Decentralized treatment and recycling of greywater from a school in rural India

Rural areas in developing countries face the twin challenges of water scarcity and risk of groundwater contamination due to lack of water treatment options. A decentralized greywater treatment system for reuse is an option that addresses both of these challenges. This study reports the performance of a decentralized greywater treatment and reuse system which was constructed and operated for over 12 months in a government-managed school in rural India. The handwash and kitchen wash wastewater streams were treated separately due to differences in the initial greywater characteristics. The treatment stages included pre-treatment using screens and grease traps, slow sand biofiltration combined with anaerobic sludge bioreactor, and aeration before the final ozone-based disinfection stage. The treated water at the end of all these stages was used for toilet-flushing in the school. The treatment system was operated for one year and sampling was performed to investigate the system performance. The overall treatment system showed removal efficiencies of 99 %, 98 %, 66 %, 73 %, 98 %, 96 % and >99.99 % for the parameters of turbidity, total suspended solids, nitrate, total phosphorus, biological oxygen demand (5 days), chemical oxygen demand and fecal coliform respectively. This study quantifies the performance of each subsystem and demonstrates for the first time that a decentralized greywater treatment can be operated effectively and economically in a rural Indian setting.