JP2012139628A - System and method for sludge treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and a method for sludge treatment that can unify a sludge conditioning step and sludge dehydrating step by efficiently combining therewith, make the whole facilities of the sludge treatment compact, reliably perform dehydrating conditioned sludge while suppressing use of the flocculant, and reduce the volume of dehydrated sludge more efficiently, in sludge treatment conditioning the sludge by injecting the flocculant so that the sludge is in a suitable state for dehydrating, and dehydrating the conditioned sludge by a centrifugal dehydrator.SOLUTION: The sludge treatment system includes: a sludge conditioner 1 for conditioning the sludge in which a polymeric flocculant is injected; a centrifugal dehydrator 2 for separating the conditioned sludge into dehydrated sludge and dehydrated and separated liquid; and a conditioned sludge supply pipe 3 for supplying the conditioned sludge to the centrifugal dehydrator 2.

Description

  The present invention relates to a treatment system and method for sludge generated in a water treatment facility (excess sludge, digested sludge, etc.), and after the sludge has been conditioned, the conditioned sludge is efficiently dehydrated.

  A large amount of sludge having a water content of 99 to 99.5% is generated in the water treatment facility, but it takes enormous energy and cost to treat and dispose of the sludge. Therefore, the volume is reduced by sludge treatment mainly for concentration and dehydration, and the reduced sludge is effectively used, carried out, landfilled, and dried and incinerated.

Concentration of sludge is roughly divided into gravity concentration and mechanical concentration. In gravity concentration, sludge stays in the tank for a certain period of time to settle and concentrate sludge having a specific gravity higher than that of water. The sedimentation efficiency of sludge affects the concentration efficiency. Mechanical concentration is a mechanical concentration method such as centrifugal concentration, atmospheric pressure flotation concentration, or belt-type filtration concentration. If necessary, flocculant is mixed with sludge and concentrated.
The concentrated sludge is subjected to a digestion treatment with microorganisms for the purpose of decomposing and stabilizing organic matter in the sludge or dehydrated as it is. Sludge dehydration includes a filtration method and a centrifugal separation method, and a flocculant is usually used for sludge dewatering and mechanical concentration.

  As described above, since the normal sludge is subjected to the concentration treatment in the sludge concentration facility and then subjected to the dewatering treatment separately in the sludge dewatering facility, the entire sludge treatment facility is large. Also, if it takes time until the concentrated sludge is dehydrated or if stirring is insufficient, the sludge may be altered, and the concentrated sludge may be denatured (anaerobic, spoilage, sludge floc dismantling, etc.). In the dehydration process, the operation was finely adjusted (sludge supply amount, coagulant injection amount, etc.) according to the degree of alteration.

  In addition, in the case of screw-type sludge dewatering machines such as screw type and belt type, depending on the amount of solids to be treated (that is, a small amount of high-concentration sludge can be treated in large quantities if low-concentration sludge), the machine specifications are However, in the case of a centrifugal sludge dehydrator, machine specifications are determined according to the amount of water to be treated (sludge supply amount) (that is, regardless of the sludge concentration level).

  Therefore, when dewatering using a centrifugal sludge dewatering machine (centrifugal dewatering machine), supplying high-concentration sludge is more efficient and energy-saving, but the properties of the supplied sludge vary. However, it is difficult to always supply high-concentration sludge to the centrifugal dehydrator. Therefore, it is assumed that a large amount of sludge is processed at a low concentration, and the machine-specific centrifugal dehydrator can process a large amount of water (sludge supply amount). Was selected.

  On the other hand, as the coagulant used for mechanical concentration and dehydration, an organic polymer coagulant is generally used, and an organic coagulant and an inorganic coagulant are selectively used according to the concentration / dehydration process. This is because by selecting a flocculant suitable for the properties of raw sludge and concentrated sludge and adjusting the amount of injection, stable concentration and dehydration can be achieved, and the flocculant used can be saved.

  Regarding an appropriate injection method for the flocculant, for example, in Patent Document 1, an inorganic flocculant and an intramolecular amphoteric polymer flocculant (amphoteric polymer) are injected in combination with organic sludge, and this is injected in a granulation concentration tank. In the method of dehydrating after concentration, the site where the amphoteric polymer flocculant is dispensed in the central part of the granulation concentration tank or the separation water is separated in order to reduce the amount of the polymer flocculant injected in the conventional method. And even when the sludge once granulated collapses while it stays in the granulation concentration tank for a long time by dispensing 10-20% with respect to the total amphoteric polymer flocculant injection amount. A technique has been disclosed in which re-granulation occurs and the operating condition of the dehydrator is improved along with a decrease in the separated water SS.

  In Patent Document 2, a coagulation concentration treatment step in which a polymer flocculant is injected into the sludge for agglomeration treatment and then a concentration treatment, and agglomeration concentration sludge from the agglomeration concentration treatment step is dehydrated by a dehydrator and dehydrated. In the sludge treatment method having a dewatering treatment step for separating sludge and dewatered separation liquid, the polymer flocculant remaining in the dewatering separation liquid is returned to the coagulation concentration treatment step by returning the dewatering separation liquid to the coagulation concentration treatment step. A technique for stabilizing the concentration process while reducing the amount of polymer flocculant to be reused and newly injected is disclosed.

Japanese Patent No. 3509169 (paragraph [0008]) Japanese Patent Laying-Open No. 2006-35166 (paragraph [0009])

  Conventionally, the sludge concentration facility and the sludge dewatering facility are often provided separately and independently, so that the entire sludge treatment facility becomes large, the construction cost is high, and a large installation area is required. In addition, the operation and maintenance became complicated, and the operation costs such as labor costs and coagulant cost increased, which hindered efficient sludge treatment.

  Particularly in the gravity concentration technology, due to the recent deterioration of sludge sedimentation, the concentration of concentrated sludge has been lowered, and the efficiency of dehydration following the latter stage has been deteriorated.

  Furthermore, by providing the sludge concentration facility and the sludge dewatering facility separately, the concentrated sludge is once stored in a sludge storage tank, etc., and then dewatered. Changes in quality (anaerobic, decay, sludge floc dismantling), adversely affecting dehydration treatment (increase in dehydrated sludge moisture content, deterioration in SS recovery rate, deterioration in water quality of dehydrated separation liquid, deterioration in dewatering performance and coagulation Increase in the amount of agent used).

  In addition, agitation equipment is provided to stir the stored sludge so that the concentrated sludge (stored sludge) stored in the sludge storage tank does not rot, and the sludge concentration is uniform. If the agglomeration flocs contained in the stored sludge are subdivided (disassembled), the flocculant must be sufficiently injected again during the dehydration process to regenerate the agglomeration flocs. This led to an increase in the amount used (floating agent cost).

  When dewatering using a centrifugal dehydrator, it is more efficient to dewater high-concentration sludge. However, because the properties of sludge vary depending on various factors, a large amount of sludge is treated at a low concentration in the facility plan. Therefore, it is necessary to select a centrifugal dehydrator with mechanical specifications that can handle a large amount of water (sludge supply amount). For this reason, not only will the equipment cost increase, but the sludge dewatering equipment has become quite large when spare machines are deployed.

  In addition, in order to perform efficient and stable dehydration treatment, it is conceivable to provide a large sludge storage tank so that the sludge can always be homogenized, but as described above, dewatering such as sludge decay and agglomeration of flocs by agitation As a result, the processing will be hindered.

  In the sludge dewatering process, it is necessary to properly inject the flocculant into the sludge in order to fully extract the dewatering performance of the centrifugal dehydrator and perform efficient dewatering. Since it changes depending on the properties of the sludge, the injection amount must be appropriately controlled in accordance with the properties of the sludge that changes over time, and the operation operation has become very complicated.

  Even if an appropriate flocculant is selected, the flocculant may not always be properly injected into sludge, etc.If the amount of flocculant injected is insufficient, it may be used for concentration treatment or dehydration treatment. Not only can the volume of sludge be reduced sufficiently, but the water quality of the concentrated and dehydrated separation liquid deteriorates, leading to an increase in the pollution load on the subsequent wastewater treatment facility. Conversely, if the amount of flocculant injected is excessive, it may affect the concentration process and dehydration process, and unreacted flocculant components may remain in the concentrated and dehydrated separation liquids. (SS recovery rate) itself deteriorates, and as a result, the water quality of the separated liquid deteriorates.

  Furthermore, even if the amount of the flocculant injected into the sludge is appropriate, if the sludge and the flocculant are mixed sufficiently and reliably and do not react (flocculate), the concentration performance and dewatering performance will deteriorate. In particular, high-concentration sludge that can be efficiently centrifugally dehydrated is difficult to mix quickly with the flocculant, and if the sludge and flocculant are mixed quickly and efficiently to form an aggregate floc, sufficient dewatering is possible. Unable to get performance.

