JP4501659B2 - Nutrient source injection method - Google Patents

Description

  The present invention relates to a method for appropriately purifying contaminants that have penetrated into soil and groundwater with microorganisms.

  Conventionally, soil and groundwater contamination purification methods include vacuum extraction method, air sparging method, pumping treatment method, iron powder method, lime injection method, microorganism utilization method, soil excavation and replacement method, soil wet cleaning method, insolubilization treatment method, etc. Depending on the harmful pollutant (organochlorine compound), it has been purified by various methods.

  In particular, the microbial utilization method is a technology that purifies by the action of indigenous microorganisms (anaerobic microorganisms) at the site where harmful pollutants flow into the ground. This is a so-called bioremediation method for growing and activating microorganisms.

  However, investigations have revealed that many microorganisms are distributed in the upper silt layer of groundwater, and nutrients are supplied to the parts where there is a large distribution of microorganisms to grow and activate the microorganisms, resulting in contamination. There was a need to purify the groundwater by microorganisms.

  This type of technology embeds electrodes upstream and downstream of groundwater contaminated with harmful pollutants until it reaches the lower silt layer, and has an injection well in the vicinity of the electrode upstream of groundwater, After setting up a pumping well near the downstream electrode, circulating groundwater, adding nutrients, etc., nutrients from sprinkler pipes and injection wells in the upper silt layer of the area contaminated with harmful pollutants, etc. There is known a method of activating microorganisms to purify harmful pollutants (organochlorine compounds). (For example, refer to Patent Document 1).

In addition, an injection well and a pumping well are provided on the upstream and downstream sides of groundwater contaminated with harmful pollutants (organochlorine compounds), and groundwater flows while circulating groundwater and adding nutrients and the like. There is known a method in which a horizontal electrode is provided on a silt layer sandwiching an aquifer and an area contaminated with a harmful pollutant, and microorganisms are activated to purify the harmful pollutant. (For example, refer to Patent Document 2).
Japanese Patent No. 3374230 Japanese Patent No. 3374232

  In such a conventional method, the equipment is large-scale, and there is a possibility of causing secondary contamination (diffusion and leakage) of groundwater contaminated with harmful pollutants (organochlorine compounds). However, there is a problem that the construction is complicated and the construction cost is enormous.

  The present invention solves such a conventional problem, and in an original position where harmful pollutants (organochlorine compounds) flow into the ground, an environment in which microorganisms tend to inhabit in an aquifer where groundwater flows is provided. The purpose is to provide a method that can be created and purified by simple construction.

  In order to achieve the above object, the present invention provides at least one nutrient well injection well upstream of groundwater in an area contaminated with harmful pollutants (organochlorine compounds), a silt layer and an aquifer. A container filled with a nutrient source and a mixture of pure sand and calcium carbonate is hung near the boundary of the stratum.

  Due to the chemical reaction between the calcium carbonate in the suspended container and the water contained in the pure sand soil, an exothermic action takes place, the temperature of the groundwater can be raised, nutrient sources are easily eluted, and microorganisms (anaerobic microorganisms) Can maintain the environment inhabited.

As a result, by carrying indigenous microorganisms in the container, harmful pollutants (organochlorine compounds) that have flowed out of the silt layer into the aquifer can be reduced in molecular weight by the action of microorganisms. It can be rendered harmless by degrading bacteria.

  In addition, microorganisms can be grown and activated in the aquifer by the nutrient source eluted from the container.

  That is, the present invention is characterized by a method for injecting a nutrient source that purifies harmful pollutants (organochlorine compounds) by microorganisms in groundwater.

  In addition, the present invention can accelerate the purification rate by groundwater containing harmful pollutants pumped from the observation well on the ground after adsorbing the harmful substances with activated carbon or the like and circulating them in the injection well. It is a feature.

  According to the present invention, in the vicinity of the boundary between the silt layer and the aquifer layer, a microorganism (anaerobic microorganism) is propagated by suspending a container filled with a nutrient source and a mixture of pure sand soil and calcium carbonate, An environment that can be activated can be created, and the area inhabited by microorganisms can be expanded.

  In other words, suspend the microbes that grow on the boundary between the silt layer and the aquifer, and the container filled with the nutrient source and the mixture of sand sand and calcium carbonate near the boundary between the silt layer and the aquifer. As a result, calcium carbonate and groundwater filled in the container can react chemically to generate heat, and at the same time as heating the natural sand soil, the nutrient source is also heated and easily dissolved.

  Thereby, in an aquifer, it can be under the environment where microorganisms are propagated and activated, and harmful pollutants (organochlorine compounds) can be reduced in molecular weight by the action of microorganisms and further detoxified.

  The method of injecting a nutrient source according to the present invention is provided with an injection well for injecting at least one nutrient source on the upstream side of groundwater in a contaminated area contaminated with harmful pollutants, and at least on the downstream side of the contaminated area. One observation well is provided, a container is filled with the nutrient source, a mixture of sand sand and calcium carbonate, and the container of the injection well is placed near the boundary between the aquifer and the silt layer. It is a thing.

  Hazardous pollutants include soil and / or groundwater containing organochlorine compounds.

  Examples of organochlorine compounds include tetrachloroethylene, trichloroethylene, dichloroethylene, vinyl chloride, dichloromethane, chloroform, carbon tetrachloride, chloroethane, dichloroethane, trichloroethane, dichloropropane, dichlorobroethylene, bromodichloromethane, chlorodibumomethane, and dioxin. Can be mentioned. It is particularly suitable for the purification of soil and / or groundwater containing at least one contaminant of tetrachlorethylene, trichlorethylene and carbon tetrachloride.

  The harmful pollutants described above are reduced in molecular weight or detoxified by microorganisms.

  In addition, the nutrient source to be filled in the inner cylinder of the container is a nutrient source mainly composed of a linear saturated carboxylic acid having 6 or more carbon atoms, and its solubility in groundwater has a slow release function. In situ, since the sustainability of the effect as a nutrient source is high, microorganisms can inhabit, activate, and grow, and harmful pollutants (organochlorine compounds) by microorganisms are reduced in molecular weight or made harmless Can do.

  That is, the nutrient source for activating the microorganism is selected from those containing a linear saturated monocarboxylic acid having 6 or more carbon atoms, and at least one kind can be used.

  A straight-chain saturated monocarboxylic acid having 6 or more carbon atoms functions not only as a substrate for anaerobic microorganisms but also as a hydrogen donor, and has a sufficiently high melting point. It becomes easier to maintain sustained release characteristics in groundwater.

  The upper limit of the carbon number of the straight-chain saturated monocarboxylic acid is not particularly limited, but those having 22 or less carbon atoms are preferred because they are industrially and easily available from natural materials.

  Further, in consideration of liquefaction from the solid state, the carbon number is most preferably 8 to 18.

  In addition, since the linear saturated monocarboxylic acid is not a multiple bond such as a double bond, the melting point is not lowered and the specific gravity with water is almost the same, so that the solid state is maintained in soil and groundwater. It becomes easy.

  The linear saturated monocarboxylic acid, that is, the fatty acid is also excellent in efficiency as a hydrogen donor.

  Examples of the linear saturated monocarboxylic acid include caprylic acid (melting point: 16.5 ° C., specific gravity: 0.91), pelargonic acid (melting point: 15 ° C., specific gravity: 0.90552), capric acid (melting point: 31.3 ° C., specific gravity: 0) 8931), lauric acid (melting point 44 ° C., specific gravity 1.0099), myristic acid (melting point 53.5 ° C., specific gravity 0.8533), palmitic acid (melting point 62.65 ° C., specific gravity 0.8414), stearic acid ( Melting point 71 ° C., specific gravity 0.8428) and mixtures of these carboxylic acids.

  Among these, myristic acid, palmitic acid, and stearic acid are particularly preferable.

  These myristic acid, palmitic acid, and stearic acid are industrially produced, and are inexpensive and easily available.

  In addition, myristic acid, palmitic acid, and stearic acid have a relatively large number of carbon atoms and low solubility in water. Therefore, they gradually dissolve in water such as ground water (sustained release), and are dissolved in soil and groundwater. It is easy to keep a solid state in position.

  Moreover, as a mixture, the mixture of the fatty acid extracted from natural raw materials, such as what selected several carboxylic acid and artificially mixed, beef tallow fatty acid, coconut oil fatty acid, may be sufficient.

