JP2000301200A - Sludge dehydrating treatment method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge dehydrating treatment method and apparatus capable of effectively obtaining a dehydrated cake low in water content by flocculation and dehydration. SOLUTION: Ferric chloride being a flocculant and slaked lime being a flocculation auxiliary are supplied to a flocculation tank 1 to which sludge is supplied and the liquid containing flocs formed by flocculation in the flocculation tank 1 is supplied to a vacuum filtering type dehydrator 20 to form a dehydrated cake on an endless filter cloth 21 and physical properties of the dehydrated cake are measured by a measuring device 25 while the separated liquid generated by dehydration is measured by a turbidity measuring device 27 to detect the formation of coarse floes in the flocculation tank 1 and, when this formation is insufficient, at least a part of the dehydrated cake is returned to the flocculation tank 1 by a return device 28 to be used as a floc nucleus forming auxiliary and, thereafter, the dehydrated cake is supplied to a pressure dehydrator 30 to obtain a dehydrated cake low in water content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of dewatering sludge for coagulating and dewatering sludge from wastewater discharged from food processing facilities, factories, and general households, for example, producing compost and the like, and dewatering thereof. It relates to a processing device.

[0002]

BACKGROUND ART A process for composting sludge in wastewater includes a flocculation process and a dehydration process for dehydrating a liquid containing flocs generated in the flocculation process to form a dewatered cake. is there.

Conventionally, ferric chloride is used as an inorganic flocculant and slaked lime is used as a flocculant in order to coagulate sludge in a flocculation step. In addition, a polymer chemical substance ( Polymer) or PAC (polyaluminum chloride). The liquid containing the coarse flocs generated in the agglomeration step is sent to the above-mentioned dehydration step, which generally comprises a vacuum filtration dehydration step and a pressure dehydration step by a belt press, and is dehydrated by the vacuum filtration dehydration step. A dewatered cake in which the coarse flocs are non-fluidized is formed, and the dewatered cake is sent to the pressurized dewatering step to be dewatered under pressure to become a low-water dewatered cake,
Thereafter, compost and the like are produced by subjecting the low-water content dehydrated cake to a predetermined treatment through various processes.

[0004]

Conventionally, a polymer or PAC, which is a chemical substance, is used in order to surely generate a coarse floc required for realizing formation of a dewatered cake in a dewatering step in an agglomeration step. Therefore, there was a problem that the compost (soil improver) obtained by this method was not of good quality for the farmland, and could not be constantly fertilized on the farmland. Unless a polymer or PAC is used, it is difficult to generate coarse flocs. Even if a dehydrated cake is obtained through a dehydration step, the dehydrated cake does not have a low water content. Will not be a product that can be used effectively thereafter.

An object of the present invention is to provide a sludge dewatering method capable of effectively obtaining a low water content dewatered cake, and a sludge dewatering apparatus for performing the method.

[0006]

SUMMARY OF THE INVENTION A sludge dewatering method according to the present invention comprises a coagulation step of supplying ferric chloride and slaked lime to a sludge for coagulation, and dewatering a liquid containing flocs produced in the coagulation step. A dewatering step of forming a dewatered cake, and when the generation of coarse flocs in the flocculation step is insufficient, at least a part of the dewatered cake obtained in the dewatering step is returned to the flocculation step and fed to the flocculation step. When the formation of coarse flocs in the step is sufficient, the whole dewatered cake obtained in the dewatering step is sent to the next step.

According to this sludge dewatering method, if the generation of coarse flocs in the flocculation step is insufficient, at least a part of the dewatered cake obtained in the dehydration step is returned and supplied to the flocculation step. The supplied dewatered cake serves as a floc nucleus generation aid to assist in the generation of coarse flocks in the aggregation step, so that coarse flocs can be reliably formed. As a result, a low water content dehydrated cake can be effectively obtained through the dehydration step.

[0008] In the above description, the case where the formation of coarse flocks in the aggregation step is insufficient includes the case where coarse flocs are not generated at all in the aggregation step.

