A low dissolved oxygen sewage treatment system and method

Abstract

The present invention belongs to the technical field of sewage treatment, and discloses a low dissolved oxygen sewage treatment system and method. The system includes an equipment control area, a low oxygen area, an air stripping area, a clarification area and a recirculation area. Sewage enters the low oxygen area, and an aeration pipe is arranged in the low oxygen area. The blower oxygenates the low oxygen area through the aeration pipe. An air stripping area is arranged at the rear end of the low oxygen area, and the sewage at the rear end of the low oxygen area is lifted to the front end of the low oxygen area by an air lifter. The sludge mixed liquid enters the clarification area after passing through the air stripping area, and the supernatant flows from bottom to top into the upper water collection weir, and the sludge is lifted to the front end of the low oxygen area by the recirculation pump at the rear end of the clarification area. The present invention controls the dissolved oxygen concentration in the low oxygen area within a relatively low range, which can realize the simultaneous nitrification and denitrification of the system, simplify the process, effectively improve the utilization rate of the carbon source in the raw water, and reduce the amount of carbon source added. The system and method of the present invention have the characteristics of small footprint, simple system operation, high degree of automation and low energy consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and more specifically, relates to a low dissolved oxygen sewage treatment system and method. Background Art

[0002] At present, the rapid construction of sewage treatment plants has brought about a huge demand for sewage treatment operation resources. With the acceleration of urbanization, a large number of sewage treatment plants have been built, and the existing professional operation and maintenance teams cannot meet the growing demand for operation and maintenance capabilities. Especially in small and medium-sized sewage treatment plants, which account for a large proportion, it is difficult for operation and maintenance units to find professional operation and maintenance personnel. At present, the main reason for the unstable operation of most sewage treatment plants is insufficient operation strength. In addition, there are other reasons such as industrial water mixing, large fluctuations in influent water quality, insufficient influent carbon source, and complex process design.

[0003] At present, the urban sewage treatment processes put into operation include oxidation, A2 / O process, activated sludge process and SBR, etc. The existing sewage treatment processes generally have the following shortcomings: first, the utilization rate of the carbon source of the influent is not high, resulting in the addition of additional carbon sources; second, the degree of automation is not high, requiring a professional operation and maintenance team; third, the ability to resist shock loads is weak, and it is difficult to achieve stable compliance when the influent water quality fluctuates.

[0004] Therefore, it is urgent to propose a system and sewage treatment process with low energy consumption, high degree of automation and ability to withstand shock loads, so as to solve the problems of existing small and medium-sized sewage treatment plants, such as long process flow, low degree of automation and frequent mixing of industrial sewage with influent, so as to meet the increasingly stringent demands for water environment supervision. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and to propose a low dissolved oxygen sewage treatment system and method. The present invention controls the dissolved oxygen concentration in the low oxygen zone within a relatively low range to achieve system synchronous nitrification and denitrification, simplify the process, effectively improve the utilization rate of carbon sources in raw water, and reduce the amount of carbon source added. The system and method of the present invention have the characteristics of small footprint, simple system operation, high degree of automation and low energy consumption.

[0006] In order to achieve the above-mentioned object, the present invention provides a low dissolved oxygen sewage treatment system on one hand, which comprises an equipment control area, a low oxygen area, a gas stripping area, a clarification area and a reflow area;

[0007] The equipment control area includes a blower, a frequency conversion control device and a dissolved oxygen meter; one end of the dissolved oxygen meter is connected to the frequency conversion control device, and the other end of the dissolved oxygen meter is arranged in the low oxygen area; one end of the blower is connected to the frequency conversion control device;

[0008] The hypoxic zone comprises a hypoxic zone tank body, a water distribution device, a traction rope, a guide groove, an aeration pipe, a blast branch pipe, a diverter valve and an air inlet pipe; the water distribution device is arranged above the hypoxic zone tank body, and is used to evenly supply water to the hypoxic zone tank body; the guide groove is arranged at the bottom of the hypoxic zone tank body, and the aeration pipe is arranged in the guide groove; one end of the traction rope is fixedly connected to the hypoxic zone tank body, and the other end of the traction rope is connected to the aeration pipe, the blast branch pipe, the diverter valve and the air outlet of the air inlet pipe in sequence;

[0009] The air lift area includes an air lift area tank body, an air lift, an air lift duct, a sewage return pipe and a return tank; the air lift is arranged in the air lift area tank body, the air outlet of the air lift duct is connected to the air lift, the air lift is used to send the sewage in the air lift area tank body into the water inlet of the return tank through the sewage return pipe, and the water outlet of the return tank is arranged at the front end of the hypoxic area tank body;

[0010] The other end of the blower is connected to the air inlet of the air inlet pipe and the air inlet of the air lift pipe;

[0011] The clarification zone includes a clarification zone tank body, a bottom water inlet, an inclined tube group and a water collection weir; the bottom water inlet is arranged at the bottom of the tank body wall between the gas stripping zone and the clarification zone; the water collection weir is arranged above the inclined tube group, and the inclined tube group and the water collection weir are used to achieve solid-liquid separation of the sludge mixed liquid in the clarification zone;

[0012] A mud inlet is provided at the bottom of the pool body wall between the recirculation zone and the clarification zone; the recirculation zone includes a recirculation pump and a sludge recirculation pipe, one end of the sludge recirculation pipe is connected to the recirculation pump, and the other end of the sludge recirculation pipe is connected to the water inlet of the recirculation tank.

[0013] According to the present invention, preferably,

[0014] The water distribution device comprises a water inlet pipe, a water distribution weir and a level regulator;

[0015] The water inlet pipe is arranged above the water distribution weir;

[0016] The horizontal regulator is used to fix the water distribution weir horizontally in the low oxygen zone.

[0017] According to the present invention, preferably, the water distribution weir is a sawtooth stainless steel water distribution weir, the weir plate height is 15-25 cm, and the opening depth is 10-20 cm.

[0018] According to the present invention, preferably,

[0019] The aeration tubes include an odd-number aeration tube and an even-number aeration tube;

[0020] The blast branch pipes include an odd-numbered blast branch pipe and an even-numbered blast branch pipe;

[0021] The diverter valve includes an odd-number diverter valve and an even-number diverter valve;

[0022] The other end of the traction rope is connected to one end of the odd-numbered aeration pipe and one end of the even-numbered aeration pipe respectively; the other end of the odd-numbered aeration pipe is connected to the odd-numbered blast branch pipe and the odd-numbered diverter valve in sequence; the other end of the even-numbered aeration pipe is connected to the even-numbered blast branch pipe and the even-numbered diverter valve in sequence;

[0023] The odd-numbered flow divider valve and the even-numbered flow divider valve are both connected to the air outlet of the air inlet pipe.

[0024] In the present invention, as a preferred solution, during normal aeration, both the odd-numbered diverter valve and the even-numbered diverter valve are opened.

[0025] According to the present invention, preferably, both the odd-numbered aeration tubes and the even-numbered aeration tubes are strip-type hoses made of PU material, and the widths of the hoses are independently 60-70 mm.

[0026] According to the present invention, preferably, the odd-numbered aeration tubes and the even-numbered aeration tubes are arranged at a spacing of 5-20 cm.

[0027] According to the present invention, preferably, the inclined tube group comprises a plurality of inclined tubes, the spacing between the inclined tubes is 45-55 mm, and the length of each inclined tube is 0.5-1.5 m.

[0028] According to the present invention, preferably, the clarification zone comprises an upper clear water layer and a lower sludge layer, the upper clear water layer has a height of 0.5-1 m, and the lower sludge layer has a height of 0.5-1.5 m.

