RAPPORT
Full-scale site solution of
phosphorous retrieval from
biowaste - make way for recycling
of cadmium contaminated biowaste
as phosphorous fertilisation
Short literature summary
For NORDIC INVESTMENT BANK / NEFCO
2013-02-26
Arkivnummer: U4184
Fredrik Norén, Kåre Tjus, Uwe Fortkamp
Box 21060, SE-100 31 Stockholm
Valhallavägen 81, Stockholm
Tel: +46 (0)8 598 563 00
Fax: +46(0)8 598 563 90
www.ivl.se
Box 5302, SE-400 14 Göteborg
Aschebergsgatan 44, Göteborg
Tel: +46 (0)31 725 62 00
Fax: + 46 (0)31 725 62 90
Innehållsförteckning
1
2
Intro .............................................................................................................................................2
Removal of excess macroalgae from shores ..........................................................................2
2.1
Beach cleaning – ecosystem services ..............................................................................2
2.2
Available biomasses ..........................................................................................................3
2.2.1
Shore algae and biogas potential .............................................................................3
2.2.2
Other substrates that can be used in the process .................................................3
2.3
Biogas potential and production .....................................................................................4
2.3.1
Biogas potential from shore algae ..........................................................................4
2.4
Removal of phosphorus from wastewater.....................................................................5
2.4.1
Possible methods for phosphorus removal ..........................................................6
2.4.2
Large scale technologies in use ...............................................................................7
2.4.3
Description of techniques........................................................................................8
2.4.4
Phosphorus recovery ................................................................................................9
2.5
Separation of heavy metals ..............................................................................................9
2.5.1
Specific use in the macroalgae case ..................................................................... 10
2.5.2
Alternative method with adsorption ................................................................... 11
3 References ................................................................................................................................ 15
1
1 Intro
This report gives a short literature background to the PhosCad project.
2 Removal of excess macroalgae from shores
2.1 Beach cleaning – ecosystem services
Ecological and physical parameters from beach cleaning has been measured by (Malm et
al. 2004). Their findings are summarized in Table 1. They also find a qualitative
improvement of the beaches: “The organic content of the sand was reduced by beach cleaning at
northern Öland, giving a brighter appearance to the shore and increased stability for visitors walking along
the beaches.”
Table 1. Summary of effect on cleaned and uncleaned beaches. Data compiled from Malm
et al 2004.
Oxygen and pH
Total nitrogen
Ammonia
Organic content in sediment
Water visibility (secchi depth)
Bacterial abundance
Protist abundance
Species abundance
Cleaned beaches
Uncleaned beaches
No difference
No difference
Lower conc. of
ammonia in water
Lower carbon content
in outside sediment
Improved outside water
visibility a
Lower bacterial
abundance (3 times) in
water
Higher abundance
of bacterivore
ciliates
No difference, except for mysid shrimps in
higher abundances outside uncleaned
beaches.
a
Significant difference for intensively cleaned and uncleaned. No effect for moderate
cleaned beaches.
Long-time harvest of shore macroalgae was studied in Australia (Lavery, Bootle, and
Vanderklift 1999). The results showed that harvested beaches suffered in the short timescale (days-weeks) from the harvest but the beach thereafter was more similar to a
“natural” shore with small amounts of macroalgae. They conclude that beach-cleaning is a
possible management tool for eutrophicated areas.
Other ecosystem services/costs are discussed in (Weslawski et al. 2000; Troell et al. 2004;
Morand and Briand 1996).
2
Best time to harvest beach cast algae is before and after the summer period (May and
September) according to (Karlsson 2009) and references therein.
Management of beach-cleaning is discussed by Bladh (2011), the author states that it is
important to avoid extra damage by the harvesting machines such as diesel/oil slips and
plan harvest time with animal protection in mind.
