Chemical mechanical polishing (CMP) wastewater in semiconductor manufactory is characterized as extremely stable dispersion of nano-size silica. Generally, coagulation- flocculation and sedimentation processes are employed by most of the semiconductor manufacturers in Taiwan. This treatment needs large area for sedimentation tank and takes long time to separate the precipitate. The Nano-sized bubble flotation technology with 2k Factorial Design and Central Composite Design of experimental design were used for treatment and reclamation of the CMP wastewater. The purpose of this study was to examine the effects of the operational variables on the efficiency of wastewater treatment and to find the optimization of the process performance. The results showed that the CMP wastewater could be treated suitably by using polyaluminum chloride as an activator and sodium oleate as a collector. The optimal operating conditions were as follows: concentration of polyaluminum chloride was between 50 and 60 mg/L as Al, the concentration of sodium oleate was between 5 and 10 mg/L, the pH values of the wastewater was between 4 and 5, the hydrolic retention time was 1 hour and the recycle ratio was between 10 and 20%. After this study, the experience gained in this study is useful for commercial process

Chemical mechanical polishing wastewater, Nano-sized bubble flotation technology, Design of experiment