  In the dehydration process (two-component method) in which high-concentration sludge is dehydrated using a combination of an inorganic flocculant and a polymer flocculant, if the sludge and the flocculant do not react reliably, strong flocs cannot be formed and separated. Not only does the performance deteriorate and the SS concentration of the separation liquid increases (SS recovery rate deteriorates), but the phosphorus contained in the sludge at a high concentration reacts with the inorganic flocculant to become an insoluble salt and is taken into the dewatered sludge. Instead of being removed, the liquid is transferred to the separation liquid and discharged. As a result, the separation liquid having poor water quality is returned to the waste water treatment facility to increase the pollution load.

  Therefore, the amount of inorganic flocculant and polymer flocculant injected into high-concentration sludge is increased or the amount of sludge treated is reduced to improve the water quality of the separation liquid (improvement of SS recovery rate and reduction of phosphorus concentration). ), But this will hinder efficient and stable sludge treatment (reducing water content of dehydrated sludge, shortening operating time, reducing operating costs such as coagulant and electricity costs). End up.

  The present invention has been made to solve the above-described problems, and injects a flocculant into sludge and tempers it into a state suitable for centrifugal dehydration (coagulation floc formation, moisture removal, volume reduction, concentration, etc.) In the sludge treatment that dehydrates this tempered sludge with a centrifugal dehydrator, the sludge tempering process and the sludge dewatering process are efficiently combined and unified to reduce the size of the entire sludge treatment facility and to use a flocculant. An object of the present invention is to provide a sludge treatment system and a sludge treatment method capable of reducing the volume of dehydrated sludge by reliably dewatering conditioned sludge while suppressing the above-mentioned.

  The sludge treatment system according to the present invention includes a sludge refining machine for injecting a polymer flocculant into the sludge and refining, a centrifugal dehydrator for separating the reconditioned sludge into dehydrated sludge and a dehydrated separation liquid, and the centrifugal dewatering A conditioned sludge supply pipe for supplying the conditioned sludge to the machine.

  The sludge treatment system according to the present invention includes an inorganic flocculant injection pipe for injecting an inorganic flocculant into conditioned sludge.

  A centrifugal dehydrator used in the present invention includes an outer body bowl and an inner body screw, and includes a taper injection tube that extends inside the inner body screw and injects an inorganic flocculant into a tapered portion of the outer body bowl. It is a thing.

  The inorganic flocculant used in the present invention is a high specific gravity inorganic flocculant having a high iron content.

  The sludge treatment system according to the present invention includes an oxidation-reduction potentiometer that measures the oxidation-reduction potential of a dehydration separation liquid, and injection of an inorganic flocculant, injection of a polymer flocculant, and centrifugal dehydration based on the measured value of the oxidation-reduction potentiometer It is equipped with a controller that controls one or more of the machine operations.

  In the sludge treatment method according to the present invention, a polymer flocculant is injected into the sludge, the sludge into which the polymer flocculant is injected is tempered with a sludge tempering machine, and the inorganic flocculant is injected into the conditioned sludge. The tempered sludge injected with the inorganic flocculant is supplied to a centrifugal dehydrator for dehydration.

According to the sludge treatment system according to the present invention, the sludge refining machine for conditioning the sludge suitable for centrifugal dewatering, the centrifugal dehydrator for centrifugally dewatering the conditioned sludge, and supplying the conditioned sludge to the centrifugal dehydrator By providing the sludge supply pipe, the following excellent effects can be obtained.
(1) Since the sludge is dehydrated immediately after tempering, the dehydration process can be completed by injecting the polymer flocculant during tempering.
(2) Since the sludge to be dewatered is reduced in volume (high concentration) due to sludge refining, it can be efficiently dewatered with a centrifugal dehydrator.
(3) Since the sludge can be dewatered immediately after it has been tempered, it is possible to prevent alteration of the tempered sludge (anaerobic, decay, disintegration of coagulated flocs, etc.) caused by long-term storage, and an increase in the moisture content of the dewatered sludge in the dewatering process Further, adverse effects such as deterioration of SS recovery rate and deterioration of water quality of the dehydrated separation liquid can be prevented.
(4) Since the alteration of the tempered sludge can be suppressed, it is possible to avoid excessive injection of the flocculant, which has been performed as a countermeasure to the conventional alteration, and to reduce the amount of the flocculant used.
(5) For model selection at the time of facility planning, we can propose a more compact model of centrifugal dehydrator, and further package the sludge tempering machine and centrifuge to further improve the overall sludge treatment facility. It can be made compact.

  According to the sludge treatment system according to the present invention, the means for injecting and mixing the inorganic flocculant into the tempered sludge can be reliably mixed with the tempered sludge and the inorganic flocculant, so that the flocculant is mixed. Even when sludge having a property that is difficult to perform is supplied, agglomerated floc suitable for dehydration can be obtained efficiently. As a result, the dewatered sludge and dehydrated separation liquid in the centrifugal dehydrator are of good quality and stabilized.

  According to the sludge treatment system of the present invention, the inorganic flocculant is directly injected into the sludge that has been dewatered to some extent by providing the taper injection pipe for injecting the inorganic flocculant into the tapered portion of the outer bowl of the centrifugal dehydrator. In addition, since it is possible to reliably mix the sludge in the centrifugal dehydrator by the conveying force and the centrifugal force, a high-quality dehydrated sludge can be efficiently obtained with a relatively small amount of the inorganic flocculant. This not only prevents excessive use of the inorganic flocculant, but also reduces the volume of sludge by refining and downsizing the centrifugal dehydrator, and the sludge storage tank that was installed outside the centrifugal dehydrator In addition, the sludge and flocculant mixing equipment can be omitted, and the sludge treatment facility can be saved in space, which is effective in reducing the operating cost and equipment cost and the equipment installation area.

  According to the sludge treatment system according to the present invention, the oxidation-reduction potentiometer for measuring the oxidation-reduction potential of the dehydrated separation liquid discharged from the centrifugal dehydrator, and various coagulants for the conditioned sludge based on the measured values of the oxidation-reduction potentiometer It is necessary to constantly monitor the fluctuation state of the dehydration separation liquid and change the injection amount of the inorganic flocculant and the operation of the centrifugal dehydrator. Therefore, stable sludge dewatering can be achieved because appropriate control is performed.

  In the sludge treatment system according to the present invention, by using a high specific gravity inorganic flocculant having a high iron content as the inorganic flocculant, a dehydration performance equivalent to or higher than that of the conventional inorganic flocculant can be stably obtained with a relatively small injection rate. In addition, the amount of flocculant used in the entire sludge treatment system can be reduced.

  According to the sludge treatment method of the present invention, the polymer flocculant is injected into the sludge and conditioned by the sludge tempering machine, and the inorganic flocculant is injected into the conditioned sludge and dehydrated by the centrifugal dehydrator. As a whole, it is possible to achieve a harmonious treatment, eliminating the need for tempered sludge storage tanks and agitation equipment during storage, reducing the size of the equipment, integrating the equipment, and centralizing operation management. In order to immediately dewater sludge, it is possible to avoid excessive injection (re-injection) of flocculant due to alteration of tempered sludge (anaerobic, decay, dismantling of flocs flocs, etc.) and reduce the amount of flocculant injected. It is possible to obtain an excellent effect that can reduce the cost and the operating cost.

<Embodiment 1>
FIG. 1 is a schematic configuration diagram of a sludge treatment system according to Embodiment 1 of the present invention.
The sludge treatment system according to the present invention includes a sludge refining machine 1A for refining sludge injected with a polymer flocculant into sludge (refined sludge) containing stable flocs at a high concentration and dewatered sludge. The basic structure is provided with a centrifugal dehydrator 2 that separates into a dehydrated separation liquid and a tempered sludge supply pipe 3 that supplies the conditioned sludge to the centrifugal dehydrator 2.

  The sludge refining machine 1A is a belt-type filtration, refining the sludge into which the polymer flocculant has been injected and separating it into a refining sludge and a refining separation liquid, and to rotate the endless belt 1a. It is schematically constituted by a pair of rotating rollers 1b, 1c and a drive mechanism (not shown) for rotating these rotating rollers 1b, 1c. This sludge refining machine 1A is configured such that sludge is supplied through the sludge supply pipe 4, and the polymer flocculant is supplied to the sludge in the sludge supply pipe 4 through the polymer flocculant injection pipe 5. It is configured as follows. The polymer flocculant injection pipe 5 is provided with a polymer flocculant injection pump 6 for injecting the polymer flocculant into the sludge supply pipe 4 and an on-off valve 6a for adjusting the injection of the polymer flocculant. The sludge refining machine 1A is limited to a filtration method such as an atmospheric pressure flotation method as long as it is a mechanism capable of refining sludge injected with a polymer flocculant and separating it into a conditioned sludge and a tempered separation liquid. It is not a thing.