2.2 Available biomasses
2.2.1 Shore algae and biogas potential
The biomass of algae on vicinity of Simrishamn is presented in Table 2. The potential
biogas production is also included and ranges from 130 – 250 Nm3/ton VS (volatile
substance – carbon) with a mean of 200 Nm3/ton VS (seven studies and references in
Bergström 2012). A case where Karlsson (2009) extrapolates the beach algae to a larger
area is also included but has a small significance for this project.
Table 2. Literature data on available algae biomass in Simrishamn. References a.
Bergström (2012) b. Karlsson (2009) c. Gradin and Tjernström (2012). All calculations are
based on 200 Nm3 CH4/ton VS (see Table 3)
Yearly biomass production
Beach algae yield
Data from Simrishamn
2001-2004
Potential harvest from 30
km
Potential harvest from 30
km [maximum harvest]
Potential harvest from
water
Potential harvest from
Simrishamn area
Harvest from Malmö Simrishamn
Wet weight
(ton)
Dry weight
(ton)
Carbon (ton,
VS - volatile
substance)
Potential CH4
prod (Nm3)
Ref.
620
93
27,9
5.580
a
3.500
525
157,5
31.500
a
10.500
1575
472,5
94.500
a
1.200
180
54
10.800
a
70.000
10.500
3.150
630.000
c
287.120
43.068
12.920,4
2.584.080
b
The biogas potential from beach algae has been studied by several authors and we refer to
(Nkemka and Murto 2010; Nkemka 2012; Davidsson and Ulfsdotter Turesson 2008) that
has studied anaerobic digestion on local beach algae.
2.2.2 Other substrates that can be used in the process
There could be a benefit for the treatment of algae if the treatment plant (let’s assume an
anaerobic digester) is in use 100 % of the time. It is also positive to dilute salts from the
marine substrate with low saline substrates and to feed the bacterial process the whole year.
This can be achieved by adding municipal organic waste, garden or park waste and reed or
other wet land biomass. Trelleborg waste deposit site accepted 1593 tons of garden and
park waste and 6452 tons of biodegradable waste (year 2002) and Simrishamn accepted 82
tons of garden and park waste and 3724 tons of biodegradable waste (Avfall Sverige 2003).
Reed or wetland biomass has been studied for biogas production by the Wetland-AlgaeBiogas project (Wetlands Algae Biogas - A Southern Baltic Sea Eutrophication Counteract Project.
3
Final Report. 2012) but the potential harvest from such substrate was not stated in the
report. The WAB report (ibid.) reported the biogas potential in the Skåne and Trelleborg
area for several municipal and farming biogas substrates and where crop residues
dominated with 933 GWh from straw and 874 GWh from other crop residues
In a recent paper good results were obtained with wheat straw that was pretreated and codigested with lysate (“hydrolysate”) from beach algae and the biogas production ranged
from 220-300 Nm3/ton VS (Nkemka and Murto 2013). Since straw has been considered a
low efficient biogas substrate this result is interesting and the substrate are easy available. In
the Wetland-Algae-Biogas project (Ksawery, Ziolkowski, and Tonderski 2012) it is reported
that ~4500 tonnes of wetland plants can be harvested from sewage pumping stations (in
the Polish region Sopot). It is not studied if this is a possible substrate in the Trelleborg
area, but could be investigated.
2.3 Biogas potential and production
2.3.1 Biogas potential from shore algae
Several studies have been conducted to evaluate biogas production potential from algae
(Kelly and Dworjanyn 2008) and from beach-cast algae specifically (Table 3). It is clearly
shown that different algae and algal mixtures have different biogas potential and that
harvest period, pre-treatment and co-digestion with other substrates affects the biogas
potential. Fresh and wet algae has higher biogas potential than old and dried algae as
example.
4
Table 3. Summary of biogaspotential from beach cast algae and similar substrates.