[0029] Another aspect of the present invention provides a method for treating low dissolved oxygen wastewater, which adopts the system and comprises the following steps:

[0030] Adding activated sludge into the hypoxic zone tank body; uniformly introducing water into the hypoxic zone tank body through the water distribution device; controlling the dissolved oxygen concentration in the hypoxic zone tank body through the equipment control area;

[0031] In the gas stripping area, the sludge mixed liquid entering the gas stripping area tank body is returned to the front end of the hypoxic area tank body through the sewage return pipe by gas stripping action;

[0032] In the clarification zone, the solid-liquid separation of the sludge mixture is achieved by using the shallow pool principle to obtain precipitated sludge and supernatant, the precipitated sludge enters the reflow zone through the sludge inlet, and the supernatant is discharged from the system through the water collection weir;

[0033] In the reflow zone, the settled sludge is reflowed to the front end of the low oxygen zone tank body through the reflow pump.

[0034] According to the present invention, preferably, the concentration of activated sludge in the hypoxic zone tank is 5000 mg / l-7000 mg / l.

[0035] According to the present invention, preferably, the ventilation volume of the aeration pipe in the hypoxic zone is 0.5-1m 3 / mh, bubble particle size is 20-50μm, and bubble rising speed is 0.3-0.8m / s.

[0036] According to the present invention, preferably, the dissolved oxygen concentration in the hypoxic zone pool is controlled to be 0.5-1.0 mg / l by the equipment control zone. In the present invention, the dissolved oxygen meter in the equipment control zone can detect the dissolved oxygen in the biochemical system of the hypoxic zone, and the frequency conversion control device calculates the frequency of the blower according to the dissolved oxygen concentration.

[0037] According to the present invention, preferably, the bubble particle size of the air lifter is 15-25 μm.

[0038] According to the present invention, preferably, the reflux ratio of the sludge mixed liquid returned from the air stripping area to the front end of the low oxygen area tank body is 20-30 times. In the present invention, the air lift adopts a small bubble lifting method, and the bubble particle size of the air lift is a tiny bubble of 15-25μm, which reduces the density of the mixed liquid and relies on the buoyancy of the gas to achieve a large amount of water with a small lift.

[0039] According to the present invention, preferably, the flow rate of the settled sludge entering the recirculation zone through the sludge inlet is above 0.3 m / s.

[0040] In the present invention, after the sludge mixed liquid passes through the bottom water inlet, the supernatant passes through the inclined tube from bottom to top and enters the water collection weir.

[0041] In the present invention, the working principle of the present invention is as follows: First, the sewage is passed through the water distribution device to achieve uniform water distribution in the low oxygen zone. After entering the low oxygen zone, the sewage is fully mixed with the activated sludge in the low oxygen zone. The dissolved oxygen in the low oxygen zone is monitored online by the dissolved oxygen meter, and the frequency conversion control device controls the blower frequency according to the monitoring data of the dissolved oxygen meter and its built-in program algorithm, so that the dissolved oxygen in the low oxygen zone is controlled at 0.5-1.0 mg / l. The distance between two adjacent aeration pipes in the low oxygen zone is 10-15 cm, and the low ventilation volume is controlled, so that a group of microbubbles with uniform size and low speed rising, which is densely distributed along the entire pool body, increases the gas-liquid contact area, prolongs the gas-liquid contact time, and improves the total transfer coefficient of oxygen. Due to the implementation of the low dissolved oxygen oxygen supply mode, the driving force of oxygen mass transfer is increased, thereby increasing the transfer rate of oxygen in the liquid phase. In this way, the limited DO can be fully utilized by microorganisms, that is, the apparent DO concentration in the liquid phase can be controlled to be very low or even zero. Under this condition, the activated sludge system undergoes synchronous nitrification and denitrification to achieve the removal of COD, TN and ammonia nitrogen in sewage.

[0042] The air lift area at the rear end of the hypoxic zone realizes sludge return from the rear end to the front end through an air lift, with a return ratio of 20-30 times. Because the air lift duct and the air inlet duct are supplied by a unified blower, the frequency conversion control device can adjust the air supply and circulation flow of the aeration zone synchronously with the change of the incoming water, which is conducive to balancing the pollutant load, avoiding large fluctuations in oxygen demand, and facilitating real-time control of low dissolved oxygen.

[0043] After passing through the air stripping area, the sewage enters the clarification area. The sludge passes through the lower sludge layer at the bottom of the clarification area by gravity. The flow rate of the precipitated sludge entering the recirculation area through the sludge inlet is above 0.3m / s to avoid sludge silting in the clarification area and the recirculation area and anaerobic fermentation. The supernatant enters the upper water collection weir through the inclined pipe, and finally achieves mud and water separation, and the sewage meets the discharge standards. The inclined pipe in the clarification area can effectively improve the mud and water separation efficiency of the clarification area by using the shallow pool principle.

[0044] The beneficial effects of the technical solution of the present invention are as follows:

[0045] The system of the present invention has a strong adaptability to changes in sewage concentration, which is mainly due to the following two designs: first, the sewage can be evenly distributed in the biochemical pool through the water distribution device; second, the sewage passes through the air lift at the end of the low-oxygen zone, and the sludge mixture at the end of the low-oxygen zone is raised to the front end. The reflux ratio is 20-30 times. The large reflux ratio can quickly dilute the incoming water.

[0046] The blower of the system of the present invention can save more than 40% energy compared with the blower of the conventional sewage treatment system, which is mainly due to the following two designs: First, the system of the present invention is equipped with a proprietary dissolved oxygen frequency conversion control device to control the dissolved oxygen at 0.5-1.0 mg / l. Low dissolved oxygen not only reduces the energy consumption of the blower, but also increases the proportion of simultaneous nitrification and denitrification, effectively reducing the dosage of carbon source; second, the system of the present invention adopts a unique PU material aeration tube. Compared with the traditional aerator, the bubble particle size of the aeration tube is 20-50μm. The smaller bubble particle size reduces the rising speed of the bubble in the mixed liquid by half, and the residence time is doubled. At the same time, smaller bubbles also bring a larger contact area, effectively improving the oxygen utilization rate.

[0047] The system of the present invention saves 30% of the floor space compared with the conventional sewage treatment system, which is mainly due to two designs. First, the activated sludge concentration of the system is about 5000mg / l-7000mg / l, which is 60% higher than that of the conventional activated sludge system. The sludge volume per unit volume is large, resulting in a small floor space in the low-oxygen zone. Second, the clarification zone utilizes the shallow layer principle and adds an inclined tube design, which increases the sedimentation efficiency of the clarification zone by 50%, further reducing the floor space of the clarification zone.

[0048] The system of the present invention has a large reflux ratio and low dissolved oxygen settings, and is particularly suitable for sewage with the following characteristics: first, the influent TN is greater than 75mg / l, and the carbon source is insufficient, and the influent C / N is less than 4; second, the influent fluctuates greatly, and the coefficient of variation of COD and ammonia nitrogen is greater than 2; third, there is some industrial water and difficult-to-degrade COD in the influent, and the BOD / COD is less than 0.3. After being treated by the system of the present invention, the effluent can stably meet the discharge standards, and can be directly used for reclaimed water reuse or landscape water reuse in some areas.

[0049] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0051] Figure 1 A schematic diagram of a low dissolved oxygen sewage treatment system provided in Example 1 of the present invention is shown.

[0052] The following are the descriptions of the reference numerals:

[0053] 1-water inlet pipe, 2-water distribution weir, 3-low oxygen zone, 4-traction rope, 5-sludge mixture, 6-aeration pipe,

[0054] 9-low oxygen zone tank body, 10-dissolved oxygen meter, 11-odd blast branch pipe, 12-even blast branch pipe, 13-odd diverter valve, 14-air inlet pipe, 15-air lift air duct, 16-reflow trough, 17-blower, 18-frequency control device, 19-sludge return pipe, 20-air lift zone, 21-sewage return pipe, 22-air lifter, 23-inclined pipe group, 24-water collection weir, 25-clarification zone, 26-reflow zone, 27-reflow pump, 28-bottom water inlet, 29-even diverter valve, 30-air lift zone tank body, 31-clarification zone tank body, 32-sludge inlet, 33-reflow zone tank body. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0056] Example 1

