JP2003080299A - Method of treating sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treating sludge by which the load in a water treatment system for performing a biological treatment of organic sewage can be reduced, dehydration effect can be improved even if it is the surplus sludge difficult to dehydration and the volume of the surplus sludge can be reduced. SOLUTION: In the method of treating the sludge by separating the sludge produced in a treating vessel for the organic sewage and dehydrating the sludge, cellulosic fiber components are recovered from the sewage flowing into the treating vessel and the sludge is dehydrated by adding these fiber components to the sludge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment method, and more particularly, to reduce the load on a water treatment system for biologically treating organic wastewater and to improve the dehydration efficiency even with excess sludge having poor dehydration property. The present invention relates to a sludge treatment method that can raise and reduce the volume of surplus sludge significantly.

[0002]

2. Description of the Related Art Conventionally, when biologically treating organic sewage such as sewage with activated sludge, as shown in FIG. 3, the influent sewage is first guided to a sand basin and sand, stones, etc. in the sewage are gravity settled. After the removal, impurities including organic substances are removed by a screen, and then the supernatant water is disinfected and discharged through the first settling tank, the reaction tank, and the final settling tank. On the other hand, the excess sludge separated by gravity settling in the final settling tank is concentrated and dehydrated to a predetermined water content, and then incinerated, landfilled, or disposed of by using green farmland. The wastewater flowing into the sewage treatment plant contains about 10% of cellulosic fiber components (including cellulose in the present specification) as suspended matter, and this suspended matter is a persistent fiber component. Along with
Since it is not removed by the conventional screen for removing contaminants containing organic matter, it is usually moved along with sludge in the water treatment system, and is finally disposed of as excess sludge.

[0003]

The excess sludge finally recovered in the water treatment system is usually dehydrated by a dehydrator to reduce its volume. However, the excess sludge has a dewatering property. Since it was bad, the dehydration efficiency was low, and there was a problem that the volume reduction was limited. Also, since the fiber content of the cellulosic suspension contained in the wastewater is difficult to decompose,
It is difficult to decompose organic sewage in a water treatment system that biologically treats it with activated sludge, which is a heavy load on this water treatment system.

In view of the problems of the above conventional sludge treatment methods, the present invention reduces the load on the water treatment system for biologically treating organic wastewater, and dehydrates even excess sludge having poor dehydration properties. An object of the present invention is to provide a sludge treatment method capable of increasing efficiency and significantly reducing the volume of excess sludge.

[0005]

In order to achieve the above object, the sludge treatment method of the present invention is a sludge treatment method in which sludge generated in a treatment tank of organic wastewater is separated and dehydrated. It is characterized by recovering a cellulosic fiber component from the inflowing wastewater and adding the fiber component to dehydrate the sludge.

In this sludge treatment method, a cellulosic fiber component is recovered from the sewage flowing into the sewage treatment tank, and the fiber component is added to dehydrate the sludge, thereby biologically treating the organic sewage. It is possible to reduce the load on the water treatment system and increase the dehydration efficiency even for excess sludge having poor dehydration properties, and to significantly reduce the volume of the excess sludge.

In this case, the fibers in the waste water can be collected by using a screen having a mesh width or a hole diameter of 1 to 2 mm.

This makes it possible to reliably collect the fiber component contained in the inflowing wastewater with a simple device.

[0009]

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 shows a flow of a water treatment process including the sludge treatment method of the present invention. In this water treatment process, for example, as shown in FIG. 1 (a), the wastewater A flowing into the sewage treatment plant is first introduced into the sand basin 10 to remove sand, stones, etc., and then the dust remover 20. After that, the fiber content recovery apparatus X of the present invention
And the cellulosic fibers are recovered from the wastewater A. Then, the wastewater A is first supplied from the settling tank 30 to the reaction tank 4
0, the sludge C and the excess sludge D removed in the water treatment step are concentrated and dehydrated, while the supernatant water B after the treatment is discharged through this treatment step. In this case, in the concentrated sludge C and the excess sludge D,
The cellulosic fiber components are added and mixed, and the sludge C and the excess sludge D to which the fiber components are added are dehydrated by a sludge dehydrator 70. The sludge after dehydration is disposed of by incineration, landfill, or use of green farmland. Further, the arrangement position of the fiber content collecting apparatus X may be before the first settling tank 30 before the water treatment step, and for example, as shown in FIG. It is also possible to do so.

