JPH04277096A - Method for treating organic waste water by photosynthesized microorganism - Google Patents

Abstract

PURPOSE:To efficiently remove org. substances, sulfide, nitrogen and phosphorus by subjecting org. waste water to acid fermentation process, a photosynthetic bacilliculture process wherein is cultured purple nonsulfur bacteria or purple sulfur bacteria alone and/or in mixture thereof and a blue alga culture process. CONSTITUTION:A method for treating org. waste liq. which comprises the steps of introducing a conc. organic waste liq. 1 through a fiber content removing device 2 into an acid fermentation tank 3 to reduce the molecular weight of succharides and other high molecular org. substances in the waste liq. to a level of lower carboxylic acid; introducing the liq. into a photosynthetic bacilliculture tank 5 having purple non-sulfur bacteria and/or purple sulfur bacteria cultivated therein; supplying a solar or artificial energy 6 and a gas 7 made low in partial oxygen pressure into the photosynthetic bacilliculture tank 5; introducing the liq. into a blue alga culture tank 13 to photosynthesize the blue alga by light energy 14, CO2 15 from the atmospheric air and further by nitrogen and phosphorus; introducing the liq. into a green alga dark culture tank 17 to decompose the org. substances under aerobic conditions with the oxygen from the blue alga culture tank 13 and the oxygen in the air supplied by a blower 19; and decomposing a very small amt. of org. substances of the liq. outflowing from the green alga dark culture tank 17 in a biological oxidizing tank 22 and discharging the liq.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating organic wastewater using photosynthetic microorganisms, and in particular, it relates to a method for treating organic wastewater using photosynthetic microorganisms.
By configuring a biological treatment process that rationally combines the respective functions of mainly photosynthetic bacteria and microalgae, human waste, livestock sewage, and various organic wastewaters containing concentrated sulfide and/or nitrogen and phosphorus can be treated. , converts organic matter, sulfide and/or water contained in wastewater into hydrogen, which is clean energy, and at the same time removes nitrogen and phosphorus,
Furthermore, the present invention relates to a processing technology for producing and extracting valuable substances such as livestock feed from fiber components and proliferating bacterial cells as residues. In addition, in the present invention, photosynthetic microorganisms are mainly involved, and since these can fix large amounts of CO2 in the atmosphere, it is an excellent treatment technology that will naturally contribute significantly to eliminating global environmental pollution. . [0002] Conventionally, human waste, sewage sludge, and
Concentrated organic wastewater is usually treated with methane fermentation, which effectively utilizes the functions of anaerobic bacteria, or biologically oxidized, which utilizes the functions of aerobic bacteria, while remaining concentrated. It's here. In addition, when wastewater contains substances that cause eutrophication such as nitrogen and phosphorus, treatment techniques such as biological denitrification, biological dephosphorization, or biological denitrification and dephosphorization are applied. Ta. These treatment technologies inevitably involve the treatment of large amounts of organic sludge, and if it is necessary to add advanced treatment depending on the environment of the discharge destination, flocculated sludge, which is extremely difficult to treat, may be added to this. That will happen. [0003] The various processing techniques described above are, almost without exception, energy-intensive and resource-intensive processing techniques. In order to eliminate these deficiencies, various research organizations have been conducting research for a long time, but these technical problems remain largely unsolved at this time. Furthermore, over the past few years, the problem of global warming has become more apparent, and there is a strong demand for solutions and improvements from a global perspective. If we evaluate conventional biological treatment technologies from this perspective, we find that both anaerobic and aerobic treatments generate a large amount of CO2 gas, and that sludge drying and incineration processes, in particular, produce a large amount of CO2 gas. A large amount of concentrated CO2 gas is generated. For this reason, there is an urgent need to research and develop new organic wastewater treatment technologies that can contribute to improving the global environment in the water treatment field. [Problems to be Solved by the Invention] As detailed above,
Conventional wastewater treatment technologies and methods consume a lot of energy and resources, and also generate large amounts of carbon dioxide, which contributes to global warming. The present invention improves this fateful defect of the conventional technology, and aims to provide an innovative method for treating organic wastewater based on a completely new idea, and to provide a new multifunctional biological treatment process. shall be. [Means for Solving the Problems] In order to achieve the above object, the present invention rationally combines the respective functions of acid-fermenting bacteria and photosynthetic microorganisms, making the functions complex and multifunctional. This is an innovative method for treating organic wastewater based on a new idea. That is, the present invention provides a method for treating organic sewage by biological means, in which organic sewage is first treated with an acid fermentation step in which polymer compounds contained in the sewage are acid-fermented, and then red non-sulfur bacteria, By performing a photosynthetic bacteria culture process using a single system and/or a mixed system of purple sulfur bacteria, and then performing a cyanobacteria culture process in which cyanobacteria are cultivated, nitrogen and nitrogen in the sewage are produced within the bacterial cells while producing hydrogen. This is a method for treating organic wastewater characterized by assimilating phosphorus. [0006] The present invention also provides the above treatment method,
This is a method for treating organic wastewater in which hydrogen is produced by further performing a green algae cultivation step or a photosynthetic bacteria cultivation step after the treatment in the cyanobacterial cultivation step. The effluent after being treated in the green algae culturing process described above can be further treated in a biological oxidation process to decompose and remove remaining pollutant components. Moreover, the microorganisms cultured in each of the above-mentioned culture steps can be taken out of the system from each step, dehydrated and dried, and recovered as valuables such as feed for livestock. As described above, the present invention first converts organic wastewater containing polluting high-molecular organic substances, other organic substances, sulfides and/or nitrogen, phosphorus, etc. into lower carboxylic acids through the action of acid-fermenting bacteria. After reducing the molecular weight to a low molecular weight, biological treatment is applied to purple non-sulfur bacteria and/or purple sulfur bacteria that produce hydrogen using organic matter and sulfide as electron donors, and microalgae that can produce hydrogen using water as an electron donor. A novel organic wastewater treatment method that makes it possible to simultaneously process organic wastewater, produce hydrogen, which is clean energy, and produce valuable substances from proliferating bacterial cells by rationally combining them within the process. It is. Next, the present invention will be explained in detail using FIGS. 1 and 2. First, if necessary, concentrated organic wastewater 1 such as human waste, sewage sludge, and industrial wastewater is passed through a fiber removal device 2 to remove fibers (cellulose and hemicellulose).
After removing the acid, it is introduced into the acid fermentation tank 3, and the sugars and other high-molecular organic substances are reduced in molecular weight to lower carboxylic acids (acetic acid, butyric acid, propionic acid, etc.). This wastewater is then contaminated with purple non-sulfur bacteria such as Rhodobacter and/or Chromatium.
The photosynthetic bacteria are introduced into a photosynthetic bacteria culture tank 5 in which purple sulfur bacteria such as P. atium are cultured. In the photosynthetic bacteria culture tank 5, sunlight energy or artificial light energy collected by a mass-light concentrator is transmitted to the inside of the tank 5 using a so-called light transmission light emitting device such as an optical fiber, a flat or curved light emitter, or a gel light emitter. and is used as energy for the growth of photosynthetic bacteria. On the other hand, CO fixed by photosynthetic bacteria
2 7 is normally supplied to the tank 5 by introducing atmospheric air. This atmosphere is converted to O
By separating as much as possible or appropriately circulating the generated gas, a gaseous body with a low oxygen partial pressure is supplied for the growth of photosynthetic bacteria and hydrogen production. The inside of the photosynthetic bacteria culture tank 5 is basically divided into two equal volumes, and wastewater is introduced alternately into each part. Photosynthetic bacteria cultivated in one tank are supplied with wastewater (mainly lower carboxylic acids and sulfides), light energy 6 and CO2 7, and sufficiently accumulate poly-β-hydroxybutyric acid within their cells. It becomes a mature bacterial cell. When this state is reached,
Hydrogen is produced under the supply of light energy and under conditions of low nitrogen gas partial pressure. Further, the other tank is operated under the same operating conditions, and both of the photosynthetic bacteria culture tanks 5 are used alternately to continuously generate H2. [0010] Surplus bacteria grown in the photosynthetic bacteria culture tank 5 are taken out of the system through a growth bacteria extraction tube 20 and processed to extract valuables and/or feed. Since a large amount of poly-β-hydroxybutyric acid is normally accumulated in the proliferating cells, it is possible to produce biodegradable polymers or high value-added substances such as polyphosphoric acid. The biological reaction formula for organic matter production and hydrogen production through photosynthesis of purple non-sulfur bacteria and purple sulfur bacteria in the photosynthetic bacteria culture tank 5 is as follows. [0011] Purple non-sulfur bacteria (eg Rhodobacter
acter )) Electron donor → Mainly lower carboxylic acid ■
Photosynthesis 6CO2 +12H2 O → C6 H
12O6 +6O2 +6H2 O ■ Hydrogen production C6 H12O6 +6H2 O → 6
CO2 +12H2 +680kcal purple sulfur bacteria (
For example, Chromatium
Electron donor → sulfide ■ Photosynthesis 6CO2 +12H2 S → C6 H
12O6 +12S+6H2 O ■ Hydrogen production C6 H12O6 +6H2 O → 6
CO2 +12H2 +680kcal [0012] H2 generated from the photosynthetic bacteria culture tank 5 is transferred to the gas transport pipe 8.
