Sustainable decentralized waste management in urban residential areas

Abstract

Proper management of wastewater is a major challenge for a developing country like India. The scarcity of water in urban areas has given rise to the requirement of reuse of treated wastewater for secondary uses. Large number of treatment processes and operations can be used in various combinations to achieve the required effluent quality of treated wastewater and large numbers of studies have been carried out on this aspect. Most of the decentralized wastewater treatment processes are land or energy intensive both of which are in shortage in urban areas. The use of non-conventional energy for treatment of domestic wastewater has not been explored. Use of non-conventional energy sources would imply adequate energy for only part of the treatment time. Such a system can be developed using solar, wind or wave energy. A laboratory scale study was carried out using a modified septic tank, anaerobic baffled wall reactor, aerobic attached growth system and constructed wetland to find out the efficiency of black water/ domestic wastewater treatment. To simulate non-conventional energy sources, partial aeration was provided to the aerobic attached growth system. The reactors were subjected to an organic loading rate (OLR) of 1.2 kg/m3/day and 24 hours HRT using synthetic wastewater. Individual reactors efficiency in terms of COD, TSS, total nitrogen, and total phosphate removal were analyzed. The reactors were placed in a sequence to depict a treatment system and the performance was evaluated based on above mentioned parameters. The performance of the wastewater treatment system was also validated using real wastewater. Pilot scale studies were carried out in an apartment block with 20-25 residents. The treatment system was meeting the effluent quality required for reuse as specified by CPHEEO. Overall, the study demonstrated that a sustainable onsite wastewater treatment using non-conventional energy source, i.e., solar power is a viable and efficient system