title: Aluminum-humic colloid formation during pre-coagulation for membrane water treatment: mechanisms and impacts.
abstract: Precoagulation has been widely used by low pressure membrane filtration (LPMF) plants to reduce membrane fouling and increase natural organic matter (NOM) removal. Formation of aluminum and aluminum-NOM moieties plays a fundamental role in this important water treatment process. This study comprehensively investigated the mechanisms of aluminum-NOM species formation during precoagulation and their impacts on LPMF performance. The results show that, at low alum doses, e.g. 0.5 mg and 1.0 mg Al L(-1), humic substances (HS) and Al species (amorphous Al(OH)3, or Al(OH)3(am)) reacted to form small Al(OH)3(am)-HS colloids. Increases in alum dose resulted in sequential transitions of the Al-HS moieties to larger particles and, eventually, precipitates. Compared to waters containing only naturally occurring organic colloids (OC) or HS, the coexistence of OC and HS facilitated the formation of Al-HS precipitates, thereby increasing the removal of HS by 7-15%, but the removal of OC was decreased by 3-20%. Interestingly, these transitions in Al-HS moieties did not affect membrane fouling. Both short-term and long-term filtration results demonstrate that OC, rather than the Al(OH)3(am)-HS colloids, primarily caused membrane fouling. These findings highlight the dynamics of particulate Al-NOM formation during precoagulation and its relationship with membrane fouling, which can be utilized to optimize the operation of integrated precoagulation-LPMF systems on full-scale installations.
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China.
authors.forename: Zhengyang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institut de Chimie des Milieux et des Matériaux de Poitiers (IC2MP; UMR: 7285), École Nationale Supérieure d'Ingénieurs de Poitiers (ENSIP), Université de Poitiers. 1 rue Marcel Doré, Bâtiment 16, 86022 Poitiers Cedex, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Teychene
authors.affiliation: Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Talia E Abbott
authors.initials: TE
authors.lastname: Chalew
authors.affiliation: Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Gaurav S
authors.initials: GS
authors.lastname: Ajmani
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhou
authors.affiliation: Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA; State Joint Key Laboratory of Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, PR China. Electronic address: huanghaiou@bnu.edu.cn.
authors.forename: Haiou
authors.initials: H
authors.lastname: Huang
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China. Electronic address: xhwoo@mail.hust.edu.cn.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Wu
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D005374:Filtration / Q000379:methods*; D006812:Humic Substances / Q000032:analysis*; D052638:Particulate Matter / Q000032:analysis; D018508:Water Purification / Q000379:methods*
chemical_list: D003102:Colloids; D006812:Humic Substances; D052638:Particulate Matter; D000535:Aluminum
keywords: Al(OH)(3(am))-HS colloids; Coagulation mechanism; Fractionated natural organic matter; Membrane fouling; Microfiltration