Municipal sewage treatment system

Abstract

The utility model relates to a municipal sewage treatment system and belongs to the technical field of sewage treatment. Each group of sewage treatment line comprises a biological selection tank, an anaerobic tank, a first-stage anoxic tank, at least one first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank which are communicated in sequence, the biological selection tank is connected with an incoming water main pipeline, the incoming water main pipeline is connected with an incoming water branch pipe, the middle part of the incoming water branch pipe is connected with a first branch, the first branch extends into the first-stage anoxic tank, and the second branch extends into the second-stage anoxic tank. The other end of the incoming water branch pipe is connected with a second branch, and the second branch extends into the first primary aerobic tank. A part of incoming water is introduced into a primary anoxic tank through an incoming water branch pipe and a first branch, so that a carbon source in the incoming water is fully utilized as a carbon source of a denitrification system, and the dosage of the carbon source is reduced; a part of incoming water is introduced into the first primary aerobic tank through the incoming water branch pipe and the second branch, so that the sludge load of the primary aerobic tank is improved, the sludge aging is relieved, and the sludge bulking problem is prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to a municipal sewage treatment system. Background Art

[0002] Municipal sewage treatment system is a kind of municipal facilities, which is widely used in municipal ground engineering. Figure 1 As shown, existing municipal wastewater treatment systems generally utilize the traditional "influent → anaerobic tank → primary anoxic tank → primary aerobic tank → secondary anoxic tank → secondary aerobic tank → secondary sedimentation tank" process technology. Internal recirculation in the primary aerobic tank achieves biological denitrification, while external recirculation in the secondary sedimentation tank removes phosphorus and maintains sludge concentration. To effectively remove total nitrogen, a large amount of carbon source must be added to the primary and secondary anoxic tanks (if necessary) to ensure an adequate C / N ratio and stable system operation. Traditional processes incorporate carbon source addition points in the primary and secondary anoxic tanks for denitrification.

[0003] This process has significant nitrogen and phosphorus removal effects, but in actual operation, actual inflow water indicators often fall below design targets, resulting in increased carbon source dosage in the municipal wastewater treatment system. Furthermore, the entire municipal wastewater treatment system operates at low load. Long-term low-load operation severely impacts sludge activity, hindering the stable operation of the effluent. In actual production, sludge aging and even sludge bulking often occur, ultimately causing effluent indicators to exceed standards. Furthermore, when inflow water contains high ammonia nitrogen levels, large amounts of carbon source must be added to the primary anoxic tank and, if necessary, the secondary anoxic tank to ensure proper operation of the denitrification system, increasing operating costs. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a municipal sewage treatment system. The technical solution of the present invention is as follows:

[0005] A municipal sewage treatment system includes two groups of sewage treatment lines and a secondary sedimentation tank. Each group of sewage treatment lines includes a biological selection tank, an anaerobic tank, a primary anoxic tank, at least one primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank that are connected in sequence. The biological selection tank is located on the right side of the anaerobic tank. The primary anoxic tank, at least one primary aerobic tank, and the secondary anoxic tank are arranged in sequence from front to back. The secondary aerobic tank is located on the right side of the secondary anoxic tank. The biological selection tank is connected to an incoming water main pipe, and a water branch pipe is connected to the middle of the incoming water main pipe. The incoming water main pipe is connected to one end of the incoming water branch pipe, and a first branch is connected to the middle of the incoming water branch pipe. The first branch extends to the primary anoxic tank, and the other end of the incoming water branch pipe is connected to There is a second branch, which extends into the first-level aerobic tank. A submersible mixer is installed on the anaerobic tank. A diversion wall is horizontally built in the middle of the bottom of the first-level anoxic tank. Two groups of parallel aisles are vertically built on the upper part of the first-level anoxic tank. A submersible flow pusher for pushing flow from left to right is respectively installed on the upper part of the right side wall of the two groups of aisles. A submersible flow pusher for pushing flow from right to left is respectively installed on the lower part of the left side wall of the two groups of aisles. Aeration devices are installed at the bottom of the first-level aerobic tank and the second-level aerobic tank. The second-level aerobic tank is connected to an outlet pipe. The outlet pipes of the two groups of sewage treatment lines are both connected to the second sedimentation tank. A nitrification liquid reflux pipe is connected between the last first-level aerobic tank and the first-level anoxic tank.

