Constructed wetland and stabilization pond combined sewage treatment method and system based on tidal flow

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses a constructed wetland and stabilization pond combined sewage treatment method and system based on tidal flow. Specific compositions contained in the system mainly comprise a composite filler and an immobilized denitrifying bacterium agent. The composite filler is prepared from gravel, modified zeolite, biochar and a calcium-based phosphorus removal agent according to a specific mass part ratio; the immobilized denitrifying bacterial agent takes sodium alginate-biochar microspheres as a carrier to load denitrifying bacteria. The preparation method comprises the following steps: sewage is pretreated and then enters the stabilization pond for primary treatment, then enters the constructed wetland for tidal operation, anaerobic strengthening, aerobic reoxygenation and filler regeneration, and finally is purified and recycled. The composition provided by the invention can provide a synergistic effect of efficient adsorption, chemical precipitation and biodegradation for pollutant removal, and has the advantage of improving the nitrogen and phosphorus removal efficiency and operation stability of a system; in addition, the preparation method disclosed by the invention has the advantages of mature process, controllable parameters and easiness in large-scale production.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically, to a wastewater treatment method and system based on a combination of artificial wetlands and stabilization ponds using tidal flow. Background Technology

[0002] In the field of wastewater treatment, constructed wetland technology is widely used in urban domestic sewage and rural decentralized sewage treatment scenarios due to its advantages such as eco-friendliness, low operating costs, and simple maintenance. Its core is to remove pollutants through the synergistic effect of filler material, plants, and microorganisms in the wetland. Stabilization pond technology, on the other hand, is often used as a pretreatment unit for the initial degradation and sedimentation of wastewater due to its simple structure and low energy consumption. By setting a certain hydraulic retention time, it reduces the pollution load of subsequent treatment units. The combination of the two has become one of the common wastewater treatment solutions, which can ensure treatment effect while taking into account economy and ecology.

[0003] However, existing wastewater treatment technologies combining constructed wetlands and stabilization ponds still have significant shortcomings: traditional constructed wetlands mostly operate with fixed inundation and drainage cycles, which cannot adaptively adjust to real-time changes in pollutant loads such as COD and ammonia nitrogen in the influent. When the influent concentration suddenly increases, the fixed cycle is difficult to match the pollutant degradation requirements, easily leading to incomplete treatment. The hydraulic retention time of stabilization ponds is also mostly preset fixed values. When facing shock loads, the initial degradation and sedimentation effects decrease significantly. Moreover, the two lack an intelligent collaborative control mechanism and cannot optimize operating parameters through real-time water quality data linkage. Ultimately, this results in the entire system having weak resistance to shock loads, poor treatment stability, and effluent water quality that is prone to fluctuations, making it difficult to continuously meet the requirements for discharge or reuse. Summary of the Invention

[0004] To address the issues of unstable treatment efficiency and insufficient resistance to shock loads in existing constructed wetland systems, this application provides a wastewater treatment method and system based on a combination of constructed wetlands and stabilization ponds using tidal flow.

[0005] Firstly, this application provides a wastewater treatment method based on a combination of constructed wetlands and stabilization ponds using tidal flow, employing the following technical solution: A wastewater treatment method based on a combination of constructed wetlands and stabilization ponds using tidal flow, the method comprising the following steps: S1. Pretreatment: The wastewater to be treated is subjected to bar filtration and grit removal to remove large suspended solids; S2. Wastewater introduction: The pretreated wastewater is transported to a stabilization pond unit for preliminary degradation and sedimentation treatment. The hydraulic retention time of the stabilization pond unit is set to 2-7 days, and the water depth is 1-2.5 meters. S3, Tidal Flow Intelligent Control: By adjusting the inlet valve, the artificial wetland unit can periodically alternate between submerged and drained states, with the submerged period lasting 4-12 hours and the drained period lasting 2-8 hours. S4. Anaerobic enhancement during flooding: When the constructed wetland unit is in a flooded state, add immobilized denitrifying bacteria and supplement liquid carbon source when the influent carbon-nitrogen ratio is monitored to be lower than 5:1 to promote anaerobic phosphorus removal and denitrification reaction. S5. Aerobic reoxygenation during the drainage period: When the constructed wetland unit is in a drained state, natural ventilation or auxiliary aeration is used to promote system reoxygenation, which is used to enhance nitrification and organic matter degradation. S6. Composite packing regeneration: During the middle of the drainage period, the composite packing layer is rinsed with intermittent micro-water flow to prevent blockage and restore its adsorption and microbial attachment capabilities. S7. Water purification and reuse: The water treated by the constructed wetland is further purified through an ecological filter or ultraviolet disinfection unit, and some of the effluent can be reused for farmland irrigation or landscape water replenishment.

[0006] By adopting the above technical solutions, large particulate suspended solids in wastewater are removed through the physical interception of bar filtration and grit removal, reducing the risk of clogging of the packing material in the subsequent stabilization pond and constructed wetland units, and lowering the pollutant load in subsequent treatment stages, thus creating more suitable water quality conditions for subsequent biological treatment. By setting a hydraulic retention time of 2-7 days and a water depth of 1-2.5 meters in the stabilization pond units, sufficient degradation time and living space are provided for microorganisms, achieving preliminary degradation of organic matter and sedimentation of some suspended solids in the wastewater, thereby reducing the treatment pressure on the constructed wetland units. By adjusting the inlet valve to control the periodic alternation of the 4-12 hour submersion period and the 2-8 hour drainage period in the constructed wetland units, anaerobic and aerobic environments are alternately created to adapt to the different metabolic needs of microorganisms, thus laying the environmental foundation for subsequent anaerobic enhancement and aerobic reoxygenation processes. By adding immobilized denitrifying bacteria during the submersion period of the constructed wetland, a stable attachment carrier is provided for the denitrifying bacteria to improve the retention rate of the bacteria, thereby enhancing the denitrification reaction under anaerobic conditions. When the carbon-to-nitrogen ratio of water is below 5:1, liquid carbon source is added to provide sufficient carbon substrate for denitrifying bacteria, thus preventing insufficient carbon source from limiting the denitrification reaction. The two work synergistically to promote efficient anaerobic phosphorus removal and denitrification. During the drainage period of the constructed wetland, natural ventilation or auxiliary aeration is used to supplement the system with oxygen to increase the dissolved oxygen concentration, which enhances the nitrification reaction and organic matter degradation capacity of aerobic microorganisms, thereby balancing some pollutants generated in the anaerobic stage and improving the overall purification effect. During the drainage period, intermittent micro-flow flushing of the composite packing layer is used to disperse suspended solids and aging biofilm trapped in the composite packing layer, which prevents the composite packing layer from becoming clogged, restores the adsorption capacity of the composite packing and the space for microbial attachment, and thus maintains the long-term stable treatment efficiency of the constructed wetland unit. Through the physical filtration, chemical adsorption and plant absorption of the ecological filter, as well as the sterilization effect of the ultraviolet disinfection unit, residual pollutants and pathogenic microorganisms in the water are further removed, so that the effluent meets the reuse needs of farmland irrigation or landscape water replenishment, realizing the resource utilization of wastewater.

[0007] Preferably, in step S4, the composite filler is composed of the following components in parts by weight: 80-120 parts gravel, 20-60 parts modified zeolite, 20-30 parts biochar, and 20-30 parts calcium-based phosphorus removal agent; the particle size range of the composite filler is 5-30 mm.

[0008] By adopting the above technical solution, the gravel in the composite packing material, combined with its particle size range and mechanical strength characteristics, supports the upper modified zeolite, biochar, and calcium-based phosphorus removal agent, preventing the composite packing layer from compacting and clogging due to its own weight or water flow impact. Simultaneously, the gaps between the gravel particles form stable water flow channels, ensuring uniform permeation and distribution of wastewater throughout the composite packing layer. The modified zeolite, with its enhanced pore structure and surface adsorption activity, directionally adsorbs ammonia nitrogen, some small-molecule organic matter, and trace heavy metal ions from wastewater. Furthermore, the porous structure of zeolite provides ample attachment sites for anaerobic microorganisms, promoting stable colonization of the microbial community. Biochar, with its high specific surface area and abundant micropores and mesopores, further enhances its function. The biochar adsorbs recalcitrant organic matter and pigments from wastewater, while providing a microenvironment for the growth and reproduction of anaerobic microorganisms such as denitrifying bacteria. Furthermore, the biochar slowly releases its own carbon content, supplementing any potentially insufficient carbon source during denitrification. The calcium-based phosphorus removal agent reacts with phosphate ions in the wastewater to form insoluble calcium phosphate precipitates, specifically removing phosphorus from the wastewater. The components are proportioned according to the above mass ratio and controlled within a particle size range of 5-30 mm, forming a complementary composite packing system. This system synergistically enhances pollutant adsorption, microbial attachment, and targeted phosphorus removal, providing a stable and functionally comprehensive reaction carrier to support the efficient anaerobic phosphorus removal and denitrification reactions during the flooding period of the constructed wetland unit.

[0009] Preferably, in step S4, the denitrifying bacteria agent is a fixed-support type, and its carrier is sodium alginate-biochar microspheres, with an agent dosage of 0.5-2 kg / m³. 3 The wetland volume is adjusted, and the addition frequency is once every 30-90 days.

[0010] By adopting the above technical solution, and designing the denitrifying bacteria agent as a fixed-support type using sodium alginate-biochar microspheres as the carrier, sodium alginate, with its gel properties, can encapsulate and fix the bacteria agent, preventing it from being lost with the wastewater flow. Biochar, with its high specific surface area and porous structure, provides additional attachment sites for the bacteria agent and maintains humidity and nutrient supply within the microenvironment. Together, they improve the retention rate and activity of the bacteria agent in the constructed wetland, thus continuously providing sufficient and efficient functional bacteria for anaerobic phosphorus removal and denitrification reactions. By controlling the dosage of the bacteria agent and combining it with the actual wetland treatment... The scale and metabolic activity of the microbial agent itself ensure that the concentration of functional bacteria in the wetland is within the range suitable for the reaction requirements. This avoids both insufficient dosage leading to insufficient driving force for denitrification and excessive dosage causing waste of microbial agent resources, thus supporting the stable development of denitrification. By setting the dosage frequency to once every 30-90 days, combined with the natural survival cycle and daily loss of denitrifying bacteria in the wetland composite packing layer, it can regularly replenish the microbial agent lost due to aging and water flow erosion, maintain the stability of the quantity and activity of functional bacterial communities in the wetland, and thus ensure the long-term and efficient advancement of anaerobic phosphorus removal and denitrification.

[0011] Preferably, in step S3, the operation of adjusting the inlet valve is to adjust the ratio of flooding and draining time in real time according to the concentrations of COD, ammonia nitrogen, and total phosphorus in the inlet water. When the COD of the inlet water is higher than 300 mg / L, the flooding period is extended by 20-40%; when the ammonia nitrogen of the inlet water is higher than 30 mg / L, the draining period is extended by 10-30%.

[0012] By adopting the above technical solution, the influent valves are adjusted in real time according to the influent COD, ammonia nitrogen, and total phosphorus concentrations to dynamically adjust the ratio of submersion to drainage time in the constructed wetland unit. This allows the anaerobic and aerobic environments within the wetland to adapt to changes in influent water quality, avoiding inadequate treatment or resource waste caused by water quality fluctuations under a fixed cycle. When the influent COD is higher than 300 mg / L, the submersion period is extended by 20-40%. The anaerobic environment created during submersion provides more reaction time for anaerobic microorganisms, thus matching the high organic load and promoting COD degradation. To avoid the impact of insufficient anaerobic time on subsequent treatment of high COD wastewater, when the influent ammonia nitrogen exceeds 30 mg / L, the drainage period is extended by 10-30%. This utilizes the aerobic environment created by natural ventilation or auxiliary aeration during the drainage period to provide nitrifying bacteria with more oxygen and reaction time. This helps to match the high ammonia nitrogen load, enhance nitrification, and thus facilitate efficient ammonia nitrogen conversion. The synergistic effect of these three factors ultimately achieves dynamic optimization of the wetland operating environment based on the concentration of core pollutants in the influent, providing suitable reaction conditions for subsequent anaerobic enhancement and aerobic reoxygenation processes, and supporting the system's stable treatment of wastewater of different qualities.

[0013] Preferably, in step S6, the flow rate of the micro-water flow rinsing is controlled at 0.5-2 L / min, the duration is 10-30 min, and the rinsing interval is once every 3-7 tidal cycles.

[0014] By adopting the above technical solution, the flow rate of the micro-flow flushing is controlled at 0.5-2 L / min. This gentle flow effectively disperses suspended solids and aged biofilm trapped within the composite packing layer, while avoiding damage to the overall structure of the composite packing layer or loss of attached functional microorganisms due to excessive flow rate. Simultaneously, it ensures that the water flow penetrates evenly to the depths of the composite packing layer, ensuring effective flushing of even deep layers and preventing localized blockages. By controlling the flushing duration to 10-30 minutes, combined with the gentle flow rate, blockages within the gaps of the composite packing are thoroughly flushed within a limited time, while avoiding water waste or excessive time commitment during drainage due to prolonged flushing. Time influences the aerobic reoxygenation effect, balancing the flushing effect with the operational requirements of other processes in the system. By setting a flushing interval of once every 3-7 tidal cycles, combined with the tidal flow pattern, the composite packing layer will retain a certain amount of pollutants after each tidal cycle. This serves to regenerate the composite packing before serious blockage occurs, avoiding the accumulation of blockages that could hinder wastewater infiltration and reduce pollutant removal efficiency. At the same time, it reduces unnecessary frequent flushing, which could interfere with the stability of the microbial community in the composite packing layer. These three factors work together to form a precise composite packing regeneration operation, continuously restoring the adsorption capacity and microbial attachment space of the composite packing, providing support for the long-term stable treatment efficiency of the constructed wetland unit.

[0015] Preferably, in step S7, aquatic plants are planted in the ecological filter pond and sulfur-iron composite filter media is laid, with a filter media layer thickness of 0.3-0.6m.

