JP4785010B2 - Precipitation tank equipped with stirring and mixing device - Google Patents

Description

The present invention provides a wastewater treatment facility, about settling tank having a 撹拌mixing apparatus used waste water and coagulant treatment mixing 撹拌.

Stir mixing is a basic operation of wastewater treatment and there are many examples of methods and equipment.
Depending on the type of wastewater and the purpose of the treatment, in many cases, uniform stirring and mixing are required, and improvements and developments are being made to improve mixing efficiency, such as wastewater treatment using chemicals.

  A typical example of wastewater treatment using chemicals is the coagulation sedimentation method. Treated water is obtained by bringing a flocculant into contact with the wastewater to precipitate the contaminated components dissolved in the wastewater as sludge, and separating the sludge. As shown in FIG. 6, a typical process flow includes a mixing tank 100 in which the flocculant P2 is added to the waste water P1 and stirred and mixed, a flocculating tank 102 in which the flocculating aid P3 is added and stirred and mixed, and then a static bath. And a coagulating sedimentation tank 104 for depositing sludge. In the coagulation sedimentation tank 104, the precipitated sludge is scraped to the center of the tank by the sludge scraper 105, pulled out from the bottom of the tank, and transferred to the outside by the sludge pulling pump (not shown). ing. Here, the mixing tank 100 may be referred to as a rapid stirring tank, and the aggregation tank 102 may be referred to as a slow stirring tank. In the mixing tank 100, the purpose is to stir and mix the waste water P1 and the flocculant P2 by high-speed stirring at about 300 rpm, and in the coagulating tank 102, the purpose is to grow aggregated flocs by slow stirring at about 50 rpm. In the mixing tank 100 and the coagulation tank 102, the stirrer 101 is often used, and the mixing tank 100 is designed with a residence time of 5 minutes or longer in the mixing tank 100 and 20 minutes or longer in the coagulation tank 102 (refer to Non-Patent Documents 1 and 371 below). ).

National Urban Cleanup Council, “Plans and Design Guidelines for Final Waste Disposal Site Development”, page 371

  Therefore, the conventionally used coagulation sedimentation method has a drawback in that the volume of the mixing tank 100 and the coagulation tank 102 increases because the residence time is long. Moreover, since there are many apparatuses, there existed a fault that a maintenance burden was large.

The present invention has been devised in view of the above problems, and its purpose is to provide a stirrer by having the function of a conventional mixing tank and the function of a coagulation tank while having a single structure of one tank. It is to provide a sedimentation tank capable of simplifying equipment by reducing the number of devices including the number of water tanks.

Abstract of the invention is a precipitation tank equipped with a stirring and mixing apparatus which mixes and stirs the waste water and coagulant,
The stirring and mixing device includes:
A cylindrical container with a closed bottom and an open top;
A pipe connected to the lower part of the cylindrical container, and an inflow pipe for allowing the waste water and the flocculant to flow into the cylindrical container;
Stirring means for generating a downward flow inside the cylindrical container;
With
While stirring and mixing the wastewater and the flocculant in the strong stirring portion formed by the wastewater flowing into the cylindrical container via the inflow pipe and the upward flow of the flocculant and the downward flow by the stirring means,
Further, on the outside of the cylindrical container, there is provided an outer cylinder that is open at both the upper and lower portions concentric with the cylindrical container, and a cutout portion is formed on the upper peripheral edge of the cylindrical container. It is provided with a coagulant aid addition means for adding a coagulant aid to the water surface part where the stirred mixed solution flows from the notch part to the outer cylinder,
The stirrer / mixer is installed such that the water surface position of the settling tank exists in a range from the top surface to the bottom surface of the cutout portion of the cylindrical container constituting the stirrer / mixer.

  Here, the installation position of the stirring and mixing apparatus is regulated as described above for the following reason. That is, when the water surface position of the settling tank is below the bottom surface of the cutout portion of the cylindrical container, the stirred mixture overflowed from the cylindrical container is below the bottom surface of the cutout portion of the cylindrical container. Since it falls to a certain surface of the water, there is no process of forming a downward flow while gently swirling between the cylindrical container and the outer cylinder, and it becomes impossible to efficiently grow flocs of coagulated sludge. Because. On the other hand, when the water surface position of the settling tank is above the upper surface of the cutout portion of the cylindrical container, the stirred mixed liquid cannot inherently overflow from the cylindrical container.

