A sewage treatment system and method for treating wastewater with high DMF content by biochemical method

Abstract

The invention discloses a sewage treatment system and method for treating wastewater with high DMF content by a biochemical method. The sewage treatment system comprises: an aeration tank for treating sewage, a fermentation device for cultivating bacteria is arranged at the front end of the aeration tank, a filler for carrying the bacteria is arranged in the fermentation device, a first pipeline is arranged between the fermentation device and the aeration tank, the first pipeline is used to circulate the filler between the fermentation device and the aeration tank, and DMF in the sewage is degraded by microbial metabolism, thereby achieving sewage purification and reducing investment and operation costs.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a wastewater treatment system and method for treating wastewater with high DMF content by a biochemical method. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] DMF, or N-dimethylformamide, is a transparent, colorless liquid known as a universal solvent. It is easily miscible with solutes such as water, alcohols, esters, ketones, ethers, unsaturated hydrocarbons and aromatic hydrocarbons, and is widely used in medicine, pesticides, industry and other fields. Especially in the pharmaceutical industry, DMF is an excellent reaction solvent, extractant and crystallization solvent, and can be used to synthesize the raw materials of sulfadiazine, doxycycline, cortisone and other drugs; in addition, it is also an excellent solvent for drugs such as sulfonamides, vitamins, quinoline, epinephrine, ammonium chloride and so on.

[0004] Since DMF is widely used as an organic solvent and does not directly participate in the reaction, almost all of the remaining DMF enters the wastewater. DMF is a low-to-moderate toxic compound and has been identified as a possible carcinogen to humans. DMF in water will cause an increase in biochemical oxygen demand and nitrogen content, and is extremely difficult to biodegrade (DMF's B / C is 0.065), posing a major problem for corporate wastewater treatment.

[0005] At present, the main methods for treating DMF wastewater in China are physical and chemical treatment methods such as adsorption, distillation, Fenton reagent, ozone catalytic oxidation, photocatalytic oxidation and supercritical water oxidation. The above treatment methods either have poor treatment effects, fail to meet emission standards, or have too high investment and operating costs, which are difficult for enterprises to accept. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the embodiments of the present invention is to provide a sewage treatment system for treating wastewater with high DMF content by biochemical method, which utilizes microbial metabolism to degrade DMF in sewage, thereby achieving sewage purification and reducing investment and operating costs.

[0007] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] A sewage treatment system for treating wastewater with high DMF content by biochemical method comprises: an aeration tank for treating sewage, a fermentation device for cultivating bacteria is arranged at the front end of the aeration tank, a filler for carrying the bacteria is arranged in the fermentation device, a first pipeline is arranged between the fermentation device and the aeration tank, and the first pipeline is used to circulate the filler between the fermentation device and the aeration tank.

[0009] Furthermore, a second pipeline is provided between the fermentation device and the aeration tank, and the second pipeline is used to transport the wastewater with high DMF content from the fermentation device to the aeration tank.

[0010] Furthermore, the filler is MBBR filler.

[0011] Furthermore, a UASB reactor is provided at the front end of the aeration tank, a third pipeline is provided between the UASB reactor and the aeration tank, the second pipeline is connected to the third pipeline, and the UASB reactor is an anaerobic sludge blanket reactor for treating pollutants with good biodegradability.

[0012] Furthermore, the aeration tank is divided into an anoxic tank and an aerobic tank, the anoxic tank comprises a carbon source dosing device, and the aerobic tank comprises a nitrification liquid reflux device.

[0013] Furthermore, a sedimentation tank is provided at the rear end of the aeration tank, and a fourth pipeline for water outlet and a fifth pipeline for sludge return are provided between the aeration tank and the sedimentation tank.

[0014] Furthermore, the fermentation device includes a fermentation tank and a circulating water system, the circulating water system includes a circulating water inlet and a circulating water outlet arranged on the wall of the fermentation tank, and the circulating water system is isolated from the sewage in the fermentation tank.

[0015] Furthermore, the fermentation device is provided with an axial flow stirring paddle and a radial flow stirring paddle.