[0016] By adopting the above technical solution, aquatic plants are planted in the ecological filter bed. The roots of these plants absorb nutrients such as nitrogen and phosphorus from the wastewater. Simultaneously, the microbial community attached to the root surface further degrades residual small-molecule organic matter in the water. Furthermore, the pores formed by the interlacing roots optimize water flow distribution and aid aeration within the filter bed, resulting in a multi-faceted enhanced pollutant removal effect. By laying sulfur-iron composite filter media, the sulfur in the media provides electron donors for sulfur-autotrophic denitrifying bacteria, promoting the deep conversion of residual ammonia nitrogen. Simultaneously, the iron ions react chemically with phosphate ions in the water to form insoluble phosphate precipitates, enhancing the final removal of phosphorus. The filter media removes pollutants, and its own particle gaps can physically trap suspended impurities in the water, playing a combined role of targeted purification and filtration. By controlling the thickness of the filter media layer to 0.3-0.6m, sufficient retention time of wastewater within the filter media layer is ensured, allowing aquatic plants to absorb, filter media to adsorb, and chemical reactions to proceed fully. At the same time, excessive thickness is avoided, which would increase water flow resistance and filter energy consumption, thus balancing purification effect and operating efficiency. These three elements work together to construct an ecological filter treatment system that integrates plant absorption, filter media purification, and structural adaptation, further reducing pollutant residues in the effluent from the constructed wetland and providing a guarantee for subsequent ultraviolet disinfection units to achieve effluent reuse.

[0017] Preferably, in step S4, the liquid carbon source is a sodium acetate solution or a plant straw extract, and the dosage is 1-5 grams of COD equivalent per cubic meter of wastewater.

[0018] By adopting the above technical solutions, sodium acetate solution is selected as the liquid carbon source. Utilizing the characteristic that sodium acetate is easily degraded and absorbed rapidly by denitrifying bacteria, it quickly replenishes the carbon source and prevents the denitrifying bacteria from stagnating due to insufficient carbon, thus providing a timely and efficient substrate for anaerobic phosphorus removal and denitrification. Plant straw extract is selected as the liquid carbon source. Relying on the natural organic components of plant straw, it not only provides the carbon source required for denitrification but also, through its slow carbon release characteristic, provides a continuous carbon supply, meeting the long-term needs of the denitrification reaction. Furthermore, plant straw is widely available and inexpensive, reducing the economic cost of carbon source addition. The choice between the two carbon sources can be flexibly adapted according to the actual wastewater properties and on-site supply conditions, meeting the carbon source supply needs of different application scenarios. By controlling the liquid carbon source addition amount to 1-5 grams of COD equivalent per cubic meter of wastewater, combined with the carbon source gap calculation when the influent carbon-nitrogen ratio is less than 5:1, it accurately replenishes the carbon source required for the denitrification reaction. This approach avoids both insufficient dosage leading to inadequate denitrification and incomplete nitrogen removal, and excessive dosage causing carbon source waste and even raising COD in the effluent. Ultimately, by selecting specific carbon source types and precisely controlling dosage, it provides stable and suitable carbon source support for the efficient advancement of anaerobic phosphorus removal and denitrification during the flooding period of constructed wetland units.

[0019] Secondly, this application provides a combined artificial wetland and stabilization pond wastewater treatment system based on tidal flow, employing the following technical solution: A combined artificial wetland and stabilization pond wastewater treatment system based on tidal flow, the system comprising: Stabilization pond unit, used for receiving and initially treating wastewater; The constructed wetland unit is connected to the stabilization pond unit via pipes and has a built-in composite filler layer and plant layer; The tidal flow intelligent control unit, including an inlet valve, a programmable controller, and an online water quality monitor, is used to achieve alternating operation of flooding and drainage; The composite packing regeneration unit, including a micro-flow flushing pipe and a solenoid valve, is installed inside the constructed wetland unit; The carbon source dosing unit includes a storage tank, a metering pump, and a carbon-nitrogen ratio detector, which is used to automatically add liquid carbon source according to the carbon-nitrogen ratio of the influent.

[0020] By adopting the above technical solution, the stabilization pond unit achieves its function through its specific structural design. The impermeable layer at the bottom of the pond effectively prevents sewage infiltration, and its volume is planned according to the designed hydraulic retention time. Internally, different functional zones are set up. The naturally formed microbial and algal communities in the facultative zone perform preliminary decomposition of organic matter in the sewage. Simultaneously, the hydraulic conditions in the sedimentation zone cause suspended solids to settle under gravity, thus completing the primary treatment of the sewage. The constructed wetland unit constructs the treatment environment through its multi-layered structure. The unit inlet is connected to the stabilization pond via a pipe to receive incoming water. The composite filler material inside is arranged in layers, with the bottom layer consisting of large-diameter gravel providing support and... The flow guide layer consists of a middle layer composed of a mixture of modified zeolite and biochar, and an upper layer covered with a calcium-based phosphorus removal agent. The particle size of each layer's filler material is strictly controlled to ensure permeability and specific surface area. Pollution-tolerant aquatic plants are planted at the top of the unit; their roots not only directly absorb nutrients but also create favorable conditions for the growth of the microbial biofilm and system reoxygenation, thus providing the necessary physical and biological environment for subsequent biochemical reactions. The tidal flow intelligent control unit switches operating modes through the coordinated operation of a series of automated components. An online water quality monitor installed at the inlet continuously collects key water quality parameters and transmits them to the program controller. The program controller, based on built-in algorithms, automatically adjusts the operating mode when the chemical oxygen demand (COD) concentration increases. The system extends the flooding period and automatically extends the drainage period when ammonia nitrogen concentration increases, thereby calculating the optimal operating cycle under the current water quality conditions. Based on this, the controller sends commands to the inlet valves to adjust their opening and closing sequence and degree, thus precisely controlling the alternation rhythm of flooding and drainage within the constructed wetland unit to match the operating conditions with the inlet load. The composite packing regeneration unit maintains the packing performance through periodic physical flushing. This unit consists of perforated pipes installed in the composite packing layer and solenoid valves connected to them. According to a preset cycle, the programmable controller sends commands to open the solenoid valves during the system's drainage phase, allowing a low-velocity water flow to uniformly penetrate the composite packing layer within a specific time, utilizing the shear force of the water flow. The process removes and flushes away suspended solids and some aged biofilm accumulated on the surface of the composite packing material, thereby maintaining the porosity and biological activity of the composite packing layer. The carbon source addition unit ensures the accuracy of carbon source replenishment through an automatic monitoring and quantitative addition mechanism. The carbon-nitrogen ratio detector monitors the carbon-nitrogen ratio in the influent in real time, and sends a signal to the program controller when insufficient carbon source is detected. The program controller calculates the required amount of sodium acetate solution or plant straw extract by combining the influent flow rate and the preset addition coefficient, and starts the metering pump to accurately extract the corresponding volume of liquid carbon source from the storage tank and inject it into the influent end of the constructed wetland unit, thereby ensuring that the subsequent denitrification and other biochemical processes can obtain sufficient reaction substrates.

[0021] Preferably, the composite packing layer comprises, from bottom to top, a gravel support layer, a modified zeolite layer, a biochar layer, and a calcium-based phosphorus removal agent layer, with a total thickness of 0.5-1.2 m; when the constructed wetland unit is in a submerged state, the composite packing layer is used to provide a carrier for anaerobic phosphorus removal and denitrification reactions.

