Using On-line Monitoring as an
Effective Tool for Wastewater
Treatment Process Optimization
Ontario WEA
Wastewater Instrumentation &
Data Management Seminar
Milton, ON
May 30, 2013
Wei Zhang,
ASA Analytics, Inc.
www.asaAnalytics.com
Outline
• Wastewater Water Treatment Process
Optimization Issues
• Applications in Single Unit BNR process
– Nitrification
– Phosphorus Removal
• Case Histories
• Consideration of on-line process analyzer
selection
Why On-line Now?
• Regulations toward TN/TP
• Technology is more mature
• More sophisticated treatment processes
• Direct Benefit – Energy Saving,
Chemical Saving
Why Monitor Nutrients?
If You Want to Control
Process Chemistry, Measure
Process Chemistry
Challenges for Today’s BNR/ENR
• Facing total nitrogen and total phosphorus
limitation
• To provide a fast-response, flexible and
reliable system capable of handling highly
variable influent nutrient loads
• Energy Saving and chemical saving
• To minimize maintenance labor
Nitrification
• A aerobic biological process to convert
ammonia nitrogen to nitrate nitrogen,
reducing nitrification and toxicity caused
by ammonia.
• Typical treatment process
– Single Stage Nitrification
– Multi-Stage Nitrification
• Process consumes oxygen and alkalinity
(reduce pH)
Single-stage Nitrification
• Influent Ammonia < 30 mg/l
• On-line monitoring issue: pH, alkalinity, NH3, NO2, NO3
and DO, etc.
OH-
Primary Eff.
Aerobic
Final
Clarifier
RAS
WAS
Two-stage Nitrification
• Influent Ammonia 30~50 mg/l
• On-line monitoring issue: pH, alkalinity, NH3, NO2, NO3
and DO, etc.
OH-
Primary Eff.
OH-
1st Stage
Aerobic
Inter.
Clarifier
RAS
2nd Stage
Aerobic
Final
Clarifier
RAS
WAS
WAS
Process Control Indicators
• DO
– 4.6 lbs O2/lb NH3-N removal
– Maintain 1~2 mg/l in the aeration basin
• Alkalinity
– 7.2 lbs Alkalinity destroyed/lb NH3-N removal
– Maintain 50~80 mg/l Alkalinity in the aeration basin
• SRT (RAS Ratio and Temperature)
• Nitrogen profile through treatment train (increase
nitrite as first indication inhibitory of Nitrobacter
organisms, or incomplete nitrification)
Nitrogen Transformations
• Decline in ammonia
concentration
• Increase, then decline
in nitrite concentration
• Increase of nitrate to
stable maximum
• Only AFTER this is
any surplus DO
produced
Ask Question
about Nitrification Process
• How much oxygen is enough?
• How much alkalinity is enough?
Nitrification & Energy Saving
• City of Orlando WWTP (WEFTEC Proceeding 1999)
– 12 mgd plant with activated sludge process
– Using ChemScan analyzer generated nitrogen profile at each aeration
basin
– Set target setpoint/level of ammonia and nitrate in each tank
– Motorized air valves and air blowers in each tank are modulated to
maintain the selected nitrogen level.
– When ammonia level is higher than setpoint, air valves open to
increase nitrification. Conversely, nitrate level higher than setpoint,
air valve reducing air….
– If adjustment of air valve can’t maintain desired nitrogen level,
further blower adjustment kick-in
– ChemScan analyzer is the core part of the process control
Phosphorus Removal
• TP > 1.0 mg/L
– biological phosphorus removal
• TP < 1.0 mg/L
– chemical precipitation, or
– combination of chemical & biological
Chemical Phosphorus Removal
– Aluminum
Al2(SO4)3.(14H2O) + 2H2PO4- + 4HCO3- –»
2AlPO4 + 4CO2 +3SO42- + 18H2O
– Ferric Iron
FeCl3.(6H2O) + 2H2PO4- + 2HCO3- –»
FePO4 + 3Cl- + 2CO2 + 8H2O
– Side Reaction
Fe3+ + OH- → Fe(OH)3
– Ferric (or aluminum) hydroxide is formed, loss of
alkalinity
Right Amount of Chemicals
US EPA Nutrient Control Design Manual (2009)
– Alum to P molar ratio
• 1.38 : 1 for 75% removal
• 1.72 : 1 for 85% removal
• 2.3 : 1 for 95% removal
– Iron to P molar ratio
• 1 : 1 is required with a supplemental amount of 10 mg/l iron
added to satisfy the formation of hydroxide.
