Answer to Question #145 Submitted to "Ask the Experts"

Q

I understand that ²²⁶radium has a half life of more than 1600 years. What are the rules for disposing of sludge, backwash, or other waste containing various levels of radiation that would be generated from the use of an ion system designed to remove radiation from our drinking water system? If our drinking water contains an average of 6 pCi/L of ²²⁶Ra and ²²⁸Ra and the ion system lowered the level to 3 pCi/L, and this was sent to through our sewer system and out to our playground via the drip system, approximately how much radium would remain in the wastewater sent to the playground? Would it be a huge problem in disposing the sludge and other waste in a municipal landfill?

A

Question 1: How much Ra goes to the playground?Answer: Assuming there is no dilution, Ra concentration in the waste water should remain at 3 pCi/L after going through the pipeline. If the radioactive waste water is mixed with other nonradioactive waste-water streams in the sewage system before it reaches the playground, a dilution should be applied to obtain the final concentration. The total amount of Ra that reaches the playground is equivalent to the multiplication of Ra concentration in the waste water and the volume of waste water sent to the playground.

Question 2: Waste DisposalAnswer: The sludge and other wastes should be classified and disposed of as radioactive waste as appropriate. Section 61.55 "Waste Classification" of 10 CFR 61 "Licensing Requirements for Land Disposal Facilities" provides guidelines for determining waste classes. Radioactive waste containing Ra should be handled and disposed of as Class A waste.

Chuan-Fu Wu, PhD, CHP