Treatment of Domestic Waste Water by Small Scale Constructed Wetland Under Different HRT Regimes.

Constructed wetlands (CW) have been considered cost-effective bioremediation systems for the removal of contaminants in waste water of domestic and commercial origin. In the  present study small scale prototype free water surface (FWS) constructed wetland (CW) system was used  for the treatment (13 parameters) of domestic waste water under different hydraulic retention time (HRT) (0, 4, 8, 12, 16, 20 days). The wetland was consisted of three laboratory-scale units (4×1.5×1.5”) of plexiglass; the first two units were containing beds of gravel (7.5 cm), sand (15 cm) and organic soil (12.5cm), planted with a common grass (Paspalum flavidum) and the third unit was just a bed (35 cm) of sand. In continuous mode (0 HRT), there was observed a considerable improvement in water quality parameters in terms of COD (72.20%), BOD₅ (72.20%), sulphates (50.74%), chlorides (63%) and microbial count (E.coli and Salmonella and Klebsiella) [MPN index (99%)] removal. Besides, further increase in HRT proved to be significantly correlated with the treatment efficiency of the system.