A method for controlling MBR membrane fouling by using microbial predation to inhibit quorum sensing

Abstract

The present invention relates to a control method for slowing down MBR membrane pollution by using microbial predation to inhibit quorum sensing, and belongs to the technical field of sewage biological treatment. The method comprises the following steps: 1. Cultivating obligate predatory bacteria with Gram-negative bacteria that can secrete signal molecules (N-acyl homoserine lactone) as the main host to obtain a quorum sensing inhibitor; 2. Directly putting the cultivated quorum sensing inhibitor into the MBR reaction pool, the quorum sensing inhibitor will carry out an obligate predation process in the MBR reaction pool; the quorum sensing inhibitor can prey on Gram-negative bacteria that secrete N-acyl homoserine lactone and inhibit quorum sensing. The present invention can effectively reduce the concentration of signal molecules in the MBR reaction pool, so that it cannot reach the threshold of triggering quorum sensing and thus avoid the production of extracellular polymers, so as to inhibit the formation of biofilm from the source, and has a significant control effect on MBR membrane pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane bioreactors in sewage treatment, and in particular relates to a control method for utilizing microbial predation to inhibit quorum sensing and thereby alleviate MBR membrane pollution. Background Art

[0002] Membrane bioreactor (MBR) is a new sewage treatment process that organically combines membrane separation technology and biological treatment technology. It uses membrane components to replace the secondary sedimentation tank in the activated sludge process. It has the advantages of good effluent quality, high sludge concentration, low organic load, small footprint, resistance to shock loads, and low sludge yield. It has been widely used in the construction and expansion of sewage treatment plants, upgrading and renovation of old plants with limited space, reuse of sewage water, and treatment of landfill leachate.

[0003] my country's MBR technology research began in the 1990s, and the total scale of MBR water plants is now at the leading level in the world. With the implementation of my country's sewage resource utilization policy, the market for sewage treatment process upgrading and transformation has expanded, and the application prospects of MBR technology will be broader. However, the membrane pollution problem has been difficult to solve and has hindered the development and practical use of this technology.

[0004] During the operation of MBR, due to the precipitation of minerals, the accumulation of colloids and soluble organic matter on the membrane surface or inside the membrane, and the formation of biofilm, the membrane pores are blocked, the transmembrane pressure (TMP) is increased, the membrane flux is reduced, and membrane pollution occurs.

[0005] Microbial communities have a gene regulation mechanism that changes the secretion of chemical signal molecules according to the density of the microbial community and environmental factors to achieve information exchange within and between species and regulate group behavior, namely quorum sensing (QS). A variety of signal molecules and related QS bacteria and regulatory genes have been proven to be widely present in MBR mixed liquor and filter cake layers. QS regulated by N-acyl-homoserine lactone (AHL) is widely present in MBR systems and can induce membrane fouling by promoting the secretion of extracellular polymeric substances (EPS), changes in microbial community structure, and biofilm formation.

[0006] For example, patent CN 110028152 A discloses a method for controlling MBR membrane pollution based on microbial quorum sensing quenching, comprising the following steps: (1) immobilizing quorum sensing quenching bacteria with an immobilized polymer material to obtain immobilized quorum sensing quenching bacteria; (2) adding the immobilized quorum sensing quenching bacteria into a pretreatment tank before the MBR reaction tank, and retaining the immobilized quorum sensing quenching bacteria in the pretreatment tank; the quorum sensing quenching bacteria can degrade acyl homoserine lactone.

[0007] At present, the research on membrane fouling control based on quorum sensing mainly focuses on the strategy mediated by quorum sensing quenching, including the technology of interfering with quorum sensing in MBR system by means of quorum sensing quenching enzymes, signal molecule degrading bacteria, etc. However, it has disadvantages such as easy inactivation, high cost, difficulty in immobilization, poor stability and low efficiency.

