Method for treating decentralized sewage based on an MBR reactor

Abstract

A sewage treatment method, comprising: the sewage after coarse filtration enters a MBR membrane reactor for treatment, wherein activated sludge is inoculated in the MBR membrane reactor, the MBR membrane reactor comprises a reactor tank body and a membrane assembly arranged in the reactor tank body, a water inlet is arranged at the upper part of the reactor tank body, aeration is carried out at the lower part of the reactor, polyurethane fillers are arranged in the reactor, the total volume of the polyurethane fillers accounts for 15-25% of the volume of the MBR membrane reactor, and the dissolved oxygen of the reactor is kept between 2.5-5 mg / L. According to the method, water is continuously produced in the concentrated period according to the water treatment amount, the permeability of the membrane is improved under the automatic recovery of the fillers and the flux in the non-water production stage, and long-time low-energy-consumption operation is realized.

Description

Technical Field

[0001] This invention relates to wastewater treatment methods, specifically to a wastewater treatment method based on MBR, and belongs to the field of environmental protection. Background Technology

[0002] In recent years, with the continuous development of membrane manufacturing technology in my country, membrane performance has been continuously improved, and the cost of membrane materials themselves has been continuously reduced. MBR has advantages such as high integration, small footprint, simple operation, and good treatment effect, and has been widely used in various wastewater treatment fields. However, membrane fouling is one of the bottlenecks limiting the application of MBR.

[0003] In conventional MBR (Mechanical Bioreactor) processes for wastewater treatment, membrane fouling occurs due to filter cake buildup and pore blockage over time, typically requiring membrane cleaning to restore operating flux. In recent years, continuous improvements have been made to MBR reactors to reduce membrane fouling, for example, by adding suspended media and activated carbon. For instance, Chinese Patent Publication No. CN107285467A discloses a process for water treatment plants that includes an aeration system, MBBR (Mechanical MBBR) suspended media, and MBR membrane modules, with a gap between the MBR membranes allowing the MBBR suspended media to pass through. During its flow, the MBBR media rubs against the MBR membranes, scraping off deposits on the membrane surface that affect membrane flux, thus cleaning the MBR membrane modules.

[0004] Although the fouling of MBR membrane modules has been reduced to some extent, the water treatment efficiency of MBR reactors still needs to be further improved. Summary of the Invention

[0005] The first objective of this application is to provide a wastewater treatment method that improves wastewater treatment efficiency by using a combination of long-term continuous effluent discharge and intermittent aeration.

[0006] The second objective of this application is to provide an integrated sewage treatment device based on MBR to facilitate the treatment of rural sewage. This device effectively overcomes the characteristics of small volume and dispersed discharge of rural sewage, and has the advantages of small footprint and high sewage treatment efficiency.

[0007] A wastewater treatment method involves feeding coarsely filtered wastewater into an MBR (Membrane Bioreactor) reactor for treatment. The MBR reactor is inoculated with activated sludge, the dominant bacterial genera of which include: Nakamurella, Ahniella, Mycobacterium, TM7a *Comamonadaceae*, norank f_norank_o_PeM15, and Candidatus_Alysiosphaera.

[0008] The MBR membrane reactor includes a reactor tank and a membrane module placed inside the reactor tank. An inlet is provided at the top of the reactor tank, and aeration is provided at the bottom of the reactor. Polyurethane packing is placed inside the reactor, and the total volume of polyurethane packing accounts for 15-25% of the volume of the MBR membrane reactor. The dissolved oxygen in the reactor is maintained between 2.5-5 mg / L.

[0009] By inoculating specific activated sludge and polyurethane packing materials into the MBR membrane reactor and adjusting process parameters, the amount of pollutants adhering to the MBR membrane surface is reduced. Furthermore, the pollutants adhering to the membrane surface are easily detached by the polyurethane packing. Therefore, for small-volume, decentralized wastewater treatment, by inoculating the reactor with specific activated sludge, adding polyurethane packing materials, and adopting a continuous, centralized water production operation, the removal efficiency is improved through the degradation of the biofilm on the activated sludge and packing material surface. Simultaneously, during non-water production phases, the packing material and aeration work together to remove pollutants from the membrane surface, restoring membrane permeability. Therefore, the system operating under this mechanism can achieve long operating cycles and good effluent quality.

