Sewage treatment and gradient resource utilization system

Abstract

The utility model discloses a sewage treatment and gradient resource utilization system which comprises a biological treatment unit and a fish and vegetable symbiosis unit connected with the biological treatment unit, the biological treatment unit comprises an anoxic tank and an aerobic tank connected with the anoxic tank, a sewage circulation part is arranged between the aerobic tank and the anoxic tank, and the sewage circulation part is used for adjusting the content of nitrogen and phosphorus in effluent of the aerobic tank to preset content values; the fish and vegetable symbiotic unit comprises a culture pond connected with the aerobic pond, economic crops which are produced by providing nutrition with nitrogen and phosphorus-rich sewage treated by the aerobic pond are cultivated at the top in the culture pond, the economic crops are cultivated according to a preset cultivation density, and a plurality of mixed ecological fishes are cultivated at the bottom in the culture pond. The multiple kinds of mixed ecological fishes are bred according to the preset breeding density, and the fishes comprise the fishes eating the root systems of the commercial crops and the fishes eating fish feces; compared with the prior art, resource utilization modes are diversified, economic benefits are high, the operation and maintenance cost is low, and energy consumption is low.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, specifically to a wastewater treatment and cascade resource utilization system. Background Technology

[0002] To promote the construction of healthy villages and continuously improve the rural living environment, the treatment of rural domestic sewage is of paramount importance. Rural domestic sewage mainly includes fecal and urine water (also known as black water), laundry water, and kitchen water (collectively known as grey water). Although its concentration is not high and the discharge volume is relatively small, long-term indiscriminate discharge will lead to the accumulation of large amounts of domestic sewage in villages, the blockage of ditches by debris, and the black and smelly water in ponds and ditches in and around the village, which will seriously affect rural construction.

[0003] Rural domestic sewage treatment must be simple, effective, and easy to operate and maintain, while also being energy-efficient, environmentally friendly, and generating economic benefits in order to truly penetrate rural areas and be accepted by farmers. In other words, rural domestic sewage treatment must follow a sustainable development path, addressing both environmental issues and resource utilization to generate economic benefits, in order to truly contribute to rural development and increase farmers' income.

[0004] Sustainable rural domestic sewage treatment technologies typically consist of two parts: biological units, which mainly include anaerobic, anoxic, and aerobic units, primarily removing organic matter and some nitrogen and phosphorus; and ecological units, which mainly include processes such as vegetable filter beds, constructed wetlands, and multifunctional oxidation ponds, primarily utilizing nitrogen and phosphorus resources through the cultivation of economically valuable plants. For biological units, simplifying them for easier maintenance and management while reducing energy consumption is a key concern; similarly, for ecological units, maximizing the resource utilization of sewage to achieve higher economic benefits is also crucial. Only by addressing these issues can rural domestic sewage treatment be truly integrated into the "agriculture, rural areas, and farmers" system, thereby increasing farmers' enthusiasm for maintenance.

[0005] CN111196669A discloses a wastewater treatment and nitrogen and phosphorus resource utilization system, which combines the characteristics of biological and ecological units to treat and utilize wastewater. Specifically, it includes a pretreatment unit, which includes a bar screen well and an equalization tank located at the outlet end of the bar screen well. The inlet end of the bar screen well is equipped with an inlet pipe for introducing wastewater into the bar screen well, and a bar screen is installed inside the bar screen well. After the pretreatment unit, a biological rotating cage integrated unit and a tailwater nitrogen and phosphorus absorption unit are arranged in sequence.

