Liquid purification or separation – With means to add treating material – Plural distinct separators
Patent
1998-12-17
2000-07-04
Cintins, Ivars
Liquid purification or separation
With means to add treating material
Plural distinct separators
210253, 210260, B01D 1500
Patent
active
060833882
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCES TO RELATED APPLICATIONS
This application is a national phase application of International Application No. PCTIFR97/00960, with an international filing date of Jun. 2, 1997.
1. Field of the Invention
The present invention relates to a water treatment plant and a battery of modular water treatment equipment produced by connecting a plurality of such plants in parallel.
2. Background of the Invention
It is known that there are several phases in physico-chemical processes for treating water (in particular river water or subterranean water for the preparation of drinking water, industrial water, residual urban water, residual industrial water, etc.): addition of inorganic coagulants such as metal salts with a contact time of the order of 0.5 to 3 minutes; the untreated water and which is carried out in one or more steps by adding flocculants or polyelectrolytes, in general based on organic polymers, with a contact or maturing time of the order of 4 to 30 minutes, and produced in the form of a settling tank, optionally equipped with lamellar modules, whose role is to increase the sedimentation rate of the particles.
In modern plants, the separation means are generally lamellar settling tanks. The settling tank proper generally has a volume which is much greater than the volume needed for the coagulation/flocculation phases. These lamellar settling tanks may be rectangular, but they are most often of square shape. They integrate the lamellar modules and they comprise a circular system for scraping in a circle contained within the area of the square.
These settling tanks have a number of associated problems, which can be ranked in two main orders: unitary production and connection of several units in parallel.
UNITARY PRODUCTION
The flocculation reactor, which is smaller than the settling tank, does not always supply (or cannot be designed to supply) the settling tank over its entire width. This results in heterogeneous hydraulic flows which are concentrated on the central part or on the sides of the settling tank, and these flow asymmetries compromise the settling by creating turbulence in a zone which should be calm.
This very widespread embodiment has the following drawbacks: in the lower corners of the construction, with a slope greater than the flow angle of the sludge (that is to say an angle in excess of 50.degree.), this being in order to prevent stagnant zones. Such "packers" are difficult to produce and sometimes have heights which are incompatible with the conventional geometry of the constructions: thus, 60.degree. "packers" in a settling tank with a side length of 20 meters would need to rise to more than 7 meters in height; drive tube of the circular scraper do not make it possible to clean the lamellar modules lying in the corners of the settling tank.
These types of settling tank do not have the drawbacks of the type described above, but are a priori more difficult to produce, especially in concrete, and it is impossible to benefit from common walls which may, where appropriate, allow several settling tanks to be arranged in parallel.
CONNECTING THE UNITS IN PARALLEL
Such parallel connection should solve the following problems:
several units in parallel requires channels or distribution tubes of great length (possibly up to 100 meters long, or even more).
FIG. 1 of the drawings schematically represents a conventional plant connecting a number of water treatment equipment units in parallel, each comprising a coagulator 1, a flocculator 2 and a settling tank 3. This figure shows, at 4, the "packers" produced as indicated above in the lower corners of the settling tank and, at 5, the channel for supplying the various equipment units which are arranged in parallel. This distributing channel 5 forms a critical element of the plant because it needs to fulfill two conflicting functions:
The transfer function needs to be done at high speed in order to prevent the sludge, sand etc. from settling; the problem may be further exacerbated when the desanding is not carried out upstream of
REFERENCES:
patent: 3353679 (1967-11-01), Hirsch
patent: 5252214 (1993-10-01), Lorenz et al.
patent: 5256299 (1993-10-01), Wang et al.
Cintins Ivars
Degremont
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