JP2008086897A - Solid-liquid separation method of sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-liquid separation method of sludge which clearly separates organic sludge into high-concentration sludge and a high-water quality supernatant liquor having a small suspended substance in a short time, and provides a low facility cost, a low operation cost and space savings. <P>SOLUTION: A method of loading the organic sludge generated from a waste water treatment apparatus with hydrogen peroxide, bringing the sludge into contact with a catalyst accelerating a hydrogen peroxide decomposition reaction to generate an air bubble and carrying out floatation solid-liquid separation of the sludge by a buoyant force of the air bubble comprises using the catalyst containing manganese oxide or an activated carbon as the catalyst accelerating the hydrogen peroxide decomposition reaction, further loading the organic sludge with a small amount of acid or flocculant together with hydrogen peroxide, and bringing the organic sludge into contact with the catalyst with a heated state of 40 to 100°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for solid-liquid separation or concentration of organic sludge.

In wastewater treatment equipment, organic sludge generated when sewage such as sewage is mixed with activated sludge in a biological treatment tank and biologically purified by aeration and agitation is solid-liquid separated in a sedimentation tank. In general, sludge is separated into solid and liquid by gravity. However, this method has a problem that not only does it take a considerable time to separate, but also there are many suspended solids in the supernatant treated water (sludge desorption liquid), and the sludge is not sufficiently concentrated.
In addition, a method of solid-liquid separation or concentration of sludge by a centrifuge is known, but the cost for the equipment is high, and it is necessary to add a flocculant when processing further, which is economically burdensome. There was a problem that it took.

On the other hand, gas such as air or carbon dioxide gas is introduced into the sludge, adheres to the solid components in the sludge, the apparent specific gravity is reduced to float the sludge solid components, the state of concentrated sludge at the top, sludge desorption liquid at the bottom There is a floating solid-liquid separation or concentration method, which can be separated into a relatively high concentration sludge. For this, a pressurization method, a fermentation method, a chemical reaction method and the like are known.
The pressurization method requires not only a flocculant and a large amount of electric power for applying a high pressure, but also has a drawback in that it requires not only running costs but also complicates and enlarges the equipment.

Further, as a fermentation method, there is a method in which digested sludge is floated and separated using carbon dioxide gas released by increasing the dissolved carbon dioxide concentration in digested sludge by anaerobic digestion and then lowering the pH. (Patent Document 1). However, not only does the anaerobic digestion process take time, but there is a disadvantage that it takes time and labor to adjust the pH and temperature, and is difficult to manage.

The chemical reaction method is a method in which a chemical reaction is caused by the addition of a chemical agent, and sludge is physically floated and separated by the generated bubbles. In this method, carbonate and acid are added to sludge to generate carbon dioxide, and the sludge is floated and separated (Patent Document 2). However, in this method, the separation of the sludge is not clear, and there are many disadvantages that the suspended matter is often mixed in the sludge desorption liquid and that the running cost is high due to the chemical cost. Furthermore, there is a method in which hydrogen peroxide is injected into the sludge, the sludge is floated, and then the sludge that has been floated and concentrated is aerated (Patent Document 3). However, the injection of hydrogen peroxide alone not only takes time for the solid-liquid separation process, but also has a problem that suspensions are likely to be mixed in the sludge desorption liquid, and it is difficult to discharge the treated water as it is.

JP-A-6-71296 JP 2003-2111199 A JP-A-9-225489

In order to solve the problems of the conventional methods as described above, the present invention clearly separates organic sludge into high-concentration sludge and high-water desorption liquid with less suspended matter in a short time, resulting in low equipment costs and low costs. The object is to provide a method for solid-liquid separation of sludge that saves operating costs and space.