[0006] The integrated biological rotating cage unit includes an anoxic tank, an aerobic tank, and a sedimentation tank arranged sequentially in the direction of water flow. The anoxic tank and sedimentation tank contain fiber bundle packing material. The aerobic tank contains a rotating cage, which includes a packing cage and a rotating shaft. The packing cage is a ring-shaped sandwich structure composed of concentric inner and outer cylinders, filled with packing material. The inner and outer cylinders are made of stainless steel and have several through holes on their walls. The rotating shaft is located at the axial center of the packing cage, horizontally positioned and perpendicular to the water flow direction. Both ends of the rotating shaft are fixed to the walls of the aerobic tank via two bearings fixed to the walls of the two tanks. The packing cage is fixedly supported on the rotating shaft, so that part of the packing cage is submerged in the aerobic tank water and part is exposed outside the water. The rotating shaft is connected to a motor, facilitating the rotation of the packing cage by the motor. Overflow weirs are provided on the corresponding tank walls of the anoxic tank and the aerobic tank, allowing water from the anoxic tank to enter the aerobic tank through the overflow weirs. The bottoms of the aerobic tank and the sedimentation tank are connected, allowing water from the aerobic tank to enter the sedimentation tank from the bottom.

[0007] The nitrogen and phosphorus absorption unit in the wastewater treatment and nitrogen and phosphorus resource utilization system mentioned above only absorbs nitrogen and phosphorus by cultivating economic crops, which is a single application. Utility Model Content

[0008] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a sewage treatment and cascade resource utilization system to solve the problem of single application in the existing technology.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a wastewater treatment and cascade resource utilization system, comprising a biological treatment unit and an aquaponics unit connected thereto;

[0010] The biological treatment unit includes an anoxic tank and an aerobic tank connected thereto. A wastewater circulation section is provided between the aerobic tank and the anoxic tank. The wastewater circulation section is used to adjust the nitrogen and phosphorus content in the effluent of the aerobic tank to a preset value.

[0011] The aquaponics unit includes an aquaculture pond connected to an aerobic pond. The top of the aquaculture pond is planted with economic crops that are grown using nitrogen- and phosphorus-rich wastewater treated by the aerobic pond as nutrients. The economic crops are planted at a preset planting density. At the bottom of the aquaculture pond, a variety of mixed ecological fish species are raised at a preset planting density. These mixed ecological fish species include fish that feed on the roots of the economic crops and fish that feed on fish excrement.

[0012] Technical principle:

[0013] Domestic sewage is treated in anoxic and aerobic tanks, and a water circulation system is formed between the sewage circulation section and the aerobic and anoxic tanks to regulate the nitrogen and phosphorus content in the effluent from the aerobic tank to preset levels. The treated sewage then enters an aquaculture pond to provide the nutrients needed for the growth of the cash crops cultivated there. At the same time, various ecological fish, including fish that feed on the roots of the cash crops and fish that feed on their excrement, are raised in the aquaculture pond to achieve a symbiotic relationship. The nitrogen and phosphorus content in the effluent is regulated in conjunction with the preset planting density of the cash crops and the preset stocking density of the ecological fish to ensure good fish-vegetable symbiosis and effectively remove nitrogen and phosphorus from the sewage, thus achieving an ecological balance.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. Diverse resource utilization methods and high economic benefits. By using aquaponics units as nitrogen and phosphorus absorption units in the wastewater treatment and cascade resource utilization system, ecological fish are raised while economic crops are cultivated. This not only allows the economic crops to absorb nitrogen and phosphorus elements from the wastewater, but also enables the rational raising of different fish species at preset stocking densities in the aquaculture ponds. This fully utilizes the roots of the economic crops as food, achieving a good symbiotic relationship. This not only provides the benefits from economic crops but also increases the benefits from ecological fish, greatly improving economic efficiency.

[0016] 2. Low operation and maintenance costs. First, both cash crops and farmed ecological fish are integrated within the space of the aquaculture pond, occupying little space and requiring minimal water pipe installation, making operation and maintenance convenient.

