JP6046990B2 - Anaerobic wastewater treatment method using carrier - Google Patents

Description

  The present invention relates to a method for treating organic waste water. Specifically, in a wastewater treatment method in which wastewater containing organic matter is biologically treated with anaerobic microorganisms grown on the carrier by passing it through a reaction tank holding the carrier, the wastewater treatment method that has already reached a certain treatment capacity. When the processing capacity of the reaction vessel is reduced, the processing capacity is restored by promoting the growth of microorganisms on the carrier and the contact efficiency with the substrate, or a certain processing capacity is achieved using anaerobic digested sludge as seed sludge. The present invention relates to a method for improving the treatment capacity of the reaction vessel by promoting the growth of microorganisms on a further carrier and the contact efficiency with a substrate.

  As a method for treating wastewater containing organic matter (organic wastewater), an anaerobic treatment method capable of collecting and reusing methane gas is widely used as a method for treating industrial wastewater. Among them, the UASB (Upflow Anaerobic Sludge Blanket) method, which forms granules with good sedimentation, passes organic wastewater in an upward flow, and performs high-load high-speed treatment, is particularly medium- It has been developed as a method for treating highly concentrated wastewater. As an extension of the UASB method, the EGSB (Expanded Granule Sludge Blanket) method, which uses a high-height reaction tank to pass water at a higher flow rate and performs anaerobic treatment with a high load, has also been put to practical use. Yes.

  A method using a fixed bed carrier or a fluidized bed carrier is also used. 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. Thus, the organism is propagated on the carrier for treatment.

  Although high treatment capacity can be expected when using a carrier, anaerobic digested sludge is used for starting up and maintaining / recovering treatment capacity regardless of whether it is a fixed bed carrier or fluidized bed carrier. The capacity was not sufficient (Patent Documents 1 and 2).

  Specifically, if the treatment capacity decreases for some reason, the microorganisms must be grown again on the carrier, but if anaerobic digested sludge is used at that time, it takes a long time to recover the capacity. There were major drawbacks. Also, the processing capacity after startup was not sufficient.

JP 2012-76000 A JP 2012-110820 A

  The present invention relates to a method of biologically treating wastewater containing organic matter with anaerobic microorganisms that have passed through a reaction vessel holding a carrier and grown on the carrier, and that has reached a certain treatment capacity. The method of recovering the treatment capacity by promoting the growth of microorganisms on the carrier and the contact efficiency with the substrate when the treatment capacity of the substrate is reduced, and the reaction tank that has reached a certain treatment capacity using the anaerobic digested sludge as the seed sludge On the other hand, it is an object of the present invention to provide a method for improving the treatment capacity by promoting the growth of microorganisms on a further carrier and the contact efficiency with a substrate.

  As a result of intensive studies, the inventors have reduced the processing capacity of the reaction tank that has already reached a certain processing capacity, or a reaction tank that has reached a certain processing capacity using anaerobic digested sludge as seed sludge. It has been found that the above problem can be solved by adding an appropriate amount of methane bacteria granules and / or a pulverized product thereof to the reaction vessel and adopting operating conditions for efficiently growing methane bacteria.

  The present invention will be specifically described below.

[1] Wastewater containing organic matter is biologically treated by anaerobic microorganisms that have passed through a reaction tank holding an acetalized polyvinyl alcohol gel carrier having an average particle diameter of 2 to 6 mm and grown on the carrier. in the method of treating organic waste water, the reactor being operated already holding the carrier, organic, characterized in that to restore or improve the processing capacity by the addition of methane bacteria granules and / or its pulverized product Wastewater treatment method.

[2] The method for treating organic waste water according to claim 1, wherein the methanogenic granules and / or the pulverized product thereof are present in an amount of 1 to 900 g per liter of the carrier.

  According to the present invention, in a method of biologically treating wastewater containing organic matter through an anaerobic microorganism grown on a carrier through a reaction tank holding the carrier, a certain treatment capacity has already been reached. By promoting the growth of microorganisms on the carrier and the contact efficiency with the substrate for the reaction tank that has reached a certain treatment capacity when the treatment capacity of the reaction tank is reduced or anaerobic digested sludge is used as seed sludge The processing power can be restored.

