Method for purifying environment

Abstract

To provide a method for purifying an environment capable of culturing a large amount of microorganisms for purifying pollutants at a low cost.SOLUTION: A method for purifying an environment including a purification target range in which contaminated groundwater is present, the method comprising: introducing a salt-tolerant or halophilic microorganism and a salt into the groundwater; and purifying contaminants present in the purification target range with the microorganism. A method for purifying an environment including a purification target range in which contaminated groundwater is present, the method comprising: a first step of adding a salt-tolerant or halotolerant microorganism and salt to pumped groundwater to culture the microorganism to obtain a culture solution; and a second step of introducing the culture solution into the purification target range to purify contaminants present in the purification target range with the microorganism.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for cleaning up an environment. [Background technology]

[0002] Bioremediation using microorganisms is used as an inexpensive method for purifying soil or groundwater contaminated with organic compounds. Bioremediation is broadly divided into biostimulation, in which chemical solutions are introduced into the soil or groundwater to activate indigenous microorganisms, and bioaugmentation, in which microorganisms cultivated outside are introduced into the soil or groundwater. Biostimulation is an inexpensive method with little impact on the local environment. Bioaugmentation is a method for treating difficult-to-treat contaminants in a short period of time.

[0003] Bioaugmentation, which treats difficult-to-treat pollutants in a short period of time, involves cultivating large quantities of microorganisms capable of treating the target pollutants outside and then introducing them into the system. However, microorganisms capable of purifying pollutants often grow slowly, and culturing them in large quantities is time-consuming and costly. Furthermore, cultivating microorganisms capable of purifying pollutants often requires adding the pollutants to the culture solution. Cultivation facilities that handle substances designated as toxic or deleterious substances are difficult to manage, making it difficult to establish facilities capable of mass cultivation. Furthermore, because contaminants are added to the culture solution, there is a risk that they will be released into the soil or groundwater without being fully decomposed.

[0004] One possible solution to these problems is to cultivate the target microorganisms using groundwater that already contains contaminants. Since the contaminants needed to cultivate specific microorganisms are already present, there is no need to add them, and there is no need to transfer, possess, or use toxic or deleterious substances, making management easier. However, because groundwater in natural environments already contains a variety of microorganisms and nutrients, it is difficult to create an environment in which the target microorganisms can grow preferentially, and there is a risk that they will be overtaken by indigenous microorganisms.

[0005] Furthermore, the introduced microorganisms are required to be non-pathogenic and to disappear naturally in the environment (see, for example, Non-Patent Document 1). Microorganisms used for contaminant remediation typically grow preferentially by utilizing the contaminant as a carbon source or electron acceptor, and therefore tend to be out-growing by indigenous microorganisms after the contaminant has completely disappeared. On the other hand, to fully remediate contaminants, it is necessary to maintain the activity of the introduced microorganisms in the target contaminated soil or groundwater until the introduced microorganisms complete their remediation. Therefore, it is difficult to properly manage the balance between the natural disappearance of contaminants in the soil or groundwater and the activity of the microorganisms. In practice, measures have been taken to fully remediate the target contaminants by introducing an excessive amount of microorganisms, thereby completing the remediation process by the time the microorganisms disappear. Introducing a large amount of microorganisms requires the prior cultivation of a large amount of microorganisms, which leads to high costs. In addition, the introduction of large amounts of nutrients into the soil or groundwater is also necessary, which is thought to increase the risk of soil and groundwater contamination.

[0006] A method described in Patent Document 1 is known as a method for purifying saline soil and groundwater using halotolerant microorganisms. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-239656 [Non-patent literature]

[0008] [Non-Patent Document 1] Guidelines for the use of microbial bioremediation Summary of the Invention [Problem to be solved by the invention]

[0009] However, Patent Document 1 does not describe a method for culturing microorganisms by adjusting the salt concentration of groundwater.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for purifying an environment that allows for the mass cultivation of microorganisms for purifying pollutants at low cost. [Means for solving the problem]

