title: Cotransport of bacteria with hematite in porous media: Effects of ion valence and humic acid.
abstract: This study investigated the influence of multiple colloids (hematite and humic acid) on the transport and deposition of bacteria (Escherichia coli) in packed porous media in both NaCl (5 mM) and CaCl2 (1 mM) solutions at pH 6. Due to the alteration of cell physicochemical properties, the presence of hematite and humic acid in cell suspensions significantly affected bacterial transport and deposition in quartz sand. Specifically, the presence of hematite (5 mg/L) decreased cell transport (increased cell deposition) in quartz sand in both NaCl and CaCl2 solutions, which could be attributed to the less negative overall zeta potentials of bacteria induced by the adsorption of positively charged hematite onto cell surfaces. The presence of a low concentration (0.1 mg/L) of humic acid in bacteria and hematite mixed suspensions reduced the adsorption of hematite onto cell surfaces, leading to increased cell transport in quartz sand in NaCl solutions, whereas, in CaCl2 solutions, the presence of 0.1 mg/L humic acid increased the formation of hematite-cell aggregates and thus decreased cell transport in quartz sand. When the concentration of humic acid was increased to 1 mg/L, enhanced cell transport was observed in both NaCl and CaCl2 solutions. The decreased adsorption of hematite onto cell surfaces as well as the competition of deposition sites on quartz sand with bacteria by the suspended humic acid contributed to the increased cell transport.
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Yang
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Ge
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wu
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China. Electronic address: tongmeiping@pku.edu.cn.
authors.forename: Meiping
authors.initials: M
authors.lastname: Tong
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
authors.forename: Jinren
authors.initials: J
authors.lastname: Ni
mesh_terms: D000327:Adsorption; D003102:Colloids / Q000032:analysis*; D004926:Escherichia coli / Q000502:physiology*; D005290:Ferric Compounds / Q000032:analysis*; D006812:Humic Substances / Q000032:analysis*; D007477:Ions / Q000737:chemistry; D016062:Porosity; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D006812:Humic Substances; D007477:Ions; D014874:Water Pollutants, Chemical; C000499:ferric oxide
keywords: Aggregates; Bacteria; Cotransport; Hematite; Humic acid