化學沉澱法處理光電業含氟廢水之探討

Treatment of TFT-LCD fluoride-containing wastewater by chemical precipitation

蘇登福(Teng-fu Su)

指導教授 ： 曾迪華

國立中央大學/工學院/環境工程研究所碩士在職專班/碩士(2011年)

摘要

本研究分別以氧化鈣(CaO)和氯化鈣(CaCl2)兩種鈣鹽，以化學沉澱法，處理光電業含氟廢水，並探討鈣鹽劑量、pH值等操作因子，對氟離子去除效率的影響。同時，探討添加混凝劑與助凝劑，對提升去除效率的可行性。此外，本研究採集實廠含氟污泥，評估污泥的基本性質，濃縮沉降性及脫水性。
研究結果顯示，原水pH＜3.9，氟離子(F-)值約94 mg/L至221 mg/L，屬於典型強酸型廢水。另外，化學沉澱法處理結果顯示， CaO劑量在Ca/F 為1.4時，氟離子的去除效率可達到77%，同樣的CaCl2劑量在Ca/F 為1.4時，但pH調整為 7至 8，氟離子去除效率可達到95%。添加混凝劑的實驗結果顯示，均可進一步提升氟離子的去除效率，但是，添加助凝劑，對於氟離子去除效率，皆無明顯影響，不過，對所生成膠羽的沉降性有很大幫助。實廠含氟污泥經由高分子調理，可明顯改善污泥的脫水性，其中以中性助凝劑為最佳，且污泥的比阻抗值(SRF)和毛細汲取時間(CST)均顯著的減少。

關鍵字

光電業含氟廢水 ； 污泥脫水 ； 氯化鈣 ； 氧化鈣 ； 化學沉澱

並列摘要

This study investigated the effectiveness of fluoride removal from TFT-LCD fluoride-containing wastewater by chemical precipitation with CaO or CaCl2 as calcium salt. The effects of calcium dosage and pH on fluoride removal were evaluated by the laboratory jar tests. Additionally, the feasibility of enhancing fluoride removal by the aid of coagulant or polymer addition was investigated. Finally, the characteristics of fluoride containing sludge and its properties of thickening and dewatering were also evaluated based on the real samples obtained from full-scale treatment plant.
The investigation results indicated that the pH of fluoride containing wastewater was less than 3.9 and the fluoride concentration was in the range of 94mg/L to 221 mg/L. The titration curve of the wastewater neutralized by NaOH revealed that the wastewater property was strong acidic. The jar test results showed that up to 77% of fluoride removal was obtained as fluoride precipitated by CaO at the dosage of Ca/F ratio was 1.4. However, using CaCl2 as precipitant at Ca/F ratio was 1.4 and pH was between 7 and 8, the fluoride removal efficiency was up to 95%. The experimental results also revealed that adding coagulant of PACl with calcium salt during chemical precipitation could further increase the removal efficiency of fluoride ion. Moreover, adding coagulant aid of polymer did not enhance the efficiency of fluoride removal, but could improve the floc formation and increased its settleability. The study also found that chemical conditioning of fluoride-containing sludge by polymer, especially nonionic polymer, could significantly improve the dewaterability of the sludge. This was verified by the reduction of SRF and CST values after sludge conditioning.

並列關鍵字

calcium chloride ； calcium oxide ； TFT-LCD fluoride-containing wastewater ； chemical precipitation ； sludge dewatering.

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