CN111533322B - Membrane pollution control method for treating microbial polluted wastewater by ultrafiltration - Google Patents
Membrane pollution control method for treating microbial polluted wastewater by ultrafiltration Download PDFInfo
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Abstract
The invention belongs to the field of wastewater treatment, and discloses a membrane pollution control method for treating microbial polluted wastewater by ultrafiltration, which comprises the following steps: 1) firstly, measuring the pH value of a solution of a polluted water body, adding a certain amount of poly dimethyl diallyl ammonium chloride and an inorganic coagulant according to the pH range of the water body, and carrying out coagulation treatment under a certain stirring condition; 2) after the step 1), transferring the reaction wastewater and the generated flocs to an ultrafiltration system together, and performing ultrafiltration treatment by using an ultrafiltration membrane; 3) and 2) backwashing the ultrafiltration membrane by using pure water after the step 2) is finished. The invention provides the dosage ranges of the inorganic coagulant and the poly dimethyl diallyl ammonium chloride optimized for wastewater with different pH values, and the coagulation efficiency and the properties of the coagulated flocs are regulated and controlled, so that the pollution degree of a coagulation-membrane filtration process to a membrane can be effectively relieved, the membrane flux recovery efficiency is improved, and the service life of the membrane is effectively prolonged.
Description
Technical Field
The invention belongs to the field of wastewater treatment, and particularly relates to a membrane pollution control method for treating microbial polluted wastewater by ultrafiltration.
Background
The ultrafiltration process is one of membrane separation technologies, is a common advanced water treatment process, has the advantages of stable effluent quality, high safety, small occupied area, easy realization of automatic control and the like, and is called as a third-generation drinking water treatment technology. Ultrafiltration has been widely used in the treatment of microbial contaminated wastewater. However, in practical applications, the decrease in membrane performance due to membrane fouling not only reduces membrane flux, but also shortens the membrane life. Therefore, an economic and efficient membrane pollution control method is sought, and the method has important significance for recovering the membrane flux and prolonging the service life of the membrane.
For the membrane pollution control method, through retrieval, related applications have been published, for example, the application with chinese patent application number 2011100441848 and publication date 7/20/2011 discloses a membrane pollution control method, which comprises the following specific steps: 1) pretreating the surface of the new membrane by adopting a nonionic surfactant; then back washing and soaking by reverse osmosis water; 2) the membrane after the treatment is used for treating sewage containing oil and cationic surfactant, and nonionic surfactant is added when the membrane is used; 3) after the membrane is polluted, the flux can be recovered by washing with reverse osmosis water. The method can effectively control the irreversible pollution of the cationic surfactant in the oily sewage to the ultrafiltration membrane.
However, the microorganism polluted water is different from the conventional turbidity-organic matter coexisting water body, and the water body simultaneously contains a large amount of microorganism cells and organic matters, so that the components are complex, and the treatment process has certain difficulty. For example, the algae-containing water contains a large amount of algae cells and algae-derived organic matters released in the growth or death process of algae; on the other hand, the algal cells are susceptible to cell wall disruption during wastewater treatment resulting in the release of more intracellular secretions. The algae metabolites are usually macromolecular organic matters, and in the membrane filtration process, not only can larger polymers be formed through intermolecular force to be trapped by the membrane surface, but also more algae cells and other secretion substances can be adhered to the membrane surface through chemical bond action, and finally more serious membrane pollution is caused. Therefore, in the ultrafiltration process of the biologically polluted water, the purposes of relieving membrane pollution and prolonging the service life of the membrane are difficult to achieve by the way of cleaning the biologically polluted water by the ionic surfactant.
The coagulation is used as the most important and basic process unit in water treatment, and can be used as pretreatment to effectively reduce the pollution of the ultrafiltration membrane. The coagulation treatment can reduce the concentration of pollutants in the ultrafiltration inlet water and improve the quality of the ultrafiltration inlet water to achieve the aim of controlling the pollution of the ultrafiltration membrane. In this process, conventional iron-based coagulants such as ferric sulfate, ferric chloride, polymeric ferric sulfate and polymeric ferric chloride are common. Titanium coagulants are a new class of inorganic metal coagulants, and have been increasingly applied to practical engineering due to their good coagulation properties. In the using process of the iron-based coagulant and the titanium-based coagulant, due to the strong electric neutralization capacity and the large size of the flocs after hydrolysis, pollutants can be effectively adsorbed and wrapped, so that organic matters can be effectively removed, and turbidity is reduced. When the membrane is used as an ultrafiltration pretreatment agent, the larger floc size of the membrane forms a looser filter cake layer, so that the surface of the membrane can be effectively protected from being directly polluted by pollutants, the flux of the membrane is ensured, the membrane is convenient to clean, and the service life of the membrane is prolonged. In addition, after the coagulant is added and used, secondary pollution to water quality can not be caused, and the concentration of residual metal ions in effluent is in the national standard range.
Poly dimethyl diallyl ammonium chloride (PDMDAAC) is a polymeric cationic high molecular organic substance, can be used as a coagulant aid to be applied to a coagulation process, and improves the efficiency of an inorganic coagulant in treating wastewater. Based on the above, the novel membrane pollution control method capable of effectively relieving microorganism pollution wastewater of ultrafiltration treatment can be invented by combining the coagulation behaviors of PDMDAAC and an inorganic coagulant.
Disclosure of Invention
1. Problems to be solved
Aiming at the problem that the membrane pollution is difficult to control when the microorganism polluted water body is treated by ultrafiltration membrane filtration, the invention provides a method for firstly coagulating by respectively adding an inorganic coagulant and PDMDAAC, and then directly ultrafiltering the coagulated solution and generated floc, so that the load of ultrafiltration membrane filtration pollution can be well reduced when the coagulated solution and the generated floc are used as a pretreatment process before ultrafiltration, the membrane pollution caused by the pollutants can be effectively relieved, the membrane flux recovery efficiency is improved, and the membrane service life is effectively prolonged.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention provides a membrane pollution control method for treating microbial polluted wastewater by ultrafiltration, which comprises the following steps:
1) firstly, measuring the pH value of a solution of a polluted water body, respectively adding a certain amount of poly dimethyl diallyl ammonium chloride and an inorganic coagulant according to the pH range of the water body, and carrying out coagulation treatment under a certain stirring condition;
2) after the step 1), transferring the reaction solution and the generated flocs to an ultrafiltration device together, and performing ultrafiltration treatment by using an ultrafiltration membrane;
3) and 2) backwashing the ultrafiltration membrane by using pure water after the step 2) is finished.
The polydimethyldiallyl ammonium chloride and the inorganic coagulant can be directly used by adopting a commercially available medicament.
Preferably, the adding amount of the inorganic coagulant in the step 1) is 20-200 mg/L, and the poly dimethyl diallyl ammonium chloride is added according to the concentration of 0.15-4.5 mg/L.
Preferably, in the step 1), when the pH value of the wastewater is 4-6, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 0.15-0.45 mg/L; when the pH value is 7-8, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 0.45-2.25 mg/L; when the pH value is 9-10, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 2.25-4.5 mg/L;
preferably, the inorganic coagulant comprises any one or combination of titanium sulfate, titanium tetrachloride, titanium gel, ferric chloride, ferric sulfate, polymeric ferric sulfate and polymeric ferric chloride.
Preferably, the concentration range of the microbial cells in the microbial-polluted wastewater is 5 x 106～6×109One per mL, the concentration of organic matter is 10-30 mg C/L.
Preferably, the microbial cells comprise algal cells or bacteria.
Preferably, the stirring conditions in step 1) are as follows: firstly, stirring for 1-3 min at the rotating speed of 200-400 rpm, and then continuously stirring for 15-30 min at the rotating speed of 40-80 rpm.
Preferably, the ultrafiltration membrane is made of PES or PVDF, and the interception range of the ultrafiltration membrane is 50-200 KDa.
Preferably, the filtering pressure in the ultrafiltration treatment process is 0.8-0.12 Mpa, and the backwashing pressure in the step 3) is 0.13-0.2 Mpa.
Preferably, the microbial cell is escherichia coli.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention relates to a membrane pollution control method for treating microbial polluted wastewater by ultrafiltration, which comprises the steps of firstly carrying out coagulation treatment by adopting a mode of respectively adding an inorganic coagulant and PDMDAAC, and then directly carrying out ultrafiltration on a coagulated solution and generated flocs, wherein the coagulation treatment can be used as a pretreatment process before ultrafiltration to better reduce the filtration pollution load of an ultrafiltration membrane;
(2) the invention discloses a membrane pollution control method for treating microbial polluted wastewater by ultrafiltration, which selects the adding modes of inorganic coagulants with different contents and PDMDAAC according to the pH environment of the microbial polluted wastewater: aiming at the acidic polluted wastewater, a relatively small amount of PDMDAAC is added, and a large amount of PDMDAAC is added under neutral and alkaline conditions, so that on one hand, the coagulation efficiency reduction caused by charge reversal caused by excessive PDMDAAC addition under the acidic condition can be effectively avoided, and the addition content is controlled to be small; on the other hand, aiming at neutral alkaline polluted wastewater, the invention effectively improves the condition that the isoelectric point of an inorganic coagulant is lower and the inorganic coagulant is difficult to exert better electric neutralization, thereby effectively improving the coagulation efficiency.
