Growth And Reproduction Law Of Naididae And Its Removel In Water Purification Process

Eutrophication can cause excessive reproduction of worm in water, when the worm enter the purification process with the source water, it will cause aquatic and microbiological risks of water quality. At the same time, the worm may carry out second reproduction within the water purification process, aggravating the risk of contamination, because micro-organisms are rich and dissolved oxygen level is high in O3/BAC, pollution is particularly serious in it. Based on this, this article first investigated and analysised the distribution and pollution type of worm in purification process, then researched on the migration mode and reproductive law of Naididae which is dominant species in worm, and the interception effect of water purification process to Naididae. It aimed to provide the theoretical basis and technical support to prediction and control Naididae pollution in water purification process. The major results are as follows:(1) The dominant species detected out in Bijiashan waterworks were Naididae, Nematode, Chironomid larvae and Aeolosoma. Nematode was extern pollution, Naididae and Chironomid larvae were endogenous pollution causing by second reproduction. Naididae pollution happened in BAC filter, but Chironomid larvae in sedimentation tank.(2) BAC filter was more suitable for the growth of Naididae. Naididae feeded by impurities in BAC filter backwash water, their number increased by 1.5 times, but Naididae feeded by sediment in sedimentation tank, no increase in the number of Naididae.There were three types of migration modes of Naididae: benthic, attachment and drift. Temperature, dissolved oxygen and oxidant had certain influence on migration modes of Naididae. When temperature was 20℃, the proportion of drifting Naididae was the highest,18.5%. The rate of random drifting Naididae was the highest under 8mg/L. When oxidant concentration was 0.1mg / L and 0.2mg / L, it will promote Naididae to drift, the rate was 33% and 32%.(3) Life Cycle Table Method was suit to research the growth and reproduction law of Naididae. The higher the temperature and dissolved oxygen, the faster the propagation rate. When temperature was 23℃, Naididae can propagation fast, doubling time is 6.56±0.91d, but increased a lot at 16℃, 24.46±4.45d. High level of dissolved oxygen was suit for Naididae's rapid growth. When dissolved oxygen was 8mg / L, the doubling time of Naididae was the shortest, 4.97±0.16d. Doubling time of Naididae in simulation experiment of BAC filter was 12.60±0.42d , population growth was obvious.(4) The process of coagulating sedimentation can remove Naididae obviously , the rate can nearly achieve 100%. Sand filter can inactivate Naididae by 100% under the experimental conditions. BAC fiter had good interception effect, the penetration of Naididae below 4% during experiment. Using V filter with air-water backwashing can remove Naididae nearly 80%.