Use of Reeds On horizontal Subsurface Flow Constructed Wetland for The Treatment of wastewater

Abstract

Horizontal Flow Subsurface Constructed Wetland was constructed in an openfield inside Bagmati Area Sewerage Project which is located near thePashupati temple at the bank of Bagmati River on the northern eastern part ofthe Kathmandu city. The sites consisted two horizontal beds of equal area anddepth (6m (length) x 2m (breadth) x 0.6m (depth)). Bed was planted withlocal reed,Phragmites karkaand Bed 2 1 was unplanted and treated as blank.The aim of study was to evaluate performance efficiency of planted andunplanted beds on removing various pollutants. Systems were fed withwastewater drawn from grit chamber of oxidation ditch and collected insettling tanks. Performance efficiencies of beds over various flow rates werealso determined. Removal efficiency of planted and unplanted horizontalsubsurface flow constructed reed beds were compared over four differentflow rates (i.e. 0.464m 3 /d, 1.56 m 3 /d, 2.26m 3 /d, 3.05m 3 /d). Planted bedshowed enhanced BOD , COD, TSS and FC removal in comparison to TKN,NH4-N and TP removal. Removal efficiency was obtained high at low flowi.e. 0.0464m 3 5 /d. Removal percentage of planted bed at flow rate 0.0464m /dwas 79.38% BOD 5 , 81.85% COD, 44.16% TKN, 58.9% NH -N, 34.27% TP,84.41% TSS, 89.8% FC. DO wasmeasured along inlet, 1 st 4 sampling port, 2 sampling port and outlet. DO increase along the bed after first sampling port.The constructed horizontal subsurface red beds exhibited good efficiency forimproving water quality from polluted waste water.