Optimization of wastewater partial nitrification in Sequencing Batch Biofilm Reactor (SBBR) at fixed do level

A fixed-film bed reactor was studied to optimize partial nitrification in wastewater treatment. Nitrogen removal improvement was based on nitritation/denitritaion process in sequencing batch biofilm reactor (SBBR). Carbon source was added to the reactor at fixed dissolved oxygen (DO) concentration to modify simultaneous nitrification/denitrification (SND). In period 1, DO was declined from 1 to 0.5 mg/l during the reactor cycle. In period 2 and 3, DO was fixed at 0.5 mg/l and changing nitrite to nitrogen gas was achieved, directly, while nitrogen loading rate (NLR) and organic loading rate (OLR) were 0.18 kgN/m3d and 1.84 kgCOD/m3d, respectively. In period 2, the increment of nitrite accumulation rate (NAR) was observed but SND efficiency was reduced. C/N ratio was increased from 10 to 12.5 in period 3 to reach SND efficiency, at least, equal to the result of period 1. In period 3 NAR was 71.4 % and SND efficiency was 96%. Partial nitrification in SBBR at fixed DO level of 0.5 mg/l resulted in TN removal efficiency of 97.2 %. Effluent nitrite, nitrate and ammonium were 1.5, 0.6 and 0.7 mg/l, respectively, in period 3. In long term study of selected operation, SND efficiency was higher than 90 %