JPH0957288A - Biological treatment using spongy carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to rapidly fluidize spongly carriers carrying microorganisms in a reaction vessel without using medicines by shrinking the carriers by pressure reduction or pressurization, then charging the carriers in which water or a liquid mixed with biological sludge is absorbed into this reaction vessel in a method for biologically treating raw water by fluidizing the carriers. SOLUTION: Raw water and return sludge are first introduced into a denitrification vessel 1 and a nitrified liquid subjected to nitrification in a nitrification vessel 2 is introduced therein and is mixed with activated sludge, by which the denitrification is executed. Next, the denitrified liquid in the denitrification vessel 1 is taken out and is introduced into an aeration vessel 32, where the air from an air supply path 12 is diffused from an air diffuser 34 to create an aerobic condition. BOD components are thus removed. The air is then diffused similarly from an air diffuser 35 to the liquid after the removal of the BOD components in the nitrification vessel 2 and nitrification is executed in the fluidizing state of the charged carriers 24 consisting of the sponge. The carriers are shrunk by the pressure reduction or pressurization and are charged into the nitrification vessel 2 in the state that the liquid in the nitrification vessel 2 is absorbed therein. As a result, the carriers 14 are fluidizied in a short period of time.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biological treatment method using a sponge-like carrier carrying microorganisms.

[0002]

2. Description of the Related Art As a method for treating an effluent containing an ammoniacal or organic nitrogen compound, there is a biological nitrification denitrification treatment method. This method uses activated sludge to remove COD,
Along with decomposing BOD components, organic nitrogen compounds are converted to ammonia nitrogen, and the ammonia nitrogen is nitrified (oxidized) into nitrite or nitrate nitrogen by nitrifying bacteria, and then denitrified (reduced) by denitrifying bacteria. Is the way. In this treatment method, a denitrification tank is provided in the preceding stage, and the nitrification solution and the separated sludge are returned to the denitrification tank and mixed with raw water to perform denitrification and at the same time decompose BOD components.

Such a biological nitrification denitrification method has a lot of achievements and is widely adopted in the field of human waste treatment. But,
In the nitrification method in the biological nitrification denitrification method, it is difficult to increase the retention amount of nitrifying bacteria in the nitrification tank, so it is necessary to lengthen the residence time in the nitrification tank, which results in a larger nitrification tank. There is a problem.

As a method of improving such problems,
A carrier such as a sponge is put into the nitrification tank, and the nitrifying bacteria are attached to the surface of the carrier to increase the amount of nitrifying bacteria retained, whereby the nitrification rate of the entire nitrification tank (NH ₄ -N removal rate)
Is known to further stabilize the nitrogen removal function (for example, JP-A-57-75192, JP-A-6-304593 and JP-A-6-356356).

In addition to this, in the ordinary activated sludge treatment method,
A method is also known in which activated sludge is adhered to a sponge to increase its density, and thus high-load treatment is performed (for example, Japanese Patent Publication No.
-55757). Further, in Japanese Patent Laid-Open No. 7-68285,
An aerobic treatment method is described in which a sponge is put into an aeration tank, and activated sludge is supported on the sponge to aerobically treat the organic waste liquid.

However, when a sponge such as polyurethane is used as a carrier, since the sponge is hydrophobic, the liquid in the tank immediately permeates into the voids of the sponge if the sponge is put into the nitrification tank or the aeration tank as it is. Therefore, even if the specific gravity of the material itself is 1 or more, it does not immediately fluidize, and some sponges are floating near the liquid surface.
Therefore, it takes some time for most of the sponge to flow in the nitrification tank or the aeration tank and to maximize the effect of adding the sponge.

In order to improve the fluidity of the sponge, Japanese Patent Publication No. 4-55757 describes a method of adding a carrier wettability improver containing a higher alcohol, a fatty acid ester or silicon oil as a main component. However, in this method, it is necessary to add the wettability improver in an amount of 0.2 to 5 g / l, which increases the cost and the treatment of the added wettability improver becomes a problem.

Further, JP-A-5-15889 describes a method for hydrophilizing a microorganism-immobilized carrier in which a porous carrier is immersed in an alcohol or surfactant solution and then charged into a reaction tank. According to this method, the pores on the surface of the carrier and the communicating pores inside are hydrophilized, so that the water to be treated easily enters the pores of the carrier quickly, and microorganisms are easily attached. However, since this method also uses the drug, the cost is increased, and a new problem arises in that the used drug must be treated.

