JP5587453B1 - Microbial composition - Google Patents

Abstract

Disclosed is a composition for microorganisms which is excellent in diffusibility in soil and groundwater without deactivating microorganisms capable of purifying organochlorine compounds in soil and groundwater.
A microbial composition comprising a polyhydric alcohol and a surfactant. The polyhydric alcohol is 62 to 68 parts by weight of one or more sugar alcohols selected from sorbitol, mannitol, and xylitol, and 8 to 10 parts by weight of glycerin, and the surfactant is 1 to 5 parts by weight. The nonionic surfactant is composed of 22 to 25 parts by weight of water.
[Selection figure] None

Description

  The present invention relates to a composition for microorganisms that is injected into soil and groundwater in order to decompose organochlorine compounds in soil and groundwater using microorganisms and purify the soil and groundwater.

  Soil and groundwater contaminated with chemical substances is a problem that breaks the balance of not only human beings but also the entire biological world, and some measures are necessary from the viewpoint of environmental protection. In addition, leaving contaminated soil and groundwater will limit the area of human activity, and measures are also needed from an economic point of view.

  Conventionally, various methods such as a lime method, an iron powder method, a soil excavation and replacement method, a soil moisture cleaning method, and a bioremediation method have been proposed to purify soil and groundwater contaminated with chemical substances. Soil and groundwater contamination is often widespread and methods such as replacing the soil itself are enormous in scale and cost.

  Bioremediation is said to be suitable as one of the methods for economically purifying soil and groundwater in situ without requiring large-scale construction. This is a method of decomposing chemical substances that are pollutants into aerobic or anaerobic microorganisms in soil and groundwater.

  For example, Clostridium microorganisms decompose organic substances into acetic acid and the like in an anaerobic atmosphere. Hydrogen is released during the process. This hydrogen can be replaced with chlorine of organic chlorine compounds such as chloroform, dichloromethane, dichloroethane, and trichloroethylene to purify these chemical substances. In other words, an organic chlorine compound can be dechlorinated and a chemical substance can be purified by a reduction reaction with hydrogen generated in an anaerobic atmosphere.

  A group of substances that generate and provide hydrogen as described above is called a hydrogen donor, and while activating microorganisms, a group of substances that become hydrogen donors (hereinafter referred to as “nutrient sources”) are put into soil and groundwater. Injecting methods have been proposed. When such a nutrient source is excessively injected, there is a concern of secondary contamination due to diffusion to a portion other than the contaminated portion. Therefore, for example, Patent Document 1 discloses a composition in which a linear fatty acid granulated or a linear fatty acid is mixed in glycerine so that it is difficult to move from the injection point.

  However, it has been found that microorganisms are inactivated under high-concentration nutrient sources, and extremely diluted nutrient sources are sent to soil and groundwater. Moreover, if the nutrient source is close to natural products, there is little toxicity and there is little need to worry about secondary contamination. Then, rather than solids or gels that do not move from the buried site, a method has been proposed in which the viscosity is rather low, and the nutrient source can be provided widely from one well by diffusing in soil and groundwater.

  Patent Document 2 discloses a technique in which a nutrient source mainly composed of sorbitol is diluted to 2000 ppm and is fed into soil and groundwater to decompose microorganisms into organochlorine compounds. More specifically, 60% sorbitol, 10% glycerin, 2% anions, and 28% water diluted to 2000 ppm are fed into soil and groundwater for diffusion. At the end of diffusion, the concentration of carbon in the nutrient source is diluted to approximately 100 ppm, so that the microorganism is at a concentration that allows co-uptake with chemicals. For this reason, decomposition of the chemical substance is promoted.

JP 2002-370085 A (Patent No. 3746726) JP 2009-11939 A (Patent No. 5023850)

  However, the following problems were found in the surfactants used for the above-mentioned nutrient sources. First, since ionic surfactants have antibacterial activity, when injected into soil and groundwater, they suppress the activity of microorganisms even though they are diluted. As a result, it has been found that the purification efficiency of the organic chlorine compound is lowered.

  Second, ionic surfactants exhibit surface activity by dissociating into ions, but the pH tends to be low in regions where anaerobic microorganisms are active in soil and groundwater. Therefore, an anionic surfactant is difficult to ionize and hardly exhibits surface activity.

  As a result, it was found that the diffusion degree of nutrients was reduced. The cationic surfactant exhibits surface activity under a low pH condition, but sticks to the surface of the microorganism that is negatively charged as a potential, and suppresses the activity of the microorganism. In the first place, because of such properties, cationic surfactants are used as preservatives.

