CN109569298B - Fermentation liquid membrane filtering method - Google Patents
Fermentation liquid membrane filtering method Download PDFInfo
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- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
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- B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
- B01D2321/16—Use of chemical agents
- B01D2321/166—Use of enzymatic agents
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Abstract
The invention relates to a fermentation liquid membrane filtration method, in particular to a cross-flow membrane filtration method and a polluted membrane cleaning method. A fermentation liquid membrane filtration method adopts a cross-flow membrane filtration method for fermentation liquid filtration, a membrane component water washing step is carried out after filtration, then a chemical cleaning step of the membrane component is carried out, and finally a water washing step of the membrane component is carried out. Wherein the chemical cleaning step further comprises the steps of injecting a cleaning liquid containing a membrane cleaning aid from the primary side to the secondary side of the membrane and injecting a cleaning liquid containing hypochlorite and a surfactant into the membrane module. The method has the advantages of long membrane filtration time, high chemical cleaning recovery rate and low cost, and ensures the stable operation of a membrane filtration system of the fermentation liquor.
Description
Technical Field
The invention relates to a fermentation liquid membrane filtration method, in particular to a cross-flow membrane filtration method and a polluted membrane cleaning method.
Background
The method for producing substances by fermentation is widely applied to our lives, and substances such as beer, white spirit, vinegar, soy sauce, monosodium glutamate, amino acid and the like are all prepared by adopting the fermentation method. In production, a fermentation liquor separation process exists, and conventional diatomite is the most common filter aid, is economical to use, has low filtration cost and is widely applied to filtration of beer fermentation liquor in the existing breweries. However, the use of the diatomite has great disadvantages that firstly, the diatomite is a non-renewable resource, and the resource is exhausted when a large amount of diatomite is used, secondly, the labor intensity of the diatomite is high during filtering, the dust of the diatomite is very unfavorable for the health of operators, and moreover, the diatomite cannot be recycled, and the waste diatomite can cause serious environmental pollution. In recent years, the membrane filtration technology has been widely applied to the water treatment industry, and with the improvement of the membrane performance, the membrane filtration technology can be applied to the fermentation liquor filtration industry except for water treatment. The fermentation liquor generally has the characteristics of high concentration of organic matters and turbid matters, such as high concentration of protein and polysaccharide, and easy pollution of membranes. Therefore, in this filtration, the cleaning of the membrane is very frequent, and the filtration performance of the membrane is recovered by the cleaning, so that the production can be continuously performed. The proper and efficient cleaning process plays an important role in the stable operation of the membrane method fermentation liquor filtration.
The known example 1 discloses a method for cleaning a draft beer membrane, which adopts the conventional manners of water washing, alkaline washing and membrane cleaning regeneration enzyme preparation washing, but the washing time is very long, the whole set of washing process needs 64-120 hours, and the time cost for washing is high.
The known example 2 discloses a membrane cleaning method for treating wastewater from membrane oil recovery, which comprises 6 cleaning steps of physical cleaning and chemical cleaning, wherein the chemical cleaning adopts the methods of acid cleaning, alkali cleaning, oxidant cleaning, membrane cleaning auxiliary agent cleaning and surfactant cleaning, and the cleaning steps are very complicated and the types of used medicaments are too many.
Known example 1: CN 102492663A.
Publicly known example 2: CN 106110895A.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the defects that the membrane is easy to pollute, the filtering time is short, the cleaning recovery rate is low, the existing cleaning method and cleaning agent are complicated, the consumed time is long, and the cleaning cost is high in the traditional high-organic-content fermentation liquid membrane method filtering process, the method which is long in membrane filtering time, low in chemical cleaning cost and high in cleaning recovery rate is provided, and the stable operation of a fermentation liquid membrane method filtering system is ensured. In addition, the object of the invention can be achieved by the following measures:
1. a fermentation liquid membrane filtration method comprises the following steps:
a. the fermentation liquor is filtered by adopting a cross-flow membrane filtration method;
b. after the step a, performing a membrane module water washing step;
c. b, contacting the membrane module with the medicament;
d. after the step c, performing a water washing step of the membrane module;
in the step a, the concentration of the sugar substances in the cross-flow membrane permeate is more than 1000mg/L and less than 100000mg/L, and the concentration of the protein is more than 50mg/L and less than 1000 mg/L; step c further comprises the step of injecting a cleaning solution containing a membrane cleaning aid from the primary side to the secondary side of the membrane and injecting a cleaning solution containing hypochlorite and a surfactant into the membrane module; the steps a-d are repeatedly and circularly carried out.
2. The method for filtering a fermented liquid membrane according to claim 1, wherein the step a comprises an operation of intermittent backwashing.
3. The fermentation liquid membrane filtration method according to the above 1 or 2, wherein the filtration time interval of the intermittent backwashing is 3min to 60min, and the backwashing time is 10s to 120 s.
4. The fermentation liquid membrane filtration method of claim 1, wherein the membrane cleaning auxiliary is an enzyme preparation or a sodium hydroxide solution.
5. The fermentation liquid membrane filtration method according to 1 or 4, wherein the enzyme preparation is protease, mannanase or β -glucanase.
6. The method for filtering a fermented liquid film according to claim 1, wherein the washing means of the washing solution containing hypochlorite and a surfactant includes a static soaking means, a chemical solution circulating means, or a washing means in which both means are alternately performed.
7. The fermentation liquid membrane filtration method according to claim 6, wherein the cross flow velocity of the membrane surface of the liquid medicine circulation is 0.1m/s to 3 m/s.
8. The fermentation liquid membrane filtration method according to the above 1, wherein the product of the concentration C of hypochlorite in mg/L and the contact time T of hypochlorite with the membrane in h in the step C satisfies the following formula 1:
9.2×105f-1400 ≦ CT ≦ 2.5(1/α) +380 formula 1
Wherein F is the ratio of the concentration mg/L of protein in the permeate liquid in the cross-flow membrane filtration in the step a to the concentration mg/L of total organic carbon in the permeate liquid; alpha is that the cross-flow membrane is soaked in 5000ppmH2O2And 300ppmFe2+In the formed Fenton reagent solution, the absolute value of the attenuation rate of the ratio of the film strength to the initial strength under different soaking time conditions is 1/h.
The invention is suitable for the original fermentation liquor substance with the saccharide substance concentration of more than 1000mg/L and less than 100000mg/L and the protein concentration of more than 50mg/L and less than 1000mg/L of the permeate after the cross-flow filtration membrane, and further preferably the original fermentation liquor substance with the saccharide substance concentration of more than 10000mg/L and less than 80000mg/L and the protein concentration of more than 100mg/L and less than 600mg/L of the permeate after the cross-flow filtration membrane. The change of the organic matter concentration before and after the fermentation liquid is filtered is related to the aperture of the filtering membrane, if the molecular weight of the organic matter in the fermentation liquid is smaller than the cut-off molecular weight of the filtering membrane, and the organic matter of the fermentation liquid completely permeates the membrane, the concentration of the permeated liquid is similar to the concentration of the original liquid. If the molecular weight of the organic matter of the fermentation liquid is larger than the molecular weight cut-off of the filtering membrane, the concentration of the permeation liquid is lower than that of the original liquid due to the cut-off of the membrane.
The membrane component can be a flat membrane, a hollow fiber membrane, a tubular membrane or a membrane component with other shapes, and the hollow fiber membrane is preferably selected due to the characteristics of large specific surface area and high filling rate. The membrane material can be an organic membrane or an inorganic membrane, preferably an organic membrane with low price, and the organic membrane material can be PES, PSF, PTFE or PVDF; the PVDF material is preferred because of its heat resistance, high physical strength and good chemical durability.
The pore diameter of the separation membrane is selected according to the size of the separation target, and a membrane having an average pore diameter of 0.01 μm or less is preferably 0.01 to 1.0 μm because the water permeability is low and a membrane having a pore diameter of more than 1.0 μm may cause leakage of microorganisms. In the case of filtration of beer fermentation liquid, in order to ensure that flavor substances in beer can permeate through the membrane and reduce membrane fouling, the membrane preferably has an average pore diameter of 0.3 μm or more and 1.0 μm or less, and more preferably 0.4 μm or more and 0.8 μm or less. When the pore size of the separation pore is 0.3 μm or less, flavor components in beer may be trapped and the tendency of contamination is large.
The filtration commonly used in water treatment is dead-end filtration, while cross-flow filtration is a better filtration mode for fermentation broth with higher organic matter concentration content. Compared with dead-end filtration, cross-flow filtration can slow down the accumulation of pollutants on the membrane surface and prolong the running time of the membrane. The cross-flow filtration can be preferably added with an intermittent backwashing step, and the intermittent backwashing can regularly flush the pollutants accumulated on the membrane surface and in the membrane holes in the filtration process, so that the filtration resistance of the membrane is reduced, and the operation time of the membrane is better prolonged. The time interval of the intermittent backwashing is preferably 3min to 60min, more preferably 5min to 30min, the filtering time is less than 3min, and the backwashing pump, the filtering pump and relevant valves are opened very frequently, which easily causes the damage of equipment. The filtering time is more than 60min, the blockage of membrane holes and membrane surfaces is serious, and the backwashing effect can not be ensured. The backwashing time is preferably 10s to 120s, more preferably 10s to 60s, and is less than 10s, and the backwashing has a limited effect of washing off the contaminants accumulated on the membrane surface and the membrane pores. The backwashing time is more than 120s, the energy consumption of the backwashing is increased, and the operation cost of the membrane filtration is increased. The filtration flux of the membrane of the cross-flow filtration is preferably 0.1m/d-3m/d, and further preferably 1m/d-2.5m/d, the filtration flux is lower than 0.1m/d, the number of required membranes is large, the operation cost is high, the filtration flux is higher than 3m/d, the membrane pollution speed is accelerated, and the cleaning frequency and the cleaning cost are increased. The backwashing flux is preferably 1m/d-10m/d, and is further preferably 3m/d-6m/d, the backwashing flux is lower than 1m/d, the backwashing effect is relatively limited, the backwashing flux is higher than 10m/d, the energy consumption of backwashing is increased, and the operation cost of membrane filtration is increased.
