Low-cod high-ammonia-nitrogen wastewater treatment device

Abstract

This invention relates to a low-COD, high-ammonia-nitrogen wastewater treatment device, comprising: an anaerobic ammonia oxidation (A / O) biological treatment unit, a sedimentation tank, and a sludge tank; the inlet of the A / O unit is used to receive the low-COD, high-ammonia-nitrogen wastewater, the outlet of the A / O unit is connected to the inlet of the A / O biological treatment unit, and the outlet of the A / O biological treatment unit is connected to the inlet of the sedimentation tank; the sludge return outlet of the sedimentation tank is connected to the sludge return inlet of the A / O biological treatment unit, forming a sludge return loop; the sludge discharge outlet of the A / O unit is connected to the inlet of the sludge tank, and the residual sludge discharge outlet of the sedimentation tank is connected to the inlet of the sludge tank. It possesses the technical advantages of high synergistic denitrification efficiency, adaptability to low-COD characteristics, low operating cost, low carbon and environmental protection, standardized sludge disposal, strong system stability, simple process flow, and wide adaptability.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment device for low COD and high ammonia nitrogen. Background Technology

[0002] Low COD, high ammonia nitrogen wastewater is a type of difficult-to-treat wastewater commonly generated in industrial production and agricultural activities. Its core characteristic is a low ratio of chemical oxygen demand (COD) to total nitrogen (TN), which is generally less than 3. This characteristic makes it difficult for traditional biological denitrification systems that rely on organic carbon sources to operate effectively. The sources of this type of wastewater are widespread, covering multiple key industries and sectors: In the waste disposal sector, especially in leachate from landfills that have been in the middle and late stages for a long time, the easily degradable organic components have been largely consumed, while the hydrolysis of protein substances releases a large amount of ammonia nitrogen, with concentrations typically between 1000–4000 mg / L, accompanied by compound pollution such as heavy metals and high salinity; biogas slurry produced during agricultural production and livestock farming, after anaerobic fermentation to produce biogas, has largely removed organic pollutants, resulting in a lower COD content, but the ammonia nitrogen concentration remains at 800–3000 mg / L, while also being rich in phosphorus and suspended particulate matter; many production processes in the chemical industry, such as ammonia synthesis, coking ammonia stripping processes, caprolactam and acrylonitrile synthesis, will discharge high-ammonia nitrogen mother liquor or reaction wastewater, with ammonia nitrogen concentrations often exceeding 1000 mg / L. The COD value is extremely low, while the MSG fermentation tail liquid, yeast extraction wastewater and aquatic product processing wastewater in the food processing industry are enriched with ammonia nitrogen due to the hydrolysis or extraction process of protein in the raw materials, and the concentration can reach 3000-8000 mg / L. In addition, antibiotic fermentation and chemical synthesis processes in the pharmaceutical industry, acidic water steam stripping wastewater in petrochemical refining, as well as electronic semiconductor wafer grinding, metal surface treatment ammonia leaching metallurgy and other processes, will also produce low COD and high ammonia nitrogen wastewater due to the use of ammonia reagents or their own process characteristics. Municipal sludge digestion liquid and flue gas ammonia desulfurization wastewater also belong to this category.

[0003] Currently, the treatment of low-COD, high-ammonia-nitrogen wastewater mainly relies on physicochemical methods and traditional biological methods. However, both technologies have significant shortcomings, resulting in high treatment costs and making it difficult to meet the demands for large-scale, low-cost treatment. Air stripping is only suitable for the pretreatment of wastewater with extremely high ammonia-nitrogen concentrations and poses a secondary pollution problem due to ammonia-nitrogen tail gas, failing to fundamentally solve the pollution issue. Breakpoint chlorination, while offering a fast reaction rate, consumes large amounts of reagents, leading to high operating costs and easily generating toxic and harmful substances such as chlorinated disinfection byproducts, limiting its application to small-volume emergency treatment scenarios. Traditional nitrification-denitrification biological denitrification processes have strict requirements on the influent C / N ratio, typically requiring a ratio greater than 4 for effective denitrification. Therefore, when applied to low-COD, high-ammonia-nitrogen wastewater, a large amount of organic carbon source must be added, significantly increasing denitrification costs and carbon emission load, contradicting the requirements of low-carbon development. In conclusion, developing treatment technologies and supporting equipment that can achieve stable emission standards while balancing low-cost operation and low carbon emissions has become an urgent need in the environmental protection field.

[0004] Anaerobic ammonia oxidation (AAO) technology, as a novel autotrophic biological nitrogen removal technology, breaks through the technological constraints of traditional biological nitrogen removal processes. It requires no additional organic carbon source, reduces power consumption by over 60%, and simultaneously reduces carbon dioxide emissions by 90%. With its significant advantages in low cost and low carbon emissions, it provides a new approach for the efficient nitrogen removal treatment of low-COD, high-ammonia-nitrogen wastewater, and has become a research hotspot in the field of environmental engineering in recent years. Autotrophic biological nitrogen removal technology can not only efficiently remove ammonia nitrogen from wastewater, but also directly reduce fugitive carbon emissions such as CO2 and N2O, while also reducing indirect carbon emissions caused by power and chemical consumption, aligning with the trend of carbon emission reduction and showing broad application prospects. However, a single AAO treatment unit is insufficient to achieve stable compliance with emission standards after wastewater treatment. It needs to be integrated with other treatment processes to construct an integrated treatment system to achieve the goal of low-cost, efficient nitrogen removal from low-COD, high-ammonia-nitrogen wastewater. Therefore, the development of a suitable integrated treatment device has significant practical significance and application value. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a low-COD, high-ammonia-nitrogen wastewater treatment device, comprising: an anaerobic ammonia oxidation device, an A / O biological treatment device, a sedimentation tank, and a sludge tank;

[0006] The inlet of the anaerobic ammonia oxidation unit is used to receive low COD, high ammonia nitrogen wastewater. The outlet of the anaerobic ammonia oxidation unit is connected to the inlet of the A / O biological treatment unit, and the outlet of the A / O biological treatment unit is connected to the inlet of the sedimentation tank.

[0007] The sludge return port of the sedimentation tank is connected to the sludge return inlet of the A / O biological treatment unit to form a sludge return loop;

[0008] The sludge discharge port of the anaerobic ammonia oxidation unit is connected to the inlet of the sludge tank, and the residual sludge discharge port of the sedimentation tank is connected to the inlet of the sludge tank.

[0009] Furthermore, the anaerobic ammonia oxidation device includes: an outer cylinder, an inner cylinder, a flow guiding device, a flow propulsion device, an aeration device, and a crushing device;

[0010] The outer and inner cylinders form a reaction chamber;

[0011] The flow guiding device includes a two-stage housing with an internal through-filling cavity, and a sieve hole is provided at the upper end of the housing;

[0012] A flow propulsion device is installed inside the sieve holes;

[0013] The aeration device is installed inside the through hole and located below the flow propulsion device;

[0014] The crushing and screening device is located below the flow guiding device.

[0015] Furthermore, the flow guiding device includes: a first inner inclined flow guiding shell with an inverted frustum shape having an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; a first outer inclined flow guiding shell with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces; a second inner inclined flow guiding shell with an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; and a second outer inclined flow guiding shell with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces.

[0016] Furthermore, a first screen hole is provided on the inclined surface of the first inner inclined guide shell, and is evenly distributed along the circumference of the inclined surface; a second screen hole is provided on the inclined surface of the second inner inclined guide shell, and is evenly distributed along the circumference of the inclined surface; the size of the first screen hole is smaller than the size of the second screen hole.

[0017] Furthermore, a granular sludge retention regulator is installed at the lower part of the flow guiding device; the granular sludge retention regulator has a circular ring structure with a ring width of 0.4m to 0.8m, and is vertically installed at the middle of the outer side of the second outer inclined flow guiding section.

[0018] Furthermore, the flow propulsion device is located below the inner cylinder and above the inner cavity of the flow guiding device; the flow propulsion device includes: a flow propulsion shell, a drive component, a flow propulsion main shaft, and flow propulsion impeller blades; the flow propulsion shell is an inverted frustum-shaped cage-like shell with an open upper part, a closed lower part, and hollowed-out sides; the drive component is installed on the lower bottom surface of the shell; the flow propulsion main shaft is connected to the drive component and passes through the lower bottom surface from the center of the lower bottom surface of the shell, extending along the center line of the shell to the inside of the shell; the flow propulsion impeller blades are installed on the flow propulsion main shaft.

[0019] Furthermore, the crushing device is disposed in the inner cavity of the first conical cylinder of the outer cylinder and located below the flow guiding device; the crushing device includes: a frame, a drive component, a transmission shaft, a blade, and a screen.

[0020] The shell is an inverted frustum-shaped shell that is open at both the top and bottom, wider at the top and narrower at the bottom. A screen with uniform mesh is installed on the bottom surface of the shell. The upper part of the shell is connected to the lower part of the flow guiding device. The drive unit is installed on the bottom surface of the shell. The drive shaft connects the drive unit and passes through the center of the bottom surface of the shell, extending along the center line of the shell to the outside of the shell. The paddle blade is installed on the drive shaft on the outside of the bottom of the shell and is located below the screen.

[0021] Furthermore, the continuous cylinder formed by the inner cylinder and the flow guiding device, as well as the flow guiding device, the flow pushing device, the aeration device, and the crushing device, divide the inner cavity of the outer cylinder into multiple zones with different functions: the area above the impeller of the flow pushing device in the inner cylinder is the inner reaction zone, and the area below the impeller and above the crushing device is the mixing reaction zone; the annular columnar channel formed by the outer side of the inner cylinder and the inner side of the first columnar cylinder is the outer downward flow channel; the annular channel formed by the outer side of the flow guiding device and the inner side of the first columnar cylinder is the outer reaction zone; and the area between the lower end of the crushing device and the first conical cylinder is the sludge particle conditioning zone.

[0022] Furthermore, the A / O biological treatment device includes an anoxic zone, an aerobic zone, and an internal reflux pump; the anoxic zone is equipped with a stirring mechanism, the top of which is connected to the aerobic zone, and the aerobic zone is equipped with an aeration mechanism connected to an external blower; the outlet pipe of the internal reflux pump is connected to the anoxic zone, and the inlet pipe is connected to the aerobic zone, transporting the activated sludge mixture in the aerobic zone to the anoxic zone 21; the effluent from the aerobic zone is connected to the inlet of the sedimentation tank through a first connecting pipe.

[0023] Furthermore, the sedimentation tank performs solid-liquid separation on the effluent from the A / O biological treatment unit. The supernatant from the sedimentation tank is discharged in compliance with standards through the effluent pipe located at the top of the sedimentation tank. The remaining sludge obtained from sedimentation is discharged into a separate sludge tank through the sludge discharge port located at the bottom of the sedimentation tank via the second connecting pipe. Another part of the sludge enters the sludge circulation pump through the sludge discharge port via the third connecting pipe and is returned to the inlet of the anoxic zone of the A / O biological treatment unit through the fourth connecting pipe.

[0024] This invention provides a low-COD, high-ammonia-nitrogen wastewater treatment device, comprising: an anaerobic ammonia oxidation unit, an A / O biological treatment unit, a sedimentation tank, and a sludge tank; the inlet of the anaerobic ammonia oxidation unit is used to receive the low-COD, high-ammonia-nitrogen wastewater, the outlet of the anaerobic ammonia oxidation unit is connected to the inlet of the A / O biological treatment unit, and the outlet of the A / O biological treatment unit is connected to the inlet of the sedimentation tank; the sludge return outlet of the sedimentation tank is connected to the sludge return inlet of the A / O biological treatment unit, forming a sludge return loop; the sludge discharge outlet of the anaerobic ammonia oxidation unit is connected to the inlet of the sludge tank, and the residual sludge discharge outlet of the sedimentation tank is connected to the inlet of the sludge tank. It possesses the technical advantages of high synergistic denitrification efficiency, adaptability to low-COD characteristics, low operating cost, low carbon and environmental protection, standardized sludge disposal, strong system stability, simple process flow, and wide adaptability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an embodiment of the low-COD, high-ammonia-nitrogen wastewater treatment device of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of an embodiment of the anaerobic ammonia oxidation device of the present invention;

[0027] Figure 3 This is a schematic diagram of the internal flow guiding device of the anaerobic ammonia oxidation device of the present invention.