  The present invention has been conceived in view of the above-described problems, and does not deactivate microorganisms capable of purifying organochlorine compounds in soil and groundwater, and has excellent diffusibility in soil and groundwater. The composition for use is provided.

  More specifically, the composition for microorganisms according to the present invention is characterized by comprising a polyhydric alcohol and a surfactant.

Furthermore, in the composition for microorganisms, the polyhydric alcohol is
62 to 68 parts by weight of one or more sugar alcohols selected from sorbitol, mannitol, and xylitol;
8 to 10 parts by weight of glycerin,
The surfactant is 1 to 5 parts by weight of a nonionic surfactant,
Furthermore, it is composed of 22 to 25 parts by weight of water.

  Moreover, the water used for the said composition for microorganisms is the water which performed the disinfection process, It is characterized by the above-mentioned.

  Further, the microorganism composition contains 1 to 4 parts by weight of a pH buffer.

  In the present invention, since the nutrient source mainly composed of polyhydric alcohol contains a nonionic surfactant, the activity of microorganisms in soil and groundwater is not suppressed. Moreover, since a nonionic surfactant expresses surface activity irrespective of pH, it can promote spreading | diffusion of a nutrient source irrespective of pH of soil and groundwater.

  In addition, since the sterilized water is used, the growth of aerobic microorganisms is suppressed particularly in the piping, so that the failure of the piping clogging is reduced.

  Moreover, by including a pH buffer, the soil becomes acidic due to the activity of the bacteria, and thereby the activity of the bacteria is not suppressed. Therefore, it has the effect that the time which processes the soil of a fixed area can be shortened.

  Hereinafter, the composition for microorganisms according to the present invention will be described. The following description exemplifies one embodiment of the present invention and can be changed without departing from the gist of the present invention. In the present specification, “weight% (wt%)” and “part by weight” are used synonymously.

  The composition for microorganisms according to the present invention contains a material for activating microorganisms in soil and groundwater, and is intended to diffuse from the injection site. Therefore, it is a liquid and has a low viscosity. Moreover, since it aims at using it in the highly diluted state with respect to the microorganisms in soil and groundwater, it needs to be water-soluble. It must function as a nutrient source for the purpose of purifying soil and groundwater.

  As such a material, sorbitol, a sugar alcohol which is a polyhydric alcohol, can be suitably used. However, mannitol and xylitol can be used similarly. Here we describe sorbitol.

  A humectant is mixed to keep the sorbitol diluted with water in the soil and groundwater. As the humectant, glycerin, which is a trivalent alcohol, can be suitably used. This is because glycerin itself can be a nutrient source for microorganisms. Further, like ethylene glycol, the freezing point can be lowered, so that it also serves as an antifreeze. This is useful when purifying soil and groundwater in places with low temperatures.

  The composition for microorganisms according to the present invention may contain water at a ratio of about 25 wt% or less. Basically, water is not necessary as a nutrient source. However, it is also necessary to adjust the concentration of nutrient sources.

  In addition, it is preferable that the water to be used has been subjected to sterilization treatment. Water contains bacteria such as water mold. This is because sorbitol can also be a nutrient source for these microorganisms, and therefore, if miscellaneous bacteria are included, the problem arises that the composition for microorganisms corrodes during storage.

  The sterilization process may be a boiling process or may be irradiated with ultraviolet rays. Moreover, you may use the water which does not contain a germ in the first place, such as a pure water and an ultrapure water.

  The nutrient source includes a nonionic surfactant. The surfactant lowers the surface energy of the soil when the nutrient source is injected into the soil and groundwater, and makes the soil easy to get wet with the nutrient source. As a result, along with the effect of capillarity, it makes it easier for nutrients to diffuse in soil and groundwater. Nonionic surfactants can exhibit surface activity regardless of the pH of the liquid.

  Thus, nonionic surfactants are independent of the pH in soil and groundwater. In soil and groundwater, an anaerobic environment can be easily obtained, so that anaerobic decomposition of organic matter proceeds and the soil tends to become acidic. Even in such an environment, the composition for microorganisms can be diffused if it is a nonionic surfactant.

  Nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene Myristyl ether, polyoxyethylene distyrenated phenyl ether, etc. are sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan distearate, etc., which are sorbitan fatty acid esters, polyoxyethylene sorbitan Polyoxyethylene sorbitan mono-coconut fatty acid ester, polyoxyethylene sorbitan laurate, polyoxy Ethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbite tetraoleate, etc. can be used .

  Furthermore, the composition for microorganisms according to the present invention may further contain a pH buffer. The pH buffer can be added from 1 to 4 parts by weight based on the total amount. When adding the pH buffering agent, the ratio with other components is appropriately adjusted.

