title: Enhancing disinfection by advanced oxidation under UV irradiation in polyphosphate-containing wastewater flocs.
abstract: In this paper, the role of naturally occurring polyphosphate in enhancing the ultraviolet disinfection of wastewater flocs is examined. It was found that polyphosphate, which accumulates naturally within the wastewater flocs in the enhanced biological phosphorus removal process, is capable of producing hydroxyl radicals under UV irradiation and hence causing the photoreactive disinfection of microorganisms embedded within flocs. This phenomenon is likely responsible for the improved UV disinfection of the biological nutrient removal (BNR) effluent compared to that of conventional activated sludge effluent by as much as 1 log. A mathematical model is developed that combines the chemical disinfection by hydroxyl radical formation within flocs, together with the direct inactivation of microorganisms by UV irradiation. The proposed model is able to quantitatively explain the observed improvement in the UV disinfection of the BNR effluents. This study shows that the chemical composition of wastewater flocs could have a significant positive impact on their UV disinfection by inducing the production of oxidative species.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, Canada M5S3E5.
authors.forename: Y
authors.initials: Y
authors.lastname: Azimi
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, Canada M5S3E5.
authors.forename: D G
authors.initials: DG
authors.lastname: Allen
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, Canada M5S3E5. Electronic address: ramin.farnood@utoronto.ca.
authors.forename: R R
authors.initials: RR
authors.lastname: Farnood
mesh_terms: D001673:Biodegradation, Environmental / Q000528:radiation effects; D019149:Bioreactors / Q000382:microbiology; D002170:Canada; D004203:Disinfection / Q000379:methods*; D005427:Flocculation / Q000528:radiation effects; D007700:Kinetics; D008751:Methylene Blue / Q000528:radiation effects; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction / Q000528:radiation effects; D010316:Particle Size; D011122:Polyphosphates / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*
chemical_list: D008751:Methylene Blue; D011122:Polyphosphates; D012722:Sewage; D062065:Wastewater
keywords: Advanced oxidation; Modeling; Phosphate accumulating organisms; Polyphosphate; Ultraviolet disinfection; Wastewater