JP5685902B2 - Organic wastewater treatment method - Google Patents

Description

  The present invention relates to a method for treating organic wastewater, and more specifically, wastewater containing organic matter is passed through a reaction tank holding a non-biological carrier and biologically treated by anaerobic microorganisms attached to the carrier. In the method, the start-up time of the apparatus is greatly reduced by promoting the attachment of microorganisms to the support at the start of operation and forming a highly active biofilm on the support surface at an early stage. The present invention also relates to a method for treating organic wastewater that performs efficient treatment later.

  Anaerobic treatment methods capable of recovering and reusing methane gas are widely used as methods for treating industrial wastewater as methods for treating wastewater containing organic matter (organic wastewater). Above all, UASB which forms high-density and sludge granular sludge, organic waste water containing soluble BOD is circulated upward, and in contact with sludge blanket to perform high load high speed processing. The Upflow Anaerobic Sludge Blanket method has been developed as a method for treating medium to high concentration wastewater. In addition, as a further development of this UASB method, EGSB is used to conduct an anaerobic treatment at a higher load by passing a liquid at a higher flow rate using a reaction vessel with a higher height, developing a sludge blanket at a higher expansion rate. The (Expanded Granule Sludge Blanket) method has also been put into practical use.

Treatment method using these granules is mainly applied to a high concentration wastewater, usually in low concentrations wastewater degree 2000 mg / L or less as COD _Cr concentration not applied. This is because granule may flow out of the reaction tank in the reaction tank, and in low-concentration wastewater, the amount of granule outflow often exceeds the amount of growth in the tank. This is because it is difficult to maintain the catalyst in the reaction tank for a long period of time.

  Conventionally, a method using a fixed bed or a fluidized bed carrier instead of granules has been applied to low-concentration wastewater. The fixed bed carrier uses a microorganism that grows on the surface of the reaction bed that holds the biofilm on the inside of the reaction vessel. The fluidized bed carrier allows a carrier with adjusted specific gravity and size to flow inside the reaction vessel. Then, the treatment is performed using the biofilm formed on the surface of the carrier.

  When a non-biological carrier is used regardless of whether it is a fixed bed carrier or a fluidized bed carrier, it takes a long time to attach microorganisms to the carrier, and as a result, there is a great drawback that it takes a lot of time to start up the apparatus. Conventionally, when starting up an apparatus, the seed sludge in a dispersed state is put into a reaction tank holding a carrier and the operation is started under a condition that the water flow rate is suppressed so that the seed sludge does not flow out. A method of performing normal operation after waiting for formation on the surface has been taken. In this method, for example, as shown in Comparative Example 1 described later, it takes 90 days to start up the apparatus. And

  Patent Document 1 proposes a mixed-bed type reaction tank in which a carrier and granules are mixed. However, the reaction tank described in Patent Document 1 always has a carrier and granules in the reaction tank. The mixed bed is formed, and it is necessary to operate under restricted conditions so that the granules in the reaction tank are not disassembled or dispersed.

  In Patent Document 2, in the treatment by the UASB method, in order to return the sludge flowing out from the reaction tank to the reaction tank when the apparatus is started up, the outflow sludge is attached to the carrier in the carrier column tank installed at the rear stage of the reaction tank. However, it does not promote the adhesion of microorganisms to the carrier in the reaction tank when the apparatus is started up.

  Patent Document 3 describes that in the treatment by the UASB method, the formation of granules at the time of startup is promoted by allowing superabsorbent polymer hydrogel particles to be present in the blanket part. This method also does not promote adhesion of microorganisms to the carrier in a method using a fixed bed or a fluidized bed carrier.

  In addition, as described in the Examples of Patent Document 4, in the UASB method, it is performed that the granular sludge obtained from the UASB reaction tank of another system is used as seed sludge when the reaction tank is started up. However, in the method using a fixed bed or a fluidized bed carrier, granule sludge is not introduced when the reaction tank is started up.

Japanese Patent Laid-Open No. 9-75982 JP-A-3-109998 Japanese Patent Laid-Open No. 7-39896 JP 2002-172399 A

  The present invention relates to a method of biologically treating wastewater containing organic matter through an anaerobic microorganism adhering to a non-biological carrier holding a non-biological carrier and starting the operation, By promoting adhesion and forming a highly active biofilm on the surface of the carrier at an early stage, the time required to start up the device can be greatly reduced, and efficient processing can be performed even after the device is started up. It is an object to provide a method for treating organic wastewater.

