Forming microbial anodes with acetate addition decreases their capability to treat raw paper mill effluent

Microbial anodes were formed under polarization at −0.3 V/SCE on graphite plates in effluents from a pulp and paper mill. The bioanodes formed with the addition of acetate led to the highest current densities (up to 6 A/m2) but were then unable to oxidize the raw effluent efficiently (0.5 A/m2). In contrast, the bioanodes formed without acetate addition were fully able to oxidize the organic matter contained in the effluent, giving up to 4.5 A/m2 in continuous mode. Bacterial communities showed less bacterial diversity for the acetate-fed bioanodes compared to those formed in raw effluents. Deltaproteobacteria were the most abundant taxonomic group, with a high diversity for bioanodes formed without acetate addition but with almost 100% Desulfuromonas for the acetate-fed bioanodes. The addition of acetate to form the microbial anodes induced microbial selection, which was detrimental to the treatment of the raw effluent.