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

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%), NH(4)-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 m(3) with effective size 41.8-1,050 m(2). 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 NH(4)-N, 33-45% of NO(3)-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.

Treatment performance of artificial floating reed beds in an experimental mesocosm to improve the water quality of river Kshipra.

The discharge of untreated wastewater in River Kshipra had brought annual average of BOD, TKN and TS levels up to 39 mg/l, 38 mg/l and 781 mg/l respectively in the study area. Treatment performance by Artificial Floating Reed Beds (AFRB) was evaluated for removal efficiency of TS, NH4-N, NO3-N, TKN and BOD from river water, initially, under a pilot scale by an AFRB of size 200 m2 planted with local reed grass, Phragmites karka, in the part of River Kshipra at the confluence with meeting point of a wastewater stream. The system performance was recorded as 43% reduction in TS, 38% reduction in TKN and 39% BOD reduction. The experimental AFRBs were buoyant structure planted with reed grass, each unit had a rectangular size and covered an effective surface area of 2 m2. The experiment with the mesocosms with treatment of River water resulted that AFRB was reducing pollution load by 55-60% of TS, 45-55% of NH4-N, 33-45% of NO3-N, 45-50% of TKN and 40-50% of BOD. AFRB may be recommended as an in-situ, eco-friendly river water treatment structures for small shallow, slow flowing (or slightly stagnant) water bodies.

Treatment of a molasses based distillery effluent in a constructed wetland in central India.

A field-scale 4-celled, horizontal subsurface constructed wetland (CW) was installed to evaluate removal efficiencies of wastewater constituents in an industrial distillery effluent. Total and dissolved solids, NH4-N, TKN, P and COD were measured. This CW design provides four serial cells with synthetic liners and a river gravel base. The first two unplanted cells provide preliminary treatment. Specific gravel depths and ensuing biofilm growth provides anaerobic treatment in Cell 1 and anaerobic treatment in Cell 2. Cell 3 was planted with Typha latifolia with an inserted layer of brick rubble (for phosphorus removal). Locally grown reed, Phragmites karka was planted in Cell 4. COD was reduced from 8420 mg/l 3000 from Cell 1 to the outlet of Cell 4. Likewise other parameters: total and dissolved solids, ammonium and total nitrogen, and total P, indicated declining trends at the 4-celled CW effluent. This study reveals how high strength distillery wastewater strongly impacts morphology, aeration anatomy in the chiseled plant tissues, reed growth; and composition of the biofilm in the specialized substratum. The reliability of a CW for organic and nutrients reduction, in association with a poorly performing conventional system is discussed. There is an immense potential for appropriately designed constructed wetlands to improve high strength wastewaters in India.