JP2002166289A - Method to treat organic waste water and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic waste water capable of improving the quality of treated waste water without increasing the facility cost. SOLUTION: After organic waste water is treated biologically in a biological treatment tank 2, sludge and water in the treated waste water in the biological treatment tank 2 are separated in a sedimentation tank 4. A part of the sludge is returned to the biological treatment tank 2, while the rest of the sludge is solubilized by thermophilic bacteria in a solubilization tank 7, and thereafter the treated water is returned to the biological treatment tank 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for treating organic wastewater, for example, sewage, human waste or organic wastewater discharged from food factories, chemical factories, etc. by utilizing a biological reaction. About.

[0002]

2. Description of the Related Art Conventionally, this kind of organic wastewater is generally treated as:
First, organic components in organic wastewater are biologically digested by aerobic or anaerobic microbial decomposition such as aerobic digestion and anaerobic methane fermentation to convert organic matter into gas components such as carbon dioxide gas and methane gas. And then subject the treated liquid containing microbial biomass (mainly microbial cells) and untreated residual sludge produced by such biological digestion to solid-liquid separation in a sedimentation tank or the like, and treated with treated water as supernatant. A concentrated liquid (sludge) is obtained, and the sludge is treated by an appropriate method. For example, as shown in FIG. 11, organic wastewater such as sewage introduced into the biological treatment tank 2 is converted into carbon dioxide or carbon dioxide by biological oxidation, which is an oxidative decomposition reaction by microorganisms, under aerobic conditions in the biological treatment tank 2. Decomposed into inorganic substances such as water,
The wastewater treated in the biological treatment tank 2 is solid-liquid separated into treated water C and sludge D in the sedimentation tank 4, and a part of the sludge D is returned to the biological treatment tank 2 as a microorganism source, and the remaining sludge is removed. Sludge is generally treated as excess sludge E.

However, in this case, the precipitated solid concentrate (sludge) containing the organic sludge separated into solid and liquid in the sedimentation tank 4 is processed through processes such as concentration, digestion, dehydration, composting, and incineration. Such processing is expensive and troublesome, and is not preferable.

[0004] For this reason, as a treatment method that produces as little sludge as possible, a large amount of sludge is retained in the reaction tank by a long aeration method in which the residence time of the sludge in the aeration tank is extended, or by attaching the sludge to the contact material surface. The proposed method has been proposed and put into practical use (published by the Japan Sewerage Association, supervised by the Sewerage Department, Urban Bureau, Ministry of Construction, Sewerage Facility Planning and Design Guide and Commentary, second edition, 1994). However, these methods require a large installation area for the aeration tank in order to lengthen the residence time of the sludge in the aeration tank. Separation will be hindered. Also,
The catalytic oxidation method is not preferable in that clogging of sludge occurs when the load increases.

In the activated sludge treatment method for treating organic sludge, Japanese Patent Application Laid-Open No. 9-276887 discloses an activated sludge treatment method capable of reducing the amount of excess sludge generated. A solid-liquid separator for solid-liquid separation of the sludge after the sludge treatment, a sludge return means for returning a part of the separated sludge to the activated sludge treatment tank,
A method of treating organic wastewater using a device having a heating device for heating to 0 to 100 ° C. and a sludge return means for returning the heated sludge to the activated sludge treatment tank. '' ing. However, in the method described in this publication,
Since the solubilization of sludge in the heating device is performed only by heating,
The solubilization solution contains a large amount of BOD components,
Since the OD component is not mineralized and remains in the solubilization solution as it is, when the solubilization solution containing a large amount of the BOD component is returned to the activated sludge treatment tank, the organic matter load in the activated sludge treatment tank becomes excessive. In addition, the oxidative decomposition of organic matter in the activated sludge treatment tank becomes insufficient, and as a result, the quality of treated water deteriorates.

Therefore, it is conceivable to lengthen the residence time of the liquid to be treated in the activated sludge treatment tank in response to the increase in the BOD load due to the solubilization treatment, that is, to increase the volume of the activated sludge treatment tank. In that case, equipment costs will increase.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an organic wastewater capable of improving treated water quality without increasing equipment costs. And a processing apparatus therefor. It is another object of the present invention to provide a method for treating organic wastewater and a treatment apparatus therefor, which can significantly reduce the amount of generated excess sludge.

