JP4493371B2 - Concentration separation method of sludge - Google Patents

Description

The present invention relates to a method for concentrating and separating sludge in sewage, industrial wastewater, domestic wastewater and the like .

  Conventionally, as a method for concentrating and separating sludge, for example, a pressurized flotation separation method as shown in FIG. That is, a storage tank 42 for storing raw water is installed in the front stage of the floating separation tank 41, and the sludge is aggregated by adding a flocculant to the storage tank 42 and stirring. The levitation separation tank 41 is provided with a pressurizing system 43 that supplies a part of raw water under pressure.

  The pressurizing system 43 includes an air compressor (not shown), a pressurizing pump 44, an air dissolving tank 45, and a pressure reducing valve 46. After the air is pressurized and dissolved in raw water, the pressure is returned to normal pressure. The fine bubbles 47 deposited at this time are attached to the sludge particles in the floating separation tank 41 to perform the floating separation.

However, in the pressurized flotation separation method, since a large amount of air is pressurized and dissolved, there is a problem that a large-scale pressurizing device for obtaining high-pressure air is necessary.
As another method, as shown in FIG. 6, there is a method in which a submerged membrane separation device 50 is provided in a membrane separation tank 49 and a sludge storage tank 51 is installed in front of the membrane separation tank 49 (for example, Patent Document 1).

According to this, the sludge supplied to the membrane separation tank 49 from the sludge storage tank 51 is membrane-separated by the membrane separation apparatus 50, and the membrane permeated water and the concentrated sludge are discharged from the membrane separation tank 49.
However, in the sludge concentration and separation method using the immersion type membrane separation device 50, when the sludge concentration in the membrane separation tank 49 increases, the sludge adheres to the membrane surface of the membrane separation device 50, and the membrane surface is blocked. There is a problem that the concentration efficiency is lowered and the membrane must be frequently washed.
JP-A-8-323399

The present invention is capable of flotation separation without using a large-scale pressurization apparatus, and can reduce membrane clogging during membrane separation, and is an efficient and low-cost method for concentrating and separating sludge. The purpose is to provide .

In order to achieve the above object, the first invention is a method for concentrating and separating sludge using a membrane separation tank for separating sludge into a membrane and a floating separation tank for levitating and separating sludge,
A concentration step of separating and concentrating the sludge in the membrane separation tank while circulating the sludge between the membrane separation tank and the floating separation tank;
When the sludge in the two tanks is concentrated to a predetermined concentration, the circulation of the sludge between the two tanks is stopped, hydrogen peroxide is supplied into the floating separation tank to generate bubbles, and the rise of the bubbles A flotation separation step for flotation separation of sludge in the flotation separation tank;
And a liquid separation step of removing the highly concentrated sludge obtained by the above-described floating separation step from the inside of the floating separation tank .

  According to this, when the sludge is concentrated to a predetermined concentration by membrane separation, in order to start the flotation separation step, the sludge concentration in the membrane separation tank is lower than the predetermined concentration when performing the concentration step, The membrane is separated. Thereby, the quantity of the sludge adhering to a film surface reduces, and the obstruction | occlusion of a film surface reduces.

  Further, in the above-described levitation separation step, bubbles are generated by a chemical reaction by supplying hydrogen peroxide into the levitation separation tank, so that it is not necessary to generate bubbles using a large pressure device. In addition, since the sludge is concentrated to a predetermined concentration, the bubbles do not rise and deaerate alone, almost all the bubbles adhere to the solid matter in the sludge and rise with the solid matter, For this reason, the efficiency of floating separation improves. Furthermore, the inside of the floating separation tank becomes an oxidizing atmosphere due to the strong oxidizing power of hydrogen peroxide. Therefore, the polymer produced by the decay of organic sludge and the like is decomposed and dispersed in the oxidizing atmosphere, and bubbles are easily attached, so that the efficiency of flotation separation is further improved.

  Moreover, in the said liquid separation process, since the highly concentrated sludge obtained by the floating separation is removed from the inside of the floating separation tank, the sludge in the floating separation tank is kept at a low concentration. Thereby, when the said concentration process is performed subsequently, since sludge circulates and mixes between both tanks, the raise of the sludge density | concentration in both tanks is suppressed.

  In addition, since membrane separation and levitation separation are performed in separate tanks, sludge containing (attached) bubbles generated by hydrogen peroxide is prevented from adhering to the membrane separation device in the membrane separation tank. can do. Therefore, when the membrane separation is resumed, the sludge holding the bubbles does not become an obstacle to the membrane separation.

Further, according to the second invention, in the levitation separation step, after the hydrogen peroxide is supplied into the levitation separation tank, the inside of the levitation separation tank is agitated .

  According to the present invention, levitation separation is possible without using a large-scale pressurizing device, and it is possible to reduce membrane clogging during membrane separation, and sludge can be concentrated and separated efficiently and at low cost.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
1 is a sludge concentration and separation facility, and is provided with a concentration tank 2 for concentration and separation of sludge, and a storage tank 3 in the preceding stage of the concentration tank 2. In the concentration tank 2, an immersion type membrane separator 4 for filtering sludge is installed. Connected to the membrane separation device 4 is a separation water extraction pipe 5 for taking out the separation water that has passed through the membrane to the outside of the concentration tank 2 and discharging it. A suction pump 7 for performing suction filtration is connected to the separated water extraction pipe 5. In addition, an aeration apparatus 6 that blows air from below the membrane separation apparatus 4 is provided in the concentration tank 2.

Further, the concentration tank 2 is provided with a hydrogen peroxide supply system 9 for supplying hydrogen peroxide (H ₂ O ₂ ) for generating bubbles 8 for floating separation. The hydrogen peroxide supply system 9 includes a hydrogen peroxide tank 10 that stores hydrogen peroxide, and a hydrogen peroxide supply line 11 that supplies the hydrogen peroxide in the tank 10 to the lower part of the concentration tank 2. The pump 23 is provided in the pipe 11. In the concentration tank 2, a stirrer 12 for stirring the supplied hydrogen peroxide is provided.

  Further, a discharge pipe 15 is connected to the upper part of the concentration tank 2 to discharge the highly concentrated sludge obtained by floating separation and overflowed or scraped off and removed from the liquid surface to the concentrated sludge storage tank 14. Yes. Further, a flocculant adding device 22 for adding a flocculant into the storage tank 3 and a pH adjusting agent adding device 24 for adding a pH adjusting agent into the concentration tank 2 are provided.

  Further, the concentration separation facility 1 includes a dehydrator 16 that dehydrates highly concentrated sludge stored in the concentrated sludge storage tank 14, a filtrate storage tank 17 that stores filtrate discharged from the dehydrator 16, and a filter. A return pipe 18 for returning the filtrate in the liquid storage tank 17 to the storage tank 3 and a sludge receiving pipe 19 for receiving waste water containing sludge in the storage tank 3 in the concentration tank 2 are provided. Pumps 20 and 21 are connected to the return pipe 18 and the sludge receiving pipe 19, respectively.

Hereinafter, a method for concentration and separation of sludge using the concentration and separation facility 1 will be described.
The sludge concentration and separation method includes a concentration step A, a flotation separation step B, and a liquid separation step C. Details of each step A to C are as follows.

  (1) In the concentration step A, first, wastewater containing sludge in the storage tank 3 is received from the sludge receiving pipe 19 into the concentration tank 2, and the aeration apparatus 6 is operated to start aeration. To start filtration by the membrane separation device 4.