  With the above configuration, the cylindrical container that functions to stir and mix the waste water and the flocculant corresponds to a conventional mixing tank. The outer cylinder that functions to form a space for growing flocs of the coagulated sludge corresponds to the conventional coagulation tank. Therefore, while having a single tank structure, it has the functions of a conventional mixing tank and a coagulation tank, thereby reducing the number of devices including a stirrer and the number of water tanks and simplifying the equipment. can do.

In addition, since the 撹拌mixing apparatus vigorous stirring part provided in the settling tank structures wastewater flocculant to reliably pass, stirred mixing efficiency is improved, it is possible to shorten the residence time, reducing the volume of the device Can do. Therefore, settling tank according to 撹拌mixing apparatus, it becomes possible to use a smaller volume.
Moreover, according to the said structure, since the downflow generate | occur | produced by the stirring means, the to-be-processed water, and the upflow of a processing agent collide and a strong stirring part of a turbulent flow is formed, stirring mixing efficiency improves. In addition, the contact time is ensured in the upward flow portion from the strong stirring portion to the overflow portion, and stirring and mixing are further promoted by rising while swirling and mixing. As described above, the stir and mixing efficiency can be improved, so that the residence time can be significantly shortened, so that the volume of the stir and mix device can be reduced.
Moreover, according to the said structure, when a stirring liquid mixture overflows, it will always overflow from a notch part. Therefore, the contact efficiency between the stirred mixed liquid and the coagulation aid is good. In addition, after the mixed liquid that has overflowed contacts the flocculation aid, a floc of sludge is efficiently grown by forming a downward flow while swirling gently between the cylindrical container and the outer cylinder. It becomes possible to make it. In order to improve the contact efficiency between the stirred mixed solution and the coagulant aid, it is preferable to limit the notched portion to one location.

According to the precipitation tank provided with the stirring and mixing apparatus according to the present invention, the apparatus including the stirrer is provided by having the function of the conventional mixing tank and the function of the coagulation tank while having a single structure of one tank. And the number of water tanks can be reduced to simplify the equipment.

The block diagram of the sedimentation tank provided with the stirring mixing apparatus which concerns on this invention. 1 is a schematic elevation view of a stirring and mixing apparatus according to the present invention. 1 is a schematic plan view of a stirring and mixing apparatus according to the present invention. The block diagram which shows the other example of application of a stirring and mixing apparatus. The block diagram which shows the further another example of application of a stirring and mixing apparatus. Flow diagram of standard coagulation sedimentation method.

  The stirring and mixing apparatus according to the present invention will be described in detail based on the embodiments. The present invention is not limited to the following embodiment.

  FIG. 1 is a configuration diagram of a precipitation tank equipped with a stirring and mixing apparatus according to the present invention, FIG. 2 is a schematic elevation view of the stirring and mixing apparatus according to the present invention, and FIG. 3 is a plan view of the stirring and mixing apparatus according to the present invention. . The settling tank 1 is equipped with the stirring and mixing apparatus 2 of the present invention. The stirring and mixing device 2 is disposed at the water surface position of the settling tank 1. More specific installation positions will be described later.

  As an outline of the processing of the sedimentation tank 1 equipped with the stirring and mixing device 2, the waste water P1 and the flocculant P2 are allowed to flow into the lower portion of the stirring and mixing device 2, and the flocculating aid P3 is introduced from the upper portion of the stirring and mixing device 2. The agglomerated sludge generated by the stirring and mixing device 2 is precipitated at the lower part of the settling tank 1. Then, the precipitated sludge is scraped to the center of the sedimentation tank 1 by the sludge scraper 3, extracted from the bottom of the sedimentation tank 1, and transferred to the outside by the sludge extraction pump 4. On the other hand, the clear treated water separated from the sludge overflows from the upper part of the settling tank 1.

Next, a specific configuration of the stirring and mixing apparatus 2 will be described.
The stirring and mixing device 2 has a cylindrical container 21. The cylindrical container 21 is closed at the lower part and opened at the upper part, and a stirring member 23 is provided therein. The stirring member 23 is driven by a motor 24. On the outside of the cylindrical container 21, an outer cylinder 22 that is open at both the upper and lower portions is provided. The outer cylinder 22 is disposed so as to be concentric with the cylindrical container 21.

