JP3433164B2 - Garbage processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a food waste processing apparatus for accommodating a mixture of food waste and a food waste processing material in a processing tank and adjusting the water content of the mixture to decompose the food waste. It is a thing.

[0002]

2. Description of the Related Art Conventionally, raw garbage is put into a treatment tank filled with porous wood chips (hole chips) which are raw garbage treating materials, and the raw garbage and the whole tip are agitated. By mixing, by the microorganisms inhabiting the mixture,
There is known a food waste processing device that decomposes food waste into water and carbon dioxide gas. In such a food waste treatment device, the treatment efficiency can be improved by adjusting the water content of the food waste / chip mixture to a range suitable for the inhabitation of microorganisms. Therefore, the food waste treatment equipment is equipped with a blower mechanism that sends air into the treatment tank and a heater that heats and dries the food waste / chip mixture in the treatment tank. A water supply device for supplying water to the garbage / chip mixture is provided to adjust the water content.

In order to automatically and optimally adjust the water content,
It is necessary to measure the water content of the food waste / chip mixture in the treatment tank. Conventionally, as a method of measuring the water content, a method of detecting the water content by contacting a pair of electrodes with the garbage / chip mixture and measuring the electrical resistance between the electrodes
(JP-A-7-33572) or a method of detecting the water content by contacting a heating resistor with the food waste / chip mixture and measuring the temperature rise of the food waste / chip mixture (JP-A-8-5
No. 7458) is proposed.

[0004]

However, in the method of measuring the water content using a pair of electrodes, when an electrolyte solution or substance is interposed between the pair of electrodes, the electric resistance between the electrodes changes significantly. Therefore, there is a problem that a large error occurs in the measured value of the water content. In addition, in the method of measuring the water content using a heating resistor, the heating resistor and raw garbage
When the adhesiveness of the chip mixture is poor, there is a problem that the measurement accuracy of the water content decreases.

Therefore, the applicant has developed a water content measuring device which improves the measurement accuracy by optically measuring the water content of the food waste / chip mixture, and has developed a food waste processing device equipped with the device. Patent pending (Japanese Patent Application No. 2000-087235, etc.). The water content measuring device comprises a tungsten lamp for irradiating the garbage / chip mixture with light, and a silicon photodiode and a pyroelectric element for detecting the light reflected from the garbage / chip mixture. The water content of the garbage / chip mixture is calculated based on the ratio of the amount of reflected light detected by using the device and the amount of reflected light detected by using the pyroelectric element.

The silicon photodiode has sensitivity in the first wavelength range (less than 1 μm) where the water transmittance is large, whereas the pyroelectric element is used in the second wavelength range (where the water transmittance is small). (1 μm or more). Therefore, while the amount of light detected by the pyroelectric element changes greatly depending on the difference in water content of the garbage / chip mixture,
The amount of light detected by the silicon photodiode hardly changes. Therefore, if the ratio of the amount of light detected by the silicon photodiode and the amount of light detected by the pyroelectric element is taken, the known Lambert-Beer equation described below is used to determine the water content of the food waste / chip mixture from the ratio of the amount of light detected. The rate can be calculated.

According to the above-mentioned water content measuring device, the water content of the garbage / chip mixture can be optically measured from the outside of the treatment tank, so that there is no problem in the conventional water content measuring method described above, A higher measurement accuracy can be obtained.

[0008] However, according to the research conducted by the applicant, in the food waste disposer including the above-mentioned water content measuring device,
It was found that a stable measurement value for the water content of the garbage / chip mixture could not be obtained. An object of the present invention is to obtain a stable measurement value of water content in a food waste treatment apparatus equipped with an apparatus for optically measuring the water content of a mixture in a treatment tank.

[0009]

[Means for Solving the Problems] The applicant has clarified the cause of the inability to obtain a stable measurement value of water content as follows. That is, in a food waste treatment device equipped with an optical water content detector, it is desirable to measure the water content in a state in which the food waste / chip mixture in the treatment tank is sufficiently stirred. As shown, when the tip of the stirring rod (2) passes through the bottom dead center, the water content detector is placed at a position facing the tip.
(6) is arranged and the water content is measured during rotation of the stir bar (2). Therefore, as shown in the figure, when the tip of the stirring rod (2) passes through the bottom dead center or immediately after the tip of the stirring rod (2) passes through the bottom dead center as shown in FIG. There is a case where light is emitted from and the amount of reflected light is detected.

As shown in FIG. 7, when light is emitted from the tungsten lamp (61) when the tip of the stirring rod (2) passes through the bottom dead center, the tip of the stirring rod (2) has a tungsten lamp ( The amount of reflected light is detected with the central portion of the irradiation area of the light from 61) covered. Also, in the process of rotating the stirring rod (2), a void portion (15) having a large number of voids is formed at the rear portion of the stirring rod (2) as shown in FIGS.
Therefore, as shown in FIG. 8, when light is emitted from the tungsten lamp (61) immediately after the tip of the stirring rod (2) passes through the bottom dead center, the center of the irradiation area of the light from the tungsten lamp (61). The amount of reflected light is detected in the state where the void (15) is formed in the part. In this way, since the state of the irradiation area of the light differs depending on the timing at which the light is emitted from the tungsten lamp (61), there is a large variation in the amount of light detected by the silicon photodiode (62) and the pyroelectric element (63). Therefore, a stable measurement value of water content cannot be obtained.

The food waste treating apparatus according to the present invention comprises a stirring device for stirring the mixture in the processing tank by rotation, a rotation angle sensor for detecting the rotation angle of the stirring device, and a water content of the mixture in the processing tank. A water content detecting device for detecting and a water content adjusting device for adjusting the water content based on the detected water content are provided. The water content detection device includes a light emitting element that irradiates the mixture with light including a first wavelength band having a large transmittance for water and a second wavelength band having a small transmittance for water, and the first wavelength. A first light-receiving element that has a sensitivity in the region, receives the reflected light from the mixture in the processing tank, and emits an output according to the amount of received light, and has a sensitivity in the second wavelength region, A second light receiving element that receives the reflected light from the mixture in the tank and emits an output according to the magnitude of the amount of received light or its change, and the stirring device based on the output signal of the rotation angle sensor during the operation of the stirring device. An arithmetic processing circuit for detecting a time point when the vehicle passes a predetermined rotation angle posture and calculating the water content of the mixture in the processing tank based on the output signals of the first and second light receiving elements at the detection time point. I am.

In the above-mentioned food waste processing apparatus, of the light emitted from the light emitting element, the first wavelength component is detected by the first light receiving element, and the second wavelength component is detected by the second light receiving element. It Here, when comparing the case where the water content of the mixture in the treatment tank is high and the case where the water content is small, the wavelength range of the light component detected by the first light receiving element (first wavelength range)
Since the transmittance for water is large, there is almost no difference in the amount of light detected by the first light receiving element, but the transmittance for water is in the wavelength range of the light component detected by the second light receiving element (second wavelength range). Is small, a difference occurs in the amount of light detected by the second light receiving element. Therefore, if the ratio of the amount of light detected by the second light receiving element to the amount of light detected by the first light receiving element is taken, the larger the ratio, the smaller the water content of the mixture, and the smaller this ratio, the larger the water content of the mixture. Become. Therefore, the water content of the mixture in the processing tank is calculated based on the output signals of the first light receiving element and the second light receiving element.

In the food waste processing apparatus according to the present invention,
During the operation of the stirrer, the water content of the mixture in the treatment tank is calculated when the stirrer passes a predetermined rotation angle posture.
Here, the state of the irradiation area of the light from the light emitting element changes according to the operation of the stirring device, but is the same state when the stirring device passes through the same rotation angle posture. Therefore, there is no large variation in the light detection amount by the first light receiving element and the light detection amount by the second light receiving element when the stirring device passes through the same rotation angle posture, and a stable measurement value of the water content can be obtained.

Specifically, the stirring device is constructed by projecting one or a plurality of stirring rods on a rotating shaft, and the processing tank has a light transmitting portion on at least a part of a wall surface with which the mixture contacts. The light emitting element, the first light receiving element, and the second light receiving element are arranged outside the processing tank so as to face the light transmitting portion,
The arithmetic processing circuit detects a time point when a tip portion of a specific stirring rod passes a second angular position that is a certain angle before the first angular position that is closest to the center of the irradiation region of the light emitting element, and The water content of the mixture in the treatment tank is calculated based on the output signals of the first and second light receiving elements at the time of detection.

