JP7746085B2 - Organic waste treatment system - Google Patents

Description

The embodiment relates to an organic waste treatment system.

Traditionally, anaerobic digestion has been one of the methods for treating organic waste such as sludge and industrial wastewater. In anaerobic digestion, the organic matter in the waste is broken down into smaller molecules in a digester tank and converted into biogas, which is primarily composed of methane and carbon dioxide, and is then removed from the treated liquid.

Anaerobic digestion can also be used to recover energy from waste. Biogas contains approximately 70% methane, a combustible gas. This methane can be converted into heat in a gas boiler and used to heat the digester tank, or generated in a gas generator for use at the treatment facility, reducing the amount of electricity purchased by the entire treatment facility. It is also possible to make a direct profit by selling the electricity.

Increasing the amount of biogas increases the amount of energy recovered. One method for increasing biogas production is solubilization. Solubilization breaks down solids in waste into smaller molecules and liquefies them, making it easier for the anaerobic digestion reaction to proceed and contributing to an increase in biogas production. One example of a solubilization method is the ozone method. For example, in the conventional ozone method, hydrogen peroxide is added to the sludge at an amount of 100 ppm or less, reducing the amount of ozone added and increasing the amount of biogas generated.

Patent No. 5916971 Patent No. 4339775 Japanese Patent Application Laid-Open No. 2019-25428

When adding hydrogen peroxide in the ozone method, if the amount of hydrogen peroxide is less than the appropriate amount, the solubilization effect will be small. On the other hand, if the amount of hydrogen peroxide exceeds the appropriate amount, not only will costs increase, but the solubilization effect will also be reduced, which is a disadvantage. Furthermore, in organic waste treatment systems, the concentration of ozone supplied to the sludge and the flow rate of ozone gas often fluctuate.

However, in conventional technology, hydrogen peroxide is supplied without taking into account fluctuations in the concentration of ozone supplied to the sludge or the flow rate of the ozone gas, which means that the amount of hydrogen peroxide supplied is sometimes not appropriate, leaving room for improvement.

The present invention aims to provide an organic waste treatment system that can optimize the amount of hydrogen peroxide supplied in the ozone method.

In order to solve the above-mentioned problems and achieve the objectives, the organic waste treatment system of this embodiment comprises a digestion facility that anaerobically digests the material to be treated, including organic matter, to produce biogas, and a solubilization facility that solubilizes the material to be treated and supplies it to the digestion facility. The solubilization equipment includes a solubilization tank that stores the material to be treated, a circulation path that circulates the material to be treated in the solubilization tank and returns it to the solubilization tank, a pressure pump that pressurizes the material to be treated in the circulation path, an ozone supply unit that supplies ozone to the material to be treated in the circulation path, a hydrogen peroxide supply unit that supplies hydrogen peroxide to the material to be treated in the circulation path, a dissolution reaction unit that is provided in the circulation path and promotes solubilization of the material to be treated by at least one of turbulence and pressurization, an ozone concentration measurement unit that measures the concentration of ozone supplied from the ozone supply unit, an ozone flow rate measurement unit that measures the flow rate of ozone supplied from the ozone supply unit, and a control unit that controls the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit.

FIG. 1 is a diagram showing the overall configuration of a conventional organic waste treatment system. FIG. 2 is a graph showing the change over time in ozone concentration and ozone gas flow rate in a conventional organic waste treatment system. FIG. 3 is a diagram showing the overall configuration of the first experimental device in the first embodiment. FIG. 4 is a diagram showing the overall configuration of the second experimental device in the first embodiment. FIG. 5 is a diagram showing the overall configuration of the organic waste treatment system according to the first embodiment. FIG. 6 is a diagram showing the overall configuration of an organic waste treatment system according to the second embodiment. FIG. 7 is a diagram showing the overall configuration of an organic waste treatment system according to the third embodiment.

The following describes embodiments (first to third embodiments) of the organic waste treatment system of the present invention. The following exemplary prior art, embodiments, and variations include similar components. Therefore, below, similar components are given the same reference numerals, and duplicate explanations will be omitted as appropriate. Parts included in the embodiments and variations can be configured by replacing them with corresponding parts in other embodiments and variations. Furthermore, the configurations and positions of parts included in the embodiments and variations are the same as those in other embodiments and variations unless otherwise specified.