[0009]

The object of the present invention is to make it possible to fluidize a sponge-like carrier charged in a reaction tank in a short period of time without using a chemical agent, and therefore at a low cost and in a used chemical agent. It is an object of the present invention to propose a biological treatment method using a sponge-like carrier, which is capable of exhibiting the effect of the sponge-like carrier in a short period of time without the need to perform the treatment.

[0010]

Means for Solving the Problems The present invention is a method of biologically treating a liquid to be treated by flowing a sponge-like carrier carrying microorganisms in a reaction tank, and after contracting the sponge-like carrier by depressurizing or pressurizing, In the biological treatment method using a sponge-like carrier, a sponge-like carrier in which water or a mixed solution of biological sludge is absorbed is charged into a reaction tank.

The biological treatment method of the present invention can be applied to any treatment method as long as it is a treatment method for biologically treating a liquid to be treated such as an organic drainage using a sponge-like carrier carrying microorganisms. . Examples of such a treatment method include a nitrification method using nitrifying bacteria, a nitrification denitrification treatment method, an activated sludge treatment method whose main purpose is the decomposition of BOD, and a biological nitrification that simultaneously decomposes BOD and denitrification. Examples thereof include denitrification treatment methods and biological treatment methods using anaerobic bacteria, and either aerobic treatment methods or anaerobic treatment methods may be used.

The sponge-like carrier is an elastic porous body having open cells, which can be compressed by decompression or pressurization, and can be completely or almost completely returned to its original shape by returning to normal pressure. A porous body that restores can be used.
Specific examples include sponges made of resin such as polyurethane.

The shape of the sponge-like carrier is not limited, and those having a dice shape, a spherical shape, an amorphous shape or the like can be used. The size is preferably such that the major axis is about 1 to 50 mm. Although the size of the pores of the sponge-like carrier is not limited, it is 50 to 10
A particle size of 00 μm, preferably 100 to 500 μm is suitable. If the pores become too large, the water that has penetrated into the pores will replace the aerated air due to aeration, so that those that do not exceed the above upper limit value are preferred. The number of pores is not limited, but the length is 2
It is preferable that the number of cells per 5 mm is 25 or more.

In the present invention, the sponge-like carrier as described above is contracted by decompressing or pressurizing it to discharge the gas (air) contained therein, and then absorb the water or the biological sludge mixed solution, This water-absorbed carrier is put into a reaction tank. To shrink the sponge-like carrier, put it in a closed container such as a vinyl bag and depressurize it with a vacuum pump.
It can be performed by a method such as a method of pressurizing with a piston or the like and compressing.

In order for the contracted sponge-like carrier to absorb water, water or a biological sludge mixture is supplied in a contracted state,
It can be performed by returning to normal pressure. As water, tap water, industrial water, treated water or the like can be used. As the biological sludge mixed solution, a solution in a reaction tank or another reaction tank into which a sponge-like carrier such as an activated sludge mixed solution is charged can be used. Among these, it is preferable to use the biological sludge mixed liquid because the sponge-like carrier can be fluidized in a shorter period of time. At the time of water absorption, a hydrophilic agent such as alcohol or a surfactant can be used in combination with water or a biological sludge mixed solution.

By absorbing water in this manner, the pores are filled with water or the biological sludge mixed solution, and the gas in the pores is replaced with the liquid. It is preferable that the pores of the sponge-like carrier fill as much space as possible with the water or the biological sludge mixed solution, but if about 1/3 of the total volume of the pores is filled with the water or the biological sludge mixed solution, Since the fluidity of the sponge-like carrier is improved, it is sufficient that the pores having a volume of about 1/3 or more are filled with water or the biological sludge mixed solution.

The spongy carrier thus absorbed has a large specific gravity because the gas in the pores is replaced by a liquid, and since microorganisms adhere to it in a short period of time, it is fluidized in a short period of time. When the biological sludge mixture is used for water absorption, 90% or more of the added sponge-like carrier is fluidized after 1 to 8 days, and when tap water is used after 1 to 12 days. These days are comparable to conventional methods of using drugs for fluidization or hydrophilization.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing a biological nitrification / denitrification treatment method of an organic waste liquid, which adopts the biological treatment method of the present invention. One aerobic tank is divided into a front aeration tank and a rear nitrification tank. This is an example of the case where a sponge-like carrier is put into a nitrification tank in the subsequent stage. In FIG. 1, 1 is a denitrification tank, 2 is a nitrification tank, 3 is a final denitrification tank, 4 is a final aerobic treatment tank, and 5 is a solid-liquid separation tank, and the nitrification tank 2 performs nitrification.