[0008]

In order to achieve the above object, the present invention provides a method for solubilizing sludge by using a thermophilic bacterium to reduce the amount of sludge by solubilization and to solubilize the sludge. Organic substances in the processing solution are decomposed by thermophilic bacteria, and the BOD of the processing solution can be reduced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for biologically treating organic wastewater, wherein the biological wastewater is subjected to biological treatment in a biological treatment apparatus, and then a part of the sludge in the biological treatment apparatus is removed. The gist of the present invention is a method for treating organic wastewater, characterized in that the solution is solubilized by a thermophilic bacterium in a solubilization treatment device and the treated solution after the solubilization treatment is returned to the biological treatment device.

Here, as the biological treatment apparatus, any of aerobic biological treatment and anaerobic biological treatment can be applied. The aeration treatment apparatus used for the aerobic biological treatment may be of a diffused type or a mechanical aerated type as long as it has an aeration unit. The aeration treatment is preferably performed at 0.1 to 0.5 vvm (vv) so that aerobic digestion and decomposition can be tolerated.
m = aeration rate / aeration tank capacity / min.) at room temperature, but depending on the load, the treatment may be performed at a higher ventilation rate with a ventilation rate higher than this. The liquid to be treated is preferably adjusted to a pH of 5.0 to 8.0. In addition, the aeration treatment apparatus includes microorganisms such as yeast to promote aerobic digestion and decomposition, and aluminum sulfate, polyaluminum chloride, ferric chloride, and ferrous sulfate to promote floc formation. A flocculant may be added. For the aerobic biological treatment, a device capable of aerobic treatment other than the aeration treatment device may be used. Examples of the apparatus used for anaerobic biological treatment include a method of stirring by circulating a liquid in a tank, a method of stirring by circulating and aeration of a generated gas, a method of installing a stirrer such as a stirring blade, an active microorganism, Any method can be used as long as it has a means for efficiently contacting the active microorganism with the organic waste liquid to be treated, such as a method having a fixing means.

In the solubilization step, sludge is decomposed by a thermophilic bacterium (for example, cells such as Bacillus stearothermophilus which is an aerobic thermophilic bacterium may be added). (For example, protease, lipase, glycosidase, etc., added alone or in combination).

As the solubilization conditions in the solubilization treatment apparatus, for example, the following conditions can be adopted in order to promote solubilization by sludge solubilizing enzymes secreted by thermophilic bacteria and heat. (1) Temperature: 50 to 90 ° C, preferably 55 to 75 ° C,
More preferably 60 to 70 ° C. (2) Sludge concentration: 1000 mg / liter or more, preferably 3
000 mg / liter or more, more preferably 5000 to 250
(3) pH: 6-9, preferably 7-8.5, more preferably 7-8 (4) Environment: aerobic or microaerobic conditions (5) Residence time: solubilization rate and sludge decomposition The determination is based on the degree of hydraulic residence time (also called HRT). HRT is obtained based on the amount of inflow liquid and the effective volume of the reaction tank, and is expressed by the following relational expression.

HRT = reactor tank volume (liter) / inflow liquid per unit time (liter / hr) According to the present invention, the solubilization of sludge is carried out by thermophilic bacteria in a solubilization treatment apparatus. As the soluble organic matter is decomposed and mineralized by the thermophilic bacteria together with the sludge reduction due to the heat treatment, the BOD of the solubilized treatment liquid can be reduced, and the biological load of the treatment liquid returned to the biological treatment apparatus is reduced. And the quality of treated water is improved.

Further, specific conditions under which sludge is decomposed satisfactorily by thermophilic bacteria and the quality of treated water can be improved are as follows.

If the HRT in the solubilization treatment apparatus is short, organic substances are not sufficiently decomposed (not mineralized), and the BOD of the treatment liquid returned to the biological treatment apparatus cannot be reduced. On the other hand, a long HRT in the solubilization treatment device is not preferable because substances that inhibit the growth of thermophilic bacteria accumulate. In this regard, the hydrodynamic residence time for solubilization in the solubilization treatment device is preferably 1 day to 8 days. In order to control the HRT, a thickening means is provided in front of the solubilization apparatus to concentrate the sludge, and the amount of the sludge fed into the solubilization apparatus is changed. Is provided, and the HRT can be controlled by a method of adjusting the liquid level in the solubilization apparatus by the liquid level sensor.

The pH of the solubilization solution in the solubilization device
Is preferably in the range of 6 to 9 suitable for the growth of thermophilic bacteria, and more preferably in the range of 7 to 8.5 suitable for secretion and activity of the sludge solubilizing enzyme. More preferably, it is within the range of 8. In order to adjust the pH, a pH sensor is provided in the solubilization treatment apparatus or in the treatment liquid path immediately before flowing into the solubilization treatment apparatus, and the pH changed by appropriately adding an acid or alkali to the treatment liquid is used as the pH sensor. The pH can be adjusted by the method of sensing with.