(Prior Art)
First, to facilitate understanding, a conventional organic waste treatment system will be described. Figure 1 is a diagram showing the overall configuration of a conventional organic waste treatment system 100. The organic waste treatment system 100 includes a digestion facility 12 and a solubilization facility 14.

The digester 12 anaerobically digests organic waste containing organic matter to produce biogas containing methane, and discharges digested sludge after the organic matter has been removed. The digester 12 has a digester tank 22.

The digester tank 22 receives the solubilized sludge solubilized by the solubilization equipment 14. The digester tank 22 contains anaerobic microorganisms, which anaerobically digest the solubilized sludge received from the solubilization equipment 14. The digester tank 22 supplies biogas containing methane to the power generation equipment 90 and other equipment, and sends the digested sludge to the dewatering equipment 92 and other equipment.

The solubilization equipment 14 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, a hydrogen peroxide tank 38, a hydrogen peroxide injection pump 40, an ozone generator 42, an ejector 44, and a dissolution reaction section 46.

The digested sludge in the solubilization tank 34 circulates through the circulation path 32, passing through the pressure pump 36, ejector 44, and dissolution reaction section 46 along the way, before returning to the solubilization tank 34.

The solubilization tank 34 stores sludge (digested sludge, solubilized sludge). The solubilization tank 34 sends the solubilized sludge to the digestion tank 22.

The hydrogen peroxide injection pump 40 injects hydrogen peroxide supplied from the hydrogen peroxide solution tank 38 into the sludge pressurized by the pressure pump 36 in the circulation path 32 downstream of the ejector 44.

The ozone generator 42 supplies ozone to the sludge flowing through the ejector 44 on the circulation path 32.

The dissolution reaction section 46 has a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54. The nozzle 50 sprays the sludge mixed with ozone and hydrogen peroxide sent from the ejector 44 into the dissolution reaction tank 54. This promotes the solubilization of the sludge. The dissolution reaction section 46 sends the solubilized sludge to the solubilization tank 34.

In such conventional organic waste treatment systems 100, the ozone concentration and ozone gas flow rate supplied to the sludge often fluctuate. Figure 2 is a graph showing the changes in ozone concentration and ozone gas flow rate over time in a conventional organic waste treatment system 100. Even when attempts are made to keep the ozone concentration and ozone gas flow rate constant, as shown in Figure 2, they often fluctuate. However, hydrogen peroxide is supplied without taking into account fluctuations in ozone concentration and ozone gas flow rate, and the amount of hydrogen peroxide supplied may not be appropriate, leaving room for improvement.

Below, we will explain a technology that can optimize the amount of hydrogen peroxide supplied in the ozone method.

(First embodiment)
The first embodiment will now be described. First, a first experiment will be described with reference to Fig. 3, which investigated the relationship between the amount of ozone added and the solubilization rate and the amount of biogas generated. Next, a second experiment will be described with reference to Fig. 4, which investigated the appropriate range of the amount of hydrogen peroxide added relative to the amount of ozone added. Next, an organic waste treatment system 10 according to the first embodiment will be described with reference to Fig. 5.

(First Experiment)
First, the first experiment will be described. Fig. 3 is a diagram showing the overall configuration of a first experimental apparatus 200 in the first embodiment. The first experimental apparatus 200 is installed, for example, in a laboratory. The first experimental apparatus 200 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, an ozone generator 42 (ozone supply unit), an ejector 44, a dissolution reaction unit 46, and a pressure adjustment valve 71. The dissolution reaction unit 46 includes a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54.

Using the first experimental apparatus 200, an experiment was conducted to solubilize sludge using only ozone addition. Sludge placed in the solubilization tank 34 was sent to the dissolution reaction section 46 by the pressure pump 36, and ozone was sucked in from the ozone generator 42 by the ejector 44. The pressure fluctuations caused by the ozone suction pulverized sludge flocs, turning them into ozone-mixed sludge. The ozone-mixed sludge was sprayed from a nozzle 50 inside the pressurized dissolution reaction section 46, and upon contact with an inner tube 52 installed inside the dissolution reaction section 46, was subjected to turbulent agitation within the dissolution reaction section 46. As a result, the ozone dissolved by the microbubbles reacted with the sludge, causing it to be solubilized.

The sludge used was digested sludge (VS 1.5%) from a sewage treatment plant, and the amount of ozone added to the sludge was 0-150 mg/L. This corresponds to an ozone injection rate per VS of sludge of 0-0.01 mg-O3/mg-VS.

In the first experimental device 200, the gas-liquid ratio of the ozone gas flow rate and the pressure pump 36 flow rate could not be set above 0.08, so the gas-liquid ratio was fixed and the amount of ozone added was adjusted by the treatment time. An ozone addition amount of 0 mg/L means that in the first experimental device 200, oxygen was supplied in a non-discharge state with no voltage applied to the ozone generator 42 in order to obtain effects other than ozone.

The VSS (loss on ignition of suspended solids) of the sludge samples after the experiment was analyzed, and the solubilization rate was obtained using equation (1).
Solubilization rate [%] = (1 - sludge sample VSS [%] ÷ untreated sludge VSS [%]) ×
100...Formula (1)

Next, a digestion test to determine the amount of gas generated was conducted as follows. Treated sludge sample and digested sludge as seed sludge were placed in a 200 mL vial in a 1:1 ratio, and the gas phase was replaced with nitrogen and sealed. The vial was placed in a thermostatic shaker at 37°C, and the amount of gas generated was measured for over 30 days. From the measured values, the amount of gas generated per VS amount of sludge sample and the gas increase ratio relative to untreated sludge were calculated using equations (2) and (3).

Gas generation rate [L/g-VS]
= Measured gas generation rate (mL) × 10 ⁻³ ÷ (sludge sample amount [mL] × VS [%] ×
10 ^-2 ) ...Formula (2)
Gas increase ratio [-] = amount of gas generated from treated liquid [mL] ÷ amount of gas generated from untreated sludge [mL]
...Formula (3)

The experimental results are shown in Table 1. A-1 is untreated sludge before it was placed in the first experimental equipment 200. Comparing A-1 and A-2, passing the sludge through the first experimental equipment 200 increased the solubilization rate by 9.8 points and the gas increase ratio by 0.07 points, even without supplying ozone. This is thought to be due to the shear force generated by the pressure fluctuations that occurred when the sludge was mixed with gas in the ejector 44, which is a pressure fluctuation pipe, causing the solid matter in the sludge to break down into smaller molecules.

Furthermore, A-2 to A-5 show that the greater the amount of ozone supplied, the greater the sludge solubilization and the amount of gas generated.

These findings suggest that by crushing the solid matter in the sludge, injecting ozone, and then pressurizing and dissolving the microbubbled ozone into the sludge, a high solubilization rate and increased biogas production can be achieved in proportion to the amount of ozone added, at least when the ozone addition amount is 150 mg/L or less.

(Second Experiment)
Next, the second experiment will be described. Fig. 4 is a diagram showing the overall configuration of a second experimental device 300 in the first embodiment. The second experimental device 300 is installed in, for example, a laboratory.

The second experimental apparatus 300 was the first experimental apparatus 200 shown in Figure 3, with the addition of a hydrogen peroxide tank 38 for storing 30% hydrogen peroxide and a hydrogen peroxide injection pump 40 (hydrogen peroxide supply unit). The hydrogen peroxide injection pump 40 then injected the hydrogen peroxide into the sludge at a predetermined rate. The experimental results are shown in Table 2.

The untreated sludge in B-1 is the sludge before it was placed in the second experimental device 300. In B-2 to B-9, the ozone addition amount was 50 mg/L, and the hydrogen peroxide solution was added in the range of 0 to 100 ppm.

