An anti-freezing artificial wetland system in cold regions and a method for temperature control thereof

Abstract

The application provides a cold region anti-freezing artificial wetland system and a temperature control method thereof. The system comprises: a vertical flow artificial wetland; a water collecting pipe is arranged at the bottom of the vertical flow artificial wetland and is filled with fillers; the water collecting pipe is communicated with a vertically arranged water level adjusting pipe, and the water level adjusting pipe comprises: at least two water level pipes with different heights. The fillers are sequentially arranged from top to bottom as: a zeolite layer, a steel slag-humus mixed layer and a volcanic rock-quartz sand layer. Deep root system plants and shallow root system plants are planted in the vertical flow artificial wetland; a water level sensor for measuring the water level height, an ice layer sensor for measuring the ice layer thickness and an air sensor for measuring the air layer thickness between the ice layer and the water surface are arranged in the vertical flow artificial wetland. The system provided by the application can significantly improve the anti-freezing performance of the artificial wetland system, guarantee the activity of microorganisms and improve the sewage treatment effect and operation efficiency.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, specifically to a cold-region frost-resistant artificial wetland system and its temperature control method. Background Technology

[0002] Constructed wetlands are artificially designed and constructed, controllable, engineered wastewater treatment ecosystems composed of packing materials, plants, and microorganisms. They purify wastewater through the combined physical, chemical, and biological processes within the system. Constructed wetlands are characterized by low investment, low operating costs, and convenient maintenance. They also possess strong degradation capabilities for organic matter, high nitrogen and phosphorus removal rates, strong adaptability to load changes, and aesthetic value, thus attracting increasing attention.

[0003] However, the winters in North China, Northeast my country, and Northwest China are cold and long, with freezing periods lasting 3-6 months. In the northern border regions, the annual minimum temperature can reach below -30℃. These harsh climatic conditions reduce the effectiveness of wastewater treatment in constructed wetland systems in these areas, sometimes even causing them to fail to meet standards.

[0004] Therefore, ensuring the effectiveness of constructed wetlands in treating wastewater during winter has become an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a cold-region frost-resistant constructed wetland system and its temperature control method to solve the defect of poor sewage treatment effect of constructed wetlands in winter in the prior art.

[0006] A cold-region frost-resistant constructed wetland system includes: a vertical flow constructed wetland, a distribution channel, and an outlet channel; the distribution channel is connected to the inlet side of the vertical flow constructed wetland; a water collection pipe is provided at the bottom of the vertical flow constructed wetland; the water collection pipe is connected to a vertically installed water level regulating pipe, the water level regulating pipe including: at least two water level pipes at different heights;

[0007] A bubble generator is also installed in the vertical flow constructed wetland; and the vertical flow constructed wetland is filled with filler material; the filler material, from top to bottom, consists of: a zeolite layer, a steel slag-peat mixed layer, and a volcanic rock-quartz sand layer;

[0008] Deep-rooted plants and shallow-rooted plants are planted in the vertical flow constructed wetland; the root depth of the deep-rooted plants is 1.2-1.5m; the root depth of the shallow-rooted plants is 20cm.

[0009] The vertical flow constructed wetland is equipped with a water level sensor for measuring water level height, an ice layer sensor for measuring ice layer thickness, and an air sensor for measuring the thickness of the air layer between the ice layer and the water surface.

[0010] Furthermore, in the cold-region frost-resistant artificial wetland system described above, the thickness of the zeolite layer is 50 cm; the thickness of the steel slag-peat mixed layer is 60 cm; and the thickness of the volcanic rock-quartz sand layer is 70 cm.

[0011] Furthermore, in the cold-region frost-resistant artificial wetland system described above, the water level regulating pipe includes: a water level pipe with a height of 1.2m and a water level pipe with a height of 0.6m.

[0012] Furthermore, in the cold-region frost-resistant constructed wetland system described above, the zeolite layer is a zeolite layer loaded with nano-iron oxide; in the steel slag-peat mixed layer, the biochar content is 30%.

[0013] Furthermore, in the cold-region frost-resistant artificial wetland system described above, the planting density of the deep-rooted plants is 6 plants / m², and the planting density of the shallow-rooted plants is 8 plants / m².

[0014] Furthermore, in the cold-region frost-resistant artificial wetland system described above, the particle diameter of the zeolite layer is 5-8 mm; the particle diameter of the steel slag-peat mixed layer is 3-5 mm; and the particle diameter of the volcanic rock-quartz sand layer is 10-15 mm.

[0015] Furthermore, in the cold-resistant artificial wetland system described above, the deep-rooted plant is cold-resistant reed; the shallow-rooted plant is marsh sedge.

[0016] Furthermore, in the cold-region frost-resistant artificial wetland system described above, graphene is added to the volcanic rock-quartz sand layer.

