Risk assessment of fluoride in groundwater in Asian countries and development of countermeasure technologies

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People living in Lamphun Province in the Chiang Mai Basin, Thailand, are suffering from fluoride intake from groundwaters. In this study, fluoride concentration in the groundwaters, the current status of health effects, and fluoride intake were investigated. Ultra-low-pressure reverse osmosis membranes were used to remove fluoride from groundwaters. It was revealed that fluoride-laden groundwater is widely distributed in Lamphun Province, and the maximum concentration was 16.1mg/L. Although their drinking water has been switched from groundwater to fluoride-free bottled water, high fluoride concentration was detected in their urine samples. Since their families still use groundwater for cooking, it was found that cooked rice was the major intake source of fluoride. When the local reverse-osmosis membrane plants were investigated, it was found that fluoride was removed by these facilities, but most of the pre-treatment processes were not functioning. Both calcium and silica cause membrane fouling and bring down the permeability, but the removal rates of fluoride went up or down depending on the condition of membrane fouling.