A hierarchical control composite ecological wetland structure for agricultural non-point source pollution control

Abstract

This invention discloses a tiered, barrier-control composite ecological wetland structure for agricultural non-point source pollution control, comprising a primary physical buffer sedimentation zone, a secondary enhanced biochemical purification zone, and a tertiary water quality stabilization and ecological restoration zone arranged sequentially along the water flow direction. The primary physical buffer sedimentation zone includes a sedimentation area, permeable baffles, and a layer of boulders. The secondary enhanced biochemical purification zone includes baffles, a layer of bagged biochar, a three-dimensional mesh packing module, and submerged plants at the front end. The tertiary water quality stabilization and ecological restoration zone includes submerged plants at the middle and rear ends. This invention significantly improves the long-term reliability and lifespan of the system, enhances the stability of total nitrogen and total phosphorus removal, and ensures the ecological stability and environmental friendliness of the final effluent.

Description

Technical Field

[0001] This invention relates to the field of water environment management and ecological engineering technology, and in particular to a graded barrier control composite ecological wetland structure for controlling agricultural non-point source pollution. Background Technology

[0002] Paddy field runoff is a major source of agricultural non-point source pollution, exhibiting significant uniqueness and complexity in its water quality. Specifically: First, the runoff contains high concentrations of suspended sediment (SS). These suspended particles are small in size, abundant in quantity, and vary greatly in settling properties. Upon entering traditional constructed wetlands, they readily and rapidly deposit on the surface and within the pores of the packing material, leading to bed siltation and blockage. With prolonged operation, the porosity of the packing material decreases significantly, reducing hydraulic conductivity and potentially causing hydraulic short-circuiting, surface overflow, or even complete system failure, severely impacting the long-term stable operation of the wetland. Second, the runoff often contains residual herbicides, pesticides, and other pesticide components. These substances are highly physiologically toxic to common aquatic plants (such as reeds, cattails, and irises), inhibiting root development, photosynthesis, and enzyme activity, resulting in poor plant growth or even large-scale plant death. Plants are the core biological component of wetland purification systems. Their absence not only significantly reduces the system's ability to absorb and degrade pollutants such as nitrogen and phosphorus, but also necessitates frequent replanting and replacement of plants, resulting in extremely high maintenance costs and making it difficult to promote and apply in practical engineering projects.

[0003] Currently, wetland technologies for farmland runoff treatment mainly fall into two categories. One category employs a single filter media, such as sand, zeolite, or ceramsite. While this can retain suspended solids to some extent, it lacks an active anti-clogging or self-cleaning mechanism to address the gradual accumulation of silt. Clogging becomes inevitable with increased operating time. The other category combines conventional plant configurations with simple filter media, but fails to adequately consider the stress of pesticide residues in the runoff on plant survival. This results in low plant survival and coverage rates, leading to low decontamination efficiency and weak system resilience. Existing technologies include some solutions that attempt to use sedimentation tanks or pre-screens for pretreatment, but these only remove larger particles and have limited effectiveness against fine silt and dissolved pesticides. Other solutions involve periodically replacing the filter media or manual dredging, but these are cumbersome, costly, and lack long-term effectiveness.

[0004] In summary, existing wetland technologies generally lack physical control mechanisms against high sediment deposition and resilient ecological configurations to address pesticide residues, making it difficult to meet the practical needs of stable, long-term, and low-maintenance farmland drainage management. Therefore, there is an urgent need to develop an artificial wetland system capable of simultaneously addressing sediment deposition and pesticide stress, achieving efficient and stable purification of paddy field drainage. To this end, the applicant, through beneficial exploration and research, has found a solution to the aforementioned problems, and the technical solution described below arose from this context. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a graded barrier and control composite ecological wetland structure for agricultural non-point source pollution control, which addresses the shortcomings of existing technologies. By combining graded barrier and control with stress-resistant ecological configuration, this structure solves problems such as easy clogging by silt, difficulty in plant survival, and low purification efficiency in farmland drainage treatment.

