River, lake and reservoir combined pollution remediation method capable of cooperatively inhibiting algae and removing pollution

Abstract

The invention belongs to the field of water environment treatment, and provides a river, lake and reservoir combined pollution remediation method with synergistic algal inhibition and decontamination, which comprises the following steps: (1) adding porous iron-based charcoal and a porous light filler into bottom mud in a river or lake and reservoir to be subjected to combined pollution remediation, and fully mixing to form a composite matrix; (2) planting aquatic plants with root systems having oxygen secreting capability on the compound substrate to carry out pollution remediation on rivers or lakes and reservoirs; in the pollution remediation process, the porous iron-based biochar catalyzes oxygen secreted by the root systems of the aquatic plants to form active oxygen species including hydroxyl free radicals, the active oxygen species oxidize and degrade organic pollutants in rivers or lakes and reservoirs and inhibit growth of algae, and meanwhile the porous iron-based biochar and the porous light filler adsorb and remove the pollutants in the rivers or the lakes and reservoirs. The method provided by the invention can effectively enhance the removal capability of the independent aquatic plants on pollutants in rivers or lakes and reservoirs and the removal capability on algae in the rivers or lakes and reservoirs, and improves the remediation effect on the combined pollution of the rivers and the lakes and reservoirs.

Description

Technical Field

[0001] The invention belongs to the field of water environment management and relates to a method for repairing complex pollution of rivers, lakes and reservoirs by synergistically inhibiting algae and removing pollution. Background Art

[0002] In recent years, with the rapid development of agriculture, urbanization and industrialization, human behaviors such as changes in land use and non-standard discharge of industrial and agricultural wastewater have led to the long-term input of nitrogen and phosphorus nutrients, heavy metals and organic matter into rivers or lakes and reservoirs, and continued to accumulate in the overlying water and sediments, causing serious water environment and water ecological problems. Nutrients such as nitrogen and phosphorus are important driving factors for eutrophication of water bodies, causing algae such as cyanobacteria and green algae and other organisms to reproduce in large numbers, causing water quality deterioration. Common heavy metals in rivers and lakes, such as copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), mercury (Hg), etc., accumulate in sediments through adsorption and may enter aquatic animals and humans through the food chain. Organic pollutants entering rivers, lakes and reservoirs consume a lot of oxygen during the decomposition process, causing water hypoxia, causing the pollutants to undergo reduction decomposition and produce a large number of metabolic byproducts, such as CH4 and H2S, causing secondary environmental pollution. At the same time, these pollutants usually exist in the form of mixtures, most of which have ecological and environmental effects such as high toxicity, difficulty in degradation, easy enrichment and food chain amplification, forming a complex, dynamic and long-chain pollution system.

[0003] Using aquatic plants for water purification and ecological restoration is an economical and environmentally friendly method, which is widely used in the field of water environment and water ecological management such as rivers and lakes. Aquatic plants can directly reduce the concentration of nitrogen, phosphorus nutrients, heavy metals and organic pollutants in water bodies through direct absorption, and improve the stability of the ecosystem. At the same time, the active substances such as oxygen and allelopathic substances secreted by the roots of aquatic plants during their growth and the attachment of specific microbial communities to their roots can drive the migration and degradation process of pollutants. At present, the research on the use of aquatic plants for water purification and ecological restoration is mostly focused on the purification effect of aquatic plant absorption and microbial metabolic processes, and the existing technology is more concerned with the removal of a certain type of pollutants by aquatic plants, and there is little research on the use of aquatic plants to repair complex pollution. However, the mineralization rate of aquatic plants for pollutants is low, the type of pollutant removal is relatively single, and the repair effect of complex pollution is poor. Therefore, if a method that can effectively enhance the removal effect of plants on pollutants and is suitable for the repair of complex pollution in rivers, lakes and reservoirs can be developed, it will have a positive significance for the treatment and repair of complex pollution in rivers and lakes. Summary of the invention

[0004] In view of the problems of low pollutant removal rate, relatively single pollutant types and poor restoration effect on complex pollution of rivers, lakes and reservoirs in existing methods of water purification and ecological restoration using aquatic plants, the present invention provides a method for repairing complex pollution of rivers, lakes and reservoirs by synergistic algae inhibition and pollution removal, so as to effectively enhance the ability of individual aquatic plants to remove pollutants from rivers or lakes and reservoirs, and simultaneously enhance the ability to remove algae from rivers or lakes and reservoirs, thereby improving the restoration effect on complex pollution of rivers, lakes and reservoirs.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0006] A method for repairing complex pollution of rivers and lakes by synergistically inhibiting algae and removing pollution, comprising the following steps:

