Biological
Phosphorus Removal
2017 ORWEF Short School
Clackamas Community College
Chris Maher, Operations Analyst
Rock Creek AWTF
Wherever there’s water, there’s Clean Water.
Outline
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Phosphorus Cycle
Players: PAOs, GAOs, OHOs, DNHOs,
DPAOs
Process Arrangements
Optimizing and Troubleshooting
Wherever there’s water, there’s Clean Water.
Extraction
Erosion
Mining (Fertilizer)
Orthophosphate
Phosphorus Cycle
Phosphate
Minerals
Plant Growth
Eat Plants
Phosphorus in
Sludge for
Beneficial Use
Clarifier
Animal Growth
Chemical P Removal
Precipitation and
Adsorption with
Alum or Ferric
Primary, Secondary,
Tertiary
Eat Animals
If Sludge goes
anaerobic, P will
be released!
Organic Phosphorus:
Phospholipids,
ADP/ATP, DNA/RNA
Energy stored in polyphosphate
in biomass
P Uptake
PAOs use PHA for energy
to grow and replenish
polyphosphate energy
reserves by bonding PO43-
Ortho Phosphate
(PO43-)
RAS
Anaerobic Zone
No O2 or NOx
Enough VFA (food for PAOs)
Enough Cations (Mg+, K+) to
balance release of PO43-
Waste Water
Excretion, Death
and Decay
Aerobic Zone
Cellular Growth and
Reproduction
PO43-and
PolyPhosphates – 85%
Organic Phosphorus – 15%
Bacterial Decomposition
Sedimentation,
Mineralization,
Compression, Uplift
Supplemental VFA?
Correct sizing?
P Release
In converting VFA to PHA,
PAOs breakdown
polyphosphate bonds for
energy, releasing PO43-
Two Steps of the BPR Process Governed by
Different Considerations
Anaerobic
Aerobic
VFA
CO2
Glycogen
CO2 + H2O
Glycogen
EMP
PHB
NADH
Ac-COA
O2
Poly-P
PHB
Energy
Cell + Poly-P
Poly-P
PO4
PO4
PO4
Released P
Influent
Wherever there’s water, there’s
Clean Water.
P
Released P
PO4
Influent
P
Fundamental fundamentals
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Bugs are creatures that live on Earth, just like
you and me.
Need Oxygen (or other e- acceptor)
Need Water
Need to Eat
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Eat carbon, but also need nitrogen, phosphorus, and
vitamins and minerals
Need Energy source
Like to reproduce
Like to eat, drink and do different things
Grow at different rates and have varying lifespans
Wherever there’s water, there’s Clean Water.
Carbon
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CBOD
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VFA Volatile Fatty Acid
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Various CHONP compounds (C6 H12 O6)
Acetic, Propionic, Butyric
CH3COOH
PHB Polyhydroxybutyrate
Wherever there’s water, there’s Clean Water.
Operator
Species
Carbon Source
Energy Source
Electron
Acceptor
WWTP Operator
CBOD
(Organic Carbon)
CBOD
(Organic Carbon)
O2
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Tends to prefer carbon in a
fermented liquid form
Wherever there’s water, there’s Clean Water.
Ordinary Heterotroph (OHO)
Species
Carbon Source
Energy Source
Electron
Acceptor
OHO
CBOD
(Organic Carbon)
CBOD
(Organic Carbon)
O2
Remember back to High
School biology…Ms
Lynch…got to sit next to
Kathy…Oh yeah…
Cellular respiration relies on
the ADP – ATP cycle where
energy is stored and
released through phosphate
bonds
Wherever there’s water, there’s Clean Water.
Denitrifying Heterotroph
(DNHO)
Species
Carbon Source
Energy Source
Electron
Acceptor
DNHO
CBOD
(including VFA)
CBOD
(including VFA)
NO3
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ADP – ATP cycle
Competes for VFA
Wherever there’s water, there’s Clean Water.
Phosphorus Accumulating
Organism (PAO)
Species
Carbon Source
Energy Source
Electron
Acceptor
PAO
VFA
VFA
O2
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ADP – ATP cycle expanded to polyphosphate chains
Competes for VFA
Specialized to store carbon under anaerobic
conditions
That stored carbon becomes the energy and carbon
source under aerobic conditions
Wherever there’s water, there’s Clean Water.
BPR Process Relies on Anaerobic/Aerobic Cycling:
The Release
Anaerobic
PAO gets energy from
breaking phosphate bonds
VFA
Energy
Poly hydroxy butyrate
PHB
The discarded phosphate
exits the cell
Poly-Phosphate
PO4-3
That energy is used to
consume VFA and convert to
polyhydroxybutyrate (PHB) –
kind of like a “fat” reserve
K+1
Mg+2
Wherever there’s water, there’s Clean Water.
