© 2014 hdr, inc., all rights reserved.jb neethling, mario benisch hdr engineering, inc. dewatering...
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© 2014 HDR Architecture, Inc., all rights reserved. © 2014 HDR Architecture, Inc., all rights reserved. © 2014 HDR Architecture, Inc., all rights reserved. © 2014 HDR, Inc., all rights reserved. © 2014 HDR, Inc., all rights reserved. © 2014 HDR, Inc., all rights reserved. © 2014 HDR, Inc., all rights reserved.
© 2015 HDR, Inc., all rights reserved.
JB Neethling, Mario Benisch HDR Engineering, Inc.
Dewatering and Phosphorus Removal and Recovery Linkages 2015 VWEA Education Seminar Richmond, VA
Type solids oPrimary/WAS oDigestion Conditioning oFerric/Alum/Lime Polymer oCationic, Other Pretreatment Liquid Matrix?
Dewatering Factors
Increase cake concentration Improve solids capture oCentrate/Filtrate quality Reduce Chemical Cost oConditioning oPolymer Reduce energy
Optimize Dewatering
Dewaterability – Water
Where is the water
Water in Sludge
A: Free B: Interstitial C: Surface D: Intracellular
Source: Julia Kopp, PhD
Water in Sludge – Free Water
A: Free Can be removed with mechanical Dewatering. Largest fraction
Source: Julia Kopp, PhD
Water in Sludge – Interstitial
B: Interstitial Bound by capillary forces between flocks
Source: Julia Kopp, PhD
Water in Sludge – Surface Adhesion
C: Surface Bound to surface by adhesive forces. Thermal only
Source: Julia Kopp, PhD
Water in Sludge – Intracellular
D: Intracellular Trapped in cells Thermal or cell destruction
Source: Julia Kopp, PhD
Dewatering and Dewaterability
Only free water can be removed with mechanical dewatering. Why does dewatering performance vary?
Source: Julia Kopp, PhD
Follow approach by Kopp Dry at constant low
temperature – 45 C Monitor weight and
calculate water loss and drying rate Use inflection points as
indicators of water bond strength
Moisture Analysis – Free, Interstitial, Bound water
Define Free Water – Linear relationship drying rate and water content
(B) (A) (C)
y = 0.0252x + 0.0537 R² = 0.9867
0.00
0.05
0.10
0.15
0.20
0.25
0.000.501.001.502.002.503.003.50
dryin
g ra
te (g
/min
)
Mw / Ms (g/g) 001 - DS
From : Kopp & Dichtl (2000)
Free Water Bound Water Interstitial Water
Define Interstitial and Bound Water based on log-linear relationship – drying rate and water content
(B) (A) (C) y = 0.0458ln(x) + 0.0735
R² = 0.9945
0.00
0.05
0.10
0.15
0.20
0.25
0.060.130.250.501.002.004.00
dryin
g ra
te (g
/hr)
Mw / Ms (g/g) 001 - DS
Free Water Bound Water Interstitial Water
From : Kopp & Dichtl (2000)
General Optimization
Optimization typically focus on selecting an appropriate polymer Bench tests oCapillary Suction Test (CST) oCentrifugation oCrown Press oHDR Bench Press Full scale trials Economic evaluation (dose, cost, $/ton) Evaluate a range of option
Performance Testing
Optimizing Dewaterability
Optimizing Dewaterability
Optimizing Dewaterability
Optimizing Dewaterability
EBPR and Dewaterability
EBPR and Dewaterability - Denver
EBPR Pilot
Example Denver R Hite WWTP
EBPR and Dewaterability – Durham CWS
0
5
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0
20
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2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
TS [%
]
Poly
[lb/
ton]
Poly Dose, 30-Day Ave Summer Poly Dose, 30-Day Ave Winter Cake, TS 30 Day Ave
Example Durham AWWTP
Example – Rock Creek AWWTP – Rock Creek
0
5
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30
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160
Dec-07 Dec-08 Dec-09 Jan-11 Jan-12 Jan-13
Cak
e [%
]
Poly
mer
[lbs
/ton]
Dew , Poly Dose -Summer Dew , Poly Dose - Winter Centr Cake, TS
Transition to EBPR
Winter Peak
P-Recovery
EPS – Extracellular Polymetric Substances Changes in water matrix of digester o Increase in orthophosphate o Increase in ammonia oReduced compounds – sulfide, VFA o Increase in potassium o Increase in mono-to-di-valent cations (M/D ratio) oColloidal particles oOther…
What Could Cause Deterioration in Dewaterability
Specifically related to EBPR
EBPR Metabolism Model
Gly
PolyP
H+Ac-
PHB
ATP
Pi
M+ Pi M+
Ac-
H+
NADH
NAD-
Anaerobic
Cell Growth
PHB
Gly
PolyP
TCA
ATP
O2
Aerobic
AcCoA
Pi M+
K. McMahon
Phosphorus Accumulating Organisms
WERF - VIP plant, 7/3/03
Anaerobic Zone (Release)
Aerobic Zone (Uptake)
PO43-
K+
Mg++
VFA
PO43-
K+
Mg++
VFA
Biological Phosphorus Removal
Anaerobic Aerobic
RAS
Clarifier
Anaerobic Zone (Release) PO4
3-
K+
Mg++
VFA - uptake
Aerobic Zone (Uptake) PO4
3-
K+
Mg++
WAS = Uptake
Biological Phosphorus Removal PLUD Digestion
Anaerobic Aerobic
RAS
Clarifier
Anaerobic Zone (Release)
PO43-
K+
Mg++
Aerobic Zone (Uptake)
WAS = Uptake
Digester Dewater Digester (Release)
Liquid
Impact of Phosphorus Recycle
Nansemond Phosphorus Mass Balance
2621
1321
2486 187
322 2299 1300
1508 2808
Potassium and Phosphorus Recycle without recycle P control
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
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200
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600
700
0 5 10 15 20 25 30 35 40 45
K an
d P,
mg/
L
Day
Centrate K, mg K/L Centrate P, mg PL P recycle, % of in
All P released in the digester is recycled
Potassium and Phosphorus Recycle with recycle P control
0%
10%
20%
30%
40%
50%
60%
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90%
100%
0
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0 5 10 15 20 25 30 35 40 45
K an
d P,
mg/
L
Day
Centrate K, mg K/L Centrate P, mg PL P recycle, % of in
EBPR Transfer P to digester and Mg and K
0
10
20
30
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60
70
0
100
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400
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700
Jan-09 Jul-09 Jan-10 Jul-10 Jan-11 Jul-11 Jan-12 Jul-12 Jan-13
sMG
[mg/
l]
PO4-
P [m
g/l]
sK
[mg/
l]
Cent, PO4-P CEN, sK CENT, sMG
Winter Summer
K
Liquid phase changes lead to poor dewaterability oChange in Mono/Divalent (M/D) ratio due to potassim (K) recycle oHigh phosphate increase water content o Ionic double layer compression oOther… Solid phase change in water retention
Hypotheses of Dewatering Impacts
Proposed Solutions
Mg addition based on recycle PO4-P goal Objective to recover P via struvite Discover dewaterability improved
Digested Sludge Recovery Process (Air-Prex)
Digested Sludge Recovery Schematic (AirPrex)
From Digester
Sludge Storage
P-Recovery
Mg
Dewatering
To Land Application
To ?
To Headworks
Add lots of Mg++ Precipitate PO4 as struvite Recover Struvite Residual oPO4 < 20 mg P/L oMg++ = ?? (high)
• M/D likely decrease
Cake increase 21.8% to 28.7% Polymer dose increase 12.5 to 15.5
kg/t (~ 28 to 35 lb/dt)
EBPR and Dewaterability – Airprex (results)
Higgins Investigation shows the relationship between M/D Ratio and PO4-P versus Dewaterability
Cake Concentration increase as M/D ratio decrease
Cake Concentration increase as PO4-P decrease
Higgins et al, (2014) Bio-P Impact Dewatering after Anaerobic Digestion? Yes, and not in a good way! WEF Residuals and Biosolids Conference, 2014.
EBPR and Dewaterability – P recovery and WASStrip
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Jan-08 Jan-09 Jan-10 Jan-11 Jan-12 Jan-13
TS [%
]
Poly
[lb/
ton]
Poly Dose, 30-Day Ave Summer Poly Dose, 30-Day Ave Winter Cake, TS 30 Day Ave
P recovery
WASSTRIP
Durham AWWTP – Schauer paper at Residuals and Biosolids Conference, Washington, June 2015
Lab scale digesters Feed: Primary + EBPR TWAS Three reactors: oBase oWASStripped oWASStrip – with K added Addition of K improved
dewaterability for unknown reason M/D ratio same
WASStrip Impact on Digester and Dewatering
Control WASStrip WASStrip + K
Cake 12.8% 13.3% 14.7%
M/D 66 38* 38
PO4-P ? ? ?
* WASStrip increase NH4+ concentration
and M/D ratio
Higgins et al, (2014) Bio-P Impact Dewatering after Anaerobic Digestion? Yes, and not in a good way! WEF Residuals and Biosolids Conference, 2014.
THP Other cell lysis? Reported to improve
dewaterability
EBPR and Dewaterability – Thermal Hydrolysis, Other
Results from Testing
Optimization Study – Polymer and Coagulant
Alum 0 Alum 1 Alum 2 Alum 3 Alum 4 MgCl2 2 MgCl2 4
Alum dose (lb/dt) 0 162 323 485 647 0 0
Polymer Dose (lb/dt) 55 55 39 55 24 43 32
MgCl2 dose 2x 4x
Pressate sPO4-P 450 450 270 210 210 100 30
Pressate sK 191 191 155 172 172 174 112
Pressate sMg 1.41 1.41 1.37 1.72 1.72 3.79 80.4
Cake 15.1% 14.4% 15.6% 15.9% 15.3% 16.8% 16.4%
Optimization study – Cake vs PO4 – Alum and MgCl2
14%
15%
15%
16%
16%
17%
17%
0 50 100 150 200 250 300 350 400 450 500
Cake
, %
sPO4-P, mg P/L
MgCl2
JB guess
Optimization study – Cake vs K – Alum and MgCl2 (Higher Mg for MgCl2)
14.0%
14.5%
15.0%
15.5%
16.0%
16.5%
17.0%
0 50 100 150 200 250
Cake
, %
Potassium, mg K/L
MgCl2
Summary
Each plant is different Field tests can identify optimal conditions EBPR reduces dewaterability Conditioning can improve Cake content oCoagulant (Alum and Ferric) Addition oMgCl2 addition oDifferent polymer Parting Shot oAdding Coagulant and MgCl2 also increase hauled solids!
Summary
Rebecca Alm et al. - Residuals and Biosolids Conference, Washington, DC June 2015
© 2015 HDR, Inc., all rights reserved.
JB Neethling, Mario Benisch HDR Engineering, Inc.
Dewatering and Phosphorus Removal and Recovery Linkages 2015 VWEA Education Seminar Richmond, VA