Further, the method for dewatering sludge according to the present invention comprises:
A coagulation step of supplying ferric chloride and slaked lime to the sludge for coagulation; and a dehydration step of dehydrating a liquid containing flocs generated in the coagulation step to form a dewatered cake. Type dewatering step, and a subsequent pressure-type dehydration step, and at least a part of the dewatered cake obtained in the pressure-type dehydration step according to the state of the dewatered cake obtained in the filtration-type dehydration step. It is characterized in that it is returned to the filtration dehydration step and not returned.

According to this, a water content of a dewatered cake obtained by a filtration type dewatering device is large and solidification does not proceed as predetermined, and a dewatered cake having a water content within a desired range can be obtained. If not, by returning the dehydrated cake obtained in the pressure dehydration step to the filtration dehydration step, the formation of a dehydration cake in the filtration dehydration step can be promoted by utilizing the cellulose in the dehydration cake. As a result, the dehydrated cake obtained through the pressurized dehydration step can be effectively reduced in water content.

In each of the above-mentioned sludge dewatering treatment methods, the supply of ferric chloride and slaked lime in the flocculation step may be performed while adjusting the amount to be an appropriate amount according to the state of flocculation of the sludge in the flocculation step. Good.

According to this, the ferric chloride and slaked lime can always be supplied only in an amount required for floc formation, and the maximum required amount of chloride in consideration of the fluctuation range of the amount of sludge supplied to the flocculation step. The conventional problem of having to always supply ferric iron and slaked lime can be solved,
It is possible to optimize the supply amounts of ferric chloride and slaked lime, and to stabilize the dewatered cake physically and chemically in the dewatering step.

In each of the above-mentioned sludge dewatering treatment methods,
The pressure applied to the dewatered cake in the pressurized dehydration step may be changed according to the state of the dewatered cake in the pressurized dehydration step following the filtration dehydration step that constitutes the dehydration step.

According to this, when the dewatered cake formed by the dewatering action in the filtration dewatering step is sent to the pressurized dewatering step, an appropriate pressure is applied to the dewatered cake according to the condition of the dewatered cake. Therefore, the water content of the dewatered cake, the dewatered cake has good physical properties, for example, the dewatered cake pressurized does not protrude from the pressurized dewatering process, and the dewatered cake is reliably separated from the pressurized dewatering process It can have physical properties.

Further, in order to obtain such good physical properties, conventionally, a multistage pressurized dehydrator for dehydrating a dehydrated cake stepwise under pressure has been used. A multistage pressurized dehydrator becomes unnecessary, and the entire device can be reduced in size.

Further, in each of the above-mentioned sludge dewatering treatment methods, if the dewatered cake in the dewatering step has a strong odor, a deodorant may be supplied to the flocculation step.

According to this, the odor generated from the dewatered cake in the dewatering process can be eliminated or reduced.
Work environment can be improved.

A sludge dewatering apparatus according to the present invention for carrying out the sludge dewatering method is provided with a flocculation apparatus to which sludge, ferric chloride and slaked lime are supplied, and a liquid containing floc is sent from the flocculation apparatus. It has a dehydrating device and a return device for returning and supplying at least a part of the dehydrated cake obtained by the dehydrating device to the aggregating device.

According to this sludge dewatering treatment apparatus, at least a part of the dewatered cake obtained by the dewatering apparatus is coarsely transferred to the flocculation step by operating the return device when the generation of coarse flocks in the flocculation step is insufficient. It can be supplied as a coarse floc nucleation aid for generating flocs.
As a result, the dewatered cake obtained through the dewatering device can be effectively reduced in water content.

Here, the case where the formation of the coarse flocks in the aggregation step is insufficient also includes the case where no coarse flocs are generated in the aggregation step.

Further, the sludge dewatering treatment apparatus according to the present invention comprises:
A coagulation device to which sludge, ferric chloride and slaked lime are supplied,
A dehydrator for sending a liquid containing floc from the aggregating device; the dehydrator includes a filtration dehydrator and a subsequent pressurized dehydrator, and is obtained by the pressurized dehydrator. The apparatus further comprises a return device for returning at least a part of the obtained dewatered cake to the filtration dewatering device.

