群體感應抑制在移動床膜生物反應器之濾膜阻塞控制研究

Evaluating the effect of quorum quenching on mitigation of membrane fouling in moving bed membrane bioreactors

黃彥博(Yan-Bo Huang)

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(2021年)

https://doi.org/10.6846/TKU.2021.00695

摘要

論文提要內容：
　　移動床膜生物反應器(moving bed membrane bioreactor, MBMBR)結合了移動床生物反應器(Moving bed biofilm reactor, MBBR)及膜生物反應器(membrane bioreactor, MBR)，具有增加生物量、提高有機負荷量、佔地面積小等優點，近年來在廢水處理領域越來越受到關注，但膜生物反應器的發展受限於濾膜使用容易堵塞之缺點。群體感應抑制法(Quorum Quenching, QQ)為近年來發展用以控制濾膜阻塞之技術，透過抑制群體感應(Quorum Sensing, QS)系統使微生物減少胞外聚合物(extra-cellular polymeric substance, EPS)及可溶性微生物產物(soluble microbial products, SMP)之產生，藉以延緩濾膜堵塞。群體感應抑制法有很多種手段，包括了使用QQ酵素法、添加QQ菌和QS抑制劑，而其中以添加能降解訊息分子AHLs 的QQ菌方法最廣為使用。雖然MBMBR相較於MBR已被報導具有延緩濾膜堵塞的能力，但也有文獻指出相反的結果。儘管MBMBR及群體感應抑制法均被提出具有控制濾膜堵塞的潛力，但目前尚未有文獻探討結合MBMBR與QQ法對延緩濾膜堵塞的成效。
　　因此，本實驗的目的是結合MBMBR以及群體感應抑制法(主要採用Rhodococcus sp. BH4菌株)，以評估系統延緩濾膜堵塞的效能，實驗上主要分為三個部分：(1)比較MBR及MBMBR濾膜堵塞速度，為了近一步探討延緩濾膜的可能原因，分別測試濾膜與載體間有無加入隔板的透膜壓力變化，(2)優化實驗參數及改良固定化方法，調整出適合的實驗的通量以及改良出在反應槽中較穩定的QQ球，(3)比較分別加入QQ球(QQ-MBMBR)及空珠(VB-MBMBR)的反應槽中，濾膜堵塞的速度。實驗過程除了探討施用群體感應抑制法對透膜壓力及EPS、SMP濃度及性質之影響，也同時觀察施用QQ法對污水處理效能的影響。
　　本研究發現，在MBR和MBMBR的實驗中，MBMBR有些微延緩濾膜堵塞的效果，延緩了約5 kPa的透膜壓力，在MBR及MBMBR將隔開濾膜及載體的隔板移開的狀況下，跟有隔板的反應槽相比，發現MBMBR受到載體的物理刮除，歷經54天都不會上升至40 kPa。在高通量下(33.5 LMH)，加入QQ球只延緩1到2天的時間。在QQ-MBMBR及VB-MBMBR的比較中，在第一輪實驗中兩反應槽的透膜壓力沒有差異，但在第二輪實驗的開始前，發現反應槽底部堆積大量污泥，經過均勻混和後，QQ-MBMBR相較於VB-MBMBR延緩了3天的時間，但在後續的實驗中，沒有再現性，在實驗最後發現反應槽污泥的循環不佳，導致槽底堆積污泥，使得在實驗期間測得的EPS及SMP沒有顯著的差異，可能是延緩效果不明顯的原因。建議之後的實驗中，透過設計或加裝外部循環，改善反應槽的污泥沉澱問題。另外在實驗期間，QQ-MBMBR與VB-MBMBR對於有機物及氨氮去除率皆在90%以上，總氮去除率在30%左右，兩個系統間沒有處理效率上的差異。

