電化學群體感應抑制法於厭氧生物廢水處理系統控制濾膜阻塞之可行性研究

A feasibility study of controlling biofouling by electrochemical quorum quenching method on anaerobic biological wastewater treatment system

許保羅(Pao-Lo Hsu)

指導教授 ： 簡義杰

淡江大學/工學院/水資源及環境工程學系碩士班/碩士(2022年)

https://doi.org/10.6846/TKU.2022.00351

摘要

將厭氧生物廢水處理系統結合膜生物反應器，可兼顧相互的優點，具有低耗能、可處理高有機負荷的廢水、產生並回收使用沼氣(CH4)和出流水質佳等特點，雖然過往有濾膜成本較高的限制，但在如今因製膜成本的不斷下降，加上回收水資源的迫切需求下，成為目前世界上各國研究的重點之一。但濾膜在長時間操作下，反應槽中的微生物及其代謝產物將會在濾膜上逐漸累積，形成生物膜而造成堵塞(biofouling)，此現象會降低處理效率並提高營運成本。生物膜的行成主要是透過群體感應(quorum sensing, QS)的調控，而用來觸發群體感應的關鍵則在於訊息分子的濃度是否達到特定的閾值。先前文獻中發現訊息分子AHLs中的內脂環(lactone rings)結構會受到pH值的影響，在pH值提高時會逐漸水解產生開環的現象，失去了原本作為訊息分子的功能。理論上可藉此延緩生物膜的產生。在本研究中利用了訊息分子與pH值的相依性，對電極施加電場，於陰極周圍產生氫氧根來提升濾膜周圍的pH值，達到水解訊息分子的目的，將此方法稱為電化學群體感應抑制(electrochemical quorum quenching, eQQ)法。
本研究中將實驗分成兩部分：一、廢水厭氧生物反應槽之建立與改進，二、廢水厭氧生物處理反應槽正式的濾膜阻塞延緩測試階段。於第一部分中設定的目標為：建立良好運作的厭氧生物處理程序以及使濾膜過濾設備適合後續電化學QQ的測試。於第二部分中設定的目標為透過膜鬆弛的手法及間歇性通電的頻率評估較佳的操作組合來輔助電化學法的對於延緩阻塞的效果。
於實驗初期即遇上濾膜快速堵塞的挑戰，經過更換反應槽體(由AnMBR改為UASB)、降低進流氮元素總量、延長HRT及改變陰極不銹鋼絲的配置方式，成功的將濾膜堵塞速度延長7倍以上，使過濾設備調整到適合後續eQQ的測試。在進入反應槽正式的濾膜阻塞延緩測試階段，經過Stage Ⅰ 至Stage ⅠⅠⅠ 的測試，以施加-1.15V的電壓並加入了膜鬆弛(頻率為抽濾25分鐘後讓膜停止抽濾鬆弛5分鐘)的控制變因下，實驗組(eQQ)最高可以達到21.3%的延緩阻塞效果。並且觀察到實驗組的經過濾膜的出流水中具有最高的pH值，並且與控制組(control)的出流水pH值在統計上具有高度顯著差異，表示通電產生的氫氧根於實驗組濾膜周圍大量產生，並且可能導致了訊息分子AHLs的水解，延緩了群體感應的產生速度。
最後在Stage Ⅰ 至Stage ⅠⅠⅠ 的運行期間，實驗組和控制組平均COD去除率皆高於95%，而於每日氣體產量、污泥pH值與ORP值皆保持穩定，顯示於反應槽中使用電化學群體感應抑制法並未對反應槽運行造成負面影響。

關鍵字

醯化高絲氨酸內酯 ； 群體感應抑制 ； 厭氧生物廢水處理系統 ； 電化學法

並列摘要

Combining the anaerobic biological wastewater treatment system with the membrane bioreactor can take into account the advantages of each other. It has the characteristics of low energy consumption, the ability to treat wastewater with high organic load, the generation and recovery of biogas (CH4), and the good effluent quality. There is a restriction on the high cost of filtration membranes, but due to the continuous decline in the cost of membrane production and the urgent need to recycle water resources, it has become one of the focuses of research in countries around the world.
However, when the filter membrane is operated for a long time, the microorganisms and their metabolites in the reaction tank will gradually accumulate on the filter membrane to form a biofilm and cause biofouling, which will reduce the treatment efficiency and increase the operating cost. The formation of biofilms is mainly regulated by quorum sensing (QS), and the key to triggering quorum sensing is whether the concentration of message molecules reaches a specific threshold. In previous literatures, it was found that the structure of lactone rings in the acyl homoserine lactone (AHL) is affected by pH value. When the pH value increases, it will gradually hydrolyze and lose its original function as a AHL. Theoretically, it can delay the formation of biofilm. In this study, the dependence of the AHLs on the pH value was utilized, and an electric field was applied to the electrodes, and hydroxide radicals were generated around the cathode to increase the pH value around the membrane to achieve the purpose of hydrolyzing the AHLs. This method is called electrochemical quorum quenching (eQQ) method.
In the early stage of the experiment, the challenge of fast fouling of the membrane was encountered. After replacing the reaction tank (from AnMBR to UASB), reducing the amount of nitrogen in the inflow, extending the HRT and changing the configuration of the cathode stainless steel wire, the fouling speed of membrane is extended by more than 7 times, so that the reaction tank is adjusted to be suitable for the subsequent eQQ method test. In the formal membrane fouling delay test stage entering the reaction tank, after the stage I to Stage III tests, a voltage of -1.15V is applied and membrane relaxation is added (After 25 minutes of suction filtration, let the membrane stop suction and relax for 5 minutes ), the experimental group (eQQ) could achieve a maximum fouling delaying of 21.3%. And it was observed that the effluent water of the eQQ had the highest pH value, and the pH value of the effluent water of the control group(control) was statistically significantly different. It is indicated that the hydroxyl radicals generated by electrification were produced in large quantities around the membrane of the eQQ, and may lead to the hydrolysis of the AHLs, delaying the quorum sensing.
Finally, during the operation period from Stage I to Stage III, the average COD removal rate of both the Eqq and the control was higher than 95%, and the daily gas production, sludge pH and ORP values remained stable. It was shown that the use of eQQ method in the reaction tank did not negatively affect the activated sludge.

並列關鍵字

Acyl-homoserine lactones(AHLs) ； Quorum quenching (QQ) ； Anaerobic biological wastewater treatment system ； Electrochemical method

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