Fluoride Removal by Contact Precipitation in Bone Char Column

摘要

The objective of this study was to investigate the contact precipitation process of fluoride on bone char in a continuous mode of operation, with particular focus on the influence of flow rate and bed depth. The experiment was designed to test five different flow rates and five different bed depths. Bone char used in this study had a grain size of 0.5 -1.0 cm, and was prepared by an ICOH incinerator operating at a partly calcination condition. The reactors were glass columns with [an] inner diameter of 2.6 cm supplied up-flow by pump. Feed water for the contact precipitation experiment was prepared by adding chemicals in CMU water supply in the molar ratio F: PO_4: Ca of 1: 1.5: 2.75. The target fluoride concentration was 10 mg/L. Bone char was packed in columns with different lengths to yield 5 different bed depths. The study bed depths were 10, 15, 20, 25 and 30 cm providing bed volumes of 53.10, 75.64, 106.18, 132.73 and 159.28 cm~3, respectively. All columns were tested at 5 different flow rates which were 200, 300, 400, 500 and 600 mL/hr. The results clearly showed that both flow rate and bed depth had effects on the fluoride removal capacity and efficiency of bone char. Based on the controlled conditions, the highest amount of water that had been treated was lower than 1.5 mg/L, the maximum contaminant level, was 35.38 L. The results revealed that the effect of bed depth is the predominant factor in this experiment.