“Common Practices”
– The following methods are often used for
determination of “right amount” chemicals
– Jar Testing or Bench Testing
– Historical Trending
– Third Party Laboratory Analysis
– Plant’s Lab Analysis
– These methods are often labor and time
consuming.
Right Solution
– Online Phosphorus Analyzer
• Real time
• Continuous monitoring
• SCADA-linked for automatic dosing control
• Flexible for “feed forward” or “feed back”
control
– Key – Chemical Saving
Chemical Injection Locations
Primary Clarification
–Popular location for reducing P loading
–Feed forward control loop
–A precious control is needed to avoid nutrient deficiency to
biological process
–Might generate more primary sludge to handle
–Monitor locations: raw influent and primary clarifier effluent
End of Aeration Basin
–Another popular location for “polishing”
–Chemical usage are more efficient
–Feed back control loop
–Monitor location: secondary clarifier effluent or final effluent
Both locations
– S. Arant, Donohue & Associates, Inc.
AppliedSpectrometry
Associates, Inc.
Installations & Case Histories
– Kiel, Wisconsin
• 0.9 mgd Activated sludge process
• Phosphorus permit limit 1.0 mg/l
• A cheese factory is the major contribution source
• Online analyzer data “feed back” to SCADA for
ferrous sulfate dosing
• 20% chemical expense saving
Installations & Case Histories
– New London, Wisconsin
• 2 mgd Activated sludge process plant
• Phosphorus permit limit 1.0 mg/l
• Online analyzer data “feed back” to SCADA for
ferric chloride dosing control
• $900 per month chemical expense saving
Installations & Case Histories
– Sheboygan, Wisconsin
– WWTP servicing population of 50,000
– Current phosphorus limit is 1.0 mg/l
– Future phosphorus limit will be 0.05 mg/l
– Ferric chloride spending $160,000 annual with
current limits
– First online phosphate analyzer installed in 2010
– Second online phosphate analyzer just installed
– data “feed back” to SCADA for ferric chloride
dosing control
Installations & Case Histories
– Hite Creek, Kentucky
• Unpredicted phosphorus load from nearby
industrial source
• Using Alum solution for phosphorus precipitation
• Plant is able to set up improved alum feed rate for
different days of the week to match the expected P
load based, using 4 months’ data collected from
online analyzer
• Daily alum dosage reduced from 200 gallon/day to
100 gallon/day
Installations & Case Histories
• Waupun, WI
• Ferric to Primary only – total sludge: 5,560 lbs/d, total ferric: 190 gal/d
– S. Arant, Donohue & Associates, Inc.
AppliedSpectrometry
Associates, Inc.
Installations & Case Histories
• Waupun, WI
• Multiple Point – total sludge: 5,160 lbs/d, total ferric: 120 gal/d
– S. Arant, Donohue & Associates, Inc.
AppliedSpectrometry
Associates, Inc.
– S. Arant, Donohue & Associates, Inc.
AppliedSpectrometry
Associates, Inc.
– S. Arant, Donohue & Associates, Inc.
AppliedSpectrometry
Associates, Inc.
