Deep denitrification system and method

Abstract

The invention discloses an advanced denitrification system and method for sewage treatment. The system comprises an anaerobic tank, a membrane aeration biological reaction tank, a fixed bed biological membrane reaction tank and an aerobic tank which are communicated in sequence. Inoculation is carried out through external return sludge, and nitrified sludge flows back from the aerobic tail end to the front end of the third anoxic tank. Waste gas of the membrane aeration bio-membrane reactor is controlled through a time sequence, and two purposes are achieved, one purpose is membrane scrubbing of the membrane aeration bio-membrane reactor; and secondly, the flexible filler of the fixed bed bio-membrane reactor is scrubbed, the membrane thickness can be controlled to avoid anaerobic fermentation of sludge so as to achieve the purpose of one gas with two purposes, and meanwhile, the power of a stirrer is saved, so that the energy consumption of the fixed bed bio-membrane reaction tank is reduced on the basis of improving the overall denitrification efficiency.

Description

Technical Field

[0001] The present invention relates to a system and method for deep denitrification of sewage treatment, and in particular to a system and method for deep denitrification. Background Art

[0002] Municipal wastewater treatment plants currently remove nitrogen by increasing the volume of anoxic tanks, adding large amounts of carbon sources to them, or adding denitrification filters or sulfur autotrophic denitrification filters to the advanced treatment stages, which require the addition of carbon sources. These processes all present challenges such as high reagent costs and high energy consumption.

[0003] To conserve carbon sources, current approaches include installing MABR reactors with simultaneous nitrification and denitrification in the anoxic section of biological reactors, and adding fillers to the anoxic section of activated sludge reactors to create FBBR processes to increase the anoxic sludge age. However, MABR reactors are expensive, and FBBR processes require increased agitation power. High sludge concentrations also require perforated air pipes to clean the flexible fillers to prevent the formation of an anaerobic environment that could cause sludge floating or even bulges in the flexible filler supports. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a deep denitrification system and method that utilizes the exhaust gas of the MABR to perform perforated aeration on the FBBR to save energy and improve the denitrification effect.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A deep denitrification system according to the present invention comprises a tank body, wherein three partitions are arranged at intervals on the left and right sides of the tank body so that the tank body is sequentially arranged from left to right to include an anaerobic tank, a membrane aerated biological reactor, a fixed-bed biofilm reactor and an aerobic tank separated from and connected to each other, wherein a stirrer is installed in each of the anaerobic tank, the membrane aerated biological reactor and the fixed-bed biofilm reactor, a membrane aerated biofilm reactor is installed in the membrane aerated biological reactor, and a fixed-bed biofilm reactor is installed in the fixed-bed biofilm reactor, wherein a first perforated pipe and a second perforated pipe are respectively installed horizontally in the membrane aerated biological reactor below the membrane aerated biofilm reactor and in the fixed-bed biofilm reactor below the fixed-bed biofilm reactor, the anaerobic tank is connected to the outlet of a sewage water pipeline, the aerobic tank is connected to a secondary sedimentation tank via a sewage pipeline, the effluent of the secondary sedimentation tank is discharged to subsequent treatment via a discharge pipeline, the settled sludge in the secondary sedimentation tank is partially returned to the anaerobic tank via an external return sludge pipeline, and partially discharged to a sludge treatment unit via a residual sludge pipeline;

[0007] The blower supplies air to the membrane aeration biofilm reactor and the fixed bed biofilm reactor through the membrane aeration bioreactor gas supply pipe and the aerobic tank gas supply pipe respectively. The outlet of the membrane aeration bioreactor gas supply pipe is arranged in the membrane aeration bioreactor, and the outlet of the aerobic tank gas supply pipe is arranged in the aerobic tank. The head end of the exhaust pipe is connected to the outlet of the membrane aeration biofilm reactor exhaust main pipe of the membrane aeration biofilm reactor, and the end is divided into two exhaust pipe branches. The first exhaust pipe branch equipped with a first control valve is connected to the first perforated pipe, which plays a role in membrane aeration. The bottom of the second exhaust pipe branch equipped with a second control valve is connected to the second perforated pipe, and part of the aerobic tank effluent is refluxed through the nitrification liquid reflux main pipe. The nitrification liquid reflux main pipe is connected to two branch pipes. The first branch pipe is connected to the inlet of the membrane aeration biological reaction tank so that part of the nitrification liquid is refluxed to the inlet of the membrane aeration biological reaction tank through the first branch pipe; the second branch pipe is connected to the inlet of the fixed bed biofilm reaction tank so that part of the nitrification liquid is refluxed to the fixed bed biofilm reaction tank through the second branch pipe.

