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.
