title: Terminating pre-ozonation prior to biological activated carbon filtration results in increased formation of nitrogenous disinfection by-products upon subsequent chlorination.
abstract: Previous research demonstrated that ozone dosed before biological activated carbon (BAC) filtration reduces the formation of disinfection by-products (DBPs) upon subsequent chlorination. The current work aimed to evaluate the impact of terminating this pre-ozonation on the ability of the BAC to remove the precursors of N-DBPs. More N-DBP precursors passed into the post-BAC water when the pre-ozonation was terminated, resulting in greater formation of N-DBPs when the water was subsequently chlorinated, compared to a parallel BAC filter when the pre-ozonation was run continuously. Moreover, the N-DBP formation potential was significantly increased in the effluent of the BAC filter after terminating pre-ozonation, compared with the influent of the BAC filter (i.e. the effluent from the sand filter). Therefore, while selectively switching pre-ozonation on/off may have cost and other operational benefits for water suppliers, these should be weighed against the increased formation of N-DBPs and potential associated health risks.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: feedwater@126.com.
authors.forename: Wenhai
authors.initials: W
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Changjun
authors.initials: C
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: gaonaiyun@126.com.
authors.forename: Naiyun
authors.initials: N
authors.lastname: Gao
authors.affiliation: Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Templeton
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Yanshen
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D002606:Charcoal / Q000737:chemistry; D002713:Chlorine / Q000737:chemistry*; D004203:Disinfection / Q000379:methods*; D005374:Filtration / Q000379:methods*; D009584:Nitrogen / Q000032:analysis*; D010126:Ozone / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D002606:Charcoal; D002713:Chlorine; D010126:Ozone; D009584:Nitrogen
keywords: Biological activated carbon (BAC); Carbonaceous disinfection by-products (C-DBPs); Nitrogenous disinfection by-products (N-DBPs); Ozonation; Soluble microbial product (SMP)