A biological and ecological coupling denitrification sewage treatment system

Abstract

This invention relates to a wastewater treatment system for biological and ecological coupled denitrification, comprising a biological tank, a sedimentation device, and an ecological treatment device connected in sequence. The biological tank has an anoxic zone inside and a transition zone and an aerobic zone outside. The bottom of the anoxic zone is connected to the transition zone, and the transition zone is connected to the aerobic zone through a stripping pipe for biological treatment of wastewater. The outlet of the aerobic zone is connected to the sedimentation device, and the sludge discharged from the bottom of the sedimentation device can be returned to the anoxic zone. The effluent pipe of the sedimentation device is connected to the ecological treatment device. The ecological treatment device includes, from top to bottom, a plant layer, a filter media layer, a quartz sand layer, a support layer, and a collection tank, for filtering and auxiliary biological treatment of the effluent from the sedimentation device.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a wastewater treatment system that couples biological and ecological processes for nitrogen removal. Background Technology

[0002] Currently, the main methods for treating rural domestic sewage include integration into urban pipe networks, centralized treatment, and decentralized treatment. Integration into urban pipe networks is only suitable for villages near towns, which has significant geographical limitations. Centralized treatment is suitable for rural areas with a relatively concentrated number of sewage production points, primarily employing methods such as AAO (Automatic Aeration and Oxidation), oxidation ditch methods, biological contact oxidation, and membrane bioreactors. These processes and equipment are relatively mature; however, their operation and maintenance costs are high, and they require specialized technical personnel for operation and management, resulting in persistently high costs for rural sewage treatment. To ensure that sewage treatment meets discharge standards, those skilled in the art face the challenge of achieving denitrification requirements in a reasonable, efficient, and low-cost manner. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a wastewater treatment system that couples biological and ecological treatment to enhance denitrification, improve the removal efficiency of ammonia nitrogen and total nitrogen, simplify operation and maintenance, reduce energy consumption, ensure more stable effluent quality, and provide a good ecological landscape effect.

[0004] The biological and ecological coupled denitrification wastewater treatment system includes a biological tank, a sedimentation device, and an ecological treatment device connected in sequence. The biological tank has an anoxic zone inside and a transition zone and an aerobic zone outside. The bottom of the anoxic zone is connected to the transition zone, and the transition zone is connected to the aerobic zone through a stripping pipe for the biological treatment of wastewater.

[0005] The outlet of the aerobic zone is connected to a sedimentation device. The sludge discharged from the bottom of the sedimentation device can be returned to the anoxic zone. The effluent pipe of the sedimentation device is connected to an ecological treatment device.

[0006] The ecological treatment device consists of a plant layer, a filter media layer, a quartz sand layer, a support layer, and a collection tank from top to bottom, which filters and provides auxiliary biochemical treatment for the effluent from the sedimentation device.

[0007] Optionally, the biological tank has a circular nested structure, with the inner layer being a circular anoxic zone and the outer layer consisting of a transition zone and an aerobic zone forming a ring structure. A circular partition wall is provided between the inner and outer layers. Both the transition zone and the aerobic zone are fan-shaped, with their inner sides connected to the partition wall and their outer sides forming the outer wall of the biological tank. The anoxic zone, transition zone, and aerobic zone have the same height.

[0008] The transition zone is provided with a first partition and a second partition on both sides to separate the transition zone from the aerobic zone. The first partition corresponds to the upstream side of the aerobic zone, and the second partition corresponds to the downstream side of the aerobic zone.

[0009] Optionally, the bottom of the partition wall between the anoxic zone and the transition zone is provided with a first outlet for inputting the permeable water from the anoxic zone into the transition zone.

[0010] The top of the first partition has a notch for overflowing the permeate from the transition zone to the upstream side of the aerobic zone;

[0011] The bottom of the second baffle has a second outlet, which allows water from the downstream side of the aerobic zone to enter the transition zone and then overflow back to the upstream side of the aerobic zone for aerobic treatment again.

[0012] Further optionally, the area ratio of the transition zone to the aerobic zone is 1:(10-15).

[0013] Optionally, the top of the biochemical tank is provided with an inlet pipe, with the inlet end of the inlet pipe located outside the biochemical tank and the outlet end located at the top of the anoxic zone, inputting raw wastewater into the anoxic zone; a stirrer is provided at the bottom of the anoxic zone.

