Treatment of wastewater and restoration of aquatic systems through an eco-technology based constructed treatment wetlands – a successful experience in Central India

Abstract

In the last couple of decades constructed wetlands (CWs) have drawn considerable interest in Central India. CWs offer an effective means of integrating wastewater treatment and resource enhancement, often at competitive cost in comparison to conventional wastewater treatments, with additional benefits of Green Urban Landscaping and wildlife habitat. This paper describes treatment performances and the design of some Sub Surface Flow CWs (SSFCW) and Artificial Floating Islands (AFIs) in Central India. Central Indian CWs show significant pollution reduction load for total suspended solids (TSS) (62–82%), biochemical oxygen demand (BOD) (40–75%), NH4-N (67–78%) and total Kjeldahl nitrogen (TKN) (59–78%). Field scale SSFCWs installed so far in Central India are rectangular, earthen, single/multiple celled having similar depths of 0.60–0.90 m, hydraulic retention capacity 18–221 m3 with effective size 41.8–1,050 m2. The major components of CWs incorporate puddled bottom/side walls, sealed with impermeable low-density polyethylene, a bed of locally available river gravel planted with Phragmites karka, and an inlet distribution and outlet collection system. A new variant on CWs are AFIs working under hydroponics. The field scale experimental AFIs installed in-situ in a slowly flowing local river were composed of hollow bamboo, a bed of coconut coir, floating arrangements and Phragmites karka as nutrient stripping plant species. The AFIs polish the aquatic system by reducing 46.6% of TSS, 45–55% of NH4-N, 33–45% of NO3-N, 45–50% of TKN and 40–50% of BOD. The study established that there is a need for further research and sufficient data to assist the development of CWs by instilling confidence in policymakers, planners and in the public.