Method for repairing aquaculture pond sediment and application thereof
By adding biochar to the bottom sediment of aquaculture ponds and planting sorghum, the problems of high cost and poor effect in bottom sediment pollution treatment have been solved. This has achieved low-cost and high-efficiency pollutant degradation and soil improvement, and improved the application value of the remediated bottom sediment in the soil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF SCI & TECH
- Filing Date
- 2026-04-08
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies for treating pollution in aquaculture pond bottom sediment suffer from high modification costs, poor effectiveness, and low economic benefits. They are difficult to effectively reduce the content of pollutants such as nitrogen, phosphorus, and heavy metals, and direct use of bottom sediment poses soil safety risks.
A method combining biochar and sorghum planting was adopted. After drying the bottom mud, 5% to 20% biochar was added, and sorghum was planted for two consecutive seasons. The biochar was used to reduce the concentration of pollutants, regulate the pH value, and promote plant growth through adsorption and microbial action.
It significantly reduces the content of pollutants such as nitrogen, phosphorus, and heavy metals in sediment, improves the remediation benefits of sediment, improves soil properties, ensures the safety and economic benefits of sorghum, and reduces the impact on subsequent crops and the environment.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of bottom sediment ecological restoration technology, and particularly relates to a method and application for the restoration of bottom sediment in aquaculture ponds. Background Technology
[0002] With the increasing intensification of aquaculture, pollution from aquaculture has become a bottleneck restricting the industry's development. Currently, pollution control measures mainly focus on the aquaculture water body, lacking sufficient understanding and research on the remediation of pond sediment pollution, making it difficult to comprehensively support pollution control efforts. Habitat restoration based on sediment remediation has become one of the key technologies urgently needing to be addressed in current aquaculture pollution control.
[0003] Pollutants in aquaculture pond sediment primarily originate from the input of aquaculture water and the deposition of aquaculture inputs. Their main components include nutrients such as nitrogen and phosphorus, as well as heavy metals and antibiotics. Nitrogen and phosphorus in the sediment not only directly affect the eutrophication level of the aquaculture water, but also, once dredged sediment enters natural water bodies, it exacerbates eutrophication in surrounding waters, inducing large-scale cyanobacterial blooms. Furthermore, heavy metals and antibiotics deposited in the sediment may directly enter farmed aquatic products through adsorption and desorption processes, posing a threat to the quality and safety of these products.
[0004] Studies have shown that using sediment in agriculture can improve soil properties; however, directly applying sediment to soil or farmland carries certain risks, potentially leading to increased soil salinity and heavy metal content. Therefore, land use of sediment requires comprehensive consideration of the complexity of pollutant composition, treatment and disposal methods, soil background values at the application site, and other natural conditions. A thorough assessment should be conducted to determine appropriate utilization methods and avoid negative impacts from improper use.
[0005] To improve the utilization rate of bottom sediment, various methods are currently being used to improve it. Based on different methods, pond bottom sediment improvement can be divided into physical, chemical, and biological methods. Physical improvement methods typically involve applying physical forces to the aquaculture environment to improve the bottom sediment. Chemical improvement methods mainly involve using chemical agents to react with pollutants in the bottom sediment through oxidation-reduction, polymerization, and precipitation reactions, thereby fixing or transforming the pollutants and improving the aquaculture environment. Currently, flocculation sedimentation and oxidation are the most common chemical improvement methods. Biological improvement methods mainly utilize the functions of microorganisms, plants, or other animals to degrade or eliminate pollutants, regulating the ecological balance of the aquaculture system through these plants and animals. However, existing improvement methods suffer from drawbacks such as high cost, low economic benefits after improvement, and poor improvement effects. Therefore, providing a low-cost, widely applicable bottom sediment remediation technology solution to treat pollutants such as nitrogen, phosphorus, and heavy metals in the bottom sediment and improve the economic benefits of remediation is particularly important. Summary of the Invention
[0006] In view of this, the purpose of this invention is to provide a method for remediating bottom mud in aquaculture ponds, which has low remediation cost, wide applicability, effectively reduces the content of pollutants such as nitrogen, phosphorus, and heavy metals in the bottom mud, and improves the economic benefits of remediation.
[0007] Another object of the present invention is to provide a repaired bottom mud obtained by the repair method described above.
[0008] Another object of the present invention is to provide an application of the remediated sediment in improving soil properties.
[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for restoring bottom mud in aquaculture ponds. The method includes: drying the bottom mud, mixing it with biochar to obtain mixed bottom mud; continuously planting two seasons of sorghum in the mixed bottom mud, and obtaining the restored bottom mud after the sorghum matures and is harvested.
[0010] Preferably, the amount of biochar added is 5% to 20% of the dry weight of the sediment.
[0011] Preferably, the biochar includes straw biochar.
[0012] Preferably, the method for preparing the straw biochar includes: carbonizing the straw for 1.5 to 2.5 hours at 650 to 750°C and with an oxygen content of <1%, followed by cooling and crushing to obtain the straw biochar.
[0013] Preferably, the particle size of the biochar is ≤2mm.
[0014] Preferably, the sorghum planting method includes: sowing germinated sorghum seeds in the mixed bottom mud, harvesting them after they mature to obtain initially repaired bottom mud; and planting a second season of sorghum in the initially repaired bottom mud using the same method.
[0015] Preferably, after sowing, the planting temperature is controlled at 20~30℃, the air humidity at 55%~65%, the daily light exposure at 10~14 hours, and the bottom mud moisture content at 60%~70%.
[0016] Preferably, the bottom sediment includes bottom sediment from freshwater aquaculture ponds.
[0017] The present invention also provides a repaired bottom mud obtained by the repair method described above.
[0018] The present invention also provides an application of the remediated sediment in improving soil properties.
[0019] The beneficial effects of this invention are: This invention adds biochar to weakly acidic sediment, effectively neutralizing acidic substances and increasing the sediment's pH value, thus promoting plant growth. Simultaneously, biochar has a strong buffering capacity, resisting drastic pH changes. The alkaline components of biochar are gradually released, slowly regulating the sediment's pH, making it more stable and more conducive to healthy root growth when returned to the field. This invention combines biochar with two rounds of sorghum planting, significantly reducing the concentration of pollutants such as nitrogen, phosphorus, and heavy metals in the sediment, minimizing the impact on subsequent crops and the environment. Biochar also reduces the heavy metal content in sorghum roots, stems, leaves, and ears, improving the safety of sorghum. This remediation method not only has low remediation costs and increases the organic matter content in the sediment, reducing pollution, but also ensures the safety of planted sorghum, improving the economic benefits of remediation. Detailed Implementation
[0020] This invention provides a method for restoring bottom mud in aquaculture ponds. The method includes: drying the bottom mud, mixing it with biochar to obtain mixed bottom mud; continuously planting two seasons of sorghum in the mixed bottom mud, and obtaining the restored bottom mud after the sorghum matures and is harvested.
[0021] In this invention, the drying method of the bottom mud is not particularly limited and can be conventionally selected according to actual needs. In some embodiments, the drying method of the bottom mud preferably includes drying the bottom mud in the shade and away from light. The moisture content after drying is preferably 1% to 5%, more preferably 2% to 4%, and more preferably 3%.
[0022] In this invention, after the bottom mud is dried, it is preferably ground, and the particle size after grinding is preferably ≤2mm.
[0023] In this invention, the biochar preferably includes straw biochar; the type of straw is not particularly limited, but preferably includes any one or more of wheat straw, corn straw, rice straw and cotton straw, and more preferably rice straw.
[0024] The preferred method for preparing the straw biochar includes: carbonizing the straw at 650-750℃ and with an oxygen content of <1% for 1.5-2.5 hours, followed by cooling and pulverizing to obtain the straw biochar. The preferred carbonization temperature is 700℃, and the preferred carbonization time is 2 hours. The preferred particle size after pulverization is ≤2mm.
[0025] In this invention, the preferred amount of biochar added is 5% to 20% of the dry weight of the sediment, for example, 5%, 10%, 15%, or 20%. The mixing method is not particularly limited; the key is to ensure that the biochar and sediment are mixed evenly so that the biochar can fully contact the sediment.