[0014] Optionally, a first aeration pipe is provided at the bottom of the transition zone for aeration of the transition zone.

[0015] Optionally, several second aeration pipes are evenly spaced in a clockwise or counterclockwise direction within the aerobic zone to provide intermittent aeration and oxygen, thereby creating an alternating cycle of oxygen deficiency, oxygen enrichment, oxygen deficiency, and oxygen enrichment within the aerobic zone. The second aeration pipes are located in the oxygen enrichment section.

[0016] Optionally, filter partitions are provided on both the upstream and downstream sides of the oxygen-deficient section, and the filter partitions separate the oxygen-deficient section from the oxygen-rich section. The raw materials for making the filter partitions include filter media, stones, and biomass. The raw materials for making the filter partitions are uniformly filled into a hollow cubic mesh cage to form the filter partitions.

[0017] The biomass comprises fibrous plants, humus-containing filter media, and microorganisms. The upstream filter wall in the oxygen-deficient section uses aerobic microorganisms, while the downstream filter wall uses anaerobic microorganisms. The fibrous plants are selected from the rhizomes of kelp, aquatic plants, and herbaceous plants. The filter media in the biomass acts as a carrier, and its large specific surface area can support humus and microorganisms.

[0018] Further optionally, the filling filter material is the same as the filter material in the biomass, and the filter partition can use conventional filter material and pebbles. The pebble particle size is 3-6mm, the filter material particle size is 2-4mm, and the fibrous strip plants are not cut or crushed and can be kept in their original strip shape.

[0019] First, the filter media is mixed evenly with an equal mass of humus to obtain filter media containing humus. Then, the filter media containing humus, fibrous plant strips, filler filter media, and pebbles are mixed evenly and then filled into the wire mesh cage. Finally, the surface of the wire mesh cage is evenly wrapped and covered with fibrous plant strips until there are no obvious holes.

[0020] Further optionally, the volume ratio of the humus-containing filter media, fibrous plant strips, pebbles, and filler filter media is 1:1:(1-1.5):(1.5-2.5).

[0021] The oxygen-rich section has a high dissolved oxygen content. If wastewater directly enters the oxygen-deficient section from the oxygen-rich section, it may affect the facultative anaerobic bacteria in the oxygen-deficient section. This invention installs filter walls on both sides of the oxygen-deficient section to physically separate the oxygen-rich and oxygen-deficient sections. Wastewater from the oxygen-rich section passes through the filter walls containing aerobic microorganisms. The oxygen in the water is consumed by the aerobic microorganisms, continuing aerobic biochemical treatment. Humus and plants provide carbon sources and nutrients for the aerobic microorganisms. Simultaneously, the filter walls perform a filtration function, removing impurities from the wastewater. The micropores of the filter walls form numerous small channels, breaking up air bubbles in the water and forming microbubbles. After the wastewater passes through the filter walls, a micro-oxygen environment is created, which is beneficial to the facultative anaerobic bacteria in the oxygen-deficient section. After passing through the oxygen-deficient section, the wastewater reaches the downstream filter wall, where the anaerobic microorganisms continue to perform biochemical functions. After passing through the filter wall, the wastewater enters the next oxygen-rich section, and the cycle continues.

[0022] Optionally, a stripping pipe may be provided in any oxygen-enriched section of the downstream region of the aerobic zone. The bottom end of the stripping pipe is located at the bottom of the aerobic zone, and the top end extends beyond the top of the partition plate and into the anoxic zone, so that the nitrified liquid flows back to the anoxic zone.

[0023] Wastewater enters the anoxic zone through the inlet pipe and undergoes anoxic biological treatment under the action of anoxic bacteria. The effluent from the anoxic zone enters the transition zone through the first outlet, where its oxygen content is increased by aeration through the first aeration pipe, and then overflows to the upstream side of the aerobic zone. The wastewater sequentially passes through oxygen-rich, oxygen-deficient, oxygen-rich, and oxygen-deficient sections in a clockwise or counterclockwise direction, undergoing aerobic, anoxic-quasi-aerobic, aerobic, and anoxic-quasi-aerobic biological treatment. The nitrified liquid from the oxygen-rich section is returned to the anoxic zone through the stripping pipe. The wastewater can circulate and be repeatedly treated within the outer aerobic zone and transition zone until it meets the treatment requirements, after which it is discharged from the biological treatment tank.