[0022] By employing the above technical solution, a bottom support layer is constructed using large-particle gravel, which supports the upper packing layer and maintains the overall structural stability, ensuring the packing layer maintains the predetermined pore distribution under long-term immersion conditions. Modified zeolite particles are laid above the support layer, utilizing their unique pore structure and ion exchange characteristics to selectively adsorb ammonia nitrogen molecules and create a habitat for microorganisms. The subsequent porous biochar layer, with its well-developed surface structure and slow carbon release characteristics, enriches organic pollutants and maintains the metabolic activity of denitrifying bacteria. The top layer uses calcium-based phosphorus removal material, which removes phosphorus through a chemical precipitation reaction with phosphate ions. This bottom-up layered structure, through the orderly combination of different functional materials, creates a physicochemical environment for gradient pollutant removal. Simultaneously, the interconnected pores between the packing layers provide suitable growth space for the microbial community, thus constructing a complete reaction carrier for phosphorus removal and denitrification processes under anaerobic conditions. By controlling the total thickness of the composite packing layer to 0.5-1.2m, a reasonable ratio is achieved with the wastewater treatment scale. This thickness range ensures sufficient contact time between wastewater and the composite packing material, guaranteeing the effective completion of physical adsorption, chemical reactions, and biodegradation processes in each functional layer. It also avoids excessive head loss due to excessively thick composite packing layers, thus achieving a good balance between treatment efficiency and operating costs. When the system is in submerged operation, this layered packing structure not only provides a stable attachment carrier for anaerobic microbial communities but, more importantly, constructs a complete pollutant removal system through the synergistic effect of each functional layer. From top to bottom, the calcium-based phosphorus removal agent layer, biochar layer, and modified zeolite layer each perform specific removal functions for different pollutants. Simultaneously, the porous structure of each packing layer provides a gradient habitat for microorganisms, allowing pollutants to be removed step-by-step during downward infiltration. This creates an excellent reaction environment for phosphorus removal and denitrification processes under anaerobic conditions.

[0023] Preferably, the program controller in the tidal flow intelligent control unit adjusts the opening and closing sequence of the inlet valve in real time based on the data fed back by the online water quality monitor.

[0024] By adopting the above technical solution, the program controller in the tidal flow intelligent control unit dynamically adjusts the opening and closing sequence of the inlet valves based on real-time feedback data of inlet chemical oxygen demand (COD) and ammonia nitrogen concentration from the online water quality monitor. Specifically, the program controller compares the monitored COD concentration with a first preset threshold. When the COD exceeds this threshold, it calculates the required extension of the flooding period based on the magnitude of the exceedance and a preset correspondence, and accordingly delays the closing time of the inlet valves. Similarly, it compares the monitored ammonia nitrogen concentration with a second preset threshold. When the ammonia nitrogen concentration exceeds this threshold, it calculates the required extension of the drainage period based on the magnitude of the exceedance and another preset correspondence, and accordingly advances the opening time of the inlet valves. Through this method of quantitatively adjusting the operating cycle based on real-time water quality parameter deviations, the duration of the anaerobic and aerobic environments in the constructed wetland unit can adaptively match the current inlet pollution load.

[0025] In summary, this application has the following beneficial effects: 1. Because this application adopts a technical solution that combines tidal flow intelligent control with stabilization pond pretreatment, the program controller adjusts the opening and closing sequence of the influent valve in real time based on the influent COD and ammonia nitrogen concentration data fed back by the online water quality monitoring instrument. This allows the constructed wetland unit to adaptively adjust the ratio of flooding and drainage cycles according to the actual pollution load. At the same time, the stabilization pond unit performs preliminary degradation and sedimentation of sewage through a hydraulic retention time of 2-7 days. The synergistic work of the two achieves the effect of improving the system's resistance to shock loads and treatment stability.

[0026] 2. In this application, a functionally graded composite packing material consisting of a gravel support layer, a modified zeolite layer, a biochar layer, and a calcium-based phosphorus removal agent layer is preferred. Since each layer of packing material utilizes its specific physical structure and chemical properties to undertake the functions of support, adsorption, microbial carrier, and chemical phosphorus removal, a synergistic mechanism for the step-by-step removal of pollutants is formed. Therefore, the system achieves the effect of enhancing the comprehensive removal effect of nitrogen, phosphorus, and organic matter while maintaining the long-term permeability and microbial activity of the composite packing layer.

[0027] 3. The method of this application combines the use of solid-loaded denitrifying bacteria agent with intelligent carbon source addition, and is combined with micro-water flow flushing maintenance during the drainage period. Since the sodium alginate-biochar microsphere carrier provides a protective habitat for denitrifying bacteria, the carbon-nitrogen ratio detector and metering pump are used together to achieve accurate carbon source replenishment, and the periodic micro-water flow flushing effectively prevents the composite packing layer from clogging. Therefore, the method achieves the effect of maintaining the long-term efficient and stable operation of the system and reducing dependence on external carbon sources and the frequency of manual maintenance. Attached Figure Description

[0028] Figure 1 This is a flowchart of a wastewater treatment method based on a combination of artificial wetlands and stabilization ponds provided in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0030] Technical concept: Existing wastewater treatment technologies combining constructed wetlands and stabilization ponds generally suffer from weak resistance to shock loads and poor treatment stability. The core reason for this is the lack of an intelligent collaborative control mechanism based on real-time water quality. On the one hand, the tidal cycle of traditional constructed wetlands is mostly a preset fixed value, which cannot be adjusted according to the dynamic changes in pollutant loads such as COD and ammonia nitrogen in the influent. When the influent concentration suddenly increases, the fixed cycle is difficult to meet the pollutant degradation requirements, which can easily lead to incomplete removal of organic matter and nitrogen. On the other hand, the hydraulic retention time of stabilization ponds is usually a fixed design value, which cannot adapt to the fluctuations in wastewater volume and water quality at different times. Moreover, constructed wetlands and stabilization ponds operate independently without parameter linkage adjustment, which means that when the system faces shock loads, the treatment units cannot respond collaboratively, ultimately causing fluctuations in effluent water quality.

[0031] This technical solution addresses the aforementioned issues by constructing an intelligent control and functional synergy system: First, an intelligent tidal flow control unit is set up. An online water quality monitoring instrument collects real-time data on influent COD, ammonia nitrogen, and total phosphorus concentrations. The programmable controller calculates the appropriate operating parameters based on preset logic and then controls the influent valves to adjust the ratio of flooding to drainage time in the constructed wetland, achieving dynamic adaptation to the tidal cycle. Second, the hydraulic retention time of the stabilization pond unit is designed to be adjustable within a range of 2-7 days. This can be optimized in conjunction with the influent load and the adjustment logic of the tidal control unit, enhancing the pretreatment effect. Simultaneously, a layered composite packing layer, on-demand addition of solidified denitrifying bacteria and liquid carbon sources form a synergistic treatment process of pretreatment, intelligent tidal purification, and functional enhancement, thereby improving the system's resistance to shock loads and treatment stability. Preparation Example 1 The preparation method of modified zeolite is as follows: Take 500 parts of natural zeolite, crush it, and sieve out particles with a diameter of 2-5 mm. Rinse repeatedly with deionized water until the rinse water is clear to remove surface dust. Add the washed zeolite particles to 1000 mL of a 1.0 mol / L sodium chloride solution and stir at 150 r / min for 6 hours at a constant temperature of 60℃. Filter out the zeolite particles and rinse with deionized water until the pH of the effluent is 7.0 ± 0.2. Then immerse it in 1000 mL of a 0.5 mol / L calcium chloride solution and modify it by shaking at 120 r / min for 4 hours at room temperature. Finally, dry the modified zeolite particles in a 105℃ oven to constant weight, cool, and seal for storage to obtain the modified zeolite product. Preparation Example 2 The preparation method of immobilized denitrifying bacteria agent is as follows: Take 10 mL of denitrifying bacteria, such as Pseudomonas, and aseptically inoculate it into 100 mL of enrichment medium containing 1 g / L sodium nitrate, 2 g / L sodium acetate, and 0.5 g / L potassium dihydrogen phosphate, pH 7.2. Incubate at 30℃ and 180 rpm for 48 hours with shaking until the bacterial concentration reaches 1 × 10⁻⁶. 8 CFU / mL or higher. Take 50 mL of the bacterial culture and centrifuge at 4℃ and 5000 r / min for 10 minutes. Discard the supernatant and collect the bacterial precipitate. Take 20 g of biochar, grind it, and pass it through a 200-mesh sieve; the particle size should be less than 75 μm. Take 1 g of the biochar powder and mix it with 10 mL of a 4% (w / v) sodium alginate solution (4% w / v = 4 g sodium alginate per 100 mL of deionized water). Stir at 30℃ and 150 r / min for 30 minutes to form a homogeneous suspension. Resuspend the bacterial precipitate in 5 mL of physiological saline and mix it with 10 mL of the sodium alginate-biochar suspension at a volume ratio of 1:5 to obtain the bacterial mixture. Prepare 200 mL of a 2% (w / v) calcium chloride solution, where 2% (w / v) means 2 g of calcium chloride in 100 mL of deionized water. Using a peristaltic pump, add the bacterial agent mixture dropwise to the calcium chloride solution at a flow rate of 0.5 mL / min, stirring gently at 100 rpm during addition, to form spherical gel microspheres with a diameter of 2-3 mm. After curing and cross-linking for 30 minutes, filter the microspheres through a stainless steel sieve and rinse three times with 50 mL of physiological saline each time. Place the microspheres in a 40℃ vacuum drying oven and dry until the moisture content is less than 10%, approximately 6 hours. This yields the finished product of a solid-supported denitrifying bacterial agent using sodium alginate-biochar microspheres as the carrier.

[0032] Preparation Example 3 The preparation method of sodium alginate-biochar microspheres is as follows: Take 100 parts of corn stalks, crush them into 2-5 mm particles, and place them in a tube furnace under nitrogen protection. Carbonize at 600℃ for 2 hours. After cooling, take 50 parts of the carbonized product and soak it in 200 mL of 1 mol / L hydrochloric acid solution for 2 hours, stirring 3 times during the process. Then wash with deionized water until the pH of the filtrate is 7.0±0.2. Dry at 105℃ and crush to 80 mesh to obtain biochar powder. Weigh 2 parts of sodium alginate and dissolve it in 100 mL of deionized water. Stir at 50℃ and 150 r / min for 30 minutes until completely dissolved. Add 1 part of biochar powder to the solution and continue stirring for 1 minute. Mix thoroughly for 2 hours; then, using a peristaltic pump, add the mixture dropwise to 200 mL of a 5% calcium chloride solution at a flow rate of 1 mL / min, with the dropper 10 cm above the liquid surface, forming gel microspheres with a diameter of 2-3 mm. After standing and solidifying for 2 hours, rinse the microspheres three times with 100 mL of deionized water each time to remove residual calcium chloride from the surface; dry in a vacuum drying oven at 60 °C for 4 hours to obtain sodium alginate-biochar microspheres. Scanning electron microscopy revealed that the microspheres were regularly spherical with a uniform porous structure, a pore size distribution ranging from 10-100 μm, and a porosity of 65% ± 15% as determined by mercury intrusion porosimetry. The microsphere particle size was measured using a laser diffraction particle size analyzer, with results of 2-5 mm, within the design range. The biochar loading was determined by thermogravimetric analysis under a nitrogen atmosphere at a temperature increased at 10 °C / min to 800 °C, with residual biochar accounting for 20% ± 10% of the total mass of the microspheres. Furthermore, Fourier transform infrared spectroscopy showed a characteristic carboxyl peak of sodium alginate at a wavenumber of 1600 cm⁻¹, confirming the successful cross-linking of biochar and sodium alginate.

[0033] Preparation Example 4 The preparation method of plant straw extract is as follows: Take 50 parts of rice straw, remove impurities, and crush into 1-3 cm pieces. Dry in an oven at 105℃ for 24 hours until constant weight. Add the dried straw to 500 parts of deionized water at a solid-liquid ratio of 1:10, and extract at 80℃ and 120 r / min for 4 hours with stirring every 30 minutes. After extraction, filter through 4 layers of gauze to remove coarse fiber impurities, and then filter through a 0.45 μm microporous membrane to obtain the primary extract. Place the primary extract in a rotary evaporator and concentrate under reduced pressure at 60℃ and 0.08 MPa, with the COD value detected by the potassium dichromate method until the COD concentration of the concentrate reaches 5000 mg / L, thus obtaining the plant straw extract. Example

[0034] This embodiment is applied to a domestic sewage treatment project in a county-level town with a permanent population of approximately 80,000, generating an average of 4,000 m³ of domestic sewage daily. The sewage mainly contains kitchen waste, organic matter, and laundry wastewater, with an influent COD concentration of approximately 200-300 mg / L and an ammonia nitrogen concentration of approximately 20-30 mg / L. A combined process is required to achieve Class A discharge standards for reuse. The specific treatment method includes the following steps: S1. Pretreatment: The wastewater to be treated is subjected to bar filtration and grit removal to remove large suspended solids; S2. Wastewater introduction: The pretreated wastewater is transported to the stabilization pond unit for preliminary degradation and sedimentation treatment. The hydraulic retention time of the stabilization pond unit is set to 4.5 days, and the water depth range is 1.75 meters. S3, Tidal Flow Intelligent Control: By adjusting the inlet valve, the artificial wetland unit can periodically alternate between submerged and drained states, with the submerged period lasting 8 hours and the drained period lasting 5 hours. The operation of adjusting the inlet valve is to adjust the ratio of flooding and drainage time in real time according to the concentrations of COD, ammonia nitrogen and total phosphorus in the inlet water. When the COD of the inlet water is higher than 300 mg / L, the flooding period is extended by 30%; when the ammonia nitrogen of the inlet water is higher than 30 mg / L, the drainage period is extended by 20%.

[0035] S4. Anaerobic enhancement during flooding: When the constructed wetland unit is in a flooded state, add immobilized denitrifying bacteria and supplement liquid carbon source when the influent carbon-nitrogen ratio is monitored to be lower than 5:1 to promote anaerobic phosphorus removal and denitrification reaction. The composite filler is composed of the following components in parts by weight: 100 parts gravel, 40 parts modified zeolite, 25 parts biochar, and 25 parts calcium-based phosphorus removal agent; the filler particle size range is 17.5 mm.