[0006] Optionally, a diversion wall is horizontally built in the middle of the bottom surface of the secondary anoxic tank, and an aisle is longitudinally built on the upper part of the secondary anoxic tank. A submersible flow pusher that pushes flow from right to left is installed on the upper part of the left side wall of the aisle, and a submersible flow pusher that pushes flow from left to right is installed on the lower part of the right side wall of the aisle.

[0007] Optionally, the aeration device is a tubular microporous aerator.

[0008] Optionally, the number of the primary aerobic tanks is four.

[0009] Optionally, a pH detector is installed at the end of the fourth primary aerobic tank, the third primary aerobic tank is connected to an alkali solution addition pipeline, the alkali solution addition pipeline is connected to an alkali solution addition pump and a valve, and the pH detector, alkali solution addition metering pump and valve are all electrically connected to the controller.

[0010] Optionally, the biological selection tank is connected to a sludge return pipe.

[0011] Optionally, valves are installed on the water inlet branch pipe, the first branch and the second branch, and each valve is electrically connected to the controller.

[0012] All the above optional technical solutions can be combined arbitrarily, and the present utility model does not provide detailed descriptions of the structures after the combinations.

[0013] By means of the above solution, the beneficial effects of the present invention are as follows:

[0014] By introducing a portion of the incoming water into the primary anoxic tank through the incoming water branch pipe and the first branch, the carbon source contained in the incoming water can be fully utilized as the carbon source for the denitrification system, thereby reducing the amount of carbon source added and lowering operating costs. By introducing a portion of the incoming water into the first primary aerobic tank through the incoming water branch pipe and the second branch, the sludge load of the primary aerobic tank can be increased, sludge aging can be reduced, and sludge bulking problems can be prevented. At the same time, the nutrient gradient ratio of the entire primary aerobic tank is increased, which can effectively inhibit the expansion of filamentous bacteria. The utility model can achieve efficient and stable carbon reduction operation of the municipal sewage treatment system.

[0015] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a sewage treatment process flow chart of the existing municipal sewage treatment system.

[0017] Figure 2 It is a top view of the plan layout of the municipal sewage treatment system provided by the utility model.

[0018] Figure 3 This is a sewage treatment process flow chart of a municipal sewage treatment system provided by the utility model. DETAILED DESCRIPTION

[0019] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0020] like Figure 2As shown, the municipal sewage treatment system provided by the present invention includes two groups of sewage treatment lines and a secondary sedimentation tank. Each group of sewage treatment lines includes a biological selection tank 1, an anaerobic tank 2, a primary anoxic tank 3, at least one primary aerobic tank 4, a secondary anoxic tank 5, and a secondary aerobic tank 6 connected in sequence. The biological selection tank 1 is located on the right side of the anaerobic tank 2. The primary anoxic tank 3, at least one primary aerobic tank 4 and the secondary anoxic tank 5 are arranged in sequence from front to back. The secondary aerobic tank 6 is located on the right side of the secondary anoxic tank 5. The biological selection tank 1 is connected to an inlet water main pipe 7, and an inlet water branch pipe 15 is connected to the middle of the inlet water main pipe 7. The inlet water main pipe 7 is connected to one end of the inlet water branch pipe 15, and a first branch 8 is connected to the middle of the inlet water branch pipe 15. The first branch 8 extends to the primary anoxic tank 3, and the other end of the inlet water branch pipe 15 A second branch 9 is connected, and the second branch 9 extends into the first primary aerobic tank 4. A submersible mixer 10 is installed on the anaerobic tank 2. A diversion wall 11 is horizontally built on the middle part of the bottom surface of the primary anoxic tank 3. Two groups of parallel aisles 12 are longitudinally built on the upper part of the primary anoxic tank 3. A submersible flow propeller 13 for pushing flow from left to right is installed on the upper part of the right side wall of each group of aisles 12, and a submersible flow propeller 13 for pushing flow from right to left is installed on the lower part of the left side wall of each group of aisles 12. An aeration device 14 is installed at the bottom of the primary aerobic tank 4 and the secondary aerobic tank 6. The secondary aerobic tank 6 is connected to an outlet pipe 19. The outlet pipes 19 of the two groups of sewage treatment lines are connected to the secondary sedimentation tank. A nitrification liquid reflux pipe 16 is connected between the last primary aerobic tank 4 and the primary anoxic tank 3.

[0021] The function of the biological selection tank 1 is to create suitable conditions for microbial growth, thereby selecting flocculant bacteria and preventing filamentous bacterial expansion. Specifically, the activated sludge load has a significant impact on the population composition of the activated sludge in the system, and a higher sludge load is conducive to the growth and reproduction of flocculant bacteria. The activated sludge continuously undergoes a high floc load stage in the biological selection tank 1, which is conducive to the growth of flocculant bacteria, improves sludge activity, and quickly removes soluble, easily degradable substrates in the wastewater through enzymatic reactions, thereby inhibiting the growth and reproduction of filamentous bacteria and avoiding the occurrence of sludge expansion. At the same time, when the biological selection tank 1 is in an anoxic environment, the small amount of nitrate nitrogen present in the return sludge can be denitrified; when the biological selection tank 1 is in an anaerobic environment, it can also create an environment conducive to phosphorus release, thereby promoting the growth of polyphosphate bacteria and preparing for biological phosphorus removal.

[0022] Anaerobic tank 2 houses anaerobic activated sludge, which primarily enhances biodegradability and removes phosphorus. Biodegradability refers to the conversion of large organic molecules into small ones through hydrolysis and acidification, effectively limiting the anaerobic reaction to the hydrolysis and acidification phase. Phosphorus removal involves the release of phosphorus by phosphate-releasing bacteria, which is then excessively absorbed in the subsequent aerobic tank. Ultimately, the phosphorus-absorbing microorganisms are separated from the sludge and water in the secondary sedimentation tank, with some of the residue discharged as excess sludge.

[0023] The main function of the primary anoxic tank 3 is denitrification. Denitrification requires a C / N ratio of 3 to 5, which consumes COD. In the traditional process, methanol, sodium acetate, glucose, etc. are added as carbon sources (i.e., COD). The utility model introduces a portion of the incoming water into the primary anoxic tank 3 through the incoming water branch pipe 15 and the first branch 8 through the process pipeline modification. Figure 2 Point a in the anoxic tank 3 can fully utilize the carbon source (COD) in the incoming water (ie sewage) as the carbon source for the denitrification system, reduce the amount of carbon source added, and reduce operating costs. The amount of carbon source that can be saved at point a is the product of the amount of water passing through point a and the COD content in the corresponding sewage. The design of the guide wall 11 and the submersible flow propeller 13 in the first-level anoxic tank 3 helps to guide the water flow in the first-level anoxic tank 3 according to the following formula: Figure 2 The flow direction indicated by the middle arrow flows into the first primary aerobic tank 4, thereby extending the treatment time of the incoming water in the primary anoxic tank 3 and ensuring that the reaction therein can be fully carried out.

[0024] The main function of the primary aerobic tank 4 is to degrade organic matter (i.e. COD) through the action of aerobic activated sludge and to carry out nitrification reaction through nitrifying bacteria, so that ammonia nitrogen is converted into nitrate nitrogen, which is conveniently pumped to the primary anoxic tank 3 through the nitrification liquid return pipe for denitrification. The utility model introduces a part of the incoming water into the first primary aerobic tank 4 through the incoming water branch pipe 15 and the second branch pipe 9 through the process pipeline modification. Figure 2 The main function of point b in the aerobic tank is to reduce sludge aging and prevent sludge bulking by increasing the sludge load in the aerobic tank. Because the wastewater flowing into point b has not undergone anaerobic and anoxic treatment, the COD value in the wastewater is greatly retained, which increases the sludge load flowing into the first primary aerobic tank 4, thereby improving the settling performance of the activated sludge. At the same time, the nutrient gradient ratio of the entire primary aerobic tank is increased, which effectively inhibits the expansion of filamentous bacteria and prevents sludge bulking caused by low load.

[0025] At the same time, since both point a and point b overflow the anaerobic tank 2, the hydraulic retention time of the system can be greatly reduced, which can effectively solve the problems of activated sludge aging and overexposure caused by low load.

[0026] The secondary anoxic tank 5 is used for secondary denitrification and denitrification, acting as the same-stage anoxic tank 3 to further denitrify.

[0027] The secondary aerobic tank 6 acts as the primary aerobic tank 4 to further degrade organic matter and provide an aerobic environment to avoid problems such as floating mud in the subsequent secondary sedimentation tank.

