Combined four-stage constructed wetland water quality purification system

Abstract

The invention discloses a combined four-stage constructed wetland water quality purification system, which relates to the technical field of ecological management, and comprises a spatial topology layout module, a water quality control module, a water quality control module and a water quality control module, the method comprises the following steps: establishing a four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-deep denitrification stage-ecological stability stage, and generating an ecological hydrological space topology layout in the descending direction of hydraulic gradient and gravitational potential energy by combining natural terrain and hydrological conditions of a site; the multi-modal pollution collaborative purification module is used for sequentially configuring multi-functional coupling reaction regions with four stages of purification target sequences, specifically implanting a structured functional medium, and establishing a multi-modal pollution collaborative purification unit through a filler-plant-animal-microorganism synergistic effect; the directional conversion module is used for driving the hydraulic retention time of each purification unit by utilizing gravitational potential energy so as to realize optimal matching of hydraulic dynamic conditions of each purification unit and biochemical reaction requirements. According to the invention, the ecological safety of effluent is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ecological management, in particular to a combined four-stage constructed wetland water purification system. BACKGROUND

[0002] The existing constructed wetland technology is mainly single-stage or two-stage in series, and the design often fails to systematically integrate the migration and transformation rules of pollutants and the natural terrain of the site, resulting in limited efficiency of the system in the coordinated removal of multi-modal pollutants and rigid configuration of functional units. Specifically, the traditional layout method cannot fully utilize the hydraulic gradient and gravitational potential, resulting in a mismatch between the hydraulic dynamics and the specific biochemical reaction requirements, and the key processes such as nitrification and denitrification cannot be carried out under optimal conditions, which causes a bottleneck in denitrification efficiency. The configuration of functional fillers and biological communities lacks pertinence, making it difficult to form a step-by-step and precisely targeted pollutant transformation chain, resulting in unstable system effluent quality and insufficient ecological safety. There are common engineering application defects such as large land occupation, easy clogging, and weak impact load resistance, and an integrated system solution is urgently needed to achieve efficient, coordinated, and targeted transformation of pollutants along the physical-chemical-biological-ecological path. SUMMARY

[0003] To solve the above technical problems, a combined four-stage constructed wetland water purification system is provided, which solves the problems of unstable system effluent quality, insufficient ecological safety, and common engineering application defects such as large land occupation, easy clogging, and weak impact load resistance.

[0004] To achieve the above purposes, the technical scheme adopted by the present application is as follows: A combined four-stage constructed wetland water purification system, comprising: a spatial topology layout module, a multi-modal pollution coordinated purification module, and a directional transformation module; The multi-modal pollution coordinated purification module is electrically connected to the spatial topology layout module, and the directional transformation module is electrically connected to the multi-modal pollution coordinated purification module. The spatial topology layout module obtains the pollution characteristics of the artificial wetland water to be treated and the target value of the effluent water quality, establishes a four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-deep denitrification stage-ecological stabilization stage, and generates an ecological hydrological spatial topology along the decreasing direction of the hydraulic gradient and gravitational potential, combined with the natural terrain and hydrological conditions of the site. The multi-modal pollution coordinated purification module is based on the ecological hydrological spatial topology layout, and sequentially configures the multi-functional coupled reaction zones corresponding to the four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-deep denitrification stage-ecological stabilization stage, and implants structured functional media in a targeted manner, to establish a multi-modal pollution coordinated purification unit through the synergistic effect of fillers-plants-animals-microorganisms. The directional conversion module, based on the multimodal pollution collaborative purification unit, uses gravitational potential energy to drive water flow and control the hydraulic residence time of each purification unit to achieve optimal matching between the hydraulic dynamic conditions and biochemical reaction requirements of each purification unit. This drives pollutants through four levels of directional conversion: physical interception, aerobic biological transformation, anoxic biological reduction, and ecological assimilation, thereby achieving deep purification of artificial wetland water quality and improving the ecological safety of the effluent.

[0005] Preferably, the spatial topology layout module specifically includes: The structured pollutant characteristic inventory unit, based on the deployment of online water quality monitoring instruments at the inlet of the constructed wetland, regularly collects water pollutant data of the water body to be treated, including COD (chemical oxygen demand), BOD (biochemical oxygen demand), etc. Data values ​​of -N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended matter and pH were collected. The average concentration and peak load of each pollutant data during the collection period were calculated. The diurnal variation and seasonal variation of each pollutant data were identified, and a structured pollutant characteristic list was generated. The priority pollutant determination unit, based on reviewing and determining the water quality standards of the receiving water body, determines the target value of the effluent water quality. According to the difference between the average concentration of the influent to the receiving water body and the target value of the effluent water quality, the concentration of each pollutant that needs to be reduced is calculated. With the ecological sensitivity of the receiving water body as a constraint, the absolute value of the concentration of each pollutant that needs to be reduced and the known ecological risk of the pollutants are combined to make a weighted priority ranking to determine the priority pollutants to be controlled. The ecological target concentration is determined based on the water quality standards of the receiving water body.

