KR101920700B1 - Biological pretreatment apparatus and method with improved separation performance of organic materials - Google Patents

Abstract

The present invention relates to a biological pretreatment (A-stage) apparatus and a method for improving the separation efficiency of organic matter, and more particularly, to a method and apparatus for biological treatment which can reduce flocculation and precipitation time of a floc, To a biological pretreatment apparatus and method capable of improving the production amount of gas. To this end, the biological pretreatment apparatus is provided with an acid device at the bottom, a mixing tank for forming and growing a contaminant contained in the for-treatment water to be introduced into fl ow; A sedimentation tank for discharging sludge formed by precipitating the flocs introduced from the mixing tank; And a sludge returning part for recovering a part of the sludge discharged from the sedimentation tank and supplying it to the mixing tank.

Description

TECHNICAL FIELD [0001] The present invention relates to a biological pretreatment apparatus and a biological pretreatment apparatus,

The present invention relates to a biological pretreatment (A-stage) apparatus and a method for improving the separation efficiency of organic matter, and more particularly, to a method and apparatus for biological treatment which can reduce flocculation and precipitation time of a floc, To a biological pretreatment apparatus and method capable of improving the production amount of gas.

Modern society has developed rapidly in various scientific and technological fields due to industrial development. However, due to the adverse effect, it is difficult for sewage, which contains agricultural and industrial wastewater, industrial wastewater, industrial wastewater, There is a problem that the exhaust gas is discharged.

These kinds of sewage pollute the water quality of public water such as inland and coastal waters and urban small and medium rivers. Especially in recent years, due to rapid industrial development, population increase and population concentration of the city, The proportion of inorganic and organic components in wastewater is increasing.

Such wastewater contains high concentrations of organic matter such as COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), SS (Suspended Substance), Nitrogen and Phosphorus and flows into rivers, As well as the destruction of ecosystems due to toxicity, which adversely affects the environment. Therefore, the wastewater is to be purified to a predetermined standard value or less by setting a certain standard.

In the meantime, conventional treatment methods for removing suspended particles in wastewater during the treatment of wastewater include chemical treatment, electrical treatment, filtration, membrane method and the like. Among the most typical treatment methods are coagulant ), It is known as the most common method so far that the surface properties of particles are changed by using an inorganic coagulant or an organic coagulant to form a floc and precipitate.

The basic process of the chemical treatment method using such coagulant is as follows.

First, the colloid in the sewage water to be treated is neutralized using a metal salt (generally, iron or an aluminum compound) to undergo an aggregation step for producing micro flocs, and then subjected to a floc formation step for collecting and growing micro flocs. This can be done by adding a polymer to the micro flocs generated in the coagulation step. Thereafter, a step of generating processed digits is performed by separating sludge produced by precipitating flocs from the for-treatment water.

It is important to chemically treat the coagulant by improving the quality of the flocculant so that the formation of the flocs, the growth and the production of the sludge are efficiently performed because the capacity of the overall sewage treatment facility including the mixing tank and the settling tank is reduced, This is because it is directly connected with the effect of cost reduction and maintenance cost reduction. Accordingly, there is a need for a technique capable of achieving an excellent water treatment effect such as reduction in facility cost by improving the conventional chemical treatment method.

Korean Patent Publication No. 10-1145049

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and it is an object of the present invention to provide a method and apparatus for separating an organic material which can reduce flocculation and sedimentation time of a floc and improve a production amount of methane gas in a biological treatment And to provide a biological pretreatment apparatus and method with improved performance.

These and other objects and advantages of the present invention will become apparent from the following description of a preferred embodiment.

The object of the present invention is to provide a mixing tank, which has an acid device at the bottom and forms and grows contaminants contained in the for-treatment water to be introduced into fl ow; A sedimentation tank for precipitating and discharging the flocs introduced from the mixing tank into a sludge form; And a sludge returning part for recovering a part of the sludge discharged from the sedimentation tank and supplying it to the mixing tank.

Preferably, the mixing tank may include an agitator for stirring the incoming water to be introduced, and the agitator may be a plurality of impellers having vanes, and a plurality of blades may be provided between the agitators. have. Also, the cavity formed in the perforated plate may have a diameter of 3 to 5 cm.