[0028] like Figure 3As shown, this is a sewage treatment process flow chart for the municipal sewage treatment system provided by the present invention. During specific implementation, 60-70% of the incoming water is controlled to enter the biological selection tank 1, and 30-40% of the water is diverted directly to the primary anoxic tank 3 and the first primary aerobic tank 4, achieving the goal of reducing costs and increasing efficiency. The specific sewage treatment process of the anaerobic tank 2, the primary anoxic tank 3, at least one primary aerobic tank 4, the secondary anoxic tank 5, the secondary aerobic tank 6, and the secondary sedimentation tank can be referred to existing treatment processes and will not be elaborated in detail in this invention.

[0029] In one embodiment, a diversion wall 11 is horizontally built in the middle of the bottom surface of the secondary anoxic pool 5, and a passage 12 is vertically built on the upper part of the secondary anoxic pool 5. A submersible flow propeller 13 for pushing flow from right to left is installed on the upper part of the left side wall of the passage 12, and a submersible flow propeller 13 for pushing flow from left to right is installed on the lower part of the right side wall of the passage 12. The design of the diversion wall 11 and the submersible flow propeller 13 in the secondary anoxic pool 5 helps to guide the water flow in the secondary anoxic pool 5 to flow from behind the diversion wall 11 into the secondary aerobic pool 6.

[0030] In a specific embodiment, the aeration device 14 is a tubular microporous aerator. The rubber diaphragm of the tubular microporous aerator is made of EPDM silicone rubber, which has the characteristics of heat resistance, oxidation resistance, acid and alkali resistance, and good chemical stability. Compared with general rubber membranes, its service life can be greatly improved. The aeration holes of the tubular microporous aerator are straight long holes, which give it good expandability and instantaneous closure. During aeration, micro bubbles with a diameter of less than 3 mm can be released to obtain a higher oxygen utilization rate, which is 30-40%. The support tube of the tubular microporous aerator is made of ABS material. The air duct is made of engineering plastic ABS and is hollow and water-filled, which greatly reduces its buoyancy in water.

[0031] In a specific embodiment, there are four primary aerobic tanks 4. By providing four primary aerobic tanks 4, it is ensured that the incoming water can react completely and be evenly mixed after passing through the primary aerobic tanks 4.

[0032] In a specific embodiment, a pH detector 17 is installed at the end of the fourth primary aerobic tank 4, and the third primary aerobic tank 4 is connected to an alkali solution addition pipeline 18, and the alkali solution addition pipeline 18 is connected to an alkali solution addition metering pump and a valve. The pH detector 17, the alkali solution addition metering pump and the valve are all electrically connected to the controller.

[0033] That is to say, the alkali solution addition point is set at Figure 2At point C in the figure, the controller can realize the interlocking of the pH detector 17 and the alkali solution dosing pump. The alkali solution dosing pump is interlocked with the pH detector 17 at the end of the fourth primary aerobic tank 4. Specifically, during the biological nitrification reaction, the alkalinity in the water will be continuously consumed. Since nitrifying bacteria themselves are autotrophic bacteria, too high a carbon source is not suitable for their growth. By setting the alkali solution addition point on the third primary aerobic tank 4, the carbon source at this position is basically degraded or assimilated by heterotrophic bacteria. Compared with the same period last year, the abundance of nitrifying bacteria in the fourth primary aerobic tank 4 is better than that in other areas. Therefore, adding alkali solution here can more quickly provide nitrifying bacteria with a pH environment suitable for their growth, speed up the response time of restoring the nitrification system in daily operation, and thus greatly reduce the amount of alkali solution added.

[0034] In a specific embodiment, the biological selection tank 1 is connected to a sludge return pipe 20 .

[0035] In one embodiment, valves are installed on the water branch pipe 15, the first branch 8, and the second branch 9, and each valve is electrically connected to a controller. The valves are solenoid valves or electrically controlled valves. By providing the valves and controller, the water branch pipe 15, the first branch 8, or the second branch 9 can be opened and closed as needed by the controller, achieving an automatic control effect.

[0036] To illustrate the effect of the present invention, the following example is given: the design treatment capacity of a municipal sewage plant is 20,000 m³ / d, the average COD of the incoming water in December is 220 mg / L, the average total nitrogen is 62 mg / L, and the average total phosphorus is 14 mg / L. If Figure 1 The wastewater treatment process shown theoretically requires a carbon source (methanol) dosage of 160 kg / h. To reduce operational costs, a reasonable methanol dosage is 61 kg / h. A lower dosage would affect the long-term stability of the system. However, with this new treatment method, the methanol dosage can be reduced to 0 kg / h without affecting any system performance. At a methanol price of 2,600 yuan / ton, this translates to a daily cost savings of 3,806 yuan.

[0037] By adding water branch pipes at points a and b, this utility model does not cause the effluent index to exceed the standard. Instead, it can achieve the goal of reducing methanol dosage without affecting the normal operation of the entire process. The water flow rate at the two points can be dynamically adjusted according to the different characteristics of each project. This utility model can provide a new approach to reducing costs and increasing efficiency for sewage treatment plants with similar processes. At the same time, it can improve the low-load operation that is currently prevalent in sewage treatment plants, and promote the stable operation of the entire system.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A municipal sewage treatment system, characterized in that: The invention comprises two groups of sewage treatment lines and a secondary sedimentation tank, each group of sewage treatment lines comprises a biological selection tank (1), an anaerobic tank (2), a primary anoxic tank (3), at least one primary aerobic tank (4), a secondary anoxic tank (5), and a secondary aerobic tank (6) which are connected in sequence. The biological selection tank (1) is located on the right side of the anaerobic tank (2), the primary anoxic tank (3), at least one primary aerobic tank (4), and the secondary anoxic tank (5) are arranged in sequence from front to back, and the secondary aerobic tank (6) is located on the right side of the secondary anoxic tank (5). The biological selection tank (1) is connected to a water main pipe (7), a water branch pipe (15) is connected to the middle of the water main pipe (7), and the water main pipe (7) is connected to one end of the water branch pipe (15). A first branch (8) is connected to the middle of the water branch pipe (15), and the first branch (8) extends to the primary anoxic tank (3). The other end of the water branch pipe (15) is connected to a second branch (9), and the second branch (9) extends to the In the first aerobic tank (4), a submersible mixer (10) is installed on the anaerobic tank (2), a diversion wall (11) is horizontally built on the middle of the bottom surface of the first anoxic tank (3), and two sets of mutually parallel passages (12) are vertically built on the upper part of the first anoxic tank (3). A submersible flow pusher (13) for pushing flow from left to right is installed on the upper part of the right side wall of each set of passages (12), and a submersible flow pusher (13) for pushing flow from left to right is installed on the lower part of the left side wall of each set of passages (12). A submersible flow propeller (13) pushes the flow from right to left. Aeration devices (14) are installed at the bottom of the primary aerobic tank (4) and the secondary aerobic tank (6). The secondary aerobic tank (6) is connected to a water outlet pipe (19). The water outlet pipes (19) of the two groups of sewage treatment lines are connected to the secondary sedimentation tank. A nitrification liquid return pipe (16) is connected between the last primary aerobic tank (4) and the primary anoxic tank (3); and the biological selection tank (1) is connected to a sludge return pipe (20).

2. The municipal sewage treatment system according to claim 1, characterized in that: A guide wall (11) is horizontally built in the middle of the bottom surface of the secondary anoxic pool (5), and an aisle (12) is longitudinally built on the upper part of the secondary anoxic pool (5). A submersible flow pusher (13) for pushing flow from right to left is installed on the upper part of the left side wall of the aisle (12), and a submersible flow pusher (13) for pushing flow from left to right is installed on the lower part of the right side wall of the aisle (12).

3. The municipal sewage treatment system according to claim 1, characterized in that: The aeration device (14) is a tubular microporous aerator.

4. The municipal sewage treatment system according to claim 1, characterized in that: The number of the primary aerobic pools (4) is four.

5. The municipal sewage treatment system according to claim 4, characterized in that: A pH detector (17) is installed at the end of the fourth primary aerobic tank (4), and the third primary aerobic tank (4) is connected to an alkali solution addition pipeline (18). An alkali solution addition pump and a valve are connected to the alkali solution addition pipeline (18). The pH detector (17), the alkali solution addition metering pump and the valve are all electrically connected to the controller.

6. The municipal sewage treatment system according to claim 1, characterized in that: Valves are installed on the water branch pipe (15), the first branch (8) and the second branch (9), and each valve is electrically connected to the controller.

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