Effects of GAC and UV/H2O2-GAC filtration on the bacterial community and opportunistic pathogens in simulated drinking water systems

Abstract

The effects of granular activated carbon (GAC) and UV/H₂O₂-GAC filtration on the bacterial community and opportunistic pathogens (OPs) in simulated drinking water systems were investigated in this study. The results indicated that GAC filtration and UV/H₂O₂-GAC filtration enhanced the dissolved organic carbon (DOC) and assimilable organic carbon (AOC) removal efficiency in the influents of drinking water distribution systems (DWDSs) by the removal of tryptophan-like proteins, fulvic acid-like, and humic acid-like compounds, compared with sand filtration (SF). The lower organic matter concentration reduced the diversity and richness of the bacterial community, inducing the production of lower extracellular polymeric substances (EPS) in these two DWDSs. EPSs with a lower content of proteins led to less bacterial attachment onto particles to form particle-associated bacteria, and adsorption onto the surface of pipes to form biofilms. This process induced a lower chlorine-resistance capability of the bacteria in water and biofilm in DWDSs. The relative abundance of Legionella at the genus level was 0.93%, 0.29%, and 0.13% in the biofilms of SF DWDSs, GAC DWDSs, and UV/H₂O₂-GAC DWDSs, respectively. Mycobacteria and Pseudomonas showed the same changes as Legionella. The quantitative polymerase chain reaction (qPCR) results also suggested that the number of Legionella pneumophila, Mycobacteria avium, and Pseudomonas aeruginosa were lower in the effluents and biofilms of GAC DWDSs and UV/H₂O₂-GAC DWDSs. Therefore, GAC filtration can be used to control OPs growth in DWDSs, and UV/H₂O₂ can improve the efficiency of GAC filtration, especially with the 48 h distribution in DWDSs.