Process for efficient degradation and synchronous denitrification of DMF-containing wastewater

Abstract

The invention discloses a process for efficient degradation and synchronous denitrification of DMF-containing wastewater, and relates to the technical field of wastewater treatment. The technology comprises the following steps: the wastewater containing high-concentration DMF enters an anaerobic reactor 1, the effluent of the anaerobic reactor 1 enters a short-cut nitrification reactor 2, the short-cut nitrification reactor 2 enters an anaerobic ammonia oxidation reactor 3, the effluent part of the anaerobic ammonia oxidation reactor 3 flows back to the anaerobic reactor 1, and the effluent part of the anaerobic ammonia oxidation reactor 3 flows back to the anaerobic reactor 1; the residual effluent enters a BAF reactor 4, and the effluent of the BAF reactor 4 enters an autotrophic nitrogen removal reactor 5; according to the method, the biotoxicity is reduced through anaerobic process pretreatment, and meanwhile, the degradation rate of DMF is increased through cooperation of easily-degradable organic matters and DMF degradation; ammonia nitrogen is released through ammonification in the anaerobic process, the short-cut nitrification-anaerobic ammonia oxidation process is added in the subsequent denitrification process, autotrophic nitrogen removal is added in the subsequent process, and the effluent can stably reach the standard.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater. Background Art

[0002] N,N-dimethylformamide (DMF) is a man-made industrial chemical. As of 2017, my country's annual DMF production is expected to reach 1 million tons. As early as 2005, my country has become the world's largest producer of DMF. Since dimethylformamide is miscible with water and organic solvents, it is widely used as a solvent in the chemical industry such as textiles and pharmaceuticals, as well as in the production of various organic chemicals and polymers such as polyurethane, rubber, dyes, wood, leather, film, paper and pesticides. Therefore, even after recovery, high concentrations of DMF can usually be found in many industrial wastewaters. It is well known that dimethylformamide can affect cell differentiation, liver toxicity and cause gastric irritation, further causing cancer. In order to avoid these adverse effects of dimethylformamide that endanger human health, its removal from industrial wastewater has received widespread attention. Although there are physical and chemical methods that can be used to treat wastewater containing dimethylformamide, its high cost of operation leads to low economic efficiency of physical and chemical methods, making it difficult to be widely used. In order to reduce operating costs, biochemical technology has been gradually introduced into industrial wastewater to gradually replace physical and chemical treatment technology, and has been promoted globally. At present, most factories still use traditional A / O and Fenton oxidation processes to denitrify production wastewater. However, due to the high energy consumption required for the whole nitrification process and the problem of insufficient carbon source, a large amount of organic carbon source for denitrification needs to be added. In addition, the traditional process has a high sludge output, but the sludge treatment cost accounts for 30-40% of the total investment of the entire sewage treatment plant. At the same time, the traditional denitrification process separates the nitrification and denitrification processes in time and space, resulting in the biological denitrification reaction being restricted by conditions such as substrate transfer rate, substrate and product inhibition, so the traditional denitrification process has a low design load of only 0.4kg / (m 3 ·d), which will require the process to have a longer HRT and a larger footprint to meet the high-nitrogen wastewater treatment needs of enterprises. Therefore, the research, application and promotion of new energy-saving and efficient biological denitrification processes have become the key to the treatment of high-nitrogen organic wastewater;

[0003] In a patent entitled "A method for treating wastewater containing N,N-dimethylformamide" with a Chinese publication number of CN116282635A, some cyclic and long-chain macromolecular organic matter is broken and degraded into small molecular organic matter by iron-carbon micro-electrolysis, thereby improving the biodegradability of the wastewater; then, part of the COD is removed by acidification treatment, and the acidification treatment can convert organic nitrogen into ammonia nitrogen under anoxic conditions, thereby removing part of the organic nitrogen; anaerobic treatment mainly carries out denitrification, two-stage aerobic treatment can increase the removal efficiency of COD and the nitrification efficiency of ammonia nitrogen, and aerated biological treatment can further remove COD, ammonia nitrogen and total nitrogen in the wastewater through the biological oxidation, adsorption and filtration of biological fillers, thereby stabilizing the effluent water quality;

