JP4627403B2 - Organic wastewater treatment apparatus and treatment method - Google Patents

Description

  The present invention relates to a treatment apparatus and treatment method for organic wastewater such as sewage, human waste and industrial wastewater.

  Conventionally, organic wastewater such as industrial wastewater and domestic wastewater is generally subjected to aerobic biological treatment (activated sludge method, nitrification denitrification method, etc.) to decompose BOD in the wastewater. In such biological treatment, 30-50% of the decomposed BOD is used for the growth of microorganisms, and sludge increases. The increased amount of sludge is withdrawn as excess sludge and disposed of as waste after concentrating, dehydrating, incineration, etc., but the disposal will incur significant costs and equipment costs, and will increase in the future. There is a tendency.

  FIG. 1 shows a general processing flow in the organic waste water treatment apparatus 1. In this way, the raw water flows into the biological treatment tank (aeration tank) 10. The biological treatment tank 10 is supplied with return sludge and is aerated and agitated by the air from the blower 12 under aerobic conditions. Therefore, organic substances in the raw water are removed by aerobic microorganisms in the sludge. The biologically treated water from the biological treatment tank 10 flows into the sedimentation tank 14, where sludge is settled and separated, and the supernatant is discharged as treated water. The sedimentation sludge in the sedimentation tank 14 is returned to the biological treatment tank 10 by the return sludge pump 16 as return sludge. A part of the precipitated sludge is discharged as excess sludge.

  As a volume reduction treatment of surplus sludge combined with activated sludge treatment, a method has been proposed in which sludge is solubilized by some means and then returned to the biological treatment process. Examples of sludge solubilizing means include alkali treatment, acid treatment, ozone treatment, ultrasonic treatment, mill crushing treatment, and Fenton treatment. Thereby, a part of solubilized sludge is decomposed | disassembled by biological treatment in a biological treatment tank, and sludge can be reduced.

  Among them, the alkali treatment is a simple device that simply mixes the alkali agent and sludge in the stirring tank, and is a device with low initial cost. Moreover, a high solubilization rate can be obtained by using a drug such as a surfactant in combination.

  However, when alkali treatment is performed, there is a problem that a long reaction time (about 10 hours) is required unless physical methods such as heating, pressurization, cavitation, bead mill, and ultrasonic waves are used in combination. . Further, when a physical method is used in combination, the treatment can be performed even for a reaction time of several minutes to several tens of minutes, but it is not preferable because a large amount of energy is required.

  For example, Japanese Patent Application Laid-Open No. 9-150197 discloses an alkali treatment step of treating at a pH of 10.5 or more and treating at a pH of 9.0 to 10.0 for the purpose of shortening the alkali treatment time. Providing a second alkali treatment step is disclosed.

JP-A-9-150197

  However, the method disclosed in Patent Document 1 still has a long reaction time and is insufficient.

  The present invention relates to a method for treating organic wastewater that decomposes organic matter by the action of aerobic organisms, solubilization of sludge, solubilization of sludge, and high-efficiency and economical solubilization of sludge by reduction. The present invention relates to an apparatus and method.

The present invention includes biological treatment means for treating organic wastewater with microorganisms, solid-liquid separation means for subjecting biological treated water from the biological treatment means to solid-liquid separation, and discharging treated water from which solid content has been removed, A separation sludge return means for returning the sludge separated by the solid-liquid separation means to the biological treatment means, and further, an organic wastewater treatment apparatus, further comprising at least the sludge separated by the solid-liquid separation means A solubilizing means for receiving a part, adding an alkaline agent, and solubilizing; and a solubilized sludge returning means for returning the sludge solubilized by the solubilizing means to the biological treatment means, The solubilizing means comprises a first reaction tank and a second reaction tank that are arranged in series, and in the first reaction tank, the alkaline agent is added to adjust the pH of the sludge. Control within the range of 11.5 to 12.5 After stagnates the sludge 5-20 min, then transferred to the second reaction vessel, treating the sludge by a certain residence time in the second reaction vessel.

