JPH09206786A - Anaerobic treatment and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic treatment method for an org. waste liquid capable of shortening stagnation time even if an anaerobic treatment is executed with high load with the waste liquid contg. solid org. matter and executing the volumetric reduction of the sludge at a low energy consumption rate and inexpensively by the simple device and operation capable of reducing the volume of the formed sludge and an apparatus therefor. SOLUTION: The in-vessel liquid 11 is withdrawn from an acid forming vessel 1 and is subjected to sepn. of solid from the liquid in a member separator 2. Part 6 of the thickened sludge is returned to the acid forming vessel 1 and other part 18 is introduced to a reforming vessel 3, such as heat treating vessel, ozone treating vessel or high-voltage pulse discharge treating vessel by which the sludge is reformed to easily decomposable sludge. This sludge is returned to the acid forming vessel 1 and is subjected to the anaerobic treatment. The volume of the generated sludge is reduced. The separated liquid of the membrane separator 2 is subjected to high-speed methane fermentation in a high-load methane fermentation vessel 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anaerobic treatment method and apparatus for treating an organic effluent by acid production and methane fermentation in the presence of sludge containing anaerobic microorganisms. The present invention relates to an anaerobic treatment method and apparatus for reducing sludge by treating it by the anaerobic treatment.

[0002]

BACKGROUND ART Anaerobic digestion is an anaerobic digestion method that treats highly concentrated organic wastewater in the form of slurry such as organic sludge, human waste, food wastewater, etc. in the presence of anaerobic microorganisms. It is also called, and is a method that has been practiced since ancient times. In this method, an organic substance is converted into methane gas in an anaerobic tank by anaerobic microorganisms through the steps of liquefaction, molecular weight reduction, organic acid production, and methane production. In the single-phase methane fermentation, the acid-producing phase and the methanogenic phase occur in parallel in a single phase. It is divided into two tanks, a fermentation tank and a desorbed liquid separation tank, as in the conventional anaerobic treatment of sewage sludge. Even in the case of two-stage treatment, if the acid production phase and the methane production phase occur in parallel in each tank, they are included in the one-phase treatment.

In such an anaerobic treatment, a large amount of sludge mainly composed of undegraded substances and anaerobic microorganisms is produced. Since this sludge is mainly composed of living cells, it is biologically stable, and it is difficult to significantly reduce the amount by biological treatment.
It was processed by landfill.

As a method for reducing the volume of sludge produced by anaerobic treatment, Japanese Patent Laid-Open No. 1-224100 discloses that anaerobic digested sludge is heated at 100 to 180 ° C.
There is described a method for treating organic sludge in which the heat-treated sludge is returned to the anaerobic digestion tank. However, such conventional methods can reduce the volume of sludge, but require long residence time, large equipment, and energy consumption because methane fermentation is performed by methanogens with a slow growth rate. There is a problem that the amount is large and the cost is high.

On the other hand, as an anaerobic treatment method for organic drainage, instead of the conventional anaerobic digestion method in which a solid organic matter and a soluble organic matter as described above are put into a digestion tank and retained for a long time for digestion, A high-load anaerobic treatment method is used in which only soluble organic substances are anaerobically treated at high load and high flow rate. This high-load anaerobic treatment method is a method in which solid organic matter with a slow digestion rate is separated and treated separately, and only soluble organic matter with a fast digestion rate is treated with high load and high speed by anaerobic treatment. It can be used for efficient processing.

Since such a high-load anaerobic treatment method mainly treats only soluble BOD, it is necessary to separate the solid content in advance in order to treat the waste liquid containing the solid organic matter. The separated solid organic matter needs to be treated separately. In particular, since excess sludge such as sewage and night soil contain a large amount of solid organic matter, it is difficult to treat the solid organic matter separated from them.

On the other hand, as a method for reducing the volume of surplus sludge produced by aerobic treatment (activated sludge treatment) of organic waste liquid, Japanese Patent Laid-Open No. 6-206088 discloses a method of treating sludge with ozone and returning it to an aeration tank. How to do is described. However, this method relates to aerobic treatment, and does not disclose the possibility of application in anaerobic treatment.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to perform an anaerobic treatment on a waste liquid containing a solid organic substance under a high load to shorten the residence time and to generate sludge. It is also an object of the present invention to propose a method and a device for anaerobic treatment of organic waste liquid, which can reduce the volume of sludge with low energy consumption and low cost by a simple device and operation. .

