Simultaneous nitrification-denitrification in a sequencing batch reactor equipped with fixed Kaldnes carriers

The main aim of this study was to evaluate the performance of a modified sequencing batch reactor (MSBR) using fixed Kaldnes carriers fed with acclimated sludge for ammonium removal via simultaneous nitrification-denitrification (SND) in synthetic wastewater. The results exhibited a SND of 82.3% within a 450-minute cycle time which was higher than that of a SBR without carrier (69.83%). Nitrite accumulation rate (NAR) increased from 16.94% to 32.83% until 120 minutes of cycle time, and then, decreased to 1.17% by 450 minutes. The biomass concentration in the bio-film (674 ± 6 mg/l) was lower than suspended biomass (1984 ± 12 mg/l). However, the specific oxygen uptake rate (SOUR) of the bio-film (5.24 ± 0.28 mg O2/mg MLVSS.d) was greater than suspended biomass (1.89 ± 0.12 mg O2/mg VSS.d), indicating the higher bioactivity of the bio-film than that of suspended biomass. Up to 3% salinity had no significant effect on MSBR performance for both chemical oxygen demand (COD) and ammonium removal. These results illustrated the high efficiency of the MSBR in the treatment of wastewater containing high salinity as well as the removal of nitrogen compounds via SND.