title: Effects of water quality on inactivation and repair of Microcystis viridis and Tetraselmis suecica following medium-pressure UV irradiation.
abstract: The transfer of invasive organisms by ballast-water discharge has become a growing concern. UV treatment has become an attractive ballast water treatment technology due to its effectiveness, no harmful disinfection byproducts and easiness to handle. Two robust algae strains Microcystis viridis and Tetraselmis suecica were selected as indicator organisms to determine efficiency of medium-pressure (MP) UV-treatment on ballast water. Inactivation and potential repair of these two algae strains following MP UV irradiation were assessed under various turbidity, total organic carbon (TOC) and salinity conditions. The investigated range of UV doses was from 25 to 500 mJ/cm(2). For M. viridis, results indicated that disinfection efficiency was negatively correlated with all of these three factors at low doses (25-200 mJ/cm(2)). Photoreactivation and dark repair were promoted at high TOC levels (6-15 mg/L) with about 6-25% higher repair levels compared with those in distilled water, whereas no significant impacts were identified for turbidity and salinity on both of the photoreactivation and dark repair. For T. suecica, increased turbidity and TOC levels both hindered the performance of UV irradiation at high doses (200-500 mJ/cm(2)). Suppressive effects on photoreactivation and dark repair were consistently observed with changes of all of the three factors. In conclusion, generally these three factors resulted in repressive effects on UV disinfection efficiency, and TOC played a more significant role in the levels of reactivation than the other two. The responses of T. suecica to these three factors were more sensitive than M. viridis.
authors.affiliation: Department of Civil & Environmental Engineering, National University of Singapore, Singapore 117576, Singapore; School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Civil & Environmental Engineering, National University of Singapore, Singapore 117576, Singapore.
authors.forename: Xiaona
authors.initials: X
authors.lastname: Chu
authors.affiliation: Department of Civil & Environmental Engineering, National University of Singapore, Singapore 117576, Singapore; School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Pengyu
authors.initials: P
authors.lastname: Chen
authors.affiliation: Department of Civil & Environmental Engineering, National University of Singapore, Singapore 117576, Singapore.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Department of Civil & Environmental Engineering, National University of Singapore, Singapore 117576, Singapore. Electronic address: ceehujy@nus.edu.sg.
authors.forename: Jiangyong
authors.initials: J
authors.lastname: Hu
mesh_terms: D000460:Chlorophyta / Q000528:radiation effects*; D004203:Disinfection / Q000295:instrumentation / Q000379:methods; D046931:Microcystis / Q000528:radiation effects*; D011312:Pressure; D054712:Salinity; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods; D060753:Water Quality
chemical_list: D014867:Water
keywords: Ballast water; Dark repair; Medium-pressure UV disinfection; Microcystis viridis; Photoreactivation; Tetraselmis suecica