JPS60202787A - Treatment of oil-containing waste water - Google Patents

Abstract

PURPOSE:To perform efficient coagulation and flotation of oil in waste water by adding a cationic polymer coagulant and/or a combination of a cationic polymer coagulant with an anionic polymer coagulant all in powder condition to oil- contg. waste water to separate oil from water. CONSTITUTION:Separation of oil from water is performed by adding a cationic polymer coagulant and/or a combination of a cationic polymer coagulant with an anionic polymer coagulant, all in powdery condition, to oil-contg. waste water contg. >=500mg/l oil and forming an O/W or W/O type emulsion. The amt. of the polymer coagulant to be added is pref. 1-10pts.wt. per 100pts.wt. oil when a cationic polymer coagulant is used alone, and 1-5pts.wt. per 100pts.wt. oil when a combination of a cationic and anionic polymer coagulant is used. The pref. proportion of the cationic and anionic polymer coagulant used in combination is 1:10-10:1.

Description

[Detailed description of the invention] The present invention relates to a method for treating oil-containing wastewater.

The forms of oil present in wastewater can be roughly divided into two types: floating oil in a layer on the surface of the wastewater (floating oil) and emulsion in the form of a minute hand within each pixel. be done. Of these, the latter oil-in-water emulsion cannot be directly separated using a gravity-type oil separator or the like, unlike floating oil. Conventionally, therefore, a method has been applied to oil-containing wastewater from a multi-oil-in-water emulsion by adding a flocculant to break the emulsion and coagulate and precipitate or float and separate the oil.

An aqueous polymer solution containing mainly cationic polymers has been considered as a flocculant, that is, an emulsion breaker for oil-containing wastewater. However, the applied concentration is very high, which poses an economic problem.

For example, it is generally necessary to add 1000 m9/1 or more to oil-containing wastewater from an automobile factory containing 8000 m9/J of oil. However, since this polymer solution generally exhibits high viscosity, it is practically impossible to increase the drug concentration too much. Furthermore, when a large amount of cationic polymer is added, it has the effect of stabilizing the emulsion (excessive addition effect). Furthermore, in the case of powdered chemicals, chemical dissolving equipment is required.

An object of the present invention is to provide a method for treating oil-containing wastewater in which oil dispersed in the form of an oil-in-water emulsion in wastewater can be efficiently aggregated and floated without causing the above-mentioned excessive injection effect. There is a particular thing.

The present invention is a method for treating oil-containing wastewater, which comprises adding a cationic polymer flocculant or a cationic polymer flocculant and an anionic polymer flocculant to oil-containing wastewater in powder form and separating the oil and water. 0 Although it is disclosed in Japanese Patent Publication No. 17923/1983 that the flocculant effect is enhanced when a flocculant is added to wastewater as a powder, the present inventors added cationic polymers (and anionic polymers) to oil-containing wastewater. By adding a flocculant (polymer) in the form of powder, they found that the oil-water separation effect was greatly improved, and the unexpected effect of not causing the above-mentioned excessive addition effect was obtained. .

The target oil-containing wastewater of the present invention is an oil-in-water type or a water-in-oil type emulsion, and preferably has an oil content of 500 m9/1 or more.

Examples of the polymer flocculant used in the present invention include the following.

1) Homopolymer of cationic polymer dimethylaminoethyl methacrylate,
or a copolymer with acrylamide, a homoprimer of its quaternized product, or a copolymer, a Mannich modified product of polyacrylamide or its quaternized product, polyvinylimidazoly/, a homo-dilimer of dimethyldiallylammonium chloride, dimethylaminoethyl methacrylate, its acid salts, homopolymers such as methyl chloride or benzyl chloride quaternized products, or copolymers with acrylamide etc., chitosan, polyethyleneimine, Hofmann decomposition products of polyacrylamide, polyamide polyamines, etc. 2) Anionic polymer sodium polyacrylate , polyacrylamide partial hydrolyzate, cardoxymethyl cellulose, polymethyl acrylate partial hydrolyzate, etc., is preferably added in an amount of 1 to 10 parts per 100 parts of oil in the case of a cationic polymer alone. When using a cationic polymer and anionic polymer together, the oil content is 10%.
It is preferably 1 to 5 parts relative to 0 parts. In addition, the combined ratio of cationic polymer and anionic polymer is 1:10 to 10:1.
It is preferable that it is in the range of .

In order to separate and remove oil from wastewater using the method of the present invention, the above-mentioned polymer flocculant is added in the form of a powder, and the oil in the emulsion state is agglomerated by stirring as appropriate, and the oil that has floated due to the aggregation is floated. It may be removed by known means such as a method. In addition, in the present invention, it may take more time to mix with raw water than when using a liquid product, but since the aggregated oil is a stable scum in the form of a strong semi-solid or a slightly fluid fluid. , cannot be destroyed again by agitation. It is sufficient to decide to end the treatment while giving an illusion of the cleanliness of the treated water.

According to the present invention, since the cationic polymer (and anionic polymer) flocculant is added to the oil-containing wastewater in the form of powder,
Not only can the oil-water separation effect be greatly improved, but the adverse effects caused by excessive input will not occur. This is because in liquid products, the flocculant envelops the emulsion particles and tends to break or stabilize the emulsion, whereas in powder products, the powder particles gradually dissolve and come into contact with the emulsion particles individually, causing the emulsion to break. This is thought to be for the purpose of contributing. In addition, the amount added is approximately equal to the effective range of pure concentration in liquid products,
After stirring for a certain period of time, if the desired effect is not achieved, additional addition can be made. For these reasons, the present invention is advantageous in terms of process since there is no failure caused by adding too much or too little of a chemical, and no chemical dissolving equipment is required at all.

Example The method of the present invention was carried out on oil-in-water emulsion type oil-containing wastewater having an oil concentration of 800 m9/l, s,oomgt7i and 8.3 wt%.

500 ml of each waste water was taken into a beaker, a predetermined amount of the polymer flocculant shown in Table 1 was added, and air agitation was performed for 1 hour.

Table 1 After the set time, stirring was stopped and the appearance of the drained water was observed to determine the effectiveness.The results are shown in Table 2.

(Margin below) □ Table-2 Umbrella: In this case only, the stirring time was 2.5 hours.

Judgment code O: Significant aggregation (floating) of oil and significant improvement in water side turbidity.

△: Oil aggregation (floating) was observed, but no improvement in turbidity was observed.

×: No change, little or no effect.

Comparative Example The same procedure as in Example was carried out, except that each drug was prepared in advance as an aqueous solution (however, the pH of the composition was adjusted to the acidic side) and then added.

The results are shown in Table-3. Symbols are the same as in the examples.

Table 3 These results show that the present invention exhibits outstanding effects.

Claims (1)

[Claims] 1. Oil-containing wastewater characterized by adding a cationic polymer flocculant or a cationic polymer flocculant and an anionic polymer flocculant in powder form to oil-containing wastewater to separate oil and water. processing method. 2. The method according to claim 1, wherein the oil-containing wastewater is an oil-in-water qx emulsion with an oil content of so o my, Q or more. 3. The method according to claim 1 or 2, wherein the cationic polymer flocculant is a homopolymer or cotelimer of a quaternized dimethylaminoethyl methacrylate.