[0010] On the other hand, the integrated wastewater treatment device of this application includes a pretreatment system, a buffer tank, and an MBR membrane reactor. The pretreatment system is connected to the buffer tank, and the buffer tank is connected to the MBR membrane reactor. The MBR membrane reactor includes a reactor and a membrane module placed inside the reactor. An inlet is provided at the top of the reactor, and an aeration element is provided inside the reactor and below the membrane module. Polyurethane packing is placed inside the reactor.

[0011] In the MBR membrane reactor of this application, combined with top inlet water and bottom aeration, the water flows downward and the gas is introduced into the bottom of the reactor and moves upward. The downward water flow combined with the upward air flow can effectively agitate the activated sludge in the reactor, allowing the sludge and wastewater to fully contact and react. Furthermore, the MBR membrane reactor contains a certain amount of polyurethane packing material. The air bubbles, water flow and packing material will form turbulence inside the system, washing the membrane surface, destroying the filter cake layer, thereby alleviating membrane fouling and improving treatment efficiency. Attached Figure Description

[0012] Figure 1 Wastewater treatment process flow diagram

[0013] Figure 2 A schematic diagram of an integrated wastewater treatment unit.

[0014] Figure 3 Schematic diagram of the structure of an MBR membrane reactor

[0015] Figure 4 Variations in membrane permeation performance of different reaction systems in an MBR membrane reactor

[0016] Figure 5 Variations in membrane permeation performance of different reaction systems in an MBR membrane reactor Detailed Implementation

[0017] The wastewater treatment method of this application is described in further detail below. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0018] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0019] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0020] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0021] The terms "implementation," "an implementation / preferred implementation," "another implementation / preferred implementation," or "certain implementations" used in this specification refer to specific elements (e.g., specific features, structures, or characteristics) described in relation to the implementation being included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0022] Definition: The term "MBR membrane bioreactor" refers to a system that organically combines membrane separation technology with biological treatment technology.

[0023] Mixed liquor suspended solids (MLSS) refers to the amount of suspended solids in the mixed liquor after wastewater and activated sludge are mixed in an aeration tank, and the unit is (mg / L).

[0024] "Relative abundance" is the proportion of a certain species in a microbial community.

[0025] "ppi" is a unit of pore density, which is the number of pores per unit inch.

[0026] The pollutants contained in the "domestic sewage" of this application are mainly organic matter (such as protein, carbohydrates, fat, urea, ammonia nitrogen, etc.) and a large number of pathogenic microorganisms (such as parasite eggs and intestinal infectious viruses, etc.).

[0027] A wastewater treatment method involves feeding coarsely filtered wastewater into an MBR (Membrane Bioreactor) reactor for treatment. The MBR reactor is inoculated with activated sludge, the dominant bacterial genera of which include: Nakamurella, Ahniella, Mycobacterium, TM7a, nclassified f_Comamonadaceae, norank f_norank_o_PeM15, and Candidatus_Alysiosphaera.

[0028] The MBR membrane reactor includes a reactor tank and a membrane module placed inside the reactor tank. An inlet is provided at the top of the reactor tank, and aeration is provided at the bottom of the reactor. Polyurethane packing is placed inside the reactor, and the total volume of polyurethane packing accounts for 15-25% of the volume of the MBR membrane reactor. The dissolved oxygen in the reactor is maintained between 2.5-5 mg / L.

[0029] In some implementations, the activated sludge concentration is 3500-4500 (mg / L MLSS) and the sludge settling ratio is 60-100 ml / g.

[0030] The relative fractions of the dominant bacterial genera in the activated sludge of this application are all greater than 1%.

[0031] In some implementations, the relative abundance of Nakamurella in the activated sludge is 23%–26.3%;

[0032] The relative abundance of Ahniella was 8.0%–11.0%;

[0033] The relative abundance of Mycobacterium was 4.0%–7.0%;

[0034] The relative abundance of TM7a is 5.0%–8.0%;

[0035] The relative abundance of Unclassified_f_Comamonadaceae ranged from 3.0% to 6.5%;

[0036] The relative abundance of norank_f_norank_o_PeM15 was 2.30%–6.0%;

[0037] The relative abundance of Candidatus Alysiosphaera ranges from 2.0% to 5.5%.

[0038] The species contained in the aforementioned dominant bacterial genera are not limited. As long as the types and relative abundance of dominant bacterial genera in the activated sludge are within the above range, the invention objective can be achieved by combining them with other process parameters of this application.

[0039] The polyurethane filler used in this application has a porosity of 35-50 ppi.

[0040] The aforementioned polyurethane packing material, placed within the reactor, allows microorganisms to adhere to its pores and surface, creating a micro-treatment environment that enhances the abundance of functional microorganisms, thereby increasing biological treatment efficiency and overall wastewater treatment efficiency. Furthermore, during wastewater treatment, the agitation from aeration and water flow propels the polyurethane packing material within the reactor, flushing the membrane surface and inhibiting the formation of a filter cake layer, thus mitigating membrane fouling. Simultaneously, it improves the removal efficiency of pollutants such as nitrogen and phosphorus. Moreover, the polyurethane packing material with a porosity of 35-50 ppi exhibits a stronger adsorption capacity for extracellular polymers and dissolved organic matter produced by microorganisms within the reactor, reducing their concentration and thus mitigating membrane fouling.

[0041] In this application, the aforementioned domestic sewage sludge containing specific bacteria is used, and the relative abundance of bacteria distributed on the polyurethane remains essentially unchanged or changes very little. When wastewater is treated in an MBR membrane reactor, the combined use of the activated sludge and polyurethane processes results in a low total amount of pollutants adhering to the membrane surface, which are easily washed away by the polyurethane. Therefore, the wastewater treatment method of this application can continuously effluent for wastewater treatment for more than 6 hours; in other words, after continuous effluent effluent for more than 6 hours, the membrane permeability decreases somewhat, but remains above 0.5 L (m³). 2 ·h·Kpa) -1 The surface will not be blocked and water will not be able to flow out.

[0042] In some embodiments, the MBR membrane reactor continuously effluents for 6-8 hours; then, effluent production is stopped, and aeration continues within the MBR membrane reactor during this stoppage phase. During this stoppage phase (i.e., the membrane's "relaxation phase"), the aeration supplies the activated sludge microorganisms with endogenous respiration, making it easier to remove the fouling layer from the membrane surface. This results in a high membrane permeability recovery level, reaching over 80%. This method of long-term continuous effluent production with intermittent aeration mitigates membrane fouling, extends the reactor's operating cycle, and effectively saves on membrane cleaning costs and energy consumption.

[0043] In existing MBR membrane reactors for wastewater treatment, the production and shutdown of wastewater alternate between very short intervals. This method easily leads to membrane fouling, requiring the removal of the membrane module for cleaning. Frequent membrane cleaning shortens the membrane's lifespan.

[0044] In some embodiments, aeration is performed intermittently. Preferably, aeration lasts for 15 minutes, followed by a 5-10 minute rest period.

[0045] In some implementations, the membrane module is a hollow fiber membrane or a flat organic membrane.

[0046] The effluent treated by the MBR membrane reactor has a COD of less than 45 mg / L, NH4-N of less than 2 mg / L, TP of less than 1.5 mg / L, TN of less than 10 mg / L, and a pH that is stable between 6 and 9. The effluent quality consistently meets the water quality standards of the "Standards for Irrigation Water" (GB 5084-2005) and the "Standards for Pollutant Discharge from Municipal Wastewater Treatment Plants" (GB18918-2002).

[0047] The wastewater treatment method provided in this application is more suitable for decentralized rural wastewater treatment. It adopts a continuous influent and continuous effluent operation mode, making it easier to achieve scheduled and location-based wastewater treatment. It centrally collects dispersed wastewater (during which water production is stopped to restore membrane permeability), and once a certain amount of wastewater has accumulated, it continuously effluents. It also has the advantages of a longer operating cycle, stronger pollution resistance, and better treatment effect. At the same time, it effectively overcomes the disadvantages of large fluctuations in water quality and quantity, and weak resistance to shock loads in wastewater treatment facilities.

[0048] The wastewater treatment method of this application is carried out in the following integrated wastewater treatment device.

[0049] On the other hand, the integrated wastewater treatment device includes a pretreatment system, a buffer tank, and an MBR membrane reactor. The pretreatment system is connected to the buffer tank, and the buffer tank is connected to the MBR membrane reactor. The MBR membrane reactor includes a reactor and a membrane module placed inside the reactor. An inlet is provided at the top of the reactor, and an aeration element is provided inside the reactor and below the membrane module. Polyurethane packing is placed inside the reactor.

[0050] In some implementations, the outlet of the membrane module is connected to the water production system, and a pump and a pressure gauge are sequentially installed on the pipeline of the water production system.

[0051] Preferably, an outlet is provided at the top of the membrane module.

