A device system for biological denitrification of nitrogen-containing organic wastewater and its use method

Abstract

The present invention relates to a device system for biological denitrification of nitrogen-containing organic wastewater and a method for using the same, including an anaerobic tank, an aerobic tank and a sedimentation tank; the anaerobic tank is provided with activated sludge containing heterotrophic aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria, the top of the other side of the anaerobic tank is provided with a first overflow port, the aerobic tank is provided with an aerator, the top of one side of the aerobic tank is provided with a second overflow port, the sedimentation tank is used to precipitate and separate the muddy water flowing into the aerobic tank, the upper clear liquid at the top of the sedimentation tank is the purified water after biological denitrification, and the sludge at the bottom of the sedimentation tank is returned to the anaerobic tank. The device system has a simple structure and is easy to operate. The intracellular carbon source stored in the body of aerobic denitrifying bacteria in the anaerobic stage can meet its demand for small molecule carbon sources in the aerobic stage, so that nitric nitrogen can be denitrified smoothly, and then the total nitrogen content in the water meets the national emission standards.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a device system for biological denitrification of nitrogen-containing organic wastewater and a use method thereof. Background Art

[0002] Excessive nitrogen content in water bodies can easily cause eutrophication, causing serious harm to the ecological environment. Denitrification of water bodies is a necessary process for purifying wastewater. Biological denitrification technology is a common technology in biochemical treatment processes, which can effectively remove nitrogen contained in wastewater. Traditional biological denitrification processes usually adopt autotrophic aerobic nitrification-heterotrophic anoxic denitrification processes. However, in traditional denitrification processes, slightly higher dissolved oxygen levels will inhibit denitrification by controlling the activity of nitrate reductase, thereby limiting the development of biological denitrification processes.

[0003] Aerobic denitrification refers to the phenomenon that denitrification can occur under aerobic conditions. This reaction is controlled by nitrate reductase that tolerates high DO. In recent years, the method of achieving biological denitrification by constructing an autotrophic nitrification-aerobic denitrification process has been widely used. However, heterotrophic-aerobic denitrifying bacteria are highly dependent on small molecular carbon sources and high C / N of sewage. There is often a phenomenon of insufficient carbon source supply, resulting in nitrate nitrogen not being denitrified smoothly, which in turn leads to excessive total nitrogen in the effluent, thus limiting the practical application of the project. Sewage plants often use external carbon sources to ensure the denitrification effect of the system, but this also leads to a significant increase in water treatment costs. Summary of the invention

[0004] The purpose of the present invention is to provide a device system for biological denitrification of nitrogen-containing organic wastewater and a method for using the device system for biological denitrification without adding an external carbon source, so that the total nitrogen in the purified water meets the national emission standard. The device system is simple, easy to operate and low in cost.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A device system for biological denitrification of nitrogen-containing organic wastewater, comprising an anaerobic tank, an aerobic tank and a sedimentation tank;

[0007] The anaerobic tank is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. A first water inlet is provided on one side of the anaerobic tank, and the first water inlet is used to receive nitrogen-containing organic wastewater to be treated, and pass the wastewater into the anaerobic tank to mix with the activated sludge; a first overflow port is provided on the top of the other side of the anaerobic tank, and the first overflow port is used to discharge the mixed sludge and sewage in the anaerobic tank into the aerobic tank;

[0008] An aerator is provided in the aerobic pool, and a second overflow port is provided at the top of the aerobic pool on one side away from the first overflow port, and the second overflow port is used to overflow the aerated muddy water in the aerobic pool into the sedimentation tank;

[0009] The sedimentation tank is used to precipitate and separate the muddy water flowing into the aerobic tank. A third overflow port is arranged on the top of one side of the sedimentation tank, and the third overflow port is used to discharge the upper clear liquid at the top of the sedimentation tank; a sludge return pipe is arranged at the bottom of the sedimentation tank, one end of the sludge return pipe is connected to the bottom of the sedimentation tank, and the other end of the sludge return pipe is connected to the anaerobic tank; the sludge return pipe is used to return the sludge at the bottom of the sedimentation tank to the anaerobic tank.

[0010] The biological denitrification device system provided by the present invention mainly includes an anaerobic tank, an aerobic tank and a sedimentation tank. The anaerobic tank is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. After the sewage to be treated is introduced, the activated sludge is mixed with the sewage. During the mixing process, the heterotrophic-aerobic denitrifying bacteria absorb the organic matter in the wastewater and convert it into an intracellular carbon source. Then, after the muddy water enters the aerobic tank, the autotrophic nitrifying bacteria convert the ammonia nitrogen in the wastewater into nitric nitrogen under aeration conditions. The aerobic denitrifying bacteria converts the nitric nitrogen into nitrogen gas under denitrification to complete biological denitrification. Then, the activated sludge after the muddy water separation can be reused. The device system has a simple structure and is easy to operate. The intracellular carbon source stored in the body of the aerobic denitrifying bacteria in the anaerobic stage can meet its demand for small molecule carbon sources in the aerobic stage, so that the nitric nitrogen can be smoothly denitrified, and then the total nitrogen content in the water meets the national emission standards.

[0011] Furthermore, the anaerobic tank is provided with a baffle device. In the anaerobic tank, sewage and sludge are mixed and overflow from the anaerobic tank to the aerobic tank. The baffle device can ensure a certain flow rate and turbulence, so that the mud and water are fully mixed, and avoid the incoming water flowing into the aerobic tank too quickly, causing the bottom of the anaerobic tank to become a dead corner, and the muddy water may become stagnant water in it.

[0012] Furthermore, a pump is provided on the sludge return pipe.

[0013] Furthermore, the first water inlet and the sludge return pipe are both provided with a flow meter and a valve, which can control the mixing of the activated sludge and sewage in the anaerobic tank.

[0014] Furthermore, the device system for biological denitrification of nitrogen-containing organic wastewater is an integrated structure.

[0015] Furthermore, an inclined plate device is provided at the bottom of the sedimentation tank, and the inclined plate device is used to receive the sedimented sludge and gather the sludge at the bottom of the sedimentation tank. The setting of the inclined plate device is more conducive to the sedimentation of the sludge at the bottom of the sedimentation tank, making the supernatant at the top of the sedimentation tank clearer.

[0016] Another object of the present invention is to provide the above-mentioned biological denitrification device system and its use method.

[0017] A method for using a device system for biological denitrification of nitrogen-containing organic wastewater comprises the following steps:

[0018] Step 1, passing the nitrogen-containing organic wastewater to be treated into the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria in the anaerobic tank, mixing the activated sludge with the sewage, and mixing for 30 minutes to 60 minutes to obtain a first mud-water mixture, and the first mud-water mixture overflows into the aerobic tank;

[0019] Step 2, aerating the first mud-water mixture in the aerobic tank to obtain a second mud-water mixture, and the second mud-water mixture overflows into the sedimentation tank;

[0020] Step 3: subjecting the second mud-water mixture overflowing into the sedimentation tank to sedimentation separation treatment, and returning the separated sludge to the anaerobic tank in step 1, and the separated water is the purified water after biological denitrification.

[0021] The biological denitrification method provided by the present invention mainly comprises three steps. The method utilizes the principle that heterotrophic bacteria in activated sludge have a storage effect on carbon sources under anaerobic conditions and can store organic matter in sewage as an intracellular carbon source. First, activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic nitrifying bacteria is domesticated, and then the activated sludge is passed into an anaerobic tank. After the nitrogen-containing organic wastewater to be treated is passed into the anaerobic tank, under anaerobic conditions, the heterotrophic-aerobic denitrifying bacteria absorb the organic matter in the wastewater and convert it into an intracellular carbon source. Then, the muddy water in the anaerobic tank is passed into an aerobic tank. Under aeration conditions, the autotrophic nitrifying bacteria convert the ammonia nitrogen in the wastewater into nitric nitrogen, and the aerobic denitrifying bacteria convert the nitric nitrogen into nitrogen gas under denitrification, thereby completing biological denitrification. The bacterial community in the sludge obtained by separation in the sedimentation tank can be repeatedly recycled. The intracellular carbon source stored in the aerobic denitrifying bacteria can meet the demand of aerobic denitrifying bacteria for small molecule carbon sources, so that nitrate nitrogen can be smoothly denitrified, and then the total nitrogen content in the water meets the national emission standards. Compared with the traditional biological denitrification process, the biological denitrification method provided by the present invention can achieve the simultaneous nitrification and denitrification, thereby reducing the time and space costs of sewage treatment; and the biological denitrification process of the present invention has low cost, does not require additional carbon sources, and can also meet the demand of heterotrophic-aerobic denitrifying bacteria for carbon sources, so that the total nitrogen in the purified water meets the national emission standards.

[0022] Furthermore, in step 1, the nitrogen-containing organic wastewater to be treated is wastewater containing organic matter, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.

[0023] Furthermore, in step 1, the COD concentration of the nitrogen-containing organic wastewater to be treated is 200 mg / L to 1000 mg / L, and the total nitrogen (the sum of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen) concentration is 20 mg / L to 150 mg / L.

[0024] Furthermore, the carbon source includes organic matter.

[0025] Furthermore, the temperature of the nitrogen-containing organic wastewater to be treated is 16°C to 28°C. When the activated sludge is below 16°C, the nitrification and denitrification reaction efficiencies are too low, which will significantly reduce the efficiency of biological denitrification. Too high a temperature will damage the bacteria, thereby affecting the biological denitrification effect. Preferably, the temperature of the nitrogen-containing organic wastewater to be treated is 20°C to 28°C, and more preferably, the temperature of the nitrogen-containing organic wastewater to be treated is 25°C to 28°C.

