Effect of Treated Domestic Wastewater on Soil Physicochemical and Microbiological Properties

Abstract

A main concern with reuse of treated domestic wastewater (DWW) in irrigation is its possible effect on the soil. Few studies have focused on DWW treated in on-site settings, which generally use low-tech systems that can be constructed and serviced locally. One such system is the recirculating vertical flow constructed wetland (RVFCW). The aim of this study was to assess short- to midterm effects of irrigation with DWW treated in the RVFCW. Four groups of plastic barrels, filled with a sandy loam soil, were irrigated for 36 mo with fresh water (FW), FW with added fertilizer, raw DWW, or DWW treated in the RVFCW followed by ultraviolet disinfection. Principal component analysis revealed that the soil irrigated with treated DWW had physicochemical properties similar to those irrigated with FW amended with fertilizer. Levels of surfactants in soil irrigated with treated DWW were identical to those expected from standard irrigation practices, abating concerns for possible changes in soil hydraulic properties. was not detected in the soil irrigated with treated DWW, demonstrating the importance of disinfection of treated effluents before reuse in irrigation. Furthermore, irrigation with treated DWW did not alter the bacterial community structure according to terminal restriction fragment analysis. This 3-yr study suggests that the practice of irrigation with RVFCW effluents is safe. Continuation of the experiment is required to determine whether longer-term irrigation might show a different pattern.