Analysis of nitrite accumulation with different recycle water properties in municipal wastewater treatment plant

This research analyzed the effect of nitritation on the characteristics of recycle water, which is the effluent of sludge treatment process from a municipal wastewater treatment plant (MWTP). The laboratory-scale reactors were operated in various operation conditions for about 200 d. Operation results of laboratory-scale reactors showed that stable nitritation was induced using recycle water, and over 80% of nitrite conversion efficiency was obtained. The nitrite conversion rate was 0.37 kg NO_2– –N/m³ d for the anaerobic digester supernatant, 0.32 kg NO_2– –N/m³ d for the sludge decanter effluent, and then 0.17 kg NO_2– –N/m³ d for the sludge thickener supernatant in order. These results showed that nitrite conversion rate was effected by ammonium nitrogen concentration and chemical oxygen demand fraction. The limit of solid retention time (SRT) was analyzed based on track study. Also, improvement of nitrite conversion rate was detected adjusting SRT from reactor operation result. The result of this research can be used as an important data for treatment of recycle water in MWTP, using nitritation.