JP2001286885A - Treatment process of sewage and sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage/sludge treatment process which enables removal of organic matter in sewage/sludge and advanced denitrification/dephosphorization treatment of the sewage/sludge by only providing a biological denitrification process with a dephosphorization function and a sludge volume reduction function through utilization of a combination of a biological treatment technique and a coagulant, and withdrawing a possible minimum amount of sludge as excess sludge. SOLUTION: This treatment process comprises returning sludge C separated in a final sedimentation vessel 4 to a completely anaerobic vessel 2 placed in the stage preceding a reaction vessel 3, concurrently, introducing a portion of the separated sludge C in the final sedimentation vessel 4 into a sludge solubilization vessel 7 to subject the sludge portion to solubilization treatment; thereafter, adding a coagulant to the solubilized sludge; introducing the solubilized sludge containing the coagulant into a sedimentation separation vessel 9, to coagulate phosphorus eluted from the above sludge portion by the solubilization treatment, to subject the resulting solubilized sludge containing coagulated phosphorus to sedimentation separation and to obtain sludge containing phosphorus and a separated liquid G; and discharging the sludge containing phosphorus to the outside as excess sludge F and returning the separated liquid G to the completely anaerobic vessel 2 or reaction vessel 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sewage and sludge, and more particularly to removing biologically and physicochemically nitrogen and phosphorus from sewage containing organic matter, nitrogen and phosphorus. The present invention relates to a method of treating sewage and sludge so as to minimize the amount of generated sludge.

[0002]

2. Description of the Related Art Conventionally, in order to treat sewage flowing into a sewage treatment plant or the like, an activated sludge method is used in which sewage is introduced into an activated sludge aeration tank, and this is aerated and stirred to perform biological treatment. I have. In recent years, not only organic matter in incoming sewage,
From the viewpoint of preventing eutrophication, removal of nitrogen and phosphorus is desired. As a method for this, a method of biologically denitrifying and dephosphorizing using a plurality of water tanks is used. On the other hand, excess sludge generated in the water treatment process is usually landfilled after dewatering, but since the disposal site is gradually disappearing, sludge can be added to the excess sludge by adding ozone. A method is adopted in which the amount of sludge generated is reduced to zero by solubilization and biodegradation in the system.

[0003]

However, according to the above-mentioned conventional methods for treating wastewater and sludge, it is necessary to reduce the amount of sludge to zero.
This can be achieved by solubilization of the sludge, but with this, there has been a problem that phosphorus contained in the sludge cannot be collected or removed at all.

The present invention has been made in view of the above-mentioned problems of the conventional methods for treating wastewater and sludge, and has a function of removing phosphorus by combining biological treatment and a flocculant and reducing the volume of sludge in biological denitrification. In addition, just pull out the minimum amount of sludge as excess sludge,
It is an object of the present invention to provide a method for treating sewage and sludge which can perform advanced treatment of removing organic substances and denitrification and dephosphorization.

[0005]

Means for Solving the Problems In order to achieve the above object, the method for treating sewage and sludge of the first aspect of the present invention biologically treats organic sewage by sludge microorganisms in a reaction tank and generates the wastewater by biological treatment. In the method for treating sewage and sludge for solubilizing the treated sludge, the sludge separated in the final sedimentation tank is returned to a completