Removal of Calcium from Semiconductor Wastewater Using a Fluidized Bed Reactor

• Main Authors: Toniady Tan, 陳佳慶
• Other Authors: 駱尚廉
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/91444129054119783446

碩士 === 國立臺灣大學 === 環境工程學研究所 === 100 === In this study, a fluidized bed reactor was employed to treat wastewater from reverse osmosis and cooling water system of one semiconductor industry in Taiwan. The main purpose was to reduce calcium content of the water for reuse. The treatment was done by crystallization in the fluidized bed reactor with quartz sand as the pellet media. The wastewater was supersaturated with calcium at different pH levels. Several chemicals were used to study the effect of nucleation on calcium removal rate. The experimental parameters include upward fluid velocity, dissolved ion concentrations in influent water and size of pebbles. The ionic concentrations of influent water were measured using ion chromatography. The crystals formed on the surface of sand were analyzed using scanning electron microscopy and x-ray diffraction. The optimum pH for effective removal was found to range from 9.5 to 10.5. The choice of chemical to be used to facilitate calcium removal depends on the concentration of carbonate in the waste water. For calcium concentrations and alkalinity used in this study, use of sodium carbonate could remove up to 99% of calcium, but resulted in a very high carbonate alkalinity. Sodium hydroxide could remove up to 60% of calcium and resulted in much clear water. Calcium hydroxide can remove up to 40% of calcium. Increasing the upward velocity resulted in better mixing and better removal. The bubbling into the reactor created a slugging bubble and decreased mixing efficiency in the reactor.