Food chain-based rural domestic sewage treatment system and application

Abstract

The application provides a rural domestic sewage treatment system based on a food chain, which comprises a regulating pool, a bacteria culture pool, an algae culture pool, a grass-carp-benthic species breeding pool and a water storage pool which are sequentially connected, a sewage inlet and a sewage outlet are arranged at the upstream and downstream of the regulating pool respectively, a regulating pump for regulating the liquid level of the bacteria culture pool is arranged between the regulating pool and the bacteria culture pool, a water valve is arranged on the pipeline connecting the bacteria culture pool and the algae culture pool, and the top of the algae culture pool is arranged to be light-transmitting. The application also provides an application of the rural domestic sewage treatment system based on the food chain. By arranging the bacteria culture unit, the algae culture unit and the grass-carp-benthic species breeding unit respectively, the metabolism and conversion rate of substances in different food chain links are strengthened, and the competition is reduced, so that the problems of low material migration and conversion efficiency and insufficient space intensity are solved.

Description

Technical Field

[0001] This invention relates to the field of rural domestic sewage treatment technology, and in particular to a rural domestic sewage treatment system and its application based on a food chain. Background Technology

[0002] Rural domestic sewage mainly originates from residents' daily lives, including activities such as toilet flushing, cooking, washing, and bathing, as well as sewage generated by rural public service facilities (schools, medical and health institutions, public toilets, administrative buildings, and other public buildings). It is characterized by numerous locations, wide distribution, and large overall volume. Currently, rural sewage treatment faces the following main problems:

[0003] 1. Wastewater treatment facilities are inadequate, and wastewater is scattered and difficult to collect, making it difficult to achieve large-scale intensive treatment.

[0004] 2. Conventional urban sewage treatment systems are complex in process, costly, and require a high degree of specialization in operation and maintenance, making them unsuitable for the treatment of rural domestic sewage;

[0005] 3. The quality and quantity of rural domestic sewage vary greatly at different times, which has a significant impact on the stable and efficient operation of sewage treatment systems.

[0006] With changes in rural lifestyles, increased demands for living environments, and greater emphasis on personal health, strengthening the construction of rural sewage discharge, collection, and treatment facilities is an important aspect of improving the living environment of rural residents.

[0007] CN 202011146611.9 discloses a natural sewage treatment system based on the food chain principle. It features interconnected algae ponds, algae-eating organism ponds, emergent plant ecological channels, and submerged plant ponds along the sewage flow direction. Utilizing the water purification capabilities of four biological levels—algae, fish, emergent plants, and submerged plants—it achieves a rational allocation of producers, consumers, and decomposers within a water-based ecosystem, exhibiting low energy consumption, high treatment efficiency, and good aesthetic appeal. However, it is primarily designed for wastewater from domestic sewage treatment plants or slightly polluted river water, and is not suitable for rural domestic sewage with high pollutant concentrations and limited available land area.

[0008] CN 202111214433.3 discloses a method for treating aquaculture wastewater based on a food chain. The method involves sequentially passing the wastewater through a fish pond, an algae cultivation pond, an ecological pond, an algae and insect purification pond, an omnivorous fish pond, and a disinfection pond. Utilizing ecological principles and biological media, and based on the energy transfer effect of the food chain, multiple treatment ponds are set up to treat the wastewater. Without adding any reagents, this method achieves the resource recovery of eutrophic water bodies, removes pollutants from the wastewater while reducing their concentration, and further brings economic benefits.

[0009] However, urban sewage treatment plant effluent, slightly polluted river water, and aquaculture wastewater are completely different from rural domestic sewage. The concentrations of various pollutants such as chemical oxygen demand, ammonia nitrogen, total nitrogen, and total phosphorus are much lower than those in rural domestic sewage. Therefore, these are considered advanced sewage treatment processes, and existing systems or methods are not applicable to rural domestic sewage.

[0010] Aquatic ecosystems possess natural self-purification capabilities, enabling them to treat wastewater. They also offer valuable ecosystem services such as carbon sequestration, environmental beautification, and product generation. However, current wastewater treatment systems based on ecosystem food chains suffer from insufficient spatial efficiency and low material transfer and transformation efficiency because they utilize the structure and functions of natural aquatic ecosystems. Furthermore, existing systems often only consider predatory food chains, neglecting saprophytic food chains, thus failing to fully exploit the wastewater treatment potential of aquatic ecosystems. In addition, rural villages typically possess various large and small unused ponds and pits, providing natural conditions for constructing aquatic ecosystems. Therefore, this characteristic can be fully utilized to artificially construct ecosystems that both treat domestic wastewater and generate economic value. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a rural domestic sewage treatment system based on a food chain. To achieve the above objectives, this invention employs the following technical solution:

[0012] A rural domestic sewage treatment system based on a food chain includes an equalization tank, a bacterial culture tank, an algae culture tank, a grass-fish-benthic culture tank, and a water storage tank connected in sequence. The equalization tank has a sewage inlet and a sewage outlet at its upstream and downstream sides, respectively. An equalization pump for adjusting the liquid level in the bacterial culture tank is installed between the equalization tank and the bacterial culture tank. A water valve is installed on the pipeline connecting the bacterial culture tank and the algae culture tank. The top of the algae culture tank is designed to be transparent.

[0013] Furthermore, a first overflow outlet is provided on one side of the algae cultivation pond, and the first overflow outlet is connected to the grass-fish-benthic culture pond.

[0014] Furthermore, a second overflow outlet is provided on one side of the grass-fish-benthic breeding pond, and the second overflow outlet is connected to the water storage pond.

[0015] Furthermore, the bacterial culture tank is equipped with suspended packing material, which is 0.3-0.5m above the water surface and has a filling ratio of 20%-40%. The packing material is made of polyolefin and / or polyamide with a density ≥2.8kg / m3.

[0016] Furthermore, the algae cultivation tank is equipped with a light-transmitting mesh at the top and a light source assembly inside.

[0017] Furthermore, the bottom of the grass-fish-benthic culture pond is equipped with a filler layer, and the two sides are respectively equipped with an insulation layer and a heating system.

[0018] Furthermore, the filler layer comprises a layer of crushed stone and a layer of gravel laid sequentially from top to bottom.

[0019] Furthermore, the algae in the algae cultivation tank are diatoms and / or green algae. When the temperature is <25℃, the algae in the algae cultivation tank are mainly diatoms, and when the temperature is >25℃, the algae in the algae cultivation tank are mainly green algae.

[0020] Furthermore, the grass in the grass-fish-benthic culture pond is a submerged plant with a planting density of 10-20 plants / m2, the fish stocking density is 5-10 fish / m2, and the benthic organism stocking density is 0.2-0.5 fish / m2.

[0021] The present invention also employs another technical solution:

[0022] An application of a food chain-based rural domestic sewage treatment system, using the treatment system described above, includes the following steps:

[0023] (1) Rural domestic sewage enters the bacterial culture tank to degrade organic matter;

[0024] (2) The effluent from the bacterial culture tank enters the algae culture tank, where algae are used to further degrade organic matter and cultivate algae;

[0025] (3) The overflow of water from the algae cultivation pond enters the grass-fish-benthic culture pond, where algae are used to raise fish, and grass-fish-benthic organisms are used to remove pollutants.

[0026] (3) When the algae produced in the algae culture pond cannot meet the growth needs of 50-70% of the fish, turn on the artificial light source system to supplement the light and promote the growth of algae; when the algae can basically meet the needs of fish growth and reproduction, turn off the artificial light source system.

[0027] (4) When the fish reach the rapid growth period of the following year, the fish are harvested to remove them from the rural domestic sewage treatment system;

[0028] (5) The water overflows into the water circulation system after being treated in the grass-fish-bottom culture pond.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. By utilizing the functional characteristics of organisms at different trophic levels in the food chain of an aquatic ecosystem, an artificial aquatic ecosystem food chain is constructed. By setting up bacterial culture units, algae culture units, and grass-fish-benthic aquaculture units, the metabolic and transformation rates of substances in different food chain links are enhanced and competition is reduced, thus solving the problems of low material migration and transformation efficiency and insufficient space utilization.

[0031] 2. Introducing benthic organisms into the grass-fish-benthic aquaculture unit increases the floating food chain, greatly improves the pollutant removal function of the aquatic ecosystem, and avoids secondary pollution of the water caused by the decay of algae and grass and fish excrement.

[0032] 3. The constructed food chain-based rural domestic sewage treatment system does not require the use of large aeration blowers, does not generate noise during system operation, and has high acceptance among residents. Compared with urban sewage treatment methods, this invention does not require the addition of additional carbon sources or other agents, does not require the maintenance of large, specialized equipment, and can basically achieve automated sewage treatment after the food chain-based rural domestic sewage treatment system is constructed once, reducing the difficulty of operation and maintenance and the cost of sewage treatment.

[0033] 4. The quality and quantity of rural domestic sewage fluctuate greatly. This invention constructs a sewage treatment system based on the food chain, which solves the problem of the difficulty in sewage treatment caused by biotechnology. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the grass-fish-benthic culture pond of the present invention.

[0037] The components include: 1. Equalization tank; 2. Bacterial culture tank; 3. Algae culture tank; 4. Grass-fish-benthic culture tank; 5. Water storage tank; 6. Regulating pump; 7. Sewage inlet; 8. Suspended packing material; 9. Water valve; 10. Light source group; 11. First overflow outlet; 12. Insulation layer; 13. Crushed stone layer; 14. Gravel layer; 15. Second overflow outlet; 16. Heating system; 17. Sewage outlet; 18. Translucent net. Detailed Implementation

[0038] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0041] like Figures 1-2 As shown, the present invention provides a technical solution, a rural domestic sewage treatment system based on a food chain, comprising an equalization tank 1, a bacterial culture tank 2, an algae culture tank 3, a grass-fish-benthic aquaculture tank 4, and a water storage tank 5 connected in sequence. The equalization tank 1 is provided with a sewage inlet 7 and a sewage outlet 17 at its upstream and downstream sides, respectively. An equalization pump 6 for adjusting the liquid level of the bacterial culture tank 2 is provided between the equalization tank 1 and the bacterial culture tank 2. A water valve 9 is provided on the pipeline connecting the bacterial culture tank 2 and the algae culture tank 3. The top of the algae culture tank 3 is designed to be transparent to light.

[0042] By constructing bacterial culture pond 2, algae culture pond 3, and grass-fish-benthic culture pond 4 respectively, the saprophytic food chain was supplemented, the length of the food chain and the number of organisms at each trophic level were optimized, the growth and reproduction rate of organisms at each trophic level was enhanced, and the removal effect of pollutants in rural domestic sewage was strengthened, thus solving the problems of high difficulty, high cost, low acceptance by residents, and inefficient use of space in rural domestic sewage treatment.

[0043] In this embodiment, the regulating tank 1 has a sewage inlet 7 on the upper part of one side and a sewage outlet 17 at the bottom of the other side. The sewage outlet 17 is connected to the regulating pump 6 pipeline to maintain a stable water volume in the regulating tank 2 and input it into the subsequent treatment unit.

[0044] In this embodiment, the bacterial culture tank 2 is equipped with a suspended packing material 8, which is 0.3-0.5m above the water surface, providing attachment sites for anaerobic bacteria.

[0045] In this embodiment, a water valve 9 is provided on the pipeline connecting the bacterial culture tank 2 and the algae culture tank 3 to prevent oxygen, algae, and other types of bacteria in the algae culture tank from entering the bacterial culture tank 2 and affecting the treatment effect of the bacterial culture tank 2.

[0046] Preferably, the filling ratio of the suspended packing material 8 is 20%-40% of the volume of the bacterial culture tank 2.

[0047] Preferably, the aspect ratio of the bacterial culture tank 2 is 2-2.5:1, and the depth is 2.5-3.5m; the bacteria cultured in the bacterial culture tank 2 are anaerobic bacteria.

[0048] Preferably, the top of the algae cultivation tank 3 is provided with a light-transmitting net 18, which blocks external impurities while ensuring the transmission of natural light to supply the growth and reproduction of algae; the interior is provided with a light source group 10, which is activated to supplement light and enhance algae production when the production of algae cannot meet the needs of subsequent fish.

[0049] Preferably, the illuminance of the light source group 10 is 8000-12000 Lux.

[0050] Preferably, the algae cultivation pond 3 is provided with a first overflow outlet 11 on one side. The first overflow outlet 11 is connected to the grass-fish-benthic culture pond 4, so that the water produced in the algae cultivation pond 3 after algae treatment and the algae with high density can overflow into the grass-fish-benthic culture pond 4 for further water treatment, and the algae can be used as feed for fish.

[0051] More preferably, the length-to-width ratio of the algae cultivation tank 3 is 5-5.5:1, and the depth is 0.5-1m. The bacteria cultivated are aerobic bacteria, and the algae are diatoms and / or green algae. When the temperature is below 25℃, diatoms are the main algae, and when the temperature is above 25℃, green algae are the main algae.

[0052] Preferably, a second overflow outlet 15 is provided on one side of the grass-fish-benthic breeding pond 4. The second overflow outlet 15 is connected to the water storage pond 5, and the water that has been treated by the grass-fish-benthic organisms and meets the water quality standards is sent to the water storage pond 5 for temporary storage for subsequent recycling.

[0053] In a further preferred embodiment, the bottom of the grass-fish-benthic culture pond 4 is provided with a packing layer, and the two sides are respectively provided with an insulation layer 12 and a heating system 16, so that the water temperature is maintained in a relatively stable state and the impact of the season is reduced.

[0054] Furthermore, the filler layer comprises, from top to bottom, a gravel layer 13 and a sand and gravel layer 14; the gravel layer 13 has a thickness of 5-10 cm and a gravel particle size of 0.8-1.5 cm; the sand and gravel layer 14 has a thickness of 3-5 cm, providing a growth environment and space for benthic organisms and submerged plants.

[0055] A primary treatment method for wastewater in suburban areas, using a treatment system as described above, includes the following steps:

[0056] (1) Rural domestic sewage enters bacterial culture tank 2 to degrade organic matter;

[0057] (2) The effluent from bacterial culture tank 2 enters algae culture tank 3, where algae further degrade organic matter and cultivate algae;

[0058] (3) The overflow of water from the algae culture pond 3 enters the grass-fish-benthic culture pond 4, where algae are used to raise fish, and grass-fish-benthic organisms are used to remove pollutants.

[0059] (3) When the algae produced in algae culture pond 3 cannot meet the growth needs of 50-70% of the fish, turn on the artificial light source system to supplement the light and promote the growth of algae; when the algae can basically meet the needs of fish growth and reproduction, turn off the artificial light source system.

[0060] (4) When the fish reach the rapid growth period of the following year, the fish are harvested to remove them from the rural domestic sewage treatment system;

[0061] (5) The water treated by the grass-fish-bottom culture pond 4 overflows into the water circulation system.

[0062] To facilitate the explanation of the effects of this invention, the following specific parameters are used to construct a rural domestic sewage treatment system:

[0063] (1) Construct a bacterial culture tank 2: 3m long, 1.3m wide, and 2.5m deep, which can hold 10t of domestic sewage and is equipped with a suspended rope-type three-dimensional elastic packing material with a filling ratio of 30%. The top of the suspended rope-type three-dimensional elastic packing material is 0.3m away from the water surface.

[0064] (2) Construct algae cultivation tank 3: 20m long, 4m wide, 1m deep, capable of holding 80t of domestic sewage, equipped with a dedicated light source for immersion algae cultivation, configured with a light intensity of 10000Lux; when the temperature is <25℃, diatoms are introduced, and when the temperature is >25℃, green algae are introduced; the algae cultivation unit is also equipped with a heat preservation system and / or a heating system 16, the heat preservation system is activated when the ambient temperature is below 20℃, and the heating system 16 is activated when the ambient temperature is below 5℃;

[0065] (3) Constructing a grass-fish-benthic aquaculture pond 4: Using existing rural ponds, construct a grass-fish-benthic aquaculture pond 4 with a length of 12m, a width of 4m, a water depth of 2.5m, and a capacity to hold 120t of domestic sewage. Lay a 5cm thick layer of sand at the bottom, and then lay an 8cm thick layer of gravel on top of the sand as filler. The gravel has a particle size of 0.8-1.5cm. Plant 800 submerged plants such as foxtail algae, goldfish algae, and black algae evenly on the filler. Then, release 400 crucian carp and silver carp, and 15 carp and catfish.

[0066] Operation of rural domestic sewage treatment systems:

[0067] (1) The sewage in the rural sewage regulating pond 1 is transported to the bacterial culture pond 2 through the pipeline and left for 12 hours to degrade the large molecular organic matter in the sewage into small molecular substances;

[0068] (2) The effluent from the bacterial culture tank 2 enters the algae culture tank 3. Diatoms and / or green algae use the degraded small molecules to grow and reproduce, further degrading and utilizing organic matter and nutrients such as nitrogen and phosphorus in the sewage to obtain a large amount of algae. In the early stage of operation of the village domestic sewage treatment system (within 15 days), in order to promote the growth of algae in the spring when the temperature is low and to ensure the fish's demand for algae, the artificial light source system is activated at night and covered with the heat preservation system.

[0069] (3) The overflow of water from the algae cultivation pond 3 enters the grass-fish-benthic culture pond 4. The large amount of algae cultivated in the algae cultivation pond 3 is used to feed the fish. At the same time, the planted submerged plants such as foxtail algae further absorb pollutants such as nitrogen and phosphorus in the water and provide food for the growth and reproduction of the fish. The excrement produced by the fish, the decaying algae and the dead branches and leaves of the submerged plants are used by the benthic organisms such as catfish, avoiding secondary pollution caused by the release of pollutants into the water due to the metabolism of grass-fish-benthic organisms.

[0070] (4) In the following year, after May or June, the fish in the grass-fish-bottom breeding pond 4 are harvested and sold to generate economic value. Then, new fish fry are released and the rural domestic sewage treatment system is circulated.

[0071] Table 1. Water quality indicators before and after treatment by rural domestic sewage treatment system (concentration unit: mg / L)

[0072]

[0073] Comparative Example 1

[0074] The method and steps are the same as above, except that bacterial culture tank 2 and algae culture tank 3 are replaced with bacterial-algae co-culture tanks to treat rural domestic sewage.

[0075] Table 2 Water quality indicators before and after treatment (concentration unit: mg / L)

[0076]

[0077] As can be seen from Table 2, the water quality after treatment by bacterial culture tank 2 and algae culture tank 3 is significantly better than the water quality after treatment by bacterial-algae co-culture tank.

[0078] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A food chain based rural domestic wastewater treatment system, characterized in that, The system comprises a regulating pool, a bacteria culture pool, an algae culture pool, a grass-fish-benthic species breeding pool and a water storage pool connected in sequence, a sewage inlet and a sewage outlet are arranged at the upstream and downstream of the regulating pool respectively, a regulating pump is arranged between the regulating pool and the bacteria culture pool to regulate the liquid level of the bacteria culture pool, a water valve is arranged on the pipeline connecting the bacteria culture pool and the algae culture pool, and the top of the algae culture pool is arranged to be light-transmitting; The bacteria culture pool is provided with a suspended filler, the distance between the suspended filler and the water surface is 0.3-0.5 m, the filling ratio is 20%-40%, and the filler is polyolefin and / or polyamide with a density of ≥2.8 kg / m3; The top of the algae culture pool is provided with a light-transmitting net, and the inside is provided with a light source group; The grass-fish-benthic species breeding pool is provided with a filler layer at the bottom, and is provided with a heat preservation layer and a heating system at two sides respectively, and the filler layer comprises a gravel layer and a sand layer arranged in sequence from top to bottom; The algae in the algae culture pool are diatoms and / or green algae, when the temperature is <25℃, the diatoms are mainly used in the algae culture pool, when the temperature is >25℃, the green algae are mainly used in the algae culture pool, the grass in the grass-fish-benthic species breeding pool is submerged plant, the planting density is 10-20 plants / m2, the fish is released at a density of 5-10 tails / m2, and the benthic organism is released at a density of 0.2-0.5 tails / m2.

2. A food chain based rural domestic wastewater treatment system as claimed in claim 1, wherein: One side of the algae culture pool is provided with a first overflow port connected with the grass-fish-benthic species breeding pool.

3. A food chain based rural domestic wastewater treatment system as claimed in claim 1, wherein: One side of the grass-fish-benthic species breeding pool is provided with a second overflow port connected with the water storage pool.

4. Use of a food chain-based rural domestic wastewater treatment system, characterized in that, The treatment system is used, and the steps are as follows: (1) the rural domestic sewage enters the bacteria culture pool to degrade organic matter; (2) the water in the bacteria culture pool enters the algae culture pool to further degrade organic matter by using algae and to culture algae; (3) the water in the algae culture pool overflows into the grass-fish-benthic species breeding pool to breed fish by using algae and to remove pollutants by using grass-fish-benthic organisms; (3) when the algae produced in the algae culture pool cannot meet the growth demand of 50-70% of the fish, the artificial light source system is started to supplement light and promote the growth of algae; when the algae can basically meet the growth and reproduction demand of the fish, the artificial light source system is turned off; (4) when the fish is bred to the rapid growth period of the next year, the fish is caught to leave the rural domestic sewage treatment system; (5) the water treated by the grass-fish-benthic species breeding pool overflows into the water circulation system.

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