Sewage treatment method of denitrification membrane bioreactor

Abstract

The invention relates to the technical field of sewage treatment, in particular to a denitrification membrane bioreactor sewage treatment method. The problem that the nitrogen and phosphorus removal efficiency of sewage is low in a traditional sewage treatment method is solved. By preparing the hydrophilic suspended filler, ammonia nitrogen molecules in sewage are effectively adsorbed and decomposed; organic matters in sewage and sludge are deeply decomposed to form an aerobic, anoxic and anaerobic gradient environment through proper aeration intensity and adjustment of hydraulic retention time among the units; the microbial growth promoter is used as an electron donor for supplying a carbon source and a nitrogen source required by growth and reproduction of microorganisms; mechanical stirring is carried out in the anoxic unit, and a proper swinging angle is arranged in each cell chamber, so that sludge is in full contact with microorganisms, the filtering capacity in the denitrification membrane bioreactor is improved, and the membrane forming time is shortened; linkage is formed among the anaerobic unit, the anoxic unit, the membrane separation area and the aerobic unit, and the nitrogen and phosphorus removal efficiency in the nitrogen removal membrane bioreactor is synergistically improved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a sewage treatment method using a denitrification membrane bioreactor. Background Art

[0002] With the acceleration of urbanization and population growth, water resources are becoming increasingly scarce. Treatment and recycling of sewage can effectively alleviate the pressure on water resources; at the same time, sewage treatment can remove harmful substances in sewage and prevent harmful substances from damaging the ecological environment. Therefore, sewage recycling is a key measure to achieve sustainable resource utilization and environmental protection.

[0003] Traditional sludge treatment methods include activated sludge method and biofilm method. The activated sludge method can adapt to sewage of different water quality and water volume, and has a strong ability to resist shock load; however, this method consumes a lot of energy during the aeration process, and the microbial activity is reduced under low temperature conditions, and the denitrification and phosphorus removal effect is unstable. The biofilm method has a high volumetric load and can treat a large amount of sewage in a smaller space; however, the anoxic area in the traditional biofilm is small, which is not conducive to the denitrification; at the same time, the carrier is easily blocked by suspended matter and organic matter in the sewage, affecting the growth and metabolism of the biofilm, thereby reducing its denitrification and phosphorus removal efficiency.

[0004] Based on the limitations of the above-mentioned treatment methods, the present invention adopts a denitrification membrane bioreactor treatment method, which combines the advantages of the activated sludge method and the biofilm method, and can improve the denitrification and phosphorus removal efficiency of domestic sewage while saving energy, processing time and land. Summary of the invention

[0005] The object of the present invention is to provide a denitrification membrane bioreactor sewage treatment method, which effectively adsorbs and decomposes ammonia nitrogen molecules in sewage by preparing hydrophilic suspended fillers; the appropriate aeration intensity and the adjustment of the hydraulic retention time between each unit enable the deep decomposition of organic matter in sewage and sludge to form an aerobic, anoxic and anaerobic gradient environment; a microbial growth promoter is used as an electron donor to supply carbon and nitrogen sources required for the growth and reproduction of microorganisms; mechanical stirring is performed in the anoxic unit, and each cell chamber is set with an appropriate swing angle to enable the sludge to fully contact with the microorganism, thereby improving the filtration capacity in the denitrification membrane bioreactor and shortening the biofilm hanging time; and the anaerobic unit, the anoxic unit, the membrane separation zone and the aerobic unit are linked to form a linkage to synergistically improve the denitrification and phosphorus removal efficiency in the denitrification membrane bioreactor.

[0006] In view of the shortcomings of the prior art, the present invention provides a denitrification membrane bioreactor wastewater treatment method. The present invention sets four reaction zones inside the biofilm denitrification reactor, and the biofilms in each reaction zone are cultured separately in different zones, which can better form a biofilm system with specific performance and ensure that each reaction zone can perform denitrification and phosphorus removal performance under its own suitable conditions.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a denitrification membrane bioreactor sewage treatment method, wherein the denitrification membrane bioreactor comprises an anaerobic unit 1, an anoxic unit 2, a membrane separation zone 3 and an aerobic unit 4 from top to bottom; the aerobic unit 4, the anoxic unit 2 and the anaerobic unit 1 are all provided with cells with swing angles and a light intensity of 2500lx;

[0009] The denitrification membrane bioreactor wastewater treatment method is as follows:

[0010] The aerobic unit 4, the anoxic unit 2 and the anaerobic unit 1 of the reaction tank are filled with a hydrophilic suspended filler accounting for 3 / 5 of the total volume of each reaction unit;

[0011] Load the activated sludge with a water content of 95% onto the hydrophilic suspended filler of each unit to fill each unit; the activated sludge is taken from a domestic sewage treatment plant in Nanjing, Jiangsu;

[0012] Sewage is injected from the bottom of the denitrification membrane bioreactor and first injected into the aerobic unit 4 through a water pump. A microbial growth promoter is added to the aerobic unit 4 and a mixed solution is obtained by suffocation for 24 hours. Then 1 / 3 of the mixed solution is discharged and sewage is continuously introduced. The aeration intensity of the aerobic unit 4 is set to 3-5 mg / L and the hydraulic retention time is 8-10 hours. The rotation speed of the electric mechanical stirring device 5 in the anoxic unit 2 is set to 20-30 rpm and the stirring power is 1.5-2.0 kW. The hydraulic retention time ratio of the aerobic unit 4, the anoxic unit 2 and the anaerobic unit 1 is set to 8-10:5-7:4-5.

