JPH06320200A - Device and method for concentration and dewatering of sludge - Google Patents

Abstract

PURPOSE:To enhance dewatering efficiency and economically obtain the dewatered cake of low water content by a method wherein, in concentrating and dewatering sewage sludge by a combination of a pelletizing and concentrating method and a centrifugal dewaterer, the pelletized and conc. sludge is sent through a filter type concentrator into the centrifugal dewaterer. CONSTITUTION:The sludge in a raw sludge storage tank 5 is sent by a pump into a refining tank 1 where it is mixed with inorg. flocculant to form a primary coagulated sludge contg. a primary flocculated product formed by a primary flocculation of ion components and solids in the sludge. This primary flocculated sludge is sent into a pelletization and concn. tank 2 where it is stirred and mixed with amphoteric high- molecular flocculant to flocculate and pelletize the primary flocculated product and unflocculated solids in the sludge to form pelletized sludge while it is undergoing concn. by separating free water from it. The pelletized sludge obtained in the pelletization and concn. tank 2 is sent into a filter type concentrator 3 to undergo concn. and after concn. is supplied into a centrifugal dewaterer 4 for further dewatering. By using the filter type concentrator 3 in this way, the breakdown of the pelletized sludge is avoided and the dewatered cake of low water content is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for concentrating and dewatering sludge generated in a sewage treatment facility.
The present invention relates to an apparatus and a method for concentrating and dehydrating by utilizing a so-called granulation concentrating method.

[0002]

2. Description of the Related Art Conventionally, sludge generated in a sewage treatment facility (hereinafter referred to as sewage sludge or raw sludge) has conventionally been subjected to a series of steps of concentration, (digestion), dehydration and incineration. Has been processed. Sewage sludge includes surplus sludge and first settling sludge, but there is a method of mixing and concentrating both in the concentration step, and a method of separating and concentrating that both are separately concentrated and then sent to a step such as incineration later. There are two ways. In any of these methods, the concentration step is generally composed of a plurality of equipments, and it is disadvantageous that construction costs, maintenance, maintenance and operation and maintenance of these equipments require a large amount of money. There is.

In order to solve such a drawback, a so-called granulation concentration method has been adopted in which a solid substance is aggregated, and the aggregate is further granulated to concentrate sludge to improve its dehydration property. There is. Unlike other concentrating methods, this granulating and concentrating method has both the function of concentrating and the function of converting the properties of sludge to facilitate dewatering, so it is more difficult to construct than conventional gravity concentrating methods. Costs and operating costs such as dehydrated cake processing costs can be reduced, and phosphorus can be removed, etc. (issued by the Japan Sewage Works Agency Technical Development Department and the Sewage Works Agency Business Extension Association in 1991) "First Report on Evaluation of Efficient Sludge Concentration Method-Granulation Concentration Method-"
-Hereinafter, simply referred to as "First Report"). However,
It goes without saying that it is preferable to further reduce the water content of the dehydrated cake in order to further reduce the processing cost of the dehydrated cake.

On the other hand, the centrifugal dehydrator is being widely adopted because it is easy to maintain and manage, has a large processing capacity per unit, and has the advantage that it is not necessary to use washing water.
In order to further reduce the water content of the granulated sludge obtained by the granulation concentration method, in concentrating and dehydrating the granulation sludge,
The use of such a centrifugal dehydrator is preferable from the viewpoints of facility simplification, cost saving, and process stability. However, when a centrifugal dehydrator is used for concentrating and dewatering the granulated sludge obtained by the granulating and concentrating method, it is once granulated by the granulating and concentrating method to improve the dewatering property and to be concentrated. The granulated sludge is destroyed and miniaturized during the process of supplying it to the next centrifugal dehydrator and during the dehydration operation in the centrifugal dehydrator, and reduces the improved dehydration property to the original level (for example, In the above-mentioned “First Report”), this tendency is more remarkable as the solid concentration of the granulated dehydrated cake is higher, and this tendency is particularly remarkable when the dehydrator is a centrifugal dehydrator. Further, in the granulation concentration step, there is a drawback that the concentration concentration in the granulation concentration step is limited in order to keep a good recovery rate of the solid matter in the raw sludge. That is, the higher the solids concentration of the centrifugal dehydrator, the larger the amount of solids treated, but the operation in the granulation concentration step cannot help lowering the concentration of the granulated sludge to about 2%. As a result, there are obstacles such as the ability of the centrifugal dehydrator cannot be fully exerted. In this case, in order to further stably perform the concentration and dehydration of the raw sludge in which the property and the solid content concentration are greatly varied, the raw sludge supply amount (primary coagulated sludge) is substantially reduced in the granulation concentration step. It is customary to keep the solids concentration in the granulated sludge discharged from the granulation concentration step substantially constant, or to operate with the concentration ratio substantially constant. However, in any case, the amount of sludge supplied to the centrifugal dehydrator and / or the solids concentration cannot be made substantially constant, that is, the amount or concentration varies depending on the fluctuation of the solids concentration. It is fluctuating, stable operation of the centrifugal dehydrator is practically impossible, and a centrifugal dehydrator with an excessive processing capacity that matches the maximum amount of sludge volume fluctuation must be selected and used. Has the disadvantage of wasting power costs. In this way, when the granulation concentrating tank and the centrifugal dehydrator are combined, the excellent performance of the granulating concentrating tank is improved regardless of the fact that the granulating concentrating tank has improved the dehydration property by being concentrated, granulated and granulated. It has been said that centrifugal dehydration of granulated sludge is not actually feasible because it cannot be fully utilized and stable operation control is difficult.