[0016] Another object of the present invention is to provide a wastewater treatment method for treating wastewater with high DMF content by biochemical method, wherein bacteria are multiplied to a predetermined number in a fermentation tank, MBBR fillers are used as mobile microbial carriers to transport the bacteria to an aeration tank, and MBBR fillers with weakened activity are periodically re-entered into the fermentation tank to re-form biofilm.

[0017] Furthermore, it also includes the screening and domestication of bacteria: inoculating activated sludge from aerobic tanks into liquid selective culture medium, culturing under constant temperature conditions, and then inoculating it into fresh selective culture medium for further culturing. After continuous transfer and culturing for a predetermined time, a set amount is spread on a solid selective culture medium, and after constant temperature culturing for a predetermined time, a single colony is picked and inoculated into LB culture medium, and cultured at a constant temperature for 24 hours, the colony morphology is observed, and physiological and biochemical identification is performed.

[0018] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0019] 1. The present invention sets a fermentation device at the front end of the aeration tank, uses the high-DMF wastewater produced within the enterprise as a raw material to ferment and cultivate special bacteria that can degrade DMF, and then uses the filler as a mobile microbial carrier to transport the special bacteria into the aeration tank. The filler with weakened activity can re-enter the fermentation device to re-form a biofilm, thereby realizing the reuse of the filler.

[0020] 2. The present invention adds a fermentation device on the basis of the existing sewage treatment system. The special bacteria that degrade DMF can efficiently degrade DMF in sewage, which can further reduce the toxic inhibition of DMF on anaerobic reactors such as UASB and increase the anaerobic load.

[0021] 3. The radial flow agitator and the axial flow agitator are provided to fully mix the MBBR filler and the wastewater, thereby ensuring that the filler biofilm formation rate is basically the same and improving the biofilm formation efficiency of the MBBR filler. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 It is a schematic flow chart of a sewage treatment system for treating wastewater with high DMF content by a biochemical method of the present invention;

[0024] Figure 2 It is a schematic diagram of a fermentation device of a sewage treatment system for treating wastewater with high DMF content by a biochemical method of the present invention;

[0025] In the figure: 1. Fermentation unit; 2. UASB reactor; 3. Aeration tank; 4. Sedimentation tank;

[0026] 21. First pipeline; 22. Second pipeline; 23. Third pipeline; 24. Fourth pipeline; 25. Fifth pipeline;

[0027] 31. Sewage inlet; 32. Vent valve; 33. Circulating water inlet; 34. Sight glass; 35. Bracket; 36. Filling outlet; 37. Stirring motor; 38. Filling inlet; 39. Air inlet pipe; 310. Radial flow stirring paddle; 311. Circulating water outlet; 312. Axial flow stirring paddle; 313. Aerator;

[0028] In order to show the positions of various parts, the distances or sizes between them are exaggerated and the schematic diagram is for reference only. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0031] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0032] Terminology explanation section: The terms "install", "connected", "connect", "fixed" and the like in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; it can be an internal connection between two elements, or an interaction relationship between two elements. For ordinary technicians in this field, the specific meaning of the terms in the present invention can be understood according to the specific circumstances.

[0033] As the background technology introduces, the main methods for treating DMF wastewater in China are: physical and chemical treatment methods such as adsorption, distillation, Fenton reagent, ozone catalytic oxidation, photocatalytic oxidation and supercritical water oxidation. The above treatment methods either have poor treatment effects, fail to meet emission standards, or have too high investment and operating costs, which are difficult for enterprises to accept. In order to solve the above technical problems, the present invention proposes a sewage treatment system for treating wastewater with high DMF content by biochemical method.

[0034] like Figure 1-Figure 2As shown, the present invention describes a sewage treatment system for treating wastewater with high DMF content by biochemical method, comprising: an aeration tank 3 for treating sewage, a fermentation device 1 for cultivating bacteria is arranged at the front end of the aeration tank 3, a filler for carrying the bacteria is arranged in the fermentation device 1, a first pipeline 21 is arranged between the fermentation device 1 and the aeration tank 3, and the first pipeline 21 is used to circulate the filler between the fermentation device 1 and the aeration tank 3. The front end refers to the front process in the sewage treatment process, and it can be understood that the back end in the following text refers to the back process in the sewage treatment process.

[0035] The applicant has studied that there are many microorganisms in nature that have the ability to degrade DMF, including bacteria from the following genera: Ochrobactrum, Pseudomonas, Alcaligenes, and Paracoccus. There is a bacterium under the genus Pseudomonas that can use DMF as a carbon source and nitrogen source for growth and can effectively degrade DMF in water. This bacterium is widely present in nature, but in low numbers, so it is necessary to first cultivate the number of this bacterium.

[0036] A fermentation device 1 is set at the front end of the aeration tank 3, and the high-DMF wastewater produced within the enterprise is used as a raw material to ferment and cultivate special bacteria that can degrade DMF. Then, the filler is used as a mobile microbial carrier to transport the special bacteria to the aeration tank 3. The filler with weakened activity can re-enter the fermentation device 1 to re-form a biofilm, thereby realizing the reuse of the filler.

[0037] A second pipeline 22 is further provided between the fermentation device 1 and the aeration tank 3 , and the second pipeline 22 is used to transport the wastewater with high DMF content from the fermentation device 1 to the aeration tank 3 .

[0038] The filler is MBBR filler, which has the advantages of large specific surface area, reasonable specific gravity, good hydrophilicity, good electrophilicity, high biological activity, fast biofilm formation, good treatment effect, UV resistance and long service life.

[0039] A UASB reactor 2 is also provided at the front end of the aeration tank 3, a third pipeline 23 is provided between the UASB reactor 2 and the aeration tank 3, the second pipeline 22 is connected to the third pipeline 23, and the UASB reactor 2 is an anaerobic sludge bed reactor, which is used to treat pollutants with good biodegradability. The anaerobic sludge bed reactor is an anaerobic biological method for treating sewage, and the sewage passes through the UASB from bottom to top. There is a high-concentration and high-activity sludge bed at the bottom of the reactor, and most of the organic pollutants in the sewage are degraded into methane and carbon dioxide through anaerobic fermentation. By adding a fermentation device 1, special bacteria that degrade DMF can efficiently degrade DMF in sewage, which can further reduce the toxic inhibition of DMF on anaerobic reactors such as UASB and increase the anaerobic load.

[0040] The aeration tank 3 is divided into an anoxic tank and an aerobic tank, the anoxic tank includes a carbon source dosing device, and the aerobic tank includes a nitrification liquid reflux device. The aeration tank 3 is a high-efficiency microbial aerobic fermentation device 1, and the aeration tank 3 of the activated sludge process is divided into an anoxic tank and an aerobic tank. The anoxic tank includes a set of carbon source dosing devices, which can provide carbon sources to the denitrification reaction in the anoxic tank, and the aerobic tank includes a set of nitrification liquid reflux equipment, which can return the nitrification liquid in the aerobic tank to the anoxic tank for denitrification.

[0041] A sedimentation tank 4 is provided at the rear end of the aeration tank 3. A fourth pipeline 24 for effluent and a fifth pipeline 25 for sludge return are provided between the aeration tank 3 and the sedimentation tank 4. The sedimentation tank 4 can realize mud-water separation, and the activated sludge enters the anoxic tank via the sludge return pump.

[0042] The fermentation device 1 includes a fermentation tank and a circulating water system, wherein the circulating water system includes a circulating water inlet 33 and a circulating water outlet 311 arranged on the wall of the fermentation tank, and the circulating water system is isolated from the sewage in the fermentation tank. By equipping the high-efficiency microbial aerobic fermentation device 1 with a circulating water system, accurate control of the fermentation temperature is achieved.

[0043] like Figure 2 As shown, the fermentation device 1 is provided with an axial flow stirring paddle 312 and a radial flow stirring paddle 310, wherein one radial flow stirring paddle is provided above and below, and an axial flow stirring paddle is provided between the two radial flow stirring paddles. A stirring motor 37 for driving the radial flow stirring paddle and the axial flow stirring paddle is installed on the top of the fermentation tank. Through the provision of the radial flow stirring paddle and the axial flow stirring paddle, the MBBR filler and the wastewater can be fully mixed, thereby improving the biofilm formation efficiency of the MBBR filler.

[0044] An aerator 313 is provided at the bottom of the fermentation tank, and the aerator 313 is connected to the outside through an air inlet pipe 39. A set of microporous aerators 313 are provided at the bottom of the high-efficiency microbial aerobic fermentation device 1, which can provide sufficient dissolved oxygen for fermentation. The contact between organic matter in the pool and microorganisms and dissolved oxygen is strengthened, thereby ensuring that the microorganisms in the pool can oxidize and decompose organic matter in sewage under the condition of sufficient dissolved oxygen.

