JPH07997A - Sludge treating device - Google Patents

Abstract

PURPOSE:To provide means for preventing the generation of malodors, reducing a treatment cost and to make easy operation control by executing a sludge treatment by automatic control with simple stages. CONSTITUTION:This method consists in preventing the leakage of the malodors by maintaining the internal pressures of a sludge receiving vessel 1, sludge dehydrating machine 4, separating liquid vessel 8, dehydrated cake vessel 7, etc., having easy hermetic constructions lower than the atm. pressure. This device is constituted to control the liquid level L1 of the sludge receiving vessel at a prescribed value by controlling a variable capacity pump 11 in such a manner that the supply rate of the centrifugal dehydrating machine 4 meets the sludge receiving rate to control a fluctuation in the amt. of the sludge (a) generated by saving of a concentrating vessel. The centrifugal dehydrating device for automatically controlling a differential velocity and the amt. of a flocculating agent to T1 and D1 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment device for dehydrating sludge generated in a sewage treatment facility.

[0002]

2. Description of the Related Art As a sludge treatment method of this type already proposed, for example, the method shown in FIG. 3 is generally used. The conventional method will be described with reference to FIG. 3. Sludge generated in a sewage treatment facility is sent to a sludge receiving tank (1) of a sludge treatment plant in a concentration of 0.5 to 1%. At the sludge treatment plant, after concentrating the sludge to a concentration of 2 to 3% in the concentrating tank (2), the dewatering machine (4) passes through the storage tank (3) and the dewatering cake (c) having a concentration of 20 to 25%. Divide into separated liquid (j) of 0.1% or less. The odors (g _{1 to} g ₄ ) generated in each tank are sucked by a blower and sent to the deodorizing device (5). The dehydrated cake is incinerated in the incinerator (6).

[0003]

However, the above sludge treatment method has the following drawbacks. 1. The odor generated from the tanks and dehydrator is sucked and deodorized, but since the tanks and dehydrator are not airtight, there is odor leakage and the surrounding environment is deteriorated. 2. Since the bad odor is sucked from the whole building where the open tank and dehydrator are installed, the amount of bad odor to be deodorized is huge and uneconomical. 3. The sludge stays in the thickening tank and the storage tank for a long time, so the property changes due to the decay of the sludge, and a bad odor is generated.
In the dehydration process, phenomena such as an increase in the coagulant addition rate and an increase in the water content of the dehydrated cake are observed. 4. In tanks, the batch control that controls the liquid level at high and low levels, and the sludge transfer and supply are constant flow rate operations, so fluctuations in the amount of sludge received can be handled by changing the operating time and operating number of the dehydrator. Because of this, driving operation becomes complicated. The present invention has been made in view of such a situation,
An object of the present invention is to provide means for performing sludge treatment by automatic control in a simple process, preventing an offensive odor, reducing treatment cost, and facilitating operation.

[0004]

FIG. 2 shows a sludge treatment process according to the present invention. FIG. 2 shows a step which is an alternative to FIG. 3, and the details of the invention are shown in FIG.

The means of the sludge treatment method according to the present invention omits the large-capacity concentrating tank (2) which occupies 80% of the tank volume. The internal pressure of the dehydrator (4), the separated liquid tank (8), the dehydrated cake tank (7), etc. is kept lower than the atmospheric pressure to prevent the leakage of offensive odor, and the sludge caused by omitting the concentrating tank ( a)
The variable level pump (11) controls the liquid level (L ₁ ) of the mud receiving tank to a predetermined value by adjusting the supply amount of the centrifugal dehydrator (4) according to the mud receiving amount. The sludge treatment method using a centrifugal dehydrator that automatically controls the differential speed and the amount of the flocculant (T ₁ and D ₁ ) is a simple and easy operation operation.