[0036] Among them, the denitrifying bacteria agent is a solid-loaded agent, and its carrier is sodium alginate-biochar microspheres. The dosage of the agent is 1.25 kg / m³ wetland volume, and the dosage frequency is once every 60 days.

[0037] The liquid carbon source is sodium acetate solution or plant straw extract, and the dosage is 3 grams of COD equivalent per cubic meter of wastewater.

[0038] S5. Aerobic reoxygenation during the drainage period: When the constructed wetland unit is in a drained state, natural ventilation or auxiliary aeration is used to promote system reoxygenation, which is used to enhance nitrification and organic matter degradation. S6. Composite packing regeneration: During the middle of the drainage period, the composite packing layer is rinsed with intermittent micro-water flow to prevent blockage and restore its adsorption and microbial attachment capabilities. The flow rate of the micro-water flow rinsing is controlled at 1.25 L / min, the duration is 20 min, and the rinsing interval is once every 5 tidal cycles.

[0039] S7. Water purification and reuse: Water treated by artificial wetlands is further purified through ecological filter ponds or ultraviolet disinfection units, and some of the effluent can be reused for farmland irrigation or landscape water replenishment. The ecological filter pond is planted with aquatic plants and laid with sulfur-iron composite filter media, with a filter media layer thickness of 0.45m. Example

[0040] This embodiment is applied to a wastewater treatment project in a rural settlement. The settlement has 120 households and approximately 450 people, generating an average of 18 m³ of wastewater daily. The wastewater mainly consists of domestic sewage and a small amount of aquaculture flushing water. The domestic sewage includes washing and kitchen wastewater. The influent COD concentration is approximately 150-200 mg / L, and the ammonia nitrogen concentration is approximately 15-25 mg / L. After treatment, the wastewater must meet the standards for farmland irrigation water. The specific treatment method includes the following steps: S1. Pretreatment: The wastewater to be treated is subjected to bar filtration and grit removal to remove large suspended solids; S2. Wastewater introduction: The pretreated wastewater is transported to the stabilization pond unit for preliminary degradation and sedimentation treatment. The hydraulic retention time of the stabilization pond unit is set to 2 days, and the water depth is 1 meter. S3, Tidal Flow Intelligent Control: By adjusting the inlet valve, the artificial wetland unit can periodically alternate between submerged and drained states, with the submerged period lasting 4 hours and the drained period lasting 2 hours. The operation of adjusting the inlet valve is to adjust the ratio of flooding and drainage time in real time according to the concentrations of COD, ammonia nitrogen and total phosphorus in the inlet water. When the COD of the inlet water is higher than 300 mg / L, the flooding period is extended by 20%; when the ammonia nitrogen of the inlet water is higher than 30 mg / L, the drainage period is extended by 10%.

[0041] S4. Anaerobic enhancement during flooding: When the constructed wetland unit is in a flooded state, add immobilized denitrifying bacteria and supplement liquid carbon source when the influent carbon-nitrogen ratio is monitored to be lower than 5:1 to promote anaerobic phosphorus removal and denitrification reaction. The composite filler is composed of the following components in parts by weight: 80 parts gravel, 20 parts modified zeolite, 20 parts biochar, and 20 parts calcium-based phosphorus removal agent; the filler particle size range is 5 mm.

[0042] Among them, the denitrifying bacteria agent is a solid-loaded agent, and its carrier is sodium alginate-biochar microspheres. The dosage of the agent is 0.5 kg / m³ wetland volume, and the dosage frequency is once every 30 days.

[0043] The liquid carbon source is sodium acetate solution or plant straw extract, and the dosage is 1 gram of COD equivalent per cubic meter of wastewater.

[0044] S5. Aerobic reoxygenation during the drainage period: When the constructed wetland unit is in a drained state, natural ventilation or auxiliary aeration is used to promote system reoxygenation, which is used to enhance nitrification and organic matter degradation. S6. Composite packing regeneration: During the middle of the drainage period, the composite packing layer is rinsed with intermittent micro-water flow to prevent blockage and restore its adsorption and microbial attachment capabilities. The flow rate of the micro-water flow rinsing is controlled at 0.5 L / min, the duration is 10 min, and the rinsing interval is once every 3 tidal cycles.

[0045] S7. Water purification and reuse: Water treated by artificial wetlands is further purified through ecological filter ponds or ultraviolet disinfection units, and some of the effluent can be reused for farmland irrigation or landscape water replenishment. The ecological filter pond is planted with aquatic plants and laid with sulfur-iron composite filter media, with a filter media layer thickness of 0.3m. Example

[0046] This embodiment is applied to a pre-treated wastewater deep treatment project in a food processing industrial park. The park mainly produces fruit juice and canned goods, generating an average of 2000 m³ of pre-treated wastewater daily. The wastewater has already undergone anaerobic + aerobic treatment, reducing COD to 300-400 mg / L, and requires further treatment before reuse as production cooling water. The specific treatment method includes the following steps: S1. Pretreatment: The wastewater to be treated is subjected to bar filtration and grit removal to remove large suspended solids; S2. Wastewater introduction: The pretreated wastewater is transported to the stabilization pond unit for preliminary degradation and sedimentation treatment. The hydraulic retention time of the stabilization pond unit is set to 7 days, and the water depth is 2.5 meters. S3, Tidal Flow Intelligent Control: By adjusting the inlet valve, the artificial wetland unit can periodically alternate between submerged and drained states, with the submerged period lasting 12 hours and the drained period lasting 8 hours. The operation of adjusting the inlet valve is to adjust the ratio of flooding and drainage time in real time according to the concentrations of COD, ammonia nitrogen and total phosphorus in the inlet water. When the COD of the inlet water is higher than 300 mg / L, the flooding time is extended by 40%; when the ammonia nitrogen of the inlet water is higher than 30 mg / L, the drainage time is extended by 30%.

[0047] S4. Anaerobic enhancement during flooding: When the constructed wetland unit is in a flooded state, add immobilized denitrifying bacteria and supplement liquid carbon source when the influent carbon-nitrogen ratio is monitored to be lower than 5:1 to promote anaerobic phosphorus removal and denitrification reaction. The composite filler is composed of the following components in parts by weight: 120 parts gravel, 60 parts modified zeolite, 30 parts biochar, and 30 parts calcium-based phosphorus removal agent; the filler particle size range is 30 mm.

[0048] Among them, the denitrifying bacteria agent is a solid-loaded agent, and its carrier is sodium alginate-biochar microspheres. The dosage of the agent is 2 kg / m³ wetland volume, and the dosage frequency is once every 90 days.

[0049] The liquid carbon source is sodium acetate solution or plant straw extract, and the dosage is 5 grams of COD equivalent per cubic meter of wastewater.

[0050] S5. Aerobic reoxygenation during the drainage period: When the constructed wetland unit is in a drained state, natural ventilation or auxiliary aeration is used to promote system reoxygenation, which is used to enhance nitrification and organic matter degradation. S6. Composite packing regeneration: During the middle of the drainage period, the composite packing layer is rinsed with intermittent micro-water flow to prevent blockage and restore its adsorption and microbial attachment capabilities. The flow rate of the micro-water flow rinsing is controlled at 2L / min, the duration is 30min, and the rinsing interval is once every 7 tidal cycles.

