Removal of azo dye acid orange 7 using aerobic membrane bioreactor

A laboratory scale aerobic membrane bioreactor (MBR) using a submerged microfiltration (MF); hollow-fiber membrane was used for treating wastewater polluted with azo dye acid orange 7 (AO7). Initial dye concentrations studied were from 50 to 400 mg/l with a COD ranging from 95 to 550 mg O2/l and hydraulic retention times (HRT) 4, 6, 8 and 24 h. Results showed that the biological process was responsible for almost 60–80% of COD removal and almost all the removal of AO7 color. Membrane microfiltration merely balanced the unstable biological treatment of COD and demonstrated almost no contribution to AO7 color removal. Trans-membrane pressure (TMP) increased with time, and with the increase of dye concentration reaching a maximum of 4.175 psi. Scanning electron microscope (SEM) images of the membrane’s filament were taken and compared with a SEM image of a virgin membrane; clear deformation in membrane’s pore structure could be noticed as well as scale formation on the outer surface of filaments, foulants were determined using the energy dispersive X-ray analysis (EDX).