The inventors of the present invention, when performing the concentration and dewatering treatment of sewage sludge by combining the so-called granulation concentrating method and the centrifugal dehydrator, use the above-mentioned method by combining the granulation concentrating method and the centrifugal dehydrator. By overcoming such disadvantages and fully utilizing the advantages of the granulation concentrating method and the centrifugal dehydrator, the sewage sludge can be concentrated and dehydrated efficiently at a low cost and with a low water content. For the purpose of obtaining a cake, as a result of diligent and repeated grinding, a filter-type concentrator is interposed between the granulation concentration tank and the centrifugal dehydrator, and the sewage sludge is continuously treated. As a result, the inventors have found that the above-mentioned object can be achieved, and based on this finding, they have arrived at the sludge concentrating and dewatering device and the sludge concentrating and dewatering method of the present invention.

[0006]

[Means for Solving the Problems] That is, one of the present invention is to mix raw sludge from a sewage treatment facility with an inorganic coagulant to primarily aggregate ionic components and solids in the raw sludge. A primary coagulation sludge containing a primary coagulation product,
The primary agglomerated sludge introduced from the conditioning tank and the amphoteric polymer aggregating agent are mixed with stirring to agglomerate and granulate the primary agglomerates and unaggregated solids in the primary agglomerated sludge. Granulating sludge, which is made into granulated sludge and is separated into the granulated sludge and free water and concentrated, a filter type concentrator for concentrating the granulated sludge, and a granulated sludge concentrated by the filter type concentrator A sludge concentrating and dewatering device, characterized in that centrifugal dehydrators for further dewatering are sequentially connected.

Another aspect of the present invention is to mix primary sludge generated from a sewage treatment facility with an inorganic flocculant to primarily condense ionic components and solids in the raw sludge to form primary flocculates. The refining step for obtaining the contained primary coagulation sludge, the primary coagulation sludge and the amphoteric polymer coagulant are mixed with stirring to obtain the above-mentioned 1
Granulation concentration step of aggregating and aggregating the primary agglomerates and unaggregated solids in the secondary agglomeration sludge into granulation sludge, and separating into the agglomeration sludge and free water, obtained in the agglomeration concentration step Destruction of the granulated sludge by sequentially passing through a concentration step of concentrating the obtained granulated sludge with a filter type concentrator into a concentrated sludge and a dehydration step of dehydrating the concentrated sludge with a centrifugal dehydrator to form a dehydrated cake It is a sludge concentration / dehydration method, characterized in that the sludge is concentrated and dewatered by suppressing as much as possible.

The granulating and concentrating tank in the present invention has a tank main body, an agitator and a screen, and a sludge supply hole and an amphoteric polymer coagulant supply hole are provided at the bottom of the tank main body, and the screen is The stirrer provided at the top of the tank main body has at least an upper stirring blade for generating a horizontal swirling flow and a lower stirring blade for generating a vertical circulating flow, and sludge is produced on the inner peripheral surface of the tank main body. It's a grain.
As a typical example of this granulation concentrating tank, the granulation concentrating tank described in the above-mentioned “First Report” and shown in FIG. 2 can be mentioned.

The filter-type concentrator used in the present invention may be any of those commonly used for concentrating sludge, and a wire screen, a filter material having slits or a coarse filter cloth may be used as a filter. It is preferable that the grain size is large and the grain size is coarser than that used for usual sludge concentration. In addition, the filter has a structure that can be washed with free water separated and discharged in the granulation concentration step, or with separated water discharged from each of the filter type concentrator and the centrifugal dehydrator, or with a scraper. preferable. Further, it is preferable that the filter type concentrator is of a continuous supply type and a continuous discharge type so as not to destroy the granulated state of the granulated sludge and of a type that does not use a pump for discharging. As the simplest filter type concentrator, for example, a filter cylinder having a built-in wire screen can be mentioned, and it is preferable. Further, it is preferable that the filter type concentrator has a mechanism for adjusting the solid matter concentration of the discharged concentrated sludge.

In the centrifugal dehydrator of the present invention, in order to prevent the destruction of the granulated sludge as much as possible, the liquid level in the rotary cylinder is deeper than that used in the ordinary concentration of sludge. is necessary. For example, a decanter type centrifugal sedimentation machine in which a screw is arranged at the center of a horizontal rotary cylinder having a conical portion is suitable.

Further, as a typical example of the decanter type centrifugal separator, there is a centrifugal dehydrator as shown in FIG. 3, which is suitable for use in the present invention. In this centrifuge, a bowl having a cylindrical portion and a conical tubular portion continuously provided at one end thereof is provided in a casing, and a cylindrical portion and an inner cone continuously provided at one end thereof are provided inside the bowl. An inner cylinder consisting of is housed, and a screw is provided on each of the outer peripheral surface of the cylindrical portion and the inner cone, and the pitch of the screw on the outer peripheral surface of the cylindrical portion is gradually reduced toward the inner cone. The bowl and the screw are rotated concentrically and independently of each other. Further, this centrifuge preferably has a small liquid surface radius in the bowl-that is, has a deep liquid surface such that the inner peripheral velocity of the bowl becomes small immediately after the supply of the concentrated sludge. This is effective for suppressing the destruction of the granulated sludge in the granulated state immediately after the granulated concentrated sludge is supplied to the centrifugal dehydrator. Further, it is preferable that the number of rotations of each of the bowl and the screw can be made different depending on the solid concentration in the concentrated sludge to be supplied (hereinafter, the difference between these numbers of rotations may be referred to as differential speed). ). Furthermore, it is preferable that the differential speed and the torque during rotation thereof can be detected.

The refining tank, the granulation concentrating tank, the filter concentrator, and the centrifugal dehydrator are directly connected to each other or, if desired, sequentially connected to each other via a pump. Further, the conditioning tank is connected to the upstream sewage treatment facility directly or, if desired, via a raw sludge storage tank. Further, at the time of this connection, a pump may be interposed in the connection path if desired. For the pump that is interposed between the granulation thickener and the filter-type thickener, a type and model must be selected that does not destroy the granulated sludge discharged from the granulation thickener as much as possible. Usually, for example, a single screw pump is preferably used. Also, instead of this pump or together with this pump, a flow rate adjusting valve such as a diaphragm type flow rate adjusting valve can be used. As the pump used in other places, a pump normally used for transporting sludge can be used.

The raw sludge to which the present invention is applied is, for example,
Sludge generated from sewage treatment facilities such as general public sewer facilities, for example, raw sludge of standard activated sludge method, excess sludge, mixed sludge of the above-mentioned raw sludge and excess sludge, anaerobic aerobic activated sludge method and It is an excess sludge of the oxidation ditch method, and may contain at least solid matter and ions. Its solids concentration and ion equivalent are:
There is no particular limitation, but in order to efficiently perform the concentration and dehydration in the present invention, in practice, each is usually about 0.4 to
2% by weight and about 0.2 to 0.5 mg equivalents per gram of total solids, preferably 0.5 to 1.5% by weight and about 0.3 to 0.4 mg equivalents per gram of total solids. It Usually, the sludge from the sewage treatment facility can be treated as it is because its solid content concentration and ion equivalent are within the above ranges.

