Abstract
Performance of a denitrification process using polyvinyl alcohol (PVA) as a organic carbon source was investigated by anoxic and aerobic RBC systems at 25°C and 30°C. PVA was well degraded under aerobic condition, but not under anoxic condition. In the experiment using phenol as a co-organic substrate for PVA degradation, the efficiency of denitrification increased from 38% to 84% as the TOC loading rate increased from 1g/m2.d to 4.2g/m2.d, while PVA-removal and nitrification efficiencies were above 90% throughout all the experiments. In the experiment using PVA as the sole organic carbon source, the efficiencies of PVA removal and nitrification increased with increasing HRT, and reached levels of 95%, and 99%, respectively at an HRT of 10 hours, whereas the efficiency of denitrification reached its maximum value of 78% at an HRT of 8 hours. These results indicated that PVA could be used as a sole electron donor for denitrification and that the optimum HRT for the simultaneous removal of PVA and nitrogen was between 8 and 10 hours. The PVA-decomposing bacteria, nitrifiers, and denitrifiers co-existed in the biofilm, but the populations of PVA-decomposing bacteria and denitrifiers in the surface layer were 1 to 2 orders of magnitude higher than those in middle and bottom layers indicating that the surface layer had a higher denitrifying activity.