[0006] Preferably, the spatial topology layout module also includes: The natural hydraulic slope unit uses a land permeameter to conduct site surveys, obtains the spatial discrete points of the soil permeability coefficient of the site, and uses spatial interpolation of the discrete points to generate a continuous digital elevation model and a soil permeability zoning map. Combined with the natural topography of the site, the natural hydraulic slope of the site is calculated, the potential water catchment paths and natural flow lines of the site are obtained, the inherent hydrological flow direction and elevation gradient of the site are identified, and the site slope distribution map and water catchment line map of the site are drawn. The path rule unit, based on a structured pollutant characteristic list and effluent water quality target values, establishes a four-stage purification target sequence: pretreatment and settling stage - main nitrification stage - deep denitrification stage - ecological stabilization stage. It defines purification path rules for each pollutant and sets target pollutant removal rates. Rule 1: COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), and SS (Suspended Solids) are removed in the pretreatment and settling stages. Rule 2: ... -N ammonia nitrogen is converted in the main nitrification stage, rule three. -N ammonia nitrogen is reduced in the deep denitrification stage. Rule 4: TN total nitrogen and TP total phosphorus are removed from residual dissolved nutrients and trace microorganisms in the ecological stabilization stage. The removal rate target setting unit presets the hydraulic retention time and the pollutant removal rate target for each stage in the four-stage purification target sequence. The Monod equation is used to calculate the effluent concentrations of various pollutants. The effluent concentrations of each pollutant are calculated starting from the pretreatment and sedimentation stage, which are used as the influent for the next stage. The HRT of each stage is iteratively adjusted until the final total effluent target is met, determining the design influent- effluent water quality, pollutant target removal rate, and theoretical hydraulic retention time for each purification stage.

[0007] Preferably, the spatial topological layout module further includes: The sequential elevation relationship diagram unit divides the site into three elevation zones based on the theoretical hydraulic retention time and the site, with the pretreatment and sedimentation stage set as the highest zone, the main nitrification stage set as the medium-high zone, the deep denitrification stage set as the medium-low zone, and the ecological stabilization stage set as the lowest zone, obtaining a preliminary purification sequence-elevation relationship diagram for the four-stage purification target; The ecological hydrological spatial topological layout unit, based on the preliminary purification sequence-elevation relationship diagram for the four-stage purification target, combines the influent point and the final total effluent target to design the total available elevation difference h. The total available elevation difference h is allocated to each purification target according to the priority of the required filler resistance and pipe loss head loss. The effluent elevation of the upper purification target enters the lower purification target by gravity flow and meets the minimum water level for the operation of the lower purification target as a constraint. By adjusting the weir height, the water depth in each purification target is controlled, realizing the switching between aerobic-low water level and filler exposure to anoxic, anaerobic-high water level and filler submerged environment. The layout and profile of the four-stage purification target plane position, design elevation, connecting irrigation canal path, and weir / valve control facility position are used as output to generate the ecological hydrological spatial topological layout.

[0008] Preferably, the multi-modal pollution collaborative purification module specifically includes: The pollutant removal mechanism and functional medium attribute mapping matrix establishment unit, for COD chemical oxygen demand, BOD biochemical oxygen demand, NH4+-N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended solids, and pH data values, combined with the corresponding removal rate target and known corresponding fillers, plants, animals, and microorganisms, establishes a pollutant removal mechanism and functional medium attribute mapping matrix.

[0009] Preferably, the multi-modal pollution collaborative purification module further includes: The multi-functional coupling reaction zone unit is based on a mapping matrix of pollutant removal mechanisms and functional medium properties, and designs multi-functional coupling reaction zones corresponding to purification targets at each level. In the pretreatment and sedimentation level, part of the BOD biochemical oxygen demand and SS suspended solids are intercepted using a grid. After preliminary interception, the water enters a grit chamber, where gravity separation is used to deposit large particles. A particle size gradient filler of large cobble at the bottom and small gravel at the top is used to enhance the water filtration capacity. A small amount of pollution-tolerant reed is planted to stabilize the filler. In the main nitrification level, the remaining BOD biochemical oxygen demand and -N ammonia nitrogen conversion, biological filler and adsorption -N ammonia nitrogen, planting reed and cattail with well-developed root systems and strong oxygen transport capacity, and in the deep denitrification level -N ammonia nitrogen, slow-release carbon source filler using wood cellulose filler and denitrification microbial carrier using pyrite-limestone composite filler, planting evergreen or submerged plants to maintain system stability and increase weir height, submerging the filler layer to create an anoxic zone to promote denitrification, and in the ecological stability level, TN total nitrogen and TP total phosphorus, using phosphorus removal filler rich in calcium / iron / aluminum ions as the bottom layer of the subsurface flow area, and planting soil as the upper layer, configuring a three-dimensional ecological community of submerged plants, floating plants, emergent plants, filter-feeding animals, and fish to achieve ecological assimilation of nutrients and system stability. Further, in the pretreatment and sedimentation level, BOD biochemical oxygen demand is treated, but the remaining BOD biochemical oxygen demand is treated in the main nitrification level.

[0010] Preferably, the multi-modal pollution collaborative purification module further includes: The purification unit is based on multi-functional coupling reaction zones corresponding to purification targets at each level, and the fillers at each level are layered to create a permeability gradient. According to the season and regional characteristics of the site, suitable plant seedlings are selected for transplanting. According to the mature wetland, active sludge or microbial inoculant is introduced for microbial biofilm formation and inoculation to accelerate the establishment of microbial flora. After the water quality of the site is stable, benthic animals and fish are gradually introduced to form a complete micro-food web. Through the synergistic effect of filler-plant-animal-microorganism, a multi-modal pollution collaborative purification unit is established.

[0011] Preferably, the directional conversion module specifically includes: The hydraulic retention time calculation unit is based on the multi-modal pollution collaborative purification unit, and combines the pretreatment and sedimentation level, the main nitrification level, the deep denitrification level, and the ecological stability level. According to the pollutant load and removal rate target, the reaction kinetics model is used to calculate the required hydraulic retention time of each unit.

[0012] Preferably, the internal directional conversion module further comprises: The matching unit drives water flow based on the gravity potential generated by the total available elevation difference h, an online water quality monitor and a flow meter are arranged at the water outlet of each unit, water quality pollutant data of the water body to be treated are collected in real time and uploaded to the central controller, the hydraulic dynamics conditions and biochemical reaction requirements of each purification unit are optimally matched by combining the required hydraulic retention time of each unit, if the ammonia nitrogen concentration of the effluent of the main nitrification stage is higher than the set threshold n, it is determined that the nitrification is insufficient, the strategy is adaptively adjusted, the aeration amount of the main nitrification stage is increased to increase the dissolved oxygen, the effluent weir height of the pretreatment and sedimentation stage is finely adjusted, the water depth of the main nitrification stage is moderately increased to increase the theoretical hydraulic retention time, and if the nitrate concentration in the effluent of the advanced denitrification stage is too high, the unit is submerged to increase the anoxic environment, and a small amount of liquid carbon source is added to the influent to promote denitrification.

[0013] Preferably, the internal directional conversion module further comprises: The water quality advanced purification unit, for the pretreatment and sedimentation stage, completes physical interception through the filler gap, maintains a short theoretical hydraulic retention time, ensures a fast water flow speed, and effectively removes large particle suspended solids, for the main nitrification stage, maintains a good aerobic environment through aeration control, ensures high dissolved oxygen and moderate hydraulic retention time, completes organic matter carbon oxidation and ammonia nitrogen nitrification, for the advanced denitrification stage, maintains an anoxic environment through water level control, prolongs the hydraulic retention time to complete the nitrate denitrification process, and for the ecological stability stage, builds a complex biological community, utilizes sunlight irradiation and long hydraulic retention time conditions to convert inorganic nutrient salts into the biomass of plants and animals, realizes ecological assimilation, drives pollutants to undergo four-stage directional conversion of physical interception, aerobic biological conversion, anoxic biological reduction and ecological assimilation, and realizes advanced purification of water quality in the artificial wetland and improvement of ecological safety of the effluent.

[0014] Compared with the prior art, the beneficial effects of the present application are that: The present application provides a combined four-stage artificial wetland water purification scheme, and the combined four-stage artificial wetland water purification system provided by the present application constructs a space topology layout, a multi-modal pollution collaborative purification and a three-stage linkage module, intelligently generates a four-stage target sequence and an ecological hydrological space layout according to pollution characteristics and topographic hydrological conditions, specifically configures a multifunctional coupled reaction zone and a structured functional medium, realizes filler-plant-animal-microorganism collaborative purification, accurately regulates hydraulic dynamics conditions and retention time by using gravity potential, drives pollutants to be directionally and efficiently converted along a four-stage path of physical interception, aerobic conversion, anoxic reduction and ecological assimilation, not only improves the depth of water quality purification and the stability of the system, but also strengthens the ecological safety of the effluent, and has the comprehensive advantages of strong adaptability, high operation efficiency, ecological friendliness and low maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a combined four-stage constructed wetland water purification system framework diagram. DETAILED DESCRIPTION

[0016] The following description is used to disclose the present application so that those skilled in the art can implement the present application. The preferred embodiments in the following description are only as examples, and other obvious variations can be thought of by those skilled in the art.

[0017] Referring to Figure 1 As shown in the figure, a combined four-stage constructed wetland water purification system comprises: a spatial topology layout module, a multi-modal pollution collaborative purification module, and a directional transformation module; The multi-modal pollution collaborative purification module is electrically connected with the spatial topology layout module, and the directional transformation module is electrically connected with the multi-modal pollution collaborative purification module. The spatial topology layout module obtains the pollution characteristics of the artificial wetland water to be treated and the target value of the effluent water quality, establishes a four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-deep denitrification stage-ecological stabilization stage, and generates an ecological hydrological spatial topology along the direction of decreasing hydraulic gradient and gravitational potential energy, combined with the natural terrain and hydrological conditions of the site. The multi-modal pollution collaborative purification module is based on the ecological hydrological spatial topology layout, and sequentially configures multi-functional coupled reaction zones corresponding to the four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-deep denitrification stage-ecological stabilization stage, and implants structured functional media, to establish a multi-modal pollution collaborative purification unit through the synergistic effect of filler-plants-animals-microorganisms. The directional transformation module is based on the multi-modal pollution collaborative purification unit, and uses gravitational potential energy to drive water flow and control the hydraulic retention time of each purification unit, to achieve optimal matching of the hydraulic kinetic conditions and biochemical reaction requirements of each purification unit, drive pollutants to undergo four-stage directional transformation of physical interception, aerobic biological transformation, anoxic biological reduction, and ecological assimilation, and achieve deep purification of artificial wetland water and improvement of the ecological safety of effluent water.

[0018] The spatial topology layout module specifically comprises: A structured pollutant characteristic list unit is based on the water inlet of the artificial wetland to deploy an online water quality monitor, regularly collects water quality pollutant data of the water to be treated, including COD chemical oxygen demand, BOD biochemical oxygen demand, NH3-N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended solids, and pH data values of acid-base degree, calculates the average concentration and peak load of each pollutant data within the collection time, identifies the day-night change and rain-dry season difference fluctuation rule of each pollutant data, and generates a structured pollutant characteristic list. The priority control pollutant determination unit determines the effluent water quality target value based on consulting and determining the receiving water body water quality standard, calculates the concentration of each pollutant that needs to be reduced according to the difference between the average concentration of the influent of the receiving water body and the effluent water quality target value, and determines the priority control pollutant by combining the absolute value of the concentration of each pollutant that needs to be reduced with the known ecological risk of the pollutant and performing weighted priority ranking. The ecological target concentration is determined based on the water quality standard of the receiving water body.

[0019] The space topology layout module further includes: The natural hydraulic gradient unit uses a land permeameter to conduct site surveying, obtains spatial discrete points of the soil permeability coefficient of the site, generates a continuous digital elevation model and a soil permeability zoning map through spatial interpolation of the discrete points, analyzes the site natural terrain, calculates the natural hydraulic gradient of the site, obtains the potential catchment path and natural flow line of the site, identifies the inherent hydrological flow direction and elevation gradient of the site, and draws a site slope distribution map and a catchment line map of the site. The path rule unit establishes a four-stage purification target sequence of pretreatment and sedimentation stage-main nitrification stage-depth denitrification stage-ecological stabilization stage based on the structured pollutant characteristic list and the effluent water quality target value, defines the purification path rules of each pollutant, sets the target pollutant removal rate, rule one, COD, BOD and SS are removed in the pretreatment and sedimentation stage, rule two, -N ammonia nitrogen is converted in the main nitrification stage, rule three, -N ammonia nitrogen is reduced in the depth denitrification stage, rule four, TN and TP remove residual dissolved nutrients and trace microorganisms in the ecological stabilization stage. The removal rate target setting unit presets the hydraulic retention time and the pollutant removal rate target for each stage in the four-stage purification target sequence, calculates the effluent concentration of each type of pollutant using the Monod equation, calculates the effluent concentration of each pollutant step by step starting from the pretreatment and sedimentation stage as the influent of the next stage, iteratively adjusts the HRT of each stage until the final effluent total target is met, and determines the design influent- effluent water quality, pollutant target removal rate and theoretical hydraulic retention time of each purification target.

[0020] The space topology layout module further includes: The sequential elevation relationship map unit divides the site into three elevation zones along the natural slope based on the theoretical hydraulic retention time and the site, sets the pretreatment and sedimentation stage as the highest zone, the main nitrification stage as the medium-high zone, the depth denitrification stage as the medium-low zone, and the ecological stabilization stage as the lowest zone, and obtains a four-stage preliminary purification sequence-elevation relationship map. The ecological hydrological space topology layout unit, based on the obtained preliminary purification order-elevation relationship diagram of the four-stage purification target, combined with the total target of the water inlet point and the final water outlet, designs the total available elevation difference h, and according to the head loss of the required filler resistance and pipeline loss of each purification target, the total available elevation difference h is allocated to each purification target according to the priority, and the water elevation of the upper purification target is used as a constraint to meet the minimum water level of the operation of the lower purification target through gravity flow, the water depth in each purification target is controlled by adjusting the weir gate height, the switching of the aerobic-low water level and the filler exposure to the anoxic-anaerobic-high water level and the filler submerged environment is realized, and the layout and profile of the planar position, design elevation, connection canal path and weir / valve control facility position of the four-stage purification target are taken as the output to generate the ecological hydrological space topology layout.

[0021] In use, the above module content is combined: The current artificial wetland design generally relies on static water quality data and empirical layout, resulting in insufficient adaptability, large fluctuation of purification efficiency, high energy consumption and lack of precise hydraulic control ability of the system when dealing with dynamic water inflow load, complex site conditions and multi-target pollutant removal. This step realizes the whole process quantitative design and dynamic control from pollution characteristic identification, priority sorting, precise allocation of hydraulic retention time to space topology layout by integrating online monitoring and dynamic data analysis, digital survey of site hydrogeology, gravity flow self-adaptive regulation of multi-stage purification target sequence and natural elevation, improves the adaptability of the system to pollutant fluctuations and site conditions, strengthens the multi-stage purification collaborative efficiency, and reduces the operation energy consumption through gravity flow and head optimization allocation, providing a scientific basis for building an efficient, stable and energy-saving ecological purification system.

[0022] The multi-modal pollution collaborative purification module specifically includes: The pollutant removal mechanism and functional medium attribute mapping matrix establishment unit is used for COD chemical oxygen demand, BOD biochemical oxygen demand, N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended solids and pH data value, combined with the corresponding removal rate target and known corresponding filler, plant, animal, microorganism, the pollutant removal mechanism and functional medium attribute mapping matrix is established.

[0023] The multi-modal pollution collaborative purification module also includes: The multifunctional coupled reaction zone unit, based on the mapping matrix of pollutant removal mechanisms and functional media properties, designs multifunctional coupled reaction zones corresponding to each stage of purification objectives. For the pretreatment and settling stages, a screen is used for initial interception of some BOD (Biochemical Oxygen Demand) and SS (Suspended Solids). After initial interception, the material enters the grit chamber, where gravity separation and sedimentation of large particles are utilized. A particle size gradient packing material with a bottom layer of large pebbles and an upper layer of small gravel enhances the water flow filtration capacity. A small amount of pollution-resistant reeds is planted to stabilize the packing material. For the remaining BOD and SS in the main nitrification stage... -N ammonia nitrogen conversion utilizes a biological packing material composed of a high specific surface area, strong hydrophilic ceramsite, zeolite, and activated carbon composite filler, combined with adsorption... -N ammonia nitrogen, planting reeds and cattails with well-developed root systems and strong oxygen-carrying capacity, targeting deep denitrification stages. -N ammonia nitrogen: slow-release carbon source filler made of lignocellulosic filler and denitrifying microbial carrier made of pyrite-limestone composite filler are selected. Evergreen or submerged plants are planted to maintain system stability, increase the height of the outlet weir, submerge the filler layer, and create an anoxic zone to promote the denitrification process. For TN total nitrogen and TP total phosphorus in the ecological stability stage, phosphorus removal filler rich in calcium / iron / aluminum ions is selected as the bottom layer of the subsurface flow zone, and the upper layer is planting soil. A three-dimensional ecological community of submerged plants, floating-leaved plants, emergent plants, filter feeders and fish is configured to achieve ecological assimilation of nutrients and system stability. To further clarify, the BOD (biochemical oxygen demand) is treated in the pretreatment and settling stages, but the remaining BOD is treated in the main nitrification stage.