In the refining step, the supplied raw sludge and the inorganic coagulant are mixed to neutralize the electric charge of the ionic components in the raw sludge to cause condensation, and at this time, the solid matter is also involved. Primary coagulation is performed to obtain a primary coagulated sludge that has been conditioned so that coagulation and granulation in the subsequent granulation and concentration step are suitably performed. A typical example of the inorganic coagulant used here is sulfuric acid second
Iron salts such as iron and ferric chloride, and aluminum sulfate and polyaluminum chloride (PAC), etc., among which polyaluminum chloride and / or ferric chloride are preferable in practical use. Practically, the amount of the inorganic flocculant used is usually about 3 to 15%, preferably about 5 to 10%, based on the weight of the solid matter in the raw sludge. The pH of the sludge to which the inorganic coagulant is added is slightly acidic in order to make the inorganic coagulant act efficiently, but when the inorganic coagulant is an iron salt, it is about 4 to 5, and when it is an aluminum salt. In practice, it is preferable to set it to about 4.5 to 5.5.

In the granulating and concentrating step, the primary coagulation sludge sent from the pre-conditioning tank and the amphoteric polymer coagulant are mixed to remove the primary coagulation and unaggregated solid matter in the primary coagulation sludge. Further, it is aggregated, granulated and concentrated to obtain granulated sludge. In the present invention, an amphoteric polymer flocculant is defined as a flocculant containing a polymer in which the ratio of the amount of anionic groups (as electric equivalent) to the amount of cationic groups is 1 or more. Specific examples include a mixture of a cation resin, an anion resin and a nonion resin, and a copolymer of a cation component, an anion component and a nonion component. As a typical example of such a copolymer, a quaternary copolymer obtained by copolymerizing a cation component with dimethylaminomethacrylate and dimethylaminoacrylate, an anion component with acrylic acid, a nonion component with acrylamide, and a conventional method is given. be able to.

In practice, the amount of the amphoteric polymer flocculant used is usually about 0.5 to 1% with respect to the weight of the solid matter in the raw sludge. When the polymer flocculant is used as a solution, the solution must be acidic in order to suppress the dissociation of anionic groups. Furthermore, the pH of the primary flocculating sludge when the polymer flocculant is added is usually slightly acidic, for example, about 4 to 5, but in order to make this polymer flocculant act efficiently, A polymer flocculant is appropriately selected according to the pH of the primary flocculation sludge. The granulated sludge thus formed is separated from the free water by the screen above the granulation thickening tank and sent to the next concentration step. The granulated sludge from which the free water has been separated is concentrated 2 to 4 times as much as the primary coagulated sludge supplied to the granulation concentration step, and the solid matter concentration is usually about 2%. It is said that.

In the concentration step, the filter sludge is used to concentrate the granulated sludge with great care so that the granulated state is not destroyed as much as possible to obtain a concentrated sludge.
The concentration of solids in this concentrated sludge is improved to about 3 to 5%.

The concentrated sludge thus obtained is sent to a centrifugal dehydrator such as a decanter centrifuge, and care should be taken here so that the granulated state of the concentrated sludge is not destroyed as much as possible. While dehydrating, a dehydrated cake is finally obtained. This dehydrated cake is, for example, if desired,
It is subjected to post-treatment such as incineration. Also, the free water from the granulation concentration step is optionally used for washing the filter of the filter type concentrator used in the concentration step, and / or
Alternatively, it is sent to a sewage treatment facility for treatment. Similarly, the separated water from each of the concentration step and the dehydration step is optionally used for cleaning the filter of the filter type concentrator and / or sent to a sewage treatment facility for treatment.

