JPS61242696A - Method for fermenting methane - Google Patents

Abstract

PURPOSE:To prevent clogging and to ferment efficiently methane by introducing raw water along with a carrier carrying bacteria into a vertical biological reaction vessel, forming a forced upward flow in the vessel and floating the carrier. CONSTITUTION:A carrier having 2-15mm grain diameter and carrying bacteria is charged along with raw water into a vertical biological reaction vessel, a forced upward flow is formed to float the carrier and hence the apparent occupying volume of the carrier is expanded to >=120% and operation is carried out. Consequently, clogging and channeling are prevented and methane fermentation is efficiently carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for performing methane fermentation by allowing microorganisms to act on raw water such as wastewater containing organic matter.

[Prior Art] Methane fermentation is a fermentation in which various anaerobic microorganisms act on organic matter to decompose it and produce methane and carbon dioxide. This methane fermentation is used to reduce the amount of sludge dumped by digesting and decomposing activated sludge produced in large quantities at sewage treatment plants, etc., or by treating human waste or biochemical oxygen demand for various industrial wastewater containing organic matter. It is used to reduce BOD).

As one method for this methane fermentation, a method is known in which a stock solution and the bacterial cells are brought into contact with each other while the bacterial cells are suspended in a reaction tank. However, in such prior art,
There is a problem in that the contact between the raw water and the bacterial cells is not good, and fermentation requires a long time. Another prior art technique to solve this problem is a so-called immobilization method in which bacterial cells are supported on a carrier and charged into a reaction tank, and methane fermentation is performed with the carrier fixedly placed in the reaction tank. Bed-type methane fermentation has been developed.

[Problems to be solved by the invention] However, fixed bed methane fermentation is effective only in the initial stage of fermentation, and as fermentation progresses, SS in the raw water accumulates between the carriers and causes clogging. New problems have arisen, such as the occurrence of

Furthermore, even if the clogging does not occur, a so-called channeling phenomenon may occur, leading to local distribution of raw water, and in any case, methane fermentation is not promoted as desired.

Therefore, an object of the present invention is to provide a methane fermentation method that promotes the progress of methane fermentation in view of the current situation described in -J-.

Means for Solving Problem E] In the present invention, a carrier with a particle size of 2 to 15 mm containing all bacterial cells is charged into a vertical biological reaction tank, and a strongly controlled -A The Ji is suspended by forming a stream to suspend the carrier.
This methane fermentation method is characterized in that it is operated by expanding the apparent occupied volume of one body to 120% or more.

[Function] According to the present invention, particles with a particle diameter of 2 to 15 m+ can be obtained by supporting bacterial cells.
By charging the carrier together with raw water into a vertical biological reaction tank and suspending the carrier by forming a strongly controlled flow in the tank, the apparent occupied volume of one body was reduced to 120%. Since the operation was carried out with the expansion above, methane fermentation proceeded efficiently in the phase body having 1:1 bacterial cells without clogging due to SS contained in the raw water.

FIG. 1 is a schematic diagram showing an example of a reaction tank configured to carry out the present invention. A carrier 5 carrying bacterial cells is placed in the reaction tank 1, and raw water containing organic raw materials to be subjected to methane fermentation is fed into the reaction tank 1 through a pipe 2. It flows in from F. The reaction tank 1
However, from near part 1 (but below the liquid level), the pipe 2
A pipe line 3 to be connected to the
A circulation pump 4 is provided in the middle.

By driving the circulation pump 4 and performing forced circulation in the direction of the arrow, the inside of the reaction tank l is forcibly circulated! Stream A can be formed. In this way, the force-1-91 is forced into the reaction tank 1.
If the flow is formed, the microbial cells supported on the carrier 5 will form a floating state in the tank, and the frequency of contact between the organic raw material and the microbial cells will increase, and methane fermentation will proceed rapidly. Furthermore, since there is no fear of clogging due to SS, etc., methane fermentation can be continued for a long period of time. CH4, CO2 and other WI salmon products produced by methane fermentation are collected through a pipe 6 connected to the top of the reaction tank 1 into a collection vessel (not shown). Further, the treated liquid after methane fermentation is discharged υ1 from a discharge pipe 7 connected to the -1 part of the reaction tank 1.

Said t-! The body 5 is generally spherical, for example made of fired brick, but may also be a Raschig ring or any other material. There are restrictions on the size of the carrier 5, and when it is spherical, the particle size is selected from 2 to 15'mm.

For shapes other than spheres, the maximum part may be 15 mm or less and the minimum part may be 2fffffl or more -1-. If such a carrier 5 is charged into the reaction tank 1 together with raw water and a forced "-A flow is formed by the circulation pump 4, 1[!! Body 5 is suspended in raw water, and Jr. A 1-shoulder difference in the apparent occupied volume in the state of loading five bodies (before floating) is observed. Then, so that this apparent occupied volume is 120% or more of that before floating,
The circulation flow rate by the circulation pump 4 is selected, thereby ensuring prevention of clogging. If it is less than 120%, floating will be incomplete and the effect of preventing clogging will be uncertain.

The reason why the particle size of the carrier 5 is limited to the above range is that the particle size is 2 mm.
The following cannot be manufactured using current granulation technology; on the other hand, if the particle size exceeds 15 filI11-1-, the phase 5
This is because it is difficult to obtain a floating state in which the apparent occupied volume is 120% or more, and it is therefore uneconomical. An example of the relationship between the particle size of the carrier 5 and the upward flow velocity LV in the tank is shown in FIG.

[Example Table 1 shows the results of the present invention examples and comparative examples. As a comparative example, an example in which bacterial cells were suspended in the reaction tank 1 without using the carrier 5 is shown. Here, the reaction tank 1 has an inner diameter of 100 mmφ.

It is a cylinder with a height of 2 mmφ. However, in Table 1, LV is the flow rate of forced upward flow by circulation pump 4, and TOC
indicates total organic carbon, and VS indicates organic substances contained in the raw water, and the reaction temperature was 37°C.

Table 1 As can be understood from Table 1, when methane fermentation is carried out using the reaction tank 1 applied to the present invention, the processing time is longer than in the conventional methane fermentation in which live bacterial cells are simply suspended. The time was short, and methane fermentation took place quickly. Further, according to the present invention, clogging and channeling phenomena that were conventionally observed are not observed, and therefore methane fermentation proceeds efficiently.

[Effect of the invention] In the present invention, the particle size of the carrier supporting bacterial cells is 2 to 15 mm.
By limiting the size of particles in this range and suspending them so that the apparent occupied volume in the reaction tank is 120% or more, the conventional problems can be solved and 1. This prevents this from occurring, allowing methane fermentation to proceed efficiently.

[Brief explanation of the drawing]

Figure 1 shows a reaction tank 1 configured to carry out Kiwasu 1.
FIG. 2 is a graph showing the relationship between the particle size of the carrier 5 and the flow rate LV. ■...Reaction tank 4...Circulation pump 5...Carrier

Claims (1)

[Claims] A carrier with a particle size of 2 to 15 mm carrying bacterial cells is charged into a vertical biological reaction tank together with raw water, and a forced upward flow is formed in the tank to suspend the carrier, thereby reducing the apparent occupation of the carrier. A methane fermentation method characterized by operating by expanding the volume to 120% or more.