From The Editor | August 27, 2015

Arsenic Update: Top Technologies Revealed

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By Kevin Westerling,
@KevinOnWater

Arsenic

The federal regulation for arsenic has been in place since 2002, and yet many utilities remain noncompliant. The culprit isn’t treatment capability, but cost. It happens that the most popular treatment technique is also quite expensive — but it doesn’t have to be.

Tom Sorg, the U.S. EPA’s foremost authority on arsenic research, talked to Water Online about the different treatment options available, and revealed a key development that’s bringing the cost of compliance way down.

While the current maximum contaminant level (MCL) for arsenic sits at 10 micrograms per liter (µg/L), or 10 ppb, it could be reduced following the EPA’s Six-Year Review due out in 2016. Recent research suggests that there could be adverse health effects at the current standard, which may prompt proposals for a lower MCL.

What follows is a short Q&A with Sorg, who shares his unique insight on the state of arsenic research and removal, with particular emphasis on the struggles of small communities.

What are the EPA-approved technologies to remove arsenic?

The EPA technically does not approve technologies for any type of contaminant. When they establish an MCL, they are required to identify what they call Best Available Technologies (BATs). This is more of a recommendation of the type of technologies that can be used by water utilities — technologies determined by the EPA to reduce arsenic down to less than the MCL. When they lowered the arsenic MCL in 2001 [effective in 2002], they included a number of different technologies for small systems: reverse osmosis, coagulation/filtration, electrodialysis, adsorptive media/activated alumina processes, and what I call iron removal — a process whereby you remove the iron and the arsenic comes along with it.

As communities started to install treatment technology, the most commonly used has been adsorptive media — probably more than 50 percent.

The second technology, in terms of frequency of use, has been iron removal. There are a number of communities, particularly in the Midwest, that have high iron in their water. Many of these communities, for many years, were not removing the iron. Utilities would get ‘red water’ complaints, but they didn’t remove it because of the cost involved. The arsenic regulation pushed them into removing the iron — so now they solve two problems.

The third most popular technology is probably coagulation/filtration, where you add iron coagulant to the water and it precipitates into iron particles, adsorbs the arsenic, and gets filtered out.

In terms of compliance, when the regulation came out in the early 2000s, the EPA estimated that about 5,000 water utilities would be noncompliant, and that the vast majority of those would be small systems.

The issue now — after 10 years and with about 800 to 1,000 communities still out of compliance — is not so much treatment technology, but funding. They're struggling to find the funds to install the technology and to support the operation and maintenance of the technologies.

What is cost-prohibitive about arsenic treatment?

Adsorptive media typically has a limited capacity, and when it can no longer remove arsenic, the common practice is to pull out the media and replace it with new media. The life of the media is dependent on many factors, including water quality. Some water utilities have had to replace their media after just three or four months of operation; others can wait four or five years.

Replacing the media is rather expensive — generally about 80 percent of the operational cost — but I've always been convinced that some media could be regenerated. It would be similar to having a water softener, which takes off calcium and magnesium and replaces it with sodium; when it reaches its capacity, you regenerate it with salt. Early on, many of the adsorptive media manufacturers indicated that the iron-based media couldn’t be regenerated, but here at EPA we always thought that it could.

So we collected exhausted media from a number of small water utilities, brought it back to the lab, and looked at regenerating the material. What we did was increase the pH, which strips off the arsenic. It doesn't impact its physical properties or have any other detrimental effects on the media. You can put it back in place and it will have nearly its original adsorption capability.

Because media replacement is the largest operational expense, we felt that regeneration could reduce costs substantially.

Is media regeneration practiced at full-scale, and to what effect?

After we essentially proved that it can be done in the lab and through pilot studies, we looked for a water utility that was interested in trying the process at full scale. We found one in California at Twentynine Palms.

They had two tanks of media. Both tanks were exhausted, and the utility was accustomed to paying approximately $20,000 on replacement media. In our discussions with them, we concluded that the media could be regenerated. They were interested, and so we worked with the State of California, which has some very stringent regulations.

We regenerated just one tank of media, opting to replace the exhausted media with virgin media in the second tank. We wanted to see if the regenerated media would perform as well as new media.

The regenerated media performed nearly as well at just 20 percent of the cost, prompting Twentynine Palms to continue with regeneration and expand it to both systems. The first tank has been regenerated at least three times, and the second tank at least twice. So we've shown, on a full-scale basis, that a water utility can greatly reduce operational costs by regenerating the media.

There's probably a cutoff point for the very, very small systems — we don't know exactly where — where replacing the media or regenerating it turns out to be about equal in cost because of the manpower and chemicals involved in the process. But for Twentynine Palms, it reduced their costs by 80 percent.

Time will tell whether it catches on and whether some of the larger utilities go to regeneration, rather than just replacing the media.

Are there any other arsenic treatment developments on the horizon?

Unfortunately, I can't say yes. There are a number of companies that have been investigating new materials that could be more cost-effective or have a higher capacity for arsenic removal, but nothing has surfaced yet. Currently, the three technologies I mentioned are the ones that are being used now, and probably into the near future.

Even if something new comes along, it's going to take a while for that technology to make it into the marketplace because the states will require substantial pilot work to prove that it’s effective and worth installing.

All states are very conservative. They won't allow a utility to put in a technology that's been somewhat unproven — and I support that to some degree — because they don’t want a water utility to take on a new project, spend a lot of funds, and then find out that the technology really doesn't work.

Image credit: "Arsenic," fdecomite © 2011, used under an Attribution­ShareAlike 2.0 Genericlicense: https://creativecommons.org/licenses/by­sa/2.0/