The temperature of the solubilized solution in the solubilizing device is preferably controlled at 55 to 75 ° C. suitable for the growth of thermophilic bacteria. In this case, if the solubilization temperature is low, the activity of the thermophile becomes insufficient, and a sufficiently high solubilization rate may not be obtained. On the other hand, if the solubilization temperature is too high, even if physicochemical thermal decomposition by heat proceeds, the activity of the thermophilic bacterium is reduced, so that a high solubilization rate cannot be obtained. The solubilization rate may be lower than without thermophiles. Therefore, as shown in detail in Examples described later, an extremely high solubilization rate can be obtained by solubilizing sludge by microbial treatment with a thermophilic bacterium at 60 to 70 ° C.

The treatment liquid treated by the biological treatment device is separated into treated water and sludge by a solid-liquid separation device, a part of the sludge is returned to the biological treatment device, and the remaining sludge is solubilized by the solubilization treatment device. After solubilization by thermophilic bacteria, the solubilized solution can be returned to the biological treatment apparatus. The solid-liquid separation device refers to, for example, a sedimentation device, a floating separation device, a centrifugal separation device, a membrane separation device, and the like.

Further, in order to reduce the amount of sludge treated in the solubilization treatment device, a concentrating device may be provided in a path from the solid-liquid separation device to the solubilization treatment device. in this case,
A method in which part of the sludge separated by the solid-liquid separation device is returned to the biological treatment device, and at least a part of the remaining sludge is concentrated by the concentration device and then solubilized by the thermophilic bacteria in the solubilization treatment device. Since at least a part of the sludge separated by the solid-liquid separation device is concentrated by the concentration device and then sent to the solubilization treatment device, nutritional conditions suitable for the growth of thermophilic bacteria are obtained, and the production of the solubilized enzyme is also achieved. By doing so, a high solubilization rate is obtained. Further, since at least a part of the sludge is sent to the solubilization treatment device after being concentrated, the amount of the treated sludge sent to the solubilization treatment device is reduced, and the size of the solubilization treatment device can be reduced.

Further, after the sludge separated by the solid-liquid separation device is concentrated by the concentration device, a part of the sludge is returned to the biological treatment device, and at least a part of the remaining sludge is removed by the solubilization treatment device. If it is a method of solubilization, the sludge separated by the solid-liquid separation device is all concentrated, and a part of the concentrated sludge is sent to the solubilization treatment device. In addition to the effect that the size of the solubilization treatment device can be reduced, part of the sludge separated by the solid-liquid separation device is sent to the biological treatment device after being concentrated, so that the amount of microorganisms in the biological treatment device is large. Therefore, the amount of microorganisms in the biological treatment device can be maintained at a high concentration, and the decomposition reaction of organic substances by microorganisms is sufficiently performed. As a result, the sludge load is reduced, thereby improving the treated water quality. There is.

In particular, as will be described in detail in Examples described below, by concentrating sludge to a water content of 99% or less (sludge concentration of 1% or more), nutrient conditions suitable for the growth of thermophilic bacteria can be obtained. In addition, the solubilization treatment is performed more efficiently, and the size of the solubilization treatment device can be further reduced.

[0022]

Embodiments of the present invention will be described below. FIG.
BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of one Example of the organic wastewater treatment apparatus which can apply the organic wastewater treatment method of this invention.

As shown in FIG. 1, raw wastewater A is introduced into a biological treatment tank 2 via a path 1, and raw wastewater, which is organic wastewater, is subjected to aerobic biological treatment in the biological treatment tank 2. In addition, aerobic biological treatment means that organic matter is decomposed into inorganic substances such as carbon dioxide or water by biological oxidation, and the aerobic microorganism used is Gram-negative or used in the activated sludge method for sewage purification. Gram-positive rods, such as Pseudomonas and Bacillus, the inoculum of which are obtained from a conventional sewage purification plant. In this case, the temperature of the biological treatment tank 2 is 10
To 50 ° C., usually, to operate in a temperature range of 20 to 30 ° C., but for more efficient treatment, a higher temperature is preferable. For example, when using a mesophilic bacterium separated from excess sewage sludge, Operate in a temperature range of 35-45 ° C. In any case, an optimal temperature condition is selected and operated from the above temperature range so that the oxidative decomposition reaction by the microorganism can efficiently and sufficiently occur. In this case, as the biological treatment tank 2, either a batch type or a continuous type can be used.

