BIOCONVERSION OF DIMETHYLFORMAMIDE IN BIOFILTERS

Bioconversion of dimethylformamide (DMF) was studied using two sets of three-stages-in-series biofilters, one packed with inoculated pig man ure and the other with coconut fiber compost-based media. The two medi a were different in carbon/nitrogen (C/N) ratio and specific area. Tes ts were made to compare effects of different C/N ratio and specific ar ea on the performance of the filter and on the variation of physicoche mical properties of the media for treating DMF. DMF concentration in t he influent air stream was in the range of 100 to 4,500 mg/m(3). The g as retention time (GRT) in the first stages of both filters was 19 to 76 sec. The volumetric loading of DMF (L) to the first stages of both filters was 3 to 97 g DMF-N/m(3).h (15.6 to 506 g DMF/m(3).h). Results indicated that DMF was successively hydrolyzed to ammonia and nitrifi ed to nitrite and nitrate or incorporated into microbial cell. Inlet p ortions of the media subjected to high DMF or ammonia loading varied g reatly in pH due to insufficient buffering capacity. The middle portio ns of the media subjected to moderate ammonia loading were suitable fo r nitrification. The coconut fiber compost media with a higher initial C/N ratio and porosity favored the elimination of DMF. For the media, DMF-N removal efficiencies of larger than 90% were obtained with L < 50 g DMF-N/m(3).h and GRT > 23 sec. The pig manure compost media with a lower initial C/N ratio favored the nitrification reaction; its maxi mum capacity was 8.58 g NO3--N/m(3).h.