The solubilization rate of B-2, which did not contain added hydrogen peroxide, was 10.4%, and the gas increase ratio was 1.19. The solubilization rates of B-3 to B-9, which contained added amounts of hydrogen peroxide ranging from 10 to 100 ppm, ranged from 9.8 to 11.9%, with an average of approximately 10.6%, and no clear differences were observed. Meanwhile, the gas increase ratio increased up to 30 ppm, being 1.29 at 10 ppm added hydrogen peroxide, 1.31 at 20 ppm, and 1.33 at 30 ppm. While the gas increase ratio was higher than B-2 at 40 ppm, it began to decrease at 30 ppm, and from 60 ppm onwards, the gas increase ratio was at or below that of B-2.

The addition of hydrogen peroxide did not significantly change the solubilization rate, suggesting that the effect of adding hydrogen peroxide is not to oxidize and decompose the floating sludge (solids) to complete solubility, as occurs with ozone. However, the gas increase ratio increased up to 30 ppm, suggesting that the addition of hydrogen peroxide cleaves the cell walls of the organic matter in the sludge, leaving it floating and easily digestible. Furthermore, the gas increase ratio was greatest at 30 ppm, suggesting that there is an optimal amount of hydrogen peroxide added; if the amount is less than this, the solubilization effect is insufficient, while if the amount is more than this, the solubilization effect is insufficient and the cost of hydrogen peroxide becomes excessive. Furthermore, the more hydrogen peroxide added above this optimal amount, the more hydrogen peroxide consumed the highly oxidizing hydroxyl radicals (OH) generated by the reaction of ozone and water, resulting in a decrease in the solubilization rate and gas increase ratio.

The amount of aqueous hydrogen peroxide to be added that results in a greater gas increase ratio than B-2 is 10 to 40 ppm, and it is thought that the optimal amount of aqueous hydrogen peroxide to be added is around 20 to 30 ppm, where the gas increase ratio was particularly high. Based on the above, it is suggested that the optimal range of aqueous hydrogen peroxide to be added is at least 10 to 40 ppm, and more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg/L to sludge.

(Configuration and operation of organic waste treatment system)
Next, the configuration and operation of the organic waste treatment system 10 of this embodiment will be described. Figure 5 is a diagram showing the overall configuration of the organic waste treatment system 10 in the first embodiment. The organic waste treatment system 10 is installed in, for example, a sewage treatment facility.

The organic waste treatment system 10 removes organic matter contained in sludge (the material to be treated), which is organic waste such as sewage sludge, by generating methane and carbon dioxide through anaerobic digestion. The organic waste treatment system 10 recovers and uses the biogas produced by anaerobic digestion, which contains approximately 70% methane, as energy. For example, the organic waste treatment system 10 converts the methane contained in the biogas into heat in a gas boiler and uses it to heat the digester tank 22. The organic waste treatment system 10 also uses the methane contained in the biogas to generate electricity in the gas generator of the power generation facility 90, and by using the generated electricity within the organic waste treatment system 10, it can reduce the amount of electricity purchased or earn profits by selling the electricity.

The organic waste treatment system 10 includes a digestion facility 12, a solubilization facility 14, and a control device 16 (control unit).

The digestion facility 12 anaerobically digests sludge containing organic matter to produce biogas containing methane, and discharges digested sludge from which the organic matter has been removed (digested sludge). The digestion facility 12 has a digestion tank 22.

The digester 22 receives organic waste from the outside and solubilized sludge solubilized by the solubilization equipment 14. The digester 22 contains anaerobic microorganisms, which anaerobically digest the solubilized sludge supplied from the solubilization equipment 14. The anaerobic microorganisms include hydrolytic bacteria, acid-producing bacteria, and methanogens. For example, the digester 22 uses hydrolytic bacteria to decompose high molecular weight organic matter, such as carbohydrates, proteins, and lipids, contained in the sludge organic matter into low molecular weight organic matter. Next, the digester 22 uses acid-producing bacteria to decompose the low molecular weight organic matter into lower fatty acids, such as acetic acid and propionic acid. Furthermore, the digester 22 uses methanogens to decompose the lower fatty acids into methane and carbon dioxide, producing biogas, and the digested sludge, from which some of the organic matter has been removed, is separated from the biogas. The digester tank 22 supplies biogas containing methane to the power generation equipment 90 and other equipment, and sends digested sludge to the dehydration equipment 92 and other equipment.

The solubilization equipment 14 solubilizes the digested sludge received from the digestion tank 22 and returns it to the digestion equipment 12. The solubilization equipment 14 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, a hydrogen peroxide tank 38, a hydrogen peroxide injection pump 40, an ozone generator 42, an ejector 44, a dissolution reaction section 46, an ozone gas flow meter 61, and an ozone concentration meter 62.

The circulation path 32 connects the solubilization tank 34, the pressure pump 36, the ejector 44, the dissolution reaction section 46, and the solubilization tank 34. The circulation path 32 circulates the sludge in the solubilization tank 34 through the pressure pump 36, the ejector 44, and the dissolution reaction section 46, in that order, before returning it to the solubilization tank 34.

The solubilization tank 34 is connected to the digestion tank 22 and the circulation path 32. The solubilization tank 34 temporarily stores sludge that is a mixture of digested sludge received from the digestion tank 22 and solubilized sludge received from the dissolution reaction section 46.

The pressure pump 36 is disposed in the circulation path 32 between the solubilization tank 34 and the ejector 44. The pressure pump 36 pressurizes the sludge in the circulation path 32. In other words, the pressure pump 36 pressurizes the sludge in the solubilization tank 34, forces it into the circulation path 32, and sends it to the ejector 44.

The ozone generator 42 is connected to the ejector 44 on the circulation path 32. The ozone generator 42 generates ozone, a gas that is mixed with the sludge. The ozone generator 42 supplies ozone as an oxidizing agent to the sludge flowing through the ejector 44 on the circulation path 32.

The ejector 44 is disposed in the circulation path 32 between the pressure pump 36 and the dissolution reaction section 46. The ejector 44 is, for example, a pressure fluctuation pipe, which is a type of pump. The ejector 44 draws in ozone supplied from the ozone generator 42. The ejector 44 mixes the ozone with the sludge pressurized by the pressure pump 36. The ejector 44 uses shear force generated by pressure fluctuations caused by the supply of ozone to crush solids in the sludge into smaller molecules and convert the ozone into microbubbles. The ejector 44 sends the sludge mixed with the microbubbled ozone to the dissolution reaction section 46.

The hydrogen peroxide tank 38 is connected to the circulation path 32 downstream of the ejector 44 via a hydrogen peroxide injection pump 40. The hydrogen peroxide tank 38 generates hydrogen peroxide to be injected (supplied) into the sludge flowing through the circulation path 32. The hydrogen peroxide tank 38 supplies liquid hydrogen peroxide containing hydrogen peroxide to the sludge as an oxidizing agent.

The hydrogen peroxide injection pump 40 is connected to the hydrogen peroxide tank 38 and to the circulation path 32 between the downstream side of the ejector 44 and the upstream side of the dissolution reaction section 46. The hydrogen peroxide injection pump 40 injects hydrogen peroxide as an oxidizing agent supplied from the hydrogen peroxide tank 38 into the sludge in the circulation path 32.

The dissolution reaction section 46 is located in the circulation path 32 between the ejector 44 and the solubilization tank 34. The dissolution reaction section 46 promotes sludge solubilization by at least one of turbulence and pressurization. The dissolution reaction section 46 solubilizes sludge supplied with ozone and hydrogen peroxide on the circulation path 32 and sends the solubilized sludge to the solubilization tank 34. The dissolution reaction section 46 has a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54. The nozzle 50 is installed in the dissolution reaction tank 54 and connected to the circulation path 32 extending from the ejector 44. The nozzle 50 injects the sludge mixed with ozone and hydrogen peroxide sent from the ejector 44 into the dissolution reaction tank 54. The inner cylinder 52 is installed in the dissolution reaction tank 54. The inner cylinder 52 disturbs the flow of sludge injected into the dissolution reaction tank 54. As a result, the inner cylinder 52 increases contact between the microbubbles of ozone and the solids in the sludge, destroying the cell walls of the organic matter in the ozone-mixed sludge with the oxidizing power of ozone and promoting the solubilization of organic matter such as carbohydrates and proteins inside the cells. It also increases contact between the hydrogen peroxide and the solids in the sludge, promoting the solubilization of organic matter. The dissolution reaction tank 54 pressurizes the sludge inside.