[0024] Optionally, the side of the ecological treatment device is provided with a water outlet trough, the bottom of which is connected to the collection pool. The water outlet trough is connected to the water outlet observation well through a drain pipe, which is used to discharge the water collected after being filtered by the ecological treatment device into the water outlet observation well.

[0025] Optionally, the plant layer consists of plants grown on the filter layer, selected from plants such as umbrella grass, cattail, water onion, water bamboo, water celery, and canna lily.

[0026] Optionally, the filter media layer is made of conventional filter media, and the support layer is made of pebbles with a particle size of 10-30mm. The thickness ratio of the filter media layer, the quartz sand layer and the support layer is (3-6):1:(1-3).

[0027] A water distribution pipe is buried at the top of the filter media layer, so that the supernatant from the sedimentation device can enter the filter media layer evenly.

[0028] The ecological treatment device of this invention utilizes a plant root zone filter media to form a micro-ecosystem, enhancing the flocculation, sedimentation, adsorption, absorption, and decomposition of organic matter in wastewater. It can absorb and reduce nitrogen and accumulate phosphorus, enriching the root zone with nutrients such as N and P for absorption. It also has excellent growth-promoting properties, encouraging microbial attachment and growth, and improving the decomposition of pollutants. The quartz sand layer acts as a filter. The support layer serves a dual function of support and filtration. Aquatic plants are planted on top of the filter media. The quartz sand and filter media serve both filtering and biological carrier purposes; the aquatic plants transport oxygen to the water, increasing its activity. The gradient distribution of the layers in the ecological treatment device creates an anaerobic environment at the bottom, a facultative anaerobic environment in the middle, and an aerobic environment at the top, providing conditions for nitrification and denitrification, further promoting pollutant degradation and improving nitrogen and phosphorus removal rates. The treated water is collected in a collection tank.

[0029] Further optionally, the drain pipe is inverted U-shaped, and a disinfection device is installed in the water outlet observation well to disinfect the water therein. The water outlet observation well is equipped with a third water outlet pipe for discharging the produced water, which can be used as recycled water.

[0030] The U-shaped top of the drain pipe is 15-20 cm lower than the water distribution pipe. When the liquid level in the filter media layer is lower than the highest point of the drain pipe, the water in the ecological treatment device cannot be discharged, and the water level in the filter media layer rises slowly. The filter media layer and the layers below it that are flooded by water are in an anaerobic and anoxic state. When the liquid level in the filter media layer exceeds the highest point of the drain pipe, water can be drained through a siphon effect, and the filter media layer and the layers below it are in an aerobic state after drainage. This intermittent drainage causes the filter bed to exhibit an alternating anaerobic and aerobic biochemical process, further improving the removal of N and P.

[0031] In this invention, the combined use of a biological treatment pond and an ecological treatment device enhances denitrification, improves effluent quality, has strong shock resistance, produces low sludge, and is easy to operate and manage. This not only saves investment costs but also enhances the ecological landscape effect.

[0032] Optionally, the filter media layer is provided with at least one biochemical treatment layer, which is made up of a number of biochemical packing cages. The biochemical packing cages include, from the outside to the inside, a first filter media layer, an aerobic biological layer, a second filter media layer, a facultative anaerobic biological layer, and a third filter media layer.

[0033] The raw materials for the aerobic biolayer include plant debris, filter media containing humus, and aerobic microorganisms, while the raw materials for the facultative anaerobic biolayer include plant debris, filter media containing humus, and facultative anaerobic microorganisms.

[0034] Optionally, the raw materials for the first filter layer, the second filter layer, and the third filter layer are all filter media and pebbles. The filter media is the same as that used in the filter media layer, and the pebbles can be ordinary pebbles with a particle size of 3-6 mm and a particle size of 2-4 mm.

[0035] The humus-containing filter media in the aerobic and facultative anaerobic biological layers are the same as those in the filter partition, and the humus can be conventional humus; the plant debris is made from the crushed roots, stems and leaves of conventional herbaceous plants.

[0036] When manufacturing the biochemical packing cage, it is made from the inside out. The filter media and pebbles of the third filter media layer are mixed evenly and filled into the innermost packing cage to form the third filter media layer. Then, the plant debris, filter media containing humus, and facultative anaerobic microorganisms of the facultative anaerobic biological layer are mixed evenly and filled into the next innermost packing cage to form the facultative anaerobic biological layer. The second filter media layer, the aerobic biological layer, and the first filter media layer are then made in sequence according to the above method.