[0011] The present invention has the following aspects. [1] A method for remediating an environment including a remediation target area where contaminated groundwater exists, comprising: A method for environmental purification, comprising the steps of introducing salt-tolerant or halophilic microorganisms and salt into the groundwater, and purifying contaminants contained in the purification target area with the microorganisms. [2] The method for purifying the environment according to [1], further comprising adding nutrients to the groundwater. [3] A method for remediating an environment including a remediation target area where contaminated groundwater exists, comprising: A first step of adding salt-tolerant or halophilic microorganisms and salt to the pumped groundwater and culturing the microorganisms to obtain a culture solution; a second step of introducing the culture solution into the area to be purified and purifying contaminants contained in the area to be purified with the microorganisms. [4] The method for purifying an environment according to [3], wherein in the first step, the amount of the salt added is 2% by mass or more relative to the total mass (100% by mass) of the culture solution. [5] The method for purifying an environment according to [3] or [4], wherein in the first step, nutrients are further added to the groundwater. [6] The method for purifying an environment according to any one of [1] to [5], wherein the environment is a freshwater environment. [7] The method for purifying an environment according to [6], wherein the freshwater environment is a freshwater environment near a coastal area. [8] The method for purifying an environment according to [6], wherein the freshwater environment is a freshwater environment far from a coastal area. [9] The method for purifying an environment according to any one of [1] to [5], wherein the environment is a saltwater environment. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for purifying an environment that allows for the mass cultivation of microorganisms for purifying pollutants at low cost. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are schematic diagrams showing a first example of an environment purification method according to one embodiment of the present invention, in which (a) shows a normal state and (b) shows a state during purification. [Figure 2] 1A and 1B are schematic diagrams showing a first example of an environment purification method according to one embodiment of the present invention, in which (a) shows a normal state and (b) shows a state during purification. [Figure 3] 1A and 1B are schematic diagrams showing a first example of an environment purification method according to an embodiment of the present invention, in which (a) shows the state during purification and (b) shows the state after purification has been completed. [Figure 4] FIG. 1 shows the results of bacterial flora analysis when groundwater contaminated with organochlorine compounds was used as a microbial source and cultured in a medium containing 1.05% NaCl. [Figure 5] FIG. 1 shows the results of bacterial flora analysis when cultured in a medium containing 2% NaCl. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Environmental purification methods] (First embodiment) An environmental purification method according to one embodiment of the present invention is a method for purifying an environment including a purification target area where contaminated groundwater exists, and includes a step of introducing salt-tolerant or halophilic microorganisms and salt into the groundwater and purifying contaminants contained in the purification target area with the microorganisms.

[0015] In the environmental purification method of this embodiment, salt-tolerant or halophilic microorganisms (hereinafter referred to as "microorganisms α") and salt are directly introduced into the contaminated groundwater present in the area to be purified in the groundwater layer, and the microorganisms α are cultivated in the groundwater present in the area to be purified, and the contaminants contained in the groundwater present in the area to be purified are purified by the microorganisms α.

[0016] The microorganism α is not particularly limited as long as it is salt-tolerant or halophilic, and for example, salt-tolerant dechlorinating bacteria of the genus Dehalogenimonas, Dehalococcoides, Dehalobium, etc. can be used.

[0017] In the purification target area, the amount of microorganism α added relative to the total mass (100% by mass) of groundwater containing microorganism α and salt is preferably 0.01% by mass to 5% by mass, more preferably 0.1% by mass to 5% by mass, and even more preferably 0.5% by mass to 5% by mass. When the amount of microorganism α added is equal to or greater than the lower limit, contaminants contained in groundwater can be purified quickly. When the amount of microorganism α added is equal to or less than the upper limit, purification costs can be reduced and a wider area can be purified with the same amount of microorganisms.

[0018] Examples of salts that can be used include sodium chloride (NaCl), potassium chloride (KCl), sodium sulfate (Na2SO4), and calcium chloride (CaCl2).

[0019] In the purification target area, the amount of salt added relative to the total mass (100% by mass) of groundwater containing microorganism α and salt is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. When the amount of salt added is equal to or greater than the lower limit, indigenous bacteria can be efficiently suppressed, and microorganism α that decomposes pollutants becomes more likely to dominate, allowing pollutants to be purified efficiently. The upper limit of the amount of salt added may be 10% by mass or less, 7% by mass or less, or 5% by mass or less.