In the sludge concentrating and dewatering method of the present invention, the following operating methods can be used. That is, (a) the primary agglomerated sludge in which the total amount of the primary agglomerates and unaggregated solids in the primary agglomerated sludge is controlled to be substantially constant is supplied to the granulation concentration step, and A method of supplying granulated sludge having a substantially constant substance concentration from the granulating and concentrating step to the concentrating step. (b) The primary agglomerated sludge in which the total amount of the primary agglomerates in the primary agglomerated sludge and the unaggregated solids is controlled within a predetermined range is supplied to the granulation concentration step, and the solids concentration is substantially reduced. The granulation sludge, which was kept constant at 1, was supplied from the granulation concentration step to the concentration step, and in the concentration step, the above-mentioned granulation sludge was concentrated to a concentration in which the solids concentration or concentration flow rate was substantially constant. A method of supplying sludge to the dehydration process. (c) The primary agglomerated sludge in which the total amount of the primary agglomerates in the primary agglomerated sludge and the non-agglomerated solids is controlled within a predetermined range is supplied to the granulation concentration step, and the solids concentration is substantially The granulated sludge, which was kept constant at 1, was supplied from the granulating and concentrating step to the concentrating step, and in the concentrating step, the granulated sludge was concentrated so that the solids concentration or the concentrating flow rate was substantially constant. A method of supplying the concentrated sludge to a dehydration step, concentrating and dehydrating the concentrated sludge in the dehydration step to form a dehydrated cake having a substantially constant cake water content, and (d) primary aggregate in the primary aggregate sludge The primary flocculation sludge whose total amount with unaggregated solid matter is controlled within a predetermined range is supplied to the granulation concentration step, and the granulation sludge whose solids concentration is kept substantially constant is granulated concentration step To the concentration step, and in the concentration step, the granulated sludge is concentrated to obtain a solid content or a concentrated stream. The concentrated sludge of which the amount is substantially constant is supplied to the dehydration step, and the concentrated sludge is dehydrated in the dehydration step to form a dehydrated cake whose cake water content is substantially constant, and the centrifugal dehydrator in the dehydration step There is a method of adjusting the amount of the amphoteric polymer coagulant used in the above-mentioned granulating and concentrating step according to the change in the differential speed or the torque.

[0020]

EXAMPLES The sludge concentrating and dewatering apparatus of the present invention will be described more specifically with reference to the drawings, and the sludge concentrating and dewatering method of the present invention will be described more specifically with reference to Examples. It is not limited to the apparatus shown in and the methods described in these examples. FIG. 1 shows a flow sheet for showing the principle of the sludge concentrating and dewatering device of the present invention. A partially cutaway perspective view of a typical granulation thickener used in the present invention is shown in FIG. A vertical section of a typical centrifugal dehydrator used in the present invention is shown in FIG. That is, the sludge concentrating and dewatering device of the present invention prepares a primary coagulation sludge containing a primary coagulant obtained by mixing an inorganic coagulant and primary coagulation of ionic components and solids in the raw sludge. Pour tank 1, primary agglomerated sludge derived from the conditioning tank 1 and an amphoteric polymer flocculant are mixed with stirring to agglomerate the primary agglomerates and unaggregated solids in the primary agglomerated sludge. A granulating thickener tank 2 which concentrates the granulated sludge by separating the granulated sludge into free granulated water while concentrating the granulated sludge into a granulated sludge, and a filter type concentrator 3 and the filter type concentrator A centrifugal dehydrator 4 for further dehydrating the concentrated sludge concentrated in 3 is connected in sequence. Further, the tempering tank 1 is connected to the upstream sewage treatment facility via the raw sludge storage tank 5, while on the other hand, even if it is directly connected to the sewage treatment facility without passing through the raw sludge storage tank 5. There is. Pumps are installed between the raw sludge storage tank 5 and the conditioning tank 1, between the conditioning tank 1 and the granulation thickening tank 2, and between the granulation thickening tank 2 and the filter concentrator 3. It has been intervened. The pump interposed between the granulation concentrating tank 2 and the filter concentrator 3 is a single screw type pump.

In the tempering tank 1, a stirrer 12 is incorporated in a cylindrical tank 11. In addition, there is a raw sludge supply hole 13 at the bottom.
Further, the inorganic coagulant supply hole 14 is opened, and the primary coagulated sludge discharge hole 15 is opened in the upper part.

In the granulation thickening tank 2, the primary coagulation sludge and the polymer coagulant are mixed with stirring, and the primary agglomerates and unaggregated solids in the primary coagulation sludge are mixed on the inner peripheral surface of the tank main body. The product is further aggregated, granulated and concentrated. Tank body 21, agitator 22
And has a screen 25. The screen 25 is provided in the upper part inside the tank body. The stirrer 22 has an upper stirring blade 23 for generating a horizontal swirling flow and a lower stirring blade 24 for generating a vertical circulating flow. The screen 25 separates the granulated sludge into free water. A sludge supply hole 26 and an amphoteric polymer coagulant supply hole 27 are provided at the bottom of the tank body 21, and free water discharge holes are provided at the top of the tank body 21 and below the screen 25, respectively. 28 and a granulation sludge discharge hole 29 are provided.

The filter-type concentrator 3 has a wire screen 32 built in a tank body 31, and a concentrated sludge discharge hole 33 and a separated water discharge hole 34 are installed in the tank body 31, respectively. . The tank 31 is provided with a cleaning nozzle (not shown in the drawing) for cleaning the filtration surface thereof continuously or intermittently with the free water.

