Characterization Of Biofilms In Water Distribution System And Their Effect On Chlorine Decay

Drink water distribution system as an essential infrastructure of city，has animportant influence on the normal production and life of urban residents. But thesecondary pollution of Drink water distribution system a potential security threat.The biofilm is particularly serious hazards. On the one hand, it makes drinkingwater color, increasing of turbidity, which causes dissatisfaction on water quality.On the other hand, the growth of microorganisms in biofilm can accelerate corrosionof pipes, which will reduce the flow area of the pipe, increase energy consumptionand produce red and yellow water. in addition, There may be a small amount ofAquatic pathogens in biofilm which is a huge threat On residents health. So,this study is aimed to research the biofilm on pipe in drink water distributionsystem.Firstly, the biofilm formation and Factors in drinking water distribution systemwas studied by using experimental network. From the research of three differentpipe materials of casting iron, PE, stainless steel, the biofilm biomass maturingwithin8days. The impact of the Residual chlorine on the biofilm biomass variedfrom pipe materials to pipe materials. Biomass of biofilm on PE and stainless steeldecreased while the concentration of Residual chlorine increased. For casting iron, itshows a totally reverse tendency. Comparing the biomass of biofilm on threedifferent pipe materials, certain regularity was obtained: casting iron>PE> stainlesssteel. The correlation between Temperature, Turbidity, biomass of bulk water andbiomass was analyzed. They all showed a positive correlation with biomass ofbiofilm.Secondly, the influence of Residual chlorine and pipe materials on the structureand composition of biofilms was analyzed, using molecular biology andculture-based method. Analysis of microorganisms in biofilms and waterphysico-chemical data showed that pipe materials influenced bacterial communitystructure and composition in our experimental DWDS. The order of bacterial specieswas: casting iron> stainless steel> PE. In addition, Sphingomonas was the onlyspecies that appeared in the biofilm of three materials. The impact of the Residualchlorine on the structure and composition of biofilms varied from pipe materials topipe materials. The impact of the Residual chlorine was obvious on the pipematerials of casting iron and stainless steel. But it was not founded on the pipematerials of PE.At last, the impact of the biofilm on chlorine decay was researched. Results showed that the process of chlorine decay could be divided into two phases, thephase with fast decay for the first30minutes and the phase with the steady decayafter30minutes. Chlorine decay has positive correlation with factors of biomass ofbiofilms and pipe materials. The influence of the structure and composition ofbiofilms on the chlorine decay was not obvious. The greater water flowed, the fasterchlorine decayed. In the fast decay phases, the high chlorine concentration was notsignificant. But In the steady decay phases, the high chlorine concentration couldaccelerate the decay of chlorine under the effect of biofilms.