JPH04284900A - Dewatering method of organic sludge - Google Patents

Abstract

PURPOSE:To facilitate the operational control of a dewatering machine by decreasing the water content of dewatered cake in a dewatering method in which organic sludge added with an organic coagulant, after being condensed by pelletizing, is mechanically dewatered with a dewatering machine. CONSTITUTION:An inorganic coagulant 4 is injected into a transfer pipe 12 which sends a sludge slurry previously condensed by pelletizing to a dewatering machine 13 (pipeline 14) to decrease the water content of dewatered cake and to improve its releasing property. The leakage of the sludge from filter cloths is thereby prevented to facilitate the operational control of the dewatering machine.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for dewatering organic sludge, and in particular, it involves adding an organic flocculant to organic sludge, granulating and concentrating it, and then dewatering it using a mechanical dehydrator. This invention relates to a method for dewatering organic sludge that significantly reduces the water content of dehydrated cake and improves the operational stability of a dehydrator.

0002

[Prior Art] Conventionally, as a method for dewatering organic sludge generated from the treatment of sewage, human waste, or organic industrial wastewater, a cationic organic polymer flocculant (cationic polymer) is applied to the sludge.
There is a method of dehydration by adding
Various improvements have been made. Specifically, the following methods (1) and (2) are known. ■ Adding and mixing a cationic polymer to sludge, partially dehydrating the generated flocs or pellets, and adding and mixing a cationic polymer to the resulting dehydrated product for mechanical dewatering (Japanese Patent Publication No. 1-17760
). ■A method in which a cationic polymer is added and mixed to sludge, and when this is dehydrated using a belt press type dehydrator, an aqueous solution of iron salt is added by showering or spraying on the gravity dewatering section of the dehydrator (Japanese Patent Application Laid-open No. 1983-1999-1). 149300).

[0003] Furthermore, a granulation concentration method is known as a means for dewatering sludge.

0004

[Problems to be Solved by the Invention] Among the above conventional methods, in method (2), flocs or pellets break during partial dehydration, and a cationic polymer is further added to and mixed with the obtained dehydrated product. However, there are drawbacks such as the need for equipment such as a kneader and stirring tank. On the other hand, method (2) requires a dilution device for preparing an aqueous iron salt solution and a dispersion device for the gravity dewatering section, and has disadvantages such as difficulty in uniform dispersion, and environmental deterioration often caused by dispersion. There is. For this reason, the current situation is that sufficient dehydration performance has not been obtained in the past.

By the way, the granulation concentration method has a high sludge reforming effect and is a powerful dewatering method, but due to the lack of obtained floc strength, the sludge is Side leaks or leaks from the filter cloth may occur. In such cases, it is necessary to extremely reduce the amount of sludge treated. Further, even when it is desired to further reduce the water content of the dehydrated cake, the amount of sludge treated must be significantly reduced using the conventional granulation and concentration method. As a result, processing efficiency is significantly reduced.

The present invention solves the above-mentioned conventional problems, and aims to reduce the water content and improve the peelability of the resulting dehydrated cake in a method of adding and mixing an organic flocculant to organic sludge for dewatering. Dehydrator operation management can be made easier,
An object of the present invention is to provide a method for dewatering organic sludge that can dewater organic sludge with high processing efficiency.

[0007]

[Means for Solving the Problems] The method for dewatering organic sludge of the present invention involves adding an organic flocculant to organic sludge, granulating it and concentrating it, and then dewatering it with a mechanical dehydrator. It is characterized by injecting an inorganic flocculant into the transfer pipe that transfers the subsequent sludge slurry to the mechanical dehydrator.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a flowchart showing an example of the present invention. In FIG. 1, organic sludge is put into a raw sludge storage tank 1 and stored therein. 1a is a stirrer. The sludge in the storage tank 1 is introduced into the bottom of the auxiliary agent reaction tank 3 via the pump 2a and piping 2b, and is stirred. 3a is a stirrer. The inorganic flocculant in the auxiliary agent dilution tank 4 is injected into the auxiliary agent reaction tank 3 via an auxiliary agent injection pump 5a and piping 5b, and the sludge is thoroughly mixed with this inorganic flocculant. As will be explained in detail later, the addition of this inorganic flocculant neutralizes the charge of the sludge and strengthens the floc core. Note that this auxiliary agent reaction tank 3 is equipped with a belt press 13, which will be described later.
The filtrate generated in is returned via piping 15.

The sludge mixed with the inorganic flocculant is then introduced into a granulation concentration tank 7 via a pipe (supply pipe) 6. An amphoteric organic polymer flocculant in a polymer dissolution tank 8 equipped with a stirrer 9 is introduced into this granulation concentration tank 7 via a pump 10a and piping (chemical injection pipe) 10. As the liquid is swirled by the rotation of the agitator 7a, the sludge is granulated into granules (pellets). The liquid that has not been pelletized in the granulation/concentration tank 7 passes through the filtration section 7b and is sent as a separated liquid to an initial settling tank (not shown) via piping 11. The granules are sent to the sludge extraction pump 12a along with a small amount of liquid.
The water is then sent to a mechanical dehydrator, in this embodiment, a belt press 13, via a pipe (transfer pipe) 12.