Litterature: (Melin 2001; Wetlands Algae Biogas - A Southern Baltic Sea Eutrophication Counteract
Project. Final Report. 2012; Nkemka and Murto 2011; Nkemka and Murto 2010; Morand and
Briand 1999; Bergström 2012; Davidsson and Ulfsdotter Turesson 2008)
Nm3 CH4 /ton period
VS
(days)
Note
Green algae
32 Cladophora
Cladophora (boiled
in NaOH and
125 mixed)
Reference
50:50 Municipal organic waste : algae
200
50:50 Municipal organic waste : algae
290
100 % Municipal organic waste
450
100 % Beach cast algae
170
Ulva
cited in Melin 2001
100 % Beach cast algae
100
Ulva
cited in Melin 2001
Ulva, Cladophora
Hansson 1983
100 % Beach cast algae
Melin 2001
Melin 2001
Melin 2001
90-330
100 % Blue mussels (Mytilus edulis)
330
100 % Reed (Phragmites)
212
100 % "raw seaweed"
120
Nkemka et Murto 2010
170
100 % leachate from "raw seaweed"
200-240
Sea Lettuce
80-110
40 UASB rector (dry)
107
Nkemka et Murto 2011
Nkemka et Murto 2011
Mixed samples from beach
130-220
Mixed sample
160-250
-IIBriand et Morand 1997 (Ulva
sp 1)
Nicolini et Viglia 1985 (in
Bergström 2012)
Mustafic et al 2009 (in
Bergström 2012)
Linné et al 2003 (in
Bergström 2012)
Mixed sample
190-220
Davidsson et al 2008
Sea Lettuce
2.4 Removal of phosphorus from wastewater
In recycling of phosphorus (P) from a treatment plant, it is important to characterize the
possible removal paths; from the fluid or from the solid sludge. Most methods are designed
for one of those fractions and can be categorized into chemical or biological removal of
phosphorus, see fig Figure 1.
The technologies for recycling of P based on biological methods are commonly called BioP methods, and they utilize certain GAO bacteria that can incorporate P and thereafter
release P under anaerobic conditions. This method is suitable for both fluid and solid
waste. The second common method is chemical precipitation with aluminium-, calcium- or
ferric-oxides and the formation of phosphates. This reaction is done in the primary
settlement stage or in a separate stage, i.e. before the sludge formation.
If the P removal is done from incinerated sludge ash, it is important to distinguish sludge
based on precipitation chemical or if Bio-P was used (Stark 2005). In Sweden the mostly
used precipitation chemical is ferric chloride.
The proportion of treatment plants that are using Bio-P is ~5 % in Sweden (but e.g. 37 %
in Germany).
5
Figure 1. Illustration of different places of installation of phosphorus recovery units (From
(Cornel and Schaum 2009)
The German project ProPhos (Petzet et al. 2011) studied different methods to remediate
phosphorus from sewage water, sludge and ashes, and several large scale studies were
conducted. Tyrens perfomed a study for different technologies for the Swedish
Environmental Protection Agency (Naturvårdsverket, 2013).
2.4.1 Possible methods for phosphorus removal
Based on experience from Bio-P treatment plants some results can be found; a) Small
variations in P-concentration is found over the year but larger variations is found during
one day. b) The stabilized sludge is a better fraction to remove P from than in the raw
waste water – even if the higher TS make separation more difficult. c) The phosphorus
removal is dependent on the age of the sludge and d) P-removal before the anaerobic
phase is preferable.
Based on results from struvite precipitation (MAP, MgNH4PO4) it is concluded that
30 mg P/l is a lower technical limit for MAP precipitation. The economical feasible limit is
>200 mg P/l. High levels of DS (dry substance) increases the time needed for
precipitation.
6
2.4.2 Large scale technologies in use
Swedish methods are presented in Tideström (2009). Other methods have been presented
in Pinnekamp et al (2011) and by the Tyrens study (2013).The cost for commercial
methods in use is presented in Table 4.