The ozone gas flow meter 61 measures the flow rate of ozone (ozone gas flow rate) supplied from the ozone generator 42 and outputs the measurement result to the control device 16.

The ozone concentration meter 62 measures the concentration of ozone supplied from the ozone generator 42 and outputs the measurement results to the control device 16.

The control device 16 is a computer having, for example, a hardware processor such as a CPU (Central Processing Unit) and storage devices such as RAM (Random Access Memory), ROM (Read Only Memory), SSD (Solid State Drive), and HDD (Hard Disk Drive). The control device 16 controls the organic waste treatment system 10 by loading a control program. Specifically, the control device 16 is connected to the hydrogen peroxide injection pump 40, ozone gas flow meter 61, and ozone concentration meter 62 so as to be able to send and receive electrical signals containing data.

The control device 16 receives the measurement results of the ozone flow rate from the ozone gas flow meter 61 and the measurement results of the ozone concentration from the ozone concentration meter 62. The control device 16 controls the amount of hydrogen peroxide supplied from the hydrogen peroxide injection pump 40 based on the concentration and flow rate of ozone supplied from the ozone generator 42. In this case, for example, the control device 16 adjusts the amount of hydrogen peroxide added to 10 to 40 ppm, more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg/L to the sludge.

Next, we will explain the operation of sludge treatment in the organic waste treatment system 10. First, organic waste is sent to the digestion tank 22. Next, the sludge is digested in the digestion tank 22. Next, the digested sludge is supplied from the digestion tank 22 to the solubilization tank 34. Next, the pressure pump 36 pressurizes the sludge that has been supplied to and stored in the solubilization tank 34, and sends it through the circulation path 32.

The ejector 44 mixes the pressurized sludge with ozone supplied from the ozone generator 42 and breaks down solid organic matter in the sludge. The hydrogen peroxide injection pump 40 injects hydrogen peroxide supplied from the hydrogen peroxide solution tank 38 into the sludge in the circulation path 32. The dissolution reaction section 46 increases contact between the solid organic matter in the sludge and the ozone and hydrogen peroxide, solubilizing it, and sends the solubilized sludge to the solubilization tank 34.

The solubilization tank 34 stores the solubilized sludge, sends a portion to the digestion tank 22, and circulates the remainder within the solubilization equipment 14. The digestion tank 22 anaerobically digests the solubilized sludge, producing biogas containing methane and digested sludge, which is the solubilized sludge from which organic matter has been removed. The digestion tank 22 sends the biogas to a power generation facility 90 or the like, and sends the digested sludge to a dewatering facility 92 or the like.

In this way, in the organic waste treatment system 10, the digested sludge in the digester tank 22 is solubilized by repeatedly performing three batch processes: "Step 1: Extracting digested sludge from the digester tank 22 to the solubilization tank 34," "Step 2: Solubilizing the digested sludge in the solubilization tank 34 in the solubilization equipment 14," and "Step 3: Returning the solubilized sludge from the solubilization tank 34 to the digester tank 22." In Step 2, ozone gas is supplied from the ozone generator 42, but as shown in Figure 2, the ozone concentration and ozone gas flow rate are often unstable, especially in the early stages of operation of the ozone generator 42.

In the organic waste treatment system 10, the ozone concentration and ozone gas flow rate of the ozone gas generated by the ozone generator 42 were measured, and the amount of ozone added was calculated from the measured ozone concentration and ozone gas flow rate. The flow rate of the hydrogen peroxide solution in the hydrogen peroxide injection pump 40 was controlled so that the amount of hydrogen peroxide solution added was 20 to 30 ppm for an ozone addition rate of 50 mg/L to the sludge. In this case, the flow rate of the hydrogen peroxide solution in the hydrogen peroxide injection pump 40 was calculated using equation (4).

