Effect of the mixing intensity on the sludge floc strength and dewatering performance

• Main Author: 黃瑞益
• Other Authors: 吳志超
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/04561127327415222783

碩士 === 逢甲大學 === 土木及水利工程研究所 === 88 === The effect of conditioning mixing intensity on the floc strength and the dewatering efficiency of alum sludge were focused in this study. At first, we examined the available operation condition of Couette flocculator used for polymer-conditioning mixing and the sensitivity and the reproducibility of floc strength measurement were also assessed. CST value, supernatant turbidity and floc strength coefficient were applied to indicate the floc strength of sludge. Centrifugation and Vacuum Filtration were respectively used to determine dewatering performance of the test sludge. In this study, alum sludge was used as the test samples. For producing the Taylor flow in the Couette flocculator, the solid content of sludge is limited under 2.5 % and the mixing G value is set within 100~360S-1. According to the compare result of floc strength measurement, the supernatant turbidity shows a better sensitivity and reproducibility than the CST. Polymer addition can enforces the floc strength of sludge and reduces the floc destruction by the mixing shear. However, the conditioned sludge with high floc strength could not produce a better dewatering efficiency of vacuum filtration. As the lower mixing intensity condition（Gc×t＝4,000）, there were litter influence on the floc strength and the dewatering performance with the different Gc/t ratio performed. As the higher mixing intensity（Gc×t＝15,000）, a weaker floc was produced under a high Gc/t ratio made. Further, the increasing in mixing intensity (with constant t) would form a small and strong floc but produced a distinct dewatering efficiency by the different dewatering force. In conclusion, for attaining a satisfied dewatering performance, the floc strength of sludge should be put in consideration. The sludge having an high floc strength is suggested for centrifugation dewatering and a middle strength is for vacuum filtration.