S4 Wastewater Treatment and Reuse Technologies and Systems: Using Less Energy while Meeting Tougher Environmental Standards by Hongbo Bobby Ding

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Green Machine- A Hybrid Process Combining Bio-Sorption andAnaerobic Digestion

Bobby, Ding Hong-Bo 1

Xiao Lan 1

Rohan Wikramanayake 1

Shouvik Chanda 2

1

Siemens, Water Technologies, Global R&D Center, Singapore2 Siemens, Industry Sector, Industry Solution, Water Technologies, Singapore



P age 2Protection notice / Copyright notice

16/5/2011 Water Technologies

Dilemma of Wastewater Treatment- Conventional P rocess

CostConventional aerobic wastewater treatment process hashigh demand of electricity for O 2 transfer.Energy price is increasing fast.

Environment Aerobic bio-process generates large amount of excessivesludge for disposal.Conventional process convert COD to CO 2, which increasethe global green house effect.

Problems





Dilemma of Wastewater Treatment- Anaerobic P rocess

Municipal WW has low COD/BOD concentration.

Waste activated sludge is difficult to digest.

Long aerobic SRT and fully nitrification make the sludge moredifficult to digest.

Low water temperature in winter significantly slows downanaerobic reaction rates and creates additional energy demand

Challenges





A Green Solution from Siemens

Green

Solution

Lower Energy Consumption : Less aerobic degradation / less aeration

Easy for Retrofit : Upgrade existing WWT P with minimum structure change

Low Sludge Yield : Combined bio-sorption & AD lead to low sludge production

Waste to Energy : Recover more energy from WWReliable Process : Activated sludge process and AD are accepted and proven

Design Flexibility : Operate with or without primary clarifiers

What is the Green Solution ?





Green Machine Process

Adsorption on cell surface and E P S.

Flocculation by inorganic flocculants.

Bioreactor 1

Bioreactor 2

Influent Effluent

WAS

RAS

Bio-Sorption Anaerobic Digestion

Concentrated COD

Biosorption Media

Sludge carries more COD to AD for biogas production.

Digested sludge provides bio-sorption media in return.

More COD conversion in AD & more biogas production

Less aerobic conversion & less aeration energy required

Less sludge product because of above two.





PFD Used for Computer Simulation

Biogas = Onsite Power

Influen t

AnaerobicDigester

WasteSludge

Bioreactor 2

WASSludge

Thickening

Clarifier

Low BODEffluent to

DownstreamPolishing

PrimaryClarifier

RAS

Bioreactor 11

2

3

45

Flow rate (m 3 /day) 350,000 [1] 350,000 [1 ] 350,000 [1] COD (mg/l) 300 [1] 600 [2 ] 800 [1 ] TSS (mg/l) 150 [1] 258 [3 ] 330 [1 ] VSS (mg/l) 117 234 312TKN (mg/l) 38 [4 ] 65 [4] 83 [4]

NH 3-N (mg/l) 25 [1 ] 43 [3] 55 [1] TP (mg/l) 10 [5 ] 10 [5] 10 [5] Temperature C 20 [5 ] 20 [5] 20 [5]

Influent characteristics for the process simulations

The energy content of CH4is 35,846 kJ/m3.

Aeration efficiency is1.52 kg. O2/kwh.

Mixing energy for anaerobicdigester is 0.008 kw/m3.(Tchobanoglous et al. 2004)

Total pumping energy is estimatedbased on flow rate= ADF=350,000m3/day, TDH=2 meters and pump andmotor total efficiency of 50%

Sludge enter anaerobic digester willbe heated up from 20 r C to 35 r C.

Down stream MBR aerationenergy is 0.2 kwh/m3 treated water.

35% of the energy in CH4 willbe converted to electricity, 65%converted to heat.

Simulation Assumptions Green Machine Flow Diagram







Pilot Study - 600 L /d per train process

Location : Ulu P andan WWT P in SingaporeTemperature : 25-35°C/ tropical climateWW Source : Raw sewageConfiguration : without primary clarifiers (the worst condition scenario)





Pilot Performance ± COD Removal

COD Removal Efficiency

0

20

060

0

100

120

0 /12/10 06/11/10 0 /10/10 10/09/10 12/0 /10 02/06/11 0 /0 /11

Conventional Procereen achine Proce

COD Removal

reen achine 90

Conventional 89

Satisfactory COD removal





Pilot Performance ± Biogas Production

Biogas Production L /d

Green Machine 40 9

Conventional 25 0

Biogas Production

0

20

0

60

0

100

0 /12/10 06/11/10 0 /10/10 10/0 /10 12/0 /10 02/06/11 0 /0 /11 B i o g a s

P r o

d u c t

i o n

a t e

, L / d

Conventional P rocessGreen Machine Process

%164%100/0.25/9.40 _

}v!d Ld L

al ConventionMachineGreen

50% more biogas production





Pilot Performance ± Sludge Yield

%50%100/39.0/20.0 _ }v!

