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POTENTIAL FOR GENERATION OF ADDITIONAL REVENUE FROM PRODUCTS OF WASTEWATER TREATMENT Dr. Damjan Nemec ( B.Sc.Chem.Eng . ). Wastewater treatment in general. Process of removing contaminants from collected sewage Household sewage Industrial sewage Nature of contaminants : - PowerPoint PPT Presentation
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POTENTIAL FOR GENERATION OF ADDITIONAL REVENUE
FROM PRODUCTS OF WASTEWATER TREATMENT
Dr. Damjan Nemec(B.Sc.Chem.Eng.)
Wastewater treatment in general
Process of removing contaminants from collected sewage Household sewage Industrial sewage
Nature of contaminants: physical (TSS) chemical (COD) biological (BOD)
Objective is to produce an environmentally-safe effluent
Wastewater treatment in general
Basic process steps
Usually regarded as the black sheep of utility services High operating costs and rarely appreciated by the public
Preliminary(physical)
• Screening• Grit removal• Grease removal
• Efficiency: - TSS = -10% - COD = - 5% - BOD = - 5%
Primary(physical, chem.)
• Sedimentation
• Efficiency: - TSS = -50% - COD = -20% - BOD = -20%
Secondary(biological)
• Aeration• Sedimentation
• Efficiency: - TSS = -95% - COD = -90% - BOD = -95%
Tertiary(advanced)
• Nutrient removal• Filtration• Adsorption• Disinfection
• Efficiency: - TSS > -99% - COD > -99% - BOD > -99%
Wastewater treatment in Mombasa
Wastewater treatment in Mombasa
Kipevu WWTP
Kizingo WWTP
Kipevu WWTP
influentKipevu WWTP
effluent
aeration tanks
sludge thickeners
screens & grit
removal
sludg
e dr
ying
bed
s
sludge
settlingtanks
Plant capacity: 196.000 P.E. 17.100 m3/d 9.580 kg/d BOD
Electricity consumption
Overall cost 5.606.400 kWh/a × 20 KSh/kWh = 112.128.000 KSh/a
Kipevu WWTP
Equipment No. of units kW per unit kW total h/d daily (kWh) annual (kWh) Aerators 16 45 720 20 14.400 5.256.000 Settlers 4 1,5 6 24 144 52.560 Return sludge pumps 4 5 15 24 360 131.400 Excess sludge pumps 2 5 5 12 60 21.900 Sludge thickeners 2 2,5 5 24 120 43.800 Screw pumps 2 15 15 4 60 21.900 Washout pump 1 4 4 24 96 35.040 General 1 10 10 12 120 43.800 Total 780 15.348 5.606.400
influentKipevu WWTP
effluent
aeration tanks
sludge thickeners
screens & grit
removal
sludg
e dr
ying
bed
s
sludge
settlingtanks
Digester #1 Digester #2Biogas cleaning
Biogas storage
Flare CHP unit
Sludge
Thickened sludge
Biogas Biogas
Biogas production from sludge
Nett production of electricity 7.635 - 1.455 = 6.180 kWh/d 2.255.700 kWh/a × 20 KSh/kWh = 45.114.000 KSh/d (40%)
Overall investment 1.826.000 € (~ 5,3 years of payback)
41% less sludge to dispose!
Biogas production from Kipevu WWTP sludge
Kipevu WWTP
Expanding services
Biogas plant has space for additional substrate Food waste from hotels can be collected as extra service
~100 hotels, ~6.500 tourists ~0,5 kg of food waste per tourist => 3,5 t/d of energy rich waste
Biogas storage
Flare CHP unit
Food waste
Digester #1 Digester #2Biogas cleaning
Sludge
Substrate
Biogas Biogas
Biogas production from sludge
Nett production of electricity 8.670 - 1.510 = 7.160 kWh/d 2.613.400 kWh/a × 20 KSh/kWh = 52.268.000 KSh/d (47%)
Overall investment 1.923.000 € (~ 4,8 years of payback)
37% less sludge to dispose!
Biogas production from Kipevu WWTP sludge
influentKipevu WWTP
effluent
aeration tanks
sludge thickeners
screens & grit
removal
sludg
e dr
ying
bed
s
sludge
settlingtanks
Can be treated further with advanced methods and reused: Urban reuse:
• Irrigation of public parks, landscapes and golf courses• Vehicle washing and decorative water features• Connecting to fire hydrants for fire protection
Industrial reuse:• Cooling water• Boiler make-up water• Industrial process water
Agricultural reuse Can even be purified to potable water standards!
Reuse of treated water from WWTP
Reuse of treated water from Kizingo WWTP
For irrigation of the golf course and local parks Only filtration and disinfection required Nutrient removal not required, their presence is beneficial!
Limited extra investment Plant is located beneath the golf course!
After treatment the water is discharged into the sea 17.100 m3/d
Focus on cooling water requirements of the local industry Usually the largest use of reclaimed water High quantities and moderate quality required Numerous petroleum refineries in the US that practice this
Reuse of treated water from Kipevu WWTP
Kipevu WWTP
Potential treatment required for cooling water standard
Corrosion concerns (filtration)• Removal of dissolved solids
Biological concerns (disinfection)• Removal of microbiological organisms (may deposit on surface)• Removal of nutrients (may contribute to microorganism growth)
Scaling concerns (chemical treatment)• Removal of Calcium, Magnesium, Phosphate and Sulphate
Reuse of treated water from Kipevu WWTP
Wastewater treatment… …is required to protect the environment (for today and tomorrow) …can be very expensive, especially if plants are under capacity …plants should be maintained regularly with skilled staff
The cost pressure can be reduced… …by “exploiting” the potential of wastewater treatment products
• Sludge for energy (biogas)• Expanding the services to collecting other energy rich waste (tipping fees)• Reuse of treated water will be gaining in importance in the coming years
Concrete results on the assessment will be made available
Current conclusions
Thank you for your attention!