Method for strengthening severe cyanobacterial bloom treatment by combining sodium percarbonate with EM bacteria

Abstract

The invention relates to the technical field of cyanobacterial bloom treatment, and discloses a method for strengthening severe cyanobacterial bloom treatment through combination of sodium percarbonate and EM bacteria. On the basis that 5 mg / L of sodium percarbonate is added, the algae cell density of an experimental group in which 0.075 mg / L of EM bacteria is further added is always lower than that of a control group in which only sodium percarbonate is added, and the reduction effect of further adding EM bacteria immediately after sodium percarbonate is added for 6 hours is the most remarkable, so that the EM bacteria have the effect of strengthening the algae treatment effect of sodium percarbonate; in addition, it is best that EM bacteria are added after sodium percarbonate is added for 6 h, when the experiment duration of an experiment group with the EM bacteria added for 6 h is 48 h, the algae cell density removal rate is 94.19%, and the algae cell density removal rate of a control group with only sodium percarbonate added is only 69.77%.

Description

Technical Field

[0001] The invention relates to the technical field of blue algae bloom control, and in particular to a method for strengthening the control of severe blue algae bloom by using sodium percarbonate in combination with EM bacteria. Background Art

[0002] In recent years, under the direct and indirect influence of human activities, a large amount of nitrogen, phosphorus and other inorganic salts and other nutrients in surface runoff such as industrial wastewater, domestic sewage, lake runoff, lake precipitation, aquaculture sewage, etc. have entered slow-flowing water bodies such as ponds, reservoirs, and lakes. After that, the water body has changed from a low-productivity oligotrophic state to a high-productivity eutrophic state, causing eutrophication of water bodies and thus destroying the aquatic ecological balance. According to a report by the Ministry of Ecology and Environment in 2019, of the 107 lakes and reservoirs monitored in China, 28% showed eutrophication characteristics, including the three important water source lakes of Taihu Lake, Chaohu Lake and Dianchi Lake, all of which were in a state of mild eutrophication. In the following years, namely in 2021 and 2022, the proportion of eutrophic lakes increased slightly, reaching 29% and 29.9% respectively. The eutrophication phenomenon of slow-flowing water bodies such as ponds, reservoirs, and lakes has intensified, and algal blooms often break out. Water bloom is defined as the accumulation of floating blue-green algae on the surface of lakes and reservoirs. Blue-green algae have unique competitive advantages, such as the ability to convert atmospheric nitrogen into biologically accessible nutrient ammonia, making them the most common type of water bloom. Researchers have analyzed data from 70 lakes around the world (including 12 lakes in China) for nearly 30 years and found that 68% of lakes have an increasing trend of blue-green algae blooms, and 10 lakes in China have also shown this trend. According to research, 163 lakes and reservoirs in 28 provinces and cities across China have experienced blue-green algae blooms. The outbreak of blue-green algae blooms will lead to a decrease in water transparency and dissolved oxygen, and is often accompanied by the production of algal toxins and odorous substances, causing water quality deterioration and damaging the aquatic ecosystem. Actively carrying out new technology research on blue-green algae bloom control is of great research significance.

[0003] Traditionally used methods for algae control include chemical, physical and biological methods. Chemical methods can kill algae quickly, but traditional chemical methods such as the well-known copper sulfate algae removal method will cause secondary pollution to the environment, such as the release of intracellular organic matter (IOM) and the increase in the concentration of heavy metal ions in the water body. Physical methods have the advantages of simple operation, mature technology and high removal efficiency, but they are generally only suitable for the control of small-scale algae water bodies. They are inefficient, consume a lot of manpower and material resources, and have serious recurrence. Biological methods have the advantages of being safe and reliable, not prone to secondary pollution, and eco-friendly when controlling algae, but they also have disadvantages such as long processing time, possible damage to the original ecosystem, and being affected by many environmental factors.