[0006]

In other words, in this sludge treatment method, the devices that generate odor have an airtight structure and the internal pressure of the devices is kept lower than the atmospheric pressure to prevent the leakage of odor.
By omitting the concentration step and shortening the residence time, it is possible to prevent difficult dehydration due to spoilage of sludge, prevent an increase in the amount of the flocculant used in the dehydration step, and reduce the water content of the dehydrated cake.
A method of automatically dehydrating sludge by providing batch control with continuous control is provided.

[0007]

As described above, according to the present invention, the following effects can be expected. 1. The equipment that was the source of odor has an airtight structure, and the internal pressure is kept lower than atmospheric pressure, so it is possible to prevent leakage of odors and improve the surrounding environment. 2. Equipment that needs deodorization has an airtight structure,
The deodorizing device can be made extremely small because it is sufficient to suck the internal pressure below the atmospheric pressure. 3. No thickening tank is required, and the installation area can be reduced by about 60%. 4. The retention time of sludge becomes about 1/10 of the conventional method,
Since there is no increase in the water content of the dehydrated cake due to sludge decay,
The cost of heavy oil required for incineration can be reduced. 5. The operating amount of the dehydration process can be reduced because the amount of the polymer flocculant that most affects the running cost can be reduced in the sludge dehydrator. 6. The sludge treatment process is simplified and automated, so operation management is easy.

[0008]

EXAMPLE A processing method to which the sludge dewatering device of the present application is applied will be described below with reference to FIG.

Concentrations generated in sewage treatment facilities 0.5-1.
0% of sludge (a) is sent to the sludge receiving tank (1). The mud receiving tank (1) is a liquid level detector (L ₁ ) used to control the liquid level in the tank and maintain an appropriate pressure space (for example, 30% of the tank volume) in the upper part, and the pressure in the upper space. 5 to 50 from atmospheric pressure
It is equipped with a pressure control device (9) that keeps hPa low (about 5 to 20 hPa as an appropriate value). In the pressure control device (9), when the space pressure in the upper part of the mud receiving tank became lower than a predetermined value, air (e) was injected into the pipe (d) until it reached a predetermined value, and the air pressure became higher than the predetermined value. In this case, it has a mechanism for discharging the internal gas (g ₁ ) from the pipe (d) and keeping it at a predetermined pressure. Since the discharged internal gas (g ₁ ) contains a foul odor,
It is treated in a small deodorizer (5) or burned in an incinerator (6).

The sludge in the sludge receiving tank (1) is centrifugally dehydrated (4) by a variable capacity sludge supply pump (11) so as to keep the liquid level in the tank at a predetermined value (for example, 70% of the tank volume). ) Sent to. The retention time in the mud receiving tank should be designed to be about 1 hour. Depending on the balance of tank capacity with the mud sending side, a preliminary tank (not shown) may be provided to temporarily store mud during an emergency.

The rotating part of the sludge (a) is an outer cylinder (casing).
It is separated into a separated liquid (j ₁ ) and a dehydrated cake (c ₁ ) by an airtight centrifugal dehydrator (4) equipped with a seal so that the outside air does not flow into the portion penetrating the. A coagulant (h ₁ ) is added for dehydration of sludge.

The airtightness of the tank and the equipment can be achieved by means such as water sealing or mechanical sealing.

The separated liquid (j ₁ ) is a liquid level detector (L ₃ ) used for controlling the liquid level and holding an appropriate pressure space (for example, 30% of the tank volume) in the upper part, and the pressure in the upper space. Is equipped with a pressure control device (9 ') that keeps the pressure lower than the atmospheric pressure by 5 to 50 hPa (about 5 to 20 hPa as an appropriate value).

The dehydrated cake (c ₁ ) is a cake position detector (L) used for sealing the outlet of the dehydrated cake tank with the dehydrated cake in order to keep the pressure in the upper space of the dehydrated cake tank (7) lower than atmospheric pressure. ₂ ) and an air flow pipe (i) for keeping the pressure in the upper space at the same pressure as the separation liquid tank. The cake in the dehydrated cake tank (7) is transferred to the incinerator (6) by the cake transfer device (10) while maintaining the height for maintaining the pressure of the upper space by the cake position detector (L ₂ ).
The cake carrier (10) is designed to prevent odor leakage.
A closed type screw conveyor or cake transfer pump is used.

