Effects of Kraft Evaporator Condensate Matrix on Methanol Removal in a High Temperature Membrane Bioreactor

Abstract

This study investigated the removal of methanol from kraft pulp mill condensate using a high temperature membrane bioreactor (MBR). The effects of the complex matrix associated with real condensate, on methanol metabolism and removal kinetics, were examined. The measured specific methanol utilization rate observed during the treatment of real condensate was lower than that previously observed with synthetic condensate. The difference could not be attributed to inhibitory effects of the real condensate matrix. Instead, the reduction was attributed to a shift in the composition of the microbial community present in the MBR. The shift resulted from competition between non-methylotrophic and methylotrophic microorganisms for the available methanol. The non-methylotrophic microorganisms exhibited a lower specific methanol utilization rate (0.45/day) than the methylotrophic microorganisms (0.81/day), resulting in a lower overall specific methanol utilization rate of 0.55/day. Nonetheless, the specific methanol utilization rate observed in the present study at 60 °C was still more than 20 % higher than previously reported values from other studies of biological treatment of condensate at much lower temperatures.