The present invention also provides a biological treatment means for treating organic wastewater with microorganisms, and a solid-liquid separation means for subjecting the biologically treated water from the biological treatment means to solid-liquid separation treatment and discharging the treated water from which solid content has been removed. And an organic wastewater treatment apparatus that returns the sludge separated by the solid-liquid separation means to the biological treatment means, and further comprising: A solubilizing means for receiving at least a part, adding an alkaline agent, and solubilizing; and a solubilized sludge returning means for returning the sludge solubilized by the solubilizing means to the biological treatment means, The solubilizing means comprises a static mixer arranged in series and provided with a plurality of blades in a tube, and a subsequent reaction tank, and the alkaline agent is added to the sludge to adjust the pH to 11.5 to 12.5. In the range The treatment with the static mixer, then, to dwell a given period of time in the transfer to the reactor.

  Further, in the organic waste water treatment apparatus, the reaction tank includes a first reaction tank and a second reaction tank that are arranged in series, and in the first reaction tank, a pH of 11. It is preferable that after treating the sludge while controlling in the range of 5 to 12.5, the sludge is transferred to the second reaction tank and retained in the second reaction tank for a certain period of time to treat the sludge.

Moreover, in the said organic waste water treatment apparatus, it is preferable that the residence time of the said sludge is 15 minutes- 100 minutes in the said reaction tank or the said 2nd reaction tank.

  Further, in the organic waste water treatment apparatus, the acid addition means for adding acid to the sludge solubilized by the solubilization means, and the sludge added with acid by the acid addition means are returned to the biological treatment means. And an acid-added sludge return means.

The present invention also includes a biological treatment process for treating organic wastewater with microorganisms, and a solid-liquid separation process for subjecting the biologically treated water from the biological treatment process to solid-liquid separation, and discharging the treated water from which solids have been removed. And a separated sludge return step for returning the sludge separated in the solid-liquid separation step to the biological treatment means, further comprising an organic wastewater treatment method, wherein the sludge separated in the solid-liquid separation step A solubilization process for adding and solubilizing at least a part of the alkali agent, and a solubilized sludge return process for returning the sludge solubilized in the solubilization process to the biological treatment process, and In the solubilization step, the alkaline agent is added to control the pH of the sludge to 11.5 to 12.5, the sludge is allowed to stay for 5 to 20 minutes, and then transferred to the sludge. 3 to 5 of the residence time in the first step A second step of processing by double residence.

  According to the present invention, the solubilization treatment is performed in a first reaction tank and a subsequent second reaction tank arranged in series, or in a rapid stirrer and reaction tank, more preferably pH. By controlling the above and the residence time, it is possible to solubilize sludge in a short time with low energy compared to the conventional method.

As a result of extensive research, the inventor has noticed that the solubilization phenomenon changes abruptly when the treatment time is around 20 minutes in the solubilization treatment of sludge with alkali. That is, from the start of the alkali treatment to about 20 minutes, although the TOC (total organic carbon) elution rate is high, there is almost no pH drop, but when it is over 20 minutes, the pH drop suddenly occurs. It was found that the TOC elution rate also decreased.

Therefore, in the solubilization reaction, the first stage in which the cell wall of the microorganism is most efficiently destroyed and the intracellular components are eluted within 20 minutes immediately after the addition of the alkaline agent, and then the eluted organic substances are gently dissolved. The present inventors have found that there is a second stage of reducing the molecular weight by hydrolysis or the like so that microorganisms can be decomposed (BOD component).

  Furthermore, the inventor has also found that the solubilization reaction can be performed remarkably efficiently by stirring rapidly.

  Next, the present invention will be described in detail below. FIG. 2 is a block diagram showing a configuration of one embodiment of the present invention. Organic wastewater such as industrial wastewater and domestic wastewater flows into the biological treatment tank 10 as raw water. In addition, although pre-processing facilities, such as a raw water adjustment tank and a raw water tank, are provided suitably as needed, it abbreviate | omits here. The inflow raw water is aerated for a predetermined time in the presence of activated sludge in which the microorganism concentration in the tank 10 is maintained at a predetermined concentration. The inside of the tank 10 is aerated and stirred by the air from the blower 12 being ejected from an air diffuser installed at the bottom of the tank. In the biological treatment tank 10, a plate-shaped contact material may be installed, and a part of the microorganisms may adhere to and grow on the contact material.

