AWWA WQTC57132

The U.S. Environmental Protection Agency (EPA) has promulgated a new Maximum Contaminant Level (MCL) of 10 micrograms per liter (ug/L) for arsenic in drinking water. All community water systems will have to comply with this new MCL by early 2006. EPA estimates that 4,100 community water systems, 97 percent of which serve 10,000 or fewer people will have to take corrective measures to meet the new, more stringent arsenic limit. Centralized treatment is not always a feasible treatment alternative, especially in areas where each home has a private well or where the treatment costs are prohibitive. In such instances, point-of-use (POU) or point-of-entry (POE) treatment alternatives are more attractive and feasible. Even though POU/POE treatment systems are easy to install and operate, there is very little information currently available in terms of actual operational data. To fill this critical data gap, the Arsenic Research Partnership comprising of American Water Works Association Research Foundation (AwwaRF), USEPA and Association of California Water Agencies (ACWA) launched a national study to evaluate the feasibility of using POU/POE treatment systems for arsenic removal. This study evaluated some of the most promising "under-the-sink" (POU) and POE treatment alternatives for arsenic removal including reverse osmosis (RO) and adsorption to iron activated alumina (Fe-AA) and granular ferric hydroxide (GFH). These technologies were evaluated at various locations, including Stagecoach, Nevada, Sun City West, Arizona, and Metropolitan Water District, Arizona over periods of up to 12 months. The POU and POE units were operated under continuous and intermittent conditions. The intermittent operation was performed to simulate the actual use in homes. The units were also shut-off for one-week durations to simulate vacation periods. In addition to arsenic, the treated water was monitored for other parameters such as total dissolved solids, silica, hardness and heterotrophic plate counts (HPCs). Consistent removal of arsenic and TDS was observed in the POU-RO treated water. No significant improvement was observed in the microbial quality after POU-RO treatment. Consistent fluxes were maintained even after operating for 8-12 weeks. The run lengths on the POU and POE adsorption systems were dependent on source water quality including pH and the presence of interfering ions such as silica. The costs for POU-RO and POU-adsorption were developed by obtaining individual quotations for significant cost items such as housing for membrane/media, membrane elements or adsorption media, flow control/measuring devices and bladder or storage tanks. The replacement frequency for media and membranes was determined based on the findings of the field POU/POE tests, consultations with manufacturers and best professional judgment. The findings of this study will be useful for systems that are impacted by the new arsenic MCL and are considering POU/POE treatment approach. Includes 11 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

15

File Size:

1 file , 370 KB