(3) According to the membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration, the adopted medicaments PDMDAAC and the inorganic coagulant have good purification effect on water bodies after being added and used, have no other effect of harming the water bodies, are environment-friendly and are beneficial to popularization.
(4) The membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration is more beneficial to improving the membrane flux recovery efficiency compared with a method of adding a composite coagulant (compounding the two in a chemical synthesis mode) under neutral and alkaline conditions, and under the neutral and alkaline conditions, the method can play a role in strengthening the inorganic coagulant by PDMDAAC in a mode of respectively adding the two, thereby promoting the improvement of the membrane flux recovery efficiency, avoids the complex steps of chemical synthesis by respectively adding the two, can adopt commercially available products, saves the treatment time, and has better membrane flux recovery efficiency when respectively adding the two under the acidic condition.
(5) The membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration has the concentration of microcystis aeruginosa of about 6 multiplied by 108The concentration of algae-derived organic matters is 30mg C/L, membrane pollution is caused during ultrafiltration, the recovery rate of membrane pollution flux can reach 87.6% -93.3% under the condition that the pH value is 4-6, and the flux recovery of a comparison group which is not treated by the method is only 35.6%; under the condition that the pH value is 7-8, the flux recovery rate can reach 71.8-72.3%, and the flux recovery rate of a comparison group which is not treated by the method is only 39.2%; the flux can be recovered under the condition that the pH value is 9-10The rate reaches 40.6-67.2%, and the flux recovery of the comparative group without the treatment of the invention is only 29.1%. Therefore, the pretreatment mode of the invention can obviously improve the membrane flux recovery efficiency and prolong the service life of the membrane.
Drawings
FIG. 1 shows the removal of organic substances from microcystis aeruginosa polluted water by PDMDAAC with different concentrations in combination with titanium tetrachloride under different pH conditions;
FIG. 2 is a graph showing the change of turbidity of water polluted by Microcystis aeruginosa when PDMDAAC with different concentrations is used in combination with titanium tetrachloride under different pH conditions.
FIG. 3 is a comparison of the membrane fouling relieving effect of Microcystis aeruginosa wastewater by PDMDAAC and titanium gel with different concentrations under different pH conditions.
Detailed Description
The invention is further described with reference to specific examples.
Example 1
The membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration comprises the following steps:
step 1), the concentration of the microcystis aeruginosa is about 6 multiplied by 109Putting the microcystis aeruginosa wastewater with organic matter concentration of about 10mgC/L and pH of 4-10 on a six-connection stirrer.
Step 2), adding 20-200 mg/L titanium tetrachloride into the wastewater obtained in the step 1), and simultaneously adding 0.15mg/L, 0.45mg/L, 2.25mg/L and 4.5mg/L PDMDAAC.
The reaction was first stirred at 400rpm for 1min and then at 80rpm for 15 min. Standing for 20min after the reaction is finished, and measuring the organic matter removal efficiency.
According to the results, according to the graphs of fig. 1 and 2, under the condition that the pH value is 4-6, the removal rates of the PDMDAAC on the organic matters are respectively 61.7%, 63.1%, 70.7%, 65.3% and 46.2% under the conditions of no adding and mixed adding of 0.15mg/L, 0.45mg/L, 2.25mg/L and 4.5 mg/L; under the condition that the pH value is 7-8, the removal rates of PDMDAAC on organic matters are respectively 43.1%, 50.7%, 58.5%, 61.5% and 69.2% when the PDMDAAC is not added or is added in a mixed manner at 0.15mg/L, 0.45mg/L, 2.25mg/L and 4.5 mg/L; under the condition that the pH value is 9-10, the removal rates of organic matters by the PDMDAAC which is not added or is added in a mixed manner by 0.15mg/L, 0.45mg/L, 2.25mg/L and 4.5mg/L are respectively 10.3%, 23.1%, 43.1%, 55.4% and 64.6%.
