JP7100482B2 - Organic waste treatment method and organic waste treatment equipment - Google Patents

Description

The present invention relates to a method for treating organic waste and an apparatus for treating organic waste.

The methane fermentation method is a method of decomposing organic matter as methane gas by the metabolic action of methane bacteria that live in an anaerobic environment without oxygen, and the biogas generated by methane fermentation can be recovered and used as energy. It has the merit of. The digestive juice after the methane fermentation treatment is solid-liquid separated by a membrane separation device or the like.

On the other hand, in the methane fermentation treatment of organic waste containing protein and magnesium, digestive juice containing ammonia and phosphoric acid purified by decomposition of protein is generated, and phosphoric acid, which is a sparingly soluble salt in the digestive juice, is generated. Magnesium ammonium (MAP) is formed.

Therefore, the membrane may be blocked as the treatment of the digestive juice with the membrane separation device is advanced, and the membrane blockage may reduce the amount of permeated liquid and the operating rate of the facility. In addition, MAP adheres to or accumulates in the piping of the methane fermentation facility or in the reactor, which makes it necessary to perform scale removal work.

For example, in International Publication No. 2009/041009, in order to suppress the formation of inorganic scale in the membrane-type methane fermentation treatment of organic waste containing a large amount of phosphorus, magnesium, etc., the digestive juice in the membrane separation tank or A method of adjusting the pH condition in the membrane separation tank to a target pH condition at which scale does not occur is described by adding a pH adjuster to the digestive juice flowing from the methane fermentation tank into the membrane separation tank.

Japanese Unexamined Patent Publication No. 2010-207699 describes a method for suppressing the production of MAP by returning the treated water generated in the nitrification denitrification step installed in the subsequent stage of the methane fermentation tank to the methane fermentation tank. ..

International Publication No. 2009/041009 Japanese Unexamined Patent Publication No. 2010-207699

However, although all of the inventions described in Cited Documents 1 and 2 have obtained certain effects on the suppression of scale formation and the suppression of film fouling, there is still room for improvement.

For example, in the invention described in Cited Document 1, the addition of chemicals is costly, and the alkalinity is lowered by lowering the pH in order to suppress the production of MAP, which may make methane fermentation unstable. Further, since the MAP production ability differs depending on the concentration of the MAP constituent elements of the raw material, if the concentration of the MAP constituent elements of the raw material is high, the MAP production can be suppressed only by controlling the pH range described in Cited Document 1. May be difficult.

In the invention described in Cited Document 2, since the amount of treated water in the membrane filtration is increased by diluting the treated water, the membrane area is increased, the initial cost and the running cost are increased, and the operating time of the apparatus is increased. There is a problem.

In view of the above problems, the present invention can suppress the formation of MAP regardless of the fluctuation of the water quality of the water to be treated, and can treat the organic waste more economically and stably while suppressing the damage or blockage of the membrane. A treatment method and a treatment apparatus for organic waste are provided.

As a result of diligent studies by the present inventors to achieve the above object, after performing a MAP generation treatment and a separation treatment of the produced MAP particles on the digestive juice and / or the organic waste obtained by methane fermentation. , It has been found that a method of adding a pH lowering agent, a phosphorus removing agent, or both to the separation liquid after separating the MAP particles and supplying the separation liquid having a reduced MAP producing ability to the membrane separation device is effective.

The organic waste treatment method according to the embodiment of the present invention completed based on the above findings is, in one aspect, a method for treating organic waste containing phosphorus, nitrogen and magnesium, and is organic waste. A step of methane fermentation of a substance in a methane fermentation apparatus, a step of supplying organic waste and / or digestive juice after methane fermentation to a MAP crystallization apparatus to crystallize MAP particles, and a step of crystallization after MAP crystallization. A step of supplying the treatment liquid to the MAP separation device and separating the MAP particles from the crystallization treatment liquid after MAP crystallization, and a chemical containing a pH lowering agent, a phosphorus removing agent, or both in the separation liquid from which the MAP particles are separated are added. Organic including a step of adding, a step of supplying a separation liquid to which a drug is added to a membrane separation device to obtain a membrane filtration concentrated digestion solution and permeated water, and a step of returning the membrane filtration concentrated digestion solution to a methane fermentation device. A method for treating sex waste is provided.

