JP4599766B2 - Soil cleaning method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a soil cleaning method and apparatus (soil cleaning system). Specifically, the present invention relates to a soil cleaning method for cleaning soil contaminated with a poorly water-soluble organic substance and an apparatus used in the method.
[0002]
[Prior art]
One of the serious environmental problems in modern times is soil contamination. Environmental stress due to such soil contamination is widespread not only around the contaminated soil, but also through contaminated water flowing out from the soil, volatilized air, and the like, and the effect is extremely serious in the ecosystem.
[0003]
Methods for avoiding such environmental stresses due to soil contamination include cancellation of contaminated soil, enclosure treatment, cement solidification treatment, soil cleaning treatment, chemical decomposition treatment, bioremediation, vacuum extraction treatment, in situ glass solidification treatment, etc. The method by is mentioned.
These methods have been performed by appropriately selecting from various conditions such as a causative agent of soil contamination, the location where the contaminated soil occurs, the scale of the contaminated soil, and the processing cost.
[0004]
Among the methods described above, the method using soil washing treatment is one of methods suitable for treating soil contaminated with poorly water-soluble organic substances.
However, in the conventionally known soil washing treatment, it is necessary to use a large amount of washing water used for soil washing.
[0005]
In addition, the treatment of poorly water-soluble organic substances such as oil is generally performed with a surfactant, but when the oil or the like is treated with a surfactant, the discharged contaminated water is emulsified, and the oil and water Separation was difficult.
Furthermore, in order to remove the oil content of the emulsified contaminated water, it is necessary to use an emulsifying agent, etc., but the emulsifying agent used at this time requires post-treatment associated with gelation, etc. There were drawbacks such as poor performance and high cost.
[0006]
[Problems to be solved by the invention]
The present invention has been carried out under such circumstances, and reduces the treatment cost when performing soil washing, and further reduces the difficulty of treating contaminated water discharged when performing soil washing. It is an object of the present invention to provide a cleaning method and apparatus.
[0007]
[Means for Solving the Problems]
In view of such a situation, as a result of intensive research efforts, the present inventors have used a nonionic surfactant, preferably a limonene together with a nonionic surfactant, and a poorly water-soluble organic substance. It was found that by washing the soil contaminated with, the poorly water-soluble organic matter floated as an oily substance by bubbles and recovered. Furthermore, by mixing and stirring divalent and / or trivalent iron salts and polymer flocculants in the contaminated water discharged in the process of washing the soil, by precipitating the poorly water-soluble organic matter in the contaminated water, It has been found that hardly water-soluble organic substances are almost removed and that the waste water can be reused for soil washing, and the present invention has been completed.
That is, the present invention is as follows.
[0008]
(1) A soil washing method for washing soil contaminated with poorly water-soluble organic matter, (a) mixing soil contaminated with poorly water-soluble organic matter, nonionic surfactant, limonene, and water; A step of washing the soil by stirring the mixed solution; and (b) supplying air bubbles to the mixed solution after the step (a), an oily layer containing a hardly water-soluble organic substance, a contaminated water layer, and the soil. A step of separating the layers, (c) a step of recovering each of the oily matter, the contaminated water, and the soil containing the hardly water-soluble organic matter from each layer, and (d) a divalent iron salt in the recovered contaminated water. And / or a trivalent iron salt and a polymer flocculant, and then a step of separating the mixed solution into concentrated contaminated soil and wastewater, and collecting each of them.
(2) Further, (e) includes a step of mixing the soil and water collected in the step (b), stirring and washing the mixture, separating the soil and contaminated water, and collecting each of them ( 1) The soil washing | cleaning method of description.
(3) The soil washing method according to (2) , wherein the weight ratio of soil to water in the mixed solution in step (e) is in the range of 1: 1 to 1: 2 .
(4) The soil washing method according to any one of (1) to (3), wherein the divalent iron salt is iron (II) chloride and the trivalent iron salt is iron (III) chloride. .
(5) The soil washing method according to any one of (1) to (4), wherein the waste water is reused in the step (a).
[0009]
(6) The weight ratio of the soil contaminated with the poorly water-soluble organic matter and the washing water for washing the soil in the mixed solution of step (a) is in the range of 1: 1 to 1: 2. )-The soil washing | cleaning method as described in any one of (5) .
