JP2018108566A - Sludge treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge treatment system for reducing a cost to transport wastewater from local treatment facilities to a central treatment facility and fluctuation of sludge properties during transportation and thus efficiently carrying out treatment at the central treatment facility.SOLUTION: In a sludge treatment system, wastewater that enters a plurality of local treatment facilities 1A, 1B, 1C, ... are collected to a central treatment facility 4 and digested there. A plurality of the local treatment facilities 1A, 1B, 1C, ... include each thickeners 2a, 2b, 2c, ... and transportation units 3a, 3b, 3c, ... to transport concentrated sludge produced in the thickeners 2a, 2b, 2c, ... to the central treatment facility 4. The central treatment facility 4 includes a digestion tank 5 to digest the concentrated sludge transported from the transportation units 3a, 3b, 3c, ... and a power generating unit 6 to generate power using a digestion gas produced in the digestion tank 5. The sludge treatment system thus reduces a transportation cost of sludge and efficiently carries out treatment at the central treatment facility.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sludge treatment system, and more particularly, to a sludge treatment system for transferring sludge concentrated in a local treatment plant to an aggregation treatment plant and digesting it.

In recent years, sludge treatment in urban areas does not have a sludge treatment facility for each individual sewage treatment plant, but as disclosed in Patent Document 1, vacuum cars and mud pipes are supplied from a plurality of sewage treatment plants (local treatment plants). In this method, sludge is collected and treated in an integrated treatment plant.
In general, in a local treatment plant, raw water flowing into a sewage treatment plant is subjected to water treatment and discharged, and sludge is sent to an intensive treatment plant in a state where primary sludge and excess sludge are mixed.
The amount of sludge and sludge properties sent from a plurality of local treatment plants have fluctuated, and it has become difficult to perform stable sludge treatment at an intensive treatment plant.

Moreover, in order to utilize the energy of a sewage sludge conventionally, like patent document 2, a biogas is produced | generated by digesting the sludge concentrated in high concentration, and fuel is used for the gas engine for driving a generator. As a supply.

JP 2002-224663 A JP 2007-066414 A

In the conventional method, the mixed sludge of the first settling sludge and excess sludge generated at the local treatment plant is concentrated at the transported aggregation treatment plant and subjected to processing such as digestion or dehydration. Therefore, the mixed sludge contains a large amount of moisture, and the conveyance cost is excessive. In addition, when transporting sludge from each local treatment plant to the central treatment plant, the sludge will rot before reaching the central treatment plant due to the increase in transport time, and stable digestion processing cannot be performed at the central treatment plant. Energy efficiency was getting worse.

In a sludge treatment system that collects and digests sewage that has flowed into a plurality of local treatment plants into a central treatment plant, the thickeners included in each of the plurality of local treatment plants and the concentrated sludge generated by the concentrator By having a transport unit that transports to the field, a digestion tank of an intensive treatment site that digests the concentrated sludge sent from the transport unit, and a power generation facility that generates power using digestion gas generated in the digestion tank In addition, the sludge transportation cost is reduced, and the processing at the intensive treatment plant can be performed efficiently.

The concentrator concentrates the concentrated sludge to a sludge concentration of 8 to 10%, so that the digestion process at the intensive treatment plant can be performed with high efficiency.

According to the present invention, after the sludge is concentrated at each local treatment plant, the sludge is transported to the intensive treatment plant, thereby removing moisture contained in the sludge and reducing the transport cost.
In addition, since sludge is transported to the intensive treatment plant in a highly concentrated state, sludge can be prevented from being spoiled, digestion treatment at the intensive treatment plant is stabilized, and digestion gas is used efficiently. Energy can be recovered.

FIG. 1 is a schematic diagram showing an outline of a sludge treatment system according to the present invention. FIG. 2 is also a schematic diagram showing an outline of the local treatment plant.

As shown in FIG. 1, the sludge treatment system according to the present embodiment has a plurality of local treatment plants 1A, 1B, 1C,... Into which sewage such as sewage flows, and each of the local treatment plants 1A, 1B, 1C. , ..., thickeners 2a, 2b, 2c, ..., and concentrated sludge transport units 3a, 3b, 3c, ..., and the local treatment plants 1A, 1B, 1C, ...・ Concentration treatment plant 4 that collects and processes the concentrated sludge generated in step 4; digestion tank 5 provided in the aggregation treatment plant 4; power generation equipment 6 that generates power using digestion gas generated in the digestion tank 5; A dehydrator 7 for dewatering the digested sludge generated in the tank 5 is provided.

FIG. 2 is a schematic diagram showing an outline of the local treatment plant.
The local treatment plant 1 includes a first sedimentation basin 8 that settles and separates inflowing sewage, a reaction tank 9 that purifies organic matter in the sewage separated in the first sedimentation basin 8, and raw sludge that is separated in the first sedimentation basin 8. Mixing the gravity concentration tank 10 for concentration, the final sedimentation tank 11 for separating the treatment liquid in the reaction tank 9, the mechanical concentration tank 12 for concentrating excess sludge separated in the final sedimentation tank 11, the gravity concentrated sludge and the mechanically concentrated sludge -The adjustment tank 13 which aggregates etc., the concentration machine 2 which concentrates the adjustment sludge of the adjustment tank 13, and the conveyance part 3 which conveys the concentration sludge produced | generated with the concentration machine 2 are provided.
The plurality of local treatment plants 1A, 1B, 1C,... Configured as described above transport concentrated sludge to the central treatment plant 4, perform digestion treatment in the central treatment plant 4, and generate electricity using the generated digestion gas. Electricity is generated by the facility 6 and the digested sludge is dehydrated by the dehydrator 7.
In the local treatment plant, one or both of the gravity concentration tank 10 and the mechanical concentration tank 12 can be omitted, and the sludge treatment system of the present invention can be applied to all local treatment plants having a concentration facility.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.
In each local treatment plant 1A, 1B, 1C, the inflowing sewage is concentrated by the concentrators 2a, 2b, 2c. The concentrated sludge is concentrated to a high concentration in order to increase the conveyance efficiency in consideration of conveyance to the intensive treatment plant 4 for treatment.
As the concentrators 2a, 2b, and 2c, in this embodiment, a drum type concentrator in which a screw is rotatably provided in a cylindrical screen is used, but other known concentrators can be used. The drum-type concentrator removes moisture by carrying the sludge supplied into a cylindrical screen with a rotating screw arranged in the screen, and performs concentration.
As shown in FIG. 2, in the former stage of the concentrator 2, it adjusts with the adjustment tank 13 which adds and mixes a flocculant according to sludge property, and concentrates sludge to high concentration. The drum type concentrator can manage the sludge concentration by controlling the number of revolutions of the screw, the number of revolutions of the cylindrical screen, the amount of the flocculant added, etc. based on the sludge properties.

Here, in the digestion process at the subsequent intensive treatment plant 4, the concentrated sludge can be efficiently digested if the concentration is high. Therefore, in order to efficiently recover the energy by digestion gas, the sludge concentration is set to 8-10. % Is preferable.

The concentrated sludge generated by the concentrators 2a, 2b, and 2c is transported to the aggregation treatment plant 4 by the transport units 3a, 3b, and 3c. Since the moisture is removed by the concentrators 2a, 2b, and 2c, the conveyance cost is greatly reduced by volume reduction.
Moreover, since the sludge is quickly transported in a concentrated state, the sludge can be prevented from being spoiled, the digestion process at the intensive treatment plant 4 can be stably performed, and a highly efficient digestion process can be performed.

The conveyance units 3a, 3b, and 3c convey the concentrated sludge from the local treatment plants 1A, 1B, and 1C to the aggregation treatment plant 4. Basically, the amount of sewage flowing into the local treatment plants 1A, 1B, and 1C is small, and the sludge is reduced in volume by the concentrators 2a, 2b, and 2c. It can be transferred from 1B, 1C to the central processing station 4 by a vehicle such as a truck. Moreover, you may send concentrated sludge using a pressure pump and the piping for concentrated sludge conveyance as the conveyance part 3a, 3b, 3c of concentrated sludge.

The concentrated sludge sent from the transport units 3a, 3b, and 3c of the local treatment plants 1A, 1B, and 1C is collected in one centralized treatment plant 4.
The concentrated sludge transported from each of the local treatment plants 1A, 1B, 1C to the intensive treatment plant 4 is temporarily stored in a mixing tank (not shown) in order to mix and make the properties uniform.
And the sludge mixed with the mixing tank is sent to the digestion tank 5, and a digestion process is performed.

In the digestion tank 5, a process for reducing the volume of sludge is performed using the activity of anaerobic bacteria. The organic matter contained in the sludge is consumed by anaerobic bacteria, and the volume of sludge is reduced by the amount discharged as carbon dioxide or methane gas.
Moreover, it takes time to decompose the organic matter of the anaerobic microorganisms, and in the digestion tank 5, it is necessary to retain and store the sludge to be treated in the digestion tank 5 for a long period of time, usually 10 days or more. And when supplying sludge with a low density | concentration, the volume of a reaction tank must be enlarged and a residence time must be ensured. Furthermore, if sludge having a lower concentration than the designed one is supplied, the residence time is shortened, so that organic matter flows out without being decomposed, and the volume reduction rate of the sludge is lowered. And since organic substance is not decomposed | disassembled, when using the generated methane gas as a resource, the energy decreases.
For this reason, the sludge to be treated is supplied in a uniform and high concentration, and the residence time in the digestion tank 5 is increased, so that the sludge is sufficiently reduced in volume and digestion gas can be obtained efficiently.
Therefore, in this invention, the digestion process in the intensive treatment plant 4 is made highly efficient by concentrating the sludge concentration of the concentrated sludge to a high concentration of 8 to 10% in each local treatment plant 1A, 1B, 1C.

Digestion gas generated in the digestion tank 5 is recovered and used as a power source for the power generation facility 6. Because digestion is performed with high efficiency, the amount of digestion gas generated increases and the amount of power generation also increases.

The digested sludge whose volume has been reduced in the digestion tank 5 is dehydrated by the dehydrator 7. The dehydrated cake may be used as a solid fuel.

1A, 1B, 1C, ... Local treatment plants 2a, 2b, 2c, ... Concentrators 3a, 3b, 3c, ... Conveying unit 4 Consolidation treatment plant 5 Digestion tank 6 Power generation equipment

Claims (2)

In the sludge treatment system that collects and digests the sewage that has flowed into a plurality of local treatment plants (1A, 1B, 1C,...)
Concentrators (2a, 2b, 2c,...) Provided in each of the plurality of local treatment plants (1A, 1B, 1C,...),
A transport unit (3a, 3b, 3c,...) That transports the concentrated sludge generated by the concentrator (2a, 2b, 2c,...) To the aggregation treatment plant (4);
A digestion tank (5) of an intensive treatment plant (4) for digesting the concentrated sludge sent from the transport unit (3a, 3b, 3c, ...);
A power generation facility (6) for generating electricity using digestion gas generated in the digestion tank (5);
A sludge treatment system characterized by comprising: The sludge treatment system according to claim 1, wherein the concentrator (2a, 2b, 2c, ...) concentrates the concentrated sludge to a sludge concentration of 8 to 10%.

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