For an invisible contaminant, arsenic is getting a surprising amount of attention recently. The colorless, odorless metalloid is a naturally occurring groundwater contaminant found in several U.S. regions, and researchers believe that it has caused illness in populations around the world.
Arsenic exists in both inorganic and organic forms. Present in natural deposits in the Earth, it can leach into bedrock aquifers and artesian wells as rock weathers naturally in contact with water. It can also be found in small concentrations in foods such as apples (seeds) and rice, and high concentrations in seafood, near smelters and some industrial sites, according to Russell Prescott, P.E., vice president of R.E. Prescott Co. Inc., who gave a presentation on arsenic removal at the recent EWQA Water Treatment Systems Training Event.
Arsenic has serious effects if present in drinking water at high enough levels. Arsenic can cause several types of cancer and symptoms such as stomach pain, blindness and hand and foot numbness from very high exposures.
The U.S. Environmental Protection Agency's original arsenic standard was 50 ppb, lowered to 10 ppb in 2006, based upon technical and economic feasibility.
Some of the people we spoke with were comfortable with the federal MCL limit.
"There is great confidence that the current MCL is safe for human consumption," says Janna San Juan, applications engineer at AdEdge Water Technologies LLC. "Even with the current MCL set, many technologies are able to treat below the MCL."
“I am comfortable with [the MCL],” agrees Prescott. “I believe that there are the experts in terms of the risk effect. I’ve seen presentations by officials from the EPA and I’m really impressed with how they set their maximum contaminant levels.”
Some states, however, are not so comfortable with the limit, and have set their own, lower MCLs for arsenic.
"New Jersey believes that 5 ppb is wrong for people in terms of health risks and they’re bringing it to 3 ppb," notes Prescott.
No matter what the MCL for arsenic in your area, homeowners should be educated and understand the risks of arsenic contamination. According to Prescott, 4,000 community water systems and 10 million private homes are affected by arsenic contamination in the U.S., so "there is a market out there for this water treatment."
While municipal water supplies must follow the arsenic MCL, some people may not be comfortable with that limit. Therefore, dealers should always know the exact level of arsenic in the municipal water supply to keep customers informed.
In the case of private water wells, even more homeowner education is necessary. While some parts of the country, including New Jersey and Michigan, require that wells be tested for arsenic before a real estate transaction is completed, according to San Juan, a majority of areas have no local regulatory laws for arsenic in wells.
"This should be adopted by all states to ensure safety for everyone," San Juan says.
"If you have a private well, if there’s no local regulatory law, then you don’t have to treat it. There are some people who don’t even test for arsenic because knowing they don’t have to treat it," says Prescott. "That’s a strange thing.”
Well owner education
While arsenic contamination has certainly been a popular news topic in the past few years, there are still plenty of well owners who are not aware of the risks and do not test regularly.
“The number of homeowners who are taking ownership of their water quality is appreciable and is increasing as awareness increases but still has a ways to go," explains San Juan. “Articles are probably the most effective way of informing the public without spreading panic. Explain that arsenic is a naturally occurring contaminant. As dealers increase their presence in the public, people will want to know why arsenic exists.”
Concurs Prescott, "It’s important for dealers to be educated in arsenic to be able to give them the correct information so they can make a logical decision on how to deal with their water if it does have arsenic.” But, dealers should not engage in discussions about toxicology, and cancer risk. They should, instead, focus on the standards.
The first step is finding out if your service area has a known arsenic problem. The U.S. Geological Survey (USGS) has developed maps that show where and to what extent arsenic occurs in groundwater across the country, according to Jessen, available at http://water.usgs.gov/nawqa/trace/arsenic/.
According to Antonio Inojal, project engineer at AdEdge Water Technologies LLC, arsenic is most prevalent in three regions of the U.S.: The Southwest, especially Arizona, Nevada and New Mexico; New England, particularly New Hampshire, Maine and Massachusetts; and the Pacific Northeast, including Oregon, Washington and Idaho. But, it can also be found in other states, including California, Michigan, Texas, Nebraska, New Jersey, Pennsylvania and Maryland.
“If a homeowner has not had their well water analyzed, they should be very concerned," advises Jessen. "Water treatment dealers have a responsibility to advise the homeowners to get their water analyzed as soon as possible. Dealers can also advise municipal water users to check their consumer confidence reports (EPA requires that all public water providers send these to their customers).”
Testing and treating
Arsenic appears in water as As (III), trivalent or non-oxidized arsenic, and As (V), pentavalent or oxidized arsenic. The most important step is determining which of the two forms are present, as As (V) is much easier to remove than As (III).
Jessen and Inojal emphasize that a state-certified laboratory is the best resource to test a home well accurately for arsenic in water. Certified labs can be found at http://water.epa.gov/scitech/drinkingwater/labcert/statecertification.cfm.
"There are also field test kits, however, some require a bit of expertise by the person handling the test kit, and their results are based on visual interpretation,” notes Inojal. "Field test kits are a good way to determine quickly a 'ball-park' value for their arsenic concentrations and we would recommend that qualified/certified dealers in known arsenic areas do a quick test when servicing their customers."
There are a number of water treatment technologies that will remove arsenic, but many are not effective on As (III) and all have advantages and disadvantages that must be considered.
POU alumina or iron oxide are the simplest treatment methods for the home. The treatment unit should be put on the pipe to the kitchen tap with a shunt to
the refrigerator water feed. POU reverse osmosis systems have low yield water production. More importantly, POE RO is not appropriate because the water would be very corrosive to the home plumbing. In addition, all RO systems are ineffective at removing As (III), produce concentrated arsenic in discharge water and tend to waste large volumes of water. Iron based POU systems will remove As (III) and As (V). Another way is to add some chlorine to oxidize it to As (V) before the POU treatment alumina or iron.
Anion exchange is another possible cost effective whole-house treatment method, however, it does backwash concentrated arsenic to a drain, significantly lower the pH of the water and does not remove As (III). There is also a slight risk that arsenic could dump with ion exchange, according to Prescott. However, anion exchange resins have the potential to produce nitrosamines that are also carcinogens.
Prescott explains that resins do not require backwash, while medias do, resins can be regenerated and the gpm per square foot is lower for medias.
Removing arsenic from water is not the easiest treatment out there. It requires many choices on the part of the homeowner and dealer when it comes to acceptable levels and testing frequency. POU is the best approach and a minor amount of system maintenance is required, mainly replacing the cartridge perhaps once per year depending upon the type of arsenic, concentration in the well and family size which determines drinking and cooking water use.. Dealers should be sure to include homeowners in all decisions to ensure they are fully informed when it comes to this dangerous, yet very common, contaminant.