JPH04141285A - Prevention and elimination of oxygen-poor water mass by lime material - Google Patents

Abstract

PURPOSE:To control the oxygen consumption and prevent the occurrence of an oxygen-poor water mass by dispersing the lime material capable of existing in water as calcium hydroxide or magnesium hydroxide uniformly in a predetermined water area. CONSTITUTION:The lime material capable of existing in water mainly as calcium hydroxide or magnesium hydroxide is dispersed uniformly in the water areas. A mere periodic dispersion of the lime material in the water areas controls the oxygen consumption, prevents the occurrence of oxygen-poor water mass and improves and eliminates the oxygen-proof water mass occurred. A uniform dispersion of the lime material produces a difficulty soluble film consisting of calcium hydroxide and calcium carbonate in a fresh water area, a difficulty soluble film consisting of calcium hydroxide, calcium carbonate and magnesium hydroxide in a sea area and both of the aforesaid films in a brackish water area. The film formed on the bottom sediment cuts off the communication of the water with the bottom sediment, thereby preventing the oxygen in the water from passing into the bottom sediment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing and eliminating the occurrence of oxygen-poor water bodies in freshwater, seawater, or brackish water.

[Prior Art] In recent years, it is said that water and bottom sediment pollution has been increasing in many bays, rivers, and lakes across the country.

In other words, as the eutrophication of water bodies progresses, there are associated phenomena such as the occurrence of red tides, the occurrence of oxygen-poor water masses, and the occurrence of blue tides.
There has been significant damage and impact on fisheries and the living environment.

These substances are not utilized by living things, and organic matter and nutrients from industrial wastewater, gray water, livestock wastewater, etc. flow in at a rate exceeding the natural circulation purification ability, and as a result, they are deposited on the seabed, riverbeds, and lakebeds. It is thought that this phenomenon occurs due to the combination of weather and sea conditions.

Bays and lakes, which have a rich natural circulation purification ability, have had a low inflow of organic matter and nutrients (mainly phosphorus (P) and nitrogen (N)) for many years, and they are also deposited in the bottom sediment as sludge. In addition, because water is exchanged sufficiently, the water clarity is extremely clear.

On the other hand, in bays and lakes that have become more polluted than their natural circulation capacity, a large amount of organic matter and nutrients (P, N) have been flowing in for many years, and these are deposited thickly on the bottom as a waste.
Water exchange is also insufficient, and the water clarity has decreased, making it cloudy.

Therefore, in order to improve highly polluted bays and lakes, it is necessary to
In addition to reducing the inflow of organic matter and nutrients (P, N) from the land through total volume control and sewerage development, we have not only reduced the amount of organic matter and nutrients (P, N) that have accumulated up until then: I? It has come to be considered that improving the bottom sediment of sludge and reducing pollution caused by the elution of pollutants from the bottom sediment is a fairly effective means. To explain the eutrophication of water in more detail, when the influx of organic matter and nutrients increases, nutrients such as salts from the sludge deposited on the bottom sediments are also re-leached into the water, especially in closed areas where there is little inflow and outflow. Bays and lakes begin to exhibit serious eutrophication phenomena.

In other words, when there are too many nutrients, etc. in the water, combined with weather conditions, this causes the abnormal growth and proliferation of algae, and when a red tide occurs, it directly clogs the gills of fish, making it impossible for them to breathe, resulting in mass death of fish. Leads to. In addition, the abnormally large amount of frankton, including this red tide, results in the death of a large number of plankton, whose carcasses and organic matter are deposited on the bottom sediment, and are decomposed by bacteria, resulting in BO
An increase in D, i.e., (8) existing oxygen in the water is consumed, and an oxygen-poor water mass is formed. Sulfate-reducing bacteria proliferate near the sludge surface, take in sulfate ions through respiration, reduce them in the body, and release highly poisonous hydrogen sulfide.The scale of this hydrogen sulfide develops to a certain extent, and depending on weather conditions, etc. When external energy is applied, the oxygen-deficient, hydrogen sulfide water mass at the bottom rises to the surface.This is commonly known as ``takashu'', and fish and shellfish are instantly destroyed. It is something that kills.

In this way, phenomena such as red tide and water pollution that accompany eutrophication of water quality, and the damage caused by them, are closely related to the deterioration of the bottom sediment.

On the other hand, as measures to improve the bottom sediment, the following methods have been proposed: ■ dredging, ■ deep water layer aeration, ■ covering the bottom sediment, and ■ drastic methods.

■ Since the dredged sediment itself is removed and recovered, it tends to be seen as highly effective, but the construction costs are high, the recovery process requires toro processing, and the dredging process involves the scattering of the sediment during dredging. This method is not necessarily foolproof, as there is the possibility of secondary contamination during work. Furthermore, if sludge accumulates again, even if it is only a few meters, the effect of dredging will be lost, so care must be taken.