  As a result of repeated investigations to solve the above problems, the present inventors have established a reaction tank for holding a non-biological support, in which the methanogenic granules as seed sludge are added to the non-biological support. The above problem is solved by adding operation at a predetermined ratio, allowing methane bacteria granules to be present in the reaction tank only at the beginning of operation, and then disassembling and dispersing the methane bacteria granules. I found that I can do it.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] An organic wastewater treatment method in which wastewater containing organic matter is passed through a reaction vessel holding a non-biological carrier and biologically treated by anaerobic microorganisms attached to the carrier. At the time of start-up, the organic wastewater in a state where the non-biological carrier and the methane bacterium granules are present in the reaction tank in a volume ratio of 100: 5 to 100: 500. And then discontinuing at least a part of the Methane granules in the reaction tank by continuing the flow of organic waste water, wherein the non-biological carrier is a resin. A method for treating organic waste water, which is a carrier made from the methane bacterium granule and has an average particle diameter of 0.5 to 3.0 mm .

[2] The organic wastewater treatment method according to [1], wherein the organic wastewater has an organic substance concentration of 2000 mg-COD _Cr / L or less.

[3] In [1] or [2], the reaction tank is a fluidized bed type reaction tank, and the organic waste water is passed through the reaction tank in an upward flow. Processing method.

[4] In any one of [1] to [3], the sludge load of the reaction tank is 0.8 to 3.0 kg-COD _Cr / kg-VSS / day, Method.

  According to the present invention, in a method in which wastewater containing organic matter is passed through a reaction tank holding a non-biological carrier and biologically treated with anaerobic microorganisms attached to the carrier, By facilitating the attachment of microorganisms and forming a highly active biofilm on the surface of the carrier at an early stage, the time required for starting up the device is greatly reduced and efficient processing is performed even after the device is started up. be able to.

  In other words, the methane bacteria granules introduced into the reaction tank at the start-up of the reaction tank are gradually enlarged or dismantled by continuing the flow of organic waste water, and flow out of the reaction tank by floating, dispersion, decomposition, etc. However, at the initial stage of operation, it contributes to the decomposition of the COD component of the organic waste water, and at the same time promotes the adhesion of microorganisms to the carrier surface as seed sludge.

  For this reason, in the initial stage of operation where the microorganisms are not sufficiently adhered to the carrier surface, the COD component of the organic waste water is decomposed by the action of the methane bacteria granules themselves, and the adhesion of microorganisms to the carrier surface is promoted. After a sufficient amount of microorganisms are supported on the surface of the carrier, even if the methane bacteria granules flow out of the reaction vessel due to disassembly and dispersion of the methane bacteria granules, the microorganism-supported carrier decomposes the COD components. It becomes like this.

  The treatment itself of the present invention is not based on granules, but is a method that uses a carrier, and therefore it is necessary to operate under conditions such that the methane bacteria granules in the reaction tank are disassembled and dispersed over time and do not flow out. And high load operation can be performed.

  For this reason, according to the present invention, it is possible to significantly reduce the time required for starting up the apparatus and to perform efficient processing after the apparatus is started up.

It is a systematic diagram which shows the structure of the biological treatment apparatus used in the Example. 6 is a graph showing changes in processing capacity with time in Example 1 and Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described in detail.

  The organic wastewater treatment method of the present invention is an organic wastewater treatment method in which wastewater containing organic matter is passed through a reaction tank holding a non-biological carrier and biologically treated by anaerobic microorganisms attached to the carrier. In the treatment method, when the reaction vessel is started up, the non-biological carrier and the methane bacterium granule are present in the reaction vessel, and the volume ratio of the non-biological carrier and the methane bacterium granule is in the range of 100: 5 to 100: 500. The organic waste water is started to flow in a state of being allowed to flow, and then the organic waste water is continuously passed to disassemble and disperse at least a part of the methane bacteria granules in the reaction tank. Features.

The present invention is characterized in that methane bacteria granules are introduced as seed sludge into a reaction tank filled with a non-biological carrier and the reaction tank is started up.
The charged methane bacteria granule gradually enlarges or dismantles by continuing operation, and flows out from the reaction tank and disappears due to floating, dispersion, decomposition, and the like. However, at the initial stage of operation, the COD component in the organic waste water is decomposed, and at the same time, the effect of forming a highly active biofilm by promoting the adhesion of microorganisms to the carrier surface as seed sludge is achieved.

In the present invention, the organic wastewater to be treated is not particularly limited as long as it contains an organic substance that can be treated by anaerobic microorganisms, and the COD concentration is not particularly specified, but high-concentration wastewater (COD _Cr concentration of about 2000 mg / L). In the case of excess), since the residence time of the reaction tank can be increased, it is possible to retain a certain amount of dispersal bacteria inside the reaction tank, and to the carrier by adding methane bacteria granules as seed sludge Biofilm adhesion promoting effect is small.

On the other hand, in low-concentration wastewater (COD _Cr concentration of about 2000 mg / L or less), it is necessary to shorten the residence time of the reaction tank in order to perform high-load treatment, and disperse bacteria in the reaction tank. I can't hold it. In this case, according to the present invention, the effect of shortening the start-up period by using methane bacteria granules as seed sludge can be significantly obtained.

Accordingly, the present invention is, _{COD Cr} concentration of 2000 mg / L or less, for example it is effective in the treatment of low-concentration wastewater of about 500 to 2000 / L.
Such wastewater includes, but is not limited to, manufacturing wastewater from food factories, organic wastewater from chemical factories, general sewage, and the like.

The methane fungus granule to be introduced into the reaction tank as seed sludge is sludge in which sludge containing anaerobic microorganisms is granulated by the self-granulating action of microorganisms into sedimentary granules, and in the usual UASB and EGSB methods The granules that are formed can be used. Methane granule contains acid-producing bacteria that produce organic acids from polymer compounds and methanogens that produce methane gas from acetic acid and hydrogen at high concentrations, with a sludge concentration of 50-100 g-VSS / L and dispersed state This is advantageous in that the concentration of bacterial cells is higher than that of sludge and the equipment and cost required for transportation are reduced.
The average particle diameter of methane bacteria granules used as seed sludge is 0.5 to 3.0 mm, particularly about 0.8 to 2.5 mm. For example, when using a fluid carrier described later as a carrier, the average of the carrier The size is preferably about 0.1 to 0.6 times the particle size.

  In the present invention, such a methane bacterium granule is used as a volume ratio of non-biological carrier: methane bacterium granule of 100: 5 to 100: 500, preferably the volume of methane bacterium granule with respect to the volume of the non-biological carrier. The volume is 0.05 to 2.0 times, particularly 0.1 to 1.0 times. If the input amount of methane bacteria granules is less than this range, the effect of the present invention due to the use of methane bacteria granules cannot be sufficiently obtained, and if it is too much, the filling rate in the reaction vessel becomes high and the granules are increased. In order to prevent the flow of granules, and to prevent the outflow of granules, a large capacity reaction tank is required, which is not preferable.

  In the present invention, at the start of operation, a non-biological carrier and methane bacteria granules are held in the reaction tank, organic waste water (raw water) is passed through the reaction tank, and the organic waste water is brought into contact with the methane bacteria granules and the carrier. Anaerobic treatment. The treatment method is not particularly limited, but as in the UASB method and EGSB method, raw water is passed upward through the reaction tank, and a non-biological carrier and methane bacteria granules are developed to form a sludge blanket. It is preferable because the contact efficiency between the raw water, the methane bacteria granules and the carrier is increased.

The methane bacteria granules in the reaction tank need only contribute to the decomposition of COD components in the reaction tank for a short period of time at the start of operation, and therefore can be operated with a higher load than the ordinary granule method. It becomes. For example, as a sludge load, a high load of 0.8 to 3.0 kg-COD _Cr / kg-VSS / day can be applied. In general, it is known that granule disintegration and dispersion proceed under such high load conditions and the granule cannot be maintained in the reaction vessel. In the present invention, granule disassembly and dispersion are known. The formation of a biofilm on the carrier is promoted during the progress of the process. During this time, highly active dispersal bacteria spread on the surface of the carrier, and thereafter, the microorganism-supported carrier on which the highly active biofilm is formed is used. Since efficient processing is performed, it is not necessary to prevent the disassembly and dispersion of granules.

  In this case, the fluid carrier to be used is not particularly limited. However, since the surface area can be increased by foaming and the specific gravity can be easily controlled, a resin carrier such as a polyolefin resin carrier, a polyurethane resin A carrier is preferable, and the average particle size of the carrier is preferably 1 to 5 mm, particularly preferably 2 to 4 mm.

  Here, the particle size of the carrier corresponds to, for example, one side of a cubic carrier, the longest side of a rectangular carrier, and a cylindrical shape of a cylindrical carrier. Corresponds to the longer of height or diameter. In the case of another irregularly shaped carrier, when the carrier is sandwiched between two parallel plates, it corresponds to the interval between the plates when the interval between the plates becomes the largest.

  The upward flow rate of the raw water into the reaction tank is preferably 3 to 20 m / hr, particularly 2 to 5 m / hr, from the viewpoint of treatment efficiency and COD decomposition efficiency.

As described above, the organic matter concentration of the raw water is preferably 500 to 2000 mg / L of COD _Cr , but the load of the reaction tank is 5 to 30 kg-COD _Cr / m ³ / day, particularly 8 to 20 kg-COD _Cr / m. ³ / day is preferred. Moreover, it is preferable that the temperature in a reaction tank shall be 25-40 degreeC, especially 30-38 degreeC. Moreover, it is preferable that the pH of the inflow water of a reaction tank is about 6.5-7.5, Therefore, it is preferable to flow raw water into a reaction tank, after adjusting pH as needed.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example 1]
By using the biological treatment apparatus shown in FIG. 1, sugar-based synthetic wastewater (COD _Cr concentration 1000 mg / L (COD component breakdown: sugar 60 wt%, protein 20 wt%, ethanol 20 wt%), pH 6.8) is used as raw water. Processed.
In this biological treatment apparatus, raw water is introduced into the pH adjustment tank 1 to adjust the pH, and then the pump P is passed through the reaction tank 2 in an upward flow, and a part of the effluent water from the reaction tank 2 is circulated as pH. While circulating to the adjustment tank 1, the remainder is discharged out of the system as treated water. 1A is a pH meter, and 2A and 2B are screens.

  At the start of operation, a reaction tank (capacity: 10 L, diameter: 15 cm, height: about 65 cm) 2, polyolefin resin carrier (column shape, diameter: 2 mm, length: 3 to 4 mm) 4 L and methane bacteria granules (sludge) as seed sludge After adding 0.5 L (concentration 60 g-VSS / L, average particle size 2.3 mm), the raw water was adjusted to pH 7.0 by adding sodium hydroxide as an alkaline agent in the pH adjusting tank 1, and then the reaction tank by pump P The upward circulated water was supplied to 2 under the following conditions.

<Water flow conditions>
HRT: 2 hr
Ascending flow velocity (LV): 3 m / hr
Circulating water flow rate: 890 mL / min
Temperature: 30 ° C

As a result, the processing capacity (load) reached 10 kg-COD _Cr / m ³ / day (1.3 kg-COD _Cr / kg-VSS / day as a sludge load) several days after the start of operation. At this time, since the biofilm is not yet formed on the carrier in the reaction tank 2, the introduced seed sludge is being treated. After that, the methane fungus granules added as seed sludge in operation for about 60 days gradually dismantle and disperse and flow out of the reaction tank. Instead, a biofilm is formed on the surface of the carrier so that it can be treated. became.
FIG. 2 (a) shows the change with time of the processing capability in Example 1. FIG.

[Comparative Example 1]
In Example 1, treatment was performed in the same manner except that 6 L of dispersed anaerobic sludge (sewage digested sludge, sludge concentration 40 g-VSS / L) was added as seed sludge instead of methane bacteria granules at the start of operation. It was.
As a result, all of the dispersed sludge introduced as seed sludge within a few days after the start of operation flowed out, and a biofilm was formed on the surface of the carrier due to the slightly attached microorganisms, but the treatment capacity (load) was 10 kg- About 90 days of operation were required to reach COD _Cr / m ³ / day.
FIG. 2B shows the change with time of the processing capability in Comparative Example 1.

  From the results of Example 1 and Comparative Example 1, in the anaerobic treatment using a non-biological carrier, according to the present invention using methane bacteria granules as seed sludge instead of the conventional dispersed sludge, Even in such a case, it can be seen that the treatment capacity can be exhibited early after the start of water flow, and a stable and high-load operation can be performed by forming a highly active biofilm on the surface of the carrier in the subsequent operation.

1 pH adjustment tank 2 Reaction tank 3 Fluid non-biological carrier 4 Methane granule

Claims (5)

In a method for treating organic wastewater, in which wastewater containing organic matter is passed through a reaction vessel holding a non-biological carrier and biologically treated with anaerobic microorganisms attached to the carrier, the startup of the reaction vessel The organic wastewater is passed in a state where the non-biological carrier and the methane bacterium granule are present in the reaction tank in a volume ratio of 100: 5 to 100: 500. Then, by continuing the flow of organic waste water, at least a part of the methanogen granules in the reaction vessel is disassembled and dispersed, wherein the non-biological carrier is a resin carrier. A method for treating organic wastewater , wherein the methanogenic granules have an average particle size of 0.5 to 3.0 mm . The organic wastewater treatment method according to claim 1, wherein an organic matter concentration of the organic wastewater is 2000 mg-COD _Cr / L or less.   The method for treating organic waste water according to claim 1 or 2, wherein the reaction tank is a fluidized bed reaction tank, and the organic waste water is passed through the reaction tank in an upward flow. In any one of claims 1 to 3, the method of treating organic waste water, wherein a sludge load of the reaction vessel is _{0.8~3.0kg-COD Cr / kg-VSS} / day. The average particle diameter of the non-biological carrier according to any one of claims 1 to 4 is 1 to 5 mm, and the average particle diameter of the methane bacteria granules is 0.1 to 0 of the average particle diameter of the non-biological carrier. Organic wastewater treatment method characterized by being 6 times larger.

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