July

201

3

TECHNICAL DIRECTOR

ENVIRONMENTAL APPLICATIONS OF ACCELERATORS

INDUSTRY CHALLENGES – SLUDGE TREATMENT

MARTIN JOLLY

Employee-owned company, founded in 1915. Engineering, consulting and construction.

• Energy • Water • Telecommunications • Management Consulting

Page - 3

Water Treatment

Works

Sewage Treatment

Works188kWh/Ml

219kWh/Ml

219kWh/Ml191kWh/Ml

447kWh/Ml

Total usage = 635GWh/a

1250Ml/d 1500Ml/d

TYPICAL UK WATER COMPANY ENERGY USAGE

Page - 4

Water Treatment

Works

Sewage Treatment

Works

1250Ml/d 1500Ml/d

Total usage = 635GWh/a

188kWh/Ml

219kWh/Ml

219kWh/Ml 191kWh/Ml

447kWh/Ml

45kWh/Ml

45kWh/Ml

41kWh/Ml

81kWh/Ml

Reduction

22%Total usage = 495GWh/a

30kWh/Ml

40kWh/Ml

TYPICAL UK WATER COMPANY ENERGY USAGE

Page - 5

TYPICAL UK WATER COMPANY ENERGY USAGE

0

100

200

300

400

500

600

700

1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055

GW

h/a

635

495

Apply significant energy saving &

generation measures

1990 Baseline

TYPICAL SEWAGE TREATMENT WORKS

Primary settlement

tank

Aeration tank requires air to treat sewage by oxidising

BOD & Ammonia

Air supplied by a blower through a

network of pipes.

Primary sludge

SAS

Digestion

Biogas for electricity generation

Sludge for disposal or recycling

Clean effluent to

river

DIGESTION- COVERT ORGANIC MATTER TO METHANE

Nitrogen Rich Organic Matter (sewage sludge)

Volatile Fatty Acids & Other Compounds

Rapid (Hydrolysis)

MethaneAmmonia Slow (Methanogenesis)

CO2

Ammonium Bicarbonate Alkalinity (Buffering)

Equilibrium is required

Page - 8

SludgeBiogasPowerLiquors

SLUDGE TREATMENT

Page - 9

1. Thermal Hydrolysis

2. Enzyme Hydrolysis

3.Thermophilic digestion

4. Ultrasound

5. Microsludge

6. OpenCEL

7. Cell Rupture

Advanced Digestion

Page - 10

THE RISE OF ADVANCED DIGESTION

Technology First trial First Full scale plant

Number of full scale plants

Thermal Hydrolysis Early 1990 1996 24

Enzyme Hydrolysis Late 1990s 2002 11

Thermophilic digestion 1950s 1954 >20

Ultrasound 1990s 2000 >10

Microsludge 2000 2004 3

OpenCEL 2000 2007 1

Cell Rupture 2004 N/A 00

10

20

30

40

50

60

70

1960 1970 1980 1990 2000 2010 2020

ADVANCED DIGESTION PROCESS FLOW SHEET

Liquor treatment

Power out

CHP

Gas holder

Excess biogas burner

Digestion

Cake Out

Digested sludge

dewatering

Cake storageSludge storage

Sludgefeed tank

Advanced digestion pre-

treatmentThickening

Sludge In

26th January 2011B&V

Description Units Existing NewCapacity of plant tds/a 39 000 91 000Maximum energy production

Mw 3.7 11.5

Digester volume m3 60 000 60 000Feed to digester Dry solids (%) 5-6 11

Photo courtesy of Cambi

Manchester wastewater plant

Page - 13

VOLATILE SOLIDS DESTRUCTION VS SLUDGE COMPOSITION

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100

Percent primary sludge (%)

VS

de

str

uc

tio

n (

%)

Electrical & mechanical treat SAS

only

Heat treatment blended sludge

32

45

58

100% SAS 100% Primary

y = -0.6831x + 64.625

R2 = 0.641

y = -0.1979x + 42.519

R2 = 0.4852

15

20

25

30

35

40

40 45 50 55 60 65 70 75

Volatile solids in cake(%)

Cak

e d

ry s

oli

ds

(%)

Conventional digestion Thermal hydrolysis and thermophilic digestion

Linear (Conventional digestion) Linear (Thermal hydrolysis and thermophilic digestion)

Page - 14EMPIRICAL CAKE DRY SOLIDS VS VOLATILE SOLIDS

Conventional treatment – 45 sites

Thermal treatment – 5 sites

Page - 15

FEED & CAKE DRY SOLIDS

20 21 22 23 24 25 26 27 28 29 30 31 32

Mesophilic digestion

Thermal hydrolysis

Enzyme Hydrolysis

Thermophilicdigestion

Ultra sound

Microsludge

OpenCEL

Cell ruptureAll processes improve

dewaterability, thermal more than others

Thermal

Thermal

Part Thermal

6%

6%

6%

6%

6%

7%

11%

6%

Digester Ammonia Concentration

0

1000

2000

3000

4000

5000

600001

-Jul

-01

08-J

ul-0

1

15-J

ul-0

1

22-J

ul-0

1

29-J

ul-0

1

05-A

ug-0

1

12-A

ug-0

1

19-A

ug-0

1

26-A

ug-0

1

02-S

ep-0

1

09-S

ep-0

1

16-S

ep-0

1

23-S

ep-0

1

30-S

ep-0

1

07-O

ct-0

1

14-O

ct-0

1

21-O

ct-0

1

28-O

ct-0

1

04-N

ov-0

1

11-N

ov-0

1

18-N

ov-0

1

25-N

ov-0

1

02-D

ec-0

1

09-D

ec-0

1

16-D

ec-0

1

23-D

ec-0

1

30-D

ec-0

1

06-J

an-0

2

13-J

an-0

2

Am

mo

nia

Co

nc

en

tra

tio

n (

mg

/l)

Digester No.1 Digester No.2

AMMONIA CONCENTRATION IN DIGESTER

Ammonia concentration in digester is a function of : 1. Feed dry solids2. Digester performance3. Sludge nitrogen content4. Up to 3000mg/l ammonia compared to conventional

MAD – 1000mg/l

LIQUORS FROM DIGESTED SLUDGE

Liquors need to be treated

Dewatering centrifuges used to produce a cake

0

500

1000

1500

2000

2500

3000

Mesophilic digestion

Thermal hydrolysis

Enzymic Hydrolysis

Thermophilic digestion

Ultra sound Microsludge OpenCEL Cell rupture

kg/d

, mg

/l

Digester ammonia content mg/l Ammonia load kg/d

Page - 18

High concentration of ammonia from thermal

hydrolysis as digesters fed at 11% dry solids

However loads from all process similar as lower

flow from thermal hydrolysis dewatering

LIQUOR TREATMENT

VALUE FOR MONEY

Mesophilicdigestion

Thermalhydrolysis

EnzymeHydrolysis

Thermophilicdigestion

Ultra sound Microsludge OpenCEL Cell rupture

Relative operating cost benefit to mesophilic

digestion

Relative capital cost to mesophilic digestion

Generally, you get what you pay for, with 1 possible exception

Struvite: (NH4)MgPO4·6(H2O)

CHALLENGES

• Energy – Water companies need to reduce from 495GWh/year to less than 100GWh/year.

• Organic matter - only able to convert a maximum of 60% to methane.

• Nitrogen – some recovery in bulk as a natural fertiliser.

• Phosphorus – recovery possible but not widespread.

THIS IS A RESOURCE