Biological denitrification with ethanol in a membrane bioreactor

Abstract

Some fundamental data on biological denitrification with ethanol are reported. The optimal pH was found to be about 8. At that pH, the carbon requirements were estimated to be 1.4–1.5 g C.g^‐1N. Within the temperature range of 10–40°C, the dependence of the specific denitrification activity on temperature and pH was expressed mathematically, and showed that a temperature change of 10°C affected the specific activity by a factor 1.9. The activation energy of the denitrification reaction was 38.3 kJ.mol^‐1. The specific denitrification activity had an average value of 0.16 kg N‐NO₃ ^‐.kg^‐1MLSS.d^‐1 at the optimal pH and 20°C. A pilot plant study of a membrane bioreactor showed that the shear stress on the ultrafiltration membranes did not affect the specific denitrification activity of the sludge. The suspended solids concentration in the bioreactor had little influence on the permeation flux through the membranes. An increase in the nitrate volumetric load by a factor of 3.3 did not impair the effluent quality. However, organic carbon remained.