JP4431979B2 - Oil purification method and equipment for soil and groundwater - Google Patents

Description

  The present invention relates to an oil purification method and purification equipment for soil and groundwater that purify oil contamination of soil and groundwater in situ by using microorganisms.

Conventional methods for purifying contaminated soil and groundwater include excavating contaminated soil and moving it to another location for purification, or purifying in situ by the action of microorganisms without excavating the soil. The method of performing is known. In this case, when purifying in situ, oxygen sources and inorganic salts are injected into the soil and groundwater in order to activate the activities of microorganisms that already exist in the soil and groundwater that decompose the pollutants. The soil and groundwater are kept aerobic. Furthermore, in addition to injecting oxygen sources and inorganic salts, artificially injecting microorganisms for decomposition have also been performed (see, for example, Patent Document 1).
JP-A-10-180237

  However, when soil and groundwater are contaminated with oil, there is a problem that the oil cannot be efficiently purified even if an oxygen source or inorganic salts are injected into the contaminated site as in the past.

  The present invention has been made in view of such circumstances, and an oil purification method and equipment for soil and groundwater that can efficiently purify oil contaminating soil and groundwater and shorten the purification period. The purpose is to provide.

  In order to achieve the above object, claim 1 of the present invention injects an inorganic salt containing at least a nitrogen source and an oxygen source into a contaminated site of soil and groundwater contaminated with oil to introduce the oil into the contaminated site. An oil purification method for soil and groundwater that is purified by existing bacteria, wherein a nitrification inhibitor is injected into the contaminated site.

  As described above, when in-situ purification is performed, cleaning can be performed by injecting an oxygen source or inorganic salts that activate bacterial activity into contaminated soil or groundwater. However, the bacteria present in soil and groundwater are complex bacteria that gather a wide variety of bacteria. Therefore, nitrification, which is an aerobic autotrophic bacterium that does not contribute to oil degradation, in addition to aerobic heterotrophic bacteria that degrade oil by injecting oxygen sources and inorganic salts into the contaminated site to keep the contaminated site aerobic. The activity of fungi is also activated. Thus, when a nitrogen source or a phosphorus source is injected as an inorganic salt, the nitrifying bacteria convert ammonium ions derived from the nitrogen source into nitrate ions, and the oxygen source is consumed accordingly. As a result, ammonium ions and oxygen sources that can be used by aerobic subordinate bacteria that degrade oil are reduced, and the oil cannot be efficiently decomposed.

  According to claim 1 of the present invention, since the nitrification inhibitor is injected into the contaminated site, the activation of nitrifying bacteria can be prevented. This prevents wasteful consumption of nitrogen and oxygen sources injected into the contaminated site by nitrifying bacteria, so that oil contaminating soil and groundwater can be efficiently removed by aerobic heterotrophic bacteria that degrade oil. Can be purified.

  A second aspect of the present invention provides the method according to the first aspect, wherein the groundwater nitrate ion concentration is measured at a position downstream of the position where the inorganic salt and the oxygen source are injected in the groundwater waterway, and the nitrification inhibition is performed based on the measurement result. It is characterized by controlling the injection amount of the substance.

  Since nitrifying bacteria convert ammonium ions into nitrate ions, the active state of nitrifying bacteria can be known by knowing how much nitrate ions are generated. According to the second aspect, since the nitrate ion concentration of the groundwater is measured and the injection amount of the nitrification inhibitor is controlled based on the measurement result, the nitrification inhibitor injection amount is not excessive or insufficient. In addition, the measurement of nitrate ion concentration was performed at a position downstream of the injection position where the inorganic salt and oxygen source were injected in the groundwater water vein, so the change in nitrate ion concentration derived from the injected nitrogen source was accurately detected. Can be measured.

  [Claim 3] An inorganic salt supplying an inorganic salt containing at least a nitrogen source in an oil purification facility for soil and groundwater that purifies contaminated sites of soil and groundwater contaminated with oil with bacteria present in the contaminated sites. A supply device, an oxygen source supply device that supplies an oxygen source, a nitrification inhibitor supply device that supplies a nitrification inhibitor, and an inorganic salt, an oxygen source, and a nitrification inhibitor supplied from each of the devices to the contaminated site An injection well to be injected, an observation well provided at a position downstream of the injection well in the groundwater water vein, a measurement device for measuring the nitrate ion concentration of the groundwater in the measurement well, and a measurement result of the measurement device And a control device for controlling the injection amount of the nitrification inhibitor substance injected into the contaminated site from the nitrification inhibitor substance supply device.