In order to achieve the above object, the sludge solid-liquid separation method of the present invention adds hydrogen peroxide to organic sludge generated from a wastewater treatment apparatus, and contacts the sludge with a catalyst that accelerates the hydrogen peroxide decomposition reaction. And generating bubbles, and the sludge is levitated and separated by the buoyancy of the bubbles.
This sludge solid-liquid separation method is a method in which hydrogen peroxide is added, and air bubbles of harmless and fine oxygen gas are generated in the entire treatment tank under catalytic activity, and physically separated by adhering to the sludge. It is. This method has an advantage that not only the solid-liquid separation rate can be improved, but also a high water quality desorbed liquid with less suspension can be obtained. Furthermore, basically, it is only necessary to inject a medicine, and it can be carried out with low equipment, low operating cost, and space saving.

As a catalyst for promoting the hydrogen peroxide decomposition reaction, a catalyst containing manganese oxide or activated carbon can be used. Thereby, the decomposition reaction of hydrogen peroxide is remarkably promoted, and the sludge solid-liquid separation process can be floated and separated to a fine suspension in the desorbed liquid in a short time.
Furthermore, in this invention, a small amount of acid or a flocculant can be added to organic sludge with hydrogen peroxide. Thereby, the cohesiveness of the fine particles in the sludge is improved, and the water quality of the sludge detachment liquid can be further improved.

In any of the above methods, the organic sludge can be brought into contact with the catalyst while being heated to 40-100 ° C. As a result, the cohesiveness of the fine particles in the sludge is improved, and at the same time, the decomposition reaction of hydrogen peroxide is dramatically accelerated, so that the high-concentration sludge and the high-water sludge with few suspensions can be separated in a very short time.

According to the present invention, organic sludge can be clearly solid-liquid separated in a short time as compared with the conventional case, and a high water quality desorbed liquid with less high concentration sludge and suspended matter can be obtained. it can.
In addition, the present invention basically requires only a small amount of drug injection, and has the effect of simplifying the wastewater treatment facility and reducing the cost. In addition, since the present invention does not require a special device or the like, the sludge treatment amount and application place restrictions are alleviated, and there is an effect that it can be suitably used for a small amount of organic sludge treatment.

The inventors of the present invention invented a method of adding chemicals to organic sludge and physically levitating and separating the sludge using gas generated by the catalyst, and the basic principle is that organic sludge Hydrogen peroxide is added to the catalyst, and the sludge is brought into contact with a catalyst that promotes the decomposition reaction of hydrogen peroxide, so that the added hydrogen peroxide is decomposed into oxygen gas and water. Is attached to the sludge, and the sludge is floated and separated clearly in a short time.
EXAMPLES Hereinafter, although an example is given and this invention is demonstrated further in detail, this invention is not limited at all by these examples.

The organic sludge according to the present invention has a sludge concentration (MLSS) of 100 to 30,000 mg / L, a moisture content of 96 to 99.9%, more preferably a sludge concentration of 1000 to 20,000 mg / L depending on the specific gravity of the sludge. L, those having a water content of 97-99% can be used, and sludge and return sludge in a normal aeration tank can be used. As described above, the present invention can be used for a wide range of sludge concentrations, and if applied in a wastewater treatment process, sludge and good treated water can be obtained.

By the solid-liquid separation of the present invention, the sludge is sufficiently concentrated, and the high concentration sludge having a sludge concentration of 30,000 mg / L or more or a water content of 96% or more and a suspension having a sludge concentration of 100 mg / L or less are hardly contained. Separation into water sludge desorption liquid.
In the present invention, the amount of hydrogen peroxide to be injected and stirred depends on the sludge concentration, but may be 0.01-1 mol of hydrogen peroxide per liter of organic sludge. For example, a clear solid-liquid interface is formed with an injection amount of about 0.1 mol of hydrogen peroxide per liter of organic sludge having a sludge concentration of about 15,000 mg / L (water content: about 98%). The sludge can be separated into sludge concentrated three times (sludge concentration of about 45,000 mg / L) and sludge desorbed liquid (sludge concentration of about 100 mg / L) with very little suspended matter at the bottom. Although the hydrogen peroxide injection amount may be increased, there is no tendency to increase the processing speed according to the injection amount.
In the present invention, the catalyst for promoting the decomposition reaction of hydrogen peroxide is, for example, a metal chemical such as manganese oxide, copper, antimony, tin or palladium, or a rough solid surface such as activated carbon, charcoal, bamboo charcoal, charcoal, zeolite, or high talc. Or a catalyst in which the above substances are mixed can be used. The catalyst form preferably has a wide contact area with hydrogen peroxide, and a powder, granular or massive catalyst can be used. Preferred catalysts and their forms are pure manganese oxide particles (particle size 1-5 mm) and activated carbon (particle size 1-5 mm). When these are used, the hydrogen peroxide decomposition reaction can be dramatically accelerated.

About the installation method of a catalyst, what is necessary is just to spread | lay down uniformly on the hydrogen peroxide reaction container bottom part, and the catalyst of thickness 0.1-5cm, Preferably 1 cm of thickness should just be spread | laid on the bottom part in the uniform layer form. By making it uniform, bubbles are generated from the entire bottom surface of the processing tank, and a clear solid-liquid interface is formed without breaking the upper sludge by convection, so that the sludge can be floated and solid-liquid separated.

Furthermore, in the practice of the present invention, by adding a small amount of acid and / or a flocculant, the fine particles in the organic sludge are aggregated, and the suspended matter in the sludge desorption liquid after solid-liquid separation can be extremely reduced. In this case, as acid and / or flocculant, in addition to acids such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid and ethyl acetate, polyiron sulfate, ferric chloride, polyaluminum chloride, sulfate band, ferric sulfate, slaked lime, Inorganic flocculants such as magnesium oxide and magnesium carbonate, anionic organic flocculants such as sodium polyacrylate, sodium alginate and maleic acid copolymer, polyethyleneimine, water-soluble aniline resin, polythiourea, quaternary ammonium Cationic organic flocculants such as salts and nonionic organic flocculants such as polyacrylamide, polyoxyethylene, and catalyzed starch can be used.

When the sludge solid-liquid separation method according to the present invention is incorporated in a general activated sludge treatment flow, the organic sludge is solid-liquid separated according to the present invention, and the resulting high-concentration sludge is scraped by a scraping frame or air flow. -By carrying it, it can be collected as concentrated sludge. The recovered concentrated sludge can be more efficiently subjected to treatments such as dehydration, solubilization, and anaerobic digestion than sludge obtained by sedimentation separation. Moreover, since the liquid phase detachment liquid after the sludge solid-liquid separation according to the present invention does not contain suspensions or environmentally hazardous substances, it can be discharged out of the waste water treatment system.
Furthermore, the sludge solid-liquid separation method according to the present invention can be carried out with a small amount of organic sludge with good reproducibility without using a special apparatus. Moreover, it can be used conveniently.

  Hereinafter, examples in which sludge solid-liquid separation according to the present invention is performed using manganese oxide and activated carbon as a hydrogen peroxide decomposition catalyst will be described, but the present invention is not limited to these examples.

The organic sludge used in the following examples was one having a sludge concentration of 13,330 mg / L, and the hydrogen peroxide used was 30% hydrogen peroxide manufactured by Santoku Chemical Industry Co., Ltd. Manganese oxide was manufactured by Nacalai Tesque Co., Ltd. (particle size: 1-5 mm), and activated carbon was Kuraray Coal Co., Ltd. (particle size: 1 mm).
The effluent turbidity was measured in order to evaluate the sludge solid-liquid separation treatment time and the amount of suspension in the effluent after solid-liquid separation. The method of measuring the solid-liquid separation treatment time was to confirm that a solid-liquid interface was clearly formed in the state of sludge on the upper part and sludge on the lower part after introducing hydrogen peroxide into the sludge. It was set as the time until the sludge on the upper side was concentrated 2 times and 3 times in volume ratio.
The sludge detachment liquid was evaluated by measuring the turbidity at the time when the sludge was concentrated 2 times and 3 times in volume ratio after confirming that the sludge was visually formed as described above. did. Turbidity was measured as the transmitted light turbidity by placing 700 μL of the desorbed liquid sample in a quartz glass square cell (optical path length: 10 mm) and measuring the absorbance at a wavelength of 660 nm with a UV-2450 spectrophotometer manufactured by SHIMADZU.

[Example 1]
A 300 mL beaker and a 100 mL graduated cylinder were prepared, and 100 mL of organic sludge (30 ° C .; pH 7.02) was placed in the beaker. A 100 mL graduated cylinder was uniformly spread with manganese oxide at the bottom as a catalyst for promoting the hydrogen peroxide decomposition reaction, and the catalyst volume was set to 1 mL. 1 mL (about 0.01 mol of H ₂ O ₂ ) of 30% hydrogen peroxide was injected into the beaker, and after thorough stirring, was immediately put into a graduated cylinder.
After feeding into the graduated cylinder, measurement of sludge solid-liquid separation treatment time was started. As a measuring method, since 1 mL of manganese oxide catalyst is contained in the graduated cylinder, when the interface between the sludge suspended in the upper part of the graduated cylinder and the sludge desorption water reaches the 51 mL scale of the graduated cylinder, the concentration is doubled. The time when the graduated cylinder reached the 68 mL scale was regarded as 3-fold concentration, and the time required for each was measured as the solid-liquid separation processing time. Moreover, the turbidity of the sludge desorption liquid at the time of 2 times and 3 times concentration was measured.
The solid-liquid separation treatment time required to concentrate the sludge twice and three times was 4 minutes 30 seconds and 12 minutes 30 seconds, respectively. Further, the turbidity of the sludge detachment liquid at the time when the sludge was concentrated 2 times and 3 times was 0.728 and 0.515, respectively.

[Example 2]
As in Example 1, a 300 mL beaker containing 100 mL of organic sludge was prepared. Activated carbon was uniformly spread on the bottom as a hydrogen peroxide decomposition catalyst in a 100 mL graduated cylinder, and the catalyst volume was 1 mL. 1 mL of 30% hydrogen peroxide solution was poured into the beaker, stirred well, and immediately put into a graduated cylinder. The sludge solid-liquid separation treatment time is measured by the method of Example 1.
The solid-liquid separation treatment time required to concentrate the sludge twice and three times was 5 minutes and 13 minutes and 45 seconds, respectively. Furthermore, the turbidity of the sludge detachment liquid at the time when the sludge was concentrated 2 times and 3 times was 1.222 and 1.307, respectively.

[Comparative Example 1]
A 300 mL beaker with 100 mL organic sludge and a 100 mL graduated cylinder without catalyst were prepared. 1 mL of 30% hydrogen peroxide solution was poured into the beaker, stirred well, and immediately put into a graduated cylinder. As a result, it took 6 minutes and 30 seconds to concentrate twice, and 17 minutes to concentrate three times. Further, the turbidity of the sludge desorbed liquid at the time when the sludge was concentrated 2 times and 3 times was 4.032 and 3.377 by correcting after dilution because the absorbance was very high.

[Example 3]
After raising the temperature of the initial sludge to 50 ° C. in a 300 mL beaker, other operations were performed at room temperature in the same manner as in Example 1 above, and the solid-liquid separation treatment time and the turbidity of the sludge desorbed liquid were measured. As a result, the solid-liquid separation processing time required to concentrate the sludge twice and three times was 3 minutes 15 seconds and 8 minutes 30 seconds, respectively. Further, the turbidity of the sludge detachment liquid at the time when the sludge was concentrated 2 times and 3 times was 0.826 and 0.687, respectively.

[Example 4]
After raising the temperature of the initial sludge to 50 ° C. in a 300 mL beaker, other operations were performed at room temperature in the same manner as in Example 2 above, and the solid-liquid separation treatment time and the turbidity of the sludge desorbed liquid were measured. As a result, the solid-liquid separation treatment time required to concentrate the sludge twice and three times was 4 minutes and 10 minutes, respectively. Furthermore, the turbidity of the sludge detachment liquid at the time when the sludge was concentrated 2 times and 3 times was 1.655 and 1.971, respectively.
[Comparative Example 2]
After the temperature of the initial sludge was raised to 50 ° C. in a 300 mL beaker, the other experimental progress was performed at room temperature in the same manner as in Comparative Example 1 above, and the solid-liquid separation processing time and the turbidity of the sludge desorbed liquid were measured. As a result, the solid-liquid separation treatment time required to concentrate the sludge twice and three times was 5 minutes and 11 minutes, respectively. Furthermore, the turbidity of the sludge desorbed liquid at the time when the sludge was concentrated 2 times and 3 times was 6.322 and 4.789, respectively.

The measured values of the solid-liquid separation treatment time and the turbidity of the sludge detachment liquid in the above examples and comparative examples are shown in FIGS. 1 and 2, respectively.
About FIG. 1, it is clear that the solid-liquid separation processing time is drastically shortened by using the catalyst. Furthermore, it was shown that the treatment time can be synergistically shortened by raising the temperature of the sludge and then separating the solid and liquid using a catalyst.

  From FIG. 2, the turbidity of each sludge desorption liquid at the time when the sludge is concentrated 2 times and 3 times shows a very low value when the catalyst is used. That is, it was shown that high-quality treated water containing almost no suspension in the sludge desorption liquid can be obtained by using the catalyst. Although not shown, even when the generation of bubbles was finished, the turbidity of the sludge desorption liquid was lower when the catalyst was used.

  Comparative Example 2 is a result of solid-liquid separation without a catalyst after raising the temperature of the sludge, and the solid-liquid separation processing time is shortened compared to Comparative Example 1. On the other hand, since the turbidity in the desorbed liquid of Comparative Example 2 was a very high value, the treatment time can be shortened only by raising the temperature, but high-quality treated water that does not contain suspensions. Cannot be obtained.

[Trial test]
For organic sludge (sludge concentration of about 15,000 mg / L), solid-liquid separation according to the present invention was performed at 10 L and 100 L. As a result, a clear sludge solid-liquid interface was not formed without a catalyst, and sufficient solid-liquid separation could not be achieved.However, by separating the catalyst, especially manganese oxide and activated carbon, evenly on the bottom of the reaction vessel, solid-liquid separation was achieved. As a result, a sludge concentrated to about three times and a sludge desorbed liquid having a good water quality with very few suspensions were obtained.

It is a figure which shows the solid-liquid separation processing time of an Example and a comparative example. It is a figure which shows the desorption liquid turbidity of an Example and a comparative example.

Claims (5)

Hydrogen peroxide is added to the organic sludge generated from the waste water treatment equipment, the sludge is brought into contact with a catalyst that promotes the decomposition reaction of hydrogen peroxide to generate bubbles, and the sludge is floated and separated by the buoyancy of the bubbles. The solid-liquid separation method of sludge characterized by the above-mentioned. The method for solid-liquid separation of sludge according to claim 1, wherein the catalyst contains manganese oxide.   The method for solid-liquid separation of sludge according to claim 1, wherein the catalyst contains activated carbon. The method for solid-liquid separation of sludge according to any one of claims 1 to 3, wherein a small amount of acid and / or flocculant is added to the organic sludge together with hydrogen peroxide and brought into contact with the catalyst. The method for solid-liquid separation of sludge according to any one of claims 1 to 4, wherein the organic sludge is brought into contact with the catalyst while being heated to 40 to 100 ° C.

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