| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 99 === Face-centered central composite design (FCD) model, a model that belongs to the response surface methodology (RSM), was used in this study to obtain the optimum operating conditions for less corrosion rate and less release of iron in the solution. Then, the best operation condition is found out through simultaneous optimization technique.
In the research, the ductile-iron of coupon is used for the bench-scale test, and the factors tested are pH (6.0-8.5), alkalinity (50-150 mg/L as CaCO3), chlorine (0.2-1.0 mg/L), phosphate inhibition (0-1 mg/L as P), contact time (2-10 days), temperature (6-38℃) and rotation (0-140 rpm). The selected range of the factors mentioned above is based on the literatures and the present drinking water standards of Taiwan.
According to fractional factorial design, the most significant factors affecting corrosion rate are temperature, rotation and alkalinity. On the other hand, pH, contact time and temperature are the main factors affecting the release of iron in the solution. Finally, pH, alkalinity and temperature are selected to build the corrosion models using response surface methodology. Based on the models, the combination of operation condition with less corrosivity in terms of weight loss of test coupon and release of iron in solution is at temperature of 6℃, pH of 8.5 and alkalinity of 50-130 mg/L.
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