A method for efficient algae removal by using monochloramine pre-oxidation to enhance coagulation

Abstract

The present invention discloses a method for high-efficiency algae removal by using monochloramine pre-oxidation to strengthen coagulation, which belongs to the field of water treatment technology, and comprises: adding monochloramine or adding ammonia nitrogen and chlorine in steps to algae-containing water source water at the water intake of a drinking water plant, reacting for more than 3 hours, and then adding a coagulant, coagulating and precipitating to obtain. The method of the present invention uses monochloramine to selectively oxidize organic matter attached to the extracellular algae cells, reduce the negative charge on the surface of the algae cells, and then promote the electrical neutralization of the coagulant and the algae cells, and improve the separation effect of the algae cells in the water, which can increase the efficiency of coagulation and algae removal by several times.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to a method for high-efficiency algae removal by utilizing monochloramine pre-oxidation enhanced coagulation. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] In recent years, algae-induced water pollution has become increasingly serious in various parts of my country, and blue algae blooms in some lakes and reservoirs (such as Erhai Lake in Yunnan) are becoming a normal occurrence. Algae blooms not only destroy the balance of lake and reservoir water ecosystems, but also seriously affect the availability of water sources, disrupt the normal operation of water plants, and threaten drinking water safety.

[0004] Coagulation is the most important algae removal unit in the water purification process, and algae cells produce a large amount of extracellular organic matter, resulting in low efficiency of coagulation algae removal. Pre-oxidation is an effective technology for strengthening coagulation algae removal, but the commonly used pre-oxidants have high algae breaking effect or affect the operation of subsequent processes. The activity of the oxidant has an important influence on the pretreatment effect of high algae water. Excessive oxidation ability can easily cause algae cell rupture during the pretreatment process (such as chlorine, chlorine dioxide, ozone), that is, high algae breaking effect, which in turn leads to the release of algal toxins and intracellular organic matter. Potassium permanganate has a relatively mild oxidative activity on algae, and the algae breaking effect is small under low-dose conditions. However, it is found in actual engineering applications that long-term addition of potassium permanganate will cause manganese oxides to accumulate in the filter tank, reduce the filter tank flux, and reduce the backwashing effect. In addition, the coexisting natural organic matter in the water often contains electron-rich functional groups (such as phenolic hydroxyl, aromatic amine, aldehyde, etc.), which will accelerate the consumption of potassium permanganate. If the amount of potassium permanganate is increased, the algae breaking rate will increase, and it may cause the water color to increase, resulting in sensory indicators exceeding the standard.

[0005] In order to reduce the impact of high-algae water on conventional water purification processes (coagulation-sedimentation-filtration-disinfection) and ensure the safety of drinking water, there is an urgent need for a pretreatment technology that has good modified algae effect, low algae destruction effect, economy, ease of use and does not affect the operation of various units of conventional treatment processes, so as to improve the coagulation and algae removal efficiency, reduce the impact of algae organic matter on subsequent treatment processes, and improve the effluent quality. Summary of the invention

[0006] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a method for efficient algae removal using monochloramine pre-oxidation enhanced coagulation. The method provided by the present invention can achieve selective oxidation of extracellular organic matter to avoid algae cell rupture and does not affect subsequent process operations.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] On the one hand, a method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation comprises the following steps:

[0009] S1. Measure the ammonia nitrogen concentration in the water to be treated. If the ammonia nitrogen concentration in the water to be treated is lower than 0.3 mg / L, add ammonia nitrogen to make the ammonia nitrogen concentration higher than 0.3 mg / L; if the ammonia nitrogen concentration in the water to be treated is higher than 0.3 mg / L, no ammonia nitrogen needs to be added;

[0010] S2. Adjust the pH value of the water obtained in S1 to greater than 6.5;

[0011] S3. Add chlorine to the water obtained in S2, control the mass ratio of chlorine to ammonia nitrogen to be 4.5 to 7.6:1, and perform pre-oxidation;

[0012] S4. After the pre-oxidation is completed, a coagulant is added to the water obtained in S3 to perform coagulation and algae removal.