  The sludge supplied to the sludge refining machine 1A is sludge / digested sludge generated from water treatment, has a high moisture content, and if dewatered as it is, the overall efficiency of the sludge treatment is poor and the scale of the entire facility increases. At the same time, inconveniences such as excessive use of energy and chemicals are likely to occur.

  For this reason, sludge is supplied to the sludge tempering machine 1A and tempered. In tempering, a polymer flocculant is injected into the sludge, and due to the aggregating action of the polymer flocculant, solids of the sludge are surely agglomerated, and a strong flocculation floc having higher separability is generated in the sludge. Such sludge can be solid-liquid separated efficiently and reliably by the sludge tempering machine 1A. As the polymer flocculant, for example, amphoteric polymer flocculants, cationic polymer flocculants, anionic polymer flocculants, nonionic polymer flocculants and the like can be used.

  The amount of solids (SS content) in the supplied sludge is usually in the range of about 0.5 to 2.0% per sludge weight. When sludge concentration is intended, the polymer flocculant is based on the amount of solids. It is possible to obtain concentrated sludge by adding so that the injection rate is about 0.2 to 0.4% by weight. In normal sludge treatment, this concentrated sludge is once stored and dehydrated, but while it is being stored, agglomeration flocs are dismantled due to agitation and rot, or aggregation inhibiting components (organic acids, etc.) are eluted from the septic sludge. It will be in the state which exerts a bad influence on dehydration processing. For this reason, before dewatering, it is necessary to inject a polymer flocculant of 0.5 to 2.0% per solid content of the concentrated sludge, and depending on the elution status of the aggregation-inhibiting component, to form an aggregation floc again. It was. However, in the present invention where refining is the purpose, the injection rate of the polymer flocculant is about 0.5 to 2.0% by weight with respect to the amount of solids, which is higher than when sludge concentration is intended. In this way, the tempered sludge that is tempered after being injected with the flocculant and subjected to dehydration is stable in the high concentration of floc floc and kept in a state suitable for dehydration. Since no injection is required and dehydration can be carried out as it is with a centrifuge, the amount of the polymer flocculant injected can be reduced as a whole sludge treatment. That is, the dehydration process can be completed with only the polymer flocculant used for tempering.

Next, the operation will be described.
First, a polymer flocculant is injected into the sludge (line injection), and the sludge (aggregated sludge) generated by the flocculent action of the polymer flocculant is supplied to the endless belt 1a of the sludge refining machine 1A, and moisture Then, the conditioned sludge containing the high-concentration and stable flocs with reduced volume is supplied to the centrifugal dehydrator 2 through the conditioned sludge supply pipe 3 and dehydrated. Separated into dehydrated sludge and dehydrated separation liquid with low water content, each is discharged out of the machine.

  According to Embodiment 1 of the present invention, a polymer flocculant is injected and mixed in sludge having a high water content, and after the flocs are formed in the sludge, the sludge is subjected to centrifugal dehydration in the sludge refining machine 1A. Is separated into a tempered sludge and a tempered separation liquid containing a high concentration and a stable coagulated floc in a state suitable for the sewage, and the tempered sludge is directly supplied to the centrifugal dehydrator 2 through the tempered sludge supply pipe 3. Thus, it can be separated into dehydrated sludge and dehydrated separation liquid having a low water content.

  According to Embodiment 1 of the present invention, the injection rate of the polymer flocculant injected into the sludge is set to about 0.5 to 2.0% by weight with respect to the amount of solids in the sludge. In the sludge refining machine 1A, the sludge refining machine 1A is used for concentration, which is necessary when a concentration step is provided by obtaining a refining sludge containing a high concentration and stable agglomerated floc suitable for centrifugal dehydration. The amount of the polymer flocculant used can be reduced. Moreover, the processing performance of the existing centrifugal dehydrator is improved by reducing the volume of sludge by refining. Alternatively, a smaller centrifugal dehydrator can be proposed at the facility planning stage.

  According to Embodiment 1 of the present invention, the sludge is made into a conditioned sludge containing a high concentration and stable flocculated floc suitable for centrifugal dewatering by the sludge refining machine 1A. Can be separated into dehydrated sludge and dehydrated separation liquid, and the entire facility becomes compact without the need for a storage facility. It is not necessary to use a flocculant higher than the normal injection rate required in connection with the adverse effects on sludge dehydration due to the dismantling of the flocculant flocs and the elution of the aggregation inhibitory components (organic acid etc.).

  According to Embodiment 1 of the present invention, the tempered sludge is subjected to rapid dehydration, so that the septic components and phosphorus elution of the conditioned sludge itself generated by anaerobic when the tempered sludge is stored are stored. It is possible to prevent the quality of the dehydrated separation liquid from deteriorating (increase in contaminants mainly organic acids and phosphorus).

<Embodiment 2>
2 is a schematic configuration diagram of a sludge treatment system according to Embodiment 2 of the present invention. The same components as those in FIG.

  In the sludge treatment system according to the second embodiment, the sludge refining machine 1A, the centrifugal dehydrator 2, and the refining sludge supply pipe 3 are packaged by being installed in one package box 7. In addition to supplying sludge and polymer flocculant, the inorganic flocculant can be injected into the sludge refining machine 1 and the inorganic flocculant can be injected into the tempered sludge supply pipe 3 in the package box 7. This is different from the first embodiment in that it is configured as described above.

  The package box 7 is configured such that its bottom can be fixed on a machine foundation on which the sludge treatment system is integrated. A sludge supply tank 8 is disposed outside the package box 7. A rotary blade 9 is provided in the sludge supply tank 8, and the sludge is stirred by this rotary blade 9, and it is possible to prevent local accumulation in the tank of sludge and anaerobic generation caused thereby. is there. Further, a sludge supply pipe 10 extending from the sludge supply tank 8 to the sludge tempering machine 1A in the package box 7 is provided, and a sludge supply pump 11 is provided in the sludge supply pipe 10. Sludge may be supplied by connecting the sludge supply pipe 10 to, for example, an excess sludge extraction pipe or a sludge return pipe from the final sedimentation basin.

  Further, a polymer flocculant tank 12 containing a polymer flocculant is disposed outside the package box 7, and a polymer flocculant injection pipe extending from the polymer flocculant tank 12 to the sludge supply pipe 10. 5 is provided.

  Further, an inorganic flocculant tank 13 for accommodating the inorganic flocculant is disposed outside the package box 7. An inorganic flocculant injection pipe 14 extends from the inorganic flocculant tank 13 into the package box 7, and the inorganic flocculant injection pipe 15 is provided with an inorganic flocculant injection pump 15. The inorganic flocculant injection pipe 14 is for injecting an inorganic flocculant into the conditioned sludge supply pipe 3 disposed in the package box 7 (line injection), and also in the sludge tempering machine 1A. The in-machine injection pipe 14a for injecting the liquid and the pre-injection pipe 14b for injecting the inorganic flocculant into the sludge supply pipe 10 are branched. The inorganic flocculant injection pipe 14, the in-machine injection pipe 14a, and the front injection pipe 14b are provided with an on-off valve 15a, an on-off valve 15b, and an on-off valve 15c for adjusting the injection of the inorganic flocculant.

  As the inorganic flocculant accommodated in the inorganic flocculant tank 13, for example, polyferric ferric sulfate (polyiron), polyaluminum chloride (PAC), polyaluminum sulfate (sulfuric acid band) and the like can be used. By injecting such an inorganic flocculant into the sludge, the sludge can be reliably agglomerated and a highly segregated floc can be generated, and it reacts with soluble pollutants (phosphorus, etc.) contained in the sludge. Insoluble salts can be removed.

  In addition, in the sludge treatment using a flocculant, the type of flocculant, the injection rate, and the place and order of injection are set by trial and error according to the properties of the sludge supplied and the state of the treatment. This setting is performed by experimental verification before the sludge treatment system according to the second embodiment is operated. For this reason, in the sludge treatment system shown in FIG. 2, the inorganic flocculant injection pipe 14 for injecting the inorganic flocculant is provided as described above so that the setting can be executed, and the tempered sludge supply pipe 3 is also provided at the injection position. Is an in-machine injection pipe 14a having the sludge tempering machine 1 as an injection position, and a pre-injection pipe 14b having the sludge supply pipe 10 as an injection position.

