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 manure and the other with coconut fiber compost-based media. The two media were different in carbon/nitrogen (C/N) ratio and specific area. Tests were made to compare effects of different C/N ratio and specific area on the performance of the filter and on the variation of physicochemical properties of the media for treating DMF. DMF concentration in the influent air stream was in the range of 100 to 4,500 mg/m(3). The gas 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 nitrified to nitrite and nitrate or incorporated into microbial cell. Inlet portions of the media subjected to high DMF or ammonia loading varied greatly in pH due to insufficient buffering capacity. The middle portions of the media subjected to moderate ammonia loading were suitable for 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 maximum capacity was 8.58 g NO3--N/m(3).h.