關鍵字

膜生物反應器 ； 移動床膜生物反應器 ； 群體感應 ； 群體感應抑制 ； 濾膜阻塞 ； 胞外聚合物 ； 可溶性微生物產物

並列摘要

Moving bed membrane bioreactor (MBMBR) technology combines moving bed biofilm reactor (MBBR) and membrane bioreactor (MBR). The advantages of MBMBR include containing high biomass thus is compatible for elevated organic loading and small footprint, therefore, this technique has attracted more and more attention in the field of wastewater treatment in recent years. However, the development and widespread application of membrane filtration related technologies, including MBMBR, is still limited by biofouling on filtration membranes. Quorum Quenching (QQ) is a recently developed apporach to control membrane biofouling. Through degrading singalling molecules in quorum sensing (QS) systems, microbial production of extracellular polymeric substance (EPS) and soluble microbial products (SMP) can be suppressed which in turn delay the fouling of the filter membrane. Currently, many QQ methods have been invented, including the use of QQ enzyme, the addition of QQ bacteria or QS inhibitors. Among these methods, the addition of QQ bacteria that can degrade the QS autoinducing molecule, acyl homoserine lactone (AHL), is the most widely applied method. Although MBMBR has been reported to have the ability to delay membrane fouling compared to MBR, there are also literatures that point out the opposite results. In addition, both MBMBR and quorum sensing suppression methods have been proposed to have the potential to control membrane fouling, there is currently no literature discussing the effectiveness of combined MBMBR and QQ method regarding to membrane biofouling control.
　　Therefore, the purpose of this experiment is to combine MBMBR and quorum quenching techniques (using Rhodococcus sp. BH4 strain) to evaluate the effectiveness of the system in delaying membrane fouling. The experiment is divided into three tasks: (1) comparison of the fouling rate of MBR and MBMBR. Two types of MBMBR were used and they differed in whether a baffle was placed between the filter membrane tank and the wastewater treatment tank, (2) adjust the suitable experiment flux and testing the experimental parameters of QQ bacteria immobilization method to improved stability of QQ beads, (3) compare the rates of the filter membrane clogging between the reactors with QQ beads (QQ-MBMBR) and with vacant beads (VB-MBMBR). In addition to explore the effects of QQ method on transmembrane pressure (TMP) and the concentration and properties of EPS and SMP, wastewater treatment efficiency was monitored as well.
　　In the experiments of comparing fouling rate between MBR and MBMBR, this study found that MBMBR slightly delayed the fouling of the filter membrane by about 5 kPa when baffle was installed. Under the condition that the baffle was removed, TMP of MBMBR did not reach 40 kPa after 54 days. This might due to additional physical collision between the carriers and the prematured biofilm on membrane surface. MBMBR operated at high flux (33.5 LMH) condition, QQ effect was suppressed and the reactor with QQ beads only delays 1 to 2 days for TMP to reach 40 kPa. In the comparison of fouling rate between QQ-MBMBR and VB-MBMBR, no difference in terms of TMP increment was observed in the first round of experiment. But before the start of the second round of experiment, it was found that a large amount of sludge had accumulated at the bottom of the reaction tank with VB-MBMBR. When the sludge was mixed manually, QQ-MBMBR showed the ability to delay biofouling by 3 days compared with VB-MBMBR. However, in subsequent experiments, the delay of biofouling was no longer observed probably due to poor sludge mixing in reactors. Results also showed that there is no significant difference (P-value of EPSprotein：0.55，P-value of EPScarbohydrate：0.40，P-value of SMP protein：0.87，P-value of SMP carbohydrate：0.29) in concentrations of EPS and SMP between QQ-MBMBR and VB-MBMBR measured during the course of experiment. It is recommended that in subsequent experiments, the better sludge and carrier circulation condition in reactors will be necessary to reveal the clear effects of QQ-MBMBR on biofouling control. Finally, during the experiment, QQ-MBMBR and VB-MBMBR had a similar removal rate against COD and ammonia nitrogen (> 90%), and a total nitrogen (~ 30%) demonstrated that there was no adverse impact of application of QQ on treatment efficiency in the studied systems.

並列關鍵字

Membrane bioreactor(MBR) ； moving bed membrane bioreactor(MBMBR) ； quorum sensing(QS) ； quorum quenching(QQ) ； membrane fouling ； Extracellular polymeric substance(EPS) ； soluble microbial products(SMP)

參考文獻

Ahmed, S., Chung, S., Sohail, N., Qazi, I. and Justin, A. (2020) Application of cell entrapping beads for Quorum Quenching technique in submerged membrane bioreactor. Water Science and Technology 81(4), 744-752.

Ahmed, Z., Cho, J., Lim, B.-R., Song, K.-G. and Ahn, K.-H. (2007) Effects of sludge retention time on membrane fouling and microbial community structure in a membrane bioreactor. Journal of membrane science 287(2), 211-218.

Chang, I.-S., Le Clech, P., Jefferson, B. and Judd, S. (2002) Membrane fouling in membrane bioreactors for wastewater treatment. Journal of environmental engineering 128(11), 1018-1029.

Chen, F., Bi, X. and Ng, H.Y. (2016) Effects of bio-carriers on membrane fouling mitigation in moving bed membrane bioreactor. Journal of membrane science 499, 134-142.

Chen, W., Westerhoff, P., Leenheer, J.A. and Booksh, K. (2003) Fluorescence excitation− emission matrix regional integration to quantify spectra for dissolved organic matter. Environmental science & technology 37(24), 5701-5710.