AN EXPERIMENTAL-STUDY ON AEROBIC DENITRIFICATION WITH POLYVINYL-ALCOHOL AS A CARBON SOURCE IN BIOFILMS

Aerobic denitrification occuring in the biofilms attached to a partial ly submerged RBC, was investigated, Denitrification using polyvinyl al cohol (PVA) as a organic carbon source, was well proceeded by aerobic RBC systems at 25 degrees C. At an influent C/N ratio of around 1.2, t he maximum net-denitrification efficiency was about 78% at a TOC loadi ng of 2g/m(2)/d. In a chemostat experiment, aerobic denitrification wa s well proceeded under the dissolved oxygen concentration of 3 to 6 mg /L. The PVA-decomposing bacteria, nitrifiers, and denitrifiers co-exis ted in the biofilm, but the population of PVA-decomposing bacteria and denitrifiers in the surface layer was 1 to 2 orders of magnitude high er than those in the middle and bottom layers. It may indicate that th e surface layer had a higher denitrifying activity, The nitrogen mass balance obtained using the experimental data clearly indicates a reaso ning for aerobic denitrification.