The centrifugal dehydrator 4 is provided with a bowl 42 consisting of a cylindrical portion and a conical tubular portion connected to one end in a cylindrical casing 41, and the cylindrical portion 43 is provided inside the bowl 42.
An inner cylinder 43 composed of 1 and an inner cone 432 connected to one end of the inner cylinder 43 is housed, and a hole 433 is formed in a peripheral wall of the inner cylinder 43. The cylindrical portion 431 and the inner cone 4
Screws 44 are respectively provided on the outer peripheral surface of 32, and the pitch of the screw 44 on the outer peripheral surface of the cylindrical portion 431 is gradually reduced toward the inner cone 432 (as it goes to the right in the drawing), The bowl 42 and the screw 44 are rotated concentrically and independently of each other. The bowl 42 and the screw 44 generate a differential speed according to the properties of the concentrated sludge supplied here. A detector is provided for detecting this differential speed and these torques (this detector is not shown). The concentrated sludge is supplied to the inside of the inner cylinder 43, and then sent from the hole 433 to the gap between the inner peripheral surface of the bowl 42 and the outer peripheral surface of the inner cylinder 43. After being dehydrated, the separated water is discharged from the separated water discharge hole 45,
On the other hand, the dehydrated cake is discharged from the dehydrated cake discharge hole 46. Part of the free water from the granulation concentrating tank 2 and the separated water from each of the filter concentrator 3 and the centrifugal dehydrator 4 are sent to the sewage treatment facility for treatment.

Comparative Example Conventionally, sludge was supplied to a granulation thickening tank with a constant supply amount regardless of fluctuations in the solid concentration, and when the solid concentration of the supplied sludge fluctuated, granulation was performed. When the solids concentration of sludge is kept constant, the amount of granulated sludge produced fluctuates greatly, and since the filter type concentrator is not used, the amount of granulated sludge supplied to the centrifugal dehydrator also changes with this fluctuation. It fluctuated greatly and the operation in the centrifugal dehydrator became unstable, making stable operation management virtually impossible. That is, when the original sludge having a solid concentration varying from 0.6 to 1.5% by weight is constantly supplied at 100 m ³ / hr, the amount of granulated sludge in the above conventional operation is
It fluctuated greatly within the range of ^{30 to} 75 m ³ / hr, and the stable operation of the centrifugal dehydrator could not be performed.

Example 1 The primary coagulation sludge was fed to the granulation thickener so that the solids concentration was constant, and the solids concentration of the granulated sludge was fed from the granulation thickener. It was controlled so that it would fall within a certain range following the solids concentration of the next coagulated sludge. That is, 100 m ³ / hr of raw sludge was supplied in the same manner as in Comparative Example. However, the solid concentration of this raw sludge is 1% by weight, so the supplied solid amount is 1000 kg / hr. The solids concentration of the primary coagulation sludge supplied to the granulation thickener is 0.6 to 1.5.
The concentration of solids in the discharged sludge was controlled to 2 to 3% by weight when it fluctuated within the range of% by weight (raw sludge supply amount was equivalent to 67 to 167 m ³ / hr). The amount of granulated sludge discharged is
It was 33 to 50 m ³ / hr, and the solid content was almost constant at 1000 kg / hr. By further controlling the concentration with a filter type concentrator, the solid concentration of the concentrated sludge is controlled to 3% by weight,
Concentrated sludge with a solid content of 3% by weight was obtained at a constant rate of 33 m ³ / hr. In this way, the concentrated sludge with a fixed solids concentration is supplied to the centrifugal dehydrator at an almost constant speed, so the centrifugal dehydrator is controlled by the existing constant torque control and separated water SS (sludge solids). The stable operation of the centrifugal dehydrator becomes possible by the constant water content control such as the differential speed control of the centrifugal dehydrator by monitoring the object). Moreover, the sludge condensing / dehydrating apparatus of the present invention is always stably maintained in the optimum operating state by the series of these controls.