The treated water B thus treated in the biological treatment tank 2 is introduced into a sedimentation tank 4 as a solid-liquid separation device via a passage 3 to be subjected to solid-liquid separation, and the supernatant is subjected to solid-liquid separation. The liquid C is subjected to tertiary treatment such as nitrification denitrification or ozone treatment, if necessary, according to the discharge standard of the discharge destination, and is used as river discharge or landscape water.

On the other hand, a part of the sludge D, which is an organic solid separated in the sedimentation tank 4, joins the path 1 via the path 5 and is introduced into the biological treatment tank 2 together with the raw wastewater A. ing. The amount of sludge sent via the route 5 is determined by the amount of microorganisms held in the biological treatment tank 2.

Further, the remaining sludge E separated in the sedimentation tank 4 is introduced into the solubilization tank 7 via the path 6. In the solubilization tank 7, the organic solid is solubilized aerobically under high temperature conditions. In this case, the inoculum of the aerobic microorganism (thermophilic bacterium) used under high temperature conditions is obtained, for example, by culturing the microorganism from a conventional aerobic digestion tank. The optimum temperature of the solubilization tank 7 is preferably 50
The operation is performed under a temperature range of up to 90 ° C., but it depends on the type of thermophilic bacterium that decomposes the organic solids contained in the sludge E to be treated at a high temperature. In the case of a thermophilic bacterium isolated from a bacterium, the temperature at a high temperature is set to 55 so that both the solubilization reaction by the microorganism (thermophilic bacterium) and the physicochemical thermal decomposition by heat can be simultaneously and sufficiently generated. Temperature range of ~ 75 ° C,
Most preferably, it is operated at 60 to 70 ° C. from the viewpoint of enzyme activity. In any case, depending on the type of the microorganism, 50 to 90 ° C. is used so that both the solubilization reaction by the microorganism (thermophilic bacterium) and the physicochemical thermal decomposition by heat can be simultaneously and sufficiently generated. What is necessary is just to set so that it may become a temperature range.

As a device for aerobically treating microorganisms in the solubilization tank 7, any device provided with a conventional air diffuser can be used. In this case, either a batch type or a continuous type can be used as the solubilization tank.

As described above, the treatment liquid F solubilized in the solubilization tank 7 joins the path 1 via the path 8 and is introduced into the biological treatment tank 2 together with the raw wastewater A to perform the biological treatment.

Next, the solubilization rate and the quality of the treated water for the solubilization conditions (aerobic conditions by adding aerobic thermophiles and anaerobic conditions without adding aerobic thermophiles) and HRT for 1 or 2 days The results of investigating the changes in the solubilization rate and the protease activity due to the difference in the sludge concentration rate, and the results of investigating the changes in the solubilization temperature and the solubilization rate will be described. (1) Investigation of solubilization rate Bacillus stearothermophilus SPT2-1 [aerobic thermophilic bacterium], which was pre-cultured, was added to excess sludge derived from a sewage treatment plant with an organic solid concentration of 2% by weight. FERMP-15395], inoculated into a glass jar fermenter having an effective volume of 2 liters, and ventilated at 65 ° C. with a flow rate of 1.0 liter / mi.
n., treated at a stirring speed of 300 rpm (redox potential = 5
0-100 mV, pH = 8.1), HRT = 1 day or 2
A solubilized sample is collected every day, its volatile solid content (VSS ₁ ) is measured, and based on the volatile solid content (VSS ₀ ) before treatment, solubilization in each HRT is performed according to the following formula. The rate (%) was measured. These VSS ₀ and VSS ₁
Was measured according to JIS-K-0102. At the same time, using the same sludge as above, the solubilization rate was investigated when HRT was 1 day under anaerobic conditions (without addition of aerobic thermophilic bacteria) at the same solubilization temperature.

Solubilization rate (%) = ((VSS ₀ -VSS ₁ )
/ VSS ₀ ) × 100 As a result, the results shown in the following Table 1 were obtained.

