JPS62129200A - Sludge dehydrating agent - Google Patents

Abstract

PURPOSE:To contrive stabilization, by using a cationic org. polymer flocculant, an anionic org. polymer flocculant and a specific water-soluble salt as a sludge dehydrating agent. CONSTITUTION:A cationic org. polymer flocculant such as dimethylaminoethyl methacrylate or dimethylaminoethyl acrylate, an anionic org. polymer flocculant such as sodium polyacrylate or acrylamide or a nonionic org. polymer flocculant (e.g., an acrylamide or methacrylamide/sodium acrylate copolymer) and a water- soluble salt bringing pH of a 5wt% aqueous solution to 4.5-8.0 such as ammonium sulfate, ammonium chloride or ammonium nitrate are used so as to be mixed in a definite ratio. Because the resulting mixture is excellent in solubility and also good in easy dispersibility, dehydration efficiency is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION G) Object of the Invention [Field of Industrial Application] The present invention relates to a dewatering agent for sludge produced by the treatment of sewage, human waste and various industrial wastewater.

[Conventional technology]

Sludge produced by the treatment of sewage, human waste, and various industrial wastewater is flocculated by adding and mixing a dehydrating agent, and then dehydrated using a dehydrator such as a centrifugal dehydrator or a squeeze type dehydrator. Conventionally, the methods for dewatering sludge described above were: (1) using a cationic organic polymer flocculant alone, and (2) adding a cationic organic polymer flocculant and an anionic organic polymer flocculant sequentially or simultaneously. Are known. However, in recent years, a method using a dehydrating agent containing a cationic organic polymer flocculant, an anionic organic polymer flocculant, etc. as active ingredients has been attracting attention.

Generally, when a cationic organic polymer flocculant and an anionic organic polymer flocculant are put into the same dissolution tank, a polyion complex is generated and insolubilized. Kaisho 58-21
A sludge dehydrating agent with good dewatering properties that avoids insolubilization has been proposed by incorporating an alkaline agent (for example, Japanese Patent Application Laid-Open No. 58-216707).

[Problem that the invention seeks to solve]

The method of mixing an acid with a cationic organic polymer flocculant and an anionic organic polymer flocculant, as disclosed in JP-A No. 58-216706, is a method of mixing iron with iron to form a strongly acidic solution. This is not necessarily a preferable method because it has negative effects such as corrosion of the dissolution tank and piping and poor solubility of the anionic organic polymer flocculant. Further, the method of blending an alkaline agent as disclosed in JP-A-58-216707 is limited to a cationic organic polymer flocculant that does not contain a quaternary ammonium salt. Furthermore, since the pH of the aqueous solution becomes strongly alkaline, ester-based cationic organic polymer flocculants such as dimethylamine ethyl (meth)acrylate-based agents lack stability due to hydrolysis of cationic groups.

(B) Structure of the Invention [Means for Solving the Problems] The present inventors have completed the present invention as a result of studying the above-mentioned problems.

That is, the present invention provides a fl+l decationic polymer flocculant, (2
) Anionic organic polymer flocculant or nonionic organic polymer flocculant and (3) pH of 5% by weight aqueous solution is 45-8.
This is a sludge dewatering agent consisting of a water-soluble salt of 0.

[Cationic organic polymer flocculant]

The cationic organic polymer flocculant in the present invention is produced by a known method, such as dimethylamine ethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylamine propyl methacrylamide, dimethylaminopropylacrylamide, or Homopolymers of quaternized or tertiary products thereof, dimethylamine, noether methacrylate, dimethylaminoethyl acrylate, dimethylamine propyl methacrylate, dimethylamine propyl methacrylamide, or dimethylaminopropylacrylamide, or quaternized products or 6-class products thereof Copolymers of compounds and acrylamide or methacrylamide, Mannich modified products of polyacrylamide or polymethacrylamide or quaternized products thereof, Hofmann decomposition products of polyacrylamide or polymethacrylamide,
Examples include a homopolymer of diallyldimethylammonium salt and acetate of chitosan.

Among these, a homopolymer of a quaternized dimethylamine ethyl methacrylate or a copolymer containing 60 mol or more of the quaternized product, so-called high cation, is preferred.

In addition, the colloid equivalent value is 6.9 to 4.8 meq/
A range of 9 is preferred.

[Anionic organic polymer flocculant]

The anionic organic polymer flocculant in the present invention is produced by a known method, such as a copolymer of sodium polyacrylate, acrylamide or methacrylamide and sodium acrylate or sodium methacrylate, polyacrylamide or polymethacrylate. Partial hydrolysates of amides, terpolymers of acrylamide or methacrylamide, sodium acrylate or sodium methacrylate, 2-acrylamide-2-methylpropanesulfonic acid, sodium alginate, and the like can be mentioned.

Among these, those with so-called weak anions to medium anions are preferable, and the colloid equivalent value is -0.7 to -3.
, 0 meq / , li+ is preferred.

[Nonionic organic polymer flocculant]

The nonionic organic polymer flocculant in the present invention is produced by a known method, such as a copolymer of acrylamide or methacrylamide and sodium acrylate or sodium methacrylate, or a partially hydrated polyacrylamide or polymethacrylamide. Examples include decomposition products, terpolymers of acrylamide or methacrylamide, sodium acrylate or sodium methacrylate, and sodium 2-acrylamide-2-methylpropanesulfonate.

The nonionic organic polymer flocculant is preferably one that forms a water-insoluble complex when mixed with the cationic organic polymer flocculant.

Moreover, the colloid equivalent value is preferably -0.1 to -0.7 meq/i.

[Water-soluble salt]

The water-soluble salt used in the present invention has a pH of 5% by weight aqueous solution.
is selected from salts having a value of 4.5 to 8.0, and at least one of these salts is blended.

Examples of these salts include ammonium sulfate, ammonium chloride, ammonium nitrate, magnesium sulfate, magnesium chloride, calcium chloride, sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, and the like. Among these, calcium chloride and ammonium chloride are preferred.

The amount of water-soluble salt varies depending on the type and weight ratio of the cationic organic polymer flocculant and anionic organic polymer flocculant, but the total amount of the cationic organic polymer flocculant and anionic organic polymer flocculant or the cation It is necessary to add 1 times or more of the total amount of the organic polymer flocculant and the nonionic organic polymer flocculant. Preferably, it is 5 to 10 times or more.

If it is less than 1 time, precipitation of insoluble coagulated substances or clouding may be observed, which is not preferable. Not too many again...
and the performance of the flocculant tends to deteriorate.

[Ratio of cationic organic polymer flocculant, anionic organic polymer flocculant and nonionic organic polymer flocculant]

The ratio of the cationic organic polymer flocculant and the anionic organic polymer flocculant used in the present invention and the ratio of the cationic organic polymer flocculant and the nonionic organic polymer flocculant used in the present invention are 95:5 to 95:5 by weight. 5:95 is preferred, 80
:20 to 20:80 is more preferable. Outside these ranges, the sludge dewatering performance tends to deteriorate.

[Addition of acid]

Ester type cationic organic polymer flocculants such as dimethylaminoethyl (meth)acrylate type hydrolyzes the cationic group in an alkaline aqueous solution, so the pH of the solution should be 65 or higher, preferably 4 to 7. Acid can be added to the sludge dehydrating agent in a sufficient amount to stabilize the aqueous solution. Especially, when using a water-soluble salt that makes the pH of the aqueous solution alkaline, it is preferable to add an acid.

[For production]

(Mechanism of dissolution) The sludge dehydrating agent of the present invention can be water-insoluble and coagulate in the presence of an appropriate amount and type of water-soluble salt even if the pH of the solution is above 6.5 and below 95. No matter is produced. Therefore, the sludge dewatering agent of the present invention is disclosed in JP-A-58-216
This invention is constructed by a different mechanism from the invention described in No. 706 or Japanese Unexamined Patent Publication No. 58-216707. In the former, the anionic nature of the anionic organic polymer flocculant is eliminated by significantly lowering the pH value, thereby eliminating the interaction with the cationic organic polymer flocculant. In the latter case, conversely, p
By significantly increasing H, the cationic nature of the cationic organic polymer flocculant is eliminated, thereby eliminating the interaction with the anionic organic polymer flocculant.

The dissolution mechanism of the sludge dehydrating agent of the present invention is not necessarily clear, but it is possible that the dissociation of cationic groups or anionic groups is suppressed due to the coexistence of a large amount of electrolyte, or that the polymer chain spreads. This is thought to be due to the fact that contact between the cationic group and the anionic group is lost due to the ions interposed between the polymer chains, as well as being significantly suppressed.

(Coagulation/Dewatering Mechanism) When the sludge dehydrating agent of the present invention is added and stirred, for example, sewage,
SS of surplus sludge such as human waste has a negative charge, so
First, a cationic organic polymer flocculant acts to neutralize the charge and generate fine flocs. On the other hand, for positively charged sludge, an anionic organic polymer flocculant first acts to form flocs. After forming flocs, another organic polymer flocculant with a charge opposite to that of the first polymer flocculant acts next, forming coarse, strong flocs with excellent f-permeability and dehydration properties. It is thought that it generates

[Dissolution of sludge dehydrating agent]

The sludge dewatering agent of the present invention is produced by dissolving a cationic organic polymer flocculant and an anionic organic polymer flocculant or a cationic organic polymer flocculant and a nonionic organic polymer flocculant in a tel-dissolution tank. is added to sludge,
As the dissolution method, various methods can be adopted including the following method.

■ A method of simultaneously mixing and adding a cationic organic polymer flocculant, an anionic organic polymer flocculant, or a cationic organic polymer flocculant, a nonionic organic polymer flocculant, and a water-soluble salt ■ After dissolving the water-soluble salt , a cationic organic polymer flocculant, and an anionic organic Hatake molecular flocculant or a method of mixing and adding a cationic organic polymer flocculant and a nonionic organic polymer flocculant■ Anionic, cationic, or nonionic organic polymer After dissolving the flocculant, the water-soluble salt is dissolved, and finally the cationic anionic or nonionic organic polymer flocculant is added. It is also possible to mix it with a molecular flocculant, an anionic organic polymer flocculant, a nonionic organic polymer flocculant, and a water-soluble salt, or it may be added after the above composition is dissolved.

Features of the sludge dewatering agent of the present invention in dissolution include the following points.

(1) Good water solubility (2) Good water dispersibility of the polymer (・(however, the dissolution method described in (1) above) (Water solubility) 21
It has better water solubility than No. 6706. Japanese Unexamined Patent Publication No. 1983-
In No. 216706, -COONa on the anionic organic polymer flocculant particle surface becomes a strongly acidic aqueous solution.
The groups are first converted to -COOH groups, and as a result, the conversion to -COOH groups gradually progresses to the center of the particles.As a result, dissociation is suppressed and the solubility and dissolution rate of the anionic organic polymer flocculant particles are significantly impaired. I'll get lost. In severe cases, the anionic organic polymer flocculant particles remain in their form as a transparent gel that is only slightly swollen.

In the sludge dewatering agent of the present invention, such conversion of anionic groups does not occur, so the water solubility of the anionic organic polymer flocculant is not impaired (and the rate of dissolution is not delayed). (Water dispersibility) The sludge dewatering agent of the present invention uses a large amount of water-soluble salt, so even if extremely fine polymer flocculant powder is used, it does not become lumpy and has good water dispersibility. Furthermore, by using fine powder, the dissolution rate is significantly improved.

(#Solubility) The dissolved concentration of the sludge dehydrating agent of the present invention in water is determined by coagulation,
An organic polymer flocculant, which is an effective ingredient in dehydration, is used in water in an amount of 0.1 to 2 weight range.

(Addition jt) The amount of the sludge dehydrating agent of the present invention varies depending on the properties of the sludge, but it is usually an active ingredient in coagulation dehydration or as a polymer.
It is about 0.5 to 6 weight percent relative to sludge solid content (SS).

[Agglutination method]

As a coagulation method, a coagulation tank may be used or the flow of piping may be used.

The circumferential speed of the stirring blade of the 1-shuzo is usually 0.5 to 5 m/crown.

[Dehydration method]

The flocs produced by the sludge dewatering agent of the present invention can be processed as they are or after being subjected to e-separation, and then passed through a centrifugal dehydrator as in the past.
Dehydrated using a dehydrator such as a vacuum dehydrator, belt press type dehydrator, screw press or filter press.