[0013] Preferably, the volume ratio of the aerobic unit 4, the anoxic unit 2 and the anaerobic unit 1 is 2:1:2.

[0014] Preferably, the aerobic unit 4 and the anaerobic unit 1 are each provided with 5 cells; the cells are staggered in the aerobic unit 4 and the anaerobic unit 1; sewage is injected into the denitrification membrane bioreactor, first injected into the aerobic unit 4 through a water pump, and passes through the 5 cells of the aerobic unit 4 in sequence; then, under the action of the water pump, the sewage is separated through the membrane separation area 3 and enters the anoxic unit 2; the speed of the electric mechanical stirring device 5 in the anoxic unit 2 is set to 20-30rpm, and the stirring power is 1.5-2.0kW, stirring and filtering are performed, and then the partition between the anoxic unit 2 and the anaerobic unit 1 is opened, so that the sewage passes through the 5 cells of the anaerobic unit 1 in sequence and then the effluent is discharged; the cells in the aerobic unit 4 and the anaerobic unit 1 can swing at an angle, and the angle of the cell swing is 60°-75° with the vertical direction of the denitrification membrane bioreactor.

[0015] Preferably, a partition is provided between the anoxic unit 2 and the anaerobic unit 1 .

[0016] Preferably, the preparation process of the hydrophilic suspension filler is as follows: 50 parts of cultured Spirulina platensis are centrifuged and concentrated, and the supernatant is removed and then rinsed with distilled water, and the algae cell solution is obtained after two centrifugation treatments; 30 parts of the algae cell solution and 40 parts of sterilized sodium alginate solution with a concentration of 1wt%-3wt% are fully mixed to form a mixed solution; the mixed solution is slowly dripped into a sterilized ferrous chloride solution with a concentration of 3% and stirred to form a cell group with a particle size of 2-3mm; the cell group is placed in a refrigerator at a temperature of 4-8°C for 24 hours, and after being taken out of the refrigerator, it is washed twice with distilled water to obtain algae cell colloid balls; 30 parts of activated carbon and 10 parts of polyethylene are added to the algae cell colloid balls to obtain the hydrophilic suspension filler.

[0017] Preferably, the microbial growth promoter comprises 30-40 parts of metal salt, 20-30 parts of putrescine, 10-15 parts of glucose and 7 parts of sodium acetate.

[0018] Preferably, the metal salt is a calcium salt CaCl 2 、Copper salt CuCl 2 、MgSO 4 and ferrous salts FeSO 4 Composition: Calcium salt CaCl 2 、Copper salt CuCl 2 、MgSO 4 and ferrous salts FeSO 4 The ratio between them is 3:1:2:2.

[0019] Preferably, the sewage reflow ratio inside the denitrification model bioreactor is 300%; and the reflow ratio between the aerobic unit 4 and the anoxic unit 2 is 1.7.

[0020] It should be noted that the “number of parts” and “number of parts ratio” mentioned in the present invention are “number of parts by mass” and “number of parts ratio by mass”.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The algae cell gel balls prepared under suitable particle size and temperature conditions work together with activated carbon and polyethylene to form a hydrophilic suspended filler; the hydrophilic suspended filler has a larger specific surface area, which can effectively adsorb and decompose ammonia nitrogen molecules in sewage, provide more attachment sites and a good growth environment for microorganisms, improve the removal efficiency of ammonia nitrogen in sewage by the denitrification membrane bioreactor, and promote the denitrification and phosphorus removal process of the denitrification membrane bioreactor.

[0023] 2. Appropriate aeration intensity of the aerobic unit and the hydraulic retention time ratio of the aerobic unit, anoxic unit and anaerobic unit are conducive to the aerobic unit to oxidize and decompose organic matter into small molecules, providing a carbon source for the denitrification of the anoxic unit; the anoxic unit removes nitrate and nitrite through denitrification, while further reducing the chemical oxygen demand; the anaerobic unit carries out anaerobic fermentation and other processes to deeply degrade organic matter; thus forming a gradient environment of aerobic, anoxic and anaerobic, promoting the synergistic effect between microorganisms, and improving the overall chemical oxygen demand removal rate of the denitrification membrane bioreactor and the efficiency of denitrification and phosphorus removal.

[0024] 3. The metal salts, putrescine, glucose and sodium acetate in the microbial growth promoter act as electron donors to provide the carbon and nitrogen sources required for the growth and reproduction of microorganisms. The synergistic effect of multiple components provides comprehensive nutrition for microorganisms, forming a good positive cycle in the entire denitrification membrane bioreactor. Microorganisms are retained in the reactor, which is conducive to the retention and growth of slowly proliferating microorganisms and improves the nitrification efficiency in the system; thereby improving the sludge concentration, effluent quality and denitrification and phosphorus removal efficiency in the denitrification membrane bioreactor.

