Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of...
Patent
1994-08-08
1997-04-15
Beisner, William
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
4352866, 4352991, 210617, 210150, C12N 100, C12M 114
Patent
active
056208910
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to biological reaction processes and bioreactors for use in such processes.
Biological reaction processes are used for the production of cell mass or biomass as well as for the production of metabolites and for biological transformations. The invention is particularly concerned with such processes wherein the microorganisms used in the process are adsorbed or immobilized onto a support medium.
The biological reaction process may involve the conversion of dissolved or colloidal polluting nutrient into cell mass such as in the treatment of sewage, industrial effluent and surface water.
For the sake of brevity and convenience, the invention will be described in relation to a biological reaction process involving the production and utilization of cell mass for treating a liquid feed such as sewage or industrial effluent so as to reduce substantially or eliminate the polluting capacity of that sewage or effluent. However, it is to be understood that the invention is not limited to the treatment of sewage or industrial effluent as it may be applied to other feeds and to other biological reaction processes in which microorganisms used in the process are adsorbed or immobilized or otherwise supported onto a support medium. The microorganisms (such as bacteria, fungi, algae and protozoa) are preferably derived from the sewage and digest nutrient that is also present in the sewage. This nutrient may contain carbonaceous material and can be in solid or soluble form, and is quantifiable in the art as Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). The biological reaction process can be used to remove nitrogen from sewage by conversion to nitrates.
BACKGROUND ART
Prior art biological reaction processes for the treatment of sewage suffer from the disadvantage, to varying degrees, of low efficiency in terms of the amount of resources required and the time taken to process a given volume of sewage.
Attempts to increase the efficiency of known biological reactions processes for the treatment of sewage have focused on various parameters of these types of reaction processes including the means for distribution of respiratory air to the reaction vessel; techniques for the reorientation of the support medium to prevent channelling and to introduce greater flow of air and liquid through the support medium; the nature of the support medium; and methods of controlling the air and liquid delivery rates to the system.
For example, Australian Patent Specification 528,760 describes a process for purifying polluted water by percolating it downwardly through a submerged, fixed granular bed. Oxygenated gas is fed upwardly from an intermediate level of the bed and treated water is discharged from the bottom of the bed. The flow of water to be treated and the flow of the oxygenated gas is adjusted in such a way that specific mathematical relationships are satisfied.
In the process described in the Australian Specification 528,760, the critical parameters for efficient operation are said to be the rate of flow of water to be treated over the granular bed and the volume of oxygen supplied to the microorganisms. Of these two parameters, regulation of the dissolved oxygen content of the water is the key to maintaining the process at its optimum rate.
In order to achieve acceptable results with this process, it is necessary to take the water through several pre- and post-treatment stages including pre-oxidation with ozone and filtration through sand.
The process described in Australian Specification 528,760 is described in an article by Barr K. G. in the journal Water of March 1988. In that process, it is intended that the water flow/oxygenated gas flow mathematical relationships achieve high concentrations of biomass growth on the granular bed to allow high loading rates or low hydraulic retention times.
Prior art processes for the treatment of sewage or polluted water have made a number of assumptions regarding the fundamental nature of the biological reaction process. All these
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Drummond Humphrey
Johnson Warren
Khoo Paul
Kopp Clinton
Vaid Aloke
Beisner William
Memtec Limited
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