In the present invention, the inorganic flocculant in the auxiliary dilution tank 4 is added to the sludge slurry in the transfer pipe 12 via the auxiliary injection pump 14a and the pipe (injection pipe) 14. The sludge slurry to which the inorganic flocculant has been added is efficiently dehydrated in the belt press 13 to obtain a dehydrated cake with an extremely low water content. As described above, the dehydrated filtrate from the belt press 13 is returned to the auxiliary agent reaction tank 3 via the pipe 15 for treatment. Reference numeral 16 denotes a discharge pipe for cleaning waste water of the filter cloth of the belt press 13.

In the present invention, no special conditions are required for the injection line of the inorganic flocculant into the transfer pipe 12, as long as the inorganic flocculant is uniformly mixed and injected into the sludge slurry to be transferred. Generally, an inorganic flocculant injection pipe is connected before or after the sludge drawing pump 12a of the transfer pipe 12, but a U-shaped bypass pipe is provided in the transfer pipe 12, and an inorganic flocculant injection pipe is connected to this bypass pipe. You can also.

[0012] The greater the amount of inorganic flocculant added to the sludge slurry in the transfer pipe, the lower the water content of the resulting dehydrated cake. It is preferably about 10 to 15% by weight based on the SS of the sludge slurry.

The inorganic flocculants used in the present invention include ferric chloride, aluminum sulfate, aluminum chloride, polyaluminum chloride, polyferric sulfate, and the like.

In the present invention, the organic sludge to be treated is not particularly limited, but includes, for example, primary sedimentation tank sludge of sewage, human waste, coagulated sludge generated in the tertiary treatment of sewage, etc., coagulated sludge of various industrial wastewater, Examples include organic sludge such as anaerobic digested sludge of human waste, aerobic digested sludge of human waste, human waste septic tank sludge, human waste digested desorbed liquid, sewage, and surplus sludge in activated sludge treatment of various industrial wastewaters.

[0015]Although the amount of the inorganic flocculant added to the auxiliary reaction tank 3 depends on the type of compound used, the pH of the organic sludge to be treated is within the range of 3.0 to 5.0. It is preferable to add it so that For example, iron-based inorganic flocculants such as ferric chloride and polyferric sulfate have a pH of 3.5 to 4.5,
Aluminum-based inorganic flocculants such as aluminum sulfate, aluminum chloride, and polyaluminum chloride have a pH of 4.0.
The highest addition effect is shown when added at a concentration of ~5.0. When the pH after addition of the inorganic flocculant is higher than 5, an acid may be added to adjust the pH.

The organic polymer flocculant used in the present invention has a cationic structural unit (cation group) amount (hereinafter referred to as "cation amount").
It is called. ), the colloid equivalent value (a value) obtained by colloid titration at pH 3 is 1.0 to 3.7 meq/g, the amount of anionic structural unit (anion group) (hereinafter referred to as "anion amount") and cationic structure. The colloid equivalent value (b value) measured by colloid titration at pH 7, which indicates the difference in unit amount, is -1.7 to 0.
The amphoteric organic polymer flocculant is preferably 7 meq/g and has a value of (ab)/a representing the ratio of anion amount/cation amount in the range of 0.8 to 1.8.

Under the condition of pH 3, it is thought that the anion groups in the amphoteric organic polymer are hardly dissociated, and on the contrary, the cation groups are mostly dissociated. The colloidal equivalent value (a value) can be regarded as the total amount of cations in the amphoteric organic polymer.

On the other hand, the colloidal equivalent value of anionic groups is usually titrated at pH 10.5, but at this pH, cationic groups in amphoteric organic polymers may be hydrolyzed to become anionic groups. The value titrated at pH 7 is used. In this case, since both the cationic group and anionic group in the amphoteric organic polymer dissociate, the result of colloid titration is the amount of extra anion or cation that cancels out the cation and anion. Therefore, the total amount of anions in the amphoteric organic polymer is the difference between the colloidal equivalent value titrated at pH 3 and the colloidal equivalent value titrated at pH 7 (a
-b).

The amphoteric organic polymer flocculant that can be used in the present invention has a colloid equivalent value (a) of 1.
0 to 3.7 meq/g, the colloid equivalent value (b) at pH 7 is -1.7 to 0.7 meq/g, and the anion amount/cation amount ratio ((a-b)/a) is 0.8 to 1.8
Any amphoteric organic polymer within the range can be used. Examples of such materials include copolymers of anionic monomer components and cationic monomer components, copolymers of anionic monomer components, cationic monomer components, and nonionic monomer components, or anionic monomer components. Examples include Mannich-modified products or Hofmann-decomposed products of copolymers of components and nonionic monomer components.