[0026] In this invention, the variety of sorghum is not specifically limited, but dwarf sorghum is preferred.
[0027] In this invention, the preferred method for planting sorghum includes: sowing germinated sorghum seeds in the mixed bottom mud, harvesting them after they mature to obtain initially repaired bottom mud; and planting a second season of sorghum in the initially repaired bottom mud using the same method.
[0028] The germinated sorghum seeds can be obtained through conventional methods. In some embodiments, after disinfecting the sorghum seeds, they are soaked in warm water, then placed on moist filter paper and germinated in the dark to obtain germinated sorghum seeds. The temperature of the warm water is preferably 25~35℃, more preferably 30℃; the soaking time is preferably 5~10h, more preferably 6h; the temperature for germination in the dark is preferably 20~30℃, more preferably 22~28℃, more preferably 25℃; and the germination time in the dark is preferably 24h or more.
[0029] After sowing, the planting temperature is preferably controlled at 20~30℃, more preferably at 22~28℃, and even more preferably at 25℃; the air humidity is preferably 55%~65%, more preferably at 58%~62%, and even more preferably at 60%; the daily light exposure is preferably 10~14h, more preferably 11~13h, and even more preferably 12h; and the bottom mud moisture content is preferably maintained at 60%~70%.
[0030] The term "mature" is preferably defined as when the grains are hardened and the moisture content of the grains in the lower part of the ear is <15%.
[0031] After harvesting, it is preferable to clean the bottom mud, removing residual roots, dead branches and leaves, etc., to obtain initially repaired bottom mud.
[0032] In this invention, the second season of sorghum is preferably planted 3 to 10 days after the first season of sorghum is harvested, and more preferably 5 days after the first season of sorghum is harvested.
[0033] In this invention, the bottom sediment preferably comprises freshwater aquaculture pond sediment. In some embodiments, the bottom sediment preferably has a pH of 6-7.5, a total nitrogen content of 3000-6000 mg / kg, an ammonia nitrogen content of 50-70 mg / kg, a nitrate nitrogen content of 80-90 mg / kg, a total phosphorus content of 3000-5000 mg / kg, an available phosphorus content of 20-40 mg / kg, a Cr content of 110-130 mg / kg, a Cu content of 60-70 mg / kg, a Zn content of 90-120 mg / kg, and a Cd content of 0.05-0.5 mg / kg. In some specific embodiments, the sediment has a pH of 6.81±0.04, a total nitrogen content of 4641.06±236.71 mg / kg, an ammonia nitrogen content of 60.01±6.64 mg / kg, a nitrate nitrogen content of 86.96±0.36 mg / kg, a total phosphorus content of 4182.16±64.01 mg / kg, an available phosphorus content of 31.47±1.31 mg / kg, a Cr content of 123.70±4.71 mg / kg, a Cu content of 67.19±1.77 mg / kg, a Zn content of 108.10±5.41 mg / kg, and a Cd content of 0.25±0.02 mg / kg.
[0034] Biochar possesses a strong adsorption capacity, effectively adsorbing harmful substances such as heavy metals, drug residues, and organic pollutants from sediment, reducing their content in the soil. The surface of biochar contains numerous functional groups, such as carboxyl, hydroxyl, and phenolic hydroxyl groups. These functional groups can adsorb heavy metal ions through ion exchange, electrostatic adsorption, and complexation, reducing their mobility and bioavailability in the sediment. The microporous structure of biochar increases the permeability and aeration of the sediment, facilitating root extension, oxygen and water penetration, and improving aeration and drainage. Furthermore, for high concentrations of nitrogen and phosphorus in sediment, the addition of biochar reduces their availability through adsorption and fixation: biochar's highly porous structure and large surface area effectively adsorb nutrients such as nitrogen and phosphorus from the soil, preventing their release into the environmental solution. The organic carbon in biochar and the colloidal substances produced by microorganisms can form stable compounds with nitrogen and phosphorus in the sediment, reducing their activity in the sediment and decreasing the possibility of their release into the solution. Biochar provides a favorable biological microenvironment, promoting the growth and activity of soil microorganisms and regulating soil microbial communities. Some microorganisms possess nitrogen and phosphorus conversion capabilities, accelerating the conversion process of nitrogen and phosphorus in the soil, making them easier for the soil to fix or convert into forms that are not easily absorbed by plants. Simultaneously, due to its weak alkalinity, biochar can improve the pH value of the sediment after application, bringing it within a suitable range. For excessively acidic sediment, applying biochar can adjust its pH value, optimizing its return to the field. Furthermore, through two rounds of sorghum planting, the concentration of pollutants in the sediment can be further reduced, minimizing the impact on subsequent crops and the environment. Biochar can reduce the absorption of heavy metals by sorghum, lowering the heavy metal content in sorghum roots, stems, leaves, and ears, thus improving the safety of sorghum. The remediation method of this invention not only has low remediation costs and increases the organic matter content in the sediment, reducing pollution, but also ensures the safety of planted sorghum, improving the economic benefits of remediation.