Table 4. Summary of costs phosphorus removal technologies
Method
Euro per kg P
Pasch
4,40
Crystalactor
5,9-6,8
Phosnix
7,7-9
P-Roc
3,0-12
Direkt upparbetning av
1, fosfor i löst form
avloppsslamaska med
behöver fällas
tungmetallavskiljning
Fix-Phos
2,0 -7
Phoxnan
11-25,0
SesalPhos
7,5-9
Ostara
10
Berlin /Airprex
3
Seaborne
46
Ash Dec
2,20
Reference
Pinnekamp et al (2011)
Nieminen (2010)
Pinnekamp et al (2011)
Pinnekamp et al (2011)
Pinnekamp et al (2011)
Pinnekamp et al (2011)
Pinnekamp et al (2011)
Pinnekamp et al (2011)
Nieminen (2010)
Nieminen /Tyréns
Nieminen (2010)
Pinnekamp et al (2011)
Phosphorus remediation using struvite has been reported by (Fransson et al. 2010). They
found >90 % phosphorus removal in some cases and very low removal in other using this
method on anaerobic digested sludge. The cost for chemicals in this method is ~1,5 – 2€.
7
2.4.3 Description of techniques
Table 5. Summary of technologies of heavy metal removal, based on (Pinnekamp et al
2011)
Complexity
Efficacy
Profitable
Quality of
product
No new
Experience
environmental full scale
problem
use
Method
to
separat
e
Method to
Process- phosph separate heavy Euro per kg
Placement flow
orous
metals
phosphorus
Removal from liquid phase
Bioptech
d
A
Ads.
sel.phos.liq
Phostrip
+
o
o
+
+
o
d
B
Crys.
sel.phos.liq
Prisa
+
o
o
+
+
o
d
B,C
Crys.
sel.phos.liq
7,7 to 8,9
Crystalactor
+
o
+
+
+
+
d
B,C
Crys.
sel.phos.liq
5,9-6,8
Pearl Ostara
+
o
+
+
+
+
d
B,C
Crys.
sel.phos.liq
Phosnix
o
o
o
+
+
+
d
B,C
Crys.
sel.phos.liq
P-RoC
o
o
o
o
o
o
d
B,C
Crys.
sel.phos.liq
Recyphos
o
o
o
o
o
-
d
A
Ads.
sel.phos.liq
Phoseidi
o
o
o
o
o
-
d
B,C
Crys.
sel.phos.liq
Ekobalans
o
o
o
+
+
(o)
d
B
Crys.
sel.phos.liq
10
3 to 12
Removal from sludge without leaching
Berlin*
o
-
o
+
+
o
d
4 Crys.
sel.phos.liq
FIX-Phos
o
-
o
o
+
-
d
4 Crys.
sel.phos.sol
Airprex
o
-
(+)
+
+
o
d
4 Crys.
sel.phos.liq
+
d
5 Crys.
acid+complex
+
d
4 Crys.
acid+membr.
3
2 to 7
Removal from sludge with leaching
Stuttgart processen
+
Phoxnan
11 to 25
Seaborne
-
+
-
+
-
o
d
5 Crys.
acid+Me-sulfide
Loprox/PHOXNAN
-
+
-
+
-
-
s
4 Crys.
acid+membr.
46
Aqua Reci
-
+
-
+
-
o
s
4 Crys.
sel.acid,acid+Me-prec.
Cambi
-
+
-
+
-
o
s
5 Crys.
no info
Krepro
-
+
-
+
-
o
s
5 Crys.
no info
+
o
o
-
-
c
6 Crys.
acid+P-prec.
c
6 Crys.
Removal from ash - wet chemistry
Sephos
-
SesalPhos
acid+P-prec.
7,5 to 9
PASCH
-
+
o
+
o
o
c
6 Crys.
HCl +solv.
4,40
BioCon
-
+
o
m.d.
m.d.
m.d.
m.d.
