A precise denitrification method for sewage based on Thiobacillus denitrificans

Abstract

The present invention relates to the technical field of sewage treatment, and in particular to a method for accurately denitrifying sewage based on Thiobacillus denitrificans, comprising a denitrification system consisting of two rows of denitrification units sequentially arranged on a branch water inlet pipe. Fillers are loaded into each denitrification unit and inoculated with Thiobacillus denitrificans, and then sewage is introduced. The super-strong reducing ability of Thiobacillus denitrificans can achieve the reduction and removal of nitrate nitrogen in the sewage. As the operation time increases, the filler layer will inevitably become compacted. At this time, the denitrification units on the two rows of branch water inlets are flipped in turn, so that the compacted and blocked filler layer can be forcibly destroyed, so that the filler layer in the denitrification unit is like a newly loaded one, without the need to replace the filler. At the same time, since the denitrification units are symmetrically arranged on the upper and lower sides, the flipped denitrification units can be used directly, while ensuring the sewage treatment effect, it also effectively reduces the operation and maintenance costs, laying a solid foundation for subsequent promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a precise denitrification treatment method for sewage based on Thiobacillus denitrificans. Background Art

[0002] Thiobacillus denitrificans is an obligate autotrophic, facultative anaerobic rod-shaped bacterium with strong adaptability and wide distribution. In the range of 8-37℃, its biological activity is not greatly affected and its denitrification ability is strong. According to experimental research, when the influent nitrate nitrogen concentration is 15mg / L, the denitrification volume load of the denitrification filler can reach 450g / m 3 d. Compared with traditional anaerobic denitrification, the use of Thiobacillus denitrificans for denitrification is more cost-effective, has higher denitrification efficiency, and can also accurately denitrify.

[0003] Using Thiobacillus denitrificans for wastewater denitrification is a hot topic. Current processes all utilize an upward flow design to facilitate flow and water quality control. Existing denitrification units typically use bottom-feed water, which is distributed through a water distributor and then denitrified by a packing layer, with water ultimately discharged from the top of the unit. This results in simple equipment, easy operation, and relatively easy maintenance.

[0004] While affirming these advantages, its process disadvantages are also obvious: since the packing layer will become clogged and compacted as the running time increases, when the frequency of the water pump remains unchanged, the water flow rate will decrease as the running time increases; since the denitrification of Thiobacillus denitrificans is a relatively balanced process, only when the total amount of nitrate nitrogen passing through the packing is exactly equal to the denitrification capacity of the packing per unit time will ammonia nitrogen not be generated. Therefore, as the water flow decreases, the nitrate nitrogen in the effluent cannot be accurately removed, and it is accompanied by the smell of hydrogen sulfide and the increase of effluent ammonia nitrogen; therefore, if applied to the actual sewage treatment process, the packing particles need to be frequently replaced to ensure the denitrification effect, which brings a lot of labor and raw material investment, greatly increasing the cost. This is also the reason why the process has not been promoted on a large scale.

[0005] Therefore, the present invention proposes a precise denitrification treatment method for sewage based on denitrifying Thiobacillus, which can effectively solve the problem of packing layer compaction, and while ensuring the denitrification effect of sewage, it can effectively reduce the operation and maintenance costs, in order to contribute to energy conservation and consumption reduction of sewage treatment plants. Summary of the Invention

[0006] The purpose of the present invention is to provide a precise denitrification treatment method for sewage based on Thiobacillus denitrificans, so as to solve the problems of the existing Thiobacillus denitrificans denitrification system, which is prone to problems such as packing layer compaction during operation, resulting in reduced denitrification efficiency, poor denitrification effect and high operation and maintenance costs.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for precise denitrification of sewage based on Thiobacillus denitrificans, comprising the following steps:

[0008] S1. Layout of denitrification system

[0009] Two parallel branch water inlet pipes are drawn from the main water inlet pipe of the sewage treatment system. Multiple denitrification units are arranged and installed on each branch water inlet pipe in sequence. The branch water inlet pipes supply water to each denitrification unit in an upward flow manner, and the sewage after deep denitrification of each denitrification unit is collected and discharged;

[0010] S2, filling each denitrification unit in S1 with sulfur autotrophic denitrification filler;

[0011] S3, feed water to the S1 denitrification system, achieve the enrichment of denitrifying Thiobacillus under natural conditions, and start the denitrification system;

[0012] S4. After the system is successfully started, gradually increase the water volume until it reaches the designed water volume. After a period of stable operation, if it is detected that the denitrification capacity of the denitrification unit has decreased, turn over each denitrification unit, backwash and regenerate the denitrification packing, and record the duration of the system's stable operation;

[0013] S5. As the system operates stably, each denitrification unit is flipped in advance according to the duration of stable operation determined in S4, and the denitrification filler is backwashed and regenerated to achieve a stable and accurate denitrification process of the denitrification system.

[0014] Furthermore, in the S1, the denitrification unit includes a tank body, a rotating shaft is provided in the middle part of the tank body, and the upper and lower sides of the tank body are symmetrically arranged relative to the rotating shaft; heads are provided at the upper and lower ends of the tank body, a screen is provided between the upper and lower heads and the tank body, a grate is provided in the middle of the inside of the tank body, a water inlet pipe is provided at the lower head, a water inlet valve is provided on the water inlet pipe, a water outlet pipe is provided at the upper head symmetrically with the water inlet pipe, a water outlet valve is provided on the water outlet pipe, and sewage pipes are symmetrically provided on the upper and lower sides of the tank body, the installation position of the sewage pipe is higher than the height of the packing layer, and a sewage valve is provided on the sewage pipe.

[0015] Furthermore, the denitrification unit is provided with a bracket, a support plate is provided in the bracket, and legs are provided around the lower part of the support plate. The support plate supports the rotating shaft, and the rotating shaft realizes the flipping of the denitrification unit under the drive of the motor.

[0016] Furthermore, in the above S1, five denitrification units are sequentially arranged on each branch water inlet pipe, and the effluent of each denitrification unit is collected in a high-level water tank and then discharged from the downpipe of the high-level water tank.

[0017] Furthermore, in the S2, the sulfur autotrophic denitrification filler is sulfur particles and calcium carbonate particles, the volume ratio of sulfur particles to calcium carbonate particles is 7:3, the particle size of sulfur particles and calcium carbonate particles is 5-8 mm, and the filling volume of the sulfur autotrophic denitrification filler is 50-60% of the denitrification unit volume.

[0018] Furthermore, in the S3, the inlet flow rate is controlled at one-third to one-half of the design flow rate, the pH of the inlet water is 6-8, the total alkalinity of the inlet water is not less than 130 mg / L, and the natural incubation time is 4-5 days.

[0019] Furthermore, in the above-mentioned S3, when the nitrate nitrogen in the effluent of the denitrification system is lower than 0.5 mg / L, the nitrite nitrogen is lower than 0.005 mg / L, and the ammonia nitrogen differs from the influent by ±0.2 mg / L, the system is successfully started.

[0020] Furthermore, in the above S4, when it is detected that the total nitrogen content in the effluent of the denitrification unit shows a stable upward trend, it is considered that the denitrification capacity of the denitrification unit has decreased, and the denitrification unit is turned over at this time.

[0021] Furthermore, in the above S5, only 1 to 3 denitrification units are flipped at a time. After the denitrification units are stably operated after flipping, the remaining denitrification units are flipped until all the denitrification units are completely flipped, and then the next operation cycle is entered.

[0022] Furthermore, in the above-mentioned S4 and S5, after the denitrification unit is flipped, the system water is opened. When water comes out from the top, the side drain valve is opened to allow the sludge-rich sewage above the packing layer to be quickly discharged from the tank body. This operation is repeated 1 to 3 times until there is no obvious difference in appearance between the outlet water and the inlet water.

[0023] Beneficial effects of the present invention:

[0024] 1. By arranging multiple denitrification units, the sewage is dispersedly treated, giving full play to the treatment capacity of each denitrification unit. Therefore, the water does not need to be fed in at a high speed, which can avoid serious blockage of the packing layer on the one hand, and make the water flow more fully contact with the packing layer on the other hand, effectively ensuring the denitrification efficiency;

[0025] 2. The reactor can be designed with a larger height-to-diameter ratio, thereby reducing raw material input and floor space, which helps reduce sewage treatment costs. In addition, the decentralized design reduces the contact time between sewage and the packing layer in a single denitrification unit, eliminating concerns about increased ammonia nitrogen and sulfide formation caused by capillary expansion and the superior reducing ability of denitrifying Thiobacillus, and effectively ensuring the effectiveness of sewage treatment.

[0026] 3. The method of flipping the denitrification unit reactor is used to forcibly destroy the compacted and blocked packing layer. The destroyed packing layer is like a newly loaded packing layer, which completely solves the problems of packing layer compaction and blockage, and is more cost-effective and efficient.

[0027] 4. The method of the present invention is low-cost, does not require the consumption of carbon sources during the process, and consumes less filler, which can effectively reduce the cost of sewage treatment and effectively ensure the effect of sewage treatment. It is of great significance for energy saving and consumption reduction in sewage treatment and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the denitrification unit structure involved in the method of the present invention;

[0029] Figure 2 Schematic diagram of the arrangement of the denitrification unit involved in the method of the present invention;

[0030] Figure 3 Schematic diagram of the connection between the denitrification unit and the branch water inlet pipe involved in the method of the present invention;

[0031] Figure 4 It is a schematic structural diagram of the denitrification device involved in Comparative Example 1 of the present invention.

[0032] The names corresponding to the marks in the figure are:

[0033] 1. Tank body; 11. Grate; 2. Head; 21. Screen; 3. Water inlet pipe; 31. Water inlet valve; 4. Water outlet pipe; 41. Water outlet valve; 5. Sewage pipe; 51. Sewage valve; 6. Rotating shaft; 7. Bracket; 71. Support plate; 72. Support leg; 8. Main water inlet pipe; 81. Branch water inlet pipe; 9. High-level water tank; 91. Sewer pipe; 10. Denitrification device; 101. Water supply pipe; 102. Drain pipe; 103. Water distribution plate; 104. Packing layer; 105. Water outlet weir plate; 106. Manhole. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] like Figure 1-3As shown, a tank body 1 is provided in the denitrification unit involved in the method of the present invention, and a head 2 is provided at the upper and lower ends of the tank body 1, a screen 21 (a stainless steel mesh with an aperture of 3 mm and covered with a stainless steel window screen) is provided between the head 2 and the tank body 1, a grate 11 with an aperture of 10 mm square is provided in the middle position inside the tank body 1, and a rotating shaft 6 is provided in the middle part of the tank body 1, and the upper and lower sides of the tank body 1 are symmetrically arranged based on the rotating shaft 6, wherein a water inlet pipe 3 is provided at the lower head 2, and a water inlet valve 31 is installed on the water inlet pipe 3, and a water outlet pipe 4 is provided at the upper head 2 corresponding to the water inlet pipe 3, and a water outlet valve 41 is installed on the water outlet pipe 4, and at the same time, sewage pipes 5 are symmetrically arranged on the upper and lower sides of the tank body 1, the height of the sewage pipe 5 is higher than the height of the packing layer, and a sewage valve 51 is arranged on the sewage pipe 5.

[0036] The denitrification unit is supported by a bracket 7 , wherein a support plate 71 is provided in the bracket 7 , and support legs 72 are provided below the support plate 71 . The support plate 71 cooperates with the rotating shaft 6 around the tank body 1 .

[0037] Two branch water inlet pipes 81 are extended from the main water inlet pipe 8 of the sewage treatment system, and multiple denitrification units are arranged in sequence on the branch water inlet pipes 81. The outlet water of each denitrification unit extends to the high-level water tank 9, and a downpipe 91 is provided below the high-level water tank 9. The return water of the downpipe 91 is discharged or used for other purposes.

[0038] like Figure 4 As shown, in the denitrification device 10 involved in Comparative Example 1, a water supply pipe 101 is provided at the bottom of the denitrification device 10, a water distribution plate 103 is provided at the bottom of the denitrification device 10, a filler layer 104 is filled on the water distribution plate 103, the incoming water passes through the outlet weir plate 105 above the denitrification device 10 and is discharged through the drain pipe 102, and a manhole 106 is provided on one side of the bottom of the denitrification device 10.