[0037] Further optionally, the volume ratio of the first filter layer, the second filter layer, and the third filter layer is (2-3):(1.5-2.5):1;

[0038] The volume ratio of the third filter layer, the facultative anaerobic biological layer, and the aerobic biological layer is 1:(0.7-1.2):(1.5-2);

[0039] The humus-containing filter media of the facultative anaerobic biolayer is a mixture of equal mass of humus and filter media, with the mass ratio of plant debris to humus-containing filter media being (0.8-1.3):1.

[0040] The aerobic biological layer contains humus-containing filter media, which is a mixture of equal mass of humus and filter media. The mass ratio of plant debris to humus-containing filter media is (2-4):1.

[0041] The present invention provides a biochemical treatment layer within the filter media layer for supplementary biochemical filtration. The sandwich structure of the biochemical packing cage allows wastewater flowing down from above to sequentially undergo filtration, aerobic biochemical treatment, filtration, facultative biochemical treatment, filtration, re-facultative biochemical treatment, filtration, re-aerobic biochemical treatment, and filtration, thereby improving the biochemical treatment effect.

[0042] The filter partition and biochemical packing cage are started up together with the biochemical pool and ecological treatment device, and then wastewater treatment is carried out. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the wastewater treatment system in Example 1;

[0044] Figure 2 This is a top view schematic diagram of the biochemical tank in Example 1.

[0045] In the attached diagram, 1-Biological tank, 2-Sedimentation device, 3-Ecological treatment device, 4-Anoxic zone, 5-Transition zone, 6-Aerobic zone, 7-Plant layer, 8-Filter media layer, 9-Quartz sand layer, 10-Supporting layer, 11-Collection tank, 12-Divider wall, 13-First partition, 14-Second partition, 15-Inlet pipe, 16-Agitator, 17-First aeration pipe, 18-Second aeration pipe, 19-Oxygen-enriched section, 20-Stripping pipe, 21-First outlet pipe, 22-Guide cylinder, 23-Reflector plate, 24-Sludge return pipe, 25-Outlet trough, 26-Drainage pipe, 27-Outlet observation well, 28-Anoxic section. Detailed Implementation

[0046] The following examples and comparative examples all treat domestic sewage from a rural area in southern Henan Province, with a treatment capacity of 50m³. 3 / day, wastewater quality is COD Cr The concentrations are 300-400 mg / L, NH3-N 35-45 mg / L, TN 50-60 mg / L, TP 2.0-3.0 mg / L, and SS 150-200 mg / L. After passing through the screen, the wastewater remains in a conventional equalization and grit chamber for 8 hours before being fed into the biological treatment tank.

[0047] Example 1

[0048] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment, such as Figures 1-2 As shown, it includes a biological treatment tank 1, a sedimentation device 2 and an ecological treatment device 3 connected in sequence. The biological treatment tank 1 has an anoxic zone 4 inside and a transition zone 5 and an aerobic zone 6 outside. The bottom of the anoxic zone 4 is connected to the transition zone 5. The transition zone 5 is connected to the aerobic zone 6 through a stripping pipe, which is used to treat sewage biologically.

[0049] The outlet of aerobic zone 6 is connected to sedimentation device 2. The sludge discharged from the bottom of sedimentation device 2 can be returned to anoxic zone 4. The effluent pipe of sedimentation device 2 is connected to ecological treatment device 3.

[0050] The ecological treatment device 3 consists of a plant layer 7, a filter media layer 8, a quartz sand layer 9, a support layer 10, and a collection tank 11 from top to bottom, which filters and assists in the biochemical treatment of the effluent from the sedimentation device 2.

[0051] The biological treatment tank 1 has a circular nested structure. The inner layer is a circular anoxic zone 4, and the outer layer consists of a transition zone 5 and an aerobic zone 6 forming a ring structure. A circular partition wall 12 is provided between the inner and outer layers. The transition zone 5 and the aerobic zone 6 are both fan-shaped. The inner sides of the transition zone 5 and the aerobic zone 6 are connected to the partition wall 12, and the outer sides are the outer walls of the biological treatment tank 1. The anoxic zone 4, the transition zone 5, and the aerobic zone 6 have the same height.

[0052] The transition zone 5 is provided with a first partition 13 and a second partition 14 on both sides to separate the transition zone 5 from the aerobic zone 6. The first partition 13 corresponds to the upstream side of the aerobic zone 6, and the second partition 14 corresponds to the downstream side of the aerobic zone 6.