[0004] Therefore, in order to overcome the drawbacks of traditional algae removal technology, the research on algae removal using advanced oxidation technology (AOPs) has received much attention. Advanced oxidation algae removal technology induces a chain reaction of oxidants by using conditions such as electrocatalytic oxidation, ultrasound synergy, transition metal synergy, and ultraviolet light activation to produce strong oxidative free radicals, thereby achieving safe and efficient removal of cyanobacterial cells. Compared with traditional chemical methods, advanced oxidation methods are more efficient, green, and free of secondary pollution in treating algae. At present, most studies focus on advanced oxidation technologies (AOPs) that produce hydroxyl radicals (·OH) such as ultraviolet light synergy, ultrasound synergy, and electrocatalytic oxidation. However, these methods have the disadvantages of difficulty in constructing equipment and the need for regular manual maintenance. They are usually limited to the treatment of small and micro water bodies and are difficult to apply to large lakes and reservoirs. Blue algae blooms frequently occur in large lakes and reservoir-type water sources such as Taihu Lake and Chaohu Lake. Therefore, there is an urgent need for an efficient, green, and environmentally friendly treatment method to treat blue algae blooms in actual lakes and reservoirs.

[0005] New green and environmentally friendly oxidants such as hydrogen persulfate and percarbonate are simple to add as chemical reagents. After dissolving in water, they can produce sulfate free radicals (SO4 - ·), hydroxyl radical (·OH), superoxide radical (O2 - ·) and other strong oxidizing groups, which can quickly and efficiently degrade organic pollutants and quickly kill microorganisms in water. Many scholars have applied sodium percarbonate and hydrogen persulfate to water treatment. For example, sodium percarbonate can be directly used to degrade organic pollutants, including benzene, trichloroethylene (TCE), etc. Potassium hydrogen persulfate can be used to degrade organic pollutants through Fe 2+ Activation energy can effectively degrade rhodamine B dye, ketoprofen, etc. At the same time, some scholars have also applied sodium percarbonate and potassium persulfate to the treatment of cyanobacteria blooms. In the process of using these green and environmentally friendly oxidants to treat cyanobacteria, scholars found that green and environmentally friendly oxidants can not only effectively treat algae, but also degrade the algal toxins released by the normal metabolism of cyanobacteria and the death of oxidative effects, thus avoiding harm to human health. It can be seen that the new green and environmentally friendly oxidants have the advantages of high efficiency, greenness and environmental protection in treating algae. Therefore, the development of new green and environmentally friendly oxidants is of great significance for the treatment of cyanobacteria blooms.

[0006] At present, although there are many research results on algae removal using potassium persulfate, there are still few studies on algae removal using sodium percarbonate, especially it is rare to see a comparative study on the removal effect of cyanobacteria on potassium persulfate and sodium percarbonate, two green and environmentally friendly oxidants. In addition, when using new green and environmentally friendly oxidants to actually treat cyanobacterial blooms in slow-flowing water bodies such as ponds, reservoirs, and lakes, in order to reduce the cost of treating cyanobacterial blooms, it is necessary to select the appropriate dosage of the new green and environmentally friendly oxidant for different bloom levels, but there are currently few relevant research results on different appropriate dosages corresponding to different bloom levels. For this reason, the inventor promptly carried out a comparative study on the algae removal effect of two new green and environmentally friendly oxidants, potassium persulfate and sodium percarbonate, and explored the appropriate dosage, and learned that the algae removal effect of sodium percarbonate is better, and for severe cyanobacterial blooms, the appropriate dosage is 5mg / L.