[0020] In addition to the microorganism α and salts, the groundwater may further contain nutrients such as lactic acid, formic acid, acetic acid, glucose, ethanol, yeast extract, citric acid, and molasses. Adding nutrients to the culture solution can promote the cultivation of the microorganism α.

[0021] In the target purification area, the amount of nutrients added relative to the total mass (100% by mass) of groundwater containing microorganisms α, salts, and nutrients is preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 5% by mass, and even more preferably 0.1% by mass to 1% by mass. When the amount of nutrients added is equal to or greater than the lower limit, the amount of microorganisms α necessary for purifying contaminants can be maintained. When the amount of nutrients added is equal to or less than the upper limit, contamination of groundwater due to the addition of excessive nutrients can be avoided.

[0022] The method for introducing the microorganism α, salt, and nutrients into the area to be purified is not particularly limited, but an example is a method in which a pipe is installed that reaches the area to be purified from the ground, and the microorganism α, salt, and nutrients are introduced through the pipe.

[0023] According to the environmental purification method of this embodiment, microorganisms α for purifying pollutants can be cultured in large quantities at low cost. Furthermore, microorganisms α can be cultured without adding additional pollutants necessary for the growth of microorganisms α. Therefore, the method is easy to handle and does not pose a risk of further contamination.

[0024] (Second embodiment) An environmental purification method according to one embodiment of the present invention is a method for purifying an environment that includes a purification target area where contaminated groundwater exists, and includes a first step of adding salt-tolerant or halophilic microorganisms and salt to pumped groundwater and culturing the microorganisms to produce a culture solution, and a second step of introducing the culture solution into the purification target area and purifying contaminants contained in the purification target area with the microorganisms.

[0025] "First step" In the first step, microorganism α and salt are added to groundwater pumped up from the groundwater layer, and the microorganism α is cultivated to produce a culture solution.

[0026] Groundwater is usually freshwater that does not contain salt, and many of the microorganisms that live in groundwater grow preferentially in freshwater environments.

[0027] The amount of microorganism α added relative to the total mass (100% by mass) of the culture solution is preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 5% by mass, and even more preferably 0.1% by mass to 1% by mass. When the amount of microorganism α added is equal to or greater than the lower limit, the concentration of microorganism α required for purification can be quickly achieved. When the amount of microorganism α added is equal to or less than the upper limit, the cost of purification can be reduced.

[0028] The salt may be the same as that used in the first embodiment.

[0029] The amount of salt added relative to the total mass (100% by mass) of the culture solution is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. When the amount of salt added is equal to or greater than the lower limit, indigenous bacteria can be efficiently suppressed, and the microorganism α that decomposes pollutants becomes more likely to dominate, allowing for efficient purification of pollutants. The upper limit of the amount of salt added may be 10% by mass or less, 7% by mass or less, or 5% by mass or less.

[0030] The culture solution may further contain nutrients in addition to the microorganism α and salts. As the nutrients, the same ones as those in the first embodiment can be used.

[0031] The amount of nutrient added relative to the total mass (100% by mass) of the culture solution is preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 5% by mass, and even more preferably 0.1% by mass to 1% by mass. When the amount of nutrient added is equal to or greater than the lower limit, the amount of microorganisms α necessary for purifying contaminants can be quickly secured. When the amount of nutrient added is equal to or less than the upper limit, contamination of groundwater due to the addition of excessive nutrient can be avoided.

[0032] When culturing microorganism α, the temperature of the culture solution is preferably 10°C to 40°C, more preferably 20°C to 37°C, and even more preferably 25°C to 35°C. When the temperature of the culture solution is above the lower limit, rapid growth can be achieved, ensuring a large amount of bacteria. When the temperature of the culture solution is below the upper limit, death due to high temperatures can be avoided.

[0033] In the first step, microorganism α and salt are added to groundwater, creating an environment (culture solution) in which microorganisms living in the groundwater (indigenous microorganisms) have difficulty growing and the target microorganism α can easily grow.

[0034] The cultivation of microorganism α in the first step may be carried out before the purification of the target area in the second step is started, or may be continued during the purification of the target area. The cultivation method of microorganism α may be batch cultivation or continuous cultivation.

[0035] Furthermore, once the degradation of the target contaminants is complete in the second step, the introduction of microorganisms α into the groundwater from outside (bioaugmentation) in the first step can be stopped and a transition can be made to biostimulation, which uses indigenous microorganisms to treat the degradation products. Alternatively, the type of microorganisms α introduced into the groundwater can be changed depending on the remaining amount and type of contaminants.

[0036] "Second step" In the second step, the culture solution containing the microorganism α cultivated in the first step is introduced into the area to be purified (the area where soil or groundwater contamination has occurred), and the contaminants contained in the area to be purified are purified by the microorganism α.

[0037] In the second step, the amount of microorganism α introduced into the area to be purified is not particularly limited. For example, when expressed as mass per unit volume of the soil or groundwater in the area to be purified, the amount is preferably 0.001 g / L to 0.5 g / L, more preferably 0.01 g / L to 0.5 g / L, and even more preferably 0.05 g / L to 0.5 g / L. When the amount of microorganism α is equal to or greater than the lower limit, contaminants contained in the groundwater can be rapidly purified. When the amount of microorganism α is equal to or less than the upper limit, purification costs can be reduced and a wider area can be purified with the same amount of microorganisms.

[0038] According to the environmental purification method of this embodiment, microorganisms α for purifying pollutants can be cultured in large quantities at low cost. Furthermore, microorganisms α can be cultured without adding additional pollutants necessary for the growth of microorganisms α. Therefore, the method is easy to handle and does not pose a risk of further contamination.

[0039] Next, an application example of the environment purification method of this embodiment will be described.

[0040] (First example) 1A and 1B are schematic diagrams showing a first example of the environmental purification method of the present embodiment, with Fig. 1A showing the normal state and Fig. 1B showing the purification state. In Fig. 1, reference numeral 1 denotes a soil layer, reference numeral 2 denotes a groundwater layer, reference numeral 3 denotes a first pipe, reference numeral 4 denotes a second pipe, and reference numeral 5 denotes a water impermeable wall. As shown in FIG. 1(b), a first pipe 3 and a second pipe 4 are buried in the depth direction of the soil layer 1, from the surface (ground surface) 1a of the soil layer 1 to the area of ​​the groundwater layer 2 to be purified. The first pipe 3 is a pipe for introducing microorganisms α and salts into the area of ​​the groundwater layer 2 to be purified. The first pipe 3 can also be used to pump groundwater from the groundwater layer 2. The second pipe 4 is a pipe for pumping groundwater or groundwater containing microorganisms α and salts from a location in the groundwater layer 2 where groundwater contamination has occurred.

[0041] A water impermeable wall 5 is placed near the second pipe 4 to separate the area to be purified in the groundwater layer 2, in other words, the area in the groundwater layer 2 where the microorganisms α and salts are introduced from other areas, and to prevent the groundwater containing the microorganisms α and salts from diffusing to areas outside the area to be purified in the groundwater layer 2. The water impermeable wall 5 is buried in the depth direction of the soil layer 1, from the surface (ground surface) 1a of the soil layer 1 to the groundwater layer 2.

[0042] In the first example, the environment containing the contaminated groundwater and the target area for remediation is a freshwater environment. Specifically, the freshwater environment is a freshwater environment far from the coast. A freshwater environment far from the coast is an environment with a salt concentration of less than 0.5%.

[0043] If the above environment is a freshwater environment far from the coast, it is necessary to add salt to the groundwater along with the microorganism α in order to utilize the microorganism α. When purifying contaminants, the microorganism α and salt are added to the groundwater to increase the salt concentration in the groundwater and activate the microorganism α. If left as is, the salt introduced along with the microorganism α will quickly flow downstream in the direction of the groundwater flow (in the direction of the arrow in Figure 1), and the above environment will quickly return to a freshwater environment. Therefore, the groundwater can be recovered downstream using a second pipe 4 to reuse the groundwater (saltwater), or a water barrier 5 can be used to prevent salt from flowing downstream. This allows the salt concentration in the groundwater to be maintained when purifying contaminants.

[0044] The impermeable wall 5 may be a steel sheet pile, a bentonite-based impermeable wall, a soil cement impermeable wall, or a chemical injection impermeable wall. The impermeable wall 5 may be installed so as to surround the area to be purified.

[0045] After the purification of contaminants is complete, the introduction of salt into the groundwater is stopped and the impermeable wall 5 is removed, washing away the salt present in the purification area and turning the water into freshwater. This is thought to result in the proliferation of microorganisms (indigenous microorganisms) that are active in freshwater environments, which will eliminate the microorganisms α introduced into the purification area. If the microorganisms α are strictly anaerobic, the elimination of the microorganisms α introduced into the groundwater can be promoted by introducing an oxidizing agent or air into the groundwater. Note that obligate anaerobes are bacteria that do not grow at all in an environment (air) containing 20% ​​oxygen molecules.

[0046] (Second example) 2A and 2B are schematic diagrams showing a second example of the environmental purification method of this embodiment, with Fig. 2A showing the normal state and Fig. 2B showing the purification state. In Fig. 2, reference numeral 11 denotes a soil layer, reference numeral 12 denotes a groundwater layer, reference numeral 13 denotes seawater, reference numeral 14 denotes a first pipe, and reference numeral 15 denotes a second pipe. As shown in FIG. 2(b), a first pipe 14 and a second pipe 15 are buried in the depth direction of the soil layer 11, from the surface (ground surface) 11a of the soil layer 11 to the area of ​​the groundwater layer 12 to be purified. The first pipe 14 is a pipe for introducing the microorganism α and salts into the area of ​​the groundwater layer 12 to be purified. The first pipe 14 can also be used to pump groundwater from the groundwater layer 2. The second pipe 4 is a pipe for pumping groundwater or groundwater containing the microorganism α and salts from a location in the groundwater layer 12 where groundwater contamination has occurred.

[0047] The second example shows a freshwater environment, including the area targeted for remediation where contaminated groundwater exists. Specifically, the freshwater environment is a coastal freshwater environment. A coastal freshwater environment is an environment with a salt concentration of less than 0.5%.

[0048] If the environment is a freshwater environment near a coastal area, adjusting the groundwater level on the site allows seawater (saltwater) 13 to be drawn into the groundwater layer 12, thereby increasing the salt concentration in the groundwater. When purifying contaminants, microorganisms α are introduced into the groundwater in the groundwater layer 12 from the first pipe 14, and groundwater is actively pumped up from the groundwater layer 12 through the second pipe 15, thereby lowering the groundwater level and promoting the introduction of seawater 13 into the groundwater layer 12. After a sufficient amount of seawater 13 has been introduced into the groundwater layer 12, the area to be purified may be surrounded by a water-impermeable wall 5 or the like shown in FIG. 1 to prevent the seawater 13 from escaping.

[0049] After the purification of contaminants is complete, the pumping of groundwater from the groundwater layer 12 via the second pipe 15 is stopped, and water is introduced into the groundwater layer 12 via the first pipe 14, thereby raising the groundwater level above sea level and desalination of the site. This is thought to result in the proliferation of microorganisms (indigenous microorganisms) that are active in freshwater environments, thereby eliminating the microorganisms α that were injected into the purification area. If the microorganisms α are anaerobic, the elimination of the microorganisms α introduced into the groundwater may be promoted by introducing an oxidizing agent or air into the groundwater.

[0050] (Third example) 3A and 3B are schematic diagrams showing a third example of the environmental purification method of this embodiment, with Fig. 3A showing the state during purification and Fig. 3B showing the state after purification is completed. In Fig. 3, reference numeral 21 denotes a soil layer, reference numeral 22 denotes a groundwater layer, reference numeral 23 denotes seawater, reference numeral 24 denotes a first pipe, and reference numeral 25 denotes a second pipe. As shown in FIG. 3(b), a first pipe 24 and a second pipe 25 are buried in the depth direction of the soil layer 21, from the surface (ground surface) 21a of the soil layer 21 to the area to be purified in the groundwater layer 22. The first pipe 24 is a pipe for introducing the microorganism α and salt into the area to be purified in the groundwater layer 22. The first pipe 24 can also be used to pump groundwater from the groundwater layer 22. The second pipe 25 is a pipe for pumping groundwater or culture solution from a location in the groundwater layer 22 where groundwater contamination has occurred.

