CA2689716A1

CA2689716A1 - A coagulant for use of water purification and a water purifying method and a water purifying apparatus with applying the same

Info

Publication number: CA2689716A1
Application number: CA 2689716
Authority: CA
Inventors: Hiroshi Sasaki; Hisashi Isogami; Akira Mochizuki
Original assignee: Hitachi Plant Technologies Ltd
Current assignee: Hitachi Ltd
Priority date: 2009-01-29
Filing date: 2010-01-05
Publication date: 2010-07-29
Anticipated expiration: 2030-01-05
Also published as: JP5277997B2; MX2010000872A; JP2010172814A; CA2689716C; CA2852552A1

Abstract

A coagulant for removing or extracting a large amount or volume of organic acid in wastewater at high speed, a water-soluble polymer 6 having an amino group is added into the wastewater containing the organic acid 5 therein, thereby producing an ionic bond 7 built up with the organic acid 5 and the water-soluble polymer 6 having an amino group. Next, with addition of a water-soluble polymer 8 having carboxyl group, an ionic bond 9 is built up with the carboxyl group of the water-soluble polymer 8 having carboxyl group and the amino group of water-soluble polymer 6 having an amino group. With this, the organic acid is precipitated as an aggregate 10. The aggregate 10 trapping the organic acid is separated when it passes through a filtering tank.

Description

SPECIFICATION
TITLE OF THE INVENTION

A COAGULANT FOR USE OF WATER PURIFICATION AND A WATER PURIFYING
METHOD AND A WATER PURIFYING APPARATUS WITH APPLYING THE SAME
BACKGROUND OF THE INVENTION

The present invention relates to a coagulant for use of water purification, and it also relates to a water purifying method and a water purifying apparatus with applying the same therein.

In wastewater or sewage generated in mining of an oil field are included a large amount of organic acid (for example, acetic acid, valeric acid, naphthenic acid, etc.) coexisting in a crude oil. In case of being discharged into seas or rivers, together with such organic matters, it affects large ill influences upon an ecological system. Accordingly, it is necessary to discharge it after removing those organic acids from it. However, an amount of the wastewater or sewage generated is massive, and therefore a technology is required for processing the large amount or volume thereof at high speed.

As a method for removing or extracting the impurity or pollution in the wastewater, a removal or extracting method of contaminated grains or particles suspending in water is shown in Fig. 1. Poly aluminum chloride (so-called "PAC") or iron sulfide is added therein, so as to form small aggregates, e. g. , micro flocs 1, being approximately several tens to several hundreds m in the particle diameter thereof. Thereafter, with adding polyacryl-amide therein, continuously, the contamination particles 2 in the water are formed into large aggregates, being so-called a "floc" 3, approximately several hundreds to several thousands m in the particle diameter thereof. Thereafter, this wastewater is divided or separated by means of a filtering container or tank, or is separated with using magnetism, after forming flocs by adding magnetic powder or particles 4 therein, in advance, when forming the flocs, and thereby removing them, and such methods are already known. Also, ion sulfide may be used in the place of PAC. With any one of those methods, it is possible to remove or extract the contamination particles at high speed. However, it is difficult to remove the organic acid, such as, acetic acid, valeric acid, naphthenic acid, etc., which are dissolved in the water.

On the other hand, it is common to remove or extract the organic acid, with applying a method of absorbing them into active carbon and/or an ion-exchange resin, etc. For example, in the following Patent Document 1, there is described a method for absorbing/removing the organic acid with applying a contact member, including fibrous active carbon therein. Also, as a method for removing or extracting the impurity or pollutant in the wastewater, for example, in the following Patent Document 2 is proposed a method for condensing oils as aggregate, by adding water-soluble polymer having ammonium salt structure and water-soluble anodic polymer into drain including the oils therein, thereby to remove or extract them therefrom.

<Prior Art Document(s)>
<Patent Document>

[Patent Document 1] Japanese Patent Laying-Open No.
2003-144839 (2003); and [Patent Document 2] Japanese Patent Laying-Open No.
2004-255349 (2004).

BRIEF SUMMARY OF THE INVENTION

As was mentioned above, with the method for removing or extracting the contaminant particles with applying the coagulant, it is suitable for processing a large amount of wastewater at high speed, but is impossible to remove or extract the organic acid dissolved in the water.

On the other hand, when letting the active carbon and/or the ion-exchange resin or the like to absorb them therein, an amount or volume of absorption is determined upon surface areas of the active carbon and/or the ion-exchange resin. For this reason, the smaller of the particle size, the larger of the surface areas thereof.
However, if the particle size is too small, then it is impossible to hold the active carbon and/or the ion-exchange resin, then it is difficult to handle them. Also, in any one of them, there is a limit in the processing capacity thereof, and therefore it is necessary to replace or renew the active carbon and/or the ion-exchange resin or a reverse-penetration membrane to be applied therein, frequently. Further, since the active carbon also absorbs organic matters other than the organic acid, an absorbing efficiency thereof is lowered, soon. On the other hand, the reverse-penetration membrane comes to be unusable if small cavities on a surface of the membrane are clogged with, not only the organic acid, but also the contaminants. Accordingly, it is impossible to process a large amount of wastewater at high speed.

As was mentioned above, with the conventional technologies, it is difficult to remove or extract the organic acid from the large amount of wastewater at high speed. An object of the present invention is to remove or extract the organic acid from the large amount of wastewater at high speed.

According to the present invention, for accomplishing the object motioned above, firstly there is provided a coagulant for condensing an organic acid as an aggregate with an aid of ionic bond, comprising: a water-soluble polymer having an amino group;
and a water-soluble polymer having an acidic group.

Further, according to the present invention, there is also provided a water purifying method for condensing an organic acid as an aggregate with an aid of ionic bond, comprising the following steps of: preparing said organic acid having a carboxyl group or a sulfonyl group; adding a water-soluble polymer having an amino group in said organic acid; and thereafter adding a water-soluble polymer having an acidic group.

Further, according to the present invention, there is also provided a water purifying apparatus, for condensing an organic acid as an aggregate with an aid of ionic bond, comprising: a first mixing tank for mixing said organic acid and a water solution of water-soluble polymer having an amino group; a second mixing tank for mixing a liquid within said first mixing tank with a water solution of water-soluble polymer having an acidic group; a first pipe provided for said organic acid to move to said first mixing tank; a second pipe provided for the liquid within said first mixing tank to move to said second mixing tank; and a filtering portion for filtering said aggregate.

According to the present invention, it is possible to remove or extract a large amount or volume of organic acid within the wastewater at high speed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a view for showing a conventional method for condensing contaminant particles as aggregate;

Fig. 2 is a view for showing scheme for forming flocs (i.e., aggregate), according to the present invention;

Fig. 3 is a block diagram of a water purifying apparatus, according to an embodiment 1 of the present invention;

Fig. 4 is a block diagram of a water purifying apparatus, according to an embodiment 2 of the present invention;

Fig. 5 is a block diagram of a water purifying apparatus, according to an embodiment 3 of the present invention;

Fig. 6 is a block diagram of a water purifying apparatus, according to an embodiment 4 of the present invention;

Fig. 7 is a block diagram of a water purifying apparatus, according to an embodiment 5 of the present invention;

Fig. 8 is a block diagram of a water purifying apparatus, according to an embodiment 6 of the present invention; and Fig. 9 is a block diagram of a water purifying apparatus, according to an embodiment 7 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings.
By referring to Fig. 2, explanation will be made on the present invention for changing the organic acid in the wastewater into aggregate thereof.

First of all, water-soluble polymer 6 having an amino group is put or added into wastewater including the organic acid 5 therein.
Herein, in relation to the organic acid 5, there is one having a sulfonyl group. In the present invention, although the explanation will be given only on the case where the organic acid having a carboxyl group, but the behavior is similar to the case where it has the sulfonyl group. With adding the water-soluble 5 polymer 6 having the amino group into the wastewater including the organic acid therein, an ionic bond 7 is produced, being composed of the water-soluble polymer 6 having the organic acid and the amino group. In this manner, the organic acid 5 is trapped on the water-soluble polymer 6 having the amino group. Herein, the amino group of the water-soluble polymer 6, having the amino group, forms the ionic bond at a ratio 1:1, together with the carboxyl group within the wastewater. For this reason, it is preferable that an amount of addition of the water-soluble polymer 6 having the amino group, when considering it as a number of the amino groups, to be larger than the number of the carboxyl groups in the wastewater.
Next, a solution of water-soluble polymer 8 having the carboxyl group is added. Herein, though description is made of the carboxyl group; however, the behavior is similar to that mentioned below even when it has the sulfonyl group. With addition of the water-soluble polymer 8 having the carboxyl group, an ionic bond 9 is produced, being composed of the carboxyl group of the water-soluble polymer 8 having the carboxyl group therein, and the amino group of the water-soluble polymer 6 having the amino group therein. With this, a bridge (i.e., crosslink) is built up between the water-soluble polymer 6 having the amino group and the water-soluble polymer 8 having the carboxyl group. With this, this cross-linked polymer 10 can be separated from, with guiding it to pass through a filtering tank, and as a result thereof, it is possible to remove or extract the organic acid 5 therefrom.

With the ion-exchange resin, which is mostly applied in the conventional art, for removing or extracting the organic acid, in general, the organic acid is trapped on the amino group on the surface of the resin particle, being from 0.1 to 2 mm in the particle diameter thereof. Since the surface area of the particle is large, as diameter of the particle is small, therefore it can trap the organic acid thereon, muchmore.However,the water-soluble polymer 6 having the amino group, according to the present invention, is soluble in water. Therefore, in the similar manner to that as if applying an ion-exchanger resin, having the particle diameter of several angstroms, it is possible to trap the organic acid at a high efficiency. For this reason, comparing to the case where the conventional ion-exchanger resin therein, an amount or volume of the organic acid becomes large, greatly, which can be trapped where the same amount of the ion-exchanger resin is added therein.
Detailed explanation will be made below, in particular, on the water-soluble polymer having the amino group therein. As the water-soluble polymer having the amino group, polyethylene-imine is suitable or preferable, judging from an aspect that the ratio of the amino group is largest in the same molecular weight. Or, a water-soluble polymer having the amino group in a chain, such as, polyvinyl-amine or polyallyl-amine, etc., is also suitable or preferable, judging from an aspect that it is relatively cheap and can be dissolved in water easily. Chitosan is low in the solubility in water, but since it can be obtained through hydrolysis of chitin, i.e. , the main or principle composition of the carapace of crab, the external skeleton of a shrimp, or the external skeleton of a living thing, such as, a beetle or a cockroach, for example, it has a characteristic of being small of a load upon the environment, judging from an aspect that a raw material thereof originates from a living thing. Polylisine or polyarginine has characteristics of originating from an amino acid and having a low toxicity.

The water-soluble polymer having the amino group generates an odor specific to amine, when a number average molecular weight thereof is small, even under a room temperature. In more details, it comes to be remarkable in case where the number average molecular weight thereof is less than 200. Then, it is preferable that the water-soluble polymer having the amino group is equal to or greater than 200 in the number average molecular weight thereof. Also, for the purpose of lowering the odor to be almost non-sensible, it is preferable that it has the number average molecular weight equal to or greater than 500, if possible.

On the other hand, if the number average molecular weight is large, even a water solution thereof comes to be high in the viscosity thereof; therefore, it is difficult to manage or control of a casting amount thereof, and to handle it in the operation when casting or throwing it into the wastewater. In more details, when the number average molecular weight thereof exceeds 1,000,000, then the viscosity is equal to or more than 3,000 Pa-s, even if obtaining a water solution of 10 weight%. Then, it is preferable that the water-soluble polymer having the amino group has the number average molecular weight equal to or less than 1, 000, 000. Also, for the purpose of lowering the viscosity to be equal to or lower than 1, 000 Pa-s, even if obtaining the water solution of 10 weight%, and thereby achieving convenience in management or control of the casting amount thereof, or in handling of the operation when casting it into the wastewater, it is desirable that the water-soluble polymer having the amino group is equal to or less than 200,000 in the number average molecular weight thereof.

However, among the water-soluble polymers having the amino group therein, it is possible to increase or improve the solubility thereof into the water, by replacing or changing the amino group with chlorate structure or nitrate structure, if water solubility thereof is low. After changing into the chlorate structure or the nitrate structure, the water-soluble polymer having the amino group is added into the wastewater, and thereby it is possible to build up the ionic bond together with the organic acid, efficiently.

Detailed explanation will be made below, in particular, on the water-soluble polymer having the acidic group. It can be considered that the water-soluble polymer having the acidic group has the carboxyl group or the sulfonyl group, as the acidic group thereof. Among of those, as the water-soluble polymer having the carboxyl group, polyacrylic acid is suitable, judging from an aspect that it is cheap and it can easily build up the ionic bond with the amino group. Other than this, also polyasparagine acid, polyglutamic acid, etc., coming from the amino acid, have the characteristics of being low in the toxicity. Argine acid is a kind of main components of a see weed, such as, sea tangle, etc. , for example, it has characteristics that the load upon the environment is small in an aspect that the raw material thereof originates from a living thing. As the water-soluble polymers having sulfonyl group can be listed polyvinyl sulfonic acid or polystyrene sulfonic acid. Since those sulfonyl groups are large in acidity thereof than that of the carboxyl group, and therefore a ratio of building up the ionic bond with the amino group, then they are desirable or preferable from an aspect that the aggregate thereof.

However, among those water-soluble polymers having the acidic group, it is possible to increase or improve the solubility into the water, by replacing or changing the acidic group with ammonium salt structure, sodium salt structure or potassium salt structure, if the water solubility thereof is low. After changing into the ammonium salt structure, the sodium salt structure or the potassium salt structure, the water-soluble polymer having the acidic group is added into the wastewater, and thereby it is possible to build up the ionic bond together with the water-soluble polymer having the amino group, efficiently.

