GRAVEL BED CONSTRUCTED WETLAND FOR TREATMENT OF SEWAGE WATERNIHARIKA SHIVHARE AND MOMITA ROYAbstract A wetland is a complex assemblage of water, substrate, plants, invertebrates (insect larvae and worms) and micro-organisms (bacteria). These are inter-related and help in improving water quality by settling suspended particulate matter, adsorption and ion-exchange on the surfaces of plants, substrate and sediment, uptake and transformation of nutrients by micro-organisms and plants etc. A constructed wetland is a shallow basin filled with a substrate (soil or gravel) and planted with vegetation tolerant of saturated conditions. In the present study the performance of subsurface horizontal flow constructed wetland for treatment of sewage water was investigated. The substrate used is gravel and vegetation is a macrophyte (Typha latifolia) as they are easily available. Environmental related parameters i.e. pH, COD, BODs, TSS, PO& nitrate and Fecal colifonn count were monitored in one complete rnacrophyte life cycle at different HRTs. At an optimum I MT of 2 days removal efficiencies of various parameters were in the range COD 1300,000%), TSS (979th) and NI-13-N (78.9%). The Fecal conform showed 2-3 log reduction. The performances of the system indicate that constructed wetland treatment system is a viable option for sewage treatment. The system is cost effective and can be implemented successfully as a decentralized system in urban and rural areas using local resources.
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