[0051] The third example shows a case where the environment containing the contaminated groundwater and the target area for remediation is a saltwater environment. Specifically, this is a coastal saltwater environment. A coastal saltwater environment is an environment containing salt with a salt concentration of 0.5% or more.

[0052] If the environment is a saltwater environment in a coastal area, the microorganism α can be introduced directly into the area to be purified, thereby making the area to be purified an environment in which the microorganism α can be activated.

[0053] After the contaminant remediation is complete, the site is desalinated by actively introducing freshwater into the remediation area to raise the groundwater level above sea level. Alternatively, the groundwater can be replaced by installing a water barrier (5) such as that shown in Figure 1 around the remediation area where microorganism α has been introduced, and pumping water from the remediation area and introducing freshwater into the remediation area. This will likely result in the proliferation of microorganisms (indigenous microorganisms) that thrive in freshwater environments, eliminating the microorganism α introduced into the remediation area. If microorganism α is an anaerobic bacterium, the elimination of the introduced microorganism α can be promoted by introducing an oxidizing agent or air into the groundwater. Once the elimination of the introduced microorganism α is confirmed, the introduction of freshwater into the remediation area can be stopped, and the soil and groundwater on the site will return to a saline environment. However, since the introduced microorganism α has already disappeared, it will not repopulate, and the original microbial environment that was formed on the site will be restored.

[0054] According to the first, second, and third examples of the environmental purification method of this embodiment, the activity of indigenous microorganisms is temporarily suppressed, and the introduced microorganisms α are activated only when desired, and the introduced microorganisms α can be effectively eliminated once purification is complete. By controlling the activation and elimination of microorganisms α, efficient purification of pollutants becomes possible, and the amount of introduced microorganisms α can be minimized, which is expected to reduce costs and environmental impact. [Example]

[0055] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0056] [Example] The results of a bacterial flora analysis when groundwater contaminated with organochlorine compounds was used as a microbial source and cultured in a medium containing 1.05% NaCl are shown in Figure 4. It is believed that a bacterial flora like that shown in Figure 4 is formed in contaminated groundwater in freshwater environments. Meanwhile, Figure 5 shows the results of a bacterial flora analysis when cultured in a medium containing 2% NaCl. The genus Dehalogenimonas, a salt-tolerant dechlorinating bacterium, accounted for approximately 79.4%, indicating the formation of a bacterial flora different from that shown in Figure 4. This shows that adding salt inhibits the growth of microorganisms that tend to grow in normal freshwater environments, creating an environment dominated by salt-tolerant microorganisms. [Explanation of symbols]

[0057] 1,11,21 soil layers 2,12,22 Groundwater layer 3,14,24 First piping 4,15,25 Second piping 5 Impermeable walls 13 Seawater

Claims

1. A method for remediating an environment including a remediation target area where contaminated groundwater exists, comprising: A method for environmental purification, comprising the steps of introducing salt-tolerant or halophilic microorganisms and salt into the groundwater, and purifying contaminants contained in the purification target area with the microorganisms.

2. 10. The method for remediating an environment according to claim 1, further comprising adding nutrients to said groundwater.

3. A method for remediating an environment including a remediation target area where contaminated groundwater exists, comprising: a first step of adding salt-tolerant or halophilic microorganisms and salt to the pumped groundwater and culturing the microorganisms to obtain a culture solution; a second step of introducing the culture solution into the area to be purified and purifying contaminants contained in the area to be purified with the microorganisms.

4. 4. The method for purifying an environment according to claim 3, wherein in the first step, the amount of the salt added is 2% by mass or more relative to the total mass (100% by mass) of the culture solution.

5. 4. The method for purifying an environment according to claim 3, wherein nutrients are further added to the groundwater in the first step.

6. The method for purifying an environment according to claim 1 or 3, wherein the environment is a freshwater environment.

7. 7. The method for purifying an environment according to claim 6, wherein the freshwater environment is a near-coastal freshwater environment.

8. 7. The method for purifying an environment according to claim 6, wherein the freshwater environment is a freshwater environment far from a coastal area.

9. The method for purifying an environment according to claim 1 or 3, wherein the environment is a saltwater environment.

Images