JP2003024999A - Sludge treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge treatment method capable of reducing the solubilization treatment quantity of sludge by obtaining a high solubilization ratio and capable of reducing return flow load to perform stable water treatment. SOLUTION: In the sludge treatment method constituted so that organic sewage is treated using the action of microorganisms in a bilogical reaction tank 1 and excess sludge F generated in the bilogical reaction tank 1 is solubilized and the solubilized sludge G is returned to the bilogical reaction tank 1 to be biologically treated, an acid mixed with hydrogen peroxide is added to the excess sludge F and physical treatment is applied to the excess sludge F to which the acid is added to solubilize the sludge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating surplus sludge generated from wastewater treatment. In particular, by obtaining a high solubilization rate, the solubilization treatment amount of sludge is reduced and the return load is reduced. The present invention relates to a sludge treatment method capable of performing stable water treatment.

[0002]

2. Description of the Related Art Conventionally, as a method for treating sewage such as sewage, the activated sludge retained in the biological reaction tank and sewage are mixed,
An activated sludge method is used in which the biological treatment is performed by aeration and stirring, the separated liquid obtained by solid-liquid separation is discharged as treated water, and the separated sludge is returned to the biological reaction tank. Since excess sludge is generated from the separated sludge, it costs a lot of money to dispose of the excess sludge, and
There was a problem that it was also necessary to secure a final disposal site.

Therefore, a technique for solubilizing the generated excess sludge and biodegrading it again in the biological reaction tank so as not to generate excess sludge has been studied. As a solubilization method, a chemical method using an acid or a physical method such as a high temperature / high pressure method is used.
The solubilization rate is only about 10%, and about 30 to 60% by the physical method.

[0004]

That is, in this conventional method for treating sludge, since the sludge solubilization rate is low, in order to prevent excess sludge from being generated, it is necessary to remove sludge several times as much as the amount of sludge to be extracted. It needs to be processed in a solubilization tank. However, the solubilized sludge has a remarkably high biochemical oxygen demand (BOD), and if a large amount of sludge is drawn out and solubilized, the load of returning water to the water treatment system becomes large and stable water is obtained. There is a problem that it becomes difficult to perform the processing.

In view of the problems of the above-mentioned conventional sludge treatment methods, the present invention provides a high solubilization rate to reduce the amount of sludge solubilization treatment and to reduce the return load and stabilize the sludge. It is an object of the present invention to provide a sludge treatment method capable of treating water.

[0006]

In order to achieve the above object, a method for treating sludge according to the present invention is a method for treating organic wastewater by the action of microorganisms in a biological reaction tank and producing excess sludge generated in the biological reaction tank. In the method for treating sludge in which the solubilization of sludge is returned to the biological reaction tank and the treated sludge is biologically treated, an acid mixed with hydrogen peroxide is added to the excess sludge, and the excess excess of the acid is added. It is characterized in that the sludge is solubilized by physically treating the sludge.

In the method for treating sludge of the present invention, an acid mixed with hydrogen peroxide is added to the excess sludge, and the excess sludge added with the acid is subjected to a physical treatment. The cell wall can be further destroyed by physical treatment, which allows a high solubilization rate to be obtained, reducing the amount of sludge to be solubilized, and reducing the return load to the water treatment system, resulting in good solubilization. With water treatment,
The cost for the solubilization process can be reduced.

In this case, a substance containing a strong acid mixed with hydrogen peroxide as a main component can be used as the acid to be added.

As a result, the cell walls of the microorganisms composing the sludge can be more effectively embrittled by the reactivity of the acid itself or the oxidizing power of the OH radical generated by adding the acid.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a sludge treatment method of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing a combination of an oxidation ditch method, which is one of the conventional sewage treatment systems, and an embodiment of the sludge treatment method of the present invention. Sewage A that has flowed into the sewage treatment plant is mixed with activated sludge in the aeration tank 1 and aerated and stirred to be biologically treated. Sewage treated in the aeration tank 1 for a certain period of time flows down to the final settling tank 2 as a mixed solution B with sludge. In the final settling tank 2, solid-liquid separation is performed on the separated liquid C and the separated sludge D by gravity settling, and the separated liquid C is discharged to the outside after being sterilized.