[0017] A method for temperature control using the cold-region frost-resistant constructed wetland system described above includes:

[0018] When the air temperature reaches or approaches the freezing point, replace the water level regulating pipe with a low water level pipe.

[0019] Low-temperature organic matter degrading bacteria, low-temperature denitrifying bacteria, and low-temperature phosphorus removal bacteria were added to vertical flow constructed wetland 1.

[0020] The water level in the vertical flow constructed wetland is monitored by a water level sensor. When the water level reaches the target height, the thickness of the ice layer is measured by an ice layer sensor. When the ice layer thickness reaches the target thickness, the water level regulating pipe is replaced with a low water level pipe to further reduce the liquid level in the vertical flow constructed wetland until the liquid level reaches the target height. This forms an "ice layer-air layer" insulation structure.

[0021] Activate the bubble generator to create a dynamic water flow under the ice layer and prevent localized freezing;

[0022] Add cold-resistant compound microbial agent, replenish once a month, and maintain a concentration of 10.6 CFU / g filler; the carrier of the cold-resistant compound bacterial agent is: biochar-sodium alginate slow-release granules;

[0023] In summer, the water level regulating pipe is replaced with a high-water-level pipe.

[0024] The cold-region antifreeze constructed wetland system and its temperature control method provided by this invention have the following beneficial effects:

[0025] (1) By adopting multi-layer composite packing, multi-level removal of pollutants and improvement of overall system performance are achieved. In low-temperature environments, it can significantly improve the antifreeze performance of constructed wetland systems, ensure the activity of microorganisms, and improve wastewater treatment effect and operating efficiency.

[0026] (2) Through the synergistic effect of the “deep root system-shallow root system” plant planting method and the multi-layer composite filler, a three-dimensional adsorption and heat slow release network was constructed, which suppressed the freezing phenomenon of the filler, thereby improving the stability of the system and the treatment efficiency of sewage.

[0027] (3) By introducing low-temperature functional microbial community targeted enhancement technology, the denitrification effect on wastewater has been improved;

[0028] (4) Based on the ice layer thickness monitoring and liquid level dynamic adjustment scheme, an "ice layer-air layer" insulation structure is formed, which reduces the heat loss rate to <15% and reduces the system operating cost;

[0029] (4) Through multi-level coordinated temperature control (packing heat storage + microbial enhancement + ice layer management), the energy consumption of sewage treatment in winter is reduced by more than 40%, thereby improving the sewage treatment effect and operating efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the cold-region antifreeze constructed wetland system provided by the present invention;

[0031] Figure label:

[0032] 1-Vertical flow constructed wetland; 2-Water distribution channel; 3-Water level regulating pipe; 4-Water collection pipe; 5-Water outlet channel; 6-Zeolite layer; 7-Steel slag-peat mixed layer; 8-Volcanic rock-quartz sand layer; 9-Deep root plants; 10-Shallow root plants. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Figure 1 The present invention provides a cold-region antifreeze constructed wetland system, which includes: a vertical flow constructed wetland 1, a water distribution channel 2, and an outlet channel 5; the water distribution channel 2 is connected to the water inlet side of the vertical flow constructed wetland 1, and a water collection pipe 4 is provided at the bottom of the vertical flow constructed wetland 1; the water collection pipe 4 is connected to a vertically arranged water level regulating pipe 3; the water level regulating pipe 3 is located in the outlet channel 5; the outlet channel 5 is located on the other side of the direct flow constructed wetland 1. A bubble generator is also installed in the vertical flow constructed wetland 1; the vertical flow constructed wetland 1 is filled with packing material; the packing material, from top to bottom, consists of: a zeolite layer 6, a steel slag-peat mixed layer 7, and a volcanic rock-quartz sand layer 8; deep-rooted plants 9 and shallow-rooted plants 10 are installed in the vertical flow constructed wetland 1; the root depth of the deep-rooted plants 9 is 1.2-1.5m; the root depth of the shallow-rooted plants 10 is 20cm; the water level regulating pipe 3 includes: at least two water level pipes at different heights; a sensor for measuring water level height, an ice layer sensor for measuring ice layer thickness, and an air sensor for measuring the thickness of the air layer between the ice layer and the water surface are installed in the vertical flow constructed wetland 1.

[0035] Specifically, the sewage slowly enters the vertical flow constructed wetland 1 from the distribution channel 2. The sewage is treated by the vertical flow constructed wetland 1, and the treated sewage is discharged from the system through the collection pipe 4 and the water level regulating pipe 3, and finally discharged through the outlet channel 5.

[0036] Furthermore, since the bottom water collection pipe 4 of the vertical flow constructed wetland 1 is connected to the water level regulating pipe 3, the system provided in this application can also precisely adjust the liquid level of the wetland system by replacing water level pipes of different heights according to seasonal changes.