(7 ) The soil washing | cleaning method as described in any one of (1)-( 6 ) whose mixing rate of the nonionic surfactant in the liquid mixture of a process (a) exists in the range of 1000-1500 ppm.
[0010]
( 8 ) Soil contaminated with poorly water-soluble organic matter, washing water for washing the soil, nonionic surfactant, limonene, mixer into which water is added, oily matter containing poorly water-soluble organic matter, soil A bubble bath into which a mixture of contaminated water is charged, and a coagulation sedimentation tank into which contaminated water containing a divalent iron salt and / or trivalent iron salt, a polymer flocculant, and a poorly water-soluble organic substance is charged The mixer includes a stirring means for cleaning the soil contaminated with the hardly water-soluble organic matter, and the bubble bath contains the mixed solution and the hardly water-soluble organic matter. A soil wash comprising means for supplying bubbles to the mixture for separating into an oily substance layer, a contaminated water layer, and a soil layer, and the coagulation sedimentation tank comprises a stirring means for stirring the contaminated water System.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The soil cleaning method and soil cleaning system of the present invention will be described with reference to FIG. The system shown in FIG. 1 shows an embodiment of the soil washing system according to the present invention. Here, belt conveyors 1 and 3, screen 2, slurry pumps 5 and 9, screw conveyors 7 and 11, mixer 8, and separation tank. 10, apparatuses such as a precipitation tank 12, a filter press or a centrifugal separator 14, and an oily substance collection tank 15 are optional components. Moreover, although the soil washing | cleaning method of this invention is demonstrated using this system, the soil washing | cleaning method of this invention is not limited to using this system.
[0012]
First, the soil contaminated with a poorly water-soluble organic substance is stirred with a nonionic surfactant and water (hereinafter, water used in this step is also referred to as “washing water”) to the mixer 4 or the like. As a result, the poorly water-soluble organic matter is desorbed from the soil particles of the contaminated soil and washed (step (a)).
At this time, it is preferable to stir limonene, preferably d-limonene, with the nonionic surfactant and the soil and washing water. This is because, by adding limonene and washing with stirring, it is possible to improve the above-described effect of removing the poorly water-soluble organic matter.
[0013]
Soil contaminated with poorly water-soluble organic matter is contaminated with crude oil and its processed products, petroleum oils such as fuel oil, light oil, and heavy oil, vegetable processing oil, and various poorly water-soluble organic compounds. Shows the soil. Usually, when these poorly water-soluble organic substances adhere to soil particles, it is difficult to remove them from the soil particles.
[0014]
In addition, as the nonionic surfactant and limonene, the hardly water-soluble organic substance adhering to the soil particles is removed, and the hardly water-soluble organic substance is floated by bubbles to form an oily substance containing the hardly water-soluble organic substance. If possible, it is not particularly limited.
Here, as the nonionic surfactant, those which do not adversely affect the environment are preferable.
Moreover, as limonene, d-limonene is preferable. Since d-limonene is a compound that can be extracted from citrus peel, it is harmless in the human body and natural environment.
[0015]
In the mixed liquid of this step (a), the weight ratio of the soil contaminated with the poorly water-soluble organic matter and the washing water for washing the soil is 1 (soil): 1 (washing water) to 1 (soil): 2 (Washing water), preferably 1 (soil): 1 (washing water) to 1 (soil): 1.2 (washing water).
Moreover, the mixing rate of the nonionic surfactant in the liquid mixture of this process (a) is 1000-1500 ppm, Preferably it exists in the range of 1300-1500 ppm.
This is because when the washing is performed at the above-described weight ratio and mixing ratio, the contaminated soil can be washed and the contaminated water discharged during washing can be effectively and efficiently treated.
[0016]
In addition, the mixer used when performing such cleaning is usually a mixer used when performing such cleaning without any particular limitation. For example, in a tank as shown in FIG. Examples include a mixer 4 in which the wings rotate, or a mixer in which the tank itself rotates.
[0017]
Next, the mixed solution containing the soil washed by the above process is put into a bubble bath 6 and the like, and bubbles are supplied to the mixed solution to obtain an oily material layer, a contaminated water layer, and a soil layer containing a hardly water-soluble organic substance. (Step (b)).
Here, the bubbles supplied to the mixed liquid are preferably fine bubbles in order to improve the separation ability of the poorly water-soluble organic matter.
The method for supplying bubbles to the mixed liquid is not particularly limited, but the air from the air compressor is passed through a perforated plate provided on the bottom surface of the bubble bath or the bottom surface of the bubble bath or the like. There is a method of supplying bubbles to the mixed solution by passing the aeration tubes arranged for aeration.
[0018]
The bubble bath that supplies the bubbles and separates them into each layer is not particularly limited. For example, the bubble bath 6 shown in FIG. By using a bubble bath, bubbles can be supplied to the liquid mixture in the bubble bath tank, and an oily layer, a contaminated water layer, and a soil layer containing a hardly water-soluble organic substance can be formed in this tank in order from the top. it can.
[0019]
Next, each of the oily substance containing the poorly water-soluble organic substance, the contaminated water, and the soil is recovered from each layer (step (c)).
The method for recovering the oily substance containing the hardly water-soluble organic substance is not particularly limited, but a method for recovering the oily substance floating by the above-mentioned process by overflowing, or adsorbing the oily substance that floated to the adsorbing member. And removing it. As such an adsorbing member, for example, an oil adsorbing member such as an oil sponge is preferable.
[0020]
Although it does not specifically limit as a method of collect | recovering soil, The method of collect | recovering the soil settled down using the screw conveyor 7 grade | etc., Is mentioned. Further, in the step of collecting the soil, it is preferable to dehydrate the collected soil in order to reduce the collected soil from containing the oil and contaminated water.
Although it does not specifically limit as a method of collect | recovering contaminated water, It can collect | recover by opening the discharge port provided in the position in the tank where the contaminated water layer is formed.
[0021]
Next, after adding a divalent iron salt and / or trivalent iron salt and a polymer flocculant to the collected contaminated water, the mixture is added to the agglomeration sedimentation tank 13 and the like, and stirred, It separates into concentrated contaminated soil and drainage and collects each (step (d)).
Here, since the collected contaminated water contains soil particles and the like, the collected contaminated water is transferred to the settling tank 12 and settled into relatively large particles. It is preferable to perform the step (d) after the removing step. Moreover, it is preferable to collect | recover the particle | grains settled in the sedimentation tank here intermittently, and to return to the mixer 4. FIG.
[0022]
In the contaminated water collected here, a hardly water-soluble organic substance is emulsified with a nonionic surfactant. In order to remove the emulsified hardly water-soluble organic matter, a divalent iron salt and a trivalent iron salt having an oil removal effect equivalent to that of the emulsifying agent, or any one of them is added.
[0023]
The divalent iron salt and trivalent iron salt to be mixed in the contaminated water are not particularly limited, but iron (II) chloride and iron (III) chloride are preferable, respectively.
Further, the polymer flocculant mixed with the contaminated water is not particularly limited, but it is preferable that the cohesive force is strong and harmless to human body and environment.
[0024]
The method of mixing the above compounds and separating the mixture into concentrated contaminated soil and wastewater is not particularly limited. For example, first, divalent iron salt and / or trivalent in contaminated water. A method in which iron salt is mixed uniformly and a polymer flocculant is added, stirred and mixed, and then the mixed solution is allowed to stand to settle the concentrated contaminated soil and separate into concentrated contaminated soil and wastewater. Is mentioned.
[0025]
Although the coagulation sedimentation tank which isolate | separates this waste_water | drain and concentrated contaminated soil is not specifically limited, The coagulation sedimentation tank 13 as shown in FIG. 1 is mentioned. The coagulation sedimentation tank 13 is provided with stirring means such as a wing rotating in the tank in order to improve the cohesive force of the coagulant.
[0026]
The method for recovering the drained water and concentrated contaminated soil thus separated is not particularly limited, but the concentrated contaminated soil can be recovered after being dehydrated by a filter press or a centrifuge 14 or the like. preferable. Moreover, about drainage, it is preferable to collect | recover a supernatant part so that concentration pollution soil may not mix.
In addition, since the wastewater collected here is almost free of poorly water-soluble organic matter, it can be reused as washing water for washing or rinsing the soil. It is preferable to reuse.
[0027]
Further, the soil collected in the step (c) described above is mixed with washing water for rinsing the soil, and this mixed solution is stirred and washed with the mixer 8, and then separated into soil and contaminated water. It is preferable to collect (step (e)). This step (e) makes it possible to remove the poorly water-soluble organic matter in the soil.
The cleaning apparatus for performing the cleaning is not particularly limited, and examples thereof include a mixer 8 in which the wings in the tank rotate and a mixer in which the tank itself rotates as shown in FIG.
Moreover, in order to perform the washing | cleaning of soil and the processing of the contaminated water by washing | cleaning efficiently, the weight ratio of the washing water for washing | cleaning (rinsing) the soil in the liquid mixture of this process (e) is 1 (soil). 1 (washing water) to 1 (soil): 2 (washing water), preferably 1 (soil): 1 (washing water) to 1 (soil): 1.2 (washing water).
[0028]
The mixed solution obtained by washing the soil in the step (e) is separated into soil and contaminated water in the separation tank 10 and the like, and each is collected. Here, as a method of collecting the soil, a method of collecting while dehydrating with the screw conveyor 11 can be mentioned. Moreover, since the contaminated water collected here contains soil particles, it is preferable to transfer the contaminated water to the sedimentation tank 12 to settle relatively large particles on the bottom of the sedimentation tank. And as above-mentioned, the contaminated water containing microparticles | fine-particles is transferred to the coagulation sedimentation tank 13, and it isolate | separates into concentrated contaminated soil and waste water (reuse water) through a coagulation sedimentation and dehydration process.
[0029]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, it cannot be overemphasized that this invention is not limited only to these Examples.
FIG. 1 is a schematic diagram showing an example of a system for performing the soil cleaning method of the present invention.
First, the soil contaminated with the poorly water-soluble organic matter was sieved through the screen 2. Then, the non-ionic surfactant is combined with the soil 4 (1000 kg) contaminated with the poorly water-soluble organic matter, the washing water (1000 kg) for washing the soil, and d-limonene. (The concentration of the nonionic surfactant in the mixed solution; 1500 ppm) was added. Then, these were mixed and stirred by the mixer 4, and the contaminated soil was washed for about 10 minutes to desorb the hardly water-soluble organic substances adhering to the soil particles.
[0030]
In addition, as a result of measuring by the n-hexane extraction method, the soil contaminated with the hardly water-soluble organic substance used at this time contained 37000 mg of the hardly water-soluble organic substance per 1 kg of the soil contaminated with the hardly water-soluble organic substance.
[0031]
Next, the mixed liquid after stirring and washing was transferred to the bubble bath 6 by the slurry pump 5, and bubbles were supplied to the mixed liquid in the bubble bath tank. The bubbles are supplied by supplying air with the air compressor 16. By performing a treatment of placing the mixed solution in a bubble bath 6 for about 10 minutes, the mixture was separated into an oily layer containing a poorly water-soluble organic substance, a contaminated water layer, and a soil layer, and then recovered from each layer.
[0032]
The soil (about 850 kg) recovered while dewatering by the screw conveyor 7 is put into the mixer 8 where the wings in the tank rotate together with the washing water (1000 kg) for rinsing the soil, and the stirring washing is carried out for about 10 minutes. went. The mixed liquid subjected to the stirring and washing was transferred to the separation tank 10 via the slurry pump 9, and the mixed liquid was allowed to stand in the separation tank 10 to be separated into drainage and soil, and each was collected.
As a result of measuring the soil after the washing by the n-hexane extraction method, it was confirmed that the poorly water-soluble organic matter was 130 mg per 1 kg of the washed soil and was almost completely removed.
[0033]
Contaminated water (about 900 kg) collected from the bubble bath 6 and contaminated water (about 900 kg) collected from the separation tank 10 are transferred to the settling tank 12, where sedimentation of soil and the like in the contaminated water is possible. The material was removed.