[0026] Furthermore, in step 1, the MLSS in the anaerobic tank is greater than or equal to 2500 mg / L. MLSS is the abbreviation of mixed liquid suspended solids, also known as mixed liquid sludge concentration. It represents the total weight (mg / L) of activated sludge solids contained in a unit volume of mixed liquid in the aeration tank.

[0027] Furthermore, in step 1, the mixing time is 30 to 40 minutes. The main purpose of step 1 is to allow heterotrophic aerobic denitrifying bacteria to absorb organic matter in sewage and convert it into intracellular carbon source under anaerobic conditions. If the mixing residence time is too short, it is not conducive to the full storage of carbon source by heterotrophic bacteria, and it will still lead to poor denitrification effect. However, if the mixing time is too long, the organic matter will be used by anaerobic heterotrophic bacteria in the activated sludge, resulting in waste of organic matter.

[0028] Furthermore, in step 2, the aeration rate is 8 L / min to 10 L / min.

[0029] Furthermore, in step 2, the aeration time is 2 hours to 4 hours.

[0030] Furthermore, in step 2, the pH of the first mud-water mixture is 6-8.

[0031] Furthermore, in step 2, the dissolved oxygen in the aerobic pool is 3 mg / L to 6 mg / L. Preferably, in step 2, the dissolved oxygen in the aerobic pool is 5 mg / L to 6 mg / L. Higher dissolved oxygen and lower exogenous toxicity can provide good nutritional conditions for autotrophic nitrifying bacteria and aerobic denitrifying bacteria at the same time. In addition, organic matter in the pool is fully removed under aerobic conditions.

[0032] Furthermore, in step 1, the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria is domesticated by the following method, comprising the following steps:

[0033] Step S1, taking activated sludge with stable denitrification effect, adjusting MLSS to 3000-5000 mg / L, using aerobic denitrification culture medium with C / N of 18-22 and nitrate as nitrogen source as influent, and operating in a first cycle sequencing batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operating a total of 8-12 first cycles; obtaining first activated sludge;

[0034] Wherein, in the anaerobic process, the stirring residence time is 20min-40min, and the stirring speed is 50-80r / min; in the aerobic process, the aeration volume is 8-10L / min, and the aeration time is 2h-3h;

[0035] Step S2, taking the first activated sludge obtained in step S1, adjusting the MLSS to 3000-5000 mg / L, using an aerobic denitrification culture medium with a C / N ratio of 2-5 and nitrate as a nitrogen source as influent, and operating the second cycle in a sequential batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operating a total of 3-4 second cycles; then adjusting the influent C / N to 18-22, and operating the third cycle in a sequential batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operating a third cycle; then repeating the operation of 3-4 second cycles and 1 third cycle for 6-9 times to obtain activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria;

[0036] Wherein, in the anaerobic process, the stirring residence time is 20min-40min, and the stirring speed is 50-80r / min; in the aerobic process, the aeration volume is 8-10L / min, and the aeration time is 2h-3h.

[0037] The domestication method provided by the present invention mainly comprises two steps. The first step is mainly to domesticate the activated sludge with stable denitrification effect into activated sludge enriched with aerobic nitrifying bacteria. The aerobic nitrifying bacteria in the activated sludge obtained in the first step adapt to the environment of C / N of 18 to 22. Then in the second step, by limiting the C / N condition in the culture medium to 2 to 5 and cyclic enrichment, the aerobic nitrifying bacteria in the finally domesticated activated sludge are more adapted to the living environment of low C / N, thereby effectively improving the efficiency of aerobic denitrifying bacteria in storing and converting organic matter under anaerobic conditions.

[0038] Furthermore, MLSS is the abbreviation of mixed liquid suspended solids, which is also called mixed liquid sludge concentration. It represents the total weight (mg / L) of activated sludge solids contained in a unit volume of mixed liquid in the aeration tank.

[0039] Further, in step S1, the aerobic denitrification culture medium mainly contains the following raw materials: 2.5g / L to 4g / L sodium acetate, 0.35g / L to 0.6g / L potassium nitrate, 0.1g / L to 0.2g / L composite potassium salt, 0.1g / L magnesium sulfate heptahydrate, 1ml / L to 5ml / L trace element solution, 1ml / L to 2ml / L ammonium ferrous sulfate solution;

[0040] The composite potassium salt is a mixture of potassium dihydrogen phosphate: dipotassium hydrogen phosphate in a ratio of 1:1.

[0041] Furthermore, in step S2, during the second cycle operation, an aerobic denitrification medium with a C / N ratio of 2 to 3 and nitrate as a nitrogen source is used as influent. During the acclimation process, a low C / N environment is provided to aerobic denitrifying bacteria, which can enrich the activated sludge of aerobic denitrifying bacteria tolerant to low C / N, which can not only effectively improve the survival ability of the bacteria in the activated sludge, but also effectively improve the ability to convert intracellular carbon sources.