In one embodiment, the method for treating organic waste according to the embodiment of the present invention includes a step of returning MAP particles separated from the crystallization treatment liquid in the MAP separation device to the MAP crystallization device.

In another embodiment of the method for treating organic waste according to the embodiment of the present invention, the ion product of the MAP constituent substance in the crystallization treatment liquid treated by the MAP crystallization device is the solubility product of MAP. It includes adjusting the MAP particle concentration in the MAP crystallizer so that the ratio to and below is 2.5 or less.

In another embodiment, the method for treating organic waste according to the embodiment of the present invention includes setting the MAP particle concentration in the MAP crystallizer to 1 g / L or more.

The method for treating organic waste according to an embodiment of the present invention comprises using a liquid cyclone as a MAP separation device in still another embodiment.

In still another embodiment of the method for treating organic waste according to the embodiment of the present invention, the step of adding the chemical is such that the pH of the separation liquid to which the chemical is added is organic waste in the MAP crystallizer. Add a drug so that the pH of the digestive juice after fermenting the substance and / or methane is 0.1 or more lower, or the orthrinic acid concentration of the separation solution to which the drug is added is organic in the MAP crystallizer. It includes the addition of a drug so as to reduce the concentration of orthoric acid in the digestive juice after sex waste and / or methane fermentation by 0.1% or more.

The organic waste treatment apparatus according to the embodiment of the present invention has, in one aspect, a methane fermentation apparatus for methane-fermenting organic waste containing phosphorus, nitrogen and magnesium, and an organic waste and / or methane fermentation. A MAP crystallization device that crystallizes MAP particles from the later digestion liquid, a MAP separation device that separates MAP particles from the crystallization treatment liquid after MAP crystallization, and a pH lowering agent or phosphorus in the separation liquid after MAP particle separation. A drug addition device that adds a drug containing a remover or both, a membrane separation device that separates the separation solution to which the drug is added into a membrane to obtain a membrane filtration concentrated digestive solution and permeated water, and a membrane filtration concentrated digestive solution with methane. An organic waste treatment apparatus is provided, including a return means for returning to the fermentation apparatus.

According to the present invention, a method for treating organic waste, which can suppress the generation of MAP regardless of the fluctuation of the water quality of the water to be treated, and can treat the organic waste more economically and stably while suppressing the damage or blockage of the membrane. An organic waste treatment apparatus can be provided.

It is a schematic diagram which shows an example of the organic waste processing apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the organic waste processing apparatus of the comparative example 1. FIG. It is a schematic diagram which shows the organic waste processing apparatus of the comparative example 2. It is a graph which shows the time-dependent change of the intermembrane differential pressure in the operation period of Examples 1 to 3 and Comparative Examples 1 to 3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. It should be noted that the embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention describes the structure, arrangement, etc. of the components as follows. It is not specific to things.

As shown in FIG. 1, the organic waste treatment apparatus according to the embodiment of the present invention includes a methane fermentation apparatus 1 for methane-fermenting an organic waste 6 containing phosphorus, nitrogen and magnesium, and an organic waste treatment apparatus. The MAP crystallization device 2 that crystallizes MAP particles from the digestive liquid 10 after methane fermentation obtained by the product 6 and / or the methane fermentation device 1, and the MAP that separates the MAP particles from the crystallization treatment liquid after MAP crystallization. The separation device 3, the drug addition device 4 for adding a drug containing a pH lowering agent, a phosphorus removing agent, or both to the separation liquid after MAP particle separation, and the separation liquid after adding the drug are membrane-separated and membrane-filtered. The membrane separation device 5 for obtaining the concentrated digested liquid and the permeated water 9 and the returning means 8 for returning the membrane filtered concentrated digested liquid to the methane fermentation device 1 are provided.

The organic waste 6 is not limited as long as it is an organic waste containing at least phosphorus, nitrogen and magnesium, and includes liquid organic waste water as well as solid matter. For example, raw materials containing organic substances such as sewage sludge, human waste treatment sludge, septic tank sludge, livestock manure, swill, various factory wastewater / waste, and hardness components such as nitrogen, phosphorus, and magnesium are organic waste according to the present embodiment. It can be suitably treated as a product 6.

