JPS6022995A - Treating process for sludge - Google Patents

Abstract

PURPOSE:To improve the digestion efficiency in a digestion tank by digesting separated initial concentrated sludge, heat-treating simultaneously hardly dedydrative concentrated sludge in a reaction vessel, and feeding generated separated liquid to the digestion tank. CONSTITUTION:Initial concentrated sludge discharged from an initial settling basin and concentrated to ca. 4% concentration, and hardly dehydrative concentrated sludge such as excess concentrated sludge of ca.4% concn. or concentrated sludge of high degree of treatment concentrated to the same degree, are fed respectively to the treating system 1 and 5. When the temp. of the initial concentrated sludge fed to the treating system 1 is 20 deg.C, a mixture of separated liquid from a feeding line 21 and filtrate is mixed with the initial concentrated sludge to elevate the temp. to 35 deg.C, which is heated by a heat exchanger 2 to 40 deg.C, and is digested in a digestion tank 3. The hardly dehydrative sludge fed to the treating system 5 is heated by a heat exchanger 8, then transported to a reaction vessel 11, where it is heat treated with the air from a feeding line 9 and steam from a feeding line 10.

Description

[Detailed description of the invention] The present invention relates to a sludge treatment method.

When treating raw sludge taken out from a settling tank,
Conventionally, this raw sludge is generally digested in a digestion tank, and the resulting dewatered sludge is dehydrated. By the way, 4. The raw sludge usually consists of initial settled thickened sludge that is concentrated after being taken out from the initial settling tank, and difficult-to-drain thickened sludge such as excess thickened sludge or higher-level treated thickened sludge, and conventionally, both are mixed together. Digestion is carried out in this state. However, in general, primary sedimentation thickened sludge has good digestion efficiency, whereas difficult-to-dehydrate thickened sludge has a characteristic of poor digestion efficiency. Therefore, in the above conventional one.

There is a problem that the digestion efficiency of the sludge as a whole is not necessarily satisfactory.

Therefore, an object of the present invention is to improve the efficiency of digestion in a digestion tank.

In order to achieve this object, the present invention separates sludge to be treated into primary sedimentation thickened sludge and difficult-to-dewatering thickened sludge, digests the primary settling thickened sludge in a digestion tank, and converts the hard-to-dewatering thickened sludge into a reaction tank. The separated liquid produced is then supplied to a 0.5-mm digestion tank.

Therefore, the initial sedimentation thickened sludge and the separated liquid containing solubilized organic matter are digested in the digestion tank, and since both have good digestion efficiency, it is possible to improve the digestion efficiency. The dewaterability of dewaterable thickened sludge can be improved by heat treatment.

An embodiment of the present invention will be described below based on the drawings.

In the drawing, (1) 1 is a treatment system for primary sedimentation thickened sludge that is concentrated after being taken out from the primary settling tank, and includes a heat exchanger (2) that receives the primary sedimentation thickened sludge and raises its temperature. , a digestion tank (3) for digesting the initially settled thickened sludge from the heat exchanger (2), and a first ψ dehydrator (4) for dewatering the digested sludge from the digestion tank (3).

In addition, (5) is a treatment system for difficult-to-dewater thickened sludge such as surplus thickened sludge and higher-level treated thickened sludge, and is a heat treatment system that receives the supply of this difficult-to-dewater thickened sludge and heat-processes it! (6)
and a second dehydrator (7) for dehydrating the heat treated sludge from the heat treatment device (6).
is the first stage for heating the supplied thickened sludge that is difficult to dewater.
The heated sludge supplied from the heat exchanger (8) and the first heat exchanger (8) is mixed in contact with air from the air supply route (ej) and mixed with steam from the steam supply route αQ.
It has a reaction vessel (b) which is heated to 5°C or less and subjected to heat treatment using a low-temperature pressurization method, a second heat exchanger (2) which cools the heat-treated sludge from one reaction vessel four, and a sludge removal valve opened. There is. σ4
is a cracked gas discharge path from the reaction vessel (II). Also(
b) is a sludge cooling and heating system, in which heated soft water is passed through the first heat exchanger (8) by cooling the heat-treated sludge in the second heat exchanger (4); The sludge is heated in the exchanger (8). rJQ is an expansion tank, %qη is a circulation pump, and these constitute a circulation system.

(To) is a transport route for transporting both the dehydrated cake from the first dehydrator (4) and the dehydrated cake from the second dehydrator (7) to an incinerator, etc. not shown.

Q: The treated sludge discharged from the reaction tank (B) is transferred to the thickening tank (
This is the discharge route for the separated liquid separated into solid and liquid in (c), and the furnace liquid discharge route from the second dehydrator (7), and both are combined to control the supply route of the mixed liquid and exchange heat. It is led to the sludge supply side of vessel (2). In addition, (2) is the exhaust route for the digestion gas generated in the digestion tank (3), which is branched in the middle, and -10 (22a) is the exhaust route for the boiler that generates steam for the reaction can (IXI), and the other (22b) ) are each connected to a boiler that generates hot water to be circulated to the heat exchanger (2). (2) is a hot water circulation path.