[0028] Figure 4 This is a schematic diagram of another embodiment of the internal flow guiding device of the anaerobic ammonia oxidation device of the present invention;

[0029] Figure 5 This is a schematic diagram of the internal flow propulsion device of the anaerobic ammonia oxidation apparatus of the present invention.

[0030] Figure 6 This is a top view of an embodiment of the internal flow propulsion device of the anaerobic ammonia oxidation apparatus of the present invention;

[0031] Figure 7 This is a schematic diagram of the structure of an embodiment of the internal crushing device of the anaerobic ammonia oxidation unit of the present invention;

[0032] Figure 8 This is a top view of an embodiment of the internal crushing device of the anaerobic ammonia oxidation apparatus of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that if the embodiments of the present invention involve directional indications, such as up, down, left, right, front, back, etc., these directional indications are only used to explain the relative positional relationships and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly. Furthermore, if the embodiments of the present invention involve descriptions such as "first," "second," "S1," "S2," "step one," "step two," etc., these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance, or implicitly indicating the number of technical features indicated or the order of method execution. Those skilled in the art will understand that anything that does not violate the inventive concept and is within the scope of the present invention should be included in the protection scope of the present invention.

[0035] like Figure 1 As shown, this invention provides a low-COD, high-ammonia-nitrogen wastewater treatment device. This device achieves deep denitrification and COD removal without or with only a small amount of external carbon source. The pollutants in the effluent, such as COD, BOD5, TN, and NH3-N, all meet the requirements of the "Grade B" standard of the "Water Quality Standard for Wastewater Discharge into Urban Sewerage Systems" (GB / T 31962-2015). Figure 1 As shown, taking the treatment of sludge digestion wastewater as an example, the whole device includes: anaerobic ammonia oxidation device 1, A / O biological treatment device 2, sedimentation tank 3, sludge tank 4;

[0036] The inlet of the anaerobic ammonia oxidation unit is used to receive low COD, high ammonia nitrogen wastewater. The outlet of the anaerobic ammonia oxidation unit is connected to the inlet of the A / O biological treatment unit, and the outlet of the A / O biological treatment unit is connected to the inlet of the sedimentation tank.

[0037] The sludge return port of the sedimentation tank is connected to the sludge return inlet of the A / O biological treatment unit to form a sludge return loop;

[0038] The sludge discharge port of the anaerobic ammonia oxidation unit is connected to the inlet of the sludge tank, and the residual sludge discharge port of the sedimentation tank is connected to the inlet of the sludge tank.

[0039] In this embodiment, a low-COD, high-ammonia-nitrogen wastewater treatment device of the present invention is provided, which has the following technical effects:

[0040] 1. High efficiency of synergistic denitrification, suitable for low COD characteristics: This device fully utilizes the advantage of anaerobic ammonia oxidation and A / O biological treatment through a series design, which fully leverages the advantages of anaerobic ammonia oxidation autotrophic denitrification that does not require an organic carbon source. It first efficiently removes most of the ammonia nitrogen in the wastewater, and then the A / O biological treatment device further treats the residual nitrogen and trace organic pollutants. This solves the core problem of low efficiency of traditional denitrification processes due to insufficient carbon source in low COD and high ammonia nitrogen wastewater, greatly improves the overall denitrification effect, and ensures that the nitrogen index of the effluent meets the standards stably.

[0041] 2. Low operating cost and low carbon emissions: On the one hand, the anaerobic ammonia oxidation unit does not require additional organic carbon source, which can significantly reduce the cost of carbon source addition compared with the traditional nitrification-denitrification process, while reducing carbon emissions caused by carbon source consumption; on the other hand, the sludge return design of the A / O biological treatment unit can maintain a stable concentration of microorganisms in the unit, improve the efficiency of biochemical reaction, reduce the amount of reagents added and power consumption, further reduce operating costs, and meet the needs of low carbon and environmental protection development.

[0042] 3. Standardized sludge disposal and strong system stability: By setting up a sedimentation tank to achieve sludge-water separation, the sludge is returned to the A / O biological treatment unit, which can ensure the stability of the microbial community structure within the unit and avoid the loss of microorganisms that would lead to a decrease in treatment efficiency. At the same time, the sludge produced by the anaerobic ammonia oxidation unit and the residual sludge in the sedimentation tank are collected together in a sludge tank for centralized disposal, avoiding secondary pollution caused by random sludge discharge and improving the operational stability and environmental compliance of the entire treatment system.

[0043] 4. Simple process flow and wide adaptability: The whole device adopts an integrated series structure of "anaerobic ammonia oxidation + A / O biochemistry + sedimentation", which is simple and easy to operate, without the need for complex control units; the operating parameters can be flexibly adjusted for low COD high ammonia nitrogen wastewater of different concentrations (such as landfill leachate, biogas slurry, chemical high ammonia nitrogen wastewater, etc.), adapting to various industrial wastewater treatment scenarios and with a wide range of applications.

[0044] Specifically, the anaerobic ammonia oxidation device 1 includes: an outer cylinder 11, an inner cylinder 12, a flow guiding device 13, a flow propulsion device 14, an aeration device 15, and a crushing device 16.

[0045] The outer and inner cylinders form a reaction chamber;

[0046] The flow guiding device includes a two-stage housing with an internal through-filling cavity, and a sieve hole is provided at the upper end of the housing;

[0047] A flow propulsion device is installed inside the sieve holes;

[0048] The aeration device is installed inside the through hole and located below the flow propulsion device;

[0049] The crushing and screening device is located below the flow guiding device.

[0050] Specifically: the outer cylinder 11 includes a first cylindrical body 111 containing an inner cavity and a first conical body 112 that is wider at the top and narrower at the bottom and closed at the bottom; the upper edge of the first conical body 112 has the same size as the lower edge of the first cylindrical body 111 and is connected as a whole; the upper part of the first cylindrical body 111 is provided with an outlet 113, and the bottom of the first conical body 112 is provided with a sludge discharge pipe 114; the inlet pipe 115 enters the inner cavity of the cylinder from the lower part of the first cylindrical body 111, passes through the second external inclined guide part 1312b of the guide device 13 and extends to the center of the inner cavity of the cylinder 11, and is located below the aeration device 15.

[0051] The inner cylinder 12 is a straight cylinder located at the upper part of the inner cavity of the first columnar cylinder 111, and its height is 30%-70% of the height of the outer cylinder 11. The lower edge of the inner cylinder 12 has the same geometric dimensions as the upper edge of the flow guiding device 13 and is connected to it, forming a continuous cylinder with an inner cavity, extending to the lower edge of the inner cavity of the first columnar cylinder 111. The continuous cylinder formed by the inner cylinder 12 and the flow guiding device 13 divides the inner cavity of the outer cylinder 11 into an inner reaction zone located inside and an outer reaction zone located outside and between the outer cylinder 11, and the inner and outer reaction zones are connected.

[0052] The flow guiding device 13 is a two-stage shell device with an internal through-cavity, comprising: a first inner inclined flow guiding shell 1311a with an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; a first outer inclined flow guiding shell 1312a with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces; a second inner inclined flow guiding shell 1311b with an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; and a second outer inclined flow guiding shell 1312b with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces. The lower edge geometric dimension D1 of the first inner inclined flow guiding shell 1311a is the same as the upper edge dimension of the first outer inclined flow guiding shell 1312a; the lower edge dimension D2 of the first outer inclined flow guiding shell 1312a is the same as the upper edge dimension of the second inner inclined flow guiding shell 1311b; and the lower edge dimension D3 of the second inner inclined flow guiding shell 1311b is the same as the upper edge dimension of the second outer inclined flow guiding shell 1312b. The upper edge dimensions of 312b are the same; the lower edge of shell 1311a, the upper edge of shell 1312a, the lower edge of shell 1312a, the upper edge of shell 1311b, the lower edge of shell 1311b, and the upper edge of shell 1312a are connected to form a through integral shell containing an inner cavity; the horizontal tilt angle θ1 of the first inner inclined guide shell is greater than the horizontal tilt angle θ2 of the second inner inclined guide shell; the horizontal tilt angle θ3 of the first outer inclined guide shell is less than the horizontal tilt angle θ4 of the second outer inclined guide shell; the upper edge dimension D0 of the first inner inclined guide shell is greater than the upper edge dimension D2 of the second inner inclined guide shell; the lower edge dimension D1 of the first inner inclined guide part is greater than the lower edge dimension D3 of the second inner inclined guide part; the lower edge dimension D4 of the second outer inclined guide part is greater than the upper edge dimension D0 of the first inner inclined guide part, and the dimensional relationship of each part is: D0 > D4 > D2 > D1 > D3. In this embodiment: 1m≤D0≤10m, 1 / 5D0≤D1≤1 / 2D0; more preferably, the included angle: 20≤θ1, θ2≤45 degrees; the lower horizontal included angle: 45≤θ3, θ4≤90 degrees.

[0053] The first inner inclined guide shell 1311a has a first screen hole 132a uniformly distributed along the circumference of the inclined surface; the second inner inclined guide shell 1311b has a second screen hole 132b uniformly distributed along the circumference of the inclined surface; the size of the first screen hole 132a is smaller than the size of the second screen hole 132b; the size of the second screen hole 132b is smaller than the lower edge dimension D3 of the second inner inclined guide part; the shape of the screen hole can be any one or more of the following: elongated, elliptical, circular, and square; taking square and circular as examples, the width of the square hole of the first screen hole is 1mm≤b≤3mm, and the diameter of the circular hole is 1mm≤Φ≤3mm; the size of the second screen hole 132b is 1.5 to 2 times that of the first screen hole 132a, and more preferably, the flow velocity of the screen hole is 3≤v≤300m / h.

[0054] The lower part of the flow guiding device 13 is provided with a granular sludge retention regulator 134; the granular sludge retention regulator 134 is a ring structure with a ring width of 0.4m to 0.8m, and is vertically set at the middle of the outer side of the second outer inclined flow guiding part 1312b.

[0055] The flow propulsion device 14 is located below the inner cylinder 12 and above the inner cavity (inside) of the flow guiding device 13; as shown in the attached diagram. Figure 5-6 As shown, the propulsion device includes: a propulsion housing 141, a drive component 142, a propulsion main shaft 143, and propulsion impeller blades 144; the propulsion housing 142 is an inverted frustum-shaped cage-like shell with an open upper part, a closed lower part, and hollowed-out sides; the drive component 142 is installed on the lower bottom surface of the housing; the propulsion main shaft 143 is connected to the drive component 142, passes through the lower bottom surface from the center of the housing, extends along the center line of the housing to the inside of the housing; the propulsion impeller blades 144 are installed on the propulsion main shaft 143; the propulsion housing is made of corrosion-resistant metal material, has a certain rigidity, and can withstand the weight of the propulsion device itself;

[0056] The aeration device 15 is located in the middle of the inner cavity of the second outer inclined guide shell 1312b of the flow guiding device 13, and is located below the flow stirring device 14 and above the crushing device 16. The aeration head of the aeration device adopts a swirling umbrella-shaped cutting aerator. The aeration head is maintenance-free and has a long service life. The aeration device is connected to an external blower through an air pipe 151.

[0057] The crushing device 16 is disposed inside the first conical cylinder 112 of the outer cylinder 11 and is located below the flow guiding device 13; the crushing device 16 includes: a frame 161, a driving component 162, a transmission shaft 163, a blade 164, and a screen 165.