[0024] The multimodal pollution synergistic purification module also includes: The purification unit, based on the multifunctional coupled reaction zone corresponding to each level of purification target, lays out each level of packing material to generate a permeability gradient. According to the season and the regional characteristics of the site, suitable plant seedlings are selected for transplantation. Based on the mature wetland, activated sludge or microbial agents are introduced for microbial biofilm inoculation to accelerate the establishment of the microbial community. After the water quality of the site stabilizes, benthic animals and fish are gradually introduced to generate a complete micro food web. Through the synergistic effect of packing material, plants, animals and microorganisms, a multimodal pollution synergistic purification unit is established.

[0025] When using it, combine the content of the above modules: Existing pollution purification modules often employ single or simple combinations of purification mechanisms, lacking targeted removal designs for different pollutants and exhibiting insufficient synergy among functional media. This results in low treatment efficiency, poor operational stability, and difficulty in meeting the complex requirements of multimodal pollution synergistic purification. The beneficial effect of this step lies in establishing a mapping matrix between pollutant removal mechanisms and functional media properties, enabling the effective treatment of COD (chemical oxygen demand), BOD (biochemical oxygen demand), and other pollutants. - Precise control of NH3-N, TN, TP, SS, and pH data, design of a multifunctional coupling reaction zone, hierarchical configuration of fillers, plants, animals, and microorganisms to form a synergistic purification unit, and improvement of pollutant removal efficiency and system stability.

[0026] The directional transformation module specifically includes: A hydraulic retention time calculation unit based on a multi-modal pollution synergistic purification unit, combined with pretreatment and sedimentation level-main nitrification level-advanced denitrification level-ecological stability level four-stage purification target sequence, the entire wetland system is generalized as a series of water tank reactor models, including pretreatment and sedimentation level, main nitrification level, advanced denitrification level, and ecological stability level four units, according to the pollutant load and removal rate target, the reaction kinetics model is used to calculate the required hydraulic retention time of each unit.

[0027] The directional transformation module also includes: A matching unit based on the gravity potential generated by the total available elevation difference h to drive water flow, online water quality monitors and flow meters are deployed at the outlet of each unit to collect water quality pollutant data of the water to be treated in real time, which is uploaded to the central controller, combined with the required hydraulic retention time of each unit, to achieve optimal matching of the hydraulic kinetics conditions and biochemical reaction requirements of each purification unit, if the ammonia nitrogen concentration of the main nitrification level effluent is higher than the set threshold n, it is determined that the nitrification is insufficient, the strategy is adjusted adaptively, the aeration amount of the main nitrification level is increased to increase the dissolved oxygen, the outlet weir height of the pretreatment and sedimentation level is fine-tuned, the water depth of the main nitrification level is moderately increased to increase the theoretical hydraulic retention time, if the nitrate concentration in the advanced denitrification level effluent is too high, the unit is submerged to increase the anoxic environment, and a small amount of liquid carbon source is added to the influent to promote denitrification.

[0028] The directional transformation module also includes: A water quality advanced purification unit, for the pretreatment and sedimentation level, physical interception is completed through the filler gap, a relatively short theoretical hydraulic retention time is maintained to ensure a fast water flow speed to effectively remove large particles of suspended solids, for the main nitrification level, a good aerobic environment is maintained through aeration control to ensure high dissolved oxygen and moderate hydraulic retention time, organic matter carbon oxidation and ammonia nitrogen nitrification are completed, for the advanced denitrification level, an anoxic environment is maintained through water level control to extend the hydraulic retention time to complete the nitrate denitrification process, for the ecological stability level, a complex biological community is constructed to convert inorganic nutrient salts into plant and animal biomass under the conditions of sunlight irradiation and long hydraulic retention time, ecological assimilation is achieved, pollutants undergo four-stage directional transformation of physical interception, aerobic biological transformation, anoxic biological reduction, and ecological assimilation, artificial wetland water quality advanced purification and improvement of effluent ecological safety are achieved.

[0029] In use, the above module content is combined: Traditional constructed wetland systems generally suffer from fixed hydraulic retention times, single pollutant removal pathways, and a lack of real-time control capabilities, leading to unstable removal efficiency for pollutants such as nitrogen and phosphorus. In particular, under high loads or fluctuating water quality, incomplete nitrification or denitrification is common, and the systems have weak shock resistance, making it difficult to achieve precise coordination and dynamic optimization of multi-stage purification processes. The beneficial effects of this approach lie in establishing a series-tank reactor model and a four-stage directional conversion sequence, enabling modular design and kinetic quantitative control of the multi-stage pollutant purification process. Based on online monitoring and a feedback mechanism from a central controller, the system can match hydraulic dynamic conditions and biochemical reaction requirements in real time, adaptively adjusting key parameters such as aeration, water level, and carbon source addition, thus improving the system's stability and efficiency in removing ammonia nitrogen and nitrate. Through gravity-driven potential energy and biological assimilation at the ecological stability level, energy consumption is reduced while enhancing the ecological safety of the effluent, ultimately achieving efficient, controllable, and sustainable deep purification of pollutants by constructed wetlands.