Examples of anionic monomer components include acrylic acid (AA), sodium acrylate (NaA
), methacrylic acid, sodium methacrylate, etc. As a cationic monomer component,
Examples include dimethylaminoethyl acrylate, dimethylaminoethyl (meth)acrylate (DAM), dimethylaminopropyl (meth)acrylate, and quaternized products thereof. As a quaternary compound,
Specific examples include dimethylaminoethyl acrylate methyl chloride quaternized product (DAA). Alternatively, dimethylaminopropylacrylamide hydrochloride (DAPAAm) may be used. Examples of nonionic monomer components include acrylamide (AAm),
Examples include methacrylamide, N,N'-dimethyl(meth)acrylamide, and the like. In addition, as a copolymer of these compounds, specifically DAA/AA/A
Am copolymer, DAM/AA/AAm copolymer, DAP
Examples include Mannich modified products of AAm/AA/AAm copolymers, DAA/AA copolymers, and NaA/AAm copolymers.

The amphoteric organic polymer flocculant as described above is preferably added in a proportion of 0.5 to 2.0% by weight based on the SS of the organic sludge.

Furthermore, in the present invention, as the mechanical dehydrator, in addition to the belt press shown in the figure, any conventionally used dehydrator such as a centrifugal dehydrator, vacuum dehydrator, screw press, or filter press can be used. It is.

[0023]

[Operation] The granulated and concentrated sludge is in the form of granules or broken granules, and the amount of mother liquor between the particles is small. When an inorganic flocculant is line-injected into the slurry containing this granulated sludge, the inorganic flocculant is dispersed and dissolved, and acts on the granulated sludge, making the surface of the drained granulated sludge particles hydrophobic. Dehydration can be improved.

At the same time, side leakage of sludge and leakage of sludge from the filter cloth during mechanical dewatering, such as a belt press, are prevented, and the peelability of the dewatered cake is also improved. As a result, processing capacity per unit time increases, and
Operation management of the dehydrator becomes easier.

Moreover, since the inorganic flocculant is added to the sludge after granulation and concentration, that is, the sludge from which the separated liquid has been removed in advance, the total amount of auxiliary added can be reduced, and It also becomes possible to collect and reuse the filtrate.

[0026]

[Examples] The present invention will be explained in more detail with reference to Examples below. In addition, in the following, "%" is "weight%"
It shows.

Example 1 Organic sludge discharged from the factories of the three companies shown in Table 1 was treated by injecting an inorganic flocculant in the amount shown in Table 1 by the method shown in FIG. Determine the moisture content of the dehydrated cake,
The moisture content of the dehydrated cake was compared with the case where the line injection of the inorganic flocculant was not performed, and the results are shown in Table 1. Furthermore, Table 1 shows the results of the investigation regarding the SS of the generated sludge.

[0028] The drugs used are as follows. Inorganic flocculant = ferric chloride organic flocculant dissolving tank 8 = amphoteric organic polymer flocculant Also, the amount of inorganic flocculant added to the auxiliary reaction tank 3 is 15%/
SS, the amount of ferric chloride added to the dissolution tank 8 to the granulation concentration tank 7 was 1.5%/SS.

[0029]

[Table 1]

From Table 1, it is clear that the line injection of the inorganic flocculant significantly reduces the water content of the dehydrated cake to about 2-6%.

[0031]

[Effects of the Invention] As detailed above, according to the organic sludge dewatering method of the present invention, (1) the water content of the dehydrated cake is significantly reduced; ■ During mechanical dewatering, side leaks and eye leaks of sludge from the filter cloth are prevented. ■ The peelability of the dehydrated cake is greatly improved. ■ From ■ and ■, the operation of the dehydrator is stabilized and operation management becomes easier. (2) The total amount of auxiliary agents added can be reduced, and the dehydrated filtrate can be recovered and reused. (2) Unlike the auxiliary spraying method disclosed in JP-A-61-149300, there is no problem of environmental deterioration, and no equipment is required for spraying. Excellent effects such as these can be achieved, and treatment efficiency and dewatering efficiency can be improved and treatment costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one implementation method of the organic sludge dewatering method of the present invention.

[Explanation of symbols]

1 Raw sludge storage tank 3 Auxiliary reaction tank 4 Auxiliary agent dilution tank 7 Granulation concentration tank 7a Stirrer 7b Filtration section 8 Polymer dissolution tank 9 Stirrer 13 Belt press

Claims (1)

[Claims] Claim 1: A method of adding an organic flocculant to organic sludge, granulating and concentrating it, and then dewatering it with a mechanical dehydrator, comprising:
A method for dewatering organic sludge characterized by injecting an inorganic flocculant into a transfer pipe that transfers sludge slurry after granulation and concentration to a mechanical dehydrator.