[0037] Deep-rooted plants, such as hardy reeds, have roots that can penetrate deep into the soil or wetland filler, reaching deeper layers. In low-temperature environments, where the surface of the soil or filler may freeze, deep-rooted plants can utilize their roots in the unfrozen layer to continue absorbing and transporting pollutants, especially nutrients such as nitrogen and phosphorus. Furthermore, the roots of deep-rooted plants also have good aeration mechanisms, which help improve the redox conditions of the wetland system, thereby facilitating the biotransformation and removal of pollutants such as nitrogen and phosphorus.

[0038] Shallow-rooted plants, such as marsh sedge, have their roots primarily distributed in the surface layer of the soil or wetland filler. Through their roots, these plants absorb and trap pollutants in the topsoil or filler, helping to reduce pollutant loss and diffusion. Furthermore, shallow-rooted plants form a surface cover, reducing evaporative heat loss and helping to maintain the temperature and humidity of the wetland system, providing favorable conditions for the growth and reproduction of microorganisms.

[0039] When deep-rooted and shallow-rooted plants are planted together in vertical flow constructed wetlands, they form a three-dimensional absorption network. This network covers not only the surface and deep layers of the soil or wetland filler, but also enhances the absorption and transformation of pollutants through the interwoven distribution of roots within the soil or filler. In low-temperature environments, deep-rooted plants continue to absorb pollutants in the unfrozen layer, while shallow-rooted plants can trap and absorb pollutants at the surface. Therefore, this combination significantly improves the removal rate of pollutants such as nitrogen and phosphorus in the wetland system.

[0040] Therefore, the cold-resistant artificial wetland system provided by this invention enhances the wetland system's ability to absorb, retain, and transform pollutants by utilizing a three-dimensional absorption network formed by a combination of deep-rooted and shallow-rooted plants, especially its adaptability to low-temperature environments, thereby improving the wetland system's removal rate of pollutants such as nitrogen and phosphorus.

[0041] In the constructed wetland system provided in this application, zeolite is used as the top layer filler. Because zeolite has a high specific surface area and adsorption capacity, it can adsorb pollutants such as ammonia nitrogen in the influent. At the same time, its high specific surface area is used to store heat and provide a certain amount of heat reserve for the system.

[0042] A mixture of steel slag and peat is used as the intermediate packing. Steel slag, a byproduct of steel production, is alkaline, while peat, rich in organic matter, provides a carbon source to promote denitrification, neutralizes acidic water, and facilitates denitrification. This application utilizes the neutralizing effect of steel slag to regulate the pH of the water, maintaining it within a suitable range for microbial growth. The carbon source provided by peat promotes the growth and reproduction of denitrifying bacteria, improving denitrification efficiency and helping to reduce nitrate concentration in the effluent. A volcanic rock-quartz sand layer is used as the bottom packing. The porous structure of volcanic rock allows for the accumulation of low-temperature microbial communities, enhancing microbial activity in low-temperature environments. Quartz sand, with its stable chemical properties and good physical properties, helps prevent freezing and clogging.

[0043] This application utilizes the enrichment of low-temperature microbial communities in volcanic rock to create a "sanctuary" for microorganisms in the lower packing layer. Even in low-temperature environments, the microorganisms maintain high activity and continue to perform their purification function. Meanwhile, the quartz sand enhances the system's freeze resistance, preventing the packing layer from freezing and clogging, thus ensuring the system's normal operation.

[0044] The system provided in this application achieves multi-level removal of pollutants and improves the overall performance of the system by arranging the packing material in the following order from top to bottom: zeolite layer 6, steel slag-peat mixed layer 7, and volcanic rock-quartz sand layer 8. In low-temperature environments, it can significantly improve the freeze resistance of the constructed wetland system, ensure the activity of microorganisms, and improve wastewater treatment efficiency and operational efficiency.

[0045] Furthermore, this application incorporates a liquid level regulation system within the vertical flow constructed wetland 1, comprising sensors for measuring water level height, ice layer thickness, and air layer thickness, as well as a distribution channel 2, an outlet channel 5, a collection pipe 4, and a water level regulating pipe 3. When a high liquid level is required, the water level regulating pipe 3 is replaced with a longer water level pipe, and the water level sensor monitors the water level within the vertical flow constructed wetland 1 until the target liquid level is reached. Similarly, when a low liquid level is required, the water level regulating pipe 3 is replaced with a shorter water level pipe, and the water level sensor monitors the water level within the vertical flow constructed wetland 1 until the target liquid level is reached. The top height of the vertically installed water level regulating pipe 3 determines the upper limit of the wetland system's liquid level.