[0052] In the permeate system, a pump draws water from the membrane modules within the MBR membrane reactor to create a negative pressure environment, which is then used for membrane filtration. A pressure gauge installed in the permeate system monitors changes in transmembrane pressure differential to determine if the membrane modules are clogged. Furthermore, a flow meter installed in the permeate system can determine the membrane flux of the membrane modules.

[0053] In some implementations, the membrane module is an ultrafiltration membrane module.

[0054] In some embodiments, the membrane module is a PVDF hollow fiber membrane with a pore size of 0.03-0.1 μm.

[0055] The contact angle of PVDF hollow fiber membranes is 60-80°. Using PVDF hollow fiber membranes avoids damage from chemical cleaning due to the excellent chemical resistance of PVDF material. The hollow fiber membrane fibers can move freely in water, effectively reducing membrane fouling. By retaining microorganisms in the water through the hollow fiber membrane, microbial discharge is effectively prevented, thereby increasing the biomass of the entire system and making it highly adaptable to the large fluctuations in the quality and quantity of rural wastewater. Furthermore, the effective retention by the membrane results in high biological activity in the membrane bioreactor, fully degrading organic matter in the wastewater and ensuring that the treated water meets discharge or even reuse requirements for COD, TP, and NH3-N levels.

[0056] In some embodiments, the maximum length of the polyurethane filler particles is less than the distance between adjacent membranes of the membrane module.

[0057] In some embodiments, the aeration element is a perforated aerator.

[0058] Preferably, the aeration element includes a pipe with multiple aeration holes provided on the pipe wall.

[0059] In some implementations, two rows of aeration holes are formed along the axial direction of the pipe wall.

[0060] The aeration element pipes are placed at the bottom of the MBR membrane reactor, with the central axis of the pipes parallel to the bottom. Two rows of aeration holes are located on both sides of the longitudinal section passing through the central axis of the pipes.

[0061] Preferably, each row of aeration holes is located below the cross-section through the central axis of the pipe; more preferably, the angle between each row of aeration holes and the cross-section through the central axis of the pipe is approximately 45°.

[0062] In some implementations, the aeration element's conduit is positioned directly below the membrane module.

[0063] By setting up these aeration elements, turbulence is created within the reactor, which drives the polyurethane packing to move over a wider range throughout the reactor. This washes away more pollutants adhering to the membrane surface, thereby improving wastewater treatment efficiency and mitigating membrane fouling.

[0064] In some embodiments, the pretreatment system includes a primary filter, a secondary filter, and a backwashing system, wherein the pore size of the primary filter is larger than that of the secondary filter.

[0065] The primary and secondary filtration devices can be of any existing structure, such as a grid structure.

[0066] Specifically, the primary filtration device is a coarse screen with a bar spacing of 16-25mm. The secondary filtration device is a fine screen with a bar spacing of 3-10mm.

[0067] Domestic sewage passes through coarse and fine screens, which filter out large particles. The sewage backwashing system periodically flushes the screens to remove pollutants adhering to them.

[0068] In some embodiments, the integrated wastewater treatment unit based on the MBR membrane also includes a disinfection tank connected to the product water system. Water treated by the MBR membrane reactor is discharged into the disinfection tank, where it can be recycled or discharged directly.

[0069] The disinfection tank has internal vents to connect to external air and ensure good ventilation. An external dosing tank is located within the disinfection tank, while an internal agitator and dosing pump administer disinfectant. The disinfected wastewater, meeting standards, can be discharged or reused as needed. For example, the treated water meets standards for agricultural irrigation and urban reclaimed water.

[0070] In some embodiments, a decentralized rural wastewater treatment device based on MBR includes a pretreatment system, a buffer tank, an influent system, control valves, an automatic control system, an aeration system, an MBR membrane reactor, a product water system, a pressure gauge, a dosing tank, a dosing pump, a disinfection tank, a sludge removal system, and an effluent system.

[0071] The system comprises: a pretreatment system connected to a buffer tank; a buffer tank connected to an MBR membrane reactor; an influent system and control valves between the buffer tank and the MBR membrane reactor; a MBR membrane reactor connected to a disinfection tank; a product water system and pressure gauges between the MBR membrane reactor and the disinfection tank; aeration elements within the MBR membrane reactor connected to an aeration system; a sludge removal system connected to the MBR membrane reactor; a dosing pump and dosing tank connected to the disinfection tank; and an effluent system connected to the automatic control system.

