Treatment of domestic wastewater by a hybrid natural system

The present study addresses performance evaluation of a hybrid natural system comprising of settling tank, sand-gravel filter (SGF), aerated constructed wetland (ACW) and vermifilter (VF) for the treatment of domestic wastewater. The sequential batch experiments were conducted in a pilot-scale experimental set-up. The biochemical oxygen demand (BOD5) was varied from 20 to 120 mg/L and the hydraulic retention time (HRT) used was from 1 to 3 d. The BOD5 removal efficiency was found to be in the range 20-40%, and 40-70%, for 3 d HRT in SGF and ACW/VF, respectively. The efficiency of the system for BOD5 removal was observed to be 80-90% at 3 d HRT and the system was found to be adequate for reducing BOD5 to a value less than 20 mg/L. The effluent can be recycled and used for non-potable purposes in a household. The developed system is a potential option for the decentralized wastewater treatment.