  In addition, since the nutrient source mainly composed of linear saturated carboxylic acid having 6 or more carbon atoms is solid, it is less affected by groundwater and has high sustainability as a nutrient source in situ. It is possible to inhabit, activate, and grow microorganisms, and the period of re-injection of nutrients is longer than that of liquid and gel-like nutrients, preventing over-injection of nutrients and the consumption of nutrients Can be kept low.

  That is, since the nutrient source mainly composed of linear saturated monocarboxylic acid is solid, it elutes little by little into the groundwater, and as an in-situ nutrient source compared to the gel nutrient source and the liquid nutrient source. The effect of this is that the sustainability of solubility in water increases.

  In other words, the effects of groundwater are small compared to gel nutrients and liquid nutrients, so the nutrient replenishment period is long and excessive dissolution in groundwater can be prevented. Can be purified.

  The amount of the nutrient source mainly composed of a linear saturated monocarboxylic acid is not particularly limited, and is appropriately set according to the type of the nutrient source, the area of the contaminated area, the amount of the contaminant, and the like. be able to.

  For example, the types and amounts of pollutants contained in the soil or groundwater sampled by surface surveys, shallow surveys, and deep surveys in contaminated areas, types and amounts of competing substances (oxidizing substances), and geological conditions (penetration, temperature) ) Etc. are analyzed and identified, and the concentration is determined from the mass of harmful pollutants contained with respect to the types of pollutants and the mass of soil and groundwater.

  And it is 0.1 to 15 times the amount of harmful pollutants in the contaminated area due to correlation with the types and concentrations of harmful pollutants, diffusibility of nutrient sources, and the amount required to replace chlorine with hydrogen. Preferably, the purification efficiency can be improved by injecting 1 to 12 times the nutrient source into the injection well.

  In addition, the inner cylinder portion of the container is filled with a nutrient source mainly composed of a straight-chain saturated carboxylic acid having 6 or more carbon atoms and a porous material, so that microorganisms are carried in the aquifer. In situ, harmful pollutants (organochlorine compounds) caused by microorganisms can be reduced in molecular weight or detoxified.

  That is, by mixing a nutrient source and a porous substance (for example, activated carbon, coal ash, charcoal, lignite, zeolite, bentonite, ceramics, wood chips), microorganisms can be easily attached in the aquifer.

  As the container, the resistance of the flow of groundwater can be reduced by adopting a stainless steel cylindrical shape.

  In addition, the same effect can be acquired if it is a shape where the resistance of the flow of groundwater does not increase, such as an elliptical shape or a polygonal shape other than a cylinder.

Further, at least a part of the circumferential portion of the container in the longitudinal direction is formed in a net shape,
It is possible to physically adjust the elution of nutrient sources, and it becomes easier to carry microorganisms.

  As a result, the flow of groundwater can be maintained without changing the flow of groundwater, and purification by microorganisms can be performed without reexamining the underground state.

  Furthermore, microorganisms (anaerobic microorganisms) inhabit by making the container structure a double structure with an outer cylinder and an inner cylinder, filling the outer cylinder with a mixture of pure sand and calcium carbonate, and filling the inner cylinder with nutrients, respectively. In addition, it is possible to create an environment that proliferates and activates in the aquifer, and it has a rust prevention effect by making the container made of stainless steel.

  In addition, the inner cylinder portion of the container is filled with 60% to 70% of a nutrient source mainly composed of a linear saturated carboxylic acid having 6 or more carbon atoms, and a porous material (for example, activated carbon, coal ash, charcoal, lignite) , Zeolite, bentonite, ceramics, and wood chips) are mixed in a proportion of 40% to 30%, whereby microorganisms can be supported in the aquifer.

  The mixing ratio of the nutrient source mainly composed of linear saturated monocarboxylic acid filled in the inner cylinder of the container and the porous material varies depending on the activation rate of the microorganisms. By making the nutrient source mainly composed of saturated monocarboxylic acid 60% to 70% and the porous material 40% to 30%, the amount of anaerobic microorganisms attached (the number of bacteria) was remarkably large.

