From The Editor | April 26, 2013

Arsenic 101: 5 Questions Answered

By Kevin Westerling
@KevinOnWater

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Arsenic in water is one thing, but arsenic in beer? This is getting out of hand.

While the drinking water supply is clearly much more of a concern than the beer supply, the sobering fact is that arsenic, a known carcinogen, is far too prevalent in the environment.

In the U.S. and other developed nations, it is highly regulated but still insidious, showing up in consumer products such as apple juice, rice — and, yes, beer. In underdeveloped nations without the advantage of modern water treatment, it is decidedly more deadly, particularly in Bangladesh. Taking up these issues and more, a symposium on arsenic contamination in food and water supplies earlier this month referred to arsenic as “one of the great historical poisons in human history.”

The federal standard for arsenic in the U.S. is 10 parts per billion (ppb), a limit that drinking water plants must abide by. That mandate continues to keep the bulk of us relatively safe, but private well owners — such as those in Pennsylvania — must drink at their own risk or find point-of-use/point-of-entry solutions.

What exactly is the risk, and how are we resolving it? To help shed light on this trending topic, I enlisted Steve Wood of Severn Trent Services for a high-level view of the problems and potential solutions associated with arsenic.

What are the health effects of arsenic exposure?

Arsenic is known to contribute to heart disease, type 2 diabetes, pancreatic cancer, and cancers of the liver, skin, lungs, and bladder. Arsenic also creates a condition called arseniasis [chronic arsenic poisoning], which results in skin lesions similar to blisters.  The effects of arsenic on children are more acute in their formative years, and ultimately lead to the health problems detailed above.

How do most municipalities plagued with high arsenic levels deal with the 10-ppb mandate?

Strategies for utilities typically include blending, acquiring new or less/uncontaminated sources, and treatment.  Smaller water supply systems often have a hard time controlling arsenic levels due to lack of funds and other resources, so they look to the nontreatment options.

Do you consider 10 ppb to be a safe level, and do you anticipate the maximum contaminant level (MCL) to drop in the future? 

The U.S. EPA and the World Health Organization have arrived at 10 ppb based on science provided to them by organizations such as the National Institutes of Health, but, in my opinion, the level should be set at less than 5 ppb.  The MCL is often a compromise between science and the cost/benefit associated with the implementation of the standard. We are now more than nine years into the domestic implementation of the 10-ppb standard, and while there are still many communities struggling with the current law, there is evolving science that suggests the standard should be reconsidered. However, I don’t see any real momentum for lowering the level, either by the EPA or the individual states, any time soon. A major contributing factor to implementation and compliance of the arsenic rule is, again, the lack of funds. In other words, it’s pretty much an unfunded mandate. Implementing a lower treatment objective, without adequate funding, would further exacerbate compliance.

Are there important distinctions to be made between organic and inorganic arsenic?

Yes.  Atoms of arsenic bond with other elements to form molecules. If carbon is one of these elements, then the arsenic compound is an organic compound.  Organic arsenic is rarely found in natural groundwater. It’s the inorganic arsenic that is typically found in groundwater and is the more toxic form linked to detrimental health effects.  If there is no carbon present, then the arsenic compound is inorganic.

What technologies do utilities use to effectively combat arsenic, and how do they differ?

The most common technologies used for arsenic removal are adsorption and coagulation filtration.  Adsorption is a more passive process, but can have higher operating costs for challenging waters when compared to coagulation filtration.  The latter entails more operator interface and routine sludge handling.  Ion exchange is sometimes used, but requires regeneration and produces a hazardous liquid waste.

Which of the above technologies have you used for arsenic removal, and what was the outcome? Would a 5-ppb arsenic limit be too burdensome for utilities? Share your comments and struggles below.

If you have a noteworthy success story that you would like to see published, please e-mail me at editor@wateronline.com.

 

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