[0007] (1) adding porous iron-based biochar and porous lightweight filler to the bottom mud of the river or lake to be remediated by composite pollution, and mixing them thoroughly to form a composite matrix;

[0008] (2) Planting aquatic plants with oxygen-secreting roots on the composite matrix to carry out complex pollution remediation of rivers or lakes; during the complex pollution remediation process, the porous iron-based biochar catalyzes the oxygen secreted by the roots of aquatic plants to form reactive oxygen species (ROS) including hydroxyl radicals. The reactive oxygen species oxidize and degrade organic pollutants in rivers or lakes while inhibiting the growth of algae. In addition, the porous iron-based biochar and porous lightweight fillers adsorb and remove pollutants in rivers or lakes.

[0009] In the above technical solution, in the composite matrix of step (1), the volume proportion of the sludge is preferably 50% to 60%, the volume proportion of the porous iron-based biochar is preferably 20% to 40%, and the volume proportion of the porous lightweight filler is preferably 10% to 30%.

[0010] In the above technical solution, the porous iron-based biochar is mainly used to catalyze the oxygen secreted by the roots of aquatic plants to form active oxygen species including hydroxyl radicals. The porous iron-based biochar is obtained by fully mixing the iron source and the carbon source and calcining them in one step. A feasible method for preparing porous iron-based biochar is as follows:

[0011] Bottom mud is taken from a river or lake, dried and crushed to obtain a carbon source, the carbon source, iron source and a chemical modifier are fully mixed to obtain a reaction precursor, and the reaction precursor is roasted at 600-1000°C for 2-4 hours in a nitrogen atmosphere to obtain porous iron-based biochar; the chemical modifier is hydrochloric acid, sulfuric acid, oxalic acid, alkali, oxalic acid, thiourea or sulfide.

[0012] In the above technical solution, when preparing porous iron-based biochar, the composition of the prepared porous iron-based biochar may be different depending on the type of active modifier, but the main active species of the porous iron-based biochar are usually zero-valent iron and Fe3C.

[0013] In the above technical solution, when preparing porous iron-based biochar, the content of the carbon source in the reaction precursor is preferably 80wt% to 90wt%, the content of the iron source is preferably 5wt% to 10wt%, and the content of the chemical modifier is preferably 5wt% to 10wt%.

[0014] In the above technical solution, when preparing porous iron-based biochar, the iron source is a water-soluble iron salt, and feasible iron sources include hydrated or non-hydrated salts of ferric nitrate, ferric sulfate, ferrous sulfide, ferrous nitrate, ferrous sulfate, ferrous sulfide, etc.

[0015] In the above technical solution, when preparing porous iron-based biochar, taking sediment from a river or lake generally refers to taking sediment from a river or lake to be remediated by complex pollution.

[0016] In the above technical solution, the particle size of the porous iron-based biochar is in the micron level, and the particle size of the iron-based biochar can usually be 10nm to 100μm; the specific surface area of ​​the porous iron-based biochar is usually 10 to 300m 2 / g, and the pore volume is usually between 0.2 and 0.8 cm 3 Porous iron-based biochar can not only catalyze the oxygen secreted by the roots of aquatic plants to form reactive oxygen species including hydroxyl radicals, but also its porous structure can adsorb and remove pollutants in rivers or lakes.

[0017] In the above technical solution, the porous lightweight filler is at least one of ceramsite, vermiculite, perlite, and volcanic rock. Furthermore, the porous lightweight filler is in granular form, and the particle size is preferably 3 to 10 mm. The porous lightweight filler not only plays a role in fixing and supporting aquatic plants, but also can absorb nitrogen in the retained water to provide a nitrogen source for aquatic plants, and promote the oxygen secretion and oxygen transfer rate of the aquatic plants into the root system.