Q _H2O2 = R _H2O2 ÷ R _O3 × (Q _O3 × C _O3 ÷60) ...Formula (4)
The parameters are as follows:
Q _H2O2 : Hydrogen peroxide injection pump flow rate [mL/min]
R _H2O2 : Amount of hydrogen peroxide added: 20 ppm
R _O3 : Amount of ozone added: 50 mg/L
Q _O3 : Ozone gas flow rate [Nm3/h]
_CO3 : ozone concentration [g/Nm3]

This allows the amount of hydrogen peroxide added to be maintained appropriately relative to the amount of ozone added, and a high gas increase ratio can be maintained through the digestion of solubilized sludge returned to the digestion tank 22, resulting in a stable increase in the amount of biogas generated.

As such, with the organic waste treatment system 10 of the first embodiment, even if the ozone concentration or ozone gas flow rate supplied to the sludge fluctuates and becomes unstable, the control device 16 ensures that the amount of hydrogen peroxide added is 10 to 40 ppm, and more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg/L to the sludge. This optimizes the amount of hydrogen peroxide supplied to the sludge, and promotes sludge solubilization.

Second Embodiment
Next, a second embodiment will be described. Figure 6 is a diagram showing the overall configuration of an organic waste treatment system 10a in the second embodiment. In the first embodiment, digested sludge from the digester 22 was sent to the solubilization tank 34, and the solubilized sludge solubilized in the solubilization equipment 14 was returned to the digester 22. In the second embodiment, as shown in Figure 6, organic waste is sent to the solubilization tank 34, and the solubilized sludge solubilized in the solubilization equipment 14 is returned to the digester 22. In this second embodiment, the same effects as those in the first embodiment can be achieved.

(Third embodiment)
Next, a third embodiment will be described. Figure 7 is a diagram showing the overall configuration of an organic waste treatment system 10b according to the third embodiment. In the third embodiment, as shown in Figure 7, the digestion equipment 12a includes a primary digestion tank 22a and a secondary digestion tank 22b. The primary digestion tank 22a receives organic waste, performs primary digestion, and sends the digested sludge to the solubilization tank 34. The solubilized sludge solubilized in the solubilization equipment 14 is then returned to the secondary digestion tank 22b. Biogas is sent from the primary digestion tank 22a and the secondary digestion tank 22b to the power generation equipment 90. The digested sludge is sent from the secondary digestion tank 22b to the dehydration equipment 92. This third embodiment can also achieve the same effects as the first embodiment.

While several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

10, 10a, 10b...organic waste treatment system, 12, 12a...digestion equipment, 14...solubilization equipment, 16...control device, 22...digestion tank, 22a...primary digestion tank, 22b...secondary digestion tank, 32...circulation path, 34...solubilization tank, 38...hydrogen peroxide water tank, 40...hydrogen peroxide injection pump, 42...ozone generator, 44...ejector, 46...dissolution reaction section, 61...ozone gas flow meter, 62...ozone concentration meter, 90...power generation equipment, 92...dehydration equipment.

Claims (2)

a digestion facility that performs anaerobic digestion on a treatment target material containing organic matter to generate biogas;
a solubilization facility that solubilizes the material to be treated and supplies the solubilized material to the digestion facility;
Equipped with
The solubilization equipment comprises:
a solubilization tank for storing the material to be treated;
a circulation path that circulates the material to be treated in the solubilization tank and returns it to the solubilization tank;
a pressure pump that pressurizes the object to be treated in the circulation path;
an ozone supply unit that supplies ozone to the object to be treated in the circulation path;
a hydrogen peroxide supply unit that supplies hydrogen peroxide to the object to be treated in the circulation path;
a dissolution reaction section provided in the circulation path and promoting solubilization of the object to be treated by at least one of turbulence and pressure;
an ozone concentration measuring unit that measures the concentration of ozone supplied from the ozone supply unit;
an ozone flow rate measuring unit that measures the flow rate of ozone supplied from the ozone supply unit;
a control unit that controls the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit, so that the amount of hydrogen peroxide added to the treatment object is 10 to 40 ppm for an ozone addition amount of 50 mg/L ;
An organic waste treatment system comprising: 2. The organic waste treatment system of claim 1, wherein the control unit controls the amount of aqueous hydrogen peroxide supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit so that the amount of aqueous hydrogen peroxide added is 20 to 30 ppm for an ozone addition amount of 50 mg/L to the treatment target.