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POTENTIAL FOR GENERATION OF ADDITIONAL REVENUE FROM PRODUCTS OF WASTEWATER TREATMENT

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 :

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POTENTIAL FOR GENERATION OF ADDITIONAL REVENUE FROM PRODUCTS OF WASTEWATER TREATMENT

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  1. POTENTIAL FOR GENERATION OF ADDITIONAL REVENUE FROM PRODUCTS OF WASTEWATER TREATMENT Dr. Damjan Nemec(B.Sc.Chem.Eng.)

  2. 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

  3. 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) Primary (physical, chem.) Secondary (biological) Tertiary (advanced) • Screening • Grit removal • Grease removal • Efficiency: • - TSS = -10% • - COD = - 5% • - BOD = - 5% • Sedimentation • Efficiency: • - TSS = -50% • - COD = -20% • - BOD = -20% • Aeration • Sedimentation • Efficiency: • - TSS = -95% • - COD = -90% • - BOD = -95% • Nutrient removal • Filtration • Adsorption • Disinfection • Efficiency: • - TSS > -99% • - COD > -99% • - BOD > -99%

  4. Wastewatertreatment in Mombasa

  5. Wastewatertreatment in Mombasa Kipevu WWTP Kizingo WWTP

  6. Kipevu WWTP

  7. Kipevu WWTP influent screens & grit removal settling tanks sludgedryingbeds sludge thickeners aerationtanks sludge effluent

  8. Kipevu WWTP • Plantcapacity: • 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 = 112.128.000KSh/a

  9. Kipevu WWTP influent screens & grit removal settling tanks sludgedryingbeds sludge thickeners aerationtanks sludge effluent

  10. Biogasproductionfromsludge Sludge Biogas storage Thickenedsludge Biogas Biogas Flare CHP unit Biogas cleaning Digester #1 Digester #2

  11. Biogas production from Kipevu WWTP 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!

  12. Kipevu WWTP

  13. 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

  14. Biogasproductionfromsludge Sludge Foodwaste Biogas storage Substrate Biogas Biogas Flare CHP unit Biogas cleaning Digester #1 Digester #2

  15. Biogas production from Kipevu WWTP 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!

  16. Kipevu WWTP influent screens & grit removal settling tanks sludgedryingbeds sludge thickeners aerationtanks sludge effluent

  17. Reuse of treated water from WWTP • 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!

  18. Reuse of treated water from KizingoWWTP • 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!

  19. Reuse of treated water from KipevuWWTP • 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

  20. Kipevu WWTP

  21. Reuse of treated water from KipevuWWTP • 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

  22. Current conclusions • 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

  23. Thank you for your attention! • damjan.nemec@gmail.com

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