Denitrification performance and mechanism of sequencing batch reactor with a novel iron-polyurethane foam composite carrier

Simultaneous nitrification and denitrification (SND) is a promising denitrification method. But so far, there have been few reports on the SND and denitrification mechanism of the coupled system with sponge iron (SI). In this paper, the denitrification performance of the mono-sludge system (only activated sludge), mono-carrier system (activated sludge + polyurethane foam) and coupled system (activated sludge + polyurethane foam and SI) was investigated. The study found that compared with the mono-sludge system, the TN removal efficiencies of the mono-carrier system and coupled system increased by 24% and 29.2%, respectively. The change of dissolved oxygen in the carrier of the coupled system showed that the time of forming anoxic and anaerobic micro-environment in one cycle decreased continuously until it reached zero. The nitrate-dependent ferric oxidizing bacteria Acidovorax and Aquabacterium appeared in the coupled system. In addition, it was found that the intervention of SI significantly increased the activity of membrane nitrate reductase (NAR). This study provides practical and useful technology for the treatment of domestic sewage.