JP4550366B2 - Method for controlling the generation of algae in freshwater areas - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for suppressing the generation of algae in a fresh water region, and more particularly, to a method for suppressing elution of nitrogen or phosphorus from the sediment in the fresh water region.
[0002]
[Prior art]
In freshwater areas such as dam lakes and lakes, environmental deterioration such as abnormal occurrence of algae (especially blue sea bream) has been progressively accelerated in recent years. Due to the abnormal occurrence of algae, the surface of the water is covered with green, which not only significantly damages the landscape but also adversely affects the aquatic habitat. Not only that, some aokos produce a toxin called “microkistin”, which has been reported to impair human health through drinking water after water purification.
[0003]
Algae abnormalities occur especially when the concentration of nutrients in water is high, especially when nitrogen (for example, ammonia nitrogen or nitrite nitrogen) and phosphorus (for example, phosphorus) are likely to become algal growth limiting factors (also called growth limiting factors). It is said that it tends to occur when the concentration of (acid) is high (see Non-Patent Document 1). Increases in nitrogen and phosphorus concentrations in freshwater areas generally result in inflows of sewage (eg, factory wastewater, household wastewater) or organic matter (eg, dead bodies of aquatic organisms) from the bottom of the freshwater area (called sediment). Elution of spoilage or decomposition products). The nitrogen concentration and phosphorus concentration of sewage flowing into the fresh water region tend to decrease with the recent increase in awareness of environmental problems. However, nitrogen-containing compounds and phosphorus-containing compounds due to sewage that have flown so far have accumulated in the sediment. For this reason, recently, the main problem of suppressing the generation of algae is to reduce the amount of nitrogen and phosphorus eluted from the sediment in the freshwater region.
[0004]
As one of the methods for reducing the amount of nitrogen and phosphorus eluted from the sediment in the fresh water region, a method of adding a maternal material such as magnesium hydroxide or magnesium oxide to the fresh water region is known (Patent Literature). 1). In this method, the sediment of the freshwater area is made weakly alkaline by the addition of the maternal material, and the ammonia-oxidizing bacteria and nitrite-oxidizing bacteria that live in the sediment are activated, so that nitrogen is used as the nitrogen gas in the freshwater area. This is a method in which phosphorus is removed to the outside and stably fixed in the fresh water region as a poorly water-soluble magnesium phosphate compound. In Example 7 of the above-mentioned patent document 1, when a sludge collected from a domestic drainage ditch where blue water is generated is spread over a 3 L beaker filled with tap water, and a bitter earth material is added thereto, There is a description that the occurrence was not seen.
[0005]
[Non-Patent Document 1]
Yoshihiko Fujita, Kaori Oshiro, “A creature called Ranga”, The University of Tokyo Press, June 25, 1989, pp. 101-107 [Patent Document 1]
Japanese Patent No. 2917096 [0006]
[Problems to be solved by the invention]
In order to suppress the generation of algae, it is desirable if both the elution amount of nitrogen and phosphorus from the sediment of the target freshwater area can be reduced, but it is only necessary to reduce the elution amount of either nitrogen or phosphorus. There is. For example, in a freshwater region where the growth limiting factor of algae is nitrogen (a nitrogen-restricted freshwater region), generation of algae can be suppressed if the amount of nitrogen eluted from the sediment can be reduced. On the other hand, in a freshwater region where the growth limiting factor of algae is phosphorus (phosphorus-restricted freshwater region), generation of algae can be suppressed if the amount of phosphorus eluted from the sediment can be reduced. In other words, depending on whether the freshwater region is nitrogen-limited or phosphorus-limited, the amount of nitrogen or phosphorus eluted from the sediment can be selectively reduced to effectively suppress the occurrence of algae. it can.
[0007]
Therefore, an object of the present invention is to develop a method that can selectively reduce the amount of nitrogen or phosphorus eluted from the sediment in a freshwater region, and to provide a method that can efficiently suppress the occurrence of algae abnormalities. There is to do.
[0008]
[Means for Solving the Problems]
The inventor of the present invention, in the fresh water region, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, dolomite calcined product, etc. so that the pH of the bottom sediment of the region is in the range of 8.5 to 9.3 When the alkaline earth metal compound is added, the amount of nitrogen eluted from the bottom is reduced, and when the alkaline earth metal compound is added so that the pH of the bottom is 9.4 or more, the amount of phosphorus eluted from the bottom is reduced. As a result, the present invention was completed.
[0009]
The present invention has a step of confirming (determining) whether it is a nitrogen-restricted region or a phosphorus-restricted region in advance , and confirming (determining) that it is a nitrogen-restricted region. From the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and dolomite calcined material, so that the pH of the bottom sediment of the region is in the range of 8.5 to 9.3. The present invention provides a method for suppressing the generation of algae in a fresh water region, characterized in that elution of nitrogen from sediment is suppressed by adding a selected alkaline earth metal compound.
The pH of the sediment can be measured by the following method.
Put the bottom mud collected from the sediment in the fresh water area into the jar for measuring BOD (volume: 0.1L) in an amount that makes the dry weight about 1g, and aeration is performed in advance to saturate the dissolved oxygen amount. After that, 0.1 L of water is poured in, the jar is left in a dark place at 25 ° C., and the bottom mud is stirred for 24 hours using a magnetic stirrer, and then the pH of the stirred product is measured.
[0010]
In the above-described method for suppressing the generation of algae, the nitrogen-limited freshwater region means a freshwater region in which the growth-limiting factor for algae (particularly blue-green algae) is nitrogen.
Algae generation in test water prepared based on the ratio of nitrogen concentration and phosphorus concentration of water in the region or by adding a nitrogen-containing compound to water in the region, for example, is a nitrogen-limited freshwater region Can be determined based on quantity.
[0011]
The present invention also provides for the freshwater areas of suppressing target generation of algae, step confirms whether the phosphorus restriction area or a previously nitrogen-restricted area (determined) and previously confirmed that phosphorus restricted area (determined, The alkali selected from the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and dolomite calcined product so that the pH of the sediment in the fresh water region is 9.4 or higher. There is also a method for suppressing the generation of algae in a fresh water region characterized by suppressing the elution of phosphorus from sediment by adding an earth metal compound.
[0012]
In the above-described method for suppressing the generation of algae, the phosphorus-restricted freshwater region means a freshwater region in which the growth-limiting factor for algae (especially blue sea bream) is phosphorus.
A phosphorus-restricted freshwater region can be generated, for example, by the generation of algae in test water prepared based on the ratio of the nitrogen concentration and phosphorus concentration of the water in the region or by adding a phosphorus-containing compound to the water in the region. Can be determined based on quantity.
[0013]
The present invention further provides magnesium oxide, magnesium hydroxide, calcium oxide in a fresh water region that has been previously determined to be nitrogen-limited so that the pH of the sediment in the region is in the range of 8.5 to 9.3. There is also a method for suppressing elution of nitrogen from the sediment in the freshwater region, which comprises adding an alkaline earth metal compound selected from the group consisting of calcium hydroxide and calcined dolomite.
[0014]
The present invention further provides magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, in a fresh water region that has been previously determined to be phosphorus-limited, so that the pH of the sediment in the region is 9.4 or higher. And an alkaline earth metal compound selected from the group consisting of calcined dolomite and a method for suppressing elution of phosphorus from the sediment in the freshwater region.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, there is no particular limitation on the fresh water region that suppresses the generation of algae (especially blue sea bream). Examples include closed freshwater areas such as dam lakes, lakes or pools.
[0016]
In the present invention, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and dolomite calcined material are used as the alkaline earth metal compound. These can be used alone or in combination of two or more. Among these alkaline earth metal compounds, magnesium compounds such as magnesium oxide, magnesium hydroxide, and calcined dolomite are preferable, and magnesium hydroxide is particularly preferable.
[0017]
As magnesium oxide, what was obtained by baking magnesium hydroxide obtained from magnesite (rhizobite), brucite (water talc), or seawater can be used. As magnesium hydroxide, those obtained by hydrating the above magnesium oxide, those obtained from brucite (water talc), or seawater can be used. As calcium oxide (quick lime), what was obtained by baking calcium carbonate (lime) by a known method can be used. As calcium hydroxide (slaked lime), what was obtained by hydrating (digesting) calcium oxide by a known method can be used. As the dolomite calcined product, a product obtained by firing (calcining) natural dolomite at a temperature of 700 to 1200 ° C. can be used.
[0018]
When suppressing the generation of algae using the method of the present invention, it is first necessary to determine whether the growth limiting factor of the algae in the target freshwater region is nitrogen or phosphorus. .
[0019]
Algae growth limiting factors are measured, for example, by measuring the nitrogen concentration (also referred to as total nitrogen concentration or TN) and phosphorus concentration (also referred to as total phosphorus concentration or TP) in the target region, It can be determined by calculating the ratio (TN / TP). Usually, when TN / TP is 10 or less, the growth limiting factor is nitrogen, and when TN / TP is 17 or more, the growth limiting factor is phosphorus.
[0020]
Algae growth limiting factors are also algae in test water prepared by separately adding a nitrogen-containing compound (for example, sodium nitrate) and a phosphorus-containing compound (for example, dipotassium hydrogen phosphate) to the water in the target area. Can also be determined by comparing the generation amount (this method is generally called the AGP method). In this method, the growth limiting factor is nitrogen when the amount of algae generated in the test water to which the nitrogen-containing compound is added is large, and the growth is restricted when the amount of algae generated in the test water to which the phosphorus-containing compound is added is large. The factor is phosphorus.
[0021]
When it is determined that the growth limiting factor of algae is nitrogen, the pH of the sediment in the target region is in the range of 8.5 to 9.3 (preferably, the range of 8.8 to 9.2). The alkaline earth metal compound is added to the target area. On the other hand, when it is determined that the algal growth limiting factor is phosphorus, the alkaline earth metal compound is adjusted so that the pH of the sediment in the target region is 9.4 or higher (preferably 9.4 to 10). To the target area. There is no restriction | limiting in particular in the addition method of an alkaline-earth metal compound. For example, a solid (powder, granule, or lump) alkaline earth metal compound may be sprayed on the surface of the target area, or a solid alkaline earth metal compound suspension may be applied to the surface of the target area. Or you may inject | pour into the vicinity. Or you may inject | pour the aqueous solution of an alkaline-earth metal compound into the bottom sediment of an object area | region.
[0022]
The amount of the alkaline earth metal compound added to bring the pH of the bottom sediment to a desired range tends to vary depending on the water quality of the target region. For this reason, it is preferable to add the alkaline earth metal compound in parallel with the measurement of the pH of the sediment in the fresh water region.
[0023]
The adjustment of the pH of the sediment by adding an alkaline earth metal compound is preferably performed in a season in which algae grows actively (May to October, particularly July to September), and the algae grows actively. It is more preferable to carry out from before the season (particularly one month or more before). The bottom pH may be adjusted over the course of the year.
[0024]
【Example】
Hereinafter, the present invention will be described with reference to examples.
In this example, the following test bottom mud and test lake water were used.
(1) Test bottom mud The bottom mud sampled from the Shinkawa river in the Kasumigaura basin using an Ekman purge mud collector was used.
(2) The lake water including the blue seawater sampled from the test lake water Yukiyuki lake was used. The pH of the test lake water was 7.3, the dissolved nitrogen concentration (DTN) was 0.588 mg / L, the dissolved phosphorus concentration (DTP) was 0.05 mg / L, and the amount of water was 100 mg / L as SS. Moreover, it was confirmed that Microcytis aeruginosa predominates in the test lake water.
[0025]
[Example 1]
Place the test bottom mud in an amount of about 1 g in dry weight (volume: 0.1 L) for BOD measurement, aerate in advance to saturate the dissolved oxygen amount, then test lake water 0. 1 L was injected. Thereafter, magnesium hydroxide powder was added in an amount of 0 to 700 mg per 1 g of dry weight of the test bottom mud. Then, on standing incubator bottle dark at 25 ° C., and the test mud was stirred for 24 hours using a magnetic stirrer. After the stirring, the pH, DTN (mg / L), and DTP (mg / L) of the stirred product were measured.
[0026]
From the measured values of DTN and DTP, the nitrogen elution amount and phosphorus elution amount per 1 g of dry weight of the bottom mud were calculated by the following formulas (1) and (2).
(1) Nitrogen elution amount (mg / g · 24 hours) = {DTN measured value (mg / L) −0.588 (mg / L)} × 0.1 (L) / dry weight of test bottom mud ( g)
(2) Phosphorus elution amount (mg / g · 24 hours) = {DTP measurement value (mg / L) −0.05 (mg / L) × 0.1 (L) / dry weight of test bottom mud (g )
[0027]
FIG. 1 shows the relationship between the amount of magnesium hydroxide powder added and the pH of the stirred product , and FIG. 2 shows the relationship between the pH of the stirred product and the amount of nitrogen and phosphorus eluted from the bottom mud. In FIG. 2, the horizontal axis represents the pH of the agitated material .
As shown in FIG. 2, in the region where the pH is 8.5 to 9.3, the nitrogen elution amount from the bottom mud is reduced, and in the region where the pH is 9.4 or more, the phosphorus elution amount from the bottom mud. It can be seen that is reduced.
[0028]
【The invention's effect】
By using the method for suppressing the generation of algae according to the present invention, it is possible to efficiently suppress the occurrence of abnormal algae in the fresh water region.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the amount of magnesium hydroxide powder added and the pH of a stirred product measured in Example 1. FIG.
FIG. 2 is a graph showing the relationship between the pH of the stirred product , the amount of nitrogen eluted from the bottom mud, and the amount of phosphorus eluted as measured in Example 1.

Claims (4)

A step of confirming whether the freshwater region is a nitrogen-restricted region or a phosphorus-restricted region in advance , and a freshwater region previously confirmed to be a nitrogen-restricted region is added to the bottom of the region. An alkaline earth metal compound selected from the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and dolomite calcined material is added so that the pH of the quality is in the range of 8.5 to 9.3 A method for suppressing the generation of algae in a fresh water region, characterized in that elution of nitrogen from sediment is suppressed. A step of confirming whether the freshwater region is a nitrogen-restricted region or a phosphorus-restricted region in advance, and a freshwater region previously confirmed to be a phosphorus-restricted region is added to the bottom of the region. By adding an alkaline earth metal compound selected from the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, and dolomite calcined product so that the pH of the quality becomes 9.4 or more A method for suppressing the generation of algae in a fresh water region, characterized by suppressing elution of phosphorus from the water. The method for suppressing the generation of algae according to claim 1 or 2, wherein the alkaline earth metal compound is magnesium hydroxide. The method for suppressing the generation of algae according to claim 1 or 2, wherein the addition of the alkaline earth metal compound is performed in parallel with the measurement of the pH of the sediment in the fresh water region.

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