Removal of nutrients from septic effluent with re-circulated hybrid tidal flow constructed wetland

Hybrid tidal flow constructed wetland (CW) with recirculation is an improved biological and engineering technique for removal of excess nutrients and certain pollutants from wastewater. This study investigated the removal efficiency of total phosphorus (TP), ammonia-nitrogen (NH3-N), and total nitrogen (TN) from septic tank effluent with the hybrid tidal flow CW system. Results showed that the removal of TP and NH3-N decreased as the hydraulic loading rate (HLR) increased, while the removal of TN increased and then decreased as the transition of HLR from 0.5 to 1.5 m3/m2/d. The removal of TN was maximized at the HLR of 1.0 m3/m2/d. The overall removal ranges of TP, NH3-N, and TN were 35.55–77.68%, 33.30–72.71%, and 16.25–53.17%, respectively. In general, an increase in recirculation frequency could increase the treatment volume of the effluent. This study suggests that the recirculation hybrid tidal flow CW has better performance in removal of nutrients than that of the traditional vertical flow CW.