[0009]

The present invention is the following method and apparatus for treating organic waste liquid. (1) An acid producing step of producing an organic acid by maintaining an organic effluent in an anaerobic state in the presence of sludge containing an acid producing bacterium, and a mixed solution of the acid producing step is subjected to solid-liquid separation to convert concentrated sludge into acid. The solid-liquid separation process that returns to the production process, the reforming process that reforms sludge produced in the acid production process to easily biodegradable and returns to the acid production process, and the separation liquid that was separated in the solid-liquid separation process An anaerobic treatment method comprising a high-load methane fermentation step of performing methane fermentation by contacting sludge containing a methanogen under high load. (2) An acid production tank for producing an organic acid by maintaining an organic effluent in an anaerobic state in the presence of sludge containing acid-producing bacteria, and a mixed solution of the acid production tank is subjected to solid-liquid separation to convert concentrated sludge into acid. The solid-liquid separation device that returns to the production process, the reformer that reforms sludge generated in the acid generation tank to easily biodegradable and returns to the acid generation tank, and the separation liquid separated by the solid-liquid separation device An anaerobic treatment apparatus equipped with a high-load methane fermentation tank that performs methane fermentation by contacting sludge containing methanogens under high load.

The organic waste liquid to be treated in the present invention is a waste liquid (including sludge) containing an organic substance treated by anaerobic treatment. A slurry containing solids is suitable for the treatment, but a liquid containing no solids may be used. Further, it may contain a biodegradable organic substance, inorganic substance, cellulose, paper, cotton, wool cloth, solid matter in human waste and the like. Such organic drainage is sewage,
Examples include sewage first settled sludge, human waste, septic tank sludge, food factory wastewater, beer waste yeast and other industrial effluents, and excess sludge generated when treating these effluents.

The acid production step is a step of producing an organic acid by maintaining an organic effluent in an anaerobic state in the presence of sludge containing an acid-producing bacterium in an acid producing tank, and liquefying an organic substance by the action of the acid-producing bacterium. → Low molecular weight → Organic acid generation step,
Converts to an organic acid that is easily decomposed by methanogens. Since it becomes acidic due to the formation of an organic acid, the pH can be adjusted by adding an alkali such as sodium hydroxide. You may circulate and neutralize a process liquid from a methane fermentation process.

As conditions for acid production, it is possible to use both mesophilic acid-producing bacteria having an optimum temperature around 35 ° C. and high-temperature acid-producing bacteria having an optimum temperature around 55 ° C. Processed at 45-60 ° C. The retention time (SRT) of sludge in the acid production tank can be set to 3 days or more, preferably about 5 to 10 days. This residence time is set to a range in which the methanogen does not substantially grow. The pH in the acid generation step is 5 to 7, preferably 5.
It is preferably set to 8 to 6.2.

The solid-liquid separation process is configured to perform solid-liquid separation of the mixed liquid in the acid production process, return the concentrated sludge to the acid production process, and send the separated liquid to the methane fermentation process. In the solid-liquid separation step, any solid-liquid separation device such as a membrane separation device, a decanter and a filtration device can be used. When using membrane separation, various membrane types such as hollow fiber, tubular, and flat membrane can be used. Further, since the purpose of the membrane separation is to separate solids, a membrane having a relatively large pore size such as MF and UF is preferable.

The reforming step is a step in which a part of the sludge produced in the acid producing step is easily biodegradable by a reforming device such as an ozone treatment device, a pulse discharge treatment device or a heat treatment device. When sludge is drawn out, it is preferable that the concentrated sludge separated by the solid-liquid separation device is drawn out to be reformed, but it may be processed by being drawn out from the acid production tank in a mixed liquid state. Further, depending on the case, these reforming devices can be provided in the acid production tank.

