Laundry greywater treatment by anaerobic filters and vertical flow constructed wetlands

Abstract

AbstractLaundry processes are huge water consumers and contribute to wastewaters in high volume. In the current report, treatment of greywater (GW) was studied from commercial laundry in BITS Pilani, KK Birla Goa Campus, India, which produces around 2–2.5 m3/day of GW. Source laundry GW showed physicochemical parameters like chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammoniacal N (NH4–N), nitrate (NO3–N), nitrite (NO2–N), orthophosphate (PO4–P) and pH in the range of 600–650 mg/L, 350–370 mg/L, 9–12 mg/L, 15–21 mg/L, 14–22 mg/L, 28–35 mg/L and 7.48–8.10, respectively. The treatment system included French‐type two‐stage vertical flow constructed wetland (VFCW) preceded by anaerobic filter tank filled with 3D plastic support. Wetland beds were made up of sand and gravel as filter media, and Canna indica was used as macrophyte. Pretreatment by anaerobic filter resulted in the increase in residence time of GW and reduction of pollutant load to wetland beds, thus preventing clogging of Stage 1 wetland. Sampling and water quality data analysis was performed weekly for 26 weeks. Outlet pollutant levels showed 96.35% removal of organic matter, 79.93% removal of nitrogen and 95.04% removal of orthophosphates. The pH of outlet water was 7.35, which is well below discharge permissible limits. Treated water quality was below Central Pollution Control Board (CPCB), India, permissible limits for discharge, and the cost of treating GW by the system is 1.11 USD/m3 which is very feasible in country like India. Treated water is suitable for nonpotable options like gardening of central lawns in BITS Pilani Goa, floor cleaning of laundry and construction purpose.