In the concrete structure, the light from the light emitting element passes through the light transmitting portion and is irradiated to the mixture in the processing tank, and the light reflected by the mixture passes through the light transmitting portion, The light is incident on the first light receiving element and the second light receiving element. Then, the first and second light receiving elements at the time point when the tip of the specific stirring rod passes the second angular position that is a certain angle before the first angular position that is closest to the center of the irradiation region of the light emitting element. The water content is calculated based on the output signal of Here, when the specific stirring rod passes the second angular position, the mixture in the processing tank is pushed toward the center of the irradiation region of the light emitting element by the stirring rod, and the treatment in the irradiation region is performed. The contact state of the mixture on the wall surface of the tank becomes stable. Thus, at the time when the specific stirring rod passes the second angular position, the contact state of the mixture with the wall of the processing tank in the irradiation region of the light emitting element is stable, so that the light from the first light receiving element at that time is stable. There is almost no variation in the detection amount and the light detection amount by the second light receiving element, and a more stable measurement value of the water content can be obtained.

[0016]

According to the food waste processing apparatus of the present invention,
A stable measurement of the water content of the mixture in the treatment tank can be obtained.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. As shown in FIGS. 1 and 2, the garbage disposal according to the present invention comprises a casing (1) having an upper opening, and a lid (11) pivotably supported at the opening of the casing (1). In the inside of the casing (1), the processing tank (1
2) has been deployed. The treatment tank (12) is made of a material, a color and a thickness capable of transmitting light having a wavelength of a wide band including a visible light region and a near infrared light region, and has a thickness of 2 mm, for example. It is formed using white polycarbonate.

A shaft (21) is horizontally installed inside the processing tank (12), and a plurality of stirring rods (2) are radially provided around the shaft (21) so as to project. One end of the shaft (21) is connected to a motor (23) through a power transmission mechanism (22), and the stirring rod (2) is rotated by driving the motor (23), It is possible to stir the garbage / chip mixture (10).

A planar heater (3) is attached to the outer surface of the treatment tank (12) to heat the food waste / chip mixture (10) in the treatment tank (12). . Further, an exhaust fan (4) is provided above the processing tank (12), and the exhaust fan (4) is connected to the exhaust port (13) through the exhaust passage (14), and the exhaust fan (4) It is possible to ventilate the inside of the processing tank (12) by driving (1). Further, a water supply mechanism (not shown) is connected to the treatment tank (12) as necessary, so that water can be supplied into the treatment tank (12).

Further, in the food waste treating apparatus according to the present invention, the water content of the food waste / chip mixture (10) in the processing tank (12) is optically measured outside the bottom wall of the processing tank (12). A water content detector (6) for measuring is attached. The water content detector (6) is arranged at a position where the tip of one stirring rod (2) faces the tip when the tip passes through the bottom dead center.
An encoder (7) for detecting the rotation angle of the stirring rod (2) is attached to the end of the shaft (21). Raw garbage·
The water content of the chip mixture (10) is measured when the rotation angle of the one stirring rod (2) reaches a predetermined value.

As shown in FIG. 3, the water content detector (6) is a tungsten lamp (6) mounted toward the treatment tank (12).
1), a silicon photodiode (62) and a pyroelectric element (63). As shown in Fig. 4 (a), tungsten lamp
(61) emits light having a wide band spanning the visible light region and the near infrared light region. Further, as shown in FIG. 4 (b), the silicon photodiode (62) has a thickness of 0.5 μm
Pyroelectric element with sensitivity in a relatively narrow wavelength range of 1.0 μm
The type (63) has a flat sensitivity characteristic in a wide wavelength range exceeding 1.0 μm.

As described above, the processing tank (12) is capable of transmitting light having a wavelength in a wide band including a visible light region and a near infrared light region, so that the light emitted from the tungsten lamp (61) is Is passed through the treatment tank (12), irradiated to the garbage / chip mixture (10), the light reflected by the garbage / chip mixture (10) passes through the treatment tank (12), It is incident on the silicon photodiode (62) and the pyroelectric element (63).

The control device (5) has a control circuit (51) composed of a microcomputer, and the lighting of the tungsten lamp (61) is controlled by the control circuit (51).
The output signals of the silicon photodiode (62) and the pyroelectric element (63) pass through the amplifiers (52) and (53), respectively, and then the control circuit.
Supplied to (51). The output signal of the encoder (7) is also supplied to the control circuit (51). Control circuit (51)
Detects the time when the rotation angle of the one stirring rod (2) reaches a predetermined value based on the signal from the encoder (7). Then, at the time of detection, the silicon photodiode
Based on the signals from (62) and the pyroelectric element (63),
The water content of the chip mixture (10) is detected, and the operations of the heater (3), the exhaust fan (4) and the motor (23) are controlled according to the results, and the raw water in the treatment tank (12) is thereby controlled. Optimally adjust the water content of the waste / chip mixture (10).

The principle of detecting the water content in the present invention will be described with reference to FIG. As described above, FIG.
Shows the spectral distribution characteristics of the tungsten lamp (61),
Light is distributed over the visible light region and the near infrared light region. 4B shows the spectral distribution characteristic P of the silicon photodiode (62) and the spectral distribution characteristic Q of the pyroelectric element (63). The silicon photodiode (62) has a spectral distribution characteristic of 0.5 μm.
The pyroelectric element (63) has a sensitivity in a relatively narrow wavelength range of .about.1.0 .mu.m, and has a flat sensitivity characteristic in a wide wavelength range of more than 1.0 .mu.m.

FIG. 4 (c) shows the spectral distribution characteristic P'of the amount of light detected by the silicon photodiode (62) and the pyroelectric element (63) when the light emitted from the tungsten lamp (61) is directly received. And the spectral distribution characteristic Q ′ of the light detection amount by However, the pyroelectric element (63) changes the amount of received light (differential).
Since it is a thermal sensor that emits a signal according to, the data corresponding to the absolute value of the received light amount can be obtained by integrating the waveform of the output signal. The peak value of the waveform of is the integrated value (light detection amount). The amount of light detected by the silicon photodiode (62) and the pyroelectric element (63) is approximately proportional to the areas of the regions surrounded by the characteristic curves P'and Q ', respectively.

FIG. 4D shows the distribution of the transmittance of light to water in the wavelength range from the visible light region to the near infrared light region, and the transmittance is about 1 in the visible light region. It can be seen that, while almost no light is absorbed, the transmittance is low in the near infrared light region, and a large amount of light is absorbed.

FIG. 4 (e) shows a case where the light emitted from the tungsten lamp (61) passes through a substance containing water and enters the silicon photodiode (62) and the pyroelectric element (63). The distribution Pn (n = 0, 40, 80) of the amount of light detected by the photodiode (62) and the distribution Qn (n = 0, 40, 80) of the amount of light detected by the pyroelectric element (63) are shown. Here, n is the water content (%) of the substance. These distributions have the spectral distribution characteristics P ′ and Q ′ shown in FIG.
This can be understood as the product of the water transmittance characteristics shown in FIG. 4 (d), and the silicon photodiode (62) and the pyroelectric element (6
The magnitude of the amount of light detected by 3) is approximately proportional to the area of the region surrounded by the distribution curves Pn and Qn.

As can be seen from FIG. 4 (e), since the transmittance of water is about 1 in the visible light range, even if the water content changes, the light detection amount of the silicon photodiode (62) is almost the same. Although no change is seen, in the near infrared region, the degree of light absorption changes according to the change in water content,
The amount of light detected by the pyroelectric element (63) changes depending on the water content.

The amount of light detected by the silicon photodiode is Ps, and the amount of light detected by the pyroelectric element is Qs.
Then, the water content W of the measurement target is expressed by the following equation 1 using the Lambert-Beer equation.

[0030]

[Equation 1] X = -log (Qs / Ps) W = a ・ X + b a, b: constant

The constants a and b in the above equation 1 are experimentally obtained. That is, as shown in FIG. 5, by plotting the value of X and the water content for a plurality of substances having known water contents, and approximating the relationship between them by a straight line, the slopes of the line and the constants a and b are calculated from the contact pieces. You can decide.

The above description of the principle is premised on the case where the light passes through the measurement object (substance containing water) and is incident on the silicon photodiode and the pyroelectric element. This is also true when the reflected light is reflected by the substance and enters the silicon photodiode and the pyroelectric element. This means that the reflected light from the object to be measured includes, in addition to the light reflected by the surface thereof, light that has penetrated into the inside of the object to be measured and is reflected by the particle surface inside, that is, diffuse reflected light. This is because the diffuse reflected light is affected by the absorption characteristics of the measurement target.

6 to 8 show the mixture of food waste and chips (10) in the processing tank (10) by rotating the one stirring rod (2).
Represents that the state of is changing. A stirring rod
(2) rotates as shown by the solid arrow in the figure. In the above garbage disposal, every 30 minutes, every few minutes,
Stirring of the garbage / chip mixture (10) is performed,
The water content of the chip mixture (10) depends on the rotation angle θ of the stirring rod (2).
Is measured at a time of 20 to 30 degrees. Here, as shown in FIG. 6, the rotation angle θ is opposite to the rotation direction of the stirring rod (2), with the angle at the time when the tip of the stirring rod (2) passes through the bottom dead center as 0 degree. The water content is measured at the time when the tip of the stirring rod (2) passes a rotation angle position before the bottom dead center.

The state of the irradiation region (16) of the tungsten lamp (61) changes with the rotation of the stirring rod (2) as shown in FIGS. 6 to 8, but the rotation angle θ of the stirring rod (2) is changed. It is in the same state when they have the same value. Further, as shown in FIG. 6, when the rotation angle θ of the stirring rod (2) reaches 20 to 30 degrees, the garbage / chip mixture (10) in the treatment tank (12) is indicated by a broken arrow in the figure. As shown, it is pushed toward the bottom of the treatment tank (12) by the stirring rod (2), and the garbage / chip mixture (10) and the treatment tank (12)
The contact state of the bottom surface of is stable. Therefore, the amount of reflected light detected using the silicon photodiode (62) and the pyroelectric element (63) at the time when the rotation angle of the stirring rod (2) becomes 20 to 30 degrees has almost no variation, and the garbage / chip A stable measurement value of the water content of the mixture (10) will be obtained.

FIG. 9 shows a water content adjusting procedure in the above-mentioned food waste treating apparatus. First, in step S1, it is judged whether or not the stirring of the food waste / chip mixture (10) by the stirring rod (2) is started.
Repeat the same judgment at 1. On the other hand, if YES in step S1, the process proceeds to step S2 to capture the output value of the encoder (7), and then in step S3, based on the captured output value, the stirring rod (2) It is determined whether the rotation angle θ of is less than 20 degrees. If YES in step S3, the process returns to step S2. If NO in step S3, the process proceeds to step S4 to determine whether the rotation angle θ is 30 degrees or more. If it is determined that the process is completed, the process returns to step S2.

If it is determined NO in step S4, the process proceeds to step S5 and the tungsten lamp (61)
Irradiate the garbage / chip mixture (10) with light. As a result, the reflected light enters the silicon photodiode (62) and the pyroelectric element (63), and the control circuit (51) captures the output signals of the silicon photodiode (62) and the pyroelectric element (63). , The amount of each light detection amount is detected. Next, in step S6, the water content of the food waste / chip mixture (10) is calculated by using the above formula (1). Then, in step S7, it is determined whether or not the water content is less than 25%, and in the case of Yes, in step S8, the display is displayed.
A water supply warning is displayed on (not shown) to prompt the user to supply water, and the stirring time by the stirring rod is shortened to increase the water content. When it is determined NO in step S7, the process proceeds to step S9, and it is determined whether the water content is higher than 50%. If YES is determined here, in step S10, the fan is rotated to ventilate the inside of the processing tank, and the stirring time by the rotation of the stirring rod is extended. By increasing the set temperature, the water content is reduced.

As a result, the water content of the food waste / chip mixture in the treatment tank is adjusted to the range of 25% to 50%,
As a result, the efficiency of the food waste decomposition process is maintained high, and the generation of an offensive odor due to the decomposition is suppressed.

In the food waste processing apparatus of this embodiment, as described above, the irradiation area of the tungsten lamp (61) is the same, and the food waste / chip mixture (10) and the processing tank are still used.
Since the water content of the food waste / chip mixture (10) is measured when the contact state of the bottom surface of (12) becomes stable, a stable measurement value of the water content can be obtained.

The configuration of each part of the present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope described in the claims. For example, although the water content detector (6) is attached to the outside of the bottom wall of the treatment tank (12), the water content detector (6) is not limited to this and may be placed outside the side wall of the treatment tank (12). Further, in the treatment tank (12), only the portion facing the water content detector (6) may be made of a light transmissive member such as polycarbonate. Further, as the light receiving element, a combination of the silicon photodiode (62) and the pyroelectric element (63) is used, but the present invention is not limited to this, and the light receiving element having sensitivity in a wavelength range where absorption by water is weak and the absorption by water. As long as it is a combination of light receiving elements having sensitivity in a strong wavelength region, various known combinations of light receiving elements such as a combination of a silicon photodiode and a germanium photodiode can be adopted.
Furthermore, the water content of the food waste / chip mixture (10) is measured when the rotation angle θ of the stirring rod (2) reaches 20 to 30 degrees. The value can be changed to an arbitrary value according to the viscosity of the food waste treatment material in (12).

[Brief description of drawings]

FIG. 1 is a sectional view of a food waste processing device according to the present invention.

FIG. 2 is a cross-sectional view of the food waste processing device in a direction orthogonal to FIG.

FIG. 3 is a block diagram showing a configuration of a water content detector and a control device.

FIG. 4 is a series of graphs explaining the principle of water content detection in the present invention.

FIG. 5 is a graph showing the relationship between the actual measurement value of water content and the logarithmic value of the output ratio of the pyroelectric element and the silicon photodiode.

FIG. 6 is a diagram showing a state of a food waste / chip mixture at a time point when a tip portion of a stirring rod passes a position before a bottom dead center.

FIG. 7 is a diagram showing a state of a food waste / chip mixture when a tip of a stirring rod passes through a bottom dead center.

FIG. 8 is a diagram showing the state of the food waste / chip mixture immediately after the tip of the stirring rod has passed through bottom dead center.

FIG. 9 is a flow chart showing a procedure of adjusting the water content in the food waste processing device of the present invention.

[Explanation of symbols]

(1) Casing (10) Garbage / chip mixture (11) Lid (12) Treatment tank (2) Stir bar (3) Heater (4) Exhaust fan (5) Control device (6) Water content detector (61) Tungsten lamp (62) Silicon photodiode (63) Pyroelectric element (7) Encoder

Continuation of the front page (56) References JP-A 61-264239 (JP, A) JP-A 9-10748 (JP, A) JP-A 8-89930 (JP, A) JP-A 8-84981 (JP , A) JP-A-8-132004 (JP, A) JP-A-6-229917 (JP, A) JP-A-10-156316 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) (Name) B09B 3/00 ZAB C05F 9/02 G01N 21/27 G01N 21/35

Claims (2)

(57) [Claims] 1. A food waste treating apparatus for accommodating a mixture of food waste and a food waste treating material in the treatment tank, adjusting the water content of the mixture, and decomposing the food waste. A stirring device for stirring the mixture, a rotation angle sensor for detecting the rotation angle of the stirring device, a water content detecting device for detecting the water content of the mixture in the treatment tank, and a water content based on the detected water content. And a water content adjusting device for adjusting the water content, wherein the water content detecting device irradiates the mixture with light including a first wavelength band having a large transmittance for water and a second wavelength band having a small transmittance for water. A light emitting element, a first light receiving element having sensitivity in the first wavelength range, receiving reflected light from the mixture in the processing tank, and emitting an output according to the amount of received light; Has sensitivity in the wavelength range and reflects from the mixture in the processing tank A second light receiving element that receives light and outputs an output according to the amount of received light or a change in the amount of received light, and during operation of the stirrer, the stirrer makes a predetermined rotation angle posture based on the output signal of the rotation angle sensor. An arithmetic processing circuit for detecting a time point at which the mixture passes through and calculating the water content of the mixture in the processing tank based on the output signals of the first and second light receiving elements at the detection time point. Raw garbage processing equipment. 2. The agitator is constructed by projecting one or a plurality of agitating rods on a rotary shaft, and the processing tank has a light transmitting portion on at least a part of a wall surface with which the mixture contacts, and the light transmitting portion is provided. The light emitting element, the first light receiving element, and the second light receiving element are arranged outside the processing tank so as to face the portion, and the tip of the specific stirring rod of the arithmetic processing circuit is the irradiation area of the light emitting element. In the processing tank, a time point at which the second angular position before the first angular position closest to the center is passed by a certain angle is detected, and based on the output signals of the first and second light receiving elements at the detection time. The food waste treatment device according to claim 1, wherein the water content of the mixture is calculated.