Preferably, the settling tank may include a circular orifice tube having a plurality of orifice holes. The orifice tube may include a branch tube disposed at the bottom of the settling tank and capable of being settled in the form of sludge while passing through the orifice hole and radially disposed in the circumferential direction from the center. At this time, the branch tube may have a plurality of orifice holes. In addition, the settling tank may include a bent plate for preventing sludge from floating.

Preferably, the sludge returning portion may include a dehydrating agent supplying portion for supplying sludge dehydrating agent to the sludge recovered in the sedimentation tank and supplied to the mixing tank, wherein the sludge dehydrating agent may be a cationic polymer material.

The above object can also be accomplished by a method of manufacturing a semiconductor device, comprising: a mixing step of supplying bubbles to an incoming water to be treated to form and grow a contaminant contained in the for-treatment water into a flock; A sedimentation step of precipitating the formed and grown flocks in the form of sludge by the mixing step and discharging them to the outside; And a sludge conveying step of recovering a part of the discharged sludge and supplying it to the mixing step.

Preferably, in the mixing step, the for-treatment water can be stirred by an impeller-type agitator having wings. At this time, a plurality of stirrers may be provided, and a perforated plate may be provided between each of the stirrers, and the cavity formed in the perforated plate may have a diameter of 3 to 5 cm.

Preferably, the precipitation step may pass the flakes through an orifice tube having a plurality of orifice holes. In addition, the sludge transporting step may supply the sludge dewatering agent to the sludge supplied to the mixing step, and the sludge dewatering agent may be a cationic polymer material.

According to the present invention, since the precipitated sludge is dehydrated and used for forming and growing the flocs, it is possible to reduce the agglomeration and settling time of the flocs by forming high quality flocs having improved size and density, And the facility cost can be reduced by reducing the capacity of the sewage treatment facility.

In addition, since all or a part of the sludge is transported to the mixing tank and circulated, the total sludge discharge amount is reduced, and only the facilities necessary for circulating the sludge to the existing sewage treatment facility and the equipment necessary for injecting the sludge dewatering agent are added. Maintenance and repair are easy.

Also, by injecting air bubbles during the growth of the flocs, it is possible to promote the secretion of EPS (Extracellular Polyeric Substance) of the microorganisms and to adsorb the organic substances and SS (suspended matter) components to the sludge so that the organic substances can be efficiently recovered. It is possible to improve the production amount of methane gas in the biological treatment step.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a schematic view of a biological pretreatment apparatus according to an embodiment of the present invention.
2 is a schematic view of an acid device according to an example.
3 is a schematic view of an acid device according to an example.
FIG. 4 is a schematic view of a mixing tank provided with an agitator and a perforated plate according to an example.
5 is a schematic view of an agitator according to an example.
6 is a schematic view of a settling tank according to an example.
7 is a schematic illustration of an orifice tube according to an example.
8 is a schematic view of an orifice tube according to an example.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

Also, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains and, where contradictory, Will be given priority.

In order to clearly illustrate the claimed invention, parts not related to the description are omitted, and like reference numerals are used for like parts throughout the specification. And, when a section is referred to as " including " an element, it does not exclude other elements unless specifically stated to the contrary. In addition, " part " described in the specification means one unit or block performing a specific function.

In each step, the identification code (first, second, etc.) is used for convenience of explanation, the identification code does not describe the order of each step, and each step does not explicitly list a specific order in the context May be performed differently from the above-described sequence. That is, each of the steps may be performed in the same order as described, or may be performed substantially concurrently or in the reverse order.

1 is a schematic view of a biological pretreatment apparatus 10 according to an embodiment of the present invention. 1, a biological pretreatment apparatus 10 according to an embodiment of the present invention includes acid devices 110 and 120 disposed at a lower portion thereof, and forms contaminants contained in the for-treatment water flowing into a flock And a mixing tank (100) for growing the mixture; A sedimentation tank 200 for sedimenting and discharging the flocs introduced from the mixing tank 100 in the form of sludge; And a sludge return unit 300 for recovering a portion of the sludge discharged from the sedimentation tank 200 and supplying the collected sludge to the mixing tank 100. According to the present invention, the precipitated sludge is dewatered and used for forming and growing a flock, so that it is possible to reduce flocculation and settling time by forming a good quality flock having improved size and density. In addition, all or a part of the sludge may be conveyed to the mixing tank 100 and circulated to reduce the total amount of sludge discharged. Also, by injecting air bubbles during the growth of the flocs, it is possible to promote the secretion of EPS (Extracellular Polyeric Substance) of the microorganisms and to adsorb the organic substances and SS (suspended matter) components to the sludge so that the organic substances can be efficiently recovered. The effect of improving the production amount of methane gas in the biological treatment step can be obtained.

In one embodiment, the mixing tank 100 forms and grows the contaminants contained in the for-treatment water supplied into the mixing tank 100 with the acid devices 110 and 120 at the bottom . The acid devices 110 and 120 supply air bubbles into the mixing tank 100. When air bubbles are supplied into the mixing tank 100, microorganisms secrete extracellular polymeric substances (EPS), and organic and suspended substances (SS) are adsorbed on the flocs or sludge. Through this, it is possible to effectively recover the organic matter, and it is possible to maximize the production amount of methane gas in the subsequent process (biological treatment process, B-stage).

The acid device 110 may use a saturator type acid device (see FIG. 2). The saturator type acid device includes a pressure dissolved chamber 111 therein and is connected to the saturator 112 via a saturator 112 and a water supply pipe 114 to which the air supply tube 114 is connected, A compressor 116 for supplying high-pressure air to the saturator 112 via the air supply tube 113 and a discharge tube 117 connected to the saturator 142 to supply air And an ejection nozzle 118 for ejecting air to form an air bubble. A plurality of spray nozzles 118 may be provided inside the mixing tank 100. The pair of spray nozzles 118 may be installed so as to face each other so that the sprayed bubbles collide with each other to form minute bubbles. .

Further, the acid device 120 may use a mixer-type acid device (see FIG. 3). The mixer type dissipating device includes a supply pipe 121 in which air and water are mixedly supplied, a pump 122 connected to the supply pipe 121 to form bubble water through pumping, And an injection nozzle 126 connected to the mixer 124 through a mixer 124 having a mixing chamber 123 and a discharge pipe 125 to form bubbles by discharging bubble water to the outside. A plurality of injection nozzles 126 may be provided inside the mixing tank 100. The pair of the injection nozzles 126 may be installed so as to face each other so as to form fine bubbles .

In one embodiment, the mixing tank 100 may include an agitator 130 that stirs the incoming water to be introduced (see FIG. 4). The stirrer 130 stirs the water to be treated so that contaminants contained in the water to be treated can grow into flocs. The stirrer 130 may be of the impeller type having wings. The impeller type stirrer 130 is not particularly limited in shape, but preferably, the outer wing portion 132 may be bent to face downward of the inner wing portion 131 (see FIG. 5) , Thereby maximizing the stirring effect by pushing the maximum amount of water in the desired direction as if the water is collected by hand and pushing the water with a strong force.

In addition, a plurality of stirrers 130 may be provided in the mixing tank 100. A plurality of stirrers 130 having different blade diameters may be disposed on the upper portion of the mixing tank 100 and the lower portion of the mixing tank 100. In this case, This is because it is possible to increase the flux production efficiency due to the faster mixing speed as the incoming water to be treated flows from the upper portion to the lower portion of the mixing tank 100.

In this case, the number of revolutions (G-value) of the blades of the stirrer 130 is not particularly limited and may be appropriately selected according to the size of the mixing and agglomeration scale or the size of the mixing tank 100, preferably 30 to 110 sec ^-1 and, more preferably, the number of revolutions of the blade diameter of the largest agitator 130 of the plurality of agitators 130 and 70 ~ 110sec ^-1, the number of revolutions of the blade diameter of the smallest agitator 130 30 ~ 50sec ^{- 1} < / RTI >

In one embodiment, the mixing tank 100 may include at least one perforated plate 140 between a plurality of agitators 130, and when the agitator 130 has one, A perforated plate 140 may be provided. The plurality of cavities formed in the perforated plate 140 are not particularly limited and may be variously selected depending on the size of the perforated plate 140 and the scale of the admixture tank 100. However, desirable.

In one embodiment, the mixing tank 100 may have a plate-shaped baffle therein, and growth may be promoted when the flap collides with the baffle. Although the number of baffles is not particularly limited, it is preferable that at least three baffles are formed on one wall surface of the mixing tank 100 for the effect of the flask coagulation.

In one embodiment, the mixing tank 100 may include control means capable of controlling the stirring speed of the stirrer 130 according to the internal temperature and the amount of formed flocs. At this time, the control means may include a temperature sensor for measuring the temperature of the upper and lower portions of the mixing tank 100, and a particle counter for calculating the amount of the flux.

In one embodiment, the admixture tank 100 may include a coagulant feeder that supplies a coagulant, including salts, polymeric materials, and the like, to the mixing tank 100 to induce the formation and growth of the flocs have. The coagulant is a substance having a relatively small molecular weight and functions as a floc seed which forms a flock by binding with organic or inorganic particles in the water to be treated.

Salt (salt) contained in the coagulant is an aluminum (Al) or iron (Fe) based metal salts _{(Al 2 (SO 4) 3} , Fe 2 (SO 4) 3, FeCl 3, Al 2 (OH) 3 Cl 2 Etc.), and it is more preferable to be an iron salt (FeM _n ) such as FeCl ₃ . Polymer contained in the coagulant (polymer) material, a poly aluminum chloride _{(Polyaluminium chloride, [Al 2 (} OH) n Cl 6- n] n), poly aluminum silicate sulfate (Polyalumium sulfate silicate, PASS, Al _a (OH) _b (SO 4) _c (SiO ₂ ) _d (H ₂ O) _x ), polyaluminum hydroxide chloride silicate, PACS, AlNa _x Si _y (OH) _z Cl _b ), polyamine and poly At least one of polyacrylamide (PAM) may be used. In particular, it is preferable that an anionic polymer material is included. Such an anionic polymer material is effective to promote flocculation, sedimentation and filtration.

In the embodiment, the settling tank 200 receives the untreated water containing the flour from the mixing tank 100, and discharges the floated flocs in a sludge form to discharge the sludge. The sludge discharge port 205) (see Fig. 6). The sedimentation tank 200 is not particularly limited, but it is preferable that the overall appearance is a cylindrical or square pillar shape, and the lower part is formed to be inclined toward the vertical center axis so that the sludge is discharged to the outside.

In one embodiment, the settling vessel 200 may include a circular orifice tube 210 at the bottom to deposit the flocs effectively in sludge form. Here, the circle is a concept including a round shape and an oval shape. The orifice tube 210 may include a plurality of orifice holes 211. That is, when the flaps guided downward along the inner wall 201 of the sedimentation tank 200 reach the circular orifice tube 210, the sludge is discharged through the orifice hole 211 at high speed and precipitated as sludge, Lt; / RTI >

More specifically, the flow Q, which is an amount that flows through a certain area over a period of time, can be expressed as a product of the cross-sectional area A and the flow velocity v, When passing through the orifice hole 211, the flow rate is the same, but the speed becomes very large as the cross-sectional area (orifice area) is sharply reduced. Thus, the flocs are deposited and discharged into the sludge as they pass through the orifice holes 211 at a very high rate.

In one embodiment, the number of the circular orifice tubes 210 may be one or two or more, and the number of the orifice tubes 210 may be appropriately selected depending on the scale of the settling vessel 200 or the amount of raw water to be settled have. Preferably, it may be two or three. In the case of a plurality of circular orifice tubes 210, the average diameter of the orifice tubes 210 may be the same or different, and more preferably, the plurality of circular orifice tubes 210 having different average diameters may be disposed in the settling tank 200 The sludge sedimentation rate can be further improved by arranging the sludge so as to have a smaller diameter from the upper side to the lower side. Here, the average diameter of the circular orifice tube 210 means the average length of the strings passing through the center of the orifice tube 210.

In one embodiment, the interior of the circular orifice tube 210 may include a branch tube 212. The branch tube (212) may have a plurality of orifice holes (211). The shape of the branch tube 212 is not particularly limited, but may be radially arranged in the circumferential direction from the center. That is, as shown in FIG. 7, the inside of the circular orifice tube 210 may be divided into three sections, or alternatively, as shown in FIG. 8, a configuration in which the inside of the circular orifice tube 210 is alternately arranged radially Lt; / RTI >

In one embodiment, the settling tank 200 may include a bend plate 220 to prevent floating of the sludge. The bent plate 220 may be manufactured in various shapes, but it is preferable that the bent shape of the bent plate 220 is in the form of a cone having an L shape in order to effectively prevent the rising of the sludge.

