Method for controlling endogenous pollution using river channel sediment solidifying agent

Abstract

The application discloses a method for controlling endogenous pollution by using river channel sediment solidifying agent, and relates to the technical field of river channel ecological restoration. The method adopts a four-component composite solidifying agent, which comprises inorganic cementing, heavy metal passivation, nitrogen and phosphorus stabilization, and water-retaining and coagulation promoting components. The treatment process comprises the following steps: simply leveling the original state of the river channel sediment without dewatering pretreatment; in-situ spreading and deep stirring and mixing of the mixed solidifying agent, and short-term curing to form the sediment. The method realizes the simultaneous realization of sediment solidification and reduction, heavy metal passivation, long-acting locking of nitrogen and phosphorus, high solidified body strength, good anti-scouring performance, good ecological compatibility, and a great reduction of the maintenance period. The pollution inhibition rate reaches more than 90%, and there is no secondary pollution. The method can long-acting control the endogenous pollution of the river channel sediment, and is suitable for in-situ restoration and treatment of various river channel sediments.

Description

Technical Field

[0001] This invention relates to the field of river ecological restoration technology, specifically to a method for controlling endogenous pollution using a riverbed sediment solidification agent. Background Technology

[0002] Riverbed sediment is the primary accumulation carrier of water pollutants, accumulating nitrogen, phosphorus, heavy metals, organic matter, and other pollutants in the water over a long period, leading to severe endogenous pollution. Even after effective control of exogenous pollution, pollutants accumulated in the sediment continue to enter the overlying water bodies through diffusion, release, and suspension, causing repeated blackening and odor of the river water and eutrophication. This is the core issue hindering the long-term sustainability of river water quality improvement efforts.

[0003] Existing technologies for treating endogenous pollution in riverbed sediments mainly include sediment dredging, in-situ covering, and single-agent solidification, all of which have significant technical drawbacks: First, sediment dredging involves large-scale engineering projects and high costs. The dredged sediment has a high water content, making disposal difficult. Furthermore, the dredging process easily disturbs the sediment, leading to secondary release and diffusion of pollutants. It also cannot completely remove deep-seated trace pollutants, making subsequent pollution rebound likely. Second, in-situ covering technologies use clay, sand, gravel, geotextiles, etc., to cover the sediment. These only physically block pollutant release and cannot solidify and stabilize pollutants within the sediment. The covering layer is easily eroded by water flow. The traditional single-component solidifying agent is mainly composed of inorganic cementitious materials such as cement and lime. It can only achieve the hardening of bottom sediment, but has no effective locking and passivation effect on nitrogen and phosphorus nutrients and heavy metals. The solidified body has large pores and poor stability. It is prone to cracking and seepage after long-term immersion in water, and the release of pollutants is serious. At the same time, the traditional solidifying agent has poor compatibility. Bottom sediment with high water content needs to be dehydrated and pretreated in advance. The construction process is complicated, the curing period is as long as 15 days or more, the construction efficiency is low, and it is easy to cause secondary pollution problems such as alkaline pollution of water bodies.

[0004] In summary, existing technologies generally suffer from limitations such as single pollutant treatment, poor solidification stability, insufficient long-term effectiveness, weak construction adaptability, susceptibility to secondary pollution, and poor ecological compatibility. There is a lack of a solidification and treatment method for sediment pollution that can simultaneously control complex endogenous pollution, is adaptable to undisturbed sediment with high water content, is easy to construct, is eco-friendly, and has long-term stable effects. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a method for controlling endogenous pollution using riverbed sediment solidification agents. It solves the technical problems of existing technologies, such as the inability to simultaneously treat nitrogen, phosphorus, and heavy metal complex endogenous pollution, poor stability of solidified bodies, poor construction adaptability of high-moisture sediments, long curing cycles, susceptibility to secondary pollution, and short-lasting treatment effects. The invention achieves the treatment goals of in-situ efficient solidification of riverbed sediments, long-term fixation of pollutants, and no damage to the ecological environment.