[0008] A deep denitrification method of the present invention comprises the following steps:

[0009] Pollutant removal process: The pre-treated sewage is transported to the anaerobic tank through the sewage supply pipeline. At the same time, the return sludge from the secondary sedimentation tank is transported to the anaerobic tank through the external return sludge pipeline for mud-water mixing and sufficient anaerobic phosphorus release. The sewage after phosphorus release enters the membrane aerated biological reactor; the blower inputs air to the membrane aerated biological reactor through the membrane aerated biological reactor air supply pipeline, and at the same time, aeration is supplied to the aerobic tank through the aerobic tank air supply pipeline. With the participation of oxygen in the air, ammonia nitrogen and COD in the influent, the membrane aerated biological reactor performs simultaneous nitrification and denitrification; membrane aerated biological reactor The mud-water mixture in the water flows into the fixed-bed biofilm reactor through the holes in the partition wall between the membrane aeration biological reactor and the fixed-bed biofilm reactor under the action of gravity for further denitrification, and then flows into the aerobic tank through the holes in the partition wall between the fixed-bed biofilm reactor and the aerobic tank under the action of gravity for decarbonization and nitrification; finally, it is discharged into the secondary sedimentation tank through the sewage pipe, and finally discharged to the subsequent treatment structure through the sewage discharge pipe; part of the settled sludge in the secondary sedimentation tank is returned to the anaerobic tank through the external return sludge pipe, and part is discharged to the sludge treatment unit through the residual sludge pipe;

[0010] Sludge nitrification liquid return process: The sludge nitrification liquid in the aerobic tank is divided into two return pipelines through the external return sludge pipe. The sludge nitrification liquid in one pipeline is returned to the membrane aeration biological reactor, and the sludge nitrification liquid in the other pipeline is returned to the fixed bed biofilm reactor;

[0011] Membrane scrubbing process: After air is input into the membrane aeration bioreactor through the membrane aeration bioreactor air supply pipe, part of the oxygen is utilized, and the remaining oxygen and most of the nitrogen are discharged through the exhaust pipe. Part of the exhaust gas is discharged to the first perforated pipe at the bottom of the membrane aeration bioreactor through the first exhaust pipe branch equipped with a first control valve for membrane scrubbing, and the other part of the exhaust gas is discharged to the second perforated pipe at the bottom of the fixed bed biofilm reactor through the second exhaust pipe branch equipped with a second control valve for membrane scrubbing. In this process, the amount of exhaust gas entering the first exhaust pipe branch and the second exhaust pipe branch is controlled by adjusting the opening of the first control valve and the second control valve.

[0012] The beneficial effects of the present invention are:

[0013] The device and method of the present invention primarily couples a membrane aerated bioreactor (MABR) and a fixed-bed biofilm reactor (FBBR) system for application in the anoxic section of a bioreactor: the MABR system is positioned in front, performing simultaneous nitrification and denitrification; the FBBR system is positioned in the back, performing denitrification and denitrification. Air is supplied to the MABR system by a blower system, where oxygen is utilized, generating exhaust gas containing a small amount of residual oxygen and a large amount of inert nitrogen. By adjusting a first control valve and a second control valve, the membranes of the MABR and FBBR systems are scrubbed, respectively. This reduces the required stirring power and mitigates various issues, such as sludge anaerobicity caused by excessive biofilm thickness in the MABR and FBBR systems, achieving dual-use while saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a system diagram of the deep denitrification system of the present invention. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1The deep denitrification system of the present invention shown in FIG. 1 includes a tank body, wherein three partitions are provided on the left and right sides of the tank body, so that the tank body is sequentially arranged from left to right to form an anaerobic tank 2, a membrane aerated biological reactor 3, a fixed-bed biofilm reactor 4, and an aerobic tank 5, which are separated and connected from each other. A stirrer 14 is installed in each of the anaerobic tank, the membrane aerated biological reactor, and the fixed-bed biofilm reactor. A membrane aerated biological reactor 23 is installed in the membrane aerated biological reactor, and a fixed-bed biofilm reactor 24 is installed in the fixed-bed biofilm reactor. A first perforated pipe 20 and a second perforated pipe 19 are installed horizontally in the membrane aerated biological reactor below the membrane aerated biological reactor and in the fixed-bed biofilm reactor below the fixed-bed biofilm reactor, respectively. The anaerobic tank is connected to the outlet of the sewage water pipe 1. The aerobic tank is connected to the secondary sedimentation tank 7 via a sewage pipe 6, and the effluent of the secondary sedimentation tank is discharged through a discharge pipe 8 for subsequent treatment. Part of the settled sludge in the secondary sedimentation tank 7 is returned to the anaerobic tank through the external return sludge pipe 10, and part is discharged to the sludge treatment unit through the residual sludge pipe 9.

[0017] Blower 15 supplies air to membrane aerated biofilm reactor 3 and fixed-bed biofilm reactor 4 via membrane aerated bioreactor gas supply pipe 16 and aerobic tank gas supply pipe 17, respectively. The outlet of membrane aerated bioreactor gas supply pipe 16 is located within the membrane aerated bioreactor, and the outlet of aerobic tank gas supply pipe 17 is located within the aerobic tank. The exhaust gas pipe 18 is connected at its head end to the outlet of the membrane aerated biofilm reactor exhaust main pipe of the membrane aerated biofilm reactor. The tail end is divided into two exhaust gas pipe branches. The first exhaust gas pipe branch, equipped with a first control valve 21, is connected to the first perforated pipe 20 to clean the membrane. The second exhaust gas pipe branch, equipped with a second control valve 22, is connected at its bottom to the second perforated pipe 19. Part of the effluent from the aerobic tank is refluxed through the nitrification liquid reflux main pipe 11. The nitrification liquid reflux main pipe 11 is connected to two branch pipes. The first branch pipe 13 is connected to the inlet of the membrane aeration biological reaction tank 3, so that part of the nitrification liquid is refluxed to the inlet of the membrane aeration biological reaction tank 3 through the first branch pipe; the second branch pipe 12 is connected to the inlet of the fixed bed biofilm reaction tank, so that part of the nitrification liquid is refluxed to the fixed bed biofilm reaction tank 4 through the second branch pipe.

[0018] See Figure 1 , a deep denitrification method, comprising the following steps:

[0019] Pollutant removal process: The pre-treated sewage is transported to the anaerobic tank 2 through the sewage supply pipe 1. At the same time, the return sludge from the secondary sedimentation tank 7 is transported to the anaerobic tank through the external return sludge pipe 10 for mud-water mixing and sufficient anaerobic phosphorus release. The sewage after phosphorus release enters the membrane aerated bioreactor 3; the blower 15 inputs air to the membrane aerated bioreactor 23 through the membrane aerated bioreactor air supply pipe 16, and at the same time aerates the aerobic tank 5 through the aerobic tank air supply pipe 17. With the participation of oxygen in the air and ammonia nitrogen and COD in the influent, the membrane aerated bioreactor performs simultaneous nitrification and denitrification; the mud-water mixture in the membrane aerated bioreactor 3 passes through the holes in the partition wall between the membrane aerated bioreactor 3 and the fixed-bed biofilm reactor 4. It flows into the fixed-bed biofilm reaction tank 4 under the action of gravity for further denitrification, and then flows into the aerobic tank 5 under the action of gravity through the holes in the partition wall between the fixed-bed biofilm reaction tank 4 and the aerobic tank 5 for decarbonization and nitrification; finally, it is discharged into the secondary sedimentation tank 7 through the sewage pipe 6, and finally discharged to the subsequent treatment structure through the sewage discharge pipe 8; part of the settled sludge in the secondary sedimentation tank 7 is returned to the anaerobic tank through the external return sludge pipe 10, and part is discharged to the sludge treatment unit through the residual sludge pipe 9.

