阅读说明：本技术 一种双层聚丙烯无纺布膜组件及其膜污染控制方法 (Double-layer polypropylene non-woven fabric membrane component and membrane pollution control method thereof ) 是由 李晓惠 许艳广 于 2021-10-21 设计创作，主要内容包括：本发明提供了一种双层聚丙烯无纺布膜组件及其膜污染控制方法,以聚丙烯无纺布作为过滤介质,形成基于双层聚丙烯无纺布的板框式膜组件,应用该双层聚丙烯无纺布膜组件于膜生物反应器,膜出水水质稳定,运行初期出水悬浮物含量低于10mg/L,当膜污染导致跨膜压力增加至20～25Kpa时,可通过物理清洗的方法恢复膜通量,有效控制膜污染。系统操作压力低,膜污染控制方法简单、环境残留小,具备节能环保的特征。(The invention provides a double-layer polypropylene non-woven fabric membrane component and a membrane pollution control method thereof, wherein a polypropylene non-woven fabric is used as a filter medium to form a plate-frame type membrane component based on the double-layer polypropylene non-woven fabric, the double-layer polypropylene non-woven fabric membrane component is applied to a membrane bioreactor, the quality of membrane effluent water is stable, the content of suspended matters in the effluent water at the initial operation stage is lower than 10mg/L, when transmembrane pressure is increased to 20-25 Kpa due to membrane pollution, the membrane flux can be recovered by a physical cleaning method, and the membrane pollution is effectively controlled. The system has low operation pressure, simple membrane pollution control method and little environmental residue, and has the characteristics of energy conservation and environmental protection.)

1. A double-layer polypropylene non-woven fabric membrane component and a membrane pollution control method thereof adopt a double-layer polypropylene non-woven fabric formed by a first layer of polypropylene non-woven fabric (1) and a second layer of polypropylene non-woven fabric (2) as a filter membrane of the membrane component, and the specific assembly mode of the membrane component is as follows: two sets of double-deck polypropylene non-woven fabrics cladding respectively in porous braced frame (3) both sides, two sheet frame (4) that play the fixed action cover respectively on two sets of double-deck polypropylene non-woven fabrics, be equipped with preformed hole (5) on porous braced frame (3) and two sheet frame (4) that play the fixed action, screw rod and nut with stainless steel compress tightly fixed with porous braced frame (3) via preformed hole (5), double-deck polypropylene non-woven fabrics (1,2) and two sheet frame (4) that play the fixed action, form the board frame membrane module based on double-deck polypropylene non-woven fabrics filter membrane.

2. The double-layer polypropylene non-woven fabric membrane component and the membrane pollution control method thereof according to claim 1, wherein the double-layer polypropylene non-woven fabric membrane component is applied to a membrane bioreactor.

3. The double-layer polypropylene non-woven fabric membrane assembly and the membrane pollution control method thereof according to claim 1, wherein the surface density of the polypropylene non-woven fabric is 25-35 g/m²。

4. The double-layer polypropylene non-woven fabric membrane assembly and the membrane pollution control method thereof according to claim 1, wherein the membrane flux of the double-layer polypropylene non-woven fabric membrane assembly is controlled to be 10-60L/(m)²H) in the range.

5. The membrane pollution control method of the double-layer polypropylene non-woven fabric membrane component according to claim 1, wherein when the transmembrane pressure is increased to 20-25 Kpa due to membrane pollution, the membrane component is taken out of the biological reaction tank and is physically cleaned, and the physical cleaning method comprises the steps of scraping off a cake layer on the surface of the membrane by using a scraper, and then washing the surface of the membrane by using clean water.

6. The membrane module and the membrane pollution control method thereof as claimed in claim 1, wherein when a cake layer is accumulated on the surface of the second polypropylene non-woven fabric (2) due to long-term operation, the physical cleaning cannot effectively recover the membrane flux, so that the membrane working cycle is less than 10 days, and chemical cleaning is required, wherein the chemical cleaning method comprises the steps of detaching the double-layer polypropylene non-woven fabric filter membrane from the membrane module, placing the double-layer polypropylene non-woven fabric filter membrane in clean water, adding alkaline detergent, performing mechanical scrubbing, and rinsing out the residual detergent by using clean water.

