Eric M.V. Hoek University of California, Los Angeles
The health issues surrounding the diminishing supply of global freshwater are well known and new ecological, agricultural, and geopolitical implications are now being recognized. It is even predicted that developed nations such as the United States will be considered "water-stressed" by 2025. Currently, polymeric membrane technology is the state-of-the-art method to produce clean, potable water from unconventional sources such as seawater or wastewater. The feed water is pumped through the highly selective plastic films and pollutants are rejected: however, the membranes quickly foul due to accumulation of rejected pollutants on the membrane surface and/or within membrane pores. A significant amount of energy and water are lost to membrane cleaning with frequent permeate backwashes and periodically cleaning with harsh chemicals that degrade membrane polymers resulting in premature replacement. The aim of this project is to develop fouling-resistant membranes to reduce increased energy demand and operating costs associated with water treatment membranes by modifying the surface of the membranes with compounds that repel or deactivate fouling materials. Membrane surface modifications have been demonstrated in past, but most have required exotic reaction conditions, long reaction times, and/or expensive reagents that limited their commercial application. The project team recently developed a novel surface modification chemistry that covalently attaches anti-adhesion and anti-bacterial compounds to the surface of polymeric membranes. The reaction is performed in water at room temperature and atmospheric pressure while using inexpensive reagents and environmentally benign processing conditions. Preliminary results demonstrate that commercial RO and UF membranes are easily modified by a variety of compounds. The membranes retain their basic separation performance characteristics, but have dramatically altered surfaces. The result is that by altering modification chemistry and conditions we can modulate bacterial adhesion to RO membranes. To determine optimal anti-fouling compound properties, several compounds will be synthesized and screened for anti-fouling behavior using High-Throughput Screening protocols previously developed by the project team. The compounds will have varying electrostatic charge, molecular weight, and anti-bacterial functionality. Commercial membranes will be modified with the new surface chemistries and evaluated for their resultant productivity, pollutant rejection, improved fouling-resistance and ease of cleaning.
This project will develop new anti-fouling membranes materials for large-scale water treatment. By modifying membrane surfaces with different properties, optimal surface properties will be ascertained to help understand the mechanisms that contribute to surface fouling and biofilm formation in aqueous environments. The result of this project will provide an effective way to produce anti-fouling membranes on a large scale to reduce energy demand and operating costs associated with converting seawater or wastewater into clean, usable water.