[0042] Furthermore, the activated sludge with stable denitrification effect refers to activated sludge with an ammonia nitrogen removal rate of not less than 8 mg / L·h. Preferably, the ammonia nitrogen removal rate is 8 mg / L·h to 12 mg / L·h.

[0043] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0044] 1. The biological denitrification device system provided by the present invention mainly includes an anaerobic tank, an aerobic tank and a sedimentation tank. The anaerobic tank is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. Through the synergistic effect of the three purification tanks, the intracellular carbon source stored in the body of the aerobic denitrifying bacteria in the anaerobic stage can meet its demand for small molecule carbon sources in the aerobic stage, so that nitric nitrogen can be smoothly denitrified, thereby making the total nitrogen content in the water meet the national emission standards. The device system has a simple structure and is easy to operate.

[0045] 2. The biological denitrification method provided by the present invention mainly includes three steps. It utilizes the principle that heterotrophic bacteria in activated sludge have a storage effect on carbon sources under anaerobic conditions, and can store organic matter in sewage as an intracellular carbon source. First, activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic nitrifying bacteria is domesticated, and then the activated sludge is passed into the anaerobic tank. After the nitrogen-containing organic wastewater to be treated is passed into the anaerobic tank, under anaerobic conditions, the heterotrophic-aerobic denitrifying bacteria absorb the organic matter in the wastewater and convert it into an intracellular carbon source. Then, the muddy water in the anaerobic tank is passed into the aerobic tank under aeration conditions. The autotrophic nitrifying bacteria convert the ammonia nitrogen in the wastewater into nitric nitrogen, and the aerobic denitrifying bacteria convert the nitric nitrogen into nitrogen gas under the action of denitrification, thereby completing biological denitrification. The intracellular carbon source stored in the aerobic denitrifying bacteria can meet the demand of the aerobic denitrifying bacteria for small molecule carbon sources, so that the nitric nitrogen can be smoothly denitrified, and then the total nitrogen content in the water meets the national emission standards. Compared with the traditional biological denitrification process, the biological denitrification method provided by the present invention can realize the simultaneous nitrification and denitrification, thereby reducing the time and space costs of sewage treatment; and the biological denitrification process of the present invention has low cost, does not require additional carbon source, and can also meet the carbon source requirements of heterotrophic-aerobic denitrifying bacteria, so that the total nitrogen in the purified water meets the national emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1-Schematic diagram of the device system structure used in the biological denitrification process in Example 1.

[0047] Icons: 1- anaerobic tank; 11- first water inlet; 111- first flow meter; 112- first valve; 12- baffle device; 13- first overflow; 2- aerobic tank; 21- second overflow; 22- aerator; 3- sedimentation tank; 31- third overflow; 32- sludge return pipe; 321- pump; 322- second flow meter; 323- second valve; 33- inclined plate device. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] MLSS is the abbreviation of mixed liquid suspended solids, also known as mixed liquid sludge concentration. It indicates the total weight (mg / L) of activated sludge solids contained in a unit volume of mixed liquid in the aeration tank.

[0050] DO refers to dissolved oxygen.

[0051] COD refers to chemical oxygen demand, and is used here as an indicator of the amount of carbon source.

[0052] Example 1

[0053] like Figure 1 As shown, a device system for biological denitrification of nitrogen-containing organic wastewater, the device system for biological denitrification of nitrogen-containing organic wastewater is an integrated structure, including an anaerobic tank 1, an aerobic tank 2 and a sedimentation tank 3;

[0054] The anaerobic tank 1 is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. A first water inlet 11 is provided on one side of the anaerobic tank 1, and a first flowmeter 111 and a first valve 112 are provided on the first water inlet 11. A first overflow port 13 is provided on the top of the other side of the anaerobic tank 1, and a baffle device 12 is provided in the anaerobic tank 1. The baffle device 12 is a baffle structure provided in the middle of the anaerobic tank 1. The water entering the anaerobic tank 1 first flows into one side of the baffle, and then flows into the other side of the baffle from the bottom of the baffle to divert the sewage. In the anaerobic tank 1, the sewage and sludge are mixed and overflow from the anaerobic tank to the aerobic tank. The baffle device can ensure a certain flow rate and turbulence, so that the mud and water are fully mixed, and avoid the incoming water flowing into the aerobic tank quickly, causing the bottom of the anaerobic tank to become a dead corner, and the muddy water may become dead water in it.

