Copyright 2013 HDR Engineering, Inc. All rights reserved.
PHOSPHORUS REMOVAL CHALLENGES AND OPPORTUNITIES
IWEA Nutrient Removal and Recovery Workshop Addison, IL
12 September 2013
JB Neethling
Outline
• Introduction • Phosphorus Removal • Las Vegas’ Gamble • Emerging Issues / Challenges
– Sidestream management – Dewaterability – Nutrient recovery
Illinois Regulatory (2012)
• Phosphorus in limiting nutrient in almost all IL streams
• 53 stream segments on 303(d) list • 1 mg/L for plants > 1mgd • New, upgrade, expanded facilities may get
lower limit
Bob Mosher, EPA, 2012. Illinois Nutrient Removal Recovery Workshop 2012
Nutrient Removal & Recovery Survey I
Mark Halm, 2012. Illinois Nutrient Removal Recovery Workshop 2012
Nutrient Removal & Recovery Survey II
Mark Halm, 2012. Illinois Nutrient Removal Recovery Workshop 2012
WERF Nutrients Challenge Goals • Develop and share credible scientific information about nutrients & their
bioavailability to help regulators make informed decisions
• Better understand existing mechanisms of nutrient removal and best available technologies so treatment plants can become more efficient and effective, enabling them to cost-effectively meet permit limits
Focus on nitrogen (N) and phosphorus (P)
Wastewater treatment related issues
Status: Ongoing, 5 – 7 year challenge
Investment: ~$3 million WERF funds (started in 2007)
In-kind, in-cash: >$10 million
Leveraged with additional funding, Collaboration, etc.
Nutrient Removal Challenge website: www.werf.org/nutrients
Nutrient Removal Challenge Strategy • Challenge is huge, Funds are limited, Knowledge is available
and growing, Need to Collaborate! • Research roadmap developed and refined with industry expert
knowledge and guidance • Volunteer experts from utilities, consultants, industry,
regulators, et al
Focus on collaboration to increase value to profession (instead of single projects)
Address fundamentals, with strong results focus
Engage stakeholders to participate in an active role
Leverage ongoing projects Use “Tom Sawyer” principle to
paint the fence together
COLLABORATION is the KEY!
Nutrient Removal Challenge NUTR1R06 – Core Team
• Collaborative team led by HDR, with AECOM + CH2M-Hill + Univ. of Washington + other Universities + Collaborators
• >30 Utilities, Universities, Consultants, and Research Organizations nationwide and abroad
• Others added as needed
• Identified and secured >$10 million in additional funds or in-kind contributions through utilities & other research
Core Team and Other Members:
• JB Neethling, HDR (principal investigator)
• Amit Pramanik, WERF
• Julian Sandino, CH2M-Hill
• H. David Stensel, University of Washington
• Roy Tsuchihashi, AECOM
• David Clark, HDR
• Stacy Passaro, Passaro
Nutrient Removal Challenge website: www.werf.org/nutrients
PHOSPHORUS REMOVAL
P Speciation
Total P
Soluble P Particulate P
Reactive P SRP pRP Sol NonReactive P
SNRP Particulate NonReactive P
pNRP Reactive P
SRP Acid Hydrolyzable
SAHP Organic SOP pRP
Acid Hydrolyzable pAHP
Organic pOP
Spec
ies
SNRP SRP Particulate P
12
Phosphorus Treatment Options
Chemical Biological
Fundamental Principle of Phosphorus Removal
There is no airborne (gaseous) form of phosphorus
The exception
15
Enhanced Biological Phosphorus Removal (EBPR)
• Discovery in 1960’s-1970’s that, under some conditions, activated sludge will accumulate phosphorus in excess of normal biological requirements
• Called “Luxury Uptake” • Long debated if this is a chemical or biological
phenomenon – Biological action now proven
17
Neisser Stain
WERF - VIP plant, 7/3/03
22
EBPR Requirements
• Anaerobic/aerobic sequence • Adequate supply of volatile fatty acids (VFAs)
in anaerobic zone • No free oxygen • No bound oxygen (nitrate)
23
Biological Phosphorus Removal
Anaerobic Aerobic
RAS
Clarifier
Conc
entr
atio
