Mechanism and effect of removing Harpacticoida with traditional drinking water treatment processes
NIE Xiao-bao1,2, LI Zhi-hong1, DING Li-jun3, HUANG Ting-lin2
1. School of Hydraulic Engineering, Changsha University of Science and Technology, Changsha 410076, China;
2. Northwest Key Laboratory of Water Resource and Environment Ecology of Ministry of Education, Xi'an University of Architecture and Technology, Xi'an 710055, China;
3. China City Environment Protection Engineering Limited Company, Wuhan 518031, China
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 300 r/min (1min), moderate stirring of 150 r/min (5min) and slow stirring of 75 r/min (5min), polymeric aluminium chloride dosage of 10 mg/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.
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NIE Xiao-bao, LI Zhi-hong, DING Li-jun, HUANG Ting-lin. Mechanism and effect of removing Harpacticoida with traditional drinking water treatment processes. CHINA ENVIRONMENTAL SCIENCECE, 2016, 36(2): 453-459.
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