Membrane Biological Reactor Treatment of Recirculated Newsprint Whitewater, 1996 Minimum Effluent Mills Symposium Proceedings

Olivier Tardif & Eric R. Hall

The University of British Columbia

The membrane biological reactor (MBR) is a novel process which integrates biological oxidation with ultrafiltration for treating wastewaters. A lab-scale MBR consisting of a 10 L aerobic reactor, a cross-flow tubular ultrafiltration unit and a progressive cavity pump was operated at temperatures ranging from 40 to 55°C and hydraulic retention times (HRT) of either 2.8, 1.1 or 0.7 days for treating a simulated closed-mill mechanical newsprint whitewater. The mixed-liquor volatile suspended solids varied with the HRT, ranging from 2 to 9 g/L. The MBR was found to be very stable under the varied operating conditions and was particularly effective at removing resin and fatty acids (RFA) (99.6% overall average removal), chemical oxygen demand (COD) (81% average removal), soluble COD (76% average removal) and dissolved organic carbon (74% average removal). The reduction of the whitewater cationic demand was good (57% removal) while the total dissolved solids (TDS) removal was only fair (25% average removal). However, 67% of the volatile fraction of the influent TDS was removed. The high removal efficiencies of RFA may be due to the fact that all suspended solids were retained by the ultrafiltration membrane. RFA have a tendency to be adsorbed by the biosolids, which cannot pass through the ultrafiltration membrane. This and other and other inherent advantages of the MBR suggest much potential for this process to treat recirculated whitewater internally in pulp and paper mills.