Arsenic removal from drinking water

In response to the carcinogenic potential of chronic arsenic (As) exposure through drinking water consumption, the United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO) have lowered their regulatory and guideline values for As in drinking water to 10 μg/L total As.; Pre-oxidation may be necessary for source water where the more reduced aqueous As oxyanion, arsenite, is present. This species is neutral in the pH range of most drinking water sources, and therefore difficult to remove from solution. Chlorine is a typical oxidant for water treatment, but unwanted chlorinated byproducts raise concerns over its use. A novel oxidation process, jet hydrodynamic cavitation is presented in Chapter 2. Physical cavitation creates highly oxidizing conditions in the immediate vicinity of the collapsing cavitation bubbles, without addition of chemicals to the water supply. Oxidation pathways induced by jet hydrodynamic cavitation can be an effective oxidizer for arsenite, and may be placed in-line in a water treatment plant. An investigation of the energy efficiency of jet hydrodynamic cavitation over acoustic cavitation is also provided.; Adsorption processes may be the most effective and affordable option for small drinking water supply systems, and particularly for point-of-use (POU) type applications. Mathematical models for comparing the adsorptive capacity of novel adsorption media are presented in Chapter 3. This theoretical treatment is followed by practical experimentation with various adsorbents in Chapter 4. Special attention is given to comparing traditional activated alumina with new adsorbents designed for As removal, particularly a proprietary aluminum oxide material and granular ferric hydroxide (GFH). Under all test conditions, GFH dramatically outperformed the other adsorbents studied.; In Chapter 5 development and testing of a new water treatment process is presented. Moving bed active filtration combines principals of co-precipitation, adsorption, and filtration. Field testing at locations in the state of Idaho showed that this process is effective for removing As from drinking water. Influent concentrations of 34–41 μg/L total As were reduced to less than 1 μg/L. Recognizing that technologies must be cost-effective in addition to their capability for As removal, a comprehensive economic analysis is provided in Chapter 6. The analysis provides comparisons to existing treatment processes that suggest moving bed active filtration may be cost-effective for several system sizes.; The impact of As is often felt most in rural areas or developing nations where high-technology removal processes are not an option. The continued search for affordable technologies that do not require large treatment plants or trained operators is necessary for the health and economic well-being of many communities. This work provides a collection of information to better understand the problem, a new way to oxidize arsenic, practical data on the performance of novel adsorbents, and a new technology that may provide the solution for some public water supply systems impacted by As.