Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1994-02-18
1995-10-24
Drodge, Joseph W.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210 962, 210202, 210259, 210650, 210663, 210806, B01D 6116, B01D 6122
Patent
active
054607230
DESCRIPTION:
BRIEF SUMMARY
The field of the invention is that of installations for the filtering and purification of liquids, notably for the treatment of water.
The installation of the invention can be applied more particularly, but not exclusively, to the treatment of types of water liable to show great variability of quality, notably surface water or water with equivalent characteristics. However, those skilled in the art could envisage using the principle of the invention for the treatment of waste water or raw water in other steps in the purification plant, or for the treatment of other liquids.
The treatment of surface water is carried out in order to clarify run-off water or discharged water feeding a natural reservoir (such as water tables, streams or rivers) as well as to provide for the direct distribution of water for consumption. In the light of the presently prevailing standards, the treatment has the following main goals:
The organic and/or ionic pollutants or contaminants to be eliminated include hydrocarbons as well as certain halogenic organics. A circular dated 16th May 1989, sent by the Direction General de Sante (the French Department of Health) to regional and district officials, thus stresses the fact that the presence of halogenic organics had been revealed, from the 1970s onwards, in treated water for human consumption. Trichloroethylene has also been identified in water tables. According to this circular, the studies carried out in different countries, including France, with a view to a better understanding of these substances and of the related risks has led to the setting up of standards and recommendations: Council comprises a general recommendation which states that for "other organochlorine compounds" that are not covered by the parameter No. 55, with a guide level of one microgram per liter, the haloform concentration should be reduced to the greatest possible extent. quality of water intended for human consumption comprises guide values that should enable the Member States to fix national limit values of content for certain products.
According to the World Health Organization, the following values are notably recommended as the limit values of concentration of these products in water for human consumption.
A conventional water treatment plant most usually comprises a succession of physical/chemical steps of the coagulation-flocculation/settling/filtration (notably sand filtration) type.
Following the filtering operation, the water is rid conventionally of pathogenic micro-organisms, microcontaminants, traces of heavy metals, unwholesome odors and flavors by means of oxidizing agents (ozone, chlorine etc.) or ultraviolet radiation, generally coupled with a refining treatment by active carbon in granular or powder form.
To eliminate microcontaminants, there also exist other special treatments such as air stripping (forced aeration) or again filtration through a sand formed by electrically charged resin beads acting as ion collectors. These sands are very useful for water softening (decarbonization, desulfurization etc.) but have little efficiency for example with respect to chlorides or, again, with respect to organic matter.
The ozone/carbon approach is relatively efficient when the quality of raw water to be treated is known and stable
However, these techniques have limitations. solvents like tetrachloroethylene. By contrast, it has only very limited effect or no effect on the THM substances (chloroform, dichlorobromethane, dibromochloromethane and bromoform). Furthermore, the ozone rates needed to oxidize the ethylenic compounds are high and therefore entail a major cost. Couplings with oxidizing agents (ozone/UV and ozone/H.sub.2 O.sub.2) may be used for certain chlorine solvents having at least one C--H bond with variable rates of efficiency; molecules of chlorinated solvents dissolved in water by filtration on an open filter or on a filter under pressure. However, the efficiency of an active carbon depends on the nature of the chlorine compound to be eliminated and on its concentration. The lower
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Bourbigot Marie-Marguerite
Corsin Pierre
Faivre Michel
Sibony Jacques
Drodge Joseph W.
Omnium de Traitement et de Valorrsation (OTV) S.A.
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