By Rick Andrew
Perchlorate contamination of groundwater has received considerable attention of late in the news media. There are now reports of concerns that real estate values in certain areas of California may be adversely affected by perchlorate contamination, and that municipalities are considering point-of-use (POU) treatment of perchlorate-contaminated water for affected residents.
The jury is still out on the seriousness of adverse health effects relating to ingestion of perchlorate-contaminated drinking water. The U.S. Environmental Protection Agency (USEPA) has indicated there are studies pointing to damage of the thyroid gland, which controls growth and metabolism from such ingestion; however, the USEPA continues to evaluate data on perchlorate before setting a national safe level in drinking water.
The state of California has been more proactive. Perchlorate contamination is more prevalent there than in many other areas and, as a result, California will set a standard for perchlorate in potable water by Jan. 1—likely in the range of 2 to 6 micrograms per liter (µg/L).
Other states have had significant detection of perchlorate in groundwater also. States in the Southwest (including Texas), as well as at least 12 other states around the country, have reported perchlorate problems. Perchlorate is a component used in the manufacture of rocket fuel—as well as high explosives and fireworks, air-bag inflators, and electroplating, leather tanning and rubber making—so any sites of production or military bases that may have used or stored rocket fuel are candidates for possible contamination of groundwater. Once contaminated, the water will be affected for the foreseeable future. Studies have shown perchlorate is quite persistent in the environment under typical conditions, potentially lasting for years.
How to treat perchlorate
Perchlorate is an anion (ClO4–). As such, it’s amenable to treatment by reverse osmosis (RO), anion exchange resins and distillation. There are many off-the-shelf and dealer-distributed POU reverse osmosis systems available for the treatment of other contaminant ions such as lead, nitrate/nitrite or arsenic. There are also dealer-distributed point-of-entry (POE) anion exchange resin systems available in the marketplace as well as POU distillation systems.
How well does treatment work without a standard?
Currently, it’s difficult to know how well these devices perform unless a specific installation is monitored and analyzed. With data from specific installations, it may be difficult to extrapolate results of treatment to other situations with different levels of contamination or water chemistry. Part of the reason for a lack of demonstrated product performance for perchlorate reduction is there are currently no requirements in any of the ANSI/NSF standards for perchlorate. This will change soon.
NSF, contacted by regulators, manufacturers and consumers over recent months, has been asked about perchlorate reduction performance of POU/POE, Drinking Water Treatment Unit (DWTU) systems. Because of this widespread interest, NSF developed a protocol for perchlorate reduction by RO in March 2003 (see Table 1).
The influent challenge level of 0.10 milligrams per liter (mg/L) was established based on a review of occurrence data from the state of California. Typically, the 95th percentile of occurrence is used as a basis for influent challenge levels in DWTU standards. The maximum allowable product water level of 0.005 mg/L was established based on several factors. The California initiative to set a standard of between 0.002 mg/L and 0.006 mg/L was taken into consideration, but ultimately the reporting limit of 0.005 µg/L in USEPA analytical method 314.0 precluded the level from being set any lower.
This protocol was validated in April through testing an off-the-shelf POU RO system that’s currently available in the marketplace. The test system marginally failed to achieve the required maximum allowable product water level, creating optimism that some off-the-shelf, currently available RO systems may pass.
Perchlorate reduction claims
NSF presented the protocol and results of the validation study to the Joint Committee on Standards for DWTUs during a May 7-8 meeting. The committee is ultimately responsible for the content and requirements of all of the standards. After discussion, it unanimously voted that a ballot be prepared for adoption of the requirements from the protocol to establish a claim for perchlorate reduction in ANSI/NSF Standard 58 for RO systems. This ballot was to be released in late May.
Results of voting on this ballot will indicate direction forward. The ballot may be approved without change for inclusion in Standard 58, or there may be comments and negative votes necessitating modifications. The one area that’s not yet fully resolved is the maximum allowable product water level. It’s likely California may set a standard for perchlorate in drinking water that’s less than the protocol level of 0.005 mg/L. In anticipating a desire to set a lower level, the NSF laboratory continues to develop the analytical methodology to achieve a lower reporting limit than the currently achievable 0.005 mg/L.
The committee also discussed the possibility of developing a perchlorate reduction claim for adoption into ANSI/NSF Standard 53 for anion resin systems. These systems must be able to reduce perchlorate even in the presence of competing anions such as chloride and sulfate. Discussions suggested challenge water used for testing would have to take competing anions into account. The other technical aspect of anion exchange resins that must be incorporated into the protocol is that they are regenerable. Work on a perchlorate reduction claim for anion resin systems will proceed. A test protocol that incorporates several cycles of regeneration, as well as a specific challenge water chemistry relating to competing anions, will likely result.
Although not discussed by the committee, other work will focus on development of a claim for distillation systems for perchlorate reduction under ANSI/NSF Standard 62.
Although the jury is still out on actual toxicity and safe level for perchlorate in drinking water, the reality is many consumers would like to reduce levels being detected in their water. Manufacturers would like to provide products that can serve this need with a performance claim backed up by conformance to national standards. Regulators would like to know how to advise constituents on the issue of treatment technologies and products for perchlorate contamination. By developing protocols, conducting validation testing, and presenting results and recommendations to the DWTU Joint Committee, NSF can ultimately help consumers, manufacturers and regulators achieve these goals.
About the author
Rick Andrew is technical manager of the DWTU Program at NSF International, of Ann Arbor, Mich. His previous experience is analytical and environmental chemistry consulting. Andrew has a bachelor’s degree in chemistry and a master’s degree in business administration from the University of Michigan. He can be reached at email@example.com.