2.3. Coagulation experiments
Two raw waters (synthetic water and river water) were used for the coagulation experiments. The synthetic water was prepared by adding kaolin to distilled water so that its turbidity became 10 NTU. Initial TAs concentrations of these waters were set to 100 μg/L. The pH of the synthetic water was 6.0. The river water was used to evaluate organic interference on coagulation efficiency. Its average characteristics are as follows; pH 8.1, alkalinity of 65 mg/L as CaCO3, DOC of 3.12 mg/L, and turbidity of 15.3 NTU. A main difference between these raw waters was organic content and alkalinity. There was no organic content and alkalinity for the synthetic water, while they were present in the river water. Since the difference in pH (6 and 8) and turbidity (10 and 15.3 NTU) between these raw waters was considered insignificant for coagulation efficiency, their adjustment was not given. While the raw water of 1 liter was mixed at 120 rpm, PACl was added as coagulant at dosages of 5∼60 mg/L. After 5 min of mixing, supernatant was filtered through a filter paper of 0.45 μm (Sartorius, Germany). The filtrate was then measured for its TAs concentrations.
2.3. Coagulation experimentsTwo raw waters (synthetic water and river water) were used for the coagulation experiments. The synthetic water was prepared by adding kaolin to distilled water so that its turbidity became 10 NTU. Initial TAs concentrations of these waters were set to 100 μg/L. The pH of the synthetic water was 6.0. The river water was used to evaluate organic interference on coagulation efficiency. Its average characteristics are as follows; pH 8.1, alkalinity of 65 mg/L as CaCO3, DOC of 3.12 mg/L, and turbidity of 15.3 NTU. A main difference between these raw waters was organic content and alkalinity. There was no organic content and alkalinity for the synthetic water, while they were present in the river water. Since the difference in pH (6 and 8) and turbidity (10 and 15.3 NTU) between these raw waters was considered insignificant for coagulation efficiency, their adjustment was not given. While the raw water of 1 liter was mixed at 120 rpm, PACl was added as coagulant at dosages of 5∼60 mg/L. After 5 min of mixing, supernatant was filtered through a filter paper of 0.45 μm (Sartorius, Germany). The filtrate was then measured for its TAs concentrations.
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