JP2017113671A - Method for treating water purification sludge and water purification sludge treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a water purification sludge high in dehydration efficiency and capable of preventing filter stain of a dehydration means, and provide a water purification sludge treatment device.SOLUTION: The water purification sludge treatment device 10 has an aggregate admixture means 30 for generating a floc, a concentration means 60 for concentrating sludge of floc, and a dehydration means 71 for dehydrating the concentrated sludge. Sludge concentration is conducted by adding poly(meth)acrylic acid salt to sludge in the concentration means 60. The poly(meth)acrylic acid salt has 0.1% salt viscosity of 2 to 5 mPa s, anion equivalent of -9.0 or less, and filter stain is prevented because sludge concentration is efficiently high and dehydration efficiency is enhanced as well as viscosity of concentrated sludge is low by using the poly (meth)acrylic acid salt.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for treating purified water sludge, and more particularly, to a method for treating purified water sludge with improved sludge concentration and dewatering efficiency, and a treatment apparatus therefor.

  Conventionally, in water purification treatment, an inorganic flocculant such as a sulfate band or polyaluminum chloride (PAC) is injected into water to be treated containing suspended solids (hereinafter also referred to as “raw water”), and suspended solids are taken in. The aggregated flocs are formed and the aggregated flocs are settled and separated in a sedimentation tank to remove suspended substances. The suspended solids that have been settled and separated become sludge (purified water sludge), which is withdrawn from the sedimentation tank and usually concentrated in a concentration tank, and then either sun-dried or mechanically dehydrated for disposal.

  When lake water or dam water is used as raw water, algae such as blue-green algae are generated at high temperatures, which may cause poor aggregation.

  The coagulation flocs at the time of coagulation failure also have poor sedimentation properties, and sludge generated is not sufficiently settled in the sedimentation tank, so that the generated sludge has a low concentration. For this reason, it cannot be concentrated to a satisfactory concentration even in a concentration tank, so it must be mechanically dehydrated at a low concentration.

  In particular, when the dehydrator is a filter press, there is a problem that the driving time is long, the dehydrated cake has a high moisture content, and the delamination of the dehydrated cake from the filter is deteriorated. There is also a problem that it takes time.

JP 7-308700 A JP-A-9-225208 JP 55-84505 A Japanese Patent Publication No. 34-612

  In the above-described conventional method for treating purified water sludge, in order to improve the concentration of purified water sludge, it has been studied to use a polyacrylamide-based anionic polymer flocculant in a concentration tank.

  According to this method, the concentration property of the sludge is certainly improved and a high concentration sludge can be obtained. However, the coagulated floc constituting the concentrated sludge becomes highly viscous, and when this concentrated sludge is dehydrated by a filter press, the peelability of the dewatered cake from the filter may be deteriorated.

  In Patent Document 1, sodium polyacrylate is added to the concentrated sludge generated from the water purification process. However, since the concentrated sludge is generally high in concentration, it is difficult to uniformly mix with the flocculant. An excess flocculant of the reaction may remain. Since the flocculant has adhesiveness, particularly when it is dehydrated with a filter press, the peelability of the dewatered cake from the filter cloth may be deteriorated.

  The present invention has been made in view of the above problems, and its purpose is to improve the peelability of a dehydrated cake when high-concentration concentrated sludge is dehydrated or dried, and to produce dry sludge with an appropriate moisture content. It is providing the processing method of the purified water sludge to be performed, and its processing apparatus.

  In order to solve the above problems, the water purification sludge treatment method of the present invention can be configured as follows.

  (1) A floc generating step of adding an inorganic flocculant to the water to be treated to generate a flocs floc, and adding a polymer flocculant to the sludge of the flocs floc separated from the water to be treated to concentrate the sludge A treatment method comprising a concentration step and a dehydration step for dewatering the concentrated sludge, wherein the polymer flocculant has a 0.1% salt viscosity of 2 to 5 mPa · s and an anion equivalent of −9.0. The following poly (meth) acrylates are used.

  (2) The polymer flocculant for sludge concentration preferably contains sodium polyacrylate, and more preferably contains sodium polyacrylate as a main component.

  (3) Mechanical dehydration is preferable in the sludge dehydration step, and filter press dehydration in which dewatering is performed using a filter is particularly preferable.

