DE4303529A1 - Chemical-physical and biological physical cleaning of soil - comprises mixing with water, coarse material is separated, and sludge is sedimented and biologically treated using fluidised bed procedure - Google Patents

Abstract

In a new procedure for cleaning contaminated soil: the soil is mixed with water in a reactor (1) in a ratio of 1:2 to 1:10 by means of at least two air/water agitation operations (2), so that the impurities are transferred to the resulting sludge or artificial sludge substitute; sludge and microorganisms are separated from the coarser material by reducing the turbulence (3, 5) and by changing the direction of flow, the resulting clean coarse material is removed (4); suspended materials are removed (6) from just below the liquid surface and are taken to a settling tank (7) with a dwell time of about 1 hr., in which the suspended material flows upwards through a bed of the separated sludge and is filtered by it; the water which is free of suspended materials is withdrawn (14) at about 20 cm below the liquid surface and is returned to the inlet of the washing system; floating materials and oils are removed (13); the sedimented foam and microorganisms (12) are introduced into an aerobic fluidised bed in which organic contaminants are broken down by microorganisms specific to them; if heavy metals are present, the sludge from the settling tank or reactor undergoes an elution procedure by which the heavy metals are separated; and the clean sludge is mixed with the previously separated coarse material. Also claimed is an appts. for carrying out this procedure. USE/ADVANTAGE - For cleaning soils or other granular materials which have a grain size less than 20 mm and are contaminated with organic materials, nutrients or heavy metals. The cost of on-site and off-site soil cleaning is reduced while maintaining the required cleaning effect, and the appts. has a high degree of mobility.

Description

The invention relates to a method and a device for chemical, physical and biological cleaning contaminated soils in on-site or off-site processes, as well as to largely reduce the biological degradable contaminants in the residue.

Various processes and systems are currently available this objective. They go in there physical processes generally assume under Use of water in the high pressure process or a Combining water and air so much energy into it to enter cleaning goods that the silt from the coarse substances is separated, assuming is that after such treatment the pollutants on Silt are adsorbed. The silt is then separated drained and either at a hazardous waste landfill for Pollutants deposited or burned.

Chemical and combined chemical-biological processes assume that the items to be cleaned are in a water bath brought and mixed with a solvent there, so that the pollutants go into solution. The contaminated aqueous phase then becomes biological or chemical processed. The resulting residues are also dumped or burned.

In general, the plants are relatively multi-tiered as well operation and energy intensive.

The aim of the invention is to reduce the technical and technological effort for the on-site and off-site floor cleaning while reaching the required degree of cleaning and a high level  Degree of mobility of the processing plant.

The invention has for its object a method for To develop decontamination of soils by simultaneous application of physical and / or chemical and / or biological processes Degree of cleaning in floor cleaning and cleaning others particulate bulk goods in a self-contained Reactor allowed. At the same time, the procedural conduct be designed so that the washed-out contaminants, as far as possible, biodegraded or chemically bound to minimize the accumulation of residues. The Wash water should be used in the cycle.

The solution to this problem results from the characterizing features of claims 1-15. The task is solved according to the invention with a procedure, where the contaminated and freed from the top grain <20 mm Floor or the bulk of a laundry with Water without or under certain Initial conditions or cleaning goals with additions of Activated carbon powder, activated sludge, clays, flocculants, Ion exchangers or pH correctors in one go at least two independently adjustable Bar drums produced water-air fluidized beds in one longitudinally flowed container is subjected, whereby by the high energy input the floor structure completely dissolved, the contaminants from the soil particles replaced and due to the high exchange surface to the Fine substances and the silt are deposited and after a calming section the fine soil and Silt particles as well as from the Soil structure triggered microorganisms 0.1-1.5 cm submerged under the water surface while the coarse material freed of contaminants sinks and with a suitable device, preferably a spiral conveyor removed from the reactor and on an appropriate warehouse or a plant is dropped, at the same time a  Gravity drainage of the cleaned soil completed becomes.

The extracted wash water is in a through a partition divided sedimentation tank initiated so that a Downward flow of silt humus microorganisms Suspension and the slow flow of the sedimented mud is forced. This will make one Mud contact filtration reached and the ascending Wash water largely freed of suspended matter, so that it if subtracted below the water surface, either directly or used again as washing water after filtration can be.

The deposited sludge is highly enriched with Contaminants and washed out of the ground Microorganisms, these to the existing Contamination are adapted. Is it biological? degradable substances are created by the simultaneous Enrichment of contaminants and adapted ones Microorganisms are prerequisites for a problem-free and Rapid degradation of pollutants achieved in one aerobic fluidized bed is realized. The after the biological treatment resulting from sludge cleaned coarse soil can be added so that this maintains natural structure. The cleaned Excess water becomes the sedimentation basin for the wash water fed.