  For example, as a result of taking out the container and measuring the number of bacteria, it was about 150 / ml when the porous material was less than 30%, and about 1000 / ml when the porous material was over 40%. When the porous material was 35%, it was about 1000000 pieces / ml.

  Further, by mixing 60% to 75% of the pure sand soil filling the outer cylinder portion of the container and 40% to 25% of the volume of calcium carbonate, the reaction of moisture contained in the true sand soil and calcium carbonate results in 40%. Since heat generation can be performed at a temperature of 60 ° C. to 60 ° C., the temperature of groundwater can be raised and dissolution of nutrient sources can be promoted, so that microorganisms can be activated.

  That is, since the mixing ratio of the pure sand soil and calcium carbonate filled in the outer cylinder of the container can generate heat of 40 ° C. to 60 ° C. by making the water contained in the true sand soil twice the equivalent of calcium carbonate. The mixing ratio takes into account the water content of pure sand, and 60% to 75% of pure sand, and 40% to 25% of calcium carbonate have the effect of increasing the temperature of groundwater and promote the dissolution of nutrients. This also produces the effect of anaerobic microorganisms to the sandy soil.

  For example, when the moisture content of the pure sand soil filled in the outer cylinder of the container is 60%, when the pure sand soil is mixed at a volume ratio of 60% and calcium carbonate is mixed at a volume ratio of 40%, an exotherm of about 60 ° C. is generated. It has been found by experiments of the inventors that the temperature can be raised from 30 ° C. to 40 ° C. in water.

  Moreover, since the nutrient tube is filled in the inner cylinder part of the container and the mixture of the pure sand soil and calcium carbonate is filled in the outer cylinder part of the container, the viscosity of the true sand soil and the nutrient source of microorganisms exist at the same time. Therefore, it becomes an environment in which microorganisms are liable to inhabit, and harmful pollutants (organochlorine compounds) caused by microorganisms can be reduced in molecular weight and further detoxified.

  That is, for the container for filling the nutrient source, the container has a double structure having an outer cylinder and an inner cylinder, and the outer cylinder portion is filled with a mixture of pure sand and calcium carbonate, and the nutrient source is provided in the inner cylinder portion. Filled ones are desirable.

  In this way, microorganisms (anaerobic microorganisms) are proliferated and activated by suspending a container filled with a nutrient source and a mixture of pure sand and calcium carbonate near the boundary between the silt layer and the aquifer. Environment can be created, and the area where microorganisms inhabit can be expanded.

  In other words, the calcium carbonate filled in the container and the groundwater undergo a chemical reaction to generate heat, thereby heating the natural sand soil and simultaneously heating the nutrient source, which facilitates dissolution.

  As a result, in the aquifer, it is possible to create an environment in which microorganisms grow and activate, and by the action of the microorganisms, harmful pollutants (organochlorine compounds) are reduced in molecular weight, thereby further detoxifying treatment. it can.

Example 1
Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a method for injecting a nutrient source in a contaminated area according to the present invention.

  Reference numeral 1 denotes a contaminated area, and the contaminated area 1 penetrates the upper silt layer 3 such as clay from the top soil 2 into the ground over a long period of time.

  Further, the harmful pollutants staying in the upper silt layer 3 gradually permeate into the aquifer 4 where the groundwater flows, causing contamination of the groundwater.

  An injection well 6 reaching the lower silt layer 5 is provided on the upstream side of the groundwater flowing through the aquifer 4 in order to purify the harmful pollutants in the contaminated area 1 by using anaerobic microorganisms that are indigenous. An observation well 7 reaching the lower silt layer 5 is provided on the downstream side of the groundwater, and the groundwater containing harmful pollutants in the aquifer 4 between the source injection well 6 and the observation well 7 is provided in the observation well 7. Water is pumped by a device (not shown), harmful pollutants are adsorbed on the activated carbon by the activated carbon tank 8 on the ground, and purified groundwater is injected again into the injection well 6.

  As for the injection of the nutrient source, the container 9 filled with the mixture of the nutrient source, the pure sand soil and the calcium carbonate is suspended in the vicinity of the boundary between the upper silt layer 3 and the aquifer 4 to indwell. The anaerobic microorganisms that are attached to the container 9 can make the harmful pollutants in the contaminated area 1 low molecular.