[0017] 3. Low energy consumption. The water entering the aquaculture pond does not require disinfection and sterilization. Instead, some microorganisms are needed to decompose the residual organic matter and fish feces in the wastewater, which reduces the system's energy consumption. The water level in the aquaculture pond is easy to control, which reduces the burden on the biological treatment unit and also reduces energy consumption. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the pretreatment unit and the biological treatment unit in one embodiment of the present invention. Figure 1 ;

[0020] Figure 3 This is a schematic diagram of the pretreatment unit and the biological treatment unit in one embodiment of the present invention. Figure 2 ;

[0021] Figure 4 This is a schematic diagram of the structure of an aerobic tank in one embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of a breeding pond in one embodiment of the present invention;

[0023] Figure 6 This is a schematic diagram of the arrangement of the tiered utilization unit in one embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of the structure of the grid well in one embodiment of the present invention.

[0025] The reference numerals in the accompanying drawings include: 1. Anoxic tank; 2. Aerobic tank; 3. Sewage circulation section; 31. Circular weir; 32. Fountain aerator; 33. Return weir; 4. Aquaculture pond; 5. Hydroponic rearing area; 6. Grille well; 61. Garbage collection chamber; 62. Pre-filtration chamber; 63. Post-filtration chamber; 64. Grille filter screen; 65. Sludge guide port; 7. Anaerobic tank; 8. Clear water tank; 9. Limiting cylinder; 10. Grid support assembly; 10. Lower grid plate; 101. Upper grid plate; 102. Detailed Implementation

[0026] The present invention will be further described in detail below through specific embodiments:

[0027] like Figures 1-7 As shown in the figure, this utility model embodiment proposes a wastewater treatment and cascade resource utilization system, including a pretreatment unit, a biological treatment unit connected to the pretreatment unit, and an aquaponics unit connected to the biological treatment unit. The biological treatment unit includes an anoxic tank 1 and an aerobic tank 2 connected to it. A wastewater circulation section 3 is provided between the aerobic tank 2 and the anoxic tank 1. The wastewater circulation section 3 is used to adjust the nitrogen and phosphorus content in the effluent of the aerobic tank 2 to a preset value. The aquaponics unit includes a breeding pond 4 connected to the aerobic tank 2. The top of the breeding pond 4 is planted with economic crops that are grown using the nitrogen- and phosphorus-rich wastewater treated by the aerobic tank 2 as nutrients. The economic crops are planted at a preset planting density. The bottom of the breeding pond 4 is planted with a mixture of multiple species of ecological fish, which are raised at a preset breeding density and include fish that feed on the roots of the economic crops and fish that feed on fish excrement.

[0028] When using:

[0029] Domestic sewage enters this sewage treatment and cascade resource utilization system. First, it undergoes pretreatment in the pretreatment unit to intercept large particulate impurities in the biological sewage. Then, the domestic sewage enters the biological treatment unit for biological treatment to remove organic matter and other substances. However, the nitrogen and phosphorus content in the domestic sewage after biological treatment is still high, only meeting irrigation standards. If there is no irrigated farmland to absorb the nitrogen and phosphorus, the effluent needs to be absorbed. Therefore, an aquaponics unit was designed. The domestic sewage then enters the aquaponics unit to absorb nitrogen and phosphorus, providing the necessary nutrients for the growth of the economic crops and ecological fish coexisting in the aquaponics unit.

[0030] This wastewater treatment and cascade resource utilization system has the following advantages: Diverse resource utilization methods and high economic benefits. By using an aquaponics unit as the nitrogen and phosphorus absorption unit for the wastewater treatment and cascade resource utilization system, ecological fish are raised while economic crops are cultivated. This not only allows the economic crops to absorb nitrogen and phosphorus elements from the wastewater, but also allows for the rational raising of different fish species at preset stocking densities in the aquaculture pond 4. This fully utilizes the roots of the economic crops as food, achieving a good symbiotic relationship. This not only provides the benefits from the economic crops but also increases the benefits from the ecological fish, significantly improving economic efficiency. Low operation and maintenance costs. First, both economic crops and raised ecological fish are integrated within the space of aquaculture pond 4, occupying little space and requiring minimal water pipe installation, making operation and maintenance convenient. Low energy consumption. The influent to aquaculture pond 4 does not require disinfection or sterilization; instead, some microorganisms are needed to decompose residual organic matter and fish feces in the wastewater, reducing system energy consumption. The water level in aquaculture pond 4 is easy to control, reducing the burden on the biological treatment unit and further reducing energy consumption.

[0031] Among them, the sewage circulation section 3 forms a water circulation with the aerobic tank 2 and the anoxic tank 1 to adjust the nitrogen and phosphorus content in the effluent of the aerobic tank 2 to the preset content value; in conjunction with the preset cultivation density of economic crops and the preset breeding density of ecological fish, it ensures good fish-vegetable symbiosis and effectively removes nitrogen and phosphorus content from domestic sewage to achieve an ecological symbiotic balance.

[0032] This wastewater treatment and cascade resource utilization system primarily treats rural domestic sewage, which is characterized by low concentration and small discharge volume. Peak discharge periods typically occur three times a day, coinciding with mealtimes. Therefore, the collected sewage does not require storage in a large temporary storage tank and can be directly fed into the pretreatment unit. After passing through the pretreatment unit and entering the biological treatment unit, the sewage can remain in the corresponding tanks of the biological treatment unit for a relatively long period during the initial operation phase, generally around 7-14 days. Only after each tank of the biological treatment unit can achieve overflow for continuous flow can the entire system be considered to be officially and stably operating.

[0033] In practical applications, it is necessary to control the COD concentration in the wastewater discharged from aerobic pond 2 to be 60-70 mg / L, the total nitrogen concentration to be 20-30 mg / L, and the total phosphorus concentration to be 2-3 mg / L. The preset planting density of economic crops in aquaculture pond 4 is: 10-15 cm between plants, 15-20 cm between rows, and 40-80 plants per square meter. The preset stocking density of ecological fish in aquaculture pond 4 is 680 per acre. -1000 fish, specifically, grass carp can be stocked at 400-600 fish / acre, silver carp at 200-300 fish / acre, and bighead carp at 80-100 fish / acre. This stocking density takes into account factors such as the fish's growth space, feed resources, and water purification capacity. Silver carp and bighead carp can utilize plankton and fish excrement in sewage, while grass carp mainly eat the roots and stems of economic crops. They cooperate with each other and can effectively utilize the resources in the breeding pond to achieve good symbiosis.

[0034] This wastewater treatment and cascade resource utilization system aims to make fuller use of resources, such as Figure 1 and Figure 6 As shown, according to another embodiment of the present invention, the wastewater treatment and cascade resource utilization system further includes a cascade utilization unit, which includes a hydroponic breeding area 5 arranged sequentially and connected by utilizing the height difference, wherein the hydroponic breeding area 5 located at the highest point is connected to the breeding pond 4.

[0035] In rural areas of hilly regions, which are mostly mountainous and have a certain height difference, multiple hydroponic breeding areas 5 are arranged by making reasonable use of the terrain. The water discharged from the breeding pond 4 is introduced into the hydroponic breeding area 5 connected to it, and then, under the action of gravity, the water is introduced into the remaining hydroponic breeding areas 5 in sequence. Fish can be raised and crops can be cultivated in the hydroponic breeding areas 5.

[0036] When raising fish in hydroponic area 5, the water depth can be controlled at 1.0-1.5 meters. Excess water can be piped to farmland for irrigation. Grass carp and silver carp can be raised in hydroponic area 5 at a stocking density of 200-500 fish per acre.

[0037] When cultivating crops in hydroponic zone 5, adjust the crops according to the season. Spring and Summer: In the first-level hydroponic zone 5, crops with high nitrogen and phosphorus requirements, such as water spinach and tomatoes, can be hydroponically grown. The first-level treatment is relatively less demanding and can meet the nitrogen and phosphorus needs of these crops. In the second-level hydroponic zone 5, crops with relatively low nitrogen and phosphorus requirements, such as bok choy and lettuce, can be hydroponically grown. The third-level hydroponic zone 5 can also grow the same crops as in the second-level zone 5. Autumn and Winter: Lettuce and other crops can be hydroponically grown in all three levels of hydroponic zones 5.