Are apart from organically degradable and nutrients too To remove heavy metals from the ground, then the Bio stage sludge before adding to cleaned soil be subjected to an elution in which the heavy metals brought into solution and chemically or from this solution can be removed by adsorption. There are known techniques for this to apply. According to the invention, this step is carried out by the Addition of special ion exchange material or clays prepared in the bottom wash, which then with the silt  be carried out and enter the organic stage.

If soils or bulk material with a low silt content are clean, are as in the washing reactor Puffed powder activated carbon, clays or Flocculant dosed, if necessary, activated sludge be added. Is a nutrient contamination Wash out, if there is insufficient humus or silt fraction in the soil activated sludge added.

For special contaminations e.g. B. BTX (Benzene, toluene, xylene) and PCB (polychlorinated biphenyls) is used to enhance the adsorption effect Silt powdered activated carbon in the washing reactor added.

The device for performing the The procedure results from the characteristic features according to claims 10-14. The object is achieved according to the invention solved in that the washing reactor as a container is formed in the at least two rod drums horizontal axes that are transverse to the flow direction are arranged, rotate and at least 10 cm, however protrude up to a third above the water surface so that a water-air-soil Fluid bed is created. The drums are preferably with equipped with a double wreath of bars, independent controllable from each other, variable speed and both forward like rotating backwards. The diameter of the drums should be are between 80 cm and 100 cm. The drum width corresponds to the width of the washing reactor, which is mobile Systems preferably 1-2 m, for stationary systems up to to 4 m.

The washing reactor itself is a container on the front has a slope over which the material introduced into the wash bath slips. The floor under the drums can  each be designed as a half-shell or flat, wherein the passage height to the drum is at least 5 cm. in the Connection to the drums is at the bottom of the container Calming device arranged a length and a Has an apex height of at least 30 cm each and to both the drum and the discharge device Inclined. The apex height can be up to half of the drum diameter raised and especially at Execution of the bottom under the drums as a half shell Raised edge are formed in a slope which passes in the collecting shaft of the discharge system ends. Income is preferably used as the discharge system Spiral conveyor used. The distance between the Overflow edge and the collecting shaft should expediently be at least 30 cm, with the Extension of the calming section the selectivity of Silt increases. Is above the entrance to the collecting shaft from the water surface to a depth of at least 10 cm a vertical chicane is attached. In the There is a calm zone behind the chicane height-adjustable drainage channel with a smooth horizontal Overflow edge over the entire reactor width. The gutter is dimensioned so that they the entire wash water supply can record. The deduction is 0.1-1.5 cm below the Water surface.

The dirty washing water is put into a sedimentation basin initiated, the at least a stay of 1 h and ensures a water level of 3.0-3.5 m. The sedimentation basin is from the surface by a chicane forth to a depth of approx. 2.5 m in two chambers divided, the one chamber about 10% of the surface of the sedimentation basin, the other about 90%. The Wash water inlet is in the smaller chamber below the water surface. The clear water drain is variably adjustable and takes place in the larger chamber the greatest distance from the inlet under the  Water surface.

Directly from the water surface become discontinuous Floating substances such as pieces of wood and oils are subtracted. These through a coarse separator and an oil separator headed.

Slopes are installed in the lower part of the sedimentation tank. On the floor there is a screw conveyor with which the settled suspension is discharged into a bioreactor, in which the biodegradation of the contaminants takes place.

The bioreactor is the same height as the sedimentation tank and is dimensioned so that with a silt fraction of 30% a stay of about 1 day is guaranteed. The Silt microorganism suspension is immediately over the bottom into the bioreactor and from there with air supply together with those in the reactor swirled existing growth carriers. The Residence time is determined by internal recirculation and the Mud return from the settling section set. The Mixture of purified silt and organic sludge withdrawn from the settling part by means of a screw conveyor and the cleaned soil added.

The advantages of this procedure and the corresponding device consist in an essential Reduction of the amount of residues to be treated. At appropriate interpretation of the calming section is with mainly remove silt <0.063 mm from the dirty water, this reduces the amount of contaminated Residual material considerably.

A further treatment of the residue is both from the possible use of chemicals, as well as from Volume and energy requirements more effective than e.g. B. the Treatment of the entire amount of wash water. At the same time the requirements for wash water quality decrease because that Water is used only as a means of transport and the Pollutants cannot be solved in it. With that a Circular use of water with very little Effort.  

The fact that at the same time with the silt the in the Soil contaminants adapted to microorganisms be washed out and the pollutants on the silt are concentrated, a rapid biodegradation in the Fluidized bed reactor enables, so that the invention operated floor cleaning largely without the occurrence of too landfilling residues is operated. It will the costs for recycling is largely reduced.