The hydrogen storage alloy 9 separates it into pure H2 along the transport pipe 8, and after mixing it with air 10, it is transferred to an electrical energy conversion device 11 such as a fuel cell.
or converted into electrical energy by a gas turbine. It is also possible to directly use the gas as thermal energy via the gas transport pipe 8. Next, the outflow water from the photosynthetic bacteria culture tank 5 is introduced into the cyanobacteria culture tank 13 through the treated water transfer pipe. In this tank 13, cyanobacteria such as Oscillatoria and Anabaena are exposed to light energy 14 and CO2 supplied from the atmosphere.
15 and/or from the exhaust gas of the green algae dark culture tank 17, and nitrogen and phosphorus supplied from the water flowing into the tank 13, photosynthesis is carried out, and bacterial cells multiply and organic matter is produced. Similar to the photosynthetic bacteria culture tank 5, this tank 13 is divided into two parts, and under the same operating conditions as the tank 5, sufficient maturation of the bacterial cells and subsequent hydrogen production under nitrogen-deficient conditions are carried out. The two divided tanks 13 are used alternately for the same purpose and operation. Hydrogen production by cyanobacteria is carried out by water decomposition, and the biological reaction formula is as follows, and at the same time oxygen, which can be used for many purposes, is generated. 2H2 O → 2H2 +O2 After sufficient hydrogen has been generated, excess bacterial cells are discharged from the system through the bacterial cell extraction tube 20 and are used for the purpose of extraction and/or production of valuable substances. Hydrogen gas generated from the cyanobacterial culture tank 13 is transferred to the electrical energy conversion device 1 through the gas transport pipe 8.
1 and/or distribution pipes, the energy is effectively utilized as electrical energy and thermal energy 12, respectively. When a fuel cell is used as the electrical energy conversion device 11 , the generated hydrogen-containing gas is concentrated and separated by the hydrogen storage alloy during the process of being transferred through the gas transport pipe 8 , and is further transported to the combustion cell 11 along with air. Supplied. Next, the outflow water from the cyanobacteria culture tank 13 is introduced into the green algae dark culture tank 17, where Chlamydomonas (Chlamydomonas)
monas), Chlorella (Chlorella
) H2 is produced by the decomposition of organic matter by dark culturing of so-called green algae such as green algae. Depending on the type of cyanobacteria cultivated in the cyanobacteria culture tank 13 for the purpose of hydrogen production, a considerable amount of organic matter produced by photosynthesis may be eluted out of the cells. Usually, the above-mentioned Oscillato
ria), Anabaena converts about 30% of the fixed CO2 into bacterial cells as polysaccharides, lower carboxylic acids such as acetic acid (CH3 COOH), and glycolic acid [CH2 (OH) COOH] in the presence of light energy. release it outside. When the amount of treated water is relatively large, H2 is removed from water and organic matter by light and dark cultivation of green algae.
However, when the amount of water to be treated is small, it is more advantageous to extract hydrogen only from organic matter by dark culture because the growth rate of green algae is faster and it does not require the supply of light energy. [0016] In the green algae dark culture tank 17, Chlamydomonas (Chlamydomonas) and Chlorella (
Green algae such as Chlorella) produce acetic acid (C
H3 COOH), glycolic acid [CH2 (OH)C
Oxygen produced in the cyanobacterial culture tank 13 in the previous step using lower carboxylic acids such as OOH] and others as energy sources,
The organic matter is decomposed under aerobic conditions by the oxygen in the air supplied from the blower 19, and a large amount of hydrogen is produced by heterotrophic growth. The biological reaction formula is as follows. CH3 COOH+2H2 O → 2CO2 +
4H2 CH2 OHCOOH+H2 O → 2
CO2 +2H2 [0017] The hydrogen gas generated from the green algae dark culture tank 17 passes through the gas transport pipe 8 and is combined with the hydrogen generated from the previous process to generate electrical energy 1
1 or thermal energy 12. In addition, the proliferating bacterial cells from this tank 17 are taken out of the system through the bacterial cell extraction tube 20, combined with the proliferating bacterial cells from the previous step, and moderately concentrated in the concentrating tank 21.
It is processed as feed, soil conditioner, or used to extract value-added substances. Here, since the green algae heterotrophically cultured in the green algae dark culture tank lacks chlorophyll, the excess bacterial cells are transferred to the enrichment tank 21 in the process of being transferred to the aeration tank 31, which is an open system that can receive sunlight. It is aerated for about a day to form chlorophyll. As the final stage of water treatment, the outflow water from the green algae dark culture tank 17 is introduced into an unspecified biological oxidation tank 22, and the remaining organic matter is removed by oxygen supplied from the blower 23.
The treated water is decomposed by aerobic microorganisms in the presence of water, and is discharged to the outside through the treated water discharge pipe 24. FIG. 2 will now be explained with reference to FIG. 1 as a modification of the biological process described in detail. As described above, most of the organic substances contained in the outflow water from the cyanobacteria culture tank 13 are lower carboxylic acids represented by acetic acid (CH3 COOH) and glycolic acid [CH2 (OH) COOH]. Since photosynthetic bacteria naturally digest lower carboxylic acids extremely well as a source of nutrients and energy, a photosynthetic bacteria culture tank 30 is provided in place of the green algae dark culture tank as shown in Figure 2, and Rhodobacter (Rhodo)
H2 may be produced from organic matter using a lower carboxylic acid as an electron donor under the supply of light ephorgy25 and CO226 using purple non-sulfur bacteria such as Bacter. In this case, there is virtually no sulfide present in the influent water, so chromatium (Chro
It is not necessary to use purple sulfur bacteria such as M. matium), and cultivation is simple. In this modified process, almost no organic matter remains in the effluent water, so the biological oxidation tank 22 and air supply 23 shown in FIG. 2 can be omitted.
There is no doubt that the process is simplified and economical. Finally, the undigested material mainly composed of fiber discharged from the fiber removal device 2 and/or the acid fermentation tank 3 is sent to the feed manufacturing device 4. As mentioned above, most of the undigested material is fiber, but it is inevitable that various components of the human waste, livestock sewage, or organic wastewater to be treated will accompany the undigested material, and it usually has a bad odor. [0020] Therefore, the undigested material is sent as an aqueous solution to 4, where it is treated with Trichoderma reesei var., which is a fibrinolytic bacterium.
ar. ) and Bacillus subtilis var., which is Bacillus natto.
) were inoculated with two types of microorganisms under aerobic conditions, and were sufficiently nutritious with useful enzymes such as cellulases, hemicellulases, proteolytic enzymes, peptide-degrading enzymes, and odor-degrading enzymes (unidentified). It is also converted into a substance that can be used as an energy source. This fermentation product is dried and then provided as feed (additive). The light energy to be supplied to the photosynthetic bacteria culture tanks 5 and 30 and the cyanobacterial culture tank 13 is naturally determined by the bacterial cell concentration, but judging from the experimental results, it is approximately 8 to 1.