The ozone treatment device performs ozone treatment by bringing sludge into contact with ozone. As a contact method,
A method of introducing digested sludge into the ozone treatment tank to blow ozone, a method of mechanical stirring, a method of using a packed bed, and the like can be adopted. As ozone, ozone-containing air, ozonized air, or the like can be used in addition to ozone gas. The amount of ozone _{0.005~0.04g-O 3 / g-VSS} , preferably it is desirable to _{0.01~0.03g-O 3 / g-VSS} . When using a packed bed, set the SV of the packed bed to 1
It is preferably from 10 to 10 hr ^-1 , and more preferably from 3 to 6 hr ^-1 .

A high-voltage pulse discharge treatment apparatus has a tungsten / electrode spacing of 3 to 10 mm, preferably 4 to 8 mm.
Sludge is allowed to exist between the positive electrode such as thorium alloy and the negative electrode such as stainless steel, and the applied voltage is 10 to 50 kV, preferably 2
It is configured to perform pulse discharge at 0 to 40 kV and a pulse interval of 20 to 80 Hz, preferably 40 to 60 Hz, and sludge can be treated while being circulated sequentially.

The heat treatment apparatus is provided with a heating means, and the sludge can be heat-treated as it is or in a state of being brought into contact with an acid, an alkali, an oxidizing agent or the like. The temperature is 60-120 ℃,
Preferably 80 to less than 100 ° C., heating time is 30 to 18
It is preferably 0 minutes, preferably about 60 to 120 minutes.
In fact, the higher the temperature is, and the longer the heat treatment time is, the more easily biodegradable it is modified.
Since the biodegradable substance is easily produced and a pressure resistant container and the like are required, the above range is appropriate in consideration of efficiency and economy.

In addition, as the reforming device, a device for performing treatment with an acid, an alkali, an oxidant or the like without heating, or other treatment for facilitating biodegradation can be adopted. Living cells contained in sludge produced in the acid production process are biologically stable and hardly biodegradable, but when they are killed, they become easily biodegradable. In addition, high molecular weight organic substances are also difficult to biodegrade, but can be easily biodegradable by lowering their molecular weight. Therefore, such a means that can be easily biodegradable can be adopted as the reforming device.

The amount of sludge to be extracted from the acid production tank for reforming is at least equal to or more than the amount of solids to be added to the acid production tank in order to secure the volume-reducing effect of sludge, and preferably twice or more. For example, in the case of an acid production tank that retains for 5 days, the circulation ratio can be set to 1/5 day ^-1 or more, preferably 2/5 day ^-1 or more. The upper limit of the circulation ratio is 1 / of the total amount of sludge in the acid production tank per day from the viewpoint of ensuring effective acid production.
3 or less, preferably 1/5 to 1/3 (solid weight)
It is desirable that the amount be equivalent to. By setting the amount of sludge to be drawn out to be at least 1 time the amount of solids to be input, it is possible to increase the volume reduction of sludge in the entire treatment system, and to increase the total amount of sludge in the acid production tank. By setting the ratio to 1/15 or less, acid generation can be effectively performed in a state where the sludge activity of the entire acid generation tank is maintained high.

In the high-load methane fermentation step, the separated liquid separated in the solid-liquid separation step is brought into contact with sludge containing methanogens in a high-load methane fermentation tank at a high load to perform methane fermentation at a high speed. , The process of converting to methane. The high-load methane fermenter is an upflow anaerobic sludge blanket (UASB) used in conventional high-load anaerobic treatment.
Type, fluidized bed type, fixed bed type, etc., in which methane fermentation bacteria are kept in a highly concentrated state in a methane fermentation tank and contacted with the liquid to be treated at high load and high speed to perform methane fermentation in a short time. Adopted.

The UASB method is a method in which a liquid to be treated is passed through an upward flow at a high speed and brought into contact with a sludge blanket made of granulated sludge formed by highly concentrating sludge containing methane-fermenting bacteria to treat the sludge. . The fluidized bed system is a system in which sludge is supported on a carrier such as sand to form a fluidized bed and is brought into contact with a liquid to be treated. The fixed bed type is a system in which a liquid to be treated is passed through and brought into contact with a fixed bed having sludge formed on a carrier. By keeping sludge in a high-concentration state in both cases, high-load and high-speed treatment is possible.

