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|Other Titles: ||Removal of lead and antimony from water by chemical coagulation process|
|Authors: ||雷佳蓉;Lei, Chia-jung|
|Keywords: ||鉛;銻;混凝;多元氯化鋁;氯化鐵;Lead;Antimony;Coagulation;Polyaluminum Chloride;Ferric Chloride|
|Issue Date: ||2010-01-11 07:31:59 (UTC+8)|
研究結果顯示單位混凝劑劑量去除鉛之效果高低依序為多元氯化鋁（PACl）、氯化鐵(FC)、硫酸鋁(Alum)，鋁鹽或鐵鹽混凝pH範圍於7.0~8.5，鉛去除率可達80%以上。ㄧ般國內淨水場以沉澱水濁度控制混凝劑加藥量，當原水含鉛時，可採加強混凝提高混凝劑加藥量以降低清水鉛濃度。相對地，鋁鹽無法有效去除銻，其去除率低於25%；鐵鹽混凝可去除銻達70%以上。國內淨水場很少採用鐵鹽混凝劑，因此當原水含銻時，混凝操作需改採用鐵鹽混凝劑，可同時去除鉛、銻。鐵鹽混凝pH範圍於5.0~9.0皆可使銻(Ⅲ)去除率達70%以上，最佳pH範圍為5.5~6.5。去除銻(Ⅴ)所需單位鐵鹽混凝劑量為去除銻(Ⅲ)之1.43~2.76倍，前加氯將銻(Ⅲ)氧化為銻(Ⅴ)，需增加混凝劑加藥量3~5倍。鐵鹽混凝同時去除鉛、銻(Ⅲ)為主時可操作於pH 7.0，若以去除銻(Ⅴ)為主則需操作於pH 5.0。此外活性碳吸附及石灰軟化皆可去除鉛。因此，淨水場採加強混凝僅可提高鉛去除，若為同時提高鉛、銻去除，則鐵鹽混凝為最佳經濟可行技術。
The objectives of this study are to investigate the removal of lead and antimony from water by chemical coagulation process and to evaluate the treatment alternatives for water treatment plant to meet the new standards. Raw water of Nei-Wan Water Plant was selected in study to assess the removal efficiency. Lead and antimony were spiked into the water samples and standard jar tests were conducted to determine the effects of solution pH, turbidity, the types and dosage of coagulant, and pre-chlorination on the removal of lead and antimony from spiked water.
The results showed that the removal efficiency of Pb (Pb removal per mg/L of coagulant) was in order of PACl, FC, and Alum. With aluminum- or ferric-based coagulants, an 80% removal of Pb was achieved at pH 7.0 to 8.5. Most of the water treatment plants in Taiwan use settled water turbidity as a reference to choose the coagulant dosage, it is recommended that the treatment plants can adopt enhanced coagulation to remove Pb when the concentration of Pb in raw water can’t meet the water quality standard. As a comparison, a poor removal of Sb (<25%) by aluminum-based coagulant was obtained. However, the Sb removal efficiency can reach 70% when iron-based coagulant was used. Since the domestic water treatment plants in Taiwan seldom use iron-based coagulant, it is recommended that the iron-based coagulant is used when the Sb concentration in raw water is high. In this way, both Pb and Sb can be removed simultaneously. In general, a 70% Sb removal can be reached at pH 5.0 to 9.0 by iron-based coagulant, and the optimum pH is between pH 5.5 and 6.5. The dosage of iron-based coagulant required for Sb(V) removal was about 1.43 to 2.76 times higher than that for removal of Sb(III). Oxidation of Sb(III) to Sb(V) due to pre-chlorination increased the coagulant dosages for about 3 to 5 times. When iron-based coagulant was used, it was observed that simultaneous removal of both Pb and Sb(III) can be obtained at the ~pH 7.0, however, better removal for Sb(V) can only be obtained at the pH 5.0. Both active carbon adsorption and lime softening are very effective for lead removal. It is concluded that enhanced coagulation with aluminum-based coagulants is useful for Pb removal. When simultaneous removal of Pb and Sb is necessary, it is recommended that iron-based coagulant should be used.
|Appears in Collections:||[水資源及環境工程學系暨研究所] 學位論文|
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