Water Defluoridation

M. Pontie, C. Diawara, A. Lhassani, H. Dach, M. Rumeau, H. Buisson, J.C. Schrotter, Water defluoridation processes A review. Application Nanofiltration (NF) for future large-scale pilot plants, in A. Tressaud (Ed.), Advances in Fluorine Science, Vol. 2, Elsevier, Amsterdam, 2006, pp. 49-80. 

Although a lot of research has been reported on the use of various carbonaceous materials in defluoridation, no known column or full-scale plant operation is easily available in open literature. One reason for this is that most carbonaceous materials show poor adsorption capacity (Table 4) for fluoride and therefore only laboratory-scale performances have so far been reported. Amorphous alumina supported on carbon nanotubes on the other hand show high capacity (28.7 mgF/g adsorbent) for fluoride and is therefore a promising material for drinking water defluoridation. 

Limestone is another promising geomaterial for drinking water defluoridation. However, it has only been tested in wastewater containing high concentration of fluoride. In a research work by Reardon and Wang [60], limestone was used in a two-column continuous flow system (limestone reactor) to reduce fluoride concentrations from wastewaters to below the MCL of 4 mg/L for wastewater. Calcite was forced to dissolve and fluorite to precipitate in the first column. The degassing condition in the second column (did not serve to remove fluoride) caused the... 

Using coal-based sorbents, Sivasamy et al. [62] evaluated their ability to remove fluoride from water. On equilibrium basis, Langmuir and Freundlich models were used to describe the data points, while the kinetic data points were interpreted in terms of reaction and mass transfer processes. Kaolinite, adioctahedral two-layered (silica and alumina) silicate (1 2 type), has also been tested in drinking water defluoridation. Recently, Sugita etal. [58] and earlier Kau etal. [63] and Weerasooriya et al. [10] presented fluoride adsorption results of kaolinite. The fluoride-binding sites in kaolinite consist of aluminol and silinol sites. The authors explained that the fluoride-kaolinite interaction led to the formations of both the inner- and outer-sphere complexes. 

Fluoride-related health hazards are associated with the use of fluoride-contaminated water for drinking and cooking. This corresponds only to 2-4 L per capita per day. Fluoride removal in rural areas in LDCs, where centralized water treatment and distribution facilities are unavailable, should consequently be carried out at a household level and the system applied should be simple and affordable. In this regard, tea bag POU system becomes handy. Although this kind of system has not been specifically reported for water defluoridation, it has been tested for arsenic [37,107], It is therefore a short-term potential technique worth considering. In this technique, adsorption medium is placed in a tea bag-like packet, which is subsequently placed in a bucket of water to be treated. To ensure faster defluoridation kinetics, the bag should be swirled inside the water. It therefore operates like a batch reactor and hence requires a relatively longer adsorption time to achieve the permissible levels. Since the swirling motion is supposed to be human-powered, the technique would require a material with very fast kinetics or very fine adsorption media. 

Aluminum oxide present in soil has been utilized to make brick pieces of 15-20 mm sizes that are effective in drinking water defluoridation. When the... 

A. Menda, Tanzania challenges and successes of water defluoridation, Available at http //www.scienceinafrica.co.za/2004/july/fluoride, (Accessed in September 2005). 

Water Defluoridation Processes A Review. Application Nanofiltration (NF) for Future Large-Scale Pilot Plants... 

Gumbo, F.J. Mkongo, G. (1995) Water defluoridation for mral fluoride affected communities in Tanzania. In Dahi, E. Bregnhoj, H. 1st International Workshop on Fluorosis Prevention and Defluorination of Water, 18-22 October 1995 Ngurdoto, Tanzania, pp. 109-114. 

Hichour, M., Persin, R, Sandeaux, X, Molenat, X Gavach, C. (1999) Water defluoridation by Donann dialysis and electrodialysis. Revue des Sciences de TEau, 12, 671-686. 

Bone char is the oldest known agent for water defluoridation used since 1940s [7]. It has also been employed successfully for the removal of arsenic from groimd water. It is produced from animal bones (Fig. 4.4) that have imdergone calcination or pyrolysis processes. Though raw bones have some defluoridation value, it is low and limited by the various organics obstructing the interfaces where chemical reactions with the fluoride can take place [8]. 

Amir, H., Sadia, N., and Qaisar, M. Strategies for low-cost water defluoridation of drinking water-a review of progress. J Chem Soc Pak 32,550-555 (2010). 

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