Example 2 In Example 1, when the primary flocculation sludge supply amount fluctuates excessively and it becomes difficult to control the granulation thickener, the fluctuation range of the primary flocculation sludge supply amount, etc. Will need to be reduced. In such a case, set the constant control range of the solids of the primary coagulation sludge to 800 to 1000kg / hr, and reduce the amount of solids when the solids concentration of the supplied primary coagulation sludge becomes low. By controlling so that the supply amount of primary coagulation sludge is 67 to 133 m ³ / hr and the amount of granulated sludge produced is 33 to 40
m ³ / hr, and when the amount of concentrated sludge produced is controlled to 30 m ³ / hr with a filter type concentrator, the solid concentration is 2.7 to 3.
In the range of 3% by weight, the fluctuation range can be suppressed to such a small extent that the stable operation control of the centrifugal dehydrator is not hindered, and as a result, similar to Example 1, the centrifugal dehydrator is stable and good. Operation control has become possible. In each of Examples 1 and 2, even if the amount of raw sludge supplied and / or the concentration of solids greatly fluctuated, it was possible to stably concentrate and dehydrate such sludge by granulation and concentration. This is because a filter type concentrator was installed between the tank and the centrifugal dehydrator.

Example 3 There is an operating method which is a further development of the operating method in each of Example 1 and Example 2. That is, Example 1
In each of Example 2 and Example 2, since the supply amount of the concentrated sludge supplied to the centrifugal dehydrator and the solid amount thereof can be made substantially constant, the change in the processing capacity of the centrifugal dehydrator is caused only by the properties of the original sludge. Will be affected. When only the solid concentration of the raw sludge fluctuates and there is substantially no qualitative change, the operating conditions such as the differential speed of the centrifugal dehydrator and the torque of the screw and the bowl are substantially the same.
Therefore, in the control operation, the large fluctuation of the differential speed and / or the torque is an indication that there is a qualitative change in the raw sludge. That is, when the differential speed stabilizes at an abnormally large value or when the torque stabilizes at an abnormally small value, it is a sign that the raw sludge qualitatively changed and became defective in coagulation. It is necessary to increase the amount of amphoteric polymer flocculant used in the grain concentrator. If the above operating conditions are reversed, the centrifugal dehydrator operation will still be successful even if the amount of amphoteric polymer flocculant used is reduced, so reduce the amount of amphoteric polymer flocculant used. Is possible. However, in this case, it is necessary to determine in advance the minimum amount of the amphoteric polymer flocculant used for stable operation of the granulation concentrating tank.

In each of the above-mentioned embodiments, in any operation method, a feature is that a filter type concentrator is arranged between the granulation concentration tank and the centrifugal dehydrator, and these are sequentially connected in sequence. It has been shown that the sludge treatment time is short, the control response is good, the function of the device is improved, and the optimum operation can be stably maintained by the above operation method.

[0030]

According to the present invention, each device is connected to each other in series with or without a pump, and the sewage sludge is continuously supplied to the device to continuously operate the device. By doing so, it is possible to efficiently concentrate sewage sludge at a low cost and obtain a dehydrated cake with a low water content even if no other equipment is used. The conservation value is extremely high.

[Brief description of drawings]

FIG. 1 is a flow sheet showing the principle of the sludge concentrating and dehydrating apparatus of the present invention.

FIG. 2 is a partially cutaway perspective view of a typical granulation concentration tank used in the present invention.

FIG. 3 is a vertical cross section of a typical centrifugal dehydrator used in the present invention.

[Explanation of symbols]

 1 Conditioning tank 11 Tank body 12 Stirrer 13 Raw sludge supply hole 14 Inorganic flocculant supply hole 2 Granulation thickener 21 Tank body 22 Stirrer 23 Upper stirring blade 24 Lower stirring blade 25 Screen 26 Sludge feeding hole 27 Polymer flocculant supply Hole 28 Free water discharge hole 29 Granulation sludge discharge hole 3 Filter type concentrator 31 Tank 32 Wire screen 33 Concentrated sludge discharge hole 34 Separation water discharge hole 4 Centrifugal dehydrator 41 Casing 42 Bowl 43 Inner cylinder 431 Cylindrical part 432 Inner cone 433 hole 44 Screw 45 Separation water discharge hole 46 Dewatered cake discharge hole 5 Raw sludge storage tank

