Method for preventing abnormal proliferation of phytoplankton and flocculant for prevention

Abstract

To provide a method for preventing abnormal proliferation of harmful phytoplankton, for suppressing and removing the phytoplankton causing red tides, and flocculant for prevention.SOLUTION: A ferric chloride solution is sprayed on a sea surface of a sea area where harmful phytoplankton constituting red tides is generated, chemical action of trivalent iron ions converts phosphorus, the nutrient salt in the sea, into insoluble iron phosphate, which suppresses photosynthesis of the phytoplankton and prevents the propagation. It also produces flocculated ferric hydroxide, which adsorbs and coagulates floating phytoplankton, causing them to settle and be removed, thereby preventing damage to the fishing industry caused by red tides.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for preventing abnormal growth of phytoplankton causing red tides and a flocculant for prevention.

Background Art

[0002] The abnormal growth phenomenon of harmful phytoplankton that causes great damage to coastal fisheries is usually called red tide. In calm places with little wave movement in coastal waters, harmful phytoplankton appears and reproduces with seasonal water temperature changes. Phytoplankton absorbs light rays and heat rays from the sun, so the surrounding seawater temperature rises and the seawater specific gravity decreases. As a result, thermocline develops and a red tide water mass is formed in the surface layer, and light is also absorbed in the upper layer. When this water mass diffuses, the damage to fisheries increases due to the expansion of the red tide water mass area.

[0003] Regarding countermeasures against this red tide, currently, it is usually to wait for natural dissipation due to changes in water temperature caused by seasonal changes. However, for methods and agents for eradicating red tides, for example, a method has been proposed in which magnesium or the like is added to the sea surface to attach and aggregate phytoplankton to the flocs of magnesium hydroxide and precipitate them.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, magnesium hydroxide does not form flocs unless the pH is such that there is a sufficient amount of hydroxide groups (OH) in seawater, and the condition is a pH of 9.6 or higher. Therefore, in seawater with a normal pH of 8.3, there is a risk of pH damage to all aquatic organisms. Also, the flocs of precipitated magnesium hydroxide are insufficient for removing phytoplankton because magnesium hydroxide dissolves in bottom seawater with a pH around 8.3.

Means for Solving the Problem

[0006] To solve the above problems, the present invention makes phosphorus ions, which are indispensable for the growth of phytoplankton, into insoluble iron phosphate (FePO4) by chemical treatment with trivalent iron ions (Fe+++), so that phytoplankton cannot utilize phosphorus and prevent growth. At the same time, it is intended to adsorb and contain floating phytoplankton with flocs of ferric hydroxide (Fe(OH)3) generated by adding trivalent iron ions to seawater and remove them by precipitation.

[0007] That is, the growth of phytoplankton is carried out by photosynthesis. The photosynthesis of phytoplankton requires nutrients such as carbonic acid, nitrogen, and phosphorus, which are indispensable for organic matter synthesis, in addition to temperature, salinity concentration, and light requirements. If any of these elements are lacking, phytoplankton cannot grow. In particular, phosphorus is required in a small amount for phytoplankton and its existing amount in seawater is also small. Therefore, by removing phosphorus from the red tide-occurring sea area, the abnormal growth of harmful phytoplankton species can be efficiently suppressed.

[0008] Also, by forming flocculent ferric hydroxide and adsorbing and containing phytoplankton to precipitate it, it becomes possible to remove the phytoplankton itself.

[0009] Specifically, the first feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that an iron(III) chloride solution is sprayed on the red tide water mass area formed by the abnormal occurrence of phytoplankton, and through the reaction with trivalent iron ions therein, phosphorus, which is a nutrient salt in the sea, is converted into insoluble iron phosphate to suppress the photosynthesis of phytoplankton and prevent its growth, and at the same time, by generating flocculent iron(III) hydroxide, the phytoplankton is adsorbed, aggregated, and precipitated and removed.

[0010] Moreover, the second feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that the iron(III) chloride solution in the first feature is composed of trivalent iron ions in an amount equal to or more than the phosphorus concentration in the sea.

[0011] Furthermore, the third feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that the iron(III) chloride solution in the first feature has a concentration of trivalent iron ions of 5 to 10 ppm.

[0012] Still further, the fourth feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that the concentration of the iron ions in the first feature is 1 / 5 or more of the phytoplankton concentration in terms of ppm ratio.

