title: Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation.
abstract: Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations.
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia; Centre for Advanced Macromolecular Design, School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: R K L
authors.initials: RK
authors.lastname: Yap
authors.affiliation: Monash Institute of Pharmaceutical Sciences (MIPS), Monash University, IVC 3052, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Whittaker
authors.affiliation: School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Diao
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: R M
authors.initials: RM
authors.lastname: Stuetz
authors.affiliation: Cranfield Water Science Institute, School of Applied Sciences, Cranfield University, Bedfordshire MK43 0AL, UK.
authors.forename: B
authors.initials: B
authors.lastname: Jefferson
authors.affiliation: Department of Chemical Engineering, Izmir Institute of Technology, Urla, 35430 Izmir, Turkey.
authors.forename: V
authors.initials: V
authors.lastname: Bulmus
authors.affiliation: Water Research Laboratory, School of Civil and Environmental Engineering, The University of New South Wales, Manly Vale, NSW 2093, Australia.
authors.forename: W L
authors.initials: WL
authors.lastname: Peirson
authors.affiliation: School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: A V
authors.initials: AV
authors.lastname: Nguyen
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: r.henderson@unsw.edu.au.
authors.forename: R K
authors.initials: RK
authors.lastname: Henderson
mesh_terms: D000498:Allyl Compounds / Q000737:chemistry; D000458:Cyanobacteria / Q000302:isolation & purification*; D005427:Flocculation; D057927:Hydrophobic and Hydrophilic Interactions; D008689:Methacrylates / Q000737:chemistry; D009757:Nylons; D011108:Polymers / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology*; D018508:Water Purification / Q000379:methods*
chemical_list: D000498:Allyl Compounds; D008689:Methacrylates; D009757:Nylons; D011108:Polymers; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D062065:Wastewater; C407037:poly(2-(dimethylamino)ethyl methacrylate); C508190:diallyldimethylammonium chloride
keywords: Algae separation; Cationic bubbles; Cyanobacteria; Flotation; PosiDAF; Water soluble polymers