 ─────────────────────────────────────────────────── ─── Continuation of front page (71) Applicant 000001063 Kurita Kogyo Co., Ltd. 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo (71) Applicant 591162022 Tomoe Kogyo Co., Ltd. 3-9-2 Nihonbashi, Chuo-ku, Tokyo (72) Inventor Tsutomu Yasuda 6-29-7 Mizukino, Moriya-cho, Kitasoma-gun, Ibaraki (72) Inventor Kosaburo Akamatsu 2-6-2 Otemachi, Chiyoda-ku, Tokyo Tokyo Sewer Service Co., Ltd. (72) Invention Katsunori Nishida 2-17-15 Tsukushima, Chuo-ku, Tokyo Tsukishima Machinery Co., Ltd. (72) Inventor Yasuhiko Watanabe 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Inventor, Yano Taira Industrial Co., Ltd. 3-9-2 Nihonbashi, Chuo-ku, Tokyo (Daini Maruzen Building)

Claims (6)

[Claims] 1. A primary flocculation sludge containing primary flocculates obtained by mixing raw sludge from a sewage treatment facility with an inorganic flocculant to primarily flocculate ionic components and solids in the raw sludge. A mixing tank, the primary coagulation sludge introduced from the conditioning tank, and the amphoteric polymer coagulant are mixed with stirring to coagulate the primary coagulation and uncoagulated solid matter in the primary coagulation sludge. , A granulation thickening tank for granulating sludge into granulated sludge, and separating and concentrating the granulated sludge into free water, a filter type concentrator for concentrating the granulated sludge, and concentration with the filter type concentrator A sludge concentrating and dewatering device, characterized in that a centrifugal dehydrator for further dewatering the concentrated sludge thus formed is successively connected. 2. A primary coagulation sludge containing primary coagulation by mixing raw sludge generated from a sewage treatment facility with an inorganic coagulant to primarily condense ionic components and solids in the raw sludge. The primary coagulation sludge and the amphoteric polymer flocculant are mixed with stirring to agglomerate and granulate the primary agglomerates and unaggregated solid matter in the primary agglomerate sludge Granulating sludge, a granulating and concentrating step of separating the granulating sludge and free water, a concentrating step of concentrating the granulating sludge obtained in the granulating and concentrating step with a filter type concentrator into a concentrated sludge, and the concentrating step. A method for concentrating and dewatering sludge, which comprises sequentially dewatering sludge with a centrifugal dewatering machine to form a dehydrated cake and suppressing destruction of the granulated sludge as much as possible. 3. A primary flocculation sludge in which the total amount of primary flocculates and non-flocculated solids in the primary flocculation sludge is controlled to be substantially constant is supplied to a granulation concentration step, and The sludge concentration / dehydration method according to claim 2, wherein the granulated sludge having a substantially constant substance concentration is supplied from the granulation concentration step to the concentration step. 4. The primary agglomerated sludge in which the total amount of the primary agglomerates and the non-agglomerated solids in the primary agglomerated sludge is controlled within a predetermined range is supplied to the granulation concentration step, and the solid concentration is increased. The granulated sludge kept substantially constant is supplied from the granulation concentrating step to the concentrating step, and in the concentrating step, the granulated sludge is concentrated so that the solids concentration or the concentrating flow rate is substantially constant. The concentrated sludge dewatering method according to claim 2, wherein the concentrated sludge is supplied to the dehydration step. 5. The primary agglomerated sludge in which the total amount of the primary agglomerates in the primary agglomerated sludge and the unaggregated solids is controlled within a predetermined range is supplied to the granulation concentration step, and the solids concentration is increased. The granulated sludge kept substantially constant is supplied from the granulation concentrating step to the concentrating step, and in the concentrating step, the granulated sludge is concentrated so that the solids concentration or the concentrating flow rate is substantially constant. The sludge concentration / dehydration method according to claim 2, wherein the concentrated sludge is supplied to the dehydration step, and the concentrated sludge is dehydrated in the dehydration step to obtain a dehydrated cake having a substantially constant cake water content. 6. The primary agglomerated sludge in which the total amount of the primary agglomerates and the unaggregated solids in the primary agglomerated sludge is controlled within a predetermined range is supplied to the granulation concentration step, and the solid concentration is increased. The granulated sludge kept substantially constant is supplied from the granulation concentrating step to the concentrating step, and in the concentrating step, the granulated sludge is concentrated so that the solids concentration or the concentrating flow rate is substantially constant. The concentrated sludge is supplied to the dehydration step, and the concentrated sludge is dehydrated in the dehydration step to form a dehydrated cake having a substantially constant cake water content,
The sludge concentrating and dewatering method according to claim 2, wherein the amount of the amphoteric polymer flocculant used in the granulating and concentrating step is adjusted in response to a change in the differential speed or torque of the centrifugal dehydrator in the dewatering step.