[0051] S7. Water purification and reuse: Water treated by artificial wetlands is further purified through ecological filter ponds or ultraviolet disinfection units, and some of the effluent can be reused for farmland irrigation or landscape water replenishment. The ecological filter pond is planted with aquatic plants and covered with sulfur-iron composite filter media, with a filter media layer thickness of 0.6m.

[0052] The specific experimental design for performance testing of the wastewater treatment system based on the embodiment is as follows: I. Pollutant Removal Efficiency Testing Experiment The experimental subjects were the county-level urban domestic sewage treatment system of Example 1, the rural settlement sewage treatment system of Example 2, and the food processing industrial park pre-treated sewage deep treatment system of Example 3. The experimental steps are as follows: Sampling points were set at three key nodes of the system in each embodiment: the effluent from pretreatment (S1), the effluent from the stabilization pond unit (S2), and the final effluent (S7). Sampling was conducted continuously for 7 days, with water samples collected at each sampling point at 8:00, 14:00, and 20:00 each day. Each sample was 500 mL, and samples were immediately stored away from light and tested within 24 hours. The detection methods followed national standards: COD was detected using the potassium dichromate method (GB11914-89), ammonia nitrogen using Nessler's reagent spectrophotometry (HJ535-2009), and total phosphorus using the ammonium molybdate spectrophotometry (GB11893-89). In the data recording and analysis phase, the overall removal rates of COD, ammonia nitrogen, and total phosphorus by each embodiment system were calculated. The calculation method was as follows: ; Simultaneously, the segmented removal rate of each unit was calculated, and the pollutant removal effects of the three embodiments under different influent concentrations were compared.

[0053] II. System Operation Stability and Shock Load Resistance Testing Experiment The experimental subjects were the complete wastewater treatment systems of the three embodiments, and the experimental period was 60 days, which covered the dosing period of the denitrifying bacteria agent in Embodiment 1. The experimental steps are as follows: During the routine operation stability testing phase, the influent water quality of each embodiment was kept stable for the first 30 days. Specifically, for Embodiment 1, the influent COD concentration was controlled at 200-300 mg / L and the ammonia nitrogen concentration at 20-30 mg / L; for Embodiment 2, the influent COD concentration was controlled at 150-200 mg / L and the ammonia nitrogen concentration at 15-25 mg / L; and for Embodiment 3, the influent COD concentration was controlled at 300-400 mg / L and the ammonia nitrogen concentration at 25-35 mg / L. Final effluent water samples were collected daily to test COD, ammonia nitrogen, and total phosphorus concentrations. Operating parameters for each system were recorded, including the flooding and draining time of the constructed wetland and the frequency of micro-flow flushing. The fluctuation range of the effluent water quality was analyzed, calculated by the standard deviation of the 7-day average. During the shock load testing phase, three water quality shocks were conducted on each embodiment on days 31, 41, and 51, with each shock increasing the influent COD concentration to the normal level. The concentration of COD and ammonia nitrogen was increased to 1.5 times the normal value, with Example 1 increasing it to 300-450 mg / L, Example 2 increasing it to 225-300 mg / L, and Example 3 increasing it to 450-600 mg / L. At the same time, the ammonia nitrogen concentration was increased to 1.2 times the normal value, with Example 1 increasing it to 24-36 mg / L, Example 2 increasing it to 18-30 mg / L, and Example 3 increasing it to 30-42 mg / L. After the shock lasted for 48 hours, normal influent was restored. During the shock, the final effluent water sample was collected every 6 hours to detect COD and ammonia nitrogen concentrations. The automatic adjustment of the tidal flow control unit of the system was recorded, such as whether the flooding period was extended by 30% as designed in Example 1. The duration of the effluent water quality exceeding the standard during the shock and the time to recover to the normal standard level after the shock were calculated. The effluent stability and recovery ability of the three example systems under the shock were compared to verify the advantages of the system in achieving shock-resistant operation through intelligent adjustment of tidal flow and adsorption of packing materials.

[0054] III. Specialized Testing Experiments on the Performance of Reclaimed Water The experimental subject was the final effluent (S7 effluent) of the three embodiment systems. The reuse scenarios for the three embodiments were urban landscape irrigation and greening in Embodiment 1, rural farmland irrigation in Embodiment 2, and industrial park production cooling water in Embodiment 3. The experimental steps were as follows: Sampling was conducted continuously at the final effluent of each embodiment for 5 days, twice a day, at 10:00 AM and 4:00 PM, with a sample volume of 1000 mL each time, for testing different reuse indicators. The detection indicators were set according to the reuse scenario. In Embodiment 1, turbidity, suspended solids, and coliform bacteria were tested. The turbidity detection method used was the scattered light method, referring to the national standard GB / T5750.4-2006, and the suspended solids detection method used was the gravimetric method, referring to the national standard GB / T11901-1989 specifies the coliform bacteria detection method using the plate count method, referring to national standard GB / T5750.12-2006, to verify whether it meets the landscape water standards, i.e., national standard GB / T18921-2019. Example 2 requires the detection of pH value, salinity, and heavy metals lead and cadmium. The pH value detection method uses the glass electrode method, referring to national standard GB / T6920-1986, and the salinity detection method uses conductivity conversion, referring to national standard GB / T5750. Example 4-2006: The heavy metal detection method adopts atomic absorption spectrophotometry, referring to the national standard GB / T7475-1987, to verify whether it meets the farmland irrigation water quality standard, i.e., the national standard GB5084-2021. Example 3 requires the detection of turbidity, hardness, and chloride ions. The turbidity detection method is the same as in Example 1. The hardness detection method adopts EDTA titration, referring to the national standard GB / T5750.4-2006. The chloride ion detection method adopts silver nitrate titration, referring to the national standard GB / T5750.5-2006, to verify whether it meets the industrial circulating cooling water standard, i.e., the national standard GB / T50102-2014. In the data processing stage, the effluent detection values ​​of each example are compared with the corresponding reuse standard limits to calculate the compliance rate. At the same time, the operating parameters of the effluent purification unit of each example are recorded, such as the filtration rate of the ecological filter and the ultraviolet disinfection time, to analyze the contribution of the unit to the reuse index and verify the advantages of the system in meeting the reuse needs of different scenarios on the basis of achieving pollutant removal.

[0055] The results of the pollutant removal efficiency test are shown in Table 1.

[0056] Table 1: The experimental results of system operation stability and shock load resistance are shown in Table 2. Table 2: The experimental data for the special test of water reuse performance are shown in Table 3.

