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

Abstract Paper machines can be made environmentally harmless by enclosing their water 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 machine is analysed in this paper. The concentration dynamics of the dissolved organic compound (DOC) and the reactor volume required in aerobic treatment are estimated. The required volume depends on the treatment; in advanced treatment it is 1 10 of the volume required in conventional treatment. The reactor can be made more productive by using higher biomass concentrations. The high biomass concentration can be consumed and maintained in a reactor by cross-flow filtration, used for separation of the sludge from treated water. A new model is proposed for the description of the concentration dynamics in the paper machine and membrane bioreactor. The model is applied for the prediction of DOC changes in whitewater, bulkwater, and treated water. Closed-cycle papermaking processes are analysed, based on a conventional reactor and a membrane reactor.