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Water Supply Engineering
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Fluorides in drinking water must neither be totally absent nor should exceed an optimum value of about 1 ppm. To ensure this, fluorides are added to waters found deficient in fluoride concentrations, under a process known as fluoridation. When the fluoride concentration in given water exceeds the limiting value of 1–1.5 ppm, the fluorides are removed from water under a process known as defluoridation. Fluorides may enter the human body through drinking water 96%–99% of it combines with bones, since fluorides have affinity for calcium phosphate in the bones. Excess intake of fluoride can lead to dental fluorosis, skeletal fluorosis, or nonskeletal fluorosis.
Cyclic variation of fluoride contents with time in a granitic aquifer in semi-arid region
Published in M.M. Sherif, V.P. Singh, M. Al-Rashed, Hydrology and Water Resources, 2020
Fluoride, an electronegative element is highly reactive and combines with most of the elements to form ionic or covalent fluorides. Areas with semi-arid climate, crystalline igneous rocks and alkaline soils are mostly affected (Handa 1975; Frencken 1992). Fluorite (CaF2) is the principle bearer of fluoride and is found in granite, granitic gneiss and pegmatite, (Rama Rao 1982). Through weathering of the primary minerals in rocks, fluoride is released to the soil and groundwater i.e. leaching of fluoride-containing minerals may yield fluoride in solution. Apart from natural sources, considerable amount of fluoride may be contributed due to anthropogenic activities. Phosphatic fertilizers, which are extensively used in agriculture often, contain fluoride as impurity, which are being leached down to the saturated zone by return irrigation flows. In water, fluoride can form a number of complexes or exist in free form, eventually precipitating as fluorite (Handa 1975; Alveteg and Jonsson, 1991). High concentrations of fluoride ions cause dental fluorosis (disfigurement of the teeth). At the same time, a concentration less than 0.8 mg/l results in dental carries. Hence, it is essential to maintain the fluoride concentration between 0.6 to 1.2 mg/l in drinking water (WHO 1984). If the limit is below 0.6 mg/l, water source need not be rejected but suitable public health measures should be taken. The highest desirable and maximum permissible limits for fluoride as prescribed by Indian Council of Medical Research are 1.0 and 1.5 mg/l respectively.
Water/Wastewater Math Operations
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
Note: The key terms used in this chapter are defined as follows: Fluoride—It is found in many waters. It is also added to many water systems to reduce tooth decay.Dental caries—It is commonly known as tooth decay.Dental Fluorosis—It is the result of excessive fluoride content in drinking water, causing mottled patches in discolored teeth.
Urinary fluoride and micronutrients intake in children from San Luis Potosi, Mexico
Published in International Journal of Environmental Health Research, 2022
Lizet Jarquin-Yañez, Jaqueline Calderon Hernandez, Laura Gonzalez, Nelly Molina-Frechero, Jose de Jesus Mejia-Saavedra
When fluoride is consumed in excessive amounts, it can be toxic in the human body. One of the main public health problems in Mexico is dental fluorosis, registering a prevalence close to 100% in areas where the concentration of fluoride in water ranges between 2.0 and 2.5 mg/L (García-Pérez et al. 2020). According to the World Health Organization (WHO) and NOM-127-SSA1-1994 the limit allowed in drinking water is 1.5 mgF/L in order to avoid dental and skeletal fluorosis and neurological, reproductive, and kidney damage (NOM-127-SSA 1996; ATSDR 2003). However, health effects have been reported at lower concentrations of fluoride in drinking water and other factors have been involved such as genetics, altitude, diet, and malnutrition (Aguilar‑Díaz et al. 2016; Jarquin-Yañez et al. 2018). A higher prevalence of the most severe cases of dental fluorosis has been reported in children with low height-for-age in areas where the concentration of fluoride in water was above 1.5 mg/L (Irigoyen-Camacho et al. 2016).
Evaluation of ground water quality and health risk assessment due to nitrate and fluoride in the Middle Indo-Gangetic plains of India
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Jitendra Maurya, Satya Narayana Pradhan, A. K. Ghosh
The groundwater fluoride concentration varied between 0.2 and 21.1 mgL−1 with a mean value of 4.06 mgL−1 and approximately, 84% of the samples contained fluoride concentration above permissible limit of 1.5 mgL−1 (World Health Organization (WHO)) 2011) and approximately 76% of the sample contains fluoride content above the permissible limit of 2.0 mg L−1(USEPA (U.S. Environmental Protection Agency) 2010). Only 2.7% of the samples were well within the optimum level of 0.5 to 1.5 mg L−1 and fluoride concentration equivalent to 14 times higher than the permissible limit (1.5 mg L−1) was found in one of the samples of the study area. However, considering the Indian guidelines of drinking water, about 93% of the water samples were above the permissible limit of 1.0 mg L−1 (Bureau of Indian Standards (BIS) 2012) for drinking purposes. Fluoride is one of the most substantial pollutants in the aquifer, overexposure of this cause skeletal fluorosis in children and adults (Narsimha and Rajitha 2018). Dental fluorosis is a very common health problem in children during the production process of teeth around the world (Yadav et al. 2019).
De-fluoridation of drinking water by co-precipitation with magnesium hydroxide in electrolysis
Published in Cogent Engineering, 2018
Tomonori Kawakami, Miki Nishino, Yuki Imai, Hikaru Miyazaki, A.A.G.D. Amarasooriya
An electrolysis system composed of carbon electrodes and two cells separated by a diaphragm was developed to remove fluoride from drinking water. Excess fluoride in drinking water has caused dental fluorosis and skeleton fluorosis mainly in developing countries. The number of the patients is estimated as more than 70 million. The electrolysis system needs no chemicals, and provides easy operation. The system performance highly depends on fluoride concentration and magnesium concentration, since fluoride is removed by co-precipitation with magnesium hydroxide which formed in the cathode cell with an increase of pH value. The applicability of the system was examined by using synthesized water and actual well water having various magnesium and fluoride concentrations. The applicability of the system to decrease the fluoride concentration less than 1 mg/L was estimated by using fluoride and magnesium of the Sri Lankan well water. It was found to be as high as 70–80%.