Using Advanced Adsorptive Media for Arsenic Treatment
New POU Technologies May Be the Answer for Small Municipalities Facing High Costs
On November 26, 2001, the new arsenic standard was signed into law—lowering the acceptable level for the contaminant from 50 parts per billion (ppb) to 10 ppb. Approximately 4,100 municipal water systems serving nearly 13 million people nationwide are affected by the law and are required to meet compliance by January 2006. According to the U.S. Environmental Protection Agency (EPA), 97 percent of these systems are small systems serving fewer than 10,000 people each. The economic impact on these small systems is likely to be large. However, there currently are options available to small municipalities that may be more affordable than central treatment.
Prior to the ruling on the arsenic standard, the EPA
commissioned three reports: the Arsenic Rule Benefits Analysis by the Science
Advisory Board, the Health Effects Study by the National Academy of Sciences
and the Cost Review Report by the National Drinking Water Advisory Council
(NDWAC). The results of these three reports prompted the EPA to finalize a new
standard after more than 20 years of debate. (See EPA’s web site—www.epa.gov—for
the full reports and see the February article in WEM, “Arsenic in
Drinking Water—The Development of Drinking Water Regulations,” by
John T. O’Connor.)
In the cost review report, NDWAC recommended that small
municipal systems serving up to 10,000 people give greater consideration to
implementing point-of-use (POU) treatment technologies instead of centralized
treatment. In response to this recommendation, the EPA Office of Ground Water
and Drinking Water awarded a grant to NSF International in December 2001 to
conduct a POU demonstration project. This project will pair a small public
water system with solution providers in order to develop and test a program
that examines each step of a cost-effective POU strategy for compliance with
the new arsenic standard.
For some small municipalities, implementing a centralized
treatment system likely will prove to be complex, cost-prohibitive and quite
challenging given the lack of technical expertise and resources. POU may be a
more cost-effective method to meet compliance with the new law, particularly
for those systems serving fewer than 3,300 people. A critical success factor
for community-wide POU applications will be the ability to implement a
technology that has demonstrated capability in POU arsenic removal.
Flexibility, Simplicity and Effectiveness
Small municipalities that choose to implement POU technology
for compliance with the new arsenic standard most likely will use adsorptive
media or reverse osmosis (RO) treatment options. These options are considered
to be Best Available Technologies (BAT) by EPA. An important issue for arsenic
removal is the understanding of arsenic speciation and its effects on selected
technologies. Arsenite (Arsenic III), as an uncharged species, often co-exists
with the oxidized form, arsenate (Arsenic V), in water. Both forms are present
in many public and private groundwater or well water supplies in the United
States, as documented by the EPA and others.
RO systems are widely used in the United States for various
water purification functions. They remove 85 to 95 percent of Arsenic V, as
well as other contaminants, from drinking water. However, RO systems have
limited capability to remove Arsenic III from water, the more harmful and
difficult to remove of the two forms. Since many small community and
non-transient systems have no form of disinfection or chemical oxidation,
indiscriminate use of RO systems leaves the possibility of inadequate arsenic
To effectively remove all forms of arsenic, new advanced
adsorptive medias (such as Apyron Technologies’ Aqua-Bind) should be
considered. Advanced adsorptive media remove up to 99 percent of both forms of
arsenic from drinking water. These media can be used independently or in
conjunction with other treatment systems, like RO.
Successfully operating in more than 200 systems across the
United States, adsorptive arsenic removal media have demonstrated the operating
flexibility, simplicity and effectiveness required for use in POU applications.
These successful results point to a logical next step—employing
adsorptive media POU technologies in compliance strategies for small
municipalities. Apyron intends to participate in the EPA-sponsored project that
will develop and test POU compliance for small public systems.
The flexibility of adsorptive media enables it to tackle
extreme arsenic levels such as those experienced in the northeast corridor of
the United States (Table 1). The technology’s flexibility stems from its
under a wide range of influent water chemistry,
both Arsenic III and V, and
high arsenic levels to below detection level (BDL).
Additional benefits of the system include reduction of heavy
metal contaminants such as lead, copper, zinc, fluoride, selenium and antimony
as well as improved taste and odor.
