title: Roles of coagulant species and mechanisms on floc characteristics and filterability.
abstract: In full scale water treatment operation, the rapid filtration process, as the last step of solid-liquid separation, is largely influenced by floc characteristics. In this study, aluminium sulphate (alum) and nano-Al13 were investigated to understand the influence of coagulant species on the formation and filterability of flocs. At neutral pH, it was found that nano-Al13, a high MW polymer, showed better floc filterability than alum. This is because of the densely compacted and well-distributed size flocs from nano-Al13, even though floc sizes of alum were generally bigger. Al specie distributions of the two coagulants at different pH levels were compared by using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) to further elucidate the reasons for the superiority of nano-Al13 in floc filterability. Depolymerisation/re-polymerisation of nano-Al13 occurred as pH changed, and Al species from nano-Al13were more abundant than that from alum, especially for the high molecular weight (MW) oligomers such as Al11, Al12, Al13 and Al14. Under the charge neutralisation mechanism, higher MW Al species was found to improve coagulation performance and floc filterability. In addition, breakage resistance and regrowth ability of nano-Al13 was better than alum, at weak acid condition. Flocs formed by the charge neutralisation mechanism readily regenerated after being thoroughly broken up. The floc regrowth ability of nano-Al13 at high shear rates (200 rpm and 300 rpm) was much better than at low shear and better than any shear applied to alum., and the flocs after breakage at 200 rpm and 300 rpm also showed better filterability than other conditions.
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, CAS, POB 2871, Beijing 100085, China.
authors.forename: Ruyuan
authors.initials: R
authors.lastname: Jiao
authors.affiliation: Australian Water Quality Centre, South Australian Water Corporation, 250 Victoria Square, Adelaide, South Australia 5000, Australia.
authors.forename: Rolando
authors.initials: R
authors.lastname: Fabris
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, CAS, POB 2871, Beijing 100085, China; Australian Water Quality Centre, South Australian Water Corporation, 250 Victoria Square, Adelaide, South Australia 5000, Australia; Centre for Water Management and Reuse, The School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
authors.forename: Christopher W K
authors.initials: CWK
authors.lastname: Chow
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, CAS, POB 2871, Beijing 100085, China; Australian Water Quality Centre, South Australian Water Corporation, 250 Victoria Square, Adelaide, South Australia 5000, Australia; Centre for Water Management and Reuse, The School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: Drikas
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, CAS, POB 2871, Beijing 100085, China; Centre for Water Management and Reuse, The School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
authors.forename: John
authors.initials: J
authors.lastname: van Leeuwen
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, CAS, POB 2871, Beijing 100085, China; Centre for Water Management and Reuse, The School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia. Electronic address: wgds@rcees.ac.cn.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Wang
mesh_terms: D000534:Alum Compounds / Q000737:chemistry*; D000536:Aluminum Hydroxide / Q000737:chemistry*; D001315:Australia; D005374:Filtration / Q000379:methods*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D000534:Alum Compounds; C016213:aluminum oxychloride; C041524:aluminum sulfate; D000536:Aluminum Hydroxide
keywords: Al species; Coagulation mechanisms; Floc breakage; Floc filterability; Flocculation index