Embodiment

The invention is based on an exemplary embodiment are explained. The associated drawings show:

Fig. 1 flow diagram of a complete plant, surrounded the periphery of the invention claim,

Fig. 2 side view of the system.

Based on exploration work, it is known that approximately 4,000 liters of diesel fuel have seeped away at one location. The pollutants are distributed in a soil volume of approx. 1000 m ³ , the soil must be decontaminated. The floor is sandy. Humus is present in the top layer.

The soil was screened. The soil to be treated is in the characterized the following.

The silt fraction <0.1 mm is 14.4%, the proportion of Size class 0.1-0.5 mm 58.4%, size class 0.5- 1.0 15.4% and greater than 1.0 mm 11%.

The floor washing is done with the invention Mobile implementation on site in on-site Method.

The performance of the floor wash is designed for 3 m ³ / h. The plant is operated for 15 hours a day.

The bottom is picked up with an excavator and placed on the slope of the washing reactor 1 via a tilting device so that the bottom slides into the water-filled container. By rotating the rod drums 2 , the soil in the water body is mixed intensively, brought into contact with air, expanded and simultaneously transported through the washing reactor 1 . The energy input creates high shear forces that lead to an overcoming of the adhesive forces between the pollutants and the soil grains. At the same time, new bonds are formed between the pollutants and the silt particles brought into direct contact with them when they are mixed. The biosorption also binds the pollutants to the microorganisms present in the soil and, as a silt-microorganism contaminant suspension after the calming section 3 of 0.3 m, is drawn off from the washing reactor behind the chicane 5 0.5 cm below the water surface via the discharge channel 6 .

The wash water, which is highly contaminated with the pollutant suspension, is introduced into a settling tank 7 in such a way that it flows downward behind the chicane 10 , passes through the suspension settled in the sludge funnel 11 and then slowly rises until the water is withdrawn 14 . After this treatment, a slight turbidity is still present in the wash water, but this is irrelevant for washing the floor, since the water is not used as a solvent but as a means of transport. If there is a concentration of pollutants in the wash water in individual cases, either a flocculant or powdered activated carbon is added to the wash water and the pollutants are adsorbed or flocculated.

The sold material is highly enriched with Diesel fuel measured as MKW  (Mineral oil hydrocarbons). These are in the subsequent biological treatment by 95-98% reduced.

The grain size composition of the deposited material is 34.7% in the range 0-0.063 mm, in the range 0.063- 0.100 mm 18.2%, in the range 0.100-0.200 mm 18.5%. The D10 value is 0.018 mm, D50 value 0.094 mm. The relatively high proportion in the ranges 0.063-0.100 mm and 0.100-0.200 mm is on the relatively short Calming section attributed. When extending the These grain sizes are calming with the Coarse matter discharged.

The cleaned floor slips into the collecting shaft of the conveying device 4 at the end of the washing container, is raised above the water level by means of a spiral conveyor, thereby drained by gravity and then thrown off. The cleaned floor is reinstalled at the extraction site.

The grain size composition of the coarse material is depending on the washing time. In the range <0.100 mm found 0.8-1.2%, in the range 0.100-1.00 mm 80- 90%.

The initial concentration of diesel in the treated soil, measured as MKW, was 2,885 mg / kg DM. With a throughput of 3.6 m ³ / h, MKW values of 100-175 mg / kg DM were found in the cleaned soil. The cleaning effect is 94-96%. The cleaning effect can be increased to 96-98% by reducing the throughput, increasing the amount of wash water or adding flocculant or activated carbon. In general, however, this is not necessary because the required installation values are also achieved in this way.

At higher starting concentrations of MKW the  contaminated soil may have been washed several times will.

The service life of the system on the contamination source shown in the example is 25 working days until the remedial work is completed.

Reference list

1 washing reactor
2 bar drums
3 calming device
4 discharge device
5 chicane in wash reactor
6 discharge channel
7 sedimentation tanks
8 Small chamber
9 Great Chamber
10 baffles in settling tanks
11 sludge funnels
12 clearing and extraction device
13 Oil and light material extraction device
14 process
15 fluidized bed reactor
16 filters for washing water treatment
17 Bio bed

Claims (15)

1.Procedure for the chemical-physical and biological physical soil cleaning of soils and other bulk materials with a grain size <20 mm contaminated with organic pollutants and / or nutrients and / or heavy metals by washing out the contaminants in their binding form to silt and subsequently reducing the pollutants characterized by biological degradation and / or chemical treatment characterized,

