JPH11179391A - Method and apparatus for treating organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for aerobic biotreatment of org. waste water which hardly generates excess sludge by a simple treating means. SOLUTION: In a method wherein after an org. waste water 5 is treated by an aerobic biotreatment 1, a part of the sludge obtd. is treated by solubilization treatment 3 and is returned to the aerobic biotreatment process 1 and is treated there, the solubilization treatment 3 is performed either by a pulse discharge treatment process 4 or by an acidic oxidation treatment process using an acidic oxidizer and an alkali treatment process using an alkali agent and the pulse discharge treatment process and as the acidic oxidizer and the alkali agent, an acidic oxidized water and an alkaline water obtd. by membrane electrolysis of a salt water can be used and the acidic oxidation treatment process and the alkali treatment process are provided in parallel or in series and they comprises respectively of a single or a plurality of processes, and a pulse discharge treatment process can be provided before or after these series of acid and alkali treatment processes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating organic wastewater, and more particularly to a method for solubilizing excess sludge obtained by treating organic wastewater with an aerobic organism.

[0002]

2. Description of the Related Art Conventionally, the biggest problem of aerobic biological treatment of organic wastewater (activated sludge method, biological nitrification denitrification method, etc.) does not exist in the process of purifying water, but rather sludge treatment. In the process. That is, the aerobic biological treatment method,
The biggest problem is that the amount of surplus activated sludge generated is very large. Excess activated sludge is currently landfilled or incinerated after dehydration, but requires a great deal of cost and equipment. The amount of surplus sludge generated by the conventional activated sludge method can be reduced to 0.6 to
It is well known that it is about 0.8 (kgSS / kgBOD).

[0003] In addition, excess sludge is hardly dehydrated in quality, so that sludge treatment becomes more and more difficult. In order to reduce such excess sludge, a conventional method of solubilizing excess sludge is to add an alkaline agent and treat it (see JP-A-2-227190). (Japanese Unexamined Patent Publication No. 2-2)
93095) is known, but even with these treatment methods, although the excess sludge is reduced to some extent, a further volume reduction method has been desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aerobic biological treatment method for organic sewage in which excess sludge is hardly generated by a simple treatment means in view of the above prior art.

[0005]

In order to solve the above-mentioned problems, according to the present invention, an organic sewage is subjected to an aerobic biological treatment.
In the method of solubilizing a part of the obtained sludge and returning it to the aerobic biological treatment step, the solubilization treatment is performed by a pulse discharge treatment. Also,
In the present invention, the organic sewage is subjected to an aerobic biological treatment, and then a part of the obtained sludge is solubilized and returned to the aerobic biological treatment step, wherein the acidic oxidizing agent is treated with an acidic oxidizing agent. The acid oxidation treatment step, the alkali treatment step using an alkali agent, and the pulse discharge treatment step are performed. In the treatment method, the acidic oxidizing agent and the alkaline agent used are preferably acidic oxidizing water and alkaline water obtained by subjecting salt water to diaphragm electrolysis.

The acidic oxidation treatment step and the alkali treatment step are provided in parallel or in series, each consisting of one or more steps, and before or after the series of acid / alkali treatment steps. Can be provided. In the acid oxidation treatment step and the alkali treatment step comprising the single or plural steps, the pulse discharge treatment step may be introduced after the single or plural alkali treatment steps, and the acid oxidation treatment step comprising the plural steps In the step and the alkali treatment step, it is preferable to introduce the entire amount of the acidic oxidizing agent or the alkaline agent into the step preceding the step, and to distribute and introduce the sludge to be treated into the steps in each step. Before returning to the aerobic biological treatment step, the solubilized sludge may be provided with a pre-aeration step to perform aeration treatment to volatilize and remove residual chlorine. Degradability is further improved by returning to the step of solubilizing treatment.

