Impact of chemical oxygen demand-to-sulfate ratio changes on spatial heterogeneity evolution of microbial communities in cathode biofilms and sulfate reduction performance of microbial electrolysis cells.
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75% confidenceThis MEC study investigates Bioelectrochemical systems, Stratification, Sulfate-containing wastewater. The research focuses on system optimization and characterization.
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Abstract
Microbial electrolysis cells (MEC) supply electrons to sulfate-reducing bacteria (SRB) within cathode biofilms, however, these SRB exhibit heterogeneous spatial distributions due to varying competitiveness for electron utilization, which ultimately impacts sulfate removal efficiency. This study investigates the underlying mechanisms driving the evolution of this spatial heterogeneity within cathode biofilms and its subsequent influence on sulfate reduction performance by modulating the chemical oxygen demand-to-sulfate (C/S) ratio. When the C/S ratio decreased from 5 to 3, the sulfate removal rate increased by nearly 10 %. At C/S = 5, Bacteroidota and Desulfovibrio were the predominant groups. After the ratio decreased, Synergistota and Aminomonas became dominant. Concurrently, gene abundances associated with assimilatory sulfate reduction (ASR) also increased. Therefore, we conclude that decreasing the C/S from 5 to 3 promotes a more active bacterial region in the biofilm surface, leading to a more efficient spatial stratification of the microbial community and, consequently, improved MEC performance.