0kw/m3 ・hr range (from solar energy to 95
% or more) is no big deal. Further, in a region where the present invention is implemented in an area where solar energy is strong and sunlight hours are long, even if the present invention is 100% dependent on solar energy, there will not be much significant difference. Also, the supply rate of light energy to be transmitted to the surface of the light emitter is 25 to 45
W/m2・hr is also sufficient. In culturing photosynthetic bacteria and/or various microalgae, it is preferable to carry out intermittent light and dark culture as appropriate, but light culture or dark culture may also be used. [Operation] The treatment method of the present invention decomposes polluting organic matter and sulfide in organic wastewater in an energy-saving manner through the interaction and synergistic effect of the respective functions of acid-fermenting bacteria, photosynthetic bacteria, and microalgae. However, by using these and the water in the system as electron donors, it is a new biological treatment that makes it possible to produce hydrogen as well as organic matter, especially feed, etc. from undigested matter and/or proliferating bacterial cells. It's technology. The conventional technology generates a large amount of sludge, which is not only very troublesome to dispose of, but also requires a large amount of construction and current costs. On the other hand, the treatment technology of the present invention recycles and utilizes undigested matter and surplus (proliferated) bacterial cells, so it is not only free from the so-called troublesome conventional sludge treatment; Valuable materials (feed, etc.) that are effectively used for various purposes are harmoniously incorporated into the natural ecosystem and accepted without resistance into the material circulation cycle of the natural world. Furthermore, the amount of CO2 gas generated from this new process is extremely small; on the contrary, a large amount of CO2 gas, which is a cause of global warming, is fixed and converted into valuable materials. Hydrogen produced through photoreactions by photosynthetic microorganisms is an extremely clean energy substance, and even when burned, it becomes H2O, which is completely harmless. Therefore, the present invention is an innovative organic wastewater treatment method that significantly contributes to the improvement of the global environment as a total process. [Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. Example 1 Pig pen wastewater from adult pigs was selected as the concentrated organic wastewater. These adult pigs are fed a compound feed, and the water quality of the wastewater after removing approximately 60% of solids (mainly fiber) is shown in Table 1 (
A). Table 1 (B) shows the water quality of the wastewater obtained by carrying out organic acid fermentation in an acid fermenter having a capacity to retain this wastewater for 3 days (wastewater amount: 0.5 liters/day). [Table 1] [0026] The volumes of the photobioreactor and dark culture reactor used as the photosynthetic bacteria culture tank 5, cyanobacterial culture tank 13, and green algae dark culture tank 17 were all 4 liters, but 5 and 13 The interior of each tank was divided into equal volumes of 2 liters, and each was used alternately. In addition, the capacity of the biological oxidation tank at the final stage of the wastewater treatment process is a square tank with a capacity of 1 liter, and the filling material is ordinary granular activated carbon. Supplied from. The wastewater under these conditions was purified in each step, and the final water quality of the effluent is shown in Table 2. As can be seen from this table, extremely good treated water was obtained. [Table 2] [0028] The residence time per wastewater in the photosynthetic bacteria tank was 4 days (2 days + 2 days), and the bacterial strain used was Rhodobacterium (Rhodobacter), which the present inventors screened from natural water systems.
obactersp. ), Chromatium bacterium ( Chr
omatium sp. ) was used. In addition, the bacterial strain used in the cyanobacteria culture was also Oscillatoria (Oscilatria).
llatoriasp. ), the green alga is Chlamydomonas sp. Ceramic filters with a pore size of 5 μm were used for bacterial cell separation in the photosynthetic bacteria culture tank, cyanobacteria culture tank, and green alga dark culture tank. The bacterial cell concentration is 3,500 to 4 for photosynthetic bacteria.
, 500mg/l, microalgae 7,000-8,000
It was adjusted to be in the range of mg/l. Light energy was supplied by a xenon lamp (visible light only) in order to obtain quantitative data, and the light energy supply rate was 5 kW/100 kW per tank volume.
m3 ・hr, 25W per light emitting area of optical fiber
It was fixed at /m2/hr. After continuous operation for about 5 months under the above conditions and confirming that the entire system was in a steady state, the amount of hydrogen produced from each tank was measured. Table 3 shows the average data for hydrogen generation over two months. [Table 3] [0031] By the biological hydrogen production process of the present invention, the solubilized solution of the adult pig breeding wastewater listed in Table 1 (B) is
m3/day (equivalent to about 6,000 adult pigs), and based on the hydrogen production obtained from continuous experiments, calculate the generated thermal energy to be approximately 600 to 600 m3/day.
50kw/hr, and if this thermal energy is converted into electrical energy using a fuel cell, it will be approximately 300 to 300 kw/hr.
25kw/hr (assuming the efficiency of the fuel cell is 50%). Example 2 The discharge ratio of the solid matter (A) discharged from the fiber removal device and the undigested matter (B) from the acid fermenter was approximately 10:1. 10 pieces of (A) and (B) in a 3 liter batch type small aeration tank
2 liters of the sample adjusted to 1:1 was injected, and Bacillus subtilis var.
lus subtilis var. ) as a bacterial weight of 0.5 g, and similarly Trichoderma reesei variety (
Trichoderma reesei var. )1
Add 1-2mg/g of dissolved oxygen to the solution using a small blower.