[0055] The aerobic tank 2 is provided with an aerator 22, a second overflow port 21 is provided at the top of one side of the aerobic tank 2, a third overflow port 31 is provided at the top of one side of the sedimentation tank 3, and an inclined plate device 33 is provided at the bottom of the sedimentation tank 3, and the inclined plate device 33 is used to receive the sedimented sludge and gather the sludge at the bottom of the sedimentation tank 3. The setting of the inclined plate device is more conducive to the deposition of sludge at the bottom of the sedimentation tank, so that the supernatant at the top of the sedimentation tank is clearer. A sludge return pipe 32 is provided at the bottom of the sedimentation tank 3, one end of the sludge return pipe 32 is connected to the bottom of the sedimentation tank 3, and the other end of the sludge return pipe 32 is connected to the anaerobic tank 1; a pump 321 is provided on the sludge return pipe 32. A second flow meter 322 and a second valve 323 are provided on the sludge return pipe 32. The setting of the flow meter and the valve can control the mixing of the activated sludge and sewage in the anaerobic tank.

[0056] The biological denitrification device system provided by the present invention mainly includes an anaerobic tank, an aerobic tank and a sedimentation tank. The anaerobic tank is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. After the sewage to be treated is introduced, the activated sludge is mixed with the sewage. During the mixing process, the heterotrophic-aerobic denitrifying bacteria absorb the organic matter in the wastewater and convert it into an intracellular carbon source. Then, after the muddy water enters the aerobic tank, the autotrophic nitrifying bacteria group converts the ammonia nitrogen in the wastewater into nitric nitrogen under aeration conditions. The aerobic denitrifying bacteria converts the nitric nitrogen into nitrogen gas under denitrification to complete biological denitrification. Then, the activated sludge after the separation of muddy water can be reused. The intracellular carbon source stored in the aerobic denitrifying bacteria can meet the demand of the aerobic denitrifying bacteria for small molecule carbon sources, so that the nitric nitrogen can be smoothly denitrified, and then the total nitrogen content in the water meets the national emission standards. The device system has a simple structure and is easy to operate.

[0057] Example 2

[0058] Take the activated sludge with good denitrification performance from the urban sewage treatment plant A and place it in a reactor equipped with an aeration device. The removal rate of ammonia nitrogen in the activated sludge can reach 10mg / L·h. Adjust the MLSS to 3500±50mg / L, and use aerobic denitrification medium with C / N of 20 and nitrate as the nitrogen source as the influent. According to the cycle sequence batch operation of "influent→anaerobic (35min, 70r / min stirring)→aerobic (3h, 10L / min aeration)→standing (1h)→effluent", a total of 10 cycles were run. During the operation, the temperature was controlled at 20±0.5℃.

[0059] Aerobic denitrification culture medium: sodium acetate 4g / L, potassium nitrate 0.6g / L, composite potassium salt (potassium dihydrogen phosphate: dipotassium hydrogen phosphate = 1:1) 0.2g / L, magnesium sulfate heptahydrate 0.1g / L, trace element solution 5ml / L, ammonium ferrous sulfate solution 2ml / L.

[0060] Example 3

[0061] Take the activated sludge enriched with aerobic denitrifying bacteria in Example 2 and place it in a reactor equipped with an aeration device, and adjust the MLSS to 3500±50mg / L. Use aerobic denitrification culture medium as the influent, and adjust the ratio of sodium acetate and potassium nitrate in the culture medium to achieve an influent C / N of 4. Follow the cycle sequencing batch operation of "influent → anaerobic (35min, 60r / min stirring) → aerobic (2.5h, 10L / min aeration) → standing (1h) → effluent", and run a total of 4 cycles. Adjust the influent C / N to 20±0.5, and run 1 cycle according to the same operating parameters. Repeat the above steps 8 times to obtain activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria.

[0062] Example 4

[0063] Using the device system described in Example 1, the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria domesticated in Example 3 was added to the anaerobic tank 1. Then, the nitrogen-containing organic wastewater to be treated was introduced into the activated sludge in the anaerobic tank 1 from the first water inlet 11. Through the control of the flow meter and the valve, the MLSS in the anaerobic tank 1 was 3800 mg / L. The COD concentration in the organic wastewater was 420±50 mg / L, the ammonia nitrogen was 120±5 mg / L, and the water temperature was 25±2°C; the wastewater and the activated sludge were mixed, and after mixing for 40 minutes, a first mud-water mixture was obtained; in the first mud-water mixture at this time, the heterotrophic-aerobic denitrifying bacteria had absorbed part of the organic matter in the wastewater and converted it into an intracellular carbon source.

[0064] Then, the first mud-water mixture overflows from the first overflow port 13 into the aerobic pool 2, and is aerated to control the dissolved oxygen DO to 5.0 mg / L. After the aeration time is 2.5 h, the second mixed mud-water is obtained.

[0065] Finally, the second mixed mud and water overflows from the second overflow port 21 into the sedimentation tank 3 for mud and water separation, and the upper clear liquid of the sedimentation tank 3 after separation overflows from the third overflow port 31 to obtain purified water after biological denitrification, and the bottom sludge of the sedimentation tank 3 after separation is returned to the anaerobic tank 1 through the sludge return pipe 32, and the activated sludge in the sludge is reused.

