Performance evaluation of horizontal flow constructed wetlands as primary and secondary treatment for university campus wastewater

Horizontal flow constructed wetland (HFCW) is an attractive green technology for wastewater treatment. In the present study, four laboratory-scale HFCWs were constructed to serve as the primary and secondary treatment of university campus wastewater. The effect of hydraulic residence time (HRT) and pre-aeration of influent were investigated. The experimental results demonstrated that the wetland vegetation played an important role in the oxygen restoration and the influence of pre-aeration was minor. In the primary treatment, effective removals of TSS and NH4-N were observed. However, the treatment of BOD and NO3-N were insignificant due to the low influent concentrations. As for secondary treatment, the HFCWs effectively reduced the concentrations of BOD, NH4-N, and NO3-N in the effluent from the Intermittent Decanted Extended Aeration (IDEA) plant. The effluent quality of all HFCWs complied with the Standard A sewage discharge. Longer HRTs brought a positive effect to the removals of organic matter and nitrogen.