[0013] The method of the present invention utilizes in-situ generated monochloramine to achieve selective oxidation modification of extracellular organic matter, which makes it easier for algae cells to be destabilized and removed during the coagulation process, and improves the efficiency of coagulation algae removal from 33% to 90%. Under the same oxidant dosage, the efficiency of coagulation algae removal is 20% and 12% higher than that of potassium permanganate and chlorine pre-oxidation, respectively. Moreover, the damage to the integrity of algae cells by the method of the present invention is significantly lower than that of chlorine and potassium permanganate pre-oxidation, and the remaining monochloramine can be used for subsequent disinfection, which plays an important role in improving the resistance of conventional water purification processes to algal blooms and ensuring the safety of drinking water.

[0014] The beneficial effects of the present invention are:

[0015] (1) The present invention utilizes ammonia nitrogen contained in the water to be treated or adds a small amount of ammonia nitrogen to react with chlorine to generate monochloramine in situ as a pre-oxidant, and utilizes it to realize the selective oxidation modification of extracellular organic matter, so that algae cells are more easily destabilized and removed during the coagulation process, and the efficiency of coagulation algae removal is increased from 33% to 90%. It is a pretreatment technology with good algae modification effect, low algae destruction effect, economy, convenience in use, and no influence on each unit of the conventional treatment process. It can reduce the impact of algae organic matter on subsequent water treatment processes and improve the effluent water quality. Under the same oxidant dosage, the efficiency of coagulation algae removal is increased by 20% and 12% respectively compared with potassium permanganate and chlorine pre-oxidation. The products of the monochloramine oxidant used in the present invention after the reaction are ammonia nitrogen and chloride ions. When 1.0 mg / L monochloramine (as Cl 2 About 0.2 mg / L of ammonia nitrogen is introduced into the water (calculated). The limit value of ammonia nitrogen in my country's "Standard for Drinking Water Quality" (GB5749-2022) is 0.5 mg / L. Therefore, the use of monochloramine pre-oxidation will not cause excessive ammonia nitrogen in the water. Surface water usually contains a lot of chloride ions (tens of mg / L), so the added chloride ions (<5 mg / L) will not significantly affect the chloride ion concentration in the water.

[0016] (2) The oxidant monochloramine used in the present invention is a soluble small molecule oxidant and a commonly used disinfectant for drinking water treatment. It does not affect the operation of conventional water treatment units. Pre-oxidation of the remaining monochloramine is beneficial to the subsequent disinfection of the water to be treated. It plays an important role in improving the resistance of conventional water purification processes to algal blooms and ensuring the safety of drinking water.

[0017] (3) The pre-oxidant monochloramine used in the present invention has a low algae-breaking effect, avoids the release of intracellular organic matter, and is conducive to reducing the generation of disinfection by-products in the subsequent disinfection process. At the same time, it also has a coagulation and filtration effect, reduces the turbidity of the precipitated water and the filtered water, and prolongs the filtration cycle.

[0018] (4) The present invention utilizes a water pipeline for reaction, does not require an additional treatment unit, and is applicable to existing processes without the need for process modification. Moreover, the corrosion of the pipe network caused by monochloramine is small, and is suitable for pre-oxidation reaction in a water pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 This is a diagram showing the improvement effect of aluminum salt coagulation and algae removal by pre-oxidation of high algae water with monochloramine in Example 1 of the present invention;

[0021] Figure 2 This is a diagram showing the improvement effect of aluminum salt coagulation and algae removal by pre-oxidation of high algae water with monochloramine in Example 2 of the present invention;

[0022] Figure 3 This is a diagram showing the improvement effect of aluminum salt coagulation and algae removal by pre-oxidation of high algae water with monochloramine in Example 3 of the present invention;

[0023] Figure 4 This is a diagram showing the effect of pre-oxidation of high-algae water with monochloramine on the surface potential of algae cells in Example 1 of the present invention;

[0024] Figure 5 This is a diagram showing the effect of pre-oxidation of high algae water with monochloramine on the surface potential change of algae cells in Example 3 of the present invention;

[0025] Figure 6 This is a diagram showing the effect of monochloramine pre-oxidation + coagulation treatment of high algae water on dissolved organic carbon in water in Example 1 of the present invention;

[0026] Figure 7 This is a diagram showing the effect of monochloramine pre-oxidation + coagulation treatment of high algae water on dissolved organic carbon in water in Example 3 of the present invention;

[0027] Figure 8This is a diagram showing the improvement effect of monochloramine pre-oxidation, chlorine and potassium permanganate pre-oxidation on coagulation and algae removal in comparative example 1 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] In view of the impact of high-algae water on conventional water purification processes and the impact on the quality of drinking water, the present invention proposes a method for highly efficient algae removal using monochloramine pre-oxidation enhanced coagulation.