According to this apparatus, since at least a part of the dewatered cake obtained from the pressurized dehydrator is returned to the filter dewaterer, the formation of the dehydrated cake in the filter dewaterer is facilitated. The dewatered cake obtained from the pressure dewatering device can be effectively reduced in water content.

In each of the above-mentioned sludge dewatering treatment apparatuses, the property of measuring the weight of the dewatered cake obtained by this filtration dehydration apparatus is provided to the filtration dehydration apparatus which constitutes the dehydration apparatus and is arranged before the pressurized dehydration apparatus. Measuring device, at least one of a turbidity measuring device for the desorbed liquid generated by the dehydration action in the filtration dewatering device is arranged, the return device to the control device to receive data from at least one of the devices The connection may be established, and the control device may control and operate the return device based on the data.

In this case, the operation of the return device can be automatically performed, and the operation can be automated.

As described above, in order to supply the ferric chloride and slaked lime in the flocculation step while adjusting the supply to an appropriate amount according to the flocculation state of the sludge in the flocculation step, it is necessary to carry out the flocculation. In the device, a coagulation status detection device that detects the coagulation status due to the supply of ferric chloride and slaked lime to the sludge is arranged, and in the control device that receives data from the coagulation status detection device, A supply device for supplying slaked lime is connected, and a control device is configured to control these supply devices based on data from the coagulation status detection device and adjust the supply amounts of ferric chloride and slaked lime to the coagulation device. Is preferred.

In this way, the detection of the coagulation state in the coagulation device and the supply of ferric chloride and slaked lime according to the coagulation state can be performed automatically, and the work can be automated.

Further, as described above, the dehydration step is provided with a filtration dehydration step in which a liquid containing floc from the aggregation step is supplied, and a pressurized dehydration step subsequent to the filtration dehydration step. In order to change the pressure applied to the dewatered cake in the pressurized dewatering step in accordance with the condition of the dewatered cake in the pressurized dewatering step, the filtration dewatering device following the filtration dewatering device is used. A pressurizing device that pressurizes the dewatered cake sent from the device and a dewatered cake status detecting device that detects the status of the dewatered cake in the pressurized dewatering device are arranged, and receive data from the dewatered cake status detecting device. It is preferable that a pressurizing device is connected to the control device, and that the control device controls and operates the pressurizing device based on data from the dewatering cake state detecting device.

With this configuration, the state of the dewatered cake in the pressurized dewatering device can be automatically detected and the dewatered cake can be pressurized in accordance with the state of the dewatered cake, so that the work can be automated. become.

Further, as described above, when a deodorant is supplied to the coagulation step when the dehydrated cake in the dehydration step has a strong odor, a deodorant supply device is provided in the coagulation device and a dehydration device is provided. , An odor detection device is arranged, and a deodorant supply device is connected to a control device that receives data from the odor detection device, and the control device controls the deodorant supply device based on the data from the odor detection device. It is preferable that the control operation is performed.

In this way, it is possible to automatically detect whether or not the dehydrated cake has a strong odor in the dehydration step, and to supply the deodorant to the aggregating step when there is a strong odor. Automation can be achieved.

In the present invention, the filtration type dehydration step and the apparatus therefor may be of a vacuum filtration type or of a gravity filtration type. However, in order to obtain a large dehydration efficiency, it is preferable to use a vacuum filtration type in which dehydration is performed by a suction action. The pressurized dewatering step and apparatus may be of any type, but it is preferable to adopt a belt press type in that efficient dewatering of the dewatered cake and continuous feeding of the dewatered cake can be achieved. .

[0032]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the entire first embodiment.