[0038] Furthermore, each of the hydroponic rearing areas 5 is equipped with a liquid level monitoring device, and is also equipped with a first water quality monitor, a first nitrate nitrogen sensor, and a first dissolved oxygen sensor. The liquid level monitoring device can be a level gauge to monitor the liquid level in the hydroponic rearing area 5; the first water quality monitor monitors the water quality; the first nitrate nitrogen sensor monitors nitrate nitrogen; and the first dissolved oxygen sensor monitors dissolved oxygen concentration. The monitored results are analyzed, and the return flow rate of the wastewater circulation section 3 is adjusted in real time to ensure the healthy growth of the fish raised or the crops cultivated in the cascade utilization unit.

[0039] like Figure 2 , Figure 3 as well as Figure 7 As shown, according to another embodiment of the present invention, the wastewater treatment and cascade resource utilization system includes a pretreatment unit comprising a bar screen 6. The bar screen 6 is located in front of the anoxic tank 1 and has a filter chamber and a waste collection chamber 61 located below the filter chamber. The filter chamber is divided into a pre-filtration chamber 62 and a post-filtration chamber 63 by a bar screen 64. The pre-filtration chamber 62 is connected to a wastewater inlet pipe, and the post-filtration chamber 63 is connected to the anoxic tank 1. The pre-filtration chamber 62 and the waste collection chamber 61 are connected by a sludge guide port 65 with a preset height. The floating matter trapped in the pre-filtration chamber 62 is transferred to the sludge guide port 65 by buoyancy or a transfer tool.

[0040] Specifically:

[0041] The sewage inlet pipe guides domestic sewage into the pre-filtration chamber 62, where a bar screen 64 intercepts large particulate impurities. These large particulate impurities are primarily floating debris. The outlet of the sewage inlet pipe is located on the bottom side wall of the pre-filtration chamber 62. The sewage inlet pipe exerts an upward force on the large particulate impurities intercepted in the pre-filtration chamber 62, guiding them from the slag guide port 65 into the garbage collection chamber 61 for collection. The domestic sewage then passes through the bar screen 64 into the post-filtration chamber 63 and subsequently enters the biological treatment unit for biological treatment.

[0042] Large particles of impurities intercepted in the pre-filter chamber 62 can also be transferred from the slag guide port 65 into the waste collection chamber 61 for collection using a transfer tool; the transfer tool can be a robotic arm, etc.

[0043] The inlet sewage pipe is equipped with an inlet pump, and both the aerobic tank 2 and the anoxic tank 1 are equipped with a second water quality monitor, a second nitrate nitrogen sensor, and a second dissolved oxygen sensor.

[0044] Here, the inlet pump provides power for domestic sewage to enter the screen well 6 and can also adjust the inlet flow rate of domestic sewage as needed; a second water quality monitor monitors water quality, a second nitrate nitrogen sensor monitors nitrate nitrogen, and a second dissolved oxygen sensor monitors dissolved oxygen concentration. Based on the monitored nitrate nitrogen and dissolved oxygen concentrations, the return flow rate of the sewage circulation section 3 is adjusted in real time. When the nitrate nitrogen concentration in the anoxic zone is too low, the return flow rate of the sewage circulation section 3 is appropriately increased; when the dissolved oxygen concentration is too high, the return flow rate of the sewage circulation section 3 is decreased to maintain a good denitrification environment in the anoxic zone.

[0045] like Figure 2 and Figure 3 As shown, according to another embodiment of the present invention, the wastewater treatment and cascade resource utilization system further includes an anaerobic tank 7 located in front of and connected to the anoxic tank 1. Specifically, the anaerobic tank 7 is connected between the post-filtration chamber 63 and the anoxic tank 1. Domestic wastewater discharged from the post-filtration chamber 63 enters the anaerobic tank 7 for treatment. Subsequently, the domestic wastewater overflows into the anoxic tank 1 and the aerobic tank 2 for biological treatment, utilizing microorganisms to decompose organic matter.

