2025 Volume 48 Pages 27-38
We examined the operation and management of the batch-type activated-sludge process widely adopted in rural sewerage treatment plants, which are necessary to achieve the required water quality levels in the International Standard ISO 16075 guidelines for treated wastewater irrigation. The study revealed that the oxidative decomposition of organic matter, promotion of nitrification in the batch tank, and sedimentation property of activated sludge were related to the BOD concentration of treated water. We found that BOD and SS concentrations of treated wastewater were likely to meet the water quality level of category A in the ISO guidelines if the DO in the batch tank was managed to be 2–3 mg L-1 at the end of the aeration period by maintaining the SVI below 100 mL g-1. The residual chlorine, hydraulic retention time, SS concentration, and water temperature of the treated water affected the number of coliform groups in the treated wastewater, thus, the number of coliform groups was likely to meet the category A quality level if the CT product was more than 2.8 mg min L-1. Reducing the SS concentration of the treated water was important to suppress the reduction of the chlorine disinfection effect.
