Effect of loading rate and sludge deposit on a VFCW treating septage

Abstract

A pilot-scale vertical flow constructed wetland (VFCW) was constructed and operated to treat septage based on hydraulic loading rate (HLR). The flow pattern illustrated that the highest hydraulic gradient existed in the deepest ponding leading to peak effluent flow rates. However, the hydraulic performance was found to be highly varying with respect to HLR. It is attributed to the accumulation of sludge deposit that produced preferential flow pathways in the wetland beds. The pilot-scale VFCW was able to retain 95% of TS, COD, and TN with sufficient sludge thickness regardless of the HLR variation. However, NH4+--N and NO3--N in the effluent are strongly correlated to the effluent flow rate, and the associated treatment efficiency is lower. Due to its promising solids removals, HLR is recommended as a practical feeding strategy as it offers a simple application and the ability to control overflow.