On the other hand, the separated sludge D is drawn out by the sludge pump 3 and sent to the aeration tank 1 as return sludge E, but part of it is sent to the solubilization reaction tank 4 as excess sludge F,
The solubilized sludge G is physically solubilized by the high pressure / high temperature method and is sent to the aeration tank 1 as solubilized sludge G. In this case, the surplus sludge F is chemically solubilized by the acid injected from the chemical tank 5 by the chemical pump 6 while being sent to the solubilization reaction tank 4.

That is, in the present embodiment, an acid or an acid capable of generating a radical is added as the chemical treatment before the solubilization. The solubilization rate of this chemical treatment alone is
As shown in Fig. 2, in the case of acid, it is about 5% at room temperature, and in the case of radical, even if sludge is treated at 50 ° C and pH 2 for several hours
It is about 0%. In this case, as the acid for generating the OH radical, a liquid containing an inorganic acid, preferably a strong acid such as sulfuric acid as a main component and mixed with hydrogen peroxide is used.

On the other hand, a physical treatment is carried out as a treatment after the solubilization. The solubilization rate of this physical treatment alone is high temperature /
As shown in FIG. 3, the solubilization rate of the high pressure method is about 60%, the mill crushing method is about 30%, and the ultrasonic crushing method is about 30%. However, as shown in FIG. 4, by performing the physical treatment by the high temperature / high pressure method together with the chemical solubilization treatment by the acid as in this embodiment, as shown in FIG.
A high degree of solubilization can be obtained.

As described above, in the sludge treatment method of this embodiment, an acid or a radical-generating acid is added to the surplus sludge F, and a physical treatment is added to the sludge F. A high solubilization rate can be obtained. In this case, in the chemical treatment with the acid in the first step, the reactivity of the acid itself or the oxidizing power of the OH radical generated by the addition of the acid damages the cell wall of the microorganism constituting the sludge, and It can be brittle and fragile. Especially in the case of OH radical,
It is known that the pretreatment has a great effect because the oxidizing power is stronger than chlorine and ozone, and the radical reaction effectively proceeds in an acidic region. Therefore, the physical treatment such as the high temperature / high pressure method, the mill crushing or the ultrasonic crushing method performed in the latter stage or at the same time is more likely to break the sludge than the single treatment,
Solubilization is performed more effectively.

[0016]

According to the sludge treatment method of the present invention, an acid is added to the excess sludge, and the excess sludge added with the acid is subjected to a physical treatment. It can be further destroyed by physical treatment, which gives a high solubilization rate, reduces the amount of sludge subjected to solubilization treatment, and reduces the return load to the water treatment system, resulting in good water treatment. And the cost of the solubilization process can be reduced.

Further, by using a substance containing a strong acid containing hydrogen peroxide as a main component as an acid to be added, the reactivity of the acid itself or the oxidizing power of the OH radical generated by adding the acid. This makes it possible to more effectively embrittle the cell walls of the microorganisms that make up the sludge.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of a sludge treatment method of the present invention.

FIG. 2 is a graph showing the ability of solubilization treatment with acid.

FIG. 3 is a graph showing the ability of solubilization treatment by a high temperature / high pressure method.

FIG. 4 is a graph showing the ability of the solubilization treatment of the present invention in which an acid and a high temperature / high pressure method are used in combination.

[Explanation of symbols]

1 Aeration tank (biological reaction tank) 2 final settling tank 3 sludge pump 4 Solubilization reaction tank 5 chemical tanks 6 chemical pump A dirty water B mixture C separation liquid D separation sludge E Return sludge F surplus sludge G Solubilized sludge

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoya Okamura             Hitachi, 3-4-1, Shimosaka, Amagasaki-shi, Hyogo             Kiden Kogyo Co., Ltd. F-term (reference) 4D028 AC03 AC09 BD00 BD11                 4D059 AA05 BC02 BC05 BK12 CA28                       DA31 DA44

Claims (2)

[Claims] 1. A biological reaction tank treats organic sewage by the action of microorganisms, solubilizes excess sludge generated in the biological reaction tank, and returns the solubilized sludge to the biological reaction tank to produce organisms. The method for treating sludge to be treated is characterized in that the sludge is solubilized by adding an acid mixed with hydrogen peroxide to the excess sludge and physically treating the excess sludge to which the acid is added. Sludge treatment method. 2. The method for treating sludge according to claim 1, wherein a substance containing a strong acid mixed with hydrogen peroxide as a main component is used as the acid to be added.