Answer to Question #14104 Submitted to "Ask the Experts"

Category: Decommissioning and Radioactive Waste Disposal — Disposal

The following question was answered by an expert in the appropriate field:

Q

We have a granular activated carbon (GAC) filter to remove radon from our drinking water. We tested at 355 Bq L-1 which is above our state's recommended limit (150 Bq L-1). I am wondering if I am able to throw this filter in regular household trash? If not, where do I get rid of it? How do I handle it?

A

First, let's define a couple of terms that are used in this answer. Residential GAC filters are installed as point-of-entry (POE) or point-of-use (POU) systems. POE systems are installed where the water enters the house and treats the whole house water supply, whereas POU systems are installed at a singular point, such as a kitchen faucet. Before I dive into addressing your question regarding disposal, I must acknowledge that the goal in reducing radon-222 (222Rn) in water is to reduce the home's indoor air radon concentration. It may seem counterintuitive, but the primary health concern of radon in water is from inhalation as opposed to ingestion. As such, GAC filters used for radon reduction are typically installed as a POE system. As a general rule-of-thumb every 270 Bq m-3 of 222Rn in your water will raise the indoor radon concentration by 0.027 Bq m-3—which is 25 percent of the US Environmental Protection Agency (EPA) action level for indoor air radon of 0.11 Bq m-3 (4 pCi L-1). Note that most of a home's indoor air radon originates from the underlying or surrounding soil.

Now, on to the main point of your question. As I'm sure you are aware, your GAC filter is removing radon from your water supply. The filter may also remove other naturally occurring radioactive material present in the water—such as radium, uranium, and thorium. The total amount of radioactivity that accumulates on the filter depends on the removal efficiency of the system, filter change frequency, and concentration of the radionuclide in the water which is highly variable depending on location. In the United States, there are several federal and state agencies that are involved with the regulation of radioactive material. I found an article presented at 2008 American Association of Radon Scientists and Technologist (AARST) Symposium that summarizes the regulatory interests of relevant federal agencies plus the state of Pennsylvania. Evaluation of your filter against these standards is difficult without laboratory analysis or theoretical calculations. In summary, spent GAC filters my become subject to federal and state regulations. Information presented on the Centers for Disease Control and Prevention web page for Radon and Drinking Water from Private Wells acknowledges that "Disposing of the carbon may require special handling if it is used at a high radon level or if it has been used for a long time."

Regulatory and disposal concerns discussed above are primarily focused on POE systems, which typically have a larger volume of filter media than POU systems and, therefore, accumulate larger quantities of radioactive material. I could not find data related to radon accumulation on small POU filters and I don't have information related to your specific filter system. Based on your question it sounds like you have a small POU system that is possibly mounted under the sink. The manufacturer/installer of your system should be able to provide you with information on filter change-out and disposal. If you have a faucet mounted unit, you should be able to dispose of the filter along with your household waste as these types of filters are ineffective at radon removal. Additionally, the manufacturer/installer of your system may offer a recycling program for your filter, which is better option than disposing in a landfill.

There have been a number of questions posted to the Health Physics Society Ask the Experts web page related to the use of GAC filters for radon reduction and radionuclides in water. Additionally, you may find the information presented on the EPA radon web page useful. If you have any additional questions on disposal or indoor air radon, feel free to reach out.

I hope this information helps,

Nick Altic, CHP

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
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