近年來由於暴雨期間強烈颱風發生的頻率節節攀升，台灣地區的山勢陡峭、河短湍急，集水區的水土保持不當，加上九二一大地震對地貌造成的傷害，每逢暴雨侵襲，鬆動的表土或是裸露岩層中的細泥便藉著河水的沖刷被帶入水庫當中，造成原水濁度攀升甚至達數十萬NTU，也對水庫的造成嚴重的淤積。如此高濁度的原水常造成淨水場處理程序停擺，避免淨水單元遭受更嚴重的損壞，對於民生及工業用水影響至鉅。 磁種凝絮技術已經被廣泛的運用在廢水中污染物的去除，如含有重金屬、有機物、硝酸鹽、砷等廢水，皆具有相當好的去除效果，藉由外加磁場更可有效提升去除效率。本研究利用磁種凝絮技術將奈米級磁性顆粒(F3O4)加入高濁度原水中，藉由顆粒表面電性相異所產生的吸引力，形成帶磁性的凝絮物，再以外加磁場提高凝絮物的沉澱效果，並結合傳統混凝程序，降低磁性顆粒的添加量。 實驗結果顯示原水的殘餘濁度會隨著奈米顆粒之加藥量增加及原水pH值的降低而提升，且磁混後原水pH具有穩定維持在中性的作用，水中有機物亦可經由磁混而被部分去除，且外加磁場強度對沉降速率有明顯的提升，可將沉澱時間從30分鐘縮短到3分鐘即可達成相同去除效果。將磁混與傳統混凝程序結合可有效減少奈米顆粒及混凝劑的加藥量，分別達到原最佳加藥量的1/3及1/10，且對原水的鹼度消耗亦可明顯減少，最後磁性顆粒的回收率及再用時的濁度去除率也分別高達95%及90%以上。 In recent years, the frequency of strong typhoon increases and causes the turbidity of source water even exceeds 100,000 NTU during storm season. The upper limit of turbidity for the potable water treatment is about 2,000 NTU, or the water treatment plant will shut down to protect the purification units. The water supply system is broken down during this period. Magnetic seeding aggregation (MSA) has been used to treat contaminants in wastewater, such as ferrihydrite, arsenic, organic matters, and nitrogen compounds. In this research, removal of turbidity using magnetite nanoparticle were studied. The raw clay attracts to magnetite by the opposite sign of charge on the surface of two types of particle. The external magnetic field was applied to remove the magnetic aggregates. Then the magnetic seeding aggregation was combined with traditional coagulation process to decrease the dosage of magnetite and PACl. The results showed that the final residual turbidity decreased with increasing dosage of magnetite and decreasing pH of raw water. Some of the organic matters were also removed after magnetic seeding aggregation. The settling velocity of the magnetic aggregates increased obviously after the external magnetic field was applied. Combining the MSA with traditional coagulation process, the dosage of magnetite and PACl are decreased to 1/3 and 1/10 of the optimal dosage, respectively. The recovery ratio of magnetite and the removal efficiency of recovered magnetite are over 95% and 90%, respectively.
