSS measurement for WWTP #51.
It can be noted that WWTPs showing either relatively high BOD5 and/or COD/TOC values in
the effluent (i.e. #18, #24, #25, #57) tend to have higher TSS emissions.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
31
TSS concentration in the influent and effluent of central physico-chemical WWTPs
500
direct organic
400
dir. org.+inor.
direct organic
ind. org.+inor.
dir. org.+inor.
inder. organic
ind. org.+inor.
300
0
32
Sed.+Air+flot.
0
67
Meca.+Sed.
042
35
27
53
OWS+Air_flot.
100
Sed.1+Filt.
inder. organic
Sed.1+Sed.2
200
Meca.+OWS+Sed.1+Flot.
65
38
46
9
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
89
90th percentile
55
75th percentile
28
50th percentile
24
25th percentile
15
10th percentile
9
Minimum
5
TSS concentration in the influent and effluent of central physico-chemical WWTPs (detail)
100
OWS+Air_flot.
46
90
80
50
40
30
20
32
10
0
Figure 2.10:
Meca.+Sed.
042
0
Sed.+Air+flot.
67
35
65
53
38
27
Sed.1+Filt.
60
Meca.+OWS+Sed.1+Flot.
TSS (mg/l)
70
Sed.1+Sed.2
direct organic
TSS (mg/l)
dir. org.+inor.
9
Number of central WWTPs
TSS concentration in the influent and effluent of central physico-chemical
WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 48 reported TSS values in the effluent (or 76 %) and only about half of
these reported TSS values in the influent.
Peaks of emissions
At two WWTPs, TSS is above 1000 mg/l (i.e. #28 with 1729 mg/l and #68 with 1900 mg/l). It
can be noted that WWTP #68 is an indirect discharger.
Averaging periods used for reporting emissions
Most of the averaging periods reported are yearly averages of 24-hour daily composite samples
(e.g. #07 reported an average of 300 random samples, #35 reported a yearly average of monthly
averages values).
32
November 2010SR/EIPPCB/Analysis questionnaires CWW
Techniques reported to minimise/reduce TSS discharge
The following pretreatment operations (carried out at the installation(s) from which the waste
waters originate) have been reported in the questionnaires:

grit separation of solids

coagulation and flocculation

sedimentation of solids

filtration

microfiltration and ultrafiltration

nanofiltration (NF).
These can also be carried out as part of a central biological treatment plant.
Treatment operations carried out in the central WWTPs are summarised in Section 1.5.4.
Membrane bioreactors achieve high TSS removal and smaller plant footprint (no need for a
secondary clarifier and tertiary filtration system, elevated mixed liquor concentrations are
possible), however energy consumption is an important cross-media effect as shown in Figure
2.3. Conventional activated sludge processes can in some cases be retrofitted to accommodate
membranes. However, membranes are not applicable to all sites.
BAT-AELs for TSS in the existing series of chemical BREFs
The BAT-AELs for TSS in the existing (adopted) series of chemical BREFs is given in Table
2.7.
BREF
(year adopted)
CWW (2003)
Abatement
efficiency
(%)
Emission
levels
(mg/l)
Load
levels
Remarks
10 – 20 (1)
Monthly average for final waste
water discharge into surface
water, without dilution with
rainwater and/or
uncontaminated cooling water
10 – 20 (2)
After treatment in a biological
WWTP
LVOC (2002)
OFC (2005)
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
10 g/t prod.
10 g/t prod.
0.5 – 2.5 kg/t
TiO2 (3)
1 – 40 kg/t TiO2 (4)
LVIC-S (2006)
LVIC-AAF
(2006)
SIC (2006)
Refineries (2003)
2 – 50 (5)
1 – 25 g/t cop (6)
(1)
Monthly average.
(2) Yearly average.
(3) Titanium dioxide – chloride route.
(4) Titanium dioxide – sulphate route.
(5) Monthly average.
(6) Yearly average. cop: crude oil or feedstock processed.
Table 2.7:
BAT AELs for TSS in the existing (adopted) series of chemical BREFs
Abatement efficiency and emission levels associated with techniques used to remove TSS as
reported in the adopted CWW BREF are given in Table 2.8.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
33
Abatement
efficiency
(%)
60 – 90
Emission
levels
(mg/l)
<10
90 – 98
85 – 96
10 – 20
Filtration
50 – 99.99
<10
Microfiltration
and ultrafiltration
about 100
close to 0
Techniques
used
Sedimentation
Air flotation
Table 2.8:
Load
levels
Remarks
After final clarifier of central
WWTP
Activated sludge after final
clarifier, input 20–250 mg/l
Activated sludge floc
Sand filter, dependent on
filter aids
Energy is an important crossmedia effect. These techniques
are used especially when water
is to be reused
Abatement efficiency and emission levels associated with techniques used to
remove TSS as reported in the adopted CWW BREF
Reported achieved performance
The TSS concentration in the effluent of central WWTPs is given in Table 2.9.
Parameter
TSS
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
1.1 (1)
9 (2)
15 (3)
28 (4)
80 (5)
150
1900
(1) #08 (DE) yearly average based on 150 measurements,
(2) #61 (CZ) yearly average of 24-hour composite samples.
(3) #59 (UK) ) yearly average of 24-hour composite samples.
(4) #27 (CEFIC) yearly average of weekly samples.
(5) #29 (CEFIC) based on spot samples once per week + online turbidity measurement.
Table 2.9:
TSS concentration in the effluent of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum TSS values reported vary around the average approximately by a factor of 1.5 to 10,
but more generally by between approximately 2 and 3.
Seasonal variations (e.g. rain period) and the treatment of storm water (sometimes from a
nearby city) may cause higher variability in TSS effluent concentration. This has to be taken
into account in deriving BAT conclusions.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), TSS is considered not quantifiable below 2 mg/l. Two international
standards, EN 872 (2005) and ISO 11923 (1997), describe a method for the determination of
suspended solids in raw waters and waste waters by filtration though glass-fibre filters. The
lower limit of the determination is in both cases approximately 2 mg/l.
Since TSS at the outlet of biological treatment plants consists mainly of organic matter and
COD/TOC also cover suspended matter, monitoring of TSS is not essential when COD/TOC is
low.
Relation between performance and techniques used as reported in the questionnaires
34
November 2010SR/EIPPCB/Analysis questionnaires CWW
The performance of the central WWTPs with respect to the removal of solids depends on the
techniques used, but also on the characteristics of the waste waters and the operating conditions
of the installations (e.g. residence time in the final clarifier in the case of sedimentation). TSS
values of mostly below 20 mg/l are achieved by installations using sand filtration (e.g. #34:
5 mg/l, #01: 6 mg/l, #61: 9 mg/l, #32: 15 mg/l, and #45: 22 mg/l). Installations using
ultrafiltration as the main solids removal step (often as part of a membrane bioreactor) also tend
to show low TSS values in the effluent (i.e. #36: <detection limit, #69: <5 mg/l, #414: 17 mg/l,
and #38: 26 mg/l). No information on TSS is available for installation #58 which uses reverse
osmosis (RO). Installations using flotation tend to show higher TSS values in the effluent (15 –
100 mg/l), although 3 out of the 8 installations reporting the use of flotation (i.e. #33, #35, #64)
achieve TSS values below 20 mg/l, the upper range of the BAT level of the current CWW
BREF. The largest spread of TSS effluent values is found when sedimentation as the main
solids removal step is used (5 – 1900 mg/l). Nevertheless, 8 out of 30 installations using
sedimentation achieve TSS values below 20 mg/l, and 3 installations implementing
sedimentation achieve TSS values below or equal to 10 mg/l.
2.2.3
AOX
Background information on AOX
AOX is a sum parameter which indicates the overall level of organohalogen compounds
(chlorine, bromine and iodine) in water samples. It is important as many organohalogen
compounds are toxic (especially the fat-soluble chlorinated group – dioxins, furans, and
polychlorinated phenolic compounds) and/or persistent. However, as a sum parameter, AOX
gives neither information on the chemical structure of organohalogen compounds present nor on
their toxicity. The AOX method has the advantage that it is quite a simple measurement if it is
compared to the alternative methods of measuring levels of individual compounds which are
complex and require costly equipment. High concentrations of organic compounds or inorganic
chlorides may interfere with the AOX measurement. AOX is an operational parameter, i.e. the
measurement procedure determines the result. AOX cannot be used to monitor very volatile
compounds.
AOX is routinely monitored in Germany. AOX or EOX is also monitored, albeit less routinely it
seems, in Austria, France (EOX), Belgium, the Czech Republic, Italy, the Netherlands (EOX)
and Spain. It is worth noting that 31 out of the 70 WWTPs (or 44%) reported AOX or EOX
values in the effluent. AOX or EOX has been reported by Austria (i.e. #68), Belgium (i.e. #50,
#53, #54), the Czech Republic (i.e. #61, #63), France (i.e. #35, #38, #60), Germany, Spain (i.e
#47, #65).
AOX values are generally higher than EOX values (possibly by a factor of 10). AOX is the only
parameter used in Germany, whereas both AOX and EOX are used in Belgium, France and the
Netherlands. Both EOX and AOX parameters are included in the basic environmental quality
standards for discharge into surface water in Belgium (Flanders). Furthermore, AOX or EOX is
included in the Flemish sectoral discharge conditions for industrial waste water.
CEFIC raised the question whether there is sufficient data on AOX/EOX to draw BAT
conclusions for the whole EU. Germany pointed out that the data delivered for Germany reflect
a broad spectrum of chemical sites (regarding production mix, large and medium size sites). For
questionnaires #17 and #36, the Organic Fine Chemicals (OFC) BREF should be referred to
where high AOX values are explained. AOX is one of the key pollutants of the European
Pollution Release and Transfer Register (E-PRTR).
4
Only a part of the whole effluent is treated by the membranes. In 2009, the average concentration was
10 mg/l compared to 17 mg/l in 2007.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
35
Specific information regarding AOX abatement presented in the vertical chemical BREFs is
discussed in the following paragraphs. It is important to note that this parameter is mainly
associated with the production of organic chemicals and silicones.
In the CAK, LVIC-AAF and LVIC-S BREFs, there is no information on AOX reported.
In SIC processes, AOX emissions are not regarded as a common general environmental issue
for the sector as a whole. AOX could be carried by the waste water from plants producing
silicones. The techniques reported for AOX abatement are chemical oxidation,
nanofiltration/reverse osmosis, adsorption, stripping, incineration, anaerobic biological
digestion and aerobic biological digestion.
In some LVOC processes, i.e. the production of lower olefins, aromatics, oxygenated
compounds, nitrogenated compounds and halogenated compounds, the waste waters contain
AOX loads after pretreatment and prior to biological treatment. Waste water streams containing
high AOX/EOX loads are preferably pretreated or recovered separately, e.g. by (chemical)
oxidation, adsorption, filtration, extraction, (steam) stripping, hydrolysis (to improve biodegradability) or anaerobic pretreatment.
The LVOC TWG acknowledged that it was difficult to describe BAT-AELs for AOX that were
applicable for all LVOC processes as the waste water characteristics are strongly influenced by
the applied processes, operational process variability, water consumption, source control
measures and the extent of pretreatment. Nevertheless, based on their expert judgement, a
general BAT-AEL for AOX was set.
In OFC processes, the main sources for waste water streams with relevant AOX loads are
processes/operations involving halogenated solvents and halogenated intermediates, products
and by-products. Mass balances for emissions inventories are mentioned as being essential for
understanding on-site processes and the development of improvement strategies. Pretreatment
includes, e.g. distillation, stripping, activated carbon adsorption, extraction and membrane
processes. The pretreatment can also be done by oxidation, e.g. chemical oxidation, high
pressure wet oxidation and low pressure wet oxidation, or disposal (incineration). After
pretreatment, the effluent is sent to biological treatment. The BAT-AELs set can be seen in
Table 2.10. It is important to notice that the OFC BREF with its diverse sectors shows
systematic similarities with the CWW BREF. In fact, the discussion on AOX was based on a
similar set of reference plants.
In POL processes, AOX emissions occur during PVC production. Since AOX also covers solid
compounds, the parameter is used to control overall PVC recovery/removal. Further, AOX
emissions can occur during viscose fibre and viscose filament yarn production. However, no
further information is reported.
Overview of central WWTP performance on AOX
Figure 2.11 presents the AOX concentration in the influent and effluent of central biological
WWTPs.
36
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.11:
AOX concentration in the influent and effluent of central biological WWTPs
The following points are woth worth mentionning:




EOX is reported for WWTP #17.
WWTPs #36 and #06 are special cases dealt with in the OFC BREF.
At WWTP #57, the use of bleach treatment as pretreatment is the reason for high AOX
At WWTP #68 (AT), 2 samples were taken in 2009 and the results showed <0.01 mg/l and
0.012 mg/l for AOX.
Number of plants reporting data
AOX values (concentrations and/or loads) have been reported by Austria (i.e. #68), Belgium
(i.e. #49, #53, and #54), the Czech Republic (i.e. #61, and #63), France (i.e. #35, #38, and #60),
Germany (i.e. #01, #02, #03, #041, #042, #06, #07, #09, #10, #11, #12, #13, #14, #15, #16, #36,
and #56), Italy (i.e. #69), Spain (i.e. #47, and #65), Industry (i.e. Questionnaires #17, #21, #22,
#25, and #57). Out of the 63 WWTPs, 31 reported AOX concentration values in the effluent (or
49 %). Of these values, 30 are of spot-type while one is given as a range-type value (i.e.
<0.20 mg/l).
Peaks of emissions
At four WWTPs (i.e. #57 with 3.6 mg/l, #17 with 9.6 mg/l – EOX, #36 with 17 mg/l, and #65
with 29.3 mg/l), AOX/EOX is above 1 mg/l. These data are not shown on the figure above.
It can be noted that for #65, the figure of 29.3 mg/l is based on a single measurement that is not
considered very reliable by the operator. The operator considers that this is due to the
complexity of the AOX analysis that requires a first stage of absorption, digestion and usually
photometric final analysis. According to Spain, depending on the interferences, it is advisable to
use absorbent polymer instead of charcoal for the absorption stage (e.g. if there are many
chlorides). Additionally, very high COD may give false on AOX.
Averaging periods used for reporting emissions
Often, the averaging periods reported are yearly averages of 24-hour daily composite samples.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
37
Techniques reported to minimise/reduce AOX discharge
The main techniques to reduce AOX emissions are the segregation and selective pretreatment of
waste water streams from processes where AOX is an issue.
The following pretreatment operations (carried out at the installation(s) from which the waste
waters originate) have been reported in the questionnaires:






oxidation (i.e. #07)
stripping (i.e. #12, #14, #15, #17, #19, #21, #22, #36, #68)
adsorption on activated carbon (i.e. #13, #15, #21)
decantation (i.e. #17)
oil-water separation (i.e. #27)
distillation (i.e. #36, #68).
Regarding AOX removal at the central WWTPs, the following techniques were reported:




