JP3389902B2 - Sludge treatment method and sludge treatment device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sludge treatment method and a sludge treatment apparatus for a water treatment process having a biological treatment step of wastewater.

[0002]

2. Description of the Related Art Conventionally, in the water treatment process of wastewater such as sewage and industrial wastewater, organic substances have been removed by biological treatment using microorganisms.

The sewage treatment plant of this water treatment process is constructed as shown in FIG. 7 and FIG. 8. FIG. 7 shows the whole construction and FIG. 8 shows a part thereof.

Then, the wastewater carried to the treatment plant 2 by the sewer pipe 1 is sent to the sedimentation basin 4 after the relatively large suspended matters such as wood chips and vinyl are removed in the sedimentation basin 3.
As a result, fine suspended solids are precipitated and separated.

Furthermore, the wastewater treated in the first settling tank 4 is sent to the aeration tank (aeration tank) 6 of the biological treatment tank 5, and this aeration tank 6 is returned from the inflowing wastewater and the final settling tank 7 in the latter stage. Mixed with the biological sludge (activated sludge), the microorganisms in the sludge are propagated by the air blown by the blower 8, and the organic matter contained in the wastewater is absorbed and adsorbed by the microorganisms to purify the wastewater.

Then, the sludge-containing liquid of the aeration tank 6 containing the activated sludge is sent to the final settling tank 7, the activated sludge is settled at the bottom of the settling tank 7, and the supernatant liquid purified by this settling is mixed with chlorine. After being sent to the pond 9 or ozone contact pond and sterilized, it is discharged to the river 10.

On the other hand, the biological sludge settled and accumulated in the final settling tank 7 is withdrawn from the bottom of the settling tank 7, and a part of it is returned to the aeration tank 6 via the returning sludge path 11 as returning sludge. The remaining excess sludge is first sent together with the settled sludge in the settling tank 4 to the sludge treatment thickening tank 12, and the thickening tank 1
After being concentrated by 2, it is mixed with a chemical in the mixing tank 13 and dehydrated by the dehydrator 4. Then, the solid matter remaining by this dehydration is incinerated and disposed of.

When biological nitrogen is removed by a biological treatment process, as shown in FIG. 9, instead of the biological treatment tank 5 shown in FIGS. 7 and 8, a denitrification tank 15 and a nitrification tank 16 are provided.
A biological treatment tank 5'comprising

The biological treatment tank 5'first nitrifies and denitrifies ammonia present in the inflowing wastewater from the settling basin 4, and at that time, organic carbon necessary for survival of denitrifying bacteria for performing denitrification treatment. In order to obtain the source from the inflowing wastewater, the denitrification tank 15 is provided in front of the nitrification tank 16, and the organic matter of the inflowing wastewater before nitrification is given to the denitrifying bacteria.

Then, the wastewater passing through the denitrification tank 15 is sent to the nitrification tank 16 for nitrification treatment, and the circulating water of the nitrification solution is returned to the denitrification tank 15 via the circulation path 17, denitrification treatment and purified. The sludge-containing liquid is sent to the final settling tank 7 via the nitrification tank 16.

At this time, a part of the sludge withdrawn from the bottom of the final settling basin 7 is returned to the denitrification tank 15 from the return sludge passage 11 'as return sludge, and the remaining sludge is unnecessary excess sludge as shown in FIG. 12 and is processed as described above.

[0012]

In the conventional sludge treatment at a sewage treatment plant or the like, the sludge withdrawn from the final settling tank 7 is divided into return sludge and excess sludge, and the excess sludge is dehydrated and incinerated. Since a large amount of excess sludge is generated, the equipment cost and operating cost for sludge treatment are high, and the amount of waste after dehydration and incineration is large, and the disposal cost is high. There is a problem.

When the biological treatment tank 5'of FIG. 9 is provided to remove biological nitrogen, not only the sludge treatment thereafter has the same problems as described above, but also the organic carbon source in the inflowing wastewater. May vary depending on the season and time of day, and there may be a shortage of organic carbon sources, and it is costly and other problems to eliminate this shortfall by adding methanol.

It is an object of the present invention to solubilize biological sludge very easily and inexpensively and efficiently, reduce excess sludge, and eliminate the shortage of organic carbon source for biological nitrogen removal.

[0015]

In order to solve the above-mentioned problems, the sludge treatment method according to claim 1 is a sludge treatment method of a water treatment process having a biological treatment step of wastewater,
It comprises a step of subjecting biological sludge generated in the biological treatment step to AC electrolysis and addition of hydrogen peroxide.

When the biological sludge is subjected to a combined treatment of alternating current electrolysis and addition of hydrogen peroxide, the sludge can be easily and efficiently solubilized at low cost.

Focusing on this solubilization, in the sludge treatment method of the second aspect, the biological sludge is solubilized by the steps of performing alternating current electrolysis and adding hydrogen peroxide to reduce excess sludge.

Therefore, in this case, the above-mentioned solubilization causes the biological sludge to be melted and the remaining amount thereof to be greatly reduced, whereby the volume and the volume of the excess sludge can be reduced, and the excess sludge can be greatly reduced at a simple and low cost. Will be reduced.

The sludge treatment method according to the third aspect of the present invention enables biological sludge to be removed by a step of subjecting wastewater to biological nitrogen removal by a biological treatment step, and performing electrolysis of alternating current and addition of hydrogen peroxide. The sludge-containing liquid after the solubilization treatment is returned to the biological treatment step as an organic carbon source.

Therefore, in this case, when biological nitrogen removal is performed as a biological treatment, the above-mentioned solubilization causes
Since the biological sludge becomes a sludge-containing liquid containing a large amount of soluble organic substances that serve as an organic carbon source, it is possible to prevent the organic carbon source from being insufficient by returning the contained liquid to the denitrification tank.

Next, the sludge treatment apparatus according to claim 4 solubilizes the biological sludge by subjecting the biological sludge generated in the biological treatment of the biological treatment tank to electrolysis of alternating current and addition of hydrogen peroxide. A sludge treatment tank for treatment and a return path for returning the sludge-containing liquid after treatment in the sludge treatment tank to the biological treatment tank are provided.

Therefore, the biological sludge after the treatment in the biological treatment tank is subjected to the above-mentioned solubilization treatment in the sludge treatment tank, and the sludge-containing liquid after the treatment in the sludge processing tank is biologically treated through the return path. It is possible to provide a concrete sludge treatment device which is returned to the tank and realizes the treatment method of claim 2.

Further, the sludge treatment device of claim 5 is provided with a denitrification tank for biological nitrogen removal of the inflowing wastewater as a biological treatment tank, and the sludge-containing liquid of the sludge treatment tank is returned to the denitrification tank as an organic carbon source. Provide a return route.

Therefore, in this case, the sludge-containing liquid produced by the solubilization of the sludge treatment tank is returned to the denitrification tank through the return path, and a specific sludge treatment device for realizing the treatment method of claim 3 is provided. it can.

[0025]

1 is a block diagram of an embodiment of the present invention.
~ It demonstrates with reference to FIG. (First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the configuration of a sludge treatment device for reducing excess sludge. In FIG. 1, the same reference numerals as those in FIGS. 7 and 8 indicate the same or corresponding parts.

In FIG. 1, the surplus withdrawal sludge that has not been used for returning sludge out of the biological sludge withdrawn from the final settling tank 7 is sent to the sludge treatment tank 18.

The sludge treatment tank 18 is provided, for example, as the concentration tank 12 of FIG. 7 and is constructed as shown in FIG.

In the sludge treatment tank 18, a pair of metal electrodes 20a and 20b are provided in the biological sludge 19 in the tank, and an AC power source 21 is provided between the metal electrodes 20a and 20b.
Is applied to subject the sludge 19 to AC electrolysis.

Simultaneously with this AC electrolysis, hydrogen peroxide (H ₂ O ₂ ) 22 is added to the sludge treatment tank 18 and added to the sludge 19.

At this time, in the sludge treatment tank 18, the sludge particles are floated and concentrated in the bubbles of hydrogen gas, oxygen gas and added hydrogen peroxide generated from the electrodes 20a and 20b, and are floated and concentrated. The sludge is directly heated by the electric power from the sludge, and the oxidative decomposition of the sludge is caused by these actions.

Due to the synergistic effect of these actions, the sludge 19 in the tank is effectively solubilized and a part of it is melted, and the sludge-containing liquid generated by this solubilization treatment flows through the return path 23. It is returned to the biological treatment tank 5 through the biological treatment sludge, and the biological sludge is biologically treated again.

The sludge left unsolubilized is efficiently dehydrated without being heated by an external heat source.

Therefore, the volume and volume of the excess sludge that is incinerated from the sludge treatment tank 18 through the mixing tank 13 and the dehydrator 14 shown in FIG. 7 are reduced, and the excess sludge that needs to be incinerated is greatly reduced. Reduction is achieved.

There is a method using ozone as one of similar techniques for reducing the volume of surplus sludge, but in the case of the present invention, since ozone is not generated, the reduction of surplus sludge can be realized easily and inexpensively. .

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the configuration of a sludge treatment device when biological nitrogen removal is performed by the same process as in FIG. 9, and in FIG.
The same reference numerals as those in FIG. 2 indicate the same or corresponding ones.

Then, also in the process of FIG.
A sludge treatment tank 18 'having the same configuration as that of the sludge treatment tank 18 shown in FIGS. 1 and 2 is provided, and the inside of the treatment tank 18 is subjected to electrolysis of alternating current and addition of hydrogen peroxide in the treatment tank 18'. The biological sludge extracted from the final settling basin 7 is solubilized based on the same action as the above.