  (2) When the concentration step A is repeated a plurality of times, the sludge in the concentration tank 2 is gradually concentrated by membrane separation, and the sludge concentration in the concentration tank 2 is concentrated to a predetermined concentration (for example, 1.5%), Next, in the levitation separation step B, the suction pump 7 is stopped, the filtration by the membrane separation device 4 is stopped, the aeration by the aeration device 6 is stopped, and the hydrogen peroxide (liquid) in the hydrogen peroxide tank 10 is stopped. Is supplied to the lower part of the concentration tank 2 and stirred by the stirrer 12. As a result, hydrogen peroxide causes a chemical reaction to generate a large amount of bubbles 8 such as oxygen gas in the concentration tank 2, and the rising of the bubbles 8 causes the sludge in the concentration tank 2 to float and be separated. Highly concentrated sludge emerges.

  (3) Thereafter, in the liquid separation step C, the supply of hydrogen peroxide to the concentration tank 2 is stopped, the highly concentrated sludge is removed from the liquid surface by overflow or scraping, and the concentrated sludge storage tank is discharged from the discharge line 15. Drain to 14. In addition, after supplying the hydrogen peroxide into the concentration tank 2, the pH adjuster adding device 24 may add a pH adjuster into the concentration tank 2 to adjust the pH in the concentration tank 2.

(4) Thereafter, the process returns to the concentration step A.
According to the sludge concentration and separation method as described above, when the sludge in the concentration tank 2 is concentrated to a predetermined concentration by the membrane separation of the membrane separation device 4, the concentration step A by the membrane separation device 4 is stopped, and the floating separation step. In order to start B, when performing the concentration step A, membrane separation is performed in a state where the sludge concentration in the concentration tank 2 is lower than a predetermined concentration. Thereby, the quantity of the sludge adhering to the membrane surface of the membrane separator 4 decreases, the blockage | closure of a membrane surface reduces, and the frequency | count of a maintenance can be reduced. Further, in the concentration step A, air bubbles blown out from the aeration device 6 rise while contacting the membrane surface of the membrane separation device 4, so that the membrane surface is washed, thereby further reducing the membrane surface blockage. .

  Further, in the above-described levitation separation process B, since hydrogen peroxide is supplied into the concentration tank 2, a large amount of bubbles 8 such as oxygen gas are generated by a chemical reaction. Therefore, the bubbles 8 are formed using a large pressure device. There is no need to generate it. Further, when the sludge concentration in the concentration tank 2 is thin, the bubbles 8 may rise and be degassed alone. However, since the sludge is concentrated to a predetermined concentration, the bubbles 8 are independent. There is no rise and degassing, and almost all of the bubbles 8 adhere to the solid matter in the sludge and rise together with the solid matter, thereby improving the efficiency of flotation separation.

  Furthermore, the inside of the concentration tank 2 becomes an oxidizing atmosphere by the strong oxidizing power of hydrogen peroxide. Therefore, the inside of the concentration tank 2 is in an aerobic state and has a sludge reforming effect. In addition, when the sludge is organic sludge, the polymer produced by the decay of the organic sludge is decomposed and dispersed in the oxidizing atmosphere, and the bubbles 8 are more likely to adhere. Improve further. In addition, there is also an effect that the decay of the organic sludge is eliminated by aeration in the concentration step A. Even if unreacted flocculant (residual polymer) flows into the concentration tank 2, the unreacted flocculant is hydrolyzed by hydrogen peroxide, so that unreacted flocculant is formed on the membrane surface of the membrane separation device 4. It is possible to prevent the agent from adhering.

  Further, in the liquid separation step C, the highly concentrated sludge is discharged from the liquid level in the concentration tank 2 to the concentrated sludge storage tank 14, so that the increase in the sludge concentration in the concentration tank 2 is suppressed, and the sludge in the concentration tank 2 is suppressed. The concentration can be kept lower than the predetermined concentration.

  In addition, the density | concentration of the hydrogen peroxide in the concentration tank 2 is 0.02-0.4% (1-25% vs. SS) with respect to SS1.5%, for example. This is because the use in the weak alkali region has higher reactivity and the bubbles 8 are more often generated.

  Further, in the experiment, when the sludge concentration in the concentration tank 2 was concentrated to 1.5% by membrane separation in the concentration step A, in the floating separation step B, when hydrogen peroxide was supplied and the floating separation was performed, After 2 to 6% of solid matter floated and this solid matter was removed, the average sludge concentration in the entire concentration tank 2 was reduced to 1% or less.

  The highly concentrated sludge stored in the concentrated sludge storage tank 14 is dehydrated by the dehydrator 16, and the filtrate discharged from the dehydrator 16 at the time of dehydration contains a flocculant. 17, and then returned to the storage tank 3 from the filtrate storage tank 17 through the return pipe 18 as return water.

In the above embodiment, once the aeration is started in the concentration step A, the aeration may be continuously performed until the intended concentration and separation of the sludge is completed.
In the said embodiment, although the filtration by the membrane separator 4 is performed using the suction pressure by the suction pump 7, you may filter using a natural head without using the suction pump 7. FIG. Moreover, although the predetermined density | concentration of sludge is set to 1.5%, for example, it is not limited to this value, You may change according to various conditions, such as the kind of sludge and the membrane separation apparatus 4. FIG.

In the above embodiment, the flocculant is added to the storage tank 3 by the flocculant adding device 22, but may be added to the concentration tank 2.
Next, a second embodiment of the present invention will be described with reference to FIGS.

  A tank body 30 is provided in the concentration and separation facility 29, and the tank body 30 is divided by a partition wall 31 into a membrane separation tank 32 that separates sludge from a membrane and a floating separation tank 33 that floats and separates sludge. ing. An immersion type membrane separation device 4 is installed in the membrane separation tank 32. The membrane separation device 4 is connected to a separation water extraction pipe 5 for taking out and discharging the separated water to the outside of the membrane separation tank 32, and a suction pump 7 is connected to the separation water extraction pipe 5. An aeration apparatus 6 is provided in the membrane separation tank 32.

The floating separation tank 33 is provided with a hydrogen peroxide supply system 9 for supplying hydrogen peroxide (H ₂ O ₂ ) for generating bubbles 8 for floating separation. The hydrogen peroxide supply system 9 includes a hydrogen peroxide tank 10, a hydrogen peroxide supply line 11, and a pump 23. A stirrer 12 for stirring the supplied hydrogen peroxide is provided in the floating separation tank 33.

  The tank body 30 is provided with a circulating means 34 for circulating the sludge supplied from the storage tank 3 between the floating separation tank 33 and the membrane separation tank 32. The circulation means 34 is formed in the circulation pipe 35 for supplying the sludge in the floating separation tank 33 to the membrane separation tank 32, the circulation pump 36 provided in the circulation pipe 35, and the partition wall 31. The communication port 37 communicates with the tanks 32 and 33.

  Further, a discharge pipe 15 is connected to the top of the flotation separation tank 33 to discharge the highly concentrated sludge obtained by flotation separation and further overflowed or scraped off and removed from the liquid surface to the concentrated sludge storage tank 14. ing.

  Further, the concentration and separation facility 28 is provided with a dehydrator 16, a filtrate storage tank 17, a return pipe 18, and a sludge receiving pipe 19 for receiving sludge in the storage tank 3 in the floating separation tank 33. ing. Further, a flocculant adding device 22 for adding a flocculant to the storage tank 3 and a pH adjusting agent adding device 24 for adding a pH adjusting agent to the floating separation tank 33 are provided.

Hereinafter, a method for concentrating and separating sludge using the concentration and separation facility 29 will be described.
The sludge concentration and separation method includes a concentration step A, a flotation separation step B, and a liquid separation step C. Details of each step A to C are as follows.

  (1) In the concentration step A, first, wastewater containing sludge in the storage tank 3 is received from the sludge receiving pipe 19 into the floating separation tank 33, the circulation pump 36 is operated, By supplying the sludge from the circulation pipe 35 to the membrane separation tank 32, the sludge in the membrane separation tank 32 flows to the floating separation tank 33 through the communication port 37. Thereby, sludge circulates between the membrane separation tank 32 and the floating separation tank 33. In this state, the aeration apparatus 6 is operated to start aeration, and the suction pump 7 is operated to perform filtration by the membrane separation apparatus 4. To start. Then, when the separated water separated by the filtration is discharged from the membrane separation tank 32 through the separated water extraction conduit 5, and when the water level in both tanks 32 and 33 falls below a predetermined water level, as described above, The sludge in the storage tank 3 is received from the sludge receiving pipe 19 into the floating separation tank 33, and the water levels in both tanks 32 and 33 are raised to a predetermined water level.

  (2) When the concentration step A is repeated a plurality of times, the sludge in both tanks 32 and 33 is gradually concentrated by membrane separation, and the sludge concentration in both tanks 32 and 33 is concentrated to a predetermined concentration. In the levitation separation step B, the circulation pump 36 is stopped, the sludge circulation between the membrane separation tank 32 and the levitation separation tank 33 is stopped, and further, the suction pump 7 is stopped and the filtration by the membrane separation device 4 is performed. And aeration by the aeration apparatus 6 is stopped. Thereafter, hydrogen peroxide (liquid) in the hydrogen peroxide tank 10 is supplied to the lower part of the floating separation tank 33 and stirred by the stirrer 12. As a result, hydrogen peroxide causes a chemical reaction to generate a large amount of bubbles 8 such as oxygen gas in the floating separation tank 33, and as the bubbles 8 rise, sludge in the floating separation tank 33 is floated and separated. Highly concentrated sludge floats on the liquid level in the levitation separation tank 33.

  (3) Thereafter, in the liquid separation step C, the supply of hydrogen peroxide to the floating separation tank 33 is stopped, and the highly concentrated sludge in the floating separation tank 33 is removed from the liquid surface by overflow or scraping, and the discharge pipe 15 is discharged to the concentrated sludge storage tank 14. In addition, after supplying the hydrogen peroxide into the floating separation tank 33, the pH adjusting agent may be added to the floating separation tank 33 by the pH adjusting agent adding device 24 to adjust the pH.

(4) Thereafter, the process returns to the concentration step A.
According to the sludge concentration and separation method as described above, when the sludge in both tanks 32 and 33 is concentrated to a predetermined concentration by membrane separation of the membrane separation device 4 while circulating the sludge in both tanks 32 and 33, the membrane In order to stop the concentration step A by the separation device 4 and start the floating separation step B, the membrane separation is performed with the sludge concentration in both tanks 32 and 33 being lower than the predetermined concentration during the concentration step A. Has been. Thereby, the quantity of the sludge adhering to the membrane surface of the membrane separator 4 decreases, the blockage | closure of a membrane surface reduces, and the frequency | count of a maintenance can be reduced. Further, in the concentration step A, air bubbles blown out from the aeration device 6 rise while contacting the membrane surface of the membrane separation device 4, so that the membrane surface is washed, thereby further reducing the membrane surface blockage. .

  Further, in the above-described levitation separation step B, since hydrogen peroxide is supplied into the levitation separation tank 33, a large amount of bubbles 8 such as oxygen gas are generated by a chemical reaction. It is not necessary to generate Further, when the sludge concentration in the levitation separation tank 33 is thin, there is a possibility that the bubbles 8 will rise alone and degas, but the sludge in both tanks 32 and 33 is concentrated to a predetermined concentration. Therefore, the bubbles 8 are not lifted up and degassed, and almost all the bubbles 8 are attached to the solids in the sludge in the floating separation tank 33 and rise together with the solids. Efficiency is improved.

  Furthermore, the inside of the floating separation tank 33 becomes an oxidizing atmosphere by the strong oxidizing power of hydrogen peroxide. Therefore, the inside of the floating separation tank 33 is in an aerobic state and has a sludge reforming effect. In addition, when the sludge is organic sludge, the polymer produced by the decay of the organic sludge is decomposed and dispersed in the oxidizing atmosphere, and the bubbles 8 are more likely to adhere. Improve further. In addition, there is also an effect that the decay of the organic sludge is eliminated by aeration in the concentration step A. Even if unreacted flocculant (residual polymer) flows into the levitation separation tank 33, the unreacted flocculant is hydrolyzed by hydrogen peroxide. It is possible to prevent the flocculant from adhering.