[0018] In the above technical scheme, the aquatic plants include at least one of submerged plants with strong oxygen secretion ability in the root system and emergent plants with strong oxygen secretion ability in the root system. Further, the aquatic plants are preferably at least one of Vallisneria, Myriophyllum, Ceratophyllum, Hydrilla, Potamogeton, Water Chestnut, Cattail, Juncus, Carex, Cyperus and Canna. In practical applications, the selection can be made according to the climate, water quality conditions and local aquatic plant types of the river or lake where the complex pollution remediation is to be carried out. Generally speaking, the submerged plants with oxygen secretion ability in the root system and the emergent plants with oxygen secretion ability in the root system can be reasonably matched in a uniform or multiple manner, combined with the local plant types, and local varieties can be preferentially selected for planting.

[0019] In the above technical solution, the planting density of aquatic plants on the composite matrix is ​​determined by referring to the existing technology based on factors such as the type and variety characteristics of the aquatic plants (such as plant morphology, root distribution, growth rate) and the ability of the aquatic plants to purify pollutants.

[0020] In the above technical solution, when the active oxygen species oxidize and degrade organic pollutants in rivers or lakes, they mainly degrade organic pollutants in the bottom mud of rivers or lakes, and can also degrade organic pollutants in the water body of rivers or lakes. Moreover, the active oxygen species can simultaneously inhibit the growth of benthic algae and floating algae in rivers or lakes. Since the pollutants in the bottom mud of rivers or lakes mainly come from the water body, and the pollutants in the bottom mud will also affect the pollution of the water body, when the above technical solution is used to degrade the organic pollutants in the bottom mud, the water pollution of rivers or lakes can be improved. In addition, the above technical solution can also effectively inhibit the outbreak of harmful algal blooms.

[0021] In the above technical scheme, the pollutants in the rivers or lakes to be repaired for complex pollution mainly include nitrogen and phosphorus nutrients, heavy metals such as copper, chromium, cadmium, lead, mercury, and organic substances such as persistent organic pollutants and new pollutants. When the above technical scheme of the present invention is used to repair complex pollution in rivers and lakes, the specific repair time is determined according to the complex pollution situation of the specific rivers and lakes, and the removal rate of target pollutants and algae can meet the actual application requirements. Usually, after 2 to 3 months of repair, the complex pollution of rivers or lakes can be effectively controlled.

[0022] The restoration principle of the river and lake complex pollution restoration method for coordinated algae inhibition and pollution removal of the present invention is mainly as follows:

[0023] The porous iron-based biochar and porous light filler are added to the bottom mud of the river or lake to be repaired for complex pollution and fully mixed to form a composite matrix. Aquatic plants with oxygen-secreting roots are planted on the composite matrix. The porous iron-based biochar catalyzes the Fenton-like advanced oxidation process, the porous iron-based biochar and the porous light filler adsorb, the aquatic plant absorption and metabolism process, and the microbial metabolic decomposition process. The composite pollution is repaired from the two aspects of endogenous pollution control of river and lake sediments and water ecological restoration, as follows:

[0024] (1) Porous iron-based biochar activates oxygen secreted by the roots of aquatic plants to form reactive oxygen species including hydroxyl radicals. Hydroxyl radicals are a type of highly oxidizing reactive oxygen species that can not only efficiently degrade pollutant hydroxyl radicals, but also effectively inhibit the growth of algae, thereby effectively enhancing the ability of aquatic plants to degrade organic pollutants in rivers or lakes, while effectively inhibiting the growth of algae in rivers or lakes;

[0025] (2) Porous iron-based biochar and porous lightweight materials have rich porous structures and large specific surface areas, and can remove pollutants such as nutrients, heavy metals, and organic matter from rivers and lakes through one or more of the following adsorption mechanisms: hydrophilic interaction, electrostatic attraction / repulsion, polar attraction, or non-polar attraction.

[0026] (3) Specific microorganisms are attached to the roots of aquatic plants. These microorganisms can quickly remove pollutants near the rhizosphere of aquatic plants through metabolism. At the same time, allelopathic substances such as polyphenols and sulfides secreted by the roots of aquatic plants can also inhibit the growth of algae. The porous iron-based biochar material will mediate the generation of allelopathic substances secreted by the roots of deep-water plants to a certain extent, promoting the inhibition of algae.

[0027] (4) Aquatic plants themselves can also directly reduce nitrogen and phosphorus nutrients and organic pollutants in rivers or lakes through direct absorption.