  After the organic matter in the raw water is decomposed by the aerobic microorganisms, it flows into the settling tank 14 and the activated sludge is settled to become clear treated water. The treated water flows out from the upper part of the settling tank 14 and the treated water channel. Instead of the precipitation tank 14, a known solid-liquid separation means such as centrifugation, flotation separation, membrane separation such as UF membrane or MF membrane, etc. may be used. Further, the precipitated sludge may be further concentrated by a centrifuge or the like and supplied to the next treatment step. Since the required amount of a known alkaline agent such as sodium hydroxide supplied to the solubilizing device 18 increases in inverse proportion to the sludge concentration, sludge having a high solid concentration is added to the solubilizing device 18 as much as possible. It is because it is desirable to supply.

  The precipitated sludge is returned to the biological treatment tank 10 as return sludge. And a part of sedimentation sludge is supplied to the solubilization processing apparatus 18 as drawing sludge, and is decomposed | disassembled and solubilized. In some cases, a part of the sludge is extracted from the biological treatment tank 10 to obtain a drawn sludge. Hereinafter, an embodiment of the alkali treatment based on the present invention will be described with reference to FIG.

FIG. 3 is a block diagram showing the configuration of one embodiment of the solubilization processing means of the present invention. The drawn sludge is introduced into the rapid reaction tank (first reaction tank) 22 by the sludge transfer pump 20. The residence time of the rapid reaction tank is 5 to 20 minutes, preferably 10 to 20 minutes. If the residence time is shorter than 5 minutes, a sufficient TOC elution amount cannot be obtained, and if it exceeds 20 minutes, a rapid pH drop occurs and sufficient TOC elution efficiency cannot be obtained. In the rapid reaction tank 22, the agitator 24 stirs. The power required for stirring is preferably 0.1 to 0.4 kW / m ³ , more preferably about 0.2 kW / m ³ . In the rapid reaction tank 22, it is preferable to maintain the pH at 11.5 to 12.5 by the alkali added from the alkali supply path 28 based on the measured value of the pH sensor 26. As for the method of adding the alkaline agent, it may be added all the time or may be added successively in a fixed amount. Of course, depending on the measured pH value, the addition amount may be changed and added sequentially. The addition concentration in the case of quantitative addition is, for example, 20 to 50 mM sodium hydroxide.

  Examples of the alkali agent to be added include known alkali agents such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium carbonate, calcium hydroxide, and sodium hydroxide is preferable. The alkaline agent is preferably added in the form of an aqueous solution in order to make it uniform quickly. The internal temperature of the rapid reaction tank 22 is preferably in the range of 10 to 30 ° C. This is because solubilization progresses slowly when the temperature is low. In order to increase the speed of solubilization (hydrolysis), it may be heated to 30 ° C. or higher, for example, 40 to 90 ° C. The amount of sludge to be solubilized is preferably about 3 to 5 times the amount of excess sludge generated. Moreover, you may add additives, such as surfactant, as an auxiliary | assistant of sludge solubilization.

Moreover, as shown in FIG. 4, you may use the rapid stirrer 34 and the same effect is acquired with shorter residence time. Here, as the rapid agitator 34, a static mixer such as a line mixer, a line disperser, a high-speed dispersion mixer, an emulsification disperser, or the like can be used. In particular, a static mixer such as a line mixer that can be directly installed in the sludge feed mud line is preferable. For example, a type in which a large number of blades (various shapes can be used) are provided in a pipe through which sludge flows can be used. Moreover, it is preferable that it is a static mixer which can disperse sludge under the pressure of 1.0-5.0 kgf / cm < ² >, and can mix an alkali. The treatment by the rapid stirrer 34, for example, the treatment by the line mixer, may be a one-pass treatment, or may be circulated for a plurality of times, for example, 2 to 20 times, preferably 5 to 10 times. .

  The reason why the effect can be obtained with a short residence time is that the flocs can be separated by rapid stirring, and the contact efficiency of alkali to the flocs increases, so that the cell wall can be broken more smoothly. It is thought to be done.

Moreover, as shown in FIG. 5, the rapid stirrer 34 and the rapid reaction tank 22 may be arranged in series and used in combination, which is preferable because the solubilizing effect is further increased. That is, for example, in the configuration shown in FIG. 3, the treatment may be performed in the rapid reaction tank 22 for 20 minutes, in the configuration shown in FIG. Then, after one pass treatment with a rapid stirrer, treatment may be performed for 20 minutes in a rapid reaction vessel.

  The addition of the alkaline agent when using the static mixer may be performed before the introduction of the sludge static mixer or in the mixer line, but is preferably performed before the introduction. The pH can be measured in the mixer line, in the rapid reaction tank, or in the slow reaction tank. The method for adding the alkaline agent is as described above.

  In the present embodiment, in the rapid reaction tank 22 or the rapid stirrer 34, cell wall components (proteins, etc.) of various microorganisms constituting the activated sludge are denatured under high pH conditions (pH 11.5 or more) and become cell walls. Damage is caused and destroyed, intracellular components are eluted by the difference in osmotic pressure inside and outside the cell wall, and microorganisms are killed to obtain the most efficient solubilizing effect.

Sludge treated at least one of the rapid reaction tank 22 and the rapid stirrer 34 flows into a slow reaction tank (second reaction tank) 30. In the slow reaction tank 30, the components eluted in the rapid reaction tank 22 and the mucosal material composed of polysaccharides on the surface of the microorganism are reduced in molecular weight and viscosity, so that the solubilization proceeds slowly and is further decomposed by microorganisms. It becomes easy to be done. The pH decreases with this reaction. Here, the residence time of the slow reaction tank 30 is preferably 3 to 5 times the residence time of the rapid reaction tank 22, that is, 15 minutes to 100 minutes , and more preferably 30 minutes to 100 minutes. The internal temperature of the slow reaction tank 30 is preferably in the range of 10 to 30 ° C. This is because solubilization progresses slowly when the temperature is low. In order to increase the solubilization rate, the temperature may be increased to 30 ° C or higher, for example, 40 to 60 ° C. The slow reaction tank 30 is stirred by the stirrer 32, and the stirring speed is preferably set smaller than the stirring speed of the stirrer 24 of the rapid reaction tank 22, and the power required for stirring of the stirrer 32 is 0.05-0. It is preferably about 2 kW / m ³ , for example, about 0.1 kW / m ³ . The sludge treated in the slow reaction tank 30 flows into the biological treatment tank 10 as a return solubilized sludge and is decomposed, so that the amount of excess sludge generated can be greatly reduced.

In the sludge solubilization treatment, a bacterial surface structure such as a cell wall of microbial bacteria in the sludge is destroyed, the cytoplasm is eluted, and a nutrient (BOD component) is formed that is decomposed by microorganisms. The inventor has examined a more efficient treatment and found that there is a marked change in the relationship between the decrease in pH and the eluted TOC. The relationship between the decrease in pH and the eluted TOC is shown in FIG. Until around ~ 20 minutes after alkaline treatment started as can be seen from FIG. 6, TOC (total organic carbon) While the decrease in the dissolution rate is higher even though pH hardly occur, lowering the pH becomes around past the 20 minutes Suddenly occurs and the elution rate of TOC also decreases. In other words, it was found that the phenomenon changes suddenly immediately after the start of the solubilization process and around 20 minutes.

The present inventors have found that in solubilization treatment, until ~ 20 minutes immediately after the start solubilization treatment to disrupt the cell walls of the microorganisms bacteria in the sludge, eluting the intracellular material takes place remarkably, 20 minutes It was found that the process of reducing the molecular weight of the cytoplasm that had been destroyed and eluted from the past by hydrolysis etc. was markedly performed, and the area of the cell membrane disruption elution process (first process) and the cytosolic elution / lowering process (first process) By providing separate areas for (2 steps), efficient processing was possible in a very short time.

In other words, the solubilization reaction consists of a first stage in which the cell walls of microorganisms are most efficiently destroyed and the intracellular components are eluted in about 20 minutes immediately after the addition of the alkaline agent, and then the second stage in which elution is gradually sustained. Can be divided into That is, the rapid reaction tank 22 in this embodiment corresponds to the first stage of the solubilization reaction, and the slow reaction tank 30 corresponds to the second stage. In the rapid reaction tank 22, the organic matter can be rapidly eluted under high pH conditions (pH 11.5 or more) with almost no drop in pH. In the slow reaction tank 30, elution is continued gradually. When the reaction is allowed to proceed in a single tank for a long time as in the prior art, the elution efficiency decreases due to the decrease in pH associated with elution.

