Effect of electric current intensity on performance of polycaprolactone/FeS-based mixotrophic biofilm-electrode reactor.

In this study, a bioelectrochemical system consisting of pyrite-based autotrophic denitrification (PAD) and heterotrophic denitrification (HD) was established to polish nitrate wastewater. The loading of electric current (EC) could stimulate the dissolution of pyrite. Appropriate EC (I ≤ 30 mA) was conducive to nitrate removal, too high EC (I = 40 mA) would inhibit nitrate removal and lead to an obvious accumulation of NO-N and NH-N. Microbial analysis revealed that the increase of EC could inhibit the diversity of heterotrophic microbes, but appropriate EC (I = 10 mA) could increase the diversity of autotrophic microbes. The EC loading was conducive to the enrichment of iron autotrophic denitrifiers (Ferritrophicum), pyrite-oxidizing bacteria (Thiobacillus, Sulfurimonas), and sulfur autotrophic denitrifiers (Dechloromonas, Thiobacillus, and Arenimonas). The EC loading enlarged the contribution of PAD, making PAD a dominant pathway in denitrification.