Nitrate removal in a combined bioelectrochemical and sulfur autotrophic denitrification system under high nitrate concentration: effects of pH.

A combined bioelectrochemical and sulfur autotrophic denitrification (CBSAD) system was established to treat high concentration nitrate under different pH conditions in this study. The microbial communities and structures were evaluated to deeply reveal the nitrate removal mechanisms in this combined system. When initial pH was adjusted to 6.5, the CBSAD system obtained 66.45% denitrification efficiency. The combined system achieved highest nitrate removal efficiency of 96.84% at pH 7.5. However, nitrate removal efficiency decreased to 87.05% when initial pH increased to 8.5. Microbial analyses demonstrated that pH value slightly influenced the bacterial abundances and bacterial species in this CBSAD system under high nitrate concentration condition. Proteobacteria was the most dominant phylum in this system, which accounted for more than 90% of the total phyla. Epsilonproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the most important classes for denitrification process. Genus Sulfurimonas was primarily responsible for high nitrate removal in this CBSAD system.