[0030] Based on the above, the specific implementation method is as follows: For a tributary flowing into a river in a riverside area that is polluted by a mixture of agricultural non-point source pollution and domestic sewage, a combined four-stage constructed wetland system was designed. An online water quality monitoring instrument was deployed at the inlet to continuously collect water quality data for 30 days. Analysis showed that the average concentration of COD (chemical oxygen demand) was 85 mg / L. The average concentrations of -N ammonia nitrogen and total phosphorus (TP) were 12 mg / L and 2.5 mg / L, respectively, to identify the rainy season. -N ammonia nitrogen peak load fluctuates by about 40%; According to the Class IV surface water quality standard: COD ≤ 30 mg / L, -N≤1.5mg / L, TP≤0.3mg / L, calculated as follows -N requires a maximum absolute reduction in concentration of 10.5 mg / L and poses a high ecological risk, therefore it has been identified as a priority pollutant for control. Using a soil permeameter to survey the site, a digital elevation model was generated, showing a natural hydraulic slope of 0.8%. Natural runoff paths from northwest to southeast were identified along the slope. Based on pollution characteristics and targets, a pretreatment and settling stage was established: removal of suspended solids (SS) and part of COD (chemical oxygen demand) – main nitrification stage: transformation. - N-ammonia nitrogen - deep denitrification stage: reduction of nitrate - ecological stability stage: removal of residual TN total nitrogen and TP total phosphorus four-stage purification sequence, through the Monod equation iterative calculation, the theoretical hydraulic retention time of each stage is determined to be 6h, 18h, 24h, 36h, combined with the site elevation, the pretreatment and sedimentation stage is arranged in the highest area, the relative elevation is +1.2m, the main nitrification stage is arranged in turn: +0.6m, the deep denitrification stage: +0.2m and the ecological stability stage: ±0.0m, according to the water head loss distribution of the total available elevation difference, the water depth is controlled by adjusting the height of the connecting weir gate of each stage to generate an ecological hydrological space topology layout diagram integrating plane layout, profile elevation and hydraulic control facilities; Based on the ecological hydrological space topology layout diagram, a multi-functional coupled reaction zone is constructed stage by stage. In the pretreatment and sedimentation stage, a grid and grit chamber are arranged for physical interception, a gradient filler layer with a bottom layer of large goose pebbles with a particle size of 80-120mm and an upper layer of small gravel with a particle size of 10-30mm is filled, and pollution-tolerant reeds are planted to stabilize the filler and preliminarily absorb organic matter. In the main nitrification stage, ceramsite-zeolite composite biological filler with a specific surface area of ≥400m 2 / g is filled, reeds and cattails are planted to enhance oxygenation, nitrifying bacteria are inoculated according to the ammonia nitrogen conversion requirements to form an aerobic biofilm system. In the deep denitrification stage, corn cob-based lignocellulosic filler is used as a slow-release carbon source, and pyrite-limestone composite filler is used to adjust pH and promote denitrification. The filler layer is in a submerged state by raising the effluent weir to create an anoxic environment, and evergreen irises are planted to maintain root microecology. In the ecological stability stage, iron ion-rich phosphorus removal filler is laid in the bottom layer, and planting soil is used in the upper layer to construct a three-dimensional ecological community of submerged plants: cattail, floating plants: water lily, emergent plants: cattail, filter-feeding river clams and fish: crucian carp, realizing the final assimilation of nutrient salts and food web migration. Each reaction zone forms a purification unit through layered filler laying, plant seedling transplanting, microbial inoculation and animal introduction, realizing the synergistic effect of filler-plant-animal-microorganism. During system operation, water flows through the four-stage units in turn driven by gravitational potential energy. The central controller dynamically adjusts the operation parameters of each unit according to online monitoring data: when the ammonia nitrogen concentration of the main nitrification stage effluent is higher than the set threshold of 1.8mg / L, the microporous aeration intensity is automatically increased to increase the dissolved oxygen, and the effluent weir height of the previous stage is adjusted to moderately increase the water depth of this unit to prolong the hydraulic retention time and strengthen the nitrification process. If the nitrate concentration of the deep denitrification stage effluent exceeds the standard by more than 5mg / L, the water level of this unit is further increased to completely submerge the filler, and a small amount of sodium acetate solution is added as a supplemental carbon source to promote denitrifying bacteria metabolism. On the directional conversion path, the pollutants successively undergo physical interception of pretreatment and sedimentation level, the SS suspended substance removal rate reaches 85%, aerobic biological conversion of main nitrification level, the ammonia nitrogen nitrification rate is greater than 90%, anoxic biological reduction of deep denitrification level, the nitrate removal rate is greater than 80%, ecological stability level of ecological assimilation, the TP total phosphorus removal rate is greater than 70%, and the final effluent COD chemical oxygen demand, The N, TP total phosphorus concentrations are respectively stabilized below 25 mg / L, 1.0 mg / L and 0.2 mg / L, the target water quality requirements are met, and the ecological safety is improved; Through the series connection of water tank models and real-time feedback regulation and control, the system realizes self-adaptive matching of hydraulic dynamic conditions and biochemical reaction requirements, and guarantees stable and efficient operation of the multi-stage purification process under the condition of low energy consumption.

[0031] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection required by the present application is defined by the appended claims and their equivalents.

