JP5866507B1 - Microbial composition - Google Patents

Abstract

The composition for microorganisms having glycerin, stearic acid, and calcium carbonate has a thixotropy, and therefore, when injected into the ground, it becomes a gel and does not diffuse in groundwater or the like. Therefore, a high sustained release property can be expected. However, although the effect was expected to continue for several years over time, a phenomenon that the effect disappeared in less than one year occurred. By containing glycerin and calcium carbonate and not containing fatty acid, it is possible to provide a microbial composition capable of purifying organochlorine compounds in soil and groundwater having practically sufficient sustained release properties. .

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.

JP 2002-370085 A (Patent No. 3746726)

  In Patent Document 1, a nutrient source (a composition for microorganisms) having a composition of 100 parts by weight of glycerin, 10 parts by weight of stearic acid having an average particle diameter of 105 microns and 20 parts by weight of calcium carbonate having an average particle diameter of 12 microns has thixotropy. Because it has, when it is injected into the ground, it becomes a gel and does not diffuse in groundwater. Therefore, a high sustained release property can be expected.

  However, although the effect was scheduled to continue for several years over time, a phenomenon that the effect disappeared in less than one year occurred.

  The present invention has been conceived in view of the above-mentioned problems, and the above phenomenon is caused by the fact that the nutrient source injected into the ground is too gelled so that neither glycerin nor fatty acids can be released. As a result of ascertaining this, it was conceived.

More specifically, the composition for microorganisms according to the present invention contains only glycerin and calcium carbonate, and the calcium carbonate is 5% by mass or more and 9% by mass or less based on the total amount of the composition for microorganisms. To do.

  The composition for microorganisms according to the present invention provides a composition for microorganisms (nutrient source) that, after being injected into the ground, becomes a gel state, stays in place, and can continuously release the nutrient source for a long period of time. be able to.

It is a figure which shows the structure of the apparatus used for the preliminary experiment. It is a figure which shows a mode that water is poured from the top of the soil in a container in the apparatus of a preliminary experiment, and the water which falls on the saucer arrange | positioned under the bottom plate is extract | collected. It is a figure showing the result of a preliminary experiment.

  The composition for microorganisms according to the present invention will be described below. The following description exemplifies a part of the embodiments and examples of the present invention, and the present invention is not limited to the following description. The following embodiments can be modified without departing from the gist of the present invention.

  The composition for microorganisms according to the present invention includes a material for activating microorganisms in soil and groundwater, and does not diffuse so much from the injection site, and remains in place, and aims to release nutrient components over a long period of time. And Therefore, when injected, it gels in the ground and does not diffuse due to groundwater or infiltration.

  That is, it is formed at the point where the gel containing the nutrient component is injected, and the nutrient component is released therefrom. On the other hand, the gel itself does not diffuse. In other words, the composition for microorganisms (nutrient source) is to form a gel in the ground in which nutrient components are contained in the gel skeleton.

  As a nutrient component of the microorganism, sugar alcohol or glycerin, which is a polyhydric alcohol, can be used. This is because these substances are easily dissolved in water and easily diffuse. In particular, glycerin is excellent in terms of moisture retention.

  Moreover, a fatty acid can also be utilized as a nutrient component. Fatty acids having a large number of carbon atoms are insoluble in water and therefore do not diffuse at a stretch. It can be degraded by microorganisms little by little and can act as a long-term hydrogen donor. However, fatty acids are not used in the composition for microorganisms according to the present invention.

  To make a liquid into a gel, thixotropy is imparted. This can be realized by including a filler component. The filler component serves as an intermediary for cross-linking the mixed solvents and builds a network throughout the solvent. That is, it has a high viscosity in a stationary state. However, since they are not chemically bonded in the first place, when shearing force is applied, they are separated and become low in viscosity.

  As a filler component, what consists of an element with little environmental impact is good. For example, calcium can be suitably used because it is not a large environmental burden and is hardly soluble in water. Among these, calcium carbonate is preferable because it is available at a low price from the viewpoint of cost.