And after the membrane filtration is finished, performing a water washing step b of the membrane component, wherein the water washing is used for washing organic pollutants in the membrane component by using water before the next chemical cleaning, so that the medicament load of the subsequent chemical cleaning is reduced. The water washing can adopt a cross flow washing and filtering mode and can also adopt a dead end filtering and washing mode.
And c, after the water washing step b is finished, carrying out a step c of contacting the membrane component with a medicament, namely a step of chemically cleaning the membrane component, wherein a good cleaning effect is a necessary condition for ensuring the normal operation of the membrane component. The step comprises the steps of injecting a cleaning liquid containing a membrane cleaning aid from the primary side to the secondary side of the membrane and injecting a cleaning liquid containing hypochlorite and a surfactant into the membrane module. The step of injecting the cleaning solution containing the membrane cleaning assistant from the primary side to the secondary side of the membrane may be performed before or after the step of injecting the cleaning solution containing hypochlorite and a surfactant into the membrane module. Since the membrane cleaning aid can decompose membrane fouling materials, it is preferred to precede the hypochlorite and surfactant cleaning step in the cleaning solution.
And injecting a cleaning solution containing a membrane cleaning auxiliary agent from the primary side to the secondary side of the membrane and keeping the membrane cleaning auxiliary agent for a certain time, wherein the membrane cleaning auxiliary agent is preferably an enzyme preparation or a sodium hydroxide solution, and the enzyme preparation is preferably protease, mannanase or beta-glucanase. Because the fermentation liquor often contains protein and carbohydrate with higher concentration, and the substances are also substances which are easy to cause membrane pollution, the substances are decomposed into micromolecular substances by adopting an enzyme preparation, and then other medicaments are adopted for cleaning, so that a better cleaning effect can be obtained. The enzyme preparation is generally washed at 30-40 deg.C for 12-40 hr. In addition, the cleaning assistant may be a sodium hydroxide solution, and the pH of the sodium hydroxide solution is preferably 10 or more and 14 or less, and more preferably 11 or more and 13 or less, and is lower than 10, so that the cleaning effect cannot be ensured, and the pH is higher than 13, which increases the cost of chemical cleaning. The cleaning temperature is preferably 20 ℃ to 50 ℃. The cleaning temperature is below 20 ℃ and a good cleaning effect cannot be obtained, and the cleaning temperature is above 50 ℃ and the energy consumption cost of cleaning is increased. The cleaning time of the sodium hydroxide is preferably 1 hour to 4 hours, the cleaning time is less than 1 hour, the cleaning effect may not be sufficient, and the cleaning time is more than 4 hours, which increases the cleaning time cost. The sodium hydroxide solution has a good dissolving effect on organic pollutants of the membrane, in the invention, the cleaning of the membrane cleaning auxiliary agent is a very key step, and a better cleaning effect can be obtained by combining with subsequent cleaning, wherein the better cleaning effect refers to that the water permeability recovery rate can reach a level of more than 80% after the membrane is cleaned. After the cleaning of the cleaning assistant, the cleaning liquid of the membrane cleaning assistant remained in the filtration membrane system is emptied, and the cleaning liquid containing hypochlorite, which can be sodium hypochlorite, calcium hypochlorite, potassium hypochlorite or the like, preferably sodium hypochlorite, and surfactant is injected into the membrane module and kept for a certain time. The sodium hypochlorite is a common agent in membrane cleaning, has low cost and good cleaning effect, but has certain requirements on the oxidation resistance of the membrane, and the optimal PVDF membrane with strong oxidation resistance is adopted, and the cleaning effect of the sodium hypochlorite can be ideal. The effective chlorine concentration of sodium hypochlorite is preferably 0.05% to 1%, more preferably 0.1% to 0.5%, and the effective chlorine concentration is less than 0.05%, and a good cleaning effect cannot be obtained, and when the effective chlorine concentration is more than 1%, the cleaning cost of the chemical agent is greatly increased.