  Moreover, the purified water sludge treatment apparatus of this invention can be set as the following structures.

  (4) The treatment apparatus is an apparatus having a coagulation / mixing means, a coagulation floc generating means, a concentration means, and a dehydrating means, and the coagulation / mixing means rapidly agitate the water to be treated to which an inorganic flocculant has been added for coagulation. The flocs are generated, and the water to be treated is slowly stirred by the flocculant floc forming means to increase the flocculent flocs and form sludge. The concentration means mixes sludge of the floc floc separated from the water to be treated and the polymer flocculant to concentrate the sludge, and the dewatering means dehydrates the concentrated sludge. Here, the polymer flocculant used by the concentration means uses a poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and an anion equivalent of −9.0 or less. .

  (5) A preferable dehydrating means is a filter press type dehydrating means having a filter and removing moisture from the sludge through the filter by pressurization.

  According to the present invention, the concentration of purified water sludge is improved, and high-concentration sludge can be obtained. Addition of specific poly (meth) acrylate improves the peelability of concentrated sludge, prevents contamination of equipment and filters during mechanical dehydration, and provides a dehydrated cake with an appropriate water content it can.

It is a schematic diagram which shows an example of the purified water sludge processing apparatus of this invention. It is a flowchart explaining the purified water sludge processing method of this invention.

  Hereinafter, the present invention will be specifically described, but the present invention is not limited to a specific example.

  As shown in FIG. 2, the present invention includes a step of adding a flocculant to water to be treated (raw water) to generate a floc floc, and a sludge of floc floc obtained by ultra-solid-liquid separation. ) Having a step of adding acrylate and concentrating, and a step of dewatering the sludge after concentration.

  First, specific examples of the flocculant used in the floc generation process and the polymer flocculant used in the sludge concentration process will be described.

[Flocting flocculant]
The flocculant for generating flocs is not particularly limited, but generally an inorganic flocculant is used, and if necessary, it is used in combination with another flocculant (polymer flocculant, etc.).

  An inorganic flocculant is not specifically limited, The inorganic flocculant normally used for a water purification process can be used. Specifically, one or both of an iron-based flocculant and an aluminum-based flocculant can be used, and more specifically, a sulfuric acid band, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate. Any one or more selected from the group consisting of (polyiron), ferric chloride, and mixtures thereof can be used.

  For the purpose of promoting floc growth, one or more auxiliaries selected from a coagulant aid, a pH adjuster, a buffer agent, and a polymer coagulant are added together with or separately from the inorganic coagulant. May be. The polymer flocculant for floc growth is preferably added to the water to be treated after the inorganic flocculant is added and rapidly stirred.

  The polymer flocculant is not particularly limited, but various materials such as poly (meth) acrylate, polyacrylamide, polyacrylamide copolymer, polyacrylate ester, acrylate copolymer can be used. Preferably, the same poly (meth) acrylic salt as used for sludge concentration is used.

[Polymer coagulant for sludge concentration]
The polymer flocculant used for sludge concentration is particularly limited as long as it contains a poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and an anion equivalent of −9.0 or less. Although the content of the poly (meth) acrylate is at least 50% by mass, preferably at least 80% by mass, particularly preferably at least 99% by mass, the poly (meth) acrylate is substantially The thing consisting of is used.

  Here, the poly (meth) acrylate is not particularly limited. For example, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethacrylic acid, polysodium methacrylate, polypotassium methacrylate. Any one or more selected from the group consisting of polyammonium methacrylate can be used, and preferably sodium polyacrylate.

  The poly (meth) acrylate may be either a homopolymer or a copolymer, and preferably contains (meth) acrylic acid or a salt thereof, maleic acid or a salt thereof, vinylsulfonic acid or a salt thereof as a polymerized unit. Copolymer or homopolymer.

  Poly (meth) acrylates can be used alone or as a mixture. When using a mixture of poly (meth) acrylates, the 0.1% salt viscosity of the entire mixture is preferably 2 to 5 mPa · s, and the anion equivalent of the entire mixture is preferably −9.0 or less. .

  In addition, the salt viscosity measured the sample which melt | dissolved the poly (meth) acrylate in the sodium chloride aqueous solution of 1N so that the density | concentration might be 0.1 mass% on 25 degreeC conditions with a B-type viscosity meter. It is a value and the unit is mPa · s.