  The size of the filler component is preferably 20 μm or more and 200 μm or less. If it is too small, the effect as a thixotropic agent will be low, and it will not become a thixotropic body as a composition for microorganisms. Also, if the filler is small, it will diffuse in the ground. If it is too large, the effect as a thixotropic agent is lowered. Moreover, if the particle size is too large, it may cause clogging of the supply port to the ground.

  The microbial composition disclosed in Patent Document 1 forms a gel-like body in the ground when injected. However, as shown in the examples described later, it was found that when a calcium compound forming a gel skeleton and a fatty acid were mixed and poured into the ground while stirring, a very strong thixotropic agent was obtained.

  Accordingly, when sugar alcohol or the like, which is a nutrient component, is released, gelation progresses, resulting in a gel that does not release the nutrient component. That is, after a certain period of time, the supply amount of hydrogen is extremely reduced and purification does not proceed.

  In order to avoid this, it was most effective to use a mixed composition of only the nutritional component and the filler component without adding any fatty acid. It is also possible to add additives such as surfactants and pH adjusters.

  Examples of the composition for microorganisms according to the present invention are shown below. As a preliminary experiment, compositions for microorganisms having different compositions were prepared, and their behavior in soil was confirmed. FIG. 1 shows the apparatus used in the experiment. The container 10 was an acrylic tube having an inner diameter of 130 mm, a wall thickness of 10 mm, and a length of 500 mm. One end was closed with a bottom plate 11 having a plurality of through holes. The soil 12 excavated from the water-permeable layer 7 m underground was filled from the bottom plate 11 to a height of 400 mm by about 3 liters.

  100 microliters of the sample 30 of the composition for microorganisms was inject | poured into the point of the depth of 100 mm from the surface of the soil in the container 10 using the syringe pump 14. FIG. Then, it was left for one day.

  Next, referring to FIG. 2, water 20 was poured from above the soil 12 in the container 10, and water 25 falling on the receiving tray 16 disposed under the bottom plate 11 was collected. This water was measured by GC (gas chromatograph), and the elution amounts of nutrient components were measured periodically. In FIG. 2, reference numeral 18 denotes a tank of water 20 with the outlet facing downward, and the liquid level of the water 20 is always at the same position. Reference numeral 30 denotes a gelled sample. The composition of each sample is shown below.

<Sample 1>
Sample 1 has a composition of 76.9% by mass of glycerin, 7.7% by mass of calcium carbonate having an average particle size of 100 μm, and 15.4% by mass of stearic acid having an average particle size of 12 μm. The composition is shown in Table 1.

<Sample 2>
Sample 2 is composed of 91% by mass of glycerin, 3% by mass of calcium carbonate having an average particle size of 100 μm, and 6% by mass of stearic acid having an average particle size of 12 μm. Sample 2 has a composition in which the amounts of calcium carbonate and stearic acid are reduced in the same ratio. The composition is shown in Table 1.

<Sample 3>
Sample 3 is composed of 91% by mass of glycerin, 6% by mass of calcium carbonate having an average particle size of 100 μm, and 3% by mass of stearic acid having an average particle size of 12 μm. Sample 3 has a composition in which the amount of calcium carbonate and the amount of stearic acid are reversed with respect to sample 2. The composition is shown in Table 1.

<Sample 4>
Sample 4 has a composition of 91% by mass of glycerin and 9% by mass of calcium carbonate having an average particle size of 100 μm. Sample 4 has a composition not containing stearic acid. The composition is shown in Table 1.

<Sample 5>
Sample 5 has a composition of 100% by mass of glycerin. Sample 5 was added as a control. The composition is shown in Table 1.

  The water poured on the soil surface was poured from the soil in the container 10 to a height of about 5 cm at a time, and then was replenished from the tank 18 so as to maintain the water level. From the container 10 into which each sample was poured, water 25 started to come out on the saucer 16 in approximately the same time after pouring water. The time when the water 25 began to appear in the tray 16 was set as the start of measurement. The water 25 accumulated in the tray 16 was sampled every 30 minutes from the start of the measurement, and the amount of glycerin was measured by GC. The measured value of the amount of glycerin was converted to the total amount of glycerin that flowed down in 30 minutes based on the weight of the water accumulated in the tray 16.

  The results are shown in FIG. Referring to FIG. 3, the horizontal axis is time, and the vertical axis is the total amount of glycerin that has flowed down. In order to compare samples, the vertical axis is normalized with the first measured value of sample 5 as 100. When the result of FIG. 3 is seen, the thing of glycerin single-piece | unit (sample 5: white circle) has flowed down most. However, after 24 hours, it was almost below the detection limit.

  In samples 1 (black circles), 2 (white triangles), and 3 (white inverted triangles) in which calcium carbonate and stearic acid were mixed with glycerin, only about half of sample 5 (only glycerin) flowed down from the start of measurement. After that, it flowed continuously, but suddenly decreased after 8 hours.

  In contrast, in sample 4 (white squares) containing no stearic acid, glycerin flowed more slowly than sample 5 without additives. Then, after 18 hours, the amount of sample 5 was larger than the outflow amount.

  When the samples 1 to 4 were cut longitudinally for each container 10 after the experiment was completed, the samples 1 and 3 were in a gel state at the injected portion in substantially the same manner. On the other hand, Sample 4 was a gel-like body, but the portion where the gel state was recognized was wider than Samples 1 to 3.

  From the above results, when calcium carbonate and stearic acid coexist, it works as a powerful gel accelerator regardless of the content within the range tested this time, and if the glycerin amount flows above a certain level, it does not allow further outflow It seems to be a firm gel.

  Next, the actual field was checked. Example 1 has the same composition as Sample 4 in Table 1, 91% by mass of glycerin, and 9% by mass of calcium carbonate having an average particle size of 100 μm. Example 2 has a composition close to that of sample 4, with 95% by mass of glycerin and 5% by mass of calcium carbonate having an average particle size of 100 μm. Comparative Example 1 has the same composition as Sample 1. Specifically, glycerin is 76.9% by mass, calcium carbonate having an average particle size of 100 μm is 7.7% by mass, and stearic acid having an average particle size of 12 μm is 15.4% by mass.

  While stirring 45 kg of the microbial composition having these compositions, the whole amount was poured into a well dug in 12 m. In addition, it was investigated that this soil contains 1.0 mg / L of trichlorethylene.

The wells of Examples 1 and 2 and Comparative Example 1 were provided at points separated by 50 m or more so as not to affect each other. A point observation well 5 m away from each well was dug, and the amount of trichlorethylene was measured. Table 2 shows the composition of each sample and the removal rate of trichlorethylene. In Table 2, the removal rate of trichlorethylene is indicated as “VOC removal rate (%)”. The removal rate was a value obtained by dividing the measured value by the initial value of 1.0 mg / L and subtracting 1 from 100. A more specific body is represented by formula (1).
Removal rate = (1−measured value / 1.0} × 100 (1)

  Referring to Table 2, one month after the installation of the wells, the removal rate of trichlorethylene at the observation point was almost the same for each well. On the other hand, after 10 months, trichlorethylene was removed in the same manner at the well observation points of Examples 1 and 2, but the removal rate was zero at the well observation point of Comparative Example 1. . When glycerin was measured at the observation point, glycerin could be observed at the observation points of Examples 1 and 2, but glycerin could not be detected at the observation point of the well of Comparative Example 1.

  As described above, when calcium carbonate and a fatty acid were allowed to coexist, it was concluded that glycerin was prevented from flowing out because it acted as a strong thixotropic promoter. Further, it was found that the nutrient source can be continuously supplied over a long period of time by containing calcium carbonate at least 5 mass% to 9 mass%.

  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.

10 container 11 bottom plate 12 soil 14 syringe pump 16 saucer 18 (water) tank

Claims (1)

A composition for microorganisms capable of purifying organochlorine compounds in soil and groundwater,
Glycerin,
Contains only calcium carbonate,
The composition for microorganisms, wherein the calcium carbonate is 5% by mass to 9% by mass with respect to the total amount of the composition for microorganisms.

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