An added feature of the medium is that it is available in a
variety of standard- and custom-sized cartridges. The product package can be
modified to fit specific space and system configurations, enhancing the cost-efficiency
and flexibility of the system. The cartridges also can be custom-designed based
on specific water characteristics and applications.
A wide range of arsenic concentrations is treated with
cartridges in one of three size configurations: 2.5* ¥ 10*,
4.5* ¥ 10* and 4.5* ¥ 20*, used in standard
pressure-rated housings. The cartridges can be used as a stand-alone treatment
system or as an addition to filtration already in place such as an RO system.
The 2.5* ¥ 10* cartridge is a cost-effective and efficient
post-RO addition, removing the Arsenic III left behind by the RO system.
Figure 1 illustrates the effectiveness of a standard
10* adsorptive media cartridge installed immediately after a conventional
under-counter RO system. An average of 40 ppb Arsenic III influent solution was
maintained in the absence of dissolved oxygen for the experiment.
A homeowner in Bow, N.H., can attest to the effectiveness of
the RO/POU adsorptive media cartridge. He contacted a local water professional
after testing his well and finding arsenic at 520 ppb. The water professional
installed an RO system followed by an adsorptive media cartridge for the
removal of both forms of arsenic. The system has successfully treated
approximately 180–220 gallons effectively to below the detection limit of
5 ppb for the past four months.
Another key benefit associated with use of advanced
adsorptive media cartridges is the longevity of the media life in atypical
conditions. A homeowner in Northport, Maine, tested his drinking water and found
that his well had arsenic levels greater than 970 ppb. He contacted a water
professional who assisted him in custom designing a POU system using twin
adsorptive media cartridges. Two 3* ¥ 40* cartridges were
installed in series with a .25 gpm flow rate to treat 1–2 gallons of
water per day for potable use. The treatment system was installed in March 2001
and has successfully treated approximately 287 gallons of water to below 5 ppb.
The Case for POU In Municipal Compliance
Homeowners commonly use POU technologies to reduce hardness,
remove heavy metals and improve taste and odor of their drinking water.
However, public or private utility use of a
point-of-use/point-of-entry(POU/POE) solution to meet an enforceable drinking water
standard is a fairly new approach. In 1996, the Safe Drinking Water Amendments
allowed utilities to consider the use of POU/POE technology to meet compliance
with various enforceable standards. Now, the EPA is required to consider
POU/POE devices as potentially affordable means of achieving compliance,
particularly for small municipal systems.
The EPA has investigated cost, performance and management
issues associated with POU/POE in compliance situations. In 30 case studies,
the agency found that POU/POE can offer an affordable and executable option to
meet drinking water standards and that consumers accept in-home access required
to ensure that systems are properly installed, maintained and monitored for
performance. The EPA previously estimated 4 to 5 percent of small water systems
(less than 500 customers) would use POU for compliance. Now, with new evidence
from the National Drinking Water Advisory Committee’s Arsenic Cost Work
Group, the percentage is significantly higher.
It is difficult to determine a precise cost estimate for
compliance with the new arsenic standard because each of the 4,100 affected
systems has unique circumstances and water profiles. The NDWAC’s report
concluded that the EPA’s original annual cost estimate of $195 million,
which focuses primarily on central treatment, is most likely accurate. However,
other studies, such as one conducted by the American Water Works Association
Research Foundation (AWWARF), claim that the national cost will be much
higher—in the $400 million-per-year range.
Both groups are in agreement that centralized treatment for
small and very small systems is more costly per capita and could be two to five
times the monthly cost compared to larger systems. POU may enable a lower cost
option for many small municipalities. At $.10 to $.20 per gallon, POU treated
water is more than 50 percent less costly than bottled water, which ranges from
$.75 to $2.00 per gallon. Initial capital costs including installation of an
adsorption-based POU system in a single home can range between $150 and $200.
Annual costs thereafter are reduced to the cost of replacement cartridges, from
$60 to $150.
Of course, there are a number of other compelling reasons
small municipalities should consider POU-based treatment options such as proven
performance, simplicity of operation and reliability. Although implementing POU
technology community-wide is a relatively new approach to meet compliance,
small municipalities owe it to their citizens, who will bear the cost, to
investigate all options.