Pilot-scale Study on Producing NO₂^- for Anammox With Municipal Wastewater

Anammox is regarded as the most economical and efficient wastewater nitrogen removal process due to its outstanding advantages of saving aeration energy consumption and organic carbon source. However, it has not yet been applied in the engineering application of the mainstream municipal wastewater treatment, and its bottleneck is the stable acquisition of nitrite (NO₂^-). Partial denitrification refers to the process of reducing nitrate to nitrite(NO₃^-→NO₂^-), which is a new approach to provide NO₂^- for anammox with the advantages of stable nitrite accumulation and high-rates production. Therefore, the feasibility of partial denitrification to provide NO₂^- for anammox has been investigated in a pilot-scale experiment. Results show that partial denitrification can be achieved with excess sludge and municipal wastewater by controlling the influent ratio and HRT when fed with the municipal wastewater and its nitrifying effluent. In the long-term operation, the nitrite production increases and the NO₃^- to NO₂^- translation ratio (NTR) is higher than 75.0%. The partial denitrification can be maintained stably with the condition of low temperature (13.7-16.2℃) and average NTR is 62.3%.This study provides a method and idea to solve the problem of stable acquisition of NO₂^- in the process of municipal wastewater nitrogen removal by anammox, which is of great significance and valuable for the application of partial denitrification coupled anammox in municipal wastewater treatment.