[0046] The liquid level regulation system provided in this application can adjust the liquid level in the wetland according to seasonal changes and the actual needs of the wetland system. Specifically, during long and cold winters, the wetland system is susceptible to freezing. The liquid level regulation system raises the liquid level through sensors and water level regulating pipe 3, lowers the liquid level after a layer of ice forms on the surface, and lowers the liquid level again when the ice on the wetland surface reaches a certain thickness. This creates an insulating "ice-air layer" structure on the wetland surface, which reduces heat loss and ensures the normal operation of the system in low-temperature environments. In summer or warmer seasons, the liquid level is lowered through water level regulating pipe 3 to promote oxygen transport and microbial activity, thus ensuring that the wetland system maintains high treatment efficiency in different seasons.

[0047] In this embodiment of the invention, the ice sensor used to measure the thickness of the ice layer can be an ultrasonic sensor. The air sensor used to measure the thickness of the air layer between the ice layer and the water surface can also be an ultrasonic sensor. Its principle is as follows: by emitting ultrasonic pulses and receiving their echoes, the distance between the sensor and the lower surface of the ice layer can be calculated. A water level sensor monitors the position of the water surface, and then, based on the water surface position and the distance between the sensor and the lower surface of the ice layer, the thickness of the air layer between the ice layer and the water surface can be calculated.

[0048] Furthermore, during extreme cold waves (temperatures below -35°C), the water and filler layers in the wetland system are prone to localized freezing due to the extremely low temperatures, which may impair or even disable the purification function of the wetland system. To address this issue, this application introduces a bubble generator within the vertical flow constructed wetland 1. The bubble generator injects microbubbles into the bottom or specific locations of the wetland system via an air pump. As these bubbles rise, they drive the surrounding water to flow, creating a dynamic water flow. This dynamic water flow increases heat exchange between the water and the filler layer, improving the temperature uniformity within the wetland system and effectively preventing localized freezing.

[0049] Furthermore, in the system provided in this application, the thickness of the zeolite layer 6 is 50 cm; the thickness of the steel slag-peat mixed layer 7 is 60 cm; and the thickness of the volcanic rock-quartz sand layer 8 is 70 cm.

[0050] Specifically, the zeolite layer is used to adsorb ammonia nitrogen and slowly release heat. Its high specific surface area allows it to effectively adsorb ammonia nitrogen even at a relatively thin thickness. A thickness of 50 cm ensures sufficient adsorption of ammonia nitrogen in wastewater while also utilizing its heat storage properties to provide some heat to the system, meeting functional requirements without affecting wastewater flow rate or the overall system structure due to excessive thickness. The steel slag-peat mixed layer is responsible for neutralizing acidic water and providing a carbon source to promote denitrification. A thickness of 60 cm is slightly thicker than the zeolite layer because the neutralization reaction of steel slag with acidic water and the process of peat providing a carbon source for denitrification require a certain amount of reaction space and time. Appropriately increasing the thickness ensures a more complete reaction and improves the removal efficiency of nitrogen from wastewater. The volcanic rock-quartz sand layer is used to prevent freezing and clogging and to enrich low-temperature bacteria. A maximum thickness of 70 cm is to provide more space to accommodate low-temperature bacteria, allowing them to grow and metabolize stably in cold environments. The thicker structure also enhances the filtration capacity for impurities in the water flow, effectively preventing the packing layer from freezing and clogging, and ensuring long-term stable operation of the system in low-temperature winter environments.

[0051] Furthermore, as depth increases, the pressure that each layer of packing needs to withstand gradually increases. A thicker volcanic rock-quartz sand layer, serving as the bottom layer, has better compressive strength, stably supporting the upper packing layers and preventing the entire packing system from deforming or collapsing due to pressure, thus maintaining the system's structural stability. The bottom layer is crucial for system insulation. Increasing the thickness of the volcanic rock-quartz sand layer can further slow heat loss from the bottom, working in conjunction with the upper packing layers and the "ice-air layer" insulation structure to reduce the overall heat loss rate of the system. This allows the system to maintain a relatively stable temperature in cold environments, which is beneficial for the survival of microorganisms and the continuous operation of wastewater treatment reactions.

[0052] Furthermore, the water level regulating pipe 3 includes a water level pipe with a height of 1.2m and a water level pipe with a height of 0.6m.

[0053] Furthermore, zeolite layer 6 is a zeolite layer loaded with nano-iron oxide; in steel slag-peat mixed layer 7, biochar accounts for 30%.

[0054] Specifically, nano-iron oxide possesses extremely high specific surface area and surface activity. Loading it onto zeolite increases the active sites on the zeolite surface, significantly enhancing the zeolite's adsorption capacity for ammonia nitrogen. Furthermore, a chemical adsorption reaction exists between nano-iron oxide and ammonia nitrogen, resulting in a more robust binding and less desorption, thus effectively removing ammonia nitrogen from wastewater. In addition, nano-iron oxide can absorb light energy and convert it into heat energy under sunlight. In cold regions with relatively long daylight hours in winter, nano-iron oxide utilizes this characteristic to convert light energy into heat energy, raising the temperature of the zeolite layer and its surrounding environment. This not only helps prevent the packing material from freezing but also provides a suitable temperature environment for microbial growth and metabolism, maintaining microbial activity and further improving wastewater treatment efficiency.