[0031] A typical embodiment of the present invention provides a method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation, the method comprising the following steps:

[0032] S1. Measure the ammonia nitrogen concentration in the water to be treated. If the ammonia nitrogen concentration in the water to be treated is lower than 0.3 mg / L, add ammonia nitrogen to make the ammonia nitrogen concentration higher than 0.3 mg / L; if the ammonia nitrogen concentration in the water to be treated is higher than 0.3 mg / L, no ammonia nitrogen needs to be added;

[0033] S2. Adjust the pH value of the water obtained in S1 to greater than 6.5;

[0034] S3. Add chlorine to the water obtained in S2, control the mass ratio of chlorine to ammonia nitrogen to be 4.5 to 7.6:1, and perform pre-oxidation;

[0035] S4. After the pre-oxidation is completed, a coagulant is added to the water obtained in S3 to perform coagulation and algae removal.

[0036] Coagulation is the most important algae removal unit in the water purification process, and algae cells produce a large amount of extracellular organic matter, resulting in low efficiency of coagulation algae removal. Algae cells have a small specific gravity and are difficult to sink. They are usually negatively charged on the surface. The Zeta potential ranges from -10mV (such as Chlorella) to -35mV (such as Scenedesmus and Lunar Algae). The isoelectric point is generally at pH 3-4. In the raw water, algae cells mostly exist in colloidal form. Inorganic metal salt coagulants (iron salts, aluminum salts, etc.) commonly used in drinking water treatment have positively charged metal ions or hydrolysis products of metal ions. They mainly destabilize algae cells through compression of the double electric layer, electrostatic attraction and electrical neutralization, and condense with coagulants to form flocs, which are then removed in the subsequent precipitation process. The metabolic secretion and apoptosis of algae cells result in a large amount of extracellular organic matter in the water, such as proteins, polysaccharides, nucleic acids, oils and other small molecular organic matter, which are the main components of soluble organic matter in high-algae water. When extracellular organic matter attaches to the surface of algal cell colloids, it will increase the electronegativity of the colloid, increase the electrostatic repulsion between particles, increase the stability of the colloid, and lead to a decrease in the coagulation effect. The decrease in coagulation effect will increase the difficulty of subsequent solid-liquid separation, leading to problems such as high moisture content of sediment, filter blockage, and algal cell penetration of the filter, which will in turn cause the deterioration of drinking water quality. Before the raw water enters the water plant for treatment, oxidants are added to the raw water for pre-oxidation to enhance the coagulation and algae removal effect. The organic matter in the oxidizing solution and attached to the surface of the algal cells can reduce the surface negative charge of the algal cells, causing the algal cells to "destabilize" and make them easier to separate from the water phase, thereby achieving the purpose of enhanced coagulation. However, the commonly used pre-oxidants currently have the problem of high algae-breaking effect or affect the operation of subsequent processes.

[0037] The present invention utilizes a method for enhancing coagulation and efficient algae removal by pre-oxidation with monochloramine, and successfully solves the above-mentioned problem by utilizing monochloramine. The mechanism of the present invention is that extracellular organic matter contains a large number of fatty amine structures and amide structures, while monochloramine can selectively react with these two chemical structures. After being oxidized by monochloramine, the structure of the extracellular organic matter changes, and it falls off from the surface of the algae cells, causing the Zeta potential of the algae cell surface to rise from -20mV to -3.8mV, and then it becomes unstable and precipitates after being electrically neutralized by the metal ions of the coagulant or the hydrolysis products of the metal ions. In addition, the cell structure hinders the reaction of monochloramine with the intracellular organic matter, and prevents the monochloramine from destroying the intracellular structure and causing the algae to die and rupture. Since the monochloramine has a weak oxidative activity, although it can oxidize and modify the extracellular organic matter, the oxidized extracellular organic matter still remains in a macromolecular state, and small molecular organic matter is difficult to remove during the coagulation process, while a small amount of macromolecular organic matter (>10kDa) has a coagulant effect, further enhancing the effect of coagulation and algae removal.

[0038] In some examples of this embodiment, the method further includes: evaluating the algae removal effect of monochloramine pre-oxidation enhanced coagulation by measuring the algae removal rate during the coagulation process.