■ Deep water layer aeration This is effective in making deep water areas such as lakes and marshes aerobic and preventing the elution of phosphorus from the bottom sediments, and does not require sludge treatment and is inexpensive. However, this method has the disadvantage that low layer water and surface layer water are mixed during the stratified period such as summer, which deteriorates surface layer water quality. There are also restrictions due to location.

■ Covering the sediment The surface of the sediment is coated with sand, fly ash, etc. This also requires a huge amount of expense, but it is effective in blocking the elution of nutrients, etc. from the sediment.

However, there are drawbacks such as a reduction in the effective water storage capacity and a decrease in water depth.

°■ Draining water This method involves draining water, drying the bottom sediment, and replacing it with fresh water, but it is not a method that can be carried out anywhere, for an hour, and is subject to cycle issues, conditions such as location, and fishing conditions. INJ
There are drawbacks that limit it.

[Problems to be solved by the invention] As described above, in waters where eutrophication has progressed, gamma flame water,
In both seawater and brackish water, an increase in oxygen consumption, especially in the summer, creates oxygen-poor water bodies, which causes damage to fisheries, adverse effects on living organisms, and environmental deterioration such as foul odors.

There is still no simple and economical method for preventing or eliminating the occurrence of oxygen-poor water bodies.

Therefore, the present inventors have discovered that if a lime-based material is sprayed in a water body, a coating of calcium hydroxide, calcium carbonate, or magnesium hydroxide will be formed, and that the lime-based material has an effect of suppressing abnormal activity of living organisms. As a result of intensive studies and efforts, we have found that the present invention is effective in preventing and eliminating the occurrence of oxygen-poor water bodies in freshwater, seawater, or brackish waters where eutrophication has progressed, such as lakes, marshes, rivers, etc.

[Means for Solving the Problems] In the method for preventing and eliminating the occurrence of oxygen-poor water bodies in freshwater, seawater, or brackish water using a lime-based material according to the present invention, calcium hydroxide or magnesium hydroxide is used as a main component in water. Possible lime-based materials are uniformly distributed in the water area.

[Function] In the method of preventing and eliminating the occurrence of oxygen-poor water bodies in freshwater, seawater, or brackish water according to the present invention, a lime-based material that can exist as calcium hydroxide or magnesium hydroxide in water as a main component is added to the water body. Since it is distributed evenly, if lime-based materials are regularly sprayed on vehicles in water bodies, it will suppress oxygen consumption and prevent the occurrence of oxygen-deficient water bodies, and also improve the occurrence of oxygen-poor water bodies.・It is a very economical and simple method because it only requires spraying lime-based materials.

When sprayed uniformly over freshwater, seawater, or brackish water, a poorly soluble film consisting of calcium hydroxide and calcium carbonate is formed in freshwater areas, and calcium hydroxide and calcium carbonate are formed in seawater areas.
A sparingly soluble compound consisting of calcium carbonate and magnesium hydroxide? l! In brackish waters, both of the above-mentioned films are formed. These 8m films are alkaline,
It has the following effects.

(1) The film formed on the bottom sediment surface blocks water and bottom sediment,
Prevents oxygen in the water from migrating to the bottom sediment. This suppresses the consumption of oxygen in the water by the sediment and prevents the formation of oxygen-poor water masses.

(2) Lime-based materials inactivate abnormal biological activity in the sediment, and in particular, the loss of biological activity near the sediment surface suppresses oxygen consumption in the water based on the respiration of living organisms, resulting in poor The formation of oxygenated water masses is prevented.

〔Example] Example-1 (Freshwater indoor experiment) (Test sample) Sediment from an urban river and dehydrated cake from a urine treatment plant were used.

After collecting the sample, it was brought back to the laboratory under water cooling and immediately subjected to measurements in its present state.

(Lime spraying) Lime powder (Ca040JCa (ott) 260 zero)
was sprayed at 25 g/112 or 6200 g/2, and the oxygen consumption was measured.

(Method for Measuring Oxygen Consumption) FIG. 1 is an explanatory diagram showing the configuration of a bottom sediment oxygen consumption measuring apparatus. As shown in the figure, reaction a! (1) (Inner capacity 8
25 ml, bottom area 98c+a2) with 2 sediment layers (2)
After filling the bottom sediment to a depth of ~3 cm, the BOD dilution solution (3) was gently filled. 20±0 at constant grinding temperature N(4)
．． 500-600 II/
into reactor H) at a rate of 1 day. Furthermore, reaction 4! F(1
) The amount of dissolved oxygen in the outflow water was continuously monitored by a DO sensor (6) and a DO claw (7).

Note that the oxygen consumption rate was calculated from the amount of dissolved oxygen using the following formula. The amount of dissolved oxygen was measured at the mouth of the vessel.

t=Measurement time interval (1/day) (Test results) The following Table 1 shows the oxygen consumption rate when a predetermined amount of lime was added to urban river sediment and dehydrated urine treatment plant cake.

As shown in Table 1, although the effect of adding lime varied depending on the sample, a significant effect was generally obtained by spraying 100 gem2 or more.

Table 1: Oxygen consumption rate results for samples A and B.
The figure is a diagram showing changes over time in the amount of dissolved oxygen in reaction vessel (1). In the figure, the dotted line indicates the sediment to which lime was applied, and the solid line indicates the sediment to which lime was not applied. ing.

As described above, it was confirmed that spreading lime on the bottom sediment has the effect of suppressing oxygen consumption, and that this suppresses the formation of oxygen-poor water bodies due to increased oxygen consumption.

Example-2 (Seawater tank test) (Test sample) The surface layer of the bottom sediment in the sea area where enrichment is progressing was collected.
It was subjected to the test in its present state. Sediment was added to the tank 20 hours after the seawater official.

(Lime spraying) The test lime was quicklime (CaO97
, 5%), and the spraying rate to the aquarium was 250 g/m2.

(Test method) Set up two aquariums in a laboratory, fill them with seawater and marine sediment,
One of the two tanks was sprayed with lime 24 hours after the sediment was added (hereinafter referred to as the lime-sprayed tank), and the other tank was filled with water N without lime sprayed (hereinafter referred to as the non-lime-sprayed tank).
The pH, temperature, and dissolved oxygen of the aquarium water were periodically measured.

The test tank conditions are as shown in Table 2 below.

(Test Results) FIG. 3 is a diagram showing changes over time in PH, water temperature, and amount of dissolved oxygen in each aquarium. In the figure, ○ indicates a water tank in which lime was sprinkled, and × indicates a water tank in which lime was not sprayed.

As shown in the figure, the dissolved oxygen in the aquarium water is
Regardless of water flow or no water flow, this is higher than in aquariums without lime spraying. This means that by spreading lime on the bottom sediment, dissolved oxygen in seawater is suppressed from being consumed by the bottom sediment. it is conceivable that.

Example 3 (Field experiment in brackish water) Small-scale lime spraying in a river tributary where seawater and freshwater are mixed (approximately 60cm deep, with almost no water flow, and the living fish were crucian carp and mullet) (5m x 15m). Before carrying out the project, we conducted a preliminary inspection of the tributary deposits before lime spraying, conducted a similar inspection after lime spraying, and conducted a comparative study.

(Scattered quicklime) Particle size 1O~30fi11 Spray amount max. 60kg (4
00g/*') (Results) The results are shown in Table 3 below.

As shown in Table 3, dissolved oxygen was three times as high after 4 hours of lime spraying as before spraying, confirming the good oxygen consumption suppressing effect of lime spraying. Moreover, the turbidity was reduced to 1/2 of the sprayed surface after 4 to 5 hours of lime spraying, and no significant increase in pH was observed due to lime spraying due to the buffering effect of various salt concentrations.

(Hereinafter, blank space) [Effects of the Invention As described above, in the present invention, in a method for suppressing oxygen consumption in freshwater, seawater, or brackish water, the main component is calcium hydroxide or magnesium hydroxide present in water. Since the lime-based material is uniformly spread over the water area, simply spraying the lime-based material on the water area on a regular basis will suppress oxygen consumption and prevent the formation of oxygen-poor water bodies.
It also improves and eliminates the oxygen-poor water mass that has occurred, and is a very economical and simple method since it only requires spraying a lime-based material.

Furthermore, in this application, by uniformly spraying over a water area, a hardly soluble film made of calcium hydroxide, calcium carbonate, magnesium hydroxide, etc. is formed, and this film blocks water and sediment, and removes oxygen in the water. It is prevented from migrating to the sediment. This suppresses the consumption of oxygen in the water by the sediment and prevents the formation of oxygen-poor water masses. Furthermore, lime-based materials inactivate abnormal biological activity in the sediment, and in particular, the loss of biological activity near the sediment surface suppresses oxygen consumption in the water based on the respiration of living organisms, resulting in poor water quality. This has the effect of preventing the formation of oxygen water masses.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the configuration of the bottom sediment oxygen consumption measurement device, Figure 2 is a diagram showing the change in dissolved oxygen amount C over time in the reaction tank, and Figure 3 is a diagram showing the pH 1 water temperature and dissolved oxygen in each water type. FIG. 2 is a diagram showing changes in oxygen amount over time. Agent: Patent Attorney Masaru Sato

Claims (1)

[Scope of Claims] A method for suppressing oxygen consumption in freshwater, seawater, or brackish water, comprising uniformly spraying a lime-based material that can exist as calcium hydroxide or magnesium hydroxide in water as a main component in the water. A method for preventing and eliminating the occurrence of oxygen-poor water bodies using lime-based materials.