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Optimizing Polymer Preparation to Enhance Sludge Dewatering

Dr.-Ing. Julia B. Koppspeaker of the german specialist group of “sludge dewateringand conditioning” (DWA KEK 2.3)

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DWA Fachausschuss AK 2 „Stabilisation, Konditionierung, Eindickung, Entwässerung und Entseuchung von Schlämmen“

Technical Guide DWA M 366Mechanical Dewatering of Sewage Sludges2013

DWA Specialist Group

Technical Guide DWA M 350Polymer Preparation2014

Technical Guide DWA M 383Sludge Characterisation2008

Technical Guide DWA M 381Sewage Sludge Thickening2007

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dewaterabilty depends on sludge properties

Quelle : DWA M-366 Dr. Denkert

Fee

d Q

[m³/

h]; P

oly

[kg/

t DS

]; D

S-c

ake

[%]

Load

[kg

DS

/h] i

n ce

ntrif

uge

DS-cake [%] Feed [m³/h] Polymer [kg/t DS] Load [kg DS/h]

Sludge A Sludge B Sludge C Sludge D

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Influence of sludge structure

DSdewatered ~ 30% DSdewatered ~ 20%

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Only the free water can be separated

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DS(A) = measurement of free water content

0.00

0.02

0.04

0.06

0.08

0.10

dryi

n g r

ate

[g/

h]

0.0 1.0 2.0 3.0 4.0 5.0

masswater/ massDS [g/g]

Y = 0.0656 + 0.00205296XEMS = 8.93501e-008R2 = 0.970

DS(A) = 100 / ( 1 + 2,15 ) = 31,8 %

A free water

15

20

25

30

35

40

in fu

ll sc

ale

proc

esse

s [%

]dr

ied

solid

s af

t er

dew

ater

ing

15 20 25 30 35 40

dried solids at point A of the drying curve - DS(A) [%]

Y = 1.777 + 0.9437X

centrifuges

filter presses± 1,5 %

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Sludge Conditioning

Flocculation of digested sludge

8overdosage

DS-cake [%] digested sewage sludge

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Dripping Test

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good = min time + max filtrate

Example – Dripping Test - Dewatering

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streaming potential measurement

Stempel

PTFE - Meßgefäß

Probe

Elektroden

Partikel adsorbiert

Partikelnicht adsorbiert

Scherebene

(Bley / Muetek)

requirement: optimal polymer conditioning

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25°CPolymer 1: shear-stabel

Polymer-demand 14,5 kg AS/t DS

Polymer-dosage 13 kg AS/ t DS

DS dewatered = 26,8% DS

Degree of separation =98,9 > 95%

DS(A) = 28%

Polymer 2: not suitable

Polymer-demand 8,6 kg AS/t DS

Polymer-dosage 12,5 kg AS/ t DS

DS dewatered = 24,3% DS

Degree of separation = 89,2 < 95%

DS(A) = 28%

Polymer Preparation

Optimal preparation is needed for an optimal dewate ring

Maturing time: > 45 min

Dilution: 2 chamber system

Dosing: within 4 hours after maturing

Control: DS of polymer solution13

polymeres Flockungsmittel Ladungsbildung Hydratisierung und Handelsware Streckung der Moleküle

Polymerproduct

Non dilutedcharging streching

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viscosity - maturing

-CH 2 -CH -CH 2 -CH -

C= O

N H 2

C= O

O

CH 2

CH 2 N (CH 3 ) 3

+ Cl - +el. conductivity

emulsion cross linked

emulsion linear

powder polymer

Maturing time

Maturing time & Usability of polymer-solution

15

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16 18 20 22 24

Zeit [h]

Eta

[mP

as]

Emulsionspolymer linear 0,5% WS-Ansatz

Emulsionspolymer vernetzt 0,5% WS-Ansatz

Time [h]

Vis

cosi

ty [m

PA

S]

Maturing time & Usability of polymer-solution

short preparation 10 min

optimal preparation 45 min

after 4 hour maturing

Influence of polymer concentration

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165

180

250

310

40

45

52

58

0

10

20

30

40

50

60

70

0

50

100

150

200

250

300

350

0,1 0,3 0,5 0,7

min

imu

m r

ipe

nin

g t

ime

[m

in]

ma

xim

um

wo

rkin

g t

ime

[m

in]

Concentration polymer solution [%]

Control of maturing time and the optimal working time of PolyChemie CP 66U

working time maturing time

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Equipment3-Champer-Systems

don‘t use:

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Recommendation: 2 - Chamber - System

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Polymer-Preparation-Pumps

� Polymer-preparation-pumps work solely with liquid products

� Gear pump produces high mixing energy

� +: needs no further pumping

� - : maturing time ist too short

� Connected maturing tank is recommended

PolymerSolutionWater

Water

Mixing Pump

PolymerSolution

Polymer-product

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Connected maturing tank is recommended!

Polymer-Preparation-Pumps

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First contact

Polymer - Water!needs high turbulence

Water

powder polymer

Inline mixer / ejector pump

Liquid polymer Mixing tank

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Quality - Control

• Take 500 gr. retain sample per delivery(date/ charge number)

• Liquid Polymer ~ 48% Active Substance (AS), rest = oil and add ons

• Powder Polymer ~ 95% AS, rest = citric acid, salt and add ons

• Check concentration of polymer solutionby DS measuring

• Documentation of consumptionkg merchandise / t DSkg AS / t DS

• Control maturing time with signal colourfrom sewage drain

• Check polymer demand by conditioning tests

concentration of polymer solution – DS solution

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DS

of p

olym

er s

olut

ion

[%]

AS in polymer solution [%]

Summary

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• Only free water can be separated by mechanical dewatering → DS(A)

• The proper selection and preparation of polymer is required to achieve good dewatering results.

• The building of shear stable flocs by conditioning is important.

• The polymer-demand and the dewatering result depend strictly on quality of polymer preparation. Mostly the maturing time is disregarded.

• By measuring viscosity of the polymer solution the maturing time can be determined. The time of utilization depends on pH and polymer-concentration.

• It will be recommended to prepare polymer solution for 45 min and use the solution during 4 hours.

• For polymer-preparation 2-Chamber-Batch-Systems will be recommended

• Check concentration of polymer-solution frequently by measuring DS

• Check polymer-consumption 4 time a year anddocument operating data accurate.

Dr.-Ing. Julia B. Kopp - tel. +49 5174 / 922 043 - www.kbkopp.de

Questions

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