Balancing pH for enhanced bacterial community performance in microbial fuel cells: implications for bio-electricity generation and pollutant reduction

Abstract

Microbial fuel cells (MFCs) represent a promising technology to generate bio-electricity and synchronously reduce wastewater pollutants. The presence of exoelectrogens in wastewater is critical for bio-electricity and pollutant reduction, but the performance of exoelectrogens at different pH levels remains unknown. This study aims to bridge this gap by offering an integrated approach to understanding the performance of exoelectrogens under varying substrate pH, particularly in bio-electricity generation and pollutant reduction in sugarbeet processing wastewater (SBWW). Three pH levels (ranging from acidic to alkaline) were studied and MFC's electricity output was measured. Later, current density, power density, and coulombic efficiency (CE) were calculated. Both pre- and post-experiment substrate samples were analysed with inductively coupled plasma (ICP). Furthermore, 16S rRNA gene analysis, DNA amplification, sequencing library preparation, and bioinformatics workflows on post-experiment samples of the substrate and anode samples were conducted. A diverse community of microorganisms was identified, especially Alphaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria (Geobacter). Bacteroidetes and Desulfovibrio were the major exoelectrogens responsible for electricity generation. Among the three pH levels tested, the most alkaline pH level (9.5±0.1) outperformed the others, achieving a 54% higher power density, 21% greater current density, and a 40% higher CE compared to the acidic pH level (6.5±0.1). Around 50–99% of pollutants were removed from the SBWW. The study revealed that Gammaproteobacteria thrive and perform better in alkaline environment.

Key findings

• ▸The performance of exoelectrogens was significantly affected by pH levels, with optimal performance observed at a pH range of 6.5-7.5.
• ▸The presence of Alphaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria was identified as key microorganisms contributing to bio-electricity generation and pollutant reduction.
• ▸The study found that pH balancing can enhance bacterial community performance, leading to improved bio-electricity generation and pollutant reduction.

Keywords

Identifiers

DOI

10.17159/wsa/2024.v50.i3.4107

Journal

Water SA

Year

2024