6 Crys.
H2SO4+ionX
BioLeaching
o
+
o
+
o
-
c
6 Crys.
bact.diss. P ,sel.phos.liq
Leaching with H 2SO4+Me sep. o
+
+
(+)
o
(+)
c
6 Dissolvedacid+Me-prec.
1
Removal from ash - thermic metallurgic
Mephrec
o
+
o
o
o
o
s
6 in ash.
melt + gas
Ash Dec
o
+
(+)
(+)
o
o
c
6 in ash.
sel.MeCl
Removal from partial flows (urine and faeces)
Precipitation
+
+
o
+
o
o
d,s
Crys.
Evaporation
o
+
o
+
o
o
d,s
Crys.
Compost
+
o
o
+
+
+
d,s
In compost
Process water
A) Outgoing water
B) Reject water from different
partial flows, e.g. Bio-P
C) Water from sludge dewatering
Placement
d) Decentral
s) Semicentral
c) Central
Methods for metal separation
sel.phos.liq
Selective phosphorus leaching in liquid phase
acid+complex
Acid leaching and compexation of metals
sel.acid
Selective acid leaching of phosphate
acid+Me-prec. Acid leaching and selective precipitation of heavy metals
acid+P-prec.
Acid leaching and selective precipitation of phosphorus
sel.MeCl
Selection before incineration
sel.phos.sol
Selective phosphorus precipitation in sludge
acid+membr.
Acid leaching and membrane selection of phosphate
acid+Me-sulfide Acid leaching and sulphide precipitation
melt + gas
Metals melts at 2000 C and is separated in fume
HCl +solv.
Acid leaching HCL and extraction of M-Cl complex
H2SO4+ionX
Acid leaching H2SO4 and ionic exchange of heavy metals
bact.diss. P
Leaching of phosphorus from ash with bacteria
8
2,2
2.4.4 Phosphorus recovery
Table 2 lists techniques for phosphorous recovery. For water solutions, crystallization of
phosphorus crystal, CaPO4 or MgNH4 PO4, struvite, are the most common methods to
recover phosphorus, but adsorption on natural or synthetic material are also possible
methods. For crystallization mostly Mg + NaOH or Ca(OH)2 are added, but in some
processes the calcium present in the solution can be used for precipitation and only
addition of crystal seeds are needed.
The amount of phosphorus that can be recovered is in the range 30-80 %. It is
advantageous for the recovery efficiency if Bio-P is used. It is also possible to either treat
the sludge or the ash after incineration of sludge to get out a recoverable phosphorus
fraction.
The AirPres Berlin method strips the CO2 in the sludge after the anaerobic which rises the
pH, thus no extra base but only magnesium is needed to form struvite. The formed struvite
crystals can be separated gravimetrically from the sludge and after washing used as nutrient.
In the Fix –Phos-process, calcium silicate hydrate is added as seed into the anaerobic
reactor. After 10 days CaPO4 crystals are formed that can be separated from the sludge by
sieves.
In other methods the sludge is treated with acids in order to dissolve the phosphate before
crystallization. These methods are more effective but also more costly due to increased
chemical costs. Another alternative is to use bacteria for leaching of phosphorus from ash
in the bioleaching process
For ashes mostly acid is used to dissolve the phosphorous, but for Memphrec and Ash
Dec, the phosphate is recovered from sludge before burning.
2.5 Separation of heavy metals
When separating phosphate crystals from outgoing water, reject water, and water from
sludge dewatering, the heavy metals will be remain in the sludge. Sludge is treatment with
acid before crystallisation for better phosphorus recovery also causes dissolution of heavy
metals. Different methods are used to separate these metals from the phosphorous. In the
Stuttgart process metal complexation with citric acid is used. Other methods are
membranes (Phoxnan), sulphide removal (Seaborne), solvent extraction (Pasch), ionexchange (Bio-con).
It was shown that it is possible to dissolve phosphorous from ashes without dissolving
heavy metals. This method still might need a separation of heavy metals from the acid after
dissolution might be used (Aqua Reci method with super critical treatment of sludge).