[0035] The present invention also provides a repaired bottom mud obtained by the repair method described above.
[0036] The present invention also provides an application of the remediated sediment in improving soil properties.
[0037] The remediated sediment produced by this invention exhibits a significant reduction in the levels of pollutants such as nitrogen, phosphorus, and heavy metals, an increase in pH, and a certain increase in available phosphorus content. While removing high-nitrogen and phosphorus pollution from the sediment, it converts inorganic phosphorus that cannot be absorbed and utilized by plants into available phosphorus that can be absorbed by plant roots, further increasing the fertility of the sediment and promoting subsequent plant growth. The remediated sediment can be used to improve soil properties, such as adjusting pH, increasing porosity, reducing bulk density, and increasing organic matter and nutrient content, thereby enhancing soil water holding capacity and cation exchange capacity, and ultimately improving plant productivity.
[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0039] Unless otherwise specified, the following embodiments are all conventional methods.
[0040] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.
[0041] Example 1 A method for restoring bottom mud in aquaculture ponds, comprising the following steps: The bottom mud was dried in the dark to a moisture content of 3%, and then mixed with biochar at a dry weight of 10% to obtain a mixed bottom mud. Germinated sorghum seeds were sown in the mixed bottom mud. After sowing, the planting temperature was controlled at 25℃, the air humidity at 60%, and the light exposure at 12 hours per day. The moisture content of the bottom mud was maintained at 60%~70%. After maturity, the seeds were harvested to obtain the bottom mud after initial repair. Using the same method, a second season of sorghum was planted in the bottom mud after initial repair. After the second season of sorghum matured and was harvested, the bottom mud after repair was obtained.
[0042] Example 2 A method for restoring bottom mud in aquaculture ponds, which differs from Example 1 in that the amount of biochar added is 5% of the dry weight of the bottom mud.
[0043] Example 3 A method for restoring bottom mud in aquaculture ponds, which differs from Example 1 in that the amount of biochar added is 20% of the dry weight of the bottom mud.
[0044] Example 4 A method for restoring bottom mud in aquaculture ponds, comprising the following steps: The bottom mud was dried in the dark to a moisture content of 1%, and then mixed with 10% biochar by dry weight of the bottom mud to obtain the mixed bottom mud. Germinated sorghum seeds were sown in the mixed bottom mud. After sowing, the planting temperature was controlled at 20℃, the air humidity at 55%, and the light exposure at 14 hours per day. The moisture content of the bottom mud was maintained at 60%~70%. After maturity, the seeds were harvested to obtain the bottom mud after initial repair. Using the same method, a second season of sorghum was planted in the bottom mud after initial repair. After the second season of sorghum matured and was harvested, the bottom mud after repair was obtained.
[0045] Example 5 A method for restoring bottom mud in aquaculture ponds, comprising the following steps: The bottom mud was dried in the dark to a moisture content of 5%, and then mixed with 10% biochar by dry weight of the bottom mud to obtain the mixed bottom mud. Germinated sorghum seeds were sown in the mixed bottom mud. After sowing, the planting temperature was controlled at 30℃, the air humidity at 65%, and the light exposure at 10 hours per day. The moisture content of the bottom mud was maintained at 60%~70%. After maturity, the sorghum was harvested to obtain the bottom mud after initial repair. Using the same method, a second season of sorghum was planted in the bottom mud after initial repair. After the second season of sorghum matured and was harvested, the bottom mud after repair was obtained.