[0025] 4. The electric mechanical stirring device is set with an appropriate speed and power, and the appropriate swing angle of each cell chamber, so that the sludge can fully contact with the microorganisms, and the sewage is filtered more evenly under more uniform water flow rate and pressure distribution. The smoothness of sewage flowing from the aerobic unit to the anoxic unit and from the anoxic unit to the anaerobic unit inside the reactor is improved, which helps to create a suitable growth environment for bacteria such as aerobic polyphosphate bacteria, denitrifying bacteria and anaerobic phosphate-releasing bacteria; improve the contact efficiency between pollutants and microorganisms in sewage, further improve the filtration speed and treatment capacity of the membrane, and further improve the efficiency of nitrogen and phosphorus removal in sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a test result diagram of the total phosphorus removal rate in sewage of Examples 7-12 and Comparative Examples 14-18 of a denitrification membrane bioreactor sewage treatment method of the present invention;

[0027] Figure 2 This is a schematic structural diagram of the denitrification membrane bioreactor of the present invention;

[0028] In the figure: 1. Anaerobic unit; 2. Anoxic unit; 3. Membrane separation area; 4. Aerobic unit; 5. Electric mechanical stirring device. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] See also Figure 1 to Figure 2 The present invention provides a denitrification membrane bioreactor sewage treatment method, and the technical scheme is as follows:

[0031] Example 1

[0032] A denitrification membrane bioreactor sewage treatment method, wherein the denitrification membrane bioreactor comprises an anaerobic unit, an anoxic unit, a membrane separation zone and an aerobic unit from top to bottom; the aerobic unit, the anoxic unit and the anaerobic unit are all provided with cells with swing angles and a light intensity of 2500lx; the cells are staggeredly distributed in each unit;

[0033] The denitrification membrane bioreactor wastewater treatment method is as follows:

[0034] First, the aerobic unit, the anoxic unit and the anaerobic unit of the reaction tank are filled with a hydrophilic suspended filler accounting for 3 / 5 of the total volume of each reaction unit;

[0035] Then, activated sludge with a water content of 95% is loaded onto the hydrophilic suspended filler of each unit to fill each unit; the activated sludge is taken from a domestic sewage treatment plant in Nanjing, Jiangsu;

[0036] Sewage was injected from the bottom of the denitrification membrane bioreactor, and first injected into the aerobic unit through a water pump, and then passed through the 5 cells of the aerobic unit in turn. A microbial growth promoter was added to the aerobic unit, and the mixed solution was obtained by suffocation for 24 hours. Then 1 / 3 of the mixed solution was discharged, and sewage was continuously introduced, and the sewage passed through the 5 cells of the aerobic unit in turn. During this period, the aeration intensity of the aerobic unit was set to 3 mg / L, and the hydraulic retention time was 8 hours. Subsequently, under the action of the water pump, the sewage was separated through the membrane separation area and then entered the anoxic unit. In the anoxic unit, the sewage was stirred and filtered under an electric mechanical stirring device with a rotation speed of 20 rpm and a stirring power of 1.5 kW, and the hydraulic retention time was 5 hours. Subsequently, the partition between the anoxic unit and the anaerobic unit was opened, so that the sewage passed through the 5 cells of the anaerobic unit in turn, and the effluent was discharged after 4 hours of hydraulic retention. During this period, the swing angle of the cells in the aerobic unit and the anaerobic unit was set to swing back and forth at 75° to the vertical direction of the denitrification membrane bioreactor.

[0037] Among them, the volume ratio of the aerobic unit, the anoxic unit and the anaerobic unit is 2:1:2.

[0038] Among them, the sewage return ratio inside the denitrification model bioreactor is 300%; the return ratio between the aerobic unit and the anoxic unit is 1.7.

[0039] The preparation process of the hydrophilic suspended filler is as follows: 50 parts of cultured Spirulina platensis are centrifuged and concentrated, and the supernatant is removed and then rinsed with distilled water, and an algae cell solution is obtained after two centrifugation treatments; 30 parts of the algae cell solution and 40 parts of a sterilized sodium alginate solution with a concentration of 1wt% are fully mixed to form a mixed solution; the mixed solution is slowly dripped into 3 parts of a sterilized ferrous chloride solution with a concentration of 3% and stirred to form a cell group with a particle size of 2mm; the cell group is placed in a refrigerator at a temperature of 5°C for 24 hours, and after being taken out of the refrigerator, it is washed twice with distilled water to obtain an algae cell jelly ball; 30 parts of activated carbon and 10 parts of polyethylene are added to the algae cell jelly ball to obtain a hydrophilic suspended filler.

[0040] The microbial growth promoter includes 38 parts of metal salt, 22 parts of putrescine, 11 parts of glucose and 7 parts of sodium acetate.

[0041] Metal salts are calcium salts CaSO 4 、Copper salt CuSO 4 、MgSO 4 and ferrous salts FeSO 4 Composition: Calcium salt CaCl 2 、Copper salt CuCl 2 、MgSO 4 and ferrous salts FeSO 4 The ratio between them is 3:1:2:2.

[0042] Embodiment 2-6

[0043] Compared with Example 1, some parameters have been adjusted, which are specifically summarized in Table 1; the temperature in Table 1 is the temperature when the cell population is placed in a refrigerator.

[0044] Table 1 Preparation parameter adjustment of Examples 1-6

[0045]

[0046] Examples 7-12

[0047] Compared with Example 1, the parameters are adjusted, which are specifically summarized in Table 2; in Table 2, the aeration intensity is the aeration intensity in the aerobic unit; the rotation speed is the rotation speed of the electric mechanical stirring device in the anoxic unit; the stirring power is the stirring power of the electric mechanical stirring device in the anoxic unit; the hydraulic retention time ratio is the hydraulic retention time ratio of the aerobic unit, the anoxic unit and the anaerobic unit; the angle is the swing angle between the cell and the vertical direction of the denitrification membrane bioreactor.

[0048] Table 2 Preparation parameter adjustment of Examples 7-12

[0049]

[0050] In order to verify the necessity of some technical solutions in the present invention to achieve the technical effects of the present invention, some comparative examples of the present invention will be shown and described below.

