Application of a GAC-coated hollow fiber module to couple enzymatic degradation of dye on membrane to whole cell biodegradation within a membrane bioreactor

Additional granular activated carbon (GAC) layers on the membrane module within a whole cell fungal membrane bioreactor (MBR) set up to treat dye wastewater was effective in minimizing enzyme washout and in improvement of decoloration (degradation of the dye). Supporting batch tests and continuous monitoring of the quality of bioreactor-supernatant and membrane-permeate revealed that biodegradation was effected by both the suspended culture and the dynamically immobilized enzyme on the GAC-coated membrane. In a control MBR, the efficiency of dye removal was variable; in contrast, 85% to near complete removal of dye was achieved using the MBRs equipped with a membrane with additional GAC layers. A combined critical effect on dye removal efficiency of hydraulic retention time (HRT), instantaneous membrane flux and the amount of GAC coating was observed. Plausible explanations are presented for novel observations such as the achievement of better removal efficiency in the case of the longer HRT, even though the dye loading under different HRTs was kept the same by varying its concentration in the synthetic wastewater. The effect of membrane fouling on removal efficiency is highlighted and approaches to achieve stable long-term performance are discussed.

► By preventing enzyme washout, a GAC-coated membrane improved dye removal by a fungal MBR.
► Both suspended culture and the immobilized enzyme on the membrane degraded dye.
► A combined effect of HRT, membrane flux and amount of GAC on removal was observed.
► Under the same dye loading, longer HRT yielded better removal efficiency.
► Membrane fouling caused deterioration of the removal efficiency.