JP2003039039A - Treatment system for organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment system for organic wastes whereby the inhibition of a methane fermentation action by ammoniac nitrogen can be avoided. SOLUTION: The treatment system is provided with a methane fermentation tank 3 that treats organic wastes by mesophilic methanogenic bacteria and a pump that feeds diluting water into the tank 3. The ammoniac nitrogen concentration in the tank 3 is detected with an ammoniac nitrogen concentration detecting part 4. Diluting water is fed into the tank 3 by the pump 6 according to a signal from the detecting part 4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic waste treatment system for treating organic waste by methane fermentation.

[0002]

2. Description of the Related Art When controlling a system for treating organic waste by methane fermentation, the measurement items include gas generation rate, gas composition, liquid phase pH, volatile organic acid (hereinafter referred to as VFA).
Abbreviated as “) concentration, ammonia concentration, etc. are used.

In methane fermentation of food waste and the like, there is a possibility that ammonia is accumulated at a high concentration as the protein is decomposed and the methane fermentation is inhibited.

[0004]

[Problems to be Solved by the Invention] It has been reported that thermophilic methane bacteria, which are widely used in methane fermentation of food waste, have a reduced methanogenic activity when the concentration of ammonia nitrogen exceeds 2500 mg / L. It is said that the one with higher resistance to ammonia nitrogen. When the raw garbage is treated without dilution, the concentration of ammonia nitrogen in the methane tank becomes about 3,000 to 8,000 mg / L. Since it is difficult to treat ammonia in high temperature methane bacteria due to the inhibition of ammonia, it is necessary to dilute the bacterium by about twice, and there is a problem that the entire system becomes large.

Further, as disclosed in Japanese Patent Application Laid-Open No. 2000-93192, there is an invention for detecting the concentration of free ammonia to prevent the inhibition of methane fermentation in advance, but there is a problem that expensive analytical equipment and a skilled technician are required. There is.

The present invention has been made in view of the above points, and an organic methane bacterium which can prevent the inhibition of methane fermentation by ammonia by using a mesophilic methane bacterium as a methane bacterium with a minimum necessary dilution water. The purpose is to provide a treatment system for toxic waste.

[0007]

The present invention is directed to a methane fermentation tank for treating organic waste, a water supply unit for supplying water to the methane fermentation tank, and an ammoniacal nitrogen concentration detection installed in the methane fermentation tank. And a control unit that controls the water supply unit based on a signal from the ammonia nitrogen concentration detection unit to supply water to the methane fermentation tank and dilute the methane fermentation tank. It is a treatment system for toxic waste.

The present invention is characterized in that the control unit controls the water supply unit so that the concentration of ammonia nitrogen in the methane fermentation tank is 5000 mg / L or less and dilutes the methane fermentation tank. It is a processing system.

The present invention further comprises a mist separator installed in a methane fermentation tank for separating water from biogas generated from the methane fermentation tank, and a water supply unit is connected to the mist separator. It is a treatment system for toxic waste.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an organic waste treatment system according to the present invention.

As shown in FIG. 1, the system for treating organic waste comprises a stock solution tank 1 for storing the organic waste, a pump 2 for supplying the organic waste, and a mesophilic methane bacterium for treating the organic waste. A methane fermentation tank 3 for performing methane fermentation treatment by means of the above, and an ammoniacal nitrogen concentration detecting unit 4 installed in the methane fermentation tank 3 for detecting the ammoniacal nitrogen concentration in the methane fermentation tank 3.
The methane fermentation tank 3 is provided with a mist separator 5 for separating water in biogas generated from the methane fermentation tank 3.

Dilution water is supplied to the methane fermentation tank 3 by a pump (water supply unit) 6, and the pump 6 is controlled by a control unit 7 based on a signal from the ammonia nitrogen concentration detection unit 4. A pump (water supply unit) is controlled by the control unit 7.
The dilution water in the mist separator 5 may be circulated into the methane fermentation tank 3 by controlling 6a.

Next, the operation of this embodiment having such a configuration will be described.