[0051] Comparative Example 1

[0052] Refer to Example 1, except that the particle size of the cell population is 0.3 mm during the preparation of the hydrophilic suspension filler.

[0053] Comparative Example 2

[0054] Refer to Example 1, except that the cell population particle size is 10 mm during the preparation of the hydrophilic suspension filler.

[0055] Comparative Example 3

[0056] Refer to Example 1, except that the cell population is placed in a -20°C refrigerator for 24 hours during the preparation of the hydrophilic suspension filler.

[0057] Comparative Example 4

[0058] Refer to Example 1, except that during the preparation of the hydrophilic suspension filler, the cell population is placed in a sealed condition at room temperature for 24 hours.

[0059] Comparative Example 5

[0060] Refer to Example 1, except that 5 parts of metal salt are added to the microbial growth promoter.

[0061] Comparative Example 6

[0062] Refer to Example 1, except that 70 parts of metal salt are added to the microbial growth promoter.

[0063] Comparative Example 7

[0064] Refer to Example 1, except that 3 parts of putrescine are added to the microbial growth promoter.

[0065] Comparative Example 8

[0066] Refer to Example 1, except that 50 parts of putrescine are added to the microbial growth promoter.

[0067] Comparative Example 9

[0068] Refer to Example 1, the difference is that 1 part of glucose is added to the microbial growth promoter.

[0069] Comparative Example 10

[0070] Refer to Example 1, the difference is that 30 parts of glucose are added to the microbial growth promoter.

[0071] Comparative Example 11

[0072] Refer to Example 1, except that the aeration intensity in the aerobic unit is set to 0.5 mg / L.

[0073] Comparative Example 12

[0074] Refer to Example 1, except that the aeration intensity in the aerobic unit is set to 10 mg / L.

[0075] Comparative Example 13

[0076] Refer to Example 1, except that the hydraulic retention time ratio of the aerobic unit, the anoxic unit and the anaerobic unit is 1:1:1.

[0077] Comparative Example 14

[0078] Refer to Example 1, except that the rotation speed of the electric mechanical stirring device in the anoxic unit is set to 5 rpm.

[0079] Comparative Example 15

[0080] Refer to Example 1, except that the rotation speed of the electric mechanical stirring device in the anoxic unit is set to 50 rpm.

[0081] Comparative Example 16

[0082] Refer to Example 1, except that the stirring power of the electric mechanical stirring device in the anoxic unit is 0.3 kW.

[0083] Comparative Example 17

[0084] Refer to Example 1, except that the stirring power of the electric mechanical stirring device in the anoxic unit is 5 kW.

[0085] Comparative Example 18

[0086] Refer to Example 1, the difference is that the five cells arranged in the aerobic unit, the anoxic unit and the anaerobic unit in the denitrification membrane bioreactor reaction tank do not have a swing function, and the cells are 90 degrees to the vertical direction of the denitrification membrane bioreactor.

[0087] Experimental Example 1

[0088] The influent ammonia nitrogen concentration and ammonia nitrogen removal rate were determined using the Nessler reagent spectrophotometer method (GB 7479-1987); the specific test results are shown in Table 3.

[0089] Table 3 Ammonia nitrogen removal rate test of wastewater treatment in Examples 1-6 and Comparative Examples 1-4

[0090] serial number Influent ammonia nitrogen concentration / mg / L Ammonia nitrogen removal rate / % Example 1 53.74 91.3 Example 2 54.41 91.6 Example 3 52.56 90.4 Example 4 57.85 92.6 Example 5 58.23 93.7 Example 6 53.52 91.1 Comparative Example 1 78.34 69.5 Comparative Example 2 41.43 73.6 Comparative Example 3 97.34 53.3 Comparative Example 4 83.65 60.2

[0091] It can be seen from the data in Table 3 that the sewage treatment test of Examples 1-6 shows that the influent ammonia nitrogen concentration of the sewage in Examples 1-6 is stable in the range of 52.0-59.0 mg / L, and the ammonia nitrogen removal rate in the sewage is higher than 90%. In the process of preparing the hydrophilic suspension filler in Comparative Example 1-2, if the particle size of the cell group formed by mixing the algae cell solution with the sodium alginate solution and the ferrous chloride solution is too large or too small, the adsorption performance of the hydrophilic suspension filler on ammonia nitrogen will decrease, thereby resulting in a decrease in the ammonia nitrogen removal rate of the sewage. This is because the hydrophilic suspension filler prepared by the cell group with too small particle size has a smaller particle size and is more likely to be lost with the water flow during the sewage treatment process; and the area of ​​the hydrophilic suspension filler with a smaller particle size available for microorganisms to attach is also correspondingly reduced, the surface energy becomes higher, and it is more unfavorable for the attachment of microorganisms, and the ammonia nitrogen is retained in the sewage, resulting in a significant increase in the influent ammonia nitrogen concentration, and a corresponding decrease in the removal efficiency of ammonia nitrogen. The cell group with a larger particle size will reduce the effective surface area of ​​the prepared hydrophilic suspension filler, and the contact area between the hydrophilic suspension filler and the ammonia nitrogen molecules in the sewage will be reduced, thereby reducing the adsorption capacity of ammonia nitrogen; and the hydrophilic suspension filler prepared by the overly large cell group will hinder the flow of water, thereby making the influent ammonia nitrogen concentration in the denitrification membrane bioreactor unevenly distributed, and reducing the removal rate of ammonia nitrogen in the sewage by the denitrification membrane bioreactor. In the process of preparing the hydrophilic suspension filler, the adsorption performance and binding performance of the hydrophilic suspension filler prepared by placing the cell group in an environment that is too high or too low are significantly reduced, thereby reducing the ammonia nitrogen removal rate of the sewage. Placing the cell group in a low temperature environment of -20°C for too long will not only freeze the water in the cell group, but also harden the sodium alginate in the cell group, thereby affecting the binding ability of sodium alginate with Spirulina platensis, resulting in a significant decrease in the binding ability and adsorption capacity of the prepared hydrophilic suspension filler with microorganisms, and failing to effectively remove ammonia nitrogen in the sewage, causing the influent ammonia nitrogen concentration to increase. If the cell group is left in a closed condition at room temperature for 24 hours, bacteria will multiply in large numbers in this environment and contaminate the hydrophilic suspended filler. At the same time, the platensis will lose its activity in an oxygen-deficient environment, resulting in a decrease in the biodegradability of the hydrophilic suspended filler. The ammonia nitrogen concentration in the influent will increase during the sewage treatment process, which is not conducive to improving the ammonia nitrogen removal rate in the sewage.

