DISTRIBUTION LAW AND INFLUENCING FACTORS OF SLUDGE YIELD OF WASTE PURIFICATION PLANTS IN L DISTRICT, SHENZHEN

The sludge yield of 12 water purification plants in L District of Shenzhen from 2016 to 2020 was investigated. The results showed that the sludge yield ranged from 0.51 to 2.66 t DS/10⁴ m³, and its average value showed an increasing trend. In most cases, upgrading the wastewater treatment process can reduce sludge yield. Influent SS and BOD₅ were positively correlated with sludge yield. The outward sludge moisture affected the sludge yield by influencing the dosage of chemicals in sludge treatment. Silo storage condition could change the weight of sludge and thus affect the sludge yield. In order to reduce the sludge yield, optimizing the wastewater treatment system, improving the influent biodegradability, reducing the dosage of chemicals and improving the silo storage conditions should be considered. It is suggested to use specific in-situ sludge reduction measures including using bypass inlet or multi-point aeration, controlling inflow suspended solids, strengthening sediment separation in the pretreatment stage, and adopting closed silos and transportation modes.