n, m
g/l
Time
BOD
Soluble P
24
EBPR Biochemistry Model
Time
Con
cent
rati
on
Sol P VFA
PHA, PHB
ANAEROBIC AEROBIC
25
Pontiac, MI. AO process for P removal
Biological Phosphorus Removal Zoned Design
Phoredox (AO)
3-stage Phoredox (A2O)*
Johannesburg*
Modified Johannesburg*
West Bank*
VFA
anaerobic
anoxic
aerobic
* removes TN and TP
Biological Phosphorus Removal Zoned Design
Modified (5-stage) Bardenpho*
UCT*
Modified UCT*
VIP (Virginia Initiative Process)*
anaerobic
anoxic
aerobic
* removes TN and TP
Biological Phosphorus Removal Mixed Design
SBR*
Biodenipho*
PhoStrip*
Trickling Filter with EBPR*
Nitrify
anaerobic
anoxic
aerobic
* removes TN and TP
Las Vegas - 3 stage Phoredox or mUCT
Anaerobic Zone
Pinery WWTP, CO
Anaerobic Zone
Virginia Initiative Plant, HRSD, Norfolk, VA
Biological Phosphorus Removal
• Many Process Options • Anaerobic Zone key to process • High influent rbCOD/P is desired
– carbon/VFA addition via fermentation • Process stability is key. Conditions that favor the
right PAO populations are need to be understood
• Typically achieve ~0.5-1.0 mg TP/L • Optimal reduce OrthoP to 0.02-0.05 mg P/L
Reliability of Biological Phosphorus Removal • WERF Study 2002
– HDR Engineering Inc
• Six Full scale facilities • Statistical data analysis • Field testing
VIP trend TP
0
1
2
3
Jul-99 Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03
mg/
L
Final Effluent, T-P
McDowell Creek
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Jul-98 Jan-99 Jul-99 Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03
TP [m
g/L]
EFF, TP
Adding a Sugar waste stabilized biological phosphorus removal.
Empire
Empire - Final Effluent Total P
0
1
2
3
4
5
6
7
8
May-01 Jun-20 Aug-09 Sep-28 Nov-17
mgP
/L
FIN EFF TP
EBPR Reliability Comparison
oP below Durham VIP Nanse-
mond McDo-
well Creek
Lower Reedy
Empire
<0.5 mg/L 69% 70% 24% 94% 53%
84%
<1 mg/L 88% 82% 64% 99% 75%
99%
<2 mg/L 97% 92% 85% 100% 91%
100%
Neethling et al. (2005) Factors Influencing the Reliability of Enhanced Biological Phosphorus Removal, WERF 2005.
PHOSPHORUS CHEMISTRY
Typical Chemical Treatment Opportunities
Primary Secondary Tertiary Polish
Solids Processing
Metal salt reaction with phosphorus Old School
Al2(SO4)3.14H2O+ 2H3(PO4) = 2Al(PO4) + 3H2SO4 + 18H2O
FeCl3 + H3(PO4) = Fe(PO4) + 3HCl3
The following illustrates a “stoichiometric reaction” of Al+++ or Fe+++ with P, But actual P removal mechanism is related to hydroxide formation.
In above 1 mole of P uses 1 mole of Al or 1 mole of Fe
Hydroxide formation can be simply represented:
FeCl3 + 3H2O = Fe(OH)3 + 3 HCl Al2(SO4)3.14H2O + 3 H2O -> 2Al(OH)3(s) + 3H2SO4
Metal hydroxide removal of P found for ferric addition • Metal hydroxide formed • Co precipitation of P into hydrous ferric
oxides structure – Fe(OH)3, Fe(OH)4
-
• Surface complexation between P and metal hydroxide compounds
• Phosphorus and Iron share oxygen molecule: • FeOOH + HOPO3 = FeOOPO3 + H2O
pH 7-->
← pH 3 Scott Smith, Wilfrid Laurier University
Fresh HFO
Scott Smith, Wilfrid Laurier University
Young HFO
Scott Smith, Wilfrid Laurier University
Aged HFO
FePO4 precipitant After 4 days. Hard !!
Scott Smith, Wilfrid Laurier University
Scott Smith, Wilfrid Laurier University
Phosphorus Removal
Chemical Dose
Phos
phor
us C
once
ntra
tion Initial removal - Stoichiometric
1:1 Equilibrium control – need higher dose
Break ~ 1 mg/L
Molar Dose Ratio From Tests
Slav Hermanowicz, Chemical Fundamentals of Phosphorus Precipitation, WERF Boundary Condition Workshop, Washington DC, 2006
02468
101214161820
0.01 0.1 1 10
ortho P res (mg/L)
Al/P
(mol
/mol
)
Full Scale 6.6 - 6.75
Lab data pH 6
Lab data pH 7.2
0.1
1
10
100
0.01 0.1 1 10
ortho P res (mg/L)
Fe/P
(m
ol/m
ol)
Lab data pH 6.5
Lab data pH 6.8
Lab data pH 7.2Lab data pH 8
Full Scale data
FULL SCALE PERFORMANCE
What is the “Performance”?