[0066] After testing, the COD in the purified water was 22mg / L, ammonia nitrogen was 3.1mg / L, and total nitrogen was 5.9mg / L.

[0067] Example 5

[0068] Using the device system described in Example 1, the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria domesticated in Example 3 is added to the anaerobic tank 1. Then the nitrogen-containing organic wastewater to be treated is passed from the first water inlet 11 into the activated sludge in the anaerobic tank 1. Through the control of the flow meter and the valve, the MLSS in the anaerobic tank 1 is 3000 mg / L. The COD concentration in the organic wastewater is 250±50 mg / L, the ammonia nitrogen is 60±5 mg / L, and the water temperature is 24±0.5°C; the wastewater and the activated sludge are mixed, and after mixing for 60 minutes, a first mud-water mixture is obtained; in the first mud-water mixture at this time, the heterotrophic-aerobic denitrifying bacteria have absorbed part of the organic matter in the wastewater and converted it into an intracellular carbon source.

[0069] Then, the first mud-water mixture overflows from the first overflow port 13 into the aerobic pool 2, aerates, controls the dissolved oxygen DO to 4.0 mg / L, and after the aeration time is 4 hours, obtains the second mixed mud-water;

[0070] Finally, the second mixed muddy water overflows from the second overflow port 21 to the sedimentation tank 3 for muddy water separation.

[0071] The upper clear liquid of the separated sedimentation tank 3 overflows from the third overflow port 31 to obtain purified water after biological denitrification, and the bottom sludge of the separated sedimentation tank 3 is returned to the anaerobic tank 1 through the sludge return pipe 32, and the activated sludge in the sludge is reused.

[0072] After testing, the COD in the purified water was 28mg / L, ammonia nitrogen was 3.5mg / L, and total nitrogen was 6.4mg / L.

[0073] Example 6

[0074] Using the device system described in Example 1, the activated sludge enriched with aerobic denitrifying bacteria in Example 2 was placed in a reactor equipped with an aeration device, and the MLSS was adjusted to 3500±50mg / L. Aerobic denitrification culture medium was used as the influent, and the ratio of sodium acetate and potassium nitrate in the culture medium was adjusted to achieve an influent C / N of 2. The cycle sequence batch operation was carried out according to "influent → anaerobic (35min, 60r / min stirring) → aerobic (2.5h, 10L / min aeration) → standing → effluent", and a total of 4 cycles were run. Then the influent C / N was adjusted to 20±0.5, and one cycle was run according to the same operating parameters. Repeat the above steps 8 times to obtain activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria.

[0075] The activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria obtained by domestication was treated and purified by the denitrification process exactly the same as in Example 4. The process parameters and the nitrogen-containing organic wastewater to be treated during the purification process were the same as in Example 4. The first mixed mud water was passed into the aerobic tank 2 for aeration, and the dissolved oxygen DO was controlled to be 5.0 mg / L. After the aeration time was 2 h, the ammonia nitrogen content in the aerobic tank 2 did not change within half an hour, and the aeration was stopped to obtain the second mixed mud water. After testing, the COD in the purified water was 20 mg / L, the ammonia nitrogen was 2.8 mg / L, and the total nitrogen was 5.5 mg / L.

[0076] The study found that aerobic denitrifying bacteria cultivated under C / N conditions of 2 were more effective in storing carbon sources and also improved the denitrification rate and effect.

[0077] Example 7

[0078] Take the activated sludge with good denitrification performance from the urban sewage treatment plant B and place it in a reactor equipped with an aeration device. The removal rate of ammonia nitrogen in the activated sludge can reach 12mg / L·h. Adjust the MLSS to 4200±50mg / L, and use aerobic denitrification medium with a C / N of 22 and nitrate as the nitrogen source as the influent. According to the cycle sequencing batch operation of "influent→anaerobic (40min, 80r / min stirring)→aerobic (3h, 9L / min aeration)→standing (1h)→effluent", a total of 12 cycles were run. During the operation, the temperature was controlled at 20±0.5℃.

[0079] Aerobic denitrification culture medium: sodium acetate 3.5 g / L, potassium nitrate 0.5 g / L, composite potassium salt (potassium dihydrogen phosphate: dipotassium hydrogen phosphate = 1:1) 0.15 g / L, magnesium sulfate heptahydrate 0.1 g / L, trace element solution 3 ml / L, ammonium ferrous sulfate solution 1.5 ml / L.

[0080] Using the device system described in Example 1, the activated sludge enriched with aerobic denitrifying bacteria was placed in a reactor equipped with an aeration device, and the MLSS was adjusted to 3500±50mg / L. Aerobic denitrification culture medium was used as the influent, and the influent C / N was 10 by adjusting the ratio of sodium acetate and potassium nitrate in the culture medium. The cycle sequence batch operation was carried out according to "influent → anaerobic (35min, 60r / min stirring) → aerobic (2.5h, 10L / min aeration) → standing → effluent", and a total of 4 cycles were run. Then the influent C / N was adjusted to 20±0.5, and one cycle was run according to the same operating parameters. Repeat the above steps 8 times to obtain activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria.

[0081] The activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria obtained by domestication was treated and purified by the denitrification process exactly the same as in Example 4. The process parameters and the nitrogen-containing organic wastewater to be treated in the purification process were the same as in Example 4. The first mixed mud water was passed into the aerobic tank 2 for aeration, and the dissolved oxygen DO was controlled to be 5.0 mg / L. After the aeration time was 3.5 h, the ammonia nitrogen content in the aerobic tank 2 did not change within half an hour, and the aeration was stopped to obtain the second mixed mud water. After testing, the COD in the purified water was 25 mg / L, the ammonia nitrogen was 4.2 mg / L, and the total nitrogen was 6.7 mg / L.

[0082] Comparative Example 1

[0083] Using the device system described in Example 1, the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria domesticated in Example 3 was added to the aerobic tank 2, and the MLSS in the aerobic tank 2 was 3800 mg / L. Then, the nitrogen-containing organic wastewater to be treated was passed into the activated sludge in the aerobic tank 2, wherein the COD concentration in the organic wastewater was 420±50 mg / L, the ammonia nitrogen concentration was 120±5 mg / L, and the water temperature was 25±2°C; then, aeration was performed to control the dissolved oxygen DO to 5.0 mg / L, and after the aeration time was 3.5 hours, the ammonia nitrogen content in the aerobic tank 2 did not change within half an hour, and aeration was stopped to obtain the second mixed muddy water;

[0084] Finally, the second mixed muddy water is passed into the sedimentation tank 3 for mud-water separation to obtain purified water after biological denitrification.

[0085] After testing, the COD in the purified water was 75mg / L, ammonia nitrogen was 41.5mg / L, and total nitrogen was 18.2mg / L.

[0086] Comparative Example 1 did not adopt the biological denitrification process provided by the present invention. The activated sludge containing heterotrophic aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria was not subjected to the operation of adsorbing and storing intracellular carbon sources in the anaerobic tank 1. Instead, the activated sludge and organic wastewater were directly passed into the aerobic tank 2 for aeration. The study found that the heterotrophic aerobic denitrifying bacteria had a strong dependence on small molecule carbon sources, resulting in insufficient carbon source supply, resulting in excessive total nitrogen content in the effluent.

[0087] Comparative Example 2

[0088] The denitrification process of Comparative Example 1 is the same as that of Example 4, except that in the anaerobic tank 1, the mixing residence time is 20 min. After testing, the COD in the purified water is 30 mg / L, the ammonia nitrogen is 5.4 mg / L, and the total nitrogen is 25.6 mg / L.