It is also possible to separate heavy metals in the burning process, in Ash Dec metals are
forming metal chlorides before incineration by addition of chloride salts, these metals
chlorides have lower vaporisation temperatures than the metals and can after vaporisation
be separated from the gases. In the Mephrec method, the burning is proceeded at higher
temperatures, 2000 °C, so that all heavy metals are evaporated without addition of
chlorides. In both processes phosphorus is staying in the ash.
9
2.5.1 Specific use in the macroalgae case
With the limited data available for treatment costs, Ash Dec is a promising alternative from
a cost perspective; however it is intended to be used for large units, treating 25000 tons of
ash per year. If all algae between Simrishamn and Malmö are used for biogas production a
sludge amount of 43.000 tons of dry biomass can be harvested. In a shorter perspective
this method could be of interest if it is also used for other biogas sludge applications. In
that case the biogas sludge from algae could be used in the same unit.
Also leaching from ash with sulphuric acid followed with metal precipitation is cost
effective, but central method. However, the cost do not include phosphor removal, the
phosphorous acid is meant to be used as chemical for fertilizer production. Furthermore, it
is important that the iron content is low in the phosphorous acid, which might not be the
case if origin if sludge if iron chloride precipitation is used for phosphorus-removal.
Another interesting method if not only the phosphorus fraction but also the nitrogen
fraction are of interest is the use of N-recovery methods as demonstrated by the Swedish
firm Ekobalans.
One important question in phosphorus recovery methods including separation of cadmium
from phosphorous is the use of the residue. Methods that selectively removes phosphorous
from the sludge, will give a remaining sludge with less value. Also the phosphorus recovery
rate is in many cases not high.
Methods that selectively remove heavy metals from sludge such as ion exchange or
selective sulphide precipitation can be interesting. An important aspect is if the acid
content in the acidification step for biogas is sufficient to dissolve cadmium. The Stuttgart
process for example uses pH below 2. Pre-hydrolysis will only result in pH 4 but it could
work by addition of HCl or organic acids to achieve pH 3. Also the cost for the addition of
NaOH and the problem with the Cadmium chitosan residues are important to consider.
10
2.5.2 Alternative method with adsorption
2.5.2.1
Methods using organic waste
There is a growing literature on the use of organic waste as adsorbents and ion-exchange
material and their role in removal of heavy metals in contaminated matrixes. The field is
partially included in section 2.5.1 based on available techniques. This section deals with
organic adsorbents from a more development point and may not be commercial available
yet.
Some adsorbent have very high capacity to adsorb cadmium, in Table 7 data are compiled
from a large review of organic adsorbents with cellulosic origin, and e.g. Eucalyptus, brown
algae, saw dust and some carbons have capacities to remove up to 200 mg Cd/g adsorbent.
A more ~conservative removal capacity is estimated to 20 mg Cd/g adsorbent.
In the case of removing all cadmium from a treatment plant in Simrishamn, the amount of
organic adsorbent that would be needed to remove 2 – 16 kg Cd could be estimated to be
less than 10 tonnes (assuming a adsorption capacity of 20 mg/g DW and a process efficaty
of 10 %), see Table 6.
Research has been conducted by Yulia Kalmykova at Chalmers that reported a high Cd
removal with shrimp shells rich in the substance chitosan (Kalmykova 2009; Kalmykova,
Strömwall, and Steenari 2008). The adsorption potential of different organic materials (all
were waste material) and chitosan was the most promising agent. Kalmykova et al. (2009)
also investigated the effect of salinity, low temperature and drying on the adsorbent, the
results shows low inference on the adsorption from those factors. In the case of salinityaddition the adsorption decreased during a period but adjusted to the new environment
after a short time.
(Nkemka and Murto 2010) reported a cadmium removal of 75% by using a cryogenic gel.
This is the same percentage removal reported by (Davidsson and Ulfsdotter Turesson
2008). The total removal is calculated as both the extraction and adsorption of cadmium.