[0039] The principle of the present invention is:

[0040] The sewage in the main water inlet pipe of the present invention comes from the effluent of the high-efficiency sedimentation tank, in which the turbidity is less than 1NTU and there are fewer suspended particles in the water, which can slow down the clogging of the filler layer in the denitrification unit by the suspended particles, thereby affecting the effluent water quality. However, the presence of suspended matter in the inlet water is inevitable during the process. Therefore, in the existing denitrification device and the denitrification unit involved in the method of the present invention, after a period of operation, the filler layer will become clogged and compacted, thereby affecting the sewage treatment effect.

[0041] In the method of the present invention, the filler layer uses sulfur autotrophic denitrification filler, and the filler particles are sulfur particles and calcium carbonate particles. The particle sizes of the two particles are basically the same, and the volume ratio of sulfur particles to calcium carbonate particles is 7:3. The particle size is selected as a reference. When the wastewater is high-concentration nitrate nitrogen, a relatively small particle size is selected; when the wastewater is low-concentration nitrate nitrogen, a relatively large particle size is selected. The particle size is proportional to the square of the surface area, which is proportional to the denitrification reaction rate, and the reaction rate is proportional to the filler consumption. Therefore, an excessively fast reaction rate will cause the filler particles to quickly become smaller, thereby increasing the filler resistance. In addition, due to the growth of microorganisms, the denitrification gas will accumulate, forming gas pockets, which will affect the denitrification effect. Therefore, in actual treatment, the selection of appropriate filler particles is very important. The particle size of the filler particles is determined by the treatment object. In actual use, it is generally suitable to be 5 to 8 mm, which is also the common particle size of sulfur particles produced by my country's petrochemical industry.

[0042] For the above-mentioned sulfur autotrophic denitrification filler, a certain amount of consumption will occur during use. During the process, the filler particles can be regarded as a spherical mathematical model, and the surface area of ​​the particles is:

[0043] Surface area = 4πd 2

[0044] Where d is the particle size.

[0045] The denitrification rate is proportional to the total surface area. The larger the surface area, the larger the contact area with the sewage, and thus the higher the denitrification rate. The larger the total surface area, the smaller the particles will be, the faster the reaction will be, and the faster the filler will be consumed, which will increase the filler density, causing the water flow resistance to increase, and the generated gas will not be easy to escape, causing the filler efficiency to decrease prematurely. As the particle size increases, the total surface area decreases, and the denitrification rate will decrease. While ensuring the denitrification effect, it also allows the filler layer to be used stably and for a long time.

[0046] The above process is similar to a chemical reaction. If there are products, there will be loss of reactants. Therefore, it is also necessary to supplement the filler. Experimental research has found that when the particle size is appropriate, the filler can be supplemented once a year. During the process, a single denitrification unit is removed from the system, and then the filler is unloaded. After screening, the small particles of filler are recovered and new filler is added to replenish the total amount of filler to the same as the initial amount. During the process, it was found that the actual annual consumption of filler will not exceed 5%, and the total amount of small particles removed by screening will not exceed 8%. Overall, the filler consumption is small and the cost investment is low.

[0047] The filling of the packing layer is generally 50-60% of the volume of the denitrification unit. In the actual design process, the height of the seasoning layer can be effectively improved by increasing the aspect ratio of the denitrification unit. When the aspect ratio is 4-8, the denitrification effect is better, which ensures the denitrification effect while effectively reducing the cost of raw materials and land. After the packing layer is filled, the sewage to be treated is directly introduced into the process. During the process, the influent flow rate is controlled at one-third to one-half of the design flow rate through natural enrichment methods. The pH of the influent is 6-8, the total alkalinity of the influent is not less than 130 mg / L, and the natural incubation time is 4-5 days. When the nitrate nitrogen in the effluent of the denitrification system is lower than 0.5 mg / L, the nitrite nitrogen is lower than 0.005 mg / L, and the ammonia nitrogen differs from the influent by ±0.2 mg / L, the system is successfully started and the denitrification unit can operate stably, thereby achieving good treatment effect.

