Analysis Of Community Structure Of Corrosion Scale And Biofilm In Water Distribution System

It might form a thick layer of pipe scale and biofilm in the inner wall of the pipe during the water distribution system,the stability of pipe scale and biofilm directly affected the water quality,unstable pipe scale and biofilm could cause pipeline“red water”.This paper respectively measured the main water quality parameters before changing the water source?characterized the morphology?XRD semi-quantitative analysis of the pipe scale and 454 high-throughput sequencing of microorganisms before and after changing the water source?MPN counting and quantitative PCR of the target genes through the pipe scale,biofilm and water samples of actual water supply network A?surface water?and B?ground water?and the pipe scale and biofilm collected from the simulated water source switch laboratory experiment based on both A and B pipe.Results of water quality parameters showed A pipe water?surface water?Larsen index was 1.34,indicated that the corrosion of A pipe water was severe than that of B pipe water.The macroscopic and microscopic study of A corrosion scale layer found that A scale layer was convex spherical nodular scale and concentrated on the inner wall of the pipe,SEM results showed that A?surface water?pipe scale layer was flaky or massive,the gap between the particles was relatively large;While B?groundwater?pipe scale was horizontal and evenly distributed in the pipe,and the gap between the particles was smaller.These results showed that the corrosion of A sample was more serious than that of B sample.Through the study of the morphology of the pipe scale changed with Danjiangkou water we fonud that the pipe scale morphology did not change much.Further study to the substances of the pipe scale,XRD results showed that the crystalline of A pipe scale mainly contained magnetite Fe₃O₄ and goethite?-FeOOH,while the content of magnetite Fe₃O₄ and goethite?-FeOOH of the pipe scale changed with Danjiangkou water were reduced,the ratio of magnetite?M?to goethite?G?was less than 1,indicating that pipe scale was not mature enough and corrosion might occur;The pipe scale B?groundwater?mainly contained magnetite Fe₃O₄ and Green Rust,thus pipe scale B was more stable.454 high-throughput sequencing results showed that the total species number and community diversity of surface water?A?were less than that of B,the total species number and community diversity of A sample after changing the water source increased while B sample became less,the results indicated that switching water source had an effect on the composition of microorganism.Further study at phylum,class and genus levels on sample analysis found the microbial communities of pipe water taken from surface water?A?and ground water?B?were single,pipe scale and biofilm were rich.At phylum level,surface water?A?and ground water?B?samples mainly contained proteobacteria,and community structure that after changing water source had a trend to be more complex;At class level,surface water?A?and ground water?B?mainly contained?-Proteobacteria,in addition,A sample after changing water source,B sample and B sample after changing water source also contained large amount of?-Proteobacteria;At genus level,community structure varied.MPN counting method of nitrate-reducing,Fe?III?-reducingandnitrate-dependentFe?II?-oxidizing microorganisms from two pipe scale showed that the three bacteria were contained.The results indicated that the iron-reducing bacteria?iron-reducing bacteria and nitrate-reducing bacteria of pipe scale and biofilm could affect pipe corrosion and corrosion products by the iron redox.Using quantitative polymerase chain reaction?q-PCR?for the study of target genes showed that the number of gene between A and B had a significant difference,and the number of gene tended to increase.