[0006] The technical problem to be solved by this invention can be achieved by the following technical solution: A graded barrier-control composite ecological wetland structure for controlling agricultural non-point source pollution includes a primary physical buffer sedimentation zone, a secondary enhanced biochemical purification zone, and a tertiary water quality stabilization and ecological restoration zone arranged sequentially along the water flow direction. The primary physical buffer settling zone includes a sedimentation zone, a permeable baffle, and a boulder layer. The sedimentation zone is located at the bottom of the primary physical buffer settling zone and at the bottom of the front section of the secondary enhanced biochemical purification zone. The permeable baffle is located at the top of the sedimentation zone, and the boulder layer is located on the permeable baffle. The secondary enhanced biochemical purification section includes a baffle, a bagged biochar layer, a three-dimensional mesh filler module, and submerged plants at the front end. The baffle is vertically installed on the permeable partition and located on one side of the rock layer. The three-dimensional mesh filler module is installed on the permeable partition and located on one side of the baffle. The bagged biochar layer is installed on the three-dimensional mesh filler module. The submerged plants at the front end are planted on the slope area of ​​the secondary enhanced biochemical purification section. The three-level water quality stabilization and ecological restoration section includes mid-level submerged plants and rear-level submerged plants. The mid-level submerged plants are planted in the shallow water area at the front of the three-level water quality stabilization and ecological restoration section, and the rear-level submerged plants are planted in the deep water area at the rear of the three-level water quality stabilization and ecological restoration section.

[0007] In a preferred embodiment of the present invention, the sedimentation zone is a deep pit structure with a base elevation of -2.5m to -1.5m, the stone layer is made of stones with a particle size of 0.15m to 0.3m, and the permeable baffle is made of HDPE or fiberglass.

[0008] In a preferred embodiment of the present invention, the baffle is made of concrete or reinforced concrete, and its top surface elevation is higher than the normal water level; the thickness of the bagged biochar layer is 0.2m to 0.3m, and its top surface elevation is -0.3m to -0.1m, wherein the biochar is selected as high-activation carbon with an iodine value greater than 800mg / g, and is packaged in corrosion-resistant nylon mesh bags; the three-dimensional mesh filler module is made of polyester or polypropylene material with high porosity.

[0009] In a preferred embodiment of the present invention, the front submerged plant is water shield grass, the middle submerged plant is a hybrid of water shield grass and Vallisneria natans, and the rear submerged plant is a hybrid of goldfish algae and Vallisneria natans; the front, middle and rear submerged plants are planted using a planting basket with substrate or a mud ball fixation technique.

[0010] In a preferred embodiment of the present invention, an impermeable membrane is laid at the bottom of the bed of the entire ecological wetland structure. The impermeable membrane is made of high-density polyethylene with a thickness of not less than 1.0 mm, and the seams are welded by double-track hot-melt welding.

[0011] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1. Unique hierarchical barrier control design: By setting up a dedicated sand and mud filter zone in the first-level section, the physical sedimentation function of the sediment is completely separated from the downstream biochemical purification function, which effectively solves the core problem of siltation and blockage in traditional wetland beds and significantly improves the reliability and lifespan of the system in long-term operation.

[0012] 2. High efficiency and stability of the composite purification mechanism: The secondary section adopts a composite subsurface flow structure and introduces three-dimensional mesh bag packing, which greatly increases the specific surface area of ​​microorganisms. This is conducive to maintaining efficient nitrification and denitrification processes under complex hydraulic conditions, and improves the removal stability of total nitrogen (TN) and total phosphorus (TP).

[0013] 3. Optimization of ecological function hierarchy: The three-level section constructs a layered community of emergent and submerged plants. In particular, the configuration of submerged vegetation in the deep water area can effectively release oxygen, improve water transparency, and ensure the ecological stability and environmental friendliness of the final effluent quality. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0017] See Figure 1The figure shows a graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control, which includes a primary physical buffer sedimentation zone 100, a secondary enhanced biochemical purification zone 200, and a tertiary water quality stabilization and ecological restoration zone 300 arranged sequentially along the water flow direction.

[0018] The primary physical buffer settling zone 100 includes a sedimentation zone 110, a permeable baffle 120, and a boulder layer 130. The sedimentation zone 110 is located at the bottom of the primary physical buffer settling zone 100 and at the front bottom of the secondary enhanced biochemical purification zone 200. Located at the very front bottom of the system, the sedimentation zone 110 employs a deep pit structure with a base elevation of -2.5m to -1.5m. During construction, a dredging channel or operating space for a mechanical grab bucket should be reserved. The effective dredging frequency of this zone (e.g., once a year during the dry season) is a core maintenance task to ensure the long-term stability of the system. The permeable baffle 120 is installed on top of the sedimentation zone 110 and is made of corrosion-resistant, high-strength HDPE or fiberglass material. The boulder layer 130 is installed on top of the permeable baffle 120 and is made of stones with a particle size of 0.15m to 0.3m, used for initial energy dissipation and coarse filtration of sediment.

[0019] The secondary enhanced biochemical purification section 200 includes a baffle 210, a bagged biochar layer 220, a three-dimensional mesh packing module 230, and submerged plants at the front end 240. The baffle 210 is vertically installed on the permeable baffle 120 and located on one side of the rubble layer 130. The baffle 210 is made of concrete or reinforced concrete and serves as an isolation layer. Its top surface elevation is higher than the normal water level to ensure stable hydraulic flow. The three-dimensional mesh packing module 230 is installed on the permeable baffle 120 and located on one side of the baffle 210. The three-dimensional mesh packing module 230 is made of high-porosity polyester or polypropylene material to ensure hydraulic conductivity and microbial attachment area. The packing layer thickness design must meet the necessary hydraulic retention time (HRT). A bagged biochar layer 220 is placed on the three-dimensional mesh packing module 230. The thickness of the bagged biochar layer 220 is 0.2m~0.3m, and its top surface elevation is -0.3m~-0.1m. The biochar used is high-activation carbon with an iodine value greater than 800mg / g, and it is packaged in corrosion-resistant nylon mesh bags for easy replacement or regeneration after adsorption saturation. Submerged plants 240 are planted on the slope area of ​​the secondary enhanced biochemical purification section 200 as a stress-resistant zone. The planting base elevation is -0.80, and the planting density is 60 plants / m². 2 The submerged plant 240 is preferably water shield grass, which is planted using a planting basket with substrate or a mud ball fixation technique to ensure its survival rate under the impact of water flow.

[0020] The tertiary water quality stabilization and ecological restoration section 300 includes mid-level submerged plants 310 and tertiary submerged plants 320. The mid-level submerged plants 310 are planted in the shallow water area at the front of the tertiary water quality stabilization and ecological restoration section 300, with a planting base elevation of -1m. The mid-level submerged plants 310 are preferably a mixture of *Hydrocotyle vulgaris* and *Vallisneria natans*, planted using substrate-supported planting baskets or mud balls for anchoring, ensuring their survival rate under water flow impact. The tertiary submerged plants 320 are planted in the deep water area at the rear of the tertiary water quality stabilization and ecological restoration section 300, with a planting base elevation of -1.2m. The tertiary submerged plants 320 are preferably a mixture of *Ceratophyllum demersum* and *Vallisneria natans*, planted using substrate-supported planting baskets or mud balls for anchoring, ensuring their survival rate under water flow impact. This creates a stable underwater forest in the tertiary water quality stabilization and ecological restoration section 300, improving water transparency and dissolved oxygen.

[0021] The overall foundation and seepage prevention requirements of the graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control of the present invention are as follows: Basic treatment: The wetland base should be compacted to ensure structural stability, especially in the sedimentation zone (6) at a depth of -2.00m, to prevent uneven settlement.

[0022] Seepage prevention requirements: The entire wetland bed must be laid with a high-density polyethylene (HDPE) geomembrane with a thickness of not less than 1.0 mm. The joints must be double-tracked hot-melt welded and an air-filling test must be conducted to ensure that the geomembrane layer is 100% intact.

[0023] Working principle and advantages: Farmland runoff first enters the primary physical buffer and settling zone 100 through inlet 10. After passing through the rock layer 130 and permeable baffle 120 for energy dissipation, the flow velocity is significantly reduced. A large amount of silt and heavy metal particles carried in the water settle to the bottom sedimentation zone 110 under gravity, thus preventing physical blockage of the downstream packing material. The supernatant passes over baffle 210 and enters the secondary enhanced biochemical purification zone 200. In this area, the water flows through the bagged biochar layer 220 and the three-dimensional mesh packing module 230. The biochar adsorbs herbicides and organic pollutants in the water, and the biofilm on the surface of the packing material removes nitrogen and phosphorus through nitrification and denitrification. Simultaneously, the submerged plants 310 (water shield grass) planted on the slope further absorb nutrients and tolerate residual pesticides. After deep treatment, the water enters the tertiary water quality stabilization and ecological restoration zone 300. In the shallow water zone, mid-level submerged plants 310 (water shield grass + Vallisneria natans) and in the deep water zone, rear-end submerged plants 320 (Ceratophyllum demersum + Vallisneria natans) release oxygen through photosynthesis and adsorb suspended solids, resulting in clear and stable effluent that ultimately meets discharge standards. This structure utilizes a complete "sedimentation-adsorption-degradation-restoration" process to achieve highly efficient, clog-resistant, and resilient purification effects.

[0024] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A graded barrier-control composite ecological wetland structure for controlling agricultural non-point source pollution, characterized in that, It includes a primary physical buffer sedimentation zone, a secondary enhanced biochemical purification zone, and a tertiary water quality stabilization and ecological restoration zone, arranged sequentially along the water flow direction. The primary physical buffer settling zone includes a sedimentation zone, a permeable baffle, and a boulder layer. The sedimentation zone is located at the bottom of the primary physical buffer settling zone and at the bottom of the front section of the secondary enhanced biochemical purification zone. The permeable baffle is located at the top of the sedimentation zone, and the boulder layer is located on the permeable baffle. The secondary enhanced biochemical purification section includes a baffle, a bagged biochar layer, a three-dimensional mesh filler module, and submerged plants at the front end. The baffle is vertically installed on the permeable partition and located on one side of the rock layer. The three-dimensional mesh filler module is installed on the permeable partition and located on one side of the baffle. The bagged biochar layer is installed on the three-dimensional mesh filler module. The submerged plants at the front end are planted on the slope area of ​​the secondary enhanced biochemical purification section. The three-level water quality stabilization and ecological restoration section includes mid-level submerged plants and rear-level submerged plants. The mid-level submerged plants are planted in the shallow water area at the front of the three-level water quality stabilization and ecological restoration section, and the rear-level submerged plants are planted in the deep water area at the rear of the three-level water quality stabilization and ecological restoration section.

2. The graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control as described in claim 1, characterized in that, The sedimentation zone is a deep pit structure with a base elevation of -2.5m to -1.5m. The rock layer is made of stones with a particle size of 0.15m to 0.3m, and the permeable baffle is made of HDPE or fiberglass.

3. The graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control as described in claim 1, characterized in that, The baffle is made of concrete or reinforced concrete, and its top surface elevation is higher than the normal water level; the bagged biochar layer has a thickness of 0.2m to 0.3m and its top surface elevation is -0.3m to -0.1m. The biochar is selected from highly activated carbon with an iodine value greater than 800mg / g and is packaged in corrosion-resistant nylon mesh bags; the three-dimensional mesh filler module is made of polyester or polypropylene material with high porosity.

4. The graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control as described in claim 1, characterized in that, The front submerged plant is water shield grass, the middle submerged plant is a hybrid of water shield grass and Vallisneria natans, and the rear submerged plant is a hybrid of hornwort and Vallisneria natans.

5. The graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control as described in claim 4, characterized in that, The submerged plants at the front, middle and rear ends are planted using planting baskets with substrate or mud balls for fixation.

6. The graded barrier-control composite ecological wetland structure for agricultural non-point source pollution control as described in any one of claims 1 to 5, characterized in that, An impermeable membrane is laid at the bottom of the bed of the entire ecological wetland structure. The impermeable membrane is made of high-density polyethylene with a thickness of not less than 1.0 mm, and the joints are welded by double-track hot-melt welding.

Images