oxidation (i.e. #65 where a wet oxidation process with H2O2 is used to remove several
pollutants including AOX);
stripping (i.e. #27, #38);
adsorption on activated carbon (e.g. #07, #34);
reverse osmosis (i.e. #58).
BAT-AELs for AOX in the existing series of chemical BREFs
The BAT-AELs for AOX in the existing (adopted) series of chemical BREFs is given in Table
2.10.
38
November 2010SR/EIPPCB/Analysis questionnaires CWW
BREF
(year
adopted)
CWW (2003)
LVOC (2002)
OFC (2005)
Abatement
efficiency
(%)
none
Emission
levels
(mg/l)
Load
levels
Split view: one Member State insists
on naming BAT-AELs for AOX
based on the examples given in
Annex 7.6.2. They state that in this
Member State on some chemical sites
with production of chloro-organic
chemicals and central waste water
treatment plants, AOX emission
levels between 0.16 and 1.7 mg/l are
achieved. The TWG did not follow
this request. The examples presented
(see Annex 7.6.2) were interpreted as
consisting of different statistical data
sets which did not allow naming
BAT-AELs. It was even mentioned
that one of the lowest AOX emission
values reported as examples
represented poor performance,
whereas the highest emission value
came from a site with very good
performance. Under these conditions,
the TWG saw it to be unsuitable to
give BAT-AELs for AOX
For waste water emissions for the
whole LVOC sector. The LVOC
BREF also defines BAT-AELs for
the illustrative processes
After treatment in a biological
WWTP.
none
<1 (1)
0.1 – 1.7 (2)
POL (2006)
PVC
Remarks
1 - 12 g/t
PVCM
AOX levels of 0.5 – 8.5 at the inlet of
the central WWTPs is the BAT-AEL.
The upper range relates to cases
where halogenated compounds are
processed in numerous processes and
the corresponding waste water
streams are pretreated and/or where
the AOX is very bioeliminable.
In the final effluent are achieved for
PVC production sites or combined
EDC, VCM and PVC production
LVIC-S
(2006)
LVIC-AAF
(2006)
SIC (2006)
Refineries
(2003)
(1) Most LVOC processes can achieve an AOX value of below 1 mg/l.
(2) Yearly average. The upper end of the range results from numerous AOX relevant productions and pretreatment
of waste water streams with significant AOX loads.
Table 2.10:
BAT-AELs for AOX in the existing (adopted) series of chemical BREFs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
39
Reported achieved performance
The AOX concentrations in the effluent and the abatement efficiencies of central WWTPs are
given in Table 2.11.
Parameter
AOX average
(mg/l)
AOX
abatement
based on
concentrations
(%) (6)
AOX
abatement
based on
loads (%) (7)
Minimum
10th
percentile
25th
percentile
50th
percentile
0.23 (4)
0.28 (4 bis)
75th
percentile
90th
percentile
Maximum
0.03 (1)
0.08 (2)
0.1 (3)
0.6 (5)
0.9
29.3 (8)
-10.0
40.0
52.5
76.7
85.7
86.7
88.9
-16.9
-16.9
40.4
59.6
78.7
83.1
89.0
(1) #09 (DE) based on 19 measurements.
(2) #56 (DE) averaging period not indicated.
(3) #11 (DE) average based on 20 measurements.
(4) #16 (DE) yearly average of 24-hour composite samples.
(4 bis) #53 (BE) 24 hours composite samples (in proportion to the volume of discharged waste water).
(5) #49 (BE) yearly average of 24-hour composite samples.
(6) 17 figures are summarised in this row.
(7) 13 figures are summarised in this row.
(8) #65 (ES) which is a physico-chemical WWTP. A maximum of 17 mg/l is achieved for WWTP #36 (DE).
Table 2.11:
AOX concentrations in the effluent and abatement efficiencies of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by 24
installations. Maximum AOX values reported vary around the average by a factor of 1.3 to 5.4,
but more generally by between approximately 2 and 3.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), AOX is considered not quantifiable below 20 µg/l. The most widely
accepted monitoring method is EN ISO 9562 (2004) which replaced the European standard EN
1485 (1997). The standard specifies a method for the direct determination of an amount of
usually 10 µg/l in water of organically-bound chlorine, bromine and iodine (expressed as
chloride) adsorbable on activated carbon. This method is applicable to test samples with
concentrations of inorganic chloride ions of less than 1 g/l. Samples with higher concentrations
are diluted prior to analysis.
No European or International standard for the determination of EOX exists. The standard for the
determination of EOX in Germany is DIN 38408/H8 (1984) and NEN 6402 (1991) in Belgium
(Flanders).
Parameters that affect performance
Organohalogen compounds are part of the organic load of waste waters. AOX is therefore a part
of COD/TOC, and, if biodegradable, also of BOD5. See therefore the discussion under the COD
parameter in Section 2.2.1.1.
Relation between performance and techniques used as reported in the questionnaires
See the discussion under the COD parameter in Section 2.2.1.1.
40
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.3
2.3.1
Metals
General
Background information on metals, their abatement and BAT conclusions reached in the
chemical BREFs
Important characteristics of (heavy) metals which influence waste water treatment are given
below:




Metals are not degradable and almost all of them are adsorbed to the sludge or passed
through the biological WWTP.
High levels of metals can inhibit the biological processes in central WWTPs, but certain
concentrations are needed for the growth of the organisms.
High metal loadings in sewage sludge cause problems for disposal (in the case of
agricultural use of sewage sludge)
Once discharged to water, metals from sediment can remobilise in the waterbody (river
or sea).
The waste waters of many chemical processes contain metals, e.g. they are contained in the
materials used for chemical processing (feedstock, auxiliaries and catalysts). The corrosion of
pipes and equipment is also an important source of metals (especially Cu, Zn, Cr, Ni) in
effluents of central WWTPs (in low concentrations, however often representing the main input
regarding loads).
Specific information regarding metals removal presented in the vertical chemical BREFs is
discussed in the following paragraphs. The OFC, SIC, LVOC and LVIC-S BREFs describe
several techniques that are used to reduce the content of metals in waste waters.
The CAK BREF covers mainly the abatement of mercury from mercury cell plants. Historical
mercury contamination of land and waterways from mercury cell plants is reported as a major
environmental problem at some sites. Considerable emissions of mercury can also occur with
run-off water. Mercury emitted to water from mercury cell facilities mainly arises from:




bleed from brine purification and condensates
the wash water from the cell cleaning operations
rainwater from the electrolysis hall
the rinsing water from maintenance areas.
In CAK processes, waste water contaminated with mercury is collected from all sources and is
generally treated in a waste water treatment plant. The amount of waste water can be reduced
by filtration and the washing of the sludges to remove mercury before feeding the condensate
back into the brine. The use of process-integrated techniques, e.g. the monitoring of possible
leakages and the recovery of mercury, good housekeeping and the use of salt with low impurity
content are reported. End-of-pipe measures include precipitation as sulphide and mercury
removal from hydrogen gas and caustic soda.
In LVIC-AAF processes, metals such as nickel and vanadium (introduced with the feedstock)
are suspended as oxides and are also partially present as salts in the soot water circuit. To
prevent an accumulation of these compounds in the water circuit, some of the extracted water
has to be drained. The waste water is treated by flocculation, applying settlers and/or filters, and
being finally discharged after biological treatment. Heavy metal emissions occur during
phosphoric acid and AN/CAN production. The use of raw materials (coke, gypsum) with lower
heavy metal content is reported as essential. No BAT-AELs were derived for metals in the
LVIC-AAF BREF.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
41
Metals are regarded as major contaminants for LVIC-S processes. The problem arises as metals
naturally occur in the main raw materials (e.g. limestone, coke, brine, feedstock and scrap iron).
In soda ash production, metals are not retained in the product, but pass through the process to be
finally released mainly with suspended solids in the waste waters from distillation. No BATAELs were defined for soda ash production. The main reason was that 90 % of the metals
emissions originate from the use of raw materials (limestone and salt brine), and the operators
have little influence on changing the currently exploited limestone or brine deposit. However,
the emissions of metals in the production of soda ash were thoroughly investigated in the LVICS BREF and detailed data from examples plants were reported. Also, the management of waste
waters from the production of soda ash was illustrated in detail.
In titanium dioxide and food phosphates production, metals are also passed to the waste waters.
BAT-AELs were set only for titanium dioxide production using the sulphate route (see Table
2.12). However, techniques are described in order to reduce the presence of metals in the waste
waters, i.e.:




the selection of raw materials which contain a lower content of metals, e.g. quality
limestone, salt brine, coke, feedstock and scrap iron
deposition and dispersion
separation of solids and filtration
sedimentation using settling ponds.
In SIC processes, the use of catalysts creates waste water contaminated with metals. Metals
could be carried by the waste water from plants producing pigments, explosives, silicones and
nickel salts. Segregation and separation of the waste water containing metals is essential. The
techniques used for their removal are sedimentation, air flotation, filtration, precipitation,
crystallisation, chemical reduction, nanofiltration/reverse osmosis, adsorption, ion exchange,
evaporation, and anaerobic biological digestion. No generic BAT conclusions on the abatement
of metals in waste water were derived. The BAT-AELs set for speciality inorganic pigments are
shown in Table 2.12.
For LVOC processes, metals are also regarded as major water pollutants. The main source is the
use of catalysts. The metals (from catalysts) are treated or recovered separately, because they
cannot be removed efficiently in biological treatment plants. The techniques used are chemical
precipitation (creating a sludge that may allow metal recovery), ion exchange, electrolytic
recovery or reverse osmosis. The treated waste water streams are discharged to a combined
biological treatment plant for further treatment. The BAT-AELs set for metals in the LVOC
BREF can be seen in Table 2.12.
In OFC processes, metals are involved in chemical processing, e.g. as feedstock, auxiliaries and
catalysts. Mass balances for emissions inventories are considered essential for understanding
on-site processes and the development of improvement strategies. The main factor to actively
influence the emission level of heavy metals is the segregation and selective pretreatment of
waste water streams from processes where heavy metals are used deliberately. If equivalent
removal levels can be demonstrated in comparison with the combination of pretreatment and
biological waste water treatment, heavy metals can be eliminated from the total effluent using
only the biological waste water treatment process, provided that the biological treatment is
carried out on-site and the treatment sludge is incinerated. The BAT-AELs set for metals in the
OFC BREF are shown in Table 2.12. It is important to notice that the OFC BREF with its
diverse sectors shows systematic similarities with the CWW BREF. In fact, the discussion on
metals was based on a similar set of reference plants.
In the POL BREF, there is little information reported on the presence of metals in waste waters
and/or their abatement.
BAT-AELs for metals in the existing series of chemical BREFs are given in Table 2.12.
42
November 2010SR/EIPPCB/Analysis questionnaires CWW
BREF
(year adopted)
CAK
CWW (2003)
LVOC (2002)
Hg
Cd
Cu, Cr, Ni, Pb
Zn, Sn
OFC (2005)
Cu
Cr
Ni
Zn
Abateme
nt
Emission
Load
efficienc
levels
Remarks
levels
y
(mg/l)
(%)
No BAT-AELs for mercury were set; however, it is reported in the document that the best
performing mercury cell plants achieve total mercury losses to air and water, with products in
the range of 0.2 – 0.5 g/t chlorine capacity as a yearly average
Split view: the following long term
mean values (yearly of 24-hour mixed
samples) in some examples of chemical
sites at the discharge point/last waste
water treatment stage could be reached
(without dilution of the waste water
with rain and cooling water): Cd 0.02 –
0.833 μg/l; Hg 0.01 – 0.84 μg/l; Pb 10 –
100 μg/l; Cr 10 – 30 μg/l; Cu 20 – 60
μg/l; Ni 10 – 80 μg/l; Zn 4 – 174 μg/l.
TWG members further state that the
none
none
values are influenced by the portion of
productions relevant to metals and
hence are dependent on the production
mix, which can cause higher values in
special cases, especially in fine
chemicals production. With regard to
releases into public sewerage systems,
the effect of the WWTP would have to
be taken into account in so far as it
would be ensured that the metals are
not shifted to other media
For waste water emissions for the
whole LVOC sector. Values refer to
1
0.05 ( )
tributary streams after dedicated
0.2 (1)
pretreatment and before final treatment.
1
0.5 ( )
The LVOC BREF also defines BAT1
2()
AELs for the illustrative processes
0.007 –
0.1 (2)
0.004 –
0.05 (2)
0.01 –
0.05 (2)
<0.1 (2)
After treatment in a biological WWTP
POL (2006)
Zn
10 – 50 g/t of viscose
staple fibres
LVIC-S (2006)
Hg
Cd
0.32 – 0.0015 mg/t
TiO2 (3)
1 – 2000 mg/t TiO2 (3)
LVIC-AAF
(2006)
SIC (2006)
Cd
Crtotal
Pb
Refineries
(2003)
(4)
<=0.1
<0.5 (4)
50 g/t end-prod. (4)
5 – 10 g/t end-prod. (4)
20 – 40 g/t end-prod. (4)
<0.1 – 4 (5)
(1) As daily averages.
(2) Yearly average. The upper end of the range results from the deliberate use of metals or heavy metal compounds in numerous
processes and the pretreatment of waste water streams from such use.
(3) Titanium dioxide – sulphate route.
4
( ) Annual average. Production of inorganic pigments.
(5) Total metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, V, Zn), monthly average. It should not be understood from this range that the
amount of very toxic metals (e.g. As, Cd, Hg, Pb) can reach concentrations of this order of magnitude. Two Member States
claimed that the group of metals should be split into two groups according to their toxicity. One Member State claimed that
ranges should be given for individual metals. These last two requests came after the agreement in the TWG meeting on total
metals.
Table 2.12:
BAT-AELs for metals in the existing (adopted) series of chemical BREFs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
43
Plants reporting data
One installation (#41) reported total concentrations for metals which were not used in the
analysis given the lack of details.
Averaging periods used for reporting emissions
Sampling frequency varies considerably, from once per day to once per year. Mostly grab
samples or composite samples over a short duration (2 – 24 h) were taken. If mentioned,
averaging periods are on a yearly basis.
Techniques reported that reduce metal discharges
The main techniques to reduce emissions of metals are the segregation and selective
pretreatment of waste water streams from processes where metals are an issue. During
biological treatment of waste water, metals can be removed by biomass as a positive effect
either through an active uptake (bioaccumulation) or by passive biosorption. The extent to
which metals are removed depends on several factors, for example pH, nature and concentration
of biomass and inorganic particles, chemical state of metal ion (oxidation state, complexation).
Parameters that affect performance
The removal of metals is a positive effect of biological waste water treatment. Increasing the
concentration of biomass during treatment and reducing solids in the effluent increases the
transfer of metals to the sludge and thus increases their removal. This is especially true for those
metals which tend to be bound to particles. Examples are given below for Total-Cr and Cu.
Organo-metallic compounds may be more difficult to remove from waste waters (this depends
on the compounds and the waste water composition. Under unfavourable conditions, the
achievable elimination may be lower and/or the treatment more difficult/expensive).
The correlation between TSS in the effluent of central WWTPs and concentration of Total-Cr in
the effluent of central WWTPs is shown in Figure 2.12.
Correlation between TSS in the effluent of central WWTPs and
concentration of total Cr in the effluent of central WWTPs
Concentration of total Cr (in microg/l) in
the effluent of central WWTPs
320
200
100
50
50
40
30
20
10
0
0
50
100
150 150
2000
TSS concentration (in mg/l) in the effluent of central WWTPs)
44
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.12:
Correlation between TSS in the effluent of central WWTPs and concentration of
Total-Cr in the effluent of central WWTPs
The correlation between TSS in the effluent of central WWTPs and concentration of Cu in the
effluent of central WWTPs is shown in Figure 2.13.
Correlation between TSS in the effluent of central WWTPs and
concentration of Cu in the effluent of central WWTPs
Concentration of total Cu (in microg/l) in
the effluent of central WWTPs
1050
200
200
150
100
50
0
0
50
100
150 150
1850
TSS concentration (in mg/l) in the effluent of central WWTPs)
Figure 2.13:
Correlation between TSS in the effluent of central WWTPs and concentration of
Cu in the effluent of central WWTPs
Relation between performance and techniques used as reported in the questionnaires
In many cases, high removal efficiencies are achieved by the central WWTP and special
pretreatment is only used for selected tributary streams (see abatement efficiencies in the tables
presented in the following sections).
Given that removal of metals is a positive effect and that applied techniques are heterogeneous
combinations of basic operations, no relationship between performance and specific techniques
could be established.
The evaluation of questionnaires pointed out that high removal efficiency with relatively low
concentrations at the outlet can be achieved by central WWTPs depending on local conditions
(see Table 2.15, Table 2.17, Table 2.19, and Table 2.20).
Limits of detection (LOD) and quantification (LOQ)
Limits of detection and quantification depend on the analytical method, the instruments and the
reagents used, but also on the presence of interfering constituents (matrix). Lower limits of
application (LLA) and LODs/LOQs are described in European (CEN) and International
standards (ISO) but are sometimes outdated.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
45
Industry considers that the WWTPs exibiting metal concentrations below the limit of detection
both in the effluent and influent cannot be considered to make conclusions on BAT.
2.3.2
Cadmium (Cd)
Background information on cadmium
Although cadmium is not expected at the outlet of central WWTPs, CEFIC indicated that
cadmium can be found as a by-product of production e.g. in the effluent of phosphate
production (cadmium is found as a trace element in phosphate rock used in chemical production
(e.g. phosphoric acid production), when catalysts are used in production. Cadmium emissions at
sites which do not use cadmium in their process are expected to be below the limit of
quantification (i.e. <2 µg/l).
Germany suggested that the CWW should not propose BAT-AELs for cadmium and that this
should be left to the relevant vertical BREFs.
Overview of central WWTP performance on Cd
Figure 2.14 presents the Cd concentration in the influent and effluent of central biological
WWTPs and Figure 2.16 presents the Cd concentration in the influent and effluent of central
physico-chemical WWTPs.
Figure 2.14:
46
Cd concentration in the influent and effluent of central biological WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.15:
Cd concentration in the influent and effluent of central physico-chemical WWTPs
It is to be noted that WWTP #69 discharges in the Venice lagoon.
Number of plants reporting data
Out of the 63 WWTPs, 26 reported Cd values in the effluent. Of these values, 10 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <dl. Cd concentrations in the influent were reported in 9
questionnaires of which 6 are reported as <X, <dl, "0", and between X and Y. Therefore, no
analysis on abatement efficiencies was performed.
Peaks of emissions
Peaks occur at plant #58 (IT) where a Cd value of 10 µg/l is reported, at plant #27 (CEFIC, UK)
where a Cd value of 5 µg/l is reported. Also, plants #24 (CEFIC, UK) and #43 (PT) report
values of <5000 µg/l and <50 µg/l, respectively.
Techniques reported to minimise/reduce Cd discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:


precipitation and filtration (with other metals)
ion exchange (with other metals).
Reported achieved performance
The Cd concentrations in the effluents of central WWTPs are given in Table 2.13.
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
Cd average
(µg/l) (1)
0.1
0.1
0.4
1.0
1.9
10.0
10.0
SR/EIPPCB/BP CWW TWG subgroup
November 2010
47
(1) Only spot-type values different from 0 are summarised in this table (10 figures). In addition, 2 plants report <0.5 µg/l, 2
plants <1 µg/l, 2 plants <10 µg/l, 1 plant <50 µg/l, and 1 plant <5000 µg/l.
Table 2.13:
Cd concentrations in the effluents of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by 11
installations. For 3 of these installations, minimum and maximum values were both exactly the
same as the average value (i.e. #21, #27, #58). For one installation, a maximum value was given
while the average was below the detection limit (i.e. #43). For the remaining 7 installations,
maximum Cd values reported vary around the average by approximately a factor of 1.25 to 2.5.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders) as well as in France, Cd is considered not quantifiable below 2 µg/l
(however, questionnaires #49 and #53 reported values of 0.4 µg/l and 1.4 µg/l respectively).
Analytical methods to measure Cd include ICP-OES with an approximate LOQ of 0.2 µg/l (EN
ISO 11885) and ICP-MS with a lower limit of application of approximately 0.1 µg/l (EN ISO
17294-1).
2.3.3
Chromium total (Total-Cr)
The corrosion of pipes and equipment is an important source of chromium in the influent of
WWTPs.
Overview of central WWTP performance on Total-Cr
Figure 2.16 presents the Total-Cr concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
48
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.16:
Total-Cr concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
It can be noted that:


WWTP #69 discharges in the Venice lagoon.
WWTPs #02 and #06 treat waste waters from the production of dyes.
Number of plants reporting data
Out of the 63 WWTPs, 30 reported Total-Cr values in the effluent. Of these values, 15 are of
spot-type while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter
could be assumed to be equivalent to <detection limit. Total-Cr concentrations in the influent
were reported by 12 questionnaires of which 3 are reported as <X, <detection limit, and "0".
Peaks of emissions
Peaks occur at installation #28 (CEFIC, UK) where a Total-Cr value of 104 µg/l is reported and
at installation #58 (IT) where a Total-Cr value of 70 µg/l is reported. Installation #43 (PT)
reports a value of <300 µg/l.
Techniques reported to minimise/reduce Total-Cr discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:



precipitation and filtration (with other metals)
ion exchange (with other metals)
activated sludge systems.
CEFIC indicated that chromium total can be effectively abated by biological treatment; this is
shown by #02 and #49. However this depends on the components that chromium is fixed upon
SR/EIPPCB/BP CWW TWG subgroup
November 2010
49
as in the case of #06 (complexed chromium cannot be effectively abated by biological treatment
and therefore all relevant waste water streams are pretreated – see the OFC BREF).
Reported achieved performance
The Total-Cr concentrations in the effluents of central WWTPs are given in Table 2.14.
Parameter
Total-Cr
average
(µg/l) (1)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.08
0.48
2.1
6
30
70
104
(1) Only spot-type values different from 0 are summarised in this table (15 figures). In addition, 3 plants report <5
µg/l, 3 plants <10 µg/l, 1 plant <50 µg/l, and 1 plant <300 µg/l.
Table 2.14:
Total-Cr concentrations in the effluents of central WWTPs
Abatement efficiencies based on concentrations and loads were calculated for 6 and 4
installations, respectively (Table 2.15).
Central WWTP
Total-Cr
abatement based
on concentrations
(%)
Total-Cr
abatement based
on loads (%)
Table 2.15:
#06
#49
#58
#02
#22
#67
46
60 – 90
92
>92
97
>99
95
97
91
43
Total-Cr abatement efficiencies of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by 16
installations. For two installations, a maximum value was given while the average was below
the detection limit (i.e. #02, #05). For the remaining 14 installations, maximum Total-Cr values
reported vary around the average by approximately a factor of 2 to 15, but more generally by
between approximately 2 and 8.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Cr total is considered not quantifiable below 10 µg/l (however,
questionnaires #49, #53 and #54 reported values of 6 µg/l, 0.48 µg/l and 1 µg/l respectively). In
France, the LOQ is 5 µg/l for chromium and chromium compounds. Analytical methods to
measure Total-Cr include ICP-OES with an approximate LOQ of 2 µg/l (EN ISO 11885) and
ICP-MS with a lower limit of application of approximately 1 µg/l (EN ISO 17294 1).
2.3.4
Chromium VI (Cr VI)
Chromium VI is not expected at the outlet of central WWTPs. Also, Germany suggested that
the CWW should not propose BAT-AELs for chromium VI which should be removed at the
source and that this should be left to the relevant vertical BREFs.
Overview of central WWTP performance on Cr VI
Figure 2.17 presents the Cr VI concentration in the influent and effluent of central biological
WWTPs and of central physico-chemical WWTPs.
50
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.17:
Cr VI concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
It can be noted that WWTP #69 discharges in the Venice lagoon.
Number of plants reporting data
Out of the 63 WWTPs, 12 reported Cr VI values in the effluent. Of these values, 2 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Cr VI concentrations in the influent are
SR/EIPPCB/BP CWW TWG subgroup
November 2010
51
reported by 4 questionnaires of which 2 are reported as <X, <detection limit, and "0".
Therefore, no analysis on abatement efficiencies was performed.
Peaks of emissions
Installation #58 (IT) reports a Cr VI value of 100 µg/l. Installation #43 (PT) reports a value of
<50 µg/l.
Techniques reported to minimise/reduce Cr VI discharge
Reduction of Cr VI to Cr III, then abatement of Total-Cr as been reported in the questionnaires.
Reported achieved performance
Given that only two installations reported emission values of a spot-type, Table 2.16 lists all
reported values.
Central
WWTP
Cr VI
(µg/l)
average
Cr VI
(µg/l)
maximum
Table 2.16:
#44
#05
#52
#61
#46
#62
#69
#06
#51
#43
#58
<dl
0
0
0.01
<0.1
<1
<2.1
<10
<10
<50
100
20
0.20
<22
100
Cr VI concentrations in the effluents of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by 4
installations (Table 2.16).
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Cr VI is considered not quantifiable below 10 µg/l. Analytical methods
to measure Cr VI include spectrometry with 1,5 Diphenylcarbazide in a concentration range of
50 – 3000 µg/l (ISO 11083) and flow analysis (FIA/CFA) in a concentration range of 2 –
2000 µg/l (EN ISO 23913).
2.3.5
Copper (Cu)
The corrosion of pipes and equipment is an important source of copper in waste waters. At
some sites, the manufacture or use of copper-based catalysts, the manufacture of organic copper
compounds (e.g. dyes) or catalyst residues from large volume organic chemical (LVOC)
production are a source of copper in waste waters.
Background information on copper
For questionnaire 27, copper from catalysts is the main source of copper emissions.
Overview of central WWTP performance on Cu
Figure 2.18 presents the Cu concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
52
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.18:
Cu concentration in the influent and effluent of central biological WWTPs
It can be noted that WWTP #69 discharges in the Venice lagoon.
Number of plants reporting data
SR/EIPPCB/BP CWW TWG subgroup
November 2010
53
Out of the 63 WWTPs, 34 reported Cu values in the effluent. Of these values, 26 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Cu concentrations in the influent were reported
by 17 questionnaires of which 2 are reported as <X, <detection limit, and "0".
Peaks of emissions
Peaks occur at installations #28 (CEFIC, UK) and #27 (CEFIC, UK) where Cu values of
581 µg/l and 202 µg/l, respectively, are reported. It can be noted that WWTP #27 has no
biological treatment and WWTP #28 has very high TSS emissions (i.e. 1729 mg/l).
Techniques reported to minimise/reduce Cu discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:



precipitation and filtration (with other metals)
ion exchange (with other metals)
activated sludge systems.
In many cases, biological treatment can be used effectively to abate copper.
Germany pointed out that for questionnaire #06, because complexing agents are present in the
waste water, a pre-treatment by precipitation and flocculation is used before the central WWTP
to remove metals.
Reported achieved performance
The Cu concentrations in the effluents and the abatement efficiencies of central WWTPs are
given in Table 2.17.
Parameter
Cu average
(µg/l) (1)
Cu abatement
based on
concentrations
(%) (2)
Cu abatement
based on
loads (%) (3)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.71
2
8
10
50
100
581
11.1
11.1
52.7
85.7
98.3
> 99.3
100
50
50
64.9
84.6
95.9
96.6
100
(1) Only spot-type values different from 0 are summarised in this row (26 figures). In addition, 1 plant reports <1 µg/l,
1 plant <10 µg/l, 1 plant <20 µg/l, 1 plant <25 µg/l, 1 plant <50 µg/l, and 1 plant <100 µg/l.
(2) 13 figures are summarised in this row.
(3) 10 figures are summarised in this row.
Table 2.17:
Cu concentration and abatement efficiencies in the effluent of central WWTPs
CEFIC indicated that for questionnaire #02 where copper values of 1095 µg/l are reported
(about 500 kg Cu/day) in the influent, high abatement efficiency is achieved (>96 %; 34 µg/l in
the effluent).
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by 19
installations. Maximum Cu values reported vary around the average by between 1.7 and 15.5,
but more generally by between approximately 2 and 6. The ratio between maximum
concentrations and average concentrations tends to be higher for installations with lower
average concentrations.
54
November 2010SR/EIPPCB/Analysis questionnaires CWW
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Cu is considered not quantifiable below 25 µg/l (however,
questionnaires #49, #53 and #54 reported values of 20 µg/l, 17 µg/l and 2 µg/l respectively). In
France, the LOQ is 5 µg/l for copper and copper compounds. Analytical methods to measure
Cu include ICP-OES with an approximate LOQ of 2 µg/l (EN ISO 11885) and ICP-MS with a
lower limit of application of approximately 1 µg/l (EN ISO 17294-1).
2.3.6
Mercury (Hg)
The production of chlorine using the mercury process as well as old productions can be
important sources of mercury for central WWTPs. Incineration processes are also sources of
mercury (from waste gas treatment).
Mercury can relatively easily adsorb onto sludge which has to be controlled if sludge is
incinerated.
Overview of central WWTP performance on Hg
Figure 2.19 presents the Hg concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
55
Figure 2.19:
Hg concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
It can be noted that:



WWTP #69 discharges in the Venice lagoon.
For WWTP #22, there is a common pretreatment for mercury from the mercury process and
from waste incineration. The questionnaire refers to a year where the process was still in
use.
WWTPs #46 and #58 are indirect dischargers.
Number of plants reporting data
Out of the 63 WWTPs, 26 reported Hg values in the effluent. Of these values, 10 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Concentrations of Hg in the influent of the
central WWTPs were reported by 11 questionnaires of which 7 are reported as <X, <detection
limit, and "0".
Peaks of emissions
Peaks occur at installations #46 (IT) and #58 (IT) where Hg values of 2 µg/l and 5 µg/l,
respectively, are reported. In addition, installations #43 (PT) and #51 (BE) report values of
<20 µg/l and <10 µg/l, respectively.
Techniques reported to minimise/reduce Hg discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:




56
precipitation and filtration
ion exchange
precipitation and ion exchange in #12
specific Hg removal in #14 (not further specified)
November 2010SR/EIPPCB/Analysis questionnaires CWW


activated carbon
activated sludge systems combined with sludge incineration/waste gas treatment.
Reported achieved performance
The Hg concentrations in the effluents of central WWTPs are given in Table 2.18.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
57
Parameter
Hg
average
(µg/l) (1)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.13
0.13
0.2
0.3
1
2
5
(1) Only spot-type values different from 0 are summarised in this row (10 figures). In addition, two plants report
<0.1 µg/l, two plants <0.2 µg/l, one plant <0.32 µg/l, one plant <1 µg/l, one plant <10 µg/l, andone1 plant <20
µg/l.
Table 2.18:
Hg concentration in the effluent of central WWTPs
Abatement efficiencies based on concentrations and loads were calculated for 4 plants, (see
Table 2.19).
Central WWTP
Hg abatement
based on
concentrations
(%)
Hg abatement
based on
loads (%)
Table 2.19:
#21
#49
#22
#042
77
75 - 90
88
100
89
100
78
#02
100
Hg abatement efficiencies of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by
8 installations. Maximum Hg values reported vary around the average by between
approximately 1 and 4, but more generally by between approximately 2 and 3.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Hg is considered not quantifiable below 0.25 µg/l. In France, the LOQ is
0.5 µg/l for mercury and mercury compounds. Analytical methods to measure Hg include
atomic fluorescence spectrometry (AFS) in a concentration range of 0.01 – 10 µg/l (EN ISO
17852) and cold vapour atomic absorption spectrometric (AAS) in a concentration range of 0.1
– 10 µg/l (EN 1483).
2.3.7
Nickel (Ni)
The corrosion of pipes and equipment is an important source of nickel together with the use of
nickel-based catalysts. Process gas scrubber/input from heavy fuel oil, catalyst manufacture or
catalyst residues from large volume organic chemical (LVOC) production are also source of
nickel emissions. Nickel in soluble form is more difficult to remove.
Overview of central WWTP performance on Ni
Figure 2.20 presents the Ni concentration in the influent and effluent of central biological
WWTPs and phycico-chemical WWTPs.
58
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.20:
Ni concentration in the influent and effluent of central biological WWTPs and
phycico-chemical WWTPs
It can be noted that WWTP #69 discharges in the Venice lagoon.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
59
Number of plants reporting data
Out of the 63 WWTPs, 31 reported Ni values in the effluent. Of these values, 20 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Concentrations of Ni in the influent of the
central WWTPs were reported by 12 questionnaires of which 2 are reported as <X, <detection
limit, and "0".
Peaks of emissions
A peak occurs at installation #60 (FR) where a Ni value of 280 µg/l is reported. In addition,
installation #43 (PT) reports a Ni concentration of <300 µg/l.
Techniques reported to minimise/reduce Ni discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:




precipitation and filtration (with other metals)
ion exchange (with other metals)
filtration (#07)
activated sludge systems.
Reported achieved performance
The Ni concentrations in the effluents of central WWTPs are given in Table 2.20.
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
Ni average
(µg/l) (1)
2
4
5
20
50
74
280
1
( ) Only spot-type values different from 0 are summarised in this row (20 figures). In addition, one plant reports
<1 µg/l, one plant <5 µg/l, two plants <10 µg/l, and one plant <300 µg/l.
Table 2.20:
Ni concentrations in the effluents of central WWTPs
Abatement efficiencies based on concentrations and loads were calculated for 9 and 7
installations, respectively (see Table 2.21).
Central WWTP
Ni abatement
based on
concentrations
(%)
Ni abatement
based on
loads (%)
Table 2.21:
#35
#49
#36
#60
#07
#02
5.6
0 - 60
43
44
55
73
11
55
73
5.6
#25
88
#46
#58
97
98
99
Ni abatement efficiencies of central WWTPs.
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by
15 installations. For one installation, a maximum value was given while the average was below
the detection limit (#05). Maximum Ni values reported vary around the average by between 1.3
and 6 except one installation with 22.7.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders) as well as in France, Ni is considered not quantifiable below 10 µg/l.
Analytical methods to measure Ni include ICP-OES with an approximate LOQ of 2 µg/l (EN
60
November 2010SR/EIPPCB/Analysis questionnaires CWW
ISO 11885) and ICP-MS with a lower limit of application of approximately 1 µg/l (EN ISO
17294-1).
2.3.8
Lead (Pb)
Overview of central WWTP performance on Pb
Figure 2.21 presents the Pb concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
61
Figure 2.21:
Pb concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
It can be noted that:


WWTP #69 discharges in the Venice lagoon.
For WWTP #32, lead-based stabiliser production is the reason for high Pb emissions.
Number of plants reporting data
Out of the 63 WWTPs, 25 reported Pb values in the effluent. Of these values, 14 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Concentrations of Pb in the influent of the
central WWTPs were reported by 11 questionnaires of which 2 are reported as <X, <detection
limit, and "0".
Peaks of emissions
A peak occurs at installation #32 (CEFIC, UK) where a Pb value of 400 µg/l is reported. In
addition, installation #43 (PT) reports a Pb concentration of <300 µg/l. It can be noted that
WWTP #32 treats waste waters arising from a speciality inorganic chemical plant producing
lead based stabilisers for PVC.
Techniques reported to minimise/reduce Pb discharge
Precipitation with sodium carbonate as a pretreatment and treatment operation as well as
activated sludge systems (carried out at the installation(s) from which the waste waters originate
or the central WWTP) has been reported in the questionnaires.
Reported achieved performance
The Pb concentrations in the effluents of central WWTPs are given in Table 2.22.
62
November 2010SR/EIPPCB/Analysis questionnaires CWW
Parameter
Pb
average
(µg/l) (1)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.8
0.8
2.8
6
30
400
400
(1) Only spot-type values different from 0 are summarised in this row (11 figures). In addition, one plant reports
<1 µg/l, three plants <5 µg/l, one plant <10 µg/l, and one plant <300 µg/l.
Table 2.22:
Pb concentrations in the effluents of central WWTPs
Abatement efficiencies based on concentrations and loads were calculated for 4 and 5
installations, respectively (see Table 2.23).
Central WWTP
#49
Pb abatement
based on
60 – 100
concentrations
(%)
Pb abatement
based on
loads (%)
Table 2.23:
#58
#46
97.0
100.0
98.6
#02
#35
#32
100.0
100
100.0
100.0
Pb abatement efficiencies of central WWTPs.
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by
10 installations. Maximum Pb values reported vary around the average by between 1.8 and 10.5
except one installation which reports exactly the same maximum value as the average value.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Pb is considered not quantifiable below 25 µg/l. In France, the LOQ is
5 µg/l for lead and lead compounds. Analytical methods to measure Pb include ICP-OES with
an approximate LOQ of 5 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application
of approximately 0.1 µg/l (EN ISO 17294-1).
2.3.9
Zinc (Zn)
The corrosion of pipes and equipment (tank insulation, building roofs) is an important source of
zinc. Raw materials are also a source of zinc that can ultimately be released into water.
Overview of central WWTP performance on Zn
Figure 2.22 presents the Zn concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
63
Figure 2.22:
64
Zn concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
It can be noted that WWTP #69 discharges in the Venice lagoon.
Number of plants reporting data
Out of the 63 WWTPs, 33 reported Zn values in the effluent. Of these values, 29 are of spottype while the others are given as range-type values (i.e. <X or <dl) or as "0". The latter could
be assumed to be equivalent to <detection limit. Zn concentrations in the influent were reported
by 17 questionnaires.
Peaks of emissions
Peaks occur at installations #24 (CEFIC, UK) and #28 (CEFIC, UK), #57 (FR) where Zn values
of 800 µg/l, 1016 µg/l, and 1440 µg/l, respectively, are reported. It can be noted that all these
WWTPs exibit high TSS emissions (i.e. 114 mg/l at #24; 1729 mg/l at #28; 122 mg/l at #57).
Techniques reported to minimise/reduce Zn discharge
The following pretreatment and treatment operations (carried out at the installation(s) from
which the waste waters originate or the central WWTP) have been reported in the
questionnaires:



precipitation and filtration (with other metals)
ion exchange (with other metals)
activated sludge systems.
Reported achieved performance
The Zn concentrations in the effluents and the abatement efficiencies of central WWTPs are
given in Table 2.24.
Parameter
Zn average
(µg/l) (1)
Zn abatement
based on
concentrations
(%)(2)
Zn abatement
based on
loads (%)(3)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
4
14
40
64
161
400
1440
28.9
46.7
56.8
82.8
85.6
99.4
99.7
20.8
20.8
49.2
80.3
85.3
88.6
94.8
(1) Only spot-type values different from 0 are summarised in this row (29 figures). In addition, 1 plant reports <1 µg/l, 1
plant <10 µg/l, and 1 plant <20 µg/l.
(2) 15 figures are summarised in this row.
(3) 12 figures are summarised in this row.
Table 2.24:
Zn concentrations in the effluent and abatement efficiencies of central WWTPs
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by
22 installations. Maximum Zn values reported vary around the average by between 1.2 and 9.3,
but more generally by between approximately 2 and 6. The ratio between maximum
concentrations and average concentrations tends to be higher for installations with lower
average concentrations.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Zn is considered not quantifiable below 25 µg/l. In France, the LOQ is
10 µg/l for zinc and zinc compounds. Analytical methods to measure Zn include ICP-OES with
an approximate LOQ of 1 µg/l (EN ISO 11885) and ICP-MS with a lower limit of application of
approximately 1 µg/l (EN ISO 17294-1). The operator of the WWTP #57 indicated a limit of
quantification for zinc of 50 µg/l.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
65
66
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.4
Other parameters
2.4.1
Nitrogen compounds
2.4.1.1
General
Background information on nitrogen compounds
While nitrogen is essential to living species, excessive concentrations of certain nitrogen species
in water can lead to significant environmental problems (eutrophication). However, nitrogen,
like phosphorus and carbon, is needed in the biological processes of waste water treatment so
that organisms that decompose the organic load can reproduce. When the industrial waste
waters do not contain enough nitrogen for optimum growth of the organisms used in treatment,
addition of inorganic nitrogen is carried out. A concentration ratio of BOD5 : N : P = 100 : 5 : 1
is often considered optimal for aerobic waste water treatment. For anaerobic treatments steps,
the ratio is BOD5 : N : P = 100 : 0.5 : 0.1 (C. Forster, Wastewater Treatment and Technology,
2003).
Nitrogen compounds and in particular nitrates are included in the indicative list of substances to
be taken into account for fixing emission limit values in Annex III of the IPPC Directive.
CEFIC pointed out that all nitrogen-related parameters (i.e. nitrogen total, ammonia, nitrate and
nitrite) are very sensitive to sampling and analytical methods (which is not so much the case for
COD).
CEFIC indicated that the removal of nitrogen undergoes a larger variety during operation. The
nitrification mechanism as autotrophic is based on very sensitive and slowly growing bacteria
compared to the heterotrophic COD degradation. Therefore the variability of maximum to
average will be much higher compared to e.g. COD or TOC performance.
The following parameters should be analysed together: nitrogen total, ammonia, nitrate and
nitrite. Expressed as NH4-N, Nitrate-N, etc.
Depending on the influent, except for total nitrogen, inorganic nitrogen compounds result partly
from the biological treatment process. Therefore, concentration in the effluent is generally a
parameter more pertinent than abatement efficiency.
2.4.1.2
Total nitrogen (Total-N)
TNb (Total Bound Nitrogen) is a measure of the concentration of ammonia, ammonium salts,
nitrites, nitrates and organic nitrogen components (dissolved nitrogen is not detected). It allows
a rapid assessment of the total nitrogen compound load in a water sample. TNb can be
determined simultaneously with TOC. The method is standardized by DIN 38409-H27 and
EN 12260. It applies for freshwater, seawater, drinking water, surface water and wastewater.
The method covers the measurement range 0.5 mg/l – 200 mg/l. More highly concentrated
samples should be diluted.
TKN (Total Kjeldahl Nitrogen) is a measure of the concentration of ammonia/ammonium
(NH3/NH4+) and organic-Nitrogen. However, a series of organic compounds is incompletely
detected by the Kjeldahl method.
In Germany, Total-Inorganic-N as the sum of NH4-N, NO2-N and NO3-N is commonly
measured. TNb, is therefore higher than Total-Inorganic-N. A comment was made that total
nitrogen should not be expressed as a sum, since it is an analytical parameter on its own (i.e.
TNb). It has to be mentioned, that the analytical methods of Total-N as TNb (by thermal
SR/EIPPCB/BP CWW TWG subgroup
November 2010
67
oxidation) and Total-N by TKN (Kjeldahl hydrolysis and stripping) lead to non-comparable
results.
Overview of central WWTP performance on Total-N
Figure 2.23, Figure 2.24 and Figure 2.25 present the Total-N (mainly as TNb), total inorganic N
and TKN concentration in the influent and effluent of central biological WWTPs and physicochemical WWTPs.
10
54
64
19
60
21
09
37
52
(TNb) Nitri./deni.
(TNb) Nitri./deni.
(TNb) Nitri./deni.
10
43
(TNb+free ammonia) Nitri./deni.
49
(Total Nitrogen, no information on analytical method used)
40
47
(TNb+free ammonia) Nitri./deni.
(TKN+NO2+NO3) Nitri./deni.
(TNb) Nitri./deni.
(TNb+free ammonia) Nitri./deni.
48
(TKN+NO2+NO3) Nitri./deni.
11
(TNb+free ammonia)
20
(TKN+NO2+NO3)
(TNb) Nitri./deni.+Adsorp.
30
(TNb+free ammonia)
40
(TKN+NO2+NO3)
50
(TNb) Nitri./deni.
Total Nitrogen (mostly as TNb) (mg/l)
60
(Sum of N-NH3, N-NO2, N-NO3 and org-N calculated from
the different measured species (i.e not TNb))
70
(Total-N (oxidative combustion + chemiluminisence))
Total Nitrogen (mostly as TNb) concentration in the influent and effluent of central biological
WWTPs
50
51
34
0
0
18
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
59
90th percentile
41
75th percentile
28
50th percentile
18
25th percentile
9
10th percentile
7
Minimum
3
Total Nitrogen (mostly as TNb) concentration in the influent and effluent of central
physico-chemical WWTPs
Total Nitrogen (mostly as TNb) (mg/l)
20
46
10
53
(TKN+NO2+NO3) Strip.
(TNb+free ammonia)
38
(TKN+NO2+NO3)
15
5
0
0
3
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
15
90th percentile
15
75th percentile
14
50th percentile
13
25th percentile
10
10th percentile
7
Minimum
6
Figure 2.23:
68
Total-N (mainly as TNb) concentration in the influent and effluent of central
biological WWTPs and physico-chemical WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
12
13
16
02
06
63
041
09
14
24
Nitri./deni.
Inciner.+Nitri./deni.
Nitri./deni.
Nitri./deni.
03
07
Nitri./deni.
11
Nitri./deni.
Nitri./deni.
22
Nitri./deni.
10
Nitri./deni.
Nitri./deni.
20
Nitri./deni.
30
Nitri./deni.
Total Inorganic N (mg/l)
40
Nitri./deni.
(Sum of NH4-N+NO2-N+NO3-N) Nitri./deni.
50
Nitri./deni.
Total Inorganic N concentration in the influent and effluent of central biological WWTPs
36
15
01
08
62
0
0
19
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
32
90th percentile
25
75th percentile
19
50th percentile
9
25th percentile
6
10th percentile
4
Minimum
0.9
Total Inorganic N concentration in the influent and effluent of central
physico-chemical WWTPs
20
15
Total Inorganic N (mg/l)
05
042
10
5
56
0
0
3
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
14
90th percentile
13
75th percentile
13
50th percentile
11
25th percentile
6
10th percentile
3
Minimum
1.5
Figure 2.24:
Total inorganic N concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
69
TKN concentration in the influent and effluent of central biological WWTPs
20
60
5
45
(TKN+NO2+NO3) Nitri./deni.
(TKN+NO2+NO3)
(<3 mg/l) Nitri./deni.
10
Nitri./deni.
TKN (mg/l)
15
58
64
69
0
0
5
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
14
90th percentile
11
75th percentile
7
50th percentile
7
25th percentile
7
10th percentile
4
Minimum
3
TKN concentration in the influent and effluent of central physico-chemical WWTPs
400
65
TKN (mg/l)
300
200
100
35
0
0
2
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
339
90th percentile
307
75th percentile
259
50th percentile
178
25th percentile
98
10th percentile
49
Minimum
17
Figure 2.25:
TKN concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
It can be noted that At WWTP #36, a disturbance over some weeks explains the large variations.
Germany considers that Questionnaire #14 is a special case because the very high nitrogen
content in the influent comes from a special biochemical process that carries out a pretreatment.
Number of plants reporting data
Out of the 63 WWTPs, 49 reported Total nitrogen values in the effluent (or 78%) and only
about half of these reported Total-N values in the influent.
70
November 2010SR/EIPPCB/Analysis questionnaires CWW
Peaks of emissions
At one WWTP, Total nitrogen in the effluent is above 100 mg/l (i.e. #65, Total-N of 339 mg/l,
indirect discharge).
Averaging periods used for reporting emissions
The majority of averaging periods reported are yearly averages (e.g. of 24-hour daily composite
samples, of weekly samples, of bi-monthly samples, of samples taken four times per year).
Techniques reported to minimise/reduce nitrogen discharge
A combination of several of the following techniques can be carried out:

Pretreatment at the installation(s) from which the waste waters originate, e.g.:
o
o
o
o
o
oxidation with UV radiation (i.e. #02: conversion of EDTA)
conversion of cyanide (see Section 2.4.6)
distillation, stripping (i.e. #02, #15, #50, #61: ammonia; #50: aniline,
nitrobenzene)
recycling of nitric acid (i.e. #11, #15)
sedimentation (i.e. #63; #69: dimethylacetamide).
Other techniques which are used to treat COD/TOC loads equally apply to organic N, e.g. wet
oxidation with hydrogen peroxide, wet air oxidation, and adsorption.