[0013] Furthermore, the fifth feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that the iron(III) chloride solution in the first feature is sprayed at a concentration of 10 to 20%.

[0014] Still further, the sixth feature of the method for preventing abnormal growth of phytoplankton according to the present invention is that the spraying of the iron(III) chloride solution in the first feature is carried out from the tip of the ship, and the ship is equipped with plate-like or rod-like bodies hanging in the water on both sides and travels.

[0015] Moreover, the first feature of the aggregating agent for preventing abnormal growth of phytoplankton according to the present invention is a ferric chloride solution sprayed on the red tide water mass area formed by abnormal occurrence of phytoplankton, which is composed of trivalent iron ions equal to or more than the equivalent amount of phosphorus concentration on the sea surface.

[0016] Furthermore, the second feature of the aggregating agent for preventing abnormal growth of phytoplankton according to the present invention is a ferric chloride solution sprayed on the red tide water mass area formed by abnormal occurrence of phytoplankton, and the concentration of trivalent iron ions is 5 to 10 ppm.

[0017] Moreover, the third feature of the aggregating agent for preventing abnormal growth of phytoplankton according to the present invention is a ferric chloride solution sprayed on the red tide water mass area formed by abnormal occurrence of phytoplankton, and the concentration of trivalent iron ions is not less than one-fifth of the phytoplankton concentration in terms of ppm ratio.

Advantages of the Invention

[0018] According to the present invention, by spraying the ferric chloride solution on the red tide water mass area, phosphorus is replaced with insoluble iron phosphate, thereby inhibiting the photosynthesis of phytoplankton and preventing its growth. At the same time, by generating flocculent ferric hydroxide, phytoplankton can be adsorbed and aggregated for precipitation and removal, making it possible to prevent damage to fisheries caused by red tides.

[0019] Also, according to the present invention, the flocs of ferric hydroxide can maintain their state as long as anaerobic conditions do not occur on the seabed, so harmful plankton can be reliably removed.

[0020] Furthermore, according to the present invention, since the ferric chloride solution is directly sprayed onto the red tide water mass in the surface layer where phytoplankton is aggregated, it becomes possible to efficiently control red tide, and it is only necessary to spray it in a concentrated manner, which can reduce the working cost. In addition, in the case of trivalent iron ions, mainly flocs of ferric hydroxide are formed by bicarbonate, so it is a method harmless to organisms other than phytoplankton without polluting the sea and is also friendly to the global environment.

Best Mode for Carrying Out the Invention

[0021] The present invention aims to suppress the growth of phytoplankton by removing phosphorus in the water mass and remove phytoplankton by spraying a solution of ferric chloride (FeCl3) onto a unique water mass where phytoplankton abnormally multiplies and usually forms red tides.

[0022] In seawater with a pH of around 8.3, flocs of insoluble ferric hydroxide {Fe(OH)3} are generated in the range of pH 4 to 12 from the reaction between the carbonate or bicarbonate of the alkalinity substance contained therein and the trivalent iron ions of the ferric chloride solution. That is, fine particles of ferric hydroxide adhere and bond to each other to form flocs. At this time, other suspended particles are simultaneously adsorbed and aggregated to precipitate, so it becomes possible to separate and remove harmful phytoplankton from the breeding water mass.

[0023] The precipitation flocs of ferric hydroxide become divalent iron ions and dissolve when a reducing atmosphere of low oxygen or no oxygen is formed on the seabed. On the other hand, as long as an anoxic condition does not occur on the seabed, the flocs of ferric hydroxide have the characteristic of maintaining that state.

[0024] In addition, harmful phytoplankton contained in the flock are inhibited in photosynthesis due to insufficient light, and ferric hydroxide, when phosphorus is present, reacts with trivalent iron ions to form insoluble iron phosphate (FePO4), making it impossible for phytoplankton to absorb phosphorus and preventing the reproduction of harmful phytoplankton. Furthermore, the flock of ferric hydroxide, when containing phosphorus, precipitates together with the harmful phytoplankton. The precipitated phytoplankton cannot obtain the amount of light required for photosynthesis and dies.