The cells were cultured for 3 days by supplying air to the cells so that the volume of the cells was 1. The results are shown in Table 4, and as can be seen from the table, the liquid product was proven to have sufficient value as livestock feed (additive). [Table 4] Table 4 [0034] Example 3 Excess bacterial cells from the photosynthetic bacteria culture tank, cyanobacterial culture tank, and green algae dark culture tank were dried, and the dry matter was mixed in equal weight and then microorganized. When the amino acid composition was measured after crushing, it was found that the content of essential amino acids was generally high, and it was proved that it has high utility value as feed for livestock and/or fish. The analysis results are shown in Table 5. [Table 5] [Effects of the Invention] According to the present invention, the following effects can be achieved. (1) Organic matter, sulfide, nitrogen, and phosphorus in concentrated organic wastewater can be efficiently removed in an extremely energy-saving and resource-saving manner. (2) It is a treatment technology that is friendly to the global environment and people, as it can fix large amounts of CO2, which is the main cause of global warming. (3) The present invention is capable of producing a large amount of hydrogen by using organic matter, sulfide, and water as hydrogen donors (electron donors) in the same way as CO2 fixation in the atmosphere, and enables energy creation based on a new technical idea. This is a unique processing technology. (4) There is no generation of organic sludge that is difficult to treat as in the prior art, and the surplus bacterial cells can be qualitatively converted into valuable materials either as they are or by being processed. (5) Feed for livestock and fish can be produced from the fibers contained in wastewater by utilizing the functions of specific microorganisms. There is no doubt that the biological treatment process based on the idea of the present invention, which rationally combines the functions of photosynthetic bacteria and microalgae, will become the mainstream of next-generation treatment technology in the future.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of the treatment method of the present invention.

FIG. 2 is a partial process diagram showing another example of the treatment method of the present invention.

[Explanation of symbols]

1: Concentrated sewage, 2: Fiber removal device, 3: Acid fermenter, 4:
Feed manufacturing equipment, 5: Photosynthetic bacteria culture tank, 6, 14, 25
: Light energy, 7, 15, 18, 26: CO2 supply, 8: Hydrogen gas transfer pipe, 9: Hydrogen storage alloy, 11: Electrical energy conversion device, 12: Thermal energy, 13: Cyanobacteria culture tank, 17: Green algae Dark culture tank, 20: Growth cell transfer tube, 21: Concentration tank, 22: Biological oxidation tank, 23: Air, 24
: Effluent water, 25: Photosynthetic bacteria culture tank

Claims (7)

[Claims] 1. A method for treating organic wastewater by biological means, in which the organic wastewater is first treated with an acid fermentation step in which polymer compounds contained in the wastewater are acid-fermented, and then purple non-sulfur bacteria, By treating with a photosynthetic bacteria cultivation step using a single system and/or a mixed system of purple sulfur bacteria, and then treating with a cyanobacteria cultivation step of culturing cyanobacteria,
A method for treating organic wastewater characterized by assimilating nitrogen and phosphorus in the wastewater into bacterial cells at the same time as producing hydrogen. 2. The method for treating organic wastewater according to claim 1, wherein after the treatment in the cyanobacteria cultivation step, hydrogen is produced by further treatment in a green algae cultivation step. 3. The method for treating organic wastewater according to claim 1, wherein after the treatment in the cyanobacterial cultivation step, the organic wastewater is further treated in a photosynthetic bacteria cultivation step to produce hydrogen. 4. The method for treating organic wastewater according to claim 2, wherein the effluent after being treated in the green algae cultivation step is treated in a biological oxidation step to decompose and remove remaining pollutant components. 5. The method for treating organic wastewater according to claim 1, wherein a fiber removal step is provided before the acid fermentation step. 6. Undigested and undecomposed fiber discharged from the fiber removal step and/or acid fermentation step is inoculated with fibrinolytic bacteria and Bacillus natto and decomposed under aerobic conditions, and 6. The method for treating organic sewage according to claim 5, wherein feed is produced. 7. The organic wastewater treatment according to claim 1, 2 or 3, wherein the microorganisms cultured in each culture step are taken out of the system from each step, dehydrated and dried, and recovered as valuable materials. Method.