Davis & Harrison & Kim.Jacobs.Wastewater Treatment for Enhanced ...

Wastewater Treatment for
Enhanced Nutrient Removal
John Davis, P.E.
Karen Harrison, P.E.
Nora Kim, P.E.
Jacobs Engineering Group
August 9 th , 2011

Outline
• What is enhanced nutrient removal (ENR)?
• Why is it required?
• Where has it been required?
• How is it accomplished?
• Issues, lessons, and observations for two key
processes:
– Three-stage treatment
– Simultaneous nitrification/denitrification (SND)

What is ENR?
Treatment Level
Typical Effluent
Nutrient Levels
Typical Process
Nutrient
Removal
Enhanced
Nutrient
Removal
Wow!
You’re Serious?
Nutrient Removal
8 mg/L TN
and/or
1 mg/L TP
3 mg/L TN
and/or
0.1 mg/L TP
1 mg/L TN
and/or

Why is ENR Required?
Nitrogen and phosphorus
waste loads in streams,
lakes, and coastal estuaries
can cause algae
proliferation,
eutrophication, & low
oxygen levels.

Where has ENR been Required?
• For Nitrogen
– Typically coastal regions
– Groundwater recharge
– Chesapeake Bay
– Florida
– Long Island Sound
• For Phosphorus
– Typically upstream of freshwater lakes
– Throughout U.S.

How is ENR accomplished?
Sample of Low Nitrogen Plants
Treatment Plant Process Supplement
Carbon
95 th %tile
TN, mg/L
Average
TN, mg/L
Truckee Meadows WRF, NV Fixed Film Nit/Denit & Filters Yes 2.5 1.7
River Oaks WWTP, FL Separate Sludge & Filters Yes 2.3 1.5
Howard F. Curran WWTP, FL Nitrification & Denit Filters Yes 3.0 NA
WSSC Western Branch WWTP, MD Separate Sludge & Filters Yes 2.2 1.5
Scituate WWTP, MA Nitrification & Denit Filters Yes 3.8 2.4
Eastern WRF, FL Bardenpho & Filters No 6.7 4.3 (Median)
WSSC Parkway WWTP, MD Bardenpho Yes 5.1 3.1
Fiesta Village, FL Simult Nit/Denit & Denit Filters Yes 2.2 1.1
Kalaska CWP, MI Ox Ditch Bardenpho No 2.8 2.2
Iron Bridge WRF, FL Ox Ditch Bardenpho & Filters No 2.4 1.9
WSSC Piscataway, WWTP, MD Step Feed & Filters No 7.2 3.1
Ten Bardenpho Plants, FL Bardenpho & Filters Yes 3.5 2.4
Five 3-Stage with Denite Filters, FL 3-Stage & Denit Filters Yes 3.0 2.1
Source: WERF/WEF Real World LOT Nutrient Removal: Achievable Limits and Statistical Reliability Workshop,
October 11, 2009

How is ENR accomplished for
Low Nitrogen?
• Typical Processes
– Separate Sludge
– Attached-Growth Denitrification
– Bardenpho
– Simultaneous Nitrification/Denitrification (SND)
PLUS
• Chemical Addition
– Methanol, Acetic Acid, Other Carbon Source

How is Nitrogen Removal
Accomplished?
A Basin Meeting Three Main Requirements
1. Nitrified Influent
2. Anoxic Conditions
3. Carbon Source

Separate Sludge
Supplemental
Carbon
Nitrification
Stage
1 st Stage
Clarifiers
De-Nitrification
Stage
2 nd Stage
Clarifiers
• Common in earliest low TN applications (70s and 80s)
• Effective
• High cost for capital and chemical

Attached-Growth Denitrification
Supplemental
Carbon
Anaerobic
Stage
Anoxic
Stage
Aerobic
Stage
Clarifiers
Denitrifying
Filters
• Combined with upstream activated sludge
• TN removal with upstream nitrification
• TN polishing with upstream 3-stage process

Bardenpho
Supplemental
Carbon
Anaerobic
Stage
1 st Anoxic
Stage
1 st Aerobic
Stage
2 nd Anoxic
Stage
2 nd Aerobic
Stage
Clarifiers
Filters
• Responds well to flow and load changes
• Limits supplemental carbon need
• Has become very common for low TN applications

Simultaneous
Nitrification/Denitrification (SND)
• More of an operational method than a
process configuration
• DO = 0.3 to 0.7 mg/L Nitrify & Denitrify
• Used in many process configurations
• Key is maintaining DO in low, narrow range
– DO too high exceed on TN
– DO too low exceed on NH 3 -N
• Supplemental carbon may not be needed

SND Mechanism
O 2
Aerobic
CO 2
Anoxic
N 2
Ammonia
NO 2
NO 3
BOD

How is ENR accomplished?
Sample of Low Phosphorus Plants
Treatment Plant BioP ChemP 95 th %tile
TP, mg/L
Average TP,
mg/L
Clark County, NV Yes Pre & Post 0.153 0.086
Rocky Creek, OR Yes Pre & Post 0.151 0.067
Blue Plains, DC Yes Pre & Co 0.161 0.067
Iowa Hill WRF, CO Yes Post 0.031 0.013
F. Wayne Hill, Gwinnett County, GA Yes Post 0.090 0.044
Cauley Creek, Fulton County, GA Yes Co (MBR) 0.116 0.077
Alexandia Sanitation Authority WWTP, VA Some Co & Post 0.101 0.046
Pinery WWTP, CO Yes Post 0.042 0.023
WSSC Piscataway, WWTP, MD Some Post 0.178 0.087
Kalispell AWWTP, MT Yes No 0.168 0.110
Kelowna WWTF, BC Yes Co 0.217 0.160
Source: WERF/WEF Real World LOT Nutrient Removal: Achievable Limits and Statistical Reliability Workshop,
October 11, 2009

How is ENR accomplished for
• Typical Processes
Low Phosphorus?
– Post-precipitation with tertiary clarifiers followed
by filters
– Co-precipitation in a Membrane Bioreactor (MBR)
– Upstream biological phosphorus removal is
warranted to save on chemical costs

Post-Precipitation
Alum or
Ferric
Alum or
Ferric
Anaerobic
Stage
Anoxic
Stage
Aerobic
Stage
Clarifiers
Chemical
Clarifiers
Chemical
Filters
• Need two sets of clarifiers plus filters
• Multiple chemical feed points are common
• Georgia has many examples on Lake Lanier, Chattahoochee

Co-Precipitation with MBR
Alum or
Ferric
Anaerobic
Stage
Anoxic
Stage
Aerobic
Stage
RAS DeOx
Tank
Membrane
Tank
• Membranes replace two sets of clarifiers, and media filters
• Air Scour DO can interfere with anaerobic/anoxic treatment
• Georgia has many examples on Lake Lanier, Chattahoochee

Minimizing Chemical Costs
As ENR standards become more common two
process approaches will standout as keys to
limiting chemical costs:
– 3-Stage Treatment
• Example: Mauldin Road WWTP
– Simultaneous Nitrification/Denitrification
• Example: Yulee/Nassau Regional WRF

3-Stage Treatment – Mauldin Rd WWTP
Anaerobic
Stage
Anoxic
Stage
Aerobic
Stage
Clarifiers
Filters
• Removes N and P to degree possible w/o chemicals
• Can achieve low TN if extended into Bardenpho or followed
by denitrifying filters
• Can achieve < 1 mg/L TP w/o chemicals

TN, mg/L
TP, mg/L
3-Stage Process - SRT Sweet Spot
30
25
20
5
4.5
4
3.5
3
15
10
5
0
0 10 20 30 40 50 60
Sludge Retention Time (SRT), days
2.5
2
1.5
1
0.5
0
TN Results
TP Results

3-Stage Process – Other Observations
• Phosphorus accumulating organisms (PAOs) and
denitrifying organisms compete for carbon
• Primary clarifiers will be counter-productive
• Biologically fixed phosphorus must be removed with
sludge
• Long SRTs due to low plant loading will interfere with
phosphorus removal
• If denitrification is carbon-limited, more nitrified
recycle won’t help TN removal.
• DO and NO 3 in RAS can interfere with
PAOs/phosphorus removal

SND - Yulee/Nassau Regional WRF
Recycle
Influent
Flow
Discharge
Screening and Flow
Split
Anoxic Aerobic Anoxic MBR
UV
Disinfection

Effluent Limits
Parameter
cBOD 5
Total Suspended Solids (TSS)
Ammonia-Nitrogen (NH 3 -N)
Total Nitrogen (TN)
Total Phosphorus (TP)
Limit
5 mg/L
5 mg/L
1 mg/L
3 mg/L
1 mg/L

Process Highlights
• SymBio® Process
– Simultaneous nitrification-denitrification (SND)
– Operates at low dissolved oxygen (0.2 – 0.5 mg/L)
• Alum feed for P removal
• Kubota flat plate membranes

Process Modeling
• BioWin model used as operational tool
• BioWin switching functions require
adjustment
• Jimenez (2010) research on SND switching
functions

Concentration, mg/L
Original Operation
8
7
Nov 2006 to Jan 2007 Effluent Data
Effluent TN
Effluent TP
6
5
4
3
2
1
0

Recommended Modifications
• Added new aeration blower with VFD – 400 to
1300 scfm capacity
• Aeration tank minimum air reduced from 600
scfm to 400 scfm
• Operation of fewer trains at low loads
• Consulted membrane vendor and reduced
minimum scour air from 1400 to 700 scfm per
membrane tank

Concentration, mg/L
Modified Operation
2010 Effluent Data
7
6
Effluent TN
Effluent TP
5
4
3
2
1
0

Questions?
john.davis@jacobs.com