Control of Partial Nitritation of Centrate in a Sequencing Batch Reactor

The research identified suitable conditions for long-term inhibition of nitrite oxidizer bacteria (NOB) in a sequencing batch reactor for the treatment of centrate by over-nitrite pathways. NOB were inhibited by free ammonia concentrations greater than 20 mgNH3-N/L combined with a DO concentration less than 0.3 mgO2/L and a temperature of 30°C. The experiments were performed in a laboratory-scale 2.5-L reactor fed with synthetic and real centrate (800–1500 mgNH4 +-N/L). The influence of the influent alkalinity to ammonium ratio (AAR) on the effluent nitrite to ammonium ratio (NAR) was also investigated. The control of the effluent NAR was possible by adjusting the influent AAR when NOB inhibition was maintained and when total alkalinity depletion took place before the end of the cycle. The maximum nitritation rate of 860 mgNO2- -N oxidized/L/day was obtained when influent NH4+-N concentration was 800 mgNH4+-N/L and HRT was 1.7 days.