JPS59385A - Anaerobic digestion of organic waste liquor - Google Patents

Abstract

PURPOSE:To improve a digesting speed and the efficiency of digestion, by dividing an anaerobic digestion tank into acid-forming and methane-fermenting zones with retaining plates, dividually charging organic liquid waste, and returning a part of digested sludge to the front part of the tank. CONSTITUTION:An anaerobic digestion tank 1 is divided into a plurality of digestion chambers 3 with retaining plates 2 formed from porous plates or the like, and organic liquid waste 4 is dividually charged in the front three digestion chambers 3 to accelerate digesting reaction. The organic waste liquor 4 sequentially flows through each of the digestion chambers 3. Acid fermentation is brought out by acid-forming bacteria in the front chambers 3, the formed organic acid is successively transferred to the next digestion chambers 3, and methane fermentation is brought out in the rear digestion chambers 3. Thus, the tank 1 is divided into the acid-forming and methane-fermenting zones. A part of digested sludge 5 is returned as seed sludge to the front three digestion chambers 3, and the acid-forming and methane-fermenting zones are held at an ordinary temp. or 30-35 deg.C and 30-35 deg.C, respectively, to accelerate the digesting reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for anaerobic digestion of organic wastewater.

Conventionally, anaerobic digestion has been used for the purpose of stabilizing and reducing the amount of organic matter in wastewater, but in conjunction with the rapid rise in prices of energy materials in recent years, it has become necessary to effectively utilize unused resources. Methane generation technology using anaerobic digestion is attracting attention from the perspective of preventing the dispersion of organic pollutants into the environment.

This anaerobic digestion method uses the action of anaerobic bacteria to decompose organic matter contained in various organic pollutants such as sewage sludge, kitchen waste, agricultural license waste, and industrial waste, and converts it into the final product. Methane (Cll4) and carbon dioxide gas (CO
2), and two types of bacteria with different properties are involved in this digestive reaction. First, in the first stage, acid-producing bacteria solubilize organic matter to produce lower organic acids such as formic acid, acetic acid, and propionic acid, and then in the second stage, methanogens dissolve the lower organic acids produced in the first stage. It is gasified to produce CH4 and CO2.

By the way, in the conventional anaerobic digestion method, in a single digestion tank,
Acidic fermentation by acidophilic bacteria and methane fermentation by methanogenic bacteria are carried out in a mixed manner. Therefore, in the conventional anaerobic digestion method, complex biochemical reactions by different types of bacteria are carried out in the same tank, and therefore the optimum growth activity conditions for acid-producing bacteria and methanogens in the digestion tank are violated. In addition to the problem of difficult maintenance and management of the digestion tank, there was also the problem of poor digestion efficiency and undigested sludge flowing out.

Therefore, the present invention improves the digestion speed and efficiency by separating the inside of the digestion tank into two phases, the acid production zone and the methane fermentation zone, and making it possible to change the optimal reaction conditions for each phase. The object of the present invention is to provide an anaerobic digestion method for organic waste liquid that increases the amount of methane gas generated.

Hereinafter, the present invention will be explained based on the accompanying drawings.

The drawing is a diagram showing one embodiment of the anaerobic digestion method of the present invention. The anaerobic digestion tank 1 is divided into a plurality of digestion chambers 3 by a retention plate 2. The above-mentioned retention plate 2 is formed of a perforated plate or the like, and is used to divide the digestion processing region of the processing liquid in the digestion tank 1 to improve the efficiency of digestion of the processing liquid.

In addition, the organic waste liquid 4 is distributed to the three digestion chambers 3 in front of the digestion tank 1.
It is designed to be divided into 2 parts and introduced.

In this way, when the organic waste liquid 4 is divided and introduced, the load on the anaerobic 11111 bacteria is reduced, and the digestive reaction is promoted. It is discharged from the organic waste section put into the digestion tank 1, but when the organic waste liquid 4 is allowed to flow into the digestion tank 1 in this way, it first undergoes acidic fermentation by acid-producing bacteria in the front digestion chamber 3. occurs, and the organic acids produced by the acid-producing bacteria are sequentially sent to the subsequent digestion chambers 3. Methane fermentation by the methane-producing bacteria occurs in the rear digestion chamber 3, and the inside of the digestion tank 1 becomes the acid-producing zone and the methane fermentation zone. Separated into zones.

Next, in the front part of the digestion tank 1, since anaerobic bacteria in the sludge is insufficient, a part of the digested sludge 5 is returned to the three front digestion chambers 3 as seed sludge. Excess digested sludge is dehydrated and then incinerated or used as compost, and the purified treated water is discharged outside the system.

Further, if the digestion temperature of the acid production zone and the methane fermentation zone is set to room temperature or 30 to 35 °C in the acid production zone, and 30 to 35 °C in the methane fermentation zone, which is suitable for the growth conditions of methane producing bacteria, Digestive reactions are promoted.

- Each of the digestion chambers 3 is provided with a stirring device 6. The purpose of this stirring is to promote the digestive reaction. That is, by stirring, the humidity distribution in the digestion chamber 3 can be made uniform, and the organic matter in the waste liquid 4 flowing into the digestion chamber 3 can be sufficiently contacted and mixed with anaerobic bacteria, Furthermore, formation of a scum layer can be prevented.

Digestion gas 7 generated in each digestion chamber 3 is extracted outside the digestion tank 1 and collected in a gas holder or the like.

As described above, in invention 1, the inside of the anaerobic digestion tank is separated into the acid production zone and the methane fermentation zone, and the organic waste liquid flows from the acid production zone to the methane fermentation zone, so that the digestion reaction occurs very smoothly, and the digestion speed and efficiency are very good. Furthermore, since the waste liquid is charged into the digester in parts, the load on anaerobic bacteria is reduced, and a portion of the digested sludge is returned to the front part of the digester as seed sludge, so the digestion reaction can be started immediately. proceed. Therefore, according to the present invention, the amount of methane gas generated can be significantly increased compared to the conventional anaerobic digestion method. ).

[Brief explanation of drawings]

The drawing is a diagram showing one embodiment of the anaerobic digestion method of the present invention. 1... Anaerobic digestion tank, 2... Retention plate, 4... Organic waste liquid, 5... Digested sludge. Patent applicant Kubota Iron Works Co., Ltd. Agent Kama 1) Text -

Claims (1)

[Claims] In the anaerobic digestion method, in which organic waste liquid is introduced into the digestion tank from the front part of the tank, and after anaerobic digestion, the treated liquid is discharged from the rear part of the digestion tank, "1. Retention in the digestion tank" By providing a plate, the inside of the digestion tank is separated into an acid production zone and a methane fermentation zone, and the organic waste liquid is inputted separately, and a part of the digested sludge is returned to the front part of the digestion tank. An anaerobic digestion method for organic wastewater characterized by: