The Near Future Of Strontium Regulation

In an effort to further protect the quality of drinking water, the EPA plans to elevate strontium from its third contaminant candidate list (CCL3) and mandate its treatment.

[UPDATE: According to the 1/4/16 Federal Register, the U.S. EPA "is delaying the final regulatory determination on strontium in order to consider additional data and decide whether there is a meaningful opportunity for health risk reduction by regulating strontium in drinking water."]

Strontium is an alkaline earth metal that naturally occurs in air, dust, soil, foods, and drinking water. It can occur at high levels in bedrock aquifers and can be an adverse contamination result of milling, coal burning, and phosphate fertilizers.

Strontium can replace the calcium in bones and will affect skeletal development and impact bone strength in people who do not consume enough calcium.

The EPA indicates that ongoing exposure to strontium at levels of more than 4,000 ppb every day may lead to negative health effects, but there is no evidence that drinking water with trace amounts of the element will cause harm.

An October 2014 news release that announced the forthcoming regulation states that because of strontium’s effects on development, the EPA is particularly concerned about potential consumption by infants, children, and adolescents. At the time of the release, the agency found strontium in 99 percent of the country’s public water systems, with 7 percent reaching “levels of concern.”

According to the Water Research Foundation (WRF), the EPA’s decision was based on a Health Reference Level (HRL) revision by the National Inorganics and Radionuclides Survey (NIRS) that lowered strontium from 4.2 mg/L to 1.5 mg/L.

Regulation Timeframe

The Safe Drinking Water Act (SDWA) requires that every five years the EPA develop a contaminant list and then make a regulatory determination for at least five contaminants on that list. The EPA’s preliminary decision to regulate strontium in drinking water marked the final stage of a three-phase process for regulating a CCL3 contaminant, the first two being health and occurrence assessments.

A 60-day period for public comment on the decision ended on December 19, 2014 and the agency now plans to make its final decision on strontium regulation sometime this year or in early 2016.

Following that decision, the regulatory schedule calls for a rule proposal within 24 months and a final decision on a rule 18 months after that. The final strontium regulation may not be determined until 2019.

Areas of Concentration

An American Water Works Association (AWWA) report on the potential regulatory implications of strontium notes that the metal is found in almost all drinking water sources in the country, at an average concentration range of 0.3 to 1.5 mg/L.

According to a U.S. Geological Society study referenced by the report, surface waters in northern and western Texas and southern New Mexico and Arizona have the highest concentrations of strontium while the other regions of the country have strontium measurements of less than 1.5 mg/L.

Treatment

The EPA found conventional treatment to be ineffective in removing strontium from water.

Instead, it has identified ion exchange and reverse osmosis (RO) as Best Available Technologies (BATs) to treat drinking water for strontium. Applying adsorptive media, RO, ion exchange, or co-precipitation followed by microfiltration are processes that will remove up to 99 percent of strontium or greater. Powdered activated carbon coupled with ion exchange resulted in greater than 90 percent removal of strontium.

WRF and AWWA have joined forces to create the “Critical Review of Treatment Options and Considerations For Strontium Removal From Water.”

The project, which is currently in progress and aims to conclude in 2016, will review existing literature on strontium removal from water and conduct lab-scale evaluations to determine the form in which strontium is found in different water quality conditions. The work will culminate in a report that recommends future research on treatment options and technologies. WRF and AWWA plan to follow this review with an “Evaluation of Treatment Options for Removal of Strontium from Water” that will build on its own recommendation.

While it may be some time before industry standards for treating strontium are established, and even longer until an EPA regulation is in place, a ruling is on its way.