In Situ Treatment of Domestic Food Waste and Bioflocculated Sewage Sludge in Decentralized Wastewater Treatment Plant

Abstract

To reduce the operating cost of wastewater treatment plants and in situ treatment of sewage sludge and domestic food waste, the current investigation of anaerobic codigestion of domestic food waste and primary bioflocculated sewage sludge was conducted in an anaerobic reactor coupled with a decentralized domestic wastewater treatment plant. The performance of the anaerobic reactor and wastewater treatment system was tested for 30 days. The anaerobic digester was placed after the flocculation chamber in the wastewater treatment plant to transfer the primary bioflocculated sludge using gravity. The 0.5 kg Day−1 of domestic food waste and 29 L Day−1 of bioflocculated sewage sludge were used as feedstock for an anaerobic codigestion and supernatant collected in the flocculation chamber were passed to the water treatment stages. The bioflocculated sludge was collected by adding flocculant in domestic raw wastewater and fed in a digester whereas food waste was added using the separate port in the digester on daily basis. The anaerobic digester was operated in continuous mode at mesophilic temperature conditions at a hydraulic retention time of 7 days. The physiochemical parameters for controlling the anaerobic digester were examined periodically which showed the maximum volatile fatty acid accumulation of 6,500 mg L−1 on the 12th day with the highest biomethane production of 0.35 L CH4 g−1 VSconsumed. The highest energy production potential of biogas was estimated as 0.35 kWh unit. The physical, chemical, organic, inorganic, and biological characteristics of treated water were tested to quantify the treatment efficiency of the process for the reuse of treated water. Results indicated that more than 90% of effluent was collected at the outlet of treatment units and the tested parameters were fulfilling the guidelines set by the different agencies for the reuse of effluent for various purposes. This paper investigates the performance of anaerobic codigestion of food waste and bioflocculated sewage sludge coupled with a decentralized wastewater treatment plant for the ease of substrate availability. Biomethane production was used to analyze the energy generation potential of domestic sewage sludge and food waste to reduce the operating cost of wastewater treatment systems. The feeding ratio used for operating the anaerobic reactor was decided based on food waste and sewage sludge availability from typical households. The limiting values of VFA with codigestion of food waste and bioflocculated sewage sludge have been reported in the current study and compared with literature values. This work provides insights to make possible the in situ treatment of domestic wastewater along with energy generation from food waste and bioflocculated sewage sludge in an integrated system which is unavailable in the literature.