[0046] The biological treatment unit also includes a clear water tank 8 located behind and connected to the aerobic tank 2. The clear water tank 8 is also connected to the aquaculture tank 4. The treated domestic sewage in the aerobic tank 2 enters the clear water tank 8 for storage and sedimentation, and then the domestic sewage is introduced into the aquaculture tank 4 for use.

[0047] In this embodiment, both the aerobic pool 2 and the anoxic pool 1 are equipped with biological packing material, and the biological packing material has a certain reserved distance between its bottom and top in either the aerobic pool 2 or the anoxic pool 1.

[0048] The biological packing material serves as a carrier for microbial biofilm formation. The type of biological packing material is highly flexible; any material that facilitates microbial attachment and the formation of a stable biofilm is acceptable. Preferred options include soft packing material (processed to mimic the shape of natural aquatic plants), modified soft packing material (using spun fiber ropes strung together with uniformly distributed plastic discs to form unit fiber bundles of a certain length), and combined packing material (combining the advantages of soft and semi-soft packing materials), such as biological rope packing material. Taking biological rope packing material as an example, it is suspended in the lower middle region of the aerobic tank 2 and the anoxic tank 1, maintaining a certain distance from both the tank bottom and the overflow outlet. This distance ensures good sag of the biological rope packing material and a relatively stable biofilm growing on it, thus guaranteeing the effectiveness of microbial degradation. In the aerobic tank 2, the distance between it and the overflow outlet ensures the normal operation of the wastewater circulation section 3.

[0049] like Figure 3 and Figure 4As shown, according to another embodiment of the present invention, the wastewater treatment and cascade resource utilization system includes a wastewater circulation section 3 comprising an annular weir 31, a fountain aerator 32, and a return weir 33. The annular weir 31 is circumferentially distributed at the top edge of the aerobic tank 2. The fountain aerator 32 is installed inside the aerobic tank 2 and is used to spray wastewater from the aerobic tank 2 into the annular weir 31. The return weir 33 is installed at the top edge of the anoxic tank 1 and communicates with the annular weir 31. The return weir 33 is also communicated with the anoxic tank 1.

[0050] In this embodiment, the fountain aerator 32 operates to aerate the water, while simultaneously raising the domestic sewage in the aerobic tank 2 to the surrounding area. Some of the domestic sewage is collected by the annular weir 31. The domestic sewage collected in the annular weir 31 is introduced into the return weir 33 through a guide hole connected to the return weir 33. The domestic sewage in the return weir 33 is then guided back to the anoxic tank 1 through a return liquid hole at its bottom that is connected to the anoxic tank 1. This creates a return liquid circulation between the aerobic tank 2 and the anoxic tank 1, which facilitates the adjustment of the nitrogen and phosphorus content in the effluent of the aerobic tank 2 to a preset value as needed.

[0051] Specifically, in aerobic tank 2, after aeration, the water is rich in oxygen. Aerobic bacteria decompose large particulate pollutants in domestic sewage into small organic debris, while simultaneously multiplying and attaching to the biological packing material to form a stable biofilm. Nitrifying bacteria convert ammonification products into nitrates, so the water in aerobic tank 2 can be called nitrified liquid. At the same time, part of the nitrified liquid is returned to anoxic tank 1 through aeration, bringing a small amount of oxygen to anoxic tank 1. The returned nitrified liquid can also be decomposed into nitrogen gas by denitrifying bacteria (facultative anaerobic bacteria) to achieve nitrogen removal. The return also brings water flow. Since domestic sewage stays in various tanks for a long time, if the water does not flow for a long time, it will inevitably turn black and smelly. The returned water is rich in oxygen and flows directly to the bottom of the tank and then overflows from the top. This process not only makes the dissolved oxygen in the water more uniform but also creates some disturbance to the water, allowing the organic matter in the sewage to come into more complete contact and interact with the biofilm.