[0072] The water production system includes centrifugal pumps and pipelines; the water inlet system includes centrifugal pumps and pipelines; and the aeration system includes blower aerators and pipelines.

[0073] The entire wastewater treatment device is automatically controlled by an automatic control system that controls the water flow rate, aeration mode, or aeration speed.

[0074] In some embodiments, the automatic control system comprises a time relay, a power adapter, a power protector, an LCD display panel, etc.

[0075] In some embodiments, the water outlet system includes an overflow weir, a Parshall flume, and an online water quality monitoring device.

[0076] The sludge removal system consists of a centrifugal pump, a sludge removal tank, etc.

[0077] Furthermore, the operation process of the aforementioned integrated wastewater treatment device based on MBR membranes includes:

[0078] 1) Rural domestic sewage enters the buffer tank through a pretreatment system;

[0079] 2) The pretreated wastewater is injected into the MBR membrane reactor through the inlet system.

[0080] 3) The reclaimed water treated in the MBR membrane reactor enters the disinfection tank. After disinfection, the reclaimed water can be reused or discharged.

[0081] In the MBR membrane reactor, the permeate flow rate is determined based on the influent flow rate and hydraulic retention time. The aeration time, aeration rate, and permeate flow rate of the permeate system are adjusted by the automatic control system. The sludge discharge rate is determined based on the sludge retention time and is discharged through the sludge discharge system.

[0082] In some implementations, the residence time of wastewater in the MBR membrane reactor is 6-8 hours.

[0083] The MBR membrane permeate flux should operate at the subcritical flux level, with the influent flow rate determined by the tank volume, permeate flow rate, and hydraulic retention time. This integrated unit operates in a continuous influent / continuous effluent mode, with the permeate operation time determined daily based on the influent flow rate. During the non-permeate phase of each day, the aeration system supplies dissolved oxygen to the reactor at set intervals to meet the metabolic needs of the microorganisms, and the forward / reverse switching of the permeate pump is changed to perform online cleaning of the membrane modules, mitigating membrane fouling and restoring filtration flux. After a certain operating cycle, if the transmembrane pressure difference exceeds a certain value, the membrane modules are removed for offline cleaning.

[0084] Compared with existing technologies, the integrated wastewater treatment device based on MBR membranes proposed in this application has the following advantages:

[0085] By adopting the influent and aeration methods of the MBR membrane reactor proposed in this application, as well as adding polyurethane packing, pollutants in wastewater can be effectively removed, significantly reducing the membrane fouling rate, extending the operating cycle, reducing operation and maintenance costs, optimizing the system, and saving energy and reducing consumption.

[0086] The integrated device of this application includes a buffer tank, which facilitates the treatment of decentralized sewage discharge in rural areas. It can effectively solve problems such as low sewage volume, high treatment difficulty, and complex operation and maintenance in rural areas, while also obtaining high-quality reclaimed water. The hydraulic retention time is set according to the standards of influent and effluent, and the water production method can be selected according to the influent volume, enabling timed and fixed-point treatment of decentralized sewage.

[0087] The following specific examples will further illustrate the integrated wastewater treatment device based on MBR membranes of this application.

[0088] like Figure 2 As shown, an integrated wastewater treatment device based on an MBR membrane includes a pretreatment system 1, a buffer tank 2, a centrifugal pump 3 for the influent system, a control valve 4, an automatic control system 5, an aerator 6, an MBR membrane reactor 7, a centrifugal pump 8 for the permeate system, an electronic pressure gauge 9, a dosing tank 10, a dosing pump 11, a disinfection tank 12, a sludge removal system 13, and an effluent system 14. The pretreatment system 1 is connected to the buffer tank 2; the buffer tank 2 is connected to the MBR membrane reactor 7 via the influent system pipeline; the MBR membrane reactor 7 is connected to the disinfection tank 12 via the permeate system pipeline. The centrifugal pump 3 and control valve 4 of the influent system are located on the influent system pipeline, and the centrifugal pump 8 and electronic pressure gauge 9 of the permeate system are located on the permeate system pipeline. The aerator 6 and the sludge removal system 13 are respectively connected to the MBR membrane reactor 7. The disinfection tank 12 is connected to the dosing tank 10, and the dosing pump 11 is installed on the pipeline between the disinfection tank 12 and the dosing tank 10. The effluent system 14 is connected to the dosing tank 14. The automatic control system 5 is connected to the centrifugal pump 3 and control valve 4 of the influent system, the centrifugal pump 8 of the product water system, and the blower aerator 6.

