JPS58153594A - Treatment of organic waste - Google Patents

Abstract

PURPOSE:To increase the rate of generation of gaseous methane and to treat the residues of digesting liquid efficiently in the stage of subjecting org, waste to solid-liquid sepn. after anaerobic digestion, by combining heat treatment for the waste with the biological nitrification and nitrification and denitrification of the digesting liquid. CONSTITUTION:Org. waste (preferably the org. waste controlled to <=5pH) 1 is admitted into a heat treating device 2, where the waste is treated under heating for a short time preferably at >=175 deg.C. Such waste is charged into an anaerobic digesting tank 3 which is heat exchanged 9 with the device 2, and is allowed to stagnate therein for the time enough for digestion and is thereby subjected to an anaerobic digesting treatment under constant or occasional agitation. The waste flowing out from the tank 3 is treated in a biological nitrifying or biological nitrifying and denitrifying tank 4, whereafter an inorg. flocculating agent 5 is added thereto and the waste is treated in a solid-liquid separating device 6. The supernatant liqueur 8 produced in the solid-liquid separating stage is returned to the water treatment system, and if necessary part thereof may be admitted into the tank 3 and treated. Separated and dehydrated cake 7 is disposed after post treatments, for example, a mechanical dehydration stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating treated sludge such as sewage and wastewater, or organic waste such as city garbage and other industrial waste.

Conventional methods for treating organic sludge from sewage and human waste treatment facilities, and the most commonly used representative treatment method, include polymer flocculants and ferric chloride, which are valuable resources for organic sludge. , a large amount of dehydration aid such as lime is added, dehydrated using a mechanical dehydrator, and dried as a dehydrated cake.
The process of incineration, rounding, drying and incineration, consumes a large amount of auxiliary fuel such as heavy oil, and in addition, the high moisture dehydrated cake with a moisture content of about 70 to 80% is dried by incineration exhaust gas or hot air and then incinerated, so it is difficult to withstand. A large amount of bad odor is generated, and as a countermeasure to prevent this odor, the process is deodorized by various deodorizing processes such as direct combustion deodorization, catalytic combustion deodorization, wet chemical cleaning, and adsorption. It was complicated and caused problems in terms of maintenance, management, and maintenance costs.

In particular, as the environment surrounding oil has deteriorated in recent years, there has been a strong demand for resource conservation, energy conservation, and energy production in forms other than oil. After that, it has been put into practice. In this form of energy production, the most proactive approach is to recover energy from waste and useful plants, and many of these have already been implemented.
Technologies have been proposed to recover wastewater treatment sludge and municipal waste in the form of methane gas and electricity through methane fermentation.However, there are still some problems with these methane fermentation technologies, and these are difficult to overcome. It is hoped that further technical progress will be made by solving this problem. For example, this prior art is sufficiently economically 11. l) There is a problem that either sufficient amount of methane gas cannot be generated or that a large amount of cost is required to process and dispose of the residue after methane fermentation. That is, in the conventional method, after energy is recovered through methane fermentation (anaerobic digestion), the fermentation residue (hereinafter referred to as digestive fluid) cannot be properly processed and disposed of, which has become a major problem. In order to treat and dispose of this, it is first necessary to separate solid-liquid, but solid-liquid separation of this digestive fluid is extremely difficult, and this solid-liquid separation operation requires more energy than is recovered in the anaerobic digestion process. The reality is that we are spending a lot of energy, and the drawback is that we don't know how much energy we are recovering.

The present invention solves many unreasonable problems in the conventional organic waste treatment process, greatly improves biodegradability, prevents the generation of foul-smelling gas, and increases the amount of methane gas generated and produced. It is an object of the present invention to provide a method for treating organic matter that can efficiently separate the residue of anaerobic digestive fluid in an extremely energy-saving manner, and can produce inexpensive energy and simplify post-treatment. A purpose and a friend.

The present invention relates to a method of anaerobically digesting organic waste such as sewage sludge and then subjecting it to solid-liquid separation treatment. For example, chemical nitrification or biological nitrification, which is characterized by solid-liquid separation by adding an inorganic flocculant after denitrification, increases the amount of methane gas generated and also reduces the solidification of the residue after methane fermentation. It can also facilitate liquid separation and 1
In order to solve the problems of heat treatment, such as eliminating odor and eliminating the desorbed liquid, and effectively utilizing the waste heat obtained in the heat treatment process, it is possible to simply heat treat organic waste, which has conventionally existed. This is an effective method that is superior to the method of performing methane fermentation first.