In relation with the number average molecular weight of the water-soluble polymer having the acidic group, if it is too low, then a number of the bridging portions of the aggregate is small, and a stability of the aggregate goes down. Also, it shows a tendency that the aggregate is liquefied, but to have high viscosity thereof .
With this, it is difficult to remove the aggregate through the filtration. Then, it is desirable or preferable that the number average molecular weight of the water-soluble polymer having the acidic group is equal to or greater than 2,000. Also, when temperature of the wastewater is equal or higher than 40 C, in particular, in the case of the number average molecular weight is 2, 000, the aggregate begins to have the viscosity. In case of the industrial drain, there is a possibility that the temperature thereof increases to be high, about 60 C. In this case, it is possible to solidify the aggregate by increasing the number average molecular weight, further, even under the high temperature. In more details, with brining up the number average molecular weight to 5, 000 or higher than that, it is possible to solidify the aggregate even if the temperature of the wastewater is 40 C. Therefore, it is desirable or preferable that the number average molecular weight of the water-soluble polymer having the acidic group is equal to or greater than 5,000. Furthermore, with brining up the number average molecular weight to be equal to or greater than 10, 000, it is possible to solidify the aggregate even if the temperature of the wastewater is 60 C. Therefore, it is further desirable or preferable that the number average molecular weight of the water-soluble polymer having the acidic group is equal to or greater than 10,000.

Also, if the number average molecular weight of the water-soluble polymer having the acidic group becomes large too much, the solubility into the water is lowered down, on the way of building up the bridge between the amino group; i.e., showing a tendency of being separated out or deposed. Thus, this means there is a possibility that they are separated out in the wastewater, before building up the bridges for all of the organic acid in the wastewater and the water-soluble polymer having the amino group, which are connected with the ionic bond. Due to this, a part of those combining the organic acid and the waster soluble polymer having the amino group, being connected through the ionic bond is remained under the condition of being melting in the wastewater.
For that reason, it is desirable that the number average molecular weight of the water-soluble polymer having the acidic group is equal to or less than 200,000.

Explanation will be made in more details thereof, about a measure for increasing of the solubility of the water-soluble polymer having the amino group or the water-soluble polymer having the acidic group. In case where the solubility of the water-soluble polymer having the amino group into the water is low, it is possible to increase the solubility into the water, by changing the amino group into the ammonium salt structure. In more details, the solubility into the water can be improved, greatly, with changing it into chlorate, nitrate, or sulfate, etc., by adding hydrochloric acid, nitric acid or sulfuric acid, etc.

Also, in case where the solubility of the water-soluble polymer having the acidic group into the water is low, it is possible to increase or improve the solubility into the water, with changing the acidic group into a salt structure by strong acid. In more details, the solubility into the water is improved, greatly, with changing the acidic group to alkali metal salt or alkaline earth metal salt, etc., by adding hydride of alkali metal or alkaline earth metal,such as,sodium hydroxide, magnesium hydroxide, etc., for example.

Explanation will be made in more details thereof, about an additive for increasing trapping of organic acid. In case where the acidity of the acidic group of the organic acid is low, a ratio is lowered of building up the iconic bond together with the amino group. Then, with adding an inorganic salt, such as, sodium chloride, or potassium chloride, etc., into the wastewater, before adding the water-soluble polymer having the acidic group, a ratio of the organic acid, which builds up the ionic bond between the amino group, goes up. This can be considered because an allowable ratio of the organic acid, which can be dissolved into the wastewater, is lowered, due to the effect similar to the salting out, i.e., separating or disposing the organic matters dissolved in the water by adding a salt. As the inorganic salt to be added can be listed the followings: a hydrochloride of alkali metal or alkaline earth metal, such as, sodium chloride, potassium chloride, magnesium chloride, or calcium chloride, etc.; a sulfate of alkali metal or alkaline earth metal, such as, sodium sulf ate, potassium sulf ate, magnesium sulfate, or calcium sulfate, etc.; a nitride of alkali metal or alkaline earth metal, such as, sodium nitrate, potassium nitrate, magnesium nitrate, or calcium nitrate, etc., for example.

Explanation will be made on an outline of an aggregating method according to the present invention. There two (2) methods for collecting the organic acid as the aggregate, as were mentioned previously. Describing them in short, they are as (1) to (4) below.
Although the explanation will be made that the acidic group is the carboxyl group in Fig. 2, but it is same to that when it is the sulfonyl group. (1) : the water-soluble polymer having the amino group is added into the wastewater having the organic acid therein.
(2) : The carboxyl group builds up the ionic bond with the amino group of the water-soluble polymer having the amino group, and the organic acid is trapped by the water-soluble polymer having the amino group. (3) : The water-soluble polymer having the carboxyl group is added. (4) : The amino group of the water-soluble polymer having the amino group and the carboxyl group of the water-soluble polymer having the carboxyl group combine each other, by a unit of the molecule thereof, through a large number of ionic bonds, and thereby building up the bridges. With this, those dissolving in the water as the polymers with each other are changed to be insoluble into the water, and come to be the aggregate.
Explanation will be made about the ratio of addition of a coagulant. Herein, it is assumed that a number of the acidic group (s) of the organic acid in the wastewater is "MA", a number of the amino group (s) of the water-soluble polymer having the amino group to be added is "PA". An adjustment is made on addition amounts of the water-soluble polymer having the amino group and the water-soluble polymer having the acidic group into the water, so as to satisfy the following inequalities mentioned below, and thereby enabling to enhance a removal or extraction ratio of the organic acid.

PB >_ MA ...(Eq. 1) PA >_ PB ... (Eq. 1) The equation (Eq. 1) means that the number of the amino groups of the water-soluble polymer having the amino group is larger than that of the acidic groups of the organic acid in the wastewater.
According to the present invention, a reaction of building up the ionic bond between the amino group of the water-soluble polymer having the amino group and the acidic group of the organic acid can be considered an equilibrium reaction, originally. For that reason, if the amino group of the water-soluble polymer having the amino group is too much, comparing to the organic acid, it is possible to enhance the trap ratio of the organic acid. If in case where the equation (Eq. 1) is B<MA, since the amino group for trapping the organic acid is less comparing to the organic acid, then there remains the organic acid, which cannot be trapped, in the wastewater, necessarily.

Also, the equation (Eq. 2) means that the number of the acidic groups of the water-soluble polymer having the acidic group is larger than the number of the amino groups of the water-soluble polymer having the amino group. With this, it is possible to separate or precipitate almost all of the water-soluble polymers having the amino groups, each trapping the organic acid thereon, as the aggregate insoluble in the water. If coming out from the addition ratio of this inequality, greatly, then the water-soluble polymers, each having the amino group trapping the organic acid dissolving in the water, are detected as the organic matters dissolving in the water. Accordingly, it is preferable to conduct the processing on the wastewater at the addition ratio of this inequality, judging from an aspect of water quality. In case where the equation (Eq.

2) is PA<PB, no water-soluble polymer having the amino group, trapping the organic acid thereon, is separated or deposited as the aggregate, but staying under the condition of being dissolved in the eater, therefore there brings about a problem that the removal or extraction ratio of the organic acid is lowered down, finally.
As was mentioned above, it is important to keep the ratio so as to satisfy the inequalities mentioned above, for the purpose of maintaining the removal or extraction ratio of the organic acid in the wastewater. Also, concluding the equations (Eq. 1) and (Eq.
2), the following equation can be obtained.

PA > PB >_ MA...(Eq. 3) In the processing of wastewater, with conducting the process under the condition of the equation (Eq. 2), it is possible to process them, but without increasing an amount of organic compounds dissolving in the water due to the processing of waster water according to the present invention. Also, with conducting the process under the condition of the equation (Eq. 3) , it is possible to remove or extract the organic acid in the wastewater with high efficiency.

As a measure for increasing the removal or extraction of the organic acid other than the above-mentioned, the water-soluble polymer having the amino group should be added, as large as possible, in an addition amount or volume thereof, when considering it to be the number of the amino groups, more than the number of the carboxyl groups in the wastewater. Also, when adding a solution of the water-soluble polymer having the acidic group into the wastewater, with agitating or stirring them as hard as possible, the water-soluble polymer having the acidic group can be spread in the entire of the wastewater; i. e . , it is possible to form or build up the aggregate with superior efficiency. Accordingly, with an enhancement of the agitation condition when adding the water-soluble polymer having the acidic group, an improvement is made of the removal or extraction ratio of the organic acid.
Other method for enhancing the removal or extraction ratio of the organic acid, there can be listed up a method of adding an inorganic salt into the wastewater, before adding the water-soluble polymer having the acidic group therein. This can be considered that the removal or extraction ratio is enhanced due to the effect similar to the salting out. The inorganic salt to be added is, preferably, sodium chloride existing abundantly in the nature. This is suitable or, in particular, in case when processing the wastewater in a submarine oil field, since the averaged concentration of sodium chloride of the seawater is about 3%, and if adding the salt up to that level, an ill influence is slight or insignificant, which is affected upon the environment.
As an order of adding the inorganic salt, it may be done before or after addition of the water-soluble polymer having the amino group, or may be added the organic salt m to the coagulant, for the purpose of accelerating the aggregation effect thereof. However, it must be added, necessarily, before addition of the water-soluble polymer having the acidic group. This is because the aggregation will not occur more than that if adding the water-soluble polymer having the acidic group therein.

Explanation will be given about large-growing of the aggregate. As was mentioned previously, when adding the water solution of the water-soluble polymer having the acidic group, the organic acid can be trapped on the aggregate, effectively, if agitating or stirring it as hard as possible. However, if the agitation is too hard, the size of the aggregate comes to be small, too much, and it clogs easily when passing through the filtering tank. Then, after building up the aggregate, poly aluminum chloride or poly acryl amide is added, thereby growing up the aggregate, to be large in size thereof. This brings about an improvement or increase of the filtering speed of the filtering tank, and in its turn, it enables to result an improvement or increase of processing of the wastewater.

Explanation will be given about an application of magnetic separation. With containing magnet power or iron power therein when forming or building up the aggregate, it is possible to remove the aggregate with an aid of magnetic separation. However, it is difficult to put the magnet power or the iron power into the aggregate after adding the water-soluble polymer having the acidic group.
Accordingly, by adding the magnet power or iron powder, before adding the water-soluble polymer having the acidic group therein, or mixing with the water-soluble polymer having the acidic group, into the wastewater, it can be contained within the aggregate.
However, for the purpose of large-growing of the aggregate, there may be a case where poly aluminum chloride and poly acryl amide may be added therein. In this case, even after adding the water-soluble polymer having the acidic group, it is possible to separate the aggregate through the magnetic separation by adding the magnet power or the iron power before adding the poly acryl amide therein.

(1) Embodiment 1 of water purifying apparatus of the present invention Next, explanation will be made on an embodiment of the water purifying apparatus, according to the present invention. First of all, explanation will be made on the basic or fundamental structure of the water purifying apparatus according to the present invention, by referring to Fig. 3. Wastewater is cast into a first mixing tank 13, with an aid of a pump 11, passing through a pipe 12. The liquid therein is agitated or stirred by means of an overhead stirrer 14. With using a pump 16, a water solution of the water-soluble polymer having the amino group is cast into the first mixing tank 13, from a tank 15 and passing through a pipe 17.

After mixing up the liquid in the first mixing tank 13, the liquid in the first mixing tank 13 is cast into a second mixing tank 20, with using a pump 18 and passing through a pipe 19. The liquid in the second mixing tank 20 was already agitated or stirred by an overhead stirrer 21.

Next, a water solution of the water-soluble polymer having the acidic group is cast into the second mixing tank 20, with using a pump 23 and passing through a pipe 24. With this, aggregate is produced in the second mixing tank 20 . The liquid under the condition of mixing the aggregate therein flows or rushes into a filtering portion 26a or a filtering portion 26b, by opening a valve 25a or a valve 25b. The liquid flowing therein is filtered within a filtering tank 27a or a filtering tank 27b, each being made of sand for use of filtration, and thereafter it is filtered, again, by means of a porous member 28a or a porous member 28b, and thereby coming out as a water reduced of the organic acid thereof.

In Fig. 3 is shown an apparatus having the filtering portion 26a and the filtering portion 26b. In beginning, filtering processing is conducted in the filtering portion 26a, and if in the filtering tank 27a is clogged and the filtering speed is lowered down, then the filtering processing is conducted within the filtering portion 26b. With exchanging the filtering tank 27a, etc., during the filtering processing within the filtering portion 26b, it is possible reduce retardation of the filtering process, as small as possible.

By the way, when the capacity is low of removing the organic acid, a water solution of sodium chloride is cast into the second mixing tank 20, with an aid of a pump 30, from a tank 29 passing through a pipe 31. With this, the ratio of the organic acid trapping on the amino group comes to be large, and thereby improving or increasing the capacity of removing or extracting the organic acid.
In the place of the sodium chloride may be used other organic salt, such as, potassium chloride, etc. In case of discharging the water purified within the water purifying apparatus into the sea water, since the sea water is salt water, it is desirable to use the sodium chloride since the ill influences affected on an ecosystem is slight or insignificant.

A tip 32a of the pipe 24 for casing the water solution of the water-soluble polymer having the acidic group into the second tank is made up, not straight, but to be widen like a fan, or widen like a showerhead, etc., so that the water solution of the water-soluble polymer having the acidic group can be cast into the second mixing tank 20 within an extent, as wide as possible.
This is because, since the aggregation starts, simultaneously, accompanying the cast of the water solution of the water-soluble polymer having the acidic group, if it is cast within a narrow area, the water solution of the water-soluble polymer having the acidic group, which is cast, is contained within the aggregate, and therefore it is not practically used for further producing the aggregation. As to the tip 32a of the pipe 24 and the tip 32b of the pipe 19, for casting the liquid into the second mixing tank 20, ports for casting liquid are provided above a surface of the liquid, so that they do not contact with that liquid surface. This is for the purpose of preventing holes or openings at the tip from being clogged or blocked, with adhesion of the aggregate, which is produced within the second mixing tank 20, at the tip 32a of the pipe 24 and at the tip 32b of the pipe 19.

(2) Embodiment 2 of water purifying apparatus of the present invention Explanation will be given on the basic or fundamental structure of one, having a sedimentation tank, among the water purifying apparatuses according to the present invention, by referring to Fig. 4. The structure of the apparatus shown in Fig.
4 has a sedimentation tank 33 therein. With such structure, the aggregate is settled down or precipitated on a lower portion of the sedimentation tank, and thereby obtaining a top or supernatant liquid can be obtained as purified water.

