WO1995000264A1

WO1995000264A1 - Method of treating contaminated soil and a device for carrying out the method

Info

Publication number: WO1995000264A1
Application number: PCT/EP1994/001622
Authority: WO
Inventors: Berndt Kühn; Peter König
Original assignee: Kuehn Berndt; Koenig Peter
Priority date: 1993-06-17
Filing date: 1994-05-19
Publication date: 1995-01-05
Also published as: DE4319992C2; DE4319992A1

Abstract

The invention concerns a method for decontaminating contaminated soil by washing the contaminants out of the contaminated layer (33, 34). Water is sprayed on the surface of the ground above the contaminated layer in the soil, and the water which passes through the contaminated layer is removed as a mixture of water and contaminants from a well (27) extending down the groundwater-flow level. This mixture is filtered and purified, and the purified water stored in a clearing pool (8). This process is continued until the contaminated layer has been completely removed. The initial dislodging of the contaminants and the subsequent decontamination are always carried out in conjunction with plants specified for the purpose.

Description

Process for the treatment of contaminated soils Device for carrying out the process

The invention relates to a method and an apparatus for the treatment of contaminated soils.

The subject matter of the invention is a decontamination process in which it is essential that the contamination layer stored in an earth, which is also referred to as a contamination lens, is detoxified without the layer reaching the earth's surface by excavation, suction or by thermal treatment must be made accessible from the earth's surface.

Methods are known in which the entire contamination lens is dug out and then treated in a specific manner in order to remove the pollutants from the contaminated soil.

In addition, so-called IN-SITU methods have also become known, in which it is not necessary to dig out the contaminated soil, which can also lie at considerable depths below a clean soil, in order to make cleaning accessible.

With such IN-SITU methods, it is known to generate a water stream on the non-contaminated earth surface, which seeps down over non-contaminated earth layers and seeps into the contamination lens (contaminated earth region).

In this way, the contaminating lens was diluted by infiltration of fresh water, so that the To get pollutants to mix with the pure water. This mixed water was then removed through appropriate extraction wells - lowered into the contamination lenses - and fed to a cleaning facility. It was known to use various cleaning methods in order to free the mixed water removed from the pollutants. Gravel filters, active carbon filters and the like were used.

A disadvantage of the known IN-SITU process is, however, that the pollutants have been mobilized only slightly or not in order to mix with the pure water. This is especially true for heavy metals.

Moreover, the further drawback with the known in-situ method has been, da _/ 9, the mixed water from the lens approximately Kontaminie¬ uncontrolled downward toward the ground water flowed, is mixed with the relatively clean ground water and poisoned the groundwater.

As a further disadvantage it should be mentioned that the soil structure is destroyed to a not inconsiderable extent by the introduction of such injection rinses, the soil structure of both the unpolluted soil and the soil contaminated with toxins being impaired. In particular, when hot water is injected, the soil destruction mentioned occurs.

The method according to the prior art is therefore a so-called wet classification method, in which the soil layers and clay minerals are irreversibly destroyed and / or important decontaminating soil microorganisms are killed. So far it has not been possible to take advantage of the detoxifying effect of microorganisms in order to detoxify contaminated soils, in particular heavy metals.

The invention therefore has the object of providing a method and an apparatus operating according to the process to further develop such da _/ 9 is ensured while maintaining an undisturbed soil structure a substantially ver¬ Patched detoxification efficiency, especially when heavy metals.

To achieve the object, the invention is characterized by a method according to the subject matter of claim 1.

A device operating according to the method is also claimed to be essential to the invention.

An essential feature of the present invention, since _/ 9 now stored in the ground above a contami- approximately lenses Anstaufläche or sprinkling area is built is built on a planting or extended. It is also essential, since _/ 9 to downstream of a groundwater flow one or more extraction wells built from which the groundwater is extracted and conveyed to the surface. It is also essential, since _/ 9 is subjected to this required mixing water purification and as / 3, the removed water from the purification stage is jammed in a polishing pond.

The process according to the invention thus consists of the following process steps: 1. Establish a damming or sprinkling area above one or more contamination lenses.

2.Berieseln the ground surface, which can be loaded or unloaded, above the Kontaminierungslinsen, so da _/ 9, the water enters the Kontaminierungslinse,

3. seepage of the mixed water into the aquifer,

4. removal of the mixed water from the aquifer via one or more extraction wells,

5. cleaning of the mixed water by one or more cleaning devices and cleaning stages,

6. Accumulation of the cleaned water in a beauty pond and, if necessary, returning the pure water to the accumulation or sprinkling area.

Attempts by the applicant have shown that _/ 9 the type and arrangement of the planting is on the Anstaufläche essential for the efficiency of decontamination in the Kontami¬ nierungslinse. It has in fact been found, since _/ 9 certain plants that are planted in the field of Anstaufläche or are already present, have properties that cause since _/ 9 facilitates layers particularly the heavy metal deposits in the contaminated Boden¬ in the introduced fresh water pass over to form a more enriched mixed water. On the other hand, it has also been shown that certain plant species are suitable for absorbing pollutants via the root body in the wood body area in order to bind the pollutants. When lead deposits have been found since _/ 9, the plants, such as Canadian Elderberry, is suitable to absorb such heavy metals over the root area in the wooden body. In addition, it has been found that / 3 z. B. Japanese knotweed is best suited to store cadmium deposits over the root area in the wood area.

It is therefore preferred in the present invention to plant flachwurzelnde and deep-rooted plants on the Anstaufläche, whereby not necessarily the root region to the rich Kontaminierungslinse mu _/ 9; however, it is preferred if deep-rooted plants also protrude with their root areas into the contamination lenses.

In addition, it has been found that the plants cause a change in the pH value in the soil, namely a shift to the acidic range, so that the harmful substances (including volatile substances) are mobilized and brought to the final washout . It is also provided that the plants absorb some of the harmful substances.

This concept represents an ecologically harmless remediation program, whereby neither soil layers are destroyed nor an uncontrollable intervention on microorganisms takes place.

The renovation is carried out without chemical or thermal intervention, which means that after this measure, the soil is not dead, but is highly macrobiologically and microbiologically activated by the ventilation close to the surface.

In the case of adjacent buildings, this type of renovation does not cause any damage from a start-up perspective on the constructions. The stability of buildings is not affected; this eliminates the need to provide evidence on the existing buildings because there are no structural damage.

The above-mentioned measure of flooding must be supplemented by planting with woody plants and perennials specially designed for the absorption of pollutants. These give off hydrogen ions and organic acids through their roots, which makes the heavy metals present as soluble chelate complexes or ions available to plants. The heavy metals which are now available to plants are deposited in the vacuoles (cavities), in the case of perennials mainly in the stem area. These can now be disposed of as contaminated goods after harvesting.

In the case of woody plants, the pollutants are permanently stored predominantly in the wooden body, so that remaining of the woody plants at the site can be regarded as problem-free. You can thus z. B. in the emergence of new landscape protection and local recreation areas. Later use of the wood for the construction area is also safe.

In the case of the invention, it is preferred if an accumulation surface is produced which is delimited by a wall running all around. This wall preferably has a height of approximately 60 cm in order to achieve a water level on the accumulation surface of approximately 15 cm.

Instead of the establishment of a damming area, another embodiment of the invention provides for sprinkling a certain area which corresponds in size to the damming area. That way too ensures that fresh water infiltrates from above through the top, contaminated or also uncontaminated layers of earth into the contamination lenses underneath.

In the following description, for reasons of simplification, a storage area is assumed.

In order to achieve optimal planting of a storage area, it is preferred if so-called trenches are built in the area of the storage areas, which are distributed troughs which run through the storage area in the form of semi-open channels in order to concentrate the water of the storage area in these trenches, so as not to grow the roots of those planted there

To affect plants by the cyclical water retention.

It is also preferred if several ventilation pipes for activating the

Root growth are driven into the ground, the ventilation pipes being driven to different depths in the unpolluted ground, with none of the ventilation pipes opening directly into the contamination lens.

In order to avoid an uncontrolled outflow of the aquifer contaminated with pollutants, it is further preferred to remove the aquifer in a controlled manner downstream of the groundwater flow below the accumulation surface. In order to avoid runoff, it is provided in a first embodiment that soil-flexible separating injections are introduced into the soil, which must reach so deep that they reach into the aquifer and the groundwater accumulate at least partially.

Here, one or more extraction wells are then built upstream of the soil-flexible separation injection, via which the polluted groundwater is conveyed to the surface.

Instead of a floor-flexible separation injection, other stowage methods can be used for the aquifer, e.g. driving sheet pile walls, sealing aprons and diaphragm walls, which can be mechanically driven into the ground from the surface of the earth to the groundwater area.

The mixed water withdrawn from the extraction well is then subjected to special filter processes, it being essential in these filter processes that filters are used with which heavy metals can also be absorbed.

The water removed from the filter device is then passed into a finishing pond, where the water is stored. The pure water can be taken from this fining pond for further use or it can also be returned to the accumulation area in the circuit in order to ensure that the cleaning chain is run through many times.

Overall, the technology according to the invention can be described as follows:

The contaminated area is modeled into a ramming area and delimited with a wall to the surrounding area. Special plant groups are selected for the chemical test results obtained by drilling out and are planted in the landscape to be decontaminated.

A pond area of only 6% of the total area to be contaminated is sufficient for the amount of water required for the accumulation and flushing process.

The water is pumped out of the pond and accumulated on the surface. The pollutants are mobilized by the infiltration of the water and discharged into the groundwater. In order to prevent an uncontrolled spreading of the pollutants, an interruption in the form of an injection wall introduced in the STRIKE or hydromilling process is effected in the direction of flow of the groundwater, while flexibility of the ground movement is still guaranteed. Immediately in front of the injection wall, the contaminated water from wells is pumped into a filter trench for natural filtration and passed directly to a so-called beauty pond.

Only a rapid flow of the accumulation water decontaminates the soil in short periods of time, which is not a problem with sandy soils. The necessary increase in the flow rate for cohesive soils is due to the negative pressure that occurs when the groundwater horizon is sucked off, so that the water is drawn off from top to bottom.

The aforementioned filter trench forms the core of the renovation concept. It consists of several layers of gravel and adsorbent as well as dense vegetation the top layer of gravel with plants capable of absorbing pollutants, e.g. phragmites and typha. The directly adjacent Schönungsteich is lined with a thin layer of gravel and sand.

The cleaned water from the Schönungsteich becomes cyclical for. further accumulation processes reused, which avoids hydraulic gradients due to water retention. Evaporated water is formed on the one hand by precipitation and on the other hand from the inflowing water

Groundwater balanced. The excess water masses that arise during heavy rainfall or when the snow melts are channeled from the Schönungsteich into a drainage ditch covered with reeds.

The soil compacted by the accumulation and flushing process is loosened with several superficial aeration levels. This restores the superficial, natural permeability. The air introduced thereby promotes root growth and the willingness of the plants to absorb pollutants as well as increased activity of the soil bacteria.

The electrochemical conditions are also restored in this way.

The boreholes and gauges previously drilled for soil investigations are to be used as analytical groundwater measurement parts. Another measuring point is the tapping point in the Schönungsteich towards the accumulation area. Thus, water investigations of the upper current and lower current of the suspected area are available.

If the indicative value in the Schönungsteich does not correspond to the reference value, a direct one is automatically created Introduction of the water in the Schönungsteich made in the filter trench to exclude a new accumulation.

The contaminated filter material saturated by the washout process must be disposed of in a special waste landfill or reprocessed using the ON-SITE process.

Contaminated plant material is disposed of as previously described.

This concept presented offers a safe, practicable solution to the problem of a livelihood that has been contaminated for decades.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another. All of the information and features disclosed in the documents, including the summary, in particular the spatial design shown in the drawings are claimed to be essential to the invention insofar as they are new to the prior art, individually or in combination.

The invention is explained in more detail below with the aid of drawings which illustrate only one embodiment. Further features and advantages of the invention which are essential to the invention emerge from the drawings and their description.

Show it: FIG. 1 shows a schematic top view of a device according to the invention,

FIG. 2: schematically shows a section in the direction of line II-II in FIG. 1,

Figure 3: a _. enlarged section through the filter trench,

Figure 4: a section through the Schönungsteich.

For decontamination of a plurality of contamination lenses 33, 34 stored in an unloaded soil, according to FIGS. 1 and 2, an accumulation surface 1 is generated on the surface of the earth, which is defined by a surrounding wall 2. The wall has a height of about 60 cm.

In the area of this accumulation surface 1, trenches 24 are erected, which are low, half-open trenches which, according to FIG. 1, extend in a parallel arrangement and at a mutual distance from one another.

The groundwater flow 3 can run parallel to the longitudinal axis of the trenches 24 or at any other angle.