Cell maintains neutral charge
by discarding +3 charges
BPR Process Relies on Anaerobic/Aerobic Cycling:
The Uptake
Aerobic
PAO now behaves like an
OHO
Use stored carbon (PHB) as
energy source and carbon
source to grow, reproduce
CO2 + H2O +
new cells
Energy
O2
Energy
Is conditioned to recharge
the poly-P battery
PHB
Poly-P
Released PO43- and influent
PO43- is stored
K+1
PO4-3
Wherever there’s water, there’s Clean Water.
Mg+2
Glycogen Accumulating
Organism (GAO)
Species
Carbon Source
Energy Source
Electron
Acceptor
GAO
VFA
VFA
O2
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ADP – ATP cycle
Competes for VFA
Specialized to store carbon under anaerobic
conditions
That stored carbon becomes the energy and carbon
source under aerobic conditions
Wherever there’s water, there’s Clean Water.
Glycogen Accumulating
Organism (GAO)
Anaerobic
VFA
Energy
Poly hydroxy butyrate
● In contrast to PAOs,
GAOs utilize energy
from glycogen
breakdown to take in
VFAs.
PHB
Glycogen
Wherever there’s water, there’s Clean Water.
● GAOs do not take in P in
the aerobic zone.
Keys to BPR
Anaerobic
● Sufficient VFA. PAOs can’t store
other forms of carbon.
● Maintain advantage for PAOs by
managing competition for VFAs
from O2 and NO3
● Minimize phosphorus release in
secondary clarifiers
Wherever there’s water, there’s Clean Water.
Aerobic
● Good oxygen supply in the initial
aerobic zones to ensure high
initial aerobic P uptake.
Keys to BPR:
VFA
Three sources of VFA:
(1) Influent wastewater
(2) Fermenter
(3) Fermentation in anaerobic zone
Wherever there’s water, there’s Clean Water.
Sec Clarifier 1 Eff S-OPO4
Sec Clarifier 2 Eff SOPO4
Sec Clarifier 4 Eff S-OPO4
Fermenter VFA to PEPS Pounds
Sec Clarifier 3 Eff S-OPO4
3.5
3,500
3.0
3,000
2.5
2,500
2.0
2,000
1.5
1,500
1.0
1,000
0.5
500
0.0
0
6/1/14
6/11/14
6/21/14
Wherever there’s water, there’s Clean Water.
7/1/14
Date
7/11/14
7/21/14
VFA Load (ppd)
Secondary Effluent OPO4 (mg/L P)
Example Bio-P Upset Due to VFA Limitation
Example Bio-P Upset Due to VFA Limitation
Sec Clarifier 1 Eff S-OPO4
Sec Clarifier 2 Eff SOPO4
Sec Clarifier 4 Eff S-OPO4
Fermenter VFA to PEPS Pounds
Sec Clarifier 3 Eff S-OPO4
3,500
Accidental
fermenter
washout
3.0
3,000
2.5
2,500
2.0
2,000
1.5
1,500
1.0
1,000
0.5
500
0.0
0
6/1/14
6/11/14
6/21/14
Wherever there’s water, there’s Clean Water.
7/1/14
Date
7/11/14
7/21/14
VFA Load (ppd)
Secondary Effluent OPO4 (mg/L P)
3.5
Keys to BPR
Anaerobic
● Sufficient VFA. PAOs can’t store
other forms of carbon.
● Maintain advantage for PAOs by
managing competition for VFAs
from O2 and NO3
● Minimize phosphorus release in
secondary clarifiers
Wherever there’s water, there’s Clean Water.
Aerobic
● Good oxygen supply in the initial
aerobic zones to ensure high
initial aerobic P uptake.
● Avoid low DO conditions that
could cause secondary release
Keys to BPR: Managing Conditions
● In presence of nitrate or oxygen, VFA in the anaerobic zone will
be used for metabolisms other than bio-P.
● 1 mg/L DO uses up ~ 3 mg/L VFA as COD.
● 1 mg/L nitrate uses up ~ 7 mg/L VFA as COD.
● Nitrate and oxygen can enter the anaerobic zone through the RAS
and/or primary effluent.
● Different process configurations that can be used to minimize
interference.
Wherever there’s water, there’s Clean Water.
Keys
to
BPR:
Managing
Conditions
A2O Configuration
PE + VFA
RAS
Anaerobic
Mixed Liquor Recycle
Anoxic
Aerobic
Johannesburg Configuration - Question: how does this configuration help?
allows RAS to use O2 and/or NO3 endogenously before VFA fed to anaerobic zone
RAS
PE + VFA
Anaerobic
Mixed Liquor Recycle
Anoxic
Wherever there’s water, there’s Clean Water.