(3) Embodiment 3 of water purifying apparatus of the present invention =

Explanation will be given on the basic or fundamental structure of one, having a mechanism for protecting the filtering tank from clogging, at the filtering portion thereof, among the water purifying apparatuses according to the present invention, by referring to Fig. 5. Continuing the filtering process, the filtering tank 27 causes clog on a surface thereof, due to the aggregate, and the filtering speed is lowered down, gradually.
Then, within the apparatus shown in Fig. 5, in vicinity of an upper surface of the filtering tank 27 is disposed a disc having concave/convex on the surface thereof, and for rotating this by a motor, there is provided a filtering tank stirrer mechanism 34.
With this, an upper surface of the filtering tank 27 is cut off, so as to dissolve the clog with the aggregate, and thereby enabling a smooth filtration.

(4) Embodiment 4 of water purifying apparatus of the present invention Explanation will be given on the basic or fundamental structure of one, utilizing the magnetic separation method therein, among the water purifying apparatuses according to the present invention, by referring to Fig. 6. The wastewater is cast into a first mixing tank 37, with an aid of a pump 35, passing through a pipe 36. The liquid in this is agitated by means of an overhead stirrer 38. Herein, with an aid of a pump 40, the water solution of the water-soluble polymer having the amino group is cast into the first mixing tank 37, from a tank 39 passing through a pipe 41.

After fully mixing up the liquid in the first mixing tank 37, with using a pump 42, the liquid in the first mixing tank 37 is cast into a second mixing tank 44, passing through a pipe 43.
The liquid in this was already agitated, by means of an overhead stirrer 45.

Next, from a tank 46, by means of a pump 47, a liquid mixed up with the water solution of the water-soluble polymer having the acidic group and the magnet power is cast into the second mixing tank 44, passing through a pipe 48. With this, aggregate is produced in the second mixing tank 44. The aggregate is in the condition of mixed up with the magnet power. This aggregate adheres on a drum 49, having a mesh-like surface and being magnetized. The drum 49 rotates in the clock-wise direction in Fig. 6, and the aggregate adhering on the surface thereof is stripped out from the mesh of the drum 49 by means of a scraper 50. The aggregate stripped out is collected in an aggregate collecting container 51 having a lower surface mesh-liked. Since the aggregate just after being collected includes water, well enough, then the water is discharged from the mesh of the lower surface of the aggregate collecting container.

On the other hand, the water passing through the mesh of the drum 49 is in the condition of being removed or extracted from the aggregate by the mesh. This water comes out as the water reduced in the impurity thereof, passing through a pipe lying at a center portion of the drum 49.

In case where the capacity is low of removing or extracting the organic acid, with an aid of a pump 54, a water solution of the sodium chloride is put into the first mixing tank 37, from a tank 53 passing through a pipe 55. With this, the radio of the organic acid trapping on the amino group comes to be large, and thereby improving or increasing the capacity of removing or extracting the organic acid. In the place of the sodium chloride may be used other organic salt, such as, potassium chloride, etc.
In case of discharging the water purified within the water purifying apparatus into the sea water, since the sea water is salt water, it is desirable to use the sodium chloride from an aspect that the ill influences affected on an ecosystem is slight or insignificant.

A tip 56a of the pipe 48, for casing the water solution of the water-soluble polymer having the acidic group into the second tank, is made up to be widen like a fan, or widen like a showerhead, etc., so that the water solution of the water-soluble polymer having the acidic group can be cast into the second mixing tank 44 within an extent, as wide as possible. This is because, since the aggregation starts, simultaneously, accompanying the cast of the water solution of the water-soluble polymer having the acidic group, if it is cast within a narrow area, the water solution of the water-soluble polymer having the acidic group, which is cast, is contained within the aggregate, and theref ore it is not practically used for further producing the aggregation.

As to the tip 56a of the pipe 48 and the tip 56b of the pipe 43, for casting the liquid into the second mixing tank 44, ports for casting liquid are provided above a surface of the liquid, so that they do not contact with that liquid surface. This is for the purpose of preventing holes or openings at the tip from being clogged or blocked, with adhesion of the aggregate, which is produced within the second mixing tank 44, at the tip 56a of the pipe 48 and at the tip 56b of the pipe 43.

Within the tank 46 is provided an overhead stirrer 57 (an impeller, etc., provided in the tank is not illustrated) , for mixing the water solution of the water-soluble polymer having the acidic group and the magnet powder therewith.

Further, the water solution of the water-soluble polymer having the acidic group and the magnet powder can be put into the second mixing tank 44, separately. However, because of a tendency of generating a deviation or offset in density of the magnet powder contained in the aggregate per a unit of volume, it is desirable to put it into the second mixing tank 44, in advance, after mixing thereof, as is done in the present apparatus.

In this apparatus, without provision of the drum 49 for conducting the magnetic separation, but a mechanism maybe provided for filtering the aggregate, af ter the sedimentation thereof. Since the aggregate contains the magnet powder therein, and then a specific gravity thereof is large, therefore it can settle down easily. Then, bringing almost of the aggregate to settle down on the lower of the second mixing tank 44, and filtering the supernatant liquid thereof, the purification of water can be made without conducting the magnetic separation therein.

(5) Embodiment 5 of water purifying apparatus of the present invention Explanation will be given on the basic or fundamental structure of one, applying a magnetic separation method and comparing two (2) sets of drums therein, among the water purifying apparatuses according to the present invention, by referring to Fig. 7. In this apparatus, after collecting the aggregate on the drum 49, made to be mesh-like on the surface thereof, a small amount or volume of water comes out from an inside of the drum. With this, the aggregate is stripped out from the mesh surface of the drum 49, directing to a drum 58, and thereby adhering it on the surface of the drum 58. The surface of this drum 58 is made of a metal place, but not mesh surface. When stripping out the aggregate therefrom, the mesh surface is scraped out by a scraper 50, but at this time, there is a possibility that the scraper is caught on the mesh, and thereby damaging the mesh. However, within the present apparatus, when stripping out the aggregate by the scraper 50, since that contacting on the mesh is the metal plate being strong comparing to the mesh, and therefore such damage will be hardly caused by the scraper 50; i. e. , it is preferable or suitable.
(6) Embodiment 6 of water purifying apparatus of the present invention Explanation will be given on the basic or fundamental structure of one, applying a magnetic separation method and providing an aggregate removal tank 59 separately, among the water purifying apparatuses according to the present invention, by referring to Fig. 8. In this, the aggregate building up in the second mixing tank 44, not being magnetically separated in the same tank, but is moved to another tank (i. e. , the aggregate removal tank 59), wherein the magnetic separation thereof is conducted.
An amount or volume of processing water put into the aggregate removal tank 59 is controlled by means of a valve 60. With applying such structure, before the magnetic separation, a considerable ratio of the aggregate remains in the second mixing tank 44, then an amount or volume of the aggregate to be removed through the magnetic separation comes to be small. For this reason, clogging hardly occurs on the mesh of the drum 49, and reduction can be achieved on maintenance of the mesh, and therefore is preferable or suitable.

