JP2003190999A - Method for accelerating solid-liquid separation of sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accelerating the solid-liquid separation of sludge capable of obtaining high concentrated sludge for a short time as compared with a conventional gravitational concentration method while reducing the cost required in equipment or chemicals. <P>SOLUTION: In the method for accelerating the solid-liquid separation of sludge for treating an organic substance in sewage using microorganisms and drawing out generated sludge to treat the same, the drawn-out sludge is heated to a degree degenerating the polymeric substance in sludge to reduce the viscosity thereof to accelerate the sedimentation properties of sludge. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for promoting solid-liquid separation of sludge, and particularly to sludge treated by an activated sludge method or the like, which suppresses the amount of chemicals such as coagulant used and is economically and efficiently. The present invention relates to a method for promoting solid-liquid separation of sludge, which is intended to promote solid-liquid separation.

[0002]

2. Description of the Related Art Conventionally, sewage such as sewage that flows into a sewage treatment plant (hereinafter referred to as "sewage") is introduced into a biological reaction tank, and the sewage and activated sludge are mixed, aerated and stirred. Biological treatment of organic components in wastewater is performed, and sludge generated along with this is precipitated, concentrated and separated from the mixed solution for treatment. Then, as a method of precipitating and concentrating and separating the sludge generated in the biological reaction tank, a gravity concentration method, a mechanical concentration method, and the like can be mentioned.

[0003]

The water content of sludge in the biological reaction tank varies depending on the treatment method, but is usually about 99%, and the sludge treatment system provided in the latter stage of the sedimentation / concentration separation operation In order to improve the efficiency of the sludge, it is important to reduce the content rate of this sludge and finally reduce the amount of sludge sent to the sludge treatment system.

However, the conventional gravity concentrating method concentrates sludge by utilizing the phenomenon that sludge, which has a higher specific gravity than water, spontaneously sediments, but when the sludge concentration increases, the sedimentation property remarkably deteriorates, As a result, there was a problem that only a sludge having a water content of about 98% was obtained, a concentrated sludge having a sufficiently high concentration could not be obtained, and a solid-liquid separation rate in the latter stage could not be obtained as expected. In addition, sedimentation by natural sedimentation
Since the concentration and separation are performed, there is a problem that it takes time and the settling tank required becomes large accordingly.

On the other hand, the mechanical concentration method includes a centrifugal separation method, a floating concentration method, and the like. In these methods, a normal water content is about 96%, and a sludge having a higher concentration than that of the gravity concentration method can be obtained. On the other hand, there is a problem that the cost of equipment becomes high, and addition of chemicals is indispensable for efficient precipitation / separation, which is inferior in economic efficiency.

In view of the problems of the above-mentioned conventional solid-liquid separation method for sludge, the present invention makes it possible to reduce the cost of equipment and chemicals to be added, while concentrating to a high concentration in a shorter time than the conventional gravity concentration method. An object of the present invention is to provide a method for promoting solid-liquid separation of sludge so that sludge can be obtained.

[0007]

In order to achieve the above object, the method for promoting solid-liquid separation of sludge of the present invention uses a microorganism to treat organic substances in wastewater such as sewage, and to remove sludge generated by this treatment. In the method for promoting solid-liquid separation of sludge to be withdrawn, the extracted sludge is heated to such an extent that the polymer substance in the sludge is denatured and the viscosity is decreased, so that the sedimentation property of the sludge is promoted. And

In this method for promoting solid-liquid separation of sludge, since the specific gravity of sludge is heavier than that of water, it becomes possible to separate solid-liquid by natural sedimentation over time, and a high-concentration sludge can be obtained. When the concentration becomes high, the settling property of the sludge becomes poor due to its own viscosity and solid-liquid separation becomes impossible. Can be promoted.

In this case, an acid or acidic coagulant is added to the extracted sludge so that the pH is 5 or less,
It can be adjusted and heated.

As a result, the polymer substance that causes the viscosity of the sludge is more surely transformed by the oxidizing power of the acid or the acidic flocculant and the heating temperature, the viscosity is reduced, and the sedimentation property is further promoted. be able to.

The heating temperature of sludge is 40 to 100 ° C.
Can be

As a result, the polymer substance that causes the viscosity of the sludge is most likely to be transformed and the viscosity is reduced,
The sedimentation property can be efficiently promoted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for promoting solid-liquid separation of sludge according to the present invention will be described below with reference to the drawings.

The method for promoting solid-liquid separation of sludge according to the present invention is a method for promoting solid-liquid separation of sludge in which an organic substance in sewage such as sewage is treated using microorganisms and the sludge generated thereby is extracted. The sludge is heated to such an extent that the polymer substance in the sludge is denatured and the viscosity is reduced, so that the sludge settling property is promoted.

Here, FIG. 1 shows the result of a sedimentation test using a graduated cylinder for demonstrating the action of the sludge solid-liquid separation promoting method of the present invention. In this experiment, sludge with a water content of about 99% was put into a 1-liter graduated cylinder and then left to stand to perform solid-liquid separation, and the ratio of the volume occupied by the sludge separated at regular intervals. Was observed.
Further, as a control, the same observation was made for the untreated sludge.

From the results of this experiment, the sludge having a water content of about 99% may be completely different in size from the actual concentration tank without any treatment, and even after 24 hours have passed. While solid-liquid separation cannot be performed at all, in the sludge kept at a temperature of 80 ° C. for 1 hour, the proportion of the separated sludge was about 95% in the first hour, but 24
It was 75% in time.

In addition, a small amount of acid (0.1% by volume, pH
5) In the sludge added and kept for 1 hour under the temperature condition of 80 ° C, the ratio of the separated sludge is 80% in the first hour,
After 24 hours, the sedimentation property was greatly improved to 50% even though the concentration tank was small.