A raw water channel 6, a sludge return channel 7, a circulating fluid channel 8 and a connecting channel 9 are connected to the denitrification tank 1, and are gently stirred by an agitator 10 so that denitrification is performed while maintaining an anaerobic state. Has become.

A partition plate 31 is provided in the aerobic tank 30 at right angles to the flow direction of the raw water, and is partitioned into an aeration tank 32 at the front stage and a nitrification tank 2 at the rear stage, and a nitrification tank 2 at the rear stage. A carrier 14 made of sponge is charged into the container, and a screen 15 for preventing the carrier 14 from flowing out is provided at the outlet of the nitrification tank 2 in the subsequent stage. A passage 9 from the denitrification tank 1 to the aeration tank 32 in the first stage, and a passage 1 to the final denitrification tank 3 in the nitrification tank 2 in the second stage.
1 is connected. Then, air is sent from the air supply path 12 to the front aeration tank 32 and the rear nitrification tank 2, and is diffused from the front aeration device 34 and the rear aeration device 35, and the BOD component of the front aeration tank 32 Removal, nitrification tank 2 in the latter stage
Then, nitrification is performed. A flow path 36 is provided on the wall surface or bottom surface of the partition plate 31 and the aerobic tank 30,
The liquid in the aeration tank 32 at the front stage flows into the nitrification tank 2 at the rear stage from the flow path 36. A wire mesh (not shown) is provided in the flow path 36 so that the carrier 14 does not flow back into the aeration tank 32 in the previous stage.

The final denitrification tank 3 is connected to the communication paths 11 and 17 and the organic material supply path 18, and is gently stirred by a stirrer 19 to maintain an anaerobic state. Communication paths 17 and 20 are connected to the final aerobic treatment tank 4, and an air supply path 21 is provided.
Air is sent from the air, and air is diffused from the final diffuser 22 to perform aerobic treatment.

The solid-liquid separation tank 5 has a communication passage 20 and a treatment water passage 23.
Also, the sludge path 24 is connected to perform solid-liquid separation by sedimentation separation. The sludge passage 24 branches into a sludge return passage 7 and a sludge discharge passage 25, and a part of the separated sludge is returned to the denitrification tank 1 through the sludge return passage 7.

To treat the raw water according to the flow shown in FIG. 1, first, the raw water containing the nitrogen compound and the BOD component is introduced into the denitrification tank 1 through the raw water channel 6, the return sludge is introduced through the sludge return channel 7, and the latter stage is performed. The nitrification liquid that has undergone nitrification in the nitrification tank 2 is introduced from the circulation liquid path 8 and mixed with the activated sludge containing the denitrifying bacteria by the stirrer 10 to perform denitrification while maintaining the anaerobic state. The circulation amount of nitrification liquid is usually 100 relative to the raw water
~ 500% by volume. In such a denitrification step, the denitrifying bacteria that reduce nitric acid or nitrite ion in the circulating liquid to nitrogen become dominant, and the nitrogen component in the raw water is removed as well as the BOD component.

The denitrifying liquid in the denitrification tank 1 is taken out part by part from the communication passage 9 and introduced into the aeration tank 32 at the previous stage, and the air supply passage 1
Air is sent from 2 to diffuse air from the air diffuser 34 in the previous stage to make it an aerobic condition, and the BOD component is substantially removed by the floating sludge to make the BOD concentration 10 mg / l or less. In this case, part of the nitrogen compound may be nitrified. The mixed liquid in the aeration tank 32 at the front stage flows into the nitrification tank 2 at the rear stage as it is from the flow path 36 without separating the sludge part by part.

In the latter nitrification tank 2, air is sent from the air supply passage 12 to the liquid from which the BOD component has been removed in the former aeration tank 32, and air is diffused from the latter air diffuser 35 to make it an aerobic condition.
Nitrification is performed by nitrifying bacteria in a state where the charged carrier 14 is flowing, and the nitrogen component in the raw water is nitrified to nitrate ions or nitrite ions. Here, the nitrifying bacteria are predominant by aeration in excess of the aeration for normal BOD removal.
In this case, the carrier 14 made of a sponge is contracted by depressurizing or pressurizing it, and then the liquid in the nitrification tank 2 is supplied to absorb water, and the nitrification tank is held with the liquid in the tank held in the pores of the sponge. Add to 2. As a result, the carrier 14 becomes fluidized in a short period of time, and the nitrification denitrification treatment system reaches a steady state in a short period of time.