Details of the control method of the present application will be described with reference to FIG.

The sludge (a) generated in the sewage treatment facility is sent to the mud receiving tank (1). The sludge receiving tank (1) controls the liquid level in the tank to a predetermined position even when the amount of sludge sent in is changed, and the flow rate of the variable capacity supply pump (11) A flow rate control device including a liquid level detector (L ₁ ) and a flow meter (F ₁ ) that are controlled to be equal to the amount is provided.

The flow rate control method includes a method of simultaneously adjusting the flow rates of F _{1 to} F _n and a method of changing F ₁ within the range of ± 50% of a predetermined flow rate to control the liquid level, and changing F _{2 to} F _n . There is a method of fixing at a predetermined flow rate. The latter control method that can expect a more stable separation result will be described below. When there is a flow rate fluctuation that cannot be controlled unless F ₁ exceeds ± 50% of the predetermined flow rate, the flow rate is changed for the purpose of liquid level control sequentially with F ₂ and F ₃ . In this way, when a plurality of control devices are changing the flow rate for the purpose of holding the liquid level, the last control device controls the liquid level, and the other flow control devices set the upper limit or the lower limit and the predetermined flow rate. It is fixed.

The centrifugal dehydrator (4) which dehydrates the sewage sludge (a) and separates it into the dehydrated cake (c) and the separated liquid (j) is A rotation speed control device that controls the rotation speed to a set speed and a differential speed control (for example, torque control) device (T) that detects a load variation and automatically adjusts to a differential speed proportional to the load amount are provided.

A coagulant (h
The addition amount of ₁ ) is the amount of sludge supplied to the centrifugal dehydrator (F ₁ )
Therefore, the concentration of the separated liquid (j ₁ ) in the centrifugal dehydrator or at least one of the excess and deficiency of the coagulant is measured, and the coagulant (h ₁ ) is proportional to the displacement amount. Is equipped with a device (D ₁ ) for controlling the amount of addition of D.

A fluid such as sewage sludge, which is highly corrosive and adherent, does not have sufficient reliability in the sensor section of the measuring machine. Therefore, when controlling, the measured value of the control equipment attached to each centrifugal dehydrator should be It is advisable to add a mechanism to prevent abnormal control by issuing a warning when the control amount exceeds a predetermined control limit from the average value of all devices and controlling the control amount to the average value or the control limit value.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sludge treatment device of the present invention.

FIG. 2 is a process diagram of a sludge treatment method of the present invention.

FIG. 3 is a conventional sludge treatment process diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mud receiving tank 4 ... Centrifugal dewatering machine 5 ... Deodorizing machine 6 ... Incinerator 7 ... Dewatering cake tank 8 ... Separation liquid tank 9 ... Pressure control device 10 ... Sludge transfer machine 11 ... Variable capacity supply pump

Claims (1)

[Claims] 1. In a sludge treatment plant for treating sewage sludge, a sludge receiving tank consisting of an airtight container, and a sludge supply amount within a prescribed treating amount of a dehydrator in order to keep the liquid level of the sludge receiving tank within a predetermined range. 5
A plurality of sludge supply facilities consisting of a variable capacity supply pump and a flow rate meter, which are controlled in the range of 0%, an airtight centrifugal dehydrator for separating the supplied sludge into a separation liquid and a dehydrated cake, and a centrifugal dehydrator of the centrifugal dehydrator. A device for controlling the number of revolutions of the screw conveyor, and a device for measuring at least one of the concentration of the separated liquid of the centrifugal dehydrator or the excess or deficiency of the coagulant, and controlling the injection amount of the coagulant from the displacement amount. A sludge treatment device comprising a plurality of sludge dewatering facilities equipped with, a separation liquid tank consisting of an airtight container, and a dehydration cake tank consisting of an airtight container, wherein the pressure of each airtight device is kept lower than atmospheric pressure. A sludge treatment device characterized in that