微波/鹼熱化學技術應用於污泥消化預處理之研究

Abstract

台灣地區隨著污水下水道之加速興建，污水處理廠陸續開始管運，都市污水廠之廢棄污泥處理與處置問題備受關注。在污泥處理程序中，好氧消化程序是常被採用之技術，然而好氧消化需達7-15日以上才足以將污泥之揮發性固體量降至某程度以下，達到污泥減量之目的，此乃因廢棄污泥含多量大分子有機固體物，在消化過程中難以快速分解，產生對消化速率之限制。因此，本研究利用微波加熱、酸鹼氧化及微波與鹼處理等技術，進行廢棄污泥在消化程序前之預處理，探討污泥中有機物之水解效率，進而檢視後續消化作用之效率是否可因而提昇。 本研究以批次實驗進行預處理之污泥水解分析，比較各處理方法之污泥水解效率並找出最佳操作條件，續以好氧消化程序檢視污泥減量效果。在預處理中，分別就污泥濃度、溫度、酸鹼條件及能量消耗等因子進行探討，微波法之最佳預處理條件為600W功率下反應2分鐘，可產生COD溶出率8%；酸鹼處理法之最佳條件為於每升污泥中添加1.5 g NaOH劑量使其於強鹼環境下作用，可促使18%之COD溶出；利用微波與鹼處理之聯合技術將大幅將提高污泥之水解效率，鹼處理後微波加熱處理(鹼-微波組)之COD溶出率為39.3%，若以微波加熱後再行鹼處理(微波-鹼組)，COD溶出率則可提高為45.5%。本研究進一步藉由好氧消化批次實驗證實經由聯合技術之微波-鹼方式，可有效提升常溫好氧消化效率，並在6日內即可達廢棄污泥減量之目的。

Proper management of wastewater sludge has become increasingly important in recent decades due to environmental and economical concerns. Aerobic digestion is commonly used for sludge treatment; however, it takes a long time to achieve a desirable level of volatile solids destruction. Degradation of large molecular-weight organic compounds is rate-limiting in the sludge. This study promoted hydrolysis of organic compounds to improve subsequent digestion by pretreatments of microwave, acid and alkaline, and combined microwave with alkali. In this study, batch-scale experiments were conducted to compare the effectiveness of various pretreatment methods on subsequent aerobic digestion. In pretreatment processes, effects of waste activated sludge concentration, temperature, pH and pretreatment methods (alkaline and microwave heating) on solubilization of COD were first investigated. Compared to conventional heating, microwave pretreatment required a shorter time in heating; and it achieved COD solubilization of 8% within 2 min at 600 W. In the alkaline pretreatment, the dose of 1.5 g NaOH/L was found optimal and the COD solubilization could reach approximately 18%. Two sequences of combined alkaline and microwave pretreatments were also evaluated, and the COD solubilization reached 39.3% (Alkali-Microwave) and 45.5% (Microwave-Alkali), respectively. As demonstrated in the batch aerobic digestion tests, the combined microwave-alkali pretreatment was proven to enhance the digestibility of volatile solids in the waste activated sludge samples.