JPH0437041B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for inhibiting the proliferation of microorganisms.
More specifically, the present invention relates to a method for inhibiting microorganisms in cooling water, which is characterized by maintaining the hydrazine concentration in open circulation cooling water at 0.1 to 20 ppm. In recent years, with the development of the chemical industry and other industries, large amounts of industrial water have become necessary. In addition to industrial tap water, seawater, lake water, river water, and groundwater are used as sources of industrial water. Various types of microorganisms are always growing in these industrial waters, and depending on the water quality and environment in which they exist, many of these microorganisms can continue to proliferate and cause various problems. For example, when water is used for cooling purposes, microorganisms living in the water proliferate and grow on the walls of water facilities, forming slime, resulting in problems such as a decrease in heat exchange efficiency and poor water flow. occurs. In particular, in the case of open-type water circulation using an open-type cooling tower, etc., the circulating water is forcibly aerated in a part of the system and comes into contact with the air, and is exposed to sunlight. The growth of aerobic microorganisms such as bacteria and algae is encouraged. Similar problems are also occurring in air conditioning systems in buildings and factories, and cooling water systems installed with small cooling towers in heating and cooling facilities. In order to prevent slime damage caused by microorganisms that have grown and multiplied in these open circulation cooling water systems, chlorine or chlorine-based organic compounds, chlorine-based inorganic compounds, quaternary ammonium salts,
Bactericidal and/or antibacterial agents such as cyanide have been used, respectively. However, these chemicals are a source of wastewater pollution, some are not practical, or they have problems such as being highly toxic to living things such as humans, livestock, and fish, and being highly corrosive to equipment materials. The development of anti-pollution agents is desired. The present inventors have traditionally focused on hydrazine as such a drug. Hydrazine itself is less toxic than conventional slime treatment agents, and has the advantage of decomposing into non-toxic water and nitrogen gas. Hydrazine is known to be an effective slime treatment agent as described in Japanese Patent Publication No. 53-17649, but in this case, hydrazine in a concentration of 20 ppm or more is generally added to open circulation cooling water. It has been said that it is preferable to treat it, and in fact, a method has been adopted in which treatment is performed by shockingly adding it to cooling water at such a concentration once every few days. However, in systems where the concentration of microbial nutrients in the cooling water is high and slime damage is significant, and in recent years due to the highly concentrated operation of circulating cooling water systems, the accumulation of microbial nutrients has made the slime damage even more severe. It has become clear that the impact of adding hydrazine is less effective. For example, even if a large amount of hydrazine (approximately 100 ppm) is shockingly added once every few days to the above-mentioned system, it will simply become economically expensive, and it will also cause fish poisoning and PH after drainage. It is not only recognized that there is a risk of an increase in the rate of increase, but also that it is often ineffective. The inventors of the present invention have conducted intensive studies to improve methods for controlling slime using hydrazine, and have unexpectedly found that the concentration of hydrazine in cooling water can be reduced.
It has been found that it is extremely effective to continuously feed hydrazine into the cooling water to maintain the concentration at a low concentration of 20 ppm or less. By the way, as a method of adding a slime control agent to a water system, an intermittent impact injection method is generally adopted as described above. This is because when drugs are administered continuously, phenomena such as the acquisition of chemical resistance and the appearance of replacement bacteria occur, so countermeasures such as increasing the concentration of the drug added or adding several drugs alternately are necessary. This is to avoid it becoming necessary and eventually becoming ineffective. In typical slime control agents that have been used in the past, continuous addition of chlorine-based chemicals is effective, but there is a problem that chemical resistance tends to occur, so an impact addition method is generally used. On the other hand, quaternary ammonium salts exhibit bactericidal properties at relatively high concentrations of, for example, 10 ppm or more, but are extremely ineffective at low concentrations of several ppm. For this reason, continuous addition at low concentrations has little effect, and shock administration at relatively high concentrations is generally used. On the other hand, hydrazine, as mentioned above,
It is effective in controlling slime when it is added continuously to maintain the hydrazine concentration in the cooling water at a low concentration. Although the bactericidal and antibacterial activity of hydrazine against slime-originating microorganisms is weak below 20 ppm, it is extremely surprising that its constant action at such low concentrations is effective in controlling slime. The slime control effect of hydrazine according to the method of the present invention is that hydrazine at a low concentration for a long period of time acts on microorganisms in the water, causing them to lose their slime-forming ability. This seems to be due to the fact that the viscosity is destroyed and the dispersion disappears. The hydrazine used in the present invention includes not only hydrated hydrazine at various aqueous solution concentrations but also various hydrazine salts that can make hydrazine (N ₂ H ₄ ) present in the water used, such as hydrazine sulfate, hydrazine hydrochloride, and other soluble salts. can be used, but hydrazine hydrazine is usually used. In the method of the present invention, the amount of hydrazine added varies depending on the degree of contamination of the cooling water system, but is generally an amount such that the concentration of hydrazine (as N ₂ H ₄ ) retained in the cooling water is 0.1 to 20 ppm, and is preferably an amount. 1
~10ppm. Furthermore, as for the method of adding to the cooling water, it is desirable to add it continuously so that the above concentration is constantly maintained, but the method of the present invention also has the effect of dispersing and removing slime that has once formed and adhered. Therefore, the injection (addition) may generally be stopped within the range where the above concentration can be maintained. As described above, we have discovered that hydrazine is extremely effective in controlling slime through its continuous action at low concentrations, and we have developed a method for treating slime problems in conventional open circulation cooling water systems, as well as ways to eliminate various problems. It has become possible to dramatically improve the processing method. The present invention will be explained in more detail below with reference to Examples. Example 1 A 5 cm square piece of wood was immersed and fixed in a beaker filled with industrial water from step 1, and a slime mainly consisting of zooglare collected from a cooling tower at the site (factory) was added to it so that the slime concentration was a certain amount. In addition, the slime adhesion prevention effect of hydrazine in the method of the present invention was tested. The test was conducted over 14 days, and industrial water with slime added to the same concentration as in the beaker was continuously supplied and blown, and the residence time in the beaker was set for 12 hours. Hydrazine should be added from the start of the test; if it is to be added by shock, it should be administered all at once into a beaker; if it should be added continuously, after adjusting the hydrazine in the beaker to a predetermined concentration, it should be added continuously to maintain that concentration. supplied. The hydrazine used was 50% hydrated hydrazine (N ₂ H ₄ .H ₂ O), and the industrial water in the beaker was stirred at 500 rpm with a magnetic stirrer and aerated to maintain dissolved oxygen at supersaturation.