  According to claim 3 of the present invention, nitrification by nitrifying bacteria is suppressed by the nitrification inhibitor, and the injection amount of the nitrification inhibitor is controlled based on the measurement result of the nitrate ion concentration. This suppresses the decrease in inorganic salts and oxygen sources due to nitrification, and prevents the degradation of aerobic heterotrophic bacteria that degrade oil, thus enabling effective use of inorganic salts and oxygen and shortening the construction period. .

  As described above, according to the oil purification method and purification equipment for soil and groundwater of the present invention, nitrification that hinders purification of soil and groundwater contaminated with oil is suppressed by supplying a nitrification inhibitor, and inorganic salts And effective use of oxygen and shortening the construction period.

  Hereinafter, preferred embodiments of the oil purification method and purification equipment for soil and groundwater according to the present invention will be described in detail with reference to the accompanying drawings.

  First, the structure of the soil and groundwater purification equipment according to the present invention will be described. FIG. 1 is a configuration diagram of a soil and groundwater purification facility according to the present invention.

  As shown in FIG. 1, the groundwater vein 4 flows in the direction of arrow A in the soil 2 where the purification facility 1 is provided, and the contaminated site 3 of the soil 2 and the groundwater vein 4 is contaminated with oil. ing. An injection well 16 and an observation well 17 are formed deeper than the groundwater vein 4 from the purification facility 1 to the soil 2, and the injection well 16 is disposed upstream of the groundwater vein 4 than the observation well 17.

  The purification facility 1 includes an oxygen source supply device 11, an inorganic salt supply device 12, and a nitrification inhibiting substance supply device 13. An oxygen source is supplied from the oxygen source supply device 11, and inorganic salts such as nitrogen and phosphorus are supplied from the inorganic salt supply device 12. The oxygen source and the inorganic salts are active substances of aerobic heterotrophic bacteria that decompose oil. Used as. The nitrification inhibitor supplying device 13 supplies a nitrification inhibitor for suppressing the progress of nitrification by nitrifying bacteria.

  As nitrification inhibitors, thiourea, 2-amino-4-chloro-6-methylpyrimidine, 2-mercaptobenzothiazole, dicyandiamide, sulfathiazole, N-2,5-dichlorophenyl, succinamic acid, 1-amidino- 2-thiourea (guanylthiourea), 4-amino-1,2,4-triazole hydrochloride and the like can be preferably used.

  Valves 20 and 21 are attached to the oxygen source supply device 11 and the inorganic salt supply device 12 respectively, and oxygen and inorganic salts as active substances of aerobic heterotrophic bacteria that decompose oil by adjusting the valves 20 and 21 Adjust the supply amount.

  A control valve 19 is attached to the nitrification inhibiting substance supply device 13, and a control device 14 is connected to the control valve 19 by a signal cable or wirelessly. The control device 14 is equipped with a measuring device 18 that measures the nitrate ion concentration of water that flows out to the observation well 17.

  The control device 14 adjusts the opening / closing amount of the control valve 19 based on the nitrate ion concentration detected by the measuring device 18 and adjusts the nitrification inhibitor supply amount from the nitrification inhibitor supply device 13.

  The oxygen source, the inorganic salts, and the nitrification inhibitor supplied from the oxygen source supply device 11, the inorganic salt supply device 12, and the nitrification inhibitor supply device 13 are mixed once by the mixer 15 and supplied to the injection well 16. The A valve 22 is attached to the mixing device 15, and the supply amount of the mixed substance is adjusted by adjusting the valve 22.

  With these configurations, the soil and groundwater purification facility of the present invention suppresses nitrification, which hinders the purification of soil and groundwater contaminated with oil, by supplying a nitrification inhibitor, and effectively utilizes inorganic salts and oxygen and the construction period. Can be shortened.

  The injection well 16 not only digs deeper than the underground water vein 4 vertically, but also is formed in an L shape like the injection well 23 shown in FIG. 2 and is located upstream of the observation well 17 of the underground water vein 4. Alternatively, a horizontal portion may be formed above the contaminated portion 3. Furthermore, instead of the injection well, as shown in FIG. 3, it may be in the shape of a groove 24 that is located upstream of the observation well 17 of the groundwater vein 4 and formed on the ground surface.

  Next, the operation of the soil and groundwater purification facility according to the present invention will be described. In the injection well 16 shown in FIG. 1, oxygen, inorganic salts, and a nitrification inhibitor are respectively mixed by an oxygen source supply device 11, an inorganic salt supply device 12, and a nitrification inhibitor supply device 13 of the purification facility 1. Are mixed and supplied.

  The supplied mixed substance penetrates into the soil 2 and the groundwater vein 4 from the injection well 16. Oxygen and inorganic salts are substances necessary for the activity of aerobic heterotrophic bacteria that break down the oil already present in the soil 2 or the groundwater vein 4, and activate the activity of aerobic heterotrophic bacteria. Oil penetration is promoted by the penetration of oxygen and inorganic salts. As a result, the purification of the contaminated part 3 contaminated with oil proceeds faster than usual, and the work period of the purification work is shortened.

  However, not only aerobic heterotrophic bacteria that decompose oil, but also nitrifying bacteria, aerobic autotrophic bacteria that convert oxygen ions from inorganic salts to nitrate ions in soil 2 or groundwater veins 4 Existing. When ammonium ions are converted to nitrate ions by this nitrifying bacteria, the oxygen and inorganic salts that can be used by aerobic heterotrophic bacteria are reduced, so the aerobic heterotrophic bacteria activity becomes dull and the degradation rate of oil is slowed. become. Therefore, in the present invention, a nitrification inhibitor is injected into the contaminated site.

  That is, since the nitrification inhibitor supplied from the purification facility 1 has the effect of suppressing the activity of nitrifying bacteria, the reduction of oxygen sources and inorganic salts due to nitrification can be suppressed. This makes it possible to effectively use inorganic salts and oxygen.

  The supply amount of the nitrification inhibiting substance is controlled by the control device 14 based on the concentration of nitrate ions measured by the measuring device 18.

  The measuring device 18 is provided in an observation well 17 formed toward the contaminated site 3 downstream from the injection well 16 of the underground water vein 4, and measures the nitrate ion concentration of the contaminated water that has flowed into the observation well 17. And inform the control device 14 of the result.

  When the nitrification is suppressed by the effect of the nitrification inhibitor supplied from the nitrification inhibitor supply device 13 to the injection well 16 and the nitrate ion concentration measured by the measuring device 18 in the observation well 17 decreases, the control device 14 nitrifies. The control valve 19 connected to the inhibitory substance supply device 13 is closed to reduce the supply amount of the nitrification inhibitory substance. When the nitrate ion concentration increases, the control valve 19 is opened to increase the supply amount of the nitrification inhibitor. As a result, the supply amount of the nitrification inhibitor can be automatically changed in accordance with the change in concentration, so that the nitrification inhibitor can be effectively used.

  As described above, according to the present invention, nitrification that hinders the purification of soil and groundwater contaminated with oil is suppressed by supplying a nitrification inhibitor, and effective use of inorganic salts and oxygen and shortening of the construction period are aimed at. It becomes possible.

Configuration diagram of soil and groundwater purification equipment according to the present invention Configuration diagram showing another form of injection well Configuration diagram with grooves formed on the ground surface instead of injection wells

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Purification equipment, 2 ... Soil, 3 ... Contamination site, 4 ... Groundwater vein, 11 ... Oxygen source supply device, 12 ... Inorganic salt supply device, 13 ... Nitrification inhibitor supply device, 14 ... Control device, 15 ... Mixing device , 16, 23 ... injection well, 17 ... observation well, 18 ... measuring device, 19 ... control valve, 20, 21, 22 ... valve, 23 ... groove

Claims (3)

An oil purification method for soil and groundwater in which an inorganic salt containing at least a nitrogen source and an oxygen source are injected into soil and groundwater contaminated sites with oil, and the oil is purified by bacteria present in the contaminated sites. There,
A method for purifying oil in soil and groundwater, wherein a nitrification inhibitor is injected into the contaminated site.   Measuring the nitrate ion concentration of the groundwater at a position downstream of the position where the inorganic salt and the oxygen source are injected in the groundwater water vein, and controlling the injection amount of the nitrification inhibitor based on the measurement result. The soil and groundwater oil purification method according to claim 1, wherein In a soil and groundwater oil purification facility for purifying soil and groundwater contaminated sites with oil, using bacteria present in the contaminated sites,
An inorganic salt supply device for supplying an inorganic salt containing at least a nitrogen source;
An oxygen source supply device for supplying an oxygen source;
A nitrification inhibitor supplying device for supplying a nitrification inhibitor,
An injection well for injecting an inorganic salt, an oxygen source, and a nitrification inhibitor supplied from each device into the contaminated site;
An observation well provided at a position downstream of the injection well in the groundwater veins;
A measurement device for measuring nitrate ion concentration of the groundwater in the measurement well;
An oil purification facility for soil and groundwater, comprising: a control device for controlling an injection amount of a nitrification inhibitor substance injected into the contaminated site from the nitrification inhibitor supply apparatus based on a measurement result of the measurement apparatus.

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