DESIGN AND USE OF A MODEL CONSTRUCTED HORIZONTAL SUBSURFACE FLOW WETLAND FOR TREATING TANNERY WASTEWATER BY MEANS OF AQUATIC PLANTS

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Department of Engineering

ABSTRACT
In this study, a Laboratory-scale Horizontal Subsurface Flow Constructed Wetland has been designed, and three replicas constructed, cultivated with selected locally available aquatic plants Phragmites australis,Polygonum salicifolium + Ipomoea carnea, respectively, with the third cell un-vegetated, and used to treat tannery effluent. The capacity or treatment efficiency or performance of the laboratory-scale Constructed Wetland in reducing the level of physicochemical parameters (Biological Oxygen Demand, Chemical Oxygen Demand, Nitrates, phosphates, suspended solids and chromium) under a 6day Hydraulic Retention Time was evaluated.Physicochemical parameters were analyzed using standard methods.Highest removal efficiency for BOD (97.9%), COD (94.2%),NO-3(54.4%), PO43- (44.1%) and Cr (98.4%) was observed in the wetland cell planted with Phragmites australis, while highest removal efficiency for TSS (92.6%) was observed in cell panted with a mix of Polygonum salicifolium + Ipomoea carnea. The un- planted cell showed lesser removal efficiency across all the selected parameters. Generally, through the 60 days of operation, the vegetated or planted cells showed better removal efficiency over the un-vegetated cell indicating that the selected aquatic plants are potential candidates for large-scale tannery wastewater treatment in Horizontal Subsurface Flow Constructed wetlands.However, evaluation of the system over longer period is required before concluding whether these plants in subsurfaceconstructed wetland are efficient for primary treatment of tannery wastewater.