[0045] The top of the fermentation tank is provided with a sewage inlet 31, a filler inlet 38 and a vent valve 32, the bottom of the fermentation tank is provided with a bracket 35, and the side wall is provided with a sight glass 34, so as to observe the reaction situation in the fermentation tank in real time.

[0046] The fermentation tank is provided with a filler outlet 36 and a sewage outlet (not shown in the figure), and the filler outlet 36 and the sewage outlet enter the aeration tank 3 through the first pipeline 21 and the second pipeline 22 respectively.

[0047] The present invention provides a sewage treatment system for treating wastewater with high DMF content by biochemical method, which is sequentially connected to an efficient microbial aerobic fermentation device 1, an aeration tank 3 and an efficient sedimentation tank 4. A UASB is arranged in front of the aeration tank 3. The high DMF wastewater first enters the efficient microbial aerobic fermentation device 1, and DMF is efficiently metabolized by bacteria as a carbon source and a nitrogen source. The bacteria using DMF as a carbon source and a nitrogen source rapidly multiply and attach to the MBBR filler. The treated wastewater directly flows into the aeration tank 3, and the various strains in the aeration tank 3 continue to metabolize the remaining DMF and other pollutants until the discharge standard is reached.

[0048] The strains with specific advantages are screened and domesticated in the high-efficiency microbial aerobic fermentation device 1 and attached to the MBBR filler, and are transported to the aeration tank 3 via the first pipeline 21 as a biological enhancer, so that the specific strains in the aeration tank 3 are always in the best active state, and the effect of the aeration tank 3 in treating DMF and other pollutants is improved. The MBBR filler in the aeration tank 3 is transported to the high-efficiency microbial aerobic fermentation device 1 by the transport pipeline, and the MBBR is reattached with the superior strains to ensure the biological activity of the MBBR seasoning.

[0049] Another aspect of the present invention provides a wastewater treatment method for treating wastewater with high DMF content by biochemical method:

[0050] 1. Screening and domestication of special bacteria that can grow using DMF as a carbon and nitrogen source.

[0051] Selective culture medium composition (g / L): dimethylformamide (DMF) 0.40, sodium chloride 1.00, dipotassium hydrogen phosphate 2.50, potassium dihydrogen phosphate 1.00, pH 7.00.

[0052] LB medium composition (g / L): peptone 10.00, beef extract 3.00, sodium chloride 1.00, dipotassium hydrogen phosphate 2.50, potassium dihydrogen phosphate 1.00, pH 7.00.

[0053] Screening and domestication of strains:

[0054] 5% of the activated sludge from the aerobic pool was inoculated into the liquid selective culture medium, and cultured at a constant temperature of 30°C for one week. Then, 10% of the inoculation amount was inoculated into the fresh selective culture medium, and cultured for another week. After continuous transfer and culture for one week, 1 mL was spread on the solid selective culture medium, and after constant temperature culture at 30°C for one week, a single colony was picked and inoculated into the LB culture medium, and cultured at the constant temperature for 24 hours. The colony morphology was observed, and physiological and biochemical identification was performed to determine that it was a bacterium of the genus Pseudomonas that could grow using DMF as a carbon source and a nitrogen source.

[0055] The selected special bacteria are inoculated into the high-efficiency microbial aerobic fermentation device at a 10% inoculation rate. The fermentation tank is filled with 30% MBBR filler and 80% high-concentration DMF pharmaceutical wastewater. The fermentation is maintained at a constant temperature of 30°C for 24 hours. After the strain is domesticated, the reactor can be started normally.