  As shown in FIGS. 2 and 3, the container 9 has a double cylindrical shape of an outer cylinder 10 and an inner cylinder 11 having a net.

  One or more containers 9 may be hung from the injection well 6 according to the state of the ground.

  As shown in FIG. 4, the method of filling the container 9 with the nutrient source and the mixture 12 of pure sand clay and calcium carbonate is to fill the outer cylinder 10 with the mixture 12 of pure sand clay and calcium carbonate and to feed the inner cylinder 11 with nutrition. By filling the source, it is possible to create an environment in which indigenous anaerobic microorganisms easily adhere to the container 9.

  Moreover, you may mix and fill with the porous substance (For example, activated carbon, coal ash, charcoal, lignite, zeolite, bentonite, ceramics, a piece of wood) to the inner cylinder 11 filled with a nutrient source.

  As a result, the distribution of the anaerobic microorganisms was concentrated between the upper silt layer 3 and the aquifer 4, but the distribution range can be widened in the aquifer and harmful pollutants in the contaminated area 1. Is made low molecular or harmless.

For example, in an actual pollution site, the contaminated aquifer is -3 m to -6 m from the ground line (GL), the contaminated area 1 is 200 m ² , the dynamic gradient is 0.0001 m / m, and the hydraulic conductivity is 2. As shown in FIG. 5, the purification of harmful pollutants in the contaminated area 1 by injection of the nutrient source of the present invention at 0.0 × 10 ⁻³ cm / s fell below the environmental standard value within 60 days.

  In this way, the soil and groundwater are purified at the original location of contamination while preventing leakage or diffusion of harmful pollutants in the contaminated area 1 to the container 9 using anaerobic microorganisms as much as possible. It became possible to do.

  In addition, this Embodiment is an Example, and it cannot be overemphasized that it becomes the most suitable purification | cleaning method to respond | correspond suitably according to the condition of the field using combining other construction methods of bioremediation.

  The soil and groundwater purification method of the present invention is contaminated with harmful pollutants around places where substances that can be harmful pollutants are used or discharged, such as electronic parts factories, metal product factories, dry cleaning sites and garbage incineration plants. It is extremely useful as a method for purifying soil and groundwater.

Cross-sectional schematic diagram of the method for purifying a contaminated area of the present invention Configuration diagram of partially mesh-shaped container of the present invention Configuration diagram of an all-round net-shaped container of the present invention Sectional view of the container of the present invention Graph of observation results of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contaminated part area 2 Topsoil 3 Upper silt layer 4 Aquifer 5 Lower silt layer 6 Injection well 7 Observation well 8 Activated carbon tank 9 Container 10 Outer cylinder 11 Inner cylinder 12 Mixture

Claims (8)

An injection well for injecting at least one nutrient source is provided on the upstream side of the ground water in the contaminated area contaminated with harmful pollutants, and at least one observation well is provided on the downstream side of the contaminated area. And filling a container with a mixture of true sand and calcium carbonate, and pouring the container of the injection well near the boundary between the aquifer and the silt layer. 2. The nutrient source according to claim 1, wherein the container is made of stainless steel having a substantially cylindrical inner cylinder and an outer cylinder, and at least a part of a circumferential portion in the longitudinal direction is formed in a net shape. Injection method. 2. The nutrient source injection method according to claim 1, wherein the nutrient source contains a linear saturated carboxylic acid having 6 or more carbon atoms as a main component. The nutrient source injection method according to claim 3, wherein the nutrient source is a solid. The inner tube portion of the container is filled with the nutrient source, and the outer tube portion of the container is filled with a mixture of pure sand soil and calcium carbonate. The nutrient source injecting method according to item. 6. The nutrient source injecting method according to claim 5, wherein the nutrient tube and a porous material are mixed and filled in an inner cylinder portion of the container. The mixture of the pure sand soil filled in the outer cylinder portion of the container and the calcium carbonate is a mixing ratio of the pure sand soil 60% to 75% and the calcium carbonate 40% to 25%. The nutrient source injecting method according to claim 2 or 5. The ratio of the mixture of the nutrient source filled in the inner cylinder portion of the container and the porous material is a mixture ratio of 70% to 60% of the nutrient source and 30% to 40% of the porous material. The method of injecting a nutrient source according to claim 6.

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