  Further, in the liquid separation step C, highly concentrated sludge is discharged from the liquid level in the floating separation tank 33 to the concentrated sludge storage tank 14, so that an increase in the sludge concentration in the floating separation tank 33 is suppressed. Thereby, when the said concentration process A is performed continuously, since sludge circulates and mixes between both tanks 32 and 33, the sludge density | concentration in both tanks 32 and 33 can be kept lower than predetermined concentration. .

  Further, in the first embodiment described above, as shown in FIG. 1, since the membrane separation and the floating separation are performed in the same tank 2, the bubbles 8 generated by hydrogen peroxide are held (attached). There is a risk that sludge may adhere to the membrane surface of the membrane separation device 4. On the other hand, in the second embodiment, as shown in FIG. 33, it is possible to prevent the sludge holding (attached) bubbles 8 generated by hydrogen peroxide from adhering to the membrane surface of the membrane separation device 4 in the membrane separation tank 32. Therefore, when the membrane separation is resumed, the sludge holding the bubbles 8 does not become an obstacle to the membrane separation.

  In the second embodiment, for example, when sludge is concentrated 10 times, it is concentrated 5 times in the concentration step A in the membrane separation tank 32 and doubled in the floating separation step B in the floating separation tank 33. Combinations such as enrichment are possible.

  In the second embodiment, the supply of hydrogen peroxide is stopped in the concentration step A. However, in order to prevent anaerobization, hydrogen peroxide is supplied to the floating separation tank 33 also in the concentration step A. Also good. Moreover, the supply amount of hydrogen peroxide can be reduced by shortening the cycle of each said process AC. Further, if the levitation separation is completed within the time when the circulation pump 36 is stopped, the membrane separation device 4 can continue to filter continuously.

  In the second embodiment, the filtration by the membrane separation device 4 is stopped in the flotation separation step B, but the filtration may be continued as it is. Further, although aeration by the aeration apparatus 6 is stopped in the floating separation step B, aeration may be continued as it is. In the concentration step A, once aeration is started, aeration may be continuously performed until the intended concentration and separation of sludge is completed.

  In the second embodiment, the flocculant adding device 22 adds the flocculant into the storage tank 3, but the flocculant may be added into the membrane separation tank 32 and the floating separation tank 33.

It is a figure of the concentration separation equipment of sludge in a 1st embodiment of the present invention. It is a flowchart which shows the procedure of the concentration separation method of sludge. It is a figure of the sludge concentration separation equipment in the 2nd embodiment of the present invention. It is a flowchart which shows the procedure of the concentration separation method of sludge. It is a figure of the conventional concentration separation equipment of sludge. It is a figure of the conventional concentration separation equipment of sludge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concentration separation equipment 2 Concentration tank 4 Membrane separation device 8 Bubble 9 Hydrogen peroxide supply system 29 Concentration separation equipment 32 Membrane separation tank 33 Floating separation tank 34 Circulation means

Claims (2)

A method for concentrating and separating sludge using a membrane separation tank for separating sludge into membranes and a levitating separation tank for levitating and separating sludge,
A concentration step of separating and concentrating the sludge in the membrane separation tank while circulating the sludge between the membrane separation tank and the floating separation tank;
When the sludge in the two tanks is concentrated to a predetermined concentration, the circulation of the sludge between the two tanks is stopped, hydrogen peroxide is supplied into the floating separation tank to generate bubbles, and the rise of the bubbles A flotation separation step for flotation separation of sludge in the flotation separation tank;
A method for concentrating and separating sludge, comprising: a liquid separation step for removing highly concentrated sludge obtained by the above-described flotation separation step from the inside of the flotation separation tank. 2. The method for concentrating and separating sludge according to claim 1, wherein in the flotation separation step, after the hydrogen peroxide is supplied into the flotation separation tank, the flotation separation tank is stirred.

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