  Examples of pH buffers that can be suitably used include lactic acid buffers, citrate buffers, phosphate buffers, and acetate buffers. These are added from 1 to 4 parts by weight.

  The reason for using the pH buffer is as follows. By injecting the composition for microorganisms as a nutrient source into soil and groundwater, the microorganisms in the soil and groundwater can be activated. However, when anaerobic decomposition proceeds by activated microorganisms, an organic acid such as acetic acid is generated, and the pH in the soil and groundwater decreases. If the pH of the soil and groundwater is too low, the activity of microorganisms will be suppressed. That is, when the composition for microorganisms is injected into soil and groundwater, a period during which decomposition of the organic chlorine compound or the like does not proceed is formed for a certain period after injection. This is called the “purification stagnation period”.

  The pH buffer agent can alleviate the decrease in pH due to the production of an organic acid such as acetic acid to some extent, and can suppress the “stagnation period of purification” due to the excessive decrease in pH. Therefore, there is no “purification stagnation period”. As a result, there is an advantage that the period required for purification of soil and groundwater is shortened.

  Examples of the composition for microorganisms according to the present invention are shown below. The example was performed at a site contaminated with tetrachlorethylene. The aquifer was 2.0 to 12.2 m from the ground surface. Moreover, the tetrachlorethylene density | concentration in groundwater was about 1.5 mg / L. In the test, an injection well having a diameter of 100 mm was installed, and a pipe was connected to the well opening to inject the composition for microorganisms.

  In addition, an observation well was provided at a location 3 m away from the injection well, and the tetrachlorethylene concentration, sorbitol concentration, and pH in the groundwater were regularly monitored. In addition, the injection well and the observation well into which each microbial composition was injected were provided sufficiently apart from each other so as not to be affected by the microbial composition.

  For each microorganism composition to be injected, an aqueous solution diluted to 2000 ppm was used, and after continuous injection at 9.0 L / min for 7 days, only monitoring was continued.

  Example 1 is a mixture of 62 wt% sorbitol, 8 wt% glycerin, 5 wt% nonionic surfactant, and 25 wt% water. In addition, polyoxyethylene lauryl ether was used as the nonionic surfactant. As the water, water obtained by boiling normal tap water for 10 minutes and cooling it to 25 ° C was used.

  In Examples 2 to 5, the content ratios of sorbitol and glycerin were changed as shown in Table 1, respectively. Other compositions were appropriately changed so that the nonionic surfactants were 3, 2, 1, 1 wt%, respectively.

  On the other hand, in Comparative Example 1, sorbitol and glycerin were 65 wt% and 10 wt%, but 5 wt% of an anionic surfactant was used. Water is 20 wt%. As the anionic surfactant, sodium lauryl sulfate was used.

  Comparative Example 2 is the same as Comparative Example 1 (Example 1) except that the anionic surfactant of Comparative Example 1 is a cationic surfactant. In addition, stearyl trimethyl ammonium chloride was used as the cationic surfactant. In Comparative Examples 3 and 4, the same nonionic surfactant (polyoxyethylene lauryl ether) as in Examples was used, and the number of parts was 0.5 wt% and 7 wt%. The amounts of sorbitol and glycerin are 65 wt% and 10 wt% as in Comparative Example 1. In Comparative Example 5, no surfactant was added.

  With reference to Table 1, as for the kind of surfactant, the nonionic property was represented by “non”, the anionic system was represented by “anion”, and the cationic system was represented by “positive”. The sign “−” indicates that no surfactant is added. Moreover, the decomposition rate was calculated | required from the density | concentration of the tetrachlorethylene before a test, and the density | concentration after 30 days, and was displayed by%. Moreover, the density | concentration (mg / L) of the sorbitol after 7 days in the sampling point 3m away from the well was shown.

  In all of Examples 1 to 5, tetrachlorethylene at a point 3 m away from the well was decomposed by 95% or more. On the other hand, in Comparative Example 1 using an anionic surfactant, it was 16.7%. The concentration of sorbitol after 7 days was 160.0 mg / L. The concentration of sorbitol at the sampled point was almost the same as that of Comparative Example 5 containing no surfactant. Moreover, since the pH of groundwater was 4-5 at this time, it is thought that the anionic surfactant was not able to improve the wettability of the soil surface.

  In the case of Comparative Example 2 using a cationic surfactant, sorbitol was detected at almost the same concentration as in Examples 1 to 5 at the sampling point. However, the decomposition rate of tetrachlorethylene was 14.5%, which could hardly be purified. Cationic surfactants seem to have dissociated in soil and groundwater and exerted surface activity, but actively attached to the surface of microorganisms that are usually charged negatively and inhibited the activity of microorganisms It is considered a thing.