[0089] The pretreatment system 1 includes a coarse screen of 16-25mm and a fine screen of 3-10mm. Wastewater is treated by the screens to remove large solid particles.

[0090] like Figure 3 As shown, the upper section of the MBR membrane reactor 7 is equipped with an inlet 15, which is connected to the buffer tank 2 via a pipeline. A membrane module 17 is installed inside the MBR membrane reactor 7, and an aeration element 16 is installed below the membrane module 17. The aeration element 16 is connected to a blower aerator 6 outside the MBR membrane reactor 7. A 20% volume ratio of polyurethane packing is added inside the MBR membrane reactor. The polyurethane packing is spherical, and the size of the spheres is smaller than the distance between adjacent membrane sheets of the membrane module; for example, the polyurethane packing spheres selected in the experiment have a diameter of 2 cm.

[0091] The aeration element 16 includes a pipe with two rows of aeration holes symmetrically arranged on the pipe wall. The pipe of the aeration element 16 is placed at the bottom of the MBR membrane reactor, with the central axis of the pipe parallel to the bottom. The two rows of aeration holes are located below the cross-section passing through the central axis of the pipe. The angle between each row of aeration holes and the cross-section of the pipe passing through the central axis is approximately 45°.

[0092] In this embodiment, the pipe is made of PVC pipe with a diameter of approximately 5 mm, with an aeration hole every 2 cm. The pipe diameter and the distance between the aeration holes are determined according to the size of the reactor.

[0093] The aeration element's piping is placed directly below the membrane module, parallel to the membrane module's frame.

[0094] The detailed procedure for this application is attached (see attached document). Figure 1 Rural sewage enters buffer tank 2 through pretreatment system 1. The pretreated sewage is then transported from buffer tank 2 to MBR membrane reactor 7 via influent system for biological treatment and membrane filtration. Centrifugal pump 8 in the permeate system draws water from the membrane modules within the MBR membrane reactor to create a negative pressure environment for membrane filtration. After filtration, the sewage enters disinfection tank 12. An electronic pressure gauge 9 is installed between centrifugal pump 8 and disinfection tank 12 to monitor transmembrane pressure differences. Disinfectant is added to the disinfection tank by dosing pump 11 to disinfect the sewage. The disinfected sewage is discharged through effluent system 14 for reuse or discharge. Excess sludge in MBR membrane reactor 7 is concentrated and discharged through sludge removal system 13. This process achieves the treatment of decentralized rural domestic sewage by the MBR reactor, thus meeting the standards for sewage discharge and reclaimed water reuse.

[0095] The influent system mainly consists of a buffer tank, an MBR membrane reactor, a level gauge, and a centrifugal pump for the influent system, and is controlled by an automatic control system. The liquid levels in the buffer tank and the MBR membrane reactor are set at certain heights. When the liquid level in the buffer tank is higher than the set level and the liquid level in the MBR membrane reactor is lower than the set level, the system receives influent.

[0096] The MBR membrane reactor houses an ultrafiltration membrane module, with an aeration system connected to a blower aerator via aeration pipeline at the bottom. The aeration system is automatically controlled by a control system that adjusts the aeration mode and rate based on the transmembrane pressure difference and permeate flow rate to ensure these parameters remain within acceptable ranges. The MBR reactor contains 20% polyurethane packing material by volume. Under aeration, the polyurethane packing material mechanically scours the membrane surface, controlling the filter cake thickness. An excessively thick filter cake layer will affect the permeate flow rate and increase power consumption.

[0097] The water production system mainly consists of a centrifugal pump and a level gauge, and is controlled by an automatic control system. A certain level is set inside the MBR membrane reactor. When the level is lower than a certain level, the water production pump stops working to prevent dry pumping.

[0098] All permeate is collected in a disinfection tank, where a certain concentration of NaClO solution is added to the dosing tank, and disinfection is completed by dosing with a dosing pump. After each operation stage, sludge is discharged by the sludge removal system 13, and the membrane modules are cleaned offline with a 0.5% NaClO solution. Based on the MBR membrane reactor, the disadvantages of small wastewater volume and dispersed discharge in decentralized wastewater treatment are overcome. A continuous influent and continuous effluent discharge method can be adopted, allowing for centralized treatment at certain times each day. Furthermore, during the non-permeate water stage, when dissolved oxygen is provided to the system through aeration, a portion of the filter cake layer is removed, thus restoring the flux to 60%-70% of the original flux. Therefore, it can effectively solve the problem of decentralized wastewater treatment in rural areas.

