title: Increase of microbial growth potential in municipal secondary effluent by coagulation.
abstract: Microbial growth is a big issue of concern in the use of reclaimed water. In this study, the variation of microbial growth potentials of municipal secondary effluents after coagulation was evaluated by measuring assimilable organic carbon (AOC). Surprisingly, the AOC levels increased significantly (55-667%) after coagulation with poly-aluminum dosages of 60 mgL(-1) for the samples investigated in this research. By ultrafiltration membrane fractionation, the microbial growth potentials of the fractions with different molecular weight (MW) were measured. The results revealed that the maximum cell densities of microbial growth in secondary effluents were lower than those in their fractions with MW<10kDa. Meanwhile, the organic component with MW>10kDa in biological treated effluents was proved to have an inhibitory effect on microbial growth. Therefore, the removal of those high MW organic matters was the main reason for the increase of microbial growth potential in secondary effluents during coagulation. Furthermore, polysaccharides and/or proteins in secondary effluents were easily removed by coagulation and were thought to be the possible key organic substances affecting the microbial growth potential during coagulation. It is suggested that post treatments would be needed after coagulation to maintain the biological stability of reclaimed water.
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, Beijing 100084, China; School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China. Electronic address: hyhu@tsinghua.edu.cn.
authors.forename: Hong-Ying
authors.initials: HY
authors.lastname: Hu
authors.affiliation: College of Environment and Resources, Inner Mongolia University, Huhhot 010021, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Su
authors.affiliation: College of Environment and Resources, Inner Mongolia University, Huhhot 010021, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Shu-Ming
authors.initials: SM
authors.lastname: Liu
mesh_terms: D064307:Microbiota / Q000502:physiology*; D008970:Molecular Weight; D009930:Organic Chemicals / Q000737:chemistry / Q000302:isolation & purification; D014462:Ultrafiltration; D014867:Water / Q000032:analysis*; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*; D014881:Water Supply
chemical_list: D009930:Organic Chemicals; D014867:Water
keywords: Assimilable organic carbon (AOC); Biological stability; Coagulation; Molecular weight distribution; Reclaimed water; Secondary effluent