  Comparative Examples 3 and 4 use a nonionic surfactant. When the comparative example 3 was seen, the decomposition rate was 25.8%. Compared to Example 5 in which no surfactant was added, the decomposition rate was improved, but it was judged that the effect of addition was small when the nonionic surfactant was 0.5 wt%. Further, Comparative Example 4 contains 7 wt%. Although the decomposition rate is 95% or more, which is slightly lower than that of the examples, it can be said that the decomposition rate is suitable.

  However, although non-ionic, surfactants are relatively stable in soils and groundwater where the temperature is constant and larger amounts must be a concern for secondary contamination. Therefore, it is preferable that the surfactant is as little as possible. In Comparative Example 4 containing 7 wt%, the decomposition rate was suitable, but it can be said that the effect is saturated or slightly lower than the Examples. Therefore, the surfactant is preferably 5 wt% or less. Further, at 0.5 wt%, the effect is still small. Therefore, the surfactant is preferably 1 wt% or more.

  Examples 1 to 5 showed a suitable purification capacity as described above, but the decomposition of organochlorine compounds from the 8th day to the 15th day was almost stagnant after being injected into the groundwater. At that time, the pH of the groundwater was lowered to 4 or less. From the 15th day, the decomposition of the organochlorine compound progressed, and at that time, the pH was 5.5 or more. This is thought to be due to the progress of anaerobic decomposition of nutrients by microorganisms and the production of organic acids such as acetic acid.

  Therefore, Examples 6 to 9 were prepared by changing the composition ratio of the composition for microorganisms. In Example 6, sorbitol was 62 wt%, glycerin 9 wt%, nonionic surfactant 4 wt%, pH buffer 1 wt%, and water 24 wt%.

  In Examples 7 to 9, sorbitol, glycerin and water were the same as in Example 6, and the total amount of the nonionic surfactant and the pH buffering agent was 5 wt%.

  In Examples 6 to 9, wells and observation wells were provided in the same manner as in Examples 1 to 5. And it inject | poured in the ground water at the same rate as Example 4. FIG. Then, the decomposition rate of tetrachloroethylene after 20 days was measured. The results are shown in Table 2. In addition, pH of Example 4 and the density | concentration of the tetrachloroethylene after a test are the value after 20 days similarly.

  In Example 4, the stagnation period of purification | cleaning has arisen, and the tetrachlorethylene in the meantime has hardly decomposed | disassembled. Therefore, the decomposition rate after 20 days was about 81.1%.

  On the other hand, Examples 6 to 9 having a pH buffering agent have already achieved the decomposition rate close to the decomposition efficiency of the organochlorine compound reached by other Examples over 30 days as of the 20th day. That is, the pH buffering agent can avoid the “stagnation period of purification” and has an effect of shortening the purification speed of the entire soil.

  Further, since the pH buffer is a source of negative ions and positive ions, it is considered that a certain amount is necessary to cause a buffering action. However, when Table 2 is seen, even if the pH buffering agent is 1 wt%, the pH can be maintained to some extent, and it can be said that it is effective. That is, at least the pH buffering agent should be 1 wt% or more.

  On the other hand, considering that the upper limit of the total amount of the surfactant is about 5 wt% from Table 1, the total amount of the surfactant and the pH buffering agent needs to be suppressed to about 5 wt%. When the lower limit of the surfactant is 1 wt%, the upper limit of the pH buffer is considered to be 4 wt%.

  As described above, the composition for microorganisms according to the present invention improves the spreadability in the ground and promotes the purification of soil by including a nonionic surfactant. Moreover, by further including a pH buffer, it is possible to suppress a decrease in underground pH that hinders the activity of microorganisms, and to eliminate the stagnation period of purification.

  The composition for microorganisms according to the present invention can be suitably used as a nutrient source for decomposing and purifying organochlorine compounds in soil and groundwater using microorganisms in soil and groundwater.

Claims (3)

A composition for microorganisms capable of purifying organochlorine compounds in soil and groundwater,
Containing polyhydric alcohol and surfactant,
The polyhydric alcohol is 62 to 68 parts by weight of one or more sugar alcohols selected from sorbitol, mannitol, and xylitol, and 8 to 10 parts by weight of glycerol.
The surfactant is 1 to 5 parts by weight of a nonionic surfactant,
Furthermore, the composition for microorganisms characterized by being comprised from 22 to 25 weight part of water.   The microbial composition according to claim 1, wherein the water is sterilized water.   The composition for microorganisms according to any one of claims 1 and 2, comprising 1 to 4 parts by weight of a pH buffer.