[0006] The technical solution used in this invention is: a method for controlling endogenous pollution using a riverbed sediment solidifier, comprising the following steps: S1. Pretreatment of riverbed sediment: Clean up floating objects, surface garbage and debris from the river to be treated, and use leveling equipment to level the surface of the riverbed sediment, maintaining the original structure of the sediment. No pretreatment such as dewatering, dredging and drying is required, thus preserving the original ecological topography of the river to the greatest extent.

[0007] S2. Preparation of composite sediment solidification agent: The components are precisely proportioned according to the mass percentage: 60% to 70% inorganic cementing component, 15% to 20% heavy metal passivation component, 8% to 12% nitrogen and phosphorus stabilizing component, and 3% to 5% water-retaining and coagulating component. After the components are evenly mixed, they are sealed and stored for later use.

[0008] Furthermore, the inorganic cementitious component is a compound of slag powder, fly ash, and light magnesium oxide in a mass ratio of 5:3:2. This ratio can quickly undergo a hydration reaction, is suitable for sediments with high water content, and rapidly builds a dense and solidified skeleton, improving the integrity and erosion resistance of the sediment. Compared with pure cement solidification, it has low heat of hydration, no alkaline residue, and avoids secondary pollution of water bodies.

[0009] Furthermore, the heavy metal passivation component uses a composite powder of high-temperature modified zeolite powder and ferrous sulfide. The modified zeolite has a multi-level microporous structure, which can physically adsorb heavy metal ions. Ferrous sulfide can form insoluble sulfide precipitates with heavy metals such as cadmium, lead, and copper, achieving dual stability of physical adsorption and chemical passivation, and completely blocking the release of heavy metals.

[0010] Furthermore, the nitrogen and phosphorus stabilizing component is composed of polyaluminum chloride, polyferric sulfate, and modified diatomaceous earth in a mass ratio of 2:2:1. The aluminum and iron salts can quickly flocculate and solidify suspended colloidal nitrogen and phosphorus in the sediment, while the porous structure of the modified diatomaceous earth can effectively adsorb and fix dissolved nitrogen and phosphorus, inhibiting the release of nitrogen and phosphorus from the sediment into the overlying water, thus solving the core problem of eutrophication.

[0011] Furthermore, the water-retaining and coagulating component is a compound of hydroxypropyl methylcellulose and anionic polyacrylamide in a mass ratio of 3:1. It can quickly flocculate fine particles of bottom mud, accelerate water separation, shorten the curing cycle, and at the same time improve the flexibility of the solidified body, avoid cracking after long-term immersion in water, and improve the stability of the solidified layer.

[0012] S3. In-situ addition and mixing: Determine the dosage based on the degree of pollution of the riverbed sediment. For lightly and moderately polluted sediment, the dosage is 8% to 12% of the wet sediment mass, and for heavily polluted sediment, the dosage is 12% to 15%. Use a spreading device to evenly cover the surface of the sediment with the solidifying agent. Use an underwater mixing device to mix the 0-35cm layer of polluted sediment for 5 to 10 minutes to ensure that the solidifying agent is fully integrated with the sediment without any local blank areas.

[0013] S4. Static Curing and Solidification: After mixing, the treated river section is sealed off, and the water flow velocity is controlled to ≤0.2m / s to avoid water flow scouring and disturbing the unformed solidified layer. Static curing is carried out at room temperature for 3-7 days, during which the bottom sediment gradually dehydrates and hardens, and the pollutants are completely stabilized and locked in, forming a dense, permeable, and stable ecological solidified layer, thus completing the treatment of endogenous pollution.

[0014] Compared with the prior art, the present invention has the following outstanding beneficial effects: (1) It solves the technical problem of single treatment of compound pollution and realizes simultaneous long-term control of multiple pollutants: The solidifying agent of the present invention adopts a four-component composite design, which breaks through the defect that the traditional single solidifying agent can only harden the bottom mud. It can simultaneously achieve the reduction of bottom mud, passivation and stabilization of heavy metals, and adsorption and locking of nitrogen and phosphorus nutrients. It has a high-efficiency inhibitory effect on typical endogenous pollutants such as COD, ammonia nitrogen, total phosphorus, lead, cadmium and copper in the bottom mud. The pollutant release inhibition rate is ≥90%, which completely solves the problem of repeated rebound of compound endogenous pollution in the river; (2) It solves the technical problem of poor adaptability and complicated construction of high water content bottom mud: The present invention does not require dehydration, drying and dredging pretreatment of the original high water content river bottom mud. It can be directly constructed in situ, greatly simplifying the construction process, reducing construction costs and construction period, adapting to various natural river bottom mud conditions, and has a wide range of applications; (3) It solves the technical problem of poor stability of solidified body, easy cracking and failure, and long maintenance cycle: Through the synergistic effect of inorganic cementing components and water-retaining and coagulating components, With the same effect, a dense and flexible solidified skeleton is quickly formed. The 28-day compressive strength of the solidified body is ≥0.6MPa. It has excellent resistance to water flow erosion and water immersion cracking. The curing cycle is only 3-7 days, which is more than 60% shorter than the curing cycle of traditional solidification technology, and the construction efficiency is greatly improved. (4) Solve the technical problems of secondary pollution and poor ecological compatibility of traditional technology: All components of the solidifying agent of this invention are environmentally friendly inorganic materials, with no toxic and harmful substances released. The hydration reaction is mild and there is no alkaline residue. The solidified body has good water permeability and air permeability, does not destroy the original ecological structure of the river bottom sediment, and can be adapted to the growth of aquatic plants and microorganisms, so as to achieve the coordinated promotion of pollution control and ecological restoration without secondary pollution. (5) Solve the technical problem of insufficient long-term effectiveness of traditional treatment technology: This invention adopts a multi-locking mechanism of physical adsorption, chemical precipitation and gel solidification. The pollutants are stably solidified in the bottom sediment skeleton and will not be released with water flow disturbance or temperature change. The treatment effect is long-term and stable, and the service life can reach more than 5 years, which is far superior to traditional covering and short-term solidification technology. Attached Figure Description

[0015] Figure 1 This is a flowchart of the overall construction process of the present invention.

[0016] Figure 2 This is a schematic diagram of the composite curing agent component system of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figures 1 to 2 As shown, a method for controlling endogenous pollution using riverbed sediment solidification agents includes the following steps: S1. Pretreatment of riverbed sediment: Clean up floating objects, surface garbage and debris from the river to be treated, and use leveling equipment to level the surface of the riverbed sediment, maintaining the original structure of the sediment. No pretreatment such as dewatering, dredging and drying is required, thus preserving the original ecological topography of the river to the greatest extent.

[0019] S2. Preparation of composite sediment solidification agent: The components are precisely proportioned according to the mass percentage: 60% to 70% inorganic cementing component, 15% to 20% heavy metal passivation component, 8% to 12% nitrogen and phosphorus stabilizing component, and 3% to 5% water-retaining and coagulating component. After the components are evenly mixed, they are sealed and stored for later use.

[0020] Furthermore, the inorganic cementitious component is a compound of slag powder, fly ash, and light magnesium oxide in a mass ratio of 5:3:2. This ratio can quickly undergo a hydration reaction, is suitable for sediments with high water content, and rapidly builds a dense and solidified skeleton, improving the integrity and erosion resistance of the sediment. Compared with pure cement solidification, it has low heat of hydration, no alkaline residue, and avoids secondary pollution of water bodies.

[0021] Furthermore, the heavy metal passivation component uses a composite powder of high-temperature modified zeolite powder and ferrous sulfide. The modified zeolite has a multi-level microporous structure, which can physically adsorb heavy metal ions. Ferrous sulfide can form insoluble sulfide precipitates with heavy metals such as cadmium, lead, and copper, achieving dual stability of physical adsorption and chemical passivation, and completely blocking the release of heavy metals.

[0022] Furthermore, the nitrogen and phosphorus stabilizing component is composed of polyaluminum chloride, polyferric sulfate, and modified diatomaceous earth in a mass ratio of 2:2:1. The aluminum and iron salts can quickly flocculate and solidify suspended colloidal nitrogen and phosphorus in the sediment, while the porous structure of the modified diatomaceous earth can effectively adsorb and fix dissolved nitrogen and phosphorus, inhibiting the release of nitrogen and phosphorus from the sediment into the overlying water, thus solving the core problem of eutrophication.

[0023] Furthermore, the water-retaining and coagulating component is a compound of hydroxypropyl methylcellulose and anionic polyacrylamide in a mass ratio of 3:1. It can quickly flocculate fine particles of bottom mud, accelerate water separation, shorten the curing cycle, and at the same time improve the flexibility of the solidified body, avoid cracking after long-term immersion in water, and improve the stability of the solidified layer.

[0024] S3. In-situ addition and mixing: Determine the dosage based on the degree of pollution of the riverbed sediment. For lightly and moderately polluted sediment, the dosage is 8% to 12% of the wet sediment mass, and for heavily polluted sediment, the dosage is 12% to 15%. Use a spreading device to evenly cover the surface of the sediment with the solidifying agent. Use an underwater mixing device to mix the 0-35cm layer of polluted sediment for 5 to 10 minutes to ensure that the solidifying agent is fully integrated with the sediment without any local blank areas.

[0025] S4. Static Curing and Solidification: After mixing, the treated river section is sealed off, and the water flow velocity is controlled to ≤0.2m / s to avoid water flow scouring and disturbing the unformed solidified layer. Static curing is carried out at room temperature for 3-7 days, during which the bottom sediment gradually dehydrates and hardens, and the pollutants are completely stabilized and locked in, forming a dense, permeable, and stable ecological solidified layer, thus completing the treatment of endogenous pollution.

[0026] First Example: Taking the treatment of endogenous pollution in the sediment of moderately polluted urban rivers as an example S1. Pretreatment: Clean up floating garbage on the surface of urban waterways, level the surface mud, and retain the original wet mud with a moisture content of 82%, which does not require dehydration treatment.

[0027] S2. Preparation of curing agent: According to the mass percentage ratio, 65% inorganic cementing component (slag powder: fly ash: light magnesium oxide = 5:3:2), 18% heavy metal passivation component, 12% nitrogen and phosphorus stabilizing component, and 5% water-retaining and coagulating component are uniformly mixed to obtain a composite curing agent.

[0028] S3. Adding and mixing: The amount of hardener added is 10% of the mass of the wet bottom mud. After spreading it evenly, stir underwater to a depth of 25cm and stir for 8 minutes to fully mix.

[0029] S4. Maintenance: Close the river section, control the water flow velocity to ≤0.2m / s, and maintain at normal temperature for 5 days.

[0030] Post-treatment testing: The moisture content of the bottom sediment decreased to below 45%, and the 28-day compressive strength of the solidified body was 0.68 MPa; the release of ammonia nitrogen and total phosphorus from the overlying water body decreased by 92% and 91%, respectively; the leaching concentration of heavy metals met the Class III standard for surface water, there was no rebound of pollutants, and the water transparency was significantly improved.

[0031] Second Implementation Example: Treating Endogenous Pollution from Bottom Sediment of Severely Polluted Rural Black and Odorous Rivers S1. Pretreatment: Clean up debris in the black and smelly river, level the surface of the bottom mud, the bottom mud moisture content is 88%, and the original structure is preserved.

[0032] S2. Preparation of curing agent: 62% inorganic cementing component, 20% heavy metal passivation component, 10% nitrogen and phosphorus stabilizing component, and 4% water-retaining and coagulating component are mixed evenly and set aside.

[0033] S3. Add and stir: The amount of curing agent added is 14% of the mass of the wet bottom mud, the stirring depth is 35cm, and the stirring time is 10min.

[0034] S4. Maintenance: Close the river section and allow it to stand still for 7 days.

[0035] Post-treatment testing showed that the sediment was uniformly solidified without loosening or cracking, with a 28-day compressive strength of 0.62 MPa; the release inhibition rate of organic pollutants, nitrogen, and phosphorus in the sediment was over 93%, heavy metals were completely passivated, the black and odorous phenomenon was completely eliminated, and the ecological environment of the river channel was significantly improved.

[0036] Compared to conventional single-curing cement technology: Ordinary silicate cement was used as a curing agent. Under the same working conditions, 10% of the cement was added and mixed thoroughly before curing for 15 days. The cured body after treatment had large pores and was prone to cracking when immersed in water. The nitrogen and phosphorus release inhibition rate was only 55%, and there was no passivation effect on heavy metals. The curing period was long. After 3 months, the eutrophication of the water body rebounded significantly, and the pH value of the water body was high, resulting in secondary pollution.

[0037] For conventional in-situ coverage techniques: The surface of the bottom sediment was covered with clay, with a thickness of 5 cm. This treatment only temporarily prevented the release of pollutants. After 6 months, the cover layer was washed away by the water flow, and a large amount of pollutants were released from the bottom sediment, causing the water quality to return to a polluted state. This treatment had no long-term effect.

[0038] As can be seen from the first and second embodiments and comparative examples, the method of the present invention is significantly superior to existing conventional technologies in terms of pollutant treatment effect, solidification stability, construction efficiency, ecological safety and long-term effectiveness, and has outstanding technical advantages and practical value.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling endogenous pollution using riverbed sediment solidification agents, characterized in that, Includes the following steps: S1. Pretreatment of riverbed sediment: Clean up floating debris and surface garbage from the river to be treated, level the surface of the riverbed sediment, and retain the original polluted sediment without dewatering or dredging pretreatment. S2. Preparation of composite sediment solidifying agent: The solidifying agent is prepared according to the following mass percentages: 60%–70% inorganic cementing component, 15%–20% heavy metal passivation component, 8%–12% nitrogen and phosphorus stabilizing component, and 3%–5% water-retaining and coagulating component; the inorganic cementing component is a mixture of slag powder, fly ash, and light magnesium oxide in a mass ratio of 5:3:2; the heavy metal passivation component is a composite powder of modified zeolite powder and ferrous sulfide; the nitrogen and phosphorus stabilizing component is a mixture of aluminum salt, iron salt, and modified diatomaceous earth; the water-retaining and coagulating component is a compound of hydroxypropyl methylcellulose and anionic polyacrylamide. S3. In-situ addition and mixing: The prepared composite sediment solidifier is evenly spread on the surface of the river sediment. The amount of solidifier added is 8% to 15% of the mass of the wet sediment. Underwater mixing equipment is used to deeply mix the 0 to 30 cm surface layer of polluted sediment for 5 to 10 minutes to ensure that the solidifier and sediment are fully in contact and integrated. S4. Static solidification and curing: After mixing, the river channel is closed and left to stand for 3-7 days to complete the in-situ solidification of the bottom sediment, forming a dense and stable solidified layer, and achieving long-term control of internal pollution.

2. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S2, the modified zeolite powder is clinoptilolite modified by high-temperature calcination and sodium hydroxide solution, with a calcination temperature of 400-500℃ and a pore size of 0.8-1.2 nm after modification.

3. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S2, the aluminum salt in the nitrogen and phosphorus stabilizing component is polyaluminum chloride, the iron salt is polyferric sulfate, and the mass ratio of polyaluminum chloride, polyferric sulfate, and modified diatomaceous earth is 2:2:

1.

4. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S2, the mass ratio of hydroxypropyl methylcellulose to anionic polyacrylamide in the water-retaining and coagulating components is 3:

1.

5. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S3, for heavily polluted riverbed sediment, the amount of solidifying agent added is increased to 12% to 15% of the mass of wet sediment, and the stirring depth is adjusted to 20 to 35 cm.

6. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, During the curing process in step S4, the water flow velocity is controlled to be ≤0.2m / s to avoid water flow scouring and disturbing the uncured layer.

7. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S2, the fineness of the prepared composite sediment solidifier is ≥200 mesh, the uniformity of mixing of each component is ≥98%, and it is stored in a sealed, dry and light-proof manner after preparation.

8. The method for controlling endogenous pollution using riverbed sediment solidification agent according to claim 1, characterized in that, In step S1, the pretreatment only removes floating debris and loose surface garbage, while preserving the original sedimentary structure and natural water content of the bottom sediment, without changing the original bottom sediment topography and hydraulic base conditions of the river channel.

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