[0020] Sludge nitrification liquid return process: The sludge nitrification liquid in the aerobic tank is divided into two return pipelines through the external return sludge pipe 10. The sludge nitrification liquid in one pipeline returns to the membrane aeration biological reactor 3, and the sludge nitrification liquid in the other pipeline returns to the fixed bed biofilm reactor 4.

[0021] Membrane scrubbing process: After air is input into the membrane aeration bioreactor 23 through the membrane aeration bioreactor air supply pipe 16, part of the oxygen is utilized, and the remaining oxygen and most of the nitrogen are discharged through the exhaust pipe 18. Part of the exhaust gas is discharged to the first perforated pipe at the bottom of the membrane aeration bioreactor 23 through the first exhaust pipe branch equipped with a first control valve 21 for membrane scrubbing, and the other part of the exhaust gas is discharged to the second perforated pipe at the bottom of the fixed bed biofilm reactor 24 through the second exhaust pipe branch equipped with a second control valve 22 for membrane scrubbing. In this process, the amount of exhaust gas entering the first exhaust pipe branch and the second exhaust pipe branch is controlled by adjusting the opening of the first control valve 21 and the second control valve 22.

[0022] Parts not mentioned in this application, such as the detection of dissolved oxygen concentration in the membrane aerated bioreactor, the detection of ammonia nitrogen concentration and dissolved oxygen concentration in the effluent of the aerobic tank, and the detection of sludge content in the secondary sedimentation tank, can be carried out using existing technologies. For example, a dissolved oxygen meter can be installed in the membrane aerated bioreactor to detect the dissolved oxygen concentration in the aerated water. The air flow in the membrane aerated bioreactor air supply pipe 16 is measured by a first air flow meter 27 installed in the membrane aerated bioreactor air supply pipe, and the aeration volume is adjusted to avoid excessive aeration by controlling the air regulating valve 25 installed in the membrane aerated bioreactor air supply pipe 16. An online ammonia nitrogen meter and a dissolved oxygen meter are installed in the aerobic tank to measure the ammonia nitrogen concentration and dissolved oxygen concentration in the effluent of the aerobic tank. A second air flow meter 28 installed in the aerobic tank air supply pipe 17 measures the air flow entering the aerobic tank air supply pipe 17. The air flow can be controlled by adjusting the control regulating valve 26 in the aerobic tank air supply pipe. Since the above content does not belong to the component of the present invention, it is only used as an example.

Claims

1. A deep denitrification system, comprising a tank body, wherein three partitions are arranged at intervals on the left and right sides of the tank body so that the tank body is sequentially arranged from left to right into an anaerobic tank (2), a membrane aeration biological reactor (3), a fixed bed biofilm reactor (4) and an aerobic tank (5) which are separated from each other and connected to each other, and a stirrer (14) is installed in each of the anaerobic tank, the membrane aeration biological reactor and the fixed bed biofilm reactor, characterized in that: A membrane aeration biofilm reactor (23) is installed in the membrane aeration bioreactor tank, a fixed bed biofilm reactor (24) is installed in the fixed bed biofilm reactor tank, a first perforated pipe (20) and a second perforated pipe (19) are respectively installed in the membrane aeration bioreactor tank below the membrane aeration biofilm reactor and the fixed bed biofilm reactor below the fixed bed biofilm reactor in the horizontal direction, the anaerobic tank is connected to the outlet of the sewage water pipe (1), the aerobic tank is connected to the secondary sedimentation tank (7) through the sewage pipe (6), the effluent of the secondary sedimentation tank is discharged to subsequent treatment through the discharge pipe (8), the precipitated sludge in the secondary sedimentation tank is partially returned to the anaerobic tank through the external return sludge pipe (10), and partially discharged to the sludge treatment unit through the residual sludge pipe (9); The blower (15) supplies air to the membrane aeration biofilm reactor (3) and the fixed bed biofilm reactor (4) through the membrane aeration bioreactor gas supply pipe (16) and the aerobic tank gas supply pipe (17), respectively. The outlet of the membrane aeration bioreactor gas supply pipe (16) is arranged in the membrane aeration bioreactor, and the outlet of the aerobic tank gas supply pipe is arranged in the aerobic tank. The exhaust gas pipe (18) is connected at its head end to the outlet of the exhaust gas main pipe of the membrane aeration biofilm reactor of the membrane aeration biofilm reactor, and at its tail end is divided into two exhaust gas pipe branches. The first exhaust gas pipe branch equipped with a first control valve (21) is connected to the first perforated pipe (20). The second branch pipe (12) is connected to the membrane aeration bioreactor tank, and plays the role of membrane scrubbing. The bottom of the second exhaust pipe branch equipped with a second control valve (22) is connected to the second perforated pipe (19). Part of the aerobic tank effluent is refluxed through the nitrification liquid reflux main pipe (11). The nitrification liquid reflux main pipe is connected to two branch pipes. The first branch pipe (13) is connected to the inlet of the membrane aeration bioreactor tank so that part of the nitrification liquid is refluxed to the inlet of the membrane aeration bioreactor tank through the first branch pipe; the second branch pipe (12) is connected to the inlet of the fixed bed biofilm reactor tank so that part of the nitrification liquid is refluxed to the fixed bed biofilm reactor tank (4) through the second branch pipe.

2. A deep denitrification method, applied to the deep denitrification system according to claim 1, characterized in that The following steps are involved: Pollutant removal process: The pretreated sewage is transported to the anaerobic tank through the sewage supply pipeline. At the same time, the return sludge from the secondary sedimentation tank is transported to the anaerobic tank through the external return sludge pipeline for mud-water mixing and sufficient anaerobic phosphorus release. The sewage after phosphorus release enters the membrane aerated biological reactor; the blower inputs air into the membrane aerated biological reactor through the membrane aerated biological reactor air supply pipeline, and at the same time, aerates the aerobic tank through the aerobic tank air supply pipeline. With the participation of oxygen, COD in the air, the membrane aerated biological reactor carries out simultaneous nitrification and denitrification; the mud-water mixture in the membrane aerated biological reactor flows into the fixed-bed biofilm reactor through the holes in the partition wall between the membrane aerated biological reactor and the fixed-bed biofilm reactor under the action of gravity, further undergoes denitrification, and then flows into the aerobic tank through the holes in the partition wall between the fixed-bed biofilm reactor and the aerobic tank under the action of gravity for decarbonization and nitrification; finally, it is discharged into the secondary sedimentation tank through the sewage pipeline, and finally discharged to the subsequent treatment structure through the sewage discharge pipeline; Part of the settled sludge in the secondary sedimentation tank is returned to the anaerobic tank through the external return sludge pipe, and part is discharged to the sludge treatment unit through the residual sludge pipe; Sludge nitrification liquid return process: The sludge nitrification liquid in the aerobic tank is divided into two return pipelines through the external return sludge pipe. The sludge nitrification liquid in one pipeline is returned to the membrane aeration biological reactor, and the sludge nitrification liquid in the other pipeline is returned to the fixed bed biofilm reactor; Membrane scrubbing process: After air is input into the membrane aeration bioreactor through the membrane aeration bioreactor air supply pipe, part of the oxygen is utilized, and the remaining oxygen and most of the nitrogen are discharged through the exhaust pipe. Part of the exhaust gas is discharged to the first perforated pipe at the bottom of the membrane aeration bioreactor through the first exhaust pipe branch equipped with a first control valve for membrane scrubbing, and the other part of the exhaust gas is discharged to the second perforated pipe at the bottom of the fixed bed biofilm reactor through the second exhaust pipe branch equipped with a second control valve for membrane scrubbing. In this process, the amount of exhaust gas entering the first exhaust pipe branch and the second exhaust pipe branch is controlled by adjusting the opening of the first control valve and the second control valve.

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