JPH06347194A - Bivalvia exterminating method for cooling water system - Google Patents

Abstract

PURPOSE:To efficiently and certainly prevent a trouble caused by attachment of bivalvia, by a method wherein hydrogen peroxide is dosed into a cooling water system for a specified period of time so that hydrogen peroxide in the cooling water reaches a specified concentration and attached organisms, i.e., young bivalves attaching themselves to pipings, heat exchangers and others, are exterminated. CONSTITUTION:Bivalvia includes blue mussels, green mussels, zebra mussels, etc., for example, which breed and grow in water and attach themselves to walls of piping, heat exchangers, etc., with their byssuses. Objective organisms for extermination are young ones among those bivalves, which have shell lengths smaller than 0.3-5mm. Byssuses of young bivalvia can be broken by dosing hydrogen peroxide into cooling water for 0.5-24 hours, preferably 0.5-12 hours, so that the concentration of hydrogen peroxide in the cooling water reaches 0.5-2%, preferably 0.1-1%. Thereby, consumption of hydrogen peroxide can be reduced because dosage of hydrogen peroxide that does not cause environmental problems is carried out only when attachment of young bivalvia occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exterminating bivalves of attached organisms in a cooling water system. More specifically, bivalve molluscs are exterminated without killing the bivalves of seawater-adhering organisms attached to the cooling water system, especially pipes using seawater as cooling water, heat exchangers, etc. It relates to a method of preventing a disorder caused by a kind.

[0002]

2. Description of the Related Art In a thermal power plant, an oil refinery, or the like that uses seawater, seawater-adhering organisms such as mussels, barnacles, worms, bryozoans, and the like adhere to the cooling water system to deteriorate its function. Among them, bivalves such as mussels have a high growth rate, and when they become adult oysters, they impede the passage of water to the water supply and cause turbulence, which causes erosion corrosion of the heat exchanger tubes.

Further, there is a problem that a large amount of bivalve molluscs account for a large amount of wastes generated during regular repairs, which makes it difficult to dispose of them. Therefore, conventionally, in order to prevent the adhesion of organisms adhering to seawater, chlorine-based agents such as sodium hypochlorite, electrolytic chlorine, tri-n-butyltin, chlorides, oxides and hydroxides of tri-n-phenyltin. Organic tin compounds and the like have been used.
However, the injection of the chlorine agent is feared that halomethane may be generated or dioxin may be generated in some cases, and the organotin compound has residual toxicity and accumulation toxicity, which is not preferable from the viewpoint of environmental pollution prevention.

Further, as a method for removing the attached seawater organisms, a method of periodically stopping the operation to open the apparatus and mechanically removing it, or a method of killing and removing the attached organisms by a temperature rising treatment It has been known. However, the above-mentioned treatment method has a drawback in that the work is complicated, and in the treatment method described later, the fallen shellfish blocks the strainer and the heat exchanger.

On the other hand, the inventors of the present invention have previously proposed a method for suppressing the adhesion of organisms adhering to seawater by adding hydrogen peroxide, which has no concern about residual toxicity or accumulation toxicity (Japanese Patent Laid-Open No. 54-16).
1592 and JP-A-59-98791). These proposals improve the ecology by adding low-concentration hydrogen peroxide continuously or intermittently (several hours a day) in the larval stage until the attached organisms such as bivalves attach to the vessel wall. It is carried out for the purpose of preventing the adhesion of the epidemic larvae to the substrate.

[0006]

[Problems to be Solved by the Invention] The methods for preventing damage to seawater animals by ordinary drugs include (1) preventing adhesion of epiphytic larvae to the substrate, (2) exterminating seawater animals once attached. Is mentioned.

For example, a highly toxic drug such as an organotin compound can kill seawater animals by adding it at a low concentration, so that it is possible to simultaneously perform the above (1) and (2). However, the hydrogen peroxide proposed above is uneconomical because a considerably high concentration of hydrogen peroxide is required to kill the bivalves attached to the substrate. In order to solve this problem, proposals have been made as shown in the above-mentioned JP-A-54-161592 and JP-A-59-98791.

It is economically preferable to carry out such a treatment only when the bivalve molluscs which become obstacles are attached. However, it is difficult to predict the occurrence and adhesion of bivalve molluscs, and since the bivalve molluscs that have once adhered cannot be exterminated, hydrogen peroxide is continuously added throughout the year regardless of the time of adhesion of the bivalve molluscs. The problem was that it should not be combined.

Therefore, it has been desired to reduce the amount of seawater used, especially in a cooling water system with a large amount of seawater. In addition, it is not rare that hydrogen peroxide injection is stopped due to a malfunction of the chemical injection pump and the bivalves attach to cause troubles. This invention
The object of the present invention is to provide a method for efficiently and surely preventing adhesion damage due to bivalves by using hydrogen peroxide.

