JPS5845796A - Anaerobic digestion of highly-concentrated organic waste water - Google Patents

Abstract

PURPOSE:To enhance the efficiency of anaerobic digesting reaction, by anaerobically digesting highly-concentrated organic waste water in a digesting vessel, ultrafiltering the digestive fluid by an ultrafiltration means, returning a part of concentrated liquid to the digesting vessel, and withdrawing filtrate as an effluent. CONSTITUTION:Highly-concentrated organic waste water is anaerobically digested in a digesting vessel 1, and the digestive liquid is ultrafiltered by an ultrafiltration means 2. The filtrate is fed as an effluent to the following secondary purifying step, where a part of concentrated liquid is returned to the vessel 1 while the remainder is discharged as excess sludge. That is, the digestive liquid formed by the anaerobic digestion in the vessel 1 is concentrated by the means 2, and the filtrate only is fed as the effluent to the secondary purifying step. Consequently, the process efficiency of anaerobic digestion can be enhanced, a load on the secondary purifying step can be alleviated, and the alleviation of a load on the secondary purifying step can be attained. Moreover, the function of precipitating and separating in the vessel 1 can be lightened or unnecessitated, so that the total volume of the digesting vessel can be made small.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for anaerobic digestion of highly concentrated organic wastewater such as human waste.

In the anaerobic digestion method applied to highly concentrated organic wastewater, one substance is brought into contact with anaerobic bacteria by heating and stirring.
A predetermined process is carried out by the action of promoting the decomposition of the substrate and the production of metabolic products such as methane gas, and the action of separating the desorbed liquid from the sludge containing multiple anaerobic bacteria. The separation of the digested sludge and the desorbed liquid is carried out by a conventional method, in which case the sludge is allowed to stand still. Because it relies on sedimentation separation, the separation effect is often not sufficient even after a long residence time, and there is a drawback that multiple solids flow out together with desorption waves. In particular, when the growth rate of anaerobic bacteria slows down due to the decomposition of the substrate in the liquid to be treated (C), the flow of bacteria into the desorbed liquid will lead to overload of the digestion process, resulting in a decrease in digestion efficiency. Cause. Sedimentation separation time to also prevent bacteria from flowing out! If the length is unnecessarily long, other drawbacks will occur, such as increasing the frequency of scum generation and suppressing gas generation, and reducing the effective volume of the tank due to the sedimentation of solids such as sand mixed in the liquid to be treated. .

An object 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 without the above-mentioned drawbacks.

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

Further, the ultrafiltration device 2 may be housed directly within the digestion tank 1. In this case, the gas pressure caused by methane fermentation in the digestion tank 1 and the water level pressure of the mixed liquid in the digestion tank can be used as part of the filtration pressure, which is efficient.

In order to efficiently carry out methane fermentation in the digestion tank 1,
It is important to maintain a high level of microorganisms in the tank, to ensure that anaerobic conditions are maintained, and to mix well. 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, so that the processing capacity in the digestion tank 1 can be maintained at a high level. In addition to being able to.

Since the concentrated liquid does not come into contact with air, the activity of methane bacteria is not impaired.

As described above, according to this inventor, the digestive fluid produced by anaerobic digestion in the digestion tank is concentrated by the ultrafiltration device, and only the P solution is sent to the secondary treatment process as the desorbed fluid. . Therefore, the throughput of the anaerobic digestion process can be increased and the burden of 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, it does not impair the activity of methane bacteria. Furthermore, when the digestive fluid is pumped to the ultrafiltration device, the exhaust pressure of the concentrated fluid can be used for stirring inside the digestion tank. In addition, in the above example, only the direct ultrafiltration of the digestive fluid was described, but the treated water obtained by solid-liquid separation of the digestive fluid by precipitation treatment, a micro strainer, a sand filter, etc., may be subjected to ultrafiltration. May be processed. ,

[Brief explanation of drawings]

The figure is a flow sheet showing an example of the steps of the method of this invention.

Claims (1)

[Claims] Highly concentrated organic wastewater is anaerobically digested in a digestion tank, this digestive fluid is ultrafiltered by an ultrafiltration device, at least a part of the concentrated liquid is returned to the digestion tank, and the r liquid is used as a desorbed liquid. A method for anaerobic digestion of high-temperature organic wastewater, characterized by taking it out to the outside.