[0007] The sludge treated in the acid oxidation treatment step and the alkali treatment step in the solubilization treatment is returned to neutrality by mixing them. However, if the pH is out of the neutral range, the acid sludge treatment is carried out. It is better to return to neutrality using water or alkaline water. Further, in the present invention, in an organic sewage treatment apparatus having an aerobic biological treatment tank and a sludge separation device sequentially provided with a solubilization means for solubilizing a part of the separated sludge, the solubilization means is a pulse discharge means. The solubilized sludge by the pulse discharge is connected so as to be introduced into the aerobic biological treatment tank. Further, in an organic sewage treatment apparatus having an aerobic biological treatment tank and a sludge separating device sequentially provided with a solubilizing means for solubilizing a part of the separated sludge, the solubilizing means may use an acidic oxidizing agent. It comprises a treatment tank, an alkaline treatment tank using an alkali agent, and pulse discharge means, and is connected so as to introduce the solubilized sludge into the aerobic biological treatment tank.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a flow of a sludge volume reduction process of the treatment method of the present invention. In FIG. 1, an organic wastewater 5 is treated in an aerobic biological treatment tank 1, and solid-liquid separated in a sedimentation tank 2 to be treated in a wastewater treatment step of obtaining treated water 6 and sludge 7, 8. Is recycled to the biological treatment tank 1 as returned sludge 7, and the other part 8 is introduced into the solubilization step 3 to solubilize and decompose the sludge. To biodegrade the soluble organic matter and sludge.

The sludge 8 introduced into the solubilization step 3 is subjected to a solubilization treatment by receiving a shock wave by a pulse discharge 4 generated from a pulse power source. The operating conditions for the pulse discharge 4 are a pulse voltage of 60 kV or less, a pulse current of 25 kA or less, a pulse width of 0.1 to 400 microseconds, and a pulse frequency of 100 Hz or less. The mode of the pulse discharge treatment is, as shown in FIG. 1, a pulse discharge generated from a pulse discharge end provided at an appropriate interval perpendicularly or parallel to the flow path of the sludge 8, and is shown in FIG. 2. As described above, a method in which the sludge 8 is pump-circulated in a tank for storing the sludge 8 and a pulse discharge end is inserted into the circulation pipe may be used. Since it is unsteady high pressure, to prevent creeping discharge,
It is necessary to incorporate a rib into an insulator in a portion existing in the atmosphere, but the shape of the pulse discharge end such as a needle, a hemisphere, and a flat plate is not limited thereto.

Next, FIG. 3 shows an example of a flow of a sludge volume reduction process using the acid / alkali treatment step of the treatment method of the present invention. In FIG. 3, the other part 8 of the generated sludge is introduced into a solubilization step 3 in which a pulse discharge treatment step and an acid / alkali treatment step are used in combination, solubilized and decomposed, and then drainage treatment is performed. Return to the biological treatment tank 1 of the process 9
Biodegradation of soluble organic matter and sludge. The sludge 8 introduced into the solubilization step 3 is introduced into a plurality (two tanks) of alkali treatment steps 15 and 15 ′ and oxidation treatment steps 14 and 14 ′, which are provided in parallel. Is brought into contact with alkaline water 24 and acidic oxidized water 23 obtained by subjecting the salt water to diaphragm electrolysis treatment. In the alkali treatment step, a pulse discharge treatment 4 is introduced after 15 'and before mixing with the sludge after the oxidation treatment step.

The operating conditions of the pulse discharge are as follows.
kV or less, pulse current 25 kA or less, pulse interval 0.1
４００400 microseconds and the number of pulses is 100 Hz or less. The mode of the pulse discharge process is as shown in FIG.
This is due to pulse discharge generated from a pulse discharge end provided at an appropriate interval perpendicularly or parallel to the flow path of sludge a. As shown in FIG. 2, sludge a is pumped in a tank for storing sludge a. It may be a method of circulating and inserting a pulse discharge end into the circulation pipe. Since it is an unsteady high pressure, it is necessary to incorporate a rib in the insulating part at the pulse discharge end to prevent creeping discharge, but the shape of the pulse discharge end such as a needle shape, a hemispherical shape, a flat plate shape is not limited. .

In the membrane electrolysis of salt water, an anode chamber 17 having an anode 19 and a cathode chamber 20 having a cathode 18 are formed by a diaphragm 21.
This is performed using a diaphragm electrolysis device 16 partitioned by the above-described method, and salt water 22 is introduced into an anode chamber 17 and a cathode chamber 18 of the device 16. In the anode chamber 17, the H ⁺ generated at the anode, it becomes acidic, Cl in saline ^- than chlorine-based oxidizing agent (HClO,
Cl _2, Cl · etc.) occurs and obtain an acidic oxide water 23, the cathode compartment 18, the cathode in OH ^- is the generated alkaline, to obtain alkaline water 24, oxidation vessel 1 acidic oxide water 23
4, alkaline water 24 is introduced into the alkaline tank 15 and used for solubilization. In addition, the alkali treatment step and the oxidation treatment step are each provided with a treatment tank in two stages, and a part of the sludges 12 and 13 introduced into each of the treatment tanks is provided in the second alkali tank 1.
5 'and the second oxidation tank 14' are separately introduced.
Then, after the second alkali treatment tank 15 ', a pulse discharge treatment is performed.

Next, the operation of these tanks will be described. First, the first alkali tank reacts the sludge with the alkali generated by the membrane electrolysis, and performs a solubilization treatment of the sludge by destruction of the sludge cells and elution of the intracellular solution under strong alkali conditions,
The second alkaline tank utilizes excess alkali from the first alkaline tank to promote sludge volume reduction. Furthermore, by performing the pulse discharge treatment, the sludge cells that have not been sufficiently destroyed in the first alkaline tank are destroyed, thereby further reducing the volume of the sludge. Next, the first oxidation tank reacts the acid and oxidizing agent generated by the membrane electrolysis with the sludge to perform oxidative decomposition treatment of the sludge cells under strong acid conditions.
The excess acid and oxidizing agent from the first oxidation tank are used to promote oxidative decomposition of sludge. In FIG. 3, the alkali treatment and the acidic oxidation treatment are performed in two lines each in parallel. However, each treatment may be performed in a single tank (only the first alkali tank and the first oxidation tank), or in each case. It may be performed in a series of tanks or more.

FIG. 4 shows another schematic flow chart of the processing method of the present invention. In FIG. 4, a pulse discharge treatment step 4 is provided after a series of acid / alkali treatments including an acid oxidation treatment step and an alkali treatment step. In FIG. 5, a series of acid / alkali treatment steps including an acid oxidation treatment step and an alkali step are provided after the pulse discharge treatment step 4. In FIG. 6, the organic wastewater 5 is introduced into the adjusting tank 11 and aerated before entering the biological treatment tank 1. Also,
The solubilized sludge 9 from the solubilization step 3 is introduced into the biological treatment tank 1 after being subjected to aeration treatment in the pre-aeration tank 10 to volatilize and remove residual chlorine in the electrolytic water used for the solubilization treatment. Note that instead of the pre-aeration tank 10, the solubilized sludge 9 was
And aeration treatment to remove residual chlorine. FIG. 7 shows a schematic flow chart for circulating a part of the solubilized sludge 9 to the solubilizing step 3. In this way, by circulating a part of the solubilized sludge, the sludge decomposability can be further improved.

[0015]

The present invention will be described below in more detail with reference to examples. Example 1 Two sets of an experimental apparatus (Run 1) shown in the processing flow of FIG. 1 and an experimental apparatus (Run 2) in which the solubilization step was removed from the flow were provided, and the quality of treated water and the amount of generated sludge were compared. R
In un1, a four-fold amount of excess sludge was introduced into the solubilization step, and a pulse discharge treatment was performed at a voltage of 20 kV, a current of 1 kA, a pulse width of 125 microseconds, and a pulse frequency of 20 Hz. In the experiment, wastewater from B food company was used as raw water (pH 7.
2, BOD 800mg / L, COD Mn 42
(0 mg / liter, SS 95 mg / liter), and run conditions of Run 1 and Run 2 were the same except that a solubilization step was provided.

Table 1 shows the properties of the sludge introduced and the sludge treated by the pulse discharge.

[Table 1]

Table 2 shows the experimental results. From Table 2, it was found that Run1 incorporating the solubilization step produced significantly less sludge than Run2, and there was almost no difference in treated water quality.

[Table 2]

Example 2 The experimental system (Run 3) shown in the processing flow of FIG. 3 and the experimental system (Run 4) in which the solubilization step was removed from the flow were provided to compare the treated water quality and the amount of sludge generated. did. R
In un3, the amount of sludge to be introduced into the solubilization step is four times the amount of excess sludge, and the amount of sludge is 2 times in the alkali treatment step.
量 amount and １ ／ amount were introduced into the oxidation treatment step, respectively. In the second alkaline tank, １ ／ of the amount of sludge introduced into the alkali treatment step was introduced, and in the second oxidation tank, １ ／ of the amount of sludge introduced into the oxidation treatment step was introduced. The residence time in each treatment tank was 4 hours. In this embodiment, a salt solution having a salt concentration of 1/2 of seawater was used as the salt water. The amount of saline used was the same as the amount of excess sludge passed through the electrolytic treatment tank. The pulse discharge treatment after the alkali treatment step is performed at a voltage of 20 kV, a current of 1 kA, and a pulse interval of 1 kA.
25 microseconds, pulse frequency 20 Hz.

Tables 3 and 4 show the conditions of the diaphragm electrolysis treatment and the properties of the obtained electrolyzed water (alkaline water and acidic oxidized water). In the experiment, wastewater from B food company was used as raw water (pH 7.
2, BOD 800mg / L, COD Mn 4
The run conditions of Run 3 and Run 4 were the same except that a solubilization step was provided.

[Table 3]

[Table 4]

Table 5 shows the properties of the introduced sludge and the solubilized sludge.

[Table 5]

Table 6 shows the experimental results. From Table 6, it can be seen that Run3 incorporating the solubilization step including the pulse discharge treatment step was used.
Showed significantly less sludge generation than Run4, and there was almost no difference in treated water quality.

[Table 6]

Example 3 The experimental system (Run 5) shown in the processing flow of FIG. 5 and the experimental system (Run 6) in which the solubilization step was removed from the flow were provided to compare the quality of treated water and the amount of sludge generated. did. R
In un5, the amount of sludge to be introduced into the solubilization step is four times the amount of excess sludge. First, a voltage of 20 kV and a current of 1.
2 kA, pulse interval 100 microseconds, number of pulses 20
A pulse discharge treatment was performed at Hz, and 2/3 of the amount was introduced into the alkali treatment step, and 1/3 of the amount was introduced into the oxidation treatment step. In the second alkaline tank, １ ／ of the amount of sludge introduced into the alkali treatment step was introduced, and in the second oxidation tank, １ ／ of the amount of sludge introduced into the oxidation treatment step was introduced. The residence time in each treatment tank was 4 hours.
In this embodiment, a salt solution having a salt concentration of 1/2 of seawater was used as the salt water. The amount of saline used was the same as the amount of excess sludge passed through the electrolytic treatment tank.

Tables 7 and 8 show the conditions of the diaphragm electrolysis treatment and the properties of the obtained electrolyzed water (alkaline water and acidic oxidized water). In the experiment, wastewater from B food company was used as raw water (pH 7.
2, BOD 800mg / L, COD Mn 4
The run conditions of Run 5 and Run 6 were the same except that a solubilization step was provided.

[Table 7]

[Table 8]

Table 9 shows the properties of the introduced sludge and the solubilized sludge.

[Table 9]

Table 10 shows the experimental results. From Table 10, it can be seen that Run incorporating the solubilization step including the pulse discharge treatment step was incorporated.
Sample No. 5 produced much less sludge than Run No. 6, and there was almost no difference in treated water quality.

[Table 10]

[0026]

According to the present invention, surplus sludge can be almost completely decomposed by pulse discharge treatment, and almost no sludge is generated. Further, according to the present invention, the treatment using the pulse discharge treatment in combination with the acidic oxidizing agent and the alkali agent further promotes the solubilization treatment, can almost completely decompose excess sludge, hardly generates sludge, By using acidic oxidized water and alkaline water obtained from the membrane treatment of salt water as the oxidizing agent and the alkaline agent, it can be easily obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a flow diagram of a sludge volume reduction process used in the treatment method of the present invention.

FIG. 2 is an explanatory view showing another method of the pulse discharge processing.

FIG. 3 is a flow chart of another sludge volume reduction process used in the treatment method of the present invention.

FIG. 4 is a flow chart of another sludge reduction process used in the treatment method of the present invention.

FIG. 5 is a flow chart of another sludge volume reduction process used in the treatment method of the present invention.

