JP2014166613A - Flocculation/sedimentation active sludge treatment system, and operational method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculation/sedimentation active sludge treatment system which enables early stable operation, and an operational method of the same.SOLUTION: A flocculation/sedimentation active sludge treatment system 100 comprises adding a first inorganic flocculating agent in an inorganic addition tank 2, additionally forming a hydroxide sludge by a second inorganic flocculating agent in a hydroxide sludge tank 5 and feeding the sludge to treatment water, and mixing an active sludge with a hydroxide sludge in the inorganic addition tank 2. Therefore, by mixing an active sludge and a hydroxide sludge in the inorganic addition tank 2 at a start-up operation, a sludge sedimentation property can be enhanced earlier than a case where only the first inorganic flocculating agent is used. This enables early stable operation of the flocculation/sedimentation active sludge treatment system 100.

Description

  The present invention relates to a coagulation sedimentation activated sludge treatment system and an operation method thereof.

  Conventionally, raw water such as organic wastewater is treated with activated sludge in an aeration tank, and the treated water from this aeration tank is solid-liquid separated in a settling tank to settle the sludge and sludge is obtained compared to a water treatment system that obtains supernatant water. A so-called coagulation sedimentation activated sludge treatment system that improves sedimentation is known (see, for example, Patent Document 1).

  The coagulation sedimentation activated sludge treatment system described in Patent Document 1 introduces organic wastewater into an aeration tank to treat activated sludge, and introduces treated water from the aeration tank into a sedimentation separation tank (precipitation part) to form a coagulant. Is added to form a flocculated floc and form a clarified layer, a flocculated floc layer, and a concentrated sludge layer in this order from the liquid level to the bottom in the tank. While improving sludge settling, this improved sludge settling improves the quality of treated water and enables stable operation.

JP-A-7-290082

  However, in the coagulation sedimentation activated sludge treatment system as described above, the period from system startup to stable operation is long, and it has been desired to shorten the period.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a coagulation sedimentation activated sludge treatment system capable of early stable operation and an operation method thereof.

  The coagulation sedimentation activated sludge treatment system according to the present invention has an activated sludge and adds a first inorganic flocculant to the biological reaction part that biologically treats the raw water to be introduced, and the treated water from the biological reaction part. The 1st inorganic flocculant addition part, the treated water which added the 1st inorganic flocculant in the 1st inorganic flocculant addition part, the precipitation part which carries out sedimentation of sludge, and the sludge which carried out precipitation separation in the precipitation part A return line for returning a part of the product as a return sludge to the biological reaction section, a hydroxide sludge created by the second inorganic flocculant, and supplied to the treated water from the biological reaction section, A mixing unit that adjusts pH and mixes activated sludge and hydroxide sludge.

  The coagulation sedimentation activated sludge treatment system according to the present invention performs an activated sludge treatment in a biological reaction section, adds a first inorganic coagulant to the treated water, precipitates and separates the sludge, and returns a part of the sludge through a return line. By having the structure which does, sludge sedimentation property can be improved. Here, when only the first inorganic flocculant is added, the settling speed is slow during the start-up operation of the system, and it is necessary to continuously add the first inorganic flocculant in order to improve the settling speed. . On the other hand, the coagulation sedimentation activated sludge treatment system according to the present invention creates hydroxide sludge not only with the first inorganic flocculant addition section but also with the second inorganic flocculant, and supplies the treated water with the hydroxide. In addition to a physical sludge creation unit, a mixing unit for mixing activated sludge and hydroxide sludge is provided. Therefore, by mixing the activated sludge and the hydroxide sludge in the mixing section during the system start-up operation, it is possible to improve the sludge sedimentation property faster than when only the first inorganic flocculant is used. . As described above, early stable operation of the coagulation sedimentation activated sludge treatment system becomes possible.

  In the coagulation sedimentation activated sludge treatment system according to the present invention, the pH of the mixing unit may be adjusted to 5 to 5.5. Thereby, the mixing property of activated sludge and hydroxide sludge can be improved in the mixing part.

  The operation method of the coagulation sedimentation activated sludge processing system which concerns on this invention has activated sludge, the biological reaction part which biologically processes the raw | natural water introduce | transduced, and the 1st inorganic flocculant in the treated water from a biological reaction part The first inorganic flocculant adding section to which the first inorganic flocculant is added, the treated water to which the first inorganic flocculant is added in the first inorganic flocculant adding section is introduced, and the sludge is settled and separated. A return line for returning a part of the separated sludge to the biological reaction section as return sludge, and an operation method of the coagulation sedimentation activated sludge treatment system, which is performed during the system start-up operation and before the system start-up operation. At least one of the steps of creating a hydroxide sludge with the second inorganic flocculant, supplying the hydroxide sludge to the treated water from the biological reaction section, adjusting the pH, and the activated sludge and water Mixing with oxide sludge And, equipped with a.

