Iron-carbon micro-electrolysis coupled to heterotrophic nitrification aerobic denitrification treating low carbon/nitrogen mariculture wastewater.

Considering the unsatisfied nitrogen (N) and phosphorus (P) treatment performance of mariculture wastewater caused by low carbon/nitrogen (C/N), a novel iron-carbon (Fe-C) micro-electrolysis coupled to heterotrophic nitrification aerobic denitrification (HNAD) process was proposed to enhance the N and P elimination. Results revealed that total nitrogen (TN) removal and total phosphorus (TP) removal efficiencies in Fe-C filter with HNAD (R-Fe) increased by 76.1% and 113.3% compared to filter packed with ceramsite (R-C). Fe-C micro-electrolysis reaction led to the decrease of microbial diversity and richness, the enrichment of heterotrophic nitrification aerobic denitrification bacteria (HNADB) and HNAD genes (napA and napB) by 7.3 times and 56.3%. Besides, a synergistic effect existed that Fe-C substances not only further accumulated main functional genes associated with the transformation of N, carbon (C) and iron (Fe), but also indirectly enhanced electron transport system activity and ATP generation, thus resulting in elevating TN removal.