Abstract
This paper describes the development of defluoridation of water by contact precipitation, where fluoride water is mixed with calcium and phosphate and brought in contact with bone char which is already saturated with fluoride. The process is studied in jar test, in manually stirred buckets and in continuously fed columns. Furthermore in a “fill, mix and filter” column both in laboratory and in a pilot plant for a period of two years. An appropriate setup is then designed and constructed using low-cost, corrosion-resistant and robust locally available materials. The removal efficiencies obtained in the batch systems were relatively low especially when manually stirred. The fill, mix and filter technique demonstrated surprisingly high removal efficiencies, 95-98 %, without any sign of break through or saturation, at dosage levels corresponding to calcium/phosphate/fluoride weigh ratio of 8.5/10.8/1. It is discussed that the main processes behind may be a crystal growth or a catalysed precipitation of fluorapatite and/or calcium fluoride, as the components are brought in close contact with fluoride saturated bone char.
| Original language | English |
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| Title of host publication | Proceedings of the 2nd International Workshop on Fluorosis Prevention and Defluoridation of Water |
| Editors | Eli Dahi, Joan Maj Nielsen |
| Number of pages | 10 |
| Publication date | 1997 |
| Pages | 128-137 |
| Publication status | Published - 1997 |
| Event | 2nd International Workshop on Fluorosis and Defluoridation of water - Nazreth, Ethiopia Duration: 19 Nov 1997 → 25 Nov 1997 |
Conference
| Conference | 2nd International Workshop on Fluorosis and Defluoridation of water |
|---|---|
| Country/Territory | Ethiopia |
| City | Nazreth |
| Period | 19/11/1997 → 25/11/1997 |
Keywords
- Defluoridation
- Drinking water
- Contact precipitation
- Bone char
- Pilot plant
- Tanzania
- Removal mechanisms
- Fill, mix and filter technique
- Apatite
- Crystal growth