asked 8 April 2016 asked by nicolas_gerard (330 points)
Hi, Coagulation-flocculation is normally a good treatment option, but that requires high levels of sulfates or poly-aluminum sulfates. Lime treatment is also quite effective, but the water must contain a lot of magnesium. At at the moment, one of the most common treatments is activated-alumina filters which reduce fluoride through adsorption. The amount of activated alumina will depend on your effluent flow, and you will need to perform lab testing because the retention capacity is highly variable depending on several different parameters. Phosphate-rich carbon is also an effective adsorbent. In any case, you need to factor in regeneration (sulfuric acid or aluminum sulfate for alumina) I suggest you try activated alumina filters as a pilot project.
Hi, HOIST makes a liquid lime product NEUTRALAC SLS 45 to precipitate fluorides in metal industry effluent. If you combined it with PAC, you might get the results you need. Here’s a link: http://www.lhoist.com/us_en/market-segment/wastewater-and-sludge