  When the 0.1% salt viscosity is less than 2, the aggregated floc does not grow sufficiently large, and improvement in sedimentation cannot be expected. On the other hand, if the 0.1% salt viscosity exceeds 5, peeling failure may occur during dehydration or the moisture content of the cake will increase. The anion equivalent of the poly (meth) acrylate is −9.0 or less, more preferably −11.0 to −9.0, and the anion equivalent is greater than −9.0 (that is, the anion equivalent is zero). When it is close to or becomes a positive value), a strong floc is not formed, and peeling failure occurs at the time of dehydration, or an increase in the moisture content of the cake is caused.

  The anion equivalent is a value that can be determined by the following measurement method, and the unit is meq / g. Prepare a 0.1% aqueous solution of poly (meth) acrylate, add 5 ml of methyl glycol chitosan solution (N / 200), add 2 to 3 drops of toidin blue indicator after stirring, and add polyvinyl potassium sulfate solution ( Titrate with PVSK, N / 400), and change the color and hold for 10 seconds or longer as the end point. A blank test is performed without adding a sample by the same operation, and an anion equivalent Av is calculated by the following formula.

Anion equivalent (Av) [meq / g] =
(Blank titration ml-Sample titration ml) x 1/2 x PVSK titer

  When using a mixture of poly (meth) acrylates, the anion equivalent value of the mixture may be measured directly, but the anion equivalent value (Av) [meq / g] of each poly (meth) acrylate is known. In the case of, the value obtained by multiplying the anion equivalent (Av) of the individual poly (meth) acrylate by the mass ratio of the poly (meth) acrylate to the whole mixture (individual mass / total mass) is added. The anion equivalent of the entire mixture.

  In general, a polymer flocculant having a colloid equivalent (meq / g) of -7 or less is highly anionic, and a polymer flocculant having a colloid equivalent of -2.8 or less and exceeding -7.0 is medium anionic. A polymer flocculant having a colloid equivalent of -0.7 or less and more than -2.8 is low anionic. The poly (meth) acrylate used in the present invention is characterized in that the anion equivalent is −0.9 or less, that is, the anionic property is higher among the high anionic flocculants.

  Next, the purified water sludge treatment apparatus of the present invention using this polymer flocculant and the purified water sludge treatment method of the present invention will be described.

[Purified water sludge treatment equipment]
The water purification sludge treatment apparatus of the present invention is not particularly limited, and any equipment can be used as long as it is a practical equipment. For example, a water purification facility having a cross-flow type precipitation facility and a water purification facility having a high-speed coagulation sedimentation facility can be mentioned. Either a slurry circulation type or a sludge / blanket type can be applied as the high-speed coagulating sedimentation equipment.

  A specific description will be given below with a water purification facility having a cross-flow type precipitation facility as an example.

  1 of FIG. 1 has shown an example of the purified water sludge processing apparatus, and this purified water sludge processing apparatus 10 is the aggregation mixing means 30 which aggregates a floc, and the aggregation floc formation means 40 which obtains sludge by increasing (growing) a floc. And a concentration means 60 for concentrating the separated floc sludge and a dewatering means 71 for the concentrated sludge. Next, the specific structure of each means 30, 60, 71 will be described.

  The agglomeration and mixing means 30 has one or more agglomeration and mixing tanks 31. The coagulation mixing tank 31 is directly connected to the raw water supply source 1 or indirectly through a pretreatment unit such as a landing well, and raw water (treated water) is fed to the coagulation mixing tank 31.

  A supply means 35 is connected to any one or more of the agglomeration and mixing tank 31 and the upstream devices (the supply source 1, the pipe 21, the landing well, etc.). By this supply means 35 or manual work, the inorganic flocculant is directly injected into the coagulation mixing tank 31 separately from the water to be treated, or indirectly from the upstream apparatus to the coagulation mixing tank 31 together with the water to be treated. Injected.

  The agglomeration mixing tank 31 is provided with stirring means such as a stirring blade and a stirring pump. The stirring means is set with a stirring speed (number of rotations) for applying predetermined stirring energy, and rapidly stirs the water to be treated into which the inorganic flocculant has been injected.

  Here, an example of the index of the stirring energy is a G value, and the G value is a square root of a value obtained by dividing the work coefficient P per unit time unit volume by the viscosity coefficient μ of the water to be treated (Japan Water Works Association Waterworks). (From Facility Design Guidelines 2000, P188).