[0052] The aerobic tank 2 is equipped with floats, and the fountain aerator 32 is mounted on the floats. The floats serve as a mounting carrier for the fountain aerator 32. A limiting cylinder 9 is fixedly installed within the aerobic tank 2, with the floats mounted on it. The limiting cylinder 9 ensures the stability of the fountain aerator 32's operation and the stability of the nitrification return liquid flow rate. The grid-like wall of the limiting cylinder 9 also ensures that it does not obstruct the water spray from the fountain aerator 32, allowing the annular cofferdam 31 to receive a large amount of water spray.

[0053] The number of fountain aerators 32 can be designed according to requirements. In this embodiment, there are two fountain aerators 32. The two fountain aerators 32 can ensure sufficient aeration to ensure the amount of dissolved oxygen in the water. On the other hand, they can ensure that the annular cofferdam 31 can receive more water splashes, thereby reducing the aeration amount of a single fountain aerator 32.

[0054] like Figure 5 As shown, according to another embodiment of the present invention, in the wastewater treatment and cascade resource utilization system, a grid support assembly 10 is provided in the aquaculture pond 4. The grid support assembly 10 includes a lower grid plate 101 and an upper grid plate 102. The lower grid plate 101 is located in the aquaculture pond 4 and below a preset maximum liquid level. The roots and stems of economic crops pass through the mesh of the lower grid plate 101 and are placed in the wastewater in the aquaculture pond 4. The upper grid plate 102 is located at the opening of the aquaculture pond 4 and above the lower grid plate 101. The upper grid plate 102 is located above the preset maximum liquid level. A constraint space is formed between the lower grid plate 101 and the upper grid plate 102. The roots and stems of economic crops pass through the mesh of the upper grid plate 102.

[0055] In this embodiment, both the lower grid plate 101 and the upper grid plate 102 are supported by a support platform formed on the inner wall of the aquaculture pond 4 for stable support. The lower grid plate 101 and the upper grid plate 102 can ensure that the cash crops can be stably cultivated in the aquaculture pond 4. The roots and stems of the cash crops can always be placed in the domestic sewage in the aquaculture pond 4 to absorb the nitrogen and phosphorus in the domestic sewage in the aquaculture pond 4, ensuring that the growth of the cash crops can obtain sufficient nutrition, while also effectively separating them from the fish.

[0056] The specific operation of this wastewater treatment and cascade resource utilization system is as follows:

[0057] The sewage inlet pipe introduces domestic sewage into the pre-filtration chamber 62. After large particles of impurities are intercepted by the bar screen 64, the domestic sewage passes through the bar screen 64 and enters the post-filtration chamber 63 to complete the pre-treatment.

[0058] The domestic sewage entering the filtration chamber 63 is sequentially transferred to the anaerobic tank 7, the anoxic tank 1 and the aerobic tank 2 to decompose organic matter. The sewage is aerated and refluxed by the operation of the fountain aerator 32. The nitrogen and phosphorus content in the effluent of the aerobic tank 2 is adjusted to the preset content value. The domestic sewage discharged from the aerobic tank 2 is stored in the clear water tank 8.

[0059] The domestic sewage in the rear clear water tank 8 enters the aquaculture tank 4. In the aquaculture tank 4, economic crops are cultivated and ecological fish are raised in a symbiotic manner according to the design, which reduces the nitrogen and phosphorus content in the domestic sewage.

