title: Escherichia coli Attenuation by Fe Electrocoagulation in Synthetic Bengal Groundwater: Effect of pH and Natural Organic Matter.
abstract: Technologies addressing both arsenic and microbial contamination of Bengal groundwater are needed. Fe electrocoagulation (Fe-EC), a simple process relying on the dissolution of an Fe(0) anode to produce Fe(III) precipitates, has been shown to efficiently remove arsenic from groundwater at low cost. We investigated Escherichia coli (E. coli) attenuation by Fe-EC in synthetic Bengal groundwater as a function of Fe dosage rate, total Fe dosed, pH, and presence of natural organic matter (NOM). A 2.5 mM Fe dosage simultaneously achieved over 4-log E. coli attenuation and arsenic removal from 450 to below 10 μg/L. E. coli reduction was significantly enhanced at pH 6.6 compared to pH 7.5, which we linked to the decreased rate of Fe(II) oxidation at lower pH. 3 mg/L-C of NOM (Suwanee River fulvic acid) did not significantly affect E. coli attenuation. Live-dead staining and comparisons of Fe-EC with chemical coagulation controls showed that the primary mechanism of E. coli attenuation is physical removal with Fe(III) precipitates, with inactivation likely contributing as well at lower pH. Transmission electron microscopy showed that EC precipitates adhere to and bridge individual E. coli cells, resulting in large bacteria-Fe aggregates that can be removed by gravitational settling. Our results point to the promising ability of Fe-EC to treat arsenic and bacterial contamination simultaneously at low cost.
authors.affiliation: †Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, United States.
authors.forename: Caroline
authors.initials: C
authors.lastname: Delaire
authors.affiliation: †Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, United States.
authors.forename: Case M
authors.initials: CM
authors.lastname: van Genuchten
authors.affiliation: †Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, United States.
authors.forename: Kara L
authors.initials: KL
authors.lastname: Nelson
authors.affiliation: †Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, United States.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Amrose
authors.affiliation: †Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, United States.|‡Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Ashok J
authors.initials: AJ
authors.lastname: Gadgil
mesh_terms: D000534:Alum Compounds / Q000494:pharmacology; D001151:Arsenic / Q000302:isolation & purification; D004564:Electrocoagulation / Q000379:methods*; D004926:Escherichia coli / Q000187:drug effects / Q000302:isolation & purification* / Q000648:ultrastructure; D060587:Groundwater / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000494:pharmacology*; D050296:Microbial Viability / Q000187:drug effects; D008856:Microscopy, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification
chemical_list: D000534:Alum Compounds; D014874:Water Pollutants, Chemical; C041524:aluminum sulfate; D007501:Iron; D001151:Arsenic