Treatment of Tunnel Construction Wastewater by Microfiltration

• Main Authors: Yi-wen Tsai, 蔡逸文
• Other Authors: Jhy-Chern Liu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/bz5gtr

碩士 === 國立臺灣科技大學 === 化學工程系 === 94 === Silica scaling is a common problem in industrial water use. Silica is also a foulant of membrane process, and it limits the usage of water. The major objective of this study was to investigate the coagulation and microfiltration processes for synthetic tunnel construction wastewater treatment. In this study, the optimal coagulation conditions were assessed through jar test. Experimental results indicated that both calcium chloride and magnesium chloride could react with soluble silica to form silicates and catalyzed the reaction of silica polymerization. Satisfactory turbidity and silica removal were achieved as a result. Magnesium chloride was found to induce higher silica removal efficiency than calcium chloride. Effects of coagulation pretreatment and operation conditions, such as transmembrane pressure and cross-flow velocity were investigated in microfiltration experiments. Pretreatment by calcium chloride resulted in higher permeate flux, and more moderate flux decline. Coagulation by magnesium chloride, though obtaining wastewater low in soluble silica, resulted in serious membrane fouling. Increasing operation pressure was found to induce higher initial permeate flux but faster flux decline as a result. Cross-flow velocity did not show significant effect on the permeate flux. According to some standards, the reuse of treated water in concrete or injection slurry may be limited by the chloride ion concentration.