Removal of chemical and microbial contaminants from greywater using a novel constructed wetland: GROW

Abstract

The availability of freshwater resources is becoming universally depleted, leading to the requirement for a focused management strategy for treating and reusing wastewater. In particular for urban and developing areas, small scale decentralized treatment systems are becoming popular. The GROW (Green Roof-top Water Recycling System) constructed wetland is one such option that provides a solution without a permanent land requirement and offering medium to high treatment efficiency. The performance of the GROW system was monitored from November 2013 to April 2015 in treating greywater from the Krishna Student Hostel in IIT Madras. The performance of the GROW wetland cells were examined over four monitoring periods in Phase 1 namely: 1) start-up stage, 2) seasonal variation 3) change of flow rate and 4) change in organic fraction (26.8, 25.9 and 25.5 g COD/cubic meter/day respectively). In Phase 2, the plants and the filling materials were changed and the performance of GROW wetland cells were evaluated. The system was fed with greywater at a flow rate of 62, 70, 82, 100 and 120 L/day respectively with hydraulic retention time of 0.7–1.3 days. The samples taken from the inlet and the outlets of the GROW system were taken weekly and analyzed for the following parameters; pH, COD, BOD, TSS, TN, NO 3 –N, TP, FC, SDS, PG and TMA. In the study, the overall removal efficiency was greater than 82% for all the parameters. The GROW wetlands reduced all the above mentioned parameters to within or closely to the USEPA standard limits for reuse. The reusable effluent water is named ‘Green Water’.