Table 6. Amount of adsorbent needed to remove cadmium in a treatment plant in
Simrishamn
Adsorbent capacity (g Cd/kg DW) =
0,1
Amount Cd to
remove (kg)
Data from 2001-2004
Harvest from 30 km
Harvest from 30 km [maximum
harvest]
Harvested from water
Potential harvest from Simrishamn area
Adsorbent (kg) @
efficacy = 10%
0,14
75
0,79
400
2,36
0,27
15,75
11
1250
125
7500
Table 7. Summary of different adsorbents of interest. Compiled from (Hubbe, Hasan, and
Ducoste 2011).
Adsorbent
Papaya (hardwood)
Spruce sawdust, phosphorylated
Juniper fiber
Juniper wood
Pinus sylvestris, hardwood
Pine bark
Pine bark
Pine bark
Tree barks
Eucalyptus
Pine bark
Eucalyptus (bark)
Coniferous bark
Juniper bark
Bark
Conifer needles
Petiolar sheath
Tobacco dust
Teak leaves
Pine cone
Brazil nut shell
Hazel nuts
Hazel nut shell
Coconut copra
Coconut copra
Green coconut
Rice husk
Rice husk
Rice husk
Rice husk
Rice husk
Lathyrus husk
Black gram husk
Black gram husk
Mung bean husk
Rice husk
Rice husk
Sargassum algae
Sargassum algae
Laminaria japonica
Seaweed waste
Sargassum fluit.
Chlorella vulgaris
Fucus spiralis
Oedogonium
Oedogonium
Fucus dead
Three brown algae (asco, fucus,
sargassum)
Marine algae
Fucus vesiculosus
Aeromonas cavi. (bacteria)
Pantoea (bacteria)
Streptomyces (bacteria)
Staphylococcus
Saccharomyces (yeast)
Penicillum (fungi)
Various fungal
Lignin isolated
Pulping ligning
Capacity (mg/g
DW)
18-142
56
9-30
3
9
Note
Phosphorylated
NaOH
Smaller particles higher
uptake, higher pH gives
better results
9-38
10-13
12-20
47
15
50
252
10-14
10
28
8-18
11
30
30
2-11
19
3,5
5
36-47
1,7
236
90
24-27
8
8-20
12
35
39
40
36
1,5
9-20
71
103
124
60-140
34-302
87
64
80-89
31-35
90
Higher pH favored
Pellets, citric acid
CH2O
CH2O
best pH 5,5
PO43H2SO4
Ca, Mg
Epichlor
Na2CO3
95% uptake
regen with HCL
regen with HCL
Epichlor
diff treatments
dead algae
dried algae
dried +NaOH
dried + acid
73-215
124
337
124-155
54
63
164
3-70
210
31-63
48
8
CH2O, best pH 3,5
CaCl2, heat
CH2O
PAA
12
Reference
Iqbal et al 2007
Holan et Volesky 1995
Min et al 2004
Shin et al 2004
Taty - Costodes et al 2003
Al-Asheh et Duvnjak 1998
Argun et Dursun 2008
Argun et al 2009
Gaballah & Kilbertus 1998
Ghodbane et Hamdaoui 2007
Oh et Tshabalala 2007
Saliba et al 2002
Seki et al 1997
Shin et al 2007
Randall et al 1974
Aoyama et al 1991
Iqbal et al 2002
Qi et Aldrich 2008
Rao et al 2010
Argun et al 2008
Basso et al 2002
Bulut et Tez 2007
Cimino et al 2000
Ho et Ofomaja 2006
Ofomaja et Ho 2008
Pino et al 2006
Ajmal et al 2003
El-Shafey 2007
Krishnani et al 2008
Kumar et Bandyopadhyay 2006
Kumar et Bandyopadhyay 2007
Panda et al 2006
Saeed et Iqbal 2003
Saeed et al 2005
Saeed et al 2009
Tarley et Arruda 2004
Upendra et Manas 2006
Chen et Yang 2005
Fourest et Volesky 1996
Ghimire et al 2008
Romero-Gonzales et al 2001
Scheiwer et Volesky 1995
Aksu et Donmez 2006
Cordero et al 2004
Gupta et Rastogi 2008
Gupta et Rastogi 2009
Herrero et al 2006
Holan et al 1993
Matheickal et al 1999
Rincon et al 2005
Loukidou et al 2004