[Table] Example 2 The slime removal effect of hydrazine by the method of the present invention was tested in the same manner as in Example 1. In this example, after the slime had been attached to the wood piece for 7 days, the addition of the chemicals was started, and then the test was conducted for 14 days using only industrial water that did not contain slime as the supplied water. The implementation results are shown in Table 2.

[Table] Example 3 Retained water volume 15m ³ , Circulating water volume 110m ³ /hr, Concentration multiple
In the open circulation cooling water system of the chemical factory in 1.5, organic matter was mixed into the system from the equipment, causing a significant slime problem. In such a system, the effect of treating hydrazine according to the method of the present invention was tested. The hydrazine used was 50% hydrated hydrazine, and each test period was 21 days. The implementation results are shown in Table 3.

【table】

[Table] Example 4 Retained water volume 120m ³ , Circulating water volume 600m ³ /hr, Concentration factor
In the open circulation cooling water system of the 2.5 machine shop, the blow water flows directly into the fish pond, making it difficult to treat it with general slime treatment agents or the impact addition of hydrazine. Therefore, we attempted a treatment using continuous injection of trace concentrations of hydrazine. As a result, by continuously adding 50% hydrated hydrazine at 8 to 12 ppm (2.6 to 3.8 ppm as N ₂ H ₄ ), the algae and slime that had previously adhered to the water tank of the cooling water system were eliminated. Almost all of the dispersion disappeared after about two weeks, and no outbreak was observed thereafter. Also, no effects on fish were observed.

Claims (1)

[Claims] 1 Continuously supply hydrazine to the open circulation type cooling water to keep the hydrazine concentration in the cooling water from 0.1 to
A method for inhibiting the proliferation of microorganisms, characterized by maintaining the concentration at 20 ppm.