Arsenic 101
On Oct. 31, 2001, the Environmental Protection Agency lowered the maximum contaminant level of arsenic in public drinking water systems from 50 to 10 parts per billion. The date by which systems must comply with the new standard is Jan. 23, 2006.Short-term ingestion to high levels of arsenic can result in gastrointestinal irritation, low blood pressure and cardiovascular attacks. Long-term ingestion of lower levels of arsenic can lead to skin, bladder, lung and prostate cancer. Noncancer effects of ingesting arsenic at low levels include cardiovascular disease, diabetes and anemia, as well as reproductive and developmental, immunological, and neurological effects.
People at greatest risk from long-term exposure are children, pregnant and lactating women, people with poor nutritional status, and individuals with pre-existing diseases that affect specific organs.
In just six months, national water standards for arsenic levels will drop considerably from 50 parts per billion to 10 ppb.
While the Environmental Protection Agency says the change will affect 10 percent of the nation's community drinking water systems, the new federal requirement is particularly challenging to the nation's smallest water systems because they have fewer customers to help pay for the compliance costs associated with upgrading centralized treatment plants. Many small systems also depend on groundwater as their source of drinking water, which, unfortunately, is the most likely place to find high levels of arsenic.
“Central treatment is not affordable,” announced Jeffery W. Stuck, with the Arizona Department of Environmental Quality (ADEQ), during a session on how small systems can comply with the new arsenic levels held at the Water Quality Association Aquatech show last March in Las Vegas.
Arizona soil contains naturally high levels of arsenic. That was not a problem when dealing with the old EPA arsenic regulations of 50 ppb. But according to the ADEQ, one-third of the state's systems exceed the 10 ppb standard - with some levels reaching as high as 200 ppb.
All water systems serving 25 or more users must meet the new arsenic standard and Arizona has more than its fair share of small systems - 287 such systems serving fewer than 10,000 people. Adding to the burden, 60 percent of these systems serve between 25 and 500 customers.
As part of an effort to help these communities comply with the stricter standards, ADEQ developed an “Arsenic Master Plan” in 2001 designed to identify effective, low-cost methods. As a result of that plan, Shannon Murphy, vice president of municipal sales at Watts Water Technologies, Phoenix, teamed up with ADEQ to run a pilot program last year on using reverse osmosis equipment to treat arsenic at the “decentralized” point of use.
“These small water systems would not be able to absorb the significant capital and annual costs associated with a large centralized treatment system,” said Murphy, who also took part in the same panel discussion with Stuck at the WQA Aquatech conference. “One of the communities that took part in our study would have had to spend an estimated $200,000 for equipment and another $30,000 each year for maintenance. If people think their water bills are high now, imagine how high they would have to be to cover those costs.”
Some Leeway
The EPA does offer communities some flexibility to help minimize the impact of new regulations on small systems.The Safe Drinking Water Act Amendments of 1996, for example, allow small water systems to use point-of-use devices in place of central treatment. Reverse osmosis equipment is one such POU device allowed.
The 1996 amendments do place some restriction on the use of POU device by small water systems:
Watts and the ADEQ chose two communities, one small and one large, for the program:
Each community had average arsenic levels higher than 10 ppb.
The Procedure: Watts and ADEQ held a series of community meetings outlining the program in late 2003, started the program at the beginning of 2004 and kept track of results over the next eight months.
The evaluation consisted of 20 reverse osmosis units installed in each community. The test homes were outfitted with Watts Premier KP-5 Manifold Systems. The system includes a 10-micron sediment filter, two 5-micron carbon blocks, a dry RO membrane, a post filter and a 3-gallon tank that stores the filtered water.
The system also has a small faucet with a total dissolved solids (TDS) monitor that checks if the RO membrane needs to be replaced
All the installations were completed in both communities within one week, with most of the units being installed within two days. In both cases, a local independent plumber completed the installations.
Two weeks following the installation of the RO units, Watts and ADEQ returned to the dwellings in order to collect water samples and drop off a survey for homeowners to complete. Additional samplings were completed in May and September 2004.
“In all cases, the RO units were capable of reducing the arsenic in the water from the highest influent arsenic level of 35 ppb down to an undetectable level,” Murphy said.
For Michael's Ranch, 100 percent of the community agreed that POU was the best financial solution for the community and were in favor of implementation. Based upon the financial impact alone, they decided to move forward with the POU program for the community. As the community's 20 units are built, the homes are being fitted with RO units during construction.
The larger community, Black Canyon City, decided to move forward with centralized treatment since the water district determined they did not want to perform the additional monitoring, time and maintenance requirements for the 750 private, public and commercial dwellings.
Even though Black Canyon City did not move forward with the POU program, they agreed the POU approach was beneficial, and less costly than the centralized treatment.
Based upon the results of the study, Murphy said some parameters can be applied when a community is considering point-of-use treatment for water compliance:
- Communities with less than 300 connections should look into the possibility of implementing POU as a solution.
- Communities should be able to solve multiple water treatment needs through POU (arsenic, nitrates, perchlorate, fluoride).
- Simple residential communities are easier to implement than a mix of private, public and commercial dwellings.
- Larger multiple functional dwellings like office buildings, schools and kitchens will require custom application, which may include larger holding tanks, and additional plumbing in order to service the water outlets.
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