Treatment of Lakeside Domestic Wastewater by an Artificial Horizontal Undercurrent Wetland

Abstract

More than 50% of pollutants found in lake waters in China are derived from rural non-point pollution sources, resulting from untreated domestic wastewater released in rivers that feed into the lakes. There is a need of cost-effective means to treat wastewater locally. To this aim, an undercurrent artificial wetland pilot system was constructed to treat domestic wastewaters of the Wucheng lakeside area. Performance of the planted wetland was assessed by measuring removal rates of chemical oxygen demand (COD), the ammonia fraction of nitrogen (NH3-N), total nitrogen (TN) and total phosphorus (TP). Water samples were taken before, during and after treatment, over a period of 7 months covering autumn through early spring. The levels of dissolved oxygen (DO) were also determined. The results showed temporal variations in pollutant concentrations in the wastewater before treatment (except for COD) with higher levels in autumn. The average removal efficiencies of the determined pollutants by the artificial wetland were 42.86% for COD, 29.46% for NH3-N, 31.35% for TN and 21.75% for TP. Removal rates of these pollutants were subject to minor seasonal variation. Along the 20 m horizontal water flow studied, the removal rates were highest in the first section. A horizontal undercurrent artificial wetland is simple to construct, easy to manage, and with low running costs it can treat waters effectively and efficiently. To ensure efficient water purification and reach optimal water quality, the hydraulic load and DO levels should be carefully managed.