Bacteria attenuation by iron electrocoagulation governed by interactions between bacterial phosphate groups and...

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Microbiology

Background:

• Iron electrocoagulation (Fe-EC) is a cost-effective method for treating groundwater contaminated with arsenic and bacteria.
• The precise mechanisms of bacterial removal and the influence of common groundwater ions on Fe-EC efficacy remain unclear.

Purpose of the Study:

• To elucidate the primary mechanisms of bacterial attenuation during Fe-EC using Escherichia coli (E. coli) as a model.
• To investigate the impact of key groundwater ions on bacterial removal efficiency and adhesion processes.

Main Methods:

• Utilized Escherichia coli (E. coli) as a model organism to study bacterial attenuation during iron electrocoagulation.
• Investigated the role of bicarbonate (HCO3-), phosphate (P), calcium/magnesium (Ca/Mg), silicon (Si), and ionic strength on bacterial removal and precipitate adhesion.
• Analyzed the influence of cell wall composition on the adhesion of electrocoagulation precipitates.

Main Results:

• Physical enmeshment in electrocoagulation (EC) precipitate flocs is the dominant bacteria attenuation mechanism, especially in the presence of bicarbonate (HCO3-).
• Bicarbonate significantly inhibits bacterial inactivation, likely by reducing the lifespan of reactive oxidants.
• Adhesion of EC precipitates to bacterial cell walls is primarily mediated by interactions with phosphate functional groups, leading to encapsulation within flocs.
• Phosphate (P) and bivalent cations (Ca/Mg) inhibited precipitate adhesion, with Ca/Mg potentially bridging phosphate groups.
• Silicon (Si) and ionic strength did not significantly affect E. coli attenuation.
• Precipitate adhesion was largely independent of cell wall composition (Gram-positive vs. Gram-negative).

Conclusions:

• Bacterial attenuation by Fe-EC is mainly through physical entrapment, with inactivation being less significant, particularly in bicarbonate-rich waters.
• Understanding ion-specific interactions, especially phosphate and bivalent cations, is crucial for optimizing Fe-EC performance in diverse water matrices.
• The findings provide critical insights for predicting and enhancing the effectiveness of Fe-EC in removing bacterial contaminants from various water sources.