JP6053427B2 - Methane fermentation apparatus and operation method thereof - Google Patents

Description

  The present invention provides a methane fermentation tank provided with an introduction part for introducing wastewater to be treated, a discharge part for discharging treated treated water, and a sludge extraction part for extracting sludge, and stirring for stirring the inside of the methane fermentation tank The present invention relates to a methane fermentation apparatus provided with an apparatus and an operation method thereof.

  Methane fermentation has long been known as an important unit process for wastewater treatment, but there is a problem that the equipment is bulky, and introduction as a relatively large-scale water treatment equipment is often considered. In such a case, as the methane fermentation tank, a methane fermentation tank provided with an introduction section for introducing the wastewater to be treated, a discharge section for discharging the treated water, and a sludge extraction section for extracting the precipitated sludge is provided. A stirrer for stirring the inside of the fermenter is provided.

  High temperature fermentation, heat treatment of sludge, and high sludge concentration can be considered as measures for improving the efficiency of methane fermentation, but these high temperature fermentation and sludge heat treatment are closely related to the heat balance. Heating energy is required to implement the process well, so eventually, the concentration of sludge becomes the most important matter.

  Therefore, it is possible to prevent the sludge concentration in the methane fermentation tank from decreasing by keeping the sludge in a granulated form to prevent the sludge from mixing into the treated water that has undergone methane fermentation and flowing out. It is considered to be. (For example, Patent Document 1)

  In the above-described conventional methane fermentation apparatus, the agitator is always operated so as to maintain the water treatment conditions in the tank as homogeneous as possible.

JP 2000-218288 A

  On the other hand, in the methane fermentation tank, surplus sludge increases with the methane fermentation of the wastewater to be treated, and the residue of the wastewater to be treated is generated in the tank and is precipitated as precipitated sludge. Then, since the sludge concentration in the tank will rise without limit, the sludge extraction operation is performed from the sludge extraction part, and sludge that does not contribute to methane fermentation and excessively grown cells are periodically discharged out of the tank Things have been done. Here, normally, in order to keep the methane fermentation conditions in the methane fermentation tank homogeneous, the agitation device is operated to perform the sludge extraction operation.

When such sludge is extracted, the sludge that does not contribute to the methane fermentation and the microbial bacteria with high methane fermentation activity in the tank are the main components at the same time that the excessively grown cells are pulled out of the tank. There is a fact that even sludge is inevitably pulled out.
Then, even if the activity of methane bacteria in the methane fermentation tank is increased by removing the sludge, the problem that the sludge concentration itself decreases and the ability of methane fermentation as a whole in the methane fermentation tank is reduced occurs. This is one of the reasons why it is difficult to achieve high concentration and high efficiency of methane fermentation.

  Therefore, in view of the above circumstances, an object of the present invention is to provide a technique for maintaining a high sludge concentration in the tank even when the precipitated sludge is extracted from the methane fermentation apparatus.

[Configuration 1]
The characteristic configuration of the operation method of the methane fermentation apparatus of the present invention for the above purpose includes an introduction part for introducing treated wastewater, a discharge part for discharging treated treated water, and a sludge extraction part for extracting precipitated sludge. A method for operating a methane fermentation apparatus comprising a methane fermentation tank and a stirring device for stirring the inside of the methane fermentation tank,
The discharge part and the sludge extraction part are constituted by a drawing path consisting of a common pipe connected to the lower part of the methane fermentation tank, and the treated treated water and the precipitated sludge in the methane fermentation tank are It is configured to be pulled out only through the pulling path,
The methane fermentation step for the first predetermined time while stirring the processed waste water introduced into the methane fermentation tank methane fermentation, by standing a second predetermined time by stopping the stirrer, the agglomerated sludge preferentially It is to perform a sludge extraction step of alternately performing a stirring stop step for precipitation and precipitation separation, and pulling out the treated treatment liquid and the precipitated sludge from the drawing path in a stirring stop state at the end of the stirring stop step. .

[Operation effect 1]
The methane fermentation apparatus anaerobically decomposes the waste water to be treated introduced into the methane fermentation tank with sludge (methane bacteria) in the tank and discharges purified treated water. In addition, the sludge generated at this time, the residue that cannot be anaerobically decomposed, etc., can be precipitated as a precipitated sludge in the lower part of the tank and extracted from the sludge extraction unit. In addition, since sedimentation sludge settles in the tank lower part, normally sludge is extracted from the sludge extraction part below a methane fermentation tank.

  Here, in order to keep the methane fermentation conditions in the methane fermentation tank homogeneous, the sludge extraction operation is performed while maintaining the operation of the stirring device, but the present inventors dare to stop the stirring operation. As a result, while the stirring device was stopped, it was found that specific gravity separation between the residue that does not contribute to the methane fermentation and the highly active sludge was achieved, and the residue could be preferentially precipitated in a relatively short time. . And, rather than the stagnation of methane fermentation during the suspension period of this relatively short stirrer, the maintenance of the activity of the entire methane fermentation tank by suppressing the outflow of highly active sludge with the residue is more effective for methane fermentation efficiency. It was revealed experimentally that it contributed to improvement.

That is, the methane fermentation process in which methane fermentation is performed for a first predetermined time while stirring the wastewater to be treated introduced into the methane fermentation tank, and the agitation sludge is preferentially stopped by stopping the stirring device and allowing to stand for a second predetermined time. The agitation is stopped by alternately performing the agitation stop process that precipitates and separates the precipitate, and at the end of the agitation stop process, the agitation is stopped by performing a sludge extraction process for extracting treated treated water and precipitated sludge from the extraction path in the agitation stopped state Because it is possible to preferentially extract the precipitated sludge mainly composed of the residue precipitated during the process, and to continue the methane fermentation by extracting the treated treatment liquid and the precipitated sludge without extracting the highly active sludge, The activity of the methane fermentation tank can be operated while maintaining high activity of the entire methane fermentation tank.

[Configuration 2]
In addition, the characteristic configuration of the methane fermentation apparatus of the present invention is provided with a methane fermentation tank equipped with an introduction part for introducing wastewater to be treated, a discharge part for discharging treated water, and a sludge extraction part for extracting precipitated sludge, A stirring device for stirring the inside of the methane fermentation tank is provided,
The discharge part and the sludge extraction part are constituted by a drawing path consisting of a common pipe connected to the lower part of the methane fermentation tank, and the treated treated water and the precipitated sludge in the methane fermentation tank are It is configured to be pulled out only through the pulling path,
The methane fermentation step for the first predetermined time while stirring the processed waste water introduced into the methane fermentation tank methane fermentation, by standing a second predetermined time by stopping the stirrer, the agglomerated sludge preferentially An operation control unit that alternately performs a stirring stop process for precipitation and precipitation separation, and performs a sludge extraction process for extracting the treated treated water and the precipitated sludge from the extraction path in a stirring stop state at the end of the stirring stop process. It is in the point provided with.

[Operation effect 2]
According to the above configuration, the operation control unit can perform the sludge extraction step of extracting the sludge from the methane fermentation tank at the end of the stirring stop step. Sludge and highly active sludge can be separated by the specific gravity difference.

Although this 2nd predetermined time changes with the magnitude | size of the said methane fermenter, the property and quantity of process waste water, it can be suitably determined based on a methane fermenter and process waste water. In a typical wastewater to be treated, it is difficult to separate specific gravity because the residue and sludge hardly settle if left standing for about 10 minutes after stopping stirring, but the residue begins to precipitate gradually after 10 minutes. The sludge that has become denser and less active begins to precipitate preferentially because the content of inorganic substances increases. Since the time that elapses 30 minutes starts to precipitate to the normal sludge by pulling with the treated process water and the precipitate which has precipitated before lapse of 10 minutes elapsed after 30 minutes as a precipitate sludge, high methane fermentation activity It has been empirically revealed that the precipitated sludge mainly composed of the residue can be extracted without much extraction of the sludge.

  Therefore, the operation control of the operation control unit removes only the precipitated sludge that is no longer necessary in the tank without reducing the concentration of the highly active sludge in the methane fermentation tank, High fermentation efficiency can be maintained.

[Configuration 3]
In the above configuration, after the sludge extraction step, the operation control unit performs a wastewater supply step of supplying the treatment target wastewater from the introduction unit, and then sequentially performs a methane fermentation step, a stirring stop step, and a sludge extraction step. Can do the original.

[Operation effect 3]
In other words, after the sludge extraction step in the above-described configuration, when the wastewater to be treated is supplied in place of the precipitated sludge extracted into the methane fermentation tank, the methane fermentation proceeds and the organic matter to be methane fermented decreases. Since the wastewater to be treated containing abundant organic matter to be methane-fermented is brought into contact with the sludge for methane fermentation that is maintained in the tank, the organic matter is efficient. A processing procedure that is often methane-fermented can be performed continuously. Here, after the wastewater to be treated is introduced and contacted with the sludge, a methane fermentation process with stirring is performed, so that high fermentation efficiency can continue to be exhibited in the methane fermentation tank.

  Therefore, in the methane fermentation tank, even when the precipitated sludge is extracted from the methane fermentation apparatus, the sludge concentration in the tank can be maintained high, an efficient methane fermentation process can be maintained, and the wastewater to be treated is high. Through efficient processing, energy can be recovered from wastewater with high efficiency, and the environmental load of wastewater can be efficiently reduced.

Flow diagram of the methane fermentation apparatus of the present invention Operation process diagram of methane fermentation equipment

  Below, the methane fermentation apparatus of this invention is demonstrated. In addition, although suitable examples are described below, these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

[Methane fermentation equipment]
The methane fermentation apparatus of the present invention, as shown in FIG.
While equipped with the solubilization tank 1 which solubilizes the garbage and coffee lees as a waste water to be treated under anaerobic conditions, it is provided with a methane fermentation tank 2 for methane fermentation of the solubilized waste water to be treated. In addition, although it is more preferable to provide the solubilization tank 1 when processing wastewater containing a high concentration of solids such as garbage or coffee cake, the property of the wastewater to be treated is If there are few things, it is good also as a structure which flows in the wastewater to be treated directly into the methane fermentation tank 2 without providing the solubilization tank 1.

[Solubilization tank]
The solubilization tank 1 is composed of a mixing tank 10 that mixes waste water to be treated with methane fermentation sludge and receives it as a processing liquid. The mixing tank 10 receives garbage and coffee lees from the processing liquid supply unit in the upper part. The receiving path L1 is connected, and a transfer path L2 for transferring the dispersed fraction of the processing liquid to the methane fermentation tank 2 is connected and provided. Moreover, the bottom part of the said solubilization tank 1 is equipped with the drawing-out path L3 in order to use for the solubilization processes, such as crushing, the fraction which is rich in the garbage and the solid content of a coffee cake in a process liquid. Further, the solubilization tank 1 may be provided with a heating unit 11 for heating the internal processing liquid to 60 ° C. to 80 ° C.

  The mixing tank 10 is provided with a pH adjusting unit 12 for adding an alkali such as caustic soda (NaOH). The amount of alkali added in the pH adjusting unit 12 is determined according to the pH of the treatment liquid in the methane fermentation tank 2 described later, and the pH inside the methane fermentation tank 2 is maintained in the range of about 6.5 to 8.5. Adjusted to

  For heating in the heating unit 11, heavy oil, city gas, electric power, or the like may be used as an energy source. However, cogeneration means (gas engine) that obtains heat and electric power using methane gas generated in a methane fermentation process described later. It is desirable to use exhaust heat obtained by a fuel cell or the like.

  The solubilization treatment of raw garbage or coffee lees in the treatment liquid is carried out by heat treatment in the coexistence of raw garbage or coffee lees and methane fermentation sludge or liquid fraction thereof, that is, in a mixed state thereof. The mixing ratio of raw garbage or coffee cake and methane fermentation sludge or liquid fraction thereof is not particularly limited, but methane fermentation sludge or liquid thereof per 100 parts by weight of dry weight of raw garbage or coffee cake. The fraction is exemplified by 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, and more preferably 100 to 300 parts by weight.

  About temperature conditions at the time of solubilization processing, what is necessary is just 30 degreeC or more, but in order to further improve the solubilization efficiency of garbage or coffee grounds, Preferably it is about 70-95 degreeC, More preferably, it is 70-80 degreeC. The degree can be raised. Methane fermentation sludge includes solubilized bacteria that decompose solids, acid-fermenting bacteria, and methane bacteria that methanate organic acids. In general, methane bacteria cannot grow at a temperature condition of 60 ° C. or higher. Therefore, in the solubilization treatment performed at a temperature condition of 60 ° C. or higher, microorganisms other than methane bacteria in the methane fermentation sludge or its liquid fraction (solubilization). It is thought that solubilization of food waste and coffee lees is performed by bacteria, acid-fermenting bacteria) or substances.

  Moreover, as a heating time at the time of the solubilization treatment, it is appropriately set according to the mixing ratio of the garbage or coffee cake and methane fermentation sludge or its liquid fraction, the heating temperature, etc., for example, 1 to 72 hours, Preferably it is 4-48 hours, More preferably, 12-24 hours are illustrated.

  As a result, the treatment liquid is subjected to a solubilization treatment, and its properties become a slurry having a particle size of 1 mm or more and 10% or less in the solid component in the liquid, and the solid organic matter contained in the garbage or coffee cake is low enough to allow methane fermentation. It is molecularized and solubilized.

[Methane fermentation tank]
The said methane fermentation tank 2 consists of the processing tank 20 provided with the transfer path L2 from the said solubilization tank as an introducing | transducing part which introduce | transduces waste water to be processed. Treat with methane fermentation. In general, anaerobic methane bacteria are used. The treatment tank 20 is provided with a discharge section for discharging treated treated water and a drawing path L4 as a sludge drawing section for drawing precipitated sludge, and the drawing path L4 draws methane fermentation sludge together with the treatment liquid for dehydration. A centrifugal separator 3 is connected. Moreover, the upper part of the said processing tank is equipped with the methane collection | recovery path L5 which collect | recovers the methane gas produced | generated by methane fermentation. The discharge unit for discharging treated process water, that consists of a common pipe sludge extraction unit withdrawing settled sludge.

  The treatment tank 20 is provided with a heating unit 21 that heats the solubilized liquid supplied into the treatment tank 20 to enable high-temperature methane fermentation. The said heating part 21 adjusts so that a methane fermentation process may be performed, maintaining the methane fermentation tank 2 at 40 to 60 degreeC.

  Furthermore, a stirring device 22 having a stirring blade 22a is provided inside the methane fermentation tank 2, and the lower end of the stirring blade 22a is arranged so as to be located slightly above the region where the precipitated sludge is deposited. The stirring device 22 is provided with an operation control unit 23 that intermittently rotates the stirring blade 22a, and is provided with a methane fermentation process for stirring for a first predetermined time and a stirring for a second predetermined time. The operation is repeated alternately with the stop process. The rotation speed of the stirring blade 22a is maintained at such a speed that the residue precipitates but the sludge does not settle in the methane fermentation process.

  When performing a methane fermentation process in this state, as shown to Fig.2 (a), while being able to maintain the methane fermentation efficiency in a methane fermentation process high, a large specific gravity residue can be precipitated, and after that When the stirring stop process is performed, it is possible to solid-liquid separate highly active sludge that easily ferments methane and sludge that has a low activity and agglomerated at a high density, and preferentially precipitate sludge with a low activity. By removing the precipitated sludge separated and precipitated in the sludge extraction step, the foreign matter in the methane fermentation tank 2 is removed without reducing the sludge concentration in the methane fermentation tank 2 so much, and the methane bacteria in the tank are removed. Helps to grow and maintain high methane fermentation efficiency.

  Moreover, the operation control part 23 performs the sludge extraction process of the precipitated sludge with the methane fermentation wastewater from the extraction path L4 at the timing of switching from the stirring stop process of the methane fermentation tank 2 to the methane fermentation process, and the sludge extraction process. Immediately after the start, a waste water supply process for supplying the solubilized liquid of the waste water to be treated is started from the transfer path L2. As a result, in the methane fermentation tank 2, the wastewater to be treated is intermittently methane-fermented and sequentially drained, and after the sludge extraction step, the wastewater supply step of supplying the wastewater to be treated is performed intermittently. Water treatment can be performed.

  In the methane fermentation treatment, the form of methane fermentation is not particularly limited, and may be any known form used in methane fermentation such as a batch type or a fixed bed type. Moreover, you may implement by supplying the solubilizate obtained by the said solubilization, and extracting the methane fermentation processed material in the methane fermentation tank 2 continuously or intermittently. In the case where the supply of the solubilized product and the extraction of the methane fermentation treatment product are performed continuously or intermittently, the supply rate of the solubilized product and the extraction rate of the methane fermentation treatment product are determined in the methane fermentation tank of the solubilization product. What is necessary is just to set suitably so that an average residence time may become the said fermentation processing time.

Thereby, treated water can receive methane fermentation, can produce 200-350m < ³ > methane gas per kg of COD conversion, and the produced | generated methane gas is collect | recovered and utilized. Further, the treatment liquid wastewater discharged together with the sludge from the extraction path L4 becomes wastewater of about 5000 to 20000 mg COD / L and is discharged to the outside.

  Specifically, under the operating condition of alternately repeating the methane fermentation process of 5.5 hours as the first predetermined time and the stirring stop process of 30 minutes as the second predetermined time, about the volume of the methane fermentation tank 2 at the end of the stirring stop process. When extracting sewage sludge with a volume of 5% and solubilizing the same amount of new wastewater to be treated and supplying it to the methane fermentation tank 2, methane fermentation is performed for 6 hours while constantly stirring. As compared with the conventional methane fermentation operation (FIG. 2 (b)) in which the sludge extraction process is performed every time, it is clear that the amount of methane generated is increased by about 10% and the methane fermentation efficiency is improved.

(Centrifuge section)
The centrifugal separation unit 3 includes a centrifugal separation device 30 that solid-liquid separates the methane fermentation sludge and the treatment liquid supplied via the extraction path L4 by centrifugal separation, and methane a part of the solid phase recovered by the centrifugal separation. A return path L6 for returning to the fermenter 2 is provided. The remaining methane fermentation sludge and treatment liquid are discarded from the disposal path L7.

Here, as the centrifugal separator 30, for example, an upper discharge type centrifugal separator is used, and the centrifugal separator 3 removes sludge from the load 10 kg CODcr / m ³ fermenter / day methane fermenter 2 by the centrifugal separator. 30 and withdrawing the sludge that has been subjected to the sludge centrifugal separation at 2.5 times the amount of treated water to be introduced (centrifugation conditions with a centrifugal force of 2000 g and a residence time of 10 minutes) so that the entire amount is returned from the return path L6. Circulate the treated water. Thus, the sludge concentration in the methane fermentation tank is maintained at 1% -10%.

  Therefore, an efficient methane fermentation process can be maintained, and various wastewater can be treated as a methane fermentation tank capable of efficiently reducing the environmental load of wastewater by highly efficient treatment of wastewater to be treated.

1: Solubilization tank 10: Mixing tank 11: Heating section 12: pH adjusting section 2: Methane fermentation tank 20: Treatment tank 22: Stirring device 22a: Stirring blade 23: Operation control section 3: Centrifugal section 30: Centrifugal apparatus L1: receiving path L2: transfer path L3: withdrawal path L4: withdrawal path L5: methane recovery path L6: return path L7: disposal path

Claims (3)

A methane fermentation tank equipped with an introduction part for introducing treated wastewater, a discharge part for discharging treated treated water, a sludge extraction part for extracting precipitated sludge, and a stirring device for stirring the inside of the methane fermentation tank are provided. A method for operating a methane fermentation apparatus,
The discharge part and the sludge extraction part are constituted by a drawing path consisting of a common pipe connected to the lower part of the methane fermentation tank, and the treated treated water and the precipitated sludge in the methane fermentation tank are It is configured to be pulled out only through the pulling path,
The methane fermentation step for the first predetermined time while stirring the processed waste water introduced into the methane fermentation tank methane fermentation, by standing a second predetermined time by stopping the stirrer, the agglomerated sludge preferentially A methane fermentation apparatus that alternately performs a stirring stop step for precipitation and precipitation separation, and performs a sludge extraction step for extracting the treated treated water and the precipitated sludge from the extraction path in the stirring stop state at the end of the stirring stop step. Driving method. A methane fermentation tank equipped with an introduction part for introducing treated wastewater, a discharge part for discharging treated treated water, a sludge extraction part for extracting precipitated sludge, and a stirring device for stirring the inside of the methane fermentation tank are provided. A methane fermentation apparatus,
The discharge part and the sludge extraction part are constituted by a drawing path consisting of a common pipe connected to the lower part of the methane fermentation tank, and the treated treated water and the precipitated sludge in the methane fermentation tank are It is configured to be pulled out only through the pulling path,
The methane fermentation step for the first predetermined time while stirring the processed waste water introduced into the methane fermentation tank methane fermentation, by standing a second predetermined time by stopping the stirrer, the agglomerated sludge preferentially An operation control unit that alternately performs a stirring stop process for precipitation and precipitation separation, and performs a sludge extraction process for extracting the treated treated water and the precipitated sludge from the extraction path in a stirring stop state at the end of the stirring stop process. A methane fermentation apparatus.   The said operation control part performs the waste water supply process which supplies the process waste water from the said introduction part after the said sludge extraction process, and then performs a methane fermentation process, a stirring stop process, and a sludge extraction process in order. Methane fermentation equipment.

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