Conventionally, when the treatment capacity is lowered by the carrier method, the water flow rate is once lowered to a load that can be treated with the carrier, and the water flow rate is gradually increased according to the growth of microorganisms on the carrier.
However, in the case of methane bacteria contained in anaerobic digested sludge, since the growth rate of the bacteria is very small, it was usual that the ability recovery took 1 to 3 months.
In addition, when anaerobic digested sludge is used as seed sludge, it is not efficient as seed sludge because it contains many bacteria and solids other than methane bacteria. Incidentally, anaerobic digestion refers to the decomposition of sludge and solids generated in sewage and human waste sludge treatment by anaerobic bacteria by refusing contact with oxygen. The sludge is called anaerobic digested sludge. It has the advantage of being easy to obtain with the permission of local governments and managers, and is often used as seed sludge.

  In the present invention, when the treatment capacity of the reaction tank that has already reached a certain treatment capacity is reduced or the reaction tank has reached a certain treatment capacity using anaerobic digested sludge as seed sludge, Can be recovered in a short period of time by adding 1 to 900 g per liter of support and / or pulverized product thereof, or promotes microbial growth and contact efficiency with substrate on further support By doing so, the processing capability can be improved.

  The methane bacterium granules and / or pulverized product thereof introduced into the reaction tank contribute to the decomposition of the organic waste water and at the same time promote the growth of microorganisms on the carrier as seed sludge.

  As described above, according to the present invention, it is possible to significantly reduce the time required for recovering the processing capability when the processing capability is reduced, and to perform efficient processing even after the processing capability is recovered, or to anaerobic It is possible to further improve the treatment capacity of the reaction tank that has reached a certain treatment capacity using the digested sludge as seed sludge.

It is a systematic diagram which shows the structure of the biological treatment apparatus used by the Example and the comparative example. 6 is a graph showing changes in processing capability over time in Example 1, Comparative Example 1 and Comparative Example 2. 6 is a graph showing a change in processing capability with time in Example 2, Comparative Example 3 and Comparative Example 4;

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

  The organic wastewater treatment method of the present invention is a method for treating organic wastewater, in which wastewater containing organic matter is passed through a reaction tank holding a carrier and biologically treated by anaerobic microorganisms grown on the carrier. In the case where the treatment capacity of the reaction tank that has already reached a certain treatment capacity decreases, or the reaction tank that has reached a certain treatment capacity using anaerobic digested sludge as seed sludge, and / or methane bacteria granules and / or The pulverized product is added in the range of 1 to 900 g per liter of the carrier.

There are various possible causes for the decline in processing capacity.For example, when a substance that is toxic to microorganisms is mixed, when the inside of the reaction tank becomes acidic or alkaline, oxygen is mixed in an anaerobic atmosphere. When the raw water concentration or flow rate fluctuates greatly, nutrient salts such as nitrogen and phosphorus, minerals such as calcium and magnesium are insufficient, volatile organic acids accumulate in the reaction tank, etc. This is a case where the required COD removal capability cannot be obtained.
In addition, when anaerobic digested sludge is started as seed sludge, anaerobic digested sludge contains a lot of bacteria and solids other than methane bacteria, as mentioned above. It is not efficient.

First of all, it is necessary to remove the cause of the downage of the above-mentioned ability and to set it to normal operating conditions. However, once the microorganisms living on the carrier are damaged, the processing ability cannot be easily recovered. .
Moreover, when anaerobic digested sludge is started as seed sludge, the wastewater treatment capacity of the carrier reaches a certain level.

  In the present invention, in a reaction tank that holds a carrier and has already reached a certain treatment capacity, or after a reduction in treatment capacity, or for a reaction tank that has reached a certain treatment capacity using anaerobic digested sludge as seed sludge, By adding a predetermined amount of granules and / or pulverized product thereof, an effect of promoting the growth of microorganisms on the carrier is obtained.