The tip of a sludge supply circuit 2 which is a sludge supply device extending from a sludge tank or a reactor (not shown) and having a pump 2A is connected to the flocculation tank 1 which is a flocculation device provided with the stirring means 1A. A coagulation tank 1 is provided with a ferric chloride supply device equipped with servo pumps 3A, 4A and 5A,
A dehydrated lime supply device, a ferric chloride tank 3, which is a deodorant supply device, a dehydrated lime tank 4, and a deodorant tank 5 are connected. The deodorant stored in the tank 5 is zeolite. Coagulation tank 1
Is provided with a flocculation status detection device 6 for detecting the status of flocculation generated in the flocculation tank 1 by adding ferric chloride as a flocculant and slaked lime as a flocculant to sludge,
The data from the detection device 6 is transmitted to the control device 7.

The servo pumps 3A, 4A, and 5A are controlled and driven by signals from the control device 7, which is a computer having a calculation function based on input data and a data output function based on the calculation result. ing.

The coagulation tank 1 is connected to a supply circuit 11 having a pump 11A for supplying a liquid in the coagulation tank 1 containing flocs generated during the coagulation to the dewatering device 10. The dehydrating apparatus 10 includes a vacuum filtration type dehydrating apparatus 20 to which the liquid is supplied from the coagulation tank 1 by the supply circuit 11, and a pressurized dehydrating apparatus 30 by a belt press into which the dewatered cake formed by the dehydrating apparatus 20 is fed. Consists of

The vacuum filtration type dehydrator 20 moves up and down with respect to an endless filter cloth 21 that rotates intermittently and a horizontal portion of the endless filter cloth 21, and when the filter cloth moves down, it comes into contact with the horizontal portion to form an agglomeration tank. The endless filter cloth 21 is provided with a movable frame 23 without a bottom, into which the liquid from 1 flows through the supply circuit 11 and the hopper 22, and a vacuum chamber 24 arranged below the horizontal portion of the endless filter cloth 21. A vacuum pump (not shown) is connected to the vacuum chamber 24, and when a certain amount of liquid including a floc is injected from the hopper 22 into the inside of the movable frame 23 which moves down and comes into contact with the horizontal portion of the endless filter cloth 21, The liquid inside the movable frame 23 is sucked into the vacuum chamber 24 through the stopped endless filter cloth 21 by the suction action of the vacuum pump, and the flocs in the liquid are filtered by the endless filter cloth 21 during this suction dehydration action. , Endless filter cloth 21
The solid component of the floc is left as a non-fluidized dewatered cake on the horizontal part of the. Thereafter, the movable frame 23
Rises, and the endless filter cloth 21 travels a certain distance in the direction of the arrow, whereby the dewatered cake separates from the endless filter cloth 21.

At the detachment point, there are provided a densitometer for detecting the hardness of the dewatered cake and a specific gravity meter for detecting the specific gravity.
A dehydration cake property measuring device 25 for measuring the physical properties of the dewatered cake is arranged by these, and after the property measurement is performed by the measuring device 25, the dewatered cake is returned and supplied to the coagulation tank 1 by a return device described later. Except for a part, the pressure is supplied to the pressurized dehydrator 30 directly or via a transfer device (not shown). Thereafter, the same operation is repeated, and dewatered cakes are sequentially formed by the vacuum filtration type dehydrator 20 and sent to the pressurized dehydrator 30 and the like.

The vacuum chamber 24 includes a vacuum chamber 24
A return circuit 26 is connected to return the desorbed liquid accumulated in the sludge tank and the reactor to the sludge tank. The return circuit 26 including the pump 26A is formed with one dehydrated cake by intermittent running of the endless filter cloth 21. A turbidity measuring device 27 for measuring the turbidity of the desorbed amount and the amount of the liquid accumulated in the vacuum chamber 24 every time is provided.

A return device 28 composed of a conveyor or the like faces the place where the dewatered cake is released from the endless filter cloth 21.
The return device 28 has a movable part that moves toward and away from the endless filter cloth 21. When the movable part approaches the endless filter cloth 21, an amount corresponding to the approach amount is provided. Only a part or all of the dewatered cake detached from the endless filter cloth 21 is received, and the main body of the return device 28 returns the dehydrated cake to the coagulation tank 1.

The data obtained by the property measuring device 25 and the data obtained by the turbidity measuring device 27 are transmitted to the control device 7, and the movable portion of the return device 28 receives the signal from the control device 7 to transmit the endless filter cloth. The operation of approaching and separating from 21 is controlled.