[0092] In summary, the algae cell colloid balls prepared under suitable particle size and temperature conditions, synergistically combined with activated carbon and polyethylene, constitute a hydrophilic suspended filler; the hydrophilic suspended filler has a larger specific surface area, which can effectively adsorb and decompose ammonia nitrogen molecules in sewage, provide more attachment sites and a good growth environment for microorganisms, improve the removal efficiency of ammonia nitrogen in sewage by the denitrification membrane bioreactor, and promote the denitrification and phosphorus removal process of the denitrification membrane bioreactor.

[0093] Experimental Example 2

[0094] The dissolved oxygen concentration of the influent was determined by the “Iodine Method for Determination of Dissolved Oxygen in Water Quality” (HJ 506-2009); the chemical oxygen demand removal rate was determined by the “Dichromate Method for Determination of Chemical Oxygen Demand in Water Quality” (HJ 828-2017); the specific test results are shown in Table 4.

[0095] Table 4 Chemical oxygen demand removal rate test of wastewater treatment in Examples 7-12 and Comparative Examples 11-13 Denitrification membrane bioreactor

[0096] serial number Influent dissolved oxygen concentration / mg / L Chemical oxygen demand removal rate / % Example 7 3.43 78.53 Example 8 3.48 78.37 Example 9 3.56 78.26 Example 10 3.27 79.13 Embodiment 11 3.52 79.21 Example 12 3.37 79.02 Comparative Example 11 1.01 33.52 Comparative Example 12 6.21 54.23 Comparative Example 13 5.80 15.34

[0097] It can be seen from the data in Table 4 that the sewage treatment test was carried out on Examples 7-13. The dissolved oxygen concentration of the sewage in Examples 7-13 was stable in the range of 3.20-3.60 mg / L, and the chemical oxygen demand removal rate in the sewage was higher than 78%. In Comparative Examples 11-12, the aeration intensity in the aerobic unit was set too high or too low, which would directly affect the dissolved oxygen concentration of the inlet water. If the dissolved oxygen concentration of the inlet water in the reactor was too high or too low, the chemical oxygen demand removal rate of the entire sewage treatment system would be reduced. When the aeration intensity of the aerobic unit was set to 0.5 mg / L, the air intake in the aerobic unit was low, and the low dissolved oxygen concentration directly affected the activity of the microorganisms in the aerobic unit, making it impossible for aerobic microorganisms to perform aerobic respiration, thereby reducing the ability to oxidize and decompose organic matter; at the same time, the organic matter that was not oxidized and decomposed by the aerobic unit would enter the anoxic unit and the anaerobic unit with the water flow, increasing the difficulty of denitrification and phosphorus removal in the subsequent process, thereby affecting the chemical oxygen demand removal rate of the entire sewage treatment system. When the aeration intensity is set to 10 mg / L, the dissolved oxygen concentration in the aerobic unit is too high, and the microorganisms over-oxidize organic matter in the high-oxygen environment, thereby producing a large amount of carbon dioxide and water; the growth and reproduction of nitrifying bacteria in the aerobic unit is inhibited, the activity of nitrifying bacteria is reduced, and the amount of nitrite generated by ammonia-oxidizing bacteria under the action of sewage ammonia nitrogen is reduced, which further leads to a decrease in the amount of nitrite converted into nitrate by nitrite-oxidizing bacteria, which is not conducive to subsequent denitrification and denitrification; secondly, excessive aeration intensity will cause part of the dissolved oxygen to diffuse into the anoxic unit and the anaerobic unit, destroying the microenvironment of the anoxic unit and the anaerobic unit, which is not conducive to the denitrification process, thereby affecting the denitrification and dephosphorization performance of the entire reactor; thirdly, excessive influent dissolved oxygen concentration will promote the growth of filamentous bacteria, thereby causing sludge swelling, thereby reducing the chemical oxygen demand removal efficiency of the sewage treatment system. In Comparative Example 13, the hydraulic retention time ratio of the aerobic unit, the anoxic unit and the anaerobic unit is set to 1:1:1, which will seriously affect the dissolved oxygen concentration of the influent in each unit, resulting in a decrease in the chemical oxygen demand removal rate of the entire sewage treatment system.When the hydraulic retention time ratio of the three units is adjusted to 1:1:1, the hydraulic retention time of the aerobic unit is greatly shortened, and the transfer and utilization time of oxygen in the aerobic unit is insufficient, which reduces the dissolved oxygen concentration in the aerobic unit and inhibits the metabolic activity of aerobic microorganisms, affecting their oxidative decomposition of organic matter and nitrification of ammonia nitrogen; resulting in a high dissolved oxygen content in the sewage entering the anoxic unit from the aerobic unit, which destroys the microenvironment of the anoxic unit and hinders the anaerobic respiration of denitrifying bacteria in the anoxic unit, resulting in a decrease in the amount of nitrate and nitrite reduced to nitrogen gas during the denitrification process, thereby affecting the anaerobic decomposition of organic matter in the subsequent anaerobic unit; the synergistic effect between the three units is weakened, the amount of organic matter oxidized and decomposed into small molecules by the aerobic unit is reduced, the denitrification and anaerobic fermentation processes of the anoxic and anaerobic units are restricted, and the small molecular organic matter produced by the aerobic unit cannot be fully utilized, resulting in a decrease in the overall removal rate of chemical oxygen demand.