Treatments at the central WWTP:
o
o
biological nitrogen elimination (nitrification/denitrification)
reverse osmosis, evaporation, crystallisation (i.e. #05: recovery of nitrate).
BAT-AELs for Total-N in the existing series of chemical BREFs
The BAT-AELs for Total-N in the existing (adopted) series of chemical BREFs are given in
Table 2.25.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
71
BREF
(year adopted)
CWW (2003)
Abatement
efficiency
(%)
none
Emission
levels
(mg/l)
Load
levels
For final waste water
discharge into surface water,
without dilution with
rainwater and/or
uncontaminated cooling water
For waste water emissions for
the whole LVOC sector. The
LVOC BREF also defines
BAT-AELs for the illustrative
processes
After treatment in a biological
WWTP
5 – 25 (1)
LVOC (2002)
10 – 25 (2)
OFC (2005)
2 – 20 (3)
Remarks
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
<0.9 kg N-NH3/t
prod. (4)
LVIC-S (2006)
Steam stripping under
controlled pH conditions
LVIC-AAF (2006)
SIC (2006)
Refineries (2003)
1.5 – 25 (5)
0.25 – 10 (7)
0.5 – 15 g/t cop (6)
0.1 – 6 g/t cop (8)
(1) Total inorganic N: sum of NH4-N, NO2-N and NO3-N.
(2) Total nitrogen: the exact figure largely depends on the applied processes and type of biological treatment system (N
removal).
(3) Yearly average, inorganic N: the upper end of the range results from production of organic compounds containing
nitrogen or from, e.g. fermentation processes.
(4) Soda ash production.
(5) Total nitrogen, monthly average. Industry believe that, where nitrogen is not a pollutant of concern in the receiving
waters, denitrification cannot be BAT as the environmental benefit to the receiving water is very low, while the
cost both in Euros (capital expenditure) and the CO2 emissions are high.
(6) Total nitrogen, yearly average. One Member State claims that the upper level of the range should be 8. They
demonstrated (based on actual data) that a figure below 8 can easily be achieved with a stripper or a
nitrification/denitrification step. cop: crude oil or feedstock processed.
(7) Ammoniacal nitrogen (as N), monthly average. One Member State claims that the upper level should be 5. Those
levels can be reached by strippers and biological nitrification/denitrification step.
(8) Total nitrogen, yearly average. One Member State claims that the upper level of the range should be 8. They
demonstrated (based on actual data) that a figure below 8 can easily be achieved with a stripper or a
nitrification/denitrification step. cop: crude oil or feedstock processed.
Table 2.25:
BAT AEL for nitrogen compounds in adopted BREFs
Reported achieved performance
The Total-N concentrations in the effluent and abatement efficiencies of central WWTPs are
given in Table 2.26.
72
November 2010SR/EIPPCB/Analysis questionnaires CWW
Parameter
Total-N
average
(mg/l)
Total-N
abatement
based on
concentrations
(%)(6)
Total-N
abatement
based on
loads (%)(7)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.9 (1)
3 (2)
7 (3)
14 (4)
25 (5)
42
339
11.6
30.2
43.4
72.8
85.0
89.4
93.8
-3.9(8)
11.6
43.9
76
85.6
89.8
93.7
(1) #62 (CZ) yearly average of grab samples.
(2) #34 (CEFIC) yearly average of weekly samples, abatement efficiency of 81.3 %.
(3) #07 (DE) ) yearly average of 365 mixed samples, abatement efficiency of 91 %.
(4) #60 (FR) yearly average of 24-hour composite samples, abatement efficiency of 35 %.
(5) #49 (BE) yearly average of 24-hour composite samples, abatement efficiency of 50 – 95 %.
(6) 28 figures are summarised in this row.
(7) 22 figures are summarised in this row.
(8) #60, possibly data error.
Table 2.26:
Total-N concentrations in the effluent and abatement efficiencies of central
WWTPs
Abatement efficiencies reported are in the range 11 – 95 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are >70 %.
Fluctuations of emissions around the average (in concentration)
Maximum Total-N values reported vary around the average by approximately a factor of
between 1.5 and 5, but more generally between approximately 2 and 3.
Large short-term variations can be explained by the nature of the microorganisms used for
nitrification/denitrification.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), Total-N is considered not quantifiable below 2 mg/l. Total-N can be
quantified by direct determination or separate determinations of TKN, nitrite, and nitrate and by
adding the three values. For the direct determination, the following international standards exist:
EN 12260 (2003) specifies a method for quantifying the TNb (total nitrogen bound) by
combustion and detection of nitrogen oxides using chemiluminescence. Typical detection limits
are around 0.5 mg/l. EN ISO 11905-1 (1998) specifies a method using oxidative digestion of
Total-N with peroxodisulphate to nitrate which is then quantified. ISO 29441 (2010) specifies a
method for the determination of total nitrogen after in-line UV digestion and flow analysis with
spectrometric detection. Mass concentrations range from 2 mg/l to 20 mg/l, but other
concentration ranges are possible, e.g. 0.2 mg/l to 2 mg/l. EN 25663 is used to dtermine
Kjeldahl nitrogen (mineralisation with selemium).
Parameters that affect performance
Ammonification
The first step in the removal of Total-N during biological treatment is conversion of organic N
to ammonia/ammonium. For domestic sewage, where organic N consists of urea and faecal
material, this already takes place to a certain extent while travelling through sewer pipes. In
case of waste waters from chemical installations, some organic N might be recalcitrant to
ammonification.
The ratio of ammonia (NH3) versus ammonium (NH4+) is affected by pH and temperature. At
conditions typical for most biological waste water treatment plants (pH of 6 to 8.5, temperatures
of 10 to 40 ºC), far more ammonium than ammonia is produced.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
73
Nitrification
Nitrification is a two-step process. Bacteria known as Nitrosomonas convert ammonia and
ammonium to nitrite. Next, bacteria called Nitrobacter finish the conversion of nitrite to nitrate.
The reactions are generally coupled and proceed rapidly to the nitrate form; therefore, nitrite
levels at any given time are usually low.
These bacteria known as 'nitrifiers' are strict 'aerobes', meaning they must have free dissolved
oxygen to perform their work. Nitrification occurs only under aerobic conditions at dissolved
oxygen levels of 1.0 mg/l or more. At dissolved oxygen (DO) concentrations of less than
0.5 mg/l, the growth rate is minimal. Nitrification requires a long retention time, a low food to
microorganism ratio (F:M), a high mean cell residence time (measured as MCRT or sludge
age), and adequate buffering (alkalinity).
The nitrification process produces acid. This acid formation lowers the pH of the biological
population in the aeration tank and can cause a reduction of the growth rate of nitrifying
bacteria. The optimum pH for Nitrosomonas and Nitrobacter is between 7.5 and 8.5; most
treatment plants are able to effectively nitrify with a pH of 6.5 to 7.0. Nitrification stops at a pH
below 6.0. The nitrification reaction (that is, the conversion of ammonia to nitrate) consumes
7.1 mg/l of alkalinity as CaCO3 for each mg/L of ammonia nitrogen oxidised. An alkalinity of
no less than 50 – 100 mg/l is required to ensure adequate buffering.
Water temperature also affects the rate of nitrification. Nitrification reaches a maximum rate at
temperatures between 30 and 35 ºC. At temperatures of 40 ºC and higher, nitrification rates fall
to near zero. At temperatures below 20 ºC, nitrification proceeds at a slower rate, but will
continue at temperatures of 10 ºC and less. However, if nitrification is lost, it will not resume
until the temperature increases to well over 10 ºC. Some of the most toxic compounds to
nitrifiers include cyanide, thiourea, phenol and metals such as silver, mercury, nickel,
chromium, copper and zinc. Nitrifying bacteria can also be inhibited by nitrous acid and free
ammonia.
Denitrification
The biological reduction of nitrate (NO3) to nitrogen gas (N2) by facultative heterotrophic
bacteria is called denitrification. 'Heterotrophic' bacteria need a carbon source as food to live.
'Facultative' bacteria can get their oxygen by taking dissolved oxygen out of the water or by
taking it off of nitrate molecules.
Denitrification occurs when oxygen levels are depleted and nitrate becomes the primary oxygen
source for microorganisms. The process is performed under anoxic conditions, when the
dissolved oxygen concentration is less than 0.5 mg/l, ideally less than 0.2. When bacteria break
apart nitrate to gain the oxygen, the nitrate is reduced to nitrous oxide (N2O), and, in turn,
nitrogen gas (N2). Since nitrogen gas has low water solubility, it escapes into the atmosphere as
gas bubbles. Free nitrogen is the major component of air, thus its release does not cause any
environmental concern.
Optimum pH values for denitrification are between 7.0 and 8.5. Denitrification is an alkalinity
producing process. Approximately 3.0 to 3.6 mg/l of alkalinity (as CaCO3) is produced per mg/l
of nitrate, thus partially mitigating the lowering of pH caused by nitrification in the mixed
liquor.
Since denitrifying bacteria are facultative organisms, they can use either dissolved oxygen or
nitrate as an oxygen source for metabolism and oxidation of organic matter. If dissolved oxygen
and nitrate are present, bacteria will use the dissolved oxygen first. That is, the bacteria will not
lower the nitrate concentration. Denitrification occurs only under anaerobic or anoxic
conditions.
74
November 2010SR/EIPPCB/Analysis questionnaires CWW
Another important aspect of denitrification is the requirement for carbon; that is, the presence of
sufficient organic matter to drive the denitrification reaction. Organic matter may be in the form
of raw waste water, or supplemental carbon. Conditions that affect the efficiency of
denitrification include nitrate concentration, anoxic conditions, presence of organic matter, pH,
temperature, alkalinity and the effects of trace metals. Denitrifying organisms are generally less
sensitive to toxic chemicals than nitrifiers, and recover from toxic shock loads quicker than
nitrifiers.
Temperature affects the growth rate of denitrifying organisms, with greater growth rate at
higher temperatures. Denitrification can occur between 5 and 40ºC, and these rates increase
with temperature and type of organic source present. The highest growth rate can be found
when using methanol or acetic acid. A slightly lower rate using raw waste water will occur, and
the lowest growth rates are found when relying on endogenous carbon sources at low water
temperatures. Three installations report the addition of external carbon sources to
ensure/improve the denitrification process (i.e. #63: methanol, #45 and #69: acetic acid).
Relation between performance and techniques used as reported in the questionnaires
The performance of biological nitrogen removal (nitrification/denitrification) depends on a
number of plant operating conditions as described above. Most of these operating conditions
were not asked for in the questionnaires. Therefore, it is difficult to establish relationships with
the reported performance levels.
2.4.1.3
Ammonia (as NH4-N)
Background information on ammonia
Ammonia can be present in the influent of central WWTPs (reported in the range 0.66 –
517 mg/l). Ammonia/ammonium is also formed as a first step in the removal of Total-N in
central WWTP using biological treatments (i.e. ammonifaction, where organic N is converted to
ammonia/ammonium, see Section 2.4.1.2). Ammonia is on one hand assimilated to bacterial
cells (leading thus to net growth) and on the other hand oxidised to nitrite and nitrate. Nitrifying
organisms are present in almost all aerobic biological treatment processes, but usually their
numbers are limited.
(From Chemistry for Environmental Engineering and Science fifth Edition)
Free ammonia in concentrations above about 0.2 mg/l can cause fatalities in several species of
fish.
Overview of central WWTP performance on ammonia
Figure 2.26 presents the ammonia concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
75
76
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.26:
Ammonia concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
Concentration in the effluent can be > concentration in the influent because of ammonification,
e.g. WWTP #29, #35, #60.
Number of plants reporting data
Out of the 63 WWTPs, 34 reported ammonia values in the effluent (or 54 %) and about 60 % of
these reported NH4-N values in the influent.
Peaks of emissions
At one WWTP, NH4-N in the effluent is above 100 mg/l, i.e. #65 with NH4-N of 158 mg/l. It
can be noted that the main treatment at WWTP #65 is oxidation with H2O2 and that the effluent
from WWTP #65 is further treated in a biological WWTP.
Averaging periods used for reporting emissions
The majority of averaging periods reported are yearly averages (e.g. of 24-hour daily composite
samples, of weekly samples, of bi-monthly samples, of samples taken four times per year).
Techniques reported to minimise/reduce ammonia discharge
A combination of several of the following techniques can be used:

Pretreatment at the installation(s) from which the waste waters originate, e.g.:
o

stripping (e.g. #21, #61).
Treatments at the central WWTP:
o
biological nitrogen elimination (nitrification/denitrification).
BAT-AELs for ammoniacal nitrogen in the existing series of chemical BREFs
The BAT-AELs for NH4-N in the existing (adopted) series of chemical BREFs are given in
Table 2.27.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
77
BREF
(year adopted)
Abatement
efficiency
(%)
Refineries (2003)
Emission
levels
(mg/l)
Load
levels
1.5 – 25 (1)
0.25 – 10 (3)
0.5 – 15 g/t
cop (2)
0.1 – 6 g/t
cop (4)
Remarks
(1) Total nitrogen, monthly average. Industry believe that, where nitrogen is not a pollutant of concern in the
receiving waters, denitrification cannot be BAT as the environmental benefit to the receiving water is very low,
while the cost both in Euros (capital expenditure) and the CO2 emissions are high.
(2) Total nitrogen, yearly average. One Member State claims that the upper level of the range should be 8. They
demonstrated (based on actual data) that a figure below 8 can easily be achieved with a stripper or a
nitrification/denitrification step. cop: crude oil or feedstock processed.
(3) Ammoniacal nitrogen (as N), monthly average. One Member State claims that the upper level should be 5.
Those levels can be reached by strippers and a biological nitrification/denitrification step.
(4) Total nitrogen, yearly average. One Member State claims that the upper level of the range should be 8. They
demonstrated (based on actual data) that a figure below 8 can easily be achieved with a stripper or a
nitrification/denitrification step. cop: crude oil or feedstock processed.
Table 2.27:
BAT-AELs for ammoniacal nitrogen in adopted BREFs
Reported achieved performance
The NH4-N concentration in the effluent of central WWTPs is given in Table 2.28.
Parameter
NH4-N
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.1 (1)
0.4 (2)
1 (3)
2.9 (4)
10 (5)
50
158
(1) #42 (DE) yearly average.
(2) #62 (CZ) yearly average of grab samples, abatement efficiency of 83.6 %.
(3) #01 (DE) yearly average of 24-hour composite samples, abatement efficiency of 98.1 %.
(4) #33 (CEFIC) daily average of 24-hour flow proportionate samples analysed daily.
(5) #06 (DE) yearly average of 24-hour composite samples.
Table 2.28:
Ammoniacal nitrogen (NH4-N) in the effluent of central WWTPs (both biological
and physico-chemical WWTPs)
Abatement efficiencies reported are in the range 24 – 99.6 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are generally >83 %.
Fluctuations of emissions around the average (in concentration)
Maximum NH4-N values reported vary around the average by approximately a factor of 1.5 to
20, but more generally between approximately 2 and 8.
Changes of temperature, seasonal effects, change of production, start-ups and shutdowns and
result in higher variability in the emissions of ammonia. However, the gap between min/max
and average values tend to be larger than for other parameters like COD.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), ammonia is considered not quantifiable below 0.25 mg/l (0.2 mgN/l).
Literature reports that ammonia nitrogen can be determined over a range of 0.02 to 2 mg/l by an
automated phenate procedure.
Parameters that affect performance
Suspended-growth nitrification and denitrification processes are very much dependent on
temperature, pH, dissolved oxygen, residence time and sludge age.
The dynamic of ammonia removal by bacteria is different than the removal of COD due to the
differing nature of the bacteria involved. It is therefore important to know that changes in
78
November 2010SR/EIPPCB/Analysis questionnaires CWW
production can occur so as to possibly take the necessary measures to minimise ammonia
emissions, if the interactions are known and the measures applicable.
Relation between performance and techniques used as reported in the questionnaires
The sensitivity of nitrification causes large variations of emissions as this can be seen in Figure
2.26.
2.4.1.4
Nitrite (as NO2-N)
Background information on nitrite and its measurement
Nitrite nitrogen seldom appears in concentrations greater than 1 mg/l in waste water effluents.
Its concentration in surface waters and groundwaters is normally much below 0.1 mg/l. For this
reason sensitive methods are needed for its measurement.
Nitrite is seldom found in waste waters from the chemical industry. Also, there are analytical
problems to measure nitrite because of its fast conversion to nitrate. This is the reason why the
monitoring of nitrite is seldom performed in the influent of the central WWTPs (only 9 plants –
or 13 % – reported nitrite concentrations in the influent of WWTPs). Nitrite in the influent of
central WWTPs is reported to be generally in the range of 0.16 – 0.8 mg/l.
Nitrite is generated when nitrification processes are used at central WWTPs. Nitrification is a
two-step process that first converts ammonia and ammonium to nitrite and then rapidly to
nitrate, so that nitrite levels at any given time are usually low.
Overview of central WWTP performance on nitrite
Figure 2.27 presents the nitrite concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
79
Figure 2.27:
Nitrite concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
Number of plants reporting data
21 out of the 63 WWTPs reported nitrite values in the effluent (or 33 %) and about 40 % of
these reported nitrite values in the influent.
Germany indicated that the nitrite emissions given in questionnaire #36 are the result of an
abnormal situation and could not be considered representative data. This is probably also the
case for questionnaires #37, #38 and #41.
Peaks of emissions
At three WWTP, nitrite in the effluent is above 1 mg/l (i.e. #37 with nitrite of 2.4 mg/l, #38 with
nitrite of 3.2 mg/l and #41 with nitrite of 3.7 mg/l).
Averaging periods used for reporting emissions
The majority of averaging periods reported are yearly averages (e.g. of 24-hour daily composite
samples, of weekly samples, of bi-monthly samples, of samples taken four times per year).
Techniques reported to minimise/reduce nitrite discharge
Nitrite is an intermediate compound generated in the nitrification process in the removal of
ammonia from waste waters. The biological conversion of ammonium to nitrate proceeds
rapidly to the nitrate form; therefore, nitrite levels at any given time are usually low.
BAT-AELs for nitrite in the existing series of chemical BREFs
No BAT-AELs for nitrite are given in the series of chemical BREFs.
Reported achieved performance
The NO2-N concentration in the effluent of central WWTPs is given in Table 2.29.
80
November 2010SR/EIPPCB/Analysis questionnaires CWW
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
NO2-N
average
(mg/l)
0.0096 (1)
0.04 (2)
0.1 (3)
0.4 (4)
0.64 (5)
2.4
3.7
(1) #03 (DE) average of continuous results of measurement over three month (14 samples, one sample/week). Might be
below the limit of detection/quantification, could DE confirm the value?
(2) #62 (CZ) yearly average of grab samples taken 3 times per week.
(3) #36 (DE) working day sample (5 x/week).
(4) #01 (DE) yearly average of 24-hour composite samples, abatement efficiency of 60 % on the load.
(5) #63 (CZ) yearly average of 24-hour composite samples taken 25 times per year.
Table 2.29:
Nitrite (as NO2-N) in the effluent of central WWTPs
Abatement efficiencies reported are in the range -50 – 91.9 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are >53 %.
Concentrations greater than 1 mg/l are generally found when a facility is partially nitrifying.
Fluctuations of emissions around the average (in concentration)
Maximum nitrite values reported vary around the average by approximately a factor of 1.5 to
20, but more generally by between approximately 3 and 8.
According to CEFIC, because the nitrite parameter, like the other nitrogen-related parameters, is
very sensitive to sampling and velocity of analytics, the use of yearly averages are sufficient to
control this parameter. Nitrate and nitrite undergo fast biodegradation and transformation
(nitrification/denitrification). Reliable information is only based on online systems. Therefore,
both nitrate and nitrite parameters should be presented as sum.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), nitrite is considered not quantifiable below 0.1 mg/l (0.03 mgN/l).
Parameters that affect performance
Suspended-growth nitrification and denitrification processes are very much dependent on
temperature, pH and dissolved oxygen. Nitrification occurs only under aerobic conditions at
dissolved oxygen levels of 1.0 mg/l or more. At dissolved oxygen (DO) concentrations less than
0.5 mg/l, the growth rate is minimal.
Relation between performance and techniques used as reported in the questionnaires
Central WWTPs are not specifically designed to remove nitrite per se (they are possibly
designed to remove Total-N) because nitrite is an 'intermediary' pollutant generated when using
nitrification processes and is rapidly converted to nitrate (except when there are disturbances).
2.4.1.5
Nitrate (as NO3-N)
Background information on nitrate and its measurement
Substances which contribute to eutrophication such as nitrates, are included in the indicative list
of substances to be taken into account for fixing emission limit values in Annex III of the IPPC
Directive.
Microbiological processes in central waste water treatment plants convert ammonia to nitrate.
(From Chemistry for Environmental Engineering and Science, fifth Edition)
Obtaining reliable nitrate nitrogen analysis is difficult. Several procedures exist.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
81
Overview of central WWTP performance on nitrate
Figure 2.28 presents the nitrate concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
NO3 - N concentration in the influent and effluent of central physico-chemical WWTPs
50
direct organic
ind. org.+inor.
dir. org.+inor.
inder. organic
direct organic
NO3-N (mg/l)
30
20
38
inder. organic
dir. org.+inor.
10
53
35
05
042
Filt.
ind. org.+inor.
direct organic
dir. org.+inor.
40
65
46
0
0
Number of central WWTPs
7
Overview of average values
(mg/l)
Maximum
14
90th percentile
11
75th percentile
9
50th percentile
6.9
25th percentile
4.9
10th percentile
2.9
Minimum
0.1
82
November 2010SR/EIPPCB/Analysis questionnaires CWW
NO3 - N concentration in the influent and effluent of central physico-chemical WWTPs (detail)
10
042
9
05
8
53
NO3-N (mg/l)
7
6
65
35
5
4
3
2
1
46
0
0
6
Number of central WWTPs
Figure 2.28:
Nitrate concentration in the influent and effluent of central biological WWTPs and
physico-chemical WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 26 reported nitrate values in the effluent (or 41 %) and about half of
these reported nitrate values in the influent.
Peaks of emissions
At one WWTP, nitrite in the effluent is above 30 mg/l (i.e. #61 with nitrate of 97 mg/l).
Averaging periods used for reporting emissions
Many averaging periods reported are yearly averages (e.g. of 24-hour daily composite samples,
of weekly samples, of bi-monthly samples, of samples taken four times per year).
Techniques reported to minimise/reduce nitrate discharge
Nitrate is converted to nitrogen gas in the denitrification process.
BAT-AELs for nitrate in the existing series of chemical BREFs
No BAT-AELs for nitrate are given in the series of chemical BREFs.
Reported achieved performance
The NO3-N concentration in the effluent of central WWTPs is given in Table 2.30.
Parameter
NO3-N
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.08 (1)
0.47 (2)
1.7 (3)
4.8 (4)
9.2 (5)
17
97
(1) #46 (IT) average of daily values. Might be below the limit of detection/quantification, could IT confirm the
value?
(2) #60 (FR) yearly average of 24-hour composite samples taken daily, abatement efficiency of 93 %.
(3) #45 (IT) average of quarterly analysis (each of 3 hours continuous sample).
(4) #35 (FR) yearly average of monthly average values, abatement efficiency of -16.9 %.
(5) #042 (DE) yearly average.
Table 2.30:
Nitrate (as NO3-N) in the effluent of central WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
83
Abatement efficiencies reported are in the range -81 – 97.9 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are >53 %.
Fluctuations of emissions around the average (in concentration)
Maximum nitrate values reported vary around the average by approximately a factor of 1.5 to
25, but more generally by between approximately 1.5 and 8.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), nitrate is considered not quantifiable below 0.5 mg/l (0.1 mg N/l).
Literature reports that ion chromatographic and capillary ion electrophoresis methods is highly
useful for analysis with nitrate nitrogen concentrations greater than about 0.2 mg/l and that with
the cadmium reduction method, nitrate concentrations as low as 0.01 mg/l can be detected.
Parameters that affect performance
Suspended-growth nitrification and denitrification processes are very much dependent on
temperature, pH and dissolved oxygen.
Relation between performance and techniques used as reported in the questionnaires
The sensitivity of nitrification causes large variations of emissions as this can be seen in Figure
2.28.
2.4.2
Phosphorus compounds
2.4.2.1
General
Background information on phosphorus compounds and their treatment
Organophosphorus compounds as well as phosphates are included in the indicative list of
substances to be taken into account for fixing emission limit values in Annex III of the IPPC
Directive.
Phosphorus is present in waste waters in inorganic and organic forms. The inorganic forms are
orthophosphates (i.e. HPO42-/H2PO4-) and polyphosphates. Organically bound phosphorus is
usually of minor importance. Polyphosphates can be used as a means of controlling corrosion.
Phosphorus discharge has to be controlled in the same way as nitrogen discharge in order to
avoid eutrophication of surface waters. It is reported that to avoid algal blooms under summer
conditions, the critical level of inorganic phosphorus is near 0.005 mg/l.
Microorganisms utilise phosphorus for cell synthesis and energy transport. As a result, 10 to 30
percent of the influent phosphorus is removed during traditional biological treatments [Metcalf
and Eddy]. Biological phosphorous removal can be enhanced by the presence of an anaerobic
tank (nitrate and oxygen are absent) prior to the aeration tank. Under these conditions a group of
heterotrophic bacteria, called polyphosphate-accumulating organisms are selectively enriched in
the bacterial community within the activated sludge. These bacteria accumulate large quantities
of polyphosphate within their cells and the removal of phosphorus is said to be enhanced.
Therefore, these bacteria do not only consume phosphorus for cellar components but also
accumulate large quantities of polyphosphate within their cells; up to a fraction of 5 – 7% of the
biomass.
When the industrial waste waters do not contain enough phosphorus for optimum growth of the
organisms used in treatment, the addition of inorganic phosphates is carried out (see also
Section 2.4.1.1). Many central WWTPs reported on the consumption of phosphoric acid (i.e.
#17, #18, #19, #21, #22, #28, #34, #40, #41, #45, #48, #50, #52, #58, #60, #61, #63, #64) and
some others unspecifically on nutrients (i.e. #25, #29, #51). Apart from the biological waste
water treatment, sludge digestion may also require the addition of nutrients.
84
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.4.2.2
Total phosphorus (Total-P)
Overview of central WWTP performance on Total-P
Figure 2.29 presents the Total-P concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
52
44
08
12
02
14
041
10
Adsorp.+Filt.+P_precip.
11
62
34
13
69
21
45
03
60
16
07
54
19
15
63
Filt.
06
61
Filt.
01
Filt.
22
P_precip.
37
Filt.
Total P (mg/l)
Total P concentration in the influent and effluent of central biological WWTPs (detail)
0
28
Number of central WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
85
Figure 2.29:
Total-P concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
Phosphorous emissions are very sensitive to the C/N/P ratio. CEFIC indicated that, in many
cases, total phosphorus emissions does not only reflect emissions from production only but also
dosing to biotreatment. In some periods, the dosing level has to be raised to ensure a solid
bacteria growth.
Germany indicated that it considers 1.5 mg/l of phosphorus (as yearly average) in the effluent to
be a high but reasonable level considering the local situation.
Number of plants reporting data
Out of the 63 WWTPs, 45 reported Total-P values in the effluent (or 71 %) and 21 WWTPs
reported Total-P values in the influent.
Peaks of emissions
At three WWTP, Total phosphorus in the effluent is above 10 mg/l, i.e. #65, with Total-P of
10.2 mg/l (indirect dicharge), #28 with 18.4 mg/l (indirect discharge and high TSS emissions –
1729 mg/l), and #38 with 23.1 mg/l (indirect discharge and high BOD5 emissions – 300 mg/l).
Averaging periods used for reporting emissions
The majority of averaging periods reported are yearly averages (e.g. of 24-hour daily composite
samples, of weekly samples, of bi-monthly samples, of samples taken four times per year).
Techniques reported to minimise/reduce Total-P discharge
A combination of several of the following techniques is used to minimise/reduce Total-P
discharges:

Pretreatment at the installation(s) from which the waste waters originate, e.g.:
o

86
precipitation.
Treatments at the central WWTP by one of the following techniques:
November 2010SR/EIPPCB/Analysis questionnaires CWW
o
o
biological phosphorus removal (P incorporated into the cell biomass)
precipitation (e.g. with lime, ferric chloride or alum, e.g. #06, #34, #36), before,
during or after the biological treatment.
It can be noted that chemical precipitation for phosphorus removal increases the volume of
sludge produced (on an average of 26 % – Sedlak 1991 –) and often results in a sludge with
poor settling and dewatering characteristics. Also, precipitation with metal salts can depress the
pH. If nitrification is required, additional alkalinity will be consumed and the pH will drop
further. With biological phosphorus removal, the need for chemical addition is reduced or
eliminated. Other benefits of biological phosphorus removal are: reduced sludge production,
improved sludge settleability and dewatering characteristics, reduced oxygen requirements, and
reduced process alkalinity requirements.
BAT-AELs for Total-P in the existing series of chemical BREFs
The BAT-AELs for Total-P in the existing (adopted) series of chemical BREFs are given in
Table 2.31.
Abatement
efficiency
(%)
BREF
(year adopted)
CWW (2003)
none
Emission
levels
(mg/l)
Load
Levels
Remarks
0.5 – 1.5 (1)
For final waste water
discharge into surface water,
without dilution with
rainwater and/or
uncontaminated cooling
water
0.2 – 1.5 (2)
After treatment in a
biological WWTP
LVOC (2002)
OFC (2005)
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
LVIC-S (2006)
LVIC-AAF (2006)
0.5 – 2 kg/t of
raw P (3)
SIC (2006)
Refineries (2003)
(1) Total P: lower range from nutrient feed in biological WWTP, upper range from production processes.
(2) Yearly average, Total-P: the upper end of the range results from the production of compounds containing P.
(3) Production of phosphorus compounds.
Table 2.31:
BAT-AELs for phosphorus compounds in adopted BREFs
Reported achieved performance
The Total-P concentrations in the effluent and the abatement efficiencies of central WWTPs are
given in Table 2.32.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
87
Parameter
Total-P
average
(mg/l)
Total-P
abatement
based on
concentrations
(%) (6)
Total-P
abatement
based on
loads (%) (7)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.03 (1)
0.16 (2)
0.49 (3)
0.7 (4)
2 (5)
4.1
23
24.6
20 – 50
46.7
64.3
87.6
95.3
98.5
46.0
46.0
54.3
78.5
90.0
97.7
97.8
(1) #042 (DE) yearly average.
(2) #22 (CEFIC) yearly average of daily qualified samples.
(3) #37 (ES) no averaging period indicated (samples taken once per week), abatement efficiency of 25 %.
(4) #15 (DE) yearly average.
(5) #53 (BE) 24 hours composite samples (in proportion to the volume of discharged waste water).
(6) 20 figures are summarised in this row.
(7) 13 figures are summarised in this row.
Table 2.32:
WWTPs
Total-P concentrations in the effluent and abatement efficiencies of central
Abatement efficiencies reported are in the range 24.6 – 98.5 %. For the 50th percentile of
central WWTPs and higher, abatement efficiencies are generally >50 %, suggesting that
chemical precipitation of phosphorus is carried out in addition to biological phosphorus
removal.
Fluctuations of emissions around the average (in concentration)
Maximum Total-P values reported vary around the average by approximately a factor of 1.2 to
10, but more generally by between approximately 1.5 and 3.
Limits of detection (LOD) and quantification (LOQ)
Two international standards for the determination of Total-P exist: EN ISO 6878 (2004)
specifies methods for the determination of different types of phosphates including Total-P after
decomposition. The methods are applicable to all kinds of water. Phosphorus concentrations
within the range of 0.005 mg/l to 0.8 mg/l may be determined. A solvent extraction procedure
allows smaller phosphorus concentrations to be determined with a detection limit of about
0.0005 mg/l. EN ISO 15681 – parts 1 and 2 (2003) specify flow methods (FIA/CFA) for the
determination of Total-P for the mass concentration range from 0.1 mg/l to 10 mg/l.
Parameters that affect performance
The key to (enhanced) biological phosphorus removal is the exposure of the microorganisms to
alternating anaerobic and aerobic conditions [Metcalf & Eddy]. Care has to be taken that
phosphorous released during sludge treatment (e.g. during sludge digestion due to cell
hydrolysis) does not re-enter into the waste water treatment.
The precipitation of phosphates is dependant on, for example, type and concentration of
flocculants, pH value, mixing regime, and residence time.
Relation between performance and techniques used as reported in the questionnaires
The performance of (enhanced) biological phosphorus removal and the precipitation of
phosphates depend on a number of plant operating conditions as described above. Most of these
operating conditions were not asked for in the questionnaires. Therefore, it is difficult to
establish relationships with the reported performance levels.
88
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.4.2.3
Phosphate (as PO4-P)
Background information on phosphate and their treatment
Substances which contribute to eutrophication such as phosphates, are included in the indicative
list of substances to be taken into account for fixing emission limit values in Annex III of the
IPPC Directive.
Overview of central WWTP performance on phosphate
Figure 2.30 presents the phosphate concentration in the influent and effluent of central
biological WWTPs.
Figure 2.30:
Phosphate concentration in the influent and effluent of central biological WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 11 reported PO4-P values in the effluent (or 17 %) and about 72 % of
these reported PO4-P values in the influent.
Peaks of emissions
At one WWTP, PO4-P in the effluent is above 5 mg/l (i.e. #41 with 12 mg/l).
Averaging periods used for reporting emissions
Many averaging periods reported are yearly averages.
Techniques reported to minimise/reduce PO4-P discharge
Treatment at the central WWTP by one of the following technique:


biological phosphorus removal (P incorporated into the cell biomass)
precipitation (e.g. with ferric chloride or alum) and further removal as chemical
precipitates (i.e. TSS).
No pretreatments have been reported in the questionnaires.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
89
BAT-AELs for PO4-P in the existing series of chemical BREFs
No BAT-AELs for phosphates are given in the series of chemical BREFs.
Reported achieved performance
The PO4-P concentration in the effluent of central WWTPs is given in Table 2.33.
Parameter
PO4-P
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0 (1)
0.03 (2)
0.13 (3)
0.6 (4)
1 (5)
1.49
12
(1) #042 (DE) yearly average. Should be interpreted as below the limit of detection/quantification.
(2) #64 (FR) yearly average based on two samples per week.
(3) #62 (CZ) yearly average of grab samples.
(4) #041 (DE) yearly average.
(5) #52 (BE) yearly average.
Table 2.33:
PO4-P in the effluent of central WWTPs
Abatement efficiencies reported are in the range 25 – 99 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are >88 %.
Fluctuations of emissions around the average (in concentration)
Maximum PO4-P values reported vary around the average by approximately a factor of 1.5 to
15, but more generally by between approximately 1.5 and 6.5.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), phosphate is considered not quantifiable below 0.15 mg/l (0.05 mg P/l).
Phosphates can be determined by the two international standards mentioned above for the
determination of Total-P: the application ranges for EN ISO 6878 (2004) are 0.005 mg/l to 0.8
mg/l and for EN ISO 15681 – parts 1 and 2 (2003) regarding ortho-phosphate 0.01 – 1.0 mg/l.
Other international standards for measuring ortho-phosphate exist, e.g. EN ISO 10304-1 (2007)
using ion chromatography.
Parameters that affect performance
See discussion under Total-P parameter in Section 2.4.2.2.
Relation between performance and techniques used as reported in the questionnaires
See discussion under Total-P parameter in Section 2.4.2.2.
2.4.3
Phenols
Background information on phenols and their treatment
Persistent hydrocarbons and persistent and bioaccumulable organic substances (some phenols
present such characteristics) are included in the indicative list of substances to be taken into
account for fixing emission limit values in Annex III of the IPPC Directive.
Phenol can be quite toxic to bacteria in concentrated solution. However, literature reports that
phenol can serve as food for aerobic bacteria without serious toxic effects at levels as high
as 500 mg/l.
CEFIC indicated that it considers that the phenol parameter as sum parameter such as the
''phenol index'' is an old fashion parameter and that emissions of phenols as individual
component from industrial installations are generally low. Consequently, CEFIC considers that
90
November 2010SR/EIPPCB/Analysis questionnaires CWW
it is not worth spending too much time on the analysis of this parameter, because phenol is
readily degradable under normal WWTP conditions.
Overview of central WWTP performance on phenols
Figure 2.31 presents the phenols concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
Figure 2.31:
Phenols concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
91
Some participants expressed concern over the fact that phenols in waste waters can be
determined by various methods and that the corresponding results would not be comparable.
For Questionnaires #46, #65, and #66 where high phenol emissions are shown, the WWTPs
discharge indirectly to the receiving water.
Number of plants reporting data
Out of the 63 WWTPs, 19 reported phenols values in the effluent (or 30 %) and about half of
these reported phenols values in the influent. High phenols concentration in the influent
corresponds to central WWTPs treating waste waters from installations where phenolic
compounds are used/produced (e.g. #47, #61, #65, #66).
Peaks of emissions
At nine WWTPs, phenols in the effluent are above 100 µg/l with phenols being above 1000 µg/l
at four WWTPs (i.e. #65, #66, #46, #28).
Averaging periods used for reporting emissions
Many averaging periods reported are yearly averages.
Techniques reported to minimise/reduce phenols discharge
A combination of several of the following techniques are reported to be used:

pretreatment at the installation(s) from which the waste waters originate, e.g.:
o
o

extraction (i.e. #57, #61)
adsorption with activated carbon (i.e. #50);
treatments at the central WWTP:
o
o
biological treatment using complete-mixed activated sludge (i.e. #28, #47, #50,
#57, #60, #61, #64)
oxidation with H2O2 (i.e. #65, #66).
BAT-AELs for phenols in the existing series of chemical BREFs
No BAT-AELs for phenols are given in the series of chemical BREFs.
Reported achieved performance
The phenols concentration in the effluent of central WWTPs are given in Table 2.34.
Parameter
Phenols
average
(µg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0 (1)
0.1 (2)
6 (3)
50 (4)
400 (5)
6700
9100
(1) #41 (FR) yearly average of 24-hour composite samples. Might be below the limit of detection/quantification,
could FR confirm the value?
(2) #02 (DE) one month composite sample. Might be below the limit of detection/quantification, could DE
confirm the value?
(3) #45 (IT) average of quarterly analysis (each of 3-hour continuous samples).
(4) #61 (CZ) yearly average of 24-hour composite samples.
(5) #47 (ES) yearly average of 24-hour composite samples.
Table 2.34:
Phenols in the effluent of central WWTPs
Abatement efficiencies reported are in the range 52 – 99.9 %. For the 50th percentile of central
WWTPs and higher, abatement efficiencies are generally >90 %.
92
November 2010SR/EIPPCB/Analysis questionnaires CWW
Fluctuations of emissions around the average (in concentration)
Maximum phenols values reported vary around the average by approximately a factor of 1 to
16, but more generally by between approximately 2 and 6.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), phenol is considered not quantifiable below 0.2 µg/l. Several
international standards for determining phenols exist. The phenol index can be measured by ISO
6439 (1990) which gives procedures for drinking waters, surface waters, brines (saline waters),
domestic waters and industrial waters. After a preliminary distillation the test sample are
analysed according to specific application by the direct colorimetric method (4aminoantipyrine) and by the chloroform extraction method. Another possibility is to use flow
analysis (flow injection analysis – FIA – and continuous flow analysis – CFA) according to EN
ISO 14402 (1999). The phenol index is an operationally defined parameter. Therefore the
results depend largely on the applied procedure.
Specific phenols can be determined by: ISO 81651-1 (1992) and ISO 8165-2 (1999): selected
monovalent phenols; EN ISO 17495 (2003): nitrophenols; EN ISO 18857-1 (2006):
alkylphenols; ISO 18857-2 (2009): alkylphenols, their ethoxylates and bisphenol A; ISO 24293
(2009) isomers of nonylphenol; EN 12673 (1998): chlorophenols.
Results from the different analytical methods are difficult to compare. Regarding the phenol
index, the recovery for distinct phenol varies considerably. In addition, different national
standards for measuring the phenol index are in use, e.g. DIN 38406-16, NF T 90-204, APAT
IRSA 5070 A1/A2.
Parameters that affect performance
The removal of phenols in activated sludge processes is reported to be sensitive to temperature
and higher performance is achieved in cold rather than warm weather.
Relation between performance and techniques used as reported in the questionnaires
The conventional treatment methods adopted for removal of phenol depend upon the
maintenance of the toxic limit of phenol concentration and adequate acclimatisation of the
biomass. The trickling filter and the activated sludge process are generally in use for the
treatment of phenolic waste water. In the activated sludge process, the requirement of air for
aeration increases with phenol concentration. The phenol loading removal is effective only up
to a certain level. Some discharged effluent standards being 0.1 mg/l, the conventional methods
are not efficient to bring down the phenol concentration to such a low level in the treated
effluent.
2.4.4
Chlorides
Background information on chlorides and their treatment
Chlorides are not included in the indicative list of substances to be taken into account for fixing
emission limit values in Annex III of the IPPC Directive.
Chloride occurs in all natural waters in widely varying concentration (very high in sea and
ocean, on average 19 g/l). Freshwater organisms can be harmed by excessive chloride
concentrations, e.g. EC10(48 h) and EC50(48 h) values of 3.9 and 12 g/l, respectively, are
reported for the standardised fish egg test with danio rerio (German Association of Chemists
(GDCh) 2005, Lammer et al. 2009 and references within). Chloride in reasonable
concentrations is not harmful to humans. At concentration above 250 mg/l it gives a salty taste
to water.
The literature reports that chloride concentrations of >1000 mg/l have a negative effect on the
biological removal of phosphorus in WWTPs. The literature reports that chloride concentrations
of >10000 mg/l have negative effects on the biological removal of nitrogen in WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
93
Germany is of the opinion that salt concentration (chloride, sulphate and/or the sum of both) is a
useful information concerning treatment conditions and the interpretation of some other
parameters (e.g. bioassays). Germany also considers that regarding salts, the abatement
efficieny of biological treatment is low and is not a pertinent parameter.
Overview of central WWTP performance on chlorides
Figure 2.32 presents the chlorides concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
94
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.32:
Chlorides concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 27 reported chloride values in the effluent (or 43 %). Of these values, 26
are of spot-type while one is given as a range-type value (i.e. <500 mg/l). Chloride values in the
influent were reported by 14 installations.
Peaks of emissions
There are very large variations on the concentrations of chlorides discharged with several values
in the range of 1000 – 10000 mg/l and a peak at 20500 mg/l (i.e. #17).
Averaging periods used for reporting emissions
Many averaging periods reported are yearly averages.
Techniques reported to minimise/reduce chlorides discharge
Waste waters loaded with chlorides can be treated by nanofiltration or reverse osmosis
(i.e. #58).
BAT-AELs for chlorides in the existing series of chemical BREFs
The BAT-AELs for chlorides in the existing (adopted) series of chemical BREFs are given in
Table 2.35.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
95
Abatement
efficiency
(%)
BREF
(year adopted)
Emission
levels
(mg/l)
CWW (2003)
LVOC (2002)
OFC (2005)
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
LVIC-S (2006)
LVIC-AAF (2006)
SIC (2006)
Refineries (2003)
(1) Titanium dioxide – chloride route.
Table 2.35:
Load
levels
Remarks
38 – 330 kg/t TiO2 (1)
BAT-AELs for chlorides in adopted BREFs
Reported achieved performance
The chlorides concentration in the effluent of central WWTPs is given in Table 2.36.
Parameter
Chlorides
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
54
64 (1)
472 (2)
1330 (3)
3468 (4)
6230
20500
(1) #62 (CZ) yearly average of grab samples.
(2) #54 (BE) yearly average of 24-hour composite samples.
(3) #07 (DE) yearly average based on weekly 24-hour mixed samples, abatement efficiency of 4 %.
(4) #65 (ES) yearly average of monthly samples, abatement efficiency of 42 %.
Table 2.36:
Chlorides in the effluent of central WWTPs
Abatement efficiencies based on concentrations are in the range of -22 – 92 %. Abatement
efficiencies reported are generally low, below 40 %, except for #58 (IT) where an abatement
efficiency of 92 % is reported (i.e. reduction from 1075 mg/l to 90 mg/l). It should be noted that
reverse osmosis is used at #58. Industry therefore considers that central WWTPs have no impact
on chloride abatement.
Fluctuations of emissions around the average (in concentration)
Maximum values above detection limits in addition to the average value were reported by
17 installations. Maximum chlorides values reported vary around the average by approximately
a factor of 1 to 3 (one installation with a factor of 10.8), but more generally by between
approximately 1.2 and 2.
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), chloride is considered not quantifiable below 25 mg/l. Several
international standards for measuring chloride exist. ISO 9297 (1989) uses titration with silver
nitrate and chromate indicator (Mohr's method) and is applicable to concentrations between 5
mg/l and 150 mg/l. Due to many interferences the method is not applicable to heavily polluted
waters of low chloride content. EN ISO 10304-1 (2007) uses ion chromatography for the
determination of chloride with a lower application limit of 0.1 mg/l.
Parameters that affect performance
Not relevant since the central WWTP is not generally used to reduce chlorides.
Relation between performance and techniques used as reported in the questionnaires
96
November 2010SR/EIPPCB/Analysis questionnaires CWW
Chlorides are basically not removed by biological and most physico-chemical treatments in the
central WWTPs. On the contrary, chlorides are often added to the waste waters, either during
neutralisation/acifdification using hydrochloric acid or during flocculation using aluminium or
iron chlorides.
CEFIC questioned if exist to abate chlorides and, if so, if BAT conclusions should be derived
for this parameter. Chlorides may be a more pertinent parameter to consider in the vertical
chemical BREFs.
Referring to a recent workshop, CEFIC informed that high salt concentrations may hinder
nitrification. Biological treatment plants (carbon removal) work even at very high salt
concentrations (<5%).
CEFIC considers that chlorides are only considered in regard to the impact on the performance
of the WWTP, i.e. sedimentation, velocity of bacterial growth, or the interference on analytics,
i.e. AOX measurements and biotests.
2.4.5
Sulphates
Background information on sulphates and their treatment
Sulphates are not included in the indicative list of substances to be taken into account for fixing
emission limit values in Annex III of the IPPC Directive. As for chlorides, sulphates may be a
more pertinent parameter to consider in the vertical chemical BREFs, e.g. in the Polymers
(POL) and OFC BREFs.
The sulphate ion is one of the major anions occurring in natural waters. It is of importance
because of its cathartic effect upon humans when it is present in excessive amounts. It is
important to control sulphates in the influent of waste water treatment plants because of the
potential to create odour (formation of hydrogen sulphide) and corrosion problems in sewers
(by oxidation of hydrogen sulphide to sulphuric acid). Freshwater organisms can be harmed by
excessive sulphate concentrations.
Overview of central WWTP performance on sulphates
Figure 2.33 presents the sulphates concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
97
Figure 2.33:
Sulphates concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 23 reported sulphates values in the effluent (or 37 %). Of these values,
22 are of spot-type while one is given as range-type value (i.e. <40 mg/l). Sulphate values in the
influent were reported by 8 installations.
98
November 2010SR/EIPPCB/Analysis questionnaires CWW
Peaks of emissions
There are very large variations on the concentrations of sulphates discharged with several values
in the range of 1000 – 5000 mg/l.
Averaging periods used for reporting emissions
Many averaging periods reported are yearly averages.
Techniques reported to minimise/reduce sulphates discharge
Waste waters loaded with sulphates can be treated by nanofiltration and reverse osmosis.
BAT-AELs for sulphates in the existing series of chemical BREFs
The BAT-AELs for sulphates in the existing (adopted) series of chemical BREFs are given in
Table 2.37.
BREF
(year
adopted)
CWW (2003)
LVOC (2002)
OFC (2005)
Abatement
efficiency
(%)
Emission
levels
(mg/l)
POL (2006)
LDPE
GPPS
PVC
ESBR
VSF
Load
levels
Remarks
200 –
300 kg/t
prod.
100 –
550 kg/t
TiO2 (1)
LVIC-S
(2006)
LVIC-AAF
(2006)
SIC (2006)
Refineries
(2003)
(1) Titanium dioxide – sulphate route.
Table 2.37:
BAT-AELs for sulphates in adopted BREFs
Reported achieved performance
The sulphates concentration in the effluent of central WWTPs is given in Table 2.38.
Parameter
Sulphates
average
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0.5 (1)
62 (2)
238 (3)
938 (4)
1481 (5)
1720
5032
(1) #45 (IT) average of quarterly analysis (each of 3-hour continuous samples). Value is quite low compared with
typical concentrations of fresh water and could be below the limit of detection/quantification. Could IT
confirm the value?
(2) #58 (IT) average of 267 samples (with a standard deviation of 27), abatement efficiency of 92 %.
(3) #01 (DE) yearly average of 52 weekly samples.
(4) #46 (IT) average of daily values.
(5) #02 (DE) 2-hour composite sample.
Table 2.38:
Sulphates in the effluent of central WWTPs
Abatement efficiencies based on concentrations are in the range of -14 – 92 %. Abatement
efficiencies reported are generally low and below 43 %, except for #58 (IT) where an abatement
SR/EIPPCB/BP CWW TWG subgroup
November 2010
99
efficiency of 92 % is reported (i.e. reduction from 737 mg/l to 62 mg/l). It should be noted that
reverse osmosis is used at #58. Industry therefore considers that central WWTPs have no impact
on sulphate abatement.
Fluctuations of emissions around the average (in concentration)
Maximum sulphates values reported vary around the average by a factor of 1.1 to 2.6 with one
exception (i.e. factor of 6.9).
Limits of detection (LOD) and quantification (LOQ)
In Belgium (Flanders), sulphate is considered not quantifiable below 25 mg/l. Several
international standards for measuring sulphate exist. EN ISO 10304-1 (2007) uses ion
chromatography for the determination of sulphate with a lower application limit of 0.1 mg/l.
ISO 22743 (2006) specifies a continuous flow analysis (CFA) method for the determination of
sulphate in various types of water including waste water. The method is applicable to samples
with a mass concentration of 30 mg/l to 300 mg/l. Other concentration ranges are applicable,
provided they cover exactly one decade of concentration units (e.g. 100 mg/l to 1000 mg/l).
Parameters that affect performance
Not relevant since the central WWTP is not generally used to reduce sulphates.
Relation between performance and techniques used as reported in the questionnaires
Sulphates are basically not removed by biological and most physico-chemical treatments in the
central WWTPs, with the exemption of the addition of calcium hydroxide or lime which may
lead to the precipitation of calcium sulphate. On the contrary, sulphates are often added to the
waste waters either during neutralisation/acidification using sulphuric acid or during
flocculation using aluminium or iron sulphates.
2.4.6
Cyanides (free)
Background information on cyanides and their measurements
Cyanides are included in the indicative list of substances to be taken into account for fixing
emission limit values in Annex III of the IPPC Directive.
Cyanides can be present in water in dissolved or particulate form. They can be found as cyanide
ions (CN-), hydrogen cyanide (HCN), complex bound cyanides, organically bound cyanides,
e.g. nitriles and cyanohydrins, and other inorganic forms, e.g. cyanogen chloride (chlorocyan,
NCCl), cyanogen bromide, trimethylsilyl cyanide ((CH3)3SiCN). Free cyanide is commonly
designated as CN-, although it is actually defined as the total of CN-and HCN.
Many cyanide-containing compounds are highly toxic, but some are not. For example, organic
cyanides and hexacyanoferrates (ferrocyanide and ferricyanide, where the cyanide is already
tightly bound to an iron ion) have low toxicities. The most dangerous cyanides are inorganic
cyanides such as hydrogen cyanide and salts derived from it, such as potassium cyanide (KCN)
and sodium cyanide (NaCN), among others. Also some compounds readily release HCN or the
cyanide ion (CN-), such as trimethylsilyl cyanide upon contact with water and cyanoacrylates
upon pyrolysis. The primary concern regarding aqueous cyanide is that it could volatilise,
especially when the pH is below 8.
The cyanide ion (CN-) has a relatively short half-life because it can serve as a source of energy
for aerobic bacteria, provided the concentration is kept below its toxic threshold to them. In the
USA, a drinking water standard of 0.2 mg/l is included to protect against industries with direct
discharges to natural waters. For context, EU drinking water standards are 0.05 mg/l (for total
cyanide).
Overview of central WWTP performance on cyanides
100
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.34 presents the cyanides concentration in the influent and effluent of central biological
WWTPs and physico-chemical WWTPs.
CN (free) concentration in the influent and effluent of central physico-chemical WWTPs
0.5
direct organic
dir. org.+inor.
ind. org.+inor.
0.4
ind. org.+inor.
direct organic
inder. organic
inder. organic
dir. org.+inor.
CN (mg/l)
direct organic
dir. org.+inor.
0.3
0.2
46
0.1
35
0.0
0
2
Number of central WWTPs
Overview of average values
(mg/l)
Maximum
0.087
90th percentile
0.083
75th percentile
0.077
50th percentile
0.068
25th percentile
0.058
10th percentile
0.052
Minimum
0
Figure 2.34:
Cyanide concentration in the influent and effluent of central biological WWTPs
and physico-chemical WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 11 reported free cyanide values in the effluent (or 17 %) and only two
reported free cyanides values in the influent.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
101
Peaks of emissions
There are very large variations on the concentrations of free cyanides discharged with two
values in the range of 0.1 – 0.5 mg/l.
Averaging periods used for reporting emissions
Some averaging periods reported are yearly averages.
Techniques reported to minimise/reduce cyanides discharge
At an adequately low level, cyanides are biodegradable in an adaptated WWTP (see OFC
BREF). The rate of biodegradation depends on the activity and adaptation of the WWTP. When
influent concentrations are high (in the range of 4 to 5 mg/l), there is a risk of toxicity for the
bacteria of the biological treatment.
The following pretreatment techniques are reported:






conversion to glyconitrile with formaldehyde and sodium hydroxide (i.e. #02, #28)
oxidation with hydrogen peroxide (i.e. #35)
bleach treatment (i.e. #57)
complexation with iron and oxidation with ozone (i.e. #61)
oxidation with hypochlorite (i.e. #63, #68)
oxidation under alkaline conditions (i.e. #69).
BAT-AELs for cyanides in the existing series of chemical BREFs
No BAT-AELs for free cyanides are given in the series of chemical BREFs.
Reported achieved performance
The free cyanides concentration in the effluent of central WWTPs is given in Table 2.39.
Parameter
Free
cyanides
(mg/l)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
0 (1)
0.0012 (2)
0.007 (3)
0.05 (4)
0.09 (5)
0.15
0.3
(1) #57 (FR) Monthly monitoring of 24-hour composite sample. Below the limit of detection/quantification, could
FR confirm the value?
(2) #69 (IT) Daily analysis in laboratory (grab samples). Averaging period not indicated. Might be below the limit of
detection/quantification, could IT confirm the value?
(3) #63 (CZ) Yearly average of 24-hour composite samples taken 12 times per year (total cyanides). Might be below
the limit of detection/quantification, could CZ confirm the value?
(4) #35 (FR) Yearly average based on monthly samples.
(5) #46 (IT) average of daily values.
Table 2.39:
Cyanides in the effluent of central WWTPs
Abatement efficiencies could not be indicated due to the lack of influent data.
Fluctuations of emissions around the average (in concentration)
Maximum cyanides values reported vary around the average by approximately a factor of 2 to
11, but more generally by between approximately 2 and 3.
Limits of detection (LOD) and quantification (LOQ)
Cyanides are usually measured as a sum parameter. Depending on the analytical method used,
more or less cyanide species are included. Easily liberatable cyanide is usually understood as
the sum of all cyanide compounds which release hydrogen cyanide at a pH value of 4, which
includes alkaline and alkaline earth cyanides. Prussiates (nitrosylcyano complexes of iron) and
cyanides of cobalt and are partially included. Total cyanide usually includes all inorganic forms
of cyanides including complex bound cyanides and also cyanohydrins. Nitriles, cyanates
(OCN-), thiocyanates (SCN-), and cyanogen chloride are not included.
102
November 2010SR/EIPPCB/Analysis questionnaires CWW
In Belgium (Flanders), free cyanides are considered not quantifiable below 0.01 mg CN-/l.
Several international standards for measuring cyanides exist: ISO 6703-1 (1984) describes the
determination of total cyanide, ISO 6703-2 (1984) the determination of easily liberatable
cyanide, and ISO 6703-3 (1984) the determination of cyanogen chloride. ISO 6703-2 consists
of three methods with different application ranges: the photometric method with
pyridine/barbituric acid: 0.002 to 0.025 mg/l; the titrimetric method using the tyndall effect:
>0.005 mg/l; the titrimetric method using an indicator: >0.05 mg/l. EN ISO 14403 (2002)
describes a method for the determination of total cyanide and free cyanide by continuous flow
analysis. The method is based on digestion with UV radiation in case of total cyanide and
spectrophotometric detection. The method is applicable to various types of water in the range of
0.002 – 0.5 mg/l.
Parameters that affect performance
Not relevant since the central WWTP is not generally used to reduce cyanides.
Relation between performance and techniques used as reported in the questionnaires
According to the OFC BREF, due to their toxicity, cyanides are removed from rich and lean
waste water streams, e.g. by pH adjustment and oxidative destruction with H2O2. Depending on
the individual case, it may be also possible to enable safe degradation of cyanides in a
biological WWTP. The use of NaOCl for pretreatment is not considered as BAT due to the
potential for formation of AOX. Reconditioning of different cyanide loaded streams can enable
re-use and substitution of raw materials. Cyanides occurring in waste water streams together
with high COD loads can be pretreated oxidatively by techniques such as wet oxidation with O2
under alkaline conditions. In such cases, cyanide levels <1 mg/l are achievable in the treated
waste water stream.
2.4.7
Toxicity
2.4.7.1
General
Relatively few toxicity data have been submitted in the questionnaires. The data submitted
mainly concern German plants with a few data corresponding to French (i.e. Questionnaires #41
and #57) and Italian installations (Questionnaire #69). It can be noted that Germany made a
special contribution titled 'Compilation of Biotest Results from Waste Water Effluents of the
Chemical Industry' dated December 2008. This contribution is included in this document as
Annex Error! Reference source not found..
Background information on toxicity and their measurements
During the last few years biological test methods/systems have raised more and more interest.
Fish/fish egg tests, daphnia tests, algae tests and luminescent bacteria tests are all common test
methods for the toxicity assessment of complex waste water streams. They are often used to
obtain additional information that can be gained from sum parameter measurements (COD,
BOD, AOX, EOX, etc.). With toxicity tests it is possible to asses the possible hazardous
character of waste water in an integrated manner and to asses all synergistic effects which may
occur because of the presence of a lot of different single pollutants. Apart from the possibility
of using the toxicity tests to estimate potential hazardous effects on the ecosystem/surface
water, these tests can help to protect or to optimise biological waste water treatment plants (see
MON BREF).
Several international standards for the measurement of toxicity in waste waters exist, e.g. EN
ISO 6341 (1996) for daphnia magna, EN ISO 8692 (2004) for algae, EN ISO 11348, parts 1–3
(2008) for luminescent bacteria, EN ISO 20079 (2006) for duckweed, EN ISO 15088 (2008) for
zebrafish eggs.
SR/EIPPCB/BP CWW TWG subgroup
November 2010
103
Toxicity tests require expertise that may not be available at all plants/regions yet and toxicity
tests are not amenable to be carried out at high frequency.
Techniques reported to minimise/reduce toxicity
There are no specific techniques to reduce toxicity in waste waters. All treatment steps as
summarised in the sections above which lead to the reduction of the concentration of toxic
organic and inorganic compounds (e.g. metals, ammonia, cyanides, phenols, and toxic parts of
COD/TOC/BOD) are applicable.
BAT-AELs for toxicity in the existing series of chemical BREFs
The BAT-AELs for toxicity in the existing (adopted) series of chemical BREFs are given in
Table 2.40.
BREF
Emission levels
Remarks
(year adopted)
CWW (2003)
LVOC (2002)
OFC (2005)
LIDF
1 – 2 (1)
LIDD
2 – 4 (1)
After treatment in a biological WWTP
LIDA
1 – 8 (1)
LIDL
3 – 16 (1)
LIDEU
1.5 (1)
POL (2006)
LVIC-S (2006)
LVIC-AAF
(2006)
SIC (2006)
Refineries
(2003)
(1) Yearly averages. Lowest ineffective dilution (LID). Refers to toxicity levels. Subscripts refer to
fish/fish eggs (F), daphnia (D), algae (A), luminescent bacteria (L), and genotoxicity (EU).
Table 2.40:
2.4.7.2
BAT-AELs for LID in adopted BREFs
Fish or fish egg toxicity
Overview of central WWTP performance for fish or fish egg toxicity
Figure 2.35 presents the fish or fish egg dilution factor in the effluent of central WWTPs.
104
November 2010SR/EIPPCB/Analysis questionnaires CWW
Figure 2.35:
Fish or fish egg dilution factor in the effluent of central WWTPs
Number of plants reporting data
19 out of the 63 WWTPs (17 from DE and 2 from CEFIC - n DE) reported fish or fish egg
toxicity values in the effluent (or 30 %).
Peaks of emissions
Peaks occurs at installation #10 (DE) where a LID value of 4 is reported and at installation #11
(DE) where LID value of 6 is reported.
Averaging periods used for reporting emissions
Averaging periods are generally not indicated. Average values are based on a number of
measurements spanning from 5 to 21.
Reported achieved performance
The toxicity to fish/fish eggs in the effluent of central WWTPs is given in Table 2.41.
Toxicity
to
fish/fish
eggs
(LIDF)
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
1 (1)
1 (2)
1 (3)
1 - 2 (4)
3 (5)
4
6
(1) #03 (DE) yearly averages of 4 samples of the supervisory body.
(2) #08 (DE) averaging period and number of samples not indicated.
(3) #13 (DE) averaging period and number of samples not indicated.
(4) #041 (DE) averaging period and number of samples not indicated.
(5) #06 (DE) averaging period and number of samples not indicated.
Table 2.41:
Toxicity to fish/fish eggs in the effluent of central WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
105
2.4.7.3
Daphnia toxicity
Overview of central WWTP performance for daphnia toxicity
Figure 2.36 presents the daphnia dilution factor in the effluent of central WWTPs.
Figure 2.36:
Daphnia dilution factor in the effluent of central WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 17 (15 from DE, 1 From France and 1 from CEFIC) reported daphnia
toxicity values in the effluent (or 27 %).
Peaks of emissions
Peaks occurs at installation #36 (DE) where a LID value of 3 is reported and at installation
#11 (DE) where LID value of 5 is reported.
Averaging periods used for reporting emissions
Averaging periods are generally not indicated (yearly averages are indicated for two sites).
Average values are based on a number of measurements spanning from 5 to 20.
Reported achieved performance
The toxicity to daphnia in the effluent of central WWTPs is given in Table 2.42.
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
Toxicity to
daphnia
(LIDD)
1 (1)
1 (2)
1 (3)
1 (4)
2 (5)
3
5
(1) #22 (CEFIC) averaging period and number of samples not indicated.
(2) #03 (DE) yearly average of 4 samples of the supervisory body.
(3) #09 (DE) 90th percentile.
(4) #15 (DE) averaging period and number of samples not indicated.
(5) #06 (DE) averaging period and number of samples not indicated.
Table 2.42:
106
Toxicity to daphnia in the effluent of central WWTPs
November 2010SR/EIPPCB/Analysis questionnaires CWW
2.4.7.4
Algae toxicity
Overview of central WWTP performance for algae toxicity
Figure 2.37 presents the algae dilution factor in the effluent of central WWTPs.
Figure 2.37:
Algae dilution factor in the effluent of central WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 17 (16 from DE and 1 from CEFIC) reported algae toxicity values in the
effluent (or 27 %).
Peaks of emissions
Peaks occur at installation #36 (DE) where a LID value of 16 is reported and at installation #06
(DE) where LID value of 24 is reported.
Averaging periods used for reporting emissions
Averaging periods are generally not indicated (yearly averages are indicated for one site). The
number of measurements span from 5 to 22.
Reported achieved performance
The toxicity to algae in the effluent of central WWTPs is given in Table 2.43.
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
Toxicity to
algae
(LIDA)
1 (1)
1 (2)
1 (3)
1 (4)
2 – 3 (5)
4
24
(1) #03 (DE) yearly average of 4 samples of the supervisory body.
(2) #08 (DE) averaging period and number of samples not indicated.
(3) #12 (DE) averaging period and number of samples not indicated.
(4) #22 (CEFIC) averaging period and number of samples not indicated.
(5) #16 (DE) averaging period and number of samples not indicated.
Table 2.43:
Toxicity to algae in the effluent of central WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
107
2.4.7.5
Bacterial luminescence toxicity
Overview of central WWTP performance for bacterial luminescence toxicity
Figure 2.38 presents the bacterial luminescence dilution factor in the effluent of central
WWTPs.
Figure 2.38:
Bacterial luminescence dilution factor in the effluent of central WWTPs
Number of plants reporting data
Out of the 63 WWTPs, 19 (16 from DE, 1 from FR, 1 from IT and 1 from CEFIC) reported
bacterial luminescence toxicity values in the effluent (or 30 %). Installation #41 (FR) reported
toxicity values in Equitox/m3 stemming from the commercial Microtox® test. Conversion to
LID values is not straightforward.
Peaks of emissions
Peaks occurs at installation #11 (DE) and #14 (DE) where a LID value of 4 is reported, at
installation #01 (DE) where a LID value of 5 is reported, at installation #15 (DE) where a LID
value of 7 is reported, and at installation #06 (DE) where LID value of 12 is reported.
Averaging periods used for reporting emissions
Averaging periods are generally not indicated (yearly averages are indicated for two sites).
Average values are based on a number of measurements spanning from 5 to 20.
Reported achieved performance
The toxicity to luminescent bacteria in the effluent of central WWTPs is given in Table 2.44.
108
November 2010SR/EIPPCB/Analysis questionnaires CWW
Parameter
Minimum
10th
percentile
25th
percentile
50th
percentile
75th
percentile
90th
percentile
Maximum
Toxicity to
luminescent
bacteria
(LIDL)
1 (1)
1 (2)
1 (3)
2 (4)
4 (5)
7
12
(1) #03 (FR) yearly average of 4 samples of the supervisory body.
(2) #08 (DE) averaging period and number of samples not indicated.
(3) #22 (CEFIC) averaging period and number of samples not indicated.
(4) #12 (DE) averaging period and number of samples not indicated.
(5) #11 (DE) average based on 22 measurements.
Table 2.44:
Toxicity to luminescent bacteria in the effluent of central WWTPs
SR/EIPPCB/BP CWW TWG subgroup
November 2010
109
3 Discussion concerning the variability of monitoring results
The information in this section is mainly drawn from the 'Statistical analysis of monitoring data
from waste water effluents of the chemical industry' – Input of the German delegation to the
TWG BREF CWW document dated 24 March 2010 submitted by Heino Falcke.
In technical terms, the spread or variability is mainly influenced by temporary changes of the
raw loads, compensatory measures (e.g. staple tanks) and the elimination rates (and maybe the
formation of substances) at the waste water treatment plant.
Parameters are expected to show a low spread when many productions at the site contribute to it
(e.g. waste water flow and TOC at large sites; comparison of the spread of TOC and AOX).
The variance associated with the sampling and chemical analysis may influence the results
especially at values near the detection limit.
In some cases, a high spread of the data may reflect the fact that there is little reason in
controlling the variation (e.g. when there is a further treatment in a municipal treatment plant or
when values are far below the emission limit values set in the permit).
The document concludes that as a fairly reproducible measure for the spread of data, Germany
prefers the 90th percentile respective the ratio of 90th percentile and average value. Depending
on the parameter, most of the data sets show a ratio of <2. Higher ratio values may be found
when average values are low or when significant trends 2007 – 2009 give an additional spread.
110
November 2010SR/EIPPCB/Analysis questionnaires CWW
4
ANNEXES
4.1
Members of the CWW TWG subgroup for the analysis of
questionnaires
Belgium:
An Derden (VITO)
Czech Republic:
Jana Brabencová (CENIA, Czech Environmental Information Agency)
France:
Pierre Chrisment (DRIRE Lorraine)
Rodolphe Gaucher (INERIS)
Pascale Vizy (Ministry for Ecology, Energy, Sustainable Development and the Sea)
Italy:
Nicoletta Trotta (Ministry of Environment)
Germany:
Heino Falcke (Landesamt fuer Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen)
Dieter Kaltenmeier (Regierungspräsidium Freiburg)
Portugal:
Inês Brás (Environment Portuguese Agency)
Célia Maria Peres (Environment Portuguese Agency)
Industry:
Stefan Dommes (CEFIC)
Peter Hartl (CEFIC)
Nicolas Lesage (CEFIC)
Nathalie Swinnen (CEFIC)
Gerhard Zimmer (CEFIC)
European Commission:
Achim Boenke (DG ENTR)
Thomas Brinkman (DG JRC/IPTS/European IPPC Bureau)
Serge Roudier (DG JRC/IPTS/European IPPC Bureau)
SR/EIPPCB/BP CWW TWG subgroup
November 2010
111
4.2
Mandate of the CWW TWG subgroup and working
methods
The TWG subgroup agreed to the following mandate for its work:






better understand/explain how data have been collected and presented (e.g. are the
maximum values real or have outlier values been removed?);
evaluate the questionnaires received, explain reasons for the environmental performance
displayed, help identify inconsistencies/errors and help correct them;
eliminate/remove double counts;
identify needs for further information (e.g. data requested but not provided in the
questionnaires, information not requested in questionnaires but deemed necessary such
as the illustration of the variability of some parameters over a certain period of time);
determine parameters important in the determination of BAT;
help determine the best way to present the information from the questionnaires in the
BREF.
No final decisions affecting the BREF, BAT or BAT-AELs will be made by the subgroup. The
TWG subgroup will make recommendations for the whole TWG to consider.
One issue that is not within the mandate of the CWW TWG subgroup includes the proposals for
BAT conclusions and associated emission and consumption levels which will be made by the
EIPPCB taking into account discussions within the CWW TWG subgroup.
112
November 2010SR/EIPPCB/Analysis questionnaires CWW
SR/EIPPCB/BP CWW TWG subgroup
November 2010
113
5
REFERENCES
Chemistry for Environmental Engineering and Science, fifth Edition
114
November 2010SR/EIPPCB/Analysis questionnaires CWW