The pH value of hypochlorite cleaning is preferably 10-14, more preferably 11-13, because the pollutants of the fermentation liquor filtering membrane mainly comprise organic matters, the high pH value condition can obtain better cleaning effect, and the pH value is lower than 10, so the cleaning effect cannot be ensured.
The surfactant is preferably a nonionic surfactant such as Tween20, Trion X-100 or octyl- β -D-glucopyranoside, and the like, preferably a nonionic surfactant having a hydrophilic lipophilic balance HLB of 12 to 18, and more preferably a nonionic surfactant having a hydrophilic lipophilic balance HLB of 13 to 17. With the nonionic surfactant in the preferred range, a better cleaning effect can be obtained.
The concentration of the surfactant is preferably 0.02% to 3% by mass, more preferably 0.02% to 1% by mass, and the surfactant concentration is 0.02% or less, and the amount of the surfactant to be added is too low to reach the critical micelle concentration of the surfactant, and thus a desired cleaning effect cannot be obtained. The addition concentration of the surfactant is more than 3%, so that the cleaning cost is increased, the surfactant is also an organic matter, and the membrane pollution is easily caused by higher concentration.
The cleaning solution of hypochlorite and surfactant can be added into the membrane component for cleaning alone or mixed with the membrane component, and the membrane component is preferably cleaned in a mixing way. In addition, the invention does not limit the cleaning steps of adding other liquid medicines besides the cleaning of the two medicines.
The cleaning temperature is preferably 20 ℃ to 50 ℃. The cleaning temperature is below 20 ℃ and a good cleaning effect cannot be obtained, and the cleaning temperature is above 50 ℃ and the energy consumption cost of cleaning is increased. The cleaning time is preferably 1 hour to 4 hours, the cleaning time is less than 1 hour, the cleaning effect is insufficient, the cleaning time is more than 4 hours, and the cleaning time cost is increased.
The cleaning mode of the cleaning solution containing hypochlorite and the surfactant comprises a static soaking mode, a liquid medicine circulation mode or a cleaning mode in which the hypochlorite and the surfactant are alternately carried out. Wherein the cross flow speed of the membrane surface for circulating the liquid medicine is preferably 0.1m/s-3 m/s. When the cross flow speed of the membrane surface is lower than 0.1m/s, the scouring force of the membrane surface is insufficient, and when the cross flow speed of the membrane surface of the liquid medicine circulation is higher than 3m/s, the cost of the required cross flow power is increased.
And c, after the membrane module is contacted with the medicament, performing water washing on the membrane module, namely firstly emptying the liquid medicament in the membrane module, and then performing water washing on the membrane module. This step is also critical, and residual chemicals, especially surfactants, in the components are also prone to contamination of the film and can affect the quality of the product produced subsequently. The rinsing step of the water is the same as the washing of the mixed washing solution containing hypochlorite and a surfactant, and a static soaking mode, a circulating mode or a rinsing mode in which the two modes are alternately carried out can be adopted.
The steps a-d are repeatedly and circularly carried out. The repeated cleaning and filtering of the membrane in the fermentation liquor filtering is a key element for normal use of the membrane, and the cleaning method can ensure the cleaning effect of the membrane, ensure the normal filtering operation of the membrane and prolong the service life of the membrane component.
Further, it is preferable to use a set of 2 parameters of the concentration of organic matter in the permeate of the membrane module and the oxidation resistance of the membrane used as the conditions for adding hypochlorite for cleaning. And (3) establishing hypochlorite adding conditions according to the two parameters to ensure long-term stable operation of the membrane module.
Specifically, the addition conditions are characterized by the product CT value [ (mg/L). h ] of the concentration Cmg/L of hypochlorite in contact with the membrane and the contact time Th of the hypochlorite with the membrane.
The CT value is selected in the oxidation resistance range of the membrane, so that not only can attached pollutants be removed, but also the degradation time of the membrane can be delayed, and the stable operation of the system can be ensured.
For example, when the CT value is high, the oxidation resistance of the film is exceeded, and the deterioration of the film is accelerated, so that the film life is shortened. In addition, when the CT value is low, the contaminants adhering to the membrane cannot be completely removed, and a good cleaning effect cannot be obtained. The amount of contaminants attached to the membrane as referred to herein is related to the concentration of the feed stock solution to the membrane module and the concentration of the permeate solution.
Therefore, in order to ensure the service life of the membrane, a good cleaning effect can be ensured. And selecting a proper CT value by adopting 2 parameters of the concentration of the permeation liquid and the oxidation resistance of the separation membrane. The selection method of each parameter is discussed in detail below.
One of the parameters is the concentration of the permeate of the membrane module, and according to the test result, if the adding condition of hypochlorite is matched with the concentration of protein in the permeate, good cleaning effect can be obtained.
