JP2003326295A - Method and apparatus for treating organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an upflow anaerobic sludge bed treatment method and an apparatus of high performance for treating organic waste water containing substances to hamper an anaerobic treating process step. <P>SOLUTION: The treatment method for the organic waste water comprising introducing the organic waste water containing the substances to hamper the anaerobic treating process step into an anaerobic treating process step, and subjecting the waste water to an anaerobic treatment, then introducing the effluent thereof into the aerobic treating process step and subjecting the effluent to the aerobic treating process step, in which a part of the sludge generated in the aerobic treating process step is admitted into the anaerobic treating process step and the substances to hamper the anaerobic treating process step contained in the organic waste water are adsorbed or stuck on the sludge and a part or the whole of the effluent of the anaerobic treating process step is admitted into the aerobic treating process step and the apparatus for the same are provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to various factories, sewage,
The present invention relates to an anaerobic sludge bed treatment method and apparatus for detoxifying organic wastewater or organic waste discharged from human waste, livestock industry facilities, etc., and more specifically, for inhibiting anaerobic treatment. TECHNICAL FIELD The present invention relates to a method and apparatus for treating an upflow anaerobic sludge bed of an organic wastewater containing a substance that exerts an influence.

[0002]

2. Description of the Related Art Organic wastewater, organic waste, etc. are sometimes decomposed by anaerobic treatment. Examples of such decomposition treatment methods include an upflow anaerobic sludge bed method (hereinafter also referred to as UASB) and a granule sludge expansion bed (hereinafter also referred to as EGSB). This is a method that has become widespread in recent years and is characterized in that the concentration of methane bacteria in the reactor can be maintained at a high concentration by granulating anaerobic bacteria such as methane bacteria into granules. Even if the concentration of organic substances therein is considerably high, the treatment can be performed efficiently. For example, in a device that embodies this method,
COD measured using potassium dichromate as an oxidant
The volume load of _cr (hereinafter referred to as COD) is 20 to 30 kg /
It has the feature that it can operate efficiently even with m ³ / d wastewater and waste.

As a substance which inhibits the anaerobic treatment process, higher fatty acids, terpenes contained in paper pulp wastewater, resin acids and the like are known. It is known that substances contained in paper pulp wastewater that inhibit the anaerobic treatment process are decomposed and removed in the aerobic treatment process (Sjon Kor).
tekaas et al., Journal of Fermen
stationation and Bioengineering
g, 86 (1), 97-110 (1998)). Inhibition here means reducing the activity of anaerobic bacteria or killing anaerobic bacteria. Examples of the method for anaerobically treating the organic wastewater containing the substance that inhibits the anaerobic treatment step include the following methods.

(A) After removing the inhibitor in advance, anaerobic treatment is performed. (B) Diluting water supplied from outside the system or a substance that inhibits anaerobic treatment by aerobic treatment is decomposed and diluted with treated water to reduce the concentration to a level that does not affect the anaerobic treatment, and then anaerobic treatment I do. (C) After acclimating the anaerobic bacteria to the inhibitory substance, anaerobic treatment is performed under a low load.

[0005]

However, the method of anaerobically treating an organic wastewater containing a substance which inhibits the anaerobic treatment step has the following problems. (B) When the anaerobic treatment is performed after the inhibitor is removed in advance, pretreatment equipment is required. (B) When performing anaerobic treatment after diluting with diluting water, etc. and reducing to a concentration that does not have an effect of inhibition, when the dilution ratio is high, equipment such as anaerobic treatment equipment is oversized due to a large amount of diluting water. Become. (C) When the anaerobic bacteria are acclimated to the inhibitor and then the anaerobic treatment is performed under a low load, the anaerobic treatment device becomes excessive.

In order to eliminate such drawbacks, the present invention provides
It is an object of the present invention to provide a high-performance upward-flow anaerobic sludge bed treatment method and apparatus for organic wastewater containing a substance that inhibits an anaerobic treatment process.