[0007] In addition, like other plant cells, algae can form protective enzymes including superoxide dismutase, peroxidase, catalase, etc. when subjected to environmental stress, which can remove oxidative free radicals and reactive oxygen to protect themselves from damage. Therefore, when green and environmentally friendly oxidants are used to treat cyanobacterial blooms, algae may relapse under the action of protective enzymes. Therefore, it is necessary to enhance the effect of new green and environmentally friendly oxidants in treating algae. It is well known that algae must continuously take in nutrients from the surrounding environment to maintain normal life activities, and microorganisms can affect the circulation of nutrients, so that algae lack the N and P elements required for growth, thereby inhibiting the abnormal growth of algae. In addition, the use of microorganisms to treat cyanobacterial blooms will not produce secondary pollution, which is very important for the treatment of cyanobacterial blooms in large lakes and reservoirs. However, microorganisms have disadvantages such as long treatment time when treating cyanobacterial blooms. New green and environmentally friendly oxidants have the characteristics of high efficiency, greenness and environmental protection in treating algae. The two can complement each other in the process of algae treatment. However, there are very few studies on the use of green and environmentally friendly oxidants in combination with microorganisms to treat blue algae blooms. It can be seen that it is very necessary to carry out research on the use of green and environmentally friendly oxidants in combination with microorganisms such as lactic acid bacteria or EM bacteria to strengthen and stabilize the treatment effect of blue algae blooms in a timely manner, which has good research significance and practical application prospects. The inventor conducted a comparative experiment on the enhanced algae removal effect of lactic acid bacteria and EM bacteria and found that the enhanced effect of EM bacteria was more significant. The key point of how EM bacteria is used in combination with sodium percarbonate as an oxidant is the time of placement. If it is placed too early, EM bacteria and blue algae will be killed or damaged by the sodium percarbonate oxidant. If it is placed too late, the blue algae damaged by the sodium percarbonate oxidant may achieve self-repair and relapse of blue algae blooms under the action of protective enzymes. The inventor found in the actual treatment of water bodies with severe blue algae blooms that the blue algae damaged on the day of treatment sank and recurred on the second day. Therefore, in order to strengthen the treatment effect of severe blue algae blooms and prevent recurrence, the present invention proposes a method for strengthening the treatment of severe blue algae blooms by using sodium percarbonate in combination with EM bacteria. Summary of the invention

[0008] The purpose of the present invention is to provide a method for strengthening the treatment of severe blue algae blooms by using sodium percarbonate in combination with EM bacteria. The method proposed by the present invention is suitable for treating severe blue algae blooms in various static water bodies such as ponds, lakes, and reservoirs. The method can not only strengthen the algae removal effect and prevent recurrence, but also strengthen the removal of algal toxins.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] The present invention provides a method for strengthening the treatment of severe blue algae blooms by using sodium percarbonate in combination with EM bacteria, and the treatment method comprises the following steps:

[0011] S1: Preparation of sodium percarbonate solution

[0012] At the site of blue algae bloom treatment, tap water or water directly from the water body to be treated is used to dilute and dissolve the sodium percarbonate granules into a liquid.

[0013] S2: Add sodium percarbonate solution

[0014] Immediately load the prepared sodium percarbonate solution into a sprayer and spray the solution evenly on the water surface by boat; if the water area is small, it can be evenly sprinkled directly on the shore. Be careful to spray while preparing the solution, and avoid preparing a lot of solution at once and then spraying slowly, otherwise the oxidizability of sodium percarbonate will deteriorate over time.

[0015] S3: Add EM bacteria

[0016] Add EM bacteria directly and sprinkle evenly into the water.

[0017] Preferably, the sodium percarbonate granules are diluted at 1:100 and dissolved into a liquid medicine.

[0018] Preferably, the dosage of sodium percarbonate is calculated based on the volume of the water body to be treated, at 5 mg / L per liter of water body.

[0019] Preferably, the dosage of EM bacteria is calculated based on the volume of the water body to be treated, at 0.075 mg / L per liter of water body.