[0028] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects:

[0029] 1. The present invention provides a method for the remediation of complex pollution in rivers and lakes with synergistic algae inhibition and pollution removal. The method first adds porous iron-based biochar and porous lightweight filler to the bottom mud in the river or lake to be remediated for complex pollution, mixes them thoroughly to form a composite matrix, and then plants aquatic plants with oxygen-secreting roots on the composite matrix to remediate the pollution in the river or lake. In the pollution remediation process of the present invention, the porous iron-based biochar catalyzes the oxygen secreted by the roots of aquatic plants to form active oxygen species including hydroxyl radicals. The active oxygen species inhibit the growth of algae while oxidizing and degrading organic pollutants in rivers or lakes. The porous iron-based biochar and porous lightweight filler can adsorb and remove pollutants in rivers or lakes. At the same time, aquatic plants can directly absorb and remove some pollutants in rivers or lakes for the growth of aquatic plants. Through the combined effect of the above factors, the present invention effectively enhances the ability of a single aquatic plant to remove pollutants from rivers or lakes, and simultaneously enhances the ability to remove algae in rivers or lakes. The present invention can solve the problems of low pollutant removal rate, relatively single type of pollutants, and poor restoration effect on complex pollution of rivers and lakes in the method of using aquatic plants for water purification and ecological restoration, thereby improving the restoration effect on complex pollution of rivers and lakes.

[0030] 2. The raw materials for preparing the porous iron-based biochar described in the present invention are cheap and easily available, and the preparation method is simple. The porous iron-based biochar catalytic Fenton advanced oxidation process is successfully constructed by utilizing the cooperation of a composite matrix containing porous iron-based biochar, porous lightweight filler and bottom mud and aquatic plants with oxygen-secreting root systems. Active oxygen species including hydroxyl radicals are generated during the complex pollution remediation process. The present invention has confirmed through experiments that after 2 months of using the method of the present invention to repair the complex pollution of rivers or lakes, hydroxyl radicals with a concentration level of 90 to 110 μmol / kg were detected around the roots of aquatic plants. These hydroxyl radicals can significantly enhance the ability of a single aquatic plant to remove organic pollutants and algae in rivers or lakes.

[0031] 3. The method of the present invention can flexibly adjust the preparation process of the iron-based biochar according to the actual water environment conditions of rivers and lakes, and then adjust the composition of the porous iron-based biochar. At the same time, it can flexibly screen aquatic plants with oxygen-secreting roots. It has the characteristics of flexibility and strong applicability, and can be applied to the restoration and treatment of complex pollution in various rivers or lakes. In addition, the method of the present invention is simple to operate, which is conducive to promotion and application in practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the restoration method for composite pollution of rivers and lakes by synergistic algae inhibition and pollution removal according to the present invention.

[0033] Figure 2These are the test results of the removal rates of total nitrogen, total phosphorus, total organic carbon and green algae in river water in Example 1 and Comparative Example 1. The algae in the figure refer to green algae.

[0034] Figure 3 These are the test results of the removal rates of total nitrogen, total phosphorus, total organic carbon and green algae in river water in Comparative Example 2. The algae in the figure refer to green algae.

[0035] Figure 4 These are the test results of the removal rates of total nitrogen, total phosphorus, total organic carbon and cyanobacteria in lakes in Example 2. The algae in the figure refer to cyanobacteria.

[0036] Figure 5 These are the test results of the removal rates of total nitrogen, total phosphorus, total organic carbon and cyanobacteria in the reservoir in Example 3. The algae in the figure refer to cyanobacteria. DETAILED DESCRIPTION

[0037] The following examples further illustrate the river and lake complex pollution remediation method for coordinated algae inhibition and pollution removal of the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The technical personnel in the relevant field make some non-essential improvements and adjustments to the present invention according to the above invention content for specific implementation, which still falls within the scope of protection of the invention.