[0046] Example 6 A method for remediating bottom mud in aquaculture ponds includes the following biochar preparation method: Select rice straw, carbonize it for 2 hours at 700℃ with an oxygen content of <1% using nitrogen as a protective gas, cool it, and pulverize it to obtain biochar with a particle size of ≤2mm. The steps of the remediation method are the same as in Example 1.
[0047] Example 7 A method for remediating bottom mud in aquaculture ponds includes the following biochar preparation method: Select rice straw, carbonize it at 650℃ with an oxygen content of <1% using nitrogen as a protective gas for 2.5 hours, cool it, and pulverize it to obtain biochar with a particle size of ≤2mm. The steps of the remediation method are the same as in Example 1.
[0048] Example 8 A method for remediating bottom mud in aquaculture ponds includes the following biochar preparation method: Select rice straw, carbonize it at 750℃ with an oxygen content of <1% using nitrogen as a protective gas for 1.5 hours, cool it, and crush it to obtain biochar with a particle size of ≤2mm. The steps of the remediation method are the same as in Example 1.
[0049] Example 9 A method for restoring bottom mud in aquaculture ponds, wherein the method for obtaining germinated sorghum seeds is as follows: after disinfecting the sorghum seeds, soak them in warm water at 30°C for 6 hours, take them out and place them on moist filter paper, and germinate them at 25°C in the dark for more than 24 hours to obtain germinated sorghum seeds. The steps of the restoration method are the same as in Example 1.
[0050] Example 10 A method for restoring bottom mud in aquaculture ponds, wherein the method for obtaining germinated sorghum seeds is as follows: after disinfecting the sorghum seeds, soak them in warm water at 25°C for 10 hours, take them out and place them on moist filter paper, and germinate them at 20°C in the dark for more than 24 hours to obtain germinated sorghum seeds. The steps of the restoration method are the same as in Example 1.
[0051] Example 11 A method for restoring bottom mud in aquaculture ponds, wherein the method for obtaining germinated sorghum seeds is as follows: after disinfecting the sorghum seeds, soak them in warm water at 35°C for 5 hours, take them out and place them on moist filter paper, and germinate them at 30°C in the dark for more than 24 hours to obtain germinated sorghum seeds. The steps of the restoration method are the same as in Example 1.
[0052] Experimental Example 1 1. Preparation of biochar: Rice straw, a biomass raw material with high adsorption performance and stability, was selected and carbonized for 2 hours at 700℃ with an oxygen content of <1% using nitrogen as a protective gas. After cooling, the carbon was pulverized to obtain biochar with a particle size of ≤2mm.
[0053] 2. Sediment remediation experiment: Bottom mud from a freshwater aquaculture pond in Huzhou, Zhejiang Province, was selected, air-dried to a moisture content of approximately 3%, and ground to a particle size ≤2mm. Prepared biochar was added to the bottom mud at mass ratios of 0%, 5%, 10%, and 20%, respectively, and thoroughly mixed. The bottom mud mixtures at different proportions were used as planting soil. Two seasons of sorghum (dwarf sorghum, commercially known as "Dwarf King") were planted in a laboratory pot experiment. The planting method was as follows: after disinfecting the sorghum seeds, they were soaked in 30℃ warm water for 6 hours, then placed on moist filter paper and germinated at 25℃ in the dark for at least 24 hours. Using plastic pots with a diameter of 40cm and a depth of 35cm, the mixed bottom mud was placed in the pots, and three germinated sorghum seeds were planted in each pot, with three replicates per group. The planting temperature was controlled at 25℃, the air humidity at approximately 60%, and the light exposure at 12 hours per day. The soil moisture content was maintained at 60%-70%. The sorghum was considered mature when the grains hardened and the moisture content of the lower ears of grains was <15%. After maturity, the sorghum was harvested, and the pH, nitrogen, phosphorus, and heavy metal content in the soil were tested. Simultaneously, the heavy metal content in the roots, stems, leaves, and ears of the sorghum plants was also tested. After the first planting, the soil from the previously planted sorghum plants was thoroughly cleaned, removing any remaining roots, dead branches, and leaves. Approximately 5 days after harvest, a second crop of sorghum was planted in the same soil using the same method. After maturity, the soil was harvested, and the pH, nitrogen, phosphorus, and heavy metal content in the soil were tested. The heavy metal content in the roots, stems, leaves, and ears of the sorghum plants was also tested. The results are shown in Tables 1-6.
[0054] Table 1. pH, nitrogen, and phosphorus content in sediments under different treatments
[0055] As shown in Table 1, compared with the original sediment, the rotation of two seasons of sorghum can reduce the content of total nitrogen and total phosphorus in the sediment to a certain extent. On the basis of sorghum rotation, the addition of biochar to the sediment can effectively increase the pH of the sediment, improve the acidification degree of the sediment, and further reduce the content of total nitrogen and total phosphorus, thereby achieving the removal of pollutants such as nitrogen and phosphorus in the sediment and realizing the remediation of the sediment.
[0056] Table 2 Heavy metal content in sediments under different treatments
[0057] As shown in Table 2, the heavy metal content decreased after the second sorghum rotation compared to the original sediment. The addition of biochar to the sediment on the basis of sorghum rotation further reduced the heavy metal content, thereby achieving the removal of heavy metals and other pollutants from the sediment, remediating the sediment, and improving its safety.
[0058] Table 3. Heavy metal content in sorghum roots under different treatments
[0059] Table 4. Heavy metal content in sorghum stems under different treatments
[0060] Table 5. Heavy metal content in sorghum leaves under different treatments
[0061] Table 6. Heavy metal content in sorghum ears under different treatments
[0062] As shown in Tables 3-6, sorghum roots, stems, leaves, and ears all exhibit a certain degree of heavy metal accumulation. However, the addition of biochar significantly reduces the accumulation of heavy metals in these components, and the content further decreases after two-season crop rotation. This invention's remediation method, employing both biochar and two-season sorghum rotation, not only achieves effective sediment remediation and reduces the content of pollutants such as nitrogen, phosphorus, and heavy metals in the sediment, but also reduces the heavy metal content in sorghum, improving the safety of sorghum crops and enhancing the economic benefits of remediation.
[0063] 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 principle 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 restoring bottom mud in aquaculture ponds, characterized in that, The remediation method includes: drying the bottom sediment, mixing it with biochar to obtain mixed bottom sediment; planting two seasons of sorghum in the mixed bottom sediment, and obtaining the remediated bottom sediment after the sorghum matures and is harvested.
2. The repair method according to claim 1, characterized in that, The amount of biochar added is 5% to 20% of the dry weight of the sediment.
3. The repair method according to claim 1, characterized in that, The biochar includes straw biochar.
4. The repair method according to claim 3, characterized in that, The method for preparing straw biochar includes: carbonizing straw for 1.5 to 2.5 hours at 650 to 750°C with an oxygen content of <1%, followed by cooling and crushing to obtain straw biochar.
5. The repair method according to claim 1, characterized in that, The biochar has a particle size ≤2mm.
6. The repair method according to claim 1, characterized in that, The method for planting sorghum includes: sowing germinated sorghum seeds in the mixed bottom mud, harvesting them after they mature to obtain the initially restored bottom mud; and planting a second season of sorghum in the initially restored bottom mud using the same method.
7. The repair method according to claim 6, characterized in that, After sowing, control the planting temperature at 20-30℃, air humidity at 55%-65%, daily light exposure at 10-14 hours, and bottom mud moisture content at 60%-70%.
8. The repair method according to claim 1, characterized in that, The sediment includes sediment from freshwater aquaculture ponds.
9. The repaired sediment obtained by the repair method according to any one of claims 1 to 8.
10. The application of the remediated sediment as described in claim 9 in improving soil properties.