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The treatment of wastewater is an essential option to solve the water deficiency issue and can help inhibit the harmful effects of algal blooms and eutrophication in the urban water system. Municipal wastewater presents a high potential for water reuse as it is available in large quantity. Treatment with membrane technology presents advantages over other treatment methods due to the low treatment cost, unit operations reduction, and constant operation. The membrane bioreactor (MBR) process is practically used as the appropriate technique to treat municipal wastewater; nevertheless, it requires an advanced treatment of the effluent such as reverse osmosis (RO), as some of the contaminants are not removed. However, treatment of wastewater using RO results in membrane fouling which causes degradation and poor performance. This study aimed to minimise fouling of an aromatic polyamide thin film composite (TFC) RO membrane through the graft polymerisation of N,N'-dimethyl aminoethyl methacrylate (DMAEMA) by redox initiation with sodium metabisulfite and potassium persulfate. Biofouling tests using a bench-scale RO system with a secondary membrane bioreactor (MBR) effluent were used to assess the impact of surface modification. Significant changes in chemical and morphological structures were observed through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis and scanning electron microscopy (SEM). The salt rejection decreased as DMAEMA concentration increased. Furthermore, the flux recovery ratio increased from 68.61 to 83.57% and the flux decline ratio decreased from 38.21 to 25.54%. The modified membrane’s sterilisation ratios were far higher than the unmodified membrane, thus showing better anti-biofouling properties when using Escherichia coli (E. coli) bacteria as model biofoulant. The DMAEMA modified membrane with the highest sterilisation ratio (76.8%) showed better anti-microbial properties against microorganism tested, obstruct growth and multiplication. This was further confirmed with the pure water flux test, where the unmodified and DMAEMA modified membranes declined by 46.0 and 37.3%, respectively.

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously.

Membrane surface modification is a favourable method to handle fouling during wastewater treatment processes. In this study, grafting of polyvinyl alcohol (PVA) through cross-link with Glutaraldehyde was applied to a thin film composite reverse osmosis membrane to enhance the resistance to flux decline. The analytical analyses attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy were performed to evaluate the impact of surface modification. Biofouling using Escherichia coli (E. coli) bacterial solution and fouling tests using a bench scale reverse osmosis system with a simulated secondary effluent from a membrane bioreactor were used to assess the impact of the surface modification initiated on antifouling properties of the membrane. It was shown that the morphological structure and the chemical properties of the membrane were altered, whereas the pure water flux slightly decreased after modification. Although a slight decrease of salt rejection was observed, the membrane resistance to fouling improved and the biofouling model used revealed the anti-biofouling capacity of the membrane. The flux decline and flux recovery ratios improved with an increase in PVA concentration. The sterilization ratio increased from 33.8 to 36.8% and the pure water flux decline decreased from 46.04 to 25.94% after modification.