An ultrafiltration system and a membrane biological reactor were operated in parallel to compare the removal efficiencies achieved for total and dissolved solids and chemical oxygen demand, from a simulated, low water-use, mechanical newsprint mill whitewater at 55°C. The ultrafiltration system was operated at water recovery fractions (Y) of 0.9, 0.95 and 0.983, while the membrane biological system was operated at water recovery fractions of 0.95, 0.975 and 0.983. In all cases, the membrane biological reactor exhibited higher removal efficiencies than the ultrafiltration system alone. The MBR demonstrated 48–58% removal of total COD, 35–45% removal of dissolved COD, 25–35% removal of total solids and 20–30% removal of dissolved solids. Maximum flux through the membranes was highest at lower water recovery fractions for both the ultrafiltration system and the membrane biological reactor. Fouling time, based on the time required for a 20% loss of flux, increased with increasing water recovery for the membrane biological reactor and decreased with water recovery fraction for the ultrafiltration system.

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