[0007]

The present invention has solved the above-mentioned problems by the means described below. (1) After introducing an organic wastewater containing a substance that inhibits the anaerobic treatment process to the anaerobic treatment process and performing the anaerobic treatment,
In the method of conducting the aerobic treatment by guiding the effluent to the aerobic treatment step, part of the sludge generated in the aerobic treatment step is allowed to flow into the anaerobic treatment step, and the sludge is anaerobically contained in the organic wastewater. A method for treating organic wastewater, which comprises adsorbing or adhering a substance that inhibits a treatment process and allowing a part or all of the effluent of the anaerobic treatment process to flow into the aerobic treatment process. (2) In the anaerobic treatment step, a gas / liquid / solid separation is formed by a baffle plate having an angle of 35 degrees or less with the device main body side wall and each occupied area being ½ or more of the device cross-sectional area. The method for treating organic wastewater according to (1) above, wherein an upward flow anaerobic sludge bed treatment device having a plurality of parts is applied.

(3) The organic effluent flowing in, a part of the effluent of the anaerobic treatment step and the sludge are mixed and subjected to acid fermentation, and then anaerobic treatment is performed. Alternatively, the method for treating organic wastewater according to (2). (4) By adding an antifoaming agent to the water to be treated,
The method for treating organic wastewater according to (2) or (3) above, wherein foaming and scum formation inside the liquid / solid-liquid separation section are prevented.

(5) An acid fermentation tank for introducing organic wastewater, an upflow anaerobic treatment apparatus for introducing the acid fermentation liquid from the acid fermentation tank, and an anaerobic treatment solution for the upflow anaerobic treatment apparatus And aerobic treatment for aerobic treatment, a settling tank for introducing the aerobic treatment liquid from the aeration tank for solid-liquid separation, and an activated sludge pipe for sending a part of the sludge settling in the settling tank to a raw water feed pipe An organic wastewater treatment device comprising:

The essence of the present invention is to add the sludge generated in the aerobic treatment step to the anaerobic treatment step, adsorb or attach a substance that inhibits the anaerobic treatment step to the sludge, and to treat the raw water as a circulating liquid of the treated water. Or by appropriately diluting with diluting water supplied from outside the system, consistently adjusting the water flow rate based on the device cross-sectional area inside the reactor of the inflow water to be 1 to 5 m / h. As a result, the added sludge does not remain in the reactor and flows out of the system together with the anaerobic treatment process effluent, and as an anaerobic treatment device at that time, the angle with the side wall of the device is 35 degrees. Below, and each occupied area is half of the device cross-sectional area
By using an upflow anaerobic sludge bed treatment device having multiple stages of gas / liquid / solid separation parts formed by baffle plates of 1 or more, the gas / liquid / solid separation performance in the reactor is increased, Granule sludge can be maintained at a high concentration in the reactor, and high-performance upflow anaerobic sludge bed treatment can be achieved for organic wastewater containing substances that interfere with the anaerobic treatment process. Further, a substance which flows into the aerobic treatment step in a state of being adsorbed or attached to sludge and which has an influence on the anaerobic treatment step is decomposed and removed in the aerobic treatment step.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a diagram exemplifying an outline of one embodiment of a treatment flow of the present invention, which is preferable for performing treatment of an organic wastewater containing a substance that has an influence on an anaerobic treatment step. FIG. 2 is a diagram exemplifying an outline of one embodiment of an upflow anaerobic treatment apparatus which is preferable for carrying out the anaerobic treatment method in the present invention. In FIG. 1, 21 is raw water, 22 is an acid fermentation tank, 23 is an upflow anaerobic sludge treatment device (UASB), 24 is an aeration tank, 25 is a settling tank, 26 is treated water, 27 is UASB treated water circulation piping, 28 is an activated sludge pipe, 29 is a return sludge pipe.

In FIG. 2, a raw water feed pipe 1 is connected to the bottom, and one end is fixed to each of the left and right side walls inside the cylindrical reactor 2 which is closed at the top and bottom, and the other end is fixed. A baffle plate 3 is installed which extends while descending toward the side wall on the opposite side. The baffle plates 3 are provided alternately in two places in the vertical direction and on the left and right sides, and each of the baffle plates 3 forms an acute-angled segmented sludge zone 4a-4b with the reactor side wall. The angle θ formed by the side wall of the reactor 2 and the baffle plate 3 is an acute angle of 35 degrees or less, and the occupied area is 1 / of the device cross-sectional area.
It is 2 or more. When the angle is more than 35 degrees, the granule sludge is deposited on the baffle plate 3 of the sludge zones 4a and 4b, the fluidity becomes insufficient, and a dead space is formed. Further, if the occupied area of the baffle plate 3 is 1/2 or less, the generated gas is not sufficiently captured, which causes a problem in separation of gas / liquid / solid. That is, the gas escapes from the center of the reactor 2 upward, and the gas cannot be sufficiently accumulated in the GSS portion 5 described later.