[0055] The porous structure of biochar provides abundant attachment sites for nitrifying bacteria and other microorganisms, enabling the adsorption and immobilization of large quantities of microorganisms. A 30% biochar content allows microorganisms to grow and reproduce stably in the steel slag-peat mixed layer. On the one hand, this increases the number of microorganisms participating in the nitrification reaction, thus improving the nitrification rate. On the other hand, biochar has excellent adsorption properties, capable of adsorbing harmful substances in wastewater and reducing their inhibitory effect on microorganisms. Simultaneously, it can adsorb and retain nutrients, providing a stable nutrient source for microorganisms. Furthermore, the presence of biochar can regulate the pH of the wastewater, making it closer to the suitable growth environment for nitrifying bacteria, further promoting the nitrification reaction and improving the removal of nitrogen from the wastewater.

[0056] Furthermore, the planting density of deep-rooted plant 9 is 6 plants / m²; the planting density of shallow-rooted plant 10 is 8 plants / m².

[0057] Specifically, the high planting density of shallow-rooted plants forms a dense surface cover. On the one hand, this reduces heat loss through evaporation from the wetland surface, helping to maintain the internal temperature of the wetland in low-temperature winter conditions; on the other hand, its covering effect also blocks some of the intrusion of cold air from the outside, further reducing heat loss. The moderate density of deep-rooted plants ensures their adsorption function without being too dense and affecting soil permeability and heat transfer. The combination of these two factors, along with the "ice-air layer" insulation structure, effectively reduces the system's heat loss rate, inhibits the freezing of the filler material, and ensures stable operation of the system in cold regions.

[0058] Furthermore, the particle diameter of zeolite layer 6 is 5-8 mm; the particle diameter of steel slag-peat mixed layer 7 is 3-5 mm; and the particle diameter of volcanic rock-quartz sand layer 8 is 10-15 mm.

[0059] Specifically, from the zeolite layer to the volcanic rock-quartz sand layer, the particle diameter gradually decreases and then gradually increases again, forming a structure similar to a "filter." As wastewater flows through each layer, the larger zeolite particles first trap larger suspended solids and impurities; then, the steel slag-peat mixed layer traps smaller suspended solids and impurities; finally, the largest particles in the volcanic rock-quartz sand layer further filter the wastewater. Due to its large pore size, it is not easily clogged, thus ensuring unobstructed water flow throughout the system and preventing system malfunctions caused by blockages. Furthermore, the zeolite particles, due to their large specific surface area, can store a certain amount of heat during ammonia nitrogen adsorption and slowly transfer it to the surrounding environment. The smaller steel slag-peat mixed layer has relatively slow heat conduction, which can, to some extent, prevent excessive heat loss. This application, through the cooperation of three layers of packing materials with different particle sizes, improves the heat distribution and transfer within the system. Combined with the "ice layer-air layer" insulation structure, it further reduces the heat loss rate, inhibits packing material freezing, and improves the system's anti-freezing performance.

[0060] Furthermore, graphene was added to the volcanic rock-quartz sand layer 8.

[0061] Specifically, graphene possesses excellent electronic conductivity and a large specific surface area. Its large specific surface area provides more attachment sites for low-temperature bacteria, increasing the amount of bacteria attached. Simultaneously, its good conductivity promotes electron transfer inside and outside microbial cells, accelerating microbial metabolic processes and enabling low-temperature bacteria to maintain high activity in cold environments, thus more effectively degrading pollutants in wastewater. Furthermore, graphene's high conductivity optimizes electron transport paths within the system, accelerating electron transfer between microorganisms and packing materials, and between microorganisms and pollutants. This promotes redox reactions, improves the decomposition and transformation efficiency of microorganisms for pollutants such as organic matter, nitrogen, and phosphorus, and ultimately enhances the overall wastewater treatment capacity of the system.

[0062] This invention also provides a method for temperature control in a cold-region frost-resistant constructed wetland system, comprising the following steps:

[0063] When the air temperature reaches or approaches the freezing point, replace water level regulating pipe 3 with a low water level pipe.

[0064] Low-temperature organic matter degrading bacteria, low-temperature denitrifying bacteria, and low-temperature phosphorus removal bacteria were added to vertical flow constructed wetland 1.

[0065] The water level in the vertical flow constructed wetland 1 is monitored by a water level sensor. When the water level reaches the target height, the thickness of the ice layer is measured by an ice layer sensor. When the ice layer thickness reaches the target thickness, the water level regulating pipe 3 is replaced with a low water level pipe to further reduce the liquid level in the vertical flow constructed wetland 1 until the liquid level reaches the target height. This forms an "ice layer-air layer" insulation structure.