[0057] This embodiment provides a low dissolved oxygen sewage treatment system, such as Figure 1 As shown, the system includes an equipment control area, a low oxygen area 3, a gas stripping area 20, a clarification area 25 and a reflux area 26;

[0058] The equipment control area includes a blower 17, a frequency conversion control device 18 and a dissolved oxygen meter 10; one end of the dissolved oxygen meter 10 is connected to the frequency conversion control device 18, and the other end of the dissolved oxygen meter 10 is arranged in the hypoxic area 3; one end of the blower 17 is connected to the frequency conversion control device 18;

[0059] The hypoxic zone 3 includes a hypoxic zone tank body 9, a water distribution device, a traction rope 4, a guide groove (not shown), an aeration pipe 6, a blast branch pipe, a diverter valve and an air inlet pipe 14; the water distribution device is arranged above the hypoxic zone tank body 9, and is used to evenly supply water to the hypoxic zone tank body 9, and the water distribution device includes a water inlet pipe 1, a water distribution weir 2 and a horizontal regulator (not shown); the water inlet pipe 1 is arranged above the water distribution weir 2; the horizontal regulator is used to fix the water distribution weir 2 horizontally in the hypoxic zone 3; the water distribution weir 2 is a serrated stainless steel water distribution weir, the weir plate height is 20 cm, and the opening depth is 15 cm; the guide groove is arranged at the bottom of the hypoxic zone tank body 9, the aeration pipe 6 is arranged in the guide groove, the aeration pipe 6 includes an odd aeration pipe and an even aeration pipe, the blast The wind branch pipe includes an odd-numbered blast branch pipe 11 and an even-numbered blast branch pipe 12, and the diverter valve includes an odd-numbered diverter valve 13 and an even-numbered diverter valve 29; one end of the traction rope 4 is fixedly connected to the hypoxic zone pool body 9, and the other end of the traction rope 4 is respectively connected to one end of the odd-numbered aeration pipe and one end of the even-numbered aeration pipe; the other end of the odd-numbered aeration pipe is connected to the odd-numbered blast branch pipe 11 and the odd-numbered diverter valve 13 in sequence; the other end of the even-numbered aeration pipe is connected to the even-numbered blast branch pipe 12 and the even-numbered diverter valve 29 in sequence; the odd-numbered diverter valve 13 and the even-numbered diverter valve 29 are both connected to the air outlet of the air inlet pipe 14; the odd-numbered aeration pipe and the even-numbered aeration pipe are both strip-type hoses made of PU material, and the hose width is 65mm; the odd-numbered aeration pipe and the even-numbered aeration pipe are arranged at a spacing of 10cm.

[0060] The air lift area 20 includes an air lift area tank body 30, an air lift 22, an air lift air duct 15, a sewage return pipe 21 and a return groove 16; the air lift 22 is arranged in the air lift area tank body 30, the air outlet of the air lift air duct 15 is connected to the air lift 22, the air lift 22 is used to send the sewage in the air lift area tank body 30 into the water inlet of the return groove 16 through the sewage return pipe 21, and the water outlet of the return groove 16 is arranged at the front end of the hypoxic zone tank body 9;

[0061] The other end of the blower 17 is connected to the air inlet of the air inlet pipe 14 and the air inlet of the air lift pipe 15;

[0062] The clarification zone 25 includes a clarification zone tank body 31, a bottom water inlet 28, an inclined tube group 23 and a water collection weir 24; the bottom water inlet 28 is arranged at the bottom of the tank body wall between the gas stripping zone 20 and the clarification zone 25; the water collection weir 24 is arranged above the inclined tube group 23, and the inclined tube group 23 and the water collection weir 24 are used to achieve solid-liquid separation of the sludge mixed liquid in the clarification zone 25; the inclined tube group 23 includes a plurality of inclined tubes, the spacing between each inclined tube is 50mm, and the length of each inclined tube is 1m. The clarification zone 25 includes an upper clear water layer and a lower sludge layer, the height of the upper clear water layer is 0.5-1m, and the height of the lower sludge layer is 1m;

[0063] A mud inlet 32 ​​is provided at the bottom of the pool wall between the recirculation zone 26 and the clarification zone 25 ; the recirculation zone 26 includes a recirculation pump 27 and a sludge recirculation pipe 19 , one end of the sludge recirculation pipe 19 is connected to the recirculation pump 27 , and the other end of the sludge recirculation pipe 19 is connected to the water inlet of the recirculation tank 16 .