(7) Embodiment 7 of water purifying apparatus of the present invention Explanation will be given on the basic or fundamental structure of one, applying a magnetic separation method and providing one (1) set of drum and an aggregate removal tank 61 separately, among the water purifying apparatuses according to the present invention, by referring to Fig. 9. In this, brining the distance to be short between a bottom of the aggregate removal tank 61 and the drum causes the aggregate to adhere on the drum 58, almost completely. In this manner, purification is conducted with using only one (1) set of drum. The aggregate adhering on the drum 58 is stripped out by means of the scraper 50. With this method, since the purification can be done with using only one (1) set of drum 58, and thereby achieving space saving of the aggregate removal tank 61, and in its turn, of the apparatus, therefore being preferable or suitable.

Examples of the present invention will be shown below.
<Example 1>

During the time when agitating one (1) liter of test water dissolving benzoic acid therein, as the organic acid, at 110 ppm (1 mmol as benzoic acid), 1 g of a water solution at 10 weight %
of polyethylene-imine (the number average molecular weight is 70, 000) is added therein (2. 33 mmol as the number of amino groups) , as the water-soluble polymer having the amino group. Next, when adding 2 g of a water solution at 10 weight % of polyacryllate (the number average molecular weight is 25,000), as the water-soluble polymer having the carboxyl group (2.78 mmol as the number of carboxyl groups), then an aggregate deposes or separates out.
Obtaining this aggregate through filtration, and when measuring an amount of benzoic acid in the filtered liquid with using a liquid chromatography, the concentration of benzoic acid goes down to 10 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be removed or extracted, with using the water-soluble polymer having the amino group and the water-soluble polymer having the carboxyl group.

<Example 2>

Trying a test similar to that of the Example 1, but except for using one (1) liter of test water dissolving acetic acid therein, at 60 ppm, in the place of one (1) liter of test water dissolving benzoic acid therein, at 110 ppm, then the concentration of acetic acid goes down to 8 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be removed or extracted, with using the water-soluble polymer having the amino group and the water-soluble polymer having the carboxyl group.

<Example 3>

Trying a test similar to that of the Example 1, but except for using 1.2 g of water solution of polyallyl-amine (the number average molecular weight is 10,000) at 10 weight % (2.16 mmol as the number of amino groups) , in the place of 1 g of the water solution of polyethylene-imine (the number average molecular weight is 70, 000) at 10 weight%, then the concentration of benzoic acid goes down to 11 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be removed or extracted, with using the water-soluble polymer having the amino group and the water-soluble polymer having the carboxyl group.
<Example 4>

Trying a test similar to that of the Example 3, but except for using 2 g of water solution of polyallyl-amine chlorate (the number average molecular weight is 10,000) at 10 weight% (2.14 mmol as the number of structures of changing from the amino group into the chlorate), in the place of 1.2 g of the water solution ofpolyallyl-amine (the number average molecular weight is 10, 000), and using 3 g of sodium polyacrylate (3.16 mmol as the number of structures of changing from the carboxyl groups to sodium salt) , in the place of 2 g of water solution polyacrylate (the number average molecular weight is 25,000) at 10 weight%, then the concentration of benzoic acid goes down to 12 ppm in the filtered liquid. Theref ore, it is confirmed that the organic acid dissolving in the water can be removed or extracted, with using the water-soluble polymer having the amino group and the carboxyl group, which are changed to the salt structures thereof.

<Example 5>

Trying a test similar to that of the Example 4, but except for using 3 g of water solution of sodium polymethacrylate at 10 weight% (2.75 mmol as the number of structures of changing from the carboxyl groups to sodium salt), in the place of 3 g of the water solution of sodium polyacrylate at 10 weight%, polyallyl-amine (the number average molecular weight is 10, 000) , then the concentration of benzoic acid goes down to 12 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be removed or extracted, with using the polymethacrylate in the place of the polyacrylate.
<Example 6>

Trying a test similar to that of the Example 4, but except for using 6 g of water solution of sodium polystyrene sulfo at 10 weight% (2.91 mmol as the number of structures of changing from the sulfonyl group to sodium salt), in the place of 3 g of the water solution of sodium polyacrylate at 10 weight%, then the concentration of benzoic acid goes down to 12 ppm in the filtered liquid. Therefore, it can be confirmed that the organic acid dissolving in the water can be removed or extracted, with using the water solution having the sulfonyl group as the water-soluble polymer having the acidic group.

<Example 7>

Trying a test similar to that of the Example 1, but except for adding a water solution of sodium chloride at 5.85 weight%, after adding a water solution of polyethylene-imine, but before adding the water solution of polyacrylate at 10 weight%, then the concentration of benzoic acid goes down to 8 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be further reduced, by adding sodium chloride, comparing to the case of not adding it therein.

<Example 8>

Trying a test similar to that of the Example 7, but except for changing the addition amount or volume of sodium chloride at 5.85 weight%, from 1 g to 10 g, then the concentration of benzoic acid goes down to 4 ppm in the filtered liquid. Furthermore, trying a test similar to that of the Example 7, but except for changing the addition amount or volume of sodium chloride at 5.85 weight%, from 1 g to 100 g, then the concentration of benzoic acid goes down to 2 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be further reduced, by enlarging an amount or volume of sodium chloride to be added.
<Example 9>

Trying a test similar to that of the Example 7, but except for using 1 g of a water solution of potassium chloride at 7.45 weight%, in the place of 1 g of water solution of sodium chloride at 5.85 weight%, then the concentration of benzoic acid goes down to 8 ppm in the filtered liquid. Also, trying a test similar to that of the Example 7, but except for using 2 g of a water solution of sulfate of magnesia at 6 weight%, in the place of 1 g of the water solution of sodium chloride at 5.85 weight%, then the concentration of benzoic acid goes down to 6 ppm in the filtered liquid. Therefore, it is confirmed that the organic acid dissolving in the water can be further reduced, by adding various kinds of inorganic salts therein.

<Example 10>

During the time when agitating one (1) liter of test water dissolving benzoic acid therein, as the organic acid, at 110 ppm (1 mmol as benzoic acid) , a water solution of polyethylene-imine (the number average molecular weight is 70,000) at 10 weight% is added as the water-soluble polymer having the amino group, by an amount or volume shown in Table 1. Next, as the water-soluble polymer having the carboxyl group, 2g of a water solution of polyacrylate (the number average molecular weight is 25, 000) at 10 weight % (2.78 mmol as the number of the carboxyl groups) , then an aggregate deposes or separates out. Obtaining this aggregate through filtration, and when measuring an amount of benzoic acid in the filtered liquid with using a liquid chromatography, the concentrations of benzoic acid in the filtered liquids result as shown in the Table 1.

= M

Addition amount or volume of water solution Concentration (ppm) of polyethylene-imine at 10 weight% of benzoic acid in test water Weight (g) Number of amino groups (mmol) 0.30 0.70 48 0.40 0.93 22 0.43 1.00 15 0.50 1.12 14 0.70 1.63 12 1.00 2.33 10 From this result, it is confirmed that, in the relationship between the number of the acidic groups (MA) in the wastewater and the number of the amino groups (PB) of the water-soluble polymer having the amino group, the removal or extraction ratio of the organic acid is low when PB<MA. Thus, it is confirmed that, as is the inequality of the equation (Eq. 1) mentioned above, the removal or extraction ratio of the organic acid can be improved by brining the number of the amino group (PB) in the wastewater and the number of the amino groups to be equal to or greater than the number of the acidic groups (MA) in the wastewater, i . e . , PB
MA.

