DMF Decomposition and Nitrogen Removal Performance by a Mesh-Filtration Bioreactor under Acidic Conditions

Abstract

N,N-Dimethylformamide (DMF) is a water-miscible polar solvent that is used in a wide variety of chemical industries. In Japan, 0.668 × 106 kg·y-1 of DMF is discharged to the sewerage system and is ranked highest in the PRTR (2006). In this work, a bench-scale mesh-filtration bioreactor was employed for aerobic biological treatment of DMF. Synthetic wastewater containing 1000 mg·L-1 of DMF was fed into the reactor at 5 or 2.5 days of hydraulic retention time (HRT) and at a volumetric loading rate of 0.125 or 0.25 kg-DMF m-3 d-1; the pH of the reaction mixture was not controlled. Performances in removal of dissolved organic carbon (DOC) and nitrogen were examined. Although the pH of the reaction mixture decreased to around 3, DOC removal remained at more than 98%, nitrification was complete, and about 45% of total nitrogen was removed. The rates of DMF decomposition, nitrification, and denitrification were evaluated by batch experiments, with the result that for these three biological reactions the sludge in the reactor showed significant activities even at pH 3. These results suggest that the sludge contained acidophilic nitrifying bacteria.