  A mounting plate 25 for mounting the motor 24 is disposed above the cylindrical container 21 and the outer cylinder 22. A bracket 41 a is formed on the lower surface of the mounting plate 25, the lower end portion of the support member 42 a is fixed to the outer cylinder 22, and the outer cylinder 22 is fixed to the mounting plate 25. The cylindrical container 21 is also fixed to the mounting plate 25 by a bracket 41b and a support member 42b, like the outer cylinder 22. Further, the upper end portion of the cylindrical container 21 is located below the upper end portion of the outer cylinder 22. A cutout portion 35 is formed in the upper peripheral edge of the cylindrical container 21. The cutout portion 35 functions to regulate the overflow position when the mixed liquid mixed and stirred inside the cylindrical container 21 overflows the outer cylinder 22. A dropping nozzle 50 for dropping the agglomeration aid P3 toward the notch portion 35 is disposed immediately above the notch portion 35.

  An inflow pipe 51 for allowing the waste water P1 and the flocculant P2 to flow into the cylindrical container 21 is connected to the lower portion of the cylindrical container 21 by piping.

  Here, the installation position of the stirring and mixing apparatus 2 will be described. In the present embodiment, as shown in FIG. 2, the stirring and mixing device 2 is installed in the settling tank 1 so that the bottom surface position of the cutout portion 35 and the water surface position L1 of the settling tank 1 are equal. The present invention is not limited to this, and the stirring and mixing device 2 is installed such that the water surface position L1 of the settling tank 1 exists in the range from the bottom surface 35a to the top surface 35b of the cutout portion 35 of the cylindrical container 21. Just do it. In this way, when the water surface position L1 of the sedimentation tank 1 is below the bottom surface 35a of the cutout portion 35 of the cylindrical container 21, the stirred mixed liquid overflowing from the cylindrical container 21 is cylindrical. The process of forming a downward flow while gently swirling between the cylindrical container 21 and the outer cylinder 22 is caused by dropping to the water surface below the bottom surface 35a of the cutout portion 35 of the cylindrical container 21. This is because it becomes impossible to efficiently grow flocs of the coagulated sludge. On the other hand, when the water surface position L1 of the settling tank 1 is above the upper surface 35b of the cutout portion 35 of the cylindrical container 21, the stirred mixed solution cannot inherently overflow from the cylindrical container 21. is there.

Next, the treatment in the precipitation tank 1 equipped with the stirring and mixing device 2 having the above-described configuration will be described in detail.
The waste water P1 and the flocculant P2 are injected into the lower part of the cylindrical container 21. Thereby, in the cylindrical container 21, waste water P1 and the flocculant P2 contact, and it stir-reacts and produces | generates agglomerated sludge. And the liquid mixture containing this coagulated sludge flows into the outer cylinder 22 side over the notch part 35. At this time, since the aggregation assistant P3 is configured to be dropped into the notch 35, the contact efficiency between the mixed solution and the aggregation assistant P3 is improved. Moreover, since the flow by the stirring member 23 is a downward flow and the inflow of the waste water P1 is in the lower part of the cylindrical container 21, the flow of the waste water is an upward flow. As a result, the downward flow and the upward flow collide with each other and the turbulent flow occurs. Thus, the contact efficiency between the waste water P1 and the flocculant P2 in the cylindrical container 21 is improved, and the generation efficiency of the coagulated sludge is improved. In addition, the contact time is ensured in the upward flow portion from the strong stirring portion to the overflow portion, and stirring and mixing are further promoted by rising while swirling and mixing.

  Next, the stirred mixed liquid rising while swirling and mixing in the cylindrical container 21 flows into the outer cylinder 22 side beyond the notch 35. At this time, since the coagulation aid P3 is dropped into the cutout portion 35, the agitated mixed liquid that has flowed into contact with the coagulation aid P3, and thereafter, the space between the cylindrical container 21 and the outer cylinder 22 is shown in FIG. A downward flow is formed while gently turning in the circumferential direction K1. Thereby, flocs of coagulated sludge grow.

  Thus, the stirring and mixing efficiency is improved and the residence time can be shortened, so that the volume of the apparatus can be reduced.

  Moreover, the cylindrical container which fulfills the function of stirring and mixing the waste water and the flocculant corresponds to a conventional mixing tank. The outer cylinder that functions to form a space for growing flocs of the coagulated sludge corresponds to the conventional coagulation tank. Therefore, although having a single structure of one tank, it has the function of a conventional mixing tank and the function of a coagulation tank, so that a process composed of three tanks, a mixing tank, a coagulation tank, and a coagulation sedimentation tank, is one tank. Can only be simplified. That is, since it has a single structure, the number of equipment including a stirrer and the number of water tanks can be reduced and facilities can be simplified compared to the conventional example.

(Experimental example)
The volume of the cylindrical chamber 21 was operated under the conditions of waste water inflow 110m ³ / d using the apparatus of 0.032 ^3. As a result, coagulated sludge and treated water having the same properties as the standard coagulation sedimentation method described in the background art were obtained. The residence time under these conditions was 0.42 minutes, and it was confirmed that the residence time can be significantly shortened compared to the standard residence time of 5 minutes.

(Other matters)
(1) In the above embodiment, the apparatus for stirring and mixing the waste water and the flocculant has been described. However, the stirring and mixing apparatus 2 according to the present invention also applies to the apparatus for stirring and mixing the raw water P4 and the pH adjuster P5 shown in FIG. Applicable. That is, the raw water P4 and the pH adjuster P5 are caused to flow into the bottom of the stirring and mixing device 2. In view of the pH of the raw water P4 and the target pH for pH adjustment, an alkali or an acid is used as the pH adjuster P5. It is preferable to control the input amount of the pH adjuster P5 by a measured value of a pH meter (not shown). The pH adjustment is performed in every process such as pre-treatment and post-treatment of a wastewater treatment facility.

  (2) In the above embodiment, the apparatus for stirring and mixing the waste water and the flocculant has been described. However, the stirring and mixing apparatus 2 according to the present invention is also applicable to the apparatus for stirring and mixing the raw water P4 and the powdered activated carbon P6 shown in FIG. it can. That is, the raw water P4 and the powder activity P6 are caused to flow into the bottom of the stirring and mixing apparatus 2. Powdered activated carbon may be charged in a dry state, but if it is suspended in water in a separate water tank in advance and charged with a pump, labor can be saved. The raw water P4 and the powdered activated carbon P6 come into contact with each other in the stirring and mixing device 2 and flow out as treated water. Thereafter, the treated water and the powdered activated carbon P6 are separated as necessary. Since the powdered activated carbon P6 can adsorb soluble organic substances and chromaticity components in the raw water P4, it can be carried out in a desired process of a wastewater treatment facility.

  The present invention relates to an agitation and mixing device for use in wastewater treatment facilities such as human waste treatment plants, sewage treatment plants, and landfill leachate treatment facilities to add coagulant to waste water to generate agglomerated sludge, and the agitation and mixing device. It can be applied to the settling tank provided.

21: Cylindrical container 22: Outer cylinder 23: Stirring member 24: Motor 25: Mounting plate 35: Notch portion 35a: Upper surface of the notch portion 35b: Bottom surface of the notch portion 35

Claims (1)

A settling tank provided with a stirring and mixing apparatus for mixing 撹拌the wastewater coagulant,
The stirring and mixing device includes:
A cylindrical container with a closed bottom and an open top;
A pipe connected to the lower part of the cylindrical container, and an inflow pipe for allowing the waste water and the flocculant to flow into the cylindrical container;
Stirring means for generating a downward flow inside the cylindrical container;
With
While stirring and mixing the wastewater and the flocculant in the strong stirring portion formed by the wastewater flowing into the cylindrical container via the inflow pipe and the upward flow of the flocculant and the downward flow by the stirring means ,
Further, on the outside of the cylindrical container, there is provided an outer cylinder that is open at both the upper and lower portions concentric with the cylindrical container, and a cutout portion is formed on the upper peripheral edge of the cylindrical container. It is provided with a coagulant aid addition means for adding a coagulant aid to the water surface part where the stirred mixed solution flows from the notch part to the outer cylinder,
The settling tank, wherein the settling apparatus is installed so that a water surface position of the settling tank exists in a range from a top surface to a bottom surface of the cutout portion of the cylindrical container constituting the stirring and mixing apparatus.

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