[0004] In the patent entitled "A Method for Treating Organic Nitrogen DMF Chemical Wastewater" with a Chinese publication number of CN105198174A, the steps are as follows: A. High-concentration DMF wastewater flows into a physical and chemical collection pool; B. The wastewater from the physical and chemical collection pool is transported to an alkalization regulating pool; C. The effluent from the alkalization regulating pool is transported to a hot stripping tower; D. The tail gas from the hot stripping tower is absorbed in series by two-stage absorption towers, and the tail gas treated by the second-stage absorption tower is discharged into the air; E. The hot stripping tower After the internal wastewater is thermally stripped, it is transported to the biochemical regulating tank; F. The effluent from the biochemical regulating tank enters the biochemical aerobic tank I; G. The effluent from the biochemical aerobic tank I is transported to the biochemical anoxic tank; H. The effluent from the biochemical anoxic tank is transported to the biochemical aerobic tank II, and the nitrified liquid from the biochemical aerobic tank II is returned to the biochemical anoxic tank; I. The sludge from the secondary sedimentation tank is returned to the biochemical aerobic tank I, and the effluent ammonia nitrogen is directly discharged below 15 mg / L. The method is simple, easy to operate, and low in cost;

[0005] However, there are still some shortcomings in the above patents. DMF wastewater is a high-organic nitrogen wastewater with complex components and DMF as a characteristic pollutant. At present, the treatment of this type of wastewater is mainly based on physicochemical technology dominated by advanced oxidation and biochemical technology dominated by traditional A / O. Due to the slow chemical degradation rate of DMF and its good water solubility, it is difficult to remove it efficiently through physicochemical technology; in addition, the traditional A / O process can effectively reduce the nitrogen content in DMF wastewater, but the free cells in the activated sludge system cannot survive for a long time under the toxic effect of high concentrations of DMF; the nitrogen content in the chemical composition of DMF is as high as 18%. During the biological treatment process, due to ammoniation, the organic nitrogen in the effluent is converted into a large amount of ammonia nitrogen. The nitrogen loss of the effluent from ammoniation is less than 5%, and it often faces the problem of excessive effluent nitrogen content. In response to the above problems, the inventors proposed a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater to solve the above problems. Summary of the invention

[0006] In order to solve the problem that the nitrogen content in the chemical composition of DMF is as high as 18%, during the biological treatment process, due to the ammoniation effect, the organic nitrogen in the effluent is converted into a large amount of ammonia nitrogen, and the nitrogen loss of the ammonia effluent is less than 5%, which often faces the problem of excessive effluent nitrogen content; the purpose of the present invention is to provide a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0008] S1: Wastewater containing high concentration of DMF enters the anaerobic reactor (1);

[0009] S2: The effluent from the anaerobic reactor (1) enters the short-range nitrification reactor (2);

[0010] S3: The short-cut nitrification reactor (2) enters the anaerobic ammonium oxidation reactor (3);

[0011] S4: Part of the effluent from the anaerobic ammonium oxidation reactor (3) is returned to the anaerobic reactor (1), and the remaining effluent enters the BAF reactor (4);

[0012] S5: The effluent from the BAF reactor (4) enters the autotrophic denitrification reactor (5).

[0013] Preferably, the DMF concentration in the wastewater containing high concentration of DMF is ≤5000 mg / L, and the ratio of DMF to easily degradable organic matter is 1:0.7 to 1:1.3 (COD Cr count).

[0014] Preferably, the pH of the wastewater containing high concentration of DMF is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor.

[0015] Preferably, the short-term nitrification stage consumes a large amount of alkalinity, and the wastewater with high concentration of DMF produces a large amount of alkalinity after anaerobic reaction, which can maintain the alkalinity consumption in the short-term nitrification stage.

[0016] Preferably, the anaerobic ammonium oxidation influent controls ammonia nitrogen: nitrite nitrogen = 1: 1.1-1.4, wherein the BAF reactor uses lightweight fillers.

[0017] Preferably, the hydraulic retention time in the anaerobic reactor is controlled by the influent flow rate, and the dosage of the anaerobic granular sludge is 30% by volume.

[0018] Preferably, the volume ratio of the anaerobic reactor to the short-cut nitrification reactor is about 1:1, and the anaerobic ammonia oxidation effluent is returned to the anaerobic reactor.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the present invention, biological toxicity is reduced by anaerobic process pretreatment, and easily degradable organic matter is used to cooperate with DMF degradation to improve the DMF degradation rate; the ammoniation action of the anaerobic process releases ammonia nitrogen, and the subsequent denitrification adds a short-range nitrification-anaerobic ammonia oxidation process, and then autotrophic denitrification is added to achieve stable effluent compliance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the treatment process flow of the present invention.