Using Ortho-phosphate to Control Ferric Feed
Figure 4-7
Phosphorus Removal with and without Reaction Tank
2.0
No Reaction Tank
Reaction Tank
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Influent OPO4-P Concentration (Online Data)
Influent OPO4-P (Lab data)
Influent TP (Lab data)
TP Limit
Effluent OPO4-P Concentration (Online data)
Effluent OPO4-P (Lab data)
Effluent TP (Lab data)
29-Jan
28-Jan
27-Jan
26-Jan
25-Jan
24-Jan
23-Jan
22-Jan
21-Jan
20-Jan
19-Jan
18-Jan
17-Jan
16-Jan
15-Jan
14-Jan
13-Jan
12-Jan
11-Jan
10-Jan
9-Jan
8-Jan
7-Jan
6-Jan
5-Jan
0.0
4-Jan
TP and OP Concentration, mg/L
Loading rate increased from
3.0 gpm/ft2 to 3.5 gpm/ft2
FeCl3
Pump
fault
Advanced BNR/ENR Processes
• Treatment plant facing discharge limitation
on both total N or total P
• Process involve more than one individual
BNR process
BNR Process Schematic
• Nitrification/Denitrification with chemical phosphorus
removal. No supplemental carbon
• Some simultaneous nitrification/denitrification (SND)
Caustic
Primary Eff.
AX
Alum
Oxidation
Ditch
AX
Final
Clarifier
RAS
WAS
Supplemental Carbon Feed Control
• Chemical feed can be 20~30% of entire operating cost
• Flow pace is still used in many plants
• Manual control based on grab sample is imprecise and
time consuming
• Manual control can lead to unnecessary chemical expense
and extra BOD discharge
• Underfeed supplemental carbon – incomplete
denitrification
• Chemical feed control scheme using nutrient
parameters are installed in many plants
BNR Process Schematic
• Post denitrification bio-filter
• Chemical feed control scheme using nutrient parameter is
well developed
Methanol
Denitrification
Filter
BOD Removal
Nitrification
BNR Process Schematic
• Modified Ludzack Ettinger (MLE) with supplemental carbon
Methanol
> 2Q
Primary Eff.
Anoxic
Aerobic
Final
Clarifier
RAS
WAS
BNR Process Schematic
• Bardenpho Process with post denitrification filter
• Two on-line nutrient analyzers
Anaerobic
Methanol
Denitrification
Filter
AX
Aerobic
AX
Final
Clarifier
RAS
Primary
Sludge
WAS
Denitrification Filter Using On-Line
Nutrients Signal in
Control Scheme (1)
Figure 4-12
Denitrification under Peak Hydraulic Loading Conditions
8.0
50
45
7.0
40
6.0
5.0
4.0
25
20
3.0
4.8 gpm/ft3 loading rate
6.0 gpm/ft3 loading rate
15
2.0
10
1.0
5
Influent NOx-N Concentration (Online data)
Influent NOx-N (Lab data)
Influent TN (Lab data)
Influent COD (Lab data)
Effluent NOx-N Concentation (Online data)
Effluent NOx-N (Lab data)
Effluent TN (Lab data)
Effluent COD (Lab data)
4-Mar
4-Mar
3-Mar
3-Mar
2-Mar
2-Mar
0
1-Mar
0.0
COD, mg/L
30
1-Mar
TN and NOx-N, mg/L
35
Denitrification Filter Using On-Line
Figure
4-13
Nutrients
Signal
in
Control
Scheme
(2)
Recovery of Denitrification After Peak Hydraulic Loading Event
8.0
No MeOH
No MeOH
7.0
6.0
4.0
3.0
2.0
1.0
Influent NOx-N Concentration (Online data)
Influent NOx-N (Lab data)
Influent TN (Lab data)
