JPH1147758A - Treatment of water containing minute suspended substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the aggregation-precipitation of suspended substances efficiently in a short time by a method in which, after a condensed polyamine and an inorganic flocculant being added into water containing minute suspended substances, a polymer flocculant is added. SOLUTION: Into water containing minute suspended substances such as paper making wastewater, after adding a condensed polyamine such as a condensate between an alkylene dichloride and an alkylene polyamine, the condensate between aniline and formalin, a condensate between an alkylenediamine and epichlorohydrin, and the condensate of ammonia and epichlorohydrin and an inorganic flocculant of iron or aluminum such as aluminum sulfate, an aluminium polychloride, and an iron (III) polysulfate, a nonionic, anionic, or cationic polymer flocculant or a polymer flocculant which is different from the above is added. In this way, the suspended substances can be aggregation-precipitated efficiently in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating water containing fine suspension, and more particularly to a method for treating water containing fine suspension such as wastewater discharged from a paper mill.

[0002]

2. Description of the Related Art In the pulp and paper industry and the like, wastewater containing fine suspension is discharged. Cleaning process in papermaking process,
Since many processes that require a large amount of water, such as the digestion process, the bleaching process, and the papermaking process, are included, the amount of wastewater generated is enormous. In the pulp and paper industry, which uses a large amount of water, such wastewater treatment involves a great deal of cost and labor. The burden of environmental protection is becoming more important nowadays. As a method of removing a suspended matter from water containing fine suspended matter such as papermaking wastewater, a flocculation treatment has been generally performed so far using a plurality of flocculants in combination.
For example, one is an inorganic flocculant such as a sulfate band or polyaluminum chloride. A nonionic or anionic polymer coagulant such as polyacrylamide or a partial hydrolyzate thereof is used in combination therewith.

[0003]

However, in the treatment of water containing fine suspensions, such as waste paper pulp wastewater,
The conventional methods described above have a low flocculation efficiency of the suspended substance. It takes a long time for aggregation. In addition, there is a disadvantage that the fine suspended matter still floats in the wastewater. In view of such a situation, the present inventors have conducted intensive studies on a method for rapidly coagulating and sedimenting fine suspended substances, and as a result, have completed the present invention. That is, an object of the present invention is to provide a method for treating a fine suspension in which a suspended substance can be efficiently aggregated and precipitated in a short time.

[0004]

The above object can be achieved by the following means. (1) A method for treating fine suspension-containing water, comprising adding a condensation-type polyamine and an inorganic flocculant to the fine suspension-containing water, and then adding a polymer flocculant. (2) The method for treating fine suspension-containing water according to the above (1), wherein the fine suspension-containing water is papermaking wastewater. (3) The above (1) or (2), wherein the inorganic coagulant is an iron or aluminum-based inorganic coagulant.
A method for treating fine suspension-containing water as described in the above. (4) The above-mentioned (1) to (1), wherein the polymer flocculant is a nonionic or anionic polymer flocculant.
The method for treating water containing fine suspension according to any one of (3).

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below.
The present invention is not limited to this. In the present invention, a condensed polyamine is added to the water contained in the fine suspension. Specific examples of the water contained in the fine suspension to which the condensed polyamine is added include papermaking wastewater. Examples of the condensed polyamine to be added to the water containing the fine suspension include a condensate of an alkylene dichloride and an alkylene polyamine, a condensate of aniline and formalin, a condensate of an alkylene diamine and epichlorohydrin, a condensate of ammonia and epichlorohydrin, and the like. Is mentioned.

The alkylenediamine condensed with epichlorohydrin includes dimethylamine, diethylamine,
Methylpropylamine, methylbutylamine, dibutylamine and the like can be mentioned. As the inorganic coagulant to be added to the water contained in the fine suspension together with the condensed polyamine, an iron-based or aluminum-based inorganic coagulant which has already been generally used as a coagulant can be used. Specific examples of such an iron-based or aluminum-based inorganic coagulant include a sulfate band, polyaluminum chloride (PAC), aluminum chloride, ferric polysulfate (polyiron), ferric chloride, and a mixture thereof. Is mentioned. The ratio of the condensed polyamine to the inorganic coagulant is adjusted so that the amount of the inorganic coagulant is 0.5 to 5 weight ratio based on the condensed polyamine.

The above-mentioned condensed polyamine and inorganic coagulant are
When used, it may be added in the form of a mixture, but such a mixture may be used in the form of an aqueous solution diluted with water in advance. Further, the condensed polyamine and the inorganic coagulant may be separately added almost simultaneously to waste water. However, it is preferable to use the mixture in the state of a mixture because the processing equipment is simple and the work load can be reduced. The addition amount of the condensed polyamine and the inorganic flocculant to the sludge is usually in the same range as in the case of general dehydration, that is, 10 to 1 in total of both.
It may be in the range of 00 ppm (product conversion). As for the method of adding the condensed polyamine and the inorganic flocculant to the sludge, it is preferable that, after the addition, the mixture be stirred rapidly at first, and then slowly stirred.

After the addition of the condensed polyamine and the inorganic coagulant,
A polymeric flocculant is added. Examples of the polymer flocculant to be added include known nonionic, anionic, and cationic polymer flocculants. For example, polyacrylamide, partially hydrolyzed polyacrylamide, acrylamide / acrylate copolymer, acrylamide / acrylamide-2-methylpropanesulfonate copolymer, modified polyacrylamide Mannich, acrylamide (meth) acryloyloxyethyl Trimethylammonium chloride copolymer and the like can be mentioned. Among them, nonionic or anionic polymer coagulants such as polyacrylamide, polyacrylamide partial hydrolyzate, acrylamide / acrylate copolymer, and acrylamide / acrylamide-2-methylpropanesulfonate copolymer are preferable.

The amount of such a polymer flocculant to be added to the water contained in the fine suspension is usually 0.1 to 10 ppm, preferably 0.5 to 5 ppm. If a polymer coagulant is added to cause coagulation, the coagulated material is separated and collected from the contained water. A known method can be used for the separation operation for separating and collecting the aggregates. For example, a sedimentation type or pressure floating type wastewater treatment apparatus may be used.

[0010]

EXAMPLES The present invention will be described more specifically with reference to the following examples. Examples were performed according to the following methods. Raw water was placed in a 500 ml beaker, a predetermined amount of a mixture of a condensed polyamine and an inorganic coagulant (hereinafter, “mixture”) was added, and the mixture was stirred at 150 rpm for 1 minute using a jar tester. Next, a predetermined amount of a polymer flocculant is added, and 50 rpm
and stirred for 5 minutes. The state of flocculated floc generated by stirring and the quality of supernatant water 5 minutes after stopping stirring were measured. The composition of the “mixture” used in the test is as shown in Table 1 below.

[0011]

[Table 1]

The polymer flocculants used in the test were as follows, and were dissolved in distilled water to 0.2% in the test. "Anionic polymer coagulant A": sodium acrylate / acrylamide copolymer (molar ratio 92/8), molecular weight 1
6 million “anionic polymer flocculant B”: sodium acrylate / acrylamide copolymer (molar ratio 85/15), molecular weight 13 million

[Examples 1 and 2], [Comparative Examples 1 to 4] pH: 6.47, SS: 12 discharged from A paper mill.
60 ppm, conductivity: 1.92 MS / cm, visibility: 1.
Using wastewater having a property of 0 cm, the above-mentioned "mixture" or the mixture shown in Table 2 was added, and then the above-mentioned "anionic polymer flocculant A" was added to carry out flocculation-precipitation treatment. Second
The results shown in the table were obtained. "Compound" in Table 1 as a comparative example
The experiment was carried out using an ordinary inorganic coagulant or a condensed polyamine in place of the above. The results are shown in Table 2.

[0014]

[Table 2]

[Examples 3 to 7], [Comparative Examples 5 to 8] pH: 7.00, SS: 29 discharged from the paper mill B
20 ppm, conductivity: 2.70 mS / cm, transparency: 0.
Example 1 except that the above mixture or polymer flocculant shown in Table 3 was used using wastewater having a property of 5 cm.
The test was performed in the same manner as in the above. The results are shown in Table 3.

[0016]

[Table 3]

Comparative Example 9 A test was performed in the same manner as in Example 1 except that the order of adding the mixture and the polymer flocculant was changed.
The results are shown in Table 4.

[0018]

[Table 4]

From the results of the above examples, it can be seen that when a mixture of a condensed polyamine and an inorganic coagulant is used in water containing a fine suspension, treated water having excellent coagulability and excellent color tone and transparency can be obtained. I understand. On the other hand, when the order of adding the mixture and the polymer coagulant was changed, all of the cohesiveness, color tone, and transparency were inferior. In Example 1, when the same test was performed without using the polymer flocculant A, sedimentation of flocculated floc was extremely slow, and the water quality of the supernatant water could not be measured.

[0020]

According to the present invention, the condensed polyamine and the inorganic coagulant are added to the water containing the fine suspension, and then the polymer coagulant is added. A method for treating a fine suspension capable of coagulating and sedimentation can be provided. Aggregates can be favorably settled and a strong floc is formed, as compared with the conventional treatment method using an inorganic coagulant and an organic polymer coagulant in combination. Carry-over to the treated water is prevented, and high-quality treated water can be obtained.

Claims (4)

[Claims] 1. A method for treating fine suspension-containing water, comprising adding a condensation-type polyamine and an inorganic flocculant to the fine suspension-containing water, and then adding a polymer flocculant. 2. The method for treating fine suspension-containing water according to claim 1, wherein the fine suspension-containing water is papermaking wastewater. 3. The method according to claim 1, wherein the inorganic coagulant is an iron or aluminum-based inorganic coagulant. 4. The polymer flocculant according to claim 1, wherein the polymer flocculant is a nonionic or anionic polymer flocculant.
The method for treating fine suspension-containing water according to any one of claims 1 to 3.