7. The double-layer polypropylene non-woven fabric membrane component and the membrane pollution control method thereof according to claim 1, wherein when the double-layer polypropylene non-woven fabric membrane component is applied to an aerobic membrane bioreactor, the quality of membrane effluent is stable, a pretreatment period is not required in the operation process, and the determination of the aeration amount of the aerobic biological reaction tank, the selection of the type of the aeration head and the installation of the position only need to consider the dissolved oxygen level requirement of aerobic biological treatment and do not need to consider the membrane surface bubble disturbance.

Technical Field

The invention belongs to the technical field of water pollution control in environmental engineering, and particularly relates to a membrane module process cost reduction and membrane pollution operation control method for a membrane bioreactor.

Background

The membrane bioreactor is an efficient water treatment process, has the advantages of small floor area, good effluent quality, high sludge concentration and the like, and is widely concerned in the fields of urban sewage treatment and the like. At present, most of membrane bioreactors in practical application adopt polyvinylidene fluoride hollow fiber microfiltration membrane components, the price of membranes is relatively high, more importantly, due to the existence of the membrane pollution problem, the membranes need to be cleaned physically and chemically at regular intervals, the operation cost and the management difficulty of sewage plants are improved, chemical cleaning agents can cause secondary environmental pollution, in addition, frequent chemical cleaning can reduce the service life of the membranes, and the operation cost is further increased by replacing the membranes with new membranes. The popularization and application of the membrane bioreactor process are greatly restricted by the problems, so that the key for further popularization of the membrane bioreactor application is to find a novel cheap membrane component with a simple and feasible membrane pollution control mode.

The non-woven fabric is used as the membrane material of the membrane bioreactor process, so that the advantages of good filtering performance and high strength of the membrane material can be exerted, and the price of the membrane material can be greatly reduced, so that the non-woven fabric membrane bioreactor has great application potential in the field of sewage treatment.

The non-woven fabric is used as a filter membrane to prepare a membrane component and the membrane component is applied to a membrane bioreactor, and the current research is mainly in the laboratory research stage. The aperture of non-woven fabrics itself is great, and at the operation initial stage, to the trapped energy ability of mixed liquid suspended solid relatively poor, the main thinking of laboratory research is at the non-woven fabrics surface one deck dynamic membrane that forms in advance, relies on the filtering action of dynamic membrane to realize the entrapment to mixed liquid suspended solid. However, controlling the formation and shedding of the dynamic membrane also increases the difficulty of operating and managing the water plant, and the effluent suspended matter content may increase in a short period of time after the dynamic membrane is shed. Therefore, the membrane component based on the non-woven fabric filter membrane, which has the advantages of good interception effect on mixed liquid suspended matters, convenient membrane pollution control and management, small environmental residue, low manufacturing cost and easy large-scale popularization and application, is developed, and has important practical significance for popularization of the membrane bioreactor technology in the fields of municipal sewage treatment and other wastewater treatment.

Disclosure of Invention

The polypropylene non-woven fabric has the characteristics of water and air permeability, ageing resistance, low cost, light weight and the like, and is widely applied to the fields of agricultural breeding, seedling raising, medical mask preparation and the like at present. In addition, the product also has the characteristics of large specific surface area, rough surface, easy attachment of microorganisms and the like, and can be used as a biomembrane carrier in the field of water treatment. The double-layer polypropylene non-woven fabric is used as a filter medium of the membrane bioreactor, and the non-woven fabric filter membrane has mechanical screening and interception effects on large-particle flocs and contact adsorption and interception effects on small-particle flocs, so that the activated sludge mixed liquid can be well separated, and the membrane pollution control method is simple and easy to realize large-scale production.

The technical scheme is as follows:

a double-layer polypropylene non-woven fabric membrane component and a membrane pollution control method thereof adopt a double-layer polypropylene non-woven fabric formed by a first layer of polypropylene non-woven fabric (1) and a second layer of polypropylene non-woven fabric (2) as a filter membrane of the membrane component, and the specific assembly mode of the membrane component is as follows: two sets of double-deck polypropylene non-woven fabrics cladding respectively in porous braced frame (3) both sides, two sheet frame (4) that play the fixed action cover respectively on two sets of double-deck polypropylene non-woven fabrics, be equipped with preformed hole (5) on porous braced frame (3) and two sheet frame (4) that play the fixed action, screw rod and nut with stainless steel compress tightly fixed with porous braced frame (3) via preformed hole (5), double-deck polypropylene non-woven fabrics (1,2) and two sheet frame (4) that play the fixed action, form the board frame membrane module based on double-deck polypropylene non-woven fabrics filter membrane.

