Ecological restoration method suitable for turbidity reduction and purification of high-turbidity urban and rural rivers in plains

Abstract

The invention discloses an ecological restoration method suitable for turbidity reduction and purification of high-turbidity urban and rural rivers in plains. The ecological restoration method comprises the following steps: ecological water level regulation and control; bottom layer fishes and reptiles are removed; substrate improvement; submerged plants are planted at the substrate I; filter-feeding freshwater mussels are stocked at the substrate II; stocking filter-feeding fish silver carps and bighead carps; and stocking rhodeinae fishes and pelteobagrus fishes. According to the ecological restoration method suitable for turbidity reduction and purification of the high-turbidity urban and rural rivers in the plain, a new biocenosis can be established in the high-turbidity urban and rural rivers in the plain, the turbidity reduction and purification effects on the high-turbidity rivers can be achieved, and meanwhile the navigation, flood discharge and other effects of the rivers can be guaranteed; the method is very conveniently applicable to urban and rural high-turbidity rivers undertaking navigation and flood discharge effects, can realize organic unification of the ecological environment benefits of turbidity descending and purification and the economic and social benefits of the rivers, and has very good market popularization and use values.

Description

Technical Field

[0001] This invention relates to the field of water ecological restoration technology, and in particular to an ecological restoration method applicable to reducing and purifying turbidity in urban and rural rivers with high turbidity in plains. Background Technology

[0002] Turbidity is a crucial indicator of river and lake ecosystems, and in 2019 it was added as a mandatory surface water monitoring indicator in China. Through vigorous efforts, water quality in some Chinese cities, such as Shanghai, has significantly improved, and the black and odorous phenomenon has largely disappeared. However, overall turbidity, low transparency, and poor sensory appeal of river water have become a prominent problem. The need to reduce turbidity and improve the sensory experience of urban rivers is urgent. In my country's plains, high-turbidity rivers often exhibit poor water flow and slow movement due to the construction of sluice gates, dams, and other water conservancy projects, leading to some degree of lacustrine and marshy characteristics. River turbidity primarily originates from suspended solids and algae, with suspended solids mainly derived from surface sediments. Suppressing suspended solids and algae produced by surface sediments, and carrying out targeted aquatic ecological restoration, are of great significance and necessity for reducing turbidity and pollution in urban rivers.

[0003] Currently, water turbidity reduction and purification technologies mainly fall into three categories: physical methods, chemical methods, and biological manipulation. Physical methods include adsorption, gravity sedimentation, and sieve retention; chemical methods primarily involve flocculation technology, traditionally using organic and inorganic flocculants, and later, biologically based flocculants such as plant tannin flocculants. However, both physical and chemical methods suffer from insufficient ecological sustainability, causing significant disturbance to the physical, chemical, and biological conditions of the aquatic ecosystem. The ecosystem heavily relies on external engineering measures or chemicals to maintain clear water, lacking the capacity to maintain clear water and low turbidity on its own. Furthermore, the potential risks of adding flocculants and other chemicals to water bodies are unclear; long-term reliance on chemical additions could have unpredictable impacts on the ecosystem. The use of microbial agents has been included in the negative list for water ecological protection and construction by relevant national documents.

[0004] Compared to physical and chemical methods, biomanipulation is more ecological, causes less disturbance to the aquatic ecosystem, has relatively lower costs, and requires less engineering work. It mainly relies on the biological communities already present in the aquatic ecosystem to restore it, and has already been applied in controlling cyanobacterial blooms. However, current biomanipulation also has some problems and shortcomings in practical applications. Existing biomanipulation technologies mainly use floating beds and floating islands as carriers, with organisms placed within them. These floating beds and islands require daily maintenance, resulting in corresponding operation and maintenance costs. The structures of floating beds and islands are fragile and easily damaged, and the workload and cost of maintenance after structural damage are significant. If organisms become injured, sick, or even die within the floating beds and islands, the purification and restoration effect drops significantly, and the purification effect is unstable. The space of a single floating bed or island is limited, resulting in a low carrying capacity for organisms and a limited purification and restoration effect. A large number of floating beds and islands are needed to achieve a certain effect, and the labor costs for deployment and the material costs of the structural framework are relatively high.

[0005] In conclusion, ecological restoration methods that involve directly planting or raising organisms in natural water bodies and regulating biological communities, suitable for reducing turbidity and purifying urban and rural rivers, still need further development. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] Another objective of this invention is to provide an ecological restoration method for reducing and purifying turbidity in urban and rural rivers in plains with high turbidity. This method can establish new biological communities in urban and rural rivers with high turbidity in plains, which can not only reduce and purify turbidity in high-turbidity rivers, but also ensure the navigation and flood discharge functions of the river channel. It is very convenient to apply to high-turbidity urban and rural rivers that undertake navigation and flood discharge functions, and can achieve the organic unity of the ecological and environmental benefits of turbidity reduction and purification and the economic and social benefits of the river. It has good market promotion and application value.

[0008] To achieve these objectives and other advantages according to the present invention, an ecological restoration method suitable for reducing and purifying turbidity in urban and rural rivers with high turbidity in plains is provided, comprising the following steps: Step 1, Ecological water level regulation: The ecological water level of the river to be purified by turbidity reduction will be regulated to less than or equal to 1.5m; Step 2: Remove bottom-dwelling fish and reptiles: bottom-dwelling fish include grass carp, common carp, and crucian carp, while reptiles include turtles and tortoises; Step 3, Substrate Improvement: Substrate improvement is carried out on the river for which turbidity reduction and purification are to be implemented. Along the direction of the river's extension, substrate I suitable for the growth of submerged plants is laid on the riverbed on both sides near the riverbank. The area of ​​substrate I is at least one-quarter of the riverbed area. Substrate II suitable for the growth of filter-feeding mussels is laid in the middle of the river. The area of ​​substrate II is at least one-quarter of the riverbed area. Step 4: Plant submerged plants in substrate I: submerged plants are Vallisneria natans and Hydrilla verticillata; Step 5: Stock filter-feeding freshwater mussels in substrate II: Step six: Stock filter-feeding fish such as silver carp and bighead carp; and Step 7: Stock the fish with fish from the subfamily Bitterlinginae and the genus Yellow Catfish.

[0009] Preferably, in step one, the ecological water level of the river to be purified by turbidity reduction is adjusted to 0.5 m - 1.5 m.

[0010] Preferably, in step three, substrate I is prepared by uniformly mixing sand, loess and silt in a volume ratio of 1:1:8, and the average thickness of substrate I is at least 10 cm; substrate II is prepared by uniformly mixing coarse sand and fine sand in a volume ratio of 1:1, and the average thickness of substrate II is at least 10 cm.

[0011] Preferably, in step four, the submerged plants are planted with a height of at least 10 cm, the ratio of *Vallisneria natans* to *Hydrilla verticillata* is 1:1, and the cumulative planting density of submerged plants is 40 plants / m². 2 - 60 plants / m 2 .

[0012] Preferably, in step five, the filter-feeding freshwater mussels are at least two years old, and the filter-feeding freshwater mussels include river clams, with a stocking density of 15 clams / m². 2 - 20 pieces / m 2 The stocking size is greater than or equal to 4 g / piece, and the stocking density of *Odontocercus dorsalis* and / or *Sailoria triangularis* is 1 piece / m². 2 - 5 per m 2 The stocking size for *Tectus acutus* is 30-50 g / each, and the stocking size for *Tectus triangularis* is 50-80 g / each.

[0013] Preferably, in step six, the silver carp are stocked at an age of 2 years or older, the bighead carp at an age of 3 years or older, the stocking ratio of silver carp to bighead carp is 1:1 to 4:6, and the total stocking density is 50 g / m³. 3 - 100 g / m 3 .

[0014] Preferably, in step seven, the fish of the Bitterlinginae subfamily are stocked at an age of 2 years or older, and the stocking density is 11 g / m³. 3 -13 g / m 3 The species of the genus *Pelteobagrus* are those caught in step two and / or introduced species of the genus *Pelteobagrus*, and the density of *Pelteobagrus* is maintained at 4 g / m³. 3 - 6 g / m 3 .

[0015] Preferably, in step three, substrate I and substrate II are laid using a substrate laying device. This device includes a feed hopper and a guide cylinder connected end-to-end. The guide cylinder has a rectangular cross-section with an aspect ratio greater than or equal to 3:1, and the angle between the axis of the guide cylinder and the axis of the feed hopper is less than 160°. Multiple permeable pipes are evenly spaced and continuously arranged on the guide cylinder, with the two ends of each pipe sealed to the two side walls of the guide cylinder corresponding to the two long sides of the rectangular cross-section. The distance between adjacent permeable pipes is greater than or equal to 10 cm. Multiple screens are arranged in pairs at both ends of the permeable pipes, flush with the two side walls of the guide cylinder, and the aperture of the screens is less than or equal to 2 mm. cm; a frame, which is detachably mounted on the hull, the frame including two symmetrically arranged main support frames, at least two crossbeams, which are laterally fixed between the two main support frames; a pair of rotating shafts, which are symmetrically distributed on both sides of the feed hopper, and the pair of rotating shafts are rotatably mounted on the two main support frames through bearings; an electric telescopic cylinder, the base of which is hinged to at least two crossbeams, and the front end of the piston rod of the electric telescopic cylinder is hinged to the side wall of the guide cylinder.

[0016] Preferably, at bottom substrate I, multiple bottom substrate protection components are evenly spaced along the river's extension direction. Each bottom substrate protection component includes a protective net layer, which is a V-shaped hollow structure; a filler material, which is filled and placed inside the hollow structure of the protective net layer, and the filler material includes pebbles, shells, and zeolite mixed in a volume ratio of 8:1:1; a straw mat layer, which is wrapped around the filler material and is placed near both ends of the protective net layer, and the ratio of the total length of the straw mat layer to the total length of the hollow structure is greater than or equal to 1:2 in the length extension direction of the hollow structure; seeds, which are wrapped inside the straw mat layer, and the seeds include at least one of calamus seeds and reed seeds; the shortest interval between two adjacent bottom substrate protection components is 5 m; and multiple U-shaped bamboo anchors, which are detachably inserted at the contact points between the multiple bottom substrate protection components and bottom substrate I. At substrate II, multiple pebble distribution zones are laid out horizontally at even intervals. In the direction of river extension, the distance between two adjacent pebble distribution zones is greater than or equal to 8 m, the width of any pebble distribution zone is less than or equal to 30 cm, and the pebble particle size in multiple pebble distribution zones is greater than or equal to 10 cm.

[0017] Preferably, it further includes: a pair of support wheels rotatably disposed near the lower end of the guide cylinder, and the lower bottom surface of the pair of support wheels is disposed at a height relatively lower than the lower end of the guide cylinder; a dust cover extending horizontally above the discharge port of the guide cylinder; a support frame located in the middle of the dust cover; and a polyester nonwoven fabric layer spread out within the support frame.

[0018] The present invention has at least the following beneficial effects: Steps one through seven establish a new biological community. Specifically, improving the surface sediment in the near-bank areas on both sides of the river, covering at least a quarter of the total riverbed area, makes it more suitable for planting submerged plants. Ensuring adequate coverage of submerged plants purifies the water, reduces the risk of eutrophication, provides habitats, foraging grounds, and breeding grounds for aquatic animals, and maintains a stable aquatic ecosystem. It also stabilizes bottom sediment, reduces sediment resuspension, and prevents water turbidity. Improving the surface sediment in the central area of ​​the river, covering at least a quarter of the total riverbed area, and stocking filter-feeding mussels effectively purifies the water, reduces turbidity, promotes nutrient cycling, improves the bottom environment, restores the river ecosystem, and establishes a stable food chain. Compared to manual dredging and chemical purification methods, this approach has advantages such as low cost, no secondary pollution, and simple maintenance. No complex equipment or continuous energy input is required, making it suitable for large-scale promotion in small and medium-sized rivers in urban and rural areas. Filter-feeding fish such as silver carp and bighead carp can filter phytoplankton in the water, precisely control algae, reduce the risk of algal blooms, optimize the ecological structure of the water body, and promote material cycling. After the fish community is established stably, the above-mentioned fish can be appropriately caught or fished to reasonably control the fish density. After the biological community is established stably, the ecological water level can be allowed to rise appropriately to about 2 meters to avoid excessive growth of submerged plants.

