Mutual effect between electrochemically active bacteria (EAB) and azo dye in bio-electrochemical system (BES)

Area of Science:

• Environmental Microbiology
• Electrochemistry
• Biotechnology

Background:

• Azo dyes are common pollutants in industrial wastewater.
• Bio-electrochemical systems (BESs) offer a promising approach for wastewater treatment.
• Understanding the interaction between azo dyes and electrochemically active bacteria (EAB) is crucial for optimizing BES performance.

Purpose of the Study:

• To investigate the mutual effect between azo dye and EAB performance in BESs.
• To determine the optimal conditions for azo dye decolorization using EAB.
• To analyze the impact of azo dye on the microbial community within BESs.

Main Methods:

• Enrichment of EAB at a controlled potential (-0.2 V vs Ag/AgCl) in single-chamber BESs.
• Decolorization experiments with varying initial concentrations of alizarin yellow R (AYR) (30-120 mg/L).
• Microbial community analysis using 16S rRNA gene sequencing.

Main Results:

• Over 95% AYR decolorization was achieved within 24 hours, irrespective of initial concentration.
• The fastest decolorization rate (4.25 times higher than open circuit) occurred at 70 mg/L AYR in closed-circuit BESs.
• Geobacter abundance increased from 77.98% to 92.22% with increasing AYR concentration, indicating selective growth promotion.

Conclusions:

• Azo dye can selectively promote the growth of exoelectrogens, such as Geobacter, in electrode biofilms.
• Electricity stimulation in BESs enhances azo dye decolorization rates and mitigates toxicity.
• BESs are effective for treating azo dye-containing wastewater, with EAB performance positively influenced by the dye under electrical stimulation.