[0058] The shell 161 is an inverted frustum-shaped shell that is open at both the top and bottom, wider at the top and narrower at the bottom. A screen 165 is installed on the bottom surface of the shell, with uniform mesh openings of 3mm in diameter. The upper part of the shell 161 is connected to the lower part of the second outer inclined guide shell 1312b of the guide device 13. The sides and bottom surface of the shell are reinforced with ribs 1661 to enhance the rigidity of the shell. The drive component 162 is installed on the bottom surface of the shell. The drive shaft 163 connects the drive component 162, passes through the center of the bottom surface of the shell, and extends along the center line of the shell to the outside of the shell. The paddle cutter 164 is installed on the drive shaft 163 on the outer side of the bottom of the shell and is located below the screen 165. The rotation diameter of the paddle cutter is equal to the diameter of the bottom surface of the shell 161. The shell is made of corrosion-resistant metal and has a certain rigidity, which can withstand the weight of the crushing device itself.

[0059] The continuous cylinder formed by the inner cylinder 12 and the flow guiding device 13, along with the flow guiding device 13, the flow pushing device 14, the aeration device 15, and the crushing device 16, divide the inner cavity of the outer cylinder 11 into multiple zones with different functions: the area above the impeller of the flow pushing device 14 in the inner cylinder is the inner reaction zone (aerobic reaction zone) 1B, and the area below the impeller and above the crushing device 16 is the mixing reaction zone 1F; the annular columnar channel formed by the outer side of the inner cylinder 12 and the inner side of the first columnar cylinder 111 is the outer downward flow channel 1C; the annular channel formed by the outer side of the flow guiding device 13 and the inner side of the first columnar cylinder 111 is the outer reaction zone 1D; and the area between the lower end of the crushing device 16 and the first conical cylinder 112 is the sludge particle conditioning zone 1E.

[0060] The effluent from the anaerobic ammonia oxidation unit is transported to the anoxic zone 21 of the A / O biological treatment unit 2 via pipeline 28.

[0061] The A / O biological treatment device 2 includes an anoxic zone 21, an aerobic zone 22, and an internal reflux pump 24. The anoxic zone 21 is equipped with a stirring mechanism 27, the top of which is connected to the aerobic zone 22. The aerobic zone 22 is equipped with an aeration mechanism 26 connected to an external blower. The outlet pipe 23 of the internal reflux pump 24 is connected to the anoxic zone 21, and the inlet pipe 25 is connected to the aerobic zone 22, transporting the activated sludge mixture from the aerobic zone to the anoxic zone 21. The effluent from the aerobic zone is connected to the inlet of the sedimentation tank 3 via a first connecting pipe 27.

[0062] The sedimentation tank 3 adopts the existing gravity sedimentation tank technology to perform solid-liquid separation on the effluent of the A / O biological treatment device 2. The supernatant of the sedimentation tank is discharged in compliance with the standard through the effluent pipe 31 located at the top of the sedimentation tank. The remaining sludge obtained by sedimentation is discharged into the separately set sludge tank 4 through the sludge discharge port 32 located at the bottom of the sedimentation tank and the second connecting pipe 33. Another part of the sludge enters the sludge circulation pump 34 through the sludge discharge port 32 and the third connecting pipe 35, and is returned to the inlet of the anoxic zone 21 of the A / O biological treatment device through the fourth connecting pipe 36.

[0063] The working process of this invention is as follows: After pretreatment (such as removing impurities by using a screen), the high ammonia nitrogen organic wastewater enters the anaerobic ammonia oxidation device through the inlet. The anaerobic ammonia oxidation device 4 is a vertical flow reactor, whose main function is to form and maintain a high concentration of anaerobic ammonia oxidation granular sludge. Under low oxygen conditions, it partially nitrifies the ammonia nitrogen in the wastewater, converting it into nitrite. Then, through the anaerobic ammonia oxidation reaction, the nitrite and ammonia nitrogen are converted into nitrogen gas and removed from the wastewater. The anaerobic ammonia oxidation device includes an outer cylinder, an inner cylinder, a flow guiding device, a flow propulsion device, an aeration device, and a crushing device. The inner cylinder and the flow guiding device form a continuous cylinder. The flow guiding device, the flow propulsion device, the aeration device, and the crushing device divide the inner cavity of the outer cylinder into multiple interconnected zones with different functions: the area above the impeller of the flow propulsion device in the inner cylinder is the inner reaction zone (aerobic reaction zone) 1B, and the area below the impeller and above the crushing device is the mixing reaction zone 1F; the annular columnar channel formed by the outer side of the inner cylinder and the inner side of the first columnar cylinder 111 is the outer downward flow channel 1C; the annular channel formed by the outer side of the flow guiding device and the inner side of the first columnar cylinder 111 is the outer reaction zone 1D; and the area between the lower end of the crushing device and the first conical cylinder 112 is the sludge particle conditioning zone 1E. The aeration device aerates upwards, and combined with the propulsion device, it pushes the air upwards, causing the inner reaction zone, the mixing reaction zone, and the particle conditioning zone to form an upward flow, while the outer downward flow channel and the outer reaction zone form a downward flow. This creates a circulating flow pattern inside the anaerobic ammonia oxidation device, with the inner cylinder cavity rising upwards and the outer cylinder cavity falling downwards.

[0064] The wastewater to be treated enters the mixing reaction zone inside the guide device 13 of the anaerobic ammonia oxidation device from below the aeration device through the inlet pipe, and mixes with the sewage and granular sludge in the device. Under the action of the upward flow, it flows upward, passes above the aeration device and enters the inner reaction zone (aerobic reaction zone). Under the action of oxygen provided by aeration and ammonia-oxidizing bacteria in the mixed liquid, the ammonia nitrogen in the wastewater is oxidized to nitrite nitrogen. This area mainly completes the nitrification of ammonia nitrogen. Under the upward push of the wastewater and granular sludge mixed liquid, it continues to flow from the upper edge of the inner cylinder 12 into the outer downward flow channel and the outer reaction zone. There is no aeration device in the outer downward flow channel and the outer reaction zone. The anaerobic ammonia-oxidizing bacteria in the anaerobic ammonia oxidation granular sludge in the mixed liquid absorb the ammonia nitrogen and nitrite nitrogen in the wastewater in a low-oxygen or anaerobic environment, convert them into nitrogen gas and remove them from the wastewater.

