HUT67593A - Cleaning waste water contaminated with oil and grease - Google Patents

Abstract

Finely divided talc with a grain size of 90 to 3 mu m is eminently suitable as an adsorbent for cleaning waste water contaminated with oil and grease, especially that from tanneries, abattoirs, refineries, large-scale painting plants and the like.

Description

Industrial processes for combating organic contamination, as well as many washing processes, result in dispersions of water-insoluble organic matter in the aqueous phase in which the organic phase is present in very fine particles and even in colloidal form. Separation of this type of dispersion is particularly difficult.

In the processes used to date for separation, in most cases, additional chemicals are used as separation aids which are present as impurities in either the treated wastewater or the precipitated sewage sludge, and this impurity must also be removed.

In oil-containing wastewater, which is a mixture of water with a wide variety of hydrocarbon compounds, hydrocarbons are present in different basic forms and purification methods have been adapted to this. In the case of hydrocarbons which are insoluble in waste water, separation can be carried out in a gravity separator for separating the light particles. However, most of the hydrocarbons are present in the wastewater dissolved or emulsified and can only be removed by physico-chemical methods, in particular flocculation, precipitation and flotation.

Flocculation is used as a general term for any process that seeks to separate emulsified or suspended materials, while precipitation refers to the removal of solutes. Flocculants are substances which, when dissolved in water, become bulky precipitates and successfully destabilize suspensions and emulsions. Meanwhile, an additional amount of sewage sludge is generated which needs to be treated further.

By flotation is meant the floatation of a substance in a liquid, which can be accomplished by introducing gas bubbles which are as small as possible. Once the float is enriched on the surface of the liquid, it can be removed from the system with a surface cleaner.

Specially adapted natural microorganisms can be used to treat oil-containing wastewater. In this case, it is a real disposal of biological material, in which the harmful substances are actually decomposed and not just stored somewhere. However, the rate of degradation is highly dependent on temperature and nutrient supply, and may take several years.

Adsorption methods are often used for wastewater treatment, in which the hydrocarbons are bound by activated charcoal or adsorbent. Adsorption on mica (AD 1 167 278) and on organophilic clay (AD 19 37 929) has also been studied.

U.S. Pat. No. 4,332,693 proposes a chemical for the treatment of oily emulsions in industrial wastewater, which is a mixture of many components and consists predominantly of acid-activated bentonite, untreated bentonite, lime and aluminum sulfate, and also contains small amounts of adipic acid, flocculant.

Further, a process for coagulating and precipitating the residues of so-called high-solids lacquers in wet separates of paint sprays is known from European Patent 0 117 586.

alkaline aqueous effluent from their torrents. Dispersion of talc, calcium oxide, hydroxide, carbonate and / or zinc stearate is added to the effluent to improve coagulation and precipitation.

Subsequent disposal of contaminated materials is usually accomplished by incineration or by regenerating the adsorbent material on a stripping column.

Surprisingly, we have found that talc, within a certain particle size range, is an excellent agent for separating oils and fats from waste water.

Talc refers to naturally occurring magnesium silicates. Talc is distinguished by its low hardness (Mohs hardness 1), its smooth grip, its hydrophobic properties and its good adsorption capacity on organic matter. According to the present invention, the use of finely divided talc has been found to be particularly advantageous in the use of talc having a particle size of 3 to 90 μπι. At this particle size, on the one hand, adsorption ability to oils and fats that contaminate water is optimal, and on the other hand, talc absorbed by these contaminants, together with other floating materials, can be easily floated and disposed of with the sludge formed.

The use of talc as an adsorbent according to the invention is desirable in all plants where large amounts of fat and oil-laden wastewater are generated. Untreated sewage from leather factories, slaughterhouses, refineries, large lacquer plants, and the like is particularly suitable for the treatment of waste water according to the invention. Practical experiments have shown that the use of talc as an adsorption agent provides good results for all animals

fats and mineral oils; both types of fat bind well to talc.

The dosage amount of finely divided talc depends primarily on the concentration of impurities to be removed in the wastewater. The amount of talc is about 100 mg / l of wastewater.

The invention is illustrated by the following example.

EXAMPLE

Finely divided talc is added to the tannery waste water as an adsorption agent. The waste water contains fat and has a CSB of up to 10,000. By treating this effluent with 30 µm of talc, the CSB value falls below 5,000 in a volume of 30-100 mg / l of effluent. A further decrease in CSB is not always desirable as it may disrupt biological processes in the clarification basin. The addition of finely divided talc not only reduces the CSB by up to 50%, but also improves the sedimentation of the precipitated sludge, making it easier to remove and dehydrate by squeezing. In addition, a significant reduction in CSB value can result in significant electrical energy savings for aerators during aerobic wastewater treatment.

Claims (5)

PATENT APPLICATION POINTS * 4 4 Use of talc as an adsorption agent for the separation of oils and fats from waste water, characterized in that it is 3-90 μτα. granular talc is used. Use according to claim 1, wherein the wastewater is a tannery wastewater. The use according to claim 1, wherein the waste water is slaughterhouse waste water. Use according to claim 1, characterized in that the waste water is from a refinery. Use according to claim 1, characterized in that the waste water is a lacquer or lacquer. 6. The use according to any one of claims 1 to 3, characterized in that it is used in a method. talc 30-100 mg / l of wastewater A r,, / A A / o / '2 of F-'S ¹ / · ¹  2, 2: Ϊ THE //