[0031]

[Table 1]

As is clear from Table 1, when the HRT was 1 day, the BO of the treatment liquid when the solubilization was performed under anaerobic conditions was performed.
It can be seen that the BOD of the treatment liquid is reduced to about 55% by solubilization with aerobic thermophilic bacteria as compared with D. Furthermore, if the solubilization by the aerobic thermophile is performed in HRT = 2 days, the B of the treatment liquid is higher than that in the case of solubilization under anaerobic conditions.
It can be seen that the OD is reduced to about 30%. (2) Change in treated water quality In order to configure the apparatus shown in FIG. 1, as the biological treatment tank 2, a square tank made of transparent vinyl chloride resin having a sectional area of 800 cm ² and a height of 60 cm and an effective volume of 40 liters is used. The biological treatment tank 2 is aerated at 10 liters / min. At 25 ° C., and as the sedimentation tank 4, a transparent pyramid-shaped square tank made of transparent vinyl chloride resin having a sectional area of 400 cm ² and a height of 40 cm and an effective volume of 7 liters is used. As the solubilization tank 7, a glass cylinder having an inner diameter of 13 cm and a height of 25 cm and an effective volume of 2 liters was used. The properties of the organic wastewater were peptone: glucose: yeast extract =
Using a ratio of 4: 4: 1, at a load of 0.4 kg BOD / m ³ / day, the amount of sludge passing through the path 5 was adjusted so that the sludge concentration in the biological treatment tank 2 was about 3000 mg / liter, In the solubilization tank 7, a solubilization treatment under aerobic conditions by adding aerobic thermophilic bacteria as described above (65 ° C., aeration rate 1.0 liter / min., Stirring speed 300 rpm, redox potential = 50-100 mV, p
H = 8.1) and a change in the quality of the treated water was investigated when a solubilization treatment (65 ° C.) was performed only by heat under anaerobic conditions.

As a result, the results shown in the following Table 2 were obtained.

[0034]

[Table 2]

As is evident from Table 2, the quality of the treated water is greatly improved by solubilization with aerobic thermophiles.

By concentrating the sludge, the amount of sludge fed into the solubilization tank is reduced.
T becomes longer, and the BOD amount of the processing solution returned from the solubilization tank to the biological processing tank can be significantly reduced. For this purpose, for example, as shown in FIG. A processing device to which the device 9 is added can be used. As the concentrator 9, a concentrator such as a membrane concentrator, a centrifugal concentrator, a floating concentrator, an evaporative concentrator, and a concentrator of a floating ring lamination type can be used.

Further, as shown in FIG. 3, after all the sludge D separated in the sedimentation tank 4 is concentrated in the concentration device 9, a part of the sludge is returned to the biological treatment tank 2 via the path 5, and the remaining sludge is returned. The sludge can be solubilized by a thermophilic bacterium in the solubilization tank 7. (3) Changes in solubilization rate and protease activity due to difference in sludge concentration rate Excess sludge collected from the final sedimentation tank of a sewage treatment plant as a sludge to be treated using a 5 L (liter) glass jar fermenter as a solubilization tank. Is concentrated to various concentrations, 2 L (liter) of sludge of which concentration is adjusted is introduced into the solubilization tank, and a thermophilic bacterium culture solution is added at a volume ratio of 1%, aeration rate is 1 L / min, and stirring is performed. Speed 300rpm, temperature 65
Solubilization treatment at 24 ° C for 24 hours, VSS after 24 hours
(Organic solids) The solubilization rate and the protease activity, one of the sludge solubilizing enzymes, were measured. The results are shown in FIGS. VSS solubilization rate (%) of the volatile solids content after 24 hours of culture and VSS _1, if a volatile solids content of preculture and VSS _0, defined by the following equation, VSS ₁ and VSS ₀ is measured according to JIS-K
-0102.

VSS solubilization rate (%) = ((VSS ₀ −
VSS ₁ ) / VSS ₀ ) × 100 As shown in FIG. 4, it can be seen that a significantly high solubilization rate can be obtained by concentrating the sludge to a water content of 99% or less (sludge concentration of 1% or more). In addition, as shown in FIG. 5, it can be seen that the protease activity supporting the solubilization rate also maintains a high activity when the water content is 99% or less (sludge concentration 1% or more). Thus, by concentrating the sludge to a water content of 99% or less, the solubilization rate can be remarkably improved. That is, for the growth and activity of aerobic thermophilic bacteria in a solubilization tank equipped with a ventilation means, it is necessary that organic matter is dissolved in the solubilization tank as a nutrient source of the thermophilic bacterium, Is concentrated to a certain concentration (99% or less water content) and put into the solubilization tank, so that the concentrated sludge is heat and solubilized by the aerobic thermophilic bacteria sludge solubilizing enzyme present in the solubilization tank. However, the lysate becomes a sufficient substrate for the growth of aerobic thermophilic bacteria in the solubilization tank and the production of sludge solubilizing enzymes, so that the aerobic thermophilic bacteria grow sufficiently and maintain high activity. . This produces a large amount of sludge solubilizing enzyme
Because of the secretion, the solubilization reaction by the aerobic thermophilic bacterium is sufficiently and continuously performed, and a high solubilization rate can be secured.

Conversely, when the sludge is introduced into the solubilization tank at a sludge concentration of 1% or less (water content of 99% or more), the substrate required for the growth of aerobic thermophilic bacteria and the production of the sludge solubilizing enzyme is insufficient. Thus, the activity of aerobic thermophilic bacteria and the secretion of sludge solubilizing enzyme can be expected only to some extent, and a high solubilization rate cannot be achieved. In addition, even if the sludge is concentrated to a water content of 90% or less, the above advantages cannot be enjoyed so much. On the contrary, when the fluidity deteriorates and the solubilization tank is operated with aerobic or microaerobic,
Since there is a disadvantage that a foaming phenomenon occurs due to aeration, the concentration of sludge by the concentrator is 90 to 99%.
It is preferable to set it in the range. Especially in aerobic conditions,
The water content of the sludge is preferably in the range of 96 to 99%. (4) Solubilization temperature and solubilization rate As the target sludge, sludge collected from the aeration tank of a sewage treatment plant was concentrated to a concentration of 1.5% by gravity concentration, and the concentrated sludge was placed in five 500 mL Sakaguchi flasks. Each one
50 mL, and into each flask, 5 mL of Bacillus stearothermophilus strain SPT2-1 [FERMP-15395], which is an aerobic thermophilic bacterium precultured as a seed, was added at each set temperature. After culturing for a period of time, VSS was measured while supplying water for evaporation. In FIG. 6, the temperature (° C.) is plotted on the horizontal axis, and the VSS solubilization rate (%) is plotted on the vertical axis.

For comparison, an experiment was conducted in which the concentrated sludge was solubilized without adding thermophilic bacteria to the concentrated sludge.

The symbol “○” in FIG. 6 indicates the case where the sludge was solubilized with thermophilic bacteria, and the symbol “●” indicates the case where the sludge was solubilized without thermophilic bacteria.

As is apparent from FIG. 6, the solubilization rate can be remarkably improved by solubilization at 60 to 70 ° C. by microbial treatment with a thermophilic bacterium. However, when the temperature is lower than 60 ° C., the activity of the thermophilic bacterium is insufficient, and a sufficiently high solubilization rate cannot be secured. On the other hand, if the solubilization temperature exceeds 70 ° C., even if physicochemical thermal decomposition by heat proceeds, the activity of the thermophilic bacterium decreases, so that a high solubilization rate cannot be obtained, and in some cases, However, the solubilization rate may be lower than without thermophiles.

Further, another embodiment of an organic wastewater treatment apparatus to which the method for treating organic wastewater of the present invention can be applied will be described with reference to FIGS.

FIG. 7 shows the membrane separation device 10 in the biological treatment tank 2.
The solid-liquid separation is performed by a membrane separation device in parallel with the biological treatment. For example, the membrane separation device 10 provided in the biological treatment tank 2 has a pore size of 0.1 to 2.5.
A membrane having a thickness of μm, preferably 0.3-0.5 μm may be used, and those formed from one or more membrane module structures are preferred. As a preferred membrane separation device, there is an immersion type membrane separation device equipped with a T-type filter element manufactured by Yuasa Corporation. Further, the membrane separation device, preferably, water pressure,
Cleaning means such as pressurization by air pressure or rubbing, vibration, or chemical injection is included or provided in parallel, and it is preferable to adopt a structure in which a substance that does not pass through the membrane is prevented from adhering to the membrane surface as much as possible. Sludge is withdrawn from the biological treatment tank 2 in order to subject a part of the treatment liquid to the next solubilization step.
The suspended solids concentration (MLSS) in the biological treatment tank 2 is maintained at a constant value, for example, 10,000 to 20,000 mg / liter, and the amount is intermittently or constantly adjusted so that digestion and decomposition by aerobic treatment are smoothly performed. It is advisable to pull out the sludge while controlling and subject it to the next solubilization step. Further, it is also possible to concentrate the sludge withdrawn from the biological treatment tank by a concentration device before subjecting the sludge to the solubilization step.