COD g TSS g COD g TSS g

al ConventionMachineGreen

Sludge Production

0

20,000

40,000

60,000

80,000

100,000

04/12/10 06/11/10 08/10/10 10/09/10 12/08/10 02/06/11 04/07/11

S l u d g e

I n v e n

t o r y

( g )

Conventional Process

Green Machine Process

Sludge Production kg -TSS /kg -CODin f luent

Green Machine 0 20Conventional 0 39 50% sludge reduction







ROI SingaporeConventional vs. G M for 20 MGD to 25 MGD Municipal WWT P Upgrade/Expansion (from 76,000 m 3/d to 95,000 m 3/d)

y Savings from aeration power: 960K

y Saving from on-site power generation: 505K

y Saving from sludge reduction: 372K

y Additional capital cost from GM: 4.7M

y Annual GM saving: 1.7 M

y ROI: 3 yrs

EnergyConsumption

Conventional GMP

Energy Recovery/Generation

kW

kW

1289

581 644871

Singapore average conditions Ambient Temperature = 30 °CDigester Temperature = 35 °CElectricity cost = US 0.17/kWhSludge disposal cost = US 50/tonne (wet)

Parameters Conventional GM GM C Aeration Basin ol ( Mgal) 5.1 5.2 1.01 Aeration P ower (kW) 1289 644 0.50Digester olume ( Mgal) 2.82 2.75 0.97Digester Feed Concentration 4.0% 7.0% 1.75Digester Loading (lbs/d) 72,188 89,655 1.24Biogas P roduction 264,469 396,704 1.50

Biogas P ower P otential (kW) 581 871 1.50 Aeration P ower Cost 1,919,287 959,643 0.50Biogas Energy alue (incl. heat value) 1,008,065 1,512,098 1.50Sludge Disposal Cost 1,489,680 1,117,260 0.50GM Added Annual O& M $67,800GM Annual Service Contract $76,000Total Annual Costs $2,400,902 $708,606 Annual G M Savings 1 692 296Estimated Capital Cost $20,737,422 $4,690,140Straight ROI (years) 3

Largest saving fromaeration cost





ROI PhilippinesConventional vs. G M for 20 MGD to 25 MGD Municipal WWT P Upgrade/Expansion (from 76,000 m 3/d to 95,000 m 3/d)

y Savings from aeration power: 790K

y Saving from on-site power generation: 428K

y Saving from sludge reduction: 104K

y Additional capital cost from GM: 4.7M

y Annual GM saving: 1.2 M

y ROI: 4 yrs

EnergyConsumption

Conventional GMP

Energy Recovery/Generation

kW

kW

1289

581 644871

Philippines average conditions Ambient Temperature = 30 °CDigester Temperature = 35 °CElectricity cost = US $0.14/kWhSludge disposal cost = US $13/tonne (wet)

Parameters Conventional GM GM C Aeration Basin ol ( Mgal) 5.1 5.2 1.01 Aeration P ower (kW) 1289 644 0.50Digester olume ( Mgal) 2.82 2.75 0.97Digester Feed Concentration 4.0% 7.0% 1.75Digester Loading (lbs/d) 72,188 89,655 1.24Biogas P roduction 264,469 396,704 1.50

Biogas P ower P otential (kW) 581 871 1.50 Aeration P ower Cost $1,580,589 $790,295 0.50Biogas Energy alue (incl. heat value) $855,420 $1,283,130 1.50Sludge Disposal Cost $417,110 $312,833 0.50GM Added Annual O& M $67,800GM Annual Service Contract $76,000Total Annual Costs $1,142,279 - $36,203 Annual G M Savings 1 178 482Estimated Capital Cost $20,737,422 $4,690,140Straight ROI (years) 4

Largest saving fromaeration cost





Conclusions

Green Machine P rocess

has actual performance similar to computer simulation;

has comparable COD removal to conventional process;has 50-60% more biogas production;

has 50% less sludge production;

Upgrade/expanding of the existing WWT P gives a ROI of 5 years for US, 3 years for Singapore, and 4 years for P hilippines.





Acknowledgement

The Green Machine P roject was financially supported by the EconomicDevelopment Board (EDB), the Environment & Water IndustryDevelopment Council (EWI), and the P ublic Utilities Board ( P UB) of theRepublic of Singapore.

Documents

S4 Wastewater Treatment and Reuse Technologies and Systems: Using Less Energy while Meeting Tougher Environmental Standards by Hongbo Bobby Ding