Explain the procedure for sludge treatment. After being taken out from the initial settling tank, the initial settled thickened sludge is concentrated to a concentration of about 4%, surplus thickened sludge concentrated to a concentration of about 4%, and highly processed thickened sludge concentrated to the same level that are difficult to dewater. and thickened sludge are respectively supplied to the treatment system (υ and (5)).

Assuming that the temperature of the initially settled thickened sludge supplied to the treatment system (υ) is 20°C, this initially settled thickened sludge is a mixture of the separated liquid from the supply route and the P' liquid (at 60°C as described later). ing)
is mixed in and heated to 85°C, both of which are heated to 40°C in a heat exchanger (2) and digested in a digestion tank (3). Digested sludge from the digestion tank (3) is transferred to the first dehydrator (4)
The patient will be dehydrated and treated with medicine.

On the other hand, the difficult-to-dewater thickened sludge supplied to the treatment system (5) is
After being heated in the first heat exchanger (8), the air is sent to the reaction vessel (In), and the air from the air supply route (9) and the steam supply route (I
Heat treated by steam from G. The heat-treated sludge from the reaction vessel (b) is cooled in the second heat exchanger (2).

Chemical-free dehydration is performed in the second dehydrator (7). 1st dehydrator (4
) and the dehydrated cake from the second dehydrator (7) are both sent to an incinerator (not shown) from the carry-out route (to) and are incinerated.

The separated liquid generated in the concentration tank (c) is discharged to the separated liquid discharge path αψ, and the P liquid from the second dehydrator (7) is discharged to the P liquid discharge path Z, and the two liquids are mixed to a temperature of 60°C. .

The sludge is led from supply route 4 to the sludge supply side of the heat exchanger (2).

As mentioned above, it is mixed into the initially settled thickened sludge and the temperature of this initially settled thickened sludge is raised. In addition, both the separated liquid and the furnace liquid contain solubilized organic matter, and this solubilized organic matter (high BOD) is combined with the initial sedimentation thickened sludge in the digestion tank (3).
) and contributes to the generation of digestive gas.

Digestion gas generated in the digestion tank (3) is sent to the boiler @ Masu as fuel via the exhaust route (goods), which generates steam to be supplied to the reactor 0 and hot water that is circulated to the heat exchanger (2). It is occurring.

As described above, according to the present invention, the initial sedimentation thickened sludge and the separated liquid containing solubilized organic matter are digested in the digestion tank (3), and both have good digestion efficiency. As shown in the table, the digestibility can be improved and the amount of gas generated per unit weight of decomposed organic matter can be increased compared to the conventional method in which difficult-to-dehydrate thickened sludge is also digested.

The values in Table 1 are based on the total amount of solids treated as 100. As in the above embodiment, P from the second dehydrator (7) is
If the liquid is also injected into the digestion tank (3), the efficiency of digestion can be further improved. The data in Table 1 also includes the p-liquid.

Furthermore, since the hard-to-dewater concentrated sludge is heat-treated to improve its dewaterability, the amount of solid matter in the dewatered cake can be reduced compared to the conventional method. In addition, 4b sludge generally has to be chemically dehydrated.
Although it is difficult to reduce the water content of the cake after dehydration to about 80% or less with this chemical injection dehydration, it is possible to dehydrate heat-treated sludge without using a filter press, etc. Since the moisture content of the cake can be reduced more than dehydration, according to the present invention, the moisture content of the cake can also be reduced compared to the conventional method. For these reasons, according to the present invention, the load on the incinerator, etc. in the primary step can be reduced.

In addition, by mixing the 1-separated liquid and the P liquid with the initially settled thickened sludge supplied to the digestion tank (3), the temperature of this initially settled thickened sludge can be raised, and a small amount of heating heat is supplied to the heat exchanger (2). 0 Note that the BOD concentration increases by solubilizing organic components through heat treatment, but 1. By charging the separated liquid and furnace liquid into the digestion tank (3 months), the above BOD concentration can be maintained. can be reduced to 178 to 1/4.I,! degrees, and separate treatment of the separated liquid and P liquid is not necessary.

As described above, according to the present invention, the initial sedimentation concentrated sludge and the separated liquid containing solubilized organic matter are digested in the digestion tank, and both of them have good digestion efficiency, so the digestion efficiency is improved. As shown in the figure, thickened sludge that is convex and difficult to dewater can improve its dewaterability through heat treatment.

[Brief explanation of drawings]

The drawings are schematic configuration diagrams for explaining one embodiment of the present invention. (3)... Digestion tank, (4)... First dehydrator, (6)
...Heat treatment equipment, (7)--Second dehydrator, (B)-
...Reactor, a...Separated liquid discharge route, 4...Filtrate discharge route,...Supply route Agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. Separate the sludge to be treated into initial settling concentrated sludge and separated water concentrated sludge, digesting the initial settling concentrated sludge in a digestion tank, heat-treating the difficult-to-dewater concentrated sludge in a reaction tank, and producing a separated liquid. A sludge processing power of 5 or more, characterized by supplying the above-mentioned digestion tank with sludge processing power.