Hydraulic and earth engineering – Soil remediation – In situ contaminant removal or stabilization
Patent
1991-07-11
1993-07-27
Corbin, David H.
Hydraulic and earth engineering
Soil remediation
In situ contaminant removal or stabilization
405 36, 405258, B09B 300, E02D 300
Patent
active
052305864
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the microbiological decontamination of soil, in which regeneration clamps, and the contaminants takes place.
Decades of industrial utilization of terrain resulted in pollution of the soil, for example caused by inappropriate deposition of residues and leakages from tank systems, pipeline systems and pump systems. Such contaminations require a treatment if they adversely influence the groundwater or when polluted soil must be excavated for building purposes.
The contaminants which lead to soil contamination can belong to a wide class of substances and can have very different origins. Examples of potential contaminants include mineral oils of all processing stages (degrees of refining), such as crude oils, diesel oils, fuel oils, gasolines, industrial oils, furthermore chlorohydrocarbons, such as trichloroethylene, tetrachloroethylene, trichloroethane and dichloromethane, organic solvents, such as, for example, phenols, alcohols, aromatic hydrocarbons, aldehydes, acids, esters, ketones and ethers, but also various plastics, various other organic and inorganic substances and, last but not least, also pesticides and herbicides.
Many procedures are possible for the sanitation of contaminated soils. For example, there are the so-called "on-site" methods, in which the contaminated soil is first removed. In a different location, the contaminants are then removed by means of various treatment methods, such as, for example, thermally, chemically, microbiologically or by means of mechanical washing, and the purified soil is used to fill up the cavities formed by removal of the soil.
A method which has proved economical is the microbiological "on-site" degradation of harmful organic substances. The desired end products of the aerobic degradation of organic substances are carbon dioxide and water. A decisive factor for optimum removal of harmful organic substances is the adjustment of so-called environmental factors--such as, for example, oxygen content, pH, moisture and the presence of sufficient amounts .of nutrients for the microorganisms. Other factors, such as, for example, the solubility of the harmful substances in water, are also highly important.
Since there is such a multitude of factors, many different methods for microbiological "on-site" degradation of harmful organic substances have been described (cf., for example, Chem.-Ing.-Tech. 59 (1987), No. 6, pages 457-464). For example, in the Shell BIOREG method (cf. Chem-Ing.-Tech. 59 (1987), No. 6, page 461, right-hand column), the excavated contaminated soil is mixed with ground pine bark on a prepared subsoil and banked up in the form of regeneration clamps (height: 1.2 m). It is also possible to additionally incorporate aeration layers equipped with drainage pipes.
In another method (cf. Chem.-Ing.-Tech. 59 (1987), No. 6, page 461, right-hand column), contaminated soil is mixed with organic material (for example straw) and then inoculated with fungi causing white rot in order to break down polycyclic aromatic hydrocarbons. The fungi possess an enzyme system which is capable of breaking down cellulose and also suitable for breaking down the polycyclic aromatic hydrocarbons.
Finally, an experiment carried out by Deurag is also known (cf. Wirtschaftswoche No. 37 of Sep. 9, 1988, pages 101 and 102) in which the contaminated soil is first simply spread and waste water from the company's own sewage plant which contained bacteria was sprinkled onto the soil. After this, all that happened was that the soil was turned over twice per year and time was allowed to pass (principle of "land farming").
A great disadvantage of the known biological soil decontamination methods is the limited applicability with regard to the nature of the soil. For example, silty clay materials are not accessible to a microbiological sanitation because of their low permeability to air and water. Other grave disadvantages of the known "on-site" methods which work with microbiological purification of the soils are, in particular, the very slow degr
REFERENCES:
patent: 4350461 (1982-09-01), Valiga et al.
patent: 4765902 (1988-08-01), Ely et al.
patent: 4849360 (1989-07-01), Norris et al.
patent: 4850745 (1989-07-01), Hater et al.
patent: 4865488 (1989-09-01), Huston et al.
Bachhausen Peter
Kersting Karl-Heinz
Rehm Hans-Jurgen
BASF Lacke & Farben Aktiengesellschaft
Corbin David H.
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