  In the operation method of the coagulation sedimentation activated sludge treatment system according to the present invention, the step of creating the hydroxide sludge with the second inorganic coagulant at the time of the system start-up operation and at least one before the system start-up operation I have. Moreover, the process of supplying hydroxide sludge to the treated water from a biological reaction part, and the process of mixing activated sludge and hydroxide sludge while adjusting pH are provided. Therefore, by mixing the activated sludge and the hydroxide sludge during the system start-up operation, the sludge settling property can be improved faster than when only the first inorganic flocculant is used. As described above, early stable operation of the coagulation sedimentation activated sludge treatment system becomes possible.

  According to the present invention, early stable operation can be achieved.

It is a block block diagram of the coagulation sedimentation activated sludge processing system which concerns on embodiment of this invention. It is a figure which shows the mixing part which concerns on a modification. It is a block block diagram of the conventional coagulation sedimentation activated sludge processing system.

  Hereinafter, an embodiment of a coagulation sedimentation activated sludge treatment system according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, the coagulation sedimentation activated sludge treatment system 100 connects an aeration tank 1, an inorganic addition tank 2, a pH adjustment tank 3, and a high speed coagulation sedimentation tank 4 into which raw water such as organic wastewater is introduced in this order. And a sludge return line L1 connecting the high-speed coagulation sedimentation tank 4 and the aeration tank 1 and an excess sludge discharge line L2 branched from the sludge return line L1. Further, the coagulation sedimentation activated sludge treatment system 100 includes a hydroxide sludge tank 5 that creates hydroxide sludge and supplies it to the treated water line L3 between the aeration tank 1 and the inorganic addition tank 2. .

  The aeration tank 1 is a tank having activated sludge and is a tank that decomposes organic components (BOD) by introducing raw water such as organic waste water and performing biological treatment (aerobic treatment) by aeration. An aeration apparatus 11 is provided at the bottom of the aeration tank 1 to supply air from a blower and aerate the treated water.

  The inorganic addition tank 2 is a tank that functions as a first inorganic flocculant addition unit in which treated water containing activated sludge from the aeration tank 1 is introduced through the line L3 and the first inorganic flocculant is added to the treated water. is there. The inorganic addition tank 2 mixes the first inorganic flocculant and the treated water, for example, by stirring or the like, thereby allowing the metal component of the inorganic flocculant to electrochemically react with the activated sludge to hydroxylate the metal component. Generate a flock of things. The inorganic addition tank 2 also functions as a mixing unit that adjusts the pH and mixes the activated sludge and the hydroxide sludge from the hydroxide sludge tank 5 at least downstream of the hydroxide sludge tank 5. It is a tank to do.

  The inorganic addition tank 2 is connected to a first inorganic flocculant supply unit 12 that can supply a first inorganic flocculant. As the first inorganic flocculant, an Al-based inorganic flocculant such as a sulfuric acid band or PAC may be used. For example, an Fe-based inorganic flocculant may be used. In short, it reacts electrochemically with activated sludge. What is necessary is just to have a metal component (Al and Fe).

The inorganic addition tank 2 is connected to an acid supply unit 13 that supplies an acid for pH adjustment. In the start-up operation of the coagulation sedimentation activated sludge treatment system 100, the acid supply unit 13 mixes the activated sludge and the hydroxide sludge from the hydroxide sludge tank 5 so that the treated water in the inorganic addition tank 2 has a pH value. The acid is supplied so that the pH is suitable for the adjustment. A suitable pH for mixing is, for example, 5 to 5.5. When the pH is lower than the lower limit, biological treatment may be affected. On the other hand, when the pH is higher than the upper limit, the cohesiveness (binding property between the activated sludge and the inorganic coagulant) may not be sufficiently increased. For example, sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (HCl) may be applied as the acid supplied by the acid supply unit 13.

The pH adjustment tank 3 is a tank that introduces treated water containing flocs from the inorganic addition tank 2 through the line L4 and adjusts the pH of the treated water. That is, the pH adjustment tank 3 has a pH suitable for wastewater treatment on the downstream side of the inorganic addition tank 2 that has been subjected to pH adjustment (adjustment to lower the pH) for mixing activated sludge and hydroxide sludge. It is the tank which adjusts so that pH may go up. The pH adjustment tank 3 is connected to an alkali supply unit 14 that supplies alkali for pH adjustment. The alkali supply unit 14 supplies the alkali so that the pH of the treated water in the pH adjusting tank 3 becomes a pH at which the settling property of the mixed sludge (sludge in which activated sludge and hydroxide sludge are mixed) is improved. Do. A suitable pH for precipitation is, for example, 6-8. For example, caustic soda (NaOH) or calcium hydroxide (Ca (OH) ₂ ) may be applied as the alkali supplied by the alkali supply unit 14.

  The high-speed agglomeration sedimentation tank 4 is a tank for generating treated flocs containing flocs from the pH adjusting tank 3 through the line L5 and adding a polymer flocculant to produce coarse flocs with coarse flocs.

  Specifically, the high-speed coagulation sedimentation tank 4 introduces treated water containing flocs from the pH adjustment tank 3 into a mixing chamber 4b disposed in an upright state in the tank 4a, and into the mixing chamber 4b. The polymer flocculant is added by being supplied from the polymer flocculant supply unit 16, and in this state, stirring by rotation of the rotary mixer (polymer flocculant stirring blade) 4c disposed in the mixing chamber 4b is performed. Do. As a result, the high-speed coagulation sedimentation tank 4 increases the contact property between the polymer flocculant and the flocs to collect the flocs to generate coarse flocs, and the treated water containing the coarse flocs in the mixing chamber 4b is generated. The horizontal and radially extending and rotating distribution pipe 4d is uniformly distributed and supplied into the tank 4a to form a uniform upward flow in the tank 4a, so that the coarse floc is settled and concentrated at the bottom of the tank 4a. While forming a layer, a coagulated floc layer and a clarified layer as a supernatant are sequentially formed on the concentrated sludge layer.

  The sludge return line L1 is for returning a part of the metal component-containing agglomerated sludge that is the agglomerated sludge of the concentrated sludge layer of the high-speed agglomerated sedimentation tank 4 to the aeration tank 1 as the returned sludge, and the excess sludge discharge line L2 In order to discharge surplus sludge, which becomes surplus in the system, out of the system.

  The hydroxide sludge tank 5 is a tank that functions as a hydroxide sludge creating section that creates hydroxide sludge using the second inorganic flocculant and supplies it to the treated water from the aeration tank 1. The hydroxide sludge tank 5 generates the metal component hydroxide of the second inorganic flocculant by adding the second inorganic flocculant to the water containing activated sludge and stirring the water. The hydroxide sludge tank 5 supplies hydroxide sludge to the treated water passing through the line L3 between the aeration tank 1 and the inorganic addition tank 2 through the line L6. In addition, even if the place which supplies hydroxide sludge is not the line L6, it is the downstream from the part by which biological treatment is made at least by activated sludge, and mixing which mixes activated sludge and hydroxide sludge Any part may be used as long as it is upstream of the unit (or may be supplied to the mixing unit itself as in a modification shown in FIG. 3 described later). Since the hydroxide sludge tank 5 is a tank provided at a position separated from the flow of treated water in the order of the aeration tank 1, the inorganic addition tank 2, the pH adjustment tank 3, and the high-speed coagulation sedimentation tank 4, At the time of system start-up operation, the activated sludge and the second inorganic flocculant can be sufficiently reacted in advance to prepare hydroxide sludge. In the hydroxide sludge tank 5, the hydroxide is efficiently produced by setting the sludge concentration to be equal to or higher than that of the aeration tank 1 and the inorganic addition tank 2.

  The hydroxide sludge tank 5 is connected to a second inorganic flocculant supply unit 17 that can supply the second inorganic flocculant. As the second inorganic flocculant, the same one as the first inorganic flocculant may be used, and an Al-based inorganic flocculant such as a sulfuric acid band or PAC may be used. For example, an Fe-based inorganic flocculant is used. In short, what is necessary is to have a metal component (Al or Fe) that electrochemically reacts with activated sludge.

The hydroxide sludge tank 5 is connected to an alkali supply unit 18 that supplies alkali for pH adjustment. The alkali supply unit 18 supplies the alkali so that the pH of the water in the hydroxide sludge tank 5 is a pH suitable for producing a hydroxide. A suitable pH for making the hydroxide is, for example, 6-8. For example, NaOH or Ca (OH) ₂ may be applied as the alkali supplied by the alkali supply unit 18.

