AWWA ACE56282

The application of low-pressure membrane filtration, including ultrafiltration and microfiltration, is increasing exponentially in the United States mostly because of regulatory drivers and the decreasing cost of this technology. As managers of water systems look at new water treatment projects or retrofit of existing treatment plants, membrane technologies are often considered because they allow managers to meet more stringent microbial removal requirements while not causing formation of byproducts that are also facing more stringent standards. Membrane filtration also offers some significant advantages over conventional treatment processes. These advantages include a high level of automation, they require fewer operators, and consistently produce high quality filter water that is not sensitive to variation and feed water conditions, or the manner in which the facility is operated. As a result, there has been tremendous growth in both the size and number of low-pressure membrane filtration systems in the United States; from the first operating facility constructed in the United States there was 100 gallons per minute (gpm) in 1993, to 1997 when there were more than 10 operating facilities, the largest which was 7 million gallons per day (mgd), to the year 2001 when there were over 60 operating facilities or facilities in design, the largest of which is 24 mgd. Larger projects are currently being evaluated including one by the City of Minneapolis, Minnesota where a 70 mgd membrane filtration facility is proposed. Not only is there growth in the size of new facilities and the number of new facilities in the United States, but there is also tremendous growth in the diversity and number of available membrane products. At the time this manuscript was written there are over a dozen commercially available membrane products in the United States. Since the early 1990's when the available products were primarily designed for filtration of raw water supplies, the industry has developed a wide range of low-pressure membrane systems each with its own set of compatibility and performance characteristics. The diversity of products today allows integration of low-pressure technology into most processes used in drinking water treatment; coagulants, lime softening, in-line addition of powered activated carbon (PAC) among others. This flexibility is due to innovation in the design in membrane systems diversity in polymers used to construct the membrane fibers and the research and development efforts of various suppliers. Includes 2 references, tables, figures.