Claims

1. A combined four-stage constructed wetland water purification system, characterized in that, include: Spatial topology layout module, multimodal pollution collaborative purification module, and directional conversion module; Among them, the multimodal pollution collaborative purification module is electrically connected to the spatial topology layout module, and the directional conversion module is electrically connected to the multimodal pollution collaborative purification module; The spatial topology layout module obtains the pollution characteristics and effluent water quality target values ​​of the water body to be treated in the constructed wetland, establishes a four-level purification target sequence of pretreatment and sedimentation stage - main nitrification stage - deep denitrification stage - ecological stability stage, and generates an eco-hydrological spatial topology layout along the hydraulic gradient and gravitational potential energy decreasing direction, in combination with the natural topography and hydrological conditions of the site. The multimodal pollution synergistic purification module, based on the eco-hydrological spatial topology layout, is configured with multifunctional coupling reaction zones corresponding to the four-level purification target sequence of pretreatment and sedimentation stage - main nitrification stage - deep denitrification stage - ecological stabilization stage. Structured functional media are specifically implanted, and a multimodal pollution synergistic purification unit is established through the synergistic effect of filler, plants, animals and microorganisms. The directional conversion module, based on the multimodal pollution collaborative purification unit, uses gravitational potential energy to drive water flow and control the hydraulic residence time of each purification unit to achieve optimal matching between the hydraulic dynamic conditions and biochemical reaction requirements of each purification unit. This drives pollutants through four levels of directional conversion: physical interception, aerobic biological transformation, anoxic biological reduction, and ecological assimilation, thereby achieving deep purification of artificial wetland water quality and improving the ecological safety of the effluent.

2. The combined four-stage constructed wetland water purification system according to claim 1, characterized in that, The spatial topology layout module specifically includes: The structured pollutant characteristic inventory unit, based on the deployment of online water quality monitoring instruments at the inlet of the constructed wetland, regularly collects water pollutant data of the water body to be treated, including COD (chemical oxygen demand), BOD (biochemical oxygen demand), etc. Data values ​​of -N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended matter and pH were collected. The average concentration and peak load of each pollutant data during the collection period were calculated. The diurnal variation and seasonal variation of each pollutant data were identified, and a structured pollutant characteristic list was generated. The priority pollutant determination unit, based on reviewing and determining the water quality standards of the receiving water body, determines the target value of the effluent water quality. According to the difference between the average concentration of the influent to the receiving water body and the target value of the effluent water quality, the concentration of each pollutant that needs to be reduced is calculated. With the ecological sensitivity of the receiving water body as a constraint, the absolute value of the concentration of each pollutant that needs to be reduced and the known ecological risk of the pollutants are combined to make a weighted priority ranking to determine the priority pollutants to be controlled. The ecological target concentration is determined based on the water quality standards of the receiving water body.

3. The combined four-stage constructed wetland water purification system according to claim 2, characterized in that, The spatial topology layout module also includes: The natural hydraulic slope unit uses a land permeameter to conduct site surveys, obtains the spatial discrete points of the soil permeability coefficient of the site, and uses spatial interpolation of the discrete points to generate a continuous digital elevation model and a soil permeability zoning map. Combined with the natural topography of the site, the natural hydraulic slope of the site is calculated, the potential water catchment paths and natural flow lines of the site are obtained, the inherent hydrological flow direction and elevation gradient of the site are identified, and the site slope distribution map and water catchment line map of the site are drawn. The path rule unit, based on a structured pollutant characteristic list and effluent water quality target values, establishes a four-stage purification target sequence: pretreatment and settling stage - main nitrification stage - deep denitrification stage - ecological stabilization stage. It defines purification path rules for each pollutant and sets target pollutant removal rates. Rule 1: COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), and SS (Suspended Solids) are removed in the pretreatment and settling stages. Rule 2: ... -N ammonia nitrogen is converted in the main nitrification stage, rule three. -N ammonia nitrogen is reduced in the deep denitrification stage. Rule 4: TN total nitrogen and TP total phosphorus are removed from residual dissolved nutrients and trace microorganisms in the ecological stabilization stage. The removal rate target setting unit presets the hydraulic retention time and pollutant removal rate target for each stage in the four-stage purification target sequence. Using the Monod equation, it calculates the effluent concentration of various pollutants. Starting from the pretreatment and settling stages, it calculates the effluent concentration of each pollutant at each stage and uses it as the influent for the next stage. It iteratively adjusts the HRT of each stage until the final effluent target is met, and determines the design influent-effluent water quality, pollutant target removal rate, and theoretical hydraulic retention time for each stage of purification.

4. The combined four-stage constructed wetland water purification system according to claim 3, characterized in that, The spatial topology layout module also includes: Based on the theoretical hydraulic retention time and the site, the site is divided into three elevation zones along the natural slope: high, medium, and low. The pretreatment and sedimentation stage is set as the highest zone, the main nitrification stage as the medium-high zone, the deep denitrification stage as the medium-low zone, and the ecological stability stage as the lowest zone, thus obtaining the preliminary purification sequence-elevation relationship diagram of the four-level purification targets. The eco-hydrological spatial topology layout unit, based on the preliminary purification sequence-elevation relationship diagram of the four-level purification targets, and combined with the inlet point and the final effluent target, designs the total available elevation difference h. According to the required packing resistance and pipeline head loss of each level of purification target, the total available elevation difference h is allocated to each level of purification target according to priority. The effluent elevation of the upper-level purification target enters the lower-level purification target by gravity flow and meets the minimum water level required for the operation of the lower-level purification target as a constraint. By adjusting the height of the weir gate, the water depth in each level of purification target is controlled, realizing the switching between aerobic-low water level and packing exposed to anoxic, and anaerobic-high water level and packing submerged environment. The layout diagram and profile diagram of the four-level purification target plan position, design elevation, connecting irrigation canal path and weir gate / valve control facility position are used as outputs to generate the eco-hydrological spatial topology layout.

5. A combined four-stage constructed wetland water purification system according to claim 1, characterized in that, The multimodal pollution synergistic purification module specifically includes: The pollutant removal mechanism and functional media property mapping matrix establishment unit targets COD (chemical oxygen demand), BOD (biochemical oxygen demand), and other pollutants. The data values ​​of -N ammonia nitrogen, TN total nitrogen, TP total phosphorus, SS suspended solids and pH were combined with the corresponding removal rate targets and known corresponding fillers, plants, animals and microorganisms to establish a mapping matrix between pollutant removal mechanisms and functional media properties.