The reason why the analysis yields the above results is mainly that: under neutral and alkaline conditions, the titanium tetrachloride has lower isoelectric point, so that a better electric neutralization effect is difficult to play, and compared with single titanium tetrachloride, the coagulation effect can be effectively improved by matching with certain PDMDAAC, and the improvement effect is particularly remarkable under the neutral and alkaline conditions. Under acidic conditions, as shown in fig. 1, the pH is 4-6, and the dosage of 4.5mg/L, the high dose of PDMDAAC causes charge reversal effect due to the large amount of positive charges in the water, thereby decreasing the removal efficiency.
Meanwhile, the change condition of the residual turbidity after the treatment of the graph 2 can be compared, the removal effect of different adding combinations on the algae cells is analyzed, and the following can be seen: the condition that the titanium tetrachloride has poor treatment effect under neutral and alkaline conditions can be effectively improved by increasing the adding amount of the PDMDAAC. Under the acidic condition with better treatment effect, excessive addition of PDMDAAC can cause charge reversal, and simultaneously, the coagulant and organic matters form some insoluble complexes to cause the phenomenon of turbidity increase, for example, the residual turbidity increases to 15.4NTU and 16.8NTU instead when the pH is 4-6 and the addition amount of 2.25mg/L and 4.5 mg/L.
Example 2
The membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration comprises the following steps:
step 1), the concentration of the microcystis aeruginosa is about 6 multiplied by 108And (4) placing the microcystis aeruginosa wastewater with the organic matter concentration of about 30mg C/L and the pH value of 4-10 on a six-connection stirrer.
Step 2), adding 20-200 mg/L of titanium gel coagulant into the wastewater obtained in the step 1), and simultaneously adding 0.15mg/L, 0.45mg/L, 2.25mg/L and 4.5mg/L of PDMDAAC.
The mixture was stirred at 200rpm for 3min and then at 40rpm for 30 min.
The preparation method of the titanium gel coagulant comprises the following steps:
(a) uniformly mixing acetylacetone and ethanol, dripping titanium tetrachloride solution, and uniformly mixing for later use; wherein the molar ratio of titanium tetrachloride to acetylacetone is 8: 1; the volume ratio of ethanol to acetylacetone is 1: 0.072;
(b) preparing a mixed solution of 5mL of ethanol and 3mL of ultrapure water (wherein the molar ratio of H2O to Ti is 3:1) as a solution B;
(c) dropwise adding the solution obtained in the step (b) into the step (a) under the condition of continuous stirring, and stirring at 100-400 rpm for 30-120 min to obtain uniform sol;
(d) drying and aging the sol obtained in the step (c) at 15-55 ℃ to constant weight to obtain a light yellow solid, namely the titanium gel coagulant.
Step 3), directly transferring the solution to an ultrafiltration device without sedimentation after the reaction in the step 2) is finished, wherein the ultrafiltration membrane is made of PES or PVDF, and the interception range of the ultrafiltration membrane is 50-200 KDa; and performing ultrafiltration by using nitrogen, wherein the nitrogen pressure is 0.8-0.12 MPa. And simultaneously, monitoring and recording the dynamic change condition of the membrane flux.
And 4) stopping membrane filtration after the membrane filtration reaches nearly 150 mL. And taking down the membrane, inverting the membrane, and performing backwashing by using 100mL of pure water, wherein the nitrogen pressure is 0.13-0.2 MPa. After the back washing is finished, the pure water is used for ultrafiltration, flux values are recorded when the flux of the pure water is stable, and the membrane flux condition and the recovery rate are calculated.
The film pollution relieving effect of the titanium gel coagulant mixed with PDMDAAC under different conditions is different, which corresponds to the coagulation effect. From the normalized flux case and recovery rate of table 1, one can see: compared with the method that the polluted water is directly ultrafiltered by CK, the reduction degree and recovery rate of the membrane flux are improved to different degrees after the pretreatment is carried out by using a coagulant. Under neutral and alkaline conditions, the coagulation effect of the original titanium gel is poor, so that a large amount of pollutants are still contained in the water body after the coagulation is finished, and a large pollution load is directly brought to the ultrafiltration membrane. After the PDMDAAC with a certain concentration is matched, the coagulation effect can be improved, and the membrane pollution can be effectively improved. Meanwhile, as the proportion of PDMDAAC increases, the effect of alleviating membrane pollution is gradually improved. Under the acidic condition, due to the excessive addition of PDMDAAC, on one hand, the coagulation efficiency is deteriorated, the membrane pollution load is increased, on the other hand, the surface of a filter cake layer formed under the acidic condition is mostly positive charge, the excessive positive charge causes stronger adsorption between the filter cake layer and the membrane surface, and the membrane pores are blocked, so that serious membrane pollution is caused, and the serious membrane pollution is difficult to remove by physical flushing. The values in the table are all statistical averages. Table 1 shows the comparison of the effect of adding a titanium gel coagulant and PDMDAAC with different concentrations in a mixed manner to alleviate the pollution of an ultrafiltration membrane, and the comparison graph is shown in figure 3.