The methane fermentation conditions can be any temperature condition in which a mesophilic methanogen having an optimum temperature near 35 ° C. and a high temperature methanogen having an optimum temperature near 55 ° C. grow. Since the mesophilic methanogen has a slow growth rate and has a long residence time (SRT), it can be treated at a relatively low temperature, which simplifies the equipment for heating and heat retention. On the other hand, in the case of high-temperature methanogens, heating and heat-retaining equipment is required, but since the growth rate is high, the residence time is short and treatment can be performed in a short time.

The load in the methane fermentation process is 5 to 20 k
g-CODcr / m ³ · day, preferably 10 to 15 k
g-CODcr / m ³ · day, residence time HRT is 3-4
8 hours, preferably 4 to 24 hours is appropriate, and U
The upward flow velocity in the ASB method is about 0.5 to 2 m / hr, preferably about 1 to 1.5 m / hr.

In the treatment method by the anaerobic treatment apparatus of the present invention, in the acid production step, the organic waste liquid is introduced into the acid production tank and mixed with the sludge containing the acid-producing bacteria to perform the anaerobic treatment. Ferment. Here, the organic substance is liquefied,
It is converted to an organic acid through the steps of lowering molecular weight and generating acid. The liquid in the acid production tank is subjected to solid-liquid separation in the solid-liquid separation device, the concentrated sludge is returned to the acid production tank, and the separated liquid is sent to the methane fermentation tank.

A part of the sludge-containing liquid or concentrated sludge in the acid production tank is easily biodegradable by ozone treatment, high-pressure pulse discharge treatment, heat treatment or the like in a reformer.
In the acid production process, bacterial cells increase due to the growth of microorganisms in sludge, but there is a limit to the volume reduction by digestion even if the living bacterial cells are concentrated and returned to the acid production tank.

However, by reforming with a reforming device such as ozone treatment, high-pressure pulse discharge treatment, heat treatment, etc., the bacterial cells in the sludge are killed and decomposed together with other organic substances, and low molecular weight organic substances and some inorganic substances are decomposed. Are produced and are easily biodegradable. By circulating such modified sludge in the acid production tank, it is utilized as a substrate for acid producing bacteria and decomposed. This reduces the volume of sludge and reduces the amount of sludge discharged as excess sludge.

Even if all the sludge discharged as excess sludge from the acid production step is reformed and circulated, the sludge grows by assimilating this and the sludge in the acid production tank increases in quantity, The sludge must be discharged as excess sludge, and the discharged sludge cannot approach zero. Therefore, if you extract more sludge than the amount of sludge generated as excess sludge, reform it and circulate it so that the amount of excess sludge becomes zero,
Balance the amount of sludge that has been extracted excessively with the amount of sludge that has multiplied,
Apparently the amount of sludge increase approaches zero. Even in this case, it is desirable to discharge the minimum digested sludge in order to avoid the accumulation of mineralized sludge.

When the excess sludge is reformed in this way, the acid production efficiency decreases, but in the acid production tank, the SRT is usually 5 to 1
Since it is operated for a relatively long time of about 0 days, it is possible to operate with a margin even if the SRT is shortened due to reforming.
The loss of efficiency is less significant.

In the high-load methane fermentation tank, the separated liquid in the solid-liquid separation step is brought into contact with sludge containing methanogens at a high load and high speed under anaerobic conditions to carry out methane fermentation to decompose organic acids into methane. In the case of UASB, the above treatment is performed by passing a sludge blanket made of granulated sludge containing methanogens in an upward flow.

The treatment liquid of the high-load methane fermentation tank can be discharged as it is to sewage or the like, but it may be discharged after aerobic biological treatment and other post-treatments. In the above treatment, the anaerobic treatment is divided into the acid production step and the methane fermentation step, and the sludge produced in the acid production step is reformed and returned, so that the waste liquid containing solid organic matter can be treated. The volume of sludge is also reduced. Since the methane fermentation process performs high-load methane fermentation, it can be processed at high speed with a small apparatus, and the overall processing time can be shortened.

