Design & Development of Antifouling & Antimicrobial Membrane Surfaces for Effective Biofouling Control in Membrane-Based Desalination

Due to rapid increase in world population and intensification of human activities, the availability of water for domestic, industrial and commercial use has become the most important challenge of the 21st century. Membrane-based technologies for the treatment, reclamation, and purification of water are currently seen as the most effective strategy to address global water quality and scarcity issues. However, a major problem with membranes is fouling due to the accumulation of organic, inorganic, or biological foulants, which result in decreased efficiency, membrane selectivity, and useful lifetime. Effective fouling control necessitates frequent chemical cleaning, which results in shortening of membrane life as well as significant increase of process cost. The design of effective fouling control strategies is therefore one of the main technical challenges in membrane-based water treatment. Antibiofouling strategies using surface modification can be classified into two mechanisms: resistance to adhesion of biocontaminants (defending) and degradation of the biocontaminants (attacking). A classic defending protocol, involves modification of membrane surface chemistry to increase wettability by introducing hydrophilic additives such as poly(ethylene glycol) (PEG), zwitterionic polymers, etc. The attacking strategy, on the other hand, involves membrane functionalization with releasable bacteria-killing substances, such as silver nanoparticles (Ag NPs)and antibiotics, or decoration with bactericidal functionalities like quaternary ammonium salts (QAS), graphene oxide, and photoactive agents for contact killing. However, both approaches mentioned above have fundamental limitations for long-term biofouling resistance in complex biological environments. Protein-resisting PEG surfaces have been proven to be ineffective in preventing bacterial deposition and colonization, and bactericidal surfaces suffer from the rapid accumulation of dead bacterial cells, which shield the surface functional groups and provide an accessible platform for microorganisms to attach and proliferate. For this reason, the main objective of the proposed work is to combine these two complementary biofouling mitigation strategies to impart both nonadhesive and bactericidal capabilities on the membrane surfaces. The primary objective will be achieved by designing and developing membranes with both antimicrobial and antifouling properties. Commercial reverse osmosis (RO) membranes will be modified in several steps with sequential grafting of polymer brushes or zwitterions, for antifouling properties, and nanoparticles or polycations, for antimicrobial activity. In addition, materials with dual characteristics i.e. both antimicrobial and antifouling properties (e.g. graphene oxide) will be explored for the development of biofilm-resistant membranes. The membranes will then be characterized using state-of-the-art techniques (FESEM, FTIR, XPS, ETC.) to determine the success of surface modification. The developed membranes will then be tested for their antifouling and antimicrobial characteristics in short-term adhesion and long-term filtration studies. The filtration experiments will be designed to mimic actual operation conditions prevalent in RO plants. To date, many antibiofouling strategies that have shown promise in short-term testing have found to be ineffective in complex environments. Post-fouling analyses of the membranes will also be performed to study the changes in surface morphology, chemistry, etc. The performance of modified membranes will then be compared with the pristine ones to determine the degree/extent of success.