The COD _Cr in the organic waste 6 is not particularly limited, and can be applied to a raw material having an organic substance concentration in the range of 500 mg / L or more and 300,000 mg / L or less. When the organic matter concentration is relatively high, it is preferable to dilute appropriately in order to alleviate the inhibition of the raw material components.

The methane fermentation apparatus 1 is an apparatus for decomposing organic waste 6 as methane gas by the metabolic action of methane bacteria that survive in an anaerobic environment. In the methane fermentation apparatus 1, an anaerobic treatment tank in an arbitrary temperature range, such as a medium-temperature methane fermentation treatment tank having an optimum temperature of 30 ° C to 40 ° C and a high-temperature methane fermentation treatment tank having an optimum temperature of 50 ° C to 60 ° C. Can be used without limitation. The methane fermentation apparatus 1 may be a one-tank type or a multi-stage type. Further, an acid fermentation tank may be provided separately. It is desirable that the digestive juice of methane fermentation is adjusted within the optimum pH of 6.5 to 8.0 for methane fermenting bacteria.

The MAP crystallization apparatus 2 refers to an apparatus in which soluble MAP constituent elements in the treatment liquid in the MAP crystallization apparatus 2 are brought into contact with the particulate MAP in the MAP crystallization apparatus 2 to be crystallized. The organic waste 6, the digestive liquid 10 after methane fermentation, or the digestive liquid 10 after methane fermentation containing the organic waste 6 can be supplied into the MAP crystallization apparatus 2. By directly supplying the organic waste 6 into the MAP crystallization device 2, phosphorus, magnesium, and ammonia, which are the MAP constituent elements dissolved in the organic waste, are crystallized, and the MAP production in the methane fermentation device 1 is suppressed. can. Further, when the digestive liquid 10 after methane fermentation is supplied into the MAP crystallization apparatus 2, the amount of ammonia produced by the decomposition of organic waste increases, and the amount of MAP crystallized without adding chemicals or the like. Has the advantage of being able to increase. When the organic waste 6 and the digestive juice 10 after methane fermentation are supplied into the MAP crystallization apparatus 2, the amount of chemicals required to bring the pH into a range suitable for crystallization can be suppressed, or the amount of chemicals added can be suppressed. , There is an advantage that the addition of chemicals can be omitted.

In the MAP crystallization device 2, it is not always necessary to promote the crystallization of the MAP particles, but in the case of promoting the crystallization, a method of increasing the pH of the MAP crystallization device 2 is effective. Since the preferable pH for accelerating the crystallization reaction of the MAP particles is 8 or more, for example, 8 to 9, it is sufficient to raise the pH in the MAP crystallization apparatus 2 by about 0.5 to 1.0. However, when an aeration treatment, a decompression treatment, or the like is used in combination, the pH is increased by decarbonation, and the MAP particles can be precipitated more efficiently. Sodium hydroxide, magnesium hydroxide, magnesium oxide and the like may be added to the MAP crystallization apparatus 2 to raise the pH.

Alternatively, a magnesium source may be added as a method for promoting the crystallization reaction of MAP. As the magnesium source added to the MAP crystallization apparatus 2, magnesium hydroxide and magnesium oxide can be used in addition to magnesium chloride. The amount of the magnesium source added is 0.1 to 10, preferably 0.5 to 3.0, and more preferably 0.8 to 1.2 in terms of molar ratio with respect to the concentration of soluble orthoric acid in the digestive juice. be. The pH in the reaction is preferably 7.0 to 11.0, preferably 7.5 to 8.5, and even more preferably 7.3 to 8.3.

In order to efficiently generate MAP particles in the MAP crystallization device 2, it is preferable to add seed crystals in the MAP crystallization device 2. As the seed crystal, MAP particles precipitated by the MAP crystallization device 2 or MAP particles precipitated by another reactor can be used.

MAP particles separated by the MAP separation device 3 described later can also be used. In this case, the MAP crystallized product separated and recovered by the MAP separation device 3 can be returned to the MAP crystallizing device 2 by the return tube 12.

In addition, powders or granules such as phosphate ore, dolomite, bone charcoal, activated carbon, silica sand, calcium silicate and the like can be used as seed crystals to be interposed in the MAP crystallization apparatus 2. The particle size of the seed crystal may be arbitrary, but is preferably 0.05 to 3.0 mm, more preferably 0.1 to 0.5 mm. By precipitating new MAP on the surface of the seed crystal, the solid-liquid separation efficiency of the MAP separation device 3 in the subsequent stage is improved.