The ionic bond between the acidic group of the organic acid and the amino group of the water-soluble polymer having the amino group can be an equilibrium reaction. For this reason, it can be considered that an excess of the amino groups increases an amount of traps (i.e., the number of the ionic bonds).

<Example 11>

During the time when agitating one (1) liter of test water dissolving benzoic acid therein, as the organic acid, at 110 ppm (1 mmol as benzoic acid), 1 g of a water solution of polyethylene-imine (the average molecular weight is 70,000) at weight% is added as the water-soluble polymer having the amino 5 group (2.33 mmol as the number of amino groups). Next, as the water-soluble polymer having the carboxyl group, the water solution of polyacrylate (the number average molecular weight is 25,000) at 10 weight% is added, by an amount or volume shown in a Table 2, then an aggregate deposes or separates out. Obtaining this 10 aggregate through filtration, and when measuring an amount of benzoic acid in the filtered liquid with using a liquid chromatography, the concentrations of benzoic acid in the filtered liquids result as shown in the Table 2.

Addition amount or volume of water solution Concentration (ppm) of polyacrylate at 10 weight% of benzoic acid in test water Weight (g) Number of carboxyl groups (mmol) 1.40 1.94 82 1.60 2.22 36 1.66 2.32 18 1.68 2.33 12 1.70 2.36 12 2.00 2.78 10 3.00 4.17 9 From this result, it is confirmed that, in the relationship between the number of the amino groups (PB) of the water-soluble polymer having the amino group, and the number (PA) of the acidic groups of the water-soluble polymer having the acidic group, the removal or extraction ratio of the organic acid is low when PA<PB.
Thus, for the purpose of increasing or heightening the removal or extraction ratio of the organic acid, it is important that PA_PB.
A reason of this can be considered that, when PA<PB, the water-soluble polymer having the amino group, which traps the organic acid, does not separate out as an aggregate, and it remains in the wastewater under the condition of dissolving therein;
therefore, the organic acid cannot be removed or extracted, fully, through the filtration, and as a result thereof, the removal or extraction ratio of the organic acid is lowered.

<Example 12>

Trying a test similar to that of the Example 1, but except for selecting the number average molecular weight of polyacrylate, not 25,000, but to be 800, 1,600, 2,000 or 3,000. Then, in case of applying polyacrylate of 800 and 1, 600 in the number average molecular weight thereof, the aggregate comes to be liquid-like, and when being filtered, it sticks or adheres on surface of a filter paper, spreading thereon, and then it clogs the meshes of the filter paper, soon. Then, filtration is conducted with using a plural number of filter papers. In case of applying polyacrylate of 2, 000 and 3,000 in the number average molecular weight thereof, the aggregate comes to be solid-like, then the meshes of the filter paper is hardly clogged therewith. Therefore, it is preferable or desirable that the number average molecular weight of polyacrylate, which is added when forming or building up the aggregate, is equal to or greater than 2,000.

Also, trying a test similar to that of the Example 1, but except for selecting the number average molecular weight of polyacrylate, not 25, 000, but to be 100, 000, 200, 000 or 1000,000.
Then, in case of applying polyacrylate of 100, 000 and 200, 000 in the number average molecular weight thereof, 2 g of water solution at 10 weight% thereof is added, and the aggregate produced is filtered, and then measurement is made upon the concentration of benzoic acid in the filtered liquid, then it is 10 ppm. On the contrary thereto, when applying the same amount of polyacrylate of 250,000 and 1,000,000 in the number average molecular weight thereof, then the concentrations of benzoic acid in the filtered liquid are 30 ppm and 80 ppm, respectively. Further, when the number average molecular weight is heightened, then the water solution thereof comes to be high in the viscosity thereof, and it is difficult to control an addition amount or volume thereof. Then, 10 g of a water solution is applied by each, at 2 weight % of polyacrylate of 250,000 and 1,000,000 in the number average molecular weight thereof.

Next, when increasing an amount or volume of polyacrylate to be added, up to two (2) times for that of 250,000 in the number average molecular weight thereof, and up to four (4) times for that of 1,000,000 in the number average molecular weight thereof, then concentration of benzoic acid in the filtered liquid goes down to 10 ppm in both cases. This can be considered that the polyacrylate, when the number average molecular weight thereof comes to be large, only builds up the ionic bonds with the amino groups of polyethylene-imine, and has a tendency of building up an aggregate being insoluble in water. For that reason, it is considered that, comparing to the cases when adding polyacrylate being small in the number average molecular weight thereof (the number average molecular weight is 25,000, 100,000 or 200,000), a relatively large proportion of the ionic bonds made of polyethylene- imine and benzoic acid is remained under the condition of dissolving in the water, and as a result thereof, the removal or extraction ratio of benzoic acid is heightened.

From the above, in an aspect that a quantity of using the water-soluble polymer having the acidic group can be reduced when building up the aggregate, determination can be made that the number average molecular weight of the water-soluble polymer having the acidic group be equal to 200,000 or less than that, preferably or desirably. Concluding the above, from the present example, it is shown that the number average molecular weight of the water-soluble polymer having the acidic group be applied, according to the present invention, is 2,000 to 200,000, preferably or desirably.

<Example 13>

In the embodiment 1, when adding the water solution of polyacrylate at 10 weight%, agitation is made with using the overhead stirrer, and the rotation speed at that time is set at 200 rpm. Then, size of the aggregate produced is about 1 to 3 mm.
Therefore, in the present example, the rotation speed of the overhead stirrer is changed to 500 rpm, then the size of the aggregate produced comes down to 0.01 to 0.3 mm, and large in dispersion of the particle diameter thereof. For that reason, this can easily clog meshes of filter papers, having various kinds mesh sizes;
therefore, an efficiency of the process is lowered down.

Then, 1. 5 g of water solution of poly aluminum chloride (PAC) at 1 weight% is added in the test water, in which the fine particles are produced, when condensing corruption particles into the large aggregate thereof, and after agitation thereof, 1 g of water solution of polyacryle-amide at 0.1 weight%, and further it is continued to be agitated under the condition of lowering the rotation speed of the overhead stirrer down to 200 rpm, then the aggregate becomes large, such as, 1 to 3 mm in the size thereof.
Since the aggregate becomes large, filtration of the aggregate with using the filter paper can be conducted, easily, with hardly clogging the mesh of the filter paper. Therefore, in case where the aggregate is small, it is possible to enlarge the size of the aggregate with adding poly aluminum chloride and polyacryle-amide therein, to be filtered easily.

<Example 14>

In the example 1, 100 mg of magnet power of ferrite group is added into the test water before adding the water solution of polyacrylate. Thereaf ter, a water solution of polyacrylate is added and after the aggregate is produced therein, a permanent magnet is put into the test water and then is lifted up after passing 30 seconds, then about 90% of the aggregate adheres on the magnet surface. The remaining thereof sticks on a surface of the overhead stirrer, which is dipped in the test water. The concentration of benzoic acid is 10 ppm. From the above, it is confirmed that the organic acid can be removed or extracted from the test water without conducting the filtration, but with using the magnet powder and the permanent magnet.

