Bacteria attenuation by iron electrocoagulation governed by interactions between bacterial phosphate groups and Fe(III) precipitates

WATER RESEARCH

卷:103

Article

Delaire, Caroline¹  van Genuchten, Case M.²  Amrose, Susan E.¹  Gadgil, Ashok J.^1,3 

[1] Univ Calif Berkeley, Dept Civil & Environm Engn, Berkeley, CA 94720 USA

[2] Univ Utrecht, Fac Geosci, Dept Earth Sci Geochem, NL-3508 TA Utrecht, Netherlands

[3] Lawrence Berkeley Natl Lab, Energy Technol Area, Berkeley, CA 94720 USA

关键词: Iron electrocoagulation;    Bacteria attenuation;    Bacterial surface functional groups;    Specific interactions;    Bivalent cations;    Oxyanions;   

DOI  :  10.1016/j.watres.2016.07.020

来源: Elsevier

【 摘 要 】

Iron electrocoagulation (Fe-EC) is a low-cost process in which Fe(II) generated from an Fe(0) anode reacts with dissolved O-2 to form (1) Fe(III) precipitates with an affinity for bacterial cell walls and (2) bactericidal reactive oxidants. Previous work suggests that Fe-EC is a promising treatment option for groundwater containing arsenic and bacterial contamination. However, the mechanisms of bacteria attenuation and the impact of major groundwater ions are not well understood. In this work, using the model indicator Escherichia coli (E. coli), we show that physical removal via enmeshment in EC precipitate flocs is the primary process of bacteria attenuation in the presence of HCO3-, which significantly inhibits inactivation, possibly due to a reduction in the lifetime of reactive oxidants. We demonstrate that the adhesion of EC precipitates to cell walls, which results in bacteria encapsulation in flocs, is driven primarily by interactions between EC precipitates and phosphate functional groups on bacteria surfaces. In single solute electrolytes, both P (0.4 mM) and Ca/Mg (1-13 mM) inhibited the adhesion of EC precipitates to bacterial cell walls, whereas Si (0.4 mM) and ionic strength (2-200 mM) did not impact E. coli attenuation. Interestingly, P (0.4 mM) did not affect E. coli attenuation in electrolytes containing Ca/Mg, consistent with bivalent cation bridging between bacterial phosphate groups and inorganic P sorbed to EC precipitates. Finally, we found that EC precipitate adhesion is largely independent of cell wall composition, consistent with comparable densities of phosphate functional groups on Gram-positive and Gram-negative cells. Our results are critical to predict the performance of Fe-EC to eliminate bacterial contaminants from waters with diverse chemical compositions. (C) 2016 Elsevier Ltd. All rights reserved.

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