potential energy recovery from wastewater treatment – study
TRANSCRIPT
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
POTENTIAL ENERGY RECOVERY FROM WASTEWATER TREATMENT – STUDY OF
UASB REACTOR IN ACCRA, GHANA
PRESENTED BY:
KOBINA MENSAH AFFUL
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Motivation
• GAMA - Inefficient sewage and faecal sludge
treatment facility GAMA
• Environmental Benefits• Less pollution to receiving water bodies
• Climate change – reduction in carbon emission
• Financial/Economic Benefits• Energy recovery (methane production)
• Nutrient recovery (fertilizer)
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Description of Plant
screen
Grit channel
Influent
Overflow
Grit channel
screen
Primary distribution boxes
Secondary distribution box
Tertiary distribution box
Sludge thickener
Gas hood
Pen stocks
UASB 1UASB 2UASB 3UASB 4UASB 5UASB 6
Effluent channel
CAPS
Trickling Filter
FST Trickling Filter
FST
Final Effluent to Korle Lagoon
Sea
out-
fall
Slud
ge D
ryin
g B
eds
Slud
ge D
ryin
g B
eds
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Background (AD process/ADM1 description)
AD process
Conversion processes in AD as used in ADM1
Hydrolysis
Acidogenesis
Acetogenesis
Methanogenesis
Homoacetogenic bacteria
Acetate oxidizing bacteria
Complex Organic Matter
Carbohydrates Proteins Lipids
Monosaccharides Amino Acids LCFA
Propionate, Butyrate, Valerate
Acetate
CH4, CO2
H2, CO2
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Model Development (Biochemical process Scheme)
Volatile fatty acids (SHAC)
Acidogenic bacteria (Xac)
Soluble degradable matter (Ss)
Particulate matter (Xc)
Inert soluble (Si)Inert Particulate (Xi)
Methanogenic bacteria (XCH4)
Methane gas (SCH4)
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
…Model Development (Process Matrices) …
Component
Process
Xs Xch4 Xac Xi Ss Shac Sch4 Si Rate
Hydrolysis -1 fxi_xs 1-fxi_xs-fsi_xs fsi_xs Acidification Yac -1 1-Yac
Methanogenesis Ych4 -1 1-Ych4
Decay of Xac 1-fxi_d-fsi_d -1 fxi_d fsi_d Decay of Xch4 1-fxi_d-fsi_d -1 fxi_d fsi_d Unit kg COD/m
3
Bio
deg
rad
able
susp
end
ed C
OD
Met
han
e p
rod
uci
ng
bio
mas
s
Aci
d p
rodu
cin
g
bio
mas
s
Iner
t su
spen
ded
org
anic
mat
ter
Bio
deg
rad
able
solu
ble
CO
D
Org
anic
aci
ds
Met
han
e
So
lub
le i
ner
ts
Component
Process Sch4 Rate
CH4 gas transfer -1 kLa (Sch4-64kH,Ch4ρgas,ch4)
Biochemical process matrix
Physico-chemical process matrix
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
…Model Development (Compartments & Links)
Diffusive
Advective
Bifurcation (for recirculaion)
Excess Sludge Collector
Outlet
Reactor
Headspace
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
…Model Input Parameters…
• Influent Flow
o Average daily flow measurements
• Influent COD fractionation
o Biodegradable Soluble (Ss)
o Biodegradable Particulate (Xs)
o Unbiodegradable Soluble (Si)
o Unbiodegradable Particulate (Xi)
• Kinetic Parameters
o Adopted as proposed by Bastone et al (2002)
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Model Calibration…
• Measured data (21/08/2002 – 21/11/2002):
o Average daily CH4 produced
o Average daily Effluent COD
o Average daily Effluent TSS
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
…Model Studies (Model Predictions)…
Scenario Model Prediction
CH4 (m3/d) Effluent COD Flux
(kgCOD/d)
Flux of Excess
Sludge (kgTSS/d)
1 2763 527 3574
2 2802 2354 3545
3 4266 5229 8477
4 4294 5428 8294
Model predictions for various scenarios
• Max. COD load for TF is 6,580 kgCOD/day
• Max. TSS load for sludge thickener is 7420 kgTSS/day
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
…Model Studies (Extra Organic Load)
• Qinf(septage+PT) of 780m3/d
• 80 trucks/d (average truck volume of 9.5m3)
• 30 trucks public toilet
• 50 trucks septage
• Estimated CH4 production of 4165m3/d
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
• 100kg COD is approximately 35m3 CH4. Therefore 4165m3 CH4 will represents 11,785kgCOD.
• 1tonne COD 3820kWh-e. With 0.85 efficiency of gas treatment unit and a motor efficiency of 40%, 11.785tonnes COD will generate 11.785 x 3820 x 0.85 x 40% = 15,306 kWh-e
• In Ghana, current 1kWh cost 0.17 GHC. Hence 15,306 kWh-e will cost approximately 2,602GHC
• Annually = 950,000GHC (equivalent to 475,000€)
Potential Economic Benefits
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Conclusions
• Showed applicability of simplified ADM 1 for UASB treating municipal waste water in the prediction of CH4 and effluent characteristics
• Wide uncertainty due to the unavailability of enough data for the model development, calibration and validation
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Recommendation
• Extensive study into influent characterisation of the various waste water streams
• Expansion of the model to describe other processes that were not considered under this study
• The predicted methane production could be treated with addition of extra unit and sold to the nearby brewery industry. Hence the need for an extensive financial model to determine the economic viability of this measure.
3rd Ghana Water Forum , College of Physicians and Surgeons – Accra, 5-7 September, 2011
WASTECARE
Thank you for your kind attention