The sludge-containing liquid produced by this solubilization has a high organic matter concentration and contains an organic carbon source at a high concentration.

The sludge-containing liquid containing a high concentration of this organic carbon source passes through the return path 23 'and the denitrification tank 1 of the biological treatment tank 5'.
Since it is returned to No. 5, the nitrification liquid returned from the nitrification tank 16 through the circulation path 17 is sufficiently denitrified regardless of the state of the inflowing wastewater and without a shortage of the organic carbon source.

By the way, the residual sludge left unsolubilized in the sludge treatment tank 18 'is greatly reduced as in the case of the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. 4, the same reference numerals as those in FIG. 3 indicate the same or corresponding ones, and in this embodiment, a high concentration organic carbon source is supplied from the sludge treatment tank 18 ′ to the denitrification tank 15 via the return path 23 ′. Paying attention to the fact that the solution containing is returned, a biological treatment tank 5 ″ is provided instead of the biological treatment tank 5 ′ in FIG.

This treatment tank 5 "is formed by providing a nitrification tank 16 in the first stage and a denitrification tank 15 in the subsequent stage, and the nitrification process and the denitrification process are reversed before and after the treatment tank 5 '. Since the treatment and the denitrification treatment are sequentially performed, the circulation path 17 in FIG.
Can be omitted, and the configuration can be simplified and the cost can be reduced.

Even in this form, the sludge-containing liquid containing the high-concentration organic carbon source in the sludge treatment tank 18 'is returned to the denitrification tank 15, so that the same effect as the second embodiment can be obtained. Of course.

[0043]

EXAMPLE Next, by carrying out the batch system under the following conditions (i) to (iv), in the sludge treatment tanks 18 and 18 ', the effect of reducing and solubilizing excess sludge described below can be obtained. Was given. Treatment conditions (i) Sludge treatment tanks 18 and 18 'are formed with a 50 ml beaker, and 30 ml of excess sludge from the sewage treatment plant is added to this beaker.
I put it in. (Ii) The power supply condition of the AC power supply 21 is 50 to 100 V (60
Hz), 1 A or less, and the metal electrodes 20a and 20b were made of iron. (Iii) As hydrogen peroxide 22, 6 ml of a 3 w / v% commercially available oxidol solution was added. (Iv) The processing time was about 25 minutes.

Then, under the above conditions, the sludge is subjected to AC electrolysis and addition of hydrogen peroxide for about 25 minutes,
When the sludge-containing liquid after treatment was subjected to solid-liquid separation with a centrifuge, the soluble organic matter concentration (DOC) in the supernatant liquid was 25 mg /
L was increased to 866 mg / L (about 35 times), and it was confirmed that the sludge was solubilized, and at the same time, the solid content volume was about 1/3.
The volume has been reduced to.

Further, the fact that the above effects are caused by the electrolysis of alternating current of the present invention and the addition of hydrogen peroxide is confirmed by the same comparative execution as the above batch system under the following conditions. It was

That is, under the following conditions, when no treatment is applied (in the case of sludge before treatment) [untreated], when AC electrolysis of the present invention and addition of hydrogen peroxide are applied [AC + H] ₂ O ₂ ], when only AC electrolysis is applied [AC alone], when only hydrogen peroxide is added [H
₂ O ₂ alone], when only DC electrolysis is applied [DC alone], and when heat is applied [heat alone], the sludge-containing liquid after treatment is subjected to solid-liquid separation, and the volume reduction rate, weight reduction rate and When the amount of eluted organic carbon was measured, the results shown in Table 1 were obtained.

Treatment conditions (i) The sludge to be treated was surplus sludge (50 ml) from the sewage treatment plant. (Ii) Energization condition of the AC power supply 21 is 100 V, 013 to
It was 0.43A. (Iii) The metal electrodes 20a and 20b are iron electrodes. (Iv) In (AC + H ₂ O ₂ ) and (H ₂ O ₂ alone),
As hydrogen peroxide, 10 ml of a 3 w / v% commercial oxidol solution was added. (V) The processing time was 20 minutes.

[0048]

[Table 1]

In Table 1, "Liquid" and "Solid" indicate the supernatant and solid matter of the centrifuge, respectively, and "DOC" is 1
It is the amount of soluble organic carbon in liter (1 L) of the supernatant.

Further, "amount of eluted organic carbon" in the same table
Indicates the amount of organic carbon per 50 ml of the sludge to be treated, which is eluted from the solid matter in the excess sludge by the treatment, and its calculation formula is as follows.

Amount of organic carbon eluted = (DOC of supernatant after treatment) × (volume of supernatant after treatment)-(DOC of supernatant before treatment) × (volume of supernatant before treatment)

Further, the graph of FIG. 5 was obtained from the volume reduction rate and the weight reduction rate of the same table, and the graph of FIG. 6 was obtained from the eluted organic carbon amount.