On the other hand, as shown in FIG. 2, the fiber-content collecting apparatus X is composed of an endless screen 1 using a wire net having a mesh width of 1 to 2 mm, which is circulated in dirty water. The screen 1 is stretched between sprockets 3 and 3 arranged at both ends, and one sprocket 3 is driven by a drive unit 2.
Is circulated by driving so that the cellulosic fiber components in the wastewater are attached to the screen surface and collected.

In this case, the sprockets 3 and 3 may be polygonal as shown in the drawing or may be a circular drum type depending on the configuration of the screen 1, whereby the sprockets 3 are driven. As a result, the screen 1 is circulated and operated at a predetermined position in the dirty water. The screen 1 may be circulated continuously or intermittently.

Further, a trough 4 is provided on the side of the screen 1 on which the deposits are collected, and the screen 1 is transferred in the direction of the trough 4 by the rotation of the sprocket 3 and the screen 1
When the adhered matter adhered to the surface is naturally or forcibly separated from the screen surface, the separated adhered matter falls into the trough 4 and is accumulated. In order to more surely remove the deposits on the screen 1, the spray nozzle 5 and the brush 6 are arranged in the upper position near the trough 4.
The spray nozzle 5 is arranged on the return path side of the screen 1 so that the cleaning water is sprayed toward the screen surface on the back surface, and the brush 6 is brought into contact with the return path side surface of the screen 1 and is separated by the brush. The attached matter should fall into the trough 4. It should be noted that only one of the brush 6 and the spray nozzle 5 may be provided, and the brush 6 may be rotated by a driving device to improve the collection efficiency. Further, as the fiber content collecting device X, in the embodiment of the present invention, the screen 1 made of a wire mesh having a mesh width of 1 to 2 mm.
This screen 1 has a hole diameter of 1-2.
It can also be configured by a punching metal of mm or the like.

Next, the system for recovering and treating the fiber components in wastewater of the present invention will be described in detail based on the water treatment process shown in FIG. In the wastewater A flowing into the sewage treatment plant, organic matter,
It contains cellulosic fibers as well as sludge.
This fiber content is generally contained in the wastewater as about 10% as a hardly degradable suspended matter, although it depends on the type of the wastewater flowing in. Therefore, as shown in FIG. 1 (a), the inflowing wastewater A is first introduced into the sand basin 10, and the inorganic substances such as stones, sand, cans, and bottles contained in the wastewater A are gravitated. After being separated and removed by sedimentation or the like, this sewage is then removed by a dust remover 20, for example, a dust remover such as a bar screen. Scrape and remove coarse material.

The wastewater from which coarse particles have been removed by the dust remover 20 then passes through the fiber content recovery device X. In this case, although the inorganic substances such as stones, sand, cans, and bottles and floating organic substances were removed in the previous stage, the sewage flowing into the fiber content recovery device X was not removed by the dust remover 20. Fiber content of about 10% is contained as a persistent decomposition material. Since this fiber component is difficult to decompose, when it is made to flow into the water treatment system together with the sludge component, a large load is placed on the water treatment system. Therefore, in this embodiment, the water is collected at a position that is an inlet to the water treatment system, for example, at a stage before the water treatment system such as the first settling basin 30 and the sand basin 10. The fiber component in the inflowing wastewater is collected by circulating the filter surface of the endless screen 1 of the fiber component collector X shown in FIG.
By passing sewage through this fiber content recovery device X,
A cellulosic fiber component, which is a persistent biodegradable matter, is removed from wastewater. Thus, at the entrance to the water treatment system,
By preliminarily recovering the cellulose-based fiber component, the load on the water treatment system can be reduced.

Sewage A from which cellulosic fibers have been removed
Is led to the water treatment process as in the past. This water treatment process is not particularly limited, but the first settling tank 3
0, reaction tank 40 such as biological treatment tank, final settling tank 50
Then, the treated supernatant water B is discharged directly or after being sterilized. On the other hand, the sludge C that has been first settled and removed in the settling tank 30 and the excess sludge D that has been settled and removed in the final settling tank 50 are combined and concentrated in a sludge thickening tank 60 to a degree that allows dewatering, and then sludge dewatering To the machine 70.

However, even if the sludge is concentrated in the sludge thickening tank 60 and directly dehydrated, the excess sludge has a poor dewatering property and the dewatering efficiency (volume reduction efficiency) is limited. ing. Therefore, in this example, in order to improve the dewatering efficiency of the concentrated excess sludge, the fiber component recovered before the water treatment step is added to the excess sludge and mixed. In this case, the recovered fiber component is added to the adjusted sludge before being applied to the sludge dehydrator 70, or to the excess sludge in the preceding stage.

As described above, after the excess sludge and the recovered fiber component are mixed, the excess sludge is supplied to the sludge dewatering machine 70 and dehydrated until the moisture content determined in advance is reached. In this case, since the fiber component is mixed with the excess sludge, the dehydration efficiency is improved, the water is effectively dehydrated, and the volume is reduced. After that, the dehydrated excess sludge should be disposed of by incineration or landfill,
Alternatively, it is used as fertilizer or soil conditioner in green farmland.

The recovery of the fiber component is considered in consideration of the reduction of the load on the reaction tank 40 which is a biological treatment tank.
It is desirable to collect the water in the former stage of the water treatment system such as the first settling tank 30 and the sand settling tank 10 before 0. In small-scale water treatment facilities, it is desirable to recover the fiber content after the fine dust remover installed at the rear of the sand basin or sand basin.

If there is no problem with the dehydration property of the excess sludge, the recovered fiber component can be transported and used in another treatment plant where the dehydration property of the excess sludge is poor.

[0021]

According to the sludge treatment method of the present invention, the cellulosic fiber component is recovered from the sewage flowing into the sewage treatment tank, and the fiber component is added to dehydrate the sludge. It is possible to reduce the load on the water treatment system that biologically treats sewage, and to improve the dehydration efficiency even for excess sludge with poor dehydration properties, and to significantly reduce the volume of the excess sludge.

By collecting the fiber component in the wastewater with a screen having a mesh width or a hole diameter of 1 to 2 mm,
The fiber component contained in the inflowing wastewater can be reliably recovered with a simple device.

[Brief description of drawings]

FIG. 1 is a flow diagram of wastewater treatment including a sludge treatment method of the present invention.

FIG. 2 is an explanatory diagram of a fiber content recovery device.

FIG. 3 is a flow chart of conventional wastewater treatment.

[Explanation of symbols]

A dirty water B Clear water after treatment C Sludge settled and removed in the first settling tank D surplus sludge X fiber recovery device 1 screen (fiber collection device) 2 drive 3 sprockets 4 troughs 5 spray nozzles 6 brushes 10 sand basin 20 dust remover 30 First settling tank 40 Reaction tank (biological treatment tank) 50 final settling tank 60 sludge thickening tank 70 Sludge dehydrator

Claims (2)

[Claims] 1. A method for treating sludge in which sludge generated in a treatment tank for organic wastewater is separated and dehydrated, and a cellulosic fiber component is recovered from the wastewater flowing into the treatment tank and the fiber component is added. A method for treating sludge, which comprises dewatering the sludge. 2. The sludge treatment method according to claim 1, wherein the fiber component in the wastewater is collected by a screen having a mesh width or a pore diameter of 1 to 2 mm.