Table 1 comparison of effects of titanium gel coagulant and PDMDAAC with different concentrations on mixing and adding ultrafiltration membrane for relieving pollution
Example 3
This embodiment is basically the same as embodiment 2 except that:
step 1), the concentration of Escherichia coli was 5X 10630mg/L of polymeric ferric sulfate, ferric sulfate and ferric chloride are respectively added into the escherichia coli wastewater with the organic matter concentration of 30mg C/L and the pH value of 8, and 2.25mg/L of PDMDAAC coagulant aid is respectively matched to serve as a comparison group. The stirring conditions were: stirring was first carried out at 300rpm for 2min and then at 60rpm for 20 min.
Step 2), directly transferring the solution to an ultrafiltration device without sedimentation, wherein the ultrafiltration membrane is made of PES or PVDF, and the interception range of the ultrafiltration membrane is 50-200 KDa; and performing ultrafiltration by using nitrogen, wherein the nitrogen pressure is 0.8-0.12 MPa.
Step 3), same as step 3) of example 2;
step 4), same as example 2, step 4).
From the results of this experiment it can be derived: compared with direct filtration of the escherichia coli wastewater, the pretreatment of the three iron-based coagulants can effectively reduce the pollution of the escherichia coli wastewater to the membrane, and finally the normalized flux is respectively promoted to 0.74, 0.76 and 0.81 from 0.56 of CK. Meanwhile, the proper amount of PDMDAAC under the alkaline condition can further effectively improve the effect of reducing membrane pollution caused by pretreatment of the iron-based coagulant. After the three coagulants are matched with 2.25mg/L PDMDAAC coagulant aid, the final normalized flux is increased to 0.91, 0.93 and 0.93. Table 2 shows the comparison of the pollution relieving effect of the ultrafiltration membrane by directly adding three iron-based coagulants and by mixing and adding the iron-based coagulants and the PDMDAAC
TABLE 2 comparison of the effect of directly adding three iron-based coagulants and PDMDAAC mixed adding ultrafiltration membrane for relieving pollution
Comparative example 1
The membrane pollution control method for treating the microbial polluted wastewater by ultrafiltration in the comparative example adopts the composite PDMDAAC/titanium gel coagulant (namely, the composite coagulant synthesized by adopting a chemical synthesis mode) to carry out a comparison experiment, and comprises the following steps:
step 1) about 5X 10 microcystis aeruginosa7And (4) putting the microcystis aeruginosa wastewater with the concentration of algae source organic matters being 10mg C/L and the pH value being 4-10 on a six-connection stirrer.
Step 2) adding 15% PDMDAAC (the content of PDMDAAC is 2.25mg/L) and a titanium gel coagulant (the concentration is 60mg/L), comparing with the above step, preparing the 15% titanium gel-poly-dimethyl diallyl ammonium chloride composite coagulant by reacting the titanium gel coagulant and the PDMDAAC with the same concentration, wherein the adding concentration of the composite coagulant is 60mg/L, and the preparation process of the composite coagulant is as follows:
(a) uniformly mixing acetylacetone and ethanol, dripping titanium tetrachloride solution, and uniformly mixing for later use; wherein the molar ratio of titanium tetrachloride to acetylacetone is 8: 1; the volume ratio of ethanol to acetylacetone is 1: 0.072;
(b) adding a PDMDAAC aqueous solution into ethanol, and uniformly stirring for later use; the PDMDAAC aqueous solution is a mixed solution of PDMDAAC and deionized water; wherein the volume ratio of the added ethanol to the ethanol in the step (a) is 1: 2; the mass ratio of the PDMDAAC added to the titanium in step (a) is 0.15: 1, the molar ratio of deionized water to titanium tetrachloride in step (a) is 3: 1;
(c) dropwise adding the solution obtained in the step (b) into the step (a) under the condition of continuous stirring, and stirring at 100-400 rpm for 30-120 min to obtain uniform sol;
(d) drying and aging the sol obtained in the step (c) at 15-55 ℃ to constant weight to obtain the titanium gel-poly (dimethyldiallylammonium chloride) composite coagulant, which is called 15% P-T coagulant for short.