[0065] The first inner inclined guide shell 1311a of the flow guiding device 13 has a first screen hole 132a on its inclined surface; the second inner inclined guide shell 1311b has a second screen hole 132b on its inclined surface; the size of the first screen hole 132a is smaller than the size of the second screen hole 132b; when the wastewater and granular sludge mixture flows through the outer reaction zone, some wastewater and small granular sludge particles with particle sizes smaller than the first and second screen holes pass through the first and second screen holes under the negative pressure generated by the flow pushing device 14 and flow back into the mixing reaction zone and the inner reaction zone. Granular sludge particles with particle sizes larger than the screen hole sizes continue to flow downward along the outer reaction zone. Some large-sized granular sludge particles are intercepted by the granular sludge retention regulator 134 set on the second outer inclined guide surface of the flow guiding device, so that the sludge residence time (SRT) of large granular sludge particles is separated from the hydraulic residence time (HRT), extending the residence time of granular sludge particles in the outer reaction zone, and using the low-oxygen and anaerobic environment of the outer reaction zone to remove more nitrite nitrogen and ammonia nitrogen.

[0066] The mixture of some large-diameter granular sludge and wastewater bypasses the granular sludge retention regulator and the bottom edge of the flow guiding device and enters the granular conditioning zone 1E. The large-diameter granular sludge is crushed by the crushing device 16, which separates the inorganic components from the biological active components in the large-diameter granular sludge (usually aged granular sludge). The inorganic components sink to the bottom of the outer cylinder and are discharged through the sludge discharge port 114. The biological active components (new granular sludge) pass through the screen 165 of the crushing device and enter the mixing reaction zone, where they continue to rise and flow, continue to undergo internal circulation, and continuously grow to form larger-diameter granular sludge. Thanks to the differences in the size and position of the screen holes on the flow guiding device 13, the through holes in the inner cavity of the flow guiding device 13, and the screens on the crushing device 16, the separation of clear liquid, flocculent sludge and fine particles, medium and large particles and large particles is achieved. Taking the sludge-water mixture of the sewage biological treatment system as an example, clear liquid, flocculent sludge and small particle sludge can enter the inner reaction zone through the small-sized screen holes (first screen holes) to carry out internal circulation; medium and large particle sludge (density slightly greater than water) is intercepted and can only fall down along the flow guiding device under the action of inertia, and enter the mixing reaction zone through the large-sized screen holes (second screen holes) to carry out internal circulation; large particle sludge (density greater) cannot pass through the screen holes of each layer, and can only bypass the bottom edge of the flow guiding device to enter the particle conditioning zone 16, pass through the screen of the sludge crushing device, and then rise and flow through the mixing reaction zone to enter the inner reaction zone.

[0067] This invention features a propulsion device 14 located at the upper part of the inner cavity of the flow guiding device 13, which pushes the mixed liquid upward. An aeration device is positioned in the middle of the inner cavity of the flow guiding device 13, below the propulsion device. This allows the gas introduced by the aeration device to move upward and combine with flocs or granular sludge, increasing the upward flow velocity. This, combined with the propulsion device positioned at the sieve openings, further amplifies the upward flow velocity of the mixed liquid. The upper inclined guide member of the flow guiding device 13 expands the upward flow in the lower part of the inner cavity, driving the fluid below to rise, thus creating a strong negative pressure near the sieve openings. This continuously draws fluid from outside the flow guiding device into the inner cavity through the sieve openings, accelerating the internal circulation process in the upper part of the reactor and promoting the granulation of the anaerobic ammonia oxidation sludge. Particulate matter and bubbles carried in the mixed liquid rise in their direction of motion, exhibiting turbulent flow. Large bubbles can be broken down into smaller bubbles by the propulsion device. Tiny bubbles that may be carried in the particulate matter are further dispersed by the turbulent flow and the propulsion device. Separation occurs through mutual collisions and other effects. After degassing, the particulate matter can better contact or adsorb dissolved substances in a turbulent mixing state. The crushing device located at the bottom of the inner cavity of the anaerobic ammonia oxidation device (near the granular conditioning zone) can crush large-diameter granular sludge particles that bypass the lowest edge of the guide device 13, separating the inorganic components from the biologically active components in the large-diameter granular sludge particles (usually aged granular sludge). The inorganic components sink to the bottom of the outer cylinder and are discharged through the sludge discharge port 114, while the biologically active components (new granular sludge) continue to rise and flow after entering the mixing reaction zone, continuing internal circulation and growing to form larger-diameter granular sludge. The aerobic reaction zone (i.e., the inner reaction zone 1B) and the anaerobic reaction zone (i.e., the outer reaction zone 1D) of the anaerobic ammonia oxidation device of this invention are completely separated, and the aerobic and anaerobic functional microorganisms cooperate efficiently, accelerating the sludge granulation speed, continuously renewing the granular sludge, and efficiently coordinating physical mass transfer and biochemical reactions, thereby improving the overall efficiency of pollution degradation reaction.

[0068] The effluent from the anaerobic ammonia oxidation unit is piped to the A / O biological treatment unit for further removal of pollutants. The A / O biological treatment unit is a conventional anoxic / aerobic activated sludge process. It removes pollutants such as COD, ammonia nitrogen, and total nitrogen from wastewater through the metabolism of activated sludge. The sludge-water mixture from the A / O biological treatment unit undergoes solid-liquid separation in sedimentation tank 3, intercepting sludge, suspended solids, and some large organic molecules in the wastewater. The supernatant obtained after sedimentation meets discharge standards. A portion of the settled sludge is returned to the anoxic zone of the A / O biological treatment unit, while the remaining sludge is discharged as surplus sludge into a separate sludge tank.

[0069] Compared with the prior art, the present invention has the following features and technical effects:

[0070] The main denitrification unit of this invention adopts anaerobic ammonia oxidation denitrification, which can save a lot of external carbon source costs and aeration power consumption, and reduce carbon emissions compared with the traditional nitrification-denitrification denitrification process.

