Fluoride in Drinking Water and Its Removal

Centre for Rural Development and Technology, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi, India.
Journal of Hazardous Materials (Impact Factor: 4.53). 10/2006; 137(1):456-63. DOI: 10.1016/j.jhazmat.2006.02.024
Source: PubMed


Excessive fluoride concentrations have been reported in groundwaters of more than 20 developed and developing countries including India where 19 states are facing acute fluorosis problems. Various technologies are being used to remove fluoride from water but still the problem has not been rooted out. In this paper, a broad overview of the available technologies for fluoride removal and advantages and limitations of each one have been presented based on literature survey and the experiments conducted in the laboratory with several processes. It has been concluded that the selection of treatment process should be site specific as per local needs and prevailing conditions as each technology has some limitations and no one process can serve the purpose in diverse conditions.

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Available from: Meenakshi Arora, Jul 01, 2015
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    • "Reverse osmosis (RO) can completely defluoridate water, but in practice, it depends on the level of pressure applied and membrane capacity [Meenakshi, Maheshwari 2006]. This process is energy intensive and it is not cost-effective. "
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    ABSTRACT: This study evaluates the feasibility of using tamarind (Tamarindus indica) seed powder for de-fluoridation of fluoride contaminated water. Batch study confirmed that tamarind seeds in dry powder form could remove 87% of fluoride from water. This bio-sorbent can be used effectively in areas where fluoride concentrations are above the permissible limits of 1.5 mg-l-1 as per WHO Standard, 1984. Tamarind seed powder was incorporated in a matrix of sodium alginate and made into gel-beads. The beads were tested for de-fluoridation efficiency by conducting column studies. The effect of various factors, such as flow rate, retention time, and the number of runs on the efficacy of fluoride removal was also studied. The results revealed that flow rate did not seem to have much effect on the percentage fluoride removal but the fluoride concentration decreased drastically upon greater retention time and multiple runs.
    Ecological Engineering 10/2015; 16(4):8-13. DOI:10.12911/22998993/00000
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    • "Fluoride removal methods can be divided into membrane and adsorption techniques. Membrane techniques include reverse osmosis (Meenakshi and Maheswari, 2006), nano-filtration (Tahaikt et al., 2007) and electrodialysis (Kabay et al., 2008). Adsorption techniques are easy to use and a lot of adsorbents have been investigated. "
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    ABSTRACT: The preparation of composite adsorbents for fluoride anion was performed from natural cow dung and cow dung impregnated by a solution of calcium and iron salts. These starting materials were dried and carbonized at 300, 500 or 700 °C for 2 h leading to Cow Dung Carbon (CDC) or Ca–Fe Impregnated Cow Dung Carbon ICDC. All these carbons were used as adsorbent in fluoride removal studies. Batch mode experiments using CDC and ICDC were conducted in which the fluoride removal varied linearly as a function of contact time, pH, adsorbent dose, initial fluoride concentration, temperature and interfering anionic species. Both kinetic and isotherm based models were checked for the applicability of the present fluoride sorption system onto CDC and ICDC. For carbonization at 300 °C, the doping with Ca and Fe increased the defluoridation activity. The most efficient carbon was CDC which was prepared at 500 °C. It showed a defluoridation activity of 15 mg g−1. This carbon was made from renewable cow dung without the need of a chemical activation. However, the recycling of F-loaded adsorbents may be carried out by washing in alkaline solution. CDC and ICDC were analyzed by scanning electron microscopy and X-ray diffraction in order to understand the reasons of their excellent defluoridation capacity. The growing of plants requires the consumption of essential inorganic nutrients such as Ca, Mg, and P which are known to be fluorophilic elements in fluoride adsorbents. After ingestion and digestion of plants by ruminants, some of these nutrients remained in cow dung and then in the corresponding carbonized materials where they acted as fluoride scavenger. This exceptional defluoridation capacity of CDC allows their use in rural countries.
    Arabian Journal of Chemistry 07/2015; 9. DOI:10.1016/j.arabjc.2015.06.028
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    • "Based on the mechanism of fluoride removal, the methods can be categorized into chemical precipitation by lime and alum (Meenakshi and Maheshwari, 2006), adsorption on to activated alumina, clay materials, and industrial waste residue (Feleke, 2001; Ghorai and Pant, 2005; Maliyekkal et al., 2008; Moges et al., 1996; Nigussie et al., 2007); ion exchange by membranes, synthetic resins, and bone char (Ayoob et al., 2008; Kaseva, 2006; Mjengera and Mkongo, 2003; Solangi et al., 2009; Viswanathan and Meenakshi, 2009); and by membrane technologies such as reverse osmosis and electro-dialysis (Kabay et al., 2008; Sehn, 2008). The methods used by industrialized countries such reverse osmosis, electro-dialysis, and ion exchange require more technical support for operation and maintenance and the capital investment cost is high (Meenakshi and Maheshwari, 2006). Despite such efforts, rural communities in the several regions of developing countries are consuming water with fluoride content that exceeds the recommended level. "
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    ABSTRACT: In this study, the removal of fluoride from water using aluminium hydroxide based adsorbent has been investigated in continuous operation. The effect of fluoride influent concentration, feed flowrate, and adsorbent bed height onto the breakthrough characteristics of the adsorption system were examined. The fixed-bed adsorption system was found to perform better with lower influent fluoride concentration, lower flowrate, and higher bed depth. Thermodynamic evaluation using the bed depth service time model indicated that the fluoride adsorption capacity was 25.8 mg F−/g of adsorbent, which is high compared to commercially available activated alumina (1.8 to 1.9 mg/g). Kinetic studies showed that the rate of adsorption in continuous studies was in the range of 6.12 × 10−3 to 39.3 × 10−3 L/mg.h under different operating conditions. The household defluoridation unit (HDU) was tested at an up-flow mode and it was determined that the HDU packed with 0.9 kg of adsorbent with 28.3 cm of bed depth resulted in a specific safe water yield of 823.79 L. Regeneration of the exhaust media using 1% NaOH and 0.1 M HCl showed that the adsorbent could be reused. The estimated running cost of the unit was 2.0 U.S. dollar/m3 of treated water, with the potential to minimize further. Hence, it was concluded that the proposed method is simple and exhibits superior performance for the treatment of fluoride-contaminated water with the potential for household application.
    Water Environment Research 06/2015; 87(6). DOI:10.2175/106143014X13975035525627
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Questions & Answers about this publication

  • Ljubomir Jacić added an answer in Toothpastes:
    Should we still accept flouride to be added to our toothpaste and to the water we drink in our homes?

    Fluoride toothpastes sold in the United States bear the following poison warning:

    “WARNING: Keep out of reach of children under 6 years of age. If you accidentally swallow more than used for brushing, seek professional help or contact a poison control center immediately.”

    Small doses (0.1 to 0.3mg,kg) of fluoride can induce symptoms of acute fluoride toxicity.  A child weighing 10 kilograms,  can suffer symptoms of acute toxicity by ingesting just 1 to 3 milligrams of fluoride in a single sitting.

    Source: http://fluoridealert.org/studies/acute03/

    Ljubomir Jacić

    Dear @Vilemar, different oppinions among ordinary people and the experts! "...The daily supplementation with fluoride is undoubtedly an important preventing factor in protecting teeth from caries, and, as an important mitogenic stimulus for osteoblasts, it may enhance mineral deposition in bone, but on the other hand fluoride, above a threshold concentration, has been demonstrated to be toxic..." Here are some good research about!

    The attached paper on toothpastes on the Belgian Market brings very good methodology and analysis!

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