Fouling mitigation in membrane bioreactors via strategic dopamine-nanoparticle incorporation: Tailored modifier type...

The aim of the present study is to prepare membranes with minimal fouling in membrane bioreactors (MBR) through using the most appropriate type (antibacterial or hydrophilic) and the best location (top layer or sublayer) of the modifier in the membrane. For this purpose, dopamine and ZnTe, ZnSe, and CdSe nanoparticles were added to the top layer of TMBR membranes and the sublayer of SMBR membranes. Structural analyses revealed that TMBR membranes have the lowest MWCO and the highest antibacterial properties, while SMBR membranes have the highest porosity and the lowest roughness. Thus, the results of filtration indicated that the FRR of the SMBR_Nanoparticle^DA membrane is 95.74%, while for the TMBR_Nanoparticle^DA membrane it is 65%. Therefore, the proper performance of the SMBR_Nanoparticle^DA membranes revealed that in response to the challenge of the modifier type, the simultaneous presence of antibacterial and hydrophilic materials; and in response to the challenge of the modifier location, the modification of the sublayer are proposed to reduce fouling in MBR. Specifically, the SMBR_ZnTe^DA membrane was introduced as the membrane with superior performance after 16 h of filtration in the MBR, with the highest water flux (50.39 LMH), highest COD removal rate (99.1%), and lowest flux decline. In addition, under the current short term testing conditions (<24 h), no detectable release of Cd, Zn, Te, or Se was observed, and phytotoxicity tests indicated no inhibition of plant growth; therefore, these findings should be considered as preliminary evidence of environmental stability rather than confirmation of long term safety under industrial scale operation. Fouling modeling indicated reduced pore blocking and a shift toward more reversible cake layer fouling. Also, the preliminary benchmarking of these membranes against commercial samples from TORAY Industries, Inc. demonstrated the superiority of these membranes with higher permeability (85-206 vs. 23-157 LMH/bar) and lower price (3.89-45.92 vs. 65-80 $/m²). These findings provide new opportunities for designing efficient membranes in industrial applications.