Effect of pipe material and disinfectant on active bacterial communities in drinking water and biofilms

Aims: We investigated the combined effects of pipe materials and disinfection chemicals on bacterial community and its active RNA fraction in water and biofilms in a pilot-scale premise plumbing system. Methods and results: The changes in bacterial communities were studied within four pipelines using copper and cross-linked polyethylene (PEX) pipe with chlorine or chloramine disinfection. The total and active bacterial communities and the presence of opportunistic pathogens (Legionella spp. and Mycobacterium spp.) were analyzed using 16S rRNA (gene) amplicon sequencing. The dominant classes were Alphaproteobacteria (31%) and Gammaproteobacteria (24%). Class Planctomycetia was increased in active fraction of chlorinated waters and PEX pipe biofilms and decreased in chloraminated waters and copper pipe biofilms. The alpha diversity of the active fractions in biofilms were highest in chloraminated PEX pipe samples (Chao1 mean = 163, P < 0.05, Kruskal–Wallis). Legionella spp. was more abundant and active in waters treated with chlorine than chloramine. Conclusions: Disinfectant had a stronger impact than pipe material on the bacterial community composition in water. A combined effect of pipe material and disinfectant was more evident on the composition and activity of the biofilm communities than the individual effect of copper, PEX, chlorine, or chloramine.