6. A combined four-stage constructed wetland water purification system according to claim 5, characterized in that, The multimodal pollution synergistic purification module also includes: The multifunctional coupled reaction zone unit, based on the mapping matrix of pollutant removal mechanisms and functional media properties, designs multifunctional coupled reaction zones corresponding to each stage of purification objectives. For the pretreatment and settling stages, a screen is used for initial interception of some BOD (Biochemical Oxygen Demand) and SS (Suspended Solids). After initial interception, the material enters the grit chamber, where gravity separation and sedimentation of large particles are utilized. A particle size gradient packing material with a bottom layer of large pebbles and an upper layer of small gravel enhances the water flow filtration capacity. A small amount of pollution-resistant reeds is planted to stabilize the packing material. For the remaining BOD and SS in the main nitrification stage... -N ammonia nitrogen conversion utilizes a biological packing material composed of a high specific surface area, strong hydrophilic ceramsite, zeolite, and activated carbon composite filler, combined with adsorption... -N ammonia nitrogen, planting reeds and cattails with well-developed root systems and strong oxygen-carrying capacity, targeting deep denitrification stages. -N ammonia nitrogen: slow-release carbon source filler made of lignocellulosic filler and denitrifying microbial carrier made of pyrite-limestone composite filler are selected. Evergreen or submerged plants are planted to maintain system stability, increase the height of the outlet weir, submerge the filler layer, and create an anoxic zone to promote the denitrification process. For TN total nitrogen and TP total phosphorus in the ecological stability stage, phosphorus removal filler rich in calcium / iron / aluminum ions is selected as the bottom layer of the subsurface flow zone, and the upper layer is planting soil. A three-dimensional ecological community of submerged plants, floating-leaved plants, emergent plants, filter feeders and fish is configured to achieve ecological assimilation of nutrients and system stability. To further clarify, the BOD (biochemical oxygen demand) is treated in the pretreatment and settling stages, but the remaining BOD is treated in the main nitrification stage.

7. A combined four-stage constructed wetland water purification system according to claim 6, characterized in that, The multimodal pollution synergistic purification module also includes: The purification unit, based on the multifunctional coupled reaction zone corresponding to each level of purification target, lays out each level of packing material to generate a permeability gradient. According to the season and the regional characteristics of the site, suitable plant seedlings are selected for transplantation. Based on the mature wetland, activated sludge or microbial agents are introduced for microbial biofilm inoculation to accelerate the establishment of the microbial community. After the water quality of the site stabilizes, benthic animals and fish are gradually introduced to generate a complete micro food web. Through the synergistic effect of packing material, plants, animals and microorganisms, a multimodal pollution synergistic purification unit is established.

8. A combined four-stage constructed wetland water purification system according to claim 7, characterized in that, The targeted conversion module specifically includes: The hydraulic retention time calculation unit, based on the multimodal pollution synergistic purification unit, combines the four-stage purification target sequence of pretreatment and settling stage - main nitrification stage - deep denitrification stage - ecological stabilization stage. The entire wetland system is generalized into a series tank reactor model, which includes four units: pretreatment and settling stage, main nitrification stage, deep denitrification stage and ecological stabilization stage. According to the pollutant load and removal rate target, the hydraulic retention time required for each unit is calculated using the reaction kinetic model.

9. A combined four-stage constructed wetland water purification system according to claim 8, characterized in that, The targeted conversion module also includes: The matching unit drives water flow based on the gravitational potential energy generated by the total available elevation difference h. Online water quality monitors and flow meters are deployed at the outlet of each unit to collect water quality pollutant data of the water to be treated in real time and upload them to the central controller. Combined with the hydraulic retention time required by each unit, the hydraulic dynamics conditions and biochemical reaction requirements of each purification unit are optimally matched. If the ammonia nitrogen concentration in the effluent of the main nitrification stage is higher than the set threshold n, it is judged as insufficient nitrification. The adaptive adjustment strategy is to increase the aeration of the main nitrification stage to increase dissolved oxygen, fine-tune the effluent weir height of the pretreatment and settling stages, and moderately increase the water depth of the main nitrification stage to increase the theoretical hydraulic retention time. If the nitrate concentration in the effluent of the deep denitrification stage is too high, the unit is submerged to increase the anoxic environment, and a small amount of liquid carbon source is added to the influent to promote denitrification.

10. A combined four-stage constructed wetland water purification system according to claim 9, characterized in that, The targeted conversion module also includes: The advanced water purification unit, targeting the pretreatment and settling stages, achieves physical interception through the gaps in the packing material, maintaining a short theoretical hydraulic retention time to ensure a fast water flow and effectively remove large suspended particles. For the main nitrification stage, aeration control maintains a good aerobic environment, ensuring high dissolved oxygen and a moderate hydraulic retention time to complete the carbon oxidation of organic matter and the nitrification of ammonia nitrogen. For the advanced denitrification stage, water level control maintains an anoxic environment, extending the hydraulic retention time to complete the nitrate denitrification process. For the ecological stabilization stage, by constructing a complex biological community, utilizing sunlight and long hydraulic retention times, inorganic nutrients are converted into plant and animal biomass, achieving ecological assimilation. This drives pollutants through four stages of directional transformation: physical interception, aerobic biological transformation, anoxic biological reduction, and ecological assimilation, achieving advanced water purification in the constructed wetland and improving the ecological safety of the effluent.

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