| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 101 === The source water with abundant algae and organic matter would lower the operational performance and worsen the quality of water supply for Tai-hu Water Treatment Plant (WTP) in Kinmen. Chlorination precede coagulation has been commonly used to reduce the activity of algae for WTP, which substantially facilitates the destabilization of algae. However, various trihalomethanes can be formed with chlorination to significantly affect the quality of water supply. Oxidation and coagulation-flotation process has been conducted with different raw water to investigate the interaction of chlorination with NaOCl and ClO2 between algae and organic matter. The effect of chlorination strategy before Alum and polysilicate iron (PSI) coagulation on the removal in algae and organic matter by flotation was also investigated to establish the optimal pre-chlorination strategy for improving the performance of coagulation and flotation for Tai-hu WTP. The results have shown that the majority of algae is Cylindrospermopsis (> 80,000 cells/mL) and organic matter (> 20 mg/L) exist in the mixed raw water from Tai-hu and Tain-Pu reservoirs. Algae cells suffer damage and break up when the chlorination with NaOCl and ClO2 was carried out, which result in the increase in the concentration of hydrophilic organic matter with less than 1 kDa in molecular weight. However, the removal in hydrophobic organic matter and Cylindrospermopsis can be effectively improved by flotation coupled with Alum or PSI coagulation and the total trihalomethane production potential (TTHMFP) can be substantially reduced. The algae counts are lower than 10,000 cells/mL and the concentration of organic matter is around 10 mg/L in the mixed raw water from Tai-hu and King-hu reservoirs, where the majority of algae is Microcystis exist. The majority of algae break up for NaOCl chlorination with and without ClO2, which effectively improves the removal in algae. However, the increase in the concentration of organic matter along with hydrophobic organic matter with larger than 10 kDa in molecular weight was occurred. Then, the removal in organic matter is poor by flotation coupled with Alum and PSI coagulation, and then the TTHMFP cannot be effectively reduced.
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