[0066] Activate the bubble generator to create a dynamic water flow under the ice layer and prevent localized freezing;

[0067] Add cold-resistant compound microbial agent, replenish once a month, and maintain a concentration of 10. 6 CFU / g filler; the carrier for the cold-resistant compound microbial agent is: biochar-sodium alginate slow-release granules;

[0068] In summer, replace water level regulating pipe 3 with a high water level pipe.

[0069] Specifically, low-temperature organic matter degrading bacteria can decompose organic pollutants in wastewater, low-temperature denitrifying bacteria can remove ammonia nitrogen and nitrate nitrogen through processes such as nitrification and denitrification, and low-temperature phosphorus removal bacteria are responsible for converting and removing phosphorus from wastewater. Because low temperatures in cold regions significantly inhibit the growth and metabolic activities of microorganisms during winter, the number of microorganisms decreases dramatically. This application addresses this by adding low-temperature organic matter degrading bacteria, low-temperature denitrifying bacteria, and low-temperature phosphorus removal bacteria to ensure that the system maintains high removal efficiency for various pollutants in wastewater under low-temperature conditions. Compared to traditional wetland systems without these bacteria, this invention significantly improves wastewater treatment efficiency in winter by adding specific bacteria. Moreover, by supplementing with bacteria adapted to low-temperature environments, the system's self-regulation and adaptability in cold climates are enhanced, making the entire wetland system more stable and reliable in low-temperature environments. The system is less susceptible to changes in the external environment (such as sudden drops in temperature or fluctuations in wastewater quality), reducing the probability of malfunctions, lowering maintenance costs, and extending the system's service life.

[0070] In summary, the system and method provided in this application have the following advantages:

[0071] 1. Improved freeze resistance

[0072] In cold conditions, a significant decrease in porosity can impair wetland treatment efficiency, potentially leading to blockages or impaired water flow. Traditional wetlands experience a 60% decrease in porosity under cold conditions, while the system provided in this application, employing multi-layered composite packing, only reduces porosity by 10-15%. This system utilizes a design with an upper layer of large-diameter zeolite (5-8 mm), a middle layer of steel slag-peat mixture (steel slag particle size 3-5 mm), and a lower layer of volcanic rock-quartz sand (volcanic rock particle size 10-15 mm), constructing a three-dimensional adsorption and heat-releasing network. The synergistic effect of each packing layer inhibits packing freezing. Compared to traditional wetlands, its structure is more rational, effectively maintaining the pore structure of the packing layers and ensuring normal flow and treatment even in low-temperature environments. Furthermore, the protective layer of "ice + air" more effectively prevents heat loss, reducing the heat loss rate to 12.3%. Furthermore, compared to the traditional soil covering insulation method, the heat loss rate is increased by 65%, creating a relatively stable temperature environment inside the wetland system, which is conducive to the survival of microorganisms and the wastewater treatment reaction, thereby further improving the wastewater treatment effect.

[0073] 2. Guarantee of microbial activity:

[0074] This application increases the nitrification rate to 80% of that at room temperature and improves the denitrification efficiency by 3 times by adding low-temperature organic matter degrading bacteria, low-temperature nitrogen-removing bacteria, and low-temperature phosphorus-removing bacteria to the wetland system, thereby greatly improving the system's treatment effect on nitrogen-containing pollutants.

[0075] 3. Energy efficiency:

[0076] This application employs a multi-stage synergistic temperature control technology, including packing heat storage (such as zeolite high specific surface area heat storage), microbial enhancement (utilizing low-temperature bacterial communities for efficient metabolic heat generation at low temperatures), and ice layer management (forming an insulating ice layer and air layer by adjusting the liquid level). These measures work together to fully utilize the heat generated by the system itself, reducing additional heating energy consumption. Compared with traditional electric heating methods, winter operating energy consumption is reduced to 1.2 kW·h / m³, saving 52%, thereby reducing operating costs.

[0077] 4. System stability:

[0078] This application utilizes ultrasonic sensors to monitor ice layer thickness in real time, providing accurate data for dynamic liquid level adjustment. When the ice layer thickness reaches a certain level (e.g., 15cm), the liquid level adjustment system promptly adjusts the liquid level, forming an "ice layer-air layer" insulation structure. This precise monitoring and adjustment mechanism can adjust the system state in a timely manner according to environmental changes, effectively preventing freezing failures in the wetland system at extreme low temperatures of -30℃, enabling the system to operate continuously for 120 days without failure, thus ensuring the continuity and stability of wastewater treatment.

[0079] Example 1:

[0080] like Figure 1 As shown, the pretreated wastewater first enters the distribution channel 2, ensuring that the influent flows into the vertical flow constructed wetland 1 with uniform quality and velocity. The vertical flow constructed wetland 1 is planted with hardy reeds and marsh sedges to form a surface cover layer and reduce evaporative heat loss. The hardy reeds are planted at a density of 6 plants / m², with a root depth of up to 1.2m. The marsh sedges are planted at a density of 8 plants / m². This combination of deep-rooted and shallow-rooted plants forms a three-dimensional absorption network, improving nitrogen and phosphorus removal rates at low temperatures.

[0081] The upper layer of the vertical flow constructed wetland 1 consists of large-diameter zeolite 6 (5-8mm), which adsorbs ammonia nitrogen and slowly releases heat (zeolite has a high specific surface area for heat storage). The middle layer is a steel slag-peat mixed layer 7 (steel slag particle size 3-5mm), which utilizes the alkalinity of steel slag to neutralize acidic water, while peat provides a carbon source to promote denitrification. The lower layer is a volcanic rock-quartz sand layer 8 (volcanic rock particle size 10-15mm), which prevents freezing and clogging and enriches low-temperature bacterial communities.

[0082] A water collection pipe 4 is laid at the bottom of the vertical flow constructed wetland 1. The water collection pipe 4 is connected to a water level regulating pipe 3, which is installed vertically inside the outlet channel 5. The height of the top of the regulating pipe 3 determines the upper limit of the liquid level in the wetland system. According to the principle of communicating vessels, the liquid level in the regulating pipe 3 is always consistent with the liquid level in the vertical flow constructed wetland 1. Therefore, by adjusting the liquid level in the regulating pipe 3, the liquid level in the vertical flow constructed wetland 1 can be controlled synchronously.

[0083] When the air temperature reaches or approaches freezing point, low-temperature organic matter degrading bacteria, low-temperature denitrifying bacteria, and low-temperature phosphorus removal bacteria are added to the vertical flow constructed wetland 1 to ensure a constant microbial biomass in the low-temperature environment wetland system. The liquid level of the wetland system is precisely increased through the water level regulating pipe 3. In winter, the liquid level can be raised to the wetland surface, and after a layer of ice forms on the surface, the liquid level is lowered to maintain a higher temperature inside the wetland filter media. When the ice thickness on the wetland surface is about 15cm, the wetland liquid level is lowered to form a protective layer of "15cm ice layer + 15cm air layer" on the wetland surface. Ice layer thickness is monitored in real time using an ultrasonic sensor.

[0084] Example 2:

[0085] This system was applied in an industrial park in Mohe City, Heilongjiang Province. The climate conditions are as follows: extreme winter temperatures reach -45℃, the freezing period lasts up to 6 months, and the number of days with an average daily temperature below -20℃ exceeds 100 days. The system treats food processing wastewater from the park, with COD 350-500 mg / L, ammonia nitrogen 80-120 mg / L, and total phosphorus 15-20 mg / L.

[0086] (1) System configuration. Deep-rooted plants in the vertical flow constructed wetland: cold-resistant reeds (density 8 plants / m², root depth 1.5m), shallow-rooted plants: Arctic cotton grass (density 10 plants / m², surface cover layer thickened to 20cm). Upgraded filler combination: The upper layer uses a modified zeolite layer (particle size 8-10mm, loaded with nano iron oxide to enhance ammonia nitrogen adsorption and photothermal conversion), with a thickness of 50cm; the middle layer uses a steel slag-biochar mixed layer (steel slag particle size 5mm, biochar content 30%), with a thickness of 60cm, pH adjusted to 7.5-8.0 to promote nitrification; the lower layer uses a volcanic rock-graphene composite layer (incorporating 5% graphene to improve conductivity and activate low-temperature bacteria), with a thickness of 70cm.

[0087] (2) Dynamic control of the liquid level regulation system. Summer (June-September): Install a long water level regulation pipe (height 1.2m) to maintain a high water level (1.0m) and extend the hydraulic residence time to 48 hours; Winter (October-April): Replace the short water level regulation pipe (height 0.6m) to lower the liquid level to 0.5m and reserve space for ice layer construction.

[0088] The thickness of the ice layer is monitored in real time by an ultrasonic sensor. When the ice layer reaches 15cm, the liquid level drops, forming a "15cm ice layer + 15cm air layer" insulation structure.

[0089] During extreme cold waves (< -35℃), additional bubble generators are added to create dynamic water flow under the ice layer to prevent localized freezing.

[0090] Add a cold-resistant compound bacterial agent (containing Pseudomonas psychrophila and Nitrosomonas cryotolerans) once a month, maintaining a concentration of 10. 6 CFU / g packing material;

[0091] Microbial agent carrier: Biochar-sodium alginate slow-release granules, which prolongs the activity of the microbial community to 90 days.