  In the present invention, the organic wastewater to be treated is not limited as long as it contains an organic substance that can be treated by anaerobic microorganisms, and its COD concentration / type is not specified. Examples include wastewater, organic wastewater from chemical factories, and general sewage. However, it is not limited to these.

The methane bacteria granules charged into the reaction tank are not particularly limited, but the granules (average particle size of 0.5 to 3.0 mm) used in the UASB method and the EGSB method are subjected to anaerobic treatment. Therefore, it is preferable to use these because they contain a lot of methane bacteria. Further, in order to increase the contact efficiency with the carrier, those granules pulverized to an average particle size of 450 μm or less may be used. Moreover, you may use both the granule and the granule grind | pulverized to the average particle diameter of 450 micrometers or less.
As methane bacteria to be introduced into the reaction tank, generally, sewage digested sludge, granules, and the like can be mentioned. It is known that granule has higher methane specific activity than sewage digested sludge. Therefore, granule is preferable to sewage digested sludge.
The method for pulverizing the granules to an average particle size of 450 μm or less is not particularly limited, and examples thereof include a method of pulverizing with a ball mill or the like, a method of pulverizing by passing through a pump, and a method of pulverizing by stirring.

  In the present invention, the methane bacteria granules are preferably present in the range of 1 to 900 g per liter of support, more preferably in the range of 1 to 500 g per liter of support, and in the range of 1 to 150 g per liter of support. More preferably, it is made to exist. Here, the amount of methane bacteria granules is the amount of volatile suspended solids (VSS). VSS refers to an index that is a measure of the total amount of organic solids. If the input amount of methane bacteria granules is less than 1 g per liter of carrier, the effect of the present invention cannot be obtained sufficiently, and if it exceeds 900 g per liter of carrier, the viscosity increases and stirring may become difficult. . Moreover, since there are many outflows of the methane bacteria granule from the inside of a reaction tank and there exists a concern about deterioration of treated water, it is unpreferable.

The carrier to be used is not particularly limited, but a polymer gel carrier excellent in microbial habitability, particularly a polyvinyl alcohol gel carrier is preferable. The average particle size of the carrier is preferably 1 to 10 mm, particularly preferably 2 to 6 mm.
The pore diameter in the hole communicating from the surface to the inside of the carrier can be freely controlled, but preferably only bacteria can inhabit the inside of the carrier, and the pore diameter near the surface is preferably from 0.1 μm to 100 μm, preferably 0.5 μm More preferably, it is 50 μm or less. If the pore diameter near the surface is smaller than 0.1 μm, there is a problem that bacteria cannot enter the inside. If it is larger than 100 μm, large organisms other than bacteria may invade and the efficiency may be lowered. There is no particular limitation on the pore diameter near the center of the carrier.

  The shape of the carrier is not limited, and can be any shape such as a cube, a rectangular parallelepiped, a cylinder, a sphere, or a macaroni. Considering the contact efficiency with methane bacteria, the spherical shape is preferable.

  The organic substance density | concentration of raw | natural water is not specifically limited, CODCr500-50000mg / L etc. can apply widely. The pH of the undiluted solution when flowing into the reaction tank is preferably about 6.5 to 7.5. Therefore, it is preferable that the raw water is adjusted to the pH if necessary and then passed through the reaction tank.

The load on the reaction tank is not particularly limited, but a high load of 5 to 50 kg-CODCr / m ³ · day can be applied. The temperature in the reaction tank is 25 to 40 ° C., particularly 30 to 38 ° C., as in the usual methane fermentation conditions.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these Examples.

[Example 1]
In accordance with the flow shown in FIG. The specifications and processing conditions of the reaction vessel were as follows.