• a) that the contaminated material is subjected to such shear forces in a reactor in which water serves as a means of transport at a solids-water ratio of 1: 2-1: 10 by the generation of at least two successive air-water vortices that the soil structure is completely dissolved and the binding forces of the contaminants adhering to the bulk material are released and these are bound to the silt contained or, in the absence of silt, to the silt substitute added;
• b) that the silt and microorganisms contained in the bulk material are separated from the coarser material by calming the turbulence and changing the flow direction;
• c) that the cleaned coarse material is discharged after the calming section;
• d) that the suspended matter is drawn off just below the water surface and introduced into a sedimentation tank with a residence time of about 1 hour in such a way that a downward flow is forced and the suspended matter is subjected to contact filtration during the passage of the silt particles that have already settled and is retained in the filter bed;
• e) that the suspended matter-free washing water is drawn off from the rising stream about 20 cm below the water surface and fed back to the washing system;
• f) that substances and oils floating on the water surface are removed;
• g) that the settled mixture of silt and autochthonous microorganisms is introduced into an aerobic fluidized bed, where the organic pollutants are broken down by the microorganisms adapted to the present pollutants after a stay of at least 4 hours and if necessary addition of nutrients;
• h) that in the presence of heavy metal contamination the sludge accumulating in the sedimentation basin or in the presence of organic and heavy metal contamination in the bioreactor is subjected to an elution, the heavy metals then being removed from the liquid phase using known methods;
• i) that the silt-biosludge mixture freed from contaminants is mixed with the already cleaned coarse fractions.

2. The method according to claim 1, characterized in that the air-water vortices are both directed towards each other, as well as forward or backward in the same direction Enter energy. 3. The method according to claim 1, characterized in that the soil or bulk material to be treated in Wash reactor additives are added.   4. The method according to claim 1 and 3, characterized in that the additives are powdered activated carbon, Clays, benthonites, flocculants, organic sludge, special sea chalk, ion exchanger or organic Solvents and wetting agents are. 5. The method according to claim 1, characterized in that added flocculant to the inlet to the sedimentation tank will. 6. The method according to claim 1, characterized in that the drain from the sedimentation tank an additional Filtration is subjected. 7. The method according to claim 1 and 6, characterized in that auxiliary substances such as powdered activated carbon, Flocculants are used when there is too Redemptions of pollutants are coming. 8. The method according to claim 1, characterized in that in the bioreactor for building the fluidized bed either the silt to be treated is used as a carrier material or another known carrier material in addition is used. 9. The method according to claim 1, characterized in that adapted microorganisms from the contaminated soil washed out, activated and multiplied with which then targeted inoculation of organic beds takes place. 10. A device for chemical-physical and biological physical floor cleaning for carrying out the method according to claims 1-9, consisting of washing reactor ( 1 ), sedimentation basin ( 7 ) and aerobic fluidized bed reactor with reversing immersion heater ( 15 ),

• a) that the washing reactor ( 1 ) consists of a partially beveled, water-filled, open-topped tank in which at least two rod drums ( 2 ) rotate about a horizontal axis, which are arranged transversely to the direction of flow, and which are at least 10 cm in diameter across the Protrude from the water surface, the floor under the drums allowing a passage height of at least 5 cm;
• b) that a calming device ( 3 ) of at least 30 cm in length and a vertex height of at least 30 cm is arranged behind the bar drums ( 2 ) at the bottom of the container and has a slope both on the drum side and towards the discharge device ( 4 );
• c) that at the end of the calming section ( 3 ) the water surface is interrupted by a chicane ( 5 ) which is at least 10 cm below the water level;
• d) that a drainage channel ( 6 ) is arranged behind the chicane ( 5 ) at a depth of 0.1-1.5 cm below the water surface;
• e) that adjoining the washing reactor ( 1 ) is the settling basin ( 7 ), which is 3.5-4.0 m high and, in its other dimensions, guarantees at least one hour of residence time for the amount of suspension to be treated;
• f) that the sedimentation basin ( 7 ) consists of two chambers, which occupy 10% (8) or 90% (9) of the surface in relation to the surface and these are separated from one another by a baffle ( 10 ), which extends at least to a depth of 2.5 m and ends in a sludge funnel ( 11 ), the inlet ( 6 a) in the smaller chamber ( 8 ) 10-50 cm below the water surface, the outlet ( 14 ) in the larger chamber ( 9 ) at the greatest distance to the inlet below the water surface;
• g) that a removal device for floating materials and oils ( 13 ) and a technically known clearing and removal device ( 12 ) for sludge (silt) are provided in the sludge hopper.

11. The device according to claim 10, characterized in that the drums ( 2 ) are independently controllable, variable in speed and can be rotated both forwards and backwards. 12. The apparatus according to claim 10, characterized in that the drums ( 2 ) are equipped with a single or multiple rod ring. 13. The apparatus according to claim 10, characterized in that the bottom under the drums ( 2 ) is designed as a half-shell. 14. The apparatus according to claim 10, characterized in that the bottom is flat under the drums ( 2 ). 15. The apparatus according to claim 10, characterized in that the discharge channel ( 6 ) has a smooth horizontal overflow edge.