The upper part of the divided sludge zones 4a, 4b is GS
The S portion 5 is formed. When the reaction starts, the gas phase portion 5a where the generated gas collects has a generated gas recovery pipe 6 communicating with the outside.
There is a discharge port. The discharge port of the generated gas recovery pipe 6 connected from the gas phase portion 5a is opened in the water of the water sealing tank 7 filled with water. The opening position is at an appropriate water depth where the water pressure is different, and the water sealing tank 7 has a gas meter 8 for measuring the flow rate of the gas discharged from the generated gas recovery pipe 6.
Is provided. Beyond the gas meter 8, the gas holder 1
1 is provided. Further, a treated water pipe 9 for discharging the supernatant liquid is opened at the upper end of the reactor 2.

The reactor 2 is used by charging granule sludge made of anaerobic bacteria. The anaerobic treatment which is the target of the present invention is an anaerobic process in all temperature ranges, such as a medium temperature methane fermentation treatment with an optimum temperature of 30 ° C to 35 ° C and a high temperature methane fermentation treatment with an optimum temperature of 50 ° C to 55 ° C. It is targeted at sexual processing. Granule sludge consisting of anaerobic bacteria is charged into Reactor 2, and raw water containing organic waste etc. is fed into the pipe.
Introduce from 1 to Reactor 2. Raw water is appropriately diluted as necessary with treated water in the anaerobic treatment step, circulating fluid with treated water in the aerobic treatment step, or dilution water supplied from outside the system, and the inflow water is passed through the reactor 2 inside. The water velocity is adjusted to be 1 to 5 m / h.

The activated sludge generated in the aerobic treatment step was previously added to the inflow section of the reactor 2 through the activated sludge inflow pipe 15, and substances which hinder the anaerobic treatment step of raw water were adsorbed or attached to the activated sludge. In that state, it passes through the inside of the reactor 2. Therefore, it becomes possible to perform the anaerobic treatment without being affected by the substance that inhibits the anaerobic treatment process. Depending on the properties of the raw water, it is appropriate that the acid fermentation treatment is carried out for about 4 hours to 4 days in the acid fermentation tank before flowing into the reactor. In this case, by supplying the activated sludge to the acid fermentation tank, the effect of adsorbing or adhering the substance contained in the raw water, which inhibits the anaerobic treatment process, becomes large. Here, the activated sludge is a microorganism generated in the aerobic treatment, and includes returned sludge in the activated sludge treatment step, concentrated sludge, microorganisms in the filter bed cleaning wastewater of the aerobic fixed bed, and the like.

In the reactor 2, the organic waste is decomposed by the inclusion of granule sludge composed of anaerobic bacteria,
Decomposition gas is generated. The generated gas is separately collected in the GSS part 5 at the upper end of each of the divided sludge zones 4a to 4b, forms a gas phase part 5a in each, and reaches the water sealing tank 7 through the generated gas recovery pipe 6. The generated amount of the generated gas is recorded by the gas meter 8 and sent to the gas holder 11. Part of the generated gas is divided into sludge zones 4a-4b.
It adheres to the granule sludge inside, reduces its apparent specific gravity, and accompanies the granule sludge to reach the water surface of the GSS part 5. Such generated gas forms bubbles and temporarily stays in the water surface bubble portion 5b. Water bubble part 5b
The air bubbles gathered in the air will eventually burst, and the generated gas and granule sludge will be separated, the granule sludge will recover its original specific gravity and dive into the water, and the generated gas will flow from the generated gas recovery pipe 6 to the water sealing tank 7. It is discharged via the system to the outside of the system. Water is discharged from the upper end of the reactor 2 through the treated water pipe 9 to the outside of the system by decomposing the organic matter to clarify.