The filling amount of the seed crystal is important for precipitation on the surface of the seed crystal. The filling amount is such that the phosphorus input amount per surface area of the seed crystal (hereinafter referred to as phosphorus surface area load) is 30 g-P / m ² / d or less, more preferably 10 g, in consideration of the phosphorus input amount and the seed crystal particle size. -P / m ² / d or less is preferable. That is, if a high concentration of MAP is maintained in the MAP crystallizer 2 for the same particle size, the reactor volume can be reduced and the initial cost can be reduced.

Further, in the MAP crystallization device 2, the ion product of the MAP constituent substance in the crystallization treatment liquid crystallized by the MAP crystallization device 2 is more preferably 2.5 or less in ratio to the solubility product of MAP. The MAP particle concentration in the MAP crystallizer 2 is adjusted so that the value is 2 or less and further 1 or less.

The method for adjusting the MAP particle concentration is arbitrary and can be determined in consideration of the amount of phosphorus input to the methane fermentation apparatus 1. For example, in consideration of the phosphorus surface area load, it is preferable to adjust the MAP particle concentration of the crystallization treatment liquid treated in the MAP crystallization apparatus 2 to be 1 g / L or more, and more preferably 10 g / L or more. Adjust so that The "MAP particle concentration" means the mass concentration of MAP particles having a particle size of 0.05 mm or more existing in the liquid in the MAP crystallizer 2, and is separated by, for example, a sieve having an opening of 0.05 mm. Can be evaluated by. Further, the magnesium source may be added and adjusted by the above addition amount.

The device type of the MAP crystallization device 2 is not particularly limited, and is a complete mixing type reactor equipped with a mechanical stirring device, a jet type stirring reactor using a pump, and a fluidized bed type filled with seed crystals at high density. Reactor, internal circulation type reactor equipped with a draft tube, external circulation type reactor and the like can be used. The crystallization treatment liquid treated in the MAP crystallization device 2 is supplied to the MAP separation device 3 via the pipe 11.

The type of the MAP separation device 3 is not particularly limited as long as it can selectively separate and recover MAP particles, but for example, a liquid cyclone can be preferably used. By arranging the liquid cyclone, the entire device can be miniaturized. The lower structure of the liquid cyclone is an inverted conical shape, and a liquid cyclone inflow pipe is provided on the side, a concentrated liquid containing fine particles (crystallized matter) is discharged on the lower side, and an overflow rising pipe is provided on the upper part.

In the hydrocyclone, the upper fluid in the MAP crystallizer 2 is supplied by pumping a pump (not shown), and descends on the inverted conical wall surface inside the hydrocyclone while causing a swirling flow, and the MAP fine particles having a heavy specific gravity (the MAP fine particles having a heavy specific gravity (). Crystallized material) is collected and concentrated on the lower wall surface side by the action of centrifugal force.

The concentrated liquid (separation liquid) containing the concentrated fine particles is continuously or intermittently withdrawn from the lower discharge pipe. The discharge pipe of the MAP separation device 3 is connected to the MAP crystallization device 2, and the concentrated liquid containing the fine particles separated in the MAP separation device 3 is passed through the return pipe 12 by the switching valve provided in the discharge pipe. It can be returned to the MAP crystallizer 2. As a result, MAP can be crystallized more efficiently from the crystallization treatment liquid to remove phosphorus.

The MAP separation liquid from which the MAP particles have been separated in the MAP separation device 3 is returned to the methane fermentation device 1 in a state where the MAP production ability is reduced by the chemical supply of the drug addition device 4, and the piping 13 used for the return is returned. Is preferably connected as close as possible to the inlet of the pipe 7 that supplies the membrane separation device 5. In addition, as a method of returning the MAP separation liquid to the methane fermentation apparatus 1, a partition wall is provided inside the methane fermentation apparatus 1, and the pipe 13 for returning the MAP separation liquid and the pipe 7 to the membrane separation device 5 are separated from each other. It is also possible to install it inside the. Alternatively, a method can be adopted in which the methane fermentation apparatus 1 is multi-staged and the return destination of the MAP separation liquid is divided into a plurality of stages.

