Liquid purification or separation – With means to add treating material – Plural distinct separators
Reexamination Certificate
1998-10-01
2001-01-09
Barry, Chester T. (Department: 1724)
Liquid purification or separation
With means to add treating material
Plural distinct separators
C210S220000, C210S221200, C210S258000, C210S416100
Reexamination Certificate
active
06171487
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a twin-flow filter for the biological purification of biological effluents, in particular water.
BACKGROUND OF THE INVENTION
It is known that various pollutant substances (ammoniacal nitrogen, carbon-based substances, etc.) contained in effluents, in particular in water, can be removed biologically. Some of the reactions—aerobic thus used are carried out by means of atmospheric oxygen and they thus require an external supply of oxygen in as much as this oxygen is not already present in the water to be treated.
Many processes and devices are known which make it possible to carry out such a biological removal in the presence of oxygen. Thus, with this aim, reactors, filters or biofilters are used.
Reactors simultaneously carry out the supplying with oxygen and the provision of physical supports for the growth and maintenance of the bacteria.
Filters use oxygen already present in the water and their filtering material serves as a support for the growth and maintenance of the bacteria. In addition to the biological reaction, filters ensure the usual functions of retention of the matter in suspension, followed by its removal during washing.
Biofilters combine the functions carried out by reactors and filters.
Thus, the production of biofilters requires the combination, in the same chamber, of all the functions required for the removal of pollutant substances biologically: bacteria-supporting functions, aerating functions and washing functions. It is seen that such a combination can lead to a complex and thus expensive production, as regards both the manufacturing costs and the operating and maintenance costs. Moreover, the internal aeration used in biofilters leads to stirring of the bed of granular material and this stirring can be detrimental to the formation of the biomass on the granular material which serves as a support for it. The internal aeration can also be detrimental, for the same reasons, to the quality of the filtered water.
BRIEF DESCRIPTION OF THE INVENTION
Consequently, the present invention proposes to provide a device for the biological removal of pollutant substances contained, in particular, in raw water to be treated, which, in a particularly cost-effective manner, advantageously combines the various functions recalled above, allowing this biological removal to be achieved. The invention is based on an embodiment of water-treatment filters known as twin-flow filters. It will be recalled that these filters consist of two filtration cells through which flows pass in series. The first cell has an ascending flow passing through it and the second cell has a descending flow passing through it. An embodiment of such a twin-flow filter is disclosed in German patent DE-A-2,355,422. This type of filter is used in particular as an active-charcoal filter.
A system of two filters arranged in series, both operating with a movement of the flow directed from the top downwards, is also known from Swiss patent CH-A-661,264, these two filters being separated by an intermediate box fitted with aeration means.
Starting from this state of the art, the present invention provides a twin-flow filter for the biological purification of effluents, in particular water, comprising at least two filtration cells, arranged in series, in hydraulic connection, such that the effluent to be treated passes through them successively, these two cells being separated by an intermediate box provided with aeration means, characterized in that the first filtration cell is of the ascending flow type and the second filtration cell is of the descending flow type, and in that the aeration in the said intermediate box takes place countercurrentwise with respect to the liquid flow moving through the said box, with a movement of the flows directed with the aid of a siphoning partition.
The invention is also directed towards a twin-flow filter for the biological purification of effluents, in particular water, comprising at least two filtration cells arranged in series and in hydraulic connection, such that the effluent to be treated passes through them successively, the cells being separated, respectively, by an intermediate box provided with aeration means, characterized in that it includes n filtration cells, through which the effluent to be treated passes successively, and n−1 intermediate boxes, each comprising the aeration means, each intermediate box being placed between two successive filtration cells and having the effluent to be treated pass through it, either with a movement of the flows directed by means of a siphoning partition, or with an ascending flow.
Thus, according to the invention, the channel located between the two cells (and which is generally used to recover the washing waters) is used to carry out an intermediate aeration and thus to increase the reaction yields on the second cell. In addition, this arrangement in accordance with the invention makes it possible to carry out the aeration without in any way disrupting the filtration processes which take place in the cells.
According to the invention, the intermediate box can be used in order to inject reagents capable of improving the biological activity (in particular nutrient of phosphate or trace element type, etc.). This same intermediate box can be used to carry out a continuous injection, for example of ammonium salts, in order to conserve a minimum amount of active biomass, in the absence of nitrogenous pollution, this injection being stopped in the event of the appearance of peaks of pollution to be nitrified. The addition can be carried out via diffusion and mixing means.
According to the invention, the aeration means can be made in the form of a diffuser, such as a static or dynamic mixer. They can also be of the type made of a rigid porous material or of the type with a porous membrane.
The aeration means can use air or pure oxygen.
Other characteristics and advantages of the present invention will become apparent from the description given below with reference to the attached drawings, which illustrate embodiments thereof without any limiting nature.
REFERENCES:
patent: 3807565 (1974-04-01), Langston et al.
patent: 3926588 (1975-12-01), Speece
patent: 4795557 (1989-01-01), Bourbigot et al.
patent: 5080793 (1992-01-01), Urlings
patent: 661264 A5 (1987-07-01), None
patent: 4103402 C1 (1992-02-01), None
“Gas-in-Liquid Dispersions, ” Chemical Engineers' Handbook, 5th ed., McGraw-Hill Book Company, New York, 1973, pp. 18/67-73.*
Moles Jacques
Rousseau Nicolas
Vital Jean-Louis
Barry Chester T.
Degremont
Pollock Vande Sande & Amernick
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