JPS5830274B2 - New composting method for organic waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for composting organic wastes such as sewage and wastewater treatment sludge, agricultural waste, and municipal waste.

Traditionally, this type of organic waste has been largely disposed of by direct dumping, incineration, or landfill.

The direct dumping method requires a vast amount of landfill land, which is becoming difficult to secure, and the anaerobic fermentation causes secondary pollution such as the generation of bad odors. All of these measures need to be reconsidered, as they are only measures to extend the life of the landfill by reducing the amount of material.

Therefore, recently there has been a growing trend to use organic waste as a soil conditioner or fertilizer for greenery and farmland as a more rational disposal method.

However, in this case, it is necessary to prevent contamination of greenery and farmland with pathogenic bacteria, parasite eggs, or plant seeds, and to prevent damage to crops due to rapid fermentation of waste in the soil.

Considering the above points, in order to sanitize the waste and make it easier to handle when putting it into the soil, the waste is subjected to aerobic fermentation over a period of 1 to 2 weeks to remove easily degradable substances in the waste. A treatment method that pre-decomposes and stabilizes is attracting attention.

In that case, the fermentation heat is said to inactivate pathogenic bacteria, parasite eggs, plant seeds, etc.

However, it has recently been reported that fermentation heat alone is not always sufficient to sterilize pathogenic bacteria and parasites, kill insects, and inactivate parasite eggs and plant seeds.

If this method of composting using artificial fermentation becomes widespread in the future, it will be necessary to ensure that large amounts of composted waste will not contaminate the soil with pathogens and other pathogens due to the input of large amounts of composted waste into greenery and farmland.

It is well known that radiation is extremely effective in sterilizing and killing pathogenic bacteria, parasites, and inactivating parasite eggs and plant seeds.

The present inventors paid attention to the effects of this radiation, and as a result of intensive research into an efficient composting method for rooted waste, they arrived at the present invention.

That is, the inventors have discovered that sanitized compost can be obtained in a short period of time by irradiating waste in advance, adding a substance containing bacteria, and fermenting the waste.

In the present invention, organic waste refers to sludge such as sewage treatment sludge, human waste treatment sludge, industrial wastewater treatment sludge, silica dung, cow dung, pig dung, and accumulated waste such as litter used in farm buildings;
Refers to waste containing large amounts of organic matter, such as kitchen waste, paper, and other municipal waste, and mixtures thereof.

Radiation in the present invention includes γ rays, β rays, α rays, χ rays,
Refers to electron beams, and also includes mixed radiation.

The bacterial cell-containing material in the present invention refers to a fermented product of organic waste, a commercially available bacterial cell-containing material for fermentation, and a fermented product fermented using the same.

The amount of radiation irradiated varies depending on the waste conditions, but ■0
Approximately 4 to 107 rad is required.

Furthermore, the dose rate during irradiation has little effect on the irradiation effect.

Sludge generally has a high moisture content, so for aerobic fermentation, add straw, rice husk, sawdust, municipal waste with low moisture content, fermented materials, etc. in advance to bring the moisture content to 40-60%. It is preferable to adjust.

These moisture regulators may be added before or after irradiation.

However, if there are bacteria harmful to fermentation in the moisture regulator, or if it is expected that harmful pathogenic bacteria may remain in the fermented product, it is clear that irradiation should be performed after addition.

It is also known that irradiation in the presence of oxygen has a higher bactericidal effect, and in order to reduce the irradiation dose, it is better to add a moisture regulator and irradiate with ventilation.

Irradiated organic waste does not ferment as it is, so it is necessary to add a substance containing bacteria as a fermentation initiator.

The fermentation initiator may be a commercially available fermentation agent or a fermentation product.

The amount added is usually 1 to 50%, preferably 10 to 20%, based on the raw material waste.

It may be more or less than this, but increasing it too much is not a good idea as it increases the volume of the fermenter.

Moreover, if it is too small, the fermentation rate will decrease.

When a substance containing bacterial cells is added to the irradiated material and aeration is performed, fermentation begins immediately and the temperature rises due to the heat of fermentation.

As the temperature rises, the distribution pattern of microorganisms changes, and 50 to 60
At temperatures above ℃, the fermentation rate decreases.

In the conventional method, in order to ensure the sanitary condition of the fermented product, a fermentation method is adopted that maintains the temperature at 70° C. or higher even at the expense of fermentation speed.

However, in the present invention, since the sanitization treatment is performed in advance,
The fermentation temperature can be selected within the optimum range for fermentation, that is, 40 to 60'C.

Therefore, the fermentation speed is fast, and the time required for fermentation is usually 1 to 3 days, although it varies depending on the raw materials and the addition rate of fermented products.

Of course, the fermentation time can be longer than this depending on the conditions for inputting greenery and farmland.

In the method of the present invention, the fermentation temperature can be maintained at 40 to 60°C, so the composting bacteria remain alive without decreasing their activity even after fermentation is completed, and by returning them, efficient fermentation can be carried out. can.

In aerobic fermentation, the supply of oxygen is unreliable;
If this is done using air, there may be concerns about contamination by bacteria in the air.

In that case, contamination by germs can be avoided by ventilating air through a sterilizing filter.

Next, an outline of the apparatus used in the embodiment of the present invention will be explained.

FIG. 1 shows the manner in which sludge is irradiated with Co-60 gamma rays.

1 is an irradiation container, 2 is a set of screw stirring blades, 3 is a stirring motor, and 4 is an air pump for ventilation.

