Reuse of Washing Machine Effluent Using Constructed Wetland: The Circular Economy of Sanitation

Currently, due to the practice of traditional linear economic model, water resources are under extreme pressure. The lack of technically efficient and economically feasible solutions for water and wastewater treatment and poor management of water assets are responsible for the lack of access to safe water in both rural and peri-urban communities. The present study attempts to achieve the fundamental principles of circular economy which consists of regeneration and restoration by treating the laundry wastewater using constructed wetland and its reuse for various other purposes. The composition of detergents used in a domestic washing machine constitutes of wide range of chemicals. Consequently, the produced laundry wastewater contains varieties of compounds including surfactants, softeners, alkalis, bleach, hydro-tropes, xenobiotic organics, sodium, phosphorus, nitrogen and micro fabrics from clothing. Based on the calculation of water balance on a domestic washing machine, the water consumption has been approximated to be 5000 MLD, while consumption of detergents was estimated to be 3800 TPD (equivalent to 3000 TPD of COD) approximately. Evidently, the treatment of laundry wastewater is the need of the hour. At IIT Bombay, the constructed wetland technology having the horizontal subsurface system entitled ‘CW4Reuse’ has been developed for treatment and management of effluents. In the present study, ‘CW4Reuse’ has been utilized for treatment of laundry wastewater from a family consisting of five members (approximately 75 L/d). The wetland bed has a plan area of 1 m2 and a depth of 0.5 m. Canna Indica (family: Cannaceae) has been used as the vegetation system for effluent treatment. The qualitative and quantitative analysis of the laundry wastewater showed a significant removal of BOD, COD, TSS, VOCS heavy metals, nitrogen, phosphorus and pathogens (proxy: MPN). The treated laundry effluent can be reused for gardening, vehicles cleaning and flushing.