In other words, when organic waste such as sewage sludge is heat-treated, the organic matter is denatured, for example, undergoes hydrolysis and becomes lower in molecular weight, and undissolved substances become soluble and become easily decomposed. Therefore, substances that cannot be broken down by normal anaerobic digestion can be biodegraded. When it comes to modifying organic substances by heat treatment, it is desirable to carry out the process in an acidic range, preferably at a pH of 5 or less.
It is preferable to add the acid as follows. In this case, the acid used is preferably an organic acid or a mineral acid, preferably hydrochloric acid.

For example, if acid fermentation is performed prior to heat treatment, organic substances that are easily biodegradable in the acid fermentation process have already been decomposed, and only organic substances that are not decomposed in the acid fermentation process are converted into biodegradable substances in heat treatment step 1. The lower the pH value, the better the fluidization of the organic waste, which improves the efficiency of the heat treatment process. In any case, heat treatment generates a large amount of biodegradable organic matter, so the amount of methane gas generated from the subsequent anaerobic digestion process is much larger than that generated from normal digestion. The amount of energy recovered can be increased by that amount. If the heat treatment is performed in an acidic range or at a pH of 5 or less, the pH within the anaerobic digestion tank is generally 70 to 8.0, so this difference in pH can promote the anaerobic digestion reaction.

As described above, when sewage/wastewater treatment sludge, which is a type of organic waste, is heat-treated, its solid-liquid separability is significantly improved, and the improvement in liquid-liquid separability due to this heat treatment is not impaired even after subsequent anaerobic digestion.

That is, after biological nitrification or additional denitrification of the digestive fluid flowing out of the anaerobic digestion tank, solid-liquid separation is performed by adding an inorganic flocculant, for example, adding ferric chloride or other acids to the digestive fluid. By adding an inorganic coagulant such as an iron salt inorganic coagulant or an inorganic coagulant based on an alkaline calcium salt or magnesium salt and performing pressure dehydration, a dehydrated cake with an extremely high water content can be obtained. In general, the alkalinity of digestion is 3,000 to 5,000 Ml/L as
Because CaCα is very high, even if inorganic flocculants such as ferric chloride, other acidic iron salts, alkaline 0 salts, Mg salts, etc. are added, they are consumed by alkalinity, and the part that is effective during solid-liquid separation of the liver and kidneys is not used. When I say a little, it's K. In other words, the optimal chemical injection rate during solid-liquid separation, which is the concentration rate necessary to adjust the optimal pH range K11l, requires a considerably large amount of chemical addition to ensure this. Furthermore, the coagulant may even react with the alkali carbon content to produce substances that adversely affect solid-liquid separation. Therefore, by using biological nitrification treatment as a method to lower the alkalinity of the digestive fluid, the alkalinity was significantly reduced, and the amount of inorganic flocculant added could also be significantly reduced. Before attempting the nitrification process, we attempted to remove alkalinity using mineral acid and K5, an inexpensive sulfuric acid, but sulfuric acid was more expensive than the aeration power used in the nitrification process, and in addition, it required an inorganic flocculant. If slaked lime is used as slaked lime, gypsum will be generated, which is negative for solid-liquid separation.'1. ．． I found out that it will happen. On the other hand, when the digestive fluid is nitrified, slaked lime is added, and the solid-liquid is separated using a pressure dehydrator, the amount of slaked lime added can be significantly reduced compared to the digestive fluid that is not nitrified. It has been found that the addition of slaked lime can also reduce the release of ammonia from sludge. The rate at which alkaline carbon is removed by nitrification is as follows: −.

NH4HCO3+3/202-NO; + H”+2H
20+ CO2↑ It can be seen that carbonic acid, which is an alkaline carbon content, will continue to be dissipated from the liquid by nitrification, and it will be dissipated very easily because the pH value will be lowered by nitrification.

In addition, in the method of the present invention, the heating temperature in the heat treatment is preferably 175°C or higher, which greatly improves the dehydration f overrate and improves the dehydration property compared to when the ri is 175°C or lower. This is because the decomposition rate of organic matter increases significantly.

In this way, in the present invention, organic waste is treated at a pH of 5.
In the following, heat treatment at 175°C or higher followed by anaerobic digestion increases biodegradability, which not only increases the amount of methane gas generated, but also improves the solid-liquid separation of the methane fermentation residue. be done. Since the heat treatment is carried out at a pH of 5 or less, the fluidity of the waste increases, the heat treatment is carried out efficiently, and the heat treatment time is shortened. This solves the problem of adhesion and allows efficient heat exchange.

By the way, heat treatment of organic waste often produces a foul odor, which is most noticeable in the heat treatment of sewage treatment sludge. In addition to eliminating the risk of secondary pollution as the components are easily removed, the chromaticity component of the heat-treated desorbed liquid is very sensitive, and it was very difficult to remove the chromaticity component using biological treatment alone, but solid-liquid During separation, it was possible to remove chromaticity components by employing a solid-liquid separation method that uses at least an inorganic flocculant such as ferric chloride.

Invent this invention! Accordingly, referring to the drawings, an organic waste (preferably one whose pH has been adjusted to 5 or lower) 1 flows into a heat treatment device 2, and preferably 1
Subjected to a short heat treatment at a temperature of 75°C or higher. Then, the waste that has been heat-treated for a predetermined period of time is put into the anaerobic digestion tank 3 that has undergone heat exchange 9 with the heat treatment device 2, and is allowed to stay there for a sufficient time for sufficient digestion.The waste is then subjected to anaerobic digestion treatment by stirring from beginning to end or as needed. do.

After the waste flowing out from this anaerobic digestion tank 3 is treated with biological nitrification or biological nitrification and denitrification rosewood 4 (hereinafter referred to as nitrification tank 4), an inorganic flocculant 5 is added, and a solid-liquid separator 6 Process with . The desorbed liquid 8 generated in the solid-liquid separation process may be returned to the water treatment system, and if necessary, a part of it may be flowed into the anaerobic digestion tank 3 for treatment. 7 is disposed of after undergoing post-processing, such as a mechanical dehydration process.

In the nitrification tank 4, the digestive fluid of organic waste is aerated, and ammonia is oxidized to nitrite or nitric acid by nitrifying bacteria, thereby lowering the pH. This pH is the pH at which nitrifying bacteria are inhibited.
The pH will be as low as about 5.5, which is in the H range, but if aeration is carried out at this pH, almost all of the alkalinity, ions, and deuterate ions will be dissipated into the atmosphere, resulting in a significant decrease in alkalinity. Digestion fluid has a high concentration, and as in the normal activated sludge treatment method, an extremely large settling tank is required to separate the nitrification tank mixture into solid and liquid and return the sludge, so nitrification is temporary. It is desirable to provide aeration. That is, after the digestive fluid is nitrified or further desilicated in the nitrification tank 4, the mixed solution is directly dehydrated. Digestive fluid from which alkalinity has been sufficiently removed is ferric chloride. After adding another acidic iron salt inorganic flocculant 5 to the digestive fluid at a solid weight ratio of 2 to 3 o, alkaline Ca Adjust the pH to 3 by adding salt or Mg salt.
Adjust to 5-5.0.

However, if the pH becomes 3.5 to 5.0 after adding ferric chloride or other acidic iron salt inorganic flocculant 5, alkaline C
There is no need to add a salt or htg salt. In addition, when only alkaline C1 salt or chlorine salt is added, it is only added to the digestive fluid in an amount of 5 to 30% by weight of solids, and subsequent pH adjustment to 1 l is not necessary. The digestive fluid to which the inorganic flocculant 5 has been added is subjected to solid-liquid separation in a pressure dehydrator.

The growth rate of nitrifying bacteria is lower than that of general BOD oxidizing bacteria, so if the sludge period in nitrification tank 4 is short, nitrifying bacteria will be washed out from nitrification tank 4 and nitrification will become impossible, so the volume of nitrification tank 4 will be reduced. can be determined from the growth rate of nitrifying bacteria as shown in the following equation.

ΔX" / Vn @ji≦μ ΔX1: Amount of surplus solids generated (147 days) vn: Volume of nitrification tank (,/) X!I: Concentration of solids in nitrification tank (~/-) μ: Maximum growth of nitrifying bacteria Speed (1/day) If it is normal wastewater, inflow BOD
The amount of surplus solids generated must be calculated from the amount of solids generated for the inflow SS and the amount of solids generated for the inflow SS, but since the biodegradable organic matter has already been decomposed and removed from the digestive fluid, all of the digestive fluid is excess solids. Therefore, the water temperature in nitrification tank 4 is 2.
Assuming that the temperature is 5° C. (μ=0.311/day), the volume of the nitrification tank 4 is calculated as follows.

Q-8O/10,000, μ≦■ Q: Digestive fluid inflow rate (-7 days) SO: Digestive fluid solids concentration (cool/-) If we assume BO = 40"ly, then the heat can be considered to be almost the same as the So. Therefore, W≧Q10.31 = 3.2Q(i).

In other words, 3.2 times the amount of digestive fluid that flows in per day is transferred to the nitrification tank 4.
The volume should be . The growth rate of nitrifying bacteria increases as the water temperature rises up to around 40°C, so the digestive fluid flowing into the nitrification tank 4 should be prepared by considering the heat dissipation due to aeration in the nitrification tank 4.
It is desirable that the water flow into the nitrification tank 4 in a state where the water temperature is as high as possible. From this point of view, it is desirable to efficiently utilize heat exchange between the heat treatment device 2 and the anaerobic digestion tank 3 to set the digestion temperature in the high temperature digestion range. The solid-liquid separator 6 is most preferably a pressurized dehydrator, and any type of pressurized dehydrator is effective, but one with a squeezing mechanism is particularly effective.
A dehydrated cake with a moisture content of 65 or less can be obtained by adding the extra time (9) minutes and the pressing time. In addition, in the present invention, the solid-liquid separability is significantly improved by performing heat treatment in advance, and this is not lost by digestion, so this improvement in solid-liquid separation is also effective in solid-liquid separation of digestive fluid. The solid-liquid separation results are even better than those obtained without prior heat treatment.

The present invention uses ferric chloride or other acidic iron salt inorganic flocculants,
9 is extremely effective for pretreatment of solid-liquid separation using alkaline Ca salt or salt formation. That is, by nitrifying the digestive fluid, the alkalinity can be drastically removed, so the pH can be easily raised or lowered by adding a small amount of these chemicals. In addition, since the bicarbonate and carbonate ions in the digestive fluid disappear, even if alkaline Ca salts and Mg salts are added, these carbonates are not generated, which prevents clogging of pressurized dehydration cloth. can do. Furthermore, since the amount of ammonia is reduced due to nitrification, the amount of ammonia released from the digestive fluid when the pH increases is reduced, and the stability of the solid-liquid separation section can be improved. The oil content in the nitrification tank 4 disappears when the pH reaches 5.0, but at pH 5.
, 0, not all ammonia is nitrified (at low pH), the nitrification reaction of nitrifying bacteria does not progress and ammonia remains.

Added alkaline Ca salt or uniform salt L? pH1rt 1
In order to completely prevent ammonia from dissipating when it rises in a trench near 1, it is sufficient to completely nitrify the ammonia, but for this purpose, add an alkaline agent to nitrification tank 4.
It is better to go H forward. Alternatively, if a denitrifying rosewood is installed in the front part of the nitrification tank and the nitrified liquid is circulated through the denitrifying rosewood, nitric acid and nitrite in the circulating liquid are reduced and denitrified.
This is particularly advantageous because the drop in H is alleviated and furthermore, pixels in the digestive fluid can be removed. The denitrification reaction is the opposite of the nitrification reaction, in which nitric acid and nitrite are reduced and decomposed under anaerobic conditions, but a reducing agent is required during deoxidation. The BOD component remaining in the digestive fluid can be used as the reducing agent, but if the amount of reducing agent is insufficient, a carbon source such as methanol may be used.

As described above, since the present invention performs heat treatment prior to anaerobic digestion of organic waste, a large amount of biodegradable organic waste is produced, and the amount of methane gas generated from the anaerobic digestion process is also increased. . This means that if a fermentation process is performed prior to heat treatment, heat treatment can be carried out at a pH of 5 or less without or with the addition of a small amount of acid, improving the fluidization of organic waste. Not only can the heat treatment be carried out efficiently, but it can also promote anaerobic digestion.In addition, the solid-liquid separation property of the digestive fluid, which has been improved by heat treatment, is not lost even when bale anaerobic digestion is performed. In particular, by using a pressure dehydrator, it is possible to obtain a dehydrated cake with a water content that is unimaginable in the past.In this solid-liquid separation process, the digestive fluid is aerated to cause a nitrification reaction. As a result, the alkalinity can be lowered, so it is possible to significantly reduce the amount of inorganic flocculant added to adjust the pH to the optimum pH range where the inorganic flocculant can contribute to solid-liquid separation. Even if alkaline Ca salts or salt-forming agents are used as agents, these carbonates will not be formed, and this will result in scale adhesion to pipes, etc., and clogging of fabrics.
b can be prevented.

