淨水程序中溶解性有機物之去除：生物濾床及污泥毯澄清池之操作評估

Abstract

摘 要 臺灣地表水源普遍受到有機物及氨氮之污染，該等有機污染物之存在，不僅干擾淨水處理效能，且也殘存於處理後清水中，衍生配水管網生物性水質之不穩定，其解決方法之一，乃於傳統淨水處理程序前增設生物濾床處理設備，而該設備對有機污染物之去除效能及對後續混沉程序之去除效能產生何種影響，係值得探討之課題。污泥毯澄清池係目前臺灣地區重要之濾前淨水處理單元，以往之研究大多關注於濁度之去除，當原水存在有機物時，該有機物種類及含量對於污泥毯澄清池去除效能影響如何，為亟待探討課題，因此有必要針對上述課題進行研究，以供提升淨水處理效率之參考。 本研究先以連續進流處理實場原水方式，通過填充網狀PU泡棉之生物濾床，探討生物濾床對有機物之去除效率及對後續混沉程序去除濁度之影響。此外，以腐植酸及水楊酸模擬水中存在之大、小分子量有機物，添加於含高嶺土濁度之人工原水，探討該等有機物對於污泥毯澄清池之泥毯形成及操作效能之影響。 研究結果發現生物濾床去除有機物部份，在控制適當操作模式下，實場原水有機物與氨氮可被有效去除達30 %及95 %以上。欲有效去除氨氮，可採取實施反沖洗操作搭配較短之空床接觸時間，或較長之空床接觸時間搭配不進行反沖洗操作來達成其效果;欲有效去除溶解性有機物，可採取較短之空床接觸時間搭配不實施反沖洗操作來達成其效果，原水經生物濾床前處理後，在pH 6.5-7.5下進行混凝沉澱，對濁度有較高之去除率，而在pH 5.5-6.5下進行混凝沉澱，對有機物有較高之去除率。 在污泥毯去除有機物部份，若原水中含有大分子有機物-腐植酸存在時，可促進加速生成穩定之泥毯，然而所生成之泥毯含有之固體濃度較低。若原水中含有小分子有機物-水楊酸存在時，則有相反之結果，縱使如此，若水中存在此二種有機物，可提升污泥毯澄清池去除濁度之效果，而且大分子有機物較易被污泥毯澄清池去除，添加混凝劑雖可縮短污泥毯生成之時間，但對於澄清池去除濁度功能並無明顯助益，為有效進行污泥毯澄清池之操作，必須注意監測水中有機物之存在及其形式。

Abstract Organic matters and ammonia nitrogen are serious contaminants of surface water in Taiwan. These contaminants can interfere with the water treatment process and cause biological instability in the finished water. One solution is to employ a biological treatment stage prior to the conventional water treatment process. A continuous flow biological filter packed with reticulated PU foam was used to remove ammonia nitrogen and organic matters before the conventional water treatment practice. The effect of its operation mode, namely, empty bed contact time (EBCT) and backwash, on the removal efficiencies of ammonia nitrogen and dissolved organic matter was examined. Also, sludge blanket clarifiers（SBC）are presently an important unit of the water treatment process in Taiwan. Most studies concerning SBC have revolved around the treatment efficiency on turbidities. In Taiwan, most of the raw water sources for water treatment plants are contaminated with organic substances, which often interferes the operation of SBC. The effects of organic materials on the formation of sludge blanket and its performance, were also examined in this study. The results of the continuous flow biological filter suggested that organic matters and ammonia nitrogen can be effectively removed up to 30 ％ and 95％, respectively, by controlling the operation mode of the biological fixed bed. Efficient ammonia nitrogen removal was achieved upon the combination of backwash mode with short EBCT or extended EBCT without backwash. Efficient organic nitrogen and DOC removals were observed at short EBCT without backwash. The optimal pH for turbidity and DOC removal of biofilter effluent water coagulated with Alum is around 6.5-7.5 and 5.5-6.5, respectively. This study provides insights into the function of biofiltration, which benefits the design of fixed-bed bioreactor for the treatment of polluted surface water. Humic acid and salicylic acid were added in water to simulate natural waters polluted with organic materials of high and low molecular weights. The addition of humic acid accelerated the formation of stable sludge blanket, however, the sludge blanket so formed contained less solid. Opposite effects were discovered with salicylic acid. Nevertheless, both organics enhanced the efficiency of turbidity removal by SBC. Large organic molecules were more easily removed by SBC. Coagulant addition had no significant effect on turbidity removal although the formation time for sludge blanket was shortened. To successfully operate SBC, the occurrence and types of organic materials must be monitored.