It is desirable that the drug supplied from the drug addition device 4 be supplied as close as possible to the discharge port of the MAP separation device 3 in order to prolong the contact time with the MAP separation solution obtained from the MAP separation device 3. ..

The agent supplied from the agent addition device 4 can include a pH lowering agent, a phosphorus removing agent, or both. Examples of the pH lowering agent include hydrochloric acid, sulfuric acid and the like. Examples of the phosphorus lowering agent include polyferric sulfate, ferric chloride, polyaluminum chloride, aluminum sulfate, calcium chloride and the like. Both the pH lowering agent and the phosphorus lowering agent may be added to the MAP separation solution.

By adding a predetermined amount of these chemicals to the MAP separation liquid, the pH of the MAP separation liquid to which the chemicals are added is higher than the pH of the organic waste and / or the digestive juice after methane fermentation in the MAP crystallizer 2. The orthrinic acid concentration of the MAP separation solution added so as to decrease by 0.1 or more, or to which the drug was added, is the orthrinic acid concentration of the organic waste in the MAP crystallizer and / or the digestive juice after methane fermentation. The drug is added so as to decrease by 0.1% or more.

As a result, the MAP separation liquid having a reduced MAP producing ability can be supplied to the membrane separation device 5, so that the generation of MAP can be suppressed regardless of the water quality fluctuation of the water to be treated, and the membrane in the membrane separation device 5 is damaged or the membrane is damaged. It is possible to process more economically and stably while suppressing clogging.

The MAP separation liquid is supplied to the membrane separation device 5 via the pipe 7, and in the membrane separation device 5, the membrane filtration concentrated digestive liquid and the permeated water are obtained. The material of the separation membrane of the membrane separation device 5 is not particularly limited, and an organic membrane such as polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), a ceramic inorganic membrane, or the like can be preferably used. As the membrane shape, a flat membrane, a hollow fiber, a tubular, a spiral, a monolith, or the like can be preferably used. The membrane separation device 5 is preferably an out-of-tank type separated from the methane fermentation device 1.

The amount of water permeated by the membrane separation device 5 is 0.1 m / d or more and 1.0 m / d or less, preferably 0.1 to 0.5 m / d. The return means 8 for returning the membrane filtration concentrated digestive liquid obtained by the membrane separation device 5 to the methane fermentation apparatus 1 may return the membrane filtration concentrated digestive liquid of about 10 to 200 with respect to the raw material ratio (volume ratio). It is preferable, more preferably 30 to 100.

If the sludge concentration of the methane fermentation apparatus 1 is too high, the pressure applied to the filtration membrane of the membrane separation apparatus in the subsequent stage increases, so the sludge is extracted (sludge treatment) and sent to the membrane separation apparatus 5. It is preferable to control the supply amount of the MAP separation liquid. This sludge treatment can be performed by connecting a sludge extraction pump (not shown) to the methane fermentation apparatus 1. By controlling the sludge concentration in the methane fermentation apparatus 1 so that the activated sludge suspended matter (MLSS) concentration is 1000 to 60,000 mg / L, it is more economical while suppressing damage or blockage of the membrane of the membrane separation apparatus 5. Targeted and stable processing is possible.

According to the method and apparatus for treating organic waste according to the embodiment of the present invention, a chemical is added to the separation liquid after separating the MAP particles subjected to the MAP crystallization treatment, and the MAP generation performance is suppressed. Since the treated liquid can be supplied to the membrane separation device 5, the equipment operating time can be increased by suppressing membrane blockage, the required membrane area can be reduced, the amount of diluted water for suppressing MAP crystallization can be reduced, and the methane fermentation facility can be used. Various effects can be expected, such as reducing the frequency of removing scale in pipes or tanks, and reducing chemical costs.

