© 2014 HDR, Inc., all rights reserved.JB Neethling, Mario Benisch HDR Engineering, Inc. Dewatering and Phosphorus Removal and Recovery Linkages 2015 VWEA Education Seminar Richmond,

© 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

10

15

20

25

30

0

20

40

60

80

100

120

140

160

180

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

10

15

20

25

30

0

20

40

60

80

100

120

140

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

100

200

300

400

500

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%

70%

80%

90%

100%

0

50

100

150

200

250

300

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

40

50

60

70

0

100

200

300

400

500

600

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

0

5

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30

0

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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