Furthermore, the double-layer polypropylene non-woven fabric membrane component is applied to a membrane bioreactor.

Further, the surface density of the polypropylene non-woven fabric is 15-35 g/m²Preferably, the polypropylene non-woven fabric has an areal density of 25 to 35g/m²。

Furthermore, the membrane flux of the double-layer polypropylene non-woven fabric membrane component can be controlled within 10-120L/(m)²H), preferably, the membrane flux of the double-layer polypropylene non-woven fabric membrane component is controlled to be 10-60L/(m)²H) in the range.

Further, the membrane pollution control method of the double-layer polypropylene non-woven fabric membrane component comprises the steps of taking the membrane component out of a biological reaction tank and carrying out physical cleaning when transmembrane pressure is increased to 20-25 Kpa due to membrane pollution, wherein the physical cleaning method comprises the steps of scraping off a filter cake layer on the surface of the membrane by using a scraper and washing the surface of the membrane by using clear water.

Further, according to the membrane pollution control method of the double-layer polypropylene non-woven fabric membrane component, when a filter cake layer is accumulated on the surface of the second layer of polypropylene non-woven fabric (2) due to long-term operation, the membrane flux cannot be effectively recovered due to physical cleaning, so that the membrane working period is less than 10 days, and chemical cleaning is required, wherein the chemical cleaning method comprises the following steps: and (3) detaching the double-layer polypropylene non-woven fabric filter membrane from the membrane component, placing the membrane component in clean water, adding a small amount of alkaline detergent, performing mechanical scrubbing, and rinsing the residual detergent by using the clean water.

Furthermore, when the double-layer polypropylene non-woven fabric membrane component is applied to an aerobic membrane bioreactor, the quality of membrane effluent water is stable, the content of suspended matters in the effluent water is lower than 10mg/L at the initial operation stage, a pretreatment period is not needed in the operation process, and the determination of the aeration amount of the aerobic biological reaction tank, the selection of the type of the aeration head and the installation of the position only need to consider the dissolved oxygen level requirement of aerobic biological treatment and do not need to consider the bubble disturbance of the membrane surface.

Under the observation of a microscope, the polypropylene non-woven fabric used in the invention has an interwoven space net-shaped irregular fiber structure (figure 2), after the aerobic membrane bioreactor runs for a long time, the surface of the first layer of polypropylene non-woven fabric forms an obvious sludge filter cake layer (figure 3) due to the mechanical screening effect, and a small amount of sludge flocs are attached to the internal fiber structure of the second layer of polypropylene non-woven fabric (figure 4) due to the contact adsorption effect.

According to the invention, the double-layer polypropylene non-woven fabric with wide source and low cost is used as the filter medium of the membrane bioreactor, and the double-layer polypropylene non-woven fabric solves the problem of high content of suspended matters in initial effluent in the membrane bioreactor which generally uses a macroporous non-woven fabric as the filter medium, and has the characteristics of low system operation pressure, simple membrane pollution control method, small environmental residue, energy conservation and environmental protection.

Drawings

FIG. 1 is a schematic view of the assembly of the membrane module of the present invention.

In fig. 1: 1 first layer polypropylene non-woven fabrics, 2 second layer polypropylene non-woven fabrics, 3 porous braced frame, 4 sheet frames, 5 preformed holes.

FIG. 2 is a photomicrograph at a magnification of 10 times of the polypropylene nonwoven fabric which has not been used.

FIG. 3 is a photomicrograph of the first polypropylene nonwoven fabric layer at 10 Xmagnification after 3 cycles of operation in the membrane bioreactor.

FIG. 4 is a photomicrograph at 10X magnification of the second polypropylene nonwoven fabric layer after 3 cycles of operation in the membrane bioreactor.

FIG. 5 shows the membrane effluent suspended matter (SS) content and transmembrane pressure of the double-layer polypropylene non-woven membrane module under different membrane fluxes.

FIG. 6 is a diagram showing the change of the transmembrane pressure with time in the process of treating simulated domestic sewage by using a double-layer polypropylene non-woven fabric membrane component.