Examples of the present invention are shown below together with comparative examples, but these examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

(Example 1)
In the organic waste 6 treatment apparatus shown in FIG. 1, a methane fermentation apparatus 1 (30 L) with MLSS: 30,000 mg / L was used. Further, 100 g of particulate MAP was added to the MAP crystallization device 2 (10 L) to adjust the concentration of the particulate MAP of the liquid in the MAP crystallization device 2 to 10 g / L. The digestive juice in the methane fermentation apparatus 1 was supplied to the MAP crystallization apparatus 2 at 1000 mL / h, and then supplied to the cyclone which is the MAP separation apparatus 3 to separate the MAP particles in the digestive juice. The treated liquid of the cyclone was supplied to the membrane separation device 5 via the methane fermentation device 1, and the membrane filtration concentrated digested liquid concentrated in the membrane separation device 5 was returned to the methane fermentation device 1. As the membrane of the membrane separation device 5, an internal pressure tubular membrane having a diameter of 5.2 mm was used. Chemicals were supplied to the supply line of the membrane separation device 5 by the chemical addition device 4. A pressure gauge was installed between the entrance and exit of the circulation flow path of the membrane separation device 5 and the suction pump of the membrane filtered water to measure the differential pressure between the membranes. The membrane filtration device backwashed the membrane-filtered water at a pressure of 0.1 MPa once every 7 days.

A waste raw material (COD _Cr : 111,000 mg / L) containing a protein and a hardness component was added to the methane fermentation apparatus 1 at 0.6 L / d, and the mixture was mixed and stirred for 21 days for methane fermentation treatment. During the test period, solid-liquid separation was performed with a membrane filtration pump at a permeation water volume of 0.2 m / d. In the supply line of the membrane separation device 5, ferric chloride was quantitatively injected at a concentration of 45 mg-Fe / L-raw material so that the concentration of orthoric acid in the digestive juice after the MAP crystallization treatment was reduced by 0.1%. In addition, hydrochloric acid was quantitatively injected with 5 mg / L-raw material so that the pH of the digestive juice was lowered by 0.1.

(Example 2)
In the organic waste 6 treatment apparatus shown in FIG. 1, a methane fermentation treatment test in which the same amount of organic waste 6 was added was carried out for 21 consecutive days after the end of the test of Example 1. During the test period, MAP crystallization treatment was performed with the same amount of treatment as in Example 1, the digested liquid was supplied to the membrane separation device 5, and solid-liquid separation was performed with the same amount of permeated water by a membrane filtration pump. Hydrochloric acid was quantitatively injected into the supply line of the membrane separation device 5 with 5 mg / L-raw material so that the pH of the digestive juice was lowered by 0.1.

(Example 3)
In the treatment apparatus for the organic waste 6 shown in FIG. 1, the waste raw material (COD _Cr : 111,000 mg / L) containing a protein and a hardness component is 0 to the methane fermentation apparatus 1 under the same treatment conditions as in Example 1. .6 L / d was added, and the mixture was mixed and stirred for 21 days to carry out methane fermentation treatment. In Example 3, MAP crystallization treatment was performed with the same amount of treatment as in Example 1, the digested liquid was supplied to the membrane separation device 5, and solid-liquid separation was performed with the same amount of permeated water by a membrane filtration pump. .. In the supply line of the membrane separation device 5, ferric chloride was quantitatively injected at a concentration of 45 mg-Fe / L-raw material so that the concentration of orthophosphoric acid in the digestive juice after the MAP crystallization treatment was reduced by 0.1%.

(Comparative Example 1)
In FIG. 1, the test was conducted using a mode in which the chemical addition device 4 is not used, that is, the organic waste 6 treatment device shown in FIG. The processing conditions of the apparatus common to FIG. 1 are the same as the conditions described in the first embodiment. In Comparative Example 1, a methane fermentation treatment test in which the same amount of organic waste 6 as in Example 1 was added was carried out for 21 consecutive days after the end of the test of Example 2. During the test period, MAP crystallization treatment was performed with the same amount of treatment as in Example 1, the digested liquid was supplied to the membrane separation device 5, and solid-liquid separation was performed with the same amount of permeated water by a membrane filtration pump.

(Comparative Example 2)
In FIG. 1, the test was conducted using a mode in which the MAP crystallization device 2, the MAP separation device 3, and the drug addition device 4 are not used, that is, the organic waste 6 treatment device shown in FIG. 3 is used. The treatment conditions of the methane fermentation apparatus 1 common to the configuration of the treatment apparatus of FIG. 1 are the same as the conditions described in Example 1. The membrane used in the membrane separation device 5 was washed by immersing it in 10 wt% citric acid before the test.

A methane fermentation treatment test in which the same amount of organic waste 6 was added was carried out for 21 consecutive days after the completion of the test of Comparative Example 1. During the test period, the methane fermentation digested liquid was supplied to the membrane separation device 5, and solid-liquid separation was performed with the same amount of permeated water by a membrane filtration pump.

