POU Technology Demonstrates Effectiveness

In March 2001, the U.S. Environmental Protection Agency (EPA) withdrew a proposal for a lower maximum contaminant level (MCL) for arsenic in drinking water that would bring the standard from 50 parts per billion (ppb) to 10 ppb. At that time, the EPA commissioned three studies to examine the benefits, costs and health effects associated with a lower standard for arsenic.

Recently, the National Drinking Water Advisory Council (NDWAC) completed its study on the costs and made a recommendation to the EPA that point-of-use (POU) applications—filtration devices attached under a household’s sink to treat the water that comes from the faucet—be given greater consideration as a method of tackling arsenic contamination. The council’s report indicates that POU is a cost-effective method for efficient and complete removal of arsenic from drinking water. NDWAC cost evaluations show that communities as large as 10,000 can benefit financially from this approach. A critical success factor in adopting POU solutions at the community level is identifying an arsenic removal technology that has demonstrated performance in a wide range of POU applications. The following technology is one option for arsenic removal.

Apyron Technology, Inc.’s Aqua-Bind MP adsorptive arsenic removal media have demonstrated the operating flexibility, simplicity and effectiveness required for adoption at the community level.

Demonstrated Flexibility, Simplicity and Effectiveness

Aqua-Bind MP uses Apyron’s unique synthesis methodology, advanced material synthesis technology (AMST). AMST allows better control of physical and chemical properties, yielding custom-designed materials with high-performance characteristics. AMST process is used to create a mixed-metal oxide adsorbent technology that offers

•                Removal of both Arsenic III and V,

•                Treatment of high arsenic levels, bringing them below detection level (BDL), and •                Operation under a wide-range of influent water quality conditions.

In addition to arsenic removal, the media are effective in removing other heavy metals including lead, copper and zinc as well as improving taste and odor. These features enable the Aqua-Bind media to successfully tackle some of the most challenging water characteristics including extreme arsenic levels such as those prevalant in the northeastern corridor of the United States. The effectiveness of this medium in POU treatment systems is illustrated in the data shown in Table 1.

Deployment as Stand-Alone or Complement to RO

Suggested deployment of the medium for under-the-counter applications typically is through the use of prefabricated, easy-to-install, up-flow cartridges. These cartridges are available in 2.5 ¥ 10-inch, 4.5 ¥ 10-inch and 4.5 ¥ 20-inch standard configurations, which are compatible with all standard pressure rated housings. (See Figure 1.)

For more extreme levels of contamination or for whole house applications, media can be incorporated into larger vessels, as shown in Figure 2. In this particular application, the Aqua-Bind media was deployed into two 3 ¥ 40-inch custom-designed cartridges to treat an influent arsenic level of 970 ppb. This stand-alone system has successfully operated for more than five months, reducing the arsenic to BDL.

As shown in Figure 3, use of the Aqua-Bind media also is an effective post treatment option for reverse osmosis (RO), removing the untreated Arsenic III, which is the more harmful form of arsenic.

The results gained from the lab scale analysis presented in Figure 3 are confirmed through field applications as noted in line 6 of Table 1. In this particular application, the Aqua-Bind MP 2.5 ¥ 10-inch cartridge was used as a post-RO polishing step to remove the effluent Arsenic III. The two applications joined to treat an influent level of 520 to BDL.

The key to selecting the most appropriate arsenic removal technology for use in community-wide POU applications is analyzing the performance and confirming the effectiveness of each technology. This particular POU arsenic removal cartridge discussed here enables effective removal of both Arsenic III and V, flexibility of integration with existing water treatment and simplicity of use as a stand-alone treatment system. This medium has proven its effectiveness in treating extremely high levels of arsenic including homes with dangerous levels more than 90 times the proposed new U.S. standard for the contaminant. After treatment, the water levels in each of the locations where the Aqua Bind solution is at work read below detection level, and the systems maintain operation under a wide range of water conditions. The results of this treatment solution confirm the NDWAC recommendations to the EPA—POU is likely to be the most cost-effective, efficient and easy-to-use method for small and medium-sized communities nationwide to meet compliance with a lower, safer standard for arsenic in drinking water.