滤池反冲洗水回用对自来水厂水质及净水效果的影响

Impact of Filter Backwash Water Reuse on the Water Quality and Treatment Efficiency:A Case Study in a Full-scale Drinking Water Treatment Plant

滤池反冲洗水是自来水厂生产废水的主要组成部分,已被水厂广泛回用。为了探讨反冲洗水直接回用对水厂各工艺段水质和各单元工艺净水效果的影响,通过对南方某大型水厂的实地调研,采用周期内监测、污染负荷计算和健康风险评估的手段综合比较了反冲洗水回用前后的水质和净水效果差异,明确了在5.0%的回用比例(反冲洗水与原水的体积比)下,反冲洗水回用会明显增加水厂工艺进水的浊度和Al3+负荷(其所占混合水负荷的比例高达70.7%和41.4%),但会降低农药类微污染物的暴露风险。与未回用相比,回用降低了混凝-沉淀工艺对UV254和溶解性有机碳(DOC)的去除,但增加了对无机物指标、CODMn和农药类微污染物的去除。此外,揭示了滤池是DOC、CODMn和农药类微污染物发生积累的关键单元,证实了反冲洗水回用不会造成出厂水水质超标。这一发现可为保障水厂供水水质安全的前提下提升水资源利用率提供重要的参考。

Filter backwash water(FBW)is a major component of residuals produced in drinking water treatment plants(DWTPs)and has been widely recycled.To investigate the impacts of FBW direct reuse on water quality across process stages and unit process treatment efficiency in DWTPs,field investigations were conducted at a prominent large-scale DWTPs located in southern China.The water quality and treatment efficiency before and after recycling FBW were comprehensively compared and evaluated by utilizing a multifaceted approach that included periodic surveillances,pollution load calculations,and health risk assessments.At a 5.0%reuse ratio(volume ratio of FBW to raw water),FBW direct reuse significantly elevated influent turbidity and Al3+load,comprising 70.7%and 41.4%of the mixed water load,respectively,while reducing the health risk of detected pesticides in drinking water exposure.Following reuse,the coagulation-sedimentation process showed reduced removal of UV254 and dissolved organic carbon(DOC)but increased removal of inorganic parameters,permanganate index(CODMn),and pesticides compared to non-reuse conditions.Moreover,the study highlighted filter beds as key units for the accumulation of DOC,CODMn,and pesticides,affirming that the implementation of FBW direct reuse did not result in the violation of the Standards for Drinking Water Quality(GB 5749-2022).This finding could provides crucial insights for enhancing water resource utilization while ensuring water quality safety.