Constructed Wetland Enhancement via Chemical Coagulation using variable Hydraulic Retention Times for wastewater Treatment

Treatment of municipal wastewater using constructed wetlands has huge advantages as green, low cost, effective, environmental friendly and aesthetic advantages. Therefore, adequate treated wastewater can be considered as an unconventional water resource according to the quality of final treated effluent. Meanwhile, separation of municipal wastewater into grey, black, and yellow water reduces the pollution parameter in the separated grey water remarkably. In this respect, grey water becomes much simpler to be treated in terms of pollution parameters removal. The treated effluent, therefore, can be reused for agriculture purposes according to the quality of the final treated effluent.The aim of the present work is to investigate the treatment of grey water via sedimentation in combination with chemical coagulation using lime and ferric chloride followed by a hybrid constructed wetland. The hybrid constructed wetland consisted of horizontal subsurface follow (SSF-CW), followed by vertical flow constructed wetland (VF-CW). The hydraulic loading rate (HLR) of 170, 85, and 56.6 m3ha-1.day-1with corresponding to organic loading rates (OLR) of 717.4, 358.70, and 239.13 kg BOD5 ha-1.day-1 at variable retention times namely (1, 2, and 3 days) were examined. The COD, BOD5, and TSS were reduced by 90.42, 90.65, and 91.4% respectively at the hydraulic residence time (HRT) of 3 days. At HRT of 2 days, on the other hand, the recorded removal rates were 90.83, 89.82, and 91.1%, respectively. The characteristics of the treated effluent using the two days HRT, and three days HRT were both in accordance with the Egyptian law of discharging the treated wastewater into the sewerage networks, as well as the Egyptian code of reuse in agriculture for restricted purposes.