Milk processing wastewater treatment in an MBR: A comparative study on the use of two synthetic anti-fouling PES-UF membranes

Recently, membrane bioreactors (MBRs) have received extensive attention as an innovative wastewater treatment technology. Nevertheless, membrane fouling as a serious barrier has avoided the widespread application of the MBAs. In the present study, two polyethersulfone (PES) antifouling ultrafiltration membranes entrapped by 0.1 wt. % of NH2 functionalized multiwalled carbon nanotubes (NH2-MWCNTs) and of O-carboxymethyl chitosan modified Fe3O4 (OCMCS-Fe3O4) nanoparticles were employed in an MBR. The effect of both modified membranes on the fouling characteristics and biological performance of bioreactor was investigated. Experimental design was conducted using central composite design (CCD) of response surface methodology (RSM). The process performance of the bioreactor treating milk processing wastewater (MPW) was analyzed at different hydraulic retention times (HRTs) and mixed liquor suspended solids (MLSS). Five dependent process and operating parameters; TKN, NO3-, TN, TP removal efficiency and flux, were measured as response for both membranes. Independent increment of the variables gave rise to an increase in the process parameters. While, simultaneous increase in the variables led to the increase in flux. The Fe3O4- OCMCS embedded membrane indicated slightly higher flux than that of NH2 -MWCNTs modified membrane. The optimum region was enclosed by high MLSS (>= 12,000 mg/l) at any HRT studied.