[0038] Example 1

[0039] In this embodiment, the method for repairing the complex pollution of rivers and lakes by coordinated algae inhibition and pollution removal of the present invention is described in detail. Specifically, the repair process of the complex pollution of rivers is simulated in a water tank in a laboratory. The size of the experimental water tank is determined according to the size of the river section to be repaired for complex pollution. The ratio of the size of the experimental water tank to the size of the river section to be repaired for complex pollution is controlled to be 1:100. The length of the river section to be repaired for complex pollution is about 600m. The steps are as follows:

[0040] (1) Take the bottom mud from the river section to be remediated for complex pollution, remove the debris such as stones and large particles, dry it naturally in the dark, crush it through a 60-mesh sieve, and use the sieved dry bottom mud as the carbon source. Use ferric nitrate nonahydrate as the iron source and oxalic acid as the chemical modifier.

[0041] The carbon source, the iron source and the chemical modifier are fully ground and mixed to obtain a reaction precursor, wherein the carbon source content is 85wt%, the iron source content is 5wt%, and the chemical modifier content is 10wt%. The reaction precursor is placed in a tube furnace, calcined at 800°C for 3h in a nitrogen atmosphere, and the calcined product is fully ground to obtain a porous iron-based biochar with a particle size between 10nm and 100μm.

[0042] The specific surface area and pore structure of the porous iron-based biochar were characterized, and the surface element analysis showed that the specific surface area of ​​the porous iron-based biochar prepared in this step was between 10 and 300 m 2 / g, pore volume is between 0.2 and 0.8 cm 3 / g, and the iron species mainly include zero-valent iron and Fe3C.

[0043] (2) Take the bottom mud from the river section to be remediated by complex pollution and add it to the experimental water tank, then add the porous iron-based biochar and the porous lightweight filler, stir and mix them thoroughly to form a composite matrix, in which the volume of the bottom mud accounts for 60%, the volume of the porous iron-based biochar accounts for 20%, and the volume of the porous lightweight filler accounts for 20%; the porous lightweight filler is spherical coal gangue expanded clay with a particle size of 8 mm.

[0044] Aquatic plants with oxygen-secreting roots, Acorus calamus, were planted on the composite substrate in the experimental water tank for composite pollution remediation. The row spacing was 10 cm, the plant spacing was 10 cm, and 2 to 3 Acorus calamus were planted in each hole. After planting, river water was added to the experimental water tank. The river water came from the river section to be remediated for composite pollution. The total nitrogen content of the river water was 5 mg / L, the total phosphorus content was 1 mg / L, and the total organic carbon content was 5 mg / L. The algae in the river water were mainly green algae, and the chlorophyll a (Chla) concentration was 100 mg / L.

[0045] In the process of complex pollution remediation, the porous iron-based biochar catalyzes the oxygen secreted by the roots of Acorus calamus to form reactive oxygen species including hydroxyl radicals. The reactive oxygen species inhibit the growth of algae while oxidizing and degrading organic pollutants. The porous iron-based biochar and porous lightweight fillers adsorb and remove pollutants.

[0046] Two months after planting calamus to repair the complex pollution, water samples were taken from the experimental water tank to test the total nitrogen content, total phosphorus content, total organic carbon content and green algae concentration, and the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and green algae removal rate were calculated. In this example, the total nitrogen removal rate of the river water was 80%, the total phosphorus removal rate was 85%, the green algae removal rate was 60%, and the total organic carbon removal rate was 70%.

[0047] Comparative Example 1

[0048] In this comparative example, the composite pollution remediation method is basically the same as that in Example 1, except that the composite matrix is ​​formed by mixing the bottom mud and the porous lightweight filler, and the porous iron-based biochar is not added. In the composite matrix, the bottom mud accounts for 80% by volume, and the porous lightweight filler accounts for 20% by volume.

[0049] Two months after planting calamus to repair the complex pollution, water samples from the experimental water tank were taken to test the total nitrogen content, total phosphorus content, total organic carbon content and green algae concentration, and the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and green algae removal rate were calculated. For this comparative example, the total nitrogen removal rate of river water was 40%, the total phosphorus removal rate was 40%, the green algae removal rate was 10%, and the total organic carbon removal rate was 20%.

[0050] The test results of Example 1 and Comparative Example 1 on the removal rate of total nitrogen, total phosphorus, green algae and total organic carbon in river water are as follows: Figure 2 As shown. Figure 2 It can be seen that compared with Comparative Example 1, Example 1 has significantly increased the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and green algae removal rate for river water, with the increase rate reaching 50% to 85%. This is mainly due to the introduction of porous iron-based biochar, which cooperates with the oxygen secreted by the roots of aquatic plants to construct a Fenton-like advanced oxidation system, thereby effectively improving the ability of individual aquatic plants to remove pollutants and algae in rivers.