[0023] In the figure: 1. anaerobic reactor; 11. anaerobic granular sludge; 2. short-range nitrification reactor; 21. carrier; 22. aeration disk; 3. anaerobic ammonium oxidation reactor; 31. anaerobic ammonium oxidizing bacteria; 4. BAF reactor; 41. lightweight filler; 42. aerator; 5. autotrophic denitrification reactor; 51. sulfur particles. DETAILED DESCRIPTION

[0024] 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.

[0025] Example 1: Figure 1 As shown, the present invention provides a technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0026] S1: The DMF concentration in the wastewater containing high concentration of DMF is 1000 mg / L, and the ratio of DMF to sodium acetate is 1:1 (COD Cr If the influent concentration does not meet this requirement, after laboratory testing and analysis, the influent flow rate is adjusted to make the influent COD concentration within this range to facilitate subsequent treatment. The pH of the wastewater with high concentration of DMF is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor. The residence time in the anaerobic reactor is controlled to be 16h.

[0027] S2. The effluent from the anaerobic reactor enters the short-range nitrification reactor, and the residence time is controlled to be 16 hours.

[0028] S3. The effluent from the short-range nitrification reactor is controlled to have ammonia nitrogen: nitrite nitrogen = 1:1.1, and the effluent enters the anaerobic ammonia oxidation reactor through a pump.

[0029] S4, part of the anaerobic ammonium oxidation effluent is returned to the anaerobic reactor with a reflux ratio of 50%, and part of it enters the BAF reactor with a residence time of 12h;

[0030] S5. Pass the wastewater in S4 into an autotrophic denitrification reactor, and the effluent can be purified wastewater, and the effluent water quality indicators are measured.

[0031] Processing Unit COD(mg / L) Ammonia nitrogen (mg / L) Wastewater containing DMF 2000 0 Anaerobic treatment of effluent 72 124 Short-cut nitrification treatment of effluent 70 55 Anaerobic ammonium oxidation treatment effluent 70 12 BAF treated effluent 63 2 Autotrophic denitrification treatment effluent 59 2

[0032] Example 2: Figure 1 As shown, the present invention provides a technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0033] S1: The DMF concentration in the wastewater containing high concentration of DMF is 5000 mg / L, and the ratio of DMF to sodium acetate is 1:1 (COD Cr If the influent concentration does not meet this requirement, after laboratory testing and analysis, the influent flow rate is adjusted to make the influent COD concentration within this range to facilitate subsequent treatment. The pH of the wastewater with high concentration of DMF is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor. The residence time in the anaerobic reactor is controlled to be 16h.

[0034] S2. The effluent from the anaerobic reactor enters the short-range nitrification reactor, and the residence time is controlled to be 16 hours.

[0035] S3. The effluent from the short-range nitrification reactor is controlled to have ammonia nitrogen: nitrite nitrogen = 1:1.1, and the effluent enters the anaerobic ammonia oxidation reactor through a pump.

[0036] S4, part of the anaerobic ammonium oxidation effluent is returned to the anaerobic reactor with a reflux ratio of 50%, and part of it enters the BAF reactor with a residence time of 12h;

[0037] S5. Pass the wastewater in S4 into an autotrophic denitrification reactor, and the effluent can be purified wastewater, and the effluent water quality indicators are measured.

[0038] Processing Unit COD(mg / L) Ammonia nitrogen (mg / L) Wastewater containing DMF 10000 0 Anaerobic treatment of effluent 87 608 Short-cut nitrification treatment of effluent 80 295 Anaerobic ammonium oxidation treatment effluent 75 56 BAF treated effluent 69 10 Autotrophic denitrification treatment effluent 65 9

[0039] Example 3: Figure 1 As shown, the present invention provides a technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0040] S1: The DMF concentration in the wastewater containing high-concentration DMF is 1000 mg / L, and the pH of the wastewater containing high-concentration DMF is controlled to be neutral. No pH adjustment is required after entering the anaerobic reactor, and the residence time in the anaerobic reactor is controlled to be 32 hours.

[0041] S2. The effluent from the anaerobic reactor enters the short-range nitrification reactor, and the residence time is controlled to be 32 hours.

[0042] S3. The effluent from the short-range nitrification reactor is controlled to have ammonia nitrogen: nitrite nitrogen = 1:1.1, and the effluent enters the anaerobic ammonia oxidation reactor through a pump.

[0043] S4, part of the anaerobic ammonium oxidation effluent is returned to the anaerobic reactor with a reflux ratio of 50%, and part of it enters the BAF reactor with a residence time of 12h;

[0044] S5. Pass the wastewater in S4 into an autotrophic denitrification reactor, and the effluent can be purified wastewater, and the effluent water quality indicators are measured.

