Views: 0 Author: Site Editor Publish Time: 2023-09-22 Origin: Site
Activated alumina is used to remove fluorine from drinking water. When the arsenic content in raw water exceeds 0.05mg/L, the process parameters of defluorination should be confirmed by experiment. In the defluorination process using activated alumina as filter material, the fluorine content of raw water in the defluorination filter should be less than 10mg/L, and the suspended matter should not exceed 5mg/L.
The particle size of activated alumina should not be larger than 2.5mm, and it should generally be 0.4 ~ 1.5mm. Activated alumina should meet the mechanical strength. Before the raw water contacts the filter material, it is appropriate to reduce the pH value, and the decline value should be confirmed by technical and economic comparison, and it is generally appropriate to adjust to between 6.0 and 7.0. Raw water can be selected to add sulfuric acid, hydrochloric acid, acetic acid and other acidic solution or add carbon dioxide gas to reduce the pH value, the dosage should be calculated according to the alkalinity and pH value of raw water or confirmed by experiment.
The filter speed can be selected in the following two ways:
(1)When the filter inlet pH value is larger than 7.0, the continuous operation mode should be selected, and the design filter speed is 2 ~ 3m/h, the continuous operation time is 4 ~ 6h, and the continuous operation time is 4 ~ 6x.
(2)When the influent pH value is less than 7.0, the continuous operation mode can be selected, and the filter speed is 6 ~ 10m/h. The flow of raw water through the filter material layer can be selected from bottom to top. When choosing sulfuric acid solution to adjust pH value, the top-down method should be selected. When choosing to adjust pH value with carbon dioxide, it is appropriate to choose bottom-up method. The fluoride content of the effluent at the end of the defluorination cycle of individual filter can be slightly higher than 1mg/L, and the fluoride value at the end should be confirmed according to mixing conditioning, but the fluoride content of the treated water after mixing should not be larger than 1.0mg/L.
The periodic adsorption capacity of filter material is mainly selected according to the fluoride content of raw water, pH value, filtration speed, filter layer thickness, final fluoride content and filter material performance.
(1)When the pH value of sulfuric acid solution is 6.0 ~ 6.5, it can generally be 4 ~ 5g(F)/kg(Al2O3).
(2)When the pH value of carbon dioxide is 6.5 ~ 7.0, it can generally be 3 ~ 4g(F)/kg(Al2O3).
The thickness of individual filter material should be selected according to the following provisions:
(1)When the fluorine content of raw water is less than 4mg/L, the thickness of the filter material should be greater than 1.5m;
(2)When the fluoride content of raw water is 4 ~ 10mgL, the thickness of the filter material should be greater than 1.8m.
Note: When pH value is adjusted with sulfuric acid, the planning is small and the filtration speed is low, the thickness of the filter layer can be reduced to 0.8 ~ 1.2m.
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