Performance analysis of the horizontal sub-surface flow constructed wetland under different hydraulic loading rates for rural domestic wastewater treatment

The performance of horizontal subsurface flow constructed wetland (HFCW) for rural domestic sewage treatment has been evaluated. The system was built as a tertiary treatment after the biological processes to improve the effluent wastewater quality. The HFCW was operated in three phases under different hydraulic loading rates (HLRs), and with three kinds of aquatic plants i.e., water spinach, Chinese celery and cress. The vegetation growth parameters such as plant height, fresh and dry weights were monitored and analyzed. The influent and effluent concentrations of the chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN) and total phosphorus (TP) were measured. The average removal efficiencies at the first phase were 52.9%, 64.7%, 58.2% and 72.8%, and it reduced to 48.6%, 52.2%, 44.04% and 64.4% in the second phase for COD, NH4+-N, TN and TP, respectively. In the third phase, the HFCW system showed the following mean removal efficiencies: 51.2%, 74.2%, 58.5% and 80.9%. The results revealed that the removal efficiencies increased with decrease in the HLR and increased temperatures. The findings confirmed that the horizontal flow constructed wet-land is more convenient for the rural wastewater treatment with efficient nutrient removal.