[0045]

[0046]

[0047] Example 4: Figure 1 As shown, the present invention provides a technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0048] S1: The DMF concentration in the wastewater containing high concentration of DMF is 1000 mg / L, and the ratio of DMF to sodium acetate is 1:1 (COD Cr If the influent concentration does not meet this requirement, the influent flow rate is adjusted through laboratory testing to keep the influent COD concentration within this range for subsequent treatment. The pH of wastewater with high DMF concentration is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor. The residence time in the anaerobic reactor is controlled to be 16h.

[0049] S2. The effluent from the anaerobic reactor enters the short-range nitrification reactor, and the residence time is controlled to be 16 hours.

[0050] S3. The effluent from the short-range nitrification reactor is controlled to have ammonia nitrogen: nitrite nitrogen = 1:1.1, and the effluent enters the anaerobic ammonia oxidation reactor through a pump.

[0051] S4, all anaerobic ammonium oxidation effluent enters the BAF reactor, and the residence time is 12h;

[0052] S5. Pass the wastewater in S4 into an autotrophic denitrification reactor, and the effluent can be purified wastewater, and the effluent water quality indicators are measured.

[0053] Processing Unit COD(mg / L) Ammonia nitrogen (mg / L) Wastewater containing DMF 2000 0 Anaerobic treatment of effluent 150 114 Short-cut nitrification treatment of effluent 138 48 Anaerobic ammonium oxidation treatment effluent 127 11 BAF treated effluent 123 2 Autotrophic denitrification treatment effluent 119 2

[0054] Example 5: Figure 1 As shown, the present invention provides a technical solution: a process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, comprising the following steps:

[0055] S1: Take the DMF wastewater from a pharmaceutical factory and analyze its water quality. The DMF concentration is 1500mg / L, the total COD concentration is 4000mg / L, and the pH is about 7.0. Use this wastewater to conduct DMF degradation test. No pH adjustment is required after entering the anaerobic reactor, and the residence time in the anaerobic reactor is controlled to be 16h.

[0056] S2. The effluent from the anaerobic reactor enters the short-range nitrification reactor, and the residence time is controlled to be 16 hours.

[0057] S3. The effluent from the short-range nitrification reactor is controlled to have ammonia nitrogen: nitrite nitrogen = 1:1.1, and the effluent enters the anaerobic ammonia oxidation reactor through a pump.

[0058] S4, part of the anaerobic ammonium oxidation effluent is returned to the anaerobic reactor with a reflux ratio of 50%, and part of it enters the BAF reactor with a residence time of 12h;

[0059] S5. Pass the wastewater in S4 into an autotrophic denitrification reactor, and the effluent can be purified wastewater, and the effluent water quality indicators are measured.

[0060] Processing Unit COD(mg / L) Ammonia nitrogen (mg / L) Wastewater containing DMF 3000 24 Anaerobic treatment of effluent 164 217 Short-cut nitrification treatment of effluent 142 108 Anaerobic ammonium oxidation treatment effluent 135 29 BAF treated effluent 127 3 Autotrophic denitrification treatment effluent 123 2

[0061] Compared with Example 1 and Example 2, the influent DMF concentration was increased to 5000 mg / L. By comparison, it was found that the process can tolerate a DMF concentration of 5000 mg / L, and the effluent COD and ammonia nitrogen can stably meet the discharge standards;

[0062] Compared with Example 1 and Example 3, Example 1 adds easily degradable COD to the influent, forms a synergistic degradation with DMF in the anaerobic reaction, and promotes the degradation of DMF; in Example 3, no easily degradable COD is added, and the effluent COD concentration is significantly increased, which easily causes the risk of excessive effluent discharge;

[0063] Compared with Example 1 and Example 4, in Example 1, part of the anaerobic ammonia oxidation effluent was returned to the anaerobic reactor. It was found that the return of nitrate nitrogen can promote the anaerobic methanogenesis of the reaction system and improve the degradation efficiency of DMF.

[0064] The DMF concentration in the wastewater containing high concentration of DMF is ≤5000 mg / L, and the ratio of DMF to easily degradable organic matter is 1:0.7 to 1:1.3 (measured in CODCr).

[0065] By adopting the above technical solution, if the influent concentration does not meet this requirement, after laboratory testing and analysis, the influent flow rate can be adjusted to make the influent COD concentration within this range, which is convenient for subsequent treatment.

