AAO (anaerobic-anoxic-oxic) sewage treatment system capable of reducing COD (chemical oxygen demand) and sludge yield at front end

Abstract

The utility model discloses an AAO (anaerobic-anoxic-oxic) sewage treatment system capable of reducing COD (chemical oxygen demand) and sludge yield at the front end, relates to the field of AAO sewage treatment, aims to solve the problems of long retention time and high civil engineering cost in the prior art, and adopts the technical scheme that an adsorption sedimentation tank is separated at the front end of an anaerobic tank, and sludge separated from a secondary sedimentation tank flows back to the adsorption sedimentation tank; the high-activity sludge is fully mixed with sewage, and organic pollutants in the sewage are adsorbed through the high-activity sludge, so that COD (Chemical Oxygen Demand) is reduced before the sludge in the wastewater begins to increase, the sludge output is reduced, the subsequent treatment load and retention time are reduced, and correspondingly, the tank volume of the tank body and the civil engineering investment can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of AAO sewage treatment, in particular to an AAO sewage treatment system with a front-end capable of reducing COD and sludge production. Background Art

[0002] Slaughterhouse and meat processing wastewater is generated during the slaughtering and meat processing process, primarily containing blood, grease, minced meat, animal hair, undigested food, feces, and urine. It is characterized by large volumes, uneven drainage, high concentrations, high levels of impurities and suspended solids, and good biodegradability. Furthermore, its significant difference from other high-concentration organic wastewater lies in its higher concentrations of total nitrogen and total phosphorus.

[0003] According to the characteristics of wastewater and the requirements of effluent treatment, the wastewater treatment process generally adopts physical and chemical + biochemical treatment process. The specific biochemical treatment process often adopts AAO process, such as Figure 1 As shown, sewage first enters a mechanical screen 1 for preliminary filtration, then passes through an ultra-fine filter 2 for fine filtration. It then undergoes physical and biochemical treatment in a flotation unit 3, a regulating tank 4, an anaerobic tank 5, an anoxic tank 6, and an aerobic tank 7. Finally, it is settled in a secondary sedimentation tank 8, where the sewage is discharged. Part of the sludge is discharged and part is returned to the anaerobic tank 5. This process simultaneously removes nitrogen and phosphorus. In actual projects, to better achieve nitrogen and phosphorus removal and ensure that the effluent meets standards, the biochemical treatment unit is typically designed with a large tank and a long retention time, resulting in excessively high civil engineering investment costs for sewage treatment plants.

[0004] From the above, it can be seen that the main direction of optimization of the conventional AAO simultaneous denitrification and phosphorus removal process for sewage is to reduce the retention time and reduce the civil engineering investment cost of the sewage station. Utility Model Content

[0005] The technical problem to be solved by the utility model is to overcome the existing defects and provide an AAO sewage treatment system with reduced COD and sludge production at the front end, which can effectively solve the problems in the background technology.

[0006] In order to achieve the above-mentioned purpose, the utility model discloses an AAO sewage treatment system with a front-end reduction in COD and sludge production. The technical solution adopted is as follows: the system comprises a regulating tank and an anaerobic tank, wherein the anaerobic tank is connected to the rear end of the regulating tank, and the rear end of the anaerobic tank is also connected to an anoxic tank, an aerobic tank and a secondary sedimentation tank, wherein the secondary sedimentation tank has a sewage discharge port and a sludge outlet, and the front end of the anaerobic tank is provided with an adsorption sedimentation tank, wherein the adsorption sedimentation tank has a sewage inlet, a sewage outlet and a sludge return port, and a sludge hopper inside. The adsorption sedimentation tank is also equipped with a stirrer, and the bottom of the sludge hopper has a sludge discharge pipe, and the top has a drainage and water collection pipe. The sludge discharge pipe is provided with a sludge discharge valve, and is connected to a sludge conveying device; the sludge outlet of the secondary sedimentation tank is connected to the sludge return port of the adsorption sedimentation tank. By returning the activated sludge to the front end of the anaerobic tank, the highly activated sludge can quickly adsorb organic pollutants in the sewage, significantly reducing the COD, thereby reducing the concentration of organic pollutants in the sewage before the sludge grows, and discharging the sludge that has adsorbed a large amount of organic pollutants, thereby reducing the amount of sludge generated, reducing the subsequent treatment load, shortening the residence time of sewage treatment, reducing the tank volume, and reducing civil engineering investment.

[0007] As a preferred technical solution of the present invention, the adsorption sedimentation tank and the anaerobic tank are connected, with a partition disposed therebetween. The partition has a water hole formed thereon, and the drainage channel corresponds to the water hole. The sewage in the upper layer of the adsorption sedimentation tank can flow through the drainage channel to the anaerobic tank at the rear end.

[0008] As a preferred technical solution of the present invention, the adsorption sedimentation tank comprises a tank body, the sludge hopper is located inside the tank body and has an inverted truncated cone-shaped sludge chamber, and the sludge discharge pipe connects the sludge chamber to the outside. The sludge that has absorbed organic pollutants is discharged from the adsorption sedimentation tank through the sludge discharge pipe.

