Algal organic matter triggers re-assembly of bacterial community in plumbing system.

Algal bloom outbreaks in upstream drinking water reservoirs inevitably lead to algal organic matter (AOM) pollution in downstream drinking water plants and distribution systems. However, the responses of indoor piped drinking water quality and microbial community to AOM remain to be well studied. In this study, we investigated the effects of low and high concentrations of Chlorella organic matters on pipe-based drinking water. We found that AOM introduced nitrogen and phosphorus contamination into drinking water and promoted massive regeneration of bacteria during stagnation, along with increased bacterial metabolic activity. Compared to the Control group, the utilization capacity of alcohols, acids, esters, and amino acids increased under the influence of AOM. In addition, AOM intrusion reduced the bacterial community diversity in drinking water. The bacterial communities became more saturated, interspecific relationships became more complex, and interspecific competition increased. Bacteria with the ability to denitrification, such as Pseudomonas putida, Sphingobium amiense, Delftia tsuruhatensis, and Acidovorax temperans, were the most abundant. Residual chlorine, ammonium, nitrite, and iron had notable effects on the bacterial community under the influence of AOM. The results help elucidate the response mechanism of microbial community to AOM contamination in indoor drinking water pipes and provide a scientific basis for drinking water safety risk management.