Effluent NOx-N Concentation (Online data)
Effluent NOx-N (Lab data)
Effluent TN (Lab data)
9-Mar
8-Mar
7-Mar
6-Mar
5-Mar
4-Mar
3-Mar
2-Mar
1-Mar
0.0
28-Feb
NOx-N, mg/L
5.0
An On-line Nutrient Monitoring Chart
Case Study: Bonnybrook WWTP Calgary, Alberta
Orthophosphate 4 Month Average Error 3.0 %
Orthophosphorous
Ammonia 4 Month Average Error 3.0 %
Ammonia
LAB
ChemScan
Nov - Dec 1996 and Jan - Feb 1997
LAB
ChemScan
Nov - Dec 1996 and Jan - Feb 1997
3
20
15
mg/l PO4-P
mg/l NH3-N
2
10
1
5
0
0
11/05
11/05
11/12
11/18
11/25
11/29
12/05
12/12
01/06
01/10
01/16
02/04
02/12
02/24
11/13
11/20
11/28
12/05
12/16
02/28
01/07
01/14
01/22
02/10
02/21
02/28
Sample Date
Sample Date
Orthophosphorous
Ammonia
ChemScan
+/- 5 % Error
Nov - Dec 1996 and Jan - Feb 1997
ChemScan mg/l NH3-N
ChemScan mg/l PO4-P
+/- 5 % Error
15
2
1.5
1
0.5
0
10
5
0
0
0.5
1
1.5
2
0
5
10
Lab mg/l PO4-P
15
Lab mg/l NH3-N
PHOSPHATE
UV-6100
AMMONIA
Lab
2.5
10
2
8
mg/l NH3-N
mg/l PO4-P
ChemScan
Nov - Dec 1996 and Jan - Feb 1997
1.5
1
0.5
UV-6100
Lab
6
4
2
0
0
-0.5
18
19
20
21
22
23
24
25
26
11/18/96 - 12/2/96
27
28
29
30
1
2
18
19
20
21
22
23
24
25
26
11/18/96 - 12/2/96
27
28
29
30
1
2
Case Study: Bonnybrook WWTP Calgary, Alberta
Nitrate 4 Month Average Error 1.7 %
Nitrate
TSS 4 Month Average Error 3.3 %
Total Suspended Solids
LAB
Nov - Dec 1996 and Jan - Feb 1997
ChemScan
40
20
30
TSS (mg/l)
15
mg/l NO3-N
Lab
Nov - Dec 1996 and Jan - Feb 1997
ChemScan
10
20
10
5
0
0
11/05
11/05
11/13
11/20
11/28
12/05
12/16
01/07
01/14
01/22
02/10
02/21
11/14
11/21
11/29
12/06
12/17
02/28
01/08
01/16
01/27
02/04
02/12
02/25
Sample Date
Sample Date
Nitrate
Total Suspended Solids
ChemScan
+/- 5 % Error
Nov - Dec 1996 and Jan - Feb 1997
ChemScan
+/- 5 % Error
25
10
ChemScan TSS (mg/l)
20
ChemScan mg/l NO3-N
8
6
4
15
10
5
2
0
0
5
10
0
2
4
6
8
20
25
10
Lab mg/l NO3-N
TSS CALIBRTION
NITRATE
UV-6100
Lab
ChemScan
120
10
100
8
80
mg/l TSS
mg/l NO3-N
15
Lab TSS (mg/l)
0
6
4
60
40
2
20
0
0
18
19
20
21
22
23
24
25
26
11/18/96 - 12/2/96
27
28
29
30
1
2
0
20
40
60
mg/l TSS
80
100
120
On-line Analyzer Selection
• Technologies
– Ion specific electrode
– Spectrophotometers
• Arrangement/configuration
– Single parameter vs. multiple parameters
– Single sample location vs. Centralized multiple sample
lines
• Look at the hidden cost
– Proprietary reagents vs. generic reagents
– some analyzers bundles with service contract
Summary
• If You Want to Control Process Chemistry,
Measure Process Chemistry
• Proven technology is available that can
provide reliable automatic chemical analysis
• Energy saving and Chemical saving
• Multi-parameter multi-sample line analyzer
system provides online nutrient analysis
required for BNR monitoring and control
Contact
Wei Zhang
ASA Analytics, Inc.
Waukesha, Wisconsin
(262) 391-8306
wei@chemscan.com
Local Contact:
Metcon Sales & Engineering, Ltd.
Concord, ON
(905) 738-2355
www.asaAnalytics.com