The pressurized dewatering device 30 includes a first endless filter cloth 31 to which the dewatered cake from the vacuum filtration dewatering device 20 is supplied.
And a second endless filter cloth 33 having a portion pressed toward the first endless filter cloth 31 by a pressure device 32 such as a hydraulic cylinder.
And a V-shaped endless belt 35 disposed inside the first endless filter cloth 31 and receiving the parallel running portion 34 of the first endless filter cloth 31 and the second endless filter cloth 33 from below. Have been. These always rotate in the direction of the arrow, and the first endless filter cloth 31
The dewatered cake supplied above is pressed and sandwiched between the parallel running portions 34 receiving the pressing force of the pressurizing device 32, and the dewatered cake that has been dewatered to have a reduced water content is subjected to the first endless filter cloth 31, By rotating the second endless filter cloth 33 and the endless belt 35 in the direction of the arrow, the second endless filter cloth 33 is detached from the parallel running section 34 and is transferred onto the transfer conveyor 36. Sent to

The transfer conveyor 36 which constitutes the end of the pressurized dehydrator 30 is provided with a razor method or the like for detecting the state of the dewatered cake in the pressurized dehydrator 30 by measuring the thickness and width of the dewatered cake. Dewatered cake status detection device 37
Are arranged, and data obtained by the detection device 37 is transmitted to the control device 7. A pressure device 32 is connected to the control device 7, and the pressure of the pressure device 32 is controlled by a signal from the control device 7.

The pressurized dehydrator 30 is provided with an odor detecting device 38 for detecting an ammonia odor, and data from the detecting device 38 is also transmitted to the control device 7.

Next, the operation will be described. The sludge from the sludge supply circuit 2, the ferric chloride from the ferric chloride tank 3, and the slaked lime from the slaked lime tank 4 are supplied to the flocculation tank 1, which is an apparatus for the flocculation step, and the liquid in the flocculation tank 1 is thereby supplied. Flocs are formed. The liquid containing this floc is sent by the supply circuit 11 to the vacuum filtration type dehydrator 20 which is the former stage of the dehydration process apparatus, and the floc is placed on the endless filter cloth 21 of the vacuum type dehydrator 20 as described above. When the dewatered cake is formed from the solid components, the physical properties of the dewatered cake are measured by the property measuring device 25, and the dehydration amount generated by dehydration for forming the dewatered cake and accumulated in the vacuum chamber 24 is turbid. The degree and liquid volume are measured by the turbidity measuring device 27,
These data are received by the control device 7.

Based on the received data, the control device 7 calculates the generation status of the coarse flocs in the coagulation tank 1. In accordance with the calculation result, when the generation of the coarse flocks is insufficient, the control device 7 causes the movable portion of the return device 28 to approach the endless filter cloth 21 in accordance with the insufficient amount, whereby the endless At least a part of the dewatered cake on the filter cloth 21 is returned to the coagulation tank 1 by the return device 28, and when the generation of the coarse flocs is sufficient, the control device 7 sets the movable portion to the endless filter cloth 2
From step 1, the whole dewatered cake is supplied to the pressurized dewatering device 30.

As described above, in the present embodiment, when the generation of the coarse flocks in the coagulation tank 1 is insufficient, at least a part of the dewatered cake is returned to the coagulation tank 1.
In this case, the returned dehydrated cake serves as a floc nucleation aid to assist in the generation of coarse flocks, thereby reliably generating coarse flocs. Therefore, the flocculation tank 1 contains a chemical substance for generating coarse flocs. There is no need to supply certain polymers or PACs.

For this reason, compost is produced from the dehydrated cake,
Even if this compost (soil improver) is applied to farmland, there is no adverse effect on farmland, and the compost becomes a constantly usable compost.

The data for judging the generation state of the coarse flocs in the flocculation tank 1 may be only the data obtained by the property measuring device 25 or the data obtained by the turbidity measuring device 27.

In the present embodiment, since the detecting device 6 for detecting the state of sludge flocculation in the flocculating tank 1 is arranged in the flocculating tank 1, the control device 7 The servo pumps 3A and 4A are controlled and driven, whereby the amounts of ferric chloride from the ferric chloride tank 3 and slaked lime from the slaked lime tank 4 supplied to the coagulation tank 1 are adjusted.

For this reason, even if the amount of sludge supplied to the flocculation tank 1 fluctuates and the amounts of ferric chloride and slaked lime required for floc generation fluctuate, ferric chloride and slaked lime Can be always properly adjusted, and at least a part of the dewatered cake is returned and supplied to the flocculation tank 1 as a floc nucleation aid from the vacuum filtration type dehydration device 20. Since the formation of coarse flocs can be promoted and ferric chloride and slaked lime are not supplied excessively, the dewatered cake in the dehydration step by the vacuum filtration dehydration device 20 and the pressure dehydration device 30 is removed. Physical,
Chemical component stabilization can be achieved.

The dewatered cake supplied to the pressurized dewatering device 30, which is the latter device of the dewatering process device, is run in parallel with the first endless filter cloth 31 and the second endless filter cloth 33 of the pressurized dewatering device 30. The pressing force of the pressurizing device 32 is applied between the portions 34, whereby the water content of the dewatered cake is reduced. After this, the dewatered cake is divided into the first endless filter cloth 31 and the second endless filter cloth 3
3. The parallel running unit 34 is rotated by the rotation of the endless belt 35 in the direction of the arrow.
The dehydrated cake status detecting device 37 detects the thickness, width, and the like of the dehydrated cake on the way to the next step on the conveyor 36 after being separated from the conveyor.
The data obtained by this is received by the control device 7,
Based on the received data, the control device 7 adjusts and controls the pressurizing force of the pressurizing device 32, and sets the pressurizing force applied to the dewatered cake pressurized and dewatered in the parallel traveling unit 34 to an appropriate value.

For this reason, the water content of the dewatered cake formed as described above from the coarse flocks as described above does not protrude from both sides of the parallel running portion 34 because the dewatered cake pressurized in the parallel running portion 34 does not protrude. And the first endless filter cloth 31, the second
The parallel running portion 34 is formed by the rotation of the endless filter cloth 33 and the endless belt 35.
Water content can be assuredly separated from the dehydrated cake, and the physical properties of the dehydrated cake can be improved.

Further, such good physical properties are such that the pressurizing device 32 provided in the pressurizing dewatering device 30 is of a variable pressing force type, and this pressurizing device 32 is provided with data from the dewatering cake status detecting device 37. The multi-stage pressurized dewatering device, which is obtained by controlling the dehydration cake in a stepwise manner by pressurizing and dehydrating the dewatered cake, is not required, so that the size of the entire dewatering device can be reduced.

Further, in this embodiment, since the odor detection device 38 for detecting the ammonia odor is disposed in the pressurized dehydrator 30, the dehydration cake sent to the pressurized dehydrator 30 has a strong ammonia odor. Then, the control device 7 that receives data from the odor detection device 38 controls and drives the servo pump 5A of the deodorant tank 5. As a result, zeolite in an amount corresponding to the intensity of the ammonia odor is supplied from the deodorant tank 5 to the coagulation tank 1. Therefore, the odor generated from the dewatered cake can be eliminated or reduced, and the working environment can be improved.

If another type of odor is expected to be generated from the dehydrated cake, the odor that can be detected by the odor detector 38 is regarded as this type of odor and stored in the deodorant tank 5. A deodorant is capable of eliminating this odor.

Although not shown in the drawings, the coagulation tank 1
Is provided with a sensor for detecting the PH and alkalinity of the sludge in the flocculation tank 1, and the control device 7 drives and controls the servo pumps 3A and 4A by inputting the detection data from this sensor to the control device 7. Thereby, the ferric chloride from the ferric chloride tank 3 supplied to the coagulation tank 1 and the slaked lime tank 4
May be adjusted so that the pH and alkalinity of the dehydrated cake obtained through the pressurized dehydration device 30 are suitable for use as a soil conditioner.

Further, a sensor for measuring the sludge interface inside the sludge tank and the reactor is disposed in the sludge tank and the reactor, and the data from this sensor is input to the control device 7, whereby the servo of the sludge supply circuit 2 is controlled by the control device 7. The drive of the pump 2A may be controlled so that the amount of sludge supplied to the flocculation tank 1 may be controlled according to the state of the sludge tank and the sludge interface in the reactor. According to this, it is possible to automatically operate a whole sludge dewatering treatment system from the sludge tank and the reactor to the pressurized dehydrator 30 and the transfer conveyor 36.

FIG. 2 shows a second embodiment of the present invention. In FIG. 2, the same reference numerals are given to the same members, devices, and the like as those in the above-described embodiment, and the operation is the same.

This embodiment is particularly effective for sludge containing a large amount of cellulose, which is a fiber component. A return device 48 is connected between the end of the transfer conveyor 36 and the hopper 22.
Has the same configuration as that of the return device 28. That is,
A return device 48 composed of a conveyor or the like is disposed facing the place where the dewatered cake is detached from the transfer conveyor 36, and the return device 48 has a movable portion that moves toward and away from the end portion of the transfer conveyor 36. When the movable part approaches the terminal end of the transfer conveyor 36, it receives a part or all of the dewatered cake detached from the conveyor 36 by an amount corresponding to the approach amount, and sends the dehydrated cake to the hopper by the hopper. The dewatered cake is fed back to the vacuum filtration dewatering device 20.

The return device 48 is controlled by a signal from the control device 7, and receives data from both the property measuring device 25 and the pollution measuring device 27 provided in the vacuum filtration type dehydrating device 20, or data from either of them. Based on the control device 7
Actuates the movable part of the return device 48.

For this reason, in this embodiment, depending on the state of the dewatered cake in the vacuum filtration dehydrator 20, all or a part of the dewatered cake obtained from the pressurized dehydrator 30 is removed. The dewatered cake obtained from the pressurized dewatering device 30 is dewatered under pressure to reduce the water content and contains a large amount of cellulose. If the dewatered cake obtained by the dewatering device 20 has a high water content and solidification has not progressed much, at least a part of the dewatered cake obtained by the pressurized dewatering device 30 is transferred to the vacuum filtration dewatering device 20. By returning the cake, the final dewatered cake obtained via the pressurized dewatering device 30 can be made into a low-moisture content solidified effectively.

Although the embodiment of FIG. 1 and the embodiment of FIG. 2 may be implemented individually, both of these embodiments may be implemented simultaneously.

[0063]

According to the present invention, an effect that a low water content dehydrated cake can be effectively obtained can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an entire apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation tank which is a coagulation apparatus 2 Sludge supply circuit which is a sludge supply apparatus 3 Ferric chloride tank which is a ferric chloride supply apparatus 4 Dehydrated lime tank which is a slaked lime supply apparatus 5 Deodorant tank which is a deodorant supply apparatus 6 Coagulation state detection device 7 Control device 10 Dehydration device 20 Vacuum filtration type dehydration device 21 Endless filter cloth 25 Dehydration cake property measurement device 27 Turbidity measurement device 28, 48 Return device 30 Pressurization type dehydration device 31, 33 Endless filter cloth 32 Addition Pressure device 35 Endless belt 37 Dewatered cake status detector 38 Odor detector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D015 BA03 BA04 BA11 BA12 BA25 BB08 BB13 CA11 DA13 DA24 EA03 EA36 EA37 FA01 FA11 4D059 AA07 BE10 BE14 BE31 BE55 BE60 BK02 CC01 CC10 DA05 DA24 DA55 EA03 EA05 EB05 EB11

Claims (11)

[Claims] A flocculating step of supplying ferric chloride and slaked lime to the sludge for coagulation; and a dewatering step of dehydrating a liquid containing flocs generated in the flocculating step to form a dewatered cake. When the generation of the coarse flocks in the aggregation step is insufficient, at least a part of the dewatered cake obtained in the dehydration step is returned to the aggregation step, and the generation of the coarse flocks in the aggregation step is sufficient. In this case, the sludge dewatering method is characterized in that the entire dewatered cake obtained in the dewatering step is sent to the next step. 2. A coagulation step of supplying ferric chloride and slaked lime to the sludge for coagulation, and a dehydration step of dehydrating a liquid containing flocs generated in the coagulation step to form a dewatered cake, This dehydration step has a filtration dehydration step and a subsequent pressure dehydration step, and the dehydration obtained in the pressure dehydration step depends on the state of the dewatered cake obtained in the filtration dehydration step. A sludge dewatering method comprising returning and not returning at least a part of the cake to the filtration dewatering step. 3. The sludge dewatering method according to claim 1, wherein the supply of ferric chloride and slaked lime in the coagulation step is performed in an appropriate amount according to the state of coagulation of the sludge in the coagulation step. Sludge dewatering method characterized in that the sludge dewatering method is performed while adjusting the temperature. 4. The sludge dewatering method according to any one of claims 1 to 3, wherein the sludge dewatering is performed according to the condition of a dewatered cake in a pressurized dewatering step subsequent to a filtration dewatering step constituting the dewatering step. A sludge dewatering method comprising changing a pressure applied to a dewatered cake in a pressure dewatering step. 5. The sludge dewatering method according to claim 1, wherein when a deodorized cake in the dewatering step has a strong odor, a deodorant is supplied to the flocculation step. A characteristic sludge dewatering method. 6. A flocculation device to which sludge, ferric chloride and slaked lime are supplied, a dehydration device to which a liquid containing floc is sent from the flocculation device, and at least a part of a dewatered cake obtained by the dehydration device And a return device for returning and supplying the sludge to the flocculation device. 7. A flocculation device to which sludge, ferric chloride and slaked lime are supplied, and a dehydration device to which a liquid containing floc is sent from the flocculation device. And a pressurized dewatering device, and a return device for returning at least a part of the dewatered cake obtained by the pressurized dewatering device to the filtration dewatering device. Sludge dewatering treatment equipment. 8. The sludge dewatering apparatus according to claim 6, wherein the filtration dehydration apparatus that constitutes the dehydration apparatus and is disposed before the pressurized dehydration apparatus includes the filtration dehydration apparatus. At least one of a property measuring device for measuring a physical property of the obtained dewatered cake and a turbidity measuring device for a desorbed liquid generated by a dehydrating action in the filtration type dehydrating device is arranged, and at least one of these devices is arranged. A sludge dewatering treatment apparatus, wherein the return device is connected to a control device that receives data from the device, and the control device controls the return device based on the data. 9. The sludge dewatering treatment apparatus according to claim 6, wherein the coagulation apparatus includes a coagulation state detection apparatus that detects a coagulation state due to supply of ferric chloride and slaked lime to the sludge. A supply device for supplying ferric chloride and slaked lime to the coagulation device is connected to the control device that receives the data from the coagulation status detection device, and the control device is configured based on the data from the coagulation status detection device. A sludge dewatering treatment apparatus characterized in that these supply devices are controlled to adjust the supply amounts of ferric chloride and slaked lime to the flocculation device. 10. The sludge dewatering treatment apparatus according to claim 6, wherein the sludge dewatering apparatus is sent from the filtration dehydration apparatus to a pressurized dehydration apparatus next to the filtration dehydration apparatus constituting the dehydration apparatus. A pressurizing device for pressurizing the dewatered cake,
A dewatering cake status detecting device for detecting the status of the dewatered cake in the pressurized dewatering device is disposed, and the pressurizing device is connected to a control device that receives data from the dewatering cake status detecting device, and detects the dewatered cake status. A sludge dewatering apparatus characterized in that the control device controls and operates the pressurizing device based on data from the device. 11. The sludge dewatering apparatus according to claim 6, wherein a deodorant supply device is disposed in the flocculation device, and an odor detection device is disposed in the dehydration device. The deodorant supply device is connected to a control device that receives data from the device, and the control device controls and operates the deodorant supply device based on data from the odor detection device. apparatus.