Aerobic
Phosphorus Removal Processes
A/O: Anaerobic/Aerobic
A2/O: Anaerobic/Anoxic/Aerobic
NO3 Recycle
Anaerobic
VFA Consumed
P Released
Aeration
P Uptake
Anaerobic
VFA Consumed
P Released
Clar
Anoxic
DN and
P Uptake
Aeration
Nite and
P Uptake
Clar
RAS
RAS
UCT: Universtiy of Cape Town
Modified UCT
ML Recycle
NO3 Recycle
Anaerobic
VFA Consumed
P Released
Anoxic
DN and
P Uptake
ML Recycle
Aeration
Nite and
P Uptake
Anaerobic
VFA Consumed
P Released
Clar
NO3 Recycle
Anoxic
DN and
P Uptake
Anoxic
DN and
P Uptake
Aeration
Nite and
P Uptake
RAS
Clar
RAS
JHB: Johannesburg
Chemical Precipitation; Primary, Secondary, Filtration
NO3 Recycle
Anaerobic
VFA Consumed
P Released
Anoxic
DN and
P Uptake
Anoxic DN
and P Uptake
Chemical
Aeration
Nite and
P Uptake
Chemical
Clar
Primary
Clarifier
Biological Treatment
Chemical
Filters
Secondary
Clarifier
RAS
Bardenpho (5 Stage)
Chemical Precipitation, Tertiary
Alum or Ferric
Polymer
pH Control
NO3 Recycle
pH Control
Anaerobic
VFA Consumed
P Released
Anoxic
DN and
P Uptake
Aeration
Nite and
P Uptake
Anoxic
DN and
P Uptake
ReAeration
RAS
Clar
Precipitation
Flocculation
Sedimentation
Ballast (Optional)
Keys to BPR: Managing competition
AB4&5 Configuration
PE
PE
RAS
PE
VFA
Anaerobic
Mixed Liquor Recycle
Anoxic
Wherever there’s water, there’s Clean Water.
Aerobic
Keys to BPR
Anaerobic
● Sufficient VFA. PAOs can’t store
other forms of carbon.
● Maintain advantage for PAOs by
managing competition for VFAs
from O2 and NO3
● Minimize phosphorus release in
secondary clarifiers
Wherever there’s water, there’s Clean Water.
Aerobic
● Good oxygen supply in the initial
aerobic zones to ensure high
initial aerobic P uptake.
Keys to BPR:
Avoid secondary P release
Anaerobic
● Secondary release occurs when
VFA
PAOs use poly-p to gain energy
but don’t store VFA at the same
time.
● If PHB is not stored, subsequent
PHB
Energy
Poly-P
PO4
Released P
Wherever there’s water, there’s Clean Water.
P uptake can’t occur
● Secondary release occurs when
the clarifier blankets go anaerobic
due to long sludge detention time
Manage Competition
Conditions Favoring GAOs over PAOs:
● High Temperatures (typically > 20 deg C).
● Low pH (typically < 7).
● High SRTs (typically > 20 days).
● Pure acetate (or acetate source such as glucose) fed to the anaerobic
zone.
● Too large unaerated zones.
● Excess VFA available.
Wherever there’s water, there’s Clean Water.
Strategies to Avoid Out-competition of PAOs
by GAOs:
 Operate at lowest possible SRT
 Try to operate with the minimum anaerobic retention time.
 Alkalinity addition when the pH drops below 7.
 Natural fermentate (combination of acetic and propionic acid) best source
of supplemental carbon for PAOs.
 Divert excess VFA if possible
Wherever there’s water, there’s Clean Water.
Plant Modifications
Plug wall holes
Wherever there’s water, there’s Clean Water.
Plant Modifications
Add
weirs
Extend
MRL pipe
Wherever there’s water, there’s Clean Water.
Troubleshooting Bio-P with Online
Instrumentation
Question: How can each of these measurements help you
troubleshoot or monitor bio-P?
OP
Wherever there’s water, there’s Clean Water.
OP
TSS
DOB
Keys to BPR: High initial DO
14
12
OP, mg/L
10
1.
Good initial P release in
first two cells
2.
Sharp drop in first anoxic
cell due to MLR dilution.
3.
Relatively flat profile
through anoxic cells
4.
Sharp initial aerobic
uptake in the first 2
aerobic cells.
5.
Most of the P entering the
aerobic zone completely
taken up less than halfway
through the aerobic zone.
8
6
4
2
0
Wherever
there’s
water,
Cell
1 Cell
2 there’s
Cell 3 Clean
CellWater.
4 Cell 5
Cell 6
Cell 7A Cell 7B Cell 7C Cell 7D Cell 7E
Summary
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VFA
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Are you VFA limited?
Are you wasting VFA with O2 or NO3?
Are you wasting VFA with GAOs?
PHB
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VFA must be converted to PHB for uptake
to happen
P Release without P uptake indicates the
wrong release
Wherever there’s water, there’s Clean Water.