[0019] In summary, the ecological restoration method for reducing and purifying turbidity in urban and rural rivers in plains provided by this invention can not only reduce and purify turbidity in high-turbidity rivers, but also ensure the navigation and flood discharge functions of the river channel. It is very convenient to apply to high-turbidity rivers that undertake navigation and flood discharge functions, and can achieve the organic unity of the ecological and environmental benefits of turbidity reduction and purification and the economic and social benefits of the river. It has good market promotion and application value.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1 This is a flowchart of an ecological restoration method for reducing and purifying turbidity in urban and rural rivers with high turbidity in plains, as described in one embodiment of the present invention; Figure 2 This is a side view of the substrate laying device according to one embodiment of the present invention, wherein the guide cylinder is a cross-sectional structure; Figure 3 This is a rear view structural schematic diagram of the substrate laying device according to one embodiment of the present invention; Figure 4 This is a top view of a partial river structure in one embodiment of the present invention, showing multiple bottom protection components and multiple pebble distribution zones; Figure 5 This is a front view structural schematic diagram of any one of the substrate protection components in one embodiment of the present invention; Figure 6 This is a schematic diagram of the cross-section of one end of any substrate protection component in one embodiment of the present invention; Figure 7 This is a side view of the substrate laying device in another embodiment of the present invention, wherein the dust cover is a cross-sectional structure. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not imply the presence or addition of one or more other elements or combinations thereof.

[0024] like Figure 1 As shown, this invention provides an ecological restoration method suitable for reducing and purifying turbidity in urban and rural rivers in plains areas, comprising the following steps: Step 1, Ecological Water Level Control: The ecological water level of the river to be purified by turbidity reduction will be controlled to less than or equal to 1.5m. Given that the current turbidity of the river to which this invention is to be applied is high, in order to ensure the survival rate of the submerged plants after planting, the river water level should be ensured not to exceed 1.5m, thereby maintaining the underwater light intensity required for the growth of the submerged plants. In addition, given that the river to which this invention is to be applied needs to remove bottom-dwelling fish and reptiles, the water level should also be controlled in advance to ensure the effectiveness of removing reptiles. Step 2: Remove bottom-dwelling fish and reptiles: Bottom-dwelling fish include grass carp, common carp, and crucian carp, and reptiles include turtles and tortoises. This is to prevent these animals from disturbing the sediment, causing it to resuspend, which would be detrimental to turbidity reduction and the creation and maintenance of submerged plant communities. It is also to prevent these animals from preying on freshwater mussels, which would be detrimental to the creation and maintenance of freshwater mussel communities. Step 3, Substrate Improvement: Substrate improvement is carried out on the river for which turbidity reduction and purification are to be implemented. Along the direction of the river's extension, substrate I suitable for the growth of submerged plants is laid on the riverbed on both sides near the riverbank. The area of ​​substrate I is at least one-quarter of the riverbed area. Substrate II suitable for the growth of filter-feeding mussels is laid in the middle of the river. The area of ​​substrate II is at least one-quarter of the riverbed area. Step 4: Plant submerged plants in substrate I: submerged plants are Vallisneria natans and Hydrilla verticillata; Step 5: Stock filter-feeding freshwater mussels in substrate II: Step six: Stock filter-feeding fish such as silver carp and bighead carp; and Step 7: Stock fish of the Bitterlinginae subfamily and fish of the Yellow Catfish genus. Among them, the Bitterlinginae subfamily fish and freshwater mussels have a mutualistic symbiotic relationship. The low density of Bitterlinginae subfamily fish and freshwater mussels can promote the growth of submerged plants. The gill filaments and fin rays of the Yellow Catfish genus fish provide a parasitic site for the development of the glochidia larvae of the Triangular Sail Mussel.

[0025] In this plan, a new biological community is established through steps one through seven. Specifically, at least one-quarter of the surface sediment in the near-shore areas on both sides of the river channel, covering the total riverbed area, is improved to make it more suitable for submerged plants. Ensuring adequate coverage of submerged plants purifies the water, reduces the risk of eutrophication, provides habitats, foraging grounds, and breeding grounds for aquatic animals, maintains the stability of the aquatic ecosystem, stabilizes the bottom sediment, reduces sediment resuspension, and prevents water turbidity. Further improvement of the surface sediment in the central area of ​​the river channel, covering at least one-quarter of the total riverbed area, followed by the introduction of filter-feeding freshwater mussels, effectively purifies the water, reduces turbidity, promotes nutrient cycling, improves the bottom environment, restores the river ecosystem, and establishes a stable food chain. Filter-feeding fish such as silver carp and bighead carp can filter phytoplankton from the water, precisely controlling algae growth, reducing the risk of algal blooms, optimizing the aquatic ecological structure, and promoting nutrient cycling. Once the fish community is established, appropriate fishing or angling can be used to control fish density. After the biological community is stable, the ecological water level can be allowed to rise appropriately to about 2 meters to prevent excessive growth of submerged plants. Compared with artificial dredging and chemical purification methods, this approach has advantages such as low cost, no secondary pollution, and simple maintenance. It requires no complex equipment or continuous energy input, making it suitable for large-scale promotion in small and medium-sized rivers in urban and rural areas.

[0026] In summary, the ecological restoration method for reducing and purifying turbidity in urban and rural rivers in plains provided by this invention can not only reduce and purify turbidity in high-turbidity rivers, but also ensure the navigation and flood discharge functions of the river channel. It is very convenient to apply to high-turbidity urban and rural rivers that undertake navigation and flood discharge functions, and can achieve the organic unity of the ecological and environmental benefits of turbidity reduction and purification and the economic and social benefits of the river. It has good market promotion and application value.

[0027] In a preferred embodiment, in step one, the ecological water level of the river to be purified by turbidity reduction is adjusted to 0.5 m - 1.5 m, for example, the ecological water level is adjusted to 0.5 m, 0.8 m, 1.2 m or 1.5 m, etc.

[0028] In a preferred embodiment, in step three, substrate I is prepared by uniformly mixing sand, loess, and silt in a volume ratio of 1:1:8, and the average thickness of substrate I is at least 10 cm, for example, 10 cm, 15 cm, or 20 cm; substrate II is prepared by uniformly mixing coarse sand and fine sand in a volume ratio of 1:1, and the average thickness of substrate II is at least 10 cm, for example, 12 cm, 18 cm, or 23 cm.

[0029] In a preferred embodiment, in step four, the specifications for planting submerged plants are as follows: the plant height is at least 10 cm, the ratio of *Vallisneria natans* to *Hydrilla verticillata* is 1:1, and the cumulative planting density of submerged plants is 40 plants / m². 2 -60 plants / m 2 For example, with plant heights of 10 cm, 13 cm, or 16 cm, the cumulative planting density of submerged plants is 40 plants / m². 2 50 plants / m 2 Or 60 plants / m 2 wait.

[0030] In a preferred embodiment, in step five, the filter-feeding freshwater mussels are stocked at an age of two years or older. Filter-feeding freshwater mussels include river clams, and the stocking density of river clams is 15 clams / m². 2 - 20 pieces / m 2 For example: the stocking density is 15 individuals / m². 2 17 per m 2 Or 20 per m 2 For example, the stocking size is greater than or equal to 4 g / animal, such as 4 g / animal, 6 g / animal, or 8 g / animal, etc.; for *Anodonta dorsiflora* and / or *Sinocyclocheilus triangularis*, the stocking density is 1 mu / m². 2 - 5 per m 2 For example: stocking density is 1 animal / m² 2 3 / m 2 Or 5 per m 2 For example, the stocking size of the toothless mussel is 30-50 g / piece, such as 30 g / piece, 40 g / piece or 50 g / piece, etc., while the stocking size of the triangular sail mussel is 50-80 g / piece, such as 50 g / piece, 65 g / piece or 80 g / piece, etc.

[0031] In a preferred embodiment, in step six, the silver carp are stocked at an age of 2 years or older, and the bighead carp are stocked at an age of 3 years or older, with a stocking ratio of 1:1 to 4:6, and a total stocking density of 50 g / m³. 3 - 100 g / m 3 For example: the total stocking density is 50 g / m³. 3 70 g / m 3 Or 100 g / m 3 Silver carp mainly filter-feed on phytoplankton, while bighead carp's diet contains a larger proportion of large cladocerans and copepods. The higher biomass of bighead carp can provide more host environments for the glochidia larvae of river clams. Therefore, the stocking ratio of silver carp and bighead carp can be maintained as much as possible while appropriately increasing the proportion of bighead carp to achieve the effect of reducing turbidity and purifying the environment.

[0032] In a preferred embodiment, in step seven, the fish of the Bitterlinginae subfamily are stocked at an age of two years or older, and the stocking density is 11 g / m³. 3 - 13 g / m 3 For example: stocking density is 11 g / m³ 3 12 g / m 3 Or 13 g / m 3 The species *Pelteobagrus* refers to the species of *Pelteobagrus* caught in step two and / or introduced species of *Pelteobagrus*, and the density of *Pelteobagrus* is maintained at 4 g / m³. 3 - 6 g / m 3 For example: a density of 4 g / m³ 3 5 g / m 3 Or 6 g / m 3 As bottom-dwelling fish, yellow catfish disturb surface sediments, causing sediments to remain suspended in the water, increasing turbidity and nutrients. Therefore, their density should be controlled.

[0033] like Figures 2-3As shown, in a preferred embodiment, in step three, substrate I and substrate II are laid using a substrate laying device 1. The substrate laying device includes a feed hopper 101 and a guide cylinder 102 connected end-to-end. The guide cylinder has a rectangular cross-section with an aspect ratio greater than or equal to 3:1, and the angle between the axis of the guide cylinder and the axis of the feed hopper is less than 160°. Multiple permeable pipes 103 are evenly spaced and continuously arranged on the guide cylinder, with both ends of the permeable pipes sealed to the two side walls of the guide cylinder corresponding to the two long sides of the rectangular cross-section. The distance between two adjacent permeable pipes is greater than or equal to 10 mm. cm; Multiple permeable pipes are installed on the feed cylinder. On the one hand, this allows some water to flow through multiple permeable pipes, reducing the impact of the water flow on the feed cylinder. On the other hand, the multiple permeable pipes can divert the bottom sediment I or bottom sediment II entering the feed cylinder, appropriately reducing the flow velocity and promoting the even spreading of bottom sediment I or bottom sediment II within the feed cylinder before falling onto the riverbed, improving laying efficiency while effectively reducing disturbance to surface sediments; Multiple screens 1031 are installed in pairs at both ends of the multiple permeable pipes, and the multiple screens are flush with the two side walls of the feed cylinder. The aperture of the multiple screens is less than or equal to 2. cm; On the one hand, multiple screens can effectively prevent large foreign objects in the water from being transported to the permeable pipe opening by the water flow and clogging the permeable pipe, thus preventing the permeable pipe from functioning properly. On the other hand, when the water flow velocity is high, multiple screens can also slow down the water flow velocity entering the permeable pipe, preventing the bottom substrate I or bottom substrate II inside the permeable pipe from not being evenly spread; The frame, which is detachably mounted on the hull, includes two symmetrically arranged main support frames 104 and at least two crossbeams 105, which are laterally fixed between the two main support frames; A pair of rotating shafts 106, which are symmetrically distributed at the inlet The hopper is mounted on two main support frames on both sides, with a pair of rotating shafts rotatably mounted on bearings. An electric telescopic cylinder 107 has its base hinged to at least two crossbeams, and the front end of its piston rod hinged to the side wall of the guide cylinder. The base of the electric telescopic cylinder can be mounted on one of the higher crossbeams to avoid collisions with the hull and disruption to construction. Alternatively, a longitudinal beam can be added on the at least two crossbeams, and the electric telescopic cylinder can be mounted on this beam to facilitate height adjustment and adapt to different equipment. In this scheme, a substrate laying device is used to lay substrate I and substrate II, which effectively improves construction efficiency while minimizing disturbance to surface sediments, rapidly improving the substrate while significantly shortening the turbidity reduction and purification time.

[0034] The specific method for laying Substrate I and Substrate II using a substrate laying device is as follows: 1) The feed hopper and guide cylinder are mounted on the frame at the rear of the ship, or between two small ships, close to the riverbank area. They can also be hoisted on the bank using hoisting equipment. 2) Adjust the tilt angle of the guide cylinder by using an electric telescopic cylinder so that it is inserted into the water body at a suitable angle and height and that its lower end is close to the riverbed, and make the extension direction of multiple permeable pipes consistent with the direction of water flow. 3) Gradually transport substrate I or substrate II into the feed hopper. As the ship or hoisting equipment moves, substrate I or substrate II is transported along the guide cylinder to the designated position on the riverbed and gradually spread out. The laying thickness is checked at fixed times and locations, and the moving speed of the ship or hoisting equipment, the flow rate and velocity of substrate I or substrate II transported into the feed hopper are adjusted in a timely manner to meet the construction requirements of the preset average laying thickness of substrate I or substrate II.

[0035] like Figures 4-6 As shown, in a preferred embodiment, at the bottom substrate I, multiple bottom substrate protection components 2 are evenly spaced along the river's extension direction. Each bottom substrate protection component includes a protective net layer 201, which is a V-shaped hollow structure; a filler 202, which is filled within the hollow structure of the protective net layer, and the filler includes pebbles, shells, and zeolite mixed in a volume ratio of 8:1:1; a straw mat layer 203, which is wrapped around the filler, and the straw mat layer is positioned near both ends of the protective net layer (to improve the permeability and filtration of the tips of the V-shaped hollow structure). In the length extension direction of the hollow structure, the ratio of the total length of the straw mat layer to the total length of the hollow structure is greater than or equal to 1:2 (for example, if the total length of the hollow structure is 2 m, the total length of the straw mat layer can be set to 1 m, 1.2 m, or 1.3 m, etc.); seeds, which are wrapped within the straw mat layer, and the seeds include at least one of calamus seeds and reed seeds; the minimum interval between two adjacent bottom substrate protection components is 5 m; multiple U The bamboo anchor 204 is detachably inserted at the contact points between multiple bottom protection components and bottom substrate I; at bottom substrate II, multiple pebble distribution zones 3 are laid horizontally at even intervals. In the direction of river extension, the distance between two adjacent pebble distribution zones is greater than or equal to 8 m, the width of any pebble distribution zone is less than or equal to 30 cm, and the pebble particle size in the multiple pebble distribution zones is greater than or equal to 10 cm.

[0036] In this scheme, multiple substrate protection components are installed at substrate I to partially cover substrate I, disperse the impact of water flow, and prevent the water flow from directly scouring the newly laid substrate I and the surrounding bottom sediment, thus avoiding sediment suspension and loss. Each substrate protection component is shaped and fixed by a protective mesh layer, maintaining an overall V-shaped structure. During installation, the pointed end of the V-shape faces upstream of the river to reduce water flow resistance and improve its stability. The filler material is mainly pebbles, providing effective counterweight for the multiple substrate protection components to pressurize and fix them, preventing them from being washed away by the water flow and quickly providing a stable three-dimensional protective layer for substrate I. Multiple substrate protection components also reduce the direct scouring of substrate I around the roots of submerged plants, improving the scouring resistance of submerged plants, effectively increasing their establishment and survival rates, and further enhancing turbidity reduction and purification efficiency. The broken shell particles are excellent attachment carriers for microorganisms; their porous surface structure provides a habitat for nitrifying bacteria, denitrifying bacteria, and heterotrophic bacteria. In addition to providing a habitat for aquatic organisms, broken shells can also physically adsorb suspended particulate matter and organic colloids in the tailwater. Zeolite has a well-developed porous structure and high mechanical strength. When turbid water flows through zeolite, the gaps between the particles can trap suspended matter such as silt, organic debris, and plankton, further reducing the turbidity of the water. Setting up a grass mat layer can provide benthic organisms with space to hide from predators and forage and reproduce. The natural fibers of the grass mat layer can also serve as an attachment carrier for microorganisms, forming a microbial film. Microorganisms decompose pollutants such as organic matter, nitrogen, and phosphorus in the water, participate in the material cycle of the river ecosystem, and provide a food base for aquatic organisms. The grass mat layer can also provide seed fixation, water retention, and fertilizer retention, promote the root growth of aquatic plants, form a complex ecosystem, and further improve the efficiency of turbidity reduction and purification. Sweet flag and reeds have strong tolerance to their habitats and can adapt to a variety of harsh and complex habitats. Their well-developed underground rhizomes can promote the fixation of sediments, inhibit sediment resuspension, and provide shelter for submerged plants, reducing the impact of water flow on submerged plants. In practical applications, to facilitate later maintenance and prevent some bottom protection components from being washed away, ropes can be used to fix the bottom protection components to facilities such as fixed piles on the shore.

[0037] Multiple pebble distribution zones are set up at the substrate II location. Larger pebbles (10-20 cm in diameter) are preferred to enhance resistance to water flow impact and prevent substrate II from being washed away. These pebbles also provide shelter for benthic organisms such as snails and clams introduced later. These organisms further purify the water by feeding on organic debris and algae. The pebbles also appropriately reduce the flow velocity, causing suspended solids to settle due to gravity or be trapped in the pores, directly reducing water turbidity. Furthermore, the pebbles create localized eddies, causing fine colloidal particles in the water to collide and aggregate, accelerating sedimentation. Snails and clams, due to their limited mobility, rely on filter feeding, requiring the water flow to transport suspended solids to their distribution area. The localized eddies near the pebbles help these snails and clams filter feed, improving their efficiency and further enhancing the turbidity reduction and purification effect.

[0038] like Figure 7 As shown, in a preferred embodiment, the system further includes: a pair of support wheels 108, rotatably disposed near the lower end of the guide cylinder, with the lower surface of the support wheels positioned at a height lower than the lower end of the guide cylinder; a dust cover 109, horizontally extending above the discharge port of the guide cylinder; a support frame 1091, located in the middle of the dust cover; and a polyester nonwoven fabric layer 1092, spread out within the support frame. The pair of support wheels assist in supporting the guide cylinder and simultaneously limit its height, preventing the lower end of the guide cylinder from contacting the riverbed. The dust cover blocks sediment stirred up by the water, promoting rapid settling of large sediment particles. The polyester nonwoven fabric layer intercepts smaller suspended sediment particles in the water, thus purifying the water.

[0039] Example 1 The river to be purified by turbidity reduction is 6.2 km long and is a typical plain agricultural river with aquatic vegetation coverage of less than 10%.

[0040] Step 1, Ecological water level regulation: The ecological water level of the river to be purified by turbidity reduction will be regulated to 0.5 m; Step 2: Remove bottom-dwelling fish and reptiles: bottom-dwelling fish are grass carp and common carp, and reptiles are soft-shelled turtles; Step 3: Improve the riverbed sediment in the core pollution area of ​​the river, covering 3 km to 4 km: Improve the riverbed sediment for the proposed turbidity reduction and purification process. Along the river's extension direction, lay substrate I suitable for the growth of submerged plants on both sides of the riverbed near the riverbank. The area covered by substrate I should be one-quarter of the riverbed area. Lay substrate II suitable for the growth of filter-feeding mussels in the middle of the river. The area covered by substrate II should also be one-quarter of the riverbed area. Substrate I is made by uniformly mixing sand, loess, and silt in a volume ratio of 1:1:8, with an average thickness of 10 cm. Substrate II is made by uniformly mixing coarse sand and fine sand in a volume ratio of 1:1, with an average thickness of 12 cm. Step 4: Plant submerged plants in substrate I: Vallisneria natans and Hydrilla verticillata. The plants should be 10 cm tall, with a plant ratio of Vallisneria natans to Hydrilla verticillata of 1:1. The total planting density should be 40 plants / m². 2 ; Step 5: Stock filter-feeding freshwater mussels at substrate II. The mussels should be at least 2 years old. Filter-feeding mussels include freshwater clams and toothless mussels. The stocking density for freshwater clams is 15 mussels / m². 2 The stocking size is 8-9 g / piece, and the stocking density of the toothless mussel is 1 mussel / m². 2 The stocking size of the toothless mussels is 45-50 g / piece. Step Six: Stock filter-feeding fish, silver carp and bighead carp. Silver carp should be 2 years old or older, and bighead carp should be 3 years old or older. The stocking ratio of silver carp to bighead carp is 1:1, and the total stocking density is 50 g / m³. 3 The higher biomass of bighead carp can provide more host environments for the glochidia larvae of river clams; and Step 7: Stock the fish with the subfamily Bitterlinginae and the genus *Pelteobagrus*. The Bitterlinginae fish should be 2 years old or older, and the stocking density should be 11 g / m³. 3 The species of the genus *Pelteobagrus* are those caught in step two and / or introduced species of the genus *Pelteobagrus*, and the density of *Pelteobagrus* is maintained at 4 g / m³. 3 .

[0041] The river's turbidity data was monitored using an online monitoring device (monitoring period of 12 months). The average turbidity (NTU) before the renovation was 78.3, the average turbidity (NTU) after 1 month was 43.1, the average turbidity (NTU) after 6 months was 21.3, and the average turbidity (NTU) after 12 months was 17.9.

[0042] Example 2 The river to be purified by turbidity reduction is 7.5 km long and is a typical plain agricultural river with an aquatic vegetation coverage of 8%.