[0009] As an optimal technical solution of the present invention, the agitator also includes a motor and a stirring paddle, the stirring paddle is connected to the motor, and the stirring paddle extends into the sludge chamber. The stirring of the stirring paddle can make the highly activated sludge and sewage fully contact, thereby reducing the concentration of organic pollutants.

[0010] As a preferred technical solution of the present invention, the top of the pool body is opened, and the opening is covered with a walkway. The motor is installed on the walkway, and the walkway is convenient for people to pass through.

[0011] As a preferred technical solution of the present invention, the drainage and water collection channel is installed on the inner wall of the pool body.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention sets an adsorption sedimentation tank at the front end of the anaerobic tank, and returns the highly active sludge produced in the secondary sedimentation tank to the adsorption sedimentation tank, so that it is in full contact with the wastewater produced in the regulating tank, and adsorbs the organic pollutants in the wastewater, thereby reducing the COD before the sludge in the wastewater begins to grow, thereby reducing the amount of sludge generated, reducing the subsequent processing load and residence time, and correspondingly reducing the pool capacity and civil engineering investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the structure of the AAO sewage treatment system in the prior art;

[0014] Figure 2 This is a schematic diagram of the structure of the utility model;

[0015] Figure 3 This is a schematic diagram of the structure of the adsorption sedimentation tank of this utility model.

[0016] In the figure: 1. Mechanical screen; 2. Ultrafine filter; 3. Flotation machine; 4. Equalization tank; 5. Anaerobic tank; 6. Anoxic tank; 7. Aerobic tank; 8. Secondary sedimentation tank; 9. Adsorption sedimentation tank; 901. Tank body; 902. Sludge hopper; 903. Drainage and collection channel; 904. Agitator; 905. Walkway; 906. Sludge discharge pipe. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0018] like Figure 2 As shown, the utility model discloses an AAO sewage treatment system with a front-end reduction in COD and sludge production. The technical solution adopted is as follows: it includes a mechanical screen 1, which performs preliminary filtration on sewage to remove large impurities. The mechanical screen 1 is connected to an ultrafine filter 2 to further filter suspended matter. In order to more deeply remove solid suspended matter, grease and various colloids, an air flotation machine 3 is connected to the rear end of the ultrafine filter 2. In order to make the water quality more uniform and the water volume more stable, a regulating tank 4 is set after the air flotation machine 3. The above structure is the physical treatment part in a conventional AAO sewage treatment system.

[0019] The subsequent part is the biochemical treatment. An adsorption sedimentation tank 9 is separated at the front end of the anaerobic tank 5. The sewage treated in the regulating tank 4 first enters the adsorption sedimentation tank 9, and then enters the anaerobic tank 5 together with the sludge. In the anaerobic tank 5, the polyphosphate bacteria in the sludge anaerobically release phosphorus to prepare for the subsequent excessive phosphorus absorption. Then the sewage and sludge enter the anoxic tank 6. The denitrifying bacteria will use carbon-containing organic matter as a carbon source to reduce the nitrate ions flowing back into the anoxic tank to nitrogen gas for release. Then the sewage and sludge enter the aerobic tank 7. The ammonia nitrogen in the water undergoes nitrification reaction to generate nitrate ions. At the same time, the organic matter in the water is oxidized and decomposed to supply energy to the polyphosphate bacteria. The polyphosphate bacteria absorb excessive phosphorus from the water in an aerobic environment. The phosphorus enters the cell tissue and is enriched in the microorganisms. After precipitation and separation in the secondary sedimentation tank 8, it is discharged from the system in the form of phosphorus-rich sludge and the sewage is discharged.

[0020] The phosphorus-rich sludge produced in the aerobic tank 7 is highly active sludge, so it is returned to the adsorption sedimentation tank 9 using a sludge pump and mixed with the sewage from the regulating tank 4 to adsorb organic pollutants in the sewage, such as Figure 3 As shown, the tank body 901 of the adsorption sedimentation tank 9 is a square tank structure with an open top. In order to fully mix the sludge with the sewage, an agitator 904 is installed in the tank body 901. In order to facilitate pedestrians to pass through the tank body 901 with an opening at the top, a walkway 905 is installed on the tank body 901. The motor of the agitator 904 is installed on the walkway 905, and the stirring paddle connected to the motor extends into the tank body 901. In order to lead the sewage with reduced organic pollutants to the anaerobic tank 5, a drainage collection channel 903 is set on the inner wall of the tank body 901. The drainage collection channel 903 is connected to the anaerobic tank 5 to collect sewage and part of the sewage. The sludge is directed to the anaerobic tank 5. In order to facilitate the discharge of sludge that has partially absorbed organic pollutants, a sludge hopper 902 is set in the tank body 901. The sludge hopper 902 is in the shape of an inverted cone. The bottom of the sludge hopper 902 is connected to the outside through a sludge discharge pipe 906. In order to send the sludge out of the sludge hopper 902, an installation well is opened on the side wall of the sludge hopper 902. The bottom surface of the installation well is flush with and connected to the bottom surface of the sludge hopper 902. A sludge pump (not shown in the figure) is installed in the installation well. The sludge pump is connected to the sludge discharge pipe 906 to transport the sludge. In order to prevent sewage from leaking from the sludge discharge pipe 906, a sludge discharge valve is installed on the sludge discharge pipe 906.

[0021] The working principle of this utility model:

[0022] After the sewage enters the AAO sewage treatment system, it is physically treated through the mechanical screen 1, ultrafine filter 2, flotation machine 3, and regulating tank 4, and then enters the adsorption sedimentation tank 9. At this time, the mud discharge valve on the mud discharge pipe 906 is closed.

[0023] The sewage level gradually rises within tank 901, reaching the level of drainage channel 903. It then flows through drainage channel 903 into anaerobic tank 5. After treatment in anaerobic tank 5, anoxic tank 6, and aerobic tank 7, phosphorus-rich sludge is produced in aerobic tank 7. This sludge and sewage enter secondary sedimentation tank 8 for solid-liquid separation before being discharged. A sludge pump then returns the phosphorus-rich sludge to adsorption sedimentation tank 9. The motor of agitator 904 is activated to thoroughly mix the sewage and phosphorus-rich sludge. The phosphorus-rich sludge absorbs organic pollutants in the sewage, reducing the COD content by up to 70% before biochemical treatment. Simultaneously, as agitation continues, some sludge flows along with the sewage through drainage channel 903 into anaerobic tank 5 and then into anoxic tank 6. The carbon-containing organic pollutants absorbed in the sludge serve as carbon bases for the denitrifying bacteria in anoxic tank 6 to initiate denitrification. The phosphorus-accumulating microorganisms (such as polyphosphate bacteria) in the phosphorus-rich sludge release phosphorus to meet the phosphorus demand of the bacteria in the anaerobic tank 5.

[0024] When it is necessary to discharge the excess sludge in the adsorption sedimentation tank 9, the agitator 904 stops running and stops transporting sewage and phosphorus-rich sludge to the adsorption sedimentation tank 9. After 30 minutes of sedimentation in the adsorption sedimentation tank 9, the sludge discharge valve is opened and the sludge pump in the installation well is started. Conventionally, 20% of the excess sludge is discharged every day. At this time, about 70% of the COD has been adsorbed in the sludge. Therefore, 14% of the COD in the sewage will be discharged from the system in the form of excess sludge every day, reducing the load on the subsequent biochemical units. At the same time, the residence time of the subsequent biochemical units can be appropriately shortened, the tank capacity of the tank body 901 can be reduced, and the civil engineering investment of the sewage station can be reduced.

[0025] The circuits and mechanical connections involved in the present invention are conventional means used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments, and they belong to common knowledge.

[0026] Components not described in detail herein are prior art.

[0027] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An AAO sewage treatment system with a front-end reduction in COD and sludge production, comprising a regulating tank (4) and an anaerobic tank (5), wherein the anaerobic tank (5) is connected to the rear end of the regulating tank (4), and the rear end of the anaerobic tank (5) is further connected to an anoxic tank (6), an aerobic tank (7) and a secondary sedimentation tank (8), wherein the secondary sedimentation tank (8) is provided with a sewage discharge port and a sludge outlet, and is characterized in that: The front end of the anaerobic tank (5) is provided with an adsorption sedimentation tank (9), the adsorption sedimentation tank (9) is provided with a sewage inlet, a sewage outlet and a sludge return port, and a sludge hopper (902) is provided inside. The adsorption sedimentation tank (9) is also provided with an agitator (904), the bottom surface of the sludge hopper (902) is provided with a sludge discharge pipe (906), and the top surface is provided with a drainage channel (903), the sludge discharge pipe (906) is provided with a sludge discharge valve, and the sludge discharge pipe (906) is connected to a sludge conveying device; the sludge outlet of the secondary sedimentation tank (8) is connected to the sludge return port of the adsorption sedimentation tank (9).

2. The AAO sewage treatment system with front-end COD and sludge production reduction according to claim 1 is characterized by: The adsorption sedimentation tank (9) and the anaerobic tank (5) are connected, with a partition provided between the two. The partition is provided with a water hole, and the drainage and water collection channel (903) corresponds to the position of the water hole.

3. The AAO sewage treatment system with front-end COD and sludge production reduction according to claim 1 is characterized by: The outside of the adsorption sedimentation tank (9) is a tank body (901), the sludge hopper (902) is located inside the tank body (901), and has an inverted frustum-shaped sludge cavity, and the sludge discharge pipe (906) connects the sludge cavity with the outside.

4. The AAO sewage treatment system with front-end COD and sludge production reduction according to claim 3 is characterized by: The agitator (904) further comprises a motor and a stirring paddle, wherein the stirring paddle is connected to the motor and extends into the interior of the sludge chamber.

5. The AAO sewage treatment system with front-end COD and sludge production reduction according to claim 4 is characterized by: The top of the pool body (901) is open, and the open position is covered with a platform (905), and the motor is installed on the platform (905).

6. The AAO sewage treatment system with front-end COD and sludge production reduction according to claim 3 is characterized by: The drainage and water collection channel (903) is installed on the inner wall of the tank body (901).

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