Next, the operation will be described.
First, various conditions such as the type of polymer flocculant and inorganic flocculant, the injection rate, and the injection location are set based on the properties of the sludge in the sludge supply tank 8 and the like. Based on this setting, the polymer flocculant is injected into the sludge in the sludge supply pipe 10 through the polymer flocculant injection pipe 5 (line injection) and mixed. If it is appropriate for the sludge conditioning to inject the inorganic flocculant into the sludge before the injection of the polymer flocculant, the inorganic flocculant is injected through the pre-injection pipe 14b branched from the inorganic flocculant injection pipe 14. Is done. In this way, agglomerated sludge is formed.
Next, the coagulated sludge supplied into the sludge tempering machine 1A through the sludge supply pipe 10 is tempered by the sludge tempering machine 1A and separated into the tempered sludge and the tempered separation liquid. When it is appropriate for the sludge treatment to inject the inorganic flocculant into the sludge being tempered, the inorganic flocculant is injected through the in-machine injection pipe 14 a branched from the inorganic flocculant injection pipe 14.
Next, this conditioned sludge supplied into the centrifugal dehydrator 2 through the conditioned sludge supply pipe 3 is dehydrated by the centrifugal dehydrator 2 and separated into a dehydrated sludge having a low water content and a dehydrated separation liquid. Is done. When it is appropriate for the sludge treatment to inject the inorganic flocculant into the conditioned sludge before the dehydration treatment, the inorganic flocculant is injected through the inorganic flocculant injection pipe 14.

  In addition, the inorganic flocculant is injected based on the above setting or based on the state of subsequent sludge treatment, one or more of the inorganic flocculant injection pipe 14, the in-machine injection pipe 14a, and the front injection pipe 14b. May be appropriately selected and used.

  According to the second embodiment of the present invention, as in the first embodiment, the polymer flocculant is injected into the sludge having a high water content and mixed to form the agglomerated sludge. The machine 1A separates the conditioned sludge suitable for dehydration and the tempered separation liquid, and supplies the conditioned sludge to the centrifugal dehydrator 2 through the conditioned sludge supply pipe 3, thereby dehydrating with a low water content. It can be efficiently separated into sludge and dehydrated separation liquid.

  According to the second embodiment of the present invention, the inorganic flocculant injection pipe 14, the in-machine injection pipe 14a, and the front injection pipe 14b are arranged, so that the properties of the supplied sludge vary, and the inorganic flocculant is injected. Even when it is necessary for sludge conditioning, the inorganic flocculant can be injected at an appropriate injection position.

  According to Embodiment 2 of the present invention, after injecting an inorganic flocculant through the pre-injection tube 14b to agglomerate soluble contaminant components (such as phosphorus) in the sludge to produce relatively fine agglomerated flocs, By injecting the polymer flocculant through the polymer flocculant injection tube 5, it is possible to further agglomerate the relatively fine aggregated floc together with the solid matter in the sludge to obtain a stable aggregated floc. As a result, the soluble pollutant component is taken into and discharged from the dewatered sludge without flowing out and refluxing together with the dehydrated separation liquid, and the effect of preventing deterioration of the water quality of the conditioned and dehydrated separation liquid is obtained.

<Embodiment 3>
FIG. 3 (A) is a schematic configuration diagram of a sludge treatment system according to Embodiment 3 of the present invention, and FIG. 3 (B) shows the opening at the tip of the tapered injection tube shown in FIG. 3 (A) and its surroundings. It is sectional drawing which expands and shows. The same components as those in FIG.

  The sludge treatment system according to Embodiment 3 is provided with a taper injection pipe 16 for injecting an inorganic flocculant into a tapered portion of an outer shell bowl (described later) in the centrifugal dehydrator 2 as an inorganic flocculant injection pipe. This is different from the first embodiment in that a water supply pipe 17 is connected to the taper injection pipe 16, and a water supply pump 18 and an on-off valve 18a for adjusting the water supply are provided in the water supply pipe 17.

  The centrifugal dehydrator 2 according to Embodiment 3 is rotatably disposed in a casing 20 having a dehydrated separation liquid discharge port 2a on one end side and a dewatered sludge discharge port 2b on the other end side. An outer body bowl 21, an inner body screw 22 rotatably disposed in the outer body bowl 21, a rotary drive machine 23 that rotationally drives the outer body bowl 21 and the inner body screw 22, and the outer body bowl 21 And a back drive motor 24 that gives a rotational difference between the inner body screw 22 and the inner body screw 22. A pool (concentration / dehydration zone) 25 is formed between the outer body bowl 21 and the inner body screw 22. Yes.

  The tempered sludge supply pipe 3 extends to the inside of the sludge supply chamber 26 in the inner cylinder screw 22, and the tip thereof is a discharge hole 3a. In the tempered sludge supply pipe 3, a taper injection pipe 16 is disposed, and the discharge hole 16a at the tip thereof is from the peripheral wall portion of the tempered sludge supply pipe 3 slightly upstream of the discharge hole 3a. The inner cylinder screw 22 opens toward the inner cylinder taper portion 22a. A two-step tapered portion 21a of the outer trunk bowl 21 is formed outside the inner trunk tapered portion 22a. In Embodiment 3, the taper portion of the outer body bowl is a two-step taper portion, but the present invention is not limited to this and may be a one-step taper portion.

  Further, the sludge supply chamber 26 is provided with a sludge supply port 26a for supplying conditioned sludge supplied from the discharge hole 3a of the conditioned sludge supply pipe 3 to the pool 25, an inner trunk taper portion 22a, and a taper. The flocculant outlet 26b for allowing the inorganic flocculant injected from the discharge hole 16a of the injection pipe 16 to flow into the pool 25 and the inner cylinder taper portion 22a in the vicinity of the flocculant outlet 26b are provided, and the sludge supply port 26a. And a flocculant outlet 26b are provided with a partition plate 26c.

  The inorganic flocculant is preferably an aqueous solution of an inorganic flocculant having a high iron content and a high specific gravity (hereinafter referred to as “high specific gravity inorganic flocculant”). As this high specific gravity inorganic flocculant, that whose specific gravity is 1.45 to 1.75 and whose iron content (iron concentration in terms of T-Fe (total Fe)) is 12.0% to 16.0% is preferable. As a component, polyferric sulfate ([Fe2 (OH) n (SO4) 3-n / 2] m) is particularly effective, but it is an iron-based high specific gravity inorganic flocculant and has the above properties. If the effect equivalent to ferrous iron is obtained, it will not restrict to this. Such a high specific gravity inorganic flocculant having a specific gravity and iron content can be more efficiently mixed (permeated) into sludge than a normal inorganic flocculant, particularly by the centrifugal effect of a centrifugal dehydrator.

  The high specific gravity inorganic flocculant can be efficiently mixed (penetrated) into the sludge by a mixing method other than mixing (penetration) by the centrifugal effect of the centrifugal dehydrator 2. In the sludge treatment system according to Embodiment 2 shown in FIG. 2, sludge or flocculant can be obtained by injecting the high specific gravity inorganic flocculant from the inorganic flocculant injection pipe 14, the in-machine injection pipe 14a, and the front injection pipe 14b. Since it can be efficiently mixed (penetrated) with the conditioned sludge, the sludge treatment system can be maintained in a good state by appropriately injecting a high specific gravity inorganic flocculant depending on the properties of the supplied sludge.

  The water supply by the water supply pipe 17 and the water supply pump 18 efficiently and surely dilutes the high specific gravity inorganic flocculant as described above in the taper injection pipe 16 to the conditioned sludge by the two-stage taper portion 21a to which a large centrifugal force is applied. The high specific gravity inorganic flocculant increased by dilution can be injected quickly and over a wide range, and when the centrifugal dehydrator 2 is shut down, water is supplied to the taper injection pipe 16 so that the taper injection pipe 16 and the discharge hole are discharged. 16a, the flocculant outlet 26b, and the like are capable of reliably washing the portion where the high specific gravity inorganic flocculant that easily adheres and solidifies comes into contact, and can prevent clogging or blockage by the high specific gravity inorganic flocculant. It is what.

Next, the operation will be described.
First, a polymer flocculant is injected into the sludge, and the sludge (flocculated sludge) generated by the flocculant action of the polymer flocculant is supplied to the endless belt 1a of the sludge tempering machine 1A, and moisture is eliminated and reduced. Next, the sewage sludge containing flocculated high concentration and stable flocs (refined sludge) is supplied to the sludge supply chamber 26 from the opening 3a of the conditioned sludge supply pipe 3 and is also inorganic. The flocculant flows out from the taper injection pipe 16 through the flocculant outlet 26b of the inner barrel taper portion 22a to the taper portion of the outer barrel bowl 21 to which a large centrifugal force is applied. Is quickly injected (tapered injection) into tempered sludge (separated sludge) that has undergone solid-liquid separation to some extent during the transition to the dewatered sludge discharge side. In addition, a water supply pipe 17 is connected to the taper injection pipe 16, and if necessary, water is supplied from the water supply pipe 17 to the taper injection pipe 16 to dilute the inorganic flocculant and dilute the inorganic flocculant (diluted). Liquid) can be quickly and widely injected into the separated sludge.