The ratio Cp/TOC of the protein concentration Cp [ mg/L ] in the permeate of the cross-flow filtration membrane in step a to the total organic carbon TOC concentration [ mg/L ] in the permeate is represented by F, and preferably satisfies the range of the following formula 2, and more preferably satisfies the range of the following formula 3.
9.2×105F-1400 ≦ CT formula 2
3.8×106F-5700 ≦ CT formula 3
The relationship between the F value and the CT value in equation 2 is shown in FIG. 2. In the filtration of fermentation liquor, the higher the F value in the filtrate, the more contaminants cause the clogging of the separation membrane. Therefore, under the condition of cleaning a polluted membrane caused by filtering the fermentation liquor, a proper CT value is selected according to the F value of the filtrate, so that the excessively low or high cleaning concentration of the liquid medicine can be avoided, and a good cleaning effect with low cost can be obtained.
Particularly, under the conditions of the present invention, when the concentration of the saccharide substance in the permeate of the membrane module membrane of the fermentation liquid is 1000mg/L to 100000mg/L, and the concentration of the protein substance is 50mg/L to 1000mg/L, the chemical cleaning method satisfying formula 2 can obtain a good cleaning effect, and a repeated filtration cleaning test can be performed.
Further preferably, a chemical cleaning method satisfying the CT value of formula 3 can obtain a better cleaning effect. The term "good cleaning effect" as used herein means that the water permeability of the membrane module after cleaning can be recovered to a level of 80% or more, as compared with the water permeability of a fresh membrane module before filtration.
The F value can also be expressed as the ratio of the protein concentration in the stock solution to the total organic carbon concentration in the stock solution.
The 2 nd parameter is defined as the oxidation resistance of the film. The oxidation resistance of the film depends on the material and structure of the film. The oxidation resistance of the film was evaluated by immersing the film in a Fenton reagent and measuring the film strength at different immersion times, and comparing the film strength with that of a new film, using a film oxidation resistance strengthening test.
The Fenton reagent is a solution containing hydrogen peroxide and an iron ion catalyst, and can generate hydroxyl radicals with strong oxidizing property. Fenton reagent is a commonly used oxidizing agent in industrial wastewater treatment. In the present invention, the compound is used as a chemical for a film oxidation test.
Specific test methods are shown below. First, Fenton reagent was prepared using hydrogen peroxide and ferrous sulfate heptahydrate, where the concentration of hydrogen peroxide was 5000ppm, Fe2+The concentration of (B) is 300 ppm. Immersing the membrane in the Fenton reagent for a certain time t [ h ]]. Before the use of the film, the film was hydrophilized with ethanol.
Soaking in Fenton reagent for t [ h]After this time, the membrane was rinsed clean with distilled water and dried under vacuum at room temperature. The dried membrane (sample M) was soaked in the Fenton reagent1Indicated) and vacuum dried membrane (as sample M) without Fenton reagent soak0Indicated) was measured for film strength. The method of measuring the film strength is not limited, and for example, a tensile tester of TENSILON/RTM-100 available from Toyo Baldwin corporation may be used to measure a sample having a length of 50mm, and the average value of the breaking force of the sample may be obtained by performing a test of 5 cycles or more under a condition of a tensile rate of 50 mm/min. The average value was divided by the cross-sectional area of the film to obtain the breaking strength of the film.
Sample M obtained by the method before immersion of Fenton reagent0Breaking strength S of0And Fenton reagent soaking for t [ h ]]Time sample MtBreaking strength S oftThe relationship of (c) is shown in fig. 3. Using the S obtainedtAnd S0Obtaining the immersion time t [ h ] of the Fenton reagent]Corresponding St/S0The ratio of (a) to (b), i.e., the initial value ratio of the film strength.
The initial value ratio S of film strength obtained by the above methodt/S0Soaking time t [ h ] with membrane Fenton reagent]The relationship of (2) is shown in FIG. 4. As the soaking time of the membrane in the Fenton reagent is prolonged, the oxidation of the membrane is promoted, and the initial value of the membrane strength is St/S0And (4) descending. St/S0At the same time t [ h ]]The relationship (A) is related to the oxidation resistance of the film, the film with strong oxidation resistance, St/S0With respect to time t [ h ]]The slope of the change of (a) is relatively small. For example, in FIG. 4, film A is compared to film B, St/S0With respect to timet[h]The slope of (a) is smaller and the oxidation resistance of film a is better than that of film B.
According to the accelerated oxidation strengthening test described above, the initial value ratio S of the film strengtht/S0Soaking time t [ h ] with membrane]The absolute value of the slope of the relationship is at an attenuation rate alpha 1/h]And (4) showing. α is a parameter that characterizes the oxidation resistance of the film, in relation to the material, structure and state of degradation of the film. To ensure the service life of the film, the film is used with a damping factor alpha 1/h]Preferably, the following formula 4 is satisfied. More preferably, the following formula 5 is satisfied, and still more preferably, the following formula 6 is satisfied.
CT ≦ 2.5(1/α) +380 formula 4
CT ≦ 1.4(1/α) +240 formula 5
CT ≦ 0.56(1/α) +95 formula 6
The relationship between α and CT value in equation 4 is shown in fig. 5. The liquid medicine cleaning satisfying the CT value of formula 4 can ensure the service life of the membrane, and can perform repeated filtration/cleaning tests. It is further preferable that the chemical cleaning satisfying formula 5 is performed, the service life of the membrane is longer, and the filtration/cleaning test can be repeated more times. Further preferably, the liquid medicine cleaning which satisfies the formula 6 can ensure longer membrane life and ensure more repeated filtration.
As described above, the chemical cleaning method satisfying the CT values of the equations 2 and 4 can obtain a desired cleaning effect while ensuring the life of the film. The CT value preferably satisfies the following formula 1. The lower limit of formula 1 is more preferably formula 3. The upper limit of formula 1 is preferably replaced by formula 5, and more preferably replaced by formula 6.
9.2×105F-1400 ≦ CT ≦ 2.5(1/α) +380 formula 1
The CT value is calculated from all parameters of the hypochlorite cleaning step in the step c. The specific calculation method is as follows.
Step c implements a contacting step of the agent containing hypochlorite with the membrane, followed by a subsequent water rinsing step d. In the step c, the chemical washing step of 1-time hypochlorite is performed, and in this case, the CT value in the washing step of 1-time is the CT value in the step c.
On the other hand, if the washing step in step c contains both hypochlorite and other chemicals, the two conditions are alternately carried out a plurality of times, and then the subsequent water washing step d is carried out. In this case, the CT values of the respective steps using hypochlorite are calculated and then summed, and the sum is the CT value of step c.
Drawings
FIG. 1 is a flow chart for using the present invention. Wherein, 1 is a fermentation liquor stock solution tank, 2 is a membrane component, 3 is a stock solution liquid feeding pump, 4 is a permeation solution tank, 5 is a cleaning water tank, 6 is a circulation control valve, 7 is a permeation solution control valve, 8-14 are valves, 15-17 are pressure gauges, 18-20 are flow meters, 21 is a backwashing pump, and 22 is a backwashing control valve.
FIG. 2 is a schematic diagram showing the relationship between the CT value and the ratio F between the protein concentration and the total organic carbon concentration in the permeate of the membrane module of the present invention.
Fig. 3 is a schematic view showing a relationship between the immersion time of the Fenton reagent and the breaking strength of the separation membrane in the present invention.
Fig. 4 is a schematic diagram showing a change relationship between the immersion time of the Fenton reagent and the initial strength value ratio of the separation membrane in the present invention.
Fig. 5 is a schematic view showing a relation between the attenuation factor α and the CT value of the separation membrane of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.
As shown in fig. 1, a fermentation liquid is put in a liquid tank 1, and is fed into a membrane module 2 by a liquid feed pump 3, and a membrane permeate is fed into a permeate tank 4. The valve 6 is a cross flow circulation control valve, when cross flow filtration is carried out, the valve 6 is opened, and part of stock solution flows back to the stock solution tank 1. In the intermittent backwashing, permeate is sent into the membrane module by a backwashing pump 21, and backwashing discharge liquid flows back to the raw liquid tank 1. In the chemical cleaning, the chemical for cleaning the chemical tank 5 is introduced into the membrane module 2 through the liquid feeding pump 3 to perform cleaning, and a cleaning method of dead-end filtration or a cleaning method of cross-flow filtration may be employed. The contamination state of the membrane module 2 is determined by the pressure on the raw liquid side and the pressure difference on the permeate side. When the dead end is filtered, the membrane pressure difference is calculated by the pressure of a pressure gauge 16 at the feed end of the stock solution and the pressure difference of a pressure gauge 17 at the outlet side. As membrane fouling occurs, the pressure differential rises. However, in the case of cross-flow filtration, the pressure loss at the stock solution side that flows back to the stock solution tank 1 in a cross-flow manner is large, and it is difficult to calculate the membrane differential pressure by the above-described method.