[0060] The domestic wastewater treated in breeding pond 4 is then introduced into the multi-stage hydroponic breeding area 5 for use, thus making full use of water resources.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A wastewater treatment and cascade resource utilization system, characterized in that, This includes a biological treatment unit and its connected aquaponics unit; The biological treatment unit includes an anoxic tank and an aerobic tank connected thereto. A wastewater circulation section is provided between the aerobic tank and the anoxic tank. The wastewater circulation section is used to adjust the nitrogen and phosphorus content in the effluent of the aerobic tank to a preset value. The aquaponics unit includes an aquaculture pond connected to an aerobic pond. The top of the aquaculture pond is planted with economic crops that are grown using nitrogen- and phosphorus-rich wastewater treated by the aerobic pond as nutrients. The economic crops are planted at a preset planting density. At the bottom of the aquaculture pond, a variety of mixed ecological fish species are raised at a preset planting density. These mixed ecological fish species include fish that feed on the roots of the economic crops and fish that feed on fish excrement.

2. The wastewater treatment and cascade resource utilization system according to claim 1, characterized in that, It also includes a tiered utilization unit, which comprises hydroponic breeding areas arranged sequentially and connected by height differences, wherein the hydroponic breeding area at the highest point is connected to the breeding pond.

3. The wastewater treatment and cascade resource utilization system according to claim 2, characterized in that, Each of the hydroponic breeding areas is equipped with a liquid level monitoring device, as well as a first water quality monitor, a first nitrate nitrogen sensor, and a first dissolved oxygen sensor.

4. A wastewater treatment and cascade resource utilization system according to any one of claims 1-3, characterized in that, The wastewater circulation unit includes: An annular cofferdam, wherein the annular cofferdam is distributed circumferentially along the top edge of the aerobic tank; A fountain aerator is installed in the aerobic tank to spray wastewater from the aerobic tank into the annular dike. A reflux weir is located at the top edge of the anoxic pool and is connected to the annular cofferdam. The reflux weir is also connected to the interior of the anoxic pool.

5. A wastewater treatment and cascade resource utilization system according to claim 4, characterized in that, The aerobic tank is equipped with floats, and the fountain aerator is installed on the floats.

6. A wastewater treatment and cascade resource utilization system according to any one of claims 1-3, characterized in that, It also includes a pretreatment unit located in front of the biological treatment unit, the pretreatment unit comprising: The bar screen well is located in front of the anoxic tank and has a filtration chamber and a waste collection chamber located below the filtration chamber. The filtration chamber is divided into a pre-filtration chamber and a post-filtration chamber by a bar screen. The pre-filtration chamber is connected to a sewage inlet pipe, and the post-filtration chamber is connected to the anoxic tank. The pre-filtration chamber and the waste collection chamber are connected by a slag guide port with a preset height. Floating matter trapped in the pre-filtration chamber is transferred to the slag guide port by buoyancy or a transfer tool.

7. A wastewater treatment and cascade resource utilization system according to claim 6, characterized in that, The wastewater inlet pipe is equipped with an inlet pump, and both the aerobic and anoxic tanks are equipped with a second water quality monitor, a second nitrate nitrogen sensor, and a second dissolved oxygen sensor.

8. A wastewater treatment and cascade resource utilization system according to claim 1, characterized in that, The aquaculture pond is equipped with a grid support assembly, which includes: The lower grid plate is set inside the aquaculture pond and located below the preset highest liquid level in the aquaculture pond. The roots and stems of the economic crops pass through the mesh of the lower grid plate and are placed in the sewage in the aquaculture pond. An upper grid plate is installed at the opening of the aquaculture pond and above the lower grid plate. The upper grid plate is located above the preset highest liquid level, and a constraint space is formed between the lower grid plate and the upper grid plate. The roots and stems of the economic crops pass through the mesh of the upper grid plate.

9. A wastewater treatment and cascade resource utilization system according to claim 1, characterized in that, The biological treatment unit also includes an anaerobic tank located in front of and connected to the anoxic tank.

10. A wastewater treatment and cascade resource utilization system according to claim 1, characterized in that, Both the aerobic and anoxic tanks are equipped with biological packing materials, and the biological packing materials are provided with a certain distance between the bottom and top of the tank.

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