[0031]

Embodiments of the present invention will now be described with reference to the drawings. 1 and 2 are system diagrams showing an anaerobic treatment apparatus according to different embodiments, FIG. 1 is an example of reforming concentrated sludge obtained by concentrating an acid production liquid by a solid-liquid separation apparatus, and FIG. 2 is an acid. The example which reforms the mixed liquid in a production tank is shown.

In FIG. 1, 1 is an acid production tank, 2 is a membrane separation device as a solid-liquid separation device, 3 is a reforming tank, and 4 is UASB.
It is a high-load methane fermentation tank by the method. The treatment apparatus of FIG. 1 introduces the organic waste liquid into the acid production tank 1 from the liquid passage 5 to be treated, and returns sludge containing the acid-producing bacteria in the return sludge and the acid production tank 1 returned through the return sludge passage 6. The mixture is mixed, and the mixture is gently stirred by the stirrer 7 to perform anaerobic treatment to generate an acid. By the acid generation treatment step performed here, the organic matter in the liquid to be treated is decomposed by the acid-producing bacterium to generate an organic acid.

The membrane separation device 2 is constructed so that a part of the mixed liquid in the acid production tank 1 is taken out from the communication passage 11, pressurized by the pump 12 and guided to the membrane separation device 2, and separated by the separation membrane 13. Has been done. Permeate 1 by membrane separation performed here
4 and concentrated sludge 15 are separated. The permeate 14 is sent to the high-load methane fermentation tank 4 by the pump 17 from the communication path 16. Part of the thickened sludge 15 is taken out from the thickened sludge take-out path 18 and introduced into the reforming tank 3, and part or all of the remaining part is returned from the return sludge path 6 to the acid production tank 1. When excess sludge is generated, it is discharged from the excess sludge discharge path 19 to the outside of the system.

An ozone treatment tank is used as the reforming tank 3, and the sludge is reformed by passing the concentrated sludge 15 through the packed bed 21 and blowing ozone from the ozone generator 22 to bring them into contact with each other for ozone treatment. It Modified sludge is modified sludge path 2
It is returned to the acid production tank 1 from 3, and is subjected to anaerobic treatment. In this way, the solid content that has been easily biodegradable by the modification is the acid generation tank 1
The volume of surplus sludge generated by the treatment system is reduced.

The separated liquid separated by the membrane separation device 2 is introduced into the lower part of the high-load methane fermentation tank 4 from the connecting passage 16 through the separated liquid inflow portion 31 by the pump 17 and is sludge blanket in an upward flow as a methane production process. Pass 32. At this time, the acid-generating liquid is anaerobically and the granulated sludge 3
3, the organic acid is anaerobically decomposed by the action of the methanogen contained in the granulated sludge 33 and converted into methane and carbon dioxide. The methane-fermented reaction liquid is separated into gas, liquid, and solid by the gas solid-liquid separation plate 34, and the separated liquid is treated as a treated liquid from the overflow portion 35 to the treated liquid passage 3
Overflow to 6. The separated solids settle as sludge on the sludge blanket 32, and the gas rises to the gas chamber 37 and is taken out from the gas discharge passage 38.

In the treatment apparatus shown in FIG. 2, a part of the mixed liquid in the acid production tank 1 is drawn as drawn sludge from the sludge drawing passage 24, and the drawn sludge is introduced into the reforming tank 3 to carry out the reforming process. Is composed of. The reforming tank 3 is configured to perform high-voltage pulse discharge processing, and has a power supply device 27 between the positive electrode 25 and the negative electrode 26.
A high-voltage pulse is applied to discharge electricity to reform the sludge. The concentrated sludge 15 of the membrane separation device 2 is returned to the acid production tank 1.

Although the membrane separator 2 is used as the solid-liquid separator in FIGS. 1 and 2, other solid-liquid separators such as a precipitation device and a centrifugal separator can be used. Further, in FIG. 1, the returning of the sludge from the returning sludge passage 6 can be omitted. Further, when a heat treatment tank is used as the reforming tank 3, a heater can be provided inside or outside the tank, and if necessary, an acid, an alkali, etc. can be added, and the heat treatment can be performed while stirring with a stirrer.