(Comparative Example 3)
In the organic waste 6 treatment apparatus shown in FIG. 1, MAP crystallization treatment was carried out for 21 days after the end of the test of Example 3 with the same amount of treatment as that of Example 1, and the digested liquid was subjected to the membrane separation apparatus 5. The solid-liquid separation was performed with the same amount of permeated water by a membrane filtration pump. In the supply line of the membrane separation device 5, ferric chloride was quantitatively injected at a concentration of 22 mg-Fe / L-raw material so that the concentration of orthophosphoric acid in the digestive juice after the MAP crystallization treatment was reduced by 0.05%.

FIG. 4 shows the time course of the intermembrane differential pressure during the operation periods of Examples 1 to 3 and Comparative Examples 1 to 3. Table 1 shows the increase values of the intermembrane pressure before and after the test period. In all of Comparative Examples 1 to 3, the differential pressure between the membranes increased as compared with Examples 1 to 3.

1 ... methane fermentation equipment 2 ... MAP crystallization equipment 3 ... MAP separation equipment 4 ... chemical addition equipment 5 ... membrane separation equipment 6 ... organic waste 7 ... piping 8 ... return means 9 ... permeated water 10 ... digestion after methane fermentation Liquid 11 ... Piping 12 ... Return pipe 13 ... Piping

Claims (6)

A method for treating organic waste containing phosphorus, nitrogen and magnesium.
The process of methane fermentation of the organic waste in a methane fermentation apparatus and
The step of supplying the organic waste and / or the digestive juice after methane fermentation to the MAP crystallizer to crystallize the MAP particles.
A step of supplying the crystallization treatment liquid after MAP crystallization to the MAP separation device and separating the MAP particles from the crystallization treatment liquid after MAP crystallization.
The step of adding a chemical containing a phosphorus removing agent to the separation liquid from which the MAP particles are separated, and
A step of supplying the separation liquid to which the drug is added to a membrane separation device to obtain a membrane filtration concentrated digestive liquid and permeated water, and a step of obtaining the permeated water.
Including the step of returning the membrane-filtered concentrated digestive juice to the methane fermentation apparatus.
The step of adding the drug is
The orthophosphoric acid concentration of the separation liquid to which the drug is added is reduced by 0.1% or more with respect to the orthophosphoric acid concentration of the organic waste and / or the digestive liquid after the methane fermentation in the MAP crystallizer. A method for treating organic waste, which comprises adding the above-mentioned chemicals as described above. The method for treating organic waste according to claim 1, further comprising a step of returning the MAP particles separated from the crystallization treatment liquid to the MAP crystallization device in the MAP separation device. The MAP particle concentration in the MAP crystallization device is adjusted so that the ion product of the MAP constituent substance of the crystallization treatment liquid treated by the MAP crystallization device is 2.5 or less in ratio to the solubility product of MAP. The method for treating organic waste according to claim 1 or 2, which comprises adjusting. The method for treating organic waste according to any one of claims 1 to 3, which comprises setting the MAP particle concentration in the MAP crystallizer to 1 g / L or more. The method for treating organic waste according to any one of claims 1 to 4, which comprises using a liquid cyclone as the MAP separation device. A methane fermentation device that methane-ferments organic waste containing phosphorus, nitrogen and magnesium, and
A MAP crystallizer for crystallizing MAP particles from the organic waste and / or the digestive juice after methane fermentation.
A MAP separation device that separates the MAP particles from the crystallization treatment liquid after MAP crystallization, and
A drug addition device that adds a drug containing a phosphorus removing agent to the separation liquid after separation of MAP particles, and
A membrane separation device that separates the separation liquid to which the drug is added into a membrane to obtain a membrane-filtered concentrated digestive liquid and permeated water.
It is provided with a return means for returning the membrane-filtered concentrated digestive solution to the methane fermentation apparatus.
The concentration of orthophosphoric acid in the separation liquid to which the phosphorus removing agent was added by the drug addition device is the concentration of orthophoric acid in the organic waste and / or the digestive juice after the methane fermentation in the MAP crystallization device. A device for treating organic waste, which comprises adding the above-mentioned chemical so as to reduce the concentration by 0.1% or more.

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