[0008] In summary, the prior art only focuses on the degradation of acyl homoserine lactones, and no research has been conducted on the source of N-acyl homoserine lactone production; furthermore, there is no method for treating the source of quorum sensing - Gram-negative bacteria that secrete N-acyl homoserine lactones. Summary of the invention

[0009] Technical problem to be solved by the present invention: The purpose of the present invention is to solve the deficiencies in the prior art and provide a control method for the source of quorum sensing, restraining Gram-negative bacteria that secrete N-acyl homoserine lactone to inhibit quorum sensing and thereby alleviate MBR membrane pollution.

[0010] The technical solution of the present invention: The present invention discloses a method for controlling MBR membrane pollution by utilizing microbial predation to inhibit quorum sensing, comprising culturing obligate predatory bacteria with Gram-negative bacteria as main hosts to obtain a quorum sensing inhibitor; directly adding the quorum sensing inhibitor into the MBR reaction pool for obligate predation, thereby inhibiting the quorum sensing process; the Gram-negative bacteria are bacteria that secrete N-acyl homoserine lactone.

[0011] Furthermore, after the quorum sensing inhibitory bacteria are added into the MBR reaction tank, the operation of the MBR and the concentration of the quorum sensing inhibitory bacteria in the reaction tank are monitored, and new quorum sensing inhibitory bacteria agent is added at a certain period.

[0012] Furthermore, the method for culturing the obligate predatory bacteria comprises using Gram-negative bacteria that secrete different N-acyl homoserine lactones as the sole nutrient source to cultivate quorum sensing inhibitory bacteria that have predatory characteristics on the Gram-negative bacteria.

[0013] Furthermore, the obligate predatory bacteria include one or more obligate phage groups of Bdellovibrio, Myxobacterium and Lysobacterium.

[0014] Furthermore, the frequency of adding the quorum sensing inhibitor is once every 1-6 days.

[0015] Furthermore, the initial sludge mass concentration in the MBR reaction tank is 7-13 g / L.

[0016] Furthermore, the volume ratio of the quorum sensing inhibitory bacteria agent added to the MBR reaction tank is 0.05%-1% v / v.

[0017] Furthermore, the hydraulic retention time in the MBR reaction tank is 6-20 hours, and the dissolved oxygen concentration in the pretreatment tank is 2-5 mg / L.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] 1. The present invention directly traces the source of N-acyl homoserine lactone production, and proposes a method for treating Gram-negative bacteria that secrete N-acyl homoserine lactone. Compared with the existing method for degrading acyl homoserine lactone, the quorum sensing inhibitory bacteria in the present invention can prey on Gram-negative bacteria that secrete N-acyl homoserine lactone and inhibit quorum sensing. Therefore, the concentration of signal molecules in the MBR reaction pool can be effectively reduced, so that it cannot reach the threshold for triggering quorum sensing and thus avoid the production of extracellular polymers, so as to inhibit the formation of biofilm from the source, and the control effect on MBR membrane pollution is significant; it will not affect the removal effect of MBR on COD, ammonia nitrogen, etc. in sewage, and the reactor operates well, and the service life of the MBR membrane can be extended by nearly 2 times.

[0020] 2. This solution does not require the addition of enzyme preparations, chemical uncouplers, oxidants and other chemical agents. The present invention inhibits the formation of biofilm by inhibiting signal molecules, reduces the content of EPS and SMP in the sludge mixed liquor, effectively slows down membrane pollution, extends the service life of the membrane, and reduces the operating costs of the MBR membrane process; the operation is simple and there are no environmental ecological and health safety issues.

[0021] 3. The operation process of the present invention is simple, and there is no need to change the process of the existing MBR process of the sewage treatment plant. It only needs to put the quorum sensing inhibitory bacteria into the MBR reaction tank. It has strong operability and is convenient for application in sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the change of transmembrane pressure difference between the blank group and the experimental group in Example 2 of the present invention;

[0023] Figure 2 This is a schematic diagram of the change of transmembrane pressure difference between the blank group and the experimental group in Example 3 of the present invention;

[0024] Figure 3Schematic diagram of changes in water quality indicators of MBR effluent in the blank group and the experimental group in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Embodiment 1:

[0027] Two laboratory-scale MBR reactors with a working volume of 3 L were constructed. The MBR membrane components were made of polyvinyl difluoride (PVDF) hollow fiber membranes with a pore size of 0.1 μm and an effective area of ​​148 cm. 2 .

[0028] The MBR reaction tank was placed in a constant temperature water bath circulator at 30°C. The water inlet pump was controlled by a liquid level controller to keep the volume of water in the MBR reaction tank at 3L. The MBR hydraulic retention time was 20h. The membrane flux was 35L / (m 2 h); use air pump and air diffuser for aeration to maintain the dissolved oxygen concentration in the MBR reaction tank at 2 mg / L.

[0029] The activated sludge in the reactor was taken from the MBR tank of a municipal sewage treatment plant, and the MLSS of the sludge was about 7g / L. The artificial simulated wastewater in the inlet tank was injected into the MBR reaction tank through the inlet pump.

[0030] The water quality conditions of artificial simulated wastewater are: chemical oxygen demand (COD) 450 mg / L, ammonia nitrogen (NH 4 + -N) 30mg / L, total nitrogen (TN) 30mg / L, total phosphorus (TP) 3mg / L, pH value 7.0~7.5.

[0031] The activated sludge was inoculated into artificial simulated wastewater and acclimated in the laboratory for 3 months until the effluent indicators were stable. Then, MBR reactor 1 was used as the control group, and 0.05% v / v of Bdellovibrio bacteria was added to MBR reactor 2 to inhibit quorum sensing. The addition frequency was once a day.

[0032] The system was operated continuously for 60 days, and the total concentration of AHL signal molecules in the reactor mud-water mixture was monitored every 10 days.

[0033] The experimental results are shown in Table 1:

[0034] Table 1

[0035]

[0036]

[0037] From the results in Table 1, it can be seen that the experimental results show that adding Bdellovibrio agents to the MBR reaction tank can effectively reduce the concentration of signal molecules. The AHL concentration in the experimental group was reduced by about 65% compared with the blank control group without adding agents, which ultimately inhibited the quorum sensing in the reactor.

[0038] Embodiment 2:

[0039] Two laboratory-scale MBR reactors with a working volume of 3 L were constructed.

[0040] The MBR reaction tank was placed in a constant temperature water bath circulator at 30°C. The water inlet pump was controlled by a liquid level controller to keep the sewage volume in the MBR reactor at 3L. The MBR hydraulic retention time was 10h. The membrane flux was 35L / (m 2 h), use air pump and air diffuser for aeration to maintain the dissolved oxygen concentration in the MBR reaction tank at 5 mg / L.

[0041] The activated sludge in the reactor was taken from the MBR tank of a municipal sewage treatment plant in Nanjing, and the MLSS of the sludge was about 13g / L. The artificial simulated wastewater in the inlet tank was injected into the MBR reaction tank through the inlet pump.

[0042] The water quality conditions of artificial simulated wastewater are: COD 500mg / L, NH 4 + -N 30mg / L, TN 30mg / L, TP 3.0mg / L, pH 7.0~7.5.

[0043] The activated sludge was inoculated into artificial simulated wastewater and acclimated in the laboratory for 3 months until the effluent index was stable. MBR reactor 1 was used as the control group, and 1.0% v / v of myxobacterium was added to MBR reactor 2 to inhibit quorum sensing. The addition frequency was once every 6 days. The total concentration of AHL signal molecules and TMP changes in the reactor sludge-water mixture were regularly monitored after 60 consecutive days of operation.

[0044] Table 2

[0045]

[0046] From the results in Table 2, it can be seen that the addition of the quorum sensing inhibitor in the present invention can reduce the AHL concentration by about 56% compared with the blank control group, so that the AHL concentration in the MBR reactor cannot reach the minimum threshold required for quorum sensing, thereby inhibiting the formation of membrane fouling.

