Wastewater Reclamation & Reuse by the cost-effective and highly efficient removal of emerging organic micropollutants using nanofiltration membranes

With increasingly stringent regulations and global water scarcity, the sustainable provision of clean and potable water to the human population has been identified as the challenge of this century. This situation is further aggravated by the continuous discharge of domestic and industrial wastewaters containing trace amounts of organic micropollutants that contaminate the surface and drinking water. The presence of these pollutants in the environment and their inevitable interaction with humans and aquatic life, presents a serious hazards due to the health risks associated with their consumption. Several factors such as their small size, nonbiodegradable nature and a diverse variety, make their complete removal or degradation very difficult. The previous few decades has witnessed an unprecedented inclination towards using membrane technology in a variety of water purification and treatment processes. With a proven capability of removing a diverse array of foulants e.g. natural organic matter, pathogens, colloids, etc. membranes are being increasingly considered as a viable alternative for municipal and industrial wastewater treatment. Among the membrane-based processes, reverse osmosis (RO) and nanofiltration (NF) are the frontrunners for efficient water purification due to the highly dense nature of the membranes used. In particular, RO is the first-choice technology for several processes including water desalination, wastewater reclamation, etc. due to its ability to reject virtually everything except for water molecules. However, the RO process is energy intensive due to high operational pressure requirements as well as elevated maintenance costs due to frequent chemical cleaning and replacement of the membranes. Nanofiltration, often termed loose RO due to its relatively larger pore size compared to the latter, is a promising alternative due to its high rejection capabilities and much lower energy requirements. Recent studies at the laboratory scale and pilot plants have shown some commercial NF membranes to be equally effective in removing a majority of the emerging organic contaminants from wastewater. In addition, detailed budget analysis of the capital expenditure and operation & maintenance costs has revealed significant economic savings compared to RO setup. Inspite of all these advantages and potential, NF membranes are prone to fouling by a variety of pollutants such as organics, microorganisms, colloidal particles, etc. like their RO counterparts. The phenomena of fouling has an adverse impact on their performance and efficiency with time that ultimately raises the O & M expenses. The objectives of the proposed research are to investigate different commercial NF membranes for their efficiency in removing emerging organic micropollutants from synthetic feed waters. A second focus will be on the surface modification of these membranes with antifouling thin films that will prevent/delay fouling without compromising on the output parameters such as permeate water flux and organic rejection. The surface modification will be carried out using facile chemical techniques e.g. layer by layer assembly, dip-coating and molecular grafting, etc. Advanced characterization techniques including FESEM, FTIR, XPS and AFM will be utilized to analyse the morphology, chemistry and topography of the membrane surfaces. The efficiency of organic rejection will be examined with membrane filtration units under standard operating conditions of pressure, temperature and feed flow. Finally, the novel membranes will be examined for their organic removal efficiency with pretreated wastewater.