[Combined use with inorganic flocculant]

The sludge dewatering agent of the present invention can also be used in combination with an inorganic flocculant such as aluminum sulfate, polyaluminum chloride, ferric chloride, or polyferric sulfate, as in the past. When used together, the inorganic flocculant is added before or after the addition of the sludge dewatering agent of the present invention.

[Examples and comparative examples]

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

The abbreviations on each side are as follows.

C1; dimethylamine ethyl methacrylate quaternary salt homocation C, dimethylamine ethyl methacrylate quaternary salt strong cation C3; dimethylamine ethyl methacrylate quaternary salt cation C4 dimethylamine ethyl methacrylate quaternary salt weak cation C1; dimethylamine ethyl methacrylate Cation A1 in tertiary salt; Sodium polyacrylate A2; Strong anion A3 in sodium acrylate/acrylamide copolymer; Anion A4 in sodium acrylate/acrylamide copolymer; Weak anion A5 in sodium acrylate/acrylamide copolymer; Nonion in sodium acrylate/acrylamide copolymer Example 1 Cationic organic polymer flocculants o, a, p and anionic organic polymer flocculant 0.2 & were mixed with sodium chloride in various proportions, added to 200-g distilled water, and dissolved by stirring with a stirrer. . Table 1 shows the dissolution state and pH value at that time.

Example 2 In the same manner as in Example 1, the common state and pH value were measured by changing the ratio of the cationic organic polymer flocculant to the anionic organic polymer flocculant and the ratio of the inorganic salts. The results are shown in Table 2.

Examples and Comparative Example 1 The sludge dewatering agent of the present invention (Example 3) and the cationic organic polymer flocculant alone (Comparative Example 1) were tested for solubility, dissolution rate, and dispersibility under the conditions shown in Table 6. I did it. The results are shown in Table 6.

It is clear that the sludge dewatering agent of the present invention has excellent solubility and easy dispersibility.

Example 4 and Comparative Example 2 Sludge dewatering agent of the present invention (Example 4) and embodiments other than the present invention (
In Comparative Example 2), a test regarding corrosion caused by a solution was conducted.

Iron test pieces (1 [] x 25 x 0.15 m) were immersed in various solutions for 90 days, and weight loss was measured. In addition,
Lysates were prepared fresh every 6 days.

The test results are shown in Table 4. It is clear that the sludge dewatering agent of the present invention exhibits the same level of corrosiveness (-) as when the cationic organic polymer flocculant is dissolved alone.

Example 5 and Comparative Example 3 A sludge dehydrating agent of the present invention (Example 5) and a sludge dehydrating agent other than the present invention (Comparative Example 2) were tested for stability of the dissolved solution under the conditions shown in Table 5.

The results are shown in Table 5.

It is clear that the sludge dehydrating agent solution of the present invention can be washed and stored stably for a long period of time.

Example 6 and Comparative Example 4 (~excess sludge in urine treatment (properties, pH 7, 2, 5S
10300 Tomi 9/l, VSS7725 Tomi 9/l)
・We conducted a dehydration performance test. The results are shown in Table 61
~is.

In the test, a sludge dewatering agent dissolved at a polymer concentration of 0.5% was added to surplus sludge 1001 at a ratio of 2.9% to SS, and 1100
Stir and mix at 0 rpm for 60 seconds. Thereafter, gravity dehydration was carried out using the Tanoche test, and the amount of liquid permeated was measured.The cake was then dehydrated using a centrifugal dehydrator (2000 rpm, 10 minutes), and the water content of the dehydrated cake was measured. The sludge dewatering agent of the present invention is
It can be seen that it is excellent as a flocculating and dehydrating agent.

(c) Effects of the Invention The sludge dehydrating agent of the present invention has good solubility in water, good stability of the obtained bath solution, excellent dehydration performance, and is not corrosive to equipment, making it suitable for industrial use. Useful.

Claims (1)

[Claims] 1. (1) a cationic organic polymer flocculant, (2) an anionic organic polymer flocculant or a nonionic organic polymer flocculant, and (3) a 5% by weight aqueous solution with a pH of 4.5 to 8.0. A sludge dewatering agent consisting of certain water-soluble salts.