The conditioned sludge into which the inorganic flocculant or the diluent has been injected is dehydrated by the centrifugal dehydrator 2, separated into a dehydrated sludge having a low water content and a dehydrated separation liquid, and each is discharged to the outside. .
When the centrifugal dehydrator 2 is shut down, water is supplied to the taper injection tube 16 so that the portion where the inorganic flocculant that tends to adhere and solidify, such as the discharge hole 16a of the taper injection tube 16 is reliably washed. The

  According to Embodiment 3 of the present invention, the polymer flocculant is injected into and mixed with the sludge having a high water content, and then the sludge is supplied to the sludge refining machine 1A, thereby being in a state suitable for dewatering. It can be separated into a tempered sludge and a tempered separation liquid containing coagulated floc that is stable at a high concentration.

  According to the third embodiment, the taper injection tube 16 has been tempered in a state in which it is difficult to mix the drug because the solid matter concentration has been increased to a certain degree by being dehydrated to the vicinity of the tapered portion 21a of the outer body bowl 21. Since the inorganic flocculant can be added directly to the sludge (separated sludge), even a small amount of inorganic flocculant can be reliably mixed by the conveying force and centrifugal force of the sludge near the taper portion. . Separation sludge and inorganic flocculant are quickly mixed and reacted to promote efficient and stable solid-liquid separation (separation of the separation liquid) of the separated sludge, resulting in a dehydrated sludge having a lower water content than before. it can.

  According to the third embodiment of the present invention, the taper injection pipe 16 for injecting the inorganic flocculant into the taper portion 21a of the outer body bowl 21 of the centrifugal dehydrator 2 is provided, so that the inorganic material is directly added to the sludge that has been dehydrated to some extent. Since it is possible to inject the flocculant and to mix it reliably by the force of conveying the sludge in the centrifugal dehydrator 2 and the centrifugal force, it is possible to efficiently produce a good quality dehydrated sludge with a relatively small amount of inorganic flocculant. Obtainable. Therefore, not only the excessive use of the inorganic flocculant is suppressed, but the installation space for the sludge and flocculant mixer installed outside the centrifugal dehydrator is also eliminated, so that the space of the facility can be saved and the operating cost can be reduced. It is effective in reducing equipment costs and equipment installation area.

  According to Embodiment 3 of the present invention, by using a high specific gravity inorganic flocculant having a high iron content as the inorganic flocculant, dehydration performance equivalent to or higher than that of the conventional inorganic flocculant is stable with a relatively small injection rate. As a result, the amount of the flocculant used in the entire sludge treatment system can be reduced.

According to Embodiment 3 of the present invention, by providing the water supply pipe 17 for supplying water to the taper injection pipe 16, the high specific gravity inorganic flocculant can be diluted efficiently and reliably in the taper injection pipe 16, and a large centrifugal effect can be obtained. With such a two-step tapered portion 21a, the high specific gravity inorganic flocculant increased by dilution to the separated sludge can be quickly and widely injected. As a result, the solid-liquid separation of the separated sludge further progresses, and the dehydrated separated liquid is separated efficiently and reliably from the separated sludge in spite of the operation at the end of the dehydration process (injection of high specific gravity inorganic flocculant). In addition, dehydrated sludge having a lower water content can be obtained, and in addition, the inorganic flocculant can be efficiently injected, so that the amount of use can be suppressed.
In addition, by diluting and increasing the high specific gravity inorganic flocculant in advance with water supply, the high specific gravity inorganic flocculant can be smoothly and evenly injected into the separated sludge via the flocculant outlet 26b. The separated sludge and the high specific gravity inorganic flocculant can be reacted quickly, and the water content of the dewatered sludge can be reduced more efficiently and reliably.
Furthermore, since the high specific gravity inorganic flocculant can be diluted with water supply, a high concentration high specific gravity inorganic flocculant stock solution can be used, and the high specific gravity inorganic flocculant tank and the high specific gravity inorganic flocculant injection pump can be downsized. Effective in reducing equipment costs and installation area.

Example 1.
Table 1 compares the physical properties of a high specific gravity inorganic flocculant with high iron content (iron-based high specific gravity inorganic flocculant) with other inorganic flocculants (4 types).

  As understood from Table 1, the iron-based high specific gravity inorganic flocculant has a high specific gravity of 1.45 or more and an iron content (iron concentration in terms of T-Fe) is a high value of 12.0% or more.

  In a comparative experiment of dehydration performance, which will be described later, as an iron-based high specific gravity inorganic flocculant, polysulfuric acid 2 with a specific gravity of 1.50 to 1.60 and an iron content (iron concentration in terms of T-Fe) of 12.5% to 14.5% Iron ([Fe2 (OH) n (SO4) 3-n / 2] m) was used.

  A comparative experiment was performed in the sludge treatment system according to the third embodiment. The results are shown in Table 2.

  In this comparative experiment, digested sludge (sludge concentration: 1.52-1.70%) from a sewage treatment plant was used, and a different type of inorganic flocculant (5 types: normal iron-based, The dewatering performance was investigated in combination with low specific gravity iron-based, high specific gravity iron-based, aluminum chloride-based and aluminum sulfate-based inorganic flocculants.

The operating conditions of the sludge refining machine and centrifugal dehydrator other than the type and addition rate of the inorganic flocculant are almost constant (Polymer flocculant injection rate: 1.41-1.58% TS, centrifugal effect: 2000G, differential speed: 1.2 ˜2.0 min ⁻¹ ).

As can be seen from Table 2, by taper-injecting a high specific gravity iron-based inorganic flocculant (polyferric sulfate), the SS concentration of the separation liquid shows a stable and low value. Solids could be recovered (solids recovery rate: 99.7% or more). Furthermore, the power consumption was 1.12 to 1.16 kWh / m ³ , and energy saving effects and greenhouse gas emission reduction effects equivalent to or better than other inorganic flocculants were obtained.

  In particular, the moisture content of dewatered sludge, which is important for dewatering performance, is shown in FIG. In FIG. 7 (comparison of dehydrated sludge moisture content relative to inorganic flocculant injection rate), the result of normal iron-based inorganic flocculant is shown by ■ (black square), and high specific gravity iron-based inorganic flocculent used in the present invention. The result of the agent is ● (black circle), the result of low specific gravity iron-based inorganic flocculant is ▲ (black triangle), the result of polyaluminum chloride-based (PAC) inorganic flocculant is ○ (white circle), polyaluminum sulfate The result of the system (sulfuric acid band) inorganic flocculant is indicated by Δ (white triangle).

  As understood from FIG. 7, when the high specific gravity iron-based inorganic flocculant is taper-injected, the water content of the dewatered sludge is clearly lower than that of other inorganic flocculants. In the inorganic flocculant injection rate (35% / TS), which is the operating condition of the dehydrating sludge, the moisture content of the dewatered sludge is in the 66% range, and the water content of 70% or less, which is the current target, can be easily achieved. And very good dewatering performance.

  Furthermore, when the injection rate of inorganic flocculant (47.5% / TS) is higher than normal operating conditions, the moisture content of dewatered sludge can be in the 61% range, and other flocculants and other sludge We were able to demonstrate very good dewatering performance that did not allow the processing equipment to follow.

  In this way, the polymer flocculant is injected into the sludge and the sludge is tempered, and the high specific gravity iron-based inorganic flocculant is taper-injected and centrifuged to stabilize efficiently without excessive injection of the flocculant. As a result, the moisture content of the dewatered sludge can be reduced, which is very effective for reducing the volume of the sludge and facilitates the subsequent disposal of the dewatered sludge, resulting in good SS recovery and power consumption. Together with this, it is extremely efficient and energy-saving, and can fully contribute to the reduction of greenhouse gases.

<Embodiment 4>
FIG. 4 is a schematic configuration diagram of a sludge treatment system according to Embodiment 4 of the present invention. The same components as those in FIG.

  The sludge treatment system according to Embodiment 4 is provided with an ORP meter 27 that measures the oxidation-reduction potential (ORP) of the dehydrated separation liquid and a controller 28 that controls injection of each flocculant based on the ORP value. Different from the third embodiment.

  More specifically, in the fourth embodiment, the deterioration of the water quality of the dehydrated separation liquid can be detected based on the ORP value of the dehydrated separation liquid measured by the ORP meter 27, and when the deterioration is detected, the processing of the centrifugal dehydrator 2 is performed. It can be judged that the situation (operating state) is bad, and in order to improve the treatment state (operating state) of the centrifugal dehydrator 2, the controller 28 injects the inorganic flocculant, the polymer flocculant, and the centrifugal dehydrator 2 It is configured to control one or more of the operations.

  The ORP meter 27 includes an ORP measurement tank 27a that stores the dehydrated separation liquid discharged from the dehydrated separation liquid discharge port 2a, a stirring blade 27b provided in the ORP measurement tank 27a, and a dehydration separation in the ORP measurement tank 27a. A measurement electrode 27c for measuring the ORP of the liquid is provided. The ORP meter 27 and the controller 28 are electrically connected so that a measurement signal of the ORP value of the dehydrated separation liquid measured by the ORP meter 27 is sent to the controller 28. The flow of the measurement signal input from the ORP meter 27 to the controller 28 is indicated by a one-dot chain line in FIG.