<Example 15>

Trying a test similar to the example 14, but except for applying a half of magnet power, i.e., 50 mg, then the aggregate about 50% of the entire thereof attaches on the magnet powder is.
About 40% of the aggregate, not attach on the magnet, but drifts in the test water. Namely, it indicates that an amount or volume of the magnet powder is insufficient for removing or extracting the aggregate in this method. However, in case where the magnet powder is added into the test water after mixing the magnet powder with the water solution of polyacrylate, i.e., adding the polyacrylate and the magnet powder at the same time, 90% of the entire aggregate attaches on the magnet powder. Also, after processing the test water with this method, the concentration of benzoic acid goes down 10 ppm. From the above, it is shown that the necessary amount or volume of the magnet powder can be reduced, by adding the magnet power and the water-soluble polymer having the acidic group, simultaneously, when adding the magnet powder into the test water.

Comparing to the test water and the water solution of polyacrylate, because the specific gravity of the magnet powder is large, it hardly exists or breaks up in the test water, uniformly, even if increasing the agitation speed for the test water. For this reason, the ratio of the magnet powder contained within the aggregate can easily differ from, depending upon that aggregate.

Then, it can be considered that the magnet powder is contained almost in uniform, with respect to the aggregate produced, by adding the magnet powder together with the water solution of polyacrylate, and as a result thereof, the aggregate can attach on the magnet with a small amount or volume of magnet powder.

The present invention may be embodied in other specific forms without departing from the spirit or essential feature or characteristics thereof. The present embodiment(s) is/are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description and range of equivalency of the claims are therefore to be embraces therein.

Claims

1. A coagulant for condensing an organic acid as an aggregate with an aid of ionic bond, comprising:

a water-soluble polymer having an amino group; and a water-soluble polymer having an acidic group.

2. The coagulant as described in the claim 1, wherein the water-soluble polymer having the amino group includes polyethylene-imine, polyvinyl -amine, polyallyl-amine, chitosan, polylysine, or polyarginine.

3. The coagulant as described in the claim 1, wherein said organic acid has a carboxyl group or a sulfonyl group.

4. The coagulant as described in the claim 1, wherein the water-soluble polymer having the acidic group includes polyacrylate, polyaspartic acid, polyglutamate, alginate, polyvinyl-sulfonate, or polystyrene-sulfonate.

5. The coagulant as described in the claim 1, wherein a number average molecular weight of said water-soluble polymer having the amino group is equal to or greater than 200 and is equal to or less than 1,000,000.

6. The coagulant as described in the claim 5, wherein the number average molecular weight of said water-soluble polymer having the amino group is equal to or greater than 200 and is equal to or less than 200,000.

7. The coagulant as described in the claim 6, wherein the number average molecular weight of said water-soluble polymer having the amino group is equal to or greater than 500 and is equal to or less than 200,000.

8. The coagulant as described in the claim 1, wherein the amino group of said water-soluble polymer having the amino group is chlorate, nitrate or sulfate structure.

9. The coagulant as described in the claim 1, wherein a number average molecular weight of said water-soluble polymer having the acidic group is equal to or greater than 2,000 and is equal to or less than 200,000.

10. The coagulant as described in the claim 9, wherein the number average molecular weight of said water-soluble polymer having the acidic group is equal to or greater than 5,000 and is equal to or less than 200,000.

11. The coagulant as described in the claim 10, wherein the number average molecular weight of said water-soluble polymer having the acidic group is equal to or greater than 10,000 and is equal to or less than 200,000.

12. The coagulant as described in the claim 10, wherein the acidic group of said water-soluble polymer having the acidic group is ammonium salt structure, alkali metal salt structure, or alkaline earth metal salt structure.

13. The coagulant as described in the claim 1, further comprising an inorganic salt.

14. A water purifying method for condensing an organic acid as an aggregate with an aid of ionic bond, comprising the following steps of:

preparing said organic acid having a carboxyl group or a sulfonyl group;

adding a water-soluble polymer having an amino group in said organic acid; and thereafter adding a water-soluble polymer having an acidic group.

15. The water purifying method, as described in the claim 14, wherein said water-soluble polymer having the amino group and said water-soluble polymer having the acidic group satisfy PA>=PB, where a number of the amino groups of said water-soluble polymer having the amino group is "PB", and a number of the acidic groups of said water-soluble polymer having the acidic group is "PA", respectively.

16. The water purifying method, as described in the claim 14, wherein further said water-soluble polymer having the amino group and said water-soluble polymer having the acidic group satisfy PA>=PB>=MA, where a number of the acidic groups of said organic acid is "MA", a number of the amino groups of said water-soluble polymer having the amino group is "PB", and a number of the acidic groups of said water-soluble polymer having the acidic group is "PA", respectively.

17. The water purifying method, as described in the claim 14, wherein an inorganic salt is added before adding said water-soluble polymer having the acidic group.

18. The water purifying method, as described in the claim 17, wherein said inorganic salt is sodium chloride.

19. The water purifying method, as described in the claim 14, wherein further polyaluminium chloride or polyacryl-amide is added in said aggregate.

20. The water purifying method, as described in the claim 14, wherein further magnet powder or iron powder is added before adding said water-soluble polymer having the acidic group.

21. The water purifying method, as described in the claim 14, wherein further magnet powder or iron powder is added, by mixing it with said water-soluble polymer having the acidic group, after adding said water-soluble polymer having the amino group in said organic acid.

22. A water purifying apparatus, for condensing an organic acid as an aggregate with an aid of ionic bond, comprising:

a first mixing tank for mixing said organic acid and a water solution of water-soluble polymer having an amino group;

a second mixing tank for mixing a liquid within said first mixing tank with a water solution of water-soluble polymer having an acidic group;

a first pipe provided for said organic acid to move to said first mixing tank;

a second pipe provided for the liquid within said first mixing tank to move to said second mixing tank; and a filtering portion for filtering said aggregate.

23. The water purifying apparatus, as described in the claim 22, further comprising:

a first tank including a water solution of inorganic salt therein.

24. The water purifying apparatus, as described in the claim 22, further comprising:

a third pipe for casting a water solution of said water-soluble polymer having the acidic group into said second mixing tank, wherein said second pipe and said third pipe do not contact on a liquid surface in said second mixing tank.

25. The water purifying apparatus, as described in the claim 22, further comprising:

a sedimentation tank for precipitating said aggregate therein.

26. The water purifying apparatus, as described in the claim 22, wherein said filtering portion has a filtering tank, and a filtration stirring mechanism, which is provided in vicinity of an upper surface of said filtering tank.

27. The water purifying apparatus, as described in the claim 22, further comprising:

a second tank having said water-soluble polymer having the acidic group and magnet power or iron powder therein; and a first drum having a mesh-like surface thereof.

28. The water purifying apparatus, as described in the claim 27, further comprising:

a second drum having a metal surface thereof.

29. The water purifying apparatus, as described in the claim 27, further comprising:

an aggregate removal tank for conducting magnetic separation therein.