  In such a coagulation sedimentation activated sludge treatment system 100, organic wastewater is introduced into the aeration tank 1 during normal operation (when the system startup operation is completed and sedimentation separation is stable and stable operation). The activated sludge is treated and treated water containing activated sludge from the aeration tank 1 is introduced into the inorganic addition tank 2 and the first inorganic flocculant is added, so that the activated sludge and the first inorganic flocculant are added. A metal component-containing primary agglomerated sludge in which the metal component reacts electrochemically and is floc is generated. Further, the treated water containing the metal component-containing agglomerated sludge from the inorganic addition tank 2 is introduced into the high-speed agglomeration sedimentation tank 4 and the polymer flocculant is added, so that the coarsened metal component-containing agglomerated sludge is generated. . By this metal component-containing aggregated sludge being uniformly distributed and supplied into the tank 3a, a concentrated sludge layer, an aggregated floc layer, and a clarified layer are formed in order from the bottom to the top, and the metal component-containing aggregated sludge of the concentrated sludge layer is formed. A part of the sludge is returned to the aeration tank 1 through the sludge return line L1 as return sludge, and the sludge concentration in the aeration tank 1 is maintained, while the excess sludge is discharged out of the system through the surplus sludge discharge line L2. During stable operation, the production and supply of hydroxide sludge in the hydroxide sludge tank 5 may be stopped, and the acid supply unit 13 in the inorganic addition tank may also be stopped.

  Next, the operation | movement at the time of the starting operation of the system of the coagulation sedimentation activated sludge processing system 100 is demonstrated.

  During the start-up operation of the system of the coagulation sedimentation activated sludge treatment system 100, raw water such as organic waste water is introduced into the aeration tank 1 in the aeration tank 1 to perform the activated sludge treatment. This treated water is introduced into the inorganic addition tank 2 and the first inorganic flocculant is supplied from the first inorganic flocculant supply unit 12.

  On the other hand, in the hydroxide sludge tank 5, the alkali is supplied to the water in the tank from the alkali supply unit 18 so that the pH becomes suitable for the production of the hydroxide sludge, and the second inorganic agglomeration is performed. The second inorganic flocculant is supplied from the agent supply unit 17. As a result, a hydroxide of a metal component is created in the hydroxide sludge tank 5. It should be noted that the hydroxide in the hydroxide sludge tank 5 may be created during the system start-up operation or may be performed in advance before the system start-up operation. It may be performed both before driving.

  The hydroxide sludge created in the hydroxide sludge tank 5 is introduced into the treated water from the aeration tank 1 and introduced into the inorganic addition tank 2 together with the treated water. In the inorganic addition tank 2, the acid is supplied from the acid supply unit 13 to adjust the pH to be suitable for mixing the hydroxide sludge and the activated sludge, and the hydroxide sludge and the activated sludge are mixed by stirring or the like. The Moreover, the 1st inorganic flocculant is supplied from the 1st inorganic flocculant supply part 12, and it reacts with activated sludge and a metal component containing primary flocculent sludge is produced | generated.

  Treated water from the inorganic addition tank 2 is introduced into the pH adjustment tank 3. In the pH adjustment tank 3, the alkali is supplied from the alkali supply unit 14 and the pH is adjusted so that the pH of the mixed sludge is improved. The treated water whose pH has been adjusted is introduced into the high-speed coagulation sedimentation tank 4 and treated in the same manner as in the normal operation described above. At this time, since a sufficient amount of hydroxide is contained in the mixed sludge, the sludge settling speed in the high-speed coagulating sedimentation tank 4 is high, and the coarse floc can be sufficiently settled and separated.

  Next, the operation and effect of the coagulation sedimentation activated sludge treatment system 100 according to the present embodiment will be described.

  First, a conventional coagulation sedimentation activated sludge treatment system 200 will be described with reference to FIG. As shown in FIG. 3, the conventional coagulation sedimentation activated sludge treatment system 200 includes an aeration tank 1, a reaction tank 6, and a high-speed coagulation sedimentation tank 4. The aeration tank 1 and the high-speed coagulation sedimentation tank 4 have the same configuration as the coagulation sedimentation activated sludge treatment system 100 according to the present embodiment. In the reaction tank 6, the alkali is supplied by the alkali supply unit 14 and the first inorganic flocculant is supplied from the first inorganic flocculant supply unit 12.

  Here, in the conventional coagulation sedimentation activated sludge treatment system 200, when the first inorganic flocculant is first added, the sedimentation rate is low, and the sludge is gradually added by continuously adding the first inorganic flocculant. Sedimentation is improved. Therefore, during system start-up operation, a predetermined amount of the first inorganic flocculant and polymer flocculant are added to the activated sludge for continuous operation, and the sedimentation tank load is checked while confirming the improvement of the coagulation sedimentation property. I was adjusting. As described above, the conventional coagulation sedimentation activated sludge treatment system 200 has a problem that the period from the system startup to the stable operation is long (several months).

