The Optimal Experimental Research on the Fluoride Removal from Efficient-Whirling Clarifier

Abstract

In this paper the experiment research of fluoride removal was based on coagulating sedimentation method, and the defluorination effect of coagulant’s kinds and dosage、parameters of rotational speed and coagulant aid’s dosage was studied and optimized, which could provide crafts parameters of efficient-whirling clarifier for engineering application . In this experiment, five coagulants was compared, which including aluminum sulfate (Al2(SO4)3)、potassium alum(KAl(SO4)2)、ferric sulphate（Fe2(SO4)3）、ferric chloride（FeCl3）and polyaluminium chloride（PAC）. Parameters of rotational speed applied in this experiment were simulated from the G state of efficient-whirling clarifier, while polyacrylamide was employed as the coagulant aid. The experiment results showed that: First, the defluorination effect of polyaluminium chloride was better than that of other coagulants. Second, the optimum parameters of rotational speed was that mixing at the speed of 400 r/min for 60 seconds，the first stage of coagulation at the speed of 160r/min for 7minutes、the second stage of coagulation at the speed of 90r/min for 8 minutes and sedimentation for 15minutes. Third, PAM was helpful for the defluorination effect of PAC. The fourth, when fluoride concentration in raw water respectively were 2.0mg/L、5.0mg/L、10mg/L, the dosages of PAC respectively were 400 mg/L、500mg/L、1300mg/L and the dosage of PAM respectively were that of PAM was 0.09mg/L、0.12mg/L、0.09mg/L, which could make the outlet of fluoride concentration achieved the national drinking water standard (GB5749-2006).