Development of a novel disinfection method for agricultural reuse of sewage treated by the primary sedimentation + DHS system

Abstract

 Arid countries are facing serious water shortage, and sewage without sufficient treatment is often used for irrigation in some countries such as Egypt. A novel sewage treatment system, a down-flow hanging sponge (DHS) reactor combined with a primary sedimentation tank (PS+DHS system), has been proposed to overcome this issue, but until today its treatment efficiency has not met the Egyptian irrigation standards in terms of fecal coliform (≦5×10³ MPN/100mL). In this study, hydraulic retention time of the DHS reactor was prolonged to 4.8 hours; nevertheless, it was still not able to meet the irrigation standards. Disinfection with copper ion was evaluated, and it was found that the treatment with 2 mg/L of copper ion for at least 2 hours was necessary to achieve the irrigation standards. Growth inhibition and copper ion accumulation were not observed when copper ion-treated water was used for tomato cultivation.