The inventors of the present invention have conducted experiments and studies on the biology of bivalves such as mussels and the efficacy of hydrogen peroxide, and as a result, have obtained the following findings. That is,
Bivalves such as mussels release eggs and sperm into seawater and fertilize in seawater. After fertilization, the development progresses to morula and sacula embryos, resulting in floating larvae called tocorosphere larvae.
After passing the Verijer larva, it becomes a D-type larva and has a shape like a bivalve. When the shell length is 0.2 mm or more, the ascidian begins to develop and the larvae attach to the base and become juveniles. The life history is repeated as young and mature shells with a shell length of 5 mm to several cm or more grow. According to the knowledge of the inventors, even if a high-concentration (1-2%) hydrogen peroxide seawater solution is added to a bivalve that has become a juvenile shell or an adult shellfish for several hours, the shell will be closed and the foot thread will be strong, so it will be a base material. It is possible to survive for a long time without deviating from the above, but at the stage of juveniles with shell lengths of 0.3 to less than 3 mm, a low concentration (0.1%) of hydrogen peroxide seawater solution is added, which is about 1/10 of that. By doing so, the present inventors have found that the byssus is cut off or falls off without enduring adhesion, and it becomes impossible to take another adhesion behavior. The present invention was completed by further researching and confirming these facts.

[0011]

Thus, according to the present invention, hydrogen peroxide is added to the cooling water system so as to have a concentration of 0.05 to 2% for 0.5 to 24 hours to be used for piping, heat exchangers and the like. Disclosed is a method for controlling bivalve molluscs in a cooling water system, which is characterized in that juvenile bivalve molluscs of adherent organisms are controlled.

Examples of the bivalve molluscs in the present invention include those occurring in seawater and fresh water, and among them, seawater bivalves are preferable. Examples of bivalves include mussels that develop and grow in water, such as mussels, green mussels, and zebra mussels that attach to the vessel walls such as pipes and heat exchangers with ascidian thread. Of these, juveniles have a shell length of 0.3 to less than 5 mm.

Even when the present invention is carried out on juvenile shells or adult shellfish having a shell length of 5 mm or more, the foot thread is not cut and cannot be removed from the substrate, which is not preferable. As the hydrogen peroxide used in the present invention, those having a commercially available concentration are preferably used. Furthermore, compounds that generate hydrogen peroxide in water, such as those generated by electrolysis, inorganic peracids such as percarbonate and perboric acid, or salts thereof or peroxidation adducts of urea, may be used. .

The extermination method of the present invention is carried out by adding a hydrogen peroxide solution having a concentration capable of cutting the byssus of a bivalve juvenile by adding it for a certain period of time. The conditions change slightly depending on the water temperature,
Hydrogen peroxide in water is 0.05 to 2% concentration, preferably 0.1 to
0.5 to 24 hours, preferably 0.5 to give a 1% concentration
By adding for ~ 12 hours, the foot thread of juvenile bivalves can be cut.

If the addition time is less than 0.5 hours, a high concentration of hydrogen peroxide is required to cut the byssus of the bivalve juvenile, which is not preferable. Further, even if the time exceeds 24 hours, it is not preferable because the concentration sufficient to cut the sock of the bivalve juveniles cannot be further reduced. In the present invention, it is possible to carry out by appropriately combining the conditions within the range of the concentration and the addition time, but if the addition time is short, the hydrogen peroxide concentration becomes high, and if the addition time is long, the hydrogen peroxide concentration becomes high. Tends to be lower.

For example, if the concentration is less than 0.05 to 0.5%, it is 5 to 24%.
When the time is 0.5 to 2%, the treatment is preferably performed in the range of 0.5 to 5 hours. As the method for adding the bivalve juveniles and hydrogen peroxide, there are a method of adding hydrogen peroxide to water and a method of adding the hydrogen peroxide in a stationary state in which the water flow of the cooling water system is cut off. The method of adding in the state is preferable because the amount of hydrogen peroxide used is further reduced.

As a concrete method of adding hydrogen peroxide in a stationary state, for example, before stopping the heat exchanger, the water supply line, etc., an aqueous hydrogen peroxide solution is prepared by a chemical injection pump proportional to the water supply flow rate. Is injected using a diffusion pipe that can be mixed in a short time, and when the hydrogen peroxide concentration at the outlet of the heat exchanger or water supply line exceeds the specified concentration, the water supply and the chemical injection pump are stopped and the inside of the heat exchanger is stopped. And a method in which the inside of the water supply pipe is kept full of water, or a method in which the cooling water is replaced by a separately prepared aqueous hydrogen peroxide solution or seawater solution and held.

The extermination method of the present invention is preferably carried out before the attached juveniles reach the juveniles. By installing a bypass channel from the cooling water system and installing a monitor column and a biological survey plate in the column, it is possible to easily know the growth stage of bivalves attached to the wall of heat exchangers, water supply lines, etc. This is preferable in that it is possible to accurately grasp the implementation timing of the present invention.

The monitor column has, for example, an inner diameter
It is possible to use those made of acrylic resin, vinyl chloride resin or the like having a length of 30 to 100 mm and a length of 10 to 100 mm. For observation, it is preferable to use a transparent column. However, it is preferable to perform in a state in which the light source such as sunlight is blocked except at the time of observation in accordance with the actual conditions of the site. The flow rate of water in the monitor column is usually
It is preferable to pass water at 0.1 to 2 m / sec.

