| There is increasing interest in the treatment and reuse of the sewered portion of the evaporator condensate from kraft pulp mills. In addition to reducing the contaminant load to the existing combined mill effluent system, reducing the raw water requirements and potentially reducing the impact of discharging the treated condensate to the environment, reusing the condensate could also result in significant energy savings if the heat content of the evaporator condensate can be recovered. A high temperature membrane bioreactor (MBR) was selected as the most promising novel technology for the treatment of evaporator condensate for reuse.; A preliminary study indicated that the biological removal of methanol from synthetic evaporator condensate using a high temperature MBR was feasible. The results suggested that the specific methanol utilization coefficient was higher during high temperature biological treatment using an MBR, than in a conventional biological treatment system. However, biological removal of methanol and RSC from synthetic condensate using a high temperature MBR was not feasible.; Further investigations revealed that it was possible to biologically remove methanol from synthetic evaporator condensate using a high temperature MBR, over the entire expected range of temperatures for evaporator condensate. Maximum specific methanol utilization coefficient and maximum specific growth coefficient were observed at an operating temperature of 60°C. Above 60°C, both the specific methanol utilization coefficient and the specific growth coefficient declined sharply.; The operating temperature was also observed to have a significant effect on the observed microbial growth yield in the MBR. At increasing operating temperatures, a larger fraction of the methanol consumed was converted to energy, reducing the observed growth yield.; The specific methanol utilization coefficient measured during the treatment of real evaporator condensate was lower than that observed when treating synthetic evaporator condensate. The reduction was attributed to a shift in the composition of the microbial community present in the MBR.; Based on assumed removal efficiencies of 99, 90 and 99% for methanol, TOC and RSC (as hydrogen sulphide and methyl mercaptan), respectively, as well as the characteristics of the evaporator condensate from a local kraft pulp mill, a conceptual design for a full-scale, high temperature MBR to treat an evaporator condensate for reuse was developed. (Abstract shortened by UMI.)... |
