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8/6/2019 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
8/6/2019 S4 Wastewater Treatment and Reuse Technologies and Systems: Using Less Energy while Meeting Tougher Environmental Standards by Hongbo Bobby Ding
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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
8/6/2019 S4 Wastewater Treatment and Reuse Technologies and Systems: Using Less Energy while Meeting Tougher Environmental Standards by Hongbo Bobby Ding
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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
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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 ?
8/6/2019 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 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.
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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
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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)
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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
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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
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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
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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
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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
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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.
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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.
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