• What permit limit can this plant meet? – Numerical – concentration – Averaging – daily, weekly, monthly, annual
0.001
0.01
0.1
1
10
0.001
0.01
0.1
1
10
Dec-04 Jul-05 Dec-05 Jul-06 Jan-07 Jul-07 Jan-08
--
Central (all), TP
Lowest value?
“Next” Lowest value?
“Repeated” Low value?
“Average” Value?
“Reliable” Value?
1% 10% 25% 75% 90% 99% 99.9%0.1% 50%0.00
0.01
0.10
1.00
10.00
Percent of values less than of equal to indicated value
mg/
L
SE TP (all)
22
3.84%
0.040
50%
0.080
95%
0.23
Technology Performance Statistics
Neethling et al. (2009) WEF Nutrient 2009, Alexandria, VA.
Ideal Median Reliable
Factors Affecting Performance “Safety Factor” • “Normal” variations • Influent variations – Flow, load, peaks • Environmental factors – Rain, temperature • External issues – Construction, toxic dump • Unexpected events – Equipment failure,
chemical supply • Plant “upsets” – Human interface, recycle
dominoes
68
Permit Period and Reliability
Period Basis (days) Sample Permit Percentile
(%)
Reliable Percentile
(%)
5 yr Excee-dance
Max Day 1 365 99.7 99.9 1.8
Max Week 7 365 98.1 99 2.6
Max Month 30 365 91.8 95 3
Ann Avg 182.5 365 50 90 0.5
Permit Period and Reliability
Period Basis (days) Sample Permit Percentile
(%)
Reliable Percentile
(%)
5 yr Excee-dance
Max Day 1 365 99.7 99.9 1.8
Max Week 7 365 98.1 99 2.6
Max Month 30 365 91.8 95 3
Ann Avg 182.5 365 50 80 1
Exceed once a year!
Acceptable Risk?
1% 10% 25% 75% 90% 99% 99.9%0.1% 50%0.00
0.01
0.10
1.00
10.00
Percent of values less than of equal to indicated value
mg/
L
SE TP (all)
22
3.84%
0.040
50%
0.080
95%
0.23
Calculate Reliability to Meet a Permit Limit – say meet 0.2 mg/L TP
Neethling et al. (2009) WEF Nutrient 2009, Alexandria, VA.
~91%
Exceed 9% Monthly Exceedance = 5.4 times in 5yr Annual Exceedence = 0.45 times in 5 yr
Evaluate Performance
• Long term data from full scale plants – Determine 80th and 95th percentiles
• Special studies – Speciation results from grab/occasional samples
• Determine the expected achievable performance based on process understanding
P Speciation
Total P
Soluble P Particulate P
Reactive P SRP pRP Sol NonReactive P
SNRP Particulate NonReactive P
pNRP Reactive P
SRP Acid Hydrolyzable
SAHP Organic SOP pRP
Acid Hydrolyzable pAHP
Organic pOP
Spec
ies
SNRP SRP Particulate P
Phosphorus TPS Plant 50% 80% 95% 50% 80% 95% 50% 80% 95%
ChemP (multiple) 25 25 25 25 55 80 50 80 120 BioP, chem/sed/fil 29 40 54 ChemP (multiple) 40 90 140 35 60 90 70 120 180 ChemP (in AS) 90 134 203 17 47 83 71 119 196 BioP, chem/sed/filt 19 44 152 60 78 102 80 116 233 BioP, MBR 50 80 120 30 40 60 80 110 160 BioP, chem/sed/filt 30 57 119 50 71 92 83 113 177 BioP, chem/sed/filt 16 31 141 53 85 169 83 148 329 BioP, filter 40 60 78 80 120 260 110 160 270 BioP, MBR 49 498 2,522 11 15 60 51 184 1,795 BioP, filter 114 240 480 ChemP 100 300 740 60 100 199 140 310 730 BioP, filter 40 70 110 110 140 180 150 190 324 BioP/ChemP/filt 130 210 810 50 60 150 170 250 950 BioP, filter 100 216 487 80 120 190 190 310 635 BioP, filter 140 210 350 110 140 190 270 350 490 BioP, chem/filter 130 250 610 160 210 304 320 440 770 BioP 105 205 511 177 272 593 340 518 1,505 BioP, filter 230 390 642 180 220 290 400 590 890 BioP 423 662 1,200 ChemP, filter 420 652 950 40 70 140 500 750 972 BioP and chemical 651 1,364 1,762
TRP TNRP TP
Phosphorus Performance TPS (avg/min)
Species 50% 80% 90%
TRP – avg 97 200 480
TRP – min 16 25 25
TNRP – avg 75 105 180
TNRP – min 10 15 60
TP – avg 200 320 650
TP – min 30 40 55
Distribution of sRP
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
sRP,
ug/L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Distribution of sRP – Optimal Estimate - 5-15 ug/L
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
sRP,
ug/L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Distribution of sNRP
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
sNRP
, ug/
L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Distribution of sNRP – Optimal Estimate – 15-25 ug/L
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
sNRP
, ug/
L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Distribution of pTP
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
pTP,
ug/L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Distribution of pTP – Optimal Estimate – 10-20 ug/L
Adapted from: Gu, A. et al. “Phosphorus Fractionation And Removal In Wastewater Treatment- Implications For Minimizing Effluent Phosphorus,” WERF Nutrient Removal Study; Draft Report 2012.
1
10
100
1000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
pTP,
ug/L
Ranking, %
MF MBR Fil/Fil Sed/Fil Filter BNR 50% 80% 95%
Estimated Optimal P Species in Advanced Treatment
SRP=Soluble Reactive P; SNRP = Soluble Nonreactive P pP=Particulate P TP = Total P
0
10
20
30
40
50
60
SRP SNRP pP TP
Conc
entra
tion
, ug
P/L
SIDESTREAM MANAGEMENT IS REQUIRED TO ACHIEVE LOW CONCENTRATIONS
Construct a Mass Balance
Primary Secondary Tertiary
Solids Processing
100 1
99
Construct a Mass Balance
Primary Secondary Tertiary
Solids Processing
100 150 110
40
1 10
9 100
149 99
50
Nan Mass Balance
Phosphorus Mass Balance
Durham Nanse-mond
VIP McDowell Creek
Lower Reedy
Total Recycle P 14% 86% 9% 26% 54%
Digester Recycle P 24% 86% 9% 23% 54%
Struvite - MAP
Magnesium Ammonium Phosphate
Struvite – Friend or Foe
• Magnesium-Ammonium Phosphate • Biological Phosphorus Removal increase
Struvite formation – PAO’s accumulate both P and Mg – Bring that to digester – Contact with Ammonia in digester – Supersaturate struvite
• Low pH depress formation
Why bother ?
Struvite Precipitation Reactor
Mg2+ + NH4+ + PO4
3-
CITY OF LAS VEGAS EXPERIENCE
Copyright 2011 HDR Engineering, Inc. All rights reserved.
1970
BNR History in Las Vegas - 1970
Las Vegas – 1980-1990
• Trickling Filter – BOD only • Fought EPA’s new phosphorus limit (0.5
mg/L) • Won – given short time to meet 1-2? mg/L TP • Solution – Chemical addition to Primary
– Increase capacity from 28 to 41 mgd – Meet phosphorus limit – Complete in 6 months
1999
BNR History in Las Vegas - 1999
Las Vegas – 1990-2000
• New permit: – TP 0.27 mg/L (mass loading) – NH4-N 0.67 mg/L
• Solution – New nitrifying activated sludge following TF – Add effluent filtration
Plant 3 + 4 Plant 1 + 2
Solids
BNR
Filtration
Headworks
Nitrification
BNR History in Las Vegas – 2000+
Las Vegas – 2000+
• Capacity increase by 30 mgd • Add new BNR process • Retain TF/nitrification with chemical addition
PSL
PSL
PSL
SCL
SCL
TF
TF
AB-NSCL
F D
HW
SCL
GTH
THC
ADDWC
Plant 1+2
BNR
Plant 3.4
Las Vegas Process Flow Diagram
Ferric Ferric
Las Vegas – 2011+
• Reduced Capacity to ~70 mgd needed – North Las Vegas gone away
• Limits reduced – TP - 0.17 mg/L – NH4 - 0.48 mg/L – Nitrate “optional”
• Proposed solution – Take TF offline – Convert nitrification process to NDN – Retain chemical P removal
Construction
Construction
Construction
Construction
Construction
TP in and out
0
2
4
6
8
10
12
14
Apr-03 Jun-03 Aug-03 Oct-03 Dec-03
mg/
L
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
mg/
L
BNR Inf, TP BNR Eff, TP
Process Performance
Aeration Basin Effluent and Clarifier Effluent oP
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04
mg/
L
BNR Eff, oP BNR Aer, oP avg
Process Performance
DEWATERABILITY OF EBPR SLUDGE
165
Hampton Roads Sanitation District, Virginia Beach, VA - Atlantic Plant
Selector online
Data Source: Hampton Roads Sanitation District, Virginia Beach, VA
MWRD, Denver, CO Robert W. Hite Treatment Facility
EBPR Pilot
Data Source: Metro Wastewater Reclamation District, Denver, CO
Biosolids dewaterability
• Due to high Mono/Di valent cation ratio? • Due to high PO4 in feed? • Other
Mass Balance – P, K
EBPR
Digest Dewater
100 / 50 0 / 20
100 / 30
100 / 0
100 / 50
Say 50/ 30
lb P / lb K
Mass Balance – P, K
EBPR
Digest Dewater
100 / 50 0 / 30
150 / 50
100 / 0
150 / 80
50/ 50
lb P / lb K
Mg++ and Ca++ uptake and released by EBPR precipitate in digester as Struvite and other precipitants
Mass Balance – P, K (round 2)
EBPR
Digest Dewater
100 / 50 0 / 50
150 / 50*
100 / 0
150 / 100
50/ 50
lb P / lb K
* In addition – the soluble K slowly increase over time
Dewatering Ongoing Research
• Impact of monovalent / divalent cation ratio • Impact of phosphate • Metal salt addition to liquid stream that ends up in
the digester • Struvite recovery • Sequestering recycle phosphorus to break “recycle”
EMERGING QUESTIONS
174
Performance Opportunities for Improvement • Improved reliability with EBPR to ~20 ug/L?
– VFA supply – Stable operation
• Improved reliability with chemical solids management
• Attenuate side stream impacts • P indexing for land application of biosolids
– All the P ends up in the solids – Bioavailable? Or not?
Phosphorus Removal/Recovery Drivers • Low PO4-P recycle required for EBPR to
function • Struvite formation nousance • Biosolids dewaterability • Product recovery opportunities
Copyright 2013 HDR Engineering, Inc. All rights reserved.
PHOSPHORUS REMOVAL CHALLENGES AND OPPORTUNITIES
IWEA Nutrient Removal and Recovery Workshop Addison, IL
12 September 2013
JB Neethling
QUESTIONS? • JB Neethling
BIOAVAILABILITY OF PHOSPHORUS
Upflow Sand Filter
Intermediate = Conventional Sedimentation
Influent
Phosphorus Bioassay Process Effluent
Michael T. Brett & Bo Li, University of Washington
BAP vs TP and TRP
02468
101214161820
P species
TP
TRP
BAP
TP
TRP BAP
Effluent (n=4)
050
100150200250300350400450500
P species
TP
TRP
BAP
TP
TRP BAP
Influent (n=4)
µg/
L
µg/
L
Brett & Li, Spokane River Interim Report, Jan 2010
Bioavailable P - Species Profile in Sedimentation/Filtration Process • Winter (a)
– No chemical upstream: • TP 2750 ug/L • BAP = 1280 ug/L
– Effluent • TP = 30 ug/L • BAP = 6 ug/L
• Summer (b) – Chemical upstream:
• TP = 470 ug/L • BAP = 280 ug/L
– Effluent • TP = 18 ug/L • BAP = 1 ug/L
Li & Brett (2012)
Relationship between Treatment and Bioavailable P
• Increased degree of treatment reduce %BAP
• Chemical addition used to achieve very low P
Li & Brett (2012)
TRP is a conservative estimate of BAP
• %BAP decrease as phosphorus concentration decrease: – Influent > Intermediate >
Effluent • %BAP decrease with
chemical addition • BAP is always less than
TRP – Use TRP as conservative
measure of BAP
Li & Brett (2012)
Key Findings – BAP Finding WQ Impact Technology Impact BAP can be measured with standard algal assay
BAP measurement may not reflect in situ availability
BAP Measurement is time consuming and complex
Chemical treatment reduce the %BAP
Treatment approach impacts the BAP fraction
Chemical addition (polishing) reduce BAP
%BAP lower in advanced treatment producing low TP concentrations
WQ impact from TP from advanced treatment processes lower
Chemical addition in advanced treatment reduce %BAP
TRP measurements exceed BAP measurements
TRP could be a conservative estimate of BAP
Measuring TRP is simpler than BAP
QUESTIONS?
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