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Reverse osmosis (RO) is affected by multiple types of fouling such as biofouling, scaling, and organic fouling. Therefore, a multi-functional membrane capable of reducing more than one type of fouling is a need of the hour. The polyacrylic acid and graphene oxide (PAA-GO) nanocomposite functionalization of the RO membrane has shown its effectiveness against both mineral scaling and biofouling. In this research, the polyacrylic acid concentration and irradiation times were optimized for the PAA-GO-coated RO membrane using the response surface methodology (RSM) approach. The effect of these parameters on pure water permeability and salt rejection was investigated. The models were developed through the design of the experiment (DoE), which were further validated through the analysis of variance (ANOVA). The optimum conditions were found to be: 11.41 mg·L−1 (acrylic acid concentration) and 28.08 min (UV activation times) with the predicted results of 2.12 LMH·bar−1 and 98.5% NaCl rejection. The optimized membrane was prepared as per the model conditions, which showed an increase in both pure water permeability and salt rejection as compared to the control. The improvement in membrane surface smoothness and hydrophilicity for the optimized membrane also helped to inhibit mineral scaling by 98%. [ABSTRACT FROM AUTHOR]

In this research, the interactions of seawater microorganisms with scalants (minerals like calcium sulfate) and antiscalants in the reverse osmosis (RO) systems were investigated. The interaction of seawater microorganisms with antiscalants was investigated by measuring the growth of bacteria in an antiscalant containing growth medium, which was added as a sole source of carbon and energy. Moreover, the interaction of microorganism with calcium sulfate (selected as a model scalant) was also investigated using scanning electron microscopy – energy dispersive x-ray spectroscopic technique. It was found that several Pseudomonas strains isolated from the marine water of Qatar are capable of using antiscalants as an energy or carbon source. It was noted that the growth curves of the strains vary with the type of the antiscalant studied. Furthermore, the results of microorganism-scalant interaction showed that the presence of bacteria induced/mediated precipitation of calcium sulfate on the RO membranes, whereas, no precipitation was noted on the control RO membranes (i.e. without bacteria) under the studied conditions. Therefore, the results of this research showed that the presence of microorganisms in seawater reverse osmosis not only causes biofouling but also enhances mineral scaling through biodegradation of antiscalants and precipitation of minerals (calcium sulfate). Unlabelled Image • Investigated the interaction of seawater microorganisms with scalants in RO • Investigated the interaction of seawater microorganisms with antiscalants in RO • Pseudomonas fragi and Pseudomonas stutzeri were isolated from Qatar's marine water. • Pseudomonas biodegraded antiscalants and utilize them as a source of energy/carbon. • The presence of bacteria induced precipitation of calcium sulfate on RO membrane. [ABSTRACT FROM AUTHOR]