  The ORP value of the dehydrated / separated liquid is measured by receiving the dehydrated / separated liquid discharged from the dehydrated / separated liquid discharge port 2a in an ORP measurement tank 27a including the measurement electrode 27c. By storing and mixing the dehydrated separation liquid at one end in the ORP measurement tank 27a, the buffering action works, and the fluctuation of the ORP value becomes gentle, so that the control is stabilized. Furthermore, even when the centrifugal dehydrator 2 is stopped for a long time, the measurement electrode 27c is immersed in the dehydrated separation liquid in the ORP measurement tank 27a, so that deterioration of the measurement electrode 27c due to drying can be prevented. When the ORP value of the dehydrated separation liquid can be stabilized by a buffering action or when there is no need to worry about deterioration due to drying of the measurement electrode 27c, the ORP measurement tank 27a may not be provided.

  The controller 28 is electrically connected to the polymer flocculant injection pump 6, the inorganic flocculant injection pump 15, the rotary drive machine 23, and the back drive motor 24, respectively, and based on the ORP value from the ORP meter 27, The injection of the polymer flocculant from the polymer flocculant injection pipe 5, the injection of the inorganic flocculant from the taper injection pipe 16, the drive of the rotary drive 23, and the drive (differential speed) of the back drive motor 24 are appropriately controlled. It is configured as follows. The flow of control commands output from the controller 28 to the polymer flocculant injection pump 6, the inorganic flocculant injection pump 15, the rotary drive machine 23, and the back drive motor 24 is indicated by a two-dot chain line in FIG. Yes. Note that the controller 28 may directly control the devices or may perform inverter control. When the controller 28 controls the injection of the polymer flocculant and the inorganic flocculant, in addition to controlling the flocculant injection pumps 6 and 15, the on-off valves 6 a and 15 a may be controlled.

Here, the oxidation-reduction potential (ORP) will be described.
ORP is a numerical value (unit: mV) representing a redox state in water. It becomes a positive value in the oxidation state and a negative value in the reduction state.

  Oxidizing substances present in water include dissolved oxygen and trivalent iron ions, while reducing substances present in water include divalent iron ions, sulfides, and organic substances. ORP in water is Depending on the balance of the amount of these substances, it may be positive or negative.

  When the ORP value of the dehydrated separation liquid flowing out from the centrifugal dehydrator 2 is a negative value, it indicates that the reducing substance contains more reducing substances than the oxidizing substances (reduced state). This means that the water quality of the dehydrated separation liquid has deteriorated (the concentration of SS, which is an organic substance, has increased).

  Conversely, when the ORP value of the dehydrated separation liquid is a positive value, it indicates that the dehydrated separation liquid contains more oxidizing substance than the reducing substance (oxidized state), that is, in the dehydrated separation liquid. This means that the SS, which is a reducing substance, is small and the water quality of the dehydrated separation liquid is good (the concentration of SS, which is an organic substance, is reduced = the SS recovery rate is good).

  Based on this action, when the ORP value is on the negative side, it is possible to determine that the water quality of the dehydrated separation liquid is poor and the processing status (operating state) of the centrifugal dehydrator 2 is not appropriate, and conversely, when the ORP value is on the positive side. Therefore, it is possible to judge that the water quality of the dehydration separation liquid is good and the processing state (operation state) of the centrifugal dehydrator 2 is appropriate.

  In the measurement of ORP, a measurement electrode 27c (a reference electrode having a predetermined oxidation-reduction potential, which is an inactive metal electrode in a solution containing an oxidation-reduction substance, such as a standard hydrogen electrode or a silver-silver chloride electrode, is available. ) Is used to determine the ORP of the solution based on the potential difference caused by the insertion of a), but is not limited to this, and the ORP meter can stably and reliably measure the ORP value of the dehydrated separation liquid If so, it may be used.

Next, the operation will be described.
First, in the same manner as in the third embodiment, the tempered sludge into which the inorganic flocculant or its diluent has been injected is dehydrated by the centrifugal dehydrator 2 and separated into the dehydrated sludge and the dehydrated separation liquid.
Next, the ORP of the dehydrated separation liquid is measured by the ORP meter 27, and the ORP value is sent to the controller 28. If the ORP value is on the positive side (except when the flocculant is injected excessively and the moisture content of the dewatered sludge does not decrease so much and the ORP value is very high: eg +80 mV or more), the water quality of the dehydrated separation liquid is good. Therefore, it is judged that solid-liquid separation (sludge dewatering treatment) of conditioned sludge is performed efficiently and satisfactorily.

  Thus, when solid-liquid separation of conditioned sludge is performed well, the moisture content of dehydrated sludge is low, and the SS recovery rate is high (= dehydrated separation liquid SS concentration is low), the polymer flocculant injection pump 6 The driving of the inorganic flocculant injection pump 15, the rotary drive machine 23 and the back drive motor 24 is controlled by the controller 28 so as to maintain the state.

  However, if the ORP value is on the minus side, it is determined that the water quality of the dewatered separation liquid has deteriorated, and the solid-liquid separation (sludge dewatering treatment) of the conditioned sludge has not been performed properly. In such a situation, the moisture content of the dewatered sludge is not low, and the SS recovery rate is low (= the concentration of the dewatered separation liquid SS is high), so that the solid-liquid separation (sludge dewatering treatment) of the conditioned sludge is efficiently and satisfactorily performed. The controller 28 controls the driving of the polymer flocculant injection pump 6, the inorganic flocculant injection pump 15, the rotary drive machine 23 and the back drive motor 24 so as to make the operation state of the centrifugal dehydrator 2 appropriate. .

  In particular, by controlling the polymer flocculant injection pump 6, the solid-liquid separation performance of the conditioned sludge is rapidly changed, and the solid-liquid separation (sludge dewatering treatment) of the conditioned sludge is improved. For example, when the ORP value is on the negative side (−40 mV to −10 mV), the controller 28 accelerates the driving of the polymer flocculant injection pump 6 and increases the injection amount of the polymer flocculant. In addition, the control of accelerating the driving of the inorganic flocculant injection pump 15 and increasing the injection amount of the inorganic flocculant can obtain an immediate effect.

  By such control, the sludge treatment system (tempering and solid-liquid separation) can be properly managed, the ORP value of the dehydrated separation liquid is measured, and the operating elements of the centrifugal dehydrator 2 are determined based on this ORP value. Controlling is a simple and effective means for judging and grasping the state (tempering / separation state, operating state) of the sludge treatment system (tempering and solid-liquid separation), and efficient and stable sludge. Contributes to the operation of the processing system.

  The ORP value of the dehydrated separation liquid flowing out from the centrifugal dehydrator 2 is generally in the range of ± 100 mV. When the SS recovery rate is high and the SS concentration of the dehydration separation liquid is low, the ORP value of the dehydration separation liquid is approximately −5 mV to +40 mV, the SS recovery rate is low, and the SS concentration of the dehydration separation liquid is high. In some cases, the ORP value of the dehydrated separation is approximately -70 mV to ± 0 mV.

  The ORP value is not constant and varies depending on the properties of the sludge and the separation liquid, the characteristics of the ORP meter 27, the environment, the measurement conditions, and the like. Therefore, when controlling the operation elements of the centrifugal dehydrator 2 based on the ORP value, it is necessary to set a suitable control range of the ORP value in advance (it is not good because it is negative and cannot be determined good because it is positive).

  Further, even if the ORP value is positive (for example, +65 mV) and the SS recovery rate is good, the polymer flocculant or the like is injected more than necessary, or the outer shell bowl 21 and the inner shell screw 22 are overfilled. If the rotation difference (differential speed) is larger than necessary, the moisture content of the dewatered sludge increases, and the centrifugal dehydrator 2 may not be in an appropriate operating state. Since there exists a suitable control range over the lower limit, it is necessary to set in advance as described above.

  In the sludge treatment system according to the fourth embodiment, when the ORP value of the dehydrated separation liquid measured by the ORP meter 27 is negative (for example, −20 mV), the rotational speed of the centrifugal dehydrator 2 (rotary drive machine 23) Controlling the rotation difference (back drive motor 24) between the outer shell bowl 21 and the inner shell screw 23 to perform stable and efficient sludge dewatering treatment (low water content of dewatered sludge and high SS recovery rate) (See FIG. 8). In addition to the control of the centrifugal dehydrator 2, the controller 28 controls the driving of the polymer flocculant injection pump 6 and the inorganic flocculant injection pump 15 based on the ORP value of the dehydrated separation liquid. Accordingly, the drive of a tempered sludge supply pump (not shown) may be controlled to increase the injection amount of various flocculants or reduce the amount of conditioned sludge supplied (see FIG. 9).