[0071] The anaerobic ammonia oxidation device of the present invention includes at least three improvements: 1. A flow-pushing device is installed at the sieve hole position to push the flow upward; 2. The aeration device is moved into the through hole and is located below the flow-pushing device, not below the entire flow-guiding device; 3. A crushing and screening device is installed below the entire flow-guiding device. These three core inventive points form a structured flow-guiding module, and its key advantage over the prior art mentioned in the background section is:

[0072] A: A flow-pushing device is installed at the sieve opening position; its main function is to reduce the internal circulation time of particles at this position: because the particle size that can pass through the sieve opening is very small, it does not require much reaction time. The flow-pushing device pushes the flow upward, which can drive the fluid below and to the side to rise, thereby forming a negative pressure below and to the side of the sieve opening. The fluid is continuously drawn into the side through the sieve opening of the guide component, selectively causing small particles such as clear water and flocs to rise rapidly, reducing the internal circulation residence time, thereby accelerating the internal circulation of the upper layer, accelerating the clear liquid output efficiency of the purified water outlet, improving the overall circulation efficiency and purification effect of the vertical flow reactor, and reducing the purification time.

[0073] B: The aeration component is moved into the flow guiding device and located below the flow propulsion device, but not below the entire flow guiding device. This has two main functions: 1. Moving it into the flow guiding device, close to the flow propulsion device, creates a synergistic structure, increasing the upward flow velocity and solving the bubble problem: After the gas introduced by the aeration device moves upward, it can quickly combine with the clear water, flocs, and other small-diameter granular sludge particles above, increasing the upward flow velocity. This, combined with the flow propulsion device located at the screen opening, further increases the upward flow velocity of the mixed liquor. More importantly, particles carried in the fluid will rise along the direction of fluid movement, exhibiting turbulent flow. Tiny bubbles that may be carried in the particles will be amplified by the turbulent flow and aeration. Separation occurs through the mutual collision of the device and the flow-driving device; after degassing, the particulate matter can better contact or adsorb with dissolved substances in a turbulent mixing state; 2. The aeration device is set inside the flow-driving device, not below it, which can completely isolate the upper internal circulation (small particles passing through the sieve holes) from the lower internal circulation (large particles blocked by the sieve holes but entering through the through holes), preventing the lower internal circulation particles from contacting the aeration device too early, providing more space and more reaction time for the lower non-clean water, such as large sludge particles blocked by the sieve holes but entering through the through holes, promoting the circulation effect of the lower non-clean water, and comprehensively improving the overall reaction effect;

[0074] C: A crushing and screening device is installed below the flow guiding device; this can accelerate the crushing of large-diameter sludge particles falling from above during the continuous growth of large-diameter sludge particles, increase the exposed area of ​​inorganic matter, promote the anaerobic reaction at this stage, further improve the reaction efficiency, and accelerate the process of participating in the internal circulation.

[0075] The design of the combination and specific positions of the four structures—the flow guiding device, the flow pushing device, the aeration device, and the crushing device—is the result of the inventor's creative labor based on the different requirements of particles of different sizes in the vertical flow reactor for reaction time, reaction position, and circulation trajectory. It is not a simple selection of conventional technology. The flow guiding module of this invention ingeniously conceives the flow guiding device, the flow pushing device, the aeration device, and the crushing and screening device into an integrated system. They work together to exert their effects, and none of them can be missing. It is perfectly applicable to granular sludge systems that have both aerobic and anaerobic conditions. It fundamentally overcomes the inherent defects of activated sludge and packing biofilm systems, such as the lack of selectivity of functional microorganisms and the blockage caused by excessive accumulation of biofilm. The propulsion device at the top of the inner cavity of the flow guiding device and the aeration device below it can create negative pressure near the screen holes, accelerate the internal circulation of the upper clear liquid, promote the aerobic (nitrification) reaction, and directly separate it from the internal circulation of the bottom granular sludge, forming completely different movement paths for clear liquid (sewage) and sludge (anaerobic ammonia oxidation granular sludge). This achieves separation of sewage retention time and sludge retention time within the same reactor. Furthermore, it significantly extends the retention (reaction) time of the anaerobic ammonia oxidation granular sludge under anaerobic conditions, accumulating more anaerobic ammonia oxidation functional microorganisms with slow self-proliferation rates, which is beneficial for improving the efficiency of anaerobic ammonia oxidation reaction and provides favorable conditions for efficient synergy among different functional microorganisms, thereby enhancing the overall autotrophic denitrification effect. In addition, the crushing and screening device below further crushes the aged, large-diameter granular sludge, separates inorganic components, promotes the renewal of granular sludge, and further improves reaction efficiency. Its beneficial effects are self-evident.

[0076] The device of this invention can achieve low-carbon and low-cost treatment of high ammonia nitrogen organic wastewater. This invention can replace the traditional membrane separation process and does not produce nanofiltration membrane or reverse osmosis membrane concentrate that requires secondary treatment, providing a new equipment for the treatment of high ammonia nitrogen organic wastewater.

[0077] The influent water quality of the sludge digestion wastewater in this embodiment is as follows: COD: 500–700 mg / L, BOD5: 100–200 mg / L, TN: 750–1200 mg / L, NH3-N: 700–1100 mg / L, SS: 500–1000 mg / L, pH: 6–8. The pollutant concentrations and removal rates of the effluent after treatment by the device of this invention are as follows:

[0078]

[0079] All pollutant indicators in the effluent were better than the limits of the "Class B standard" in the "Water Quality Standard for Wastewater Discharge into Urban Sewers (GB / T 31962-2015)".