FIG. 8 shows an example in which the phosphorus component in the organic wastewater is removed by microorganisms. Phosphorus is released from the microorganisms in the anaerobic tank 2a, and then aerobic in the aerobic tank 2b. Microbial digestion and ingestion of phosphorus components by microorganisms (retention in the body). Next, the treated liquid subjected to the biological treatment is placed in the sedimentation tank 4 in the primary sludge x in which the phosphorus component is concentrated.
And primary treated water a. In order to release the phosphorus component from the microorganisms in the primary sludge x, the following phosphorus release device 1
In 1, the phosphorus component is released to the liquid phase by anaerobic treatment, heat treatment, ultrasonic treatment, ozone treatment, alkali treatment, etc., and sedimentation separation, flotation separation, centrifugation, membrane separation (including separation by a dehydrator), etc. , And is separated into secondary treatment water b and secondary sludge z containing a high phosphorus component. In this case, the phosphorus release is
Anaerobic treatment and heat treatment (60 to 90 ° C.) are preferable, and solid-liquid separation is preferably sedimentation separation or flotation separation. Next, an aggregating agent is added to the secondary treatment water b, and the phosphorus component is aggregated as a solid component in the phosphorus separation device 12 to obtain a tertiary treatment water c substantially free of the phosphorus component and a solid phosphorus component y. This solid phosphorus component y can be used as a raw material for producing fertilizers and phosphorus compounds. The secondary sludge z is solubilized in the solubilization tank 7 to further reduce the volume of the sludge component.

FIG. 9 shows that there is little loss of heat energy, there is little nitrogen-containing organic or inorganic matter in the treated water discharged to the outside of the treatment system, and it is possible to remove the odor of the exhaust gas emitted to the atmosphere. This is an example of the case, and a nitrification device 13 and a denitrification device 14 are arranged in a treatment liquid path leading to the biological treatment tank 2.
Part of the sludge separated in the sedimentation tank 4 is returned to the nitrification device 13 via the reflux path 15, and the processing solution solubilized in the solubilization tank 7 is removed via the heat exchanger 16 and the return path 17. It is returned to the nitriding device 14. Further, the air that has passed through the path 18 into the solubilization tank 7 passes through the path 19 into the nitrification device 13. The NH ₄ ⁺ min in organic wastewater, NO ₂ by nitrifying bacteria in the nitrification device 13 ^- or NO ₃ ^- to be changed, the NO ₂ ^- of denitrifying bacteria and hydrogen donating agent in the denitrification device 14 ^- or NO ₃ By action, it is changed to N ₂ . Since the gas (gas containing mainly NH ₃ ) discharged from the solubilization tank 7 is diffused into the atmosphere after being introduced into the nitrification device 13, the odor of the gas diffused into the atmosphere is significantly reduced, and the solubilization is performed. The heat of the gas discharged from the tank 7 is supplied to the nitrification device 1
In No. 3, the heat energy is effectively used for the nitrification treatment, so that the heat energy loss is small. Further, the nitrogen-containing organic component or the nitrogen-containing inorganic component in the treated water discharged out of the treatment system is substantially zero. If the organic content of raw water is not so high,
It is preferable to denitrify with a denitrification device after nitrification with a nitrification device as shown in (1).

However, when the organic matter in the raw water is large, the number of microorganisms oxidizing and decomposing the organic matter increases and the nitrification action of the nitrifying bacteria is hindered. After that, it is preferable to perform nitrification treatment with nitrifying bacteria in a nitrification device. By returning the treatment liquid after the nitrification treatment to the denitrification device, treated water containing almost no nitrogen can be discharged from the precipitation tank 4 to the outside.

FIG. 10 shows an example in which the amount of air supplied can be reduced when biologically treating organic wastewater. The solubilizing tank 7a is closed, and a compressor is provided near the solubilizing tank 7a. Install 20 and compressor 2
From 0, the treatment liquid after the solubilization treatment by the high-pressure air passed into the solubilization tank 7a is introduced into the biological treatment tank 2c together with the high-pressure air through the pipeline 21. , The oxygen dissolving efficiency in the solubilization treatment liquid in the solubilization tank 7a is increased, so that the amount of supplied air can be reduced, and the calorific value of the solubilization tank taken out into the atmosphere together with the exhaust gas. Can be reduced. In this case, the treatment liquid in the solubilization tank 7a can be introduced into the biological treatment tank 2c separately from the high-pressure air. Biological treatment tank 2
By supplying a gas having heat from the solubilization tank 7a to c, the biological activity of the biological treatment tank 2c is increased, and the quality of treated water can be improved.

[0049]

Since the present invention is configured as described above, the following effects can be obtained.

According to the first aspect of the present invention, the amount of sludge is reduced by solubilization, and at the same time, soluble organic substances are decomposed and mineralized by thermophilic bacteria. Can be achieved.

According to the second to fourth aspects of the present invention, conditions suitable for the growth of thermophilic bacteria are shown, and the quality of treated water can be greatly improved.

According to the fifth and sixth aspects of the present invention, it is possible to secure an extremely high solubilization rate, greatly reduce the amount of excess sludge generated, and further reduce the size of the solubilization treatment apparatus. .

According to the seventh and eighth aspects of the present invention, it is possible to provide a processing apparatus suitable for implementing the processing method of the first to fourth aspects.

According to the ninth aspect of the present invention, there is provided the fifth aspect,
A processing apparatus suitable for performing the processing method described in Item 6 can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an organic wastewater treatment apparatus to which an organic wastewater treatment method of the present invention can be applied.

FIG. 2 is a schematic configuration diagram of another embodiment of an organic wastewater treatment apparatus to which the organic wastewater treatment method of the present invention can be applied.

FIG. 3 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus to which the method for treating organic wastewater of the present invention can be applied.

FIG. 4 is a diagram showing a change in a solubilization rate due to a difference in sludge concentration rate.

FIG. 5 is a diagram showing a change in protease activity due to a difference in sludge concentration rate.

FIG. 6 is a diagram showing changes in solubilization temperature and solubilization rate.

FIG. 7 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus to which the organic wastewater treatment method of the present invention can be applied.

FIG. 8 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus to which the organic wastewater treatment method of the present invention can be applied.

FIG. 9 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus to which the organic wastewater treatment method of the present invention can be applied.

FIG. 10 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus to which the organic wastewater treatment method of the present invention can be applied.

FIG. 11 is a schematic configuration diagram of a conventional organic wastewater treatment apparatus.

[Explanation of symbols]

 2, 2c ... biological treatment tank 4 ... sedimentation tank 7, 7a ... solubilization tank 9 ... concentrator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriaki Shiota 2-3-20-406, Konan-cho, Higashinada-ku, Kobe-shi, Hyogo (72) Inventor Kiyoshi Nasu 1-24-1-13 Minowa, Toyonaka-shi, Osaka F-term 4D006 GA02 KA01 KA71 KB22 KB23 MA21 PA02 PC64 4D028 AC01 BC17 BC19 BC28 BD16 BE00 BE01 4D059 AA05 BA01 BE37 BE41 BE42 CA28 EA20 EB20

Claims (9)

[Claims] 1. A method for biologically treating an organic wastewater, wherein the organic wastewater is biologically treated by a biological treatment device, and a part of the sludge in the biological treatment device is solubilized by the solubilization treatment device. A method for treating organic wastewater, comprising solubilizing with a thermophilic bacterium and returning the treated solution after the solubilization treatment to a biological treatment apparatus. 2. The method for treating organic wastewater according to claim 1, wherein the hydraulic retention time for solubilization in the solubilization treatment device is 1 to 8 days. 3. The pH of a solubilization solution in a solubilization apparatus.
The organic wastewater treatment method according to claim 1 or 2, wherein the number of the organic wastewater is 6 to 9. 4. The method according to claim 1, wherein the temperature of the solubilizing solution in the solubilizing apparatus is controlled at 55 to 75 ° C.
4. The method for treating organic wastewater according to 2 or 3. 5. The method according to claim 1, wherein the water content of the sludge fed into the solubilization treatment device is 99% or less.
5. The method for treating organic wastewater according to 3 or 4. 6. A solubilization treatment device using a thermophilic bacterium for 60 to 7 days.
The method for treating organic wastewater according to claim 5, wherein the organic wastewater is solubilized at 0 ° C. 7. An apparatus for biologically treating organic wastewater, comprising: a biological treatment apparatus for biologically treating organic wastewater; and a solubilization apparatus for solubilizing organic solids by thermophilic bacteria. An organic wastewater treatment apparatus, comprising: a treatment apparatus; and a treatment liquid path from the biological treatment apparatus to the biological treatment apparatus through the solubilization treatment apparatus again. 8. An apparatus for biologically treating organic wastewater, comprising: a biological treatment apparatus for biologically treating organic wastewater; and a solubilization apparatus for solubilizing organic solids by thermophilic bacteria. A treatment liquid having a treatment device, and a solid-liquid separation device for separating the treatment liquid into treated water and sludge is disposed in a path of the treatment liquid following the biological treatment device, and the treatment liquid from the solid-liquid separation device to the biological treatment device And a path for a treatment liquid from the solid-liquid separation device to the biological treatment device through the solubilization treatment device. 9. An organic wastewater treatment apparatus according to claim 8, wherein a concentration apparatus is provided in a path of the treatment liquid from the solid-liquid separation apparatus to the solubilization treatment apparatus.