Further, the biological attachment plate is, for example, 5 m
Examples include those that have created a m-shaped Cremona net in a cylindrical shape,
Such an attachment plate can be attached by means such as insertion into the inner wall of the monitor column. In addition, it is preferable to remove the fallen juveniles outside the system in order to clean the inside of the system.

It is preferable that the extermination method of the present invention is repeatedly carried out after the fallen juveniles have been removed to the outside of the system, and before the adhering juveniles reach the juveniles, the influence of the season and water temperature is also exerted. However, it is recommended to repeat once every 1 to 3 weeks when the bivalves attach.

[0022]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 A water flow test was conducted in the spring, which is the period when mussels adhere, using a temporary model water channel installed on the quay in the coastal area.
The seawater flow rate in each channel was 10 m ³ / hr and the average flow velocity was 0.3 m / s.

[0024] In the waterway, a fishing net lap net (100 cm ² ) was immersed for the measurement of adhered mussels, and the number of adhered mussels,
The average shell length was investigated. When the test canal was operated without treatment, the shell length was 0.5 mm, which was visible to the naked eye after about 7 days.
Some mussels attached. When it was left to stand, it grew to a maximum shell length of 2 mm and an average shell length of about 1.5 mm after about 25 days.

At this point, a predetermined amount of hydrogen peroxide was injected into the water inlet of each water channel by a pump for a predetermined time. 24 after infusion
The adhesion situation of mussels was investigated over time. The results are shown in Table 1. The number of deposits is the result of conversion per 1 m ² .

[0026]

[Table 1]

Example 2 Seawater in Tokyo Bay was pumped up during the breeding period of mussels, and water was passed through the four test channels made of acrylic test pipes having an inner diameter of 30 mm and a length of 60 cm for 3 months. (Water flow rate 0.7 m ³ / hour).

The seawater temperature during the passage of water was between 10 and 20 ° C. In one of the routes (hereinafter referred to as route A), the passage of water is blocked, the seawater in the waterway is replaced with a seawater solution containing 0.35% hydrogen peroxide, and the water is held for 2 hours, and then the seawater is reused. The operation of temporarily passing water was performed once every two weeks. Similarly, in the other route (hereinafter referred to as route B), the passage of water is interrupted, the seawater in the waterway is replaced with a seawater solution containing 0.1% hydrogen peroxide, and the water is held for 12 hours, and then again. The operation of temporarily passing water was carried out once every two weeks.

Another route (hereinafter referred to as route C)
Replaced the test pipe every two weeks and passed seawater for 3 months. The remaining one route was continuously supplied with seawater as a control for 3 months. After the test was completed, the deposits on the test tube pipe were peeled off, and the attached organisms were observed and measured.

However, for the C route, the same observation and measurement were performed for the test pipes replaced every two weeks. As a result, 170 to 10200 juveniles having a shell length of 0.3 to 1 mm / m ^{2 were} attached to the C-path test pipes that were replaced every two weeks. 35,000 pieces / m ² of juvenile mussels and juveniles (shell length of about 1 to 15 mm) were attached to the control area.
No attachment of mussels was observed in the A route.
Similar results were obtained in the B route, and it is considered that the mussels were completely removed during the juvenile season.

[0031]

EFFECTS OF THE INVENTION According to the present invention, hydrogen peroxide, which does not cause environmental problems, can be used only when the bivalve molluscs are attached, so that the amount of hydrogen peroxide used can be reduced. Have an effect.

Front Page Continuation (72) Inventor Toru Tainaga 2-10-15 Higashi-Awaji, Higashiyodogawa-ku, Osaka City Katayama Chemical Industry Research Institute Co., Ltd. (72) Keiji Fujiwara 2-10-10 Higashi-awaji, Higashiyodogawa-ku, Osaka No. 15 Incorporated company Katayama Chemical Industry Research Institute (72) Inventor Takayuki Dono 2-10-15 Higashi-Awaji, Higashiyodogawa-ku, Osaka City Incorporated Company Katayama Chemical Industry Research Institute (72) Tomohiko Matsumoto East, Higashiyodogawa-ku, Osaka City 2-10-15 Awaji Co., Ltd. Inside the Katayama Chemical Research Institute

Claims (5)

[Claims] 1. Disinfecting bivalve juveniles of adhering organisms adhering to pipes, heat exchangers, etc. by adding hydrogen peroxide to the cooling water system at a concentration of 0.05 to 2% for 0.5 to 24 hours. And a method for controlling bivalves in a cooling water system. 2. The extermination method according to claim 1, wherein the hydrogen peroxide is added in a stationary state in which the passage of seawater to the cooling water system is blocked. 3. The extermination method according to claim 1 or 2, which is carried out before the bivalve molluscs reach the juvenile shells. 4. A bypass water channel is installed by a cooling water system,
The extermination method according to claim 3, wherein a monitor column equipped with a biological survey plate is attached in the water channel, and hydrogen peroxide is added based on the observation result. 5. The extermination method according to claim 1, wherein the exterminated bivalve juveniles are removed outside the cooling water system.