Mixed sulfate-reducing bacteria-enriched microbial fuel cells for the treatment of wastewater containing copper

•SRB enriched MFC system was developed for investigating heavy metal removal.•Ten successive batches for voltage generation showed excellent reproducibility.•Maximum copper tolerance concentration in the biological anodic chamber was 20 mg/L.•Among SRB, Desulfovibrio (38.1%) was the most abundant genus at the anode.

Microbial fuel cells (MFCs) have been widely investigated for organic-based waste/substrate conversion to electricity. However, toxic compounds such as heavy metals are ubiquitous in organic waste and wastewater. In this work, a sulfate reducing bacteria (SRB)-enriched anode is used to study the impact of Cu2+ on MFC performance. This study demonstrates that MFC performance is slightly enhanced at concentrations of up to 20 mg/L of Cu2+, owing to the stimulating effect of metals on biological reactions. Cu2+ removal involves the precipitation of metalloids out of the solution, as metal sulfide, after they react with the sulfide produced by SRB. Simultaneous power generation of 224.1 mW/m2 at lactate COD/SO42− mass ratio of 2.0 and Cu2+ of 20 mg/L, and high Cu2+ removal efficiency, at >98%, are demonstrated in the anodic chamber of a dual-chamber MFC. Consistent MFC performance at 20 mg/L of Cu2+ for ten successive cycles shows the excellent reproducibility of this system. In addition, total organic content and sulfate removal efficiencies greater than 85% and 70%, respectively, are achieved up to 20 mg/L of Cu2+ in 48 h batches. However, higher metal concentration and very low pH at <4.0 inhibit the SRB MFC system. Microbial community analysis reveals that Desulfovibrio is the most abundant SRB in anode biofilm at the genus level, at 38.1%. The experimental results demonstrate that biological treatment of low-concentration metal-containing wastewater with SRB in MFCs can be an attractive technique for the bioremediation of this type of medium with simultaneous energy generation.

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