[0048] The number of parallel units and the capacity of each unit are designed based on the packing's denitrification load and the inlet and effluent quality requirements. Ten treatment units are typically designed, with each treating 10% of the influent. This decentralized design fully utilizes the processing capacity of each denitrification unit. High influent speed is not required, preventing suspended particles in the influent from being carried deeper into the packing, thereby preventing serious clogging and compaction of the packing layer. At the same time, excessively high influent linear speeds can disrupt turbulent flow between the influent and the packing, resulting in inadequate contact and affecting denitrification efficiency. Furthermore, since each denitrification unit only treats 10% of the influent, the reduced influent treatment volume means reduced processing time. This allows for a larger aspect ratio in the reactor, reducing raw material input and floor space. Furthermore, the reduced processing time eliminates concerns about elevated ammonia nitrogen and sulfide formation caused by capillary expansion and the superior reducing power of Thiobacillus denitrificans. The cumbersome flushing and backwashing equipment configuration and operation are eliminated, ensuring treatment effectiveness while effectively reducing operation and maintenance costs.

[0049] In the above process, the capillary expansion and denitrification reaction are carried out on the surface of the packing. The relatively fixed capillary flow will gradually turn into a coarse water flow as the reaction proceeds, that is, the capillary expansion phenomenon, so that the nitrate nitrogen in the middle part of the water flow cannot contact the surface of the packing, which is considered to be a decrease in efficiency and incomplete denitrification. As for the super reduction ability of denitrifying thiobacillus, experimental research has shown that the biological reduction of denitrifying thiobacillus is extremely strong. Regardless of winter or summer, denitrifying thiobacillus is not very sensitive to temperature and no obvious change in efficiency has been found. As for the compaction of the packing layer, the accumulation of suspended particles will cause the packing to compact, and the denitrification reaction will also cause the packing to compact due to the generation of new microorganisms. Regardless of the cause of the packing compaction, it will interfere with or damage the water inlet method. The water flow will bypass the compaction, and large agglomerates will cause the water flow to short-circuit, thereby affecting the water output effect.

[0050] In addition, the super-strong reducing ability is also reflected in that as the sewage retention time increases, Thiobacillus denitrificans can reduce the added 12 mg / L standard substance nitrobenzene to aniline:

[0051] Nitrobenzene + Thiobacillus denitrificans → Aniline

[0052] And it can reduce 80mg / L sulfate to 21mg / L sulfide:

[0053] SO4 2- +Thiobacillus denitrificans → S 2-

[0054] By extending the contact time between sewage and filler, ammonia nitrogen can be found in the effluent. In the denitrification reaction, ammonia nitrogen and nitrate nitrogen cannot coexist. The reaction mechanism in the process is:

[0055] NO3 - →NO2 - →NO→N2O→N→NH3

[0056] Among them, N is a nitrogen atom, which is reduced to ammonia before it can generate nitrogen gas, thus seriously affecting the denitrification effect.

[0057] The present invention utilizes an integrally reversible packing reactor, which can completely avoid the shortcomings of single-type reactors, such as capillary expansion, air blockage caused by microbial growth, and localized packing boundaries. Furthermore, with the decentralized design, if a water quality abnormality occurs in a unit, such as an effluent ammonia nitrogen content of 2 mg / L, the contribution to the overall effluent ammonia nitrogen increase is only 10%, or 0.2 mg / L. Furthermore, if a unit needs to be shut down for maintenance, the other nine units will bear the burden of that unit's water volume. Since the water volume increase is only 10%, each unit only increases by approximately 1%, resulting in a relatively small increase in water volume. Experiments have found that a small change in water volume (0-5%) within a short period of time (1-2 days) has a limited impact on the effluent results. Denitrification unit reversal can be planned based on actual operational conditions. Ideally, only one denitrification unit should be reversed and flushed at a time, followed by subsequent reversal and cleaning in a sequential order. This minimizes the impact on the overall effluent water quality and is more conducive to stable system operation and precise denitrification.

[0058] When the reactor is turned over, the microbial precipitate inside the filler is turned out. Since the specific gravity of the microbial precipitate is slightly greater than that of water, it will be semi-suspended in water for a long time (the specific gravity of the filler is 2.6 for sulfur and 2.7 for calcium carbonate, so the filler will settle quickly). At this time, the system water inlet is opened. When water comes out from the top, the side drain valve is opened to allow the sludge-rich sewage on the upper layer of the filler to be quickly discharged from the tank. The process is repeated 1 to 3 times until there is no obvious difference in appearance between the outlet water and the inlet water. During the process, the grate 11 can break up the compacted filler layer, thereby dispersing the filler. Since the filler layer occupies 50 to 60% of the reactor volume, as the dirty water is discharged, most of the microorganisms in the water will be intercepted by the filler layer (microorganisms are attached to the filler layer). Subsequently, the water supply is restored and the treatment capacity of the denitrification unit can be quickly restored (about 1 to 2 days).

[0059] In the method of the present invention, the setting of the denitrification unit design parameters, such as the packing layer height H, the water residence time T, the total volume V of the packing, and the number n of reactors, can all be calculated using relevant formulas. The denitrification of wastewater using Thiobacillus denitrificans is a membrane reaction. After the denitrification conditions in the denitrification reactor are fixed, at an appropriate residence time, denitrification exhibits a zero-order reaction, namely:

[0060] C 出水 =C 进水 -k1*H

[0061] Where: C 出水 is the concentration of nitrate nitrogen in the effluent of the denitrification reactor in mg / L;

[0062] C 进水 is the concentration of nitrate nitrogen in the denitrification reactor influent, mg / L;

[0063] K1 is the denitrification constant of the denitrification unit, mg / L·m 3 ;

[0064] H is the straight path of water flow in the denitrification reactor, that is, the packing height, m.

[0065] Therefore, after the denitrification constant of the denitrification unit is determined, the required height H of the packing layer can be calculated based on the water quality of the influent.

[0066] After the denitrification conditions of the denitrification reactor are fixed, there is still a zero-order reaction between the inlet water residence time and the outlet water quality, that is:

[0067] C 出水 =C 进水 -K2*T

[0068] K2 is the denitrification constant of the denitrification unit, mg / m 3 ·h;

[0069] T is the residence time of the influent in the packing of a single denitrification unit, h.

[0070] K1 and K2 are both denitrification constants of the denitrification unit. The two have mathematical correlation and can be converted into each other. According to the influent water quality, the residence time T can be calculated.

[0071] The formula for a zero-order reaction can also be expressed as:

[0072] C 出水 =C 进水 -k3*V

[0073] Where: C 出水 is the nitrate nitrogen concentration of the total effluent, mg / L;

[0074] C 进水 is the nitrate nitrogen concentration of the incoming water, mg / L;

[0075] k3 is the denitrification capacity of a single denitrification reactor, mg / L·m 3 ;

[0076] V is the total volume of the packing in the denitrification unit, m 3 .

[0077] Once the number, structure and packing of the denitrification reactor are determined, K3 is a constant that can be used to calculate the total volume of the packing in the denitrification unit.

[0078] In addition, the formula for zero-order reaction can also be expressed as:

[0079] C 出水 =C 进水 -k4*n

[0080] Where: n is the number of reactors;

[0081] When K4 operates normally, k4=k3*10%.

[0082] This formula guides producers to open several units according to their needs to accurately meet emission requirements.

[0083] Alternatively, the nitrate nitrogen value of the effluent can be determined by the denitrification retention time:

[0084] C 出水 =C 进水 -k5*t

[0085] Where: K5 is the denitrification capacity of the overall denitrification system, mg / L·h;

[0086] t is the contact time of the influent in the packing, h. (This time is related to the number of denitrification units opened. For a certain influent volume, the number of opened units determines the treatment capacity of each denitrification unit, and the water treatment capacity affects the contact time t)

[0087] All these operations and calculations are based on the relatively stable denitrification load of the denitrification filler. The operation and regulation of the denitrification system require the coordination of detailed calculations and tests.

[0088] Example 1

[0089] 1. Design parameters of denitrification unit

[0090] In this embodiment, the denitrification unit is designed to have a total height of 2.6m, a diameter of 0.4m, a water inlet branch pipe diameter of DN15, an inlet and outlet water pipe diameter of DN90, an effective filling volume of 180L, a screen aperture of 3mm, and a grate aperture of 10mm; when arranged, two rows are arranged in a line with a spacing of 3.5m, and the spacing between reactors is 0.8m.

[0091] The denitrification load of the packing is 450g / m 3 ·d, a single device processes 81g of nitrate nitrogen per day, the nitrate nitrogen concentration in the effluent of the high-efficiency sedimentation tank of the sewage plant is 13mg / L, and a single denitrification unit processes 9m3 of sewage per day. 3 , one set of experiments treated 90m3 of water 3 The single flow rate is 375L / h, the water inlet linear velocity is 4.59m / h (linear velocity refers to the height from the water flow entering the packing to the height from the water flow leaving the packing divided by the time. The linear velocity can reflect the impact of the water flow on the packing), and the hydraulic retention time is 18min.

[0092] 2. The denitrification system was tracked and monitored for about 60 days, and the data obtained are shown in the following table:

[0093] Table 1 Denitrification unit sewage treatment effect table

[0094]

[0095] It can be found that after the system stabilizes, the precise denitrification period reaches about 40 days (when the nitrate nitrogen level is around 0.3 mg / L, it is considered that complete denitrification has been achieved), and the treatment effect is good. When the ammonia nitrogen level is found to be elevated, the denitrification unit is reversed. After the reversal, the denitrification effect can be restored to normal levels after about 2 days. (Note: After the reversal, the wastewater cannot be completely emptied at once. The packing needs to be watered to avoid the impact of packing dehydration on the microbial system.)

[0096] In actual operation, in order to ensure the treatment effect, corresponding scheduling can be carried out, such as flipping once every 30 days, without waiting for the ammonia nitrogen to rise before flipping, thereby ensuring stable and efficient sewage treatment; it can be found that for small sewage discharge units, to remove total nitrogen pollution, the present invention provides a good way. The method of the present invention develops this sewage denitrification process that does not require a carbon source, has an extremely low treatment cost, and can operate continuously, making a positive contribution to energy conservation and consumption reduction in sewage treatment plants.

[0097] Comparative Example 1

[0098] The existing denitrification device was compared with Example 1 of the present invention. During the process, a fixed-frequency water inlet pump was used. The device had a diameter of 3.5 m and a total height of 6 m. The water distribution area was 0.5 m high, the packing layer height was 4.5 m, and the effective void space of the packing was 40%. The water linear velocity at the initial stage of the experiment was 9.4 m / h. The obtained data are as follows:

[0099] Table 2 Sewage treatment effect of existing denitrification equipment

[0100]

[0101] It can be seen that with the extension of time, the water flow rate decreases significantly, indicating that the packing resistance becomes larger and the internal blockage is serious, which will cause water flow turbulence, local vortex, and excessively long residence time of local water flow. Due to the super-strong reducing ability of denitrifying Thiobacillus, ammonia nitrogen is generated; after 30 days of operation, nitrate nitrogen shows an upward trend, which is caused by capillary expansion; with the operation of the device, nitrite nitrogen also shows an upward trend, which is a phenomenon that cannot continue to be reduced due to capillary expansion and microbial growth.

[0102] During the experiment, after the filler failed, the water was opened for 60m 3 / h forward flushing, the effluent water is black, the black water is tested, and the ammonia nitrogen and sulfide are all above 2mg / L. Continue flushing until the effluent water becomes clear. Continue to follow the 36m 3 / h flow rate operation, the effluent data, nitrate nitrogen and ammonia nitrogen, cannot reach the state values ​​at the beginning of the operation.

[0103] The system was stopped, all the packing was unloaded, rinsed with clean water, and then loaded into the reactor again and started to operate. The operating conditions in April were almost repeated. Compared with the method of the present invention, the existing denitrification device cannot achieve a stable and efficient denitrification process.