[0038]

【Example】

Example 1 and Comparative Example 1 Using a jar fermenter with an effective capacity of 2 liters, an acid production tank with a liquid volume of 1.2 liters was used, and the excess sludge of the sewage treatment plant was concentrated to about 2% by weight of raw sludge. Once a day 2
Each was supplied by a syringe by 00 ml. A membrane separator having a flat membrane UF module with a molecular weight cut-off of 30,000 and a membrane area of 177 cm ² was connected to the acid production tank and circulated by a pump.
The liquid in the tank was filtered by 200 ml per day and circulated so that the amount of liquid in the tank was constant. The acid production tank is controlled at a temperature of 35 ° C,
About 50 ml of UASB granules was added as seed sludge.

In Example 1, a heat treatment tank was used as a reforming treatment tank, and 200 ml of sludge, which was the same amount as the amount of the raw sludge supplied, was drawn out from the acid generation tank once a day by a syringe and introduced at 85 ° C. After heat treatment for 1 hour, it was returned to the acid generation tank. In Comparative Example 1, a control system in which no heat treatment was performed was simultaneously tested to compare changes in sludge concentration in the tank.

In both Example 1 and Comparative Example 1, the methane fermentation tank was a small UASB apparatus (the reaction section had a capacity of 1.6 mm) in which a gas-solid three-phase separator was installed above a cylindrical column having a diameter of 5 cm and a height of 100 cm. liter) was used to carry out the methane fermentation test of the permeate. UA that processes beer wastewater in the tank
About 1 lit of granulated sludge collected from the SB actual equipment
er filled. The permeate was supplied at a rate of 1.5 liter per day, the temperature of the apparatus was controlled at 35 ° C., and the permeate of the heat treatment system and the control system was subjected to methane fermentation treatment for 2 weeks each.

FIG. 3 shows the daily change of the TS concentration in the above treatment. The heat treatment system of Example 1 had a TS concentration of 22,000 mg / l in the acid generation tank as compared with the control system of Comparative Example 1, but the decomposition rate of Comparative Example 1 was low and the TS concentration in the tank was remarkable. Increased. Therefore, the operation of Comparative Example 1 is TS5.
Discontinuation was reached when the amount reached 10,000 mg / l. Example 1
Table 1 shows the water qualities of the in-tank liquid and the permeated liquid on the 58th day, and the in-tank liquid and the permeated liquid on the 30th day of Comparative Example 1.

[0042]

[Table 1]

As is clear from the above results, the SS concentration is low in both cases because the permeate is a membrane permeate, but the soluble CODcr concentration is more than doubled in Example 1. This is because the solid matter is reformed by heat treatment and converted into an organic acid or the like, and this is methane gasified by UASB in the subsequent stage.

Table 2 shows the results of methane fermentation of the permeates of Example 1 and Comparative Example 1 by UASB. In both systems, organic acids were decomposed by UASB, and good methane fermentation proceeded. In Example 1, the COD at the inlet was higher, so that the gas generation amount was larger. From these facts, it is clear that by incorporating the heat treatment into the acid production tank, the solid matter is solubilized and the volume reduction effect is large, and the liquefied organic matter is decomposed into methane gas.

[0045]

[Table 2]

Example 2 In Example 2, an ozone treatment tank was used as the reforming treatment tank in Example 1, and 200 ml of sludge having the same amount as the amount of raw sludge supplied was drawn out with a syringe once a day to measure the ozone injection rate. 0.0
Back to the acid generation chamber after processing modification by ozone treatment under the condition of _{5g-O 3 / g-TS} . The same test as in Example 1 was performed to compare the change in sludge concentration in the tank with Comparative Example 1 in which no ozone treatment was performed.

As a result, in the same manner as in Example 1, in Example 2 in which the ozone treatment was performed, the sludge concentration in the acid production tank was about 60 days.
Although S was stable at 23,000 to 25,000 mg / l, Comparative Example 1 continuously increased and exceeded 50,000 mg / l about 30 days after the start of operation. From these results, it is clear that, similarly to Example 1, Example 2 has a higher sludge decomposition rate than Comparative Example 1, and the volume is reduced to the extent that substantially no excess sludge is present. .

Example 3 In Example 3, a high-pressure pulse discharge device was used as a reforming treatment apparatus, and once a day, the sludge 200 m of the same amount as the raw sludge supply amount was used.
1 was drawn out with a syringe and introduced into a cell having a capacity of 250 ml, and an electrode interval was 5 mm and an applied voltage was 30 k between a positive electrode made of a tungsten / thorium alloy and a negative electrode made of stainless steel.
V, pulse interval: High-voltage pulse discharge was performed at 50 Hz for 10 minutes for reforming treatment, and then returned to the acid generation tank.

The same test as in Example 1 was conducted to compare the change in the sludge concentration in the tank with Comparative Example 1 in which no modification treatment was performed. FIG. 4 shows the daily change of the TS concentration in each of the above tests. As a result, in Example 3, the TS concentration in the tank was about 60.
Stable at 20,000-24,000 mg / l daily.
Therefore, in Example 3, the sludge decomposition rate is higher than in Comparative Example 1, and it is understood that the volume is reduced to the extent that substantially no excess sludge is produced.

[0050]

EFFECTS OF THE INVENTION According to the present invention, since the sludge in the acid production step is modified to be easily biodegradable and circulated and solid-liquid separated, the separated liquid is treated by high-load methane fermentation. Anaerobic treatment of the waste liquid containing it is also performed at high load to shorten the residence time and the volume of the generated sludge can be reduced, and the volume and volume of the sludge can be reduced by a simple device and operation with low energy consumption and low cost. It can be performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an anaerobic treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a system diagram showing an anaerobic treatment apparatus according to another embodiment of the present invention.

FIG. 3 is a graph showing changes with time of TS concentration in Example 1 and Comparative Example 1.

FIG. 4 is a graph showing changes over time in TS concentration in Example 3 and Comparative Example 1.

[Explanation of symbols]

 1 Acid production tank 2 Membrane separation device 3 Reforming tank 4 High load methane fermentation tank 5 Liquid to be treated 6 Returned sludge passage 7, 22 Stirrer 11, 16 Connecting passage 12, 17 Pump 13 Separation membrane 14 Permeate 15 Concentrated sludge 18 Condensed sludge discharge route 19 Excess sludge discharge route 21 Packed bed 22 Ozone generator 23 Reforming sludge route 24 Sludge extraction route 31 Separation liquid inflow part 32 Sludge blanket 33 Granule sludge 34 Gas solid-liquid separation plate 35 Overflow part 36 Treatment Liquid channel 37 Gas chamber 38 Gas discharge channel

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[Procedure amendment]

[Submission date] February 8, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

[Fig. 2]

Claims (2)

[Claims] 1. A concentrated sludge in which an acid production step of producing an organic acid by maintaining an organic effluent in an anaerobic state in the presence of sludge containing an acid-producing bacterium, and a liquid mixture of the acid production step is subjected to solid-liquid separation. -Liquid separation process that returns the acid to the acid generation process, a reforming process that reforms sludge generated in the acid generation process to easily biodegradable and returns to the acid generation process, and the separation that was separated in the solid-liquid separation process An anaerobic treatment method comprising a high-load methane fermentation step of performing methane fermentation by bringing a liquid into contact with sludge containing a methanogen under a high load. 2. A concentrated sludge obtained by solid-liquid separation of an acid generation tank for maintaining an organic effluent in an anaerobic state to generate an organic acid in the presence of sludge containing an acid-producing bacterium and solid-liquid separation of a mixed solution of the acid generation tank. -Liquid separation device that returns the sludge to the acid production process, a reformer that reforms sludge produced in the acid production tank to easily biodegradable and returns it to the acid production tank, and the separation separated by the solid-liquid separation device An anaerobic treatment apparatus equipped with a high-load methane fermentation tank that performs methane fermentation by contacting a liquid with sludge containing methanogens under a high load.