Characteristics of biofilm community structure in a reclaimed water cast iron pipeline

Cast iron tubing, even if the lined cast iron tubing is prone to corrosion due to lining aging, shedding, and so forth, remains in use. The biofilm is one of the factors inducing corrosion. It affects the corrosion process of cast iron through microbiologically influenced corrosion. Therefore, investigating the community structure and development characteristics of the biofilm is a prerequisite for studying the corrosion of cast iron, and it is also the basis for understanding the changes in water quality in the transport of reclaimed water. In this study, by conducting a reclaimed water pipe simulation and employing a barcoded Illumina paired-end sequencing method to investigate the biofilm community structure and development characteristics in different tubes, the dynamics of the microbial community structure in the biofilm were examined to determine the dominant genera. The results indicate that the main biofilm communities in different pipe materials are significantly different from each other. With the passage of time, the richness and diversity of the microbial community in the cast iron pipe biofilm shows a downwards trend. The biofilm diversity in cast iron tubing is lower than that in high-density polyethylene tubing and stainless steel tubing. At the beginning of its development process, the compositions of the biofilm community in the cast iron pipe are similar to those in other pipes and are mainly comprised of Proteobacteria and Bacteroidetes. Significant differences appear later on in the development process which reveal that the proportion of Proteobacteria in the cast iron tubing biofilm (55.51% to 63.39%) is slightly greater than that in other tubing biofilms (30.60% to 48.31%). Throughout the developmental period, two kinds of operational taxonomic units (OTUs) of Rhodocyclaceae have an absolute abundance advantage in the cast iron pipe biofilm. The 18 characteristic OTU abundance values in the cast iron tubing biofilm are significantly greater than those on other tubes, including Geothrix of Acidobacteria and Azospirillum of Betaproteobacteria.