JPS61181598A - Anaerobic digestion treatment of organic sewage - Google Patents

Abstract

PURPOSE:To keep the low-temp. methane bacteria as the dominant species, to enable the activity to be kept even at low temp. and to perform sufficiently the energy recovery by adding bacteriophage for middle-temp. methane bacteria to the sludge treating an organic sewage. CONSTITUTION:In case of performing the methane fermentation by introducing an organic sewage into an anaerobic digestion vessel of the temp.-nonregulation, bacteriophage for middle-temp. methane bacteria is added in the above- mentioned anaerobic digestion treating vessel and the middle-temp. methane bacteria are selectively sterilized by the bacteriolysis action and the low-temp. methane bacteria are always kept in the system as the dominant species. Thereby the activity can be kept even at low temp. and the energy recovery can be sufficiently performed and also the treatment of the low-concn. organic sewage can be performed.

Description

[Detailed Description of the Invention] [The invention in the field of industrial application relates to a method for anaerobic digestion of organic sewage such as human waste, sludge, industrial wastewater, and sewage. Because effective methane fermentation can be performed without heating, sufficient energy can be recovered with simple equipment.

[Prior Art] Anaerobic digestion methods have been widely used as a method for treating highly concentrated organic wastewater such as human waste and sludge.

In this method, methane gas is obtained as a result of processing,
It has the advantage of being able to recover energy. In areas with high temperatures, there are some that do not require heating, but generally the digestion tank is heated to about 30 to 36 degrees Celsius for effective processing.

[Problem to be solved by this invention (1) Conventional anaerobic digestion uses mesophilic methane bacteria that are active at temperatures of about 30 to 36°C, so they become active when the temperature inside the digester drops in winter. fell, and sufficient processing could not be carried out. Also,
In order to solve this problem, the inside of the tank has been heated, but if this is done, energy cannot be recovered sufficiently. In addition, when anaerobically digesting low-concentration wastewater such as sewage, the anaerobic digestion tank becomes very large and the amount of gas generated per 1 liter of treated water is extremely small, making it impossible to heat it. It is. This invention maintains low-temperature methane bacteria, which are active even at around 20°C, as the dominant species in the digestion tank, and allows sufficient treatment to be carried out even in winter without heating.
To provide an anaerobic digestion method for organic wastewater that can be applied to the treatment of low-concentration non-organic wastewater and can efficiently recover energy.

[Means for solving the problem 1] In this invention, a specific methane bacteria (hereinafter referred to as low-temperature methane bacteria) that is active at a low temperature of around 20° C. is used. These low-temperature methane bacteria include Methanobacterium 8-G (Huikoken Bacteria No. 7873), Methanobacter 8-N4 (Huikoken Bacteria No. 7).
No. 874), Methane Bacteria 8-1P (Feikoken Bacteria @ 78
No. 75), Methanobacterium 16-11-L (Feikoken Bacteria No. 7)
Bacteria such as No. 876) are used. By using this low-temperature methane bacteria, methane fermentation can be carried out without heating even in winter, making it possible to effectively recover energy. However,
The activity of this low-temperature methane bacteria is almost the same as that of mesophilic methane bacteria at around 30°C, and the activity is lower than that of mesophilic methane bacteria at temperatures higher than that. For this reason, if the digester is operated at a temperature of 30° C. or higher in the summer, mesophilic methane bacteria will change to low-temperature methane bacteria and become the dominant species. and,
If the operation continues as it is, sufficient treatment will not be possible in the winter.

Therefore, in this application, 4 Bacterio 77-no against mesophilic methane bacteria is added to the sludge in the anaerobic digestion treatment system, and the mesophilic methane bacteria are selectively assembled with its lytic action, and the low-temperature methane bacteria are always the dominant species. As a result, there are 4 in the system.

[Configuration 1 of Example 1 10 descriptions of embodiments of the invention with reference to drawings.

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

1 is an inflow pipe that introduces organic wastewater such as human waste, sludge, livestock manure, industrial wastewater, and sewage into the pneumatic digestion tank 2; 3
64 is a gas diffuser 3 provided at the center bottom of the digestion tank 2, and a gas discharge pipe 64 leads the methane gas generated in the anaerobic digestion tank to a gas tank (not shown). Reference numeral 5 is a drainage pipe for the digestion liquid, which is connected to the sedimentation tank 6. 7 is a treated water discharge pipe for discharging the supernatant liquid from the settling tank 6. A sludge return pipe 8 is connected to the bottom of the settling tank 6 and returns the settled sludge in the settling tank 6 to the anaerobic digestion tank 2. Reference numeral 9 denotes a surplus sludge discharge pipe, which discharges a portion of the returned sludge in the sludge return pipe 8 as surplus sludge to the outside of the treatment system. 10 is a bacteriophage introduction tube for adding bacteriophage to the anaerobic digestion tank 2.

[Effect 1 of Example 1 Organic wastewater is introduced into the digestion tank 2 through the inflow pipe 1. The inside of this anaerobic digestion tank 2 is agitated by the gas ejected from the aeration device 3, and the inflowing sewage and sludge containing methane bacteria come into contact with each other.

Then, an anaerobic digestion process is performed in which the organic matter in the inflowing wastewater is decomposed into methane gas, carbon dioxide gas, etc. by the action of anaerobic bacteria including methane bacteria.

Here, since oxygen must not be introduced into the anaerobic digestion tank 2, a part of the gas generated in the anaerobic digestion tank 2 is circulated and used in the aeration device 3. Further, the gas generated here is introduced into the gas tank through the gas exhaust pipe 4, and is combusted to recover energy. The residence time in this anaerobic digestion tank 2 is usually about 20 days. In addition to the stirring bar in the tank and the gas stirring in this embodiment, the stirring may be carried out by any suitable means such as mechanical stirring. Here, low-temperature methane bacteria are predominantly present in the anaerobic digestion tank 2, and effective anaerobic digestion is always performed even without heating means in the tank. The anaerobic digestion solution is then transferred to a sedimentation tank 6 through a discharge pipe 5.
The solid-liquid is separated here, and the supernatant liquid is discharged from the treated water discharge pipe 7 as treated water. Further, the settled sludge is returned to the anaerobic digestion tank 2 through the sludge return pipe 8 as seed sludge.

A part of the settled sludge is discharged out of the system as surplus sludge from the surplus sludge discharge pipe 9 and is treated separately. In this invention, Bacteriophage 7age against mesophilic methane bacteria is added to the anaerobic digestion tank 2 from the bacteriophage introduction pipe 10. be done. The added bacterium 7ar) lyses mesophilic methanogens in the sludge by its already known bacteriolytic action. This bacteriolytic action is caused by Bacterio 77-no destroying the bacterial cell membrane and invading the inside of the cell, and replicating approximately 100 to 200 individual Bacterio 77-no from the Bacterio 77-no gene and bacterial protoplasm. It is done in the form of This phenomenon is called bacteriophage reproduction, and the time required for reproduction is about 30 minutes to 3 hours. Therefore, anaerobic digester 2
If some bacteriophages are introduced into the anaerobic digester, they will be replicated within the anaerobic digester, so there is no need to introduce new bacteriophages. In particular, the activity of mesophilic methane bacteria is low in the winter, so it is usually sufficient to introduce the bacteriophage once in the summer (when the temperature inside the tank reaches about 25°C).

Therefore, even if the temperature inside the digestion tank is high, mesophilic methane bacteria cannot proliferate, and low-temperature methane bacteria can be maintained as a dominant species in the anaerobic digestion tank 2.

Even when the temperature inside the tank drops during the winter, the processing function does not deteriorate significantly, and sufficient processing and methane fermentation can be maintained, allowing effective energy recovery.

Furthermore, when bacteriophages attach to bacteria, factors such as calcium ions may be necessary, and factors such as the type and concentration of mesophilic methanogens that are attached to the host bacteria, temperature, and degree of multiinfection have an effect. However, since these conditions can be easily found by those skilled in the art, detailed explanation will be omitted.

Here, human waste with a BOD of 12,000 mg/l was subjected to anaerobic digestion treatment at 30° C. and retained for 30 days. The gas generation rate at that time was about 8 times that of input human urine.

Next, when the treatment tank was operated at a temperature of 25°C, the gas generation rate increased six times. Furthermore, increase the temperature to 20°C
As a result, the gas generation rate steadily decreased, methane fermentation no longer occurred, and treatment became impossible.

On the other hand, in the method of the present invention, in which the above-mentioned low-temperature methane bacteria is initially seeded and a bacteriophage against mesophilic methane bacteria is added thereto, the temperature can be lowered to 20 °C after operating at 30 °C for one month. , maintains 8 times the gas generation rate,
Good processing was performed.

Furthermore, even if bacteriophage is added to the returned sludge,
May be added to wastewater.

[Configuration 1 of Embodiment 2 FIGS. 2 to 4 are schematic diagrams showing a second embodiment of the present invention. In FIG. 2, 21 is an inflow pipe that introduces organic wastewater into an anaerobic digestion tank 22.

Reference numeral 23 denotes a contact filter medium installed in the anaerobic digestion tank 22, and has a configuration as described below. In this example, stirring means is not provided in the tank, but gas is supplied into the contact filter medium 23 to generate an upward flow, but a slit pipe or the like may be provided to circulate the liquid in the tank.

A gas discharge pipe 24 is connected to the top of the anaerobic digestion tank 22, and an excess sludge discharge pipe 25 is connected to the hopper-shaped bottom. A treated water discharge passage 26 is formed in a part of the contact filter medium 23, and a treated water discharge pipe 27 is connected to the upper part of the treated water discharge passage 26.

Each type is provided with a bacteriophage introduction tube 28 for introducing bacteriophage 77-) into the tank.

3 and 4 show an example of the contact filter medium 23. FIG. In this example, the contact filter medium 23 includes a plurality of plate-shaped flocked fiber cloths 30 arranged in parallel in the vertical direction and spaced apart from each other. Flocked fabric 3
0 consists of a plate-shaped base cloth 32 and countless short i-fibers 33 planted therein and protruding. The flocked fabric 30 may be made of commercially available artificial turf, but it can be made with different lengths (several meters +
Those in which short fibers (~several Qm) are planted are particularly suitable.

[Effect 1 of Embodiment 2 Organic wastewater is introduced from the upper part into the digestion tank 22 through the inflow pipe 21. The sewage passes through the contact filter medium 23 and the contact filter medium 2
It comes into contact with methane bacteria etc. held in 3 and undergoes treatment. The treated water, in which the organic matter contained therein has been decomposed, passes through the treated water discharge path 26 and is discharged from the treated water discharge pipe 27. Methane gas generated within the tank is exhausted through the gas exhaust pipe 24 and energy is recovered. Further, surplus sludge is discharged from the surplus sludge discharge pipe 25. Here, the wastewater may be divided into a plurality of tanks and supplied continuously, or may be sequentially supplied to each type. Also, if a circulation means is provided in the tank, the contact will be better and the risk of short circuit will be reduced.
Puyo self-harm city entry 5 fI-, +7. It can prevent sub-19L-yiER from adhering.

Methane bacteria can be effectively retained by using a plate-like flocked fiber cloth as a contact filter medium. Unlike aerobic bacteria, methane bacteria do not easily adhere to filter media. For this reason, it is preferable to use one that can reliably hold methane bacteria within a narrow gap, such as in this example. In addition, the contact filter medium must allow the generated gas to escape upward. With a shape like this example, gas can easily escape upward. Furthermore, short fibers that are oriented diagonally upward as shown in the figure can more effectively retain methane bacteria.

Then, Bacterio 7age against mesophilic methane bacteria was added into the tank from the bacteriophage introduction tube, and this suppressed the growth of mesophilic methane bacteria with the same effect as in Example 1, maintaining the low-temperature methane bacteria as the dominant species. be done.

Even when winter temperatures drop, effective methane fermentation can occur without heating.

In this example, sufficient treatment was possible even if the residence time was set to 173 as in Example 1, that is, 10 days.

In addition, Bacterio 77-no may be added to inflowing sewage.6 [Effect of the invention 1 As described above, according to the present invention, bacteriophage against mesophilic methane bacteria can be added to sludge for treating organic sewage. As a result, low-temperature methane bacteria can be maintained as the dominant species, activity can be maintained even at low temperatures, sufficient energy can be recovered, and low-concentration organic wastewater can be treated.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing one embodiment of the present invention, Fig. 2 is a schematic diagram showing another embodiment, and Figs. 3 and 4 are enlarged views showing an example of the contact filter medium in Fig. 2. . 2... Anaerobic digestion tank, 6...
Sedimentation tank, 10.28...Bacterio7ar)
Introductory tube, 23...Contact filter material

Claims (1)

[Claims] Organic sewage is introduced into an anaerobic digestion tank with no temperature control, and methane is fermented there. Bacteriophage against mesophilic methane bacteria is added to the anaerobic digestion tank, and low-temperature methane bacteria are the dominant species in the tank. A method for anaerobic digestion of organic wastewater, characterized by retaining it as