How Much is E “N”OUGH?
Optimizing Nitrification and Denitrification
at the Water Reclamation Plants
Joe Chang, Water Reclamation Plants
LA County Sanitation Districts:
Background Information
• Established in 1923
• Provide Wastewater and Solid Waste
Management for ~ 5.7 million people
• 1400 miles of main trunk sewers
• 11 wastewater treatment plants
• 3 active landfills
Presentation Outline
•
•
•
Regulatory Requirements
Nitrification/Denitrification Basics
Case Studies:
• Valencia WRP
New Nitrogen Discharge Limits
• In 1994, Los Angeles RWCQB set new
nitrogen discharge limits effective in 2003:
• Ammonia: Nominally 2 mg/L
• Nitrate + Nitrite: 10 mg/L (in some cases
lower)
Biological Removal of Nitrogen
Nitrification/
Denitrification (NDN) Process
Nitrification/Denitrification
++
NH
NH44 -- N
N
Nitrifying
Nitrifying
Bacteria
Bacteria
(Nitrosomonas)
(Nitrosomonas)
Ammonia
Ammonia
Aerobic
Aerobic
--
NO22 - N
Nitrifying
Nitrifying
Bacteria
Bacteria
(Nitrobactor)
(Nitrobactor)
Aerobic
Aerobic
Nitrite
--
NO33 - N
Nitrate
Denitrifying
Denitrifying
Bacteria
Bacteria &
&
Carbon
Source
Carbon Source
Anoxic
N22
Nitrogen
Gas
Oxidation Reaction
Reduction
Reaction
Nitrification
Nitrification
(Aerobic)
(Aerobic)
Denitrification
Denitrification
(Anoxic)
(Anoxic)
• Modified Ludzack Ettinger (MLE) NDN Process
Primary
Effluent
Anoxic
AnoxicZone
Zone
Aerobic
AerobicZone
Zone
Final
Clarifier
Tertiary
Treatment
Internal Recycle
Waste Activated
Sludge (WAS)
Return Activated Sludge
• Step Feed NDN Process
Primary
Effluent
Anoxic
Anoxic Aerobic
Aerobic
Anoxic Aerobic
Aerobic Anoxic
RAS
Final
Clarifier
Tertiary
Treatment
Waste Activated
Sludge (WAS)
Valencia Water Reclamation Plant
Valencia
JAO
Valencia WRP
Aerial
Aerial Photo
Photo
Six Flags Magic
Mountain
Santa Clara River
Golden State Freeway
North
Valencia Water Reclamation Plant:
Background Information
• Built in 1967
• Serves ~ 170,000 residents in Santa
Clarita Valley
• Rated for 21.6 MGD
• Current influent flow ~16 MGD
• Discharges to Santa Clara River
• Handles all solids from Valencia and
Saugus WRPs
Nitrogen Discharge Limits at
Valencia WRP
• In 1994:
RWQCB set new nitrogen limits effective in
June 2003:
Ammonia: 2.0 mg/L
Nitrate + Nitrite: 10 mg/L
Valencia WRP
Stage Five Expansion and NDN Facilities
GO BEARS
Valencia WRP
Aeration Modifications
RAS/Filtrate
RAS/Filtrate Treatment
Treatment Tanks
Tanks
it 1
n
U
it 2
n
U
it 5
n
U
it
Un
it 3
n
4U
Valencia WRP
Filtrate
Raw
Raw and
and Waste
Waste
Activated
Activated
Sludge
Sludge
(Valencia
(Valencia &
&
Saugus
Saugus WRPs)
WRPs)
Solids dewatering
filter press
Anaerobic
digesters
Valencia WRP
Filtrate
Raw
Raw and
and Waste
Waste
Activated
Activated
Sludge
Sludge
(Valencia
(Valencia &
&
Saugus
Saugus WRPs)
WRPs)
Biosolids
for land
application
Anaerobic
digesters
R A S/Filtrate
treatment tanks
Solids dewatering
filter press
Filtrate (1.5 MG/wk
ammonia conc. ~900 mg/l)
Valencia WRP
Filtrate
Raw
Raw and
and Waste
Waste
Activated
Activated
Sludge
Sludge
(Valencia
(Valencia &
&
Saugus
Saugus WRPs)
WRPs)
Biosolids
for land
application
Anaerobic
digesters
Solids dewatering
filter press
R A S/Filtrate
treatment tanks
Aeration
Units
Filtrate (1.5 MG/wk
ammonia conc. ~900 mg/l)
Valencia WRP
Ammonia Load
40
38.6
38.6
From
From Filtrate
Filtrate
30
Ammonia
Conc.
13.0
13.0
25.6
22.6
23.7
SJC-E
SJC-W
25.5
26.1
LC
LB
24.8
24.1
24.1
20
25.6
(mg/L)
10
0
VAL
POM
Water
WaterReclamation
ReclamationPlants
Plants
WN
SAUG
Valencia WRP NDN Start
-Up
Start-Up
••
••
Modified
Modified Ludzack
Ludzack Ettinger
Ettinger (MLE)
(MLE) Mode
Mode
Start
-Up began
Start-Up
began in
in May,
May, 2003
2003
Pri
Pri.. Effluent
Effluent
Anoxic Zone
150%Q
150%Q
RAS/Filtrate
RAS/Filtrate
IR
Aerobic Zone
Aerobic Zone
*
To Final Clarifiers
* Effluent
Sample
Goal
Ammonia (NH4+-N)
< 1 mg/L
< 2 mg/L
Nitrate (NO3--N)
14 mg/L
< 10 mg/L
Valencia WRP High Nitrate:
Rising Sludge
Rising
Rising Sludge
Sludge due
due
to
to high
high nitrate
nitrate
Normal
Normal situation
situation in
in
the
the final
final clarifier
clarifier
Mixed
Mixed Liquor
Liquor
sample
sample
NO3- - N
D
DN
N
Anoxic
Nitrate Anoxic
Solids settle to the
bottom of the tank
N2
Nitrogen
Gas
Valencia WRP Start
-Up Problems: Short
Start-Up
Circuiting
Primary
Primary
Effluent
Effluent
Aerobic
Aerobic Zone
Zone
Anoxic
Anoxic Zone
Zone
RAS/Filtrate
RAS/Filtrate
II R
R
Aerobic
Aerobic Zone
Zone
To
To Final
Final Clarifiers
Clarifiers
•
Internal Recycle Pump
Discharge piping:
30” diameter
Short Circuiting Solution
•• Eliminate
Eliminate Internal
Internal Recycle
Recycle flow
flow Short
Short Circuiting
Circuiting
• When IR rate at 250%Q: Effluent Nitrate: ~10 mg/L
Valencia WRP Start
-Up Problems:
Start-Up
Incomplete Denitrification
•• Not
Not enough
enough COD
COD available
available for
for
complete
complete denitrification
denitrification to
to occur:
occur:
•• Typically
Typically need
need 55 grams
grams COD
COD per
per gram
gram
NO
N for
for complete
complete dentrification
dentrification
NO33--N
•• Not
Not enough
enough retention
retention time
time in
in anoxic
anoxic zones
zones
Biological Removal of Nitrogen
Nitrification/
Denitrification (NDN) Process
Nitrification/Denitrification
++
NH
NH44 -- N
N
Nitrifying
Nitrifying
Bacteria
Bacteria
(Nitrosomonas)
(Nitrosomonas)
Ammonia
Ammonia
Aerobic
Aerobic
--
NO22 - N
Nitrifying
Nitrifying
Bacteria
Bacteria
(Nitrobactor)
(Nitrobactor)
Aerobic
Aerobic
Nitrite
--
NO33 - N
Nitrate
Denitrifying
Denitrifying
Bacteria
Bacteria &
&
Carbon
Source
Carbon Source
Anoxic
N22
Nitrogen
Gas
Oxidation Reaction
Reduction
Reaction
Nitrification
Nitrification
(Aerobic)
(Aerobic)
Denitrification
Denitrification
(Anoxic)
(Anoxic)
Incomplete Denitrification Solutions
•• Stopped
Stopped anionic
anionic polymer
polymer addition
addition at
at
Primary
Primary Tanks
Tanks
•• Extended
Extended anoxic
anoxic zones
zones from
from ~33%
~33% of
of tank
tank
volume
volume to
to ~50%
~50% of
of tank
tank volume
volume
Extended Anoxic Zone
Pri. Effluent
Anoxic Zone
(33%)
RAS/Filtrate
Aerobic Zone
IR
Aerobic Zone (67%)
To Final Clarifiers
Pri. Effluent
Anoxic Zone (50%)
RAS/Filtrate
IR
Aerobic Zone (50%)
To Final Clarifiers
Effluent Nitrate Results: Before and
After Modifications
Before units
modified
After all
units
modified*
* Six Month Average
Unit 3
NO3-- N
13 mg/L
Unit 4
NO3-- N
13.3 mg/L
Unit 5
NO3-- N
12.1 mg/L
7.4 mg/L
6.3 mg/L
7.0 mg/L
Nitrogen Limits at Valencia WRP
• In 1994:
RWQCB set new nitrogen limits effective in 2003:
Ammonia: 2.0 mg/L
Nitrate + Nitrite: 10 mg/L
• In 2003:
RWQCB revised nitrogen limits effective in
2009:
Ammonia: 1.75 mg/L
Nitrate + Nitrite: 6.8 mg/L
Revised Permit Limits and New
Performance Concerns
12
Effluent NO 3 -N (mg N/L)
10
2003 NO3-N limit
8
2009 NO3-N limit
6
4
2
0
Jul-03
Oct-03 Jan-04 Apr-04 Jul-04
Oct-04 Jan-05
Valencia WRP
Aeration Units 1 and 2: MLE Mode
To Final Clarifiers
Aerobic
Zone
Aerobic
Zone
Primary
Primary
Effluent
Effluent
Anoxic
Zone
RAS
RAS//
Filtrate
Filtrate
Swing Zone
IR
IR
Valencia WRP
Aeration Units 1 and 2: Step Feed
Anoxic
Zone
To Final Clarifiers
Aerobic
Zone
Anoxic
Zone
Aerobic
Zone
Primary
Primary
Effluent
Effluent
RAS
RAS//
Filtrate
Filtrate
Anoxic
Zone
Valencia WRP
Aeration Units 1 and 2: Hybrid
Anoxic
Zone
To Final Clarifiers
Aerobic
Zone
Anoxic
Zone
Aerobic
Zone
Primary
Primary
Effluent
Effluent
RAS
RAS//
Filtrate
Filtrate
Anoxic
Zone
IR
IR
• Step Feed NDN Process: Unit 1
Final
Clarifier
Primary
Effluent
Tertiary
Treatment
Waste Activated
Sludge (WAS)
RAS
••Hybrid
Hybrid NDN Process: Unit 2
Primary
Effluent
Final
Clarifier
Tertiary
Treatment
Waste Activated
Sludge (WAS)
IR
RAS
••MLE
MLE NDN Process: Unit 3
Primary
Effluent
Final
Clarifier
Tertiary
Treatment
IR
RAS
Waste Activated
Sludge (WAS)
Performance Comparison
Mid-day NO3-N Levels
NO3-N Concentration (mg/L)
16.0
MLE
Step Feed
Hybrid
12.0
8.0
4.0
0.0
0.0
0.1
1.0
10.0
30.0
50.0
70.0
90.0
Cumulative Frequency
99.0
99.9
100.0
Unit 5: Convert from MLE to Hybrid
MLE Mode
Pri. Effluent
Anoxic Zone
RAS/Filtrate
IR
Aerobic Zone
To Final Clarifiers
Hybrid Mode
Pri. Effluent
Anoxic Zone
RAS/Filtrate
Aerobic Zone
IR
Aerobic Zone
To Final Clarifiers
Anoxic Zone
GO BEARS
Effluent Nitrate Results: Hybrid vs.
MLE
6/2006 to 12/2006
Peak NO3– N
Unit 3
MLE
8.2 mg/L
Unit 4
MLE
8.3 mg/L
Unit 5
Hybrid
6.4 mg/L
Baffle Boxes and Internal Recycle
Diffuser
Pri. Effluent
RAS/Filtrate
IR
Anoxic Zone
Aerobic Zone
To Final Clarifiers
Aerobic Zone
Anoxic Zone
Filtrate Equalization
Valencia WRP: Additional NDN
Optimization
•
•
•
•
Converted All Units to Hybrid
Baffle Modifications and IR Diffusers
Filtrate Equalization
Optimized RAS and Internal Recycle Flow
Rates
• Higher MLSS
• Permanent Submerged Mixers in New
Anoxic Zones
Valencia: Effluent Nitrogen
Concentrations
Effluent NO3-N and NH4-N (mg N/L)
10
Nitrate
8
Ammonia
2009 NO3-N limit
6
4
2009 NH4-N limit
2
0
Jun-03
Jun-04
Jun-05
Jun-06
Jun-07
Jun-08
Jun-09
Jun-10
Acknowledgements
• WRP Operations, Maintenance, E&I,
and Engineering
• Wastewater Research Section
• Laboratories
• Monitoring Section
• Wastewater Design Section