Are NORMs Accumulated in Filters of Drinking Water Facilities?

Groundwater is used as raw water to produce mineral drinking water through filtering processes in bottled water facilities. Although natural occurring radioactive materials (NORMs) exist in groundwater, accumulation of NORMs were rarely studied due to their low concentrations in groundwater. The goal of this study is to evaluate potential accumulation of NORMs in filters used at the drinking water facilities. Raw water and treated water after each filtering step, bottled water, and used filters were collected from a total of 13 bottled water facilities to analyze major dissolved ions and NORMs. Additionally, surface radioactive dose rate were measured at individual filter housings. The measured concentrations of NORMs in raw and treated water were quite low. However, the surface radioactivity dose rates dramatically increased around filter housing located at very first step regardless of filter type (i.e., activated carbon or membrane filter) in 4 out of 6 facilities. Some used filters showed approximately 20 times greater contents of Pb-210 than the Korean regulation level of 1 Bq g-1. Also, the concentrations of uranium and thorium were detected up to 75 µg g-1filter and 2 µg g-1filter, respectively, in 4 water facilities. These results implies potential accumulation of NORMs in filters used at bottled water facilities. Therefore, the filters need to be monitored during manufacturing processes of bottled water, and may be properly managed after use.