The organic waste stored in the stock solution tank 1 is sent to the methane fermentation tank 3 by the pump 2. The organic waste is decomposed into biogas containing methane as a main component in the methane fermentation tank 3 by methane fermentation using mesophilic methane bacteria. The ammonia nitrogen concentration in the methane fermentation tank 3 is detected by the ammonia nitrogen concentration detector 4. When the detected value of this ammoniacal nitrogen concentration exceeds a constant value, for example, 5000 mg / L as described later, the control unit 4 supplies a required minimum amount of dilution water into the methane fermentation tank 3 by a pump 6. . In this case, in order to reduce the amount of dilution water supplied, the water separated by the mist separator 4 is pumped by the pump 6a.
May be sent to the methane fermentation tank 3.

2 and 3 show the relationship between ammoniacal nitrogen and the concentration of volatile organic acids.

FIG. 2 is a diagram showing the relationship between ammoniacal nitrogen and acetic acid and propionic acid (volatile organic acid (VFA)). FIG. 3 is a diagram showing the relationship between ammoniacal nitrogen and acetic acid and propionic acid (volatile organic acid (VFA)) in association with the elapsed days. When the raw garbage is treated without dilution, the concentration of ammonia nitrogen in the methane fermentation tank 3 becomes 3000 to 8000 mg / L. At this time, if the methane bacteria are not acclimatized with ammoniacal nitrogen,
When the concentration of ammonia nitrogen exceeds 5000 mg / L, the concentrations of acetic acid and propionic acid in the methane fermentation tank 3 increase, which may make the methane fermentation operation in the methane fermentation tank 3 difficult (see FIG. 2). And FIG. 3).

That is, as shown in FIG. 3, when the concentration of ammonia nitrogen exceeds 5000 mg / L, the concentration of acetic acid and propionic acid increases, which may cause difficulty in the methane fermentation action. In this case, the control unit 4 controls the pump 6 to supply a fixed amount of dilution water into the methane fermentation tank 3 to dilute the inside of the methane fermentation tank 3 so that the ammonia nitrogen concentration becomes 5000 mg / L or less. be able to. This reduces the concentration of acetic acid and propionic acid,
The methane fermentation action can be restored.

According to the present embodiment, when the concentration of ammonia nitrogen in the methane fermentation tank 3 exceeds a certain value, a fixed minimum amount of dilution water is temporarily supplied to the methane fermentation tank 3. By supplying, the organic waste can be diluted. By diluting the organic waste in this manner, it can be minimized, and thus the inhibition of the methane fermentation action by ammonia nitrogen can be avoided.

[0020]

As described above, according to the present invention,
When the concentration of ammonia nitrogen in the methane fermentation tank exceeds a certain value, it is possible to avoid the inhibition of the methane fermentation action by ammonia nitrogen by temporarily supplying a certain amount of dilution water to the methane fermentation tank. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an organic waste treatment system according to the present invention.

FIG. 2 is a diagram showing a relationship between ammoniacal nitrogen and acetic acid and propionic acid.

FIG. 3 is a diagram showing a relationship between ammoniacal nitrogen and acetic acid and propionic acid.

[Explanation of symbols]

1 stock solution tank 2 pumps 3 methane fermentation tank 4 Concentration detector 5 mist separator 6 pumps 6a pump 7 control unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Mine             1-1 Shibaura, Minato-ku, Tokyo Co., Ltd.             Toshiba headquarters office F-term (reference) 4D004 AA01 AA03 BA03 CA18 CB04                       CC07 DA01 DA02 DA10                 4D059 AA07 BA12 BA22 EA20 EB11

Claims (3)

[Claims] 1. A methane fermentation tank for treating organic waste, a water supply unit for supplying water to the methane fermentation tank, an ammonia nitrogen concentration detection unit installed in the methane fermentation tank, and an ammonia nitrogen concentration detection unit. A system for treating organic waste, comprising: a control unit that controls a water supply unit based on a signal from the unit to supply water to the methane fermentation tank and dilute the methane fermentation tank. 2. The control unit controls the water supply unit to dilute the methane fermentation tank so that the concentration of ammonia nitrogen in the methane fermentation tank becomes 5000 mg / L or less.
The described organic waste treatment system. 3. A mist separator installed in a methane fermentation tank, for separating water from biogas generated from the methane fermentation tank, further comprising a water supply unit connected to the mist separator. The described organic waste treatment system.