Removal of dissolved organic compounds from paper machine whitewater by membrane bioreactors: a comparative analysis

Paper machines can be made environmentally harmless by enclosing their wate r systems. However, consumption of dissolved solids then takes place in the whitewater. A purification system can be used to prevent this consumption. The integration of biological treatment into the water system of a paper m achine is analysed in this paper. The concentration dynamics of the dissolv ed organic compound (DOC) and the reactor volume required in aerobic treatm ent are estimated. The required volume depends on the treatment; in advance d treatment it is 1/10 of the volume required in aerobic treatment. The rea ctor can be made more productive by using higher biomass concentrations. Th e high biomass concentration can be consumed and maintained in a reactor by cross-flow filtration, used for separation of the sludge from treated wate r. A new model is proposed for the description of the concentration dynamic s in the paper machine and membrane bioreactor. The model is applied for th e prediction of DOC changes in whitewater, bulkwater, and treated water. Cl osed-cycle papermaking processes are analysed, based on a conventional reac tor and a membrane reactor. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.