Grey water treatment and reuse using a baffled constructed wetland

Abstract

Water is one of the world’s most valuable resources. However it is under constant threat due to urbanization, explosive population growth and pollution. The most promising efforts to stem water crisis are to treat the wastewater in a sustainable way and reuse for non-potable applications. Grey water (GW) being highly voluminous and relatively less polluted, recycling for non-potable uses like urinal and toilet flushing, landscaping etc will decrease the stress on fresh water consumption and protect the environment from residual pollutant disposal. This paper discusses about the performance of a hybrid baffled constructed wet land for the treatment of grey water from a hostel located in Indian Institute of Technology Madras, Chennai, India campus. The hybrid constructed wetland is a combination of vertical and horizontal flow wetland achieved by providing baffles in the system. The objectives of this study were to evaluate the performance of newly developed baffled constructed wetlands in the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), nitrate – nitrogen (NO3-N), suspended solids (SS), fecal contamination (FC), sodium do-decyl sulphate (SDS), propylene glycol (PG) and trimethyl amine (TMA) at different hydraulic retention times (HRT) and various organic loading rates (OLRs). The overall removal efficiencies obtained were in the range of 84-92%, 86-94%, 88-95%, 92-98%, 85-99%, 86-98%, 94-97% and 94-98% for BOD5, COD, NO3-N, SS, FC, SDS, PG and TMA, respectively for an HRT of 12.5 to 16.5 days. The system showed a distinct solids removal at higher HRT. The hybrid CW was able to eliminate the emerging contaminants such as SDS, PG and TMA from the treated water. The efficient performance of the baffled unit was due to the longer pathway provided by the baffles which in turn provided more contact of the wastewater with the plant, microbes and the matrix.