・ Reaction tank specifications Reaction tank: Capacity 8L
Tank temperature: 35-37 ° C
Carrier filled in reaction tank: acetalized polyvinyl alcohol gel carrier (diameter: about 4 mm, specific gravity: 1.025)
Reaction tank carrier filling amount: 40% by volume (relative to tank volume)
・ Treatment conditions Raw water CODCr concentration: 5000 mg / L

As an anaerobic fluidized bed using a carrier, high-concentration raw water flows in a series in which continuous operation is carried out at a volumetric load of 20 kg-CODCr / m ³ · day under the above specifications and processing conditions of the reaction tank, Due to the accumulation of volatile organic acid in the tank, the treatment capacity was lowered, and the volume load had to be reduced to 13 kg-CODCr / m ³ · day. At that time, 15 (g-VSS / L-carrier) of granules were added. As a result, the original volumetric load of 20 kg-CODCr / m ³ · day could be recovered within a few days. Further, the continuous operation was continued for one month or more, but the processing capacity did not decrease, and the CODCr removal rate always remained 90% or more, which was very good.

[Comparative Example 1]
According to the flow shown in FIG. 1, in a series in which the specification tank capacity and processing conditions of the reaction tank are the same as those in Example 1, and continuous operation is performed at a volume load of 20 kg-CODCr / m ³ · day, Inflow and accumulation of volatile organic acid in the reaction tank lowered the treatment capacity, and the volume load had to be reduced to 13 kg-CODCr / m ³ · day. When the operation was continued as it was, the processing capacity gradually decreased, and it became difficult to continue the operation after 30 days.

[Comparative Example 2]
According to the flow shown in FIG. 1, in a series in which the specification tank capacity and processing conditions of the reaction tank are the same as those in Example 1, and continuous operation is performed at a volume load of 20 kg-CODCr / m ³ · day, Inflow and accumulation of volatile organic acid in the reaction tank lowered the treatment capacity, and the volume load had to be reduced to 13 kg-CODCr / m ³ · day. At that time, 15 (g-VSS / L-carrier) of anaerobic digested sludge was added. As a result, although the volume load recovered to 17 kg-CODCr / m ³ · day in about 10 days, the processing capacity gradually decreased thereafter.

[Example 2]
According to the flow shown in FIG. 1, the specification tank capacity and processing conditions of the reaction tank are the same as those in Example 1, and anaerobic digested sludge is used as seed sludge. The maximum volume load is 20 kg-CODCr / m ³ · day continuously. In order to further increase the processing capacity in the series in which the operation was carried out, 15 granules (g-VSS / L-carrier) were added. As a result, the volume load reached 30 kg-CODCr / m ³ · day in about one week. Thereafter, continuous operation was carried out for another month or more under the same load, but the processing capacity did not decrease, and the CODCr removal rate always remained at 90% or more, which was very good. The accumulated removal amount for 40 days was 1072 kg-CODCr.

[Comparative Example 3]
According to the flow shown in FIG. 1, the specification tank capacity and processing conditions of the reaction tank are the same as those in Example 1, and anaerobic digested sludge is used as seed sludge. The maximum volume load is 20 kg-CODCr / m ³ · day. Continued to drive the series that was running. The accumulated removal amount for 40 days was 811 kg-CODCr.

[Comparative Example 4]
According to the flow shown in FIG. 1, the specification tank capacity and processing conditions of the reaction tank are the same as those in Example 1, and anaerobic digested sludge is used as seed sludge. The maximum volume load is 20 kg-CODCr / m ³ · day continuously. In the series in which the operation was carried out, 15 (g-VSS / L-carrier) of anaerobic digested sludge was charged. As a result, although the volume load reached 23 kg-CODCr / m ³ · day in about one week, the processing capacity gradually decreased thereafter. The accumulated removal amount for 40 days was 858 kg-CODCr.

DESCRIPTION OF SYMBOLS 1 ... Raw water 2 ... Anaerobic reaction tank 3 ... Reaction gas 4 ... Treated water

Claims (2)

Organic wastewater containing organic matter is biologically treated by anaerobic microorganisms that have passed through a reaction tank holding an acetalized polyvinyl alcohol gel carrier having an average particle diameter of 2 to 6 mm and grown on the carrier. in the processing method, the reaction vessel is operated already holding the carrier, the processing of organic waste water, characterized in that to restore or improve the processing capacity by the addition of methane bacteria granules and / or its pulverized product Method. The method for treating organic waste water according to claim 1, wherein the methanogenic granules and / or the pulverized product thereof are present in an amount of 1 to 900 g per liter of the carrier.

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