Membrane and other treatment technologies-Pros and cons

Abstract

Although ion exchange and biological reduction are currently among the most widely used treatment technologies for perchlorate contamination,1,2 other treatment technologies, such as membrane filtration and electrodialysis, may be useful under certain environmental conditions. This chapter provides a brief overview of membrane-based technologies and their underlying principles, mechanisms by which they remove perchlorate from contaminated water, factors that affect their performance, and technical limitations. Comparisons between membrane and other treatment technologies are reviewed and tabulated as general guidance for selecting the best water treatment technology under site-specific conditions. Membrane-based technologies may be divided into three categories: i) reverse osmosis (RO), ii) nanofiltration (NF) and ultrafiltration (UF), and iii) electrodialysis (ED). These technologies have been utilized for decades in water deionization and desalinization.3In membrane-based processes, water is forced through a semi-permeable membrane while dissolved salts are unable to pass through the membrane (Figure 1). Membrane permeability to different anions and cations may be adjusted by engineering the membrane pore size and selectivity. In general, two streams are produced in the membrane process: the filtrate or permeate, which is nearly deionized water, and the brine concentrate or rejectate, which contains all rejected salts or dissolved materials including perchlorate. The membrane is the key component of the technology and is usually made of organic polymers. As such, membrane fouling and scaling by alkaline earth and transition metals or metal oxides, dissolved organic matter, silicates and suspended solids sometimes present a problem, depending on their concentrations in the feed water. While the use of membrane technology for treatment of perchloratecontaminated water is still under investigation, it is generally anticipated that this process could be effective and ideal for point-of-use treatment, such as home water purification and some small-scale water treatment systems. 4,5. © 2006 Springer Science+Business Media, Inc.