Furthermore, ammonia is reduced by nitrifying the digestive juices, so even if the pH is increased using alkaline salt or salt-forming during solid-liquid separation, the amount of ammonia released is small, and the amount of ammonia released is small. As a result, in the separated liquid of solid-liquid separation, BOD is reduced at the same time as ammonia through nitrification, and phosphorus is removed by using ferric chloride and alkaline C and a salt, so it is returned to the water treatment system. Moreover, in the present invention, by performing anaerobic digestion after heat treatment, the odor components are considerably removed and the risk of secondary pollution is eliminated.Also, regarding the chromaticity components, In the solid-liquid separation of digestive juices, ferric chloride or other acidic iron salt inorganic flocculants or alkaline carbon salts, Mg salts and nine inorganic flocculants are used, but at least ferric chloride or acidic iron salts are used as inorganic flocculants. By using flocculants, we were able to remove a considerable amount of the chromaticity components.Here, the amount of these flocculants added was such that the pH after the straining was 3.5 to 50, and the solids of the digestive fluid were However, if these are added as coagulation aids and solid-liquid separation is performed, colored components generated during the heat treatment process can be removed at the same time as solid-liquid separation.

The present invention not only increases the biodegradability of organic waste and increases the amount of methane gas generated, but also improves the solid-liquid decomposition of anaerobic digestion fluid and reduces the amount of flocculant added for solid-liquid separation. At this time, even if an alkaline Ca salt or salt forming agent is used as an inorganic flocculant, scale adhesion to piping and the like and clogging of the cloth of the solid-liquid separator will not occur.

In addition, as for the desorbed liquid of solid-liquid separation, BO is removed by nitrification.
D and ammonia are reduced, phosphorus is removed by using ferric chloride or alkaline Ca salt 1Mg salt for solid-liquid separation, and coloration, which has traditionally been the biggest problem with heat-treated desorbed liquids, has been reduced. Since the components can also be removed by using ferric chloride or acidic iron salt inorganic flocculants, the desorbed liquid can be returned to the water treatment system without any trouble.

Moreover, the odor generated during the heat treatment operation is removed in the subsequent anaerobic digestion process, and by efficiently exchanging heat with the heat treatment process at 175°C or higher, anaerobic digestion can be carried out with what is generally called high temperature digestion. This not only shortens the residence time in the digester, but also shortens the subsequent nitrification process. Preferably, if heat treatment is performed with the pH adjusted to 5 or less, the flow of organic waste in the heat treatment equipment will increase, and the heat treatment will be carried out efficiently. This also solves the problem of scale adhesion inside.

Next, examples based on the present invention and conventional methods as comparative examples will be described.

Example l Total solid content (hereinafter referred to as TS) 3.511, volatile solids concentration (hereinafter referred to as ■S) 2.81g, loss on ignition (hereinafter referred to as ■s/T8) 78.411i, p
H5,6 sewage sludge was placed in an autoclave with a capacity of 5JO and heat-treated at 175°C for (capital) minutes, resulting in a pH of 5,9 and T.
S: 3.5-, VS: 2.8-+”/la near B,
2-Heat-treated sludge was obtained, and the odor concentration was 930.0.
00, and the chromaticity of the desorbed liquid was 520. This heat-treated sludge is maintained at 52±IC and retained for 82 days in an anaerobic digestion tank that is continuously stirred (the capacity of the digestion tank is 24 tons).
) and 54- of VS are decomposed and the gas is 57.1 per day.
1, pH 7.6, T town, 2.0%, VS: 1
．． Anaerobically digested sludge with a concentration of 3%, ``!/ya:62.:M'' was obtained. This was aerated for 3 days in an aeration tank with a capacity of 10J (water temperature approximately (9)U), and then chlorinated sludge was added. Add iron to the solid substance, stir and mix, then apply overpressure: 4b
/j, filtration time = 30 minutes, pressing pressure crab 9Kt/j, pressing time: When pressurized dehydration was performed under the conditions of addition, water content:
A dehydrated cake of 64.3- was obtained. Table 1 shows the properties of the anaerobic digestive fluid, nitrification fluid, and pressurized dehydration fluid.