5 is a Co-601J source.

The sludge is placed in an irradiation container and exposed to γ under aeration while being stirred.
irradiated with radiation.

FIG. 2 shows the manner in which sludge is irradiated with an electron beam.

6 is a sludge feeder, and sludge is sent to the sludge prefiner 7 at a constant speed.

Sludge that has reached a certain thickness is moved by an irradiation conveyor 8, subjected to electron beam irradiation by an electron accelerator 9, and stored in a storage 10.

FIG. 3 shows an outline of the sludge fermentation apparatus.

11 is a fermentation container, 12 is a stirring blade, and 13 is a stirring motor.
14 is an air pump for ventilation, 15 is a temperature controller, and 16 is a gas analyzer.

A mixture of irradiated sludge and fermented material is placed in a fermentation container and fermented while stirring and aerating.

The progress of fermentation is monitored by changes in temperature, carbon dioxide gas, and ammonia concentration.

Next, the present invention will be explained by implementation.

Example 1 Sewage treatment sludge (moisture content 80%, coliform bacteria 1.4 x 108
500 g of rice husk was added to a total number of strokes of 5.4 x 10 8 x 1 ky/g, and 1 M rad was irradiated with C0-60 gamma rays at a dose rate of 50 x 10 5 rad/hr using the apparatus shown in FIG.

At this time, the Oban bacteria group in the sludge was below the detection limit, and the total number of strokes was 1.
It was less than 0.03 pieces/g.

To this was added 100 g of commercially available bacterial cells (trade name: Thomas Bacteria, manufactured by Thomas Research Institute, Japan), and fermentation was carried out using the apparatus shown in Figure 3 while aerating (air) at a rate of 0.21 per minute. .

After about 5 hours, the temperature inside the fermentation container will change from room temperature (22℃) to 50℃.
rose to

Thereafter, fermentation was continued while controlling the fermentation temperature and maintaining it at 50°C, and the fermentation was completed in about 40 hours.

The fermented sludge turned brown, had no sludge odor or ammonia odor, and had a compost odor.

In addition, the Oban bacteria group was below the detection limit.

Example 2 Fermentation was carried out under exactly the same conditions as in Example 1, but without controlling the fermentation temperature.

The temperature reached 65°C from room temperature (22°C) in about 15 hours, and then the temperature and carbon dioxide gas generation gradually decreased, and the fermentation was completed in about 60 hours.

The condition of the fermented sludge was the same as in Example 1.

Example 3 Sewage treatment sludge (dehydrated cake with a water content of 80%) was reduced to a thickness of 1 crrL using the apparatus shown in Fig. 2, and a 3Mev electron beam was applied to it using a Kotscroft type electron accelerator.
．． It was irradiated with 5 M rad.

In this case, the Oban bacteria group and the total number of strokes were present at 7.3 x 107 cells/g and 1.4 x 109 cells/g, but due to irradiation, the Oban bacteria group was reduced to below the detection limit, and the total number of strokes was 5×
It decreased to 103 pieces/g or less.

500 g of the fermented product obtained in Example 1 was added to 1 kg of this sludge, and the mixture was heated at a rate of 0.0 per minute using the apparatus shown in FIG. The mixture was aerated and fermented at a rate of :1.

The temperature reached 72°C in about 7 hours, and then the temperature and the amount of carbon dioxide gas generated gradually decreased, and the fermentation was completed in about 50 hours.

The condition of the sludge after fermentation was the same as in Examples 1 and 2.

Example 4 A mixture of 500 g of silica feces and 500 g of kitchen waste was exposed to Co-60 gamma rays at 5 x 10' ra using the apparatus shown in Figure 1.
After irradiating with IM rad at a dose rate of d/hr to completely sterilize the large bacterial group and reduce the total number of strokes to 102 A or less, 1 kg of fermented material was added to this, and the apparatus shown in Figure 3 was used. Fermentation was carried out by aerating at a rate of 0.21 per minute.

The temperature reached 50°C in about 5 hours. Thereafter, fermentation was continued while maintaining the temperature at 50°C, and the fermentation was completed in about 38 hours.

The contents after fermentation turned brown and had a compost odor.

In addition, the Oban bacterial group was below the detection limit.

[Brief explanation of the drawing]

FIG. 1 shows a sludge irradiation device using Co-60γ rays, FIG. 2 shows a sludge irradiation device using electron beams, and FIG. 3 shows a sludge fermentation device. 1 is an irradiation container, 2 is a stirring blade, 3 is a motor, 4 is an air pump, and 5 is a Co-60 radiation source. 6 is a sludge feeder, 7 is a sludge prefiner, 8 is a conveyor, 9 is an electron accelerator, and 10 is a sludge storage. 11 is a fermentation container, 12 is a stirring blade, and 13 is a stirring motor.
14 is an air pump, 15 is a temperature recording controller, and 16 is a gas analyzer.

Claims (1)

[Scope of Claims] 1. Organic waste such as sewage/wastewater treatment sludge, accumulated waste, and municipal garbage is irradiated with ionizing radiation to sanitize the organic waste, and a substance containing bacteria is added to the organic waste. and increase the fermentation temperature to 4
A method for composting organic waste, characterized by carrying out fermentation treatment while maintaining the temperature at 0 to 60°C. 2. The method according to claim 1, characterized in that the irradiation with ionizing radiation is carried out in the presence of a moisture regulator. 3. The method according to claim 1, wherein the irradiation with ionizing radiation is performed in the presence of oxygen.