[0051] Comparative Example 2

[0052] In this comparative example, a composite pollution remediation method substantially the same as that in Example 1 was used, except that aquatic plants were not planted on the composite substrate.

[0053] After using the above method to repair the river complex pollution for 2 months, water samples were taken from the experimental water tank to test the total nitrogen content, total phosphorus content, total organic carbon content and algae concentration, and the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and green algae removal rate were calculated. The results are as follows Figure 3 As shown, the total nitrogen removal rate of river water in this comparative example is 20%, the total phosphorus removal rate is 25%, the green algae removal rate is 8%, and the total organic carbon removal rate is 0%.

[0054] Combination Figures 2-3 It can be seen that compared with Comparative Example 2, the removal rates of total nitrogen, total phosphorus, green algae and total organic carbon in river water in Example 1 are significantly increased, with an increase rate of more than 70%. It can be seen that the composite matrix containing porous iron-based biochar itself has a very limited ability to remove total nitrogen, total phosphorus, total organic carbon and green algae in the sediment. Only after aquatic plants with oxygen-secreting roots are planted on the composite matrix, can a Fenton-like advanced oxidation system be constructed together with the porous iron-based biochar, and the generated active oxygen species including hydroxyl radicals can be used to enhance the removal capacity of total nitrogen, total phosphorus, total organic carbon and green algae.

[0055] After Example 1 and Comparative Example 1 repaired the river complex pollution for 2 months, samples around the roots of aquatic plants were taken to detect the concentration of hydroxyl radicals. The results showed that the concentration of hydroxyl radicals around the roots of aquatic plants in Example 1 was 70 μmol / kg, while almost no hydroxyl radicals were detected around the plants in Comparative Example 1. After Comparative Example 2 repaired the river complex pollution for 2 months, the composite matrix was taken to detect the concentration of hydroxyl radicals. The results showed that no hydroxyl radicals were detected in the composite matrix of Example 2. This further shows that only after aquatic plants with oxygen-secreting roots are planted on the composite matrix containing porous iron-based biochar, the oxygen generated by the roots of the aquatic plants can be used together with the porous iron-based biochar to construct a Fenton-like advanced oxidation system to form active oxygen species including hydroxyl radicals to enhance the removal ability of pollutants and algae in the river.

[0056] Example 2

[0057] In this embodiment, the method for repairing the complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal of the present invention is described in detail. Specifically, the repair process of complex pollution of lakes is simulated in a water tank in a laboratory. The size of the experimental water tank is determined according to the size of the lake area to be repaired by complex pollution. The ratio of the size of the experimental water tank to the size of the lake area to be repaired by complex pollution is controlled to be 1:100. The length of the lake area to be repaired by complex pollution is about 300m. The steps are as follows:

[0058] (1) Take the bottom mud from the lake area to be remediated for complex pollution, remove the debris such as stones and large particles, dry it naturally in the dark, crush it through an 80-mesh sieve, and use the sieved dry bottom mud as the carbon source. Use ferric nitrate nonahydrate as the iron source and oxalic acid as the chemical modifier.

[0059] The carbon source, the iron source and the chemical modifier are fully ground and mixed to obtain a reaction precursor, wherein the carbon source content is 85wt%, the iron source content is 5wt%, and the chemical modifier content is 10wt%. The reaction precursor is placed in a tubular furnace, calcined at 800°C for 4h in a nitrogen atmosphere, and the calcined product is fully ground to obtain a porous iron-based biochar with a particle size between 10nm and 100μm.

[0060] (2) Bottom mud is taken from the lake area to be remediated for complex pollution and added to the experimental water tank. Then, porous iron-based biochar and porous lightweight filler are added and stirred thoroughly to form a composite matrix. In the composite matrix, the volume of the bottom mud accounts for 50%, the volume of the porous iron-based biochar accounts for 30%, and the volume of the porous lightweight filler accounts for 20%; the porous lightweight filler is volcanic rock with a particle size of 3.5 mm.

[0061] The aquatic plant Vallisneria with oxygen-secreting roots was planted on the composite substrate in the experimental water tank for composite pollution remediation. The row spacing was 3 cm, the plant spacing was 3 cm, and 3 to 4 Vallisneria were planted in each hole. After the planting was completed, lake water was added to the experimental water tank. The lake water came from the lake area to be remediated for composite pollution. The total nitrogen content of the lake water was 7 mg / L, the total phosphorus content was 0.9 mg / L, and the total organic carbon content was 4 mg / L. The algae in the lake water were mainly cyanobacteria, and the chlorophyll a (Chla) concentration was 80 mg / L.

[0062] In the process of complex pollution remediation, the porous iron-based biochar catalyzes the oxygen secreted by the roots of Vallisneria sinensis to form reactive oxygen species including hydroxyl radicals. The reactive oxygen species inhibit the growth of algae while oxidizing and degrading organic pollutants. The porous iron-based biochar and porous lightweight fillers adsorb and remove pollutants.

[0063] Two months after planting Vallisneria sinensis to repair the complex pollution of the lake, water samples were taken from the experimental water tank to test the total nitrogen content, total phosphorus content, total organic carbon content and cyanobacteria concentration, and the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and cyanobacteria removal rate were calculated. The results are as follows: Figure 4 As shown, in this embodiment, the total nitrogen removal rate of lake water is 86%, the total phosphorus removal rate is 88%, the blue algae removal rate is 70%, and the total organic carbon removal rate is 75%.

[0064] Two months after the complex pollution of the lake was repaired in this example, samples around the roots of aquatic plants were taken to detect the concentration of hydroxyl radicals. The results showed that the concentration of hydroxyl radicals around the roots of aquatic plants was 90 μmol / kg.

[0065] Example 3

[0066] In this embodiment, the method for repairing the complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal of the present invention is described in detail. Specifically, the repair process of the complex pollution of the reservoir is simulated in a water tank in the laboratory. The size of the experimental water tank is determined according to the size of the reservoir area to be repaired for complex pollution. The ratio of the size of the experimental water tank to the size of the reservoir area to be repaired for complex pollution is controlled to be 1:100. The length of the reservoir area to be repaired for complex pollution is about 400m. The steps are as follows:

[0067] (1) Take the bottom mud from the reservoir area to be remediated for complex pollution, remove the debris such as stones and large particles, dry it naturally in the dark, crush it through an 80-mesh sieve, and use the sieved dry bottom mud as the carbon source. Use ferric nitrate nonahydrate as the iron source and thiourea as the chemical modifier.

[0068] The carbon source, the iron source and the chemical modifier are fully ground and mixed to obtain a reaction precursor, wherein the carbon source content is 80wt%, the iron source content is 10wt%, and the chemical modifier content is 10wt%. The reaction precursor is placed in a tube furnace, calcined at 1000°C for 2h in a nitrogen atmosphere, and the calcined product is fully ground to obtain a porous iron-based biochar with a particle size between 10nm and 100μm.

[0069] (2) Bottom mud is taken from the reservoir area to be remediated for composite pollution and added to the experimental water tank. Then, porous iron-based biochar and porous lightweight filler are added and stirred to form a composite matrix. In the composite matrix, the volume of the bottom mud accounts for 50%, the volume of the porous iron-based biochar accounts for 30%, and the volume of the porous lightweight filler accounts for 20%; the porous lightweight filler is perlite particles with a particle size of 5 mm.

[0070] On the composite substrate in the experimental water tank, aquatic plants with oxygen-secreting roots, snapdragons, were planted for composite pollution remediation. The planting row spacing was 4 cm, the plant spacing was 4 cm, and 3 to 4 snapdragons were planted in each hole. After planting, reservoir water was added to the experimental water tank. The reservoir water came from the reservoir area to be remediated for composite pollution. The total nitrogen content of the reservoir water was 6 mg / L, the total phosphorus content was 1.2 mg / L, and the total organic carbon content was 5 mg / L. The algae in the reservoir water were mainly cyanobacteria, and the chlorophyll a (Chla) concentration was 78 mg / L.

[0071] In the process of complex pollution remediation, the porous iron-based biochar catalyzes the oxygen secreted by the roots of snapdragon to form reactive oxygen species including hydroxyl radicals. The reactive oxygen species inhibit the growth of algae while oxidizing and degrading organic pollutants. The porous iron-based biochar and porous lightweight fillers adsorb and remove pollutants.

[0072] Two months after planting snapdragon to repair the complex pollution, water samples were taken from the experimental tank to test the total nitrogen content, total phosphorus content, total organic carbon content and cyanobacteria concentration, and the total nitrogen removal rate, total phosphorus removal rate, total organic carbon removal rate and cyanobacteria removal rate were calculated. The results are as follows: Figure 5 As shown, in this embodiment, the total nitrogen removal rate of the reservoir water body is 90%, the total phosphorus removal rate is 85%, the blue algae removal rate is 90%, and the total organic carbon removal rate is 80%.

[0073] Two months after the composite pollution of the reservoir was repaired in this embodiment, samples around the roots of aquatic plants were taken to detect the concentration of hydroxyl radicals. The results showed that the concentration of hydroxyl radicals around the roots of aquatic plants was 110 μmol / kg.

[0074] Those skilled in the art will appreciate that the embodiments described herein are intended to help technicians understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for repairing complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal, characterized in that: The following steps are involved: (1) adding porous iron-based biochar and porous lightweight filler to the bottom mud of the river or lake to be remediated by composite pollution, and mixing them thoroughly to form a composite matrix; (2) Aquatic plants with oxygen-secreting roots are planted on the composite matrix to carry out pollution remediation of rivers or lakes. During the pollution remediation process, the porous iron-based biochar catalyzes the oxygen secreted by the roots of the aquatic plants to form reactive oxygen species including hydroxyl radicals. The reactive oxygen species oxidize and degrade organic pollutants in the rivers or lakes while inhibiting the growth of algae. In addition, the porous iron-based biochar and porous lightweight fillers adsorb and remove pollutants in the rivers or lakes.

2. The method for repairing river and lake complex pollution by synergistic algae inhibition and pollution removal according to claim 1 is characterized in that: In the composite matrix of step (1), the volume proportion of the sludge is 50% to 60%, the volume proportion of the porous iron-based biochar is 20% to 40%, and the volume proportion of the porous lightweight filler is 10% to 30%.

3. The method for repairing river and lake complex pollution by synergistic algae inhibition and pollution removal according to claim 1 is characterized in that: The preparation method of the porous iron-based biochar is as follows: bottom mud is taken from a river or lake, dried and crushed to obtain a carbon source, the carbon source, the iron source and a chemical modifier are fully mixed to obtain a reaction precursor, and the reaction precursor is roasted at 600 to 1000° C. for 2 to 4 hours in a nitrogen atmosphere to obtain porous iron-based biochar; the chemical modifier is hydrochloric acid, sulfuric acid, oxalic acid, alkali, oxalic acid, thiourea or sulfide.

4. The method for repairing complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal according to claim 3 is characterized in that: In the reaction precursor, the content of the carbon source is 80wt% to 90wt%, the content of the iron source is 5wt% to 10wt%, and the content of the chemical modifier is 5wt% to 10wt%.

5. The method for repairing complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal according to claim 3 is characterized in that: The iron source is a water-soluble iron salt.

6. The method for repairing complex pollution of rivers, lakes and reservoirs by synergistic algae inhibition and pollution removal according to any one of claims 1 to 5, characterized in that: The particle size of porous iron-based biochar is in the micrometer range.

7. The method for repairing complex pollution of rivers, lakes and reservoirs by synergistic algae inhibition and pollution removal according to any one of claims 1 to 5, characterized in that: The porous lightweight filler is at least one of ceramsite, vermiculite, perlite and volcanic rock.

8. The method for repairing complex pollution of rivers and lakes by synergistic algae inhibition and pollution removal according to claim 7 is characterized in that: The porous lightweight filler is in granular form, and the particle size is 3 to 10 mm.

9. The method for repairing complex pollution of rivers, lakes and reservoirs by synergistic algae inhibition and pollution removal according to any one of claims 1 to 5, characterized in that: The aquatic plants include at least one of submerged plants whose roots have the ability to secrete oxygen and emergent plants whose roots have the ability to secrete oxygen.

10. The method for repairing river and lake complex pollution by synergistic algae inhibition and pollution removal according to claim 9 is characterized in that: The aquatic plants include at least one of Vallisneria, Foxtail Algae, Ceratophyllum, Hydrilla, Potamogeton, Water Chestnut, Cattail, Juncus, Carex, Cyperus and Canna.

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