[0025] Note that in an oxygen-poor or oxygen-free atmosphere, iron ions react with hydrogen sulfide (H2S) generated by sulfate-reducing bacteria to form iron sulfide (FeS) and are rendered harmless. In addition, ferric chloride is neutralized by the alkalinity substances abundant in seawater, so the pH of the seawater hardly changes and no harm is done to aquatic organisms.

[0026] The initial breeding stage of harmful phytoplankton in coastal waters progresses from solids to patchy water masses. The amount of trivalent iron ions of ferric chloride required at this initial breeding stage needs to be at a concentration of around 5 ppm for the target water mass of phytoplankton. A ferric chloride solution with a concentration of 5 - 10 ppm is used for spraying.

[0027] When the reproduction of harmful phytoplankton is in progress, water masses are formed, so more than one-fifth of the phytoplankton concentration in ppm ratio is required. Specifically, for a phytoplankton concentration of 50 ppm, an iron ion concentration of 10 ppm is required, and for a phytoplankton concentration of 100 ppm, an iron ion concentration of 20 ppm is required.

[0028] Regarding the removal of phosphorus, since it becomes iron phosphate, the phosphorus concentration of the breeding water mass is measured, and trivalent iron ions equal to or more than that amount are sprayed into the water mass.

[0029] The concentration of the ferric chloride solution to be dispersed is appropriately diluted and used according to the occurrence situation of red tides. However, in order for trivalent iron ions to be quickly mixed and dispersed in seawater to form flocs, it is desirable to disperse a ferric chloride solution with a trivalent iron ion concentration of 10 to 20%. The ferric chloride solution is dispersed from a ship. In order to improve the efficiency of stirring and mixing of the ferric chloride solution, it is desirable to perform the dispersion from the tip of the ship and attach plate-like or rod-like bodies suspended in water to both sides of the tip of the ship and travel.

Industrial Applicability

[0030] Although it is premised that commercially available ferric chloride solution is used in the present invention, in order to enhance the economy, since the slag generated in electric furnace steelmaking using scrap iron as a raw material mainly consists of iron oxide, a cheaper ferric chloride solution can be obtained by dissolving it with hydrochloric acid.

Claims

1. A solution of ferric chloride is sprayed in areas where red tide water masses are formed due to the abnormal proliferation of phytoplankton. The solution reacts with the trivalent iron ions in the solution to convert phosphorus, a nutrient salt in the ocean, into insoluble iron phosphate, which inhibits the photosynthesis of phytoplankton and prevents their proliferation, while also producing flocs of ferric hydroxide, which adsorbs, coagulates, and precipitates the phytoplankton for removal. A method for preventing abnormal proliferation of phytoplankton, comprising:

2. the ferric chloride solution is composed of trivalent iron ions in an amount equal to or greater than the phosphorus concentration in the seawater; 2. The method for preventing abnormal proliferation of phytoplankton according to claim 1 .

3. The ferric chloride solution has a concentration of ferric ions of 5 to 10 ppm; 2. The method for preventing abnormal proliferation of phytoplankton according to claim 1 .

4. The iron ion concentration is at least one-fifth of the phytoplankton concentration in terms of ppm ratio; 2. The method for preventing abnormal proliferation of phytoplankton according to claim 1 .

5. The ferric chloride solution is sprayed at a concentration of 10 to 20%.

2. The method for preventing abnormal proliferation of phytoplankton according to claim 1 .

6. The ferric chloride solution is sprayed from the front of the ship, The ship travels with plates or rods attached to both sides of the ship suspended in the water; 2. The method for preventing abnormal proliferation of phytoplankton according to claim 1 .

7. A ferric chloride solution to be sprayed in a red tide water mass area formed by an abnormal growth of phytoplankton, characterized in that the solution is composed of trivalent iron ions in an amount equal to or greater than the phosphorus concentration on the sea surface. A flocculant used to prevent abnormal proliferation of phytoplankton.

8. A ferric chloride solution to be sprayed in red tide water mass areas formed by the abnormal growth of phytoplankton, the ferric chloride solution having a concentration of 5 to 10 ppm of trivalent iron ions; A flocculant for preventing abnormal proliferation of phytoplankton, characterized by:

9. A ferric chloride solution to be sprayed in red tide water mass areas formed by the abnormal growth of phytoplankton, the concentration of trivalent iron ions being at least one-fifth of the concentration of phytoplankton in terms of ppm ratio. A flocculant for preventing abnormal proliferation of phytoplankton, characterized by: