JPS6147640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a filtration or dehydration medium in which a medium for filtration or dehydration of organic sludge is chemically washed and regenerated.

For dehydration of organic sludge that is difficult to dewater, such as water treatment sludge and sludge, methods include excessive dehydration using a permeable medium such as cloth, dehydration using a dehydrating medium such as a sponge, or dehydration using a combination of both.
Excessive dehydration using cloth is carried out by running a cloth belt endlessly, supplying mud onto the cloth and dehydrating it by gravity, or dehydrating it by applying pressure. For dewatering using a sponge, sludge is supplied onto a sponge roll or a sponge belt, and the water in the sludge is sucked in and dehydrated by the capillary action of the sponge.The dehydrated sludge is scraped off the surface of the sponge, and the water sucked into the sponge is removed by squeezing. Then, the mud was supplied again.
It is made to dehydrate. Dehydration using both methods involves gravity dehydration using a cloth, followed by dehydration by capillary action by bringing a sponge into contact with the back side of the cloth, and then squeezing the sludge as necessary to squeeze out the water in the sludge.

During such dewatering operations, the dehydrated medium is cleaned by pressure water or pressurized air injection after scraping the dehydrated sludge, but even such constant cleaning cannot completely clean it, and dirt gradually accumulates. This will cause clogging and reduce dehydration capacity. Conventionally, as a cleaning and regenerating method for dehydrating media with reduced capacity, the media was taken out of the equipment and cleaned by flushing, etc., but the cleaning effect was low despite the amount of labor involved, and chemical cleaning using oxalic acid, etc. A cleaning method was also used, but the cleaning effect was low.

It is an object of the present invention to eliminate such drawbacks and provide a method for efficiently cleaning and regenerating filtration and dehydration media whose capacity has decreased.

The present invention is a method for chemically cleaning and regenerating a filtration/dehydration medium made of a cloth or sponge for filtration or dewatering of organic sludge, characterized in that cleaning is carried out by bringing a cleaning solution containing peroxide and an alkali into contact with the medium. This is a method for cleaning dehydrated media.

The sludge to be dehydrated with a filtration and dehydration medium includes all kinds of organic sludge such as water treatment sludge and sludge, but the present invention is particularly applicable to activated sludge, digested sludge, etc. discharged from sewage treatment plants, human waste treatment plants, etc. Suitable for cleaning media used for dewatering organic sludge. Such organic sludge contains sticky substances that adhere to the interstices of the medium and cause clogging, but the cleaning method of the present invention can efficiently clean and remove clogging caused by such substances. can.
Further, the present invention is suitable for cleaning a medium for dewatering organic sludge by adding an organic polymer flocculant thereto. Such a flocculant promotes the adhesion of sludge to the medium through its flocculating action, and the cleaning method of the present invention can also efficiently clean and remove clogging caused by this.

In the present invention, the medium to be cleaned is a permeable medium such as a cloth or screen, or a dehydrating medium such as a sponge or felt. Dehydration devices equipped with these media include those equipped only with a permeable medium, those equipped only with a dehydration medium, those equipped with both, and those equipped with a pressurizing or squeezing mechanism. The media of either device is subject to cleaning according to the present invention.

An aqueous solution containing a peroxide and an alkali is used as the cleaning liquid, but when an alkaline peroxide is used, it may not be necessary to separately add an alkali. Hydrogen peroxide, sodium peroxide, sodium percarbonate, etc. can be used as peroxides.
As the alkali, caustic alkalis such as sodium hydroxide and potassium hydroxide can be used. When hydrogen peroxide and sodium hydroxide are used, they are used as an aqueous solution containing 0.5 to 3% (preferably 1 to 2%) hydrogen peroxide and 2 to 8% (preferably 3 to 6%) sodium hydroxide. If the hydrogen peroxide content is less than 0.5%, the stain removal effect will be small, and if it exceeds 3%, it will have an adverse effect on the medium (particularly the sponge), which is not preferable.
If the amount of sodium hydroxide is less than 2%, the stain removal effect will be low, and if it exceeds 8%, the effect will not increase.

The cleaning method is carried out by bringing the clogged medium into contact with a cleaning liquid, but the method of contact is not particularly limited.
In the case of cloth, it is preferable to sprinkle the agent on the cloth and allow it to pass through, and repeat this process. In the case of a sponge, it is preferable to spray it on the surface of the sponge and let it penetrate into the sponge, and then squeeze it out by squeezing, and repeat this process. In either case, there is no need to remove the medium from the device; it is better to stop the mud supply while the device is in operation, rinse with water for a while, then spray the cleaning liquid, and perform cleaning while circulating the cleaning liquid.

During cleaning, peroxide not only has an oxidizing effect, but also has a physical cleaning effect by foaming. Alkali also dissolves organic substances and promotes the decomposition of peroxides. In the present invention, due to the synergistic effect of the two, it is possible to achieve a cleaning effect that is better than when either one is used alone, and it is possible to efficiently clean filtration and dehydration media used for organic sludge, which is ineffective with conventional cleaning methods. I can do it.

Hereinafter, a case will be described in which the present invention is applied to cleaning the dewatering apparatus shown in the drawings. The drawing is a front view of the dehydrator. To dewater sludge using this dewatering device, sludge is supplied from a sludge supply device 2a, 2b onto two endlessly running cloth belts 1a, 1b, and the cloth belt is rotatable or non-rotating leachate flowing means 3a. ,3
While running on the sludge, moisture in the sludge is leached out to the back side of the cloth by gravity, and the leached water is transmitted through the leaching water flow means and flows down to the chutes 4a and 4b, thereby performing gravity over-drying.

One of the cloth belts 1a that has passed through the gravity dewatering section is reversed, and the sludge layer on the surface is placed on top of the sludge layer of the other cloth belt 1b, and the sludge layer is sandwiched in between and pressed together. roll 5
a, 5b, and 5c, and are conveyed by contacting and press-bonding, and during this time, the water in the sludge is sucked and dehydrated by the suction force of the sponge roll. The sponge roll has a cleaning water pipe 6a,
Washing water is sprayed from 6b and 6c for washing, and the water sucked out by squeezing rolls 7a, 7b and 7c is squeezed out and rotated, and the squeezed water is sent to chute 8a,
Collect at 8b and 8c.

The fabric belt that has passed through the suction and dewatering section using sponge rolls is transferred to pressing rolls 9a, 9 while remaining in a crimped state.
Runs while being crimped by b, 9c, 9d, and 9e,
The water in the sludge sandwiched in between is compressed and dehydrated. The squeezed out water is transferred to the water flow down means 10a, 10b,
Shoot 11 by transmitting 10c, 10d, and 10e.
flow down to.

The cloth belt that has passed through the compression and dehydration section is released from the compressed state by drive rolls 12a and 12b and separated, and the adhered sludge is removed by scrapers 13a and 13b, respectively, and washed water pipes 14a and 14b are removed.
The cleaning water is sprayed from the chute 15a,
15b, passed through tension rolls 16a and 16b, and then circulated to the gravity dewatering section.

In this dewatering device, sponge rolls 5a, 5b,
5c and pressing rolls 9a, 9b, 9c, 9
d, 9e have smaller diameters from the running start end to the running end, and the drive roll 12 is provided at the running end side.
Since the rollers a and 12b are driven, the cloth is more strongly pressed against the rolls toward the end of the run, and the dewatering effect becomes greater.

Now, the cleaning of the sponge roll and cloth in this dehydration device is carried out by washing water pipes 6a, 6b, 6c, 1
Washing water is injected from 4a and 14b to constantly wash the sludge during the dewatering process, but as mentioned above, washing with water alone is not complete.
The chemical cleaning of the present invention is carried out in response to the formation of clogging.

To perform chemical cleaning, first the mud supply devices 2a, 2
The supply of mud from b is stopped, the cloth belts 1a and 1b are run in the same way as in the dewatering process, and the washing water pipes 6a and 6 are
Water washing is continued by spraying washing water from b, 6c, 14a, and 14b for a while. At this time, shoots 4a, 4b, 8a, 8b, 8c, 11, 15
The waste water flowing out from a, 15b is transferred from the drain pipes 17a, 17b...17n to the collection pipe 1, as in the dewatering process.
8 and is discharged into the series through a collection valve 19.

Next, the cleaning liquid containing the above-mentioned peroxide and alkali is prepared in the chemical tank 20, and the cleaning water pipes 6a, 6
b, 6c, 14a, 14b is stopped, the pump 21 is driven, and the liquid sending pipes 22a, 2
Washing water pipes 14a, 14 via 2b...22n
The cleaning liquid is uniformly sprayed onto the cloth belt and the sponge roll from the cleaning liquid pipes 23a, 23b, and 23c. During this time, the cloth belt is running and the valve 1
9 and open the valve 24 to circulate the cleaning liquid. The cleaning liquid flowing back into the chemical tank 20 contains suspended matter, so either it is left in the chemical tank 20 to settle the suspended matter, and only the supernatant liquid is sent from the pump 21, or the pump 21 sucks the liquid. Install a strainer or the like in the tube to prevent suspended solids from being pumped out again.

The means for spraying the cleaning liquid onto the cloth belt or sponge roll may also be used as a washing water pipe, may be provided separately, or may be installed only during chemical cleaning. In any case, a slit-like or porous spreading means is provided so that the cleaning liquid can be uniformly spread over the entire width of the cloth or sponge roll.

After chemical cleaning with the cleaning liquid continues for a while, the drive of the pump 21 is stopped and the cleaning water pipe 6
Water cleaning is performed by spraying cleaning water from a, 6b, 6c, 14a, and 14b, and the cleaning liquid in the chemical tank 20 is neutralized by injecting acid to complete the cleaning process.

The dewatering equipment shown in the drawing was operated continuously for a long period of time to dehydrate excess activated sludge from a human waste treatment plant with the addition of a polymer flocculant, and the fabric belt turned dark brown and the water absorption rate of the sponge rolls increased to 14.5/hr. A case where chemical cleaning is performed when the temperature has decreased will be described below. Stop the slurry supply as described above, and add hydrogen peroxide 2
When a cleaning solution containing 5% sodium hydroxide and 5% sodium hydroxide was sprayed onto the cloth belt and sponge roll, and the cleaning solution was circulated and washed for 10 minutes, the stains on the cloth were transferred to the cleaning solution, and the cleaning solution, which was clear and colorless, turned brown. , the cloth returned to its original color, and the water absorption performance of the sponge roll was almost restored to its original level of 34.3/hr. In the early stages of cleaning, it was observed that foaming occurred actively on the cloth belt and sponge roll surface, and the soiled substances were forcibly removed. Hydrogen peroxide in the washing waste liquid was decomposed and it simply became a sodium hydroxide solution with organic matter dissolved, so hydrochloric acid was added to neutralize it.
It was added to the raw water of the activated sludge treatment equipment.

When cleaning for 10 minutes using 2% hydrogen peroxide as the cleaning solution, foaming was observed at first and a certain amount of dirt could be removed, but the foaming properties gradually disappeared and further cleaning was no longer possible. The cloth did not return to its original color completely, and the stains inside the sponge roll could not be removed. When using 5% hydrogen peroxide solution, most of the cloth could be cleaned, but although the sponge of the sponge roll could be cleaned to some extent, the mechanical performance of the sponge deteriorated after repeated washing several times, and the water absorption function also deteriorated. The purpose of cleaning could not be achieved due to the deterioration. When 5% and 10% sodium hydroxide solutions were used, the cleaning solution turned brown and it was observed that contaminants had migrated from the cloth, but the cloth was still brown and the water absorption performance of the sponge roll was poor. It never recovered.

The present invention has been described above, and according to the present invention, a cloth that has become clogged by dehydrating sludge that is difficult to dewater,
It is possible to efficiently wash filtered and dehydrated media such as sponges with simple operations and regenerate them in a short time. It is possible to efficiently wash and regenerate media that cannot be washed and regenerated using conventional methods, such as media that have become clogged by dewatering organic sludge, especially organic sludge to which an organic polymer flocculant has been added. Moreover, the waste liquid produced by washing can be treated by an activated sludge treatment method or the like by simply neutralizing it, and no special treatment equipment is required.

[Brief explanation of the drawing]

The drawing is a front view of the dewatering device used in the example, in which 1a and 1b are cloth belts, 2a and 2b are mud supply devices, 3a and 3b are leachate flow means, and 5a and 5
b, 5c are sponge rolls, 9a, 9b...9e
2 is a pressing roll, and 20 is a chemical solution tank.

Claims (1)

[Claims] 1. A method for chemically cleaning and regenerating a filtration/dehydration medium made of cloth or sponge for filtration or dewatering of organic sludge, in which the medium is brought into contact with a cleaning solution containing peroxide and an alkali for cleaning. A method for cleaning a super-dehydrated medium, characterized by: 2. The method for cleaning a perhydration and dehydration medium according to claim 1, wherein the peroxide is hydrogen peroxide. 3. The method for cleaning a percolation/dehydration medium according to claim 1 or 2, wherein the alkali is sodium hydroxide. 4. The method for cleaning a percolation and dehydration medium according to claim 1, wherein the cleaning liquid is an aqueous solution containing 0.5 to 3% hydrogen peroxide and 2 to 8% sodium hydroxide. 5. A method for cleaning a filtration and dehydration medium according to any one of claims 1 to 4, in which a cleaning liquid is circulated.