常规净水工艺对猛水蚤的去除机理及效果

Mechanism and effect of removing Harpacticoida with traditional drinking water treatment processes

为实现对桡足类生物泄露风险的高效控制,以猛水蚤为研究对象,开展了常规净水工艺对桡足类生物的去除作用机理及效果研究,重点研究了猛水蚤去除与絮体颗粒形态特性关系和在石英砂滤床的分布规律.结果表明:优化操作条件下,混凝沉淀和过滤对猛水蚤去除率均可达99%,最佳工况包括快速搅拌300r/min(1min)、中速搅拌150r/min(5min)和低速搅拌75r/min(5min),聚合氯化铝(PAC)投加量10mg/L,沉淀时间0.5h,滤速9m/h,过滤周期1d.混凝对猛水蚤的去除效率主要决定于猛水蚤与絮体的有效吸附,絮体颗粒粒径越大、分形维数越低,猛水蚤去除率越高;过滤水冲刷携带引起的被动迁移,是导致猛水蚤穿透砂滤池的主要原因,适当降低滤速和缩短过滤周期,控制猛水蚤被动迁移规模,可以达到提高猛水蚤去除率效果.

Recently, the leakage risk for copepods is becoming a challenging problem for drinking water plants in China. In order to prevent drinking water distribution systems from copepods＇ efflux, the control of copepods with traditional drinking water treatment processes was investigated by using Harpacticoida as a research subject. More attention was paid to the relationship between the removal of Harpacticoida and morphological characteristics of flocs in a coagulation tank, and distribution of Harpacticoida in a sand filter bed. The results showed that high removal efficiency of 99% was obtained under the optimum operational conditions, which includes fast stirring of 300r/min（1min）, moderate stirring of 150r/min（5min） and slow stirring of 75r/min（5min）, polymeric aluminium chloride dosage of 10mg/L, sedimentation time of 0.5h, filtration rate of 9m/h, and filtration cycle of 1d. The removal efficiency of coagulation on Harpacticoida was mainly determined by the effective adsorption of Harpacticoida onto flocs, and the larger particle size and the lower fractal dimension of flocs, the higher removal efficiency of Harpacticoida. During filtration, the passive migration of Harpacticoida in a sand filter bed, primarily induced by scouring and carrying of filtration flow, was the major factor resulting in copepods＇ efflux eventually. Therefore, high removal efficiency would be promised by decreasing the filtration rate and shortening the filtration cycle, because such operations could limit passive migration scale of Harpacticoida.