[0098] In summary, the appropriate aeration intensity of the aerobic unit and the hydraulic retention time ratio of the aerobic unit, anoxic unit and anaerobic unit are conducive to the aerobic unit to oxidize and decompose organic matter into small molecules, providing a carbon source for the denitrification of the anoxic unit; the anoxic unit removes nitrate and nitrite through denitrification, while further reducing the chemical oxygen demand; the anaerobic unit carries out anaerobic fermentation and other processes to deeply degrade organic matter; thus forming a gradient environment of aerobic, anoxic and anaerobic, promoting the synergistic effect between microorganisms, and improving the overall chemical oxygen demand removal rate of the denitrification membrane bioreactor and the efficiency of denitrification and phosphorus removal.

[0099] Experimental Example 3

[0100] The sludge concentration was determined by the weight method; the total nitrogen removal rate was determined by the "Determination of Total Nitrogen in Water Quality - Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometry" (HJ 636-2012); the specific test results are shown in Table 5.

[0101] Table 5 Total nitrogen removal rate test of wastewater treatment in Examples 1-6 and Comparative Examples 5-10 Denitrification membrane bioreactor

[0102] serial number Sludge concentration / mg / L Total nitrogen removal rate / % Example 1 4423 76.26 Example 2 4235 75.84 Example 3 4567 77.63 Example 4 4325 76.56 Example 5 4672 78.67 Example 6 4723 79.42 Comparative Example 5 3423 65.38 Comparative Example 6 2374 53.28 Comparative Example 7 3786 67.43 Comparative Example 8 3834 69.67 Comparative Example 9 3245 56.12 Comparative Example 10 5963 58.43

[0103] As can be seen from the data in Table 5, the sewage treatment test of Examples 1-6 shows that the sludge concentration of the sewage in Examples 1-6 is stable in the range of 4200-4800 mg / L, and the total nitrogen removal rate in the sewage is higher than 75%. In Comparative Example 5, when the amount of metal salt added to the microbial growth promoter is too small, the microbial growth promoter lacks important components of the microbial cell structure such as calcium salt, magnesium salt, copper salt, and ferrous salt, and cannot provide sufficient nutrients for the microorganisms in the reactor and participate in the transfer of electrons, resulting in a decrease in the denitrification activity of the microorganisms, and hindering the growth and reproduction, resulting in a decrease in the sludge concentration and the total nitrogen removal rate in the reactor. In Comparative Example 6, when the amount of metal salt added to the microbial growth promoter is too much, the calcium salt, magnesium salt and other salt substances in the microbial growth promoter are excessive, which will make the osmotic pressure of the extracellular environment of the microbial cells too high, and the water in the cells will overflow, resulting in dehydration of the microbial cells in the activated sludge, thereby reducing the sludge concentration in the reactor; secondly, the excessive calcium salt will combine with the phosphate in the sewage to form a precipitate, resulting in a reduction in the phosphorus source that can be used by microorganisms; and the excessive copper salt and ferrous salt will destroy the cell membrane structure of the microorganism, affect the normal physiological function of the cell, have a toxic effect on the denitrification microorganism, and inhibit the progress of the nitrification and denitrification stages; the mutual influence between the multiple factors causes a significant decrease in the total nitrogen removal rate in the reactor. Since putrescine can participate in the cell division and protein synthesis of microorganisms, it promotes the secretion of extracellular polymers with flocculation effect by microorganisms, thereby improving the flocculation effect of sludge; in Comparative Example 7, when too little putrescine is added to the microbial growth promoter, the growth and reproduction of microorganisms are restricted, resulting in the weakening of the ability of microorganisms to secrete extracellular polymers, making it difficult for the sludge in the reactor to settle and separate, and the sewage will carry a large amount of suspended matter when it is discharged, which not only affects the effluent water quality and the operating efficiency of the sewage treatment system, but also leads to a decrease in the sludge concentration and total nitrogen removal rate in the reactor. In Comparative Example 8, when too much putrescine is added to the microbial growth promoter, it will interfere with the normal function of the microbial cell membrane, the permeability of the cell membrane will change, some substances harmful to microorganisms will enter the cells more easily, and the transaminase and metabolites in the cells will leak, so that the microorganisms lack sufficient energy during nitrogen metabolism, further reducing the total nitrogen removal rate. Glucose, as an important carbon source for microbial growth, provides a large amount of energy for the growth and reproduction of microorganisms. In Comparative Example 9, too little glucose was added to the microbial growth promoter, i.e., the microorganisms lacked sufficient carbon source during their growth and reproduction, resulting in slow growth and low concentration of activated sludge on the hydrophilic suspended filler; in the anoxic unit, denitrifying bacteria could not effectively reduce nitrate and nitrite to nitrogen gas, thereby reducing the total nitrogen removal rate in the system.In Comparative Example 10, too much glucose was added to the microbial growth promoter, which promoted the excessive reproduction of microorganisms and resulted in the massive reproduction of filamentous bacteria in the sludge. The overgrown filamentous bacteria would make the sludge flocs loose and difficult to settle. During the sewage treatment process, too much sludge and pollutants accumulated on the surface of the membrane separation zone, reducing the permeability of the membrane while increasing the trans-membrane pressure difference, reducing the sewage treatment efficiency of the membrane, and thereby reducing the total nitrogen removal rate and total phosphorus removal rate in the reactor.

