Study on Resource Utilization of Supernatant from Reused Sludge Discharge Water in High-Turbidity River Water Treatment Plants

The direct discharge of sludge water from water purification plants in recent years has caused both environmental contamination and substantial resource depletion. This study focuses on the resource utilization of supernatant from reused sludge discharge water in high-turbidity river water treatment plants. Through single-factor and orthogonal experiments, we systematically investigated the effects of coagulant dosage, reflux ratio, and supernatant turbidity on coagulation efficiency, ultimately determining the optimal reuse parameters. Under optimal conditions (PAC dosage 4 mg/L, reflux ratio 2%, turbidity 67.5 NTU), the effluent turbidity, chroma, ammonia nitrogen, and total phosphorus were analyzed to investigate the safety of sludge water reuse. The results demonstrate that sludge water reuse significantly enhances coagulation efficiency, with turbidity and chroma removal rates increasing by 5.53% and 10.48%, respectively. After reuse, the permanganate index met the standard, while manganese and arsenic concentrations increased slightly but remained well below drinking water quality standards. Under appropriate reuse conditions, the turbidity, aluminum, and iron in settled water all complied with effluent water quality standards. Finally, through Zeta potential, floc morphology, and particle size analyses, the mechanism of enhanced coagulation efficiency by reused water was revealed. This study aims to provide reference for the resource utilization of supernatant from sludge discharge water in high-turbidity river water treatment plants.