[0066] The pH of the wastewater with high DMF concentration is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor.

[0067] By adopting the above technical solution, the effluent from the anaerobic reactor does not need to be pH-adjusted when entering the short-range nitrification reactor.

[0068] The short-term nitrification stage consumes a large amount of alkalinity. The wastewater with high concentration of DMF produces a large amount of alkalinity after anaerobic reaction, which can maintain the alkalinity consumption in the short-term nitrification stage.

[0069] By adopting the above technical solution, after the wastewater produces a large amount of alkalinity through anaerobic reaction, there is no need to add additional alkalinity, thus reducing investment costs.

[0070] The anaerobic ammonium oxidation influent controls ammonia nitrogen: nitrite nitrogen = 1: 1.1~1.4, and the BAF reactor uses lightweight fillers.

[0071] By adopting the above technical solution, lightweight fillers are used to reduce filler compaction.

[0072] The hydraulic retention time in the anaerobic reactor is controlled by the influent flow rate, and the dosage of the anaerobic granular sludge is 30% of the volume ratio.

[0073] By adopting the above technical solution, the hydraulic retention time in the anaerobic reactor is 16-24 hours.

[0074] The volume ratio of the anaerobic reactor and the short-range nitrification reactor is about 1:1, and the anaerobic ammonia oxidation effluent flows back to the anaerobic reactor.

[0075] By adopting the above technical solution, the reflux ratio of the anaerobic ammonia oxidation effluent back to the anaerobic reactor is 50%.

[0076] Working principle: In the present invention, wastewater containing high concentration of DMF is introduced from the bottom of anaerobic reactor 1, 30% anaerobic granular sludge 11 is filled in the anaerobic reactor 1, and the hydraulic retention time is controlled to be 16-24h; the effluent of anaerobic reactor 1 is introduced from the bottom of short-range nitrification reactor 2 through a pump, an aeration device 22 is arranged below the short-range nitrification reactor 2, and a high molecular polymer filler 31 is filled in the reactor, which can load short-range nitrification bacteria, reduce the loss of bacteria, and improve the nitrification rate; the effluent of short-range nitrification reactor 2 is introduced from the bottom of anaerobic ammonia oxidation reactor 3 through a pump, and part of the effluent is pumped to BAF reactor 4, and part of it is refluxed to anaerobic reactor 1, and the reflux ratio is 50%; an aeration device 42 is arranged below the BAF reactor 4, and a lightweight filler 41 is filled in the reactor, which can reduce the caking phenomenon; the effluent of BAF reactor 4 is introduced from the bottom of autotrophic denitrification reactor 5 through a pump, and the bottom of the reactor can be backwashed for regular nitrogen removal, sulfur particles are filled inside, and water is discharged from the top of the reactor.

[0077] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater, characterized in that: The following steps are involved: S1: Wastewater containing high concentration of DMF enters the anaerobic reactor (1); S2: The effluent from the anaerobic reactor (1) enters the short-range nitrification reactor (2); S3: The short-cut nitrification reactor (2) enters the anaerobic ammonium oxidation reactor (3); S4: Part of the effluent from the anaerobic ammonium oxidation reactor (3) is returned to the anaerobic reactor (1), and the remaining effluent enters the BAF reactor (4); S5: The effluent from the BAF reactor (4) enters the autotrophic denitrification reactor (5).

2. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The DMF concentration in the wastewater containing high concentration of DMF is ≤5000mg / L, and the ratio of DMF to easily degradable organic matter is 1:0.7~1:1.3 (COD Cr count).

3. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The pH of the wastewater with high DMF concentration is controlled to be neutral, and no pH adjustment is required after entering the anaerobic reactor.

4. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The short-term nitrification stage consumes a large amount of alkalinity. The wastewater with high concentration of DMF produces a large amount of alkalinity after anaerobic reaction, which can maintain the alkalinity consumption in the short-term nitrification stage.

5. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The anaerobic ammonium oxidation influent controls ammonia nitrogen: nitrite nitrogen = 1: 1.1~1.4, and the BAF reactor uses lightweight fillers.

6. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The hydraulic retention time in the anaerobic reactor is controlled by the influent flow rate, and the dosage of the anaerobic granular sludge is 30% of the volume ratio.

7. A process for efficient degradation and simultaneous denitrification of DMF-containing wastewater as claimed in claim 1, characterized in that: The volume ratio of the anaerobic reactor and the short-range nitrification reactor is about 1:1, and the anaerobic ammonia oxidation effluent flows back to the anaerobic reactor.

Images