[0104] In summary, the metal salts, putrescine, glucose and sodium acetate in the microbial growth promoter act as electron donors to provide the carbon and nitrogen sources required for the growth and reproduction of microorganisms. The synergistic effect of multiple components provides comprehensive nutrition for the microorganisms, forming a good positive cycle in the entire denitrification membrane bioreactor. The microorganisms are retained in the reactor, which is conducive to the retention and growth of slowly proliferating microorganisms and improves the nitrification efficiency in the system; thereby improving the sludge concentration, effluent quality and denitrification and phosphorus removal efficiency in the denitrification membrane bioreactor.

[0105] Experimental Example 4

[0106] The total phosphorus removal rate was determined using the "Water Quality-Determination of Total Phosphorus-Ammonium Molybdate Spectrophotometric Method" (GB 11893-1989); the specific test results are shown in Table 6 and Figure 1 As shown in the data.

[0107] Table 6 Total phosphorus removal rate test of wastewater treatment in denitrification membrane bioreactor of Examples 7-12 and Comparative Examples 14-19

[0108]

[0109]

[0110] From Table 6 and Figure 1The data show that the sewage treatment test of Examples 7-12 shows that the total phosphorus removal rate of the sewage in Examples 7-12 is higher than 86%. In Comparative Examples 1-4, the particle size of the prepared cell mass is too large or too small, and the cell mass is placed in a low temperature or room temperature environment, which will lead to a decrease in mass transfer efficiency and the inactivation of most of the platen Spirulina, which will be detrimental to the adsorption and decomposition performance of the hydrophilic suspended material, thereby affecting its metabolism and removal ability of phosphorus-containing substances. The function of the electric mechanical stirring device in the anoxic unit is to prevent the phosphorus in the sludge from precipitating too quickly, and to enable the sludge to fully contact with the microorganisms through stirring, thereby effectively removing nitrogen and phosphorus elements from the sewage. In Comparative Examples 14 and 16, when the speed of the electric mechanical stirring device in the anoxic unit is set too slow and the stirring power is too low, the sludge is more likely to produce a large amount of precipitation in the anoxic unit, nitrates and organic matter are unevenly dispersed in the sludge, some microorganisms lack nutrients, grow slowly or even die, and the activity of denitrifying bacteria in the anoxic unit is inhibited, a large amount of phosphorus compounds are deposited in the sludge, the mass transfer efficiency becomes low, and the phosphorus removal effect in the entire reactor becomes weak. In Comparative Examples 15 and 17, when the speed of the electric mechanical stirring device in the anoxic unit is set too fast and the stirring power is too high, excessive shear force will be generated on the sludge, thereby destroying the microbial community in the sludge and the aggregates formed by them, making the overall structure of the sludge loose, and being quickly pushed to other units under the action of excessive shear force, thereby affecting the process of phosphorus absorption and release by polyphosphate bacteria, thereby reducing the overall phosphorus removal effect. The swinging cell with a suitable swinging angle can make the sewage be filtered more evenly under the condition of more uniform water flow rate and pressure distribution, improve the smoothness of sewage flowing from the aerobic unit to the anoxic unit and from the anoxic unit to the anaerobic unit inside the reactor, and help create a suitable growth environment for bacteria such as aerobic polyphosphate bacteria, denitrifying bacteria and anaerobic phosphate-releasing bacteria; improve the contact efficiency between pollutants and microorganisms in sewage, further improve the filtration speed and treatment capacity of the membrane, shorten the film hanging time, and thus further improve the efficiency of nitrogen and phosphorus removal in sewage. However, the five cells arranged in the aerobic unit, anoxic unit and anaerobic unit in the reaction tank of the denitrification membrane bioreactor in Comparative Example 18 do not have a swinging function, and the cells are 90° to the vertical direction of the denitrification membrane bioreactor; at this time, the flow of sewage is relatively single, and the oxygen distribution in the aerobic unit is not as uniform as before, thereby slowing down the growth and metabolism of nitrifying bacteria, resulting in a decrease in the efficiency of converting ammonia nitrogen into nitrate nitrogen, and an increase in the ammonia nitrogen content in the effluent of the aerobic unit; after the sewage enters the anoxic unit, the dissolved oxygen concentration is uneven during the denitrification process under a relatively smooth flow state, thereby resulting in a decrease in the denitrification efficiency and a decrease in the total nitrogen removal rate; when the cells cannot swing and are arranged vertically, under the condition of relatively limited flow, local microbial dead zones will appear in the anaerobic unit, thereby reducing the overall sewage denitrification and phosphorus removal efficiency.