[0057] Table 3: Summary of Experimental Results and Notes on Key Influencing Factors I. Summary of Pollutant Removal Efficiency Experiments The system effectively removes core pollutants in various scenarios, including urban domestic sewage, rural residential sewage, and pre-treated industrial wastewater. The synergistic effect of the stabilization pond and constructed wetland is crucial in this process. The stabilization pond, through preliminary sedimentation and microbial degradation, reduces the pollution load for subsequent treatment stages, directly lowering the treatment burden on the constructed wetland. Meanwhile, the constructed wetland relies on the synergistic effect of composite packing material and immobilized denitrifying bacteria. The composite packing material provides a stable attachment carrier for microorganisms and possesses its own adsorption capacity, while the denitrifying bacteria specifically promote phosphorus removal and denitrification reactions under anaerobic conditions. The combined effect of these two elements further enhances the degradation and adsorption of pollutants. Furthermore, the supplementation of liquid carbon source provides sufficient substrate for microbial reactions when the carbon-to-nitrogen ratio is insufficient, ensuring the continuous and efficient biochemical reactions. These factors work together to maintain a stable pollutant removal capacity under different influent water quality conditions.

[0058] II. Summary of System Operation Stability and Shock Load Resistance Experiments During long-term routine operation, the system maintains stable effluent quality and operating parameters, primarily due to the precise regulation of its operation by the tidal flow intelligent control unit. This unit maintains the necessary biochemical environment for microorganisms within the constructed wetland based on preset flooding and drainage times, minimizing the impact of parameter fluctuations on the effluent. When faced with influent quality shocks, the system adjusts the flooding time within the tidal cycle to provide microorganisms with more time to adapt to load changes. Simultaneously, the composite filler within the constructed wetland buffers some of the pollutant impact through adsorption. These two mechanisms work synergistically to effectively prevent effluent quality from exceeding standards. This synergistic mechanism of regulation and adsorption not only allows the system to maintain stable effluent under shock conditions but also enables it to quickly return to normal operating conditions, demonstrating the system's excellent adaptability to water quality fluctuations.

[0059] III. Summary of Water Reuse Performance Tests The system is designed for various reuse scenarios, including urban landscaping, rural farmland irrigation, and industrial park cooling, ensuring that the effluent meets corresponding standards. The key lies in the precise matching of the effluent purification unit configuration with reuse requirements. The ecological filter utilizes the synergistic effect of aquatic plants and sulfur-iron composite filter media. The plants absorb some pollutants, while the filter media further purifies the water through physical filtration and chemical adsorption. The ultraviolet disinfection unit specifically controls microbial indicators, and the combination of these two elements ensures the safety of the effluent under different reuse scenarios. Furthermore, adjustments to the filtration rate of the ecological filter and the duration of ultraviolet disinfection can adapt to the specific water quality requirements of different reuse scenarios, ensuring a high degree of alignment between purification effects and reuse needs. This ultimately achieves safe reuse of the effluent, demonstrating the system's adaptability and practicality in resource recycling.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A wastewater treatment method combining constructed wetlands and stabilization ponds based on tidal flow, characterized in that: The method includes the following steps: S1. Pretreatment: The wastewater to be treated is subjected to bar filtration and grit removal to remove large suspended solids; S2. Wastewater introduction: The pretreated wastewater is transported to a stabilization pond unit for preliminary degradation and sedimentation treatment. The hydraulic retention time of the stabilization pond unit is set to 2-7 days, and the water depth is 1-2.5 meters. S3, Tidal Flow Intelligent Control: By adjusting the inlet valve, the artificial wetland unit can periodically alternate between submerged and drained states, with the submerged period lasting 4-12 hours and the drained period lasting 2-8 hours. S4. Anaerobic enhancement during flooding: When the constructed wetland unit is in a flooded state, add immobilized denitrifying bacteria and supplement liquid carbon source when the influent carbon-nitrogen ratio is monitored to be lower than 5:1 to promote anaerobic phosphorus removal and denitrification reaction. S5. Aerobic reoxygenation during the drainage period: When the constructed wetland unit is in a drained state, natural ventilation or auxiliary aeration is used to promote system reoxygenation, which is used to enhance nitrification and organic matter degradation. S6. Composite packing regeneration: During the middle of the drainage period, the composite packing layer is rinsed with intermittent micro-water flow to prevent blockage and restore its adsorption and microbial attachment capabilities. S7. Water purification and reuse: The water treated by the constructed wetland is further purified through an ecological filter or ultraviolet disinfection unit, and some of the effluent can be reused for farmland irrigation or landscape water replenishment.

2. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S4, the composite filler is composed of the following components in parts by weight: 80-120 parts gravel, 20-60 parts modified zeolite, 20-30 parts biochar, and 20-30 parts calcium-based phosphorus removal agent; the particle size range of the composite filler is 5-30 mm.

3. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S4, the denitrifying bacteria agent is a fixed-support type, with sodium alginate-biochar microspheres as the carrier, and the dosage of the agent is 0.5-2 kg / m³. 3 The wetland volume is adjusted, and the addition frequency is once every 30-90 days.

4. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S3, the operation of adjusting the inlet valve is to adjust the ratio of flooding and draining time in real time according to the concentrations of COD, ammonia nitrogen and total phosphorus in the inlet water. When the COD of the inlet water is higher than 300 mg / L, the flooding period is extended by 20-40%; when the ammonia nitrogen of the inlet water is higher than 30 mg / L, the draining period is extended by 10-30%.

5. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S6, the flow rate of the micro-water flow rinsing is controlled at 0.5-2 L / min, the duration is 10-30 min, and the rinsing interval is once every 3-7 tidal cycles.

6. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S7, aquatic plants are planted in the ecological filter pond and sulfur-iron composite filter media is laid, with a filter media layer thickness of 0.3-0.6m.

7. The wastewater treatment method based on tidal flow using a combination of constructed wetlands and stabilization ponds according to claim 1, characterized in that: In step S4, the liquid carbon source is a sodium acetate solution or a plant straw extract, and the dosage is 1-5 grams of COD equivalent per cubic meter of wastewater.

8. A combined artificial wetland and stabilization pond wastewater treatment system based on tidal flow, characterized in that, The wastewater treatment method based on tidal flow combined with an artificial wetland and stabilization pond, as described in any one of claims 1-7, comprises: Stabilization pond unit, used for receiving and initially treating wastewater; The constructed wetland unit is connected to the stabilization pond unit via pipes and has a built-in composite filler layer and plant layer; The tidal flow intelligent control unit, including an inlet valve, a programmable controller, and an online water quality monitor, is used to achieve alternating operation of flooding and drainage; The composite packing regeneration unit, including a micro-flow flushing pipe and a solenoid valve, is installed inside the constructed wetland unit; The carbon source dosing unit includes a storage tank, a metering pump, and a carbon-nitrogen ratio detector, which is used to automatically add liquid carbon source according to the carbon-nitrogen ratio of the influent; The effluent purification unit includes an ecological filter and ultraviolet disinfection equipment for advanced treatment and reuse.

9. A combined artificial wetland and stabilization pond wastewater treatment system based on tidal flow according to claim 8, characterized in that: The composite packing layer consists of a gravel support layer, a modified zeolite layer, a biochar layer, and a calcium-based phosphorus removal agent layer from bottom to top, with a total thickness of 0.5-1.2m. When the constructed wetland unit is in a submerged state, the composite packing layer is used to provide a carrier for anaerobic phosphorus removal and denitrification reactions.

10. A combined artificial wetland and stabilization pond wastewater treatment system based on tidal flow according to claim 8, characterized in that: The program controller in the tidal flow intelligent control unit adjusts the opening and closing sequence of the inlet valve in real time based on the data fed back by the online water quality monitor.

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