酸化/鹼化對淨水場污泥減量與脫水性之影響

Effect of Acidification/Alkalization on Water Treatment Plant Sludge Reduction and Dewaterability

彭文良(Wen-Liang Peng)

指導教授 ： 康世芳

淡江大學/工學院/水資源及環境工程學系碩士班/碩士(2009年)

https://doi.org/10.6846/TKU.2009.00502

摘要

本研究探討酸化/鹼化對淨水污泥減量與脫水性之影響，實驗用淨水污泥採至台北自來水事業處公館淨水場污泥濃縮槽。以鋁鹽回收率、鋁鹽溶出效率、污泥固體物與體積減量評估污泥減量，以毛細汲取時間(CST)及過濾比阻抗試驗值(SRF)表示污泥脫水性。此外，以Roberts沉降公式評估污泥沉降性。污泥酸化/鹼化實驗採瓶杯試驗。
研究結果顯示污泥酸化與鹼化最適pH分別為2、12，鋁鹽回收率與污泥減量於酸化比鹼化佳。酸化pH=2之鋁鹽回收率、鋁鹽溶出溶度、污泥固體物與污泥體積減量分別為78%、1,092 mg/L、12.3% 及32%。然而，鹼化時溶解性有機物（DOC）溶出濃度為310 mg/L高於酸化時之溶出DOC為75 mg/L，此乃由於原水中天然有機物如腐植酸易溶解於鹼性。酸化於pH 1時鋁鹽回收率雖達最高為97%，但因鋁鹽溶出效率（以單位氫莫耳溶出鋁鹽莫耳數表示）為0.009低於pH 2時之 0.098最佳，故污泥減量酸化之最佳pH 為2。
污泥酸化/鹼化對污泥沉降性影響之研究結果顯示，酸化/鹼化皆可提高污泥沉降性，沉降速度於酸性範圍隨pH減少而增加，相對地，於鹼性範圍隨pH增加而增加。污泥酸化對污泥脫水性SRF值影響不顯著，但鹼化使污泥脫水性隨鹼化pH增加而變差，換言之SRF值隨pH增加而增加。此外，污泥先酸化後再調整污泥至中性(原濃縮污泥pH 7)，SRF值降低30%，顯示再調整pH可改善污泥脫水性。故污泥減量、鋁鹽回收與後續脫水處理之最適pH可分別控制2與7。

關鍵字

淨水污泥、酸化、混凝劑回收、污泥減量、脫水

並列摘要

The objectives of this study are to investigate the effects of acidification and alkalization on water treatment sludge reduction and dewaterability. The sludge was sampled from a sludge thickener tank at the Gongguan water treatment plant of Taipei Water Department. The parameters such as aluminum recovery rate, aluminum dissolution efficiency, reduction of solid and volume were used to evaluate the efficiencies of sludge reduction. Moreover, the sludge dewaterability was measured by the capillary suction time (CST) and specific resistance value (SRF). The sludge settleabiltiy was evaluated by Roberts’ equation. The sludge reduction experiments were conducted by the Jar test.
The results showed that the optimum pH of sludge acidification and alkalization were 2 and 12, respectively. Both aluminum recovery rate and sludge reduction by acidification were better than that by alkalization. Sludge acidification at pH 2, the aluminum recovery rate, aluminum dissolution concentration, and reduction of solid and reduction were 78%, 1,092 mg/L, 12.3% and 32%, respectively. However, the dissolution of dissolved organic carbon (DOC) by alkalization was higher than that by acidification. The DOC dissolution concentrations were 75 mg/L and 310 mg/L at pH 2 and pH 12, respectively. This is due to natural occurring matters, such as humic acid highly dissolves at alkali conditions but acidic conditions. Furthermore, aluminum recovery rate reached up to 97% at pH 1, whereas the aluminum dissolution efficiency (expressed by mol of aluminum dissolution per mol of hydrogen ion) was 0.009, which was lower than that of 0.098 at pH 2. Therefore, the optimum pH for sludge acidification was 2.
The results of effect of acidification/alkalization on sludge settleability showed that both acidification and alkalization can raise sludge settleability. The sludge settlement velocity increased with the decrease of pH at acidic conditions. In contract, it increased with the increase of pH at basic conditions. The sludge dewaterability expressed by SRF values were insignificantly affected by acidification. However, SRF values increased with the increase with pH. This implied that the sludge dewaterability became worse by alkalization. In addition, when sludge pH was adjusted to pH 7 (pH of thickened sludge) again after sludge acidification, it observed that SRF value reduced about 30%. It concluded that the optimum pH for aluminum recovery, sludge reduction and the followed-up dewatering can be controlled at pH 2, and 7, respectively.

並列關鍵字

water treatment sludge, acidification, coagulant recovery, sludge reduction, dewatering

參考文獻

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