high conc fluoride removal 1

[fredE]

I need to remove 500-1000ppm Fluoride from a waste stream with a flowrate of 50,000gpd down to 4.5ppm, pH is 2. One suggestion was lime or RO. Are these the best options which will have minimal waste to dispose of?

 

[smile1]

with a pH of 2, lime will be expensive, although that is the typical method. Levels below 1 ppm are typical with lime at a pH of 7. I can only assume that the waste stream is to be recycled in the plant, with a pH of 2.

 

[bimr]

Your only option is lime precipitation.

You probably have other things in that analyses that you are not telling us about that would most likely foul an RO.

 

[cub3bead]

There is a F specific anion exchange resin but it is very expensive.

If you are going to discharge the water then you will have to get the pH up into the 6-9 range so the lime precipitation may be cost effective.

If the water chemistry is suitable for RO what are you going to do with the concentrate stream? The F concentration will be higher but you will have a smaller volume to deal with. You are going to need to raise the pH to protect the membranes.

If you are considering evaporation be careful as F attacks Ti.

 

[fredE]

The wastewater will combine with other streams which will raise the pH before being discharged. So pH adjustment is not an issue. The reject stream in RO is a reason we do not want to use RO. I have also read about using activated alumina, aluminum sulphate or CaCl2 to remove F. Are any of these a better choice than lime?

 

[Muggle]

AWS Consultants out of florida is doing some tests using lanthanum chloride - contact Art Suma at DCHPPAGE@aol.com for more info. The fluoride is from phosphate mine and the numbers are 1-2x higher then yours.

 

[JaccoH]

Dear fredE & others

Traditionally, neutralisation of fluoride-containing wastewater with lime is used. But frequently, the amount of lime required for neutralisation is insufficient for adequate fluoride removal. Furthermore, the separation of calcium fluoride from the wastewater is difficult and huge quantities of sludge are produced that might also contain other compounds in high concentrations. This bulky sludge often has to be disposed of as chemical waste.

Fluoride removal by crystallisation in a fluidised bed achieves effluent concentrations down to 5 (or even 2 mg/l with an additional filtration unit) in one reactor. The high upflow velocity of 40 to 75 m/h through the reactor results in a small footprint. The product is calcium fluoride pellets that are compact and virtually water free. They do not have to be landfilled but can be sold as a fluoride resource.

This technology is used for wastewater treatment or for removal of fluoride from water loops (reuse of water). When you search under the name " Crystalactor " you will probably find a supplier for this technology.

So FredE: The fluoride effluent concentration fits with your demand, the "waste" becomes a resource, the footprint is small and the technology is proven. I trust this has helped you

Jacco