[0047] Depend on Figure 1 The results show that in the 60-day operation cycle, the blank control group reached the peak of membrane contamination on the 22nd day, while the experimental group with the addition of predatory bacteria did not reach the peak of membrane contamination until the 38th day. In addition, the membrane of the blank control group was contaminated for three cycles within 60 days, while that of the experimental group was only contaminated for one cycle, indicating that the addition of predatory bacteria greatly reduced the consumption of the membrane and extended the membrane service life.

[0048] Embodiment three:

[0049] The experiment was conducted by adding quorum sensing inhibitor to the aerobic membrane bioreactor of a certain urban sewage treatment plant. The sewage treatment plant has a water capacity of 10,000 m 3 / d, there are two parallel aerobic-MBR processes, the initial sludge concentration in the two processes is controlled at about 10g / L, one group is used as a control group, and the other group is used as an experimental group. The hydraulic retention time of the membrane bioreactor is 15h, and the dissolved oxygen concentration is 3mg / L.

[0050] A mixed predatory agent containing Bdellovibrio, Myxobacterium and Lysobacterium was added to the membrane bioreactor of the experimental group to inhibit quorum sensing in the MBR. The quorum sensing inhibitor was directly added to the membrane bioreactor at a volume ratio of 0.5% v / v, and the addition frequency was once every 3 days. After 60 days of continuous operation, the signal molecule concentration and membrane fouling of the mud-water mixture in the membrane bioreactor, as well as the water quality of the reactor effluent were regularly monitored.

[0051] Table 3

[0052]

[0053] From the results in Table 3, it can be seen that the addition of quorum sensing inhibitory bacteria in the present invention can greatly reduce the AHL concentration, thereby inhibiting the formation of membrane fouling.

[0054] from Figure 2 It can be seen that the blank control group had serious membrane fouling after 12 days, with TMP reaching 50 kPa; while the experimental group had membrane fouling after 31 days after the addition of quorum sensing inhibitory bacteria. This shows that quorum sensing inhibitory bacteria greatly enhanced the sustainable filtration of the membrane, extending the membrane service life by nearly 2 times.

[0055] Depend on Figure 3 It can be seen that during the continuous operation, the effluent COD and NH 4 + -N, TN and TP concentrations can all reach the Class A standard. In the process of using quorum sensing to inhibit bacteria for membrane fouling and sludge yield control, the system's removal effect on COD, total nitrogen and total phosphorus will not be affected, and the effluent quality is good and can be used as recycled water.

[0056] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for controlling MBR membrane fouling by using microbial predation to inhibit quorum sensing, characterized in that: Cultivating obligate predatory bacteria with Gram-negative bacteria as main hosts to obtain a quorum sensing inhibitor; directly adding the quorum sensing inhibitor into the MBR reaction tank for obligate predation, thereby inhibiting the quorum sensing process; The Gram-negative bacteria are bacteria that secrete N-acyl homoserine lactone.

2. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 1, characterized in that: After the quorum sensing inhibitory bacteria are added into the MBR reaction tank, the operation of the MBR and the concentration of the quorum sensing inhibitory bacteria in the reaction tank are monitored, and new quorum sensing inhibitory bacteria agents are added at a certain period.

3. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 1, characterized in that: The method for culturing the obligate predatory bacteria comprises taking Gram-negative bacteria that secrete different N-acyl homoserine lactones as the sole nutrient source and culturing quorum sensing inhibitory bacteria that have predatory characteristics on the Gram-negative bacteria.

4. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to any one of claims 1 to 3, characterized in that: The obligate predatory bacteria include one or more obligate phages of Bdellovibrio, Myxobacterium and Lysobacterium.

5. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 2 is characterized in that: The frequency of adding new quorum sensing inhibitor is once every 1-6 days.

6. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 1, characterized in that: The initial sludge mass concentration in the MBR reaction tank is 7-13 g / L.

7. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 6 is characterized in that: The volume ratio of the quorum sensing inhibitory bacteria agent added to the MBR reaction tank is 0.05%-1% v / v.

8. The MBR membrane pollution control method using microbial predation to inhibit quorum sensing according to claim 7 is characterized in that: The hydraulic retention time in the MBR reaction tank is 6-20h.

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