Accumulation Mechanism and Effects of Naturally Occurring Radioactive Materials in the Filters of Bottled Mineral-Water Facilities

Woosik Shin,Jina Jeong,Jeong-Hee Han,Byung-Uck Chang,Sungwook Choung

doi:10.3390/w12040930

Abstract

Groundwater contains naturally occurring radioactive materials (NORMs) through water–rock interactions. Although a recent study found that the NORMs are accumulated into the filters utilized in bottled mineral-water facilities, the accumulation mechanism and effects have rarely been studied. This study is, therefore, conducted to determine the mechanism of NORM accumulation in filters during water treatment processes and to provide a first estimate of the level of radiological risk for workers in five bottled-mineral-water facilities. The level of Rn-222 decreased dramatically at the first filters (FF) encountered after passing through water storage tanks, while surface radiation sharply increased. The increase of radioactivity on the FF was mainly caused by the accumulation of short-lived radon progenies through decay processes inside the water tanks. Although the estimated radiological risk was lower under certain circumstances compared to the public dose limit of 1 mSv yr−1, the radiological risk should be properly managed in case of direct and/or close handling of the used filters during filter replacement procedures.

Highlights

Groundwater that has been used as a source of drinking water could contain naturally occurring radioactive materials (NORMs) such as uranium, radium, and radon through long time-scale water–rock interactions
The uranium concentrations in raw groundwater were significantly different depending on the pumping well locations even in the same facility, they consistently declined to the low level of ≤ 30 μg L−1 after the water filtering processes
The activated carbon filters (ACFs) contributed to the decrease of uranium irrespective of filter location [19]

Summary

Introduction

Groundwater that has been used as a source of drinking water could contain naturally occurring radioactive materials (NORMs) such as uranium, radium, and radon through long time-scale water–rock interactions. Numerous studies have investigated their occurrences and geological relationships in the groundwater environments [1,2,3,4,5,6], as well as health risks via water ingestion [7,8,9]. The accumulation mechanisms and effects of NORMs (e.g., health risk by external radiation) are, rarely studied due to typically low concentration of radionuclides in groundwater. In the case of bottled-mineral-water facilities, relatively deep groundwater is filtered using membrane filters (MFs) and activated carbon filters (ACFs). A variety of micro-sized MFs is used as the main filters in many bottled-mineral-water facilities. Because of the low removal efficiency of radionuclides by MFs and ACFs [17,18], it is expected that NORMs are unlikely to accumulate in the MFs and ACFs

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