[0111] In summary, the electric mechanical stirring device is set with an appropriate speed and power, and each cell chamber has an appropriate swing angle, so that the sludge can fully contact with the microorganisms, and the sewage is filtered more evenly under a more uniform water flow rate and pressure distribution. The smoothness of the sewage flowing from the aerobic unit to the anoxic unit and from the anoxic unit to the anaerobic unit inside the reactor is improved, which helps to create a suitable growth environment for bacteria such as aerobic polyphosphate bacteria, denitrifying bacteria and anaerobic phosphate-releasing bacteria; improve the contact efficiency between pollutants and microorganisms in sewage, further improve the filtration speed and treatment capacity of the membrane, shorten the film hanging time, and further improve the efficiency of nitrogen and phosphorus removal in sewage.

[0112] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A denitrification membrane bioreactor wastewater treatment method, characterized in that: The denitrification membrane bioreactor comprises, from top to bottom, an anaerobic unit (1), an anoxic unit (2), a membrane separation zone (3) and an aerobic unit (4); the aerobic unit (4) and the anaerobic unit (1) are both provided with cells with a swing angle of 60°-75° with respect to the vertical direction of the denitrification membrane bioreactor and a light intensity of 2500 lx; The denitrification membrane bioreactor sewage treatment method is as follows: Fill each reaction unit with a hydrophilic suspension filler accounting for 3 / 5 of the total volume; Loading activated sludge onto the hydrophilic suspended filler of each unit to fill each unit; Inject sewage from the bottom of the denitrification membrane bioreactor and first inject it into the aerobic unit (4) through a water pump, add a microbial growth promoter into the aerobic unit (4), and expose for 24 hours to obtain a mixed solution; Then, 1 / 3 of the mixed liquid is discharged, and the sewage is continuously introduced; the aeration intensity of the aerobic unit (4) is set to 3-5 mg / L, and the hydraulic retention time is 8-10 h; the rotation speed of the electric mechanical stirring device (5) in the anoxic unit (2) is set to 20-30 rpm, and the stirring power is 1.5-2.0 kW; the hydraulic retention time ratio of the aerobic unit (4), the anoxic unit (2) and the anaerobic unit (1) is set to 8-10:5-7:4-5.

2. A denitrification membrane bioreactor wastewater treatment method according to claim 1, characterized in that: The volume ratio of the aerobic unit (4), the anoxic unit (2) and the anaerobic unit (1) is 2:1:

2.

3. A denitrification membrane bioreactor wastewater treatment method according to claim 1, characterized in that: The aerobic unit (4) and the anaerobic unit (1) are each provided with five cells; the cells are staggeredly distributed in the aerobic unit (4) and the anaerobic unit (1); the sewage is injected into the denitrification membrane bioreactor, first injected into the aerobic unit (4) through the water pump, and then passes through the five cells of the aerobic unit (4) in sequence; Subsequently, under the action of the water pump, the sewage is separated through the membrane separation zone (3) and then enters the anoxic unit (2); the rotation speed of the electric mechanical stirring device (5) in the anoxic unit (2) is set to 20-30 rpm, and the stirring power is 1.5-2.0 kW, and stirring and filtration are performed, and then the partition between the anoxic unit (2) and the anaerobic unit (1) is opened, so that the sewage passes through the five cells of the anaerobic unit (1) in sequence and then the effluent is discharged; the cells in the aerobic unit (4) and the anaerobic unit (1) can swing at an angle, and the swing angle of the cells is 60°-75° with respect to the vertical direction of the denitrification membrane bioreactor.

4. A denitrification membrane bioreactor wastewater treatment method according to claim 1, characterized in that: The preparation process of the hydrophilic suspended filler is as follows: 50 parts of cultured Spirulina platensis are subjected to centrifugal concentration treatment, and the supernatant is removed and then rinsed with distilled water, and an algae cell solution is obtained after two centrifugal treatments; 30 parts of the algae cell solution and 40 parts of a sterilized sodium alginate solution with a concentration of 1wt%-3wt% are fully mixed to form a mixed solution; the mixed solution is slowly dripped into a sterilized ferrous chloride solution with a concentration of 3% and stirred to form a cell group with a particle size of 2-3mm; the cell group is placed in a refrigerator at a temperature of 4-8°C for 24 hours, taken out of the refrigerator, and washed twice with the distilled water to obtain an algae cell jelly ball; 30 parts of activated carbon and 10 parts of polyethylene fixed algae cell jelly balls are added to the algae cell jelly balls to obtain the hydrophilic suspended filler.

5. A denitrification membrane bioreactor wastewater treatment method according to claim 1, characterized in that: The microbial growth promoter comprises 30-40 parts of metal salt, 20-30 parts of putrescine, 10-15 parts of glucose and 7 parts of sodium acetate.

6. A denitrification membrane bioreactor wastewater treatment method according to claim 5, characterized in that: The metal salt is composed of calcium salt CaCl2, copper salt CuCl2, magnesium salt MgSO4 and ferrous salt FeSO4; the proportion ratio between the calcium salt CaCl2, the copper salt CuCl2, the magnesium salt MgSO4 and the ferrous salt FeSO4 is 3:1:2:

2.

7. A denitrification membrane bioreactor wastewater treatment method according to claim 1, characterized in that: The sewage reflow ratio inside the denitrification model bioreactor is 300%; the reflow ratio between the aerobic unit (4) and the anoxic unit (2) is 1.7.

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