title: Effects of assimilable organic carbon and free chlorine on bacterial growth in drinking water.
abstract: Assimilable organic carbon (AOC) is one of the most important factors affecting the re-growth of microorganisms in drinking water. High AOC concentrations result in biological instability, but disinfection kills microbes to ensure the safety of drinking water. Free chlorine is an important oxidizing agent used during the disinfection process. Therefore, we explored the combined effects of AOC and free chlorine on bacterial growth in drinking water using flow cytometry (FCM). The initial AOC concentration was 168 μg.L(-1) in all water samples. Without free chlorine, the concentrations of intact bacteria increased but the level of AOC decreased. The addition of sodium hypochlorite caused an increase and fluctuation in AOC due to the oxidation of organic carbon. The concentrations of intact bacteria decreased from 1.1 × 10(5) cells.mL(-1) to 2.6 × 10(4) cells.mL(-1) at an initial free chlorine dose of 0.6 mg.L(-1) to 4.8 × 10(4) cells.mL(-1) at an initial free chlorine dose of 0.3 mg.L(-1) due to free chlorine originating from sodium hypochlorite. Additionally, free chlorine might be more obviously affected AOC concentrations than microbial growth did. These results suggested that AOC and free chlorine might have combined effects on microbial growth. In this study, our results showed concentrations determined by FCM were higher than those by HPC, which indicated that some E. coli detected by FCM might not be detected using HPC in drinking water. The level of free chlorine might restrain the consumption of AOC by inhibiting the growth of E. coli; on the other hand, chlorination might increase the level of AOC, thereby increase the potential for microbial growth in the drinking water network.
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing, 100085, China.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Liu
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing, 100085, China.
authors.forename: Jingqi
authors.initials: J
authors.lastname: Wang
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing, 100085, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Liu
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing, 100085, China.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Kong
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: He
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jin
authors.affiliation: College of Biological Sciences and Technology, P. O. Box 162, Beijing Forestry University, Beijing 100083, China.
authors.forename: Bolin
authors.initials: B
authors.lastname: Zhang
mesh_terms: D058491:Bacterial Load; D002244:Carbon / Q000494:pharmacology*; D002713:Chlorine / Q000494:pharmacology*; D060766:Drinking Water / Q000382:microbiology*; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D005434:Flow Cytometry; D018508:Water Purification
chemical_list: D060766:Drinking Water; D002713:Chlorine; D002244:Carbon