Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Patent
1988-12-06
1991-10-01
Wyse, Tom
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
210761, 210762, 210912, C02F 1108
Patent
active
050531425
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for degrading or decomposing undesirable oxidizable materials contained in various waste materials such as industrial or domestic waste-water, sewage or polluted soil.
In the modern industrialized world, increasing amounts of wastes have to be disposed of. Conventionally, wastes are disposed of either by depositing or dispersing them in suitable places in the environment, such as in dumps or land-fills or in the sea, or by decomposing or degrading them by chemical, microbiological or mechanical means, or by simple combustion.
Until quite recently the disposal of certain types of wastes was often carried out in a rather careless manner, often by merely depositing the waste more or less directly in the soil, or by burning the waste leading to emission of undesirable materials into the environment. Other forms of waste materials, such as industrial or domestic waste water, were often led directly into rivers, streams, lakes, or the sea. The consequences of these lax methods of waste disposal are now becoming increasingly apparent.
Among the most serious acute problems are the leaching of toxic or otherwise undesirable substances into the environment from soil in which they have been deposited, leading to pollution of ground water and/or other sources of drinking water. Great efforts are now being made to stop the leaching of toxic matter from waste material deposited in soil, and in many cases it has been found necessary to dig up and isolate the polluted soil in order to remove the undesirable substances.
Methods which have been used to treat such soil include extraction, thermal processes, chemical treatment, microbiological treatment, stabilization and encapsulation:
The extraction process employs water to which various chemicals, such as acids or bases, may be added. The use of extraction processes permits only partial removal of heavy metals, cyanides hydrocarbons and chlorinated hydrocarbons.
Thermal processes for the treatment of polluted soil entail e.g. counter current treatment with steam, after which the contaminated steam must be condensed and treated Heating polluted soil to 500.degree.-600.degree. C. leads to evaporation of volatile pollutants, and t gas-air mixture is then burned at ca. 1400.degree. C. or otherwise treated. In total combustion processes the combustion takes place at ca. 1200.degree. C. and the exhaust gases must then be treated The use of all these procedures normally leads to satisfactory destruction of all organic matter. However, this purification process is extremely energy. consuming and therefore very expensive to carry out. One disadvantage is that most of the heavy metals are not removed.
Chemical treatment entails the addition of chemicals which react with the pollutants in question, whereby these are destroyed or modified. A significant disadvantage of this method is that the soil is brought into contact with potentially dangerous substances which themselves have to be removed after treatment. Detailed knowledge of the concentration of pollutants is also required.
Microbiological degradation of organic material is a process which is well-known in the field of waste-water purification, e.g. in municipal purification plants where microorganisms, in the form of biofilm or active sludge, degrade organic material in a cheap and effective manner. In microbiological soil treatment, microorganisms and nutrients are added to the soil and degradation takes place by aerating the soil by mechanical cultivation, or in a process resembling compost formation. One of the disadvantages of this process is the wide variation of biodegradability of different compounds. The introduction of soil containing toxic substances can lead to the death of microorganims or, at best, very low degradation grades.
Stabilization and encapsulation processes are not purification processes as such and will not be discussed further.
The Presence of undesirable substances in industrial or domestic waste-water, sewage and sludge is also a problem, and a variety of di
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Bjerre Belinda
Jensen Bror S.
Jensen Jorgen
Rasmussen Erik
Sorensen Emil
Forskningscenter Riso
NKT A/S
Wyse Tom
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