The following steps were carried out in accordance with the procedure of example 2.
The results are as follows:
the 15 percent P-T composite coagulant, the inorganic coagulant and the coagulant aid are directly and separately added, so that the treatment efficiency of the algae-containing water is different to a certain extent. Although the coagulation effect is not as good as that of a 15% P-T composite coagulant when the titanium gel and the PDMDAAC are separately added under the acidic condition of pH 4-6, the recovery rate of the membrane flux is only 71.5% and is slightly lower than that of the composite coagulant (86.0%), the medicament cost and the complexity of the operation steps can be effectively reduced under the separate adding conditions.
And under the conditions that the pH value is 7-8 and 9-10, the recovery rates of the separated adding on the membrane flux are 85.3% and 53.6%, and the membrane flux is respectively recovered to 81.4% and 47.9% after the treatment of the composite coagulant. The reason why the separate adding effect is better than the composite use under the pH condition is that: after the titanium gel and the PDMDAAC are separately added, the respective coagulation behavior of the titanium gel and the PDMDAAC can be well kept, and the algae cells and organic matters are removed by performing the functions of electrical neutralization and net-catching roll sweeping through the hydrolysis action of the inorganic titanium gel after the inorganic titanium gel is added into water; in the process, the cation PDMDAAC is added, so that the electric neutralization capacity of the titanium gel coagulant under an alkaline condition can be enhanced, and the long-chain structure of the titanium gel coagulant can be used for enhancing the effects of adsorption bridging and net trapping, rolling and sweeping, so that the coagulation efficiency is effectively improved, and a better membrane pollution relieving effect is achieved.
TABLE 3 comparison of separate addition of coagulant and coagulant aid with the pollution-relieving effect of 15% P-T composite coagulant on ultrafiltration membrane
Claims (6)
1. A membrane pollution control method for treating microbial polluted wastewater by ultrafiltration is characterized by comprising the following steps: the microbial cells comprise algal cells or bacteria; the method comprises the following steps:
1) firstly, measuring the pH value of a solution of a polluted water body, respectively adding a certain amount of poly dimethyl diallyl ammonium chloride and an inorganic coagulant according to the pH range of the water body, and carrying out coagulation treatment under a certain stirring condition; when the pH value of the wastewater is 4-6, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 0.15-0.45 mg/L; when the pH value is 7-8, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 0.45-2.25 mg/L; when the pH value is 9-10, the poly dimethyl diallyl ammonium chloride is added according to the concentration of 2.25-4.5 mg/L, and the inorganic coagulant comprises any one or combination of titanium sulfate, titanium tetrachloride and titanium gel; the adding amount of the inorganic coagulant is 20-200 mg/L;
2) after the step 1), transferring the reaction solution and the generated flocs to an ultrafiltration device together, and performing ultrafiltration treatment by using an ultrafiltration membrane;
3) and 2) backwashing the ultrafiltration membrane by using pure water after the step 2) is finished.
2. The membrane fouling control method for ultrafiltration treatment of wastewater contaminated with microorganisms according to claim 1, characterized in that: the concentration range of microbial cells in the microbial polluted wastewater is 5 multiplied by 106~6×109One per mL, the concentration of organic matter is 10-30 mg C/L.
3. The membrane fouling control method for ultrafiltration treatment of wastewater contaminated with microorganisms according to claim 1, wherein: the stirring conditions in the step 1) are as follows: firstly, stirring for 1-3 min at the rotating speed of 200-400 rpm, and then continuously stirring for 15-30 min at the rotating speed of 40-80 rpm.
4. The membrane fouling control method for ultrafiltration treatment of wastewater contaminated with microorganisms according to claim 1, wherein: the ultrafiltration membrane is made of PES or PVDF, and the interception range of the ultrafiltration membrane is 50-200 KDa.
5. The membrane fouling control method for ultrafiltration treatment of wastewater contaminated with microorganisms according to claim 1, wherein: the filtering pressure in the ultrafiltration treatment process is 0.8-0.12 Mpa, and the backwashing pressure in the step 3) is 0.13-0.2 Mpa.
6. The membrane fouling control method for ultrafiltration treatment of wastewater contaminated with microorganisms according to claim 1, wherein: the microbial cells are escherichia coli.
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