  Moreover, the effect similar to the above-mentioned rapid reaction tank 22 is acquired in a shorter time by making it react with an alkali agent, disperse | distributing a floc with the rapid stirrer 34. FIG. Microorganisms in the sludge exist together with other substances as flocs. Here, the treatment with the rapid stirrer is considered to be able to perform the reaction in a shorter time because the microorganisms can be efficiently alkali-reacted by dispersing and miniaturizing the floc, and heating, Compared with techniques such as pressurization, cavitation, bead mill, and ultrasonic waves, the amount of energy required for this embodiment is overwhelmingly small.

This solubilized sludge is returned to the biological treatment tank 10 as a return solubilized sludge and biologically decomposed into CO ₂ and H ₂ O by aerobic microorganisms. Here, it is preferable that the BOD load on the biological treatment tank 10 is designed based on the total amount of the BOD of the raw water flowing in and the BOD of the solubilized sludge so as to prevent the deterioration of the treated water quality in advance.

  Further, the solubilization process, that is, the process in the rapid reaction tank 22 and the slow reaction tank 30, may be a continuous process as described above, but may be a batch process. In the case of batch processing, after the drawn sludge is transferred to the rapid reaction tank 22, an alkaline agent is added while stirring the sludge, adjusted to a predetermined pH, and after a rapid reaction step in which stirring is performed for a predetermined time, a slow reaction tank. And a slow reaction step in which the mixture is further stirred for a predetermined time. After the reaction, the solubilized sludge is transferred to the biological treatment tank 10 or the like. The rapid reaction step and the slow reaction step may be performed in separate tanks as described above, but may be performed in one tank.

  The capacity of the slow reaction tank 30 is preferably larger than the capacity of the rapid reaction tank (first reaction tank) 22, and the capacity of the slow reaction tank 30 is 3 to 5 times that of the rapid reaction tank 22. More preferred. Further, the slow reaction tank (second reaction tank) 30 may have a structure in which the inside is divided into a plurality of parts. By dividing into a plurality, the pH gradually decreases from the upstream tank to the downstream tank, and a more efficient hydrolysis reaction occurs. Further, the slow reaction tank 30 has a large tank capacity and a high viscosity of sludge, so it tends to be difficult to mix the whole tank completely. Hydrolysis is likely to proceed.

  Further, the solubilized sludge may be neutralized by adding an acid, for example, in a neutralization tank provided after the solubilizer 18. Examples of the acid to be added include known acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and sulfuric acid is preferred. In order to avoid a rapid neutralization reaction, the acid is preferably added as an aqueous solution of 5% to 30%, preferably 10% to 20%. At this time, the amount of acid to be added is determined by a measured value by a pH sensor provided in the biological treatment tank 10, and the pH range is preferably maintained at 6.5 to 8.5. The neutralized sludge is returned to the biological treatment tank 10 and similarly decomposed by the activated sludge in the biological treatment tank 10. The neutralization reaction of the solubilized sludge may be performed in a neutralization tank, but may be neutralized by adding an acid to the biological treatment tank 10.

  Moreover, since it is necessary to neutralize the raw water by adding alkali in a pretreatment facility such as a raw water adjustment tank in order to show acidity, the solubilized sludge may be returned to the raw water adjustment tank or the like. In that case, a pH sensor may be provided in the raw water adjustment tank or the like. An acid may be added based on the measured value if the pH rises above a predetermined pH.

  Further, at least a part of the sludge solubilized by the solubilizing means or the sludge added with the acid by the acid adding means may be subjected to a treatment such as concentration, dehydration, or the like to obtain surplus sludge.

  The organic wastewater treatment method and treatment apparatus of the present invention can be used without particular limitation as long as it treats organic wastewater, and in particular, wastewater containing a large amount of organic matter such as sewage, septic tank, and food factory wastewater, and relatively little inorganic matter. It can be preferably used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

(Experimental example 1)
Activated sludge (MLSS: 10000 mg / L) was introduced into the first reaction vessel (0.6 L) at a flow rate of 30 mL / min, and at a temperature of 20 ° C., an aqueous NaOH solution (30 mM) and a surfactant (50 mg / L, Sepia D200 (manufactured by Organo) was continuously added to maintain the pH = 12.0 and allowed to stay for 20 minutes. After staying for 20 minutes, it was transferred to a second reaction tank (3.0 L) arranged in series with the first reaction tank and allowed to stay for 100 minutes. After 100 minutes, the pH of the second reactor dropped to 11.5. The eluted TOC was 110 mg · TOC / g · SS.

(Comparative Example 1)
Activated sludge (MLSS: 10000 mg / L) was introduced into the reaction vessel (10.8 L) at a flow rate of 30 mL / min, and at a temperature of 20 ° C., an aqueous NaOH solution (30 mM) and a surfactant (50 mg / L, Sepia D200: Organo The product was allowed to stay for 6 hours while maintaining pH = 11.1. After 6 hours, the eluted TOC was 102 mg · TOC / g · SS. Compared with Comparative Example 1, Experimental Example 1 showed an elution effect equal to or higher than that of 1/3.

(Experimental example 2)
Activated sludge (MLSS: about 10000 mg / L) was introduced into the sludge solubilization tank, and at a temperature of 20 ° C., a 25% NaOH aqueous solution was added to adjust the pH to 12.0 (only the pH was adjusted initially). And then no adjustments). The elution TOC after NaOH addition was measured with a TOC meter (TOC-5000, manufactured by Shimadzu Corporation) for each elapsed time. The measurement results are shown in FIG. Moreover, the change of pH in the solubilization tank accompanying the elapsed time at this time is shown in FIG. It can be seen that the pH decreases with time.

(Comparative Example 2)
Activated sludge (MLSS: about 10,000 mg / L) was introduced into a sludge solubilization tank, and at a temperature of 20 ° C., a 25% NaOH aqueous solution was added to adjust the pH = 11.0 to be maintained for 6 hours. The total amount of the aqueous NaOH solution added after 6 hours was about 20% larger than the amount of the aqueous NaOH solution added initially in Experimental Example 2. The eluted TOC was measured every time elapsed since the first addition of NaOH. The measurement results are shown in FIG. Moreover, the change of pH in the solubilization tank accompanying the elapsed time at this time is shown in FIG. As is clear from FIG. 7, the amount of eluted TOC for each elapsed time was lower than that in Experimental Example 2 (72.0 after 2 hours and 72.0, after 6 hours passed). 98.0 vs. 110.0). From FIG. 8, the pH in the tank is kept substantially constant.

(Experimental example 3)
To activated sludge (MLSS: about 10000 mg / L), 25% NaOH aqueous solution was added at a temperature of 20 ° C., and adjusted to pH = 12.0 (only pH adjustment was performed at the initial stage, and no adjustment was made thereafter) ). After the adjustment, a 5-pass treatment was performed with a line mixer at a water supply pressure of 2.0 kgf / cm ^{2 and the} mixture was introduced into a sludge solubilization tank. The eluted TOC after adding NaOH was measured at each elapsed time. The measurement results are shown in FIG. As is clear from FIG. 9, the amount of elution TOC immediately after the line mixer treatment is higher than that of Experimental Example 2 (initial elution TOC: 3.0 vs. 90.0). In addition, even after the lapse of 6 hours, Ri your higher against Experimental Example 2, the effect of the line mixer has emerged.

  The present invention provides a treatment apparatus and treatment method for organic wastewater such as industrial wastewater and domestic wastewater, particularly organic wastewater containing a large amount of organic matter such as sewage, septic tank, and food factory wastewater and relatively little inorganic matter. According to the present invention, it is possible to solubilize sludge in a very short time with low energy compared to the conventional method.

It is a figure which shows the processing flow of the conventional organic waste water treatment. It is a figure which shows the structure of one Embodiment of the organic waste water treatment equipment of this invention. It is a figure which shows the structure of one Embodiment of the solubilization processing apparatus in the organic waste water treatment apparatus of this invention. It is a figure which shows the structure of another embodiment of the solubilization processing apparatus in the organic waste water treatment apparatus of this invention. It is a figure which shows the structure of another embodiment of the solubilization processing apparatus in the organic waste water treatment apparatus of this invention. It is a figure which shows the relationship between the consumption of [OH < ^- >] and elution TOC in one Embodiment of this invention. It is a figure which shows the relationship between elapsed time and elution TOC in Experimental example 2 and Comparative example 2 of this invention. It is a figure which shows the relationship between elapsed time and pH in Experimental example 2 and Comparative example 2 of this invention. It is a figure which shows the relationship between elapsed time and elution TOC in Experimental example 2 and Experimental example 3 of this invention.

Explanation of symbols

  1,3 Organic wastewater treatment equipment, 10 Biological treatment tank, 12 Blower, 14 Precipitation tank, 16 Return sludge pump, 18 Solubilization treatment equipment, 20 Sludge transfer pump, 22 Rapid reaction tank (first reaction tank), 24 Stirrer, 26 pH sensor, 28 alkali supply path, 30 slow reaction tank (second reaction tank), 32 stirrer, 34 rapid stirrer.

Claims (6)

Biological treatment means for treating organic wastewater with microorganisms;
Solid-liquid separation means for subjecting the biologically treated water from the biological treatment means to solid-liquid separation, and discharging the treated water from which the solid content has been removed,
A separation sludge return means for returning the sludge separated by the solid-liquid separation means to the biological treatment means;
An organic wastewater treatment apparatus having
Furthermore, a solubilization means for receiving at least a part of the sludge separated by the solid-liquid separation means, adding an alkaline agent, and solubilizing;
Solubilized sludge return means for returning the sludge solubilized by the solubilizing means to the biological treatment means;
Have
The solubilizing means is composed of a first reaction tank and a second reaction tank following the first reaction tank, which are arranged in series.
In the first reaction tank, the alkaline agent is added to control the pH of the sludge within a range of 11.5 to 12.5, and the sludge is allowed to stay for 5 to 20 minutes, and then the second reaction. Transferred to the tank,
An organic wastewater treatment apparatus, wherein the sludge is treated by staying in the second reaction tank for a certain period of time. Biological treatment means for treating organic wastewater with microorganisms;
Solid-liquid separation means for subjecting the biologically treated water from the biological treatment means to solid-liquid separation, and discharging the treated water from which the solid content has been removed,
A separation sludge return means for returning the sludge separated by the solid-liquid separation means to the biological treatment means;
An organic wastewater treatment device having
Furthermore, a solubilization means for receiving at least a part of the sludge separated by the solid-liquid separation means, adding an alkaline agent, and solubilizing;
Solubilized sludge return means for returning the sludge solubilized by the solubilizing means to the biological treatment means;
Have
The solubilizing means comprises a static mixer having a plurality of blades arranged in a tube, and a reaction vessel following the static mixer.
After adding the alkaline agent to the sludge to make the pH in the range of 11.5 to 12.5, treating with the static mixer, and then transferring to the reaction vessel and retaining for a certain period of time. Wastewater treatment equipment. The organic waste water treatment apparatus according to claim 2 ,
The reaction tank is composed of a first reaction tank and a second reaction tank that are arranged in series, which are arranged in series.
In the first reaction tank, the sludge is treated in a pH range of 11.5 to 12.5, and then transferred to the second reaction tank.
An organic wastewater treatment apparatus, wherein the sludge is treated for a certain period of time in the second reaction tank. An organic wastewater treatment apparatus according to any one of claims 1 to 3 ,
In the said reaction tank or the said 2nd reaction tank, the residence time of the said sludge is 15 minutes- 100 minutes , The organic waste water treatment apparatus characterized by the above-mentioned. The organic waste water treatment apparatus according to any one of claims 1 to 4 ,
Furthermore, an acid addition means for adding an acid to the sludge solubilized by the solubilization means,
Acid-added sludge return means for returning the sludge added with acid by the acid addition means to the biological treatment means;
An organic wastewater treatment apparatus characterized by comprising: A biological treatment process for treating organic wastewater with microorganisms;
A solid-liquid separation step of subjecting the biologically treated water from the biological treatment step to solid-liquid separation, and discharging the treated water from which the solid content has been removed;
A separated sludge return step for returning the sludge separated in the solid-liquid separation step to the biological treatment means;
An organic wastewater treatment method comprising:
Furthermore, a solubilization step of adding an alkali agent to at least a part of the sludge separated in the solid-liquid separation step and solubilizing;
A solubilized sludge return step for returning the sludge solubilized in the solubilization step to the biological treatment step;
Have
The solubilization step includes:
Adding the alkaline agent, controlling the pH of the sludge to 11.5 to 12.5, retaining the sludge for 5 to 20 minutes, and then transferring the first step;
A second step in which the sludge is treated by retaining 3 to 5 times the residence time in the first step;
An organic wastewater treatment method comprising:

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