[0080] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A wastewater treatment device for low COD and high ammonia nitrogen, characterized in that, include: The system includes an anaerobic ammonia oxidation unit, an A / O biological treatment unit, a sedimentation tank, and a sludge tank. The inlet of the anaerobic ammonia oxidation unit is used to receive low-COD, high-ammonia-nitrogen wastewater. The outlet of the anaerobic ammonia oxidation unit is connected to the inlet of the A / O biological treatment unit, and the outlet of the A / O biological treatment unit is connected to the inlet of the sedimentation tank. The sludge return outlet of the sedimentation tank is connected to the sludge return inlet of the A / O biological treatment unit, forming a sludge return loop. The sludge discharge port of the anaerobic ammonia oxidation device is connected to the inlet of the sludge tank, and the residual sludge discharge port of the sedimentation tank is connected to the inlet of the sludge tank; wherein, the anaerobic ammonia oxidation device includes: an outer cylinder, an inner cylinder, a flow guiding device, a flow propulsion device, an aeration device, and a crushing and screening device; the outer cylinder and the inner cylinder form a reaction chamber; the outer cylinder includes a first cylindrical body containing an inner cavity and a first conical cylinder that is wider at the top and narrower at the bottom and closed at the bottom; The flow guiding device is a two-stage shell with an internal through-cavity, comprising: a first inner inclined flow guiding shell with an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; a first outer inclined flow guiding shell with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces; a second inner inclined flow guiding shell with an inner cavity that is wider at the top and narrower at the bottom and open at both the top and bottom surfaces; and a second outer inclined flow guiding shell with an inner cavity that is narrower at the top and wider at the bottom and open at both the top and bottom surfaces; a sieve hole is provided at the upper end of the shell; The propulsion device is located below the inner cylinder and above the inner cavity of the flow guiding device. It includes: a propulsion shell, a propulsion drive component, a propulsion main shaft, and propulsion impeller blades. The propulsion shell is an inverted frustum-shaped cage-like shell with an open upper part, a closed lower part, and hollowed-out sides. The propulsion drive component is installed on the lower bottom surface of the propulsion shell. The propulsion main shaft is connected to the propulsion drive component and extends from the center of the lower bottom surface of the propulsion shell through the lower bottom surface, along the center line of the propulsion shell, into the interior of the propulsion shell. The propulsion impeller blades are installed on the propulsion main shaft. The aeration device is installed inside the through hole of the flow guiding device and is located below the flow propulsion device; The crushing and screening device is located inside the first conical cylinder of the outer cylinder and below the flow guiding device. It includes: a shell frame, a crushing drive component, a drive shaft, a paddle cutter, and a screen. The shell frame is an inverted frustum-shaped shell that is open at both the top and bottom, wider at the top and narrower at the bottom. A screen with uniform mesh openings is installed on the bottom surface of the shell frame. The upper part of the shell frame is connected to the lower part of the flow guiding device. The crushing drive component is installed on the bottom surface of the shell frame. The drive shaft connects the crushing drive component, passes through the center of the bottom surface of the shell frame, and extends along the center line of the shell frame to the outside of the shell frame. The paddle cutter is installed on the drive shaft on the outer side of the bottom of the shell frame and is located below the screen.

2. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The upper edge of the first conical cylinder is the same size as the lower edge of the first cylindrical cylinder and they are connected as a whole. The upper part of the first cylindrical cylinder is provided with a water outlet, and the bottom of the first conical cylinder is provided with a sludge discharge pipe. The water inlet pipe enters the inner cavity of the cylinder from the lower part of the first cylindrical cylinder, passes through the second outer inclined guide shell of the guide device, and extends to the center of the inner cavity of the first cylindrical cylinder, and is located below the aeration device.

3. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The inner cylinder is a straight cylinder located at the upper part of the inner cavity of the first columnar cylinder, with a height of 30%-70% of the height of the outer cylinder. The lower edge of the inner cylinder has the same geometric dimensions as the upper edge of the flow guiding device and is connected to it, forming a continuous cylinder with an internal cavity, extending to the lower edge of the inner cavity of the first columnar cylinder. The continuous cylinder formed by the inner cylinder and the flow guiding device divides the inner cavity of the outer cylinder into an inner reaction zone located inside and an outer reaction zone located outside and between the outer cylinder, with the inner and outer reaction zones connected.

4. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The first inner inclined guide shell has a first screen hole on its inclined surface, which is evenly distributed along the circumference of the inclined surface; the second inner inclined guide shell has a second screen hole on its inclined surface, which is evenly distributed along the circumference of the inclined surface; the size of the first screen hole is smaller than the size of the second screen hole.

5. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The lower part of the flow guiding device is equipped with a granular sludge retention regulator; the granular sludge retention regulator is a circular ring structure with a ring width of 0.4m to 0.8m, and is vertically installed at the middle of the outer side of the second outer inclined flow guiding shell.

6. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The continuous cylinder formed by the inner cylinder and the flow guiding device, along with the flow guiding device, the flow pushing device, the aeration device, and the crushing and screening device, divides the inner cavity of the outer cylinder into multiple zones with different functions: the area above the impeller of the flow pushing device in the inner cylinder is the inner reaction zone, and the area below the impeller and above the crushing and screening device is the mixing reaction zone; the annular columnar channel formed by the outer side of the inner cylinder and the inner side of the first columnar cylinder is the outer downward flow channel; the annular channel formed by the outer side of the flow guiding device and the inner side of the first columnar cylinder is the outer reaction zone; and the area between the lower end of the crushing and screening device and the first conical cylinder is the sludge particle conditioning zone.

7. The low-COD, high-ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that, The A / O biological treatment unit includes an anoxic zone, an aerobic zone, and an internal reflux pump. The anoxic zone is equipped with a stirring mechanism, the top of which is connected to the aerobic zone. The aerobic zone is equipped with an aeration mechanism connected to an external blower. The outlet pipe of the internal reflux pump is connected to the anoxic zone, and the inlet pipe is connected to the aerobic zone, transporting the activated sludge mixture in the aerobic zone to the anoxic zone. The effluent from the aerobic zone is connected to the inlet of the sedimentation tank through a first connecting pipe.

8. The low-COD, high-ammonia nitrogen wastewater treatment device according to any one of claims 1 to 7, characterized in that, The sedimentation tank performs solid-liquid separation on the effluent from the A / O biological treatment unit. The supernatant from the sedimentation tank is discharged through the effluent pipe located at the top of the sedimentation tank, and the remaining sludge obtained from sedimentation is discharged into the sludge tank through the sludge discharge port located at the bottom of the sedimentation tank via the second connecting pipe. Another part of the sludge enters the sludge circulation pump through the sludge discharge port via the third connecting pipe, and is returned to the inlet of the anoxic zone of the A / O biological treatment unit through the fourth connecting pipe.

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