A planting 35, which preferably consists of the previously mentioned plants, is now directed onto the accumulation area 1, trees, bushes, grass and perennials also being used.

In the area of the accumulation surface 1, a series of ventilation pipes 25 are driven into the unpolluted soil in order to ensure that the root growth of the To ensure water-based planting 35.

Downstream of the groundwater flow 3, a flexible ground injection in the form of a sealing skirt 4 is preferably driven into the ground, the lower edge of the sealing skirt 4 being below the lowest groundwater level.

This results in a build-up of the groundwater and upstream of the sealing apron 4, a series of extraction wells 27 are now built, which must extend into the groundwater stream 3.

The water of the accumulation surface 1 now seeps down in the direction of arrow 37 and penetrates into the contamination lenses 33, 34, where, according to the measures explained above, optimal washing out of pollutants occurs, so that this comes out of the contamination lens 33 , 34 downward flowing mixed water 36 is enriched with pollutants. This mixed water 36 is conveyed upwards by the extraction well 37. The pumping takes place via several pipelines 29, 30, which finally introduce the water into a filter trench 9. Here, the discharge into a drain pipe 17 laid at the bottom of the filter trench 9 takes place. The mixed water emerges radially outward from the slots of the drain pipe 17 and enters a first filter gravel layer 16, where a rough cleaning takes place. It then passes into a filter sand layer 18 and then into an adsorbent layer 19, which is designed accordingly depending on the amount of pollutants.

If, for example, the removal of heavy metals is concerned, the adsorbent layer is suitable for taking up corresponding heavy metals. If volatile hydrocarbons are to be absorbed, then the adsorbent layer is designed as an activated carbon layer, for example.

After passing through the adsorbent layer 19, the water reaches another filter sand layer 18 and then another filter gravel layer 16. The direction of flow of the mixed water emerging from the drain pipe 17 is thus directed upward in the direction of arrow 38.

It is important that the filter trench is also planted with appropriate swamp and aquatic plants 21 in order to use the important detoxifying effect of the swamp and aquatic plants according to the root space method.

The swamp and aquatic plants 21 planted on the filter trench thus serve to further purify the water in the filter trench. The water rising upwards in the filter trench then flows in the direction of the arrow 22 via an overflow threshold 14 into an adjoining treatment pond 8. Here, instead of the overflow threshold 14, there may be a spatial separation of the filter trench 9 and the treatment pond 8. In this case, the pure water reaching the surface of the filter trench is introduced into the pond 8 with pumps and via pipes. The pure water 12 is dammed up in the beauty pond.

A threshold 11 can be arranged in the fining pond, which defines a pump sump 10, from which the pure water is removed again with the aid of a pump 7, in order to be reintroduced into the accumulation surface 1 in the arrow directions 23 via a pipeline 6. However, if the water from the finishing pond 8 is still to have a certain undesirable degree of pollution, then it is provided that this water is fed back into the drainage pipe 17 of the filter trench 9 via a branch 32 in order to be cleaned again. run through.

The filter trench 9 and the finishing pond 8 have a waterproof lining 15 which e.g. can consist of a PE film.

A root protection layer 20 is arranged above the adsorber layer 19 in order to prevent the roots of the swamp and water plants 21 from penetrating into the adsorbent layer 19.

In the area of the accumulation surface 1, one or more control pipes 26 can be introduced, the ends of which extend into the groundwater flow in order to measure the groundwater level and to determine the direction of flow of the groundwater flow 3. In addition, 26 water samples can be taken via the control tube, and the emerging mixed water 36 can be analyzed.

The mixed water is removed from the extraction well 27 with the aid of submersible pumps 28.

On the accumulation surface 1, therefore, always pure or cleaned accumulation water 5 is stored, which only through

Penetration into the contamination lenses 33, 34 is transferred into the mixed water 36.

With the concept according to the invention, the biologically effective detoxification power of plants is thus exploited for the first time to remove pollutants from the soil. Instead of the filter trench 9 described, other filter devices can also be used, such as, for example, above-ground filter containers in which corresponding filter devices are arranged.

Instead of establishing a damming surface - which was described above - it is also possible to continuously sprinkle the surface corresponding to the damming surface in order also to allow water in the arrow directions 37 to penetrate onto the contamination lenses 33, 34.

Instead of the finishing pond 8 described here, the pure water can be removed from the filter trench 9 immediately.

The Schönungsteich 8 serves only as a water reservoir to ensure that the accumulation surface is flooded with accumulation water 5 only at regular intervals; the flooding cycles depend on the type and condition of the soil and on the type of planting 35.

There is therefore a cyclical flooding of the accumulation area 1 with accumulation water 5.

Drawing legend

1 accumulation surface 26 control tube

2 Wall 27 sampling wells

3 Groundwater flow 28 submersible pump

4 sealing apron 29 pipeline

5 backwater 30 pipeline

6 pipeline

7 Pump 32 branch

8 Schönungsteich 33 contamination

9 filter trench 34 II

10 pump sump 35 planting

11 Threshold 36 Mixed water

12 pure water 37 arrow direction

13 38 Direction of arrow

14 overflow threshold

15 lining

16 filter gravel layer

17 drainage pipe

18 filter sand layer

19 adsorber layer

20 Root protection layer

21 swamp and aquatic plants

22 arrow direction

23 direction of arrow

24 Rigole

25 ventilation pipe

Claims

Patent claims

1. A method for detoxifying contaminated soils, in which the contaminating lens is washed out, so that sprinkling and / or. Onto the upper layer of the earth above the contaminating lens (33, 34) in the ground area

Damming up with water takes place such that the water which has penetrated through the contamination lens (33, 34) is removed from a sampling well (27) in the groundwater stream (3) as mixed water (36), that the mixed water (36) is filtered and cleaned and that the purified water is dammed up in a finishing pond (8), this process being continued until the contamination lens (33, 34) is detoxified.

2. A method for detoxifying contaminated soil according to claim l, characterized in that the accumulation surface (1) is planted with shallow-rooted and / or deep-rooted plants which are able to mobilize and absorb the toxins from the soil, the deep-rooted plants preferably reach the contamination lens (33,34).

3. A method for detoxifying contaminated soils according to claim 2, d a d u r c h g e k e n n z e i c h ¬ n e t that the accumulation surface (l) is infiltrated by trenches (24).

4. A method for detoxifying contaminated soils according to one of claims 1 to 3, characterized characterized in that the accumulation surface (1) is sprinkled cyclically with the water from the Schönungsteich (8) and / or dammed up.

5. Device for the detoxification of contaminated soils, in which the contamination lens is washed out, characterized in that above the contamination lenses (33, 34) an accumulation surface (1), which corresponds at least to the size of the contamination lens (33, 34), is delimited is that below a groundwater stream (3) located below the contamination lens (33, 34) there is at least one extraction well (27) downstream, that the extraction fountain (27) is followed by a cleaning system which is assigned a finishing pond (8).

6. Device for the detoxification of contaminated soils according to claim 5, d a d u r c h g e k e n n ¬ z e i c h n e t that the cleaning system consists of a filter trench (9) consisting of several gravel and

Absorber layers (18), as well as a dense planting of plants capable of absorbing pollutants, e.g. Phragmites and Typha species is formed.

7. Device for the detoxification of contaminated soil according to claim 5, d a d u r c h g e k e n n ¬ z e i c h n e t that the accumulation area (1) is delimited by a wall (2).

8. Device for detoxifying contaminated soil according to one of claims 5 to 7, characterized in that the accumulation surface (1) is provided with a planting (35) pollutant-collecting plants, which are preferably separated from one another by trenches (24).

9. Device for the detoxification of contaminated soils according to one of claims 5 to 8, d a d u r c h g e k e n n z e i c h n e t that the unpolluted soil layer above the contaminating lens (33,34) contains ventilation pipes (25).

10. Device for detoxifying contaminated soil according to one of claims 5 to 9, d a d u r c h g e k e n n z e i c h n e t that downstream of the

Groundwater streams (3) behind the extraction well (27) are flexible, flexible separating injections into or below the aquifer to prevent the spread of pollutants in the groundwater.

11. Device for detoxification of contaminated soils according to claim 10, d a d u r c h g e k e n e z e i c h n e t that sheet piling, sealing aprons (4) or diaphragm walls in the ground water flow (3) are available for damming the ground water and preventing the spread of pollutants in the ground water.

12. Device for the detoxification of contaminated soils according to one of claims 5 to 11, d a d u r c h g e k e n n z e i c h n e t that the ratio between the size of the accumulation area (1) and the area of the Schönungsteiches (8) is approximately 100: 6.