[0099] The following examples are all performed in the above-described wastewater treatment system.

[0100] Example 1

[0101] 1) After the domestic sewage passes through the pretreatment unit 1, some of the coarse materials and suspended solids are removed. The effluent from the pretreatment unit enters the buffer tank. When the water level in the buffer tank exceeds the predetermined water level, the water inlet system starts to produce water.

[0102] 2) Activated sludge is added to the MBR membrane reactor. The main dominant bacterial genera in the activated sludge include Nakamurella (relative abundance 24.3%), Ahniella (relative abundance 9.3%), Mycobacterium (relative abundance 5.67%), TM7a (relative abundance 6.4%), unclassified f_Comamonadaceae (relative abundance 4.7%), norank_f_norank_o_PeM15 (relative abundance 4.3%), and Candidatus_Alysiosphaera (relative abundance 3.29%). Wastewater enters the MBR membrane reactor with a sludge concentration of 4000 mg / L MLSS and a sludge settling ratio of 80 ml / g. The aeration conditions are: aeration for 15 minutes, followed by 5-10 minutes of settling, with dissolved oxygen in the reactor maintained at 2.5-5 mg / L.

[0103] The membrane module uses hollow fiber membranes, and the reactor is built into 20% polyurethane packing.

[0104] Under the above conditions, water was continuously fed into and discharged for 8 hours in the MBR membrane reactor, and then discharged for 16 hours (during which intermittent aeration was maintained). This process was repeated for 15 days, and the water treatment results are shown in Table 1.

[0105] Table 1

[0106]

[0107]

[0108] Example 2

[0109] In this embodiment 2, except that a flat-plate composite MBR membrane reactor was used, the other conditions are as shown in embodiment 1.

[0110] Under the above conditions in the MBR membrane reactor, water was continuously discharged for 8 hours, followed by a 16-hour period of cessation of water discharge (during which intermittent aeration was maintained). This process was repeated for 15 days, and the water treatment results are shown in Table 2.

[0111]

[0112] In Tables 1 and 2, TP represents the total phosphorus content in the water, and TN represents the total nitrogen content in the water.

[0113] Experimental Example 1

[0114] This experimental example is to illustrate the wastewater treatment method of this application. Following the wastewater treatment methods of Examples 1 and 2, the total operating time was 288 hours, the water production time was 96 hours, and the permeation performance of the membrane module was measured.

[0115] For the permeation performance of the hollow fiber membrane (the membrane module is a PVDF hollow fiber membrane with a pore size of 0.03 μm), the initial value was 2.92 L (m³). 2 ·h·Kpa) -1 After 12 days of operation, the concentration dropped to 0.81 L (m³). 2 ·h·Kpa) -1 The average initial permeability during operation was 2.31 L (m³). 2 ·h·Kpa) -1 The average permeability at the end of operation was 0.90 L (m³). 2 ·h·Kpa) -1 .

[0116] For the permeation performance of the flat sheet membrane (PVDF flat sheet membrane, pore size 0.01 μm), from the initial 13.49 L (m 2 ·h·Kpa) -1 After 12 days of operation, the concentration dropped to 1.01 L (m³). 2 ·h·Kpa) -1 The average initial permeability during operation was 5.63 L (m³). 2 The average end-of-operation permeability was 1.19 L / (m³) (·h·Kpa)⁻¹. 2 ·h·Kpa)-1.

[0117] Comparative Example 1

[0118] This comparative example examines the impact of long-term permeate flow on membrane permeability with different packing materials or no packing material in the MBR membrane reactor. Three MBR reactor systems are included: 1) the MBR reactor containing the polyurethane packing material of this invention; 2) the MBR reactor containing the combined packing material of this invention; and 3) the MBR reactor without packing material. Specifically, following the wastewater treatment methods of Examples 1 and 2, continuous effluent flow lasts for 8 hours, followed by a 16-hour stop-effluent phase (during which intermittent aeration is maintained), for a total operating time of 288 hours and a permeate flow time of 96 hours. The permeate performance of the membrane module is detailed in the appendix. Figure 4 , Figure 5 .

[0119] Figure 4 To assess the permeability of hollow fiber membranes (the membrane module is a PVDF hollow fiber membrane with a pore size of 0.03 μm), the changes in membrane permeability in the three reaction systems were investigated before and after each 8-hour continuous water output within a total operating time of 288 hours. The membrane recovery process occurred during the water output cessation phase before each continuous water output.