  Control of various flocculant injection pumps is effective, but the differential speed (the difference in the rotational speed between the outer body bowl 21 and the inner body screw 22 rotating in the same direction causes the back drive motor 24 to rotate the inner body screw 22. Control is also effective, and when the ORP value is low (for example, −15 mV and the SS concentration of the dehydrated separation liquid is high), the differential recovery rate is increased to improve the SS recovery rate and the ORP value is high. (For example, at + 50mV, the SS concentration of the dewatered separation liquid is low but the water content of the dewatered sludge is not low). The operation can be easily controlled by reducing the differential speed and reducing the water content of the sludge. Separation performance can be demonstrated (maintained).

  According to Embodiment 4 of the present invention, the polymer flocculant is injected into and mixed with the sludge having a high water content, and then the sludge is supplied to the sludge refining machine 1A, thereby being in a state suitable for dewatering. It can be separated into tempered sludge and tempered separation liquid.

  According to Embodiment 4 of the present invention, the ORP of the dehydrated separation liquid from the centrifugal dehydrator 2 is measured by the ORP meter 27, and the operating condition of the centrifugal dehydrator 2 is judged (estimated) from the ORP value, From the determination result, the sludge treatment (solid-liquid separation) can be stably and appropriately performed by appropriately adjusting the injection of the flocculant, the supply amount of the sludge, and the operation of the centrifugal dehydrator 2.

Example 2
In the sludge treatment system according to the fourth embodiment, when the ORP value of the dehydrated separation liquid is −25 mV, the controller 28 controls the polymer flocculant injection pump 6 to control the injection amount of the polymer flocculant to 10%. Increased to some extent (1.0% / sludge SS → 1.1% / sludge SS).
As a result, the ORP value is +10 mV, the moisture content of the dewatered sludge is reduced by 3 points from 75% to 72%, and the SS recovery rate is improved by 5 points from 92% to 97%. Reduced water content and concentration of dehydrated separation liquid SS).

<Embodiment 5>
FIG. 5 is a schematic configuration diagram of a sludge treatment system according to Embodiment 5 of the present invention. The same components as those in FIGS.

  The sludge treatment system according to the fifth embodiment is different from the first and second embodiments in that a sludge refining machine, a polymer flocculant mixer, and an inorganic flocculant mixer are combined.

  More specifically, in the fifth embodiment, a polymer flocculant mixer 29 for mixing the polymer flocculant with sludge is provided in the sludge supply pipe 4, and the sludge tempering machine is replaced with the sludge tempering machine 1. 30 and an inorganic flocculant mixer 31 for mixing the inorganic flocculant with the conditioned sludge from the sludge refining machine 30 is provided.

  The sludge refining machine 1B includes a water tank 1d, a cylindrical rotating body 1f provided in the water tank 1d in a vertical direction, and a plurality of strip-shaped separation blades 1e disposed on the circumferential surface with a gap between the water tank 1d and the cylinder. A center well 1g that is provided in the upper center of the cylindrical rotating body 1f and receives sludge mixed with a polymer flocculant, and a drive unit (not shown) that rotates the cylindrical rotating body 1f at a low speed. ing. In FIG. 5, a cylindrical rotating body 1f has a plurality of strip-like separation blades 1e arranged with gaps. For example, a cylindrical rotating body made of punching metal having a plurality of holes opened at intervals. If it is a cylindrical rotating body having a structure having a plurality of gaps on the peripheral surface, the present invention is not limited to these.

  The inorganic flocculant mixer 31 includes a mixer main body 31a that contains the inorganic flocculant in the tempered sludge, and a stirring blade 31b that stirs and mixes the tempered sludge and the inorganic flocculant in the mixer main body 31a. Yes. The conditioned sludge supply pipe 3 is provided with a conditioned sludge supply pump 32.

Next, the operation will be described.
First, the sludge is mixed with the polymer flocculant in the polymer flocculant mixer 29 to form a floc floc, and the sludge formed by the floc floc rotates from the center well 1g of the sludge refining machine 1B into a cylindrical shape. It is supplied to the inside of the body 1f and separated into a tempered sludge and a tempered separation liquid. That is, even if the aggregation floc is rotated by the cylindrical rotating body 1f, the interval (slit) provided between the separation blades 1e of the cylindrical rotating body 1f is shaped so that the aggregation floc in the cylindrical rotating body 1f does not easily flow out. The floc flocs are set in the dimensions and do not go out of the cylindrical rotating body 1e, so that they are held in large quantities inside the cylindrical rotating body 1e and discharged from the lower part as conditioned sludge, and are fed to the inorganic flocculant mixer 31. Supplied. The polymer flocculant mixer 29 may be any mechanism that can reliably and stably mix sludge and polymer flocculant. Examples thereof include inorganic flocculant mixers 31, 34, 35, and 36 described later.
Next, the conditioned sludge is mixed with the inorganic flocculant in the inorganic flocculant mixer 31 by the stirring blade 31b, and then supplied into the centrifugal dehydrator 2 through the conditioned sludge supply pipe 3, and the centrifugal dehydrator. 2 is dehydrated and separated into a dehydrated sludge having a low water content and a dehydrated separation liquid.

  According to Embodiment 5 of the present invention, by providing the polymer flocculant mixer 29, the sludge to be supplied has a high mixing ratio of digester sludge, a high solid content, and the sludge supply pipe 4 has a high concentration. Even when the polymer flocculant is injected, the sludge and the polymer flocculant can be reliably mixed even in a situation where the sludge is not easily mixed, and the sludge refining in the sludge refining machine 1B can be performed stably. it can.

  According to Embodiment 5 of the present invention, by providing the sludge refining machine 1B, sludge can be retained in a large amount inside the cylindrical rotating body 1f as agglomerated flock, so that the conditioned sludge and the conditioned separation liquid can be efficiently used. And can be separated.

  According to Embodiment 5 of the present invention, by providing the inorganic flocculant mixer 31, even if the inorganic flocculant is injected into the conditioned sludge supply pipe 3, the conditioned sludge and the inorganic flocculant are not easily mixed. In this case, the tempered sludge can be reliably mixed with the inorganic flocculant, so that the tempered sludge can be brought into a state suitable for dehydration.

<Embodiment 6>
FIG. 6 (A) is a schematic configuration diagram of a sludge treatment system according to Embodiment 6 of the present invention, and FIGS. 6 (B) and 6 (C) show the inorganic flocculant mixing shown in FIG. 6 (A), respectively. It is sectional drawing which shows the other example of a container. The same components as those in FIG.

  The sludge treatment system according to the sixth embodiment is a combination of the sludge tempering machine having both functions of the sludge tempering machine and the polymer flocculant mixer according to the fifth embodiment and an inorganic flocculant mixer. Different from 5.

  More specifically, as shown in FIG. 6A, in the sixth embodiment, instead of the polymer flocculant mixer 29 and the sludge refining machine 1B of the fifth embodiment, the polymer flocculant is added to sludge. 1C, and the sludge refining machine 1C for refining the sludge is disposed, and instead of the sludge refining machine 1C, the inorganic flocculant mixer 31 of the fifth embodiment is used instead. In addition, an inorganic flocculant mixer 34 that mixes the inorganic flocculant with the conditioned sludge from the sludge refining machine 1C and conveys it to the centrifugal dehydrator 2 while continuing the mixing is provided. Yes.

  The sludge refining machine 1C differs from the sludge refining machine 1 of the first embodiment and the like in a cylindrical refining machine main body 1h that is installed inclined with respect to the horizontal direction, and in this refining machine main body 1h. A disc-shaped screen 1j that is fixed to the central shaft 1i and that allows moisture to pass without passing through solid components, and a rotating blade that rotates about the central shaft 1i so as to slide on the upper surface of the screen 1j 1k. The sludge refining machine 1C is connected to a sludge supply pipe 4 for supplying sludge onto the screen 1j in the refining machine body 1h, and a flocculant floc is generated by injecting a polymer flocculant into the sludge. A polymer flocculant injection tube 5 is connected.

  The inorganic flocculant mixer 34 includes a tempered sludge supply pipe 3 and a screw conveyor 34a disposed in the tempered sludge supply pipe 3. An inorganic flocculant injection pipe 14 for injecting an inorganic flocculant into the conditioned sludge is connected to the upstream side of the conditioned sludge supply pipe 3.

  In Embodiment 6, instead of the inorganic flocculant mixer 34 shown in FIG. 6 (A), for example, the inorganic flocculant mixer 35 shown in FIG. 6 (B) or the inorganic flocculant mixer shown in FIG. 6 (C). Other types of inorganic flocculant mixers, such as flocculant mixer 36, can be used as well.

  As shown in FIG. 6B, the inorganic flocculant mixer 35 includes a tempered sludge supply pipe 3 and one or more protrusions 35a formed on the inner wall of the tempered sludge supply pipe 3. ing. An inorganic flocculant injection pipe 14 for injecting an inorganic flocculant into the conditioned sludge is connected to the upstream side of the conditioned sludge supply pipe 3.

