Energy generation in the treatment of effluent from washing of municipal solid waste collection trucks

The washing of vehicles used to collect Municipal Solid Waste (MSW) requires 400-500 L of water for each vehicle, producing effluent with characteristics similar to the leachate from young sanitary landfills. The treatment process commonly used for this type of effluent is coagulation/flocculation. In this study, effluents from three sites were submitted to physicochemical treatment alone or combined with anaerobic biological treatment. Physicochemical treatment has better results with effluents with high total suspended solids (TSS) content. For effluents with low TSS concentrations, this treatment has high turbidity removal but low chemical oxygen demand (COD) removal. The anaerobic biodegradability and the methane generation potential from raw effluents or after physicochemical treatment were evaluated with and without nutritional supplementation. The effluent after physicochemical treatment does not require nutritional supplementation, obtaining 92% COD removal (final COD of 168 mg/L) and specific methane production of 150.6 mL methane (STP)/g CODremoved. A comparison of operational cost between the physicochemical and anaerobic biological processes for treating 20 m3/day of effluent showed that the latter, in addition to presenting low cost, can generate up to 13.5 kWh/day for the MSW collecting company.