[0039] In some examples of this embodiment, the water to be treated is surface water affected by algae.

[0040] In some examples of this embodiment, the ammonia nitrogen concentration is the ammonia nitrogen mass concentration, measured in N.

[0041] In some examples of this implementation mode, the addition of ammonia nitrogen is the addition of a pre-dissolved ammonium salt stock solution, wherein the solvent in the stock solution is distilled water, natural surface water or tap water; and the ammonium salt is ammonium chloride, ammonium sulfate or ammonium nitrate.

[0042] In some examples of this implementation mode, in S2, the pH is adjusted to be greater than or equal to 7.0. Because monochloramine will be converted into dichloramine under acidic conditions, which has strong oxidizing properties under acidic conditions, the high pH value ensures that the generated chloramine exists in the form of monochloramine, ensuring that its algae-breaking effect is low, avoiding the release of intracellular organic matter, and enhancing the coagulation algae removal effect.

[0043] In some examples of this embodiment, the chlorine is hypochlorous acid or a stock solution of a hypochlorite, wherein the hypochlorite is sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, or potassium hypochlorite; and the solvent in the stock solution is distilled water.

[0044] In some embodiments of this embodiment, in S3, the chlorine mass concentration is Cl 2 count.

[0045] In some embodiments of this implementation mode, the pre-oxidation process is carried out in a water pipeline, specifically: ammonia nitrogen and chlorine are added at the water intake of the drinking water plant, and the flow of water in the water pipeline is used to achieve effective mixing of ammonia nitrogen and chlorine, thereby achieving pre-oxidation treatment of the water to be treated.

[0046] In some examples of this implementation mode, in S3, the mass ratio of chlorine to ammonia nitrogen is 4.5-5.0:1; and the pre-oxidation time is not less than 3 hours.

[0047] In the present invention, the key to the method is the mass ratio of chlorine to ammonia nitrogen and the reaction time.

[0048] When the mass ratio of chlorine to ammonia nitrogen is less than 4.5, part of the ammonia nitrogen is not effectively converted into monochloramine and cannot play an oxidizing role. When the mass ratio of chlorine to ammonia nitrogen is greater than 5.0, excessive chlorine will continue to react with monochloramine to generate dichloramine and part of nitrogen, the residual chlorine concentration will decrease, and the pre-oxidation effect will decrease. When the mass ratio of chlorine to ammonia nitrogen reaches 7.6-9.0, chlorine will be directly converted into invalid chloride ions, while ammonia nitrogen will be converted into nitrogen, and the system will lose its oxidizing effect. When the ratio of chlorine to ammonia nitrogen increases further, the oxidant in the water exists in the form of free chlorine, and chlorine pre-oxidation can easily cause algae cells to rupture, release intracellular organic matter, and damage water quality.

[0049] Compared with the currently commonly used pre-oxidants, monochloramine has a lower redox potential (E 0 =1.13V NHE ), is a weak oxidant, and its reaction rate with extracellular organic matter is not high. It usually takes 3 hours or more to effectively transform extracellular organic matter. However, most of my country's drinking water sources are located in the suburbs of cities, and it is common for water treatment plants to draw water from lakes and reservoirs at long distances. Taking the common economic flow rate of 1.0 m / s in pipelines as an example, it takes about 3 to 6 hours to transport water from a water source 10 to 20 kilometers away from the water plant. This provides conditions for using the water transportation process to implement monochloramine pre-oxidation enhanced coagulation and efficient algae removal.

[0050] In some examples of this embodiment, the coagulant is an aluminum salt, an iron salt or polyacrylamide. The aluminum salt includes aluminum chloride, aluminum sulfate, polyaluminum chloride, and polyaluminum sulfate; the iron salt includes ferric chloride, ferric sulfate, polyferric chloride, and polyferric sulfate.

[0051] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0052] In the following embodiment, the monochloramine pre-oxidation process of the method for enhancing coagulation and high-efficiency algae removal using monochloramine pre-oxidation is carried out in a water pipeline.