[0056] The high-efficiency microbial aerobic fermentation device is filled with MBBR seasoning and inoculated with bacteria of the genus Pseudomonas that can use DMF as a carbon source and nitrogen source for growth. Pharmaceutical wastewater containing high concentrations of DMF is input into the fermenter. During the system startup phase, glucose should be added to the reactor as a carbon source to allow the inoculated bacteria to multiply to a certain number (about 2000 mg / L). The addition of glucose can be stopped and wastewater can be fed normally. DMF is decomposed into carbon dioxide and ammonium ions through the metabolic reaction of special bacteria. The ammonium ions are reabsorbed and utilized by special bacteria as a nitrogen source. The special bacteria proliferate on the MBBR filler as an attachment point, and the bacteria proliferate while purifying the water. The proliferated special bacteria are transported to the aeration tank by the bacterial liquid supplement pipeline as a bio-enhancer, so that the specific bacteria in the aeration tank are always in the best active state, enhancing the ability of the aeration tank to degrade DMF and other pollutants.

[0057] After purification, high-DMF wastewater is mixed with other biodegradable wastewater and enters the aeration tank. In the aerobic section of the aeration tank, ammonia nitrogen and a part of DMF are metabolized into nitrate and carbon dioxide by various microorganisms in the aerobic tank. Nitrate enters the anoxic tank through the nitrification liquid return pipeline. In the anoxic tank of the aeration tank, denitrifying bacteria absorb nitrate brought by the nitrification liquid return and the carbon source added in the anoxic tank to carry out denitrification reaction, and metabolize nitrate into nitrogen gas, thereby achieving the purpose of denitrification.

[0058] Since the special bacteria that efficiently degrade DMF have a long reproduction cycle and are at a competitive disadvantage in the aerobic tank, the special bacteria attached to the MBBR will be slowly replaced by other bacteria, thus losing the ability to degrade DMF. In view of this, the MBBR fillers in the aeration tank must be regularly transported to the high-efficiency microbial aerobic fermentation device for re-biofilm cultivation. The circulation of fillers between the fermentation tank and the aeration tank can be achieved by existing means, such as pumps.

[0059] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A sewage treatment system for treating wastewater with high DMF content by biochemical method, characterized in that: include: An aeration tank for treating sewage, wherein an aerobic fermentation device for cultivating bacteria is disposed at the front end of the aeration tank, wherein fillers for carrying the bacteria are disposed in the aerobic fermentation device, and a first pipeline is disposed between the aerobic fermentation device and the aeration tank, wherein the first pipeline is used to circulate the fillers between the aerobic fermentation device and the aeration tank; The aerobic fermentation device is provided with an axial flow stirring paddle and a radial flow stirring paddle, wherein one radial flow stirring paddle is provided at the top and one at the bottom, and an axial flow stirring paddle is provided between the two radial flow stirring paddles; The bacteria are bacteria of the genus Pseudomonas that can grow using DMF as a carbon source and a nitrogen source; High-DMF wastewater first enters the aerobic fermentation device, where DMF is efficiently metabolized by bacteria as a carbon and nitrogen source. Bacteria using DMF as a carbon and nitrogen source multiply rapidly and attach to the filler; The treated wastewater flows directly into the aeration tank, where the bacteria continue to metabolize the remaining DMF and other pollutants until they meet the discharge standards; The fillers in the aeration tank are regularly transported to the aerobic fermentation device for re-biofilm cultivation; A second pipeline is also provided between the aerobic fermentation device and the aeration tank, and the second pipeline is used to transport the treated high-DMF content wastewater from the aerobic fermentation device to the aeration tank; A UASB reactor is also provided at the front end of the aeration tank, a third pipeline is provided between the UASB reactor and the aeration tank, the second pipeline is connected to the third pipeline, the UASB reactor is an anaerobic sludge blanket reactor, and highly biodegradable wastewater enters the anaerobic sludge blanket reactor.

2. The sewage treatment system for treating high DMF content wastewater by biochemical method as claimed in claim 1, characterized in that: The filler is MBBR filler.

3. The sewage treatment system for treating high DMF content wastewater by biochemical method as claimed in claim 1, characterized in that: A sedimentation tank is arranged at the rear end of the aeration tank, and a fourth pipeline for water outlet and a fifth pipeline for sludge return are arranged between the aeration tank and the sedimentation tank.

4. The sewage treatment system for treating high DMF content wastewater by biochemical method as claimed in claim 1, characterized in that: The fermentation device comprises a fermentation tank and a circulating water system, wherein the circulating water system comprises a circulating water inlet and a circulating water outlet arranged on the wall of the fermentation tank, and the circulating water system is isolated from the sewage in the fermentation tank.

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