Detailed Description

Example 1 Membrane effluent suspended matter (SS) content and transmembrane pressure of double-layer polypropylene non-woven membrane module under different membrane fluxes

A double-layer polypropylene non-woven fabric membrane component and a membrane pollution control method thereof adopt a double-layer polypropylene non-woven fabric formed by a first layer of polypropylene non-woven fabric (1) and a second layer of polypropylene non-woven fabric (2) as a filter membrane of the membrane component, and the specific assembly mode of the membrane component is as follows: two sets of double-deck polypropylene non-woven fabrics cladding respectively in porous braced frame (3) both sides, two sheet frame (4) that play the fixed action cover respectively on two sets of double-deck polypropylene non-woven fabrics, be equipped with preformed hole (5) on porous braced frame (3) and two sheet frame (4) that play the fixed action, screw rod and nut with stainless steel compress tightly fixed with porous braced frame (3) via preformed hole (5), double-deck polypropylene non-woven fabrics (1,2) and two sheet frame (4) that play the fixed action, form the board frame membrane module based on double-deck polypropylene non-woven fabrics filter membrane.

The surface density of the polypropylene non-woven fabric is 25g/m²。

Placing a plate-frame type membrane assembly based on a double-layer polypropylene non-woven fabric filter medium in an aerobic reaction tank, wherein the volume of mixed liquor in the aerobic reaction tank is 4.5L, the suspended solid content of the mixed liquor is 3976mg/L, and the effective filtering area of the double-layer polypropylene non-woven fabric filter membrane is 164cm²Aerating with microporous aeration disc at aeration rate of 0.2L/min, pumping water out of the membrane and controlling membrane flux at 10.12, 20.06, 40.12, 60.00, 79.68, 99.75, 134.06, 168.75 and 199.88L/(m) respectively²H) operating time of 30 minutes for each membrane flux condition, and measuring transmembrane pressure of the membrane module at the different membrane fluxes described aboveThe results of the force and the suspended matter content of the membrane effluent are shown in FIG. 5.

The operation result shows that the suspended matter content (SS) of the membrane effluent under different membrane fluxes is less than 8mg/L, and the requirement of the first-class A standard of pollutant discharge Standard of municipal wastewater treatment plant (GB 18918-; when the membrane flux is from 10L/(m)²H) to 200L/(m)²H), the transmembrane pressure is increased from 0.1KPa to 0.27KPa, which shows that the membrane resistance of the double-layer polypropylene non-woven filter membrane is very small at the initial stage of operation and does not change greatly along with the membrane flux.

Example 2 simulation of domestic wastewater treatment by aerobic membrane bioreactor based on double-layer polypropylene non-woven fabric membrane module

A double-layer polypropylene non-woven fabric membrane component and a membrane pollution control method thereof adopt a double-layer polypropylene non-woven fabric formed by a first layer of polypropylene non-woven fabric (1) and a second layer of polypropylene non-woven fabric (2) as a filter membrane of the membrane component, and the specific assembly mode of the membrane component is as follows: two sets of double-deck polypropylene non-woven fabrics cladding respectively in porous braced frame (3) both sides, two sheet frame (4) that play the fixed action cover respectively on two sets of double-deck polypropylene non-woven fabrics, be equipped with preformed hole (5) on porous braced frame (3) and two sheet frame (4) that play the fixed action, screw rod and nut with stainless steel compress tightly fixed with porous braced frame (3) via preformed hole (5), double-deck polypropylene non-woven fabrics (1,2) and two sheet frame (4) that play the fixed action, form the board frame membrane module based on double-deck polypropylene non-woven fabrics filter membrane.

The surface density of the polypropylene non-woven fabric is 35g/m²。

Placing a plate-frame type membrane assembly based on a double-layer polypropylene non-woven fabric filter medium in an aerobic reaction tank, wherein the volume of mixed liquid in the aerobic reaction tank is 4.5L, and the effective filtering area of the double-layer polypropylene non-woven fabric filter membrane is 164cm²The suspended solid content of the mixed liquid is 1809-4427 mg/L, a microporous aeration disc is adopted for aeration, the aeration rate is 0.16-0.24L/min, the dissolved oxygen concentration of the mixed liquid is controlled to be 2-3 mg/L by adjusting the aeration rate, the raw water is simulated domestic sewage, and the main water quality indexes are as follows: COD 320-450 mg/L, NH₃-N 20～30mg/L，TP 1.8～3.6mg/L, adopting a constant flux filtration mode, pumping membrane effluent by using a peristaltic pump and controlling the membrane flux to be 20L/(m)²H), run for 54 days, record the change in transmembrane pressure over time during the run, and the results are shown in FIG. 6.

As shown in fig. 6, the double-layer polypropylene nonwoven membrane module was operated for 3 cycles in total during a 54-day run time. The first cycle was run for 19 days, with a slow increase in transmembrane pressure from 0.5Kpa to 20.5Kpa over the first 17 days, but a rapid increase in transmembrane pressure from 20.5Kpa to 65.6Kpa over the following 2 days; after the first period is finished, taking the membrane module out of the aerobic biological reaction tank, and carrying out physical cleaning, wherein the physical cleaning method comprises the steps of scraping off a filter cake layer on the surface of the membrane by using a scraper, washing the surface of the membrane by using clear water, and putting the membrane module into operation for the second period again after the physical cleaning; the second cycle was run for 17 days, during the first 15 days the transmembrane pressure was slowly increased from 2.5Kpa to 22Kpa, and during the following 2 days the transmembrane pressure was rapidly increased from 22Kpa to 66.2 Kpa; after the second period is finished, taking the membrane module out of the aerobic biological reaction tank, and carrying out physical cleaning, wherein the physical cleaning method comprises the steps of scraping off a filter cake layer on the surface of the membrane by using a scraper, washing the surface of the membrane by using clear water, and putting the membrane module into operation for the third period again after the physical cleaning; the third cycle was run for 18 days, during the first 15 days the transmembrane pressure was slowly increased from 2.6Kpa to 23Kpa, and during the following 3 days the transmembrane pressure was rapidly increased from 23Kpa to 67.1 Kpa; after the third period, the membrane module is taken out of the aerobic biological reaction tank, then the double-layer polypropylene non-woven fabric is detached from the membrane module, the first layer polypropylene non-woven fabric and the second layer polypropylene non-woven fabric are respectively subjected to microscopic examination by using a microscope, and the result shows that after the aerobic membrane bioreactor runs for a long time, an obvious sludge cake layer is formed on the surface of the first layer polypropylene non-woven fabric due to mechanical screening (figure 3), and a small amount of sludge flocs are attached to the internal fiber structure of the second layer polypropylene non-woven fabric due to contact adsorption (figure 4).

The 3-cycle operation result of the double-layer polypropylene non-woven fabric membrane component for processing simulated domestic sewage shows that when the transmembrane pressure is increased to 20-25 Kpa due to membrane pollution, if the operation is continued, the transmembrane pressure is rapidly increased, and the result shows that physical cleaning is needed when the transmembrane pressure of the double-layer polypropylene non-woven fabric membrane component is increased to 20-25 Kpa. The operation result of 3 periods shows that the work period of the double-layer polypropylene non-woven fabric membrane component in the aerobic membrane bioreactor is about 15 days.

After the first physical cleaning, the transmembrane pressure is recovered to 2.5KPa, after the second physical cleaning, the transmembrane pressure is recovered to 2.6KPa, and the operation time of each period does not show an obvious reduction trend along with the period, which indicates that the simple physical cleaning can effectively recover the membrane flux of the double-layer polypropylene non-woven fabric membrane.

When the second polypropylene non-woven fabric (2) accumulates a filter cake layer on the surface due to long-term operation, the physical cleaning cannot effectively recover the membrane flux of the double-layer polypropylene non-woven fabric filter membrane, so that the membrane working period is less than 10 days, and chemical cleaning is needed.

In the operation process of the aerobic membrane bioreactor, the effluent quality of the double-layer polypropylene non-woven fabric membrane component is stable, the effluent suspended matter content is lower than 10mg/L at the initial operation stage of each period, and the operation process does not need a pretreatment period.

When the double-layer polypropylene non-woven fabric membrane component is applied to an aerobic membrane bioreactor, the determination of the aeration quantity of the aerobic biological reaction tank, the selection of the type of the aeration head and the installation of the position only need to consider the dissolved oxygen level requirement of the aerobic biological treatment, and do not need to consider the bubble disturbance of the membrane surface.