Evaluation of the use of powdered activated carbon in membrane bioreactor for the treatment of bleach pulp mill effluent.

In this paper, the use of powered activated carbon (PAC) in membrane bioreactor (MBR) employed in the treatment of bleach pulp mill effluents was evaluated. The MBR was operated with hydraulic residence time of 9.5 h and PAC concentration of 10 g/L. The addition of PAC to the MBR reduced the average concentration of chemical oxygen demand (COD) in the permeate from 215 mg/L (82% removal efficiency) to 135 mg/L (88% removal efficiency), producing an effluent that can be reused on bleaching stage. Moreover, the addition of PAC to the MBR resulted in the reduction in applied pressure and provided a more stable operation during the monitoring period. This occurrence was probably due to the increase of critical flux after the addition of PAC. The fouling mechanism was investigated and the results showed that controlling the concentration of soluble microbial products (SMP) and extracellular polymeric substance (EPS) by using PAC and keeping the operational flux below critical flux is of major importance for MBR operational sustainability.