JPH0318955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for anaerobically digesting highly concentrated organic wastewater such as human waste. In the anaerobic digestion method applied to highly purulent organic wastewater, the substrate is brought into contact with anaerobic bacteria by heating and stirring, which promotes the decomposition of the substrate and the production of metabolic products such as methane gas. A predetermined treatment is performed by separating the sludge containing a large amount of anaerobic bacteria from the desorbed liquid. In conventional methods, this separation of the digested sludge and the desorbed liquid is based on the sedimentation separation effect caused by standing still, and the separation effect is often not sufficient even after a long residence time, and the separated liquid and the desorbed liquid The disadvantage is that a large amount of solid matter flows out.
In particular, if the substrate in the liquid to be treated is difficult to decompose and the growth rate of anaerobic bacteria is slowed down, the flow of bacteria into the desorption liquid may lead to overload of the digestion process and cause a decrease in digestion efficiency. Become. Furthermore, if the sedimentation separation time is unnecessarily prolonged in order to prevent the outflow of bacteria, the frequency of scum generation will increase and gas generation will be suppressed, and solids such as sand mixed in the liquid to be treated will settle and cause This results in other disadvantages such as reducing the effective volume of the device.

This invention does not have the above-mentioned drawbacks, and
The purpose of the present invention is to provide an anaerobic digestion method that can increase the efficiency of the anaerobic digestion reaction and reduce the burden of subsequent processing.

Next, an example of the steps of the method of this invention will be explained with reference to the drawings. In FIG. 1, highly concentrated organic wastewater such as human waste is first introduced into a digestion tank 1, and is digested under anaerobic conditions to undergo methane fermentation. The digestive fluid is then sent to the ultrafiltration device 2 and filtered by the pressure difference. The filtrate is sent to the subsequent secondary treatment process as a desorbed liquid.
A part of the concentrated liquid is returned to the digestion tank 1, and the remainder is discharged as surplus sludge. Incidentally, the entire concentrated liquid may be returned to the digestion tank 1, and the excess sludge may be directly discharged from the digestion tank 1.

Here, the weight lies in the more specific configuration of the present invention. That is, in the present invention, the ultrafiltration device 2 is provided integrally with the digestion tank 1 or is housed directly within the digestion tank 1. With this configuration, the digestion tank 1
The gas pressure from methane fermentation in the digester and the water level pressure of the mixed liquid in the digester can be used as part of the filtration pressure, allowing efficient and economical operation.

In order to efficiently carry out methane fermentation in the digestion tank 1, the concentration of microorganisms in the tank must be maintained at a high level.
It is important to ensure anaerobic conditions and good agitation. According to this invention, the digestive juice produced in the digestion tank 1 is concentrated by removing the desorbed liquid by the action of the ultrafiltration device 2.
In addition to maintaining high processing capacity in the digestion tank 1,
Either the ultrafiltration device 2 is provided integrally with the digestion tank 1, or
Since it is configured to be housed in the digestion tank 1, the airtightness of the ultrafiltration device 2 can be easily maintained, and since the concentrated liquid does not come into contact with air, the activity of the methane fermentation bacteria is not impaired. .

As described above, according to the present invention, the digestive fluid produced by the anaerobic digestion treatment in the digestion tank is
The ultrafiltration device utilizes the gas pressure of the digester tank and/or the water level pressure of the digester mixed liquid to efficiently and economically concentrate, and only the filtrate is sent to the secondary treatment process as the desorbed liquid. . Therefore, the throughput of anaerobic digestion treatment can be increased, and the load on the secondary treatment process can be reduced. Furthermore, since the sedimentation separation function within the digestion tank can be reduced or eliminated, the total volume of the digestion tank can be reduced. Moreover, since the ultrafiltrated concentrate is circulated without coming into contact with the atmosphere, the activity of the methane bacteria is not impaired.

[Brief explanation of the drawing]

The figure is a flow sheet showing an example of the steps of the method of this invention. 1... Digestion tank, 2... Ultrafiltration device.

Claims (1)

[Claims] 1 Highly concentrated organic wastewater is anaerobically digested in a digestion tank, and this digestive fluid is either provided integrally in the digestion tank, or the gas pressure in the digestion tank is reduced by using an ultrafiltration device housed in the digestion tank. and/or ultrafiltration is performed using the water level pressure of the digester mixed liquid as filtration pressure, at least a part of the concentrated liquid is returned to the digester, and the filtrate is taken out as a separated liquid. Anaerobic digestion method for highly concentrated organic wastewater.