Characteristics of biological denitrification with methane-utilizing mixed culture in the chemostat

Abstract

The methane-utilizing mixed culture isolated from activated sludge by selective enrichment at $45\,^\circ\!C$ and pH 7.1 was used for biological denitrifrication of wastewater. It was found that the rate of denitrification (65 ppm/hr) could be enhanced by adding a methanol concentration of 0.5 ppm, but inhibited by excessive methanol concentration. But the denitrification rates obtained for oxygen and methane-limiting condition were 61 and 35 (ppm/hr), respectively. The denitrification rate mainly depended on dissolved oxygen concentration and carbon dioxide was necessary to initiate the growth of methane-utilizing mixed culture, but was independent of the denitrification performance. The values of saturation constants and mass transfer coefficients on both oxygen and methane were determined as $1.563 \times 10^{-6}\; (MO_2/1),\; 4.33 \times 10^{-6}\; (MCH_4/1),\; 109.4hr^{-1}$, and $89.67hr^{-1}$, respectively. The total growth yields on both oxygen and methane were higher for the oxygenlimited than for the methane-limited conditions and increased slightly with the increase of dilution rate.