[0053] Example 1

[0054] The method of using monochloramine pre-oxidation to enhance coagulation and remove algae efficiently has the following specific steps:

[0055] The pH of the water to be treated is 7. If the ammonia nitrogen concentration in the water to be treated is higher than 0.3 mg / L, chlorine is added to the water at the water intake according to the mass concentration ratio of chlorine to ammonia nitrogen of 4.5 to 5.0:1. If the ammonia nitrogen concentration in the water to be treated is lower than 0.3 mg / L, additional ammonia nitrogen is added to adjust the ammonia nitrogen concentration to 0.3 mg / L, and then chlorine is added to the water at the water intake so that the concentration of monochloramine in the water to be treated (measured as Cl 2 The concentration of aluminum chloride (in terms of aluminum) in the water to be treated is 1.5 mg / L. The water delivery process is used to mix ammonia nitrogen and chlorine and oxidize algae. The time for monochloramine pre-oxidation is different depending on the distance between the water intake and the water plant. After 1, 2, 3, 4, 5, 6, and 7 hours of pre-oxidation, aluminum chloride (in terms of aluminum) is added to the water so that the concentration of aluminum chloride (in terms of aluminum) in the water to be treated is 1.5 mg / L. Stir rapidly for 1 minute, then stir slowly for 10 to 15 minutes, and let it settle for 30 minutes. Compared with the coagulation and algae removal process without monochloramine pre-oxidation, the algae removal rate is increased from 37% to 48%, 66%, 63%, 80%, 89%, 89% and 90%. For specific effect comparison data, see Figure 1 This example shows that the method can significantly improve the effect of coagulation and algae removal.

[0056] The changes in the surface potential of algae cells during the monochloramine oxidation process were detected. The surface charge of algae cells increased from -20.2mV to -14.7, -6.9 and -3.8mV after 1, 4 and 7 hours of monochloramine pre-oxidation. Figure 4 .

[0057] The changes in the concentration of dissolved organic carbon in the water to be treated during the oxidation of monochloramine were detected. After 0, 1, 2, 3, 4, 5, 6, and 7 hours of pre-oxidation, the concentration of dissolved organic matter in the water to be treated after coagulation and algae removal became 5.7, 5.5, 6.4, 6.9, 6.7, 7.1, 7.2, and 7.7 mg / L, respectively. For specific effect comparison data, see Figure 6 .

[0058] Example 2

[0059] A method for efficient algae removal by using monochloramine pre-oxidation to enhance coagulation

[0060] The difference between this embodiment and embodiment 1 is that the concentration of ammonia nitrogen is adjusted to 0.4 mg / L, and the dosage of chlorine is: the concentration in the water to be treated reaches 2.0 mg / L. After 1, 2, 3, 4, 5, 6, and 7 hours of pre-oxidation, the coagulation algae removal efficiency reaches 54%, 63%, 64%, 75%, 84%, 91%, and 91%, respectively. For specific effect comparison data, see Figure 2 .

[0061] Example 3

[0062] A method for efficient algae removal by using monochloramine pre-oxidation to enhance coagulation

[0063] The difference between this embodiment and embodiment 1 is that the concentration of ammonia nitrogen is adjusted to 0.5 mg / L, and the dosage condition of chlorine is: the concentration of chlorine in the water to be treated reaches 2.5 mg / L. After 1, 2, 3, 4, 5, 6, and 7 hours of pre-oxidation, the coagulation algae removal efficiency reaches 65%, 71%, 89%, 89%, 91%, 86%, and 64%, respectively. The long-term oxidation of high-concentration monochloramine leads to a decrease in the coagulation algae removal effect because the oxidation causes the algae cells to rupture. For specific effect comparison data, see Figure 3 .

[0064] The changes in the surface potential of algae cells during the monochloramine oxidation process were detected. Pre-oxidation with monochloramine for 3 hours increased the surface charge of algae cells from -20.2mV to -5.0mV, while pre-oxidation for 7 hours caused the surface potential to change to -13.5mV. Long-term oxidation with high-concentration monochloramine caused algae cells to rupture, and the intracellular organic matter was released and adsorbed on the surface of algae cells, resulting in the surface potential of algae cells after 7 hours of pre-oxidation being lower than that of algae cells after 3 hours of pre-oxidation. For specific effect comparison data, see Figure 5 .

[0065] The changes in the concentration of dissolved organic carbon in the water to be treated during the monochloramine oxidation process were detected. After 1, 2, 3, 4, 5, 6, and 7 hours of pre-oxidation, the concentrations of dissolved organic matter in the water to be treated after coagulation and algae removal became 5.7, 5.8, 5.8, 5.9, 6.7, 7.3, 9.5, and 11.5 mg / L, respectively. Long-term oxidation with high-concentration monochloramine causes algae cells to rupture and release intracellular organic matter, resulting in a significant increase in the concentration of dissolved organic matter in the water after 7 hours of pre-oxidation. For specific effect comparison data, see Figure 7 .