[0104] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A method for accurate denitrification of sewage based on Thiobacillus denitrificans, characterized in that: The following steps are involved: S1. Layout of denitrification system; Two branch water inlet pipes (81) connected in parallel are drawn from the main water inlet pipe (8) of the sewage treatment system. A plurality of denitrification units are sequentially arranged and installed on each branch water inlet pipe (81). The branch water inlet pipe (81) supplies water to each denitrification unit in an upward flow manner, and the sewage after deep denitrification of each denitrification unit is collected and discharged; The denitrification unit comprises a tank body (1), a rotating shaft (6) is provided in the middle of the tank body (1), and the upper and lower sides of the tank body (1) are symmetrically arranged relative to the rotating shaft (6); heads are provided at the upper and lower ends of the tank body (1), a screen (21) is provided between the upper and lower heads and the tank body (1), a grate (11) is provided in the middle of the tank body (1), a water inlet pipe (3) is provided at the lower head, a water inlet valve (31) is provided on the water inlet pipe (3), a water outlet pipe (4) is provided at the upper head symmetrically with the water inlet pipe, a water outlet valve (41) is provided on the water outlet pipe (4), a sewage pipe (5) is symmetrically provided on the upper and lower sides of the tank body (1), the sewage pipe (5) is installed at a position higher than the height of the packing layer, and a sewage valve (51) is provided on the sewage pipe (5); A bracket (7) is provided on the denitrification unit, a support plate (71) is provided in the bracket (7), and legs (72) are provided on the lower periphery of the support plate (71). The support plate (71) supports the rotating shaft (6), and the rotating shaft (6) realizes the flipping of the denitrification unit under the drive of the motor; S2, filling denitrification fillers into each denitrification unit in S1; The denitrification filler is a sulfur autotrophic denitrification filler, which is composed of sulfur particles and calcium carbonate particles. The volume ratio of sulfur particles to calcium carbonate particles is 7:3, and the particle size of sulfur particles and calcium carbonate particles is 5-8 mm. The filling volume of the sulfur autotrophic denitrification filler is 50-60% of the denitrification unit volume. S3, feed water into the S1 denitrification system, cultivate denitrifying Thiobacillus under natural conditions, and start the denitrification system; S4. After the system is successfully started, gradually increase the water volume until it reaches the designed water volume. After a period of stable operation, if it is detected that the denitrification capacity of the denitrification unit has decreased, turn over each denitrification unit, backwash and regenerate the denitrification packing, and record the duration of the system's stable operation; S5. As the system operates stably, each denitrification unit is turned over in advance according to the duration of stable operation determined in S4, and the denitrification filler is backwashed and regenerated to achieve a stable and accurate denitrification process of the denitrification system; In the above-mentioned S4 and S5, after the denitrification unit is turned over, the system is opened to water inlet. When water is discharged from the top, the side drain valve (51) is opened to allow the sludge-rich sewage above the packing layer to be quickly discharged from the tank body (1). The above operation is repeated 1 to 3 times until there is no obvious difference in appearance between the outlet water and the inlet water; the grate (11) breaks up the compacted packing layer to disperse the packing.

2. The method for accurate denitrification of sewage based on Thiobacillus denitrificans according to claim 1, characterized in that: In the aforementioned S1, five denitrification units are sequentially arranged on each branch water inlet pipe (81), and the effluent of each denitrification unit is collected by the high-level water tank (9) and then discharged from the downpipe (91) of the high-level water tank (9).

3. The method for accurate denitrification of sewage based on Thiobacillus denitrificans according to claim 1, characterized in that: In the above-mentioned S3, the inlet flow rate is controlled at one-third to one-half of the design flow rate, the pH of the inlet water is 6-8, the total alkalinity of the inlet water is not less than 130 mg / L, and the natural incubation time is 4-5 days.

4. The method for accurate denitrification of sewage based on Thiobacillus denitrificans according to claim 1, characterized in that: In the above S3, when the nitrate nitrogen in the effluent of the denitrification system is lower than 0.5 mg / L, the nitrite nitrogen is lower than 0.005 mg / L, and the ammonia nitrogen differs from the influent by ±0.2 mg / L, the system is successfully started.

5. The method for accurate denitrification of sewage based on Thiobacillus denitrificans according to claim 1, characterized in that: In the above-mentioned S4, when it is detected that the total nitrogen content in the effluent of the denitrification unit shows a stable upward trend, it is considered that the denitrification capacity of the denitrification unit has decreased, and at this time, the denitrification unit starts to be turned over.

6. The method for accurate denitrification of sewage based on Thiobacillus denitrificans according to claim 2, characterized in that: In the above-mentioned S5, only 1 to 3 denitrification units are flipped at a time. After the denitrification units are stably operated after flipping, the remaining denitrification units are flipped until all the denitrification units are completely flipped, and then the next operation cycle is entered.

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