Since the technology of product process continuously is improved some of the specific pollutants potentially cause serious problems on operation and treatment of the wastewater treatment plant in the industrial parks. Further, these pollutants could increase the cost of operation and maintainance for the wastewater treatment plant. Thus, it is important to set up reasonable fee criteria for these specific wastewaters. The purpose of this study is to evaluate the effects of chemical mechanical planarization (CMP) wastewater on the removal efficiency of chemical treatment process in a wastewater treatment plant. Moreover, characteristics of the wastewater including high turbidity, low suspended solid (SS) and micro-size particles, which result in interference on the floc formation in the coagulation process, are also investigated.
The results indicated pH value of the wastewater reaches limit level that generated the highest effect on the floc formation. It is suggested that the optimum coagulant (aluminum sulfate, Al2(SO4)3) dose is 350 ppm when the pH level is adjusted to 10. However, without the CMP wastewater, the optimum coagulant dose for the general wastewater decreases to 50 ppm. The optimum dose for the simulated synthetic water is 100 ppm. When the raw wastewater mixed with the CMP wastewater was filtrated using the 0.45μm and 0.2μm filters, the optimum dose of the mixed wastewater is 50 ppm that is equal to general wastewater. Moreover, if the wastewaters were classified based on the pollution sources, the added amount of aluminum sulfate in CMP wastewater is two times than that of in general water with the similar coagulation efficiency.
The fee criteria about wastewater discharged into wastewater treatment system in the industrial park is performed based on the concentration of SS through 1μm filter. In this case, the measured SS concentration cannot reflect on the pollution level for the CMP wastewater because some of the SS in the CMP wastewater can penetrate the 1μm filter. We suggested that the 0.45μm filter is used to measure SS concentration of the CMP wastewater which is a proper way for the cost assessment. Moreover, the increase in the fee according to the SS concentration is approximate 40%, which reduce the loading of operation cost.