Fluoride in Groundwater

Groundwater being a major source of drinking water in several countries contains fluoride that may affect individuals through oral ingestion. Drinking water containing excess fluoride leads to health issues like dental or skeletal fluorosis. Fluoride concentration in groundwater is governed by natural and anthropogenic interactions. The temporal and spatial concentrations of the ion vary depending on the source, process, and the nature of recharge. In addition, it interacts with other ions in water and tries to participate in thermodynamic reactions. The chapter provides a comprehensive overview from a global perspective by focusing on different sources, health issues of fluoride, distribution in groundwater, its association with different ions, heavy metals and isotopes, and different treatment methods adopted from various studies. The analytical techniques using ion selective, colorimetric, and other significant methods for the determination of fluoride adopted by different authors are also compiled. An overview is presented on the different geochemical plots, statistical techniques, and thermodynamic and modeling approaches to determine processes governing the fluoride in groundwater. The distribution of fluoride in groundwater from different countries is mapped with respect to lithology to reveal the significance of mineral source and the water–rock interaction process. Fluorite-bearing minerals, igneous, metamorphic, sedimentary rocks interactions, and anthropogenic activities in groundwater are leading to fluoride toxicity. The review infers that groundwater with higher fluoride concentrations was observed in several countries that spiked up to 160 mg/L. The hazard health risk index for fluoride in water would help to estimate the effects and preventive measures to be applied by different treatment techniques. An observation of the different treatment methods indicates that natural materials act as good adsorbents and can precipitate fluoride in different forms. Fluoride and its impact due to other associated species in water change the behavior of water, and accordingly, treatment methods such as reverse osmosis, nanofiltration, electrocoagulation, and Nalgonda technique can be adopted.