  As a result of rapid stirring in the agglomeration mixing tank 31, the suspended matter in the water to be treated aggregates and grows as fine flocs (micro flocs).

  The aggregation floc forming means 40 is installed downstream of the inorganic flocculant supply means 35. If necessary, the flocculant floc forming means 40 may be provided with other flocculant supply means, and a polymer flocculant for floc growth may be added to the water to be treated on which fine flocs are grown. Is slowly stirred in the agglomeration mixing tank 31 or the floc forming tank 41 on the downstream side. For example, in the slow stirring, the rotational speed and the like are set so that the G value is lower than that in the rapid stirring, and the fine flocs aggregate and grow into a huge floc without collapsing.

  In order to solid-liquid-separate the grown flocs, it is preferable to install a sedimentation basin 51 on the downstream side of the agglomeration mixing tank 31 or the floc formation tank 41 in the cross-flow type precipitation facility. Although the structure of the sedimentation basin 51 is not particularly limited, generally, an inclined plate or an inclined pipe is provided therein, and when water to be treated is sent to the sedimentation basin 51, a sediment (sludge) mainly containing giant flocs, The giant floc is separated into the separated liquid phase.

  This liquid phase is sent to filtration means 55 including at least one of a filtration tower and a filtration membrane (filter). Residual floc and excessive additives (polymer flocculant) may remain in the liquid phase, but these residual contaminants pass, for example, through filtration towers filled with filtration sand (silica sand) or anthracite. In the meantime, it is removed to become purified water 6.

  On the other hand, the floc settled and separated from the liquid phase is collected by a collecting means such as clarifier and sent to the concentrating means 60 as purified water sludge.

  The concentrating means 60 has one or more concentrating tanks 65, and other equipment such as a mud pond 61 is installed between the concentrating tank 65 and the sedimentation basin 51 as necessary. The sedimentation basin 51 is provided with a withdrawal device such as a sludge withdrawal valve, and the purified water sludge is withdrawn regularly or irregularly and sent to the waste mud basin 61. The drainage pond 61 has a stirring means, and stores the purified water sludge while stirring.

  A sludge drain device (sludge pump 62) for sending purified water sludge to the concentration tank 65 is connected to the sludge pond 61 or downstream thereof, and a predetermined amount of sludge is discharged at a predetermined interval or continuously. It is sent from the pond 61 to the concentration tank 65.

  The concentration tank 65 is not particularly limited as long as it is an apparatus for further concentrating the purified water sludge, but gravity concentration or mechanical concentration, preferably gravity concentration is performed, and the sludge settled and concentrated in the lower part of the concentration tank 65 is a scraping plate or the like. Scraping and sending to the dehydrating means 71.

  This dehydrating means is a device that performs dehydration by either one of mechanical dehydration and drying (sunlight or heat drying), and at least performs mechanical dehydration from the viewpoint of efficiency.

  A variety of methods can be used for this mechanical dehydration. For example, a belt press type, a centrifugal dehydration type, a screw press type, a vacuum dehydration type, or the like can be used alone or in combination of two or more types. The filter press-type dewatering means 71 is most preferable in terms of high capacity and low running cost.

  The filter press type dewatering means 71 is not particularly limited, such as a filter cloth traveling type, a filter cloth fixed type, a diaphragm type, etc., all of which are devices for separating moisture from sludge solids through a filter cloth (filter) by pressurization. It is.

  Although the filter is not particularly limited, for example, a fiber having a single fiber diameter of about 0.1 to 0.3 mm is formed into a sheet shape as a nonwoven fabric or a woven fabric (eg, satin weave, plain weave, twill weave, sugi twill, felt, double weave) The material is not particularly limited, for example, nylon, polyester, polypropylene, rayon, acetate, promix, cupra, vinylon, vinylidene, polyvinyl chloride, acrylic, polyethylene, polyurethane, carbon fiber, Any one or more kinds of fibers selected from fluorine fibers, polyamides and the like can be used.

  In any case, the water of the purified water sludge passes through the filter by pressurization, but the solid content does not pass through the filter and remains as a dehydrated cake 75.

  Since concentrated sludge has a higher dewatering efficiency as its solid content concentration increases, the conventional apparatus sometimes adds a polyacrylamide polymer flocculant to concentrate the sludge. However, in this method, the viscosity of the concentrated sludge is high, the filter peelability of the dewatered cake 75 is deteriorated, the filter is clogged, the water runs out poorly, and the amount of sludge driven into the dewatering means 71 is reduced. It will cause high stagnation.

  In order to solve this problem, in the purified water sludge treatment apparatus 10 of the present invention, the polymer flocculant supply means 45 is installed in the concentration means 60, and the polymer flocculant for sludge concentration is provided by the supply means 45 or by manual work. (Poly (meth) acrylate) is added to the purified water sludge.

  The supply means 45 is preferably provided with a dissolution tank, and an aqueous solution in which the polymer flocculant is dissolved (dispersed) is accommodated in the dissolution tank. A desired amount of the polymer flocculant can be injected by adjusting the flow rate of the polymer flocculant aqueous solution with a flow rate control means or the like.

  Although the installation place of the supply means 45 is not particularly limited, it is connected to one or more of the apparatuses upstream of the dehydrating means 71, preferably the concentration tank 65 or the apparatus upstream of the concentration tank 65. More preferably, the supplying means 45 is connected to the pipe 23 at a position between the concentrating tank 65 and the waste mud basin 61 (pipe 23), particularly preferably between the connection point of the mud pump 62 and the thickening tank 65. The sludge that is connected and uniformly stirred in the mud pond 61 is mixed with the polymer flocculant in the pipe 23, a mixing tank (not shown), or the concentration tank 65.

Next, a purified water sludge treatment method using this purified water sludge treatment facility 10 will be described.
[Purified water sludge treatment method]
The treated water to be treated in the present invention is not particularly limited, and it is possible to treat industrial wastewater, domestic wastewater, seawater, etc., but particularly suitable is river water, lake water, reservoir water, rainwater, underground water , Groundwater, well water.

  If necessary, the quality of the water to be treated is checked in advance by a jar test or the like, the injection amount of the inorganic flocculant is set in advance according to the water quality, and the water to be treated 1 is manually prepared by the supply means 35 or the operator. The inorganic flocculant is injected within a range of 5 to 200 mg, preferably 10 to 100 mg per liter, and rapidly stirred in the flocculent mixing tank 31.

  Next, the water to be treated on which the fine floc has grown is gently stirred to further grow the floc. If necessary, an appropriate amount of a polymer flocculant for floc growth (about 0.05 to 20 mg per liter of water to be treated) may be added before the start of slow stirring or during slow stirring. Furthermore, together with the inorganic flocculant or the polymer flocculant or separately from these flocculants, one or more additives such as a pH adjusting agent, a buffering agent, an aggregating aid, and a bactericidal agent may be added.

  The treated water in which the floc has grown is solid-liquid separated in the sedimentation basin 51, and the separated floc (purified water sludge) is sent to the mud basin 61. In the sedimentation basin 51, the sludge is stirred, and the sludge in which the solid content is uniformly dispersed is sent from the waste mud basin 61 to the concentration tank 65.

  A polymer flocculant for sludge concentration is dissolved (dispersed) in one or more kinds of water selected from tap water, distilled water, purified water 6 and water to be treated, and other additives (pH adjusters if necessary) 1 or more of a buffering agent, a dispersing agent, a bactericidal agent, other polymer flocculants, etc.) are added to prepare an aqueous polymer flocculant solution, which is stored in the dissolution tank of the supply means 45.

  Then, a desired amount (for example, 5 to 100 mg per liter of sludge before dehydration) of polymer flocculant is added to and mixed with the sludge. The means for mixing the sludge and the polymer flocculant is not particularly limited, but when the mixing tank is installed in the upstream (upstream side) of the concentration tank 65, the mixing tank is used. When the mixing tank is not installed, the water flow in the pipe 23 is used. It is preferable to mix.

  The sludge after mixing the polymer flocculant is concentrated by gravity or mechanically. In the case of gravity concentration, the sludge is allowed to stand still in the concentration tank 65 or a tank downstream from the concentration tank, or the sludge is stirred or sent at a slow speed that causes sedimentation (eg, pressure sedimentation), and concentrated for a predetermined time. .