Since the gas pressure of the gas phase portion 5a of each GSS portion 5 is different, it is advisable to adjust the pressure difference in the water sealing tank 7. It is necessary to keep the water sealing pressure high in the order of getting closer to the raw water feed side. There are many methods for adjusting the pressure for gas recovery other than the method using the water sealing tank 7. For example, a pressure valve or the like may be used. In the anaerobic treatment method of the present invention, the generated gas generated in each divided sludge zone can be recovered, so that the generated gas amount per unit cross-sectional area of the reactor is reduced. In particular, the amount of gas per unit cross-sectional area of the reactor becomes small at a position closest to the treated water pipe 9 through which treated water flows out. Therefore, the amount of granulated sludge flowing out of the system can be extremely reduced.

In the reactor in which the GSS section is installed in multiple stages, by setting the water flow rate to 1 to 5 m / h, the flow state of the granule sludge layer becomes good, and 90% or more of the granule sludge in the reactor is Has a particle size of 0.5-
It is 1.5 mm and the sedimentation velocity is 5 to 40 m / h. Activated sludge has a lower sedimentation rate than granule sludge, and
Since the sedimentation speed is lower than the water flow speed in the reactor, the activated sludge flows out together with the treated water without depositing in the reactor. On the other hand, the granulated sludge remains in the reactor.

Substances which are adsorbed or attached to the activated sludge flowing out from the anaerobic treatment step and which inhibit the anaerobic treatment step are decomposed and removed in the aerobic treatment step. for that reason,
Even if the activated sludge of the aerobic treatment process is allowed to flow into the anaerobic treatment process, it does not hinder the anaerobic treatment process.

In the case of foamable raw water, the gas phase portion 5a in the GSS part 5 and the generated gas recovery pipe 6 are blocked, and it becomes difficult to recover the generated gas. In such a case, foaming in the GSS part 5 can be suppressed by adding the defoaming agent 10 to the inflow water of the reactor 2 in advance. This method is more effective for defoaming in a closed space than a method of dropping and spraying an antifoaming agent in the GSS part 5. The defoaming agent 10 has a defoaming effect according to the state of the raw water, and is suitable for defoaming the fermentation broth at an intermediate temperature (30 to 35).
A defoaming agent that does not lose the defoaming effect at (C) or at a high temperature (50 to 55C) is used. As the type of defoaming agent, either a silicone defoaming agent or an alcohol defoaming agent can be applied.

When the scum is easily formed due to the influence of the raw water, etc., the scum is formed on the surface and inside of the bubble portion 5b in the GSS portion 5, and it becomes difficult to collect the generated gas. In such a case, by connecting the generated gas blowing pipe 13 to the generated gas recovery pipe 6 or the diffuser pipe 12 and supplying the generated gas in the gas holder 11 into the GSS section 5,
The scum can be destroyed or the scum can be prevented from forming.

When the generated gas blowing pipe 13 is connected to the generated gas recovery pipe 6 and the scum in the GSS section 5-1 is to be destroyed / removed, the valve 14a is closed and the entire GSS section 5-1 is vaporized. Then, the scum is discharged from the GSS section 5-1. The discharged scum is the GSS part 5-2.
In order to stay inside, close the valve 14b and
The entire inside of 2 is used as a vapor phase section 5-2a, scum is discharged from the GSS section 5-2, and this is discharged together with the treated water.

When the generated gas blowing pipe 13 is connected to the diffuser pipe 12, the scum is destroyed by the bubbles blown from the diffuser pipe 12, and the destroyed scum is discharged as treated water together with the liquid flow in the reactor 2. To be done.
In the case of this method, opening / closing of the valves 14a and 14b does not matter. When operating by opening the valves 14a and 14b, the gas blown from the diffuser pipe 12 is recovered from the generated gas recovery pipe 6. When the valves 14a and 14b are closed and operated, in addition to the scum destruction effect due to the bubbles blown from the air diffuser 12, the scum discharge effect when the generated gas blowing pipe 13 is connected to the generated gas recovery pipe 6 can be expected. . In addition, in order to destroy and remove the scum inside the GSS part 5, the gas blown into the GSS part 5 may be a gas that does not contain oxygen such as nitrogen gas and that does not affect biological treatment such as methane fermentation. It is desirable to use the gas generated by the anaerobic treatment. The frequency of blowing gas into the GSS part 5 depends on the nature of the wastewater, but it is effective to destroy and remove the scum inside the GSS part 5 by setting it once a day to once a week.

[0024]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

Examples and Comparative Examples FIG. 2 shows an upflow anaerobic sludge bed (UAS) used in the experiment.
B) Shows an outline of the apparatus. The A to C series devices have the same structure, two inclined baffles are attached, the angle between the device side wall and the baffle is 30 degrees, the defoaming agent is added to the raw water, and the generated gas is blown from the diffuser pipe. Added the function to destroy and remove scum. Bubbling of generated gas from the diffuser is 1 per day
It was time. The volume of the liquid layer is 1 m ³ . The temperature of the water in the reactor is controlled to 35 ° C. Raw water includes kraft pulp black liquor wastewater (COD: about 2500
The inorganic nutrient salts (nitrogen, phosphorus, etc.) added to 0 mg / liter, SS about 500 mg / liter) were used.

FIG. 3 shows an outline of the processing flow. Note that the figure
The same parts as those shown by 1 are designated by the same reference numerals.
Activated sludge treatment is performed as aerobic treatment for all A to C series.
It was Aeration tank capacity is 2m ³The inner diameter of the sedimentation tank is φ0.5m
Is. MLSS of aeration tank to 5000 mg / liter
Set.

In the A series, the activated sludge treatment was performed after the UASB treatment. The returning sludge concentration was 20000 mg / liter, and the returning ratio was 0.25 times the raw water. (Fig. 3 (a)
In the B series, raw water is subjected to acid fermentation treatment, and then activated sludge treatment is performed to dilute the anaerobic treatment-inhibiting substance by decomposing and removing it by 10 times with settling pond overflow water (activated sludge treated water), which is then diluted with UASB. After the treatment, activated sludge treatment was performed. The returning sludge concentration was 20000 mg / liter, and the returning ratio was 3 times the raw water. (See Fig. 3 (b)) In Series C, return sludge was added to raw water, and SS4000mg /
After adjusting to liter, acid fermentation treatment, UASB treatment, and activated sludge treatment were performed. A part of the UASB effluent was introduced into the UASB together with the acid fermentation treated water, and the water flow rate was set to 2 m / h. Return sludge concentration is 20000mg /
The liter and the return ratio were 0.25 times the raw water to the acid fermentation tank and 0.1 times the raw water to the aeration tank. The C series is a series based on the present invention. (See Fig. 3 (c))

FIGS. 4 to 7 show the progress of the experiment, and Table 1 shows the processing result. In the A series, the experiment was started at a COD load of UASB (hereinafter, simply referred to as COD load) of 1 kg / m ³ / d, but COD was hardly removed by the UASB treatment. (See Figure 5)

In the B series, the COD load up to the 60th day is 8
COD of UASB treated water is 3000 at kg / m ³ / d
mg / liter, the COD of the treated water was 1000 mg / liter, and the COD removal rate was 96%. After 60 days, when the COD load was set to 12 kg / m ³ / d, the activated sludge treatment was performed because the residence time of the aeration tank was shortened due to the increase in the amount of water in the activated sludge treatment and the water area load in the sedimentation basin was increased. Since it deteriorated and the treated water COD increased to 5000 mg / liter, the aeration tank capacity was increased to 5 m ³ and the settling tank inner diameter was increased to φ1.2 m. As a result, at the COD load of 15 kg / m ³ / d up to 100 days, the COD of UASB-treated water was 3000 mg / liter and the COD of treated water was 1
The treatment was 000 mg / liter and the COD removal rate was 96%. After 100 days, the COD load is 20 kg / m ³ /
When d was set, the water flow rate inside the UASB increased, a large amount of granulated sludge flowed out, the UASB treatment could not be performed, and the COD of the treated water deteriorated to 8000 mg / liter. (See Figure 6)

In the C series, after 110 days, a COD load of 25 kg / m ³ / d and a UASB-treated water COD of 7,000 m
g / liter, solubility COD 2500 mg / liter,
COD of treated water is 1000 mg / liter or less, COD
Treatment with a removal rate of 96% was possible. The COD of UASB-treated water is as high as 7,000 mg / liter,
The returned sludge that has flowed into the UASB does not stay in the UASB and flows out as it is, and the SS of the UASB-treated water is 4000 to 5000 m.
Due to the increase in g / liter. (Refer to FIG. 7) The C sequence, which is the method of the present invention, is
It showed a high COD removal performance and was a space-saving processing method.

