Liquid purification or separation – Processes – Treatment by living organism
Patent
1998-08-11
2000-02-15
Wyse, Thomas G.
Liquid purification or separation
Processes
Treatment by living organism
210150, 210205, 210903, C02F 312, C02F 330
Patent
active
060248769
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a reactor of the mixed-cultures type which is intended for the biological removal of organic pollution from water, as well as for the biological removal of nitrates by the anoxic route.
Before explaining the invention, it is appropriate to restate a certain number of definitions and, in particular, those of the term "mixed cultures" in relation to activated sludges and to fixed cultures: unaerated tank; appearance of the equipment is most frequently comparable to a filter; what will be referred to hereinbelow as bioparticles, which are maintained in suspension in the water flow to be treated.
Moreover, the fixed cultures provide a function of "selection and enrichment of the biomass in bacteria which are specific to the treatment conditions, in particular the denitrifying heterotrophic bacteria in the case of biological denitration reactors", a feature which is advantageously utilized in the case of mixed cultures.
Devices are known which permit the implementation of biological treatments of effluents. Among these devices, there are some which utilize induced circulations of the effluents by "air lift" or "gas lift". By way of example of this prior art, it is possible to cite in particular WO-A 93 25485, JP-A 60-122095 and EP-0010571. Such systems cannot be utilized to carry out a denitrification, that is to say treatments by the anoxic or anaerobic routes. It is, moreover, impossible to utilize them where it is desired to carry out treatments with the aid of mixed cultures, given that the "air lift" or "gas lift" circulation systems have the major disadvantage of releasing the cultures from the supports on which they are fixed.
Devices are, moreover, already known which permit the performance of a denitrification of effluents with the aid of bacteria which reduce nitric nitrogen to a lower state of oxidation. These known devices are, in particular, the following:
These known devices have the disadvantage: supplementary equipment, in particular to ensure the maintenance of the hydraulic conditions (elutriations, disagglomerations, etc.), and of consuming energy.
The object of the invention is to create a reactor which is more compact than those of the systems incorporating activated sludges, which is more economical both in terms of equipment costs and in terms of operating costs and which permits the biological removal of pollution, in particular nitrogenous pollution, to be ensured under the best conditions.
To this end, the subject of the present invention is a reactor of the mixed-cultures type which is intended for the biological removal of organic pollution from water, as well as for the biological removal of nitrates by the anoxic route, characterized in that it comprises: part and within which the biological treatment takes place, which reactor contains a suspension of a fixed biomass, of low concentration of the order of a few grams per liter, said agitated reactor including at least one propelling screw positioned within an internal jacket and coaxial with said reactor, to ensure the circulation of the water to be treated, the latter circulating in accordance with an ascending or descending current within said jacket and in the opposite direction, descending or ascending, outside the latter and at a speed which is selected so that the bioparticles remain in suspension within said agitated reactor, communicating with the lower part of the latter, the water treated within this agitated reactor escaping through said release zone, to the upper part of the latter, in accordance with an ascending current at a speed such that, on the one hand, the speed of decantation of the bioparticles is greater than the speed of the water and, on the other hand, the speed of decantation of the excess biomass produced by the biological reactions, in particular of denitrification, is less than the speed of the water, and zone.
According to an embodiment of the invention, the water to be treated is introduced into the jacket, for example at the lower part of the latter, and the current
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Patent Abstracts of Japan, vol. 009, No. 271 (C-311), Oct., 1985.
Pannier Michele
Truc Alain
Vion Patrick
Degremont
Wyse Thomas G.
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