Therefore, if sludge is treated by the method for promoting solid-liquid separation of sludge of the present invention, even if the sludge cannot be concentrated by the conventional gravity settling method and the mechanical concentration method is required, gravity settling can be performed. A sludge of sufficiently high concentration can be obtained only by the method.

FIG. 2 is a flow chart of a water treatment process showing an embodiment in which the sludge solid-liquid separation promoting method of the present invention is applied to an activated sludge method.

The sewage A sent to the sewage treatment plant is introduced into the biological reaction tank 1, mixed with the activated sludge in the biological reaction tank 1, and aerated and agitated so that the organic substances contained in the sewage A are biological. It is processed. The sewage treated in the biological reaction tank 1 is sent to the final settling basin 2 as a mixed solution B together with the activated sludge, where it is solid-liquid separated into treated water C and separated sludge D by gravity settling.

The treated water C thus obtained is appropriately disinfected and discharged to a river or the like, and the separated sludge D is drawn out from the final settling tank 2 by the sludge pump 3. The part is sent again to the biological reaction tank 1 as returning sludge E, and the excess surplus sludge F is sent to the sludge treatment tank 4.

A heater 5 for heating is installed in the sludge treatment tank 4, and a very small amount of acid or acidic coagulant can be added from the chemical tank 7 by the chemical pump 6. However, in this case, the addition of the acid or acidic coagulant is carried out by adjusting the pH to 5 or less. Then, excess sludge F sent to the sludge treatment tank 4
Is mixed with the acid added from the chemical tank 7,
After being subjected to heat treatment at 100 ° C., preferably about 80 ° C. or lower, it is allowed to stand to cause precipitation separation.

As described above, the acid or acidic coagulant is added to the sludge so that the pH is adjusted to 5 or less, mixed and stirred, and then heated to improve sludge sedimentation. The solid-liquid separation is performed by using the natural sedimentation of the treated sludge in the gravity sedimentation tank provided in the subsequent stage.

The excess sludge F obtained by this treatment is concentrated to a high concentration and discharged as a concentrated sludge G out of the system, or is used for sludge dewatering treatment. The separated liquid H is returned to the biological reaction tank 1 after its pH is adjusted if necessary.

Thus, according to the conventional gravity concentration method,
It takes about 12 hours to concentrate 1% of sludge to 3%, but according to the method for promoting solid-liquid separation of sludge of the present invention, in order to show the same level of ability, it is necessary to perform heat treatment for 1 hour. 6 for liquid separation
It only takes a long time, and the sludge can be concentrated in about half the amount of conventional sludge. Further, if the method for promoting solid-liquid separation of sludge of the present invention is used, highly concentrated concentrated sludge can be obtained in a shorter time than the conventional gravity concentration method without providing particularly complicated equipment and without incurring a large cost. be able to.

When the water content of the sludge extracted from the biological reaction tank 1 is 99% or more, which is sufficiently high, solid-liquid separation by gravity precipitation is performed in advance to reduce the water content, and then the sludge of the present invention is treated. By carrying out the solid-liquid separation promoting treatment method,
It is possible to reduce the processing amount and further reduce the processing cost.

[0027]

According to the method for promoting solid-liquid separation of sludge of the present invention, since the specific gravity of sludge is heavier than that of water, solid-liquid separation is possible by natural sedimentation over time, and a high-concentration sludge can be obtained. However, especially when the concentration becomes high, the sludge, which has a poor viscosity due to its own viscosity and cannot be solid-liquid separated, must be heated to such an extent that the polymer substances in the sludge are denatured and the viscosity decreases. By this, the sedimentation property of sludge can be promoted. As a result, sludge settling ability is promoted, high-concentration sludge can be obtained in a short time, and sludge is treated at a cost much lower than the capital investment and operating costs required for mechanical concentration. be able to.

Further, by adding and adjusting an acid or an acidic coagulant to the extracted sludge so that the pH becomes 5 or less, and heating this, the polymer that causes the viscosity of the sludge is added. The substance can be more surely transformed by the oxidizing power of the acid or the acidic flocculant and the heating temperature, the viscosity is reduced, and the sedimentation property can be further promoted.

The heating temperature of the sludge is 40 to 100 ° C.
By so doing, the polymer substance that causes the viscosity of the sludge is most likely to be denatured and the viscosity is reduced, so that the sedimentation property can be efficiently promoted.

[Brief description of drawings]

FIG. 1 is a graph showing the results of a sedimentation test using a graduated cylinder.

FIG. 2 is a flow chart of a water treatment process in which the method for promoting solid-liquid separation of sludge of the present invention is incorporated into activated sludge treatment.

[Explanation of symbols]

1 biological reaction tank 2 final settling tank 3 sludge pump 4 Sludge treatment tank 5 heater 6 chemical pump 7 Chemical tank A dirty water B mixture C treated water D separation sludge E Return sludge F surplus sludge G concentrated sludge H separation liquid

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Claims (3)

[Claims] 1. A method for promoting solid-liquid separation of sludge, which comprises treating an organic substance in sewage such as sewage using microorganisms, and extracting the sludge generated thereby. A method for promoting solid-liquid separation of sludge, characterized in that the sludge settling property is promoted by heating to a degree such that the sludge is denatured and the viscosity is reduced. 2. The solid-liquid sludge according to claim 1, wherein an acid or acidic coagulant is added to the extracted sludge so as to have a pH of 5 or less, and the sludge is heated. Separation promotion method. 3. The method for promoting solid-liquid separation of sludge according to claim 1 or 2, wherein the heating temperature of the sludge is set to 40 to 100 ° C.