In one embodiment, the settling vessel 200 may include a baffle 202 spaced a certain distance from the inner wall 201. When the for-treatment water containing flocs is supplied between the inner wall 201 of the settling tank 200 and the baffle 202, the fluids including the flocs move to the lower part of the settling tank 200 by gravity. At this time, the flow is blocked by the installed baffle 202 to the upper or central portion of the settling tank 200, and the flow direction can be stably guided to the lower side along the inner wall 201. At this time, the clean water from which the flakes have been removed can be discharged through the upper part of the settling tank 200.

In one embodiment, the settling tank 200 may include a guide plate 203 between the inner wall 201 and the baffle 202. As the guide plate disperses the flow of the fluid containing the flock (the water to be treated), it is possible to minimize the re-deposition of the sludge to be precipitated. The number of the guide plates 203 is not particularly limited, but may be one to three.

The swash plate 204 may be provided at the distal end of the baffle 202 so that the floc or sludge does not float to the upper part of the settling tank 200 but stably moves toward the circular orifice tube 210 side. At this time, it is preferable that the end of the swash plate 204 is directed toward the center of the settling tank 200 in the inclined direction of the swash plate 204.

In one embodiment, the sludge return section 300 recovers a portion of the sludge discharged from the sedimentation tank 200 and supplies the collected sludge to the admixing tank 100. The sludge supplied to the mixing tank 100 is recovered Formation and growth. In addition, since a part of the sludge is conveyed and circulated, an effect of reducing the total sludge discharge amount can also be obtained.

In one embodiment, the sludge return unit 300 may include a dehydrating agent supply unit for supplying the sludge dehydrating agent to the sludge recovered in the sedimentation tank 200 and supplied to the mixing tank 100. The sludge dehydrated by the sludge dewatering agent has an increased density, and it is possible to grow a high quality flock with increased size and density of the flour in the mixing tank 100. The sludge dehydrating agent may be a polymer material, and preferably, a cationic polymer material may be used.

Next, a biological pretreatment method of the for-treatment water capable of improving the separation performance of the organic matter will be described. In describing the biological pretreatment method, the biological pretreatment apparatus 10 described above will be described for convenience of explanation, but the present invention is not limited thereto. Further, redundant description with respect to the biological preprocessing apparatus 10 is omitted.

A biological pretreatment method according to an embodiment of the present invention includes: a mixing step of supplying bubbles to an incoming water to be treated to form and grow contaminants contained in the for-treatment water into a flock; A sedimentation step of precipitating the formed and grown flocks in the form of sludge by the mixing step and discharging them to the outside; And a sludge conveying step of recovering a part of the discharged sludge and supplying the recovered sludge to the mixing step. According to the present invention, the precipitated sludge is dewatered and used for forming and growing a flock, so that it is possible to reduce flocculation and settling time by forming a good quality flock having improved size and density. In addition, all or a part of the sludge may be returned to the mixing step and circulated, thereby reducing the overall sludge discharge amount. Also, by injecting air bubbles during the growth of the flocs, it is possible to promote the secretion of EPS (Extracellular Polyeric Substance) of the microorganisms and to adsorb the organic substances and SS (suspended matter) components to the sludge so that the organic substances can be efficiently recovered. The effect of improving the production amount of methane gas in the biological treatment step can be obtained.

In one embodiment, the blending step may be stirred using an agitator to effectively form and grow the contaminants contained in the incoming water to be treated in a flock. The stirrer is an impeller type stirrer having blades, and may be a plurality of stirrers. When there are a plurality of stirrers, a perforated plate may be provided between each stirrer. At this time, the number of cavities formed in the perforated plate is not particularly limited, and may be variously selected according to the size of the perforated plate, the scale of the admixture, and the like, but it is preferable that the diameter is 3 to 5 cm.

In one embodiment, the precipitation step is a step of precipitating the flocs out of the sludge form and discharging them outwardly, preferably through an orifice tube having a plurality of orifice holes for effectively depositing the flocs in the form of sludge. In general, the flow rate Q which is a constant flow rate over a certain period of time can be expressed as a product of the pipe sectional area A and the flow velocity v. When the fl ux passes through a plurality of orifice holes formed in a circular orifice tube, But the speed becomes very large as the cross-sectional area (orifice area) is sharply reduced. Thus, the flocs can be deposited and discharged into the sludge as they pass through the orifice holes at very high rates.

In one embodiment, the sludge transporting step is a step of recovering a portion of the sludge formed by the sedimentation step and supplying it to the mixing step again, and the sludge recovered and supplied to the mixing step may promote the formation and growth of the flocs . In addition, since a part of the sludge is conveyed and circulated, an effect of reducing the total sludge discharge amount can also be obtained.

The sludge conveying step may supply the sludge dewatering agent to the sludge supplied to the mixing step. The sludge dehydrated by the sludge dewatering agent has an increased density, so that it is possible to grow a high quality flock with increased size and density of the flour at the mixing stage. The sludge dehydrating agent may be a polymer material, and preferably, a cationic polymer material may be used.

It is to be understood that the present invention is not limited to the above embodiments and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

10: Biological pretreatment device
100: mixing tank
110: Mountain Devices
111: Pressure Dissolution Room
112: saturator
113:
114: water supply pipe
115: pump
116: compressor
117: discharge pipe
118: injection nozzle
120: live appliances
121: Supply pipe
122: pump
123: Mixing room
124: Mixer
125: discharge pipe
126: injection nozzle
130: stirrer
131: Inner wing
132: outer wing
140: Perforated plate
200: settling tank
201: inner wall
202: Baffle
203: guide plate
204: swash plate
205: Sludge outlet
210: Orifice tube
211: Orifice hole
212: branch pipe
220: Bent plate
300: sludge conveying section

Claims (20)

A mixer tank provided with an acidic device at a lower portion thereof and forming and growing a contaminant contained in the for-treatment water to be introduced into a flock;
A sedimentation tank for precipitating and discharging the flocs introduced from the mixing tank into a sludge form; And
And a sludge returning unit for recovering a part of the sludge discharged from the settling tank and supplying the collected sludge to the mixing tank,
In the mixing tank,
A plurality of stirrers of an impeller type having wings,
However,
A supply pipe in which air and water are mixedly supplied;
A pump connected to the supply pipe to form bubble water through pumping;
A mixer having a mixing chamber therein to receive bubble water supplied from a pump; And
And a pair of spray nozzles connected to the mixer through a discharge pipe to spray bubble water to the outside to form bubbles,
The pair of spray nozzles are provided so as to face each other in the mixing tank so that the bubbles injected from the injection nozzle collide with each other to form minute bubbles,
The sludge-
And a dehydrating agent supply unit for supplying the cationic polymer material to the sludge recovered in the sedimentation tank and supplied to the mixing tank. delete delete The method according to claim 1,
Characterized in that a porous plate is provided between each of the agitators. 5. The method of claim 4,
Wherein the cavity formed in the perforated plate has a diameter of 3 to 5 cm. The apparatus according to claim 1,
And a circular orifice tube having a plurality of orifice holes. 7. The orifice tube according to claim 6,
Characterized in that it is arranged at the bottom of the settling tank and is deposited in the form of sludge while passing through the orifice hole. 7. The orifice tube according to claim 6,
And a branch tube radially disposed in the circumferential direction from the center. 9. The apparatus according to claim 8,
Characterized in that it has a plurality of orifice holes. 7. The apparatus according to claim 6,
And a bending plate for preventing the sludge from floating. delete delete A blending step of supplying bubbles to the incoming water to be treated to form and grow a contaminant contained in the for-treatment water into a flock;
A sedimentation step of precipitating the formed and grown flocks in the form of sludge by the mixing step and discharging them to the outside; And
And a sludge returning step of recovering a part of the discharged sludge and supplying it to the mixing step,
In the mixing step,
The for-treatment water is agitated by a plurality of impeller-type agitators having wings,
In the mixing step, the bubbles are fed by an acid apparatus,
However,
A supply pipe in which air and water are mixedly supplied;
A pump connected to the supply pipe to form bubble water through pumping;
A mixer having a mixing chamber therein to receive bubble water supplied from a pump; And
And a pair of injection nozzles which are installed so as to face each other so that the bubbles blown from the injection nozzle collide with each other to form fine bubbles, Forming a bubble,
In the sludge returning step,
Characterized in that the cationic polymer material is supplied to the sludge supplied to the mixing step. delete delete 14. The method of claim 13,
Characterized in that a perforated plate is provided between each agitator. 17. The method of claim 16,
Wherein the cavity formed in the perforated plate has a diameter of 3-5 cm. 14. The method of claim 13,
Characterized in that the flock is passed through an orifice tube having a plurality of orifice holes. delete delete

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