Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Treating gas – emulsion – or foam
Patent
1996-11-18
1998-05-05
Tsang, Cecilia
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Treating gas, emulsion, or foam
4352525, 423220, 423239, 95149, 296 1, B01D 5334, B01D 5300, B01D 5336, B01D 5322, C01B 1716, C12M 104, C12N 120
Patent
active
057473315
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the removal of sparingly-soluble gaseous contaminants from gases. The gases to be purified especially comprise industrial and/or agricultural waste gases which contain as noxious components gases such as carbon disulfide, hydrogen sulfide, dimethyl sulfide, mercaptane, styrene, toluene, etc. which are sparingly soluble and which are mostly toxic. The present invention also relates to a purification apparatus for use in the process as well as a microorganism which is advantageously utilized in the process.
The venting of various waste gases into the environment is restricted due to environmental protection and various regulations. While certain measures can be used to reduce the amount of emissions, it has not been possible to eliminate the generation of noxious gases in various situations.
Bioscrubbing and biofiltration are traditional biological processes for the purification of waste gases. In bioscrubbers the noxious components of a gas are absorbed into water or into an active sludge and the degradation takes place in a subsequent separate stage. According to the prior art a satisfactory bioscrubbing will be achieved only when purifying a gas which is easily dissolved in the scrubbing liquid.
Biofilters utilize filters filled with an organic material such as compost, peat, wood bark or a corresponding material, or packed reactors filled with inert packing bodies, so called trickling filters. Microorganisms capable of degrading the noxious component are immobilized in the solid packing and said microorganisms degrade the component as the gas passes through the filter. According to the prior art, biofiltration has been used also for sparingly-soluble gases.
Recently, microorganisms have been found which are capable of degrading several noxious and toxic gases which previously were considered non-degradable. Thus, a publication called "VDI Berichte 735, Biologische Abgasreinigung, VDI Verlag, Dusseldorf, 1989" discloses processes for the biological degradation of gases such as xylene, toluene, styrene, dichloromethane, 1,2-dichloroethane, hydrogen sulfide, carbon disulfide, etc. by the action of microorganisms.
Various microorganisms useful for biological degradation purposes are commercially available from various depositories. Moreover, the person skilled in the art knows that microorganisms tolerating the pollutant in question will usually often be found living in samples taken from the polluted site such as the sewage or the like locality of an industrial site or farm. By performing a selection of the microbe cultures in such samples it will be possible to find strains of microorganisms which are capable of degrading the pollutant in question, provided that the pollutant is at all biologically degradable.
It is, for example, known that it is possible to remove hydrogen sulfide and carbon disulfide from waste gases by biofiltration in certain circumstances. In the above mentioned publication, VDI Berichte 735, there are several occurrences disclosing biodegradation of carbon disulfide and/or hydrogen sulfide. Thus, pages 129 to 138 of said VDI publication disclose the use of Thiobacillus microorganisms for the degradation of hydrogen sulfide in waste gases generated in a waste water purification plant. After an adaption time, the microorganisms were able to degrade more than 99% of the hydrogen sulfide in the raw waste gas. The degradation was performed in a trickling filter operating in a counter-current fashion.
Said VDI publication suggests, on pages 293 to 312, the removal of hydrogen sulfide from a waste gas by using a compost or peat filter including microorganisms of the genus Thiobacillus. However, the filter material had to be changed as soon as after 8 weeks of tests due to the formation of sulfurous deposits.
Said VDI publication further suggests, on pages 331 to 339, the removal of hydrogen sulfide and carbon disulfide from waste gases in a compact compost filter by the use of microorganisms such as those belonging to the genus Thiobacillus. Th
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Hartikainen Tarja Terttu
Kallstrom Markku Tapio
Martikainen Pertti Juhani
Mutka Kari Antero
Nyronen Timo Martti Tapio
Borin Michael
Tsang Cecilia
Vapo Oy
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