[0092] Operational performance monitoring is shown in Table 1 (Winter 2023 data):

[0093] Table 1

[0094] index Influent concentration effluent concentration Removal rate Standards COD 420mg / L 28mg / L 93.3% <50mg / L (1A) ammonia nitrogen 105mg / L 5.2 mg / L 95.0% <8 mg / L (1A) Total phosphorus 18mg / L 0.5 mg / L 97.2% <1 mg / L (1A) System energy consumption — 0.9kW·h / m³ — 60% lower than electric heating method Porosity variation Initial value 35% Winter low of 29.8% ↓14.9% Traditional systems ↓58%

[0095] This embodiment demonstrates that the system provided in this application can efficiently treat high-concentration industrial wastewater under extreme low-temperature environments through composite packing optimization, intelligent ice layer regulation, and slow-release measures of cold-resistant bacteria. Its freeze resistance and pollutant removal rate are significantly better than those of traditional wetlands, providing a reliable solution for the treatment of industrial wastewater in cold regions.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cold-region frost-resistant constructed wetland system, comprising: A vertical flow constructed wetland (1), a water distribution channel (2), and an outlet channel (5); the water distribution channel (2) is connected to the water inlet side of the vertical flow constructed wetland (1); a water collection pipe (4) is provided at the bottom of the vertical flow constructed wetland (1); characterized in that the water collection pipe (4) is connected to a vertically arranged water level regulating pipe (3), the water level regulating pipe (3) includes: at least 2 water level pipes of different heights; A bubble generator is also installed in the vertical flow constructed wetland (1); and the vertical flow constructed wetland (1) is filled with filler material; the filler material, from top to bottom, is: zeolite layer (6), steel slag-peat mixed layer (7), and volcanic rock-quartz sand layer (8); the particle diameter of the zeolite layer (6) is larger than that of the steel slag-peat mixed layer (7), the particle diameter of the steel slag-peat mixed layer (7) is smaller than that of the volcanic rock-quartz sand layer (8), and the particle diameters of the three filler layers are all different; Deep-rooted plants (9) and shallow-rooted plants (10) are planted in the vertical flow constructed wetland (1); the root depth of the deep-rooted plants (9) is 1.2-1.5m; the root depth of the shallow-rooted plants (10) is 20cm. The vertical flow constructed wetland (1) is equipped with a water level sensor for measuring water level height, an ice layer sensor for measuring ice layer thickness, and an air sensor for measuring the thickness of the air layer between the ice layer and the water surface. The zeolite layer (6) is a zeolite layer loaded with nano-iron oxide; the biochar content in the steel slag-peat mixed layer (7) is 30%; and graphene is added to the volcanic rock-quartz sand layer (8).

2. The cold-region frost-resistant constructed wetland system according to claim 1, characterized in that, The thickness of the zeolite layer (6) is 50 cm; the thickness of the steel slag-peat mixed layer (7) is 60 cm; and the thickness of the volcanic rock-quartz sand layer (8) is 70 cm.

3. The cold-region frost-resistant constructed wetland system according to claim 1, characterized in that, The water level regulating pipe (3) includes a water level pipe with a height of 1.2m and a water level pipe with a height of 0.6m.

4. The cold-region frost-resistant constructed wetland system according to claim 1, characterized in that, The planting density of the deep-rooted plants (9) is 6 plants / m²; the planting density of the shallow-rooted plants (10) is 8 plants / m².

5. The cold-region frost-resistant constructed wetland system according to claim 1, characterized in that, The particle diameter of the zeolite layer (6) is 5-8 mm; the particle diameter of the steel slag-peat mixed layer (7) is 3-5 mm; and the particle diameter of the volcanic rock-quartz sand layer (8) is 10-15 mm.

6. The cold-region frost-resistant constructed wetland system according to claim 1, characterized in that, The deep-rooted plant (9) is cold-resistant reed; the shallow-rooted plant (10) is marsh sedge.

7. A method for temperature control using the cold-region antifreeze constructed wetland system as described in claim 1, characterized in that, include: During winter, the water level regulating pipe (3) is replaced with a low water level pipe; Low-temperature organic matter degrading bacteria, low-temperature denitrifying bacteria, and low-temperature phosphorus removal bacteria were added to the vertical flow constructed wetland (1); The water level in the vertical flow constructed wetland (1) is monitored by a water level sensor. When the water level reaches the target height, the thickness of the ice layer is measured by an ice layer sensor. When the ice layer thickness reaches the target thickness, the water level regulating pipe (3) is replaced with a low water level pipe so that the liquid level in the vertical flow constructed wetland (1) is further reduced until the liquid level reaches the target liquid level height; thus forming an "ice layer-air layer" insulation structure. Activate the bubble generator to create a dynamic water flow under the ice layer and prevent localized freezing; Add cold-resistant compound microbial agent, replenish once a month, and maintain a concentration of 10. 6 CFU / g filler; the carrier of the cold-resistant compound bacterial agent is: biochar-sodium alginate slow-release granules; In summer, the water level regulating pipe (3) is replaced with a high water level pipe.

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