BACKGROUND Reverse osmosis (RO) is becoming the predominant technology for the future of desalinated of seawater. Nonetheless, operational challenges such as membrane biofouling in RO desalination plants result in membrane deterioration and high energy costs. In this regard, pre-treatment technologies, such as microfiltration (MF) membranes, are proven to reduce the impact of membrane biofouling in RO systems. Hence, surface modifications of commercial cellulose MF membranes with graphene oxide nanosheets (GONSs) at different concentrations were carried out in this research study. The new membranes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy amongst other methods of analysis. A continuous cross-flow MF system was used to investigate the performance of the new cellulose/GONS membranes with regards to total bacteria count (TBC) removal, water flux, and biofouling resistance. RESULTS TBC removal efficiency of 93.6 +/- 2.4% and 27.4 +/- 12.5% was achieved using the new cellulose/GONS membranes and control pristine cellulose membranes, respectively. This higher removal efficiency was achieved at a water flux of 334.7 +/- 10.4 L/(m(2) h). Furthermore, a dramatic 55% increase in the transmembrane pressure (TMP) of the pristine cellulose membrane was observed after 24 h operation compared to only a 6% increase in the newly fabricated cellulose/GONS membranes, reflecting their strong anti-fouling properties. CONCLUSION Surface modification of MF membranes with anti-fouling nanomaterials such as GONS has the potential to be implemented in the pretreatment of seawater to improve the RO performance and lower the energy consumption. (c) 2020 Society of Chemical Industry