[0064] The method for treating low dissolved oxygen sewage using the above system includes the following steps:

[0065] Add activated sludge into the hypoxic zone tank body 9; uniformly introduce water into the hypoxic zone tank body through the water distribution device; control the dissolved oxygen concentration in the hypoxic zone tank body to be 0.5-1.0 mg / l through the equipment control area; wherein the activated sludge concentration in the hypoxic zone tank body is 5000 mg / l-7000 mg / l; the ventilation volume of the aeration pipe in the hypoxic zone is 0.5-1m 3 / mh, bubble diameter is 20-50μm, bubble rising speed is 0.5m / s;

[0066] In the air stripping area 20, the sludge mixed liquid entering the air stripping area tank body 30 is refluxed to the front end of the hypoxic area tank body 9 through the sewage return pipe 21 by air stripping; wherein the bubble particle size of the air lift 22 is 20 μm; the reflux ratio of the sludge mixed liquid refluxed from the air stripping area 20 to the front end of the hypoxic area tank body 9 is 20-30 times;

[0067] In the clarification zone 25, the solid-liquid separation of the sludge mixture is achieved by using the shallow pool principle to obtain precipitated sludge and supernatant. The precipitated sludge enters the reflow zone 26 through the mud inlet 32 ​​with a flow rate of more than 0.3 m / s. The supernatant is discharged from the system through the water collection weir 24.

[0068] In the reflow zone 26 , the precipitated sludge is reflowed to the front end of the low oxygen zone tank body 9 through the reflow pump 27 .

[0069] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for treating low dissolved oxygen wastewater, characterized in that: The system used in the method includes an equipment control area, a low oxygen area, a gas stripping area, a clarification area and a reflux area; The equipment control area includes a blower, a frequency conversion control device and a dissolved oxygen meter; one end of the dissolved oxygen meter is connected to the frequency conversion control device, and the other end of the dissolved oxygen meter is arranged in the low oxygen area; One end of the blower is connected to a frequency conversion control device; The hypoxic zone comprises a hypoxic zone tank body, a water distribution device, a traction rope, a guide groove, an aeration pipe, a blast branch pipe, a diverter valve and an air inlet pipe; the water distribution device is arranged above the hypoxic zone tank body, and is used to evenly supply water to the hypoxic zone tank body; the guide groove is arranged at the bottom of the hypoxic zone tank body, and the aeration pipe is arranged in the guide groove; one end of the traction rope is fixedly connected to the hypoxic zone tank body, and the other end of the traction rope is connected to the aeration pipe, the blast branch pipe, the diverter valve and the air outlet of the air inlet pipe in sequence; The air lift area includes an air lift area tank body, an air lift, an air lift duct, a sewage return pipe and a return tank; the air lift is arranged in the air lift area tank body, the air outlet of the air lift duct is connected to the air lift, the air lift is used to send the sewage in the air lift area tank body into the water inlet of the return tank through the sewage return pipe, and the water outlet of the return tank is arranged at the front end of the hypoxic area tank body; The other end of the blower is connected to the air inlet of the air inlet pipe and the air inlet of the air lift pipe; The clarification zone includes a clarification zone tank body, a bottom water inlet, an inclined tube group and a water collection weir; the bottom water inlet is arranged at the bottom of the tank body wall between the gas stripping zone and the clarification zone; the water collection weir is arranged above the inclined tube group, and the inclined tube group and the water collection weir are used to achieve solid-liquid separation of the sludge mixed liquid in the clarification zone; A mud inlet is provided at the bottom of the tank body wall between the recirculation zone and the clarification zone; the recirculation zone includes a recirculation pump and a sludge recirculation pipe, one end of the sludge recirculation pipe is connected to the recirculation pump, and the other end of the sludge recirculation pipe is connected to the water inlet of the recirculation tank; The method comprises the following steps: Adding activated sludge into the hypoxic zone tank body; uniformly introducing water into the hypoxic zone tank body through the water distribution device; controlling the dissolved oxygen concentration in the hypoxic zone tank body through the equipment control area; In the gas stripping area, the sludge mixed liquid entering the gas stripping area tank body is returned to the front end of the hypoxic area tank body through the sewage return pipe by gas stripping action; In the clarification zone, the solid-liquid separation of the sludge mixture is achieved by using the shallow pool principle to obtain precipitated sludge and supernatant, the precipitated sludge enters the reflow zone through the sludge inlet, and the supernatant is discharged from the system through the water collection weir; In the reflow zone, the precipitated sludge is reflowed to the front end of the low oxygen zone tank body through the reflow pump; The ventilation volume of the aeration pipe in the hypoxic zone is 0.5-1m 3 / mh, bubble diameter is 20-50μm, bubble rising speed is 0.3-0.8m / s; The dissolved oxygen concentration in the hypoxic zone pool is controlled to be 0.5-1.0 mg / l by the equipment control zone; The bubble particle size of the air lifter is 15-25 μm; The reflux ratio of the sludge mixed liquid from the gas stripping area to the front end of the hypoxic area tank body is 20-30 times; The flow rate of the settled sludge entering the recirculation zone through the sludge inlet is above 0.3 m / s; The influent TN is greater than 75 mg / l, and the carbon source is insufficient; the influent C / N is lower than 4; the coefficient of variation of influent COD and ammonia nitrogen is greater than 2; the influent BOD / COD is lower than 0.

3.

2. The method for treating low dissolved oxygen wastewater according to claim 1, wherein: The water distribution device comprises a water inlet pipe, a water distribution weir and a level regulator; The water inlet pipe is arranged above the water distribution weir; The horizontal regulator is used to fix the water distribution weir horizontally in the low oxygen zone.

3. The method for treating low dissolved oxygen sewage according to claim 2, wherein: The water distribution weir is a sawtooth stainless steel water distribution weir, the weir plate height is 15-25cm, and the opening depth is 10-20cm.

4. The method for treating low dissolved oxygen wastewater according to claim 1, wherein: The aeration tubes include an odd-number aeration tube and an even-number aeration tube; The blast branch pipes include an odd-numbered blast branch pipe and an even-numbered blast branch pipe; The diverter valve includes an odd-number diverter valve and an even-number diverter valve; The other end of the traction rope is connected to one end of the odd-numbered aeration pipe and one end of the even-numbered aeration pipe respectively; the other end of the odd-numbered aeration pipe is connected to the odd-numbered blast branch pipe and the odd-numbered diverter valve in sequence; the other end of the even-numbered aeration pipe is connected to the even-numbered blast branch pipe and the even-numbered diverter valve in sequence; The odd-numbered flow divider valve and the even-numbered flow divider valve are both connected to the air outlet of the air inlet pipe.

5. The method for treating low dissolved oxygen wastewater according to claim 4, wherein: The odd-numbered aeration tubes and the even-numbered aeration tubes are both strip-type hoses made of PU material, and the width of the hoses is independently 60-70 mm; The odd-numbered aeration tubes and the even-numbered aeration tubes are arranged at a spacing of 5-20 cm.

6. The method for treating low dissolved oxygen wastewater according to claim 1, wherein: The inclined tube group comprises a plurality of inclined tubes, the spacing between the inclined tubes is 45-55 mm, and the length of each inclined tube is 0.5-1.5 m.

7. The method for treating low dissolved oxygen wastewater according to claim 1, wherein: The clarification zone includes an upper clear water layer and a lower sludge layer, the upper clear water layer has a height of 0.5-1 m, and the lower sludge layer has a height of 0.5-1.5 m.

8. The method for treating low dissolved oxygen wastewater according to claim 1, wherein: The concentration of activated sludge in the hypoxic zone tank is 5000mg / l-7000mg / l.

Images