污泥毯澄清池去除濁度、硬度及有機物之探討

Abstract

台灣地區淨水場使用污泥毯澄清設備之比例很高，然而卻缺乏對於此設備之研究，本實驗分別以人工原水以及高屏溪原水研究探討污泥毯處理濁度、硬度及有機物之效率及特性。 以人工原水處理之結果發現，當污泥毯形成穩定後，處理一定範圍內之原水濁度可維持其出流水濁度相同。污泥毯進流前之快混單元G 值不宜過大。因慢混時間越長可形成較大之膠羽，故加藥後至污泥毯前之時間愈長對於污泥毯形成及出流水質有所助益。當污泥毯形成後，出流水濁度以粒徑分布在25 µm以上之顆粒為主。污泥毯單元在以鋁鹽做為混凝劑，劑量為60 mg/l時，可去除約80%之TOC，操作pH值在4~8均有TOC去除之效果，但pH < 3時污泥毯會淘洗出TOC。 由處理實際原水得到，當進流水中含有硬度，提高操作pH至9.5時，可提升污泥毯澄清池對硬度及濁度之去除效率。碳酸鈣及碳酸鎂能增加污泥毯之緻密度，進而降低出流水濁度。當進流水中含有250 mg/L as CaCO3之硬度時，提高pH為9.5後，以PACl或Alum作為混凝劑皆能達相近之濁度及硬度去除效果。即使減少混凝劑添加劑量，或提高進流流速，仍皆可獲良好之殘餘濁度。

Floc blanket Clarifiers have been scarcely studied although they are wildly used in Taiwan. This research discusses the removal characteristics of turbidity, hardness and TOC by floc blanket using synthetic water and the water from the Kao-Ping River as target waters. In the experiment with the synthetic water, a range of turbidities were treated with the same effluent turbidity. The G in the rapid mixing must be kept small to protect the flocs. The introduction of delay time between the addition of a coagulant and its entry into the floc blanket leads to improved settled water due to the formation of bigger flocs in longer flocculation time. After the floc blanket stabilized, the particles in the effluent are mostly larger than 25 µm. When using aluminum sulfate as coagulant at dosage of 60 mg/l, 80% TOC was removed by the floc blanket. The pH must be kept between 4 and 8 for effective operation. If the pH is left lower than 3, the TOC will be washed out. Results with the Kao-Ping River water shows that, maintaining pH at 9.5 can increase the efficiency of turbidity and hardness removals. The presence of CaCO3 and MgCO3 can increase the density of the floc blanket which decreased the turbidity of the effluent. At raw water condition of hardness 250 mg/l as CaCO3 and pH 9.5, similar turbidity and hardness removals can be achieved by both Alum and PACl. The effluent quality would not be affected by increasing the flow rate or decreasing the dosage.