Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1998-11-19
2000-04-11
Popovics, Robert
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210652, 210693, 210694, 210791, 210799, 210805, 210806, 210167, 210170, 210259, 210409, 21050021, 2105021, 210503, 2105101, 210908, C02F 140, B60S 300
Patent
active
060484616
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and to a system for cleansing water from oil, and more particularly for cleansing water spillage in gasoline or petrol stations.
The present invention is concerned more particularly with cleansing vehicle wash water with respect to its oil and heavy metal content.
DESCRIPTION OF THE RELATED ART
Many countries stipulate that sewage water from vehicle-washing facilities shall be essentially free from oil, or at least have a very low oil content. Under Swedish regulations, the oil content of sewage water must be below 50 mg/l as from the year 1997.
One known method of extracting oil from oil-contaminated waste water is to feed the water into a flocculating chamber connected to a slime separator located at the gasoline station. This method achieves a purification of 75%-85%. However, the method is not sufficiently effective to achieve the aforesaid purification level, and the water leaving the purification plant will typically have an oil concentration of 150 mg/l or higher.
Filters with which the oil content of oil-contaminated water can be greatly reduced are known to the art. The membrane filter is one such filter type. Such filters are expensive, however. Furthermore, membrane filters have a relatively low capacity with regard to the amount of oil that is extracted, and consequently it would be necessary to connect a large number of membrane filters in parallel in order to cleanse satisfactorily sewage water that derives from vehicle-washing plants, this water normally having an oil concentration as high as 150 mg/l.
It would appear that although waste water cleansing or purifying techniques are known to the art, the techniques are not economically viable with regard to vehicle-washing plants, where a typical water consumption is about 400 liters with each vehicle wash.
The present invention solves this cleansing problem and provides a relatively inexpensive arrangement which has a very high cleansing efficiency.
SUMMARY OF THE INVENTION
The present invention thus relates to a method of extracting oil from water, particularly spillage water from gasoline stations, including water that emanates from vehicle-washing plants, having filters to which contaminated water from the vehicle-washing plant and possibly other contaminated water spillage is passed. The water is cleansed in one or more mutually sequential filters in the flow direction of the water by causing the water to flow through a collection filter in which oil and coarse particles are collected in a first cleansing or purifying stage. The water from the collecting filter is caused to pass through a fine filter which is adapted to lower the oil content of the water to a level below approximately 50-75 mg/l in a second cleansing or purifying stage. The water from the fine filter is caused to flow through a membrane filter which is adapted to filter-off at least 75% of the oil remaining in the water in a third cleansing or purifying stage. At least a substantial part of at least the water cleansed in the membrane filter is recycled back to the vehicle-washing plant while any residual part of said water is discharged to a municipal sewage network.
The present invention also relates to apparatus for carrying out the inventive method.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to two exemplifying embodiments thereof and also with reference to the accompanying drawing.
FIGS. 1 and 2 are each flowsheets that show a respective embodiment of the present invention in which conventional fluid system symbols have been used. Consequently, not all units will be described in the following.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a first embodiment of the invention, wherein the numeral 1 identifies a feed pump, numeral 2 identifies a flocculating chamber, numeral 3 identifies a flocculating agent metering tank, numeral 4 identifies a collection filter and numeral 5 identifies a fine filter.
The collection fi
REFERENCES:
patent: 4784773 (1988-11-01), Sandberg
Foxhammar AB
Mangels Alfred J.
Popovics Robert
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