  The sedimented and concentrated sludge is sufficiently concentrated by the addition of the poly (meth) acrylate described above and the viscosity of the concentrated sludge is lower than that of the conventional flocculant. It is done well and its filter contamination is also prevented.

  The present invention is not particularly limited as long as it is a method and apparatus for adding the poly (meth) acrylate in the sludge concentration step, or between the floc generation step and the sludge concentration step, or between the sludge concentration step and the dehydration step. Other steps may be inserted between the steps, or one or more of these steps may be repeated a plurality of times, and the apparatus to be used, the drug (additive), and the timing of the addition are not particularly limited.

  Hereinafter, the present invention will be described more specifically with reference to examples.

<Example 1>
To the extracted sludge (DS: 9.5 g / L) generated from the water purification plant corresponding to the flocculating and mixing means 30 and the flocculating floc forming means 40 in FIG. 1, sodium polyacrylate (0.1% salt viscosity) is used as a polymer flocculant. Is 3.5 mPa · s and anion equivalent is −9.4 meq / g), and 20 mg per liter of extracted sludge (water content) is added and stirred with a stirrer “Three-One Motor” manufactured by Shinto Chemical Co., Ltd. Allowed to stand for a while to produce concentrated sludge. “DS” means the dry mass of solids in the sludge (dry mass g / sludge L).

The obtained concentrated sludge (DS: 32 g / L) was squeezed with a filter press tester at 14 kgf / cm ² for 10 minutes and dehydrated. The water content of the dehydrated cake after dehydration was 73.2%, and the filter surface was less dirty at a level where there was no problem.

<Comparative Example 1>
When concentrated sludge was produced under the same conditions as in Example 1 except that sodium polyacrylate was not used, the obtained concentrated sludge concentration DS was 12 g / L. When this concentrated sludge was subjected to filter press treatment under the same conditions as in Example 1, the water content of the dehydrated cake was 80.8%. It is considered that the sludge concentration was low, so that sludge could not be driven in sufficiently and the moisture content of the cake was increased.

<Comparative example 2>
Example except that a medium anionic acrylamide / sodium acrylate copolymer (0.1% salt viscosity 6.0 mPa · s, anion equivalent −2.5 meq / g) was used as the polymer flocculant. When concentrated sludge was produced under the same conditions as in No. 1, the obtained concentrated sludge concentration DS was 34 g / L. When this concentrated sludge was subjected to a filter press treatment under the same conditions as in Example 1, the moisture content of the dehydrated cake was 72.8%, and the moisture content was improved as compared with Comparative Example 1, but the filter surface A portion of the dehydrated cake adhered to the surface. Although this stain was washed with tap water, it could not be completely removed.

DESCRIPTION OF SYMBOLS 1 Supply source 10 Purified water sludge processing apparatus 21, 23 Piping 30 Coagulation mixing means 31 Coagulation mixing tank 35 Inorganic flocculant supply means 40 Aggregation floc formation means 41 Flock formation tank 45 Polymer flocculant supply means 51 Precipitation basin 55 Filtration means 60 Concentration means 61 Waste mud pond 62 Waste mud pump 65 Concentration tank 71 Dehydration means (filter press type)

Claims (5)

A flock generating step of generating an agglomerated floc by adding an inorganic flocculant to the water to be treated;
A poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and an anion equivalent of −9.0 or less is added to the sludge of the aggregated floc separated from the water to be treated. And a concentration step for concentrating the sludge,
A dehydration step of dewatering the concentrated sludge;
A method for treating purified water sludge.   The method for treating purified water sludge according to claim 1, wherein the poly (meth) acrylate is sodium polyacrylate.   The method for treating purified water sludge according to claim 1 or 2, wherein the dehydration step is mechanical dehydration using a filter press. Agglomeration and mixing means for rapidly stirring water to be treated with an inorganic flocculant to produce agglomerated floc;
Aggregated floc forming means for slowly stirring the water to be treated and increasing the aggregated floc to obtain sludge of the aggregated floc;
The sludge separated from the water to be treated is mixed with a poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and an anion equivalent of −9.0 or less and concentrated. A concentration means;
Dewatering means for dewatering the concentrated sludge to obtain a dehydrated cake;
A purified water sludge treatment apparatus characterized by comprising:   The purified water sludge treatment according to claim 4, wherein the dewatering means is a filter press type dewatering means.

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