In the aerobic tank 30, a wire net is stretched over the flow path 36 below the partition plate 31 so that the carrier 14 in the nitrification tank 2 in the subsequent stage does not flow into the aeration tank 32 in the preceding stage. In this way, the aerobic tank 30 is divided, the BOD component is removed by the aeration tank 32 at the front stage, and the carrier is flown in the nitrification tank 2 at the rear stage to nitrify the nitrifying bacteria in the carrier 14 in a short period of time. Then, a large amount is retained, and high nitrification activity is maintained.

The conditions of the aerobic tank 30 are as follows: pH 6-9, preferably 7-8.5, temperature 0-40 ° C., preferably 15
It is desirable to set the temperature to 35 ° C.

A part of the nitrification solution that has been nitrified in the subsequent nitrification tank 2 is introduced into the final denitrification tank 3 from the communication path 11, and an organic matter such as methanol as a hydrogen donor is supplied to the organic matter supply path 18
And denitrification is performed in the same manner as in the denitrification tank 1. The final denitrification liquid in the final denitrification tank 3 is re-aerated in the final aerobic treatment tank 4 to remove the residual organic matter.

The final aerobic treatment liquid in the final aerobic treatment tank 4 is taken out part by part from the communication passage 20 and introduced into the solid-liquid separation tank 5 for solid-liquid separation to separate it into a separated liquid and separated sludge. . The separated liquid is discharged from the treated water channel 23 as treated water. The separated sludge is taken out from the sludge passage 24, and part of it is returned to the denitrification tank 1 from the sludge return passage 7 as return sludge. The rest is discharged as excess sludge from the sludge discharge path 25 to the outside of the system. In the method of FIG. 1, the final denitrification tank 3 and the final aerobic treatment tank 4 can be omitted.

FIG. 2 is a flow chart showing an aerobic treatment method of an organic waste liquid which employs the biological treatment method of the present invention, which is an embodiment in the case of introducing a sponge-like carrier into an aeration tank.
In this example, the excess sludge is treated with ozone and then introduced into an aeration tank for aerobic treatment to reduce the volume of the excess sludge. In FIG. 2, 41 is an aerobic treatment system, 42 is an ozone treatment system, 43 is an aeration tank, 44 is a solid-liquid separation tank, 45 is a carrier made of sponge, and 46 is an ozone treatment tank.

In order to treat the raw water according to the flow of FIG. 2, the raw water is introduced into the aeration tank 43 from the raw water channel 51 and the carrier 4
5. Return sludge returned from the sludge return passage 52, ozone treated sludge circulated from the ozone treatment sludge circulation passage 53, and floating activated sludge in the aeration tank 43, and air is sent from the air supply passage 54 to diffuse the air. Aerate from 55 and perform aeration,
Perform aerobic treatment. This decomposes BOD. In this case, the carrier 45 made of a sponge is decompressed or pressurized to shrink it, and then the liquid in the tank of the aeration tank 43 is supplied to absorb water, and the liquid in the tank is held in the pores of the sponge. Throw in 43. As a result, the carrier 45 becomes fluidized in a short period, and the aerobic treatment system reaches a steady state in a short period. The amount of the carrier 45 charged is 5 to 40 of the aeration tank 43 capacity.
%, Preferably 10 to 30%.

A part of the mixed liquid (in-tank liquid) in the aeration tank 43 is guided to the solid-liquid separation tank 44 through the screen 56 so that the carrier 45 does not flow out, and solid-liquid separation is performed. The separated liquid is discharged from the treated water channel 57 as treated water, and a part of the separated sludge is returned to the aeration tank 43 by the pump P ₁ as returned sludge from the sludge return passage 52.

On the other hand, the other part of the separated sludge is treated as ozone-treated sludge and circulated from the sludge extraction passage 58 to the ozone treatment tank 46 by the pump P ₂ . Here, ozone is supplied from the ozone supply path 59 to bring the sludge to be treated into contact with ozone to perform ozone treatment. As a result, the ozone-treated sludge is oxidatively decomposed by ozone and converted into BOD and a trace amount of biodegradable COD. The ozone-treated sludge is returned (circulated) from the ozone-treated sludge circulation path 53 to the aeration tank 43,
Aerobic treatment as load. The ozone exhaust gas is discharged from the exhaust ozone passage 60. When excess sludge is generated, it is discharged from the excess sludge discharge path 61.

When performing aerobic treatment according to the flow of FIG.
After a part of the separated sludge is ozone-treated and converted into BOD, it is returned to the aeration tank 43 for aerobic treatment, so the amount of surplus sludge discharged is reduced, and when a large amount of separated sludge is ozone-treated, it is excessive. Sludge can be reduced to zero. in this case,
In order to carry out a stable treatment without degrading the aerobic treatment performance, it is necessary to retain a certain amount of aerobic microorganisms in the aeration tank 43.
Turn on 5.

[0035]

Next, test examples of the present invention will be described. Test Example 1 A synthetic effluent mainly composed of peptone and yeast extract was used in a BOD tank load of 1 kg / m ³ · day using a 10 liter transparent vinyl chloride aeration tank, and the MLSS concentration of the aeration tank was 2500.
Aerobic treatment was carried out under the condition of mg / l. 5x5 in this aeration tank
A water-absorbing sponge (25 cells per length 25 mm) made of polyurethane foam in the shape of a cuboid of 5 mm (25 cells per length 25 mm) was added at a rate of 30% of the aeration tank capacity, and fluidization of the sponge was evaluated. The water absorption method and evaluation method for the sponge are as follows.

[Water Absorption Method] The sponge was placed in a vinyl bag, the pressure was reduced by a vacuum pump to shrink the volume to ⅕, and then the tank liquid of the aeration tank was supplied to absorb water. [Evaluation Method] The volume of the sponge floating just below the liquid surface in the aerated state was measured (floating sponge). The volume of the floating sponge was subtracted from the total volume of the added sponge to obtain the amount of flowing sponge, and the ratio of the flowing sponge was calculated. The results are shown in FIG. The test conducted using a sponge that did not absorb water was used as a control.

Test Example 2 Test Example 2 was carried out in the same manner as in Test Example 1 except that a sponge in which tap water was absorbed was used instead of the liquid in the tank. The results are shown in FIG.

From the results of FIG. 3, in Test Examples 1 and 2,
It can be seen that 90% or more of the sponge flows in 2 to 3 days after the addition, and flows in a shorter period than the control (untreated).

Test Example 3 In the same manner as in Test Example 1, except that sponges having different numbers of cells were used and the liquid to be absorbed had an MLSS concentration of about 200.
The test was carried out by changing to a 0 mg / l activated sludge mixture. FIG. 4 shows the results.

From FIG. 4, the number of cells per length of 25 mm is 2
It can be seen that for five or more sponges, the period required for flow is shorter.

[0041]

EFFECT OF THE INVENTION In the biological treatment method of the present invention, the sponge-like carrier is contracted under reduced pressure or pressure, and then the sponge-like carrier in which water or the biological sludge mixed liquid is absorbed is put into the reaction tank. The spongy carrier can be fluidized in a short period of time without using a drug. Therefore, the treatment can be performed at low cost, and it is not necessary to treat the used medicine, and the effect of the sponge-like carrier can be exhibited in a short period of time.

[Brief description of drawings]

FIG. 1 is a flow chart showing a biological nitrification denitrification treatment method adopting the biological treatment method of the present invention.

FIG. 2 is a flow chart showing an aerobic treatment method adopting the biological treatment method of the present invention.

FIG. 3 is a graph showing the results of Test Examples 1 and 2.

FIG. 4 is a graph showing the results of Test Example 3.

[Explanation of symbols]

 1 Denitrification tank 2 Nitrification tank 3 Final denitrification tank 4 Final aerobic treatment tank 5 Solid-liquid separation tank 6 Raw water channel 7 Sludge return channel 8 Circulating fluid channel 9, 11, 17, 20 Communication channel 10, 19 Stirrer 12, 21 Air Supply channel 13 Air diffuser 14 Carrier 15 Screen 18 Organic matter supply channel 22 Final air diffuser 23 Treated water channel 24 Sludge channel 25 Sludge discharge channel 30 Aerobic tank 31 Partition plate 32 Aeration tank 34 Front air diffuser 35 Rear air diffuser Equipment 36 Flow path 41 Aerobic treatment system 42 Ozone treatment system 43 Aeration tank 44 Solid-liquid separation tank 45 Carrier 46 Ozone treatment tank 51 Raw water channel 52 Sludge return channel 53 Ozone treatment sludge circulation channel 54 Air supply channel 55 Air diffuser 56 Screen 57 Treated water channel 58 Sludge extraction channel 59 Ozone supply channel 60 Exhaust ozone channel 61 Excess sludge discharge channel

Claims (1)

[Claims] 1. A method for biologically treating a liquid to be treated by flowing a sponge-like carrier carrying microorganisms into a reaction tank, wherein the sponge-like carrier is contracted by depressurizing or pressurizing, and then water or a biological sludge mixture is added. A biological treatment method using a sponge-like carrier, which comprises charging a water-absorbed sponge-like carrier into a reaction tank.