[0120] Figure 5To investigate the permeability of flat sheet membranes (PVDF flat sheet membrane, pore size 0.01μm), the changes in membrane permeability in three reaction systems were observed before and after each 8-hour continuous water output within a total operating time of 288h. The membrane recovery process was carried out during the water output cessation phase before each continuous water output.

[0121] from Figure 4 , 5 It can be seen that the membrane permeability performance of the reaction system using polyurethane filler is far superior to that of the other two reaction systems after prolonged continuous water output (e.g., 8 hours). During the membrane recovery process after water output stops, the membrane permeability recovery is also significantly better than that of the other two systems.

[0122] In the appendix Figure 4-5 In the figures, the membrane permeation performance variation curve in the reaction system with the polyurethane packing of the present invention placed in the MBR membrane reactor is represented by curve 1; the membrane permeation performance variation curve in the reaction system without packing in the MBR reactor is represented by curve 2; and the membrane permeation performance variation curve in the reaction system with the combined packing of the present invention placed in the MBR reactor is represented by curve 3. In some time periods, the curves of the two systems overlap, without specific numerical distinction; or in the accompanying figures, only two values ​​are shown for certain time periods (e.g., 1, 2), in which case the corresponding other curve represents the third value.

Claims

1. A method for treating domestic sewage, comprising: The wastewater after coarse filtration is fed into the MBR membrane reactor for treatment, whereby... Activated sludge is inoculated into the MBR membrane reactor. The dominant bacterial genera of the activated sludge include: Nakamurella , Ahniella Mycobacteria TM7a Trichomonas vaginalis norank_f_norank_o_PeM15 , Candidatus Alysiosphaera , Among them, activated sludge, Nakamurella The relative abundance was 23% to 26.3%. Ahniella The relative abundance was 8.0%–11.0%. The relative abundance of mycobacteria was 4.0%–7.0%. TM7a The relative abundance was 5.0% to 8.0%. The relative abundance of *Trichomonas vaginalis* was 3.0%–6.5%. norank_f_norank_o_PeM15 The relative abundance was 2.30%–6.0%. Candidatus_Alysiosphaera The relative abundance was 2.0%–5.5%; The MBR membrane reactor includes a reactor tank and a membrane module placed inside the reactor tank. An inlet is provided at the top of the reactor tank. An aeration element is installed inside the reactor below the membrane module. Polyurethane packing is placed inside the reactor, and the total volume of the polyurethane packing accounts for 15-25% of the volume of the MBR membrane reactor. The porosity of the polyurethane packing is 35-50 ppi. The dissolved oxygen in the reactor is maintained between 2.5-5 mg / L.

2. The method for treating domestic sewage according to claim 1, characterized in that, The activated sludge concentration is 3500-4500 mg / L MLSS, and the sludge settling ratio is 60-100 ml / g.

3. The method for treating domestic sewage according to claim 1, characterized in that, The MBR membrane reactor continuously produces water for 6-8 hours; then, water production is stopped, and aeration continues inside the MBR membrane reactor during the water production stoppage phase.

4. The method for treating domestic sewage according to any one of claims 1-3, characterized in that, Intermittent aeration is used for aeration.

5. The method for treating domestic sewage according to claim 4, characterized in that, Aerate for 15 minutes, then let stand for 5-10 minutes.

6. The method for treating domestic sewage according to any one of claims 1-3, characterized in that, During the water production shutdown phase, aeration continues within the MBR membrane reactor using an intermittent aeration method.

7. The method for treating domestic sewage according to claim 6, characterized in that, Aerate for 15 minutes, then let stand for 5-10 minutes.

8. The method for treating domestic sewage according to any one of claims 1-3, characterized in that, The aeration element is a perforated aerator, which includes a pipe with two rows of aeration holes opened axially on the pipe wall.

9. The method for treating domestic sewage according to claim 8, characterized in that, The aeration element pipes are placed at the bottom of the MBR membrane reactor, with the central axis of the pipes parallel to the bottom. Two rows of aeration holes are located on both sides of the longitudinal section passing through the central axis of the pipes.

10. The method for treating domestic sewage according to claim 8, characterized in that, Each row of aeration holes is located below the cross-section passing through the central axis of the pipe, and the angle between each row of aeration holes and the cross-section passing through the central axis of the pipe is 45°.

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