[0053] The bottom of the partition wall 12 of the anoxic zone 4 corresponding to the transition zone 5 is provided with a first outlet for inputting the product water of the anoxic zone 4 into the transition zone 5.

[0054] The top of the transition zone 5 is provided with an opening to allow the product water from the transition zone 5 to overflow to the upstream side of the aerobic zone 6;

[0055] The bottom of the second baffle 14 is provided with a second outlet, which is used for water from the downstream side of the aerobic zone 6 to enter the transition zone 5 and then overflow back to the upstream side of the aerobic zone 6 for aerobic treatment again.

[0056] The area ratio of the transition zone 5 to the aerobic zone 6 is 1:10.

[0057] The top of the biochemical tank 1 is provided with an inlet pipe 15. The inlet end of the inlet pipe 15 is located outside the biochemical tank 1, and the outlet end is located at the top of the anoxic zone 4, so as to input raw wastewater into the anoxic zone 4.

[0058] A stirrer 16 is installed at the bottom of the anoxic zone 4 to agitate the wastewater in the anoxic zone 4 and improve the treatment efficiency.

[0059] The first outlet is equipped with a first filter screen to prevent a large amount of sludge from the anoxic zone 4 from entering the transition zone 5.

[0060] The bottom of the transition zone 5 is equipped with a first aeration pipe 17 to aerate the transition zone 5, increase the dissolved oxygen content, and prepare the water body to enter the aerobic zone 6.

[0061] Four second aeration pipes 18 are evenly spaced counterclockwise within the aerobic zone 6 to provide intermittent aeration and oxygen, creating an alternating cycle of oxygen deficiency, oxygen enrichment, oxygen deficiency, and oxygen enrichment within the aerobic zone 6. The second aeration pipes 18 are located in the oxygen enrichment section 19. The aerobic zone 6 can still undergo alternating hypoxia-aerobic-hypoxia-aerobic treatment, improving the nitrogen removal efficiency.

[0062] The last oxygen-enriched section 19 in the downstream region of the aerobic zone 6 is provided with a stripping pipe 20. The bottom end of the stripping pipe 20 is at the bottom of the aerobic zone 6, and the top end extends beyond the top of the partition plate and into the anoxic zone 4, so that the nitrified liquid flows back to the anoxic zone 4.

[0063] The upper part of the downstream area of ​​the aerobic zone 6 is provided with a first water outlet pipe 21, which is used to connect the sedimentation device 2.

[0064] The sedimentation device 2 has a flow guide cylinder 22 at its center, with openings at the top and bottom and the top of the flow guide cylinder 2 being higher than the liquid level inside the sedimentation device 2. A reflector plate 23 is provided below the flow guide cylinder 22. The first water outlet pipe 21 is connected to the middle of the flow guide cylinder 22, and the water from the oxidation zone is fed into the flow guide cylinder 22. The water flows downward to the reflector plate 23 and spreads outward to achieve uniform water distribution. The water flows upward and the sludge settles downward, thus achieving mud-water separation.

[0065] The sedimentation device 2 is provided with an outlet weir at the top edge, the outlet weir is connected to the second outlet pipe, and the second outlet pipe is connected to the ecological treatment device 3.

[0066] The bottom of the sedimentation device 2 is conical to facilitate the discharge of collected sludge. The bottom outlet is connected in parallel to a sludge return pump and a sludge storage area. The sludge return pump is connected to a sludge return pipe 24, which extends to the top of the anoxic zone 4 to return sludge to the anoxic zone 4.

[0067] The ecological treatment device 3 is provided with a water outlet trough 25 on its side. The bottom of the water outlet trough 25 is connected to the collection pool 11. The water outlet trough 25 is connected to the water outlet observation well 27 through a drain pipe 26, which is used to discharge the water collected after being filtered by the ecological treatment device 3 into the water outlet observation well 27.

[0068] The plant layer 7 consists of plants grown on the filter layer 8, namely water chestnut and water celery, which have both economic value and can be used as landscape plants.

[0069] The filter media layer 8 is made of conventional filter media, and the support layer 10 is made of pebbles with a particle size of 10-30mm. The thickness ratio of the filter media layer 8, the quartz sand layer 9 and the support layer 10 is 3:1:1.5.

[0070] A water distribution pipe is buried at the top of the filter media layer 8 so that the supernatant from the sedimentation device 2 can enter the filter media layer 8 evenly.

