Concept and Experiences of wastewater treatment In Cakung Slaughterhouse PD Dharma Jaya PUSAT PENGKAJIAN DAN PENERAPAN TEKNOLOGI LINGKUNGAN Badan Pengkajian dan Penerapan Teknologi UTEC
The main functional areas of Cakung Slaughterhouse Stabling of cattle Slaughtering in main slaughterhouse Slaughtering in traditional slaughterhouse Power supply, workshop Administration Sanitary facilities
Concept of the Wastewater treatment Low running costs, means low demand for manpower, energy and chemicals, even if the investment cost might be higher Simple and clear operation procedure to simplify the work for operators and minimize the risk of miss management Minimization of sludge production and demand of sludge handling Utilization of renewable energy and nutrients Energy production in form of biogas and current production as benefit Utilization of sludge in composting process
Figure 3. The system plan for waste and wastewater treatment process
Table 1. The most important equipment of the WWTP PositionFabricateTypesize Step screenMcCoyStep screen Fine screenHaaseStatic screen Mixing/storage tankTirtakreasiConcrete basin200 m³ Pre-sedimentationTirtakreasiConcrete basin40 m³ Fixed bed digesterTirtakreasiConcrete tank with support material Tot-Vol.: 590 m³ Eff.-Vol.: 400 m³ Final sedimentationTirtakreasiSteel tank50 m³ Gas holderMuchePlastic bag in container20 m³ GensetDimagNet-parallel45 kW
The main requirements Step screen eliminates suspended solids >3 mm particle size Fine screen separates suspended solids >1mm particle size Pre-sedimentation eliminates >90 % of suspended solids Fixed bed digester degrades >70 % of dissolved COD Over all efficiency of WWTP > 80 % of COD-total
Actual condition of wastewater Total amount of wastewater 100 – 200 m 3 /day COD total 6000 – 8000 mg/l COD dissolved mg/l
Inflow WWTP COD mgO2/l 100% Step screen 386 mg/l 5.1 % Screenings Fine screen 526 mg/l 7.1 % Screenings Mixing / Storage tank 600 mg/l 8.8 % Loses of dissolved COD by anaerobic process in this tank Pre- sedimentation mg/l 49.1 % Sludge Anaerobic Fixed Bed Digester mg/l 18.5 % Biogas Final sedimentation 39 mg/l 0.5 % Sludge Effluent WWTP COD 813 mgO2/l 10.9% Total efficiency 89.1% Figure 5. Mass balance and efficiency of component
Fixed Bed Digester Performance Amount of wastewater: 353 m³/d Gas production:220 m³/d Methane content: 75 % Amount of sludge: 5 m³/d
Figure 6. Feeding rate of digester during start up period
Figure 7. Biogas production of digester during start up period
Calculation of current production: Power output:35 kW Gas uptake:15.6 m³/h Gas production:220 m³/d Current production:495 kWh/d
Balance of demand and production: Demand:122 kWh Production:495 kWh Surplus:373 kWh Benefit: The benefit from electrical generation by Biogas is: Current tariff (December 2002): Rp/kWh Surplus current:373 kWh Benefit: 215,541 Rp/d 6,466,218 Rp/month
RESUME I The presented system is very suitable to treat the wastewater from slaughterhouse and stable area. - All components of the plant are dimensioned by hydraulic load and flow rates. Therefore it is in general very important to minimize the amount of waste- water to reduce the size/capacity of equipment and investment costs.
RESUME II - The volume of the storage and mixing tank might be chosen smaller, because the fixed bed digester is able to handle discontinuous flow, furthermore it was found out that a part of dissolved COD is already degraded during the storage time. The consequence is a lower production of biogas. - The digester is dimensioned for minimum hydraulic retention time of 3 days. It might be possible to reduce the minimum retention time to less than 2 days. High load tests showed that the digester is very flexible and is able to handle shock loads.
RESUME III - The final sedimentation eliminates only 0,5 % of pollution, but is an expensive component. It might be suitable to drive a system without final sedimentation. - In general very important to increase the amount of slaughtering of cattle to increase the performance of wastewater treatment plant.