Table 1 Properties of anaerobic digestion fluid, nitrification treatment fluid, and pressurized dehydration solution Example 2 Hydrochloric acid was added to the same sludge as in Example 1 to adjust the pH to 49, and the mixture was placed in a 5-ton autoclave and heated at 175°C. After 15 minutes of lock heat treatment, pH 5.0, TS: 3.51G,
A heat-treated sludge with VS: 2.8L"/ra: 78.2- was obtained, and the odor concentration was 1,010,000
The chromaticity of the desorbed liquid was 610. This heat treated sludge is
52±lcK and retained in an anaerobic digestion tank with continuous stirring for 8 days (the capacity of the digestion tank is 24 tons).
S 6211 decomposed and got gas for a day! >56.9
1 occurred, pH 7.7, TS: 1.81G, V
S: 1.11G, vha: 57.611 (
D flll pneumatic digestion sludge power II b し*.

After sufficiently aerating this in an aeration tank with a capacity of 2 OL for 4 days (water temperature approximately 30'C), slaked lime was added to the solids at a rate of 1011
After adding and stirring and mixing, pressurized dehydration was performed under the conditions of overpressure: 44/j, filtration time = 30 minutes, squeezing pressure crab 9Kt/j = squeezing time: 20 minutes, water content: 62 .7
- A dehydrated cake can be obtained. Table 2 shows the properties of the anaerobic digestion fluid, nitrification treatment fluid, and pressurized dehydration fluid.

Table 2 Comparative example of properties of anaerobic digestive fluid, nitrification fluid, and dehydration fluid The same sewage sludge as in Examples 1 and 2 was placed in an autoclave with a capacity of 5 tons, and when heat-treated at 175C during heating, the pH became 5.8,
TS: 3.51g, VS: 2811, ”
A heat-treated sludge of 21G was obtained. The odor concentration of this heat-treated sludge is 930,000°, and the chromaticity of the desorbed liquid is 5.
At 20°C, this was maintained at ±1°C in the house and retained in an anaerobic digestion tank with continuous stirring for 15 days (the capacity of the digestion tank was 45 tons), and vS05191 decomposed and gas was released at 53.2°C per day. 24, pH 7.6, TS: Obtained.

If this device is used for one day, it will settle and concentrate, and the total volume of the concentrated sludge will be 2391! Therefore, TS: 7.41G, V
Thickened sludge with fS: 4.8- is obtained. The precipitated and separated water at this time had a chromaticity of 550 and an odor source [near 6G].

Add TS Akuri ferric chloride to the obtained thickened sludge!
, 5011 slaked lime was added, filtration pressure: 44/j,
Filtration time: (9) minutes.

When pressurized dehydration was performed under the conditions of pressurized crab 9b/ai and pressurization time: addition, a dehydrated cake with a moisture content of 67.1- was obtained. This dehydrated solution has a color [:17. Odor concentration:
330 and nine.

[Brief explanation of drawings]

The drawing is a 70-sheet of one embodiment of the method of the invention. 1...Organic waste, 2...Heat treatment equipment, 3...
Anaerobic digestion tank, 4...Nitrification or nitrification, denitrification rosewood, 5
... Inorganic flocculant, 6 ... - Liquid separation device, 7 ... Dehydrated cake, 8 ... Desorption liquid, 9 ... Heat exchange.

Claims (1)

[Claims] 1. After heating the organic waste, it is subjected to anaerobic digestion treatment, and the anaerobic digestive liquid is subjected to biological nitrification or biological nitrification and denitrification treatment, and then an inorganic flocculant is added. A method for treating organic waste with a focus on solid-liquid separation. 2. The processing method according to claim 1, wherein the heat treatment step is performed at a heating temperature of 175° C. or higher. 5. Claim l#!, wherein the heat treatment step is to heat treat the organic waste after adjusting the pH to 5 or less. The processing method described in item 1 or 2. 4. The processing method according to at least one of claims 1 to 3, wherein the anaerobic digestion knee is performed by exchanging heat with the heat treatment step. 5. The solid-liquid separation step uses ferric chloride or acidic iron salt,
5. The treatment method according to claim 1, wherein the treatment is performed by adding an inorganic flocculant such as an alkaline calcium salt or an alkaline magnesium salt. & The solid-liquid separation step is carried out by adding an inorganic flocculant such as ferric chloride or a ferric iron salt together with an alkaline calcium salt or magnesium salt as a flocculation aid. A processing method as described in at least one of the ranges 1 to 4.