[0066] Comparative Example 1

[0067] The difference between this embodiment and embodiment 1 is that chlorine (the dosage of chlorine is: the concentration of chlorine in the water to be treated reaches 1.5 mg / L) and potassium permanganate (the dosage of potassium permanganate is: the concentration of potassium permanganate in the water to be treated reaches 4.0 mg / L) are added to the water to be treated, and the pre-oxidation time is 7 hours. For specific effect comparison data, see Figure 8 The algae removal efficiency of monochloramine pre-oxidation + coagulation is 21% higher than that of chlorine pre-oxidation + coagulation, and 12% higher than that of potassium permanganate pre-oxidation + coagulation. This example shows that the method of the present invention improves the algae removal effect by coagulation better than the traditional chlorine pre-oxidation and potassium permanganate pre-oxidation.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for efficient algae removal using monochloramine pre-oxidation enhanced coagulation, characterized in that: The method comprises the following steps: S1. Measure the ammonia nitrogen concentration in the water to be treated. If the ammonia nitrogen concentration in the water to be treated is lower than 0.3 mg / L, add ammonia nitrogen to make the ammonia nitrogen concentration higher than 0.3 mg / L; if the ammonia nitrogen concentration in the water to be treated is higher than 0.3 mg / L, no ammonia nitrogen needs to be added; S2. Adjust the pH value of the water obtained in S1 to greater than 6.5; S3. Add chlorine to the water obtained in S2, control the mass ratio of chlorine to ammonia nitrogen to be 4.5~7.6:1, and perform pre-oxidation; S4. After the pre-oxidation is completed, a coagulant is added to the water obtained in S3 to perform coagulation and algae removal; The pre-oxidation time is not less than 3 hours; Ammonia nitrogen reacts with chlorine to generate monochloramine in situ as a pre-oxidant. Extracellular organic matter contains aliphatic amine structures and amide structures, and monochloramine can react selectively with these two chemical structures. The adding of ammonia nitrogen in step S1 is adding a pre-dissolved ammonium salt reserve solution; The chlorine added in step S3 is a stock solution of hypochlorous acid or hypochlorite.

2. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The method further comprises: evaluating the algae removal effect of monochloramine pre-oxidation enhanced coagulation by measuring the algae removal rate during the coagulation process.

3. The method for efficient algae removal by pre-oxidation and enhanced coagulation using monochloramine according to claim 1, characterized in that: The water to be treated is surface water affected by algae.

4. The method for efficient algae removal by pre-oxidation and enhanced coagulation using monochloramine according to claim 1, characterized in that: The ammonia nitrogen concentration is the ammonia nitrogen mass concentration, measured in N.

5. The method for efficient algae removal by pre-oxidation and enhanced coagulation using monochloramine according to claim 1, characterized in that: The solvent in the stock solution is distilled water, natural surface water or tap water.

6. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The ammonium salt is ammonium chloride, ammonium sulfate or ammonium nitrate.

7. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: In the S2, the pH is adjusted to be greater than or equal to 7.

0.

8. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The hypochlorite is sodium hypochlorite, calcium hypochlorite, lithium hypochlorite or potassium hypochlorite.

9. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The solvent in the stock solution is distilled water.

10. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: In said S3, the chlorine mass concentration is calculated as chlorine.

11. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The pre-oxidation process is carried out in the water pipeline. Specifically, ammonia nitrogen and chlorine are added at the water intake of the drinking water plant, and the flow of water in the water pipeline is used to achieve effective mixing of ammonia nitrogen and chlorine, thereby achieving pre-oxidation treatment of the water to be treated.

12. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: In the S3, the mass ratio of chlorine to ammonia nitrogen is 4.5-5.0:

1.

13. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 1, characterized in that: The coagulant is aluminum salt, iron salt or polyacrylamide.

14. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 13, characterized in that: The aluminum salts include aluminum chloride, aluminum sulfate, polyaluminum chloride, and polyaluminum sulfate.

15. The method for efficient algae removal by using monochloramine pre-oxidation enhanced coagulation according to claim 13, characterized in that: The iron salts include ferric chloride, ferric sulfate, polyferric chloride and polyferric sulfate.

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