Effects of important factors on hydrogen-based autotrophic denitrification in a bioreactor

Effects of biomass, pH, temperature, nitrate loading, C/N on autohydrogenotrophic denitrification were investigated in a lab-scale bioreactor. Nitrate degradation rate increased as biomass increased. When OD600 was 0.173, NO3--N was rapidly reduced down to zero in 3.0 h. The optimum pH for the reactor was 6.0-7.0, high pH values caused accumulated nitrite and decrease of denitrification rate. The average nitrate reduction rate increased from 4.50 to 17.15 mg NO3--N L-1 h(-1) as temperature increased from 20 to 35 degrees C. However, there was a slight decline in denitrification rate at temperature of 40 degrees C. High nitrate loading of 155 mg NO3--N L-1 aroused decrease of denitrification rate. Although C/N value was not directly influence the nitrate reduction rate, it could contribute to increase pH value in order to inhibit the reductase's activity to hinder the denitrification process.