## 4 Conclusions  
Novel PES membranes incorporated with the synthesized GO with a high content of oxygen containing groups were fabricated using the phase inversion method, and their properties and performance were compared against neat PES or commercial UF membranes. The data obtained showed that the prepared membranes possessed strong hydrophilicity and negative surface charge, with an increase in porosity and pore size. Importantly, PES/GO membranes exhibited remarkable improvement in water flux with over 3-fold increases for M7 and M8 samples compared to the neat PES membrane.  
The PES/GO membranes indicated better resistance to organic fouling compared to the neat PES membranes, as modelled by filtration of BSA solutions, with a marked decrease in irreversible fouling seen across all PES/GO membranes. The PES/GO membranes exhibited superior inhibition of bacterial growth on the membrane surface for both Gram-positive and Gram-negative bacterial species. The composite membranes displayed more robust and stronger biofouling resistance as shown by the increase in FRR values and the higher normalized flux after filtration with both TSE and bacterial suspension. The enhanced performance can be attributed to the increase in negative surface charge, along with the increased hydrophilicity of the prepared PES/GO membranes.  
Figure 16: Photo of images of agar plates containing cellulose discs after filtration of TSE (treated sewage effluent) Feed and TSE permeate of M8 PES/GO membrane and commercial TriSep membrane.  
Finally, the prepared PES/GO membranes were successful in abolishing the presence of any bacterial forms in the permeate that was collected from TSE filtration using the PES/GO membranes. Overall, these findings point to the synergistic action of both AG and GO additives in improving the performance and biofouling resistance of UF membranes through their anti-adhesive properties as a result of their increased negative surface charge and hydrophilicity.  
The following are available online at [[http://www.mdpi.com/2076-3417/9/3/513/s1](http://www.mdpi.com/2076-3417/9/3/513/s1)]([http://www.mdpi.com/2076-3417/9/3/513/s1](http://www.mdpi.com/2076-3417/9/3/513/s1)); Figure S1. TGA and DTGA thermograms for M1 neat PES (a). MB PES/GO (b) and TGA thermograms overlay for selected PES/GO and neat membranes. Figure S2. DSC curve overlay for selected PES/GO and neat membranes. Figure S3. Viscosity as a function of shear rate plotted for selected casting solutions for neat PES and selected PES/GO membranes. Figure S4. Graph showing flux readings for filtration of real TSE for selected fabricated membranes and the UF commercial membrane (a) and the normalized flux for each of the three membranes calculated as the final reading at the end of the filtration over the initial reading at the beginning of the filtration test. Figure S5. Membrane fluxes before and during incubation with real TSE at different time points.  
Conceptualization, V.K. and M.A.A.; Data curation, A.N., R.A.G. and S.S.; Formal analysis, A.N.; Methodology, A.N., R.A.G. and S.S.; Supervision, V.K. and M.A.A.; Writing--original draft, A.N.; Writing--review & editing, V.K.  
This research received no external funding.  
The authors would like to acknowledge the kind support given by Qatar Environment and Energy Institute (QEERI), in particular the following members of the Core laboratories: [PERSON], [PERSON], [PERSON] and [PERSON]. The publication of this article was funded by the Qatar National Library.  
The authors declare no conflict of interest.