  On the other hand, the coagulation sedimentation activated sludge treatment system 100 according to the present embodiment not only adds the first inorganic flocculant in the inorganic addition tank 2, but also creates hydroxide sludge using the second inorganic flocculant, and treats it. A hydroxide sludge tank 5 for supplying water is provided, and activated sludge and hydroxide sludge are mixed in the inorganic addition tank 2. Therefore, by mixing activated sludge and hydroxide sludge in the inorganic addition tank 2 at the time of system start-up operation, sludge settling can be improved at an earlier stage than when only the first inorganic flocculant is used. Can be made. As described above, early stable operation of the coagulation sedimentation activated sludge treatment system 100 becomes possible.

  In the coagulation sedimentation activated sludge treatment system 100 according to the present embodiment, the pH is adjusted to 5 to 5.5 in the inorganic addition tank 2. Thereby, in the inorganic addition tank 2 which functions as a mixing part, the mixing property of activated sludge and hydroxide sludge can be improved.

  The present invention is not limited to the embodiment described above.

  In the above-described embodiment, the inorganic addition tank 2 functions as a first inorganic flocculant addition unit for adding the first inorganic flocculant and at the same time functions as a mixing unit for mixing activated sludge and hydroxide sludge. It was. Instead, the part functioning as the first inorganic flocculant addition part and the part functioning as the mixing part are separated (may be used as separate tanks or may be provided with a partition in one layer). May be.

  Moreover, although the aeration tank 1 and the inorganic addition tank 2 were comprised as another tank, for example, as shown in FIG. 2, a part of the aeration tank 1 is partitioned, the upstream side is set as the aeration section 21, and the downstream side It is good also as the mixing part 22 of hydroxide sludge and activated sludge. An acid for pH adjustment is supplied from the acid supply unit 13 to the mixing unit 22, and hydroxide sludge is supplied from the hydroxide sludge tank 5. In addition, a 1st inorganic flocculant may be added to the mixing part 22, and you may add in another tank.

  In the above-described embodiment, the polymer flocculant is added to the mixing chamber 4b of the high-speed coagulation sedimentation tank 4, but a coagulation tank for adding the polymer flocculant may be provided separately.

  DESCRIPTION OF SYMBOLS 1 ... Aeration tank (biological reaction part), 2 ... Inorganic addition tank (1st inorganic flocculant addition part, mixing part), 4 ... High-speed coagulation sedimentation tank (precipitation part), 5 ... Hydroxide sludge tank (hydroxylation) Waste sludge making part), 100 ... coagulation sedimentation activated sludge treatment system, L1 ... return line.

Claims (3)

A biological reaction section having activated sludge and biologically treating the raw water introduced;
A first inorganic flocculant addition section for adding a first inorganic flocculant to treated water from the biological reaction section;
A treated portion into which the first inorganic flocculant is added in the first inorganic flocculant adding portion is introduced, and a settling portion that separates and separates sludge;
A return line for returning a part of the sludge settled and separated in the sedimentation part to the biological reaction part as a return sludge;
Creating a hydroxide sludge with a second inorganic flocculant, and supplying a hydroxide sludge to the treated water from the biological reaction section;
A coagulation sedimentation activated sludge treatment system comprising a mixing unit for adjusting pH and mixing the activated sludge and the hydroxide sludge.   The coagulation sedimentation activated sludge treatment system according to claim 1, wherein the pH is adjusted to 5 to 5.5 in the mixing unit. A biological reaction section having activated sludge and biologically treating the raw water introduced;
A first inorganic flocculant addition section for adding a first inorganic flocculant to treated water from the biological reaction section;
A treated portion into which the first inorganic flocculant is added in the first inorganic flocculant adding portion is introduced, and a settling portion that separates and separates sludge;
A return line for returning a part of the sludge separated and separated in the sedimentation part to the biological reaction part as a return sludge, and an operation method of the coagulation sedimentation activated sludge treatment system comprising:
Creating hydroxide sludge with the second inorganic flocculant during the system startup operation and at least one before the system startup operation;
Supplying the hydroxide sludge to treated water from the biological reaction section;
A method for operating a coagulation sedimentation activated sludge treatment system comprising adjusting the pH and mixing the activated sludge and the hydroxide sludge.

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