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Pilot demonstrations of arsenic treatment technologies in U.S. Department of Energy Arsenic Water Technology Partnership program

Aragon, Alicia R.; Dwyer, Brian P.; Everett, Randy L.

The Arsenic Water Technology Partnership program is a multi-year program funded by a congressional appropriation through the Department of Energy. The program is designed to move technologies from benchscale tests to field demonstrations. It will enable water utilities, particularly those serving small, rural communities and Indian tribes, to implement the most cost-effective solutions to their arsenic treatment needs. As part of the Arsenic Water Technology Partnership program, Sandia National Laboratories is carrying out field demonstration testing of innovative technologies that have the potential to substantially reduce the costs associated with arsenic removal from drinking water. The scope for this work includes: (1) Selection of sites and identification of technologies for pilot demonstrations; (2) Laboratory studies to develop rapid small-scale test methods; and (3) Pilot-scale studies at community sites involving side-by-side tests of innovative technologies. The goal of site selection is to identify sites that allow examination of treatment processes and systems under conditions that are relevant to different geochemical settings throughout the country. A number of candidate sites have been identified through reviews of groundwater quality databases, conference proceedings and discussions with state and local officials. These include sites in New Mexico, Arizona, Colorado, Oklahoma, Michigan, and California. Candidate technologies for the pilot tests are being reviewed through vendor forums, proof-of-principle benchscale studies managed by the American Water Works Association Research Foundation (AwwaRF) and the WERC design contest. The review considers as many potential technologies as possible and screens out unsuitable ones by considering data from past performance testing, expected costs, complexity of operation and maturity of the technology. The pilot test configurations will depend on the site-specific conditions such as access, power availability, waste disposal options and availability of permanent structures to house the test. Conducting pilot tests for media comparison at all sites in need of arsenic treatment would be extremely time consuming and costly. Laboratory studies are being conducted using rapid small-scale column tests (RSSCTs) to predict the performance of pilot-scale adsorption columns. RSSCTs are a rapid and inexpensive method of investigating innovative technologies while varying water quality and/or system design. RSSCTs are scaled down columns packed with smaller diameter adsorption media that receive higher hydraulic loading rates to significantly reduce the duration of experiments. Results for RSSCTs can be obtained in a matter of days to a few weeks, whereas pilot tests can take a number of months to over a year. In the pilot tests, the innovative technologies will be evaluated in terms of adsorptive capacity for arsenic; robustness of performance with respect to water quality parameters including pH, TDS, foulants such as Fe, Mn, silica, and organics, and other metals and radionuclides; and potentially deleterious effects on the water system such as pipe corrosion from low pH levels, fluoride removal, and generation of disinfection by-products. The new arsenic MCL will result in modification of many rural water systems that otherwise would not require treatment. Simultaneous improvement of water quality in systems that will require treatment for other contaminants such as uranium, radon and radium would be an added benefit of this program.