Taxonomic relatedness and environmental pressure synergistically drive the primary succession of biofilm microbial communities in reclaimed wastewater distribution systems

Abstract Compared to drinking water, the higher bacterial abundance, diversity, and organic matter concentration in reclaimed wastewater suggest that it is more likely to form biofilms. Nevertheless, little is known regarding many important aspects of the biofilm ecology in reclaimed wastewater distribution systems (RWDS), such as the long-term microbial community succession and the underlying driving factors. In the present study, by sampling and analysing microbial compositions of pipe wall biofilms from six frequently used pipe materials under NaClO disinfection (sodium hypochlorite-treated), NON disinfection (without disinfection), and UV disinfection (UV-treated) treatments over one year, it was found that the succession of microbial community structure followed a primary succession pattern. This primary succession pattern was reflected as increases in live cell number and α-diversity, along with metagenic succession in taxonomic composition. Proteobacteria , Nitrospirae , Bacteroidetes , Acidobacteria , Planctomycetes , Actinobacteria , and Verrucomicrobia comprised the dominant phyla in biofilm samples. Compared to biofilms in the NaClO disinfection reactor, the bacterial communities of biofilms in NON disinfection and UV disinfection reactors were distributed more evenly among different bacterial phyla. Principal component analysis revealed a clear temporal pattern of microbial community structures in six kinds of pipe wall biofilms albeit a difference in microbial community structures among the three reactors. Adonis testing indicated that the microbial community composition variation caused by disinfection methods (R 2  = 0.283, P 2  = 0.070, P 2  = 0.057, P Sphingomonadaceae , known to show chlorine tolerance and powerful biofilm-forming ability in NaClO disinfection reactors, evidenced the habitat filtering consequent to environment pressure. Correlation-based network analysis revealed that taxonomic relatedness such as similar niches, cooperation, taxa overdispersion, and competition all functioned toward driving the bacterial assembly succession in RWDS.