  As shown in FIG. 6C, the inorganic flocculant mixer 36 includes a tempered sludge supply pipe 3 and one or more bent portions 36a formed by folding the tempered sludge supply pipe 3. ing. An inorganic flocculant injection pipe 14 for injecting an inorganic flocculant into the conditioned sludge is connected to the upstream side of the conditioned sludge supply pipe 3.

  Each of the inorganic flocculant mixers 34, 35, and 36 shown in FIGS. 6A to 6C can be used alone, but is not limited thereto, and may be used in combination with each other. For example, the protrusion 35a of the inorganic flocculant mixer 35 is provided on the inner wall of the tempered sludge supply pipe 3 provided with the screw conveyor 34a or on the inner wall of the tempered sludge supply pipe 3 formed with the bent portion 36a, respectively. It may be provided. In addition, the inorganic flocculant mixers 34, 35, and 36 may be used in combination with the inorganic flocculant mixer 31 of the fifth embodiment or a mixer equipped with another mechanism as required.

Next, the operation will be described.
First, when sludge is supplied into the sludge refining machine 1C, the polymer flocculant is injected into the sludge on the screen 1j, and the sludge and the polymer flocculant are mixed by the rotation of the rotary blade 1k. Agglomerated flocs are formed on the surface. The aggregated floc is scraped up obliquely on the inclined screen 1j by the rotation of the rotary blade 1k, and the water in the sludge containing the aggregated floc is removed by passing through the screen 1j to obtain a tempered separation liquid. Discharged. Aggregated floc in the sludge remains on the screen 1j, and is further scraped up by the rotation of the rotary blade 1k, and is supplied to the inorganic flocculant mixer 34 as tempered sludge.
Next, the conditioned sludge is supplied into the centrifugal dehydrator 2 while being mixed with the inorganic flocculant in the conditioned sludge supply pipe 3 of the inorganic flocculant mixer 34 by the screw conveyor 34a. Is dehydrated and separated into a dehydrated sludge having a low water content and a dehydrated separation liquid.

  In addition, when supplying refining sludge to the inorganic flocculant mixer 35, the refining sludge flows in the recirculation physically repetitively by the protrusion 35a in the refining sludge supply pipe 3 of the inorganic flocculant mixer 35. Disturbance occurs and the opportunity to mix with the inorganic flocculant increases, so that it becomes easy to mix with the inorganic flocculant. The tempered sludge in such a mixed state is supplied into the centrifugal dehydrator 2 and dehydrated by the centrifugal dehydrator 2 to be separated into a dehydrated sludge having a low water content and a dehydrated separation liquid.

  Further, when supplying the conditioned sludge to the inorganic flocculant mixer 36, the conditioned sludge is physically recirculated by the bent portion 36a in the conditioned sludge supply pipe 3 of the inorganic flocculant mixer 36. Disturbance occurs and the opportunity to mix with the inorganic flocculant increases, so that it becomes easy to mix with the inorganic flocculant. The tempered sludge in such a mixed state is supplied into the centrifugal dehydrator 2 and dehydrated by the centrifugal dehydrator 2 to be separated into a dehydrated sludge having a low water content and a dehydrated separation liquid. In FIG. 6C, the straight body portion 36b is illustrated between the bent portions 36a, but the bent portion 36a may be formed in a zigzag or coil shape.

  According to Embodiment 6 of the present invention, by providing the sludge tempering machine 1C, the sludge and the polymer flocculant supplied to the sludge tempering machine 1C are disposed in the upper part of the screen 1j in the sludge tempering machine 1C. Since the mixing is ensured by the rotation of the rotary blade 1k, high-quality tempered sludge (the solid concentration is high, the aggregation is stable, etc.) is obtained. Further, such a high quality conditioned sludge has a high viscosity and it becomes difficult to mix the inorganic flocculant and transport it to the centrifugal dehydrator. Therefore, by providing the inorganic flocculant mixer 34, the conditioned sludge supply pipe is provided. Mixing with an inorganic flocculant during conveyance of the conditioned sludge according to 3 can reliably overcome the above-mentioned difficulties.

It is a schematic block diagram of the sludge processing system by Embodiment 1 of this invention. It is a schematic block diagram of the sludge processing system by Embodiment 2 of this invention. It is a schematic block diagram of the sludge processing system by Embodiment 3 of this invention. It is an expanded sectional view of the taper injection pipe part of FIG. 3 (A). It is a schematic block diagram of the sludge processing system by Embodiment 4 of this invention. It is a schematic block diagram of the sludge processing system by Embodiment 5 of this invention. It is a schematic block diagram of the sludge processing system by Embodiment 6 of this invention. The inorganic flocculant mixer used for the sludge treatment system by Embodiment 6 of this invention is sectional drawing of another inorganic flocculant mixer. The inorganic flocculant mixer used in the sludge treatment system according to Embodiment 6 of the present invention is a sectional view of still another inorganic flocculant mixer. It is a comparative experiment result in Example 1 of the present invention. In the case of using a centrifugal dehydrator, the moisture content of dewatered sludge (%) and SS recovery rate (%) when the differential speed between the outer body bowl and the inner body screw of the centrifugal dehydrator is controlled based on the ORP value. It is explanatory drawing which shows each change. In the case of using a centrifugal dehydrator, an explanation showing each change in dehydrated sludge moisture content (%) and SS recovery rate (%) when the injection amount (rate) of the polymer flocculant is controlled based on the ORP value. FIG.

1A sludge refining machine 1B sludge refining machine 1C sludge refining machine 1a endless belt 1b, 1c rotating roller 1d water tank 1e separating blade 1f cylindrical rotating body 1g center well 1h refining machine main body 1i central shaft 1j screen 1k rotating blade 2 Centrifugal dehydrator 2a Dehydrated separation liquid outlet 2b Dehydrated sludge outlet 3 Conditioned sludge supply pipe 3a Opening 4 Sludge supply pipe 5 Polymer flocculant injection pipe 6 Polymer flocculant injection pump 6a On-off valve 7 Package box 8 Sludge supply tank 9 Rotating blade 10 Sludge supply pipe 11 Sludge supply pump 12 Polymer flocculant tank 13 Inorganic flocculant tank 14 Inorganic flocculant injection pipe 14a In-machine injection pipe 14b Pre-injection pipe 15 Inorganic flocculant injection pumps 15a, 15b, 15c On-off valve 16 Taper injection pipe 16a Discharge hole 17 Water supply pipe 18 Water supply pump 18a On-off valve 20 Casing 21 Outer body bowl 21a Step taper part 22 Inner cylinder screw 22a Inner cylinder taper part 22b Screw blade 23 Rotation drive machine 24 Back drive motor 25 Pool 26 Sludge supply chamber 26a Sludge supply port 26b Coagulant outlet 26c Partition plate 27 ORP meter 27a ORP measurement tank 27b Stirring Blade 27c Measuring electrode 28 Controller 29 Polymer flocculant mixer 31 Inorganic flocculant mixer 31a Mixer body 31b Agitation blade 32 Conditioned sludge supply pump 34 Inorganic flocculant mixer 34a Screw conveyor 35 Inorganic flocculant mixer 35a Projection Part 36 inorganic flocculant mixer 36a bent part 36b straight body part

Claims (6)

A sludge tempering machine for injecting a polymer flocculant into the sludge
A centrifugal dehydrator for separating the conditioned sludge into dehydrated sludge and dehydrated separation liquid;
A sludge treatment system, comprising: a conditioned sludge supply pipe for supplying the conditioned sludge to the centrifugal dehydrator. The sludge treatment system according to claim 1, further comprising an inorganic flocculant injection pipe for injecting an inorganic flocculant into the conditioned sludge. The centrifugal dehydrator is
Having an outer body bowl and an inner body screw,
Stretching the inner body screw,
The sludge treatment system according to claim 1 or 2, further comprising a taper injection pipe for injecting an inorganic flocculant into the taper portion of the outer body bowl. The inorganic flocculant is
The sludge treatment system according to any one of claims 1 to 3, wherein the sludge treatment system is a high specific gravity inorganic flocculant having a high iron content. Based on the redox potential meter for measuring the redox potential of the dehydrated separation liquid and the measured value of the redox potential meter,
Among inorganic flocculant injection, polymer flocculant injection and centrifugal dehydrator operation,
A sludge treatment system according to any one of claims 1 to 4, further comprising: a controller that controls one or more of them. Injecting the polymer flocculant into the sludge,
Conditioning sludge injected with polymer flocculant with sludge tempering machine,
Injecting an inorganic flocculant into the conditioned sludge,
A sludge treatment method characterized in that conditioned sludge into which an inorganic flocculant has been injected is supplied to a centrifugal dehydrator for dehydration.

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