Denitrification in an anoxic rotating biological contactor under two carbon/nitrogen ratios

Abstract

The aim of the present work was to compare the performance of an anoxic bench-scale rotating biological contactor (RBC), in terms of the denitrification process, applied to treat synthetic wastewater under two carbon/nitrogen (C/N) molar ratios (1.5 and 3). The average removal efficiency in terms of nitrogen-nitrate was of about 90.4% at a C/N=1.5 lowering to 73.7% at a C/N=3. Considering carbon-acetate removal an overall efficiency of 82.0% and 63.6% was attained at a C/N ratio of 1.5 and 3, respectively. These results evidence that, for the tested conditions, the use of C/N=1.5 is advantageous. The increase of nitrogen-nitrate and carbon-acetate influent concentrations, keeping C/N constant, and the decrease of hydraulic retention time (HRT) had a slight negative effect in terms of substrate removal. The accumulation of nitrite was observed in both experiments, which could probably be lowered with an increase in phosphorus influent concentration. Results show that an anoxic RBC using acetate as a carbon source is a convenient and reliable process for the removal of nitrate from wastewater.