[0020] Preferably, the EM bacteria are added immediately 6 hours after the sodium percarbonate solution is added.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] When the present invention uses sodium percarbonate in combination with EM bacteria to treat algae, the algae cell density of the experimental group adding EM bacteria is always lower than that of the control group, and the addition of EM bacteria 6 hours after the addition of sodium percarbonate reduces the algae cell density most significantly, indicating that EM bacteria has the effect of strengthening the algae treatment effect of sodium percarbonate, and it is best to add EM bacteria 6 hours after the addition of sodium percarbonate. When the experimental group adding EM bacteria at 6 hours lasts for 48 hours, the algae cell density removal rate is as high as 94.19%, and the degree of water bloom is reduced from severe water bloom to mild water bloom and close to no obvious water bloom; while the removal rate of the control group adding only sodium percarbonate is only 69.77%, and the degree of water bloom is still in the severe water bloom range, just close to the boundary line of moderate water bloom. Moreover, at the end of the experiment, the final algae toxin content of the control group that only added sodium percarbonate was 67.10% of the initial content, and the algae toxin removal rate was 32.90%; while the algae toxin content of the experimental group that added EM bacteria at 6 hours was the lowest, only 61.06% of the initial content, and the algae toxin removal rate increased by 6.04% over the control group, reaching 38.94%. This shows that when sodium percarbonate kills a large number of cyanobacterial cells, it will not cause the dead algae cells to release more algae toxins, but can also remove the original algae toxins in the water to a certain extent, and the addition of EM bacteria will further enhance the removal of algae toxins. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The graphs of the algae cell density changes over time in the control group and the experimental group with EM bacteria added at different times;

[0024] Figure 2 The graph shows the initial value, final value and removal rate of algae toxins in the control group and the experimental group with EM bacteria added at different times. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for strengthening the treatment of severe blue algae blooms by using sodium percarbonate in combination with EM bacteria, and the treatment method comprises the following steps:

[0027] S1: On-site preparation of sodium percarbonate solution

[0028] Use tap water to dilute and dissolve the sodium percarbonate granules into a liquid medicine.

[0029] S2: Add sodium percarbonate solution

[0030] Immediately and evenly sprinkle the prepared sodium percarbonate solution into the water body to be treated.

[0031] S3: Add EM bacteria

[0032] EM bacteria are directly and evenly spread into the water body to be treated.

[0033] In this example, the treatment target is a small micro-water body with severe blue algae blooms, and the initial algae cell density is 4.3*10 8 cells / L.

[0034] In this embodiment, the sodium percarbonate granules are diluted at 1:100 and dissolved into a liquid medicine.

[0035] In this embodiment, the dosage of sodium percarbonate is calculated based on the volume of the water body to be treated, at 5 mg / L per liter of water body.

[0036] In this embodiment, the dosage of EM bacteria is calculated based on the volume of the water body to be treated, at 0.075 mg / L per liter of water body.

[0037] In this embodiment, the EM bacteria is added immediately after 6 hours of adding the sodium percarbonate solution.

[0038] After 48 hours of treatment, the algae cell density removal rate reached 94.19%, and the water body was reduced from the initial severe bloom to a mild bloom, and close to the no obvious bloom boundary. In addition, the algae toxin content was reduced to only 67.10% of the initial content.

[0039] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for strengthening the treatment of severe blue algae blooms by using sodium percarbonate in combination with EM bacteria, characterized in that: After adding sodium percarbonate, EM bacteria are further added to enhance the effect of controlling severe cyanobacteria blooms.

2. The method for strengthening the treatment of severe blue algae blooms by combining sodium percarbonate with EM bacteria according to claim 1, characterized in that: EM bacteria were further added immediately 6 hours after the sodium percarbonate was added.

3. The method for strengthening the treatment of severe blue algae blooms by combining sodium percarbonate with EM bacteria according to claim 1, characterized in that: The dosage of sodium percarbonate is 5 mg / L, that is, 5 mg of sodium percarbonate is added per liter of the water body to be treated; the dosage of EM bacteria is 0.075 mg / L, that is, 0.075 mg of EM bacteria is added per liter of the water body to be treated.

4. The method for strengthening the treatment of severe blue algae blooms by combining sodium percarbonate with EM bacteria according to claim 1, characterized in that: Sodium percarbonate granules should be diluted at 1:100 to form a liquid and then sprayed or sprinkled evenly into the water immediately; EM bacteria should be directly sprinkled into the water in a dry state.

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