FIG. 6 is another schematic flow chart of the processing method of the present invention.

FIG. 7 is another schematic flow chart of the processing method of the present invention.

[Explanation of symbols]

1: aerobic biological treatment tank, 2: sedimentation tank, 3: solubilization step,
4: pulse discharge end, 5: organic wastewater, 6: treated water, 7:
Returned sludge, 8: excess sludge, 9: solubilized sludge, 10: pre-aeration tank, 11: conditioning tank, 12, 13: part of excess sludge, 1
4: 1st oxidation tank, 14 ': 2nd oxidation tank, 15: 1st alkali tank, 15': 2nd alkali tank, 16: diaphragm electrolysis apparatus, 17: anode chamber, 18: cathode chamber, 19: anode, 20:
Cathode, 21: diaphragm, 22: salt water, 23: acidic oxidized water, 2
4: Alkaline water

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Watanabe 4-2-1 Motofujisawa, Fujisawa City, Kanagawa Prefecture Inside Ebara Research Institute, Inc. No. 1 Inside EBARA Research Institute

Claims (12)

[Claims] 1. A method of treating an organic wastewater with an aerobic biological treatment and then solubilizing a part of the obtained sludge and returning the sludge to the aerobic biological treatment step, wherein the solubilizing treatment is a pulse discharge treatment. A method for treating organic wastewater, which is performed in a process. 2. A method of treating an organic sewage with an aerobic biological treatment and then solubilizing a part of the obtained sludge and returning the sludge to the aerobic biological treatment step, wherein the solubilizing treatment is performed with an acidic oxidizing agent. A method for treating organic sewage, comprising a step of performing an acidic oxidation treatment step using an organic solvent, an alkali treatment step using an alkali agent, and a pulse discharge treatment step. 3. The method for treating organic sewage according to claim 2, wherein the acidic oxidizing agent and the alkaline agent are acidic oxidized water and alkaline water obtained by subjecting salt water to diaphragm electrolysis. 4. The method according to claim 1, wherein the acid oxidation treatment step and the alkali treatment step are provided in parallel or in series, and a pulse discharge treatment step is provided before or after the series of acid / alkali treatment steps. The method for treating organic sewage according to claim 2 or 3. 5. The method according to claim 4, wherein the acidic oxidation treatment step and the alkali treatment step are provided in parallel, and the alkali treatment step and the pulse discharge treatment step are provided in series in this order. The method for treating organic sewage according to the above. 6. The method for treating organic sewage according to claim 4, wherein the acid oxidation treatment step and the alkali treatment step each comprise a plurality of steps. 7. The organic sewage according to claim 6, wherein in the acid oxidation treatment step and the alkali treatment step comprising the plurality of steps, a pulse discharge treatment step is introduced after the plurality of alkali treatment steps. Processing method. 8. In the acid oxidation treatment step and the alkali treatment step comprising the plurality of steps, the acid oxidizing agent or the alkali agent is introduced in its entirety into the preceding step, and the sludge to be treated is distributed to each step. The method for treating organic sewage according to claim 6, wherein the wastewater is introduced after being introduced. 9. The sludge subjected to solubilization treatment is subjected to an aeration treatment by providing a pre-aeration treatment before returning to the aerobic biological treatment treatment. Organic wastewater treatment method. 10. The organic wastewater treatment according to claim 1, wherein a part of the solubilized sludge is returned to the step of solubilization and treated again. Method. 11. An organic sewage treatment apparatus having an aerobic biological treatment tank and a sludge separation device sequentially provided with a solubilization means for solubilizing a part of the separated sludge, wherein the solubilization means is a pulse discharge means. An organic sewage treatment apparatus, wherein the apparatus is connected to introduce the solubilized sludge by the pulse discharge into the aerobic biological treatment tank. 12. An organic sewage treatment apparatus having an aerobic biological treatment tank and a sludge separation device sequentially provided with a solubilization means for solubilizing a part of the separated sludge, wherein the solubilization means uses an acidic oxidizing agent. An organic sewage treatment comprising an acidic oxidation treatment tank and an alkali treatment tank using an alkali agent, and a pulse discharge means, wherein the sludge solubilized is connected so as to be introduced into the aerobic biological treatment tank. apparatus.