oa Efficient Inhibition of SulfateReducing Bacteria in Inject Sea Water by “Green” Chitosan/ZnO nanocomposite

Oil producing companies utilize water injection as a common oil recovery method for decades, especially for offshore fields, where seawater is typically used as inject water. Due to the size and complexity of the injection system and the high salinity of the water (∼55,000 mg/L); several challenges are faced during this process including microbial growth, fouling and corrosion in the pipeline. Biofilms accelerate corrosion in a biologically conditioned metal–solution interface. Oil producing companies including those in Qatar use biocides to disinfect the water and inhibit biofilm formation caused mainly by sulfate reducing bacteria (SRB). However, traditional biocides may induce bacterial resistance and/or be detrimental to environment. In this study we synthesized chitosan/ZnO nanocomposite (CZNCs) and evaluated its antimicrobial activity against SRB biofilm in inject seawater. CZNCs showed stable behavior when exposed to higher salt concentrations of inject water. The inhibition of SRB activity was concentration-dependent and more than 73% and 43% inhibition of sulfate reduction and TOC removal, respectively, was observed at 250 μg/mL CZNCs at 10% initial ZnO loading. Scanning electron microscopy (SEM) coupled with lactate dehydrogenase (LDH) release assay indicated obvious damages to the cellular membrane which resulted in release of cytoplasmic materials from the bacterial cells. Significant decrease in concentration of EPS extracts was obtained. This work has demonstrated that the exposure of synthesized CZNCs could cause significant SRB anti-biofouling properties. This is the first ever study of antimicrobial potential of chitosan based biocides for SRB inhibition. We are confident that this work will make the scientific as well as the industrial communities to appreciate the application of nanomaterials based biocides. This is the first ever study of antimicrobial potential of any ENM generally, and chitosan based biocides, particularly, for SRB enriched biofilm inhibition. Taking into account tremendous interest to nanomaterials as antimicrobial agents, we anticipate a major impact from a much better material reported in his paper.