The calculation of the pressure difference during cross-flow filtration is obtained by recording the pressure P1 of the permeate side pressure gauge 17 when the permeate control valve 7 is closed during the circulating filtration of the stock solution between the stock solution tank 1 and the membrane module 2, recording the pressure P2 of the permeate side pressure gauge 17 when the permeate control valve 7 is opened during the circulating filtration of the stock solution between the stock solution tank 1 and the membrane module 2, wherein the difference between P1 and P2 is the pressure difference DeltaP between membranes, judging the pollution state of the membranes through the DeltaP, and generally, carrying out chemical cleaning on the membrane module 2 when the DeltaP is increased to 200-250 kPa. The tests involved in the examples and comparative examples are illustrated below:
(1) determination of Water permeability recovery
The recovery rate of the water permeability of the agent cleaning refers to the ratio of the pure water permeability coefficient of the membrane after cleaning to the pure water permeability coefficient of the fresh membrane that is not used. The pure water permeability coefficient was measured by supplying pure water to the membrane module under a pressure of 50kPa and at 25 ℃ and measuring the amount of water permeated through the membrane, and the water permeability recovery of the membrane was calculated by the following equation.
Water permeability coefficient of pure water [ m ]3/m2/h]Amount of permeated water [ m3]V (membrane area [ m)2]X test time [ hr])
Water permeability recovery [% ]]Water permeability coefficient [ m ] of pure water after cleaning3/m2/hr]Pure water permeability coefficient [ m ] of the novel film3/m2/hr]×100
(2) Determination of Total organic carbon concentration
Total organic carbon concentration of the samples was measured using a TOC tester, model TOC Lch from Shimadzu corporation.
(3) Measurement of saccharide concentration
The saccharide concentration was measured by phenol-concentrated sulfuric acid method, 0.5ml of 0.8% phenol was added to 2ml of the sample, 5ml of concentrated sulfuric acid was added, the mixture was left at room temperature for 20min, and the absorbance was measured at 486 nm. The standard curve is prepared by adopting a glucose standard solution, and the concentration of the carbohydrate in the sample is calculated according to the standard curve.
(4) Measurement of protein concentration
The protein of the sample was measured using Bradford reagent (manufactured by Beijing Saichi Biotech Co., Ltd., No. 300001-B2). To 0.5ml of the sample was added 2ml of Bradford reagent, and the absorbance was measured at 595 nm. The standard curve is prepared by bovine serum albumin standard samples, obtained by the same test method, and the protein concentration in the samples is calculated according to the standard curve.
(5) Fenton reagent enhanced oxidation test
The Fenton reagent is prepared by adopting hydrogen peroxide and ferrous sulfate heptahydrate, wherein the concentration of the hydrogen peroxide is 5000ppm, and the Fe content is2+The concentration of (2) was 300ppm, and the membrane was hydrophilized with ethanol. And soaking the membrane in the Fenton reagent for 25 hours, 50 hours, 100 hours, 150 hours and 250 hours, washing the membrane by using distilled water after soaking is finished, and drying the membrane in vacuum at room temperature.
(6) Calculation of the attenuation Rate alpha
The film strength of the new film not subjected to the intensified oxidation soaking test and the film of each soaking time of the intensified oxidation soaking test were measured by the following method.
Film strength S according to a fresh film not subjected to the intensified oxidation soak test0Membrane strength S after soaking with Fenton reagenttCalculating the initial value ratio of film strength, plotting the initial value ratio of film strength and soaking time to obtain the absolute value of slope as the decay rate alpha 1/h]。
(7) Measurement of film Strength
A tensile tester Tensilon/RTM-100 (Toyo Baldwin Co.) was used to measure a 50mm length sample, and the average tensile strength of the sample was obtained by conducting 5-pass test at a tensile rate of 50 mm/min. The average value was divided by the cross-sectional area of the film to obtain the breaking strength of the film.
Example 1
Adopting cross-flow membrane filtration method to treat commercially available raw stockThe beer was filtered, and the commercially available virgin pulp beer A was Arcobrau virgin pulp beer, Germany, having a membrane permeate sugar concentration of 31000mg/L, a protein concentration of 175mg/L, and an F value of 0.0028. The filtering membrane is made of PVDF, the pore diameter of the membrane is 0.6 mu m, and the alpha value is 5 x 10-51/h, the membrane filtration flux is 2m/d, the filtration time is 2 hours, after the filtration step a, the membrane module is washed by pure water, then the membrane module is chemically cleaned, firstly, the beta-glucanase is injected from the primary side to the secondary side of the membrane module, the soaking temperature is 35 ℃, the soaking time is 20 hours, and after the soaking is finished, the beta-glucanase solution is emptied. Then injecting sodium hypochlorite and nonionic surfactant Tween20(HLB16.7) into the membrane module, wherein the concentration of the sodium hypochlorite is 0.3%, the concentration of the Tween20 is 0.05%, the pH value of the medicament is 12, the temperature is 35 ℃, and the cleaning is carried out circularly for 2 hours, wherein the cross flow speed of the circulation of the liquid medicament is 1.5 m/s. And after the cleaning is finished, the cleaning agent in the membrane module is emptied. And d, carrying out a pure water washing step d on the membrane module, wherein the washing condition is the same as that of chemical cleaning, the cross flow speed is 1.5m/s, the washing time is 5min, and emptying the membrane module after the washing is finished. Then a repeat of 5 flushes was performed. And repeating the step 3 of a-d, and testing the pure water permeability coefficient of the membrane module after the step is finished, wherein the calculated water permeability recovery rate of the agent cleaning is 95%.