[0031]

[Table 1]

[0032]

INDUSTRIAL APPLICABILITY In the present invention, sludge generated in the aerobic treatment step is added to the anaerobic treatment step, a substance that inhibits the anaerobic treatment step is adsorbed or attached to the sludge, and the added sludge is placed in the reactor. By allowing the treated water to flow out of the system together with the treated water, the gas in the reactor
The liquid / solid separation performance is improved and it becomes possible to maintain a high concentration of granule sludge in the reactor, and organic wastewater containing substances that interfere with anaerobic treatment can be treated with high efficiency and upward flow anaerobic sludge bed. Processing can be done. The C series, which is the method of the present invention, has a higher COD removal performance than the conventional A and B series and is a space-saving processing method.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an organic wastewater treatment apparatus of the present invention.

FIG. 2 is a schematic explanatory view showing an example of an upward circulation aeration processing device used in the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional (A series, B series) and an organic wastewater treatment apparatus of the present invention (C series) used in Examples.

FIG. 4 is a diagram showing the relationship between the COD loads of the A to C series used in the experiment and the number of elapsed days.

FIG. 5 is a diagram showing a relationship between a conventional (A series) COD and the number of elapsed days.

FIG. 6 is a diagram showing a relationship between a conventional (B series) COD and the number of elapsed days.

FIG. 7 is a diagram showing the relationship between COD and the number of days elapsed according to the present invention (C series).

[Explanation of symbols]

1 Stock solution delivery pipe 2 reactor 3 baffles 4a Classification sludge zone 4b Classification sludge zone 5-1a Gas phase part 5-2a Gas phase part 5-1b Liquid phase part 5-2b Liquid phase part 6 Generated gas recovery piping 7 water sealed tank 8 gas meters 9 Treated water piping 10 Defoamer injection tube 11 gas holder 12 Air diffuser 13 Generated gas suction pipe 14a valve 14b valve 15 Activated sludge inflow piping 21 Raw water 22 Acid fermenter 23 UASB 24 aeration tank 25 settling pond 26 Treated water 27 UASB treated water circulation piping 28 Activated sludge piping 29 Return sludge piping 30 Activated sludge treated water piping

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 3/28 C02F 3/28 AZ F term (reference) 4D011 CA01 CB01 4D040 AA02 AA04 AA23 AA27 AA32 AA34 AA42 AA58 AA61 BB01 BB42 BB51 BB82 BB91 4D051 AA04 AB03 EA01 EB04

Claims (5)

[Claims] 1. An organic wastewater containing a substance that inhibits an anaerobic treatment step is introduced into an anaerobic treatment step and, after anaerobic treatment, the effluent thereof is introduced into an aerobic treatment step to perform aerobic treatment. In the method to be performed, a part of the sludge generated in the aerobic treatment step is caused to flow into the anaerobic treatment step, and the sludge is adsorbed or adhered with a substance which inhibits the anaerobic treatment step contained in the organic wastewater, and the anaerobic A method for treating organic wastewater, characterized in that a part or all of the effluent of the treatment step is caused to flow into the aerobic treatment step. 2. In the anaerobic treatment step, an angle with the side wall of the main body of the device is 35 degrees or less, and each occupied area is 2 of the cross-sectional area of the device.
Gas, liquid, etc.
2. The method for treating organic wastewater according to claim 1, wherein an upflow anaerobic sludge bed treatment device having a plurality of solid separation sections is applied. 3. The anaerobic treatment is carried out after mixing the inflowing organic wastewater, a part of the effluent of the anaerobic treatment step and the sludge, and performing acid fermentation. The method for treating organic wastewater according to. 4. The foaming and the formation of scum inside the gas / liquid / solid-liquid separation part are prevented by adding an antifoaming agent to the water to be treated. The method for treating organic wastewater described. 5. An acid fermentation tank for introducing an organic wastewater, an upflow anaerobic treatment apparatus for introducing an acid fermentation solution from the acid fermentation tank, and an anaerobic treatment solution for an upflow anaerobic treatment apparatus are introduced. An aeration tank for aerobic treatment, a sedimentation tank for introducing the aerobic treatment liquid from the aeration tank into solid-liquid separation, and an activated sludge pipe for sending a part of the sludge settled in the sedimentation tank to the raw water delivery pipe. An apparatus for treating organic wastewater, which comprises: