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Bau und Erprobung einer FRAK-Anlage fuer Bodensanierung

Das Projekt "Bau und Erprobung einer FRAK-Anlage fuer Bodensanierung" wird vom Umweltbundesamt gefördert und von Hegemann Engineering durchgeführt. Objective: A FRAK installation for facilitating the clean-up of heavy soils is to be designed and built. The aggregate consists of a series of pipes mounted on a hydraulic excavator; the pipes are equipped with venting holes at their ends and can be pushed into the ground. By high-pressure air blasts from the vents will change the entire pore structure of the soil, opening consolidated soil structures in particular. Similar installations have been tested to improve agricultural soil structure; the main difference is the heavy-duty layout of the installation. General Information: In-situ treatment of polluted soil is frequently prevented by the soil structure: if the soil contains much clay or has been compressed by heavy loads, neither water nor air will penetrate the dense layer, save along a few channels that are correspondingly washed out, forming channels to guide water and air through the soil layer without much affecting the layer itself. To extend the range of soils to be treatable, the FRAK process has been conceived, which works by applying gas shocks to the dense soil and thus changing the entire pore structure of the soil. The Commission of the European Communities has, within the frame of the ACE 89 demonstration programme, granted financial assistance to the development of a FRAK apparatus that is able to work under the condition of industrial grounds, i.e., stones and other obstacles occurring from time to time, and of not impairing industrial use of the ground; the site selected for demonstration was a railway station polluted with oil. The construction was carried out by the Bremen-based DETLEF HEGEMANN ENGINEERING GmbH who made a very flexible apparatus, operating vertically as well as in inclined mode, the four venting pipes being each separately adjustable for optimal re-shuffling of the entire soil. Commission assistance was restricted to the period of 1-10-90 through 30-4-92, during which time the FRAK apparatus was constructed and tested in operation. First results show that the FRAK apparatus performs according to expectations in rugged industrial environment, increasing the water flow rate through the treated soil by a factor of 5. Every blast will reshuffle up to 60 m2 of soil. The working depth extending up to 4 m, up to 240 m3 of soil may be treated by this apparatus in every drilling step; up to 25 drilling steps may be made per hour. Thus, with Commission assistance, a major break-through has been achieved to make polluted soils of low permeability accessible to in-situ treatment. This will be particularly important for the application of biological treatment systems whose performance usually suffer from bad aeration of the soil to be treated. FRAK will help to condition this kind of soil for biological in-situ treatment...

Mikrobielle 'in situ'-Sanierung mittels Frac-Verfahren

Das Projekt "Mikrobielle 'in situ'-Sanierung mittels Frac-Verfahren" wird vom Umweltbundesamt gefördert und von Osthannoversche Eisenbahnen durchgeführt. Objective: The project is to clean up the soil of the Nettelbeck railway station that is contaminated by hydrocarbons due to approximately 30 years of trans-shipment activities. Soil excavation not being possible without seriously disturbing normal operation at the station, OHE decided to wash the soil using the FRAK technology for breaking up the bound soil structures. The soil is then percolated in situ with water enriched with nutrients and oxygen in order to create optimum conditions for microbial activity; the groundwater whose level is closely below the surface is extracted and hydrocarbons are skimmed off by an external skim reactor. General Information: After two years of operation, German authorities accepted the FRAK-assisted microbial clean-up of the railway trans-shipment site of OSTHANNOVERSCHE EISENBAHNEN AG (OHE) at Nettelbeck near Hamburg which had been contaminated with mineral oil as satisfactory. This demonstration of the efficiency of the FRAK installation was granted assistance by the European Commission, within its ACE 89 programme on demonstration projects on clean technologies and contaminated site monitoring and rehabilitation. The project demonstrated the successful clean-up of soil contaminated by mineral oil at an average concentration of 3.500 mg hydrocarbons per kg. The goal was to clean up the soil to concentration values below 1000 mg/kg and groundwater to concentrations of less than 0,1 mg/l, the national tolerability limits being 0,4 mg/l. It was shown that this in-situ clean-up had no adverse effects on the neighbouring groundwater environment. The process was to extract polluted groundwater, remove oil beyond the dilution limits of approximately 5 mg/l, load the cleaned-up water with oxygen and nutrients and percolate the soil with the recycled water. Within this cycle, microbes feeding on mineral oil digested the remaining hydrocarbons. It could be shown that the initial nutrient reservoir was used up during digestion, which made the addition of phosphate and nitrate necessary in later phases of the cycle. To achieve clean-up to the goals set, the percolating water - ca. 75 times the average rainfall quantity - had to be recycled for approximately 160 times. The rate of hydrocarbon removal was remarkable: within eight weeks on the average, approximately 90 per cent of the contaminants could be removed. The digestion and percolation processes were greatly enhanced by air-pressure-assisted tear-up of the soil structure using a FRAK installation that had been constructed by DETLEF HEGEMANN ENGINEERING GmbH with Commission assistance within the ACE 89 programme; water percolation was drastically enhanced by a factor of five, which made the microbial in-situ treatment of soils with low penetrability (kF) value below 10-4 feasible...

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