In addition, as a result of measuring the contaminated water which combined these by the n-hexane extraction method, 210 mg of slightly water-soluble organic substance was contained per 1L of contaminated water.
[0034]
The contaminated water that had been treated by the settling tank 12 was transferred to the coagulation settling tank 13. In the middle of the transfer, iron (III) chloride was added to the contaminated water at a concentration of 625 ppm, and after feeding and stirring, the polymer flocculant was added at a concentration of 3.75 ppm.
[0035]
The contaminated water to which each compound was added as described above was stirred in the coagulation sedimentation tank 13 by the rotating wings in the tank, and allowed to stand to separate into drainage and concentrated contaminated soil.
The concentrated contaminated soil was recovered after draining with a filter press or a centrifugal separator 14.
[0036]
Moreover, as for the waste water, the supernatant portion of the coagulation sedimentation tank 13 was collected, and as a result of measuring the waste water by the n-hexane extraction method, it was confirmed that the hardly water-soluble organic matter per 1 liter of the waste water was 5 mg or less and almost completely removed Turned out to be.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a soil cleaning method and apparatus capable of reducing the load of wastewater treatment, facilitating treatment operations, and further reducing treatment costs.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a system for performing a soil washing method in an embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Belt conveyor 2 ... Screen 3 ... Belt conveyor 4 ... Mixer 5 ... Slurry pump 6 ... Bubble bath 7 ... Screw conveyor 8 ... Mixer 9 ... Slurry Pump 10 ... separation tank 11 ... screw conveyor 12 ... precipitation tank 13 ... coagulation sedimentation tank 14 ... filter press or centrifuge 15 ... oil recovery tank 16 ... air compressor

Claims (8)

A soil cleaning method for cleaning soil contaminated with poorly water-soluble organic matter,
(A) washing the soil by mixing the soil contaminated with the poorly water-soluble organic matter, the nonionic surfactant, limonene, and water , and stirring the mixture;
(B) supplying air bubbles to the mixed solution after the step (a), and separating it into an oily layer containing a poorly water-soluble organic substance, a contaminated water layer, and a soil layer;
(C) recovering each of the oily substance, the contaminated water, and the soil containing the hardly water-soluble organic substance from each layer;
(D) After mixing divalent iron salt and / or trivalent iron salt and polymer flocculant into the recovered contaminated water, this mixed solution is separated into concentrated contaminated soil and waste water, and each is recovered. The soil washing | cleaning method characterized by including the process to do.   The method further comprises the step of (e) mixing the soil and water collected in the step (b), stirring and washing the mixture, separating the soil and contaminated water, and collecting each of them. Soil washing method.   The soil washing | cleaning method of Claim 2 whose weight ratio of the soil and water in the liquid mixture of a process (e) exists in the range of 1: 1-1: 2.   The soil washing method according to any one of claims 1 to 3, wherein the divalent iron salt is iron (II) chloride and the trivalent iron salt is iron (III) chloride.   The soil washing method according to any one of claims 1 to 4, wherein the waste water is reused in the step (a).   The weight ratio of the soil and water contaminated with the poorly water-soluble organic matter in the mixed solution in the step (a) is in the range of 1: 1 to 1: 2, according to any one of claims 1 to 5. Soil cleaning method. The soil washing | cleaning method as described in any one of Claims 1-6 whose mixing rate of the nonionic surfactant in the liquid mixture of a process (a) exists in the range of 1000-1500 ppm. A mixer charged with soil contaminated with poorly water-soluble organic matter, nonionic surfactant, limonene, and water;
A bubble bath into which a mixed liquid composed of oily substances, poorly water-soluble organic matter, soil, and contaminated water is introduced;
A soil washing system comprising a divalent iron salt and / or a trivalent iron salt, a polymer flocculant, and a coagulation sedimentation tank into which contaminated water containing a hardly water-soluble organic substance is charged,
The mixer comprises a stirring means for washing soil contaminated with poorly water-soluble organic matter,
The bubble bath comprises means for supplying bubbles to the mixed solution for separating the mixed solution into an oily layer containing a poorly water-soluble organic substance, a contaminated water layer, and a soil layer,
The coagulation sedimentation tank is a soil washing system provided with a stirring means for stirring the contaminated water.

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