The effects, mechanisms, and applications of sulfide as both an inhibitor and electron donor in novel biological nitrogen removal process.

The impacts of sulfide on biological nitrogen removal have been investigated repeatedly, but the impacts in terms of the removal technologies have not been systematically organized and discussed yet. This review recapped the dual character of sulfide in novel biological nitrogen removal and proposed the coupling mechanisms of nitrogen removal and sulfide interaction. The dual character of sulfide was basically divided into the advantage as electron donors and the disadvantage as cytotoxic agent to wide bacteria. The positive character of sulfide has been utilized for improving the performances of denitrification and anaerobic ammonium oxidation in laboratory and polit scales. Intriguingly, the sulfide cytotoxicity was feasibly turned into the profit which was to trigger the partial nitrification by selectively inhibiting ammonia oxidizing bacteria and nitrite oxidizing bacteria. Thus, this productive conversion dramatically promoted the importance of sulfide in sewage treatment. In order to maximize the favorable aspect of sulfide utilization, it was crucial to manage the sulfide concentration for fear of the side reactions with untargeted substances. Furthermore, S/N ratio in sewage may be the keystone that decides if sulfide benefits biological nitrogen removal. In sum, our work can facilitate the dialectical development of effective strategies for sulfide utilization in biological nitrogen removal.