squeezing the sludge. thermal hydrolysis to improve wwtp...

June 25-28, 2013 Santiago de Compostela ● Spain

Pedro P. Nieto Sara I. Pérez Elvira & Fernando Fdz-Polanco

Squeezing the sludge.

Thermal hydrolysis to improve WWTP sustainability


1. PRETREATMENTS: Overview

2. Experimental results on Continuous Thermal Hydrolysis (CTH)

Removal 25%

Effluent: 10%

COD in sewage

1ary sludge 30%

2ary sludge 35%

Sludge waste 60-70%

BIOSOLIDS 40% DQO

Biogas 30-40% SLUDGE

>60% COD

Surplus sludge: 1-5%

Over 60% COD is converted into sludge COD = energy

Effluent

1ary sludge 2ary sludge

Biogas

COD in sewage

BIOSOLIDS

Hydrolysis is the limiting step

Energy

CO2

WHY pretreatments?

COD balance at a conventional WWTP

Energy content and organic matter (VS)

(-∆UC) ~ 3.4 Wh/gCOD ~ constant

kJ/gTS(1) kJ/g COD Wh/g COD

Wastewater 3.2 14.70 4.08

Primary sludge 15.9 11.12 3.08

Secondary

sludge 12.4 12.05 3.34

Biosolids 12.7 11.68 3.25

AVERAGE 12.38 3.43

Stream energy balance

E = F (m3/h).c(gCOD/m3). -∆UC (wh/gVS) = Wh/h

(1) From: Shizas and Bagley. (2004). J. Energ. Eng.130 (2)

Mass and energy balances for a conventional WWTP.

400.000 persons. SRT = 5 d

1ary 2ary

A.D

50 t COD/d

203.5 MWh/d

61 MWh/d

142.5 MWh/d

54.9 Mwh/d

67.1 MWh/d

61 MWh/d

20.5 MWh/d

61 MWh/d

35 t COD/d

15 t COD/d

5 t COD/d

15 t COD/d15 t COD/d

13.5 t COD/d

16.5 t COD/d

EECons = 25.2 MWh/d

EEProd = 19.2 “

1ary 2ary

A.D

50 t COD/d

203.5 MWh/d

61 MWh/d

142.5 MWh/d

54.9 Mwh/d

67.1 MWh/d

61 MWh/d

20.5 MWh/d

61 MWh/d

35 t COD/d

15 t COD/d

5 t COD/d

15 t COD/d15 t COD/d

13.5 t COD/d

16.5 t COD/d

EECons = 25.2 MWh/d

EEProd = 19.2 “

Garrido J.M., Fdz-Polanco M., Fdz-Polanco F. (2013). Wat. Sci. Tech. 67.10. 2094-2301

Well-contrasted technologies full-scale

Pre-

treatments

Chemical

Biolog.

Physic.

Acid or alkaline hydrolysis Ozonation

High pressure homogenizers Impact grinding Stirred ball mills Ultrasonic homogenizers High performance pulses Lysat centrifuge Gamma irradiation

THERMAL

Enzymatic treatment Incubation of enzymes

Thermal hydrolysis

How to increase biogas production from sludge

Hydrolysis limiting step

→ Pre-hydrolyze = Pre-treat

IMPACT RING HIGH SHEAR ZONE

VALVE SEAT VALVE STEM

MICROSLUDGE

TECHNOLOGY DESCRIPTION

- High pressure pump: sludge pressurization

- Cell disruption valve: formation of cavitation bubbles

OPERATION CONDITIONS

Constant flow

High pressure: 827 bar

Acceleration: 310 m/s in 2 s

PROCESS DEVELOPMENT

First plant: Mera, 2007

2 plants in North America

PRE-TREATMENT PRINCIPLE

High pressure homogeneizer

CROWN


- Macerator: crush solids

- Progressive cavity pump: 12 bar

- Mixer: homogeneus suspension

- Disintegrator: cavitation through a nozzle

Crown® Disintegration System SLUDGE

THICKENER

DIGESTER

DISCHARGE PUMP

DISINTEGRATION

NOZZLE

MACERATOR PRESURIZATION

PUMP HIGH SPEED MIXER

RECIRCULATION

PUMP


Constant flow

Presurization to: 12 bar

Feed: WAS 3-5%DS (30% influent to AD)

PROCESS DEVELOPMENT

Developed in Germany

> 20 installations in Europe


Controlled cavitation process

ULTRASOUND TECHNOLOGY


Ultrasound producing cavitation


PROCESS DEVELOPMENT

Industrial scale

EIMCO® Sonolizer™, SONICO® Sonix™ , IWEtec


Concentrated sludge

Power and time

Energy

Frecuency 20 -40 kHz


Energy: 300 kWh/ton solids treated

Time < 500 ms

Temperature increase: 20ºF


- Cilindrical treatment chamber between two electrodes

- Rapidly pulsing, high voltage beam

- Formation of tiny pores in the membrane

OPENCEL

PROCESS DEVELOPMENT

First plant: Mera, 2007

2 plants in North America


Focused Pulsed Technology


6 CSTR at 42ºC

HRT: 2-3 days upstream AD

Feed sludge : 6-8%ST

MONSAL


- Endogenous enzymes

- Enzymic Hydrolysis (EH)

- Enhanced Enzymic Hydrolysis (EEH)

PROCESS DEVELOPMENT

First plant: Macclesfield, 2002

11 plants in the UK


Phased biological hydrolysis

EH: Solubilization

EEH: Solubilization + Pasteurization


Concentrated sludge

No use of chemicals

T: 150-230ºC; time: 20-60 min

THERMAL HYDROLYSIS


- Heating under pressure

- Different process configuration (batch/continuous; heating mechanism)

- Different energy recovery schemes

PROCESS DEVELOPMENT

Most references for Cambi and Veolia


Thermal pre-treatment

TurboTec ®

Integrating pretreatment in WWTP

Key parameters for a full picture

1. Type of sluge ( 1ary, 2ary, mixed) / Concentration

2. COD and VS removal /Reology (viscosity) / Mixing energy / Foam formation

3. Dewaterability. / Filtrability / Centrifugability

4. Sanitation / PPCP’s removal

5. COD + nutrients / recirculation to WWTP / recovery.

6. Energy to PT (electrical or thermal) and WWTP (electrical)

WWTP PT

A.D

EWWTP EPT

EBG

1

2

3 4

5

6

1ary

2ary A.D

35ºC.

B

H.W. C.W.

E.E.

CHP E.G

PRETREATMENT ENERGETIC FEASIBILITY

H.W. C.W.

E.E.

CHP

1ary

2ary PT

A.D

35ºC.

E.PT

Δ B

B

H.W. C.W.

ΔE.E

E.E.

CHP E.G

PRETREATMENT ENERGETIC FEASIBILITY

Type of Pretreatment.

Consuming heat: E.PT ≤ (E.G + ΔE.G)

“ electricity: E.PT ≤ ΔE.E

E.E = Cost, profit

E.G = Waste, free

H.W. C.W.

E.E.

CHP ΔE.G

Pretreatment technologies operating with electricity. EPT ≤ ΔEE

E = (3.77 c ηAD ) kwh/m3 sludge

ΔEE = 0.20 c

0

20

40

60

0 50 100 150c (kg ST/m

3)

AE

E (

kw

h/m

3)

AEE

US

PEF

MS

CTH

0

50

100

150

0 20 40 60c (kg ST/m

3)

AE

E (

kw

h/m

3)

AEE

US

MW

Lab scale ultrasound and microwaves totally out of balance ∆EE < E PT

Lab scale

Full scale

Guidelines for selecting pretreatment.

- Many different and attractive technologies.

BUT …..

- Only a few are realistic.

- Many papers are useless or misleading

(out of energy range and only covering partial parameters)

(remember not always 1 kwh = 1 kwh; 1kwhELEC ≠ 1 kwhHEAT)

YOU NEED …..

- Perform realistic mass and energy balances.

(concentration is a key parameter).

- Completing the puzzle. Quantify all the parameters involved:

Type of sluge ( 1ary, 2ary, mixed) / Concentration

COD and VS removal / Reology (viscosity) / Mixing energy / Foam formation

Dewaterability. / Filtrability / Centrifugability

Sanitation / PPCP’s removal

COD + nutrients / recirculation to WWTP / recovery.

Energy to PT (electrical or thermal) and WWTP (electrical)


2. Experimental results on Continuous Thermal Hydrolysis (CTH)

1

15

13

11

6

5

4

3

2

12

10

9

8

7

14

16

ACTYLIS Conceptual Design

ACTYLIS Prototype

ACTYLIS Characteristics

3,000 kg ST/h. (14% ST). 400,000 P.E.

Reactor

Volume = 1.5 m3;

HRT < 15 min;

T=170ºC

Footprint 20 m2

Steam direct injection (0,17 kg steam 12 bar/kg TS)

CTH Prototype

A B C

CTH

2ary

1ary

AD experimental set-up

Reactors characteristics

Volume 200 L

Continuous operation

Mixing: biogas recirculation / sludge reirculation

Feed 50% VS 1ary + 50% VS 2ary

HRT A = C = 21 d.

B = 13 d

21 d 21 d 13 d

A

A B

C

21 d 13 d

21 d

A C B

C

B

A

Biogas productivity

Average Δ biogas (1 year)

A – C → 23%

B - C → 17%

Industrial 32%

Foam destruction

and

Spring 2013

Both collapsed by persistent

foam

1ary + fresh 2ary

1ary + CTH

2ary No

foam

1ary + fresh 2ary

Foam

CHANGE

Sludge (170 ºC, 15 min).

40x . Microthrix parvicella

Fresh sludge

Industrial AD Reactor C

Reactor A & B

Abundance of filamentous bacteria

Eikelboom Criterion Experimental results

Foam destruction

T (ºC)

TH + SE TH

Time (min) Time (min)

5 15 30 5 15 30

120 5 4 4 5 5 5

150 4 4 3 5 4 4

170 3 2 2 4 3 3

Thermal hydrolysis breaks filamentous bacteria

Steam explosion improves filamentous bacteria destruction

No foam formation

Rotational viscosimeter

μF = 4 μTH

Mixing energy

Viscosity

Dewaterability

Centrifugability Cake

Liquid

1 ary + 2ary sterilized

CTH

A

D Pathogens free

CTH

AD

1ary

2ary (?)

sterilized Pathogens regrowth (?)

Thermal hydrolysis sterilizes secondary sludge.

After AD of mixed sludge 6/7 samples are free of E. coli and 3/7 samples are salmonella free.

Regrowth can be important factor.

Average values for 7 samples. 1 sample / week

Forming Colonies Unit (FCU / g sludge)

Pathogens destruction

and regrowth

Pharmaceutical and Personal Care Products (PPCP’s) Removal

(WAS + PPCP)

(WAS + PPCP) + (TH)

Lyophilization (90 h)

Pressurized Liquid

Extraction PLE

LC-Ms-Ms (QqQ)

Specialized lab

1008210010010010067Ibuprofen

1009610010010010070Diclofenac

100100100100100100100BP-3

100100100100100100100Bezabifrate

99999999999987Clofibric Acid

92888590898636Propyl paraben

3845316229350Methylparaben

************32Salicylic Acid

100901006910010083Naproxen

999599999910068Carbamazepine

78788156826744Propanolol

99999999999945Metropolol

10093100931009596Caffeine

99**99**99**99Acetominophen

TH +ADTHTH +ADTHTH +ADTHAD

AcidBasicNeutralFreshCOMPOUND

1008210010010010067Ibuprofen

1009610010010010070Diclofenac

100100100100100100100BP-3

100100100100100100100Bezabifrate

99999999999987Clofibric Acid

92888590898636Propyl paraben

3845316229350Methylparaben

************32Salicylic Acid

100901006910010083Naproxen

999599999910068Carbamazepine

78788156826744Propanolol

99999999999945Metropolol

10093100931009596Caffeine

99**99**99**99Acetominophen

TH +ADTHTH +ADTHTH +ADTHAD

AcidBasicNeutralFreshCOMPOUND

Centrate characteristics

Conclusions

Acknowledgements


Pedro P. Nieto Sara I. Pérez Elvira & Fernando Fdz-Polanco

Squeezing the sludge.

Thermal hydrolysis to improve WWTP sustainability

squeezing the sludge. thermal hydrolysis to improve wwtp...

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