Specific parameters are shown in table 1.
Examples 2-15, the procedure was the same as in example 1 except for the conditions listed in table 1, wherein beer B was a Qingdao laoshan mai virgin stock beer.
Examples 16 to 18
The procedure was the same as in example 1 except for the conditions listed in Table 2, with the parameters of filtration time and intermittent backwash time being increased mainly, with a backwash flux of 4 m/d.
Comparative example 1
As shown in table 3, the procedure was the same as that performed in example 1 except that the conditions listed in table 3 were used, and the membrane cleaning operation was performed in a single cleaning step using a 0.3% NaClO & 0.05% Tween20 reagent, and the cleaning recovery was only 65%.
Comparative example 2
As shown in Table 3, the procedure of example 1 was the same except for the conditions shown in Table 3, and the membrane cleaning operation was carried out in a single cleaning step using 0.01mol/L NaOH, and the cleaning recovery was only 50%.
Comparative example 3
As shown in Table 3, the procedure of example 1 was the same except for the conditions shown in Table 3, and the target substance was an enzyme preparation fermentation broth, and the washing recovery rate was only 60% under the washing conditions shown in Table 2.
Comparative example 4
As shown in Table 3, the procedure of example 1 was the same except for the conditions shown in Table 3, and the target substance was a liquid sugar fermentation broth, and the washing recovery rate was only 68% under the washing conditions shown in Table 2.
TABLE 1
TABLE 2
TABLE 3
Comparing the examples and the comparative examples, it can be seen that, aiming at the fermentation liquor with the sugar concentration of the membrane permeate liquid being more than 1000mg/L and less than 100000mg/L and the protein concentration being more than 50mg/L and less than 1000mg/L, the method of the invention can prolong the filtration time of the membrane, simultaneously obtain more ideal chemical cleaning recovery rate and ensure the long-term stable operation of the membrane filtration.
Claims (7)
1. A fermentation liquid membrane filtration method comprises the following steps:
a. the fermentation liquor is filtered by adopting a cross-flow membrane filtration method;
b. after the step a, performing a membrane module water washing step;
c. b, contacting the membrane module with the medicament;
d. after the step c, performing a water washing step of the membrane module;
the method is characterized in that: in the step a, the concentration of the sugar substances in the cross-flow membrane permeate is more than 1000mg/L and less than 100000mg/L, and the concentration of the protein is more than 50mg/L and less than 1000 mg/L; step c further comprises the step of injecting a cleaning solution containing a membrane cleaning aid from the primary side to the secondary side of the membrane and injecting a cleaning solution containing hypochlorite and a surfactant into the membrane module; the steps a to d are repeatedly and circularly carried out; the product of the concentration C of hypochlorite in step C, which is in mg/L, and the contact time T of the hypochlorite with the membrane, which is in h, satisfies the following formula 1:
9.2×105f-1400 ≦ CT ≦ 2.5(1/α) +380 formula 1
Wherein F is the ratio of the concentration mg/L of protein in the permeate liquid in the cross-flow membrane filtration in the step a to the concentration mg/L of total organic carbon in the permeate liquid; alpha is that the cross-flow membrane is soaked in 5000ppmH2O2And 300ppmFe2+In the formed Fenton reagent solution, the absolute value of the attenuation rate of the ratio of the film strength to the initial strength under different soaking time conditions is 1/h.
2. The fermentation liquid membrane filtration method according to claim 1, wherein: the step a comprises an operation step of intermittent backwashing.
3. The fermentation liquid membrane filtration method according to claim 2, wherein: the filtration time interval of the intermittent backwashing is 3min-60min, and the backwashing time is 10s-120 s.
4. The fermentation liquid membrane filtration method according to claim 1, wherein: the membrane cleaning auxiliary agent is an enzyme preparation or a sodium hydroxide solution.
5. The fermentation liquid membrane filtration method according to claim 4, wherein: the enzyme preparation is protease, mannase or beta-glucanase.
6. The fermentation liquid membrane filtration method according to claim 1, wherein: the cleaning mode of the cleaning solution containing hypochlorite and the surfactant comprises a static soaking mode, a liquid medicine circulation mode or a cleaning mode in which the hypochlorite and the surfactant are alternately carried out.
7. The fermentation liquid membrane filtration method according to claim 6, wherein: the membrane surface cross flow speed of the liquid medicine circulation is 0.1-3 m/s.
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