Volume 45 Number 7
Perchlorate -- New Contaminant Reduction Claims for DWTU Standards
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 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
How well does treatment work without a standard?
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
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.
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Table 1. Protocol for testing RO systems for perchlorate reduction
1 Average influent challenge levels shall be specified with a tolerance of ± 10 percent.