Facilitation of partial nitrification in anaerobic digestion effluent through continuous supply of sulfide with oxygen limitation

Abstract

Reactor schematic showing low dissolved oxygen and continuous sulfide supply suppressing nitrite-oxidizing bacteria activity and promoting partial nitrification. Appropriate treatment of nitrogen-containing wastewater is essential for protecting water resources and aquatic ecosystems. Although low-environmental-impact nitrogen removal systems have been actively developed, partial nitrification, which serves as a core enabling technology, continues to face challenges related to treatment efficiency and process stability. In this study, partial nitrification of anaerobic digestion effluent was promoted under the combined conditions of continuous S2− supply and low dissolved oxygen (DO) concentrations. As a result, rapid removal of more than 99% of NH4+ and partial nitrification efficiencies exceeding 80% were achieved under conditions involving continuous S2− supply at 32–128 mg-S L−1 d−1 and a low-DO concentration of 0.3 mg L−1. Partial nitrification did not occur when either of these conditions was absent, suggesting that the simultaneous application of S2− loading and oxygen limitation facilitated stable partial nitrification. The observed stable partial nitrification performance using real wastewater across a wide range of S2− loading rates demonstrates the potential applicability of the proposed operational strategy and provides a foundation for the further development of nitrogen removal technologies.