Applicability Evaluation and Effect on Soil Environment of Treated Rural Sewage for Irrigation in Agricultural Facilities

Abstract

In Japan, direct irrigation in agricultural facilities using treated rural sewage without dilution requires validation of sewage treatment processes and impact evaluation of soil by treated sewage irrigation. In this study, we evaluated water quality fluctuation in treated rural sewage, and examined additional water treatment processes for pathogen reduction using faecal coliform number as a human health risk indicator. We also cultivated tomato in an agricultural greenhouse and tested soil columns using treated rural sewage. The results suggest that for raw crops, additional treatment is desirable before irrigation with treated rural sewage, such as chlorine efficiency enhancement, UV treatment, or membrane treatment. Moreover, although the impact of the application of treated water on the soil environment could not be confirmed in the short-term cultivation of tomato in the greenhouse, the soil column test results suggest that salt accumulation in soil and changes in soil organic matter composition need to be considered when treated rural sewage is used for a long term.