[0043] Step 1, Ecological water level regulation: The ecological water level of the river to be purified by turbidity reduction will be regulated to 1.2 m; Step 2: Remove bottom-dwelling fish and reptiles: bottom-dwelling fish are grass carp and common carp, and reptiles are soft-shelled turtles; Step 3: Improve the riverbed sediment in the core pollution area of ​​the river, covering 3 km to 4 km: Improve the riverbed sediment for the proposed turbidity reduction and purification process. Along the river's extension direction, lay substrate I suitable for the growth of submerged plants on both sides of the riverbed near the riverbank. The area covered by substrate I should be one-quarter of the riverbed area. Lay substrate II suitable for the growth of filter-feeding mussels in the middle of the river. The area covered by substrate II should be two-quarters of the riverbed area. Substrate I is made by uniformly mixing sand, loess, and silt in a volume ratio of 1:1:8, with an average thickness of 15 cm. Substrate II is made by uniformly mixing coarse sand and fine sand in a volume ratio of 1:1, with an average thickness of 18 cm. Step 4: Plant submerged plants in substrate I: Vallisneria natans and Hydrilla verticillata. The plants should be 13 cm tall, with a 1:1 ratio of Vallisneria natans to Hydrilla verticillata. The total planting density should be 50 plants / m². 2 ; Step 5: Stock filter-feeding freshwater mussels at substrate II. The mussels should be at least 2 years old. Filter-feeding mussels include freshwater clams and triangular sail mussels. The stocking density of freshwater clams is 17 mussels / m². 2 The stocking size is 6-7 g / piece, and the stocking density of the triangular sail mussel is 3 mussels / m². 2 The stocking size of the triangular sail mussel is 75-80 g / piece. Step Six: Stock filter-feeding fish, silver carp and bighead carp. Silver carp should be 2 years or older, and bighead carp 3 years or older. The stocking ratio of silver carp to bighead carp is 9:11, and the total stocking density is 70 g / m³. 3 The higher biomass of bighead carp can provide more host environments for the glochidia larvae of river clams; and Step 7: Stock the fish with the subfamily Bitterlinginae and the genus *Pelteobagrus*. The Bitterlinginae fish should be 2 years old or older, and the stocking density should be 12 g / m³. 3 The species of the genus *Pelteobagrus* refers to the species of *Pelteobagrus* caught in step two and / or introduced species of *Pelteobagrus*, and the density of *Pelteobagrus* is maintained at 5 g / m³. 3 .

[0044] The river's turbidity data was monitored using an online monitoring device (monitoring period of 12 months). The average turbidity (NTU) before the renovation was 81.3, the average turbidity (NTU) after 1 month was 39.2, the average turbidity (NTU) after 6 months was 21.3, and the average turbidity (NTU) after 12 months was 16.5.

[0045] Example 3 The river to be purified by turbidity reduction is 8.7 km long and is a typical plain agricultural river with an aquatic vegetation coverage of 7%.

[0046] Step 1, Ecological water level regulation: The ecological water level of the river to be purified by turbidity reduction will be regulated to 1.5 m; Step 2: Remove bottom-dwelling fish and reptiles: bottom-dwelling fish are grass carp and common carp, and reptiles are soft-shelled turtles; Step 3: Improve the riverbed sediment in the core pollution area of ​​the river, from 4 km to 4.5 km: Improve the riverbed sediment for the proposed turbidity reduction and purification process. Along the river's extension direction, on both sides of the riverbed near the banks, use a sediment laying device to lay sediment I suitable for the growth of submerged plants. The area covered by sediment I is one-quarter of the riverbed area. In the middle of the river, use a sediment laying device to lay sediment II suitable for the growth of filter-feeding mussels. The area covered by sediment II is three-quarters of the riverbed area. Sediment I is prepared by uniformly mixing sand, loess, and silt in a volume ratio of 1:1:8, with an average laying thickness of 20 cm. Sediment II is prepared by uniformly mixing coarse sand and fine sand in a volume ratio of 1:1, with an average laying thickness of 23 cm. Subsequently, at substrate I, multiple substrate protection components are evenly spaced along the river's extension direction. The total length of the hollow structure of any substrate protection component is 2 m, and the total length of the grass mat layer is 1 m. Seeds, including calamus and reed seeds, are wrapped inside the grass mat layer. The distance between two adjacent substrate protection components is 6 m. Multiple substrate protection components are fixed by multiple U-shaped bamboo anchors. At substrate II, multiple pebble distribution zones are set up. In the river's extension direction, the distance between two adjacent pebble distribution zones is 10 m - 11 m. The width of any pebble distribution zone is 30 cm - 40 cm, and the pebble size in multiple pebble distribution zones is 10 cm - 15 cm. Step 4: Plant submerged plants in substrate I: Vallisneria natans and Hydrilla verticillata. The plants should be 16 cm tall, with a 1:1 ratio of Vallisneria natans to Hydrilla verticillata. The total planting density should be 60 plants / m². 2 ; Step 5: Stock filter-feeding freshwater mussels at substrate II. The mussels should be at least 2 years old. Filter-feeding mussels include freshwater clams, toothless mussels, and triangular sail mussels. The stocking density for freshwater clams is 20 clams / m². 2 The stocking size is 4-5 g / piece, and the stocking density of both the toothless mussel and the triangular sail mussel is 5 pieces / m². 2 The stocking size for *Echinochloa crus-galli* was 30-35 g / each, and for *Cyprinus triangularis* it was 50-55 g / each. Step Six: Stock filter-feeding fish, silver carp and bighead carp. Silver carp should be 2 years or older, and bighead carp 3 years or older. The stocking ratio of silver carp to bighead carp is 4:6, and the total stocking density is 100 g / m³. 3 The higher biomass of bighead carp can provide more host environments for the glochidia larvae of river clams; and Step 7: Stock the fish with the subfamily Bitterlinginae and the genus *Pelteobagrus*. The Bitterlinginae fish should be 2 years old or older, and the stocking density should be 13 g / m³. 3 The species of the genus *Pelteobagrus* are those caught in step two and / or introduced species of the genus *Pelteobagrus*, and the density of *Pelteobagrus* is maintained at 6 g / m³. 3 .

[0047] The river's turbidity data was monitored using an online monitoring device (monitoring period of 12 months). The average turbidity (NTU) before the renovation was 84.3, the average turbidity (NTU) after 1 month was 29.1, the average turbidity (NTU) after 6 months was 19.3, and the average turbidity (NTU) after 12 months was 15.2.

[0048] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. An ecological restoration method suitable for reducing turbidity and purifying plain high-turbidity urban and rural rivers, characterized in that, The method comprises the following steps: Step one, ecological water level regulation: the ecological water level of the river to be implemented for turbidity reduction and purification is regulated to be less than or equal to 1.5 m; Step two, removing bottom fish and reptiles: the bottom fish are grass carp, common carp and crucian carp, and the reptiles are turtles and soft-shelled turtles; Step three, bottom improvement: the bottom of the river to be implemented for turbidity reduction and purification is improved, and the bottom of the river is paved with bottom substrate I suitable for the growth of submerged plants on both sides near the river bank along the extension direction of the river, the paving area of the bottom substrate I accounts for at least one fourth of the area of the river bottom, and the middle of the river is paved with bottom substrate II suitable for the growth of filter-feeding mussels, and the paving area of the bottom substrate II accounts for at least one fourth of the area of the river bottom; Step four, planting submerged plants in the bottom substrate I: the submerged plants are pondweed and black algae; Step five, breeding filter-feeding mussels in the bottom substrate II; Step six, breeding filter-feeding fish such as silver carp and bighead carp; and Step seven, breeding fish of the Acheilognathus subfamily and fish of the Pelteobagrus genus.

2. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In step one, the ecological water level of the river to be implemented for turbidity reduction and purification is regulated to be 0.5 m - 1.5 m.

3. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In step three, the bottom substrate I is uniformly mixed by sand, loess and silt in a volume ratio of 1:1:8, and the average paving thickness of the bottom substrate I is at least 10 cm; and the bottom substrate II is uniformly mixed by coarse sand and fine sand in a volume ratio of 1:1, and the average paving thickness of the bottom substrate II is at least 10 cm.

4. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In step four, the submerged plants are planted with a height of at least 10 cm, and the ratio of Vallisneria and Hydrilla verticillata is 1:1, and the cumulative planting density of the submerged plants is 40 plants / m 2 - 60 plants / m 2 .

5. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In step five, the filter-feeding river bivalve is 2 years old or above, the filter-feeding river bivalve includes river clam, the stocking density of the river clam is 15 / m 2 - 20 / m 2 , the stocking size of the river clam is greater than or equal to 4 g per clam, the stocking density of the toothless bivalve and / or the triangular paddle mussel is 1 / m 2 - 5 / m 2 , the stocking size of the toothless bivalve is 30 - 50 g per clam, and the stocking size of the triangular paddle mussel is 50 - 80 g per clam.

6. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In step six, the age of the silver carp is 2 years and above, the age of the bighead carp is 3 years and above, the ratio of the silver carp and the bighead carp is 1:1 - 4:6, and the total density of the silver carp and the bighead carp is 50 g / m 3 - 100 g / m 3 .

7. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In the seventh step, the age of the fish of the subfamily Acheilognathinae is 2 years and above, and the stocking density is 11 g / m 3 - 13 g / m 3 The fish of the genus Procyprinus is the fish of the genus Procyprinus captured in the second step and / or the alien fish of the genus Procyprinus, and the density of the genus Procyprinus is maintained at 4 g / m 3 - 6 g / m 3 .

8. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 1, characterized in that, In the step three, the bottom substrate I and the bottom substrate II are paved by a bottom substrate paving device, wherein the bottom substrate paving device comprises a feeding hopper and a guide cylinder connected in head-to-tail, the guide cylinder is a rectangular cross-section cylinder structure, the length-width ratio of the rectangular cross-section of the guide cylinder is greater than or equal to 3:1, the included angle between the axis of the guide cylinder and the axis of the feeding hopper is less than 160°; a plurality of water permeable pipes are uniformly and spaced through the guide cylinder, and the two end edges of the plurality of water permeable pipes are respectively and sealingly connected to the two side walls of the guide cylinder corresponding to the two long sides of the rectangular cross-section, and the spacing distance between adjacent two water permeable pipes is greater than or equal to 10 cm; a plurality of screens are arranged in pairs at the two ends of the plurality of water permeable pipes, and the plurality of screens are flush with the two side walls of the guide cylinder, and the pore size of the plurality of screens is less than or equal to 2 cm; a frame is detachably arranged on the ship body, the frame comprises two main support frames arranged symmetrically, at least two cross beams are fixedly arranged between the two main support frames; a pair of rotating shafts are symmetrically distributed on both sides of the feeding hopper, and the pair of rotating shafts are rotatably arranged on the two main support frames through bearings; and an electric telescopic cylinder is hingedly arranged on the at least two cross beams, and the front end of the piston rod of the electric telescopic cylinder is hingedly arranged on the side wall of the guide cylinder.

9. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 8, characterized in that, At the bottom I, along the extension direction of the river, a plurality of bottom protection pieces are uniformly spaced apart, any bottom protection piece includes a protective net layer, which is a hollow structure in the shape of V; a filler, which is filled in the hollow structure of the protective net layer, the filler includes pebbles, shells and zeolite mixed in a volume ratio of 8:1:1; a grass felt layer, which is wrapped on the filler, and the grass felt layer is arranged near both ends of the protective net layer, in the length extension direction of the hollow structure, the total length of the grass felt layer is greater than or equal to 1:2 of the total length of the hollow structure; seeds, which are wrapped in the grass felt layer, the seeds include at least one of acorus calamus seeds and reed seeds; the shortest interval distance between two adjacent bottom protection pieces is 5 m; a plurality of U-shaped bamboo anchors are detachably inserted at the contact between the plurality of bottom protection pieces and the bottom I; At the bottom II, a plurality of pebble distribution belts are uniformly spaced apart and laid transversely, in the extension direction of the river, the interval distance between two adjacent pebble distribution belts is greater than or equal to 8 m, the width of any pebble distribution belt is less than or equal to 30 cm, and the particle size of the pebbles in the plurality of pebble distribution belts is greater than or equal to 10 cm.

10. The ecological restoration method for purifying and reducing the turbidity of high-turbidity urban and rural rivers in plains according to claim 8, characterized in that, Further comprising: A pair of support wheels rotatably arranged near the lower end of the material guide cylinder, and the lower bottom surface of the pair of support wheels is arranged at a height lower than that of the lower end of the material guide cylinder; a dust cover horizontally extending above the discharge port of the material guide cylinder; a support frame is opened in the middle of the dust cover; a polyester non-woven fabric layer is spread in the support frame.

Images