In water distribution systems, biofilm survival has been reported despite the regulatory presence of residual disinfectants. Natural organic matter (NOM), which is ubiquitous in drinking water systems, contributes to biofilm growth as a carbon source as well as increasing disinfectant
demand. In this study, strains from an opportunistic pathogen, Pseudomonas aeruginosa (both wild type and mutant strains) with different extracellular polymeric substance (EPS) secretion capabilities were used to cultivate single species biofilms. Biofilms were grown in a continuous
flow system under low nutrient condition simulating drinking water distribution system. After chlorine disinfection, biofilm was visualized using a confocal laser scanning microscope (CLSM) followed by image analysis to quantify biofilm EPS content and viability spatial distribution. The survival
rate of detached cells from PAO1 biofilm was analyzed by flow cytometry to differentiate live, dead and membrane compromised cells considering the presence or absence of disinfectant consumption substrate (NOM). Both biofilm and detachment viability were confirmed by plate count method. The
results show that the amount of EPS is positively related to biofilm viability. Resistance was significantly enhanced in EPS overproduction biofilm compared to EPS deficient strains. Due to chemical reaction between NOM and residual disinfectants, the presence of NOM improved detached biofilm
resistance to chlorine residuals.
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