[0089] The biological denitrification method provided by the present invention mainly comprises three steps, and utilizes the principle that heterotrophic bacteria in activated sludge have a storage effect on carbon sources under anaerobic conditions, and can store organic matter in sewage as an intracellular carbon source. First, activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic nitrifying bacteria is domesticated, and then the activated sludge is passed into an anaerobic tank. After the nitrogen-containing organic wastewater to be treated is passed into the anaerobic tank, under anaerobic conditions, the heterotrophic-aerobic denitrifying bacteria absorbs the organic matter in the wastewater and converts it into an intracellular carbon source. Then, the muddy water in the anaerobic tank is passed into an aerobic tank. Under aeration conditions, the autotrophic nitrifying bacteria convert the ammonia nitrogen in the wastewater into nitric nitrogen, and the aerobic denitrifying bacteria convert the nitric nitrogen into nitrogen gas under the action of denitrification, so as to complete biological denitrification. The intracellular carbon source stored in the aerobic denitrifying bacteria in the anaerobic stage can meet its demand for small molecule carbon sources in the aerobic stage, so that the nitric nitrogen can be smoothly denitrified, and then the total nitrogen content in the water meets the national emission standards. Compared with the traditional biological denitrification process, the biological denitrification method provided by the present invention can realize the simultaneous nitrification and denitrification, thereby reducing the time and space costs of sewage treatment; and the biological denitrification process of the present invention has low cost, does not require additional carbon source, and can also meet the carbon source requirements of heterotrophic-aerobic denitrifying bacteria, so that the total nitrogen in the purified water meets the national emission standards.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for using a device system for biological denitrification of nitrogen-containing organic wastewater, characterized in that: It includes an anaerobic tank (1), an aerobic tank (2) and a sedimentation tank (3); The anaerobic tank (1) is provided with activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria. A first water inlet (11) is provided on one side of the anaerobic tank (1). The first water inlet (11) is used to receive nitrogen-containing organic wastewater to be treated and pass the wastewater into the anaerobic tank (1) to mix with the activated sludge. A first overflow port (13) is provided on the top of the other side of the anaerobic tank (1). The first overflow port (13) is used to discharge the mixed sludge and sewage in the anaerobic tank (1) into the aerobic tank (2). An aerator (22) is provided in the aerobic tank (2), and a second overflow port (21) is provided at the top of the aerobic tank (2) on a side away from the first overflow port (13), and the second overflow port (21) is used to overflow the aerated muddy water in the aerobic tank (2) into the sedimentation tank (3); The sedimentation tank (3) is used to perform sedimentation and separation treatment on the muddy water flowing into the aerobic tank (2); a third overflow port (31) is provided on the top of one side of the sedimentation tank (3); the third overflow port (31) is used to discharge the upper clear liquid on the top of the sedimentation tank (3); A sludge return pipe (32) is provided at the bottom of the sedimentation tank (3), one end of the sludge return pipe (32) is connected to the bottom of the sedimentation tank (3), and the other end of the sludge return pipe (32) is connected to the anaerobic tank (1); the sludge return pipe (32) is used to return the sludge at the bottom of the sedimentation tank (3) to the anaerobic tank (1); The following steps are involved: Step 1, passing the nitrogen-containing organic wastewater to be treated into the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria in the anaerobic tank (1), mixing the activated sludge with the sewage, and obtaining a first mud-water mixture after mixing for 30 minutes to 60 minutes, and the first mud-water mixture overflows into the aerobic tank (2); Step 2, aerating the first mud-water mixture in the aerobic tank (2) to obtain a second mud-water mixture, and the second mud-water mixture overflows into the sedimentation tank (3); Step 3, subjecting the second sludge-water mixture overflowing into the sedimentation tank (3) to sedimentation separation treatment, and returning the separated sludge to the anaerobic tank (1) in step 1, and the separated water is the purified water after biological denitrification; In the step 1, the activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria is domesticated by the following method, which includes the following steps: Step S1, taking activated sludge with stable denitrification effect, adjusting MLSS to 3000-5000 mg / L, using aerobic denitrification medium with C / N of 18-22 and nitrate as nitrogen source as influent, and operating in a first cycle sequencing batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operating a total of 8-12 first cycles; obtaining first activated sludge; Wherein, in the anaerobic process, the stirring residence time is 20min-40min, and the stirring speed is 50-80r / min; in the aerobic process, the aeration volume is 8-10L / min, and the aeration time is 2h-3h; Step S2, taking the first activated sludge obtained in step S1, adjusting the MLSS to 3000-5000 mg / L, using an aerobic denitrification medium with a C / N ratio of 2-5 and nitrate as a nitrogen source as influent, and operating in a second cycle sequential batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operating 3-4 second cycles in total; Then adjust the influent C / N to 18-22, and operate the third cycle sequential batch mode according to "influent-anaerobic process-aerobic process-standing-effluent", and operate one third cycle; then repeat the operation of 3-4 second cycles and 1 third cycle 6-9 times to obtain activated sludge containing heterotrophic-aerobic denitrifying bacteria and autotrophic aerobic nitrifying bacteria; Wherein, in the anaerobic process, the stirring residence time is 20min-40min, and the stirring speed is 50-80r / min; in the aerobic process, the aeration volume is 8-10L / min, and the aeration time is 2h-3h; In step S1, the aerobic denitrification culture medium mainly contains the following raw materials: 2.5g / L to 4g / L sodium acetate, 0.35g / L to 0.6g / L potassium nitrate, 0.1g / L to 0.2g / L composite potassium salt, 0.1g / L magnesium sulfate heptahydrate, 1ml / L to 5ml / L trace element solution, 1ml / L to 2ml / L ammonium ferrous sulfate solution; the composite potassium salt is a mixture of potassium dihydrogen phosphate: dipotassium hydrogen phosphate = 1:

1.

2. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to claim 1, characterized in that: The device system for biological denitrification of nitrogen-containing organic wastewater is an integrated structure.

3. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to claim 1, characterized in that: The first water inlet (11) and the sludge return pipe (32) are both provided with a flow meter and a valve.

4. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to claim 1, characterized in that: The sludge return pipe (32) is provided with a pump (321).

5. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to any one of claims 1 to 4, characterized in that: The bottom of the sedimentation tank (3) is provided with an inclined plate device (33), and the inclined plate device (33) is used to receive sedimentation sludge and gather the sludge at the bottom of the sedimentation tank (3).

6. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to claim 1, characterized in that: In the step 1, the mixing residence time is 30 min to 40 min.

7. The method for using the device system for biological denitrification of nitrogen-containing organic wastewater according to claim 1, characterized in that: In the step S2, during the operation of the second cycle, an aerobic denitrification culture medium with a C / N ratio of 2 to 3 and nitrate as a nitrogen source is used as influent.

Images