[0071] The drain pipe 26 is inverted U-shaped. A disinfection device is installed in the water outlet observation well 27 to disinfect the water therein. The water outlet observation well 27 is equipped with a third water outlet pipe for discharging the produced water, which is then used as recycled water.

[0072] The top of the U-shaped drain pipe 26 is 15cm lower than the water distribution pipe. When the liquid level in the filter media layer 8 is lower than the highest point of the drain pipe, the water in the ecological treatment device 3 cannot be discharged, and the water level in the filter media layer 8 rises slowly. The filter media layer 8 and the layers below it that are flooded by water are in an anaerobic and hypoxic state. When the liquid level in the filter media layer 8 exceeds the highest point of the drain pipe, the water can be drained through the siphon phenomenon. After the water is drained, the filter media layer 8 and the layers below it are in an aerobic state.

[0073] The hydraulic retention time of wastewater in the anoxic zone is 2 hours, with a sludge concentration of 3500-3800 mg / L. The hydraulic retention time of wastewater in the aerobic zone is 4 hours, with a sludge concentration of 3500-4000 mg / L. The filtration rate of wastewater in the ecological treatment device is 4.0 m / h, and the support layer height is 0.4 m. The effluent quality from the observation well includes: COD... Cr The concentrations of pollutants are <50 mg / L, NH3-N is <5 mg / L, TN is <15 mg / L, TP is <0.5 mg / L, and SS is <10 mg / L, which meets the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0074] Comparative Example 1

[0075] The biological and ecological coupled denitrification wastewater treatment system provided in this comparative example is the same as that in Example 1, except that no ecological treatment device is set up, and the supernatant effluent from the sedimentation device is the product water.

[0076] Example 2

[0077] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in Embodiment 1, except that a second aeration pipe is uniformly arranged inside the aerobic zone, and there is no distinction between oxygen-rich and oxygen-poor zones within the aerobic zone.

[0078] Example 3

[0079] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in Embodiment 1, except that filter partitions are provided on both the upstream and downstream sides of the oxygen-deficient section 28, which separate the oxygen-deficient section 28 from the oxygen-rich section 19. The raw materials for making the filter partitions include filter media, gravel, and biomass. The raw materials for making the filter partitions are uniformly filled into a hollow cubic mesh cage to form the filter partitions.

[0080] The biomass includes fibrous plants, humus-containing filter media, and microorganisms. The upstream filter wall of the oxygen-deficient section uses aerobic microorganisms, while the downstream filter wall uses anaerobic microorganisms. The fibrous plants are kelp and aquatic plants.

[0081] The filter media used is the same as that used in biomass. The filter partition can be made of conventional filter media and pebbles. The pebble size is 3-6mm and the filter media size is 2-4mm. The fibrous strip plants can be left uncut and intact.

[0082] First, the filter media is mixed evenly with an equal mass of humus to obtain filter media containing humus. Then, the filter media containing humus, fibrous plant strips, filler filter media, and pebbles are mixed evenly and then filled into the wire mesh cage. Finally, the surface of the wire mesh cage is evenly wrapped and covered with fibrous plant strips until there are no obvious holes.

[0083] The volume ratio of the humus-containing filter media, fibrous plant strips, pebbles, and filler filter media is 1:1:1:1.5.

[0084] Example 4

[0085] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in embodiment 3, except that the volume ratio of the filter media containing humus, fibrous strip plants, pebbles and filling filter media is 1:1:1.5:2.5.

[0086] Example 5

[0087] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in embodiment 3, except that the volume ratio of the filter media containing humus, fibrous strip plants, pebbles and filling filter media is 1:1:1.6:2.6.

[0088] Example 6

[0089] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in embodiment 1, except that a biochemical treatment layer is provided in the filter media layer of the ecological treatment device. The biochemical treatment layer is made up of ten biochemical packing cages. The biochemical packing cages include, from the outside to the inside, a first filter media layer, an aerobic biological layer, a second filter media layer, a facultative anaerobic biological layer, and a third filter media layer.

[0090] The raw materials for the aerobic biolayer include plant debris, filter media containing humus, and aerobic microorganisms, while the raw materials for the facultative anaerobic biolayer include plant debris, filter media containing humus, and facultative anaerobic microorganisms.

[0091] The raw materials for the first filter media layer, the second filter media layer, and the third filter media layer are all filter media and pebbles. The filter media is the same as the filter media used in the filter media layer. The pebbles are conventional pebbles with a particle size of 3-6 mm, and the filter media has a particle size of 2-4 mm.

[0092] The humus-containing filter media in the aerobic and facultative anaerobic biological layers are the same as those in the filter partition, and the humus can be conventional humus; the plant debris is made from the crushed roots, stems and leaves of conventional herbaceous plants.

[0093] The biochemical packing cage is manufactured from the inside out. An equal mass of filter media and pebbles from the third filter layer are mixed evenly and filled into the innermost packing cage to form the third filter layer. Then, plant debris, humus-containing filter media, and facultative anaerobic microorganisms from the facultative anaerobic biological layer are mixed evenly and filled into the next innermost packing cage to form the facultative anaerobic biological layer. An equal mass of filter media and pebbles from the second filter layer are mixed evenly and filled into the packing cage outside the facultative anaerobic biological layer to form the second filter layer. Then, plant debris, humus-containing filter media, and aerobic microorganisms from the aerobic biological layer are mixed evenly and filled into the packing cage outside the second filter layer to form the aerobic biological layer. An equal mass of filter media and pebbles from the first filter layer are mixed evenly and filled into the packing cage outside the aerobic biological layer to form the first filter layer.

[0094] The volume ratio of the first filter layer, the second filter layer, and the third filter layer is 2:1.5:1;

[0095] The volume ratio of the third filter layer, the facultative anaerobic biological layer, and the aerobic biological layer is 1:0.7:1.5;

[0096] The humus-containing filter media of the facultative anaerobic biolayer is a mixture of equal mass of humus and filter media, with a mass ratio of plant debris to humus-containing filter media of 0.8:1.

[0097] The aerobic biological layer contains humus-containing filter media, which is a mixture of equal masses of humus and filter media, with a mass ratio of plant debris to humus-containing filter media of 2:1.

[0098] Example 7

[0099] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in Embodiment 1, except that the volume ratio of the third filter layer, the facultative anaerobic biological layer and the aerobic biological layer is 1:1.2:2.

[0100] Example 8

[0101] The biological and ecological coupled denitrification wastewater treatment system provided in this embodiment is the same as that in Embodiment 1, except that the volume ratio of the third filter layer, the facultative anaerobic biological layer and the aerobic biological layer is 1:0.6:1.4.

[0102] Table 1 Comparison of wastewater treatment effects between the examples and comparative examples

[0103]

[0104]

[0105] As can be seen from the table above, the wastewater treatment system of the present invention adopts a treatment process that combines biochemical and ecological treatment, which can significantly improve the treatment effect. In addition, the design of the filter partition wall of the biochemical tank and the biochemical packing cage of the ecological treatment device can further improve the treatment effect and ensure that the effluent meets the standards.

Claims

1. A wastewater treatment system for biological and ecological coupled denitrification, characterized in that, It includes a biological treatment tank, a sedimentation device and an ecological treatment device connected in sequence. The biological treatment tank has an anoxic zone inside and a transition zone and an aerobic zone outside. The bottom of the anoxic zone is connected to the transition zone, and the transition zone is connected to the aerobic zone through a stripping pipe. It is used for biological treatment of sewage. The outlet of the aerobic zone is connected to a sedimentation device. The sludge discharged from the bottom of the sedimentation device can be returned to the anoxic zone. The effluent pipe of the sedimentation device is connected to an ecological treatment device. The ecological treatment device consists of a plant layer, a filter media layer, a quartz sand layer, a support layer, and a collection tank from top to bottom, which filters and assists in the biochemical treatment of the effluent from the sedimentation device. The aerobic zone is configured with alternating oxygen-deficient, oxygen-enriched, oxygen-deficient, and oxygen-enriched zones. Filter walls are provided on both the upstream and downstream sides of the oxygen-deficient zone, separating the oxygen-deficient zone from the oxygen-enriched zone. The raw materials for making filter walls include filter media, gravel, and biomass. The raw materials for making filter walls are evenly filled into hollow cubic mesh cages to form filter walls. The biomass includes fibrous plants, humus-containing filter media, and microorganisms. The upstream filter wall of the oxygen-deficient section uses aerobic microorganisms, while the downstream filter wall uses anaerobic microorganisms. First, the filter media is mixed evenly with an equal mass of humus to obtain filter media containing humus. Then, the filter media containing humus, fibrous plants, filler filter media, and pebbles are mixed evenly and then filled into the wire mesh cage. Finally, the surface of the wire mesh cage is evenly wrapped and covered with fibrous plants until there are no obvious holes. The volume ratio of the filter media containing humus, fibrous plant strips, pebbles, and filler filter media is 1:1:(1-1.5):(1.5-2.5); The filter media layer contains at least one biochemical treatment layer, which is made up of several biochemical packing cages. The biochemical packing cages include, from the outside to the inside, a first filter media layer, an aerobic biological layer, a second filter media layer, a facultative anaerobic biological layer, and a third filter media layer. The raw materials for the aerobic biolayer include plant debris, filter media containing humus, and aerobic microorganisms; the raw materials for the facultative anaerobic biolayer include plant debris, filter media containing humus, and facultative anaerobic microorganisms. The volume ratio of the third filter layer, the facultative anaerobic biological layer, and the aerobic biological layer is 1:(0.7-1.2):(1.5-2).

2. The wastewater treatment system for biological and ecological coupled denitrification according to claim 1, characterized in that, The biological tank has a circular nested structure. The inner layer is a circular anoxic zone, and the outer layer consists of a transition zone and an aerobic zone forming a ring structure. A circular partition wall is provided between the inner and outer layers. Both the transition zone and the aerobic zone are fan-shaped. The inner sides of the transition zone and the aerobic zone are connected to the partition wall, and the outer sides are the outer walls of the biological tank. The transition zone is provided with a first partition and a second partition on both sides to separate the transition zone from the aerobic zone. The first partition corresponds to the upstream side of the aerobic zone, and the second partition corresponds to the downstream side of the aerobic zone.

3. The biological and ecological coupled denitrification wastewater treatment system according to claim 2, characterized in that, The bottom of the partition wall between the anoxic zone and the transition zone is provided with a first outlet for inputting the permeable water from the anoxic zone into the transition zone. The top of the first partition has a notch for overflowing the permeate from the transition zone to the upstream side of the aerobic zone; The bottom of the second baffle has a second outlet, which allows water from the downstream side of the aerobic zone to enter the transition zone and then overflow back to the upstream side of the aerobic zone for aerobic treatment again.

4. The wastewater treatment system for biological and ecological coupled denitrification according to claim 2, characterized in that, The top of the biochemical tank is equipped with an inlet pipe, with the inlet end of the inlet pipe located outside the biochemical tank and the outlet end located at the top of the anoxic zone, feeding raw wastewater into the anoxic zone; a stirrer is installed at the bottom of the anoxic zone. The bottom of the transition zone is equipped with a first aeration pipe for aeration of the transition zone.

5. The wastewater treatment system for biological and ecological coupled denitrification according to claim 1, characterized in that, Several second aeration pipes are evenly spaced along a clockwise or counterclockwise direction within the aerobic zone to provide intermittent aeration, creating an alternating cycle of oxygen deficiency, oxygen enrichment, oxygen deficiency, and oxygen enrichment within the aerobic zone. The second aeration pipes are located in the oxygen enrichment section.

6. The wastewater treatment system for biological and ecological coupled denitrification according to claim 1, characterized in that, The side of the ecological treatment device is provided with a water outlet trough, the bottom of which is connected to the collection pool. The water outlet trough is connected to the water outlet observation well through a drain pipe, which is used to discharge the water collected after being filtered by the ecological treatment device into the water outlet observation well. The support layer is made of pebbles with a particle size of 10-30mm, and the thickness ratio of the filter layer, the quartz sand layer and the support layer is (3-6):1:(1-3); A water distribution pipe is buried at the top of the filter media layer, so that the supernatant from the sedimentation device can enter the filter media layer evenly.

7. The biological and ecological coupled denitrification wastewater treatment system according to claim 1, characterized in that, The raw materials for the first, second, and third filter media layers are all filter media and pebbles, with the pebble particle size being 3-6 mm and the filter media particle size being 2-4 mm. The volume ratio of the first filter layer, the second filter layer, and the third filter layer is (2-3):(1.5-2.5):1; The humus-containing filter media of the facultative anaerobic biolayer is a mixture of equal mass of humus and filter media, with the mass ratio of plant debris to humus-containing filter media being (0.8-1.3):

1. The aerobic biological layer contains humus-containing filter media, which is a mixture of equal mass of humus and filter media. The mass ratio of plant debris to humus-containing filter media is (2-4):1.

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