利用外加磁場降低暴雨期濁度之研究

Abstract

台灣地區暴雨發生時河川水的濁度可能上升至10000 NTU以上，淨水廠常因此被迫減量供水甚至關場停水。如何提升淨水廠對高濁度原水處理的能力，是目前不容忽視的問題。磁性絮聚分離技術 主要是利用磁性顆粒 (Fe3O4)與水中的污染物結合，再利用磁場對磁性顆粒的磁力作用將污染物與水分離，若能將此技術運用在高濁度原水的處理上，應可達到降低原水濁度、減少混凝劑之加藥量及污泥量的效果。 本研究針對高濁度的原水進行外加磁場之磁性絮聚實驗，藉由外加磁場所產生之磁力提供額外的吸引力，以提升混凝沉澱程序去除濁度的效率，並尋求適當的磁種添加量、混凝劑添加量、水質參數及外加磁場強度等操作條件，期望能達到降低原水濁度、減少混凝劑之加藥量及污泥量的效果。另外，本研究亦探討磁種回收再利用的可行性。 實驗結果顯示，以Fe2+/Fe3+混合溶液滴入鹼液的方式所合成之磁種磁性絮聚的效果最佳。且磁種經磁化後，磁性絮聚的效果會增強。本磁性絮聚分離技術可有效降低不同pH值、不同初始濁度以及不同地區之原水濁度。此外，添加少量混凝劑於磁性絮聚程序中，更可有效減少磁種劑量，達到降低加藥成本的目的。在磁種回收方面，陽離子界面活性劑 (CTAB)處理的磁種再生率最高可達99.8%。磁種經0.5CMC之CTAB再生後，重覆使用次數可高達5次。 關鍵字：濁度、磁性絮聚分離、磁性顆粒、外加磁場、 界面活性劑、再生率

In Taiwan, turbidity of rivers might rise to above 10000 NTU during rainstorm period which makes water treatment plants failed to supply applicative water. However, the technology of Magnetic Aggregation and Separation can offer an advantage of separating pollutant from water by magnetic force. In this research, high turbidity water treated by magnetic aggregation method with applied magnetic field is studied and the operating parameters are appropriate dosage of magnetite particles, dosage of coagulant, water quality parameters and the strength of applied magnetic field. In addition, the feasibility of reusing magnetite particles is also discussed. The results indicates that magnetite particles synthesized by Fe2+/Fe3+ mixing solution dripped into alkaline solution has the best efficiency of magnetic aggregation which also can be enhanced by magnetized magnetite particles. The method of Magnetic Aggregation and Separation can reduce the turbidity of raw water at different pH values, of different initial turbidity and from different areas. In addition, the addition of coagulant into Magnetic Aggregation Process can both reduce the dosage of magnetite particles and dosage cost. As for the recycle of magnetite particles, the regeneration percentage of magnetite particles treated by cationic surfactant can reach 99.8% and the magnetite particles regenerated by CTAB can also be reused up to 5 times. Keywords：Turbidity, Magnetic Aggregation and Separation, Magnetite particle (Fe3O4), Applied magnetic field, Surfactant, Regeneration percentage