Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Cleaning using a micro-organism or enzyme
Patent
1996-04-19
1997-06-10
Redding, David A.
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Cleaning using a micro-organism or enzyme
435266, 210610, 210614, 210615, 210618, D06M 1600, C02F 300
Patent
active
056374984
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention related to a method for biological cleaning of a gas flow containing at least one contaminant. The present invention relates more particularly to a method for biological cleaning of a gas flow making use of a liquid containing micro-organisms.
BACKGROUND OF THE INVENTION
Known biological gas purification systems comprise a biowasher, wherein the micro-organisms are dispersed in the liquid, and a so-called biotrickling filter (abbreviated below to BTF), wherein the micro-organisms ore situated at least partially on the packing material.
In the case of a biowasher the micro-organisms degrade the contamination absorbed from the gas flow by the liquid. The micro-organisms herein grow and the quantity of biomass thereby increases. This results eventually in draining of excess biomass.
In the case of a BTF the micro-organisms grow on the packing material in the form of a biofilm. The contaminants from the liquid are absorbed into the liquid which drips along the biofilm and diffuse into the biofilm. The micro-organisms degrade the contaminants and the degradation products such as water, carbon dioxide and occasionally mineral salts or acids, are relinquished to the liquid. This liquid can moreover contain nutrients for the micro-organisms in addition to acid or alkali to buffer the liquid to a neutral pH.
Due to excessive growth the biofilm can increase in size such that this results in an increased pressure drop over the BTF and ultimately even to blocking of the BTF. All kinds of mechanical and chemical procedures are applied to remove at least a part of the biofilm. The micro-organisms are for instance poisoned to enable easier mechanical removal thereof. As a result of the fact that the BTF must be taken temporarily out of service for maintenance, it is necessary to install two BTF installations to enable continuous biological cleaning of a gas flow. An additional problem is that the released biofilm forms waste which has to be processed and discharged separately.
SUMMARY OF THE INVENTION
The invention has for its object to provide a method for biological cleaning of a gas flow, such as for application in a biowasher and a biotrickling filter (BTF), wherein the inherent increase of the biomass as a consequence of the biological degradation of the contamination is to a great extent inhibited, while at the same time degradation of the contamination by the micro-organisms does not decrease, or does so to a much lesser extent.
This is achieved with the method according to the invention for biological cleaning of a gas flow containing at least one contaminant, comprising of: wherein the contamination is absorbed by the liquid and is degraded by micro-organisms in contact with the liquid; and fractional inhibition of the growth rate of the micro-organisms is greater than the fractional decrease in the degradation rate of the contamination.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 identifies a maximum growth rate as a function specified process parameter;
FIG. 2 identifies a degradation rate for ethanol under specified process conditions;
FIG. 3 shows the effect of an increasing NaCl concentration on the maximum growth rate;
FIG. 4 shows a specific degradation rate for methyl methacrylate;
FIG. 5 shows a decrease in the maximum growth rate under specified process conditions;
FIG. 6 shows the decrease in the specific degradation rate for dichloromethane under specified process conditions;
FIG. 7 shows the influence of an increasing NaCl concentration on the maximum growth of Xanthobacter autotrophicus under specified process conditions; and
FIG. 8 shows the effect of an increasing NaCl concentration on the specific degradation rate of dichloroethane.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the discovery that the effect of an increasing control salt concentration on the maximum growth rate of micro-organisms differs to a large degree from the effect on the degradation rate of the contamination. By increasing the control salt con
REFERENCES:
patent: 5064763 (1991-11-01), Bonte
Diks Robertus M. M.
Ottengraf Simon P. P.
van Lith Christianus P. M.
ClairTech B.V.
Redding David A.
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