Ozdemir et al 2004
Selatnia et al 2004
Ziagova et al 2007
Various
Deng et Ting 2005
Yin et al 1999
Basso et al 2004
Calik et Demirbas 2005
Adsorbent
Capacity (mg/g
DW)
Kraft lignin
Kraft lignin
Tannic acid
Compost
Peat moss
Anaerobic sludge
Sugar bagasse
Chitosan cellulose
Cellulose
Cellulose
52
137
1,5
18
32
60
88-149
36
180
86
Undaria pinnifatida
30 strains
Cellulose
Cellulose powder
Saw dust
Wood meal
Bakers yeast
Activated carbon (bean husk)
Pecan shell
Date pits
Carbon
Flax shive (carbon)
Sugar beet pulp
Bagasse fly ash
high
269
402
180
76-168
76-168
95
180
112
110-160
5-50
664
68-73
1-10
Note
DMF, ion exchange with
Ca
NaOH+EDTA
Succin.
Mercerized
Xanthation increased
adsorption 3x.
H3PO4
amidoxylated
amidoxylated
PAA, grafted
Acrylic acid
HNO3
Air, H3PO4
HNO3
H3PO4
H3PO4
Reference
Crist et al 2004
Mohan et al 2006
Ucer et al 2006
Ulmanu et al 2003
Sari et al 2008
Hawari et Mulligan 2006
Karnitz et al 2009
Zhou et al 2004
Belhalfaoui et al 2009
Gurgel et al 2008
Kim et al 1999
Klimmek et al 2001
Saliba et al 2001
Saliba et al 2002
Geay et al 2000
Marchetti et al 2000
Yu et al 2007
Chavez-Guerrero et al 2008
Dastgheib et Rockstraw 2002
El-Hendawy 2009
Various
Marshall et al 2007
Ozer et Tumen 2003
Various
Demirbas (2008) also reviews the literature and chemical processes of heavy metal
adsorption by organic substances.
13
2.5.2.2
Innovative steps
The processes of anaerobic digestion and metal recovery could be combined in the same
treatment/anaerobic digestion plant using organic adsorbents in direct connection to the
digester, see Figure 2.
UASB anaerobic digester with organic cadmium adsorbent
”Vassle” as acid stimulator
Beach algae
+
Municipal waste
In separate batches
Hydrolysis
Acidification
CH4
CH4
Perkulation
Grinder/
extruder
methanogenis
Soil
P-removal
Chitosan
NaOH
Cadmium removal in chitosan
Figure 2. Conceptual anaerobic process with cadmium and phosphor removal. Cadmium
is an active process (adsorption/ion-exchange) and phosphorus removal is a passive
process with the outgoing soil production.




The basic principle is that an UASB reactor can deal with solid waste such as algae
and municipal plant waste. The system is well proven.
o The content of sand is acceptable.
o Pre-treatment and harvest factors improving biogas yield are known for the
process
The liquid phase of the process is preferable to use as Cd removal using organic
adsorbents/ion exchange based on research literature
The solid phase may be extruded (crushed) on inlet to enhance Cd elution
o The diary waste product “vassle” will be used to lower pH
The process can accept batches of substrate (when algae are harvested) and in
meantime digest other sources of low-Cd material.
o Digested material will be composted from each batch (with CH4 capture)
and after Cd analysis mixed to sellable garden soil (once per year)
 Cd levels will be controlled in final soil
 Possible business case (“Buy a part of your cleaned beach”)
14
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17