In FIG. 5, two solid columns a,
In b, the solid column a on the left side shows the volume reduction rate, and the solid column b on the right side shows the weight reduction rate.

From Table 1 and FIGS. 5 and 6, the sludge is extremely effectively solubilized only by the electrolysis of the alternating current and the addition of hydrogen peroxide according to the present invention, and the excess sludge is greatly reduced. It was confirmed that the amount of organic carbon was reduced and the amount of organic carbon in the contained liquid was significantly increased.

By the way, it goes without saying that the frequency and voltage of the AC power supply 21, the amount of hydrogen peroxide added, and the like may be appropriately set according to the processing scale and the like.

The present invention can be applied to various water treatment processes having biological treatment steps.

[0057]

The present invention has the following effects. First, in the case of the sludge treatment method of the present invention according to claim 1, since the biological sludge is subjected to a combined treatment of alternating current electrolysis and addition of hydrogen peroxide, the sludge can be solubilized easily, inexpensively and efficiently. be able to.

Further, in the case of the sludge treatment method of the present invention according to claim 2, since the biological sludge is melted by the above-mentioned solubilization and the remaining amount is greatly reduced, the volume and the volume of the excess sludge are reduced. As a result, excess sludge can be significantly reduced easily and inexpensively.

Further, in the case of the sludge treatment method of the present invention according to claim 3, the biological sludge becomes an organic carbon source due to the solubilization when biological nitrogen removal is performed as a biological treatment. Since the sludge-containing liquid contains a large amount of soluble organic substances, the contained liquid can be returned to the denitrification tank to prevent the shortage of the organic carbon source.

Next, in the case of the sludge treatment apparatus of the present invention according to claim 4, the sludge treatment tank 18 performs the above-mentioned solubilization treatment on the biological sludge after the treatment in the biological treatment tank. Since the sludge-containing liquid after the treatment of 18 is returned to the biological treatment tank 5 through the return path 23 thereof, it is possible to provide a concrete sludge treatment device which realizes the treatment method of claim 2.

Further, in the case of the sludge treatment apparatus of the present invention according to claim 5, the sludge-containing liquid produced by the solubilization of the sludge treatment tank 18 'is returned to the denitrification tank 15 via the return passage 23'. It is possible to provide a concrete sludge treatment device that realizes the treatment method of claim 3.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a structural explanatory view of the sludge treatment tank of FIG.

FIG. 3 is a process explanatory diagram of the second embodiment of the present invention.

FIG. 4 is a process explanatory diagram of the third embodiment of the present invention.

FIG. 5 is an actual measurement diagram of a volume reduction rate and a weight reduction rate of sludge according to an example of the present invention.

FIG. 6 is an actual measurement chart of the amount of organic carbon in a solubilized sludge-containing liquid according to an example of the present invention.

FIG. 7 is a process explanatory diagram of a sewage treatment channel.

FIG. 8 is a process explanatory diagram of a conventional example.

FIG. 9 is another process explanatory view of the conventional example.

[Explanation of symbols]

5,5 ', 5 "biological treatment tank 15 denitrification tank 16 Nitrification tank 18,18 'Sludge treatment tank 21 AC power supply 22 Hydrogen peroxide 23,23 'Return path

Claims (5)

(57) [Claims] 1. A sludge treatment method of a water treatment process having a biological treatment step of wastewater, comprising a step of subjecting biological sludge generated in the biological treatment step to AC electrolysis and addition of hydrogen peroxide. A sludge treatment method characterized by that. 2. The sludge treatment method according to claim 1, wherein the biological sludge is solubilized by a step of performing alternating current electrolysis and addition of hydrogen peroxide to reduce excess sludge. 3. A biological sludge is subjected to biological nitrogen removal by a biological treatment step, and biological sludge is solubilized by a step of subjecting alternating current to electrolysis and addition of hydrogen peroxide to contain sludge after treatment. The sludge treatment method according to claim 1, wherein the liquid is returned to the biological treatment step as an organic carbon source. 4. A sludge treatment device for a water treatment process for biologically treating inflowing wastewater by a biological treatment tank, wherein alternating current electrolysis and addition of hydrogen peroxide are performed on biological sludge generated by the biological treatment. A sludge treatment device, comprising: a sludge treatment tank for subjecting the biological sludge to a solubilization treatment; and a return path for returning the sludge-containing liquid after the treatment in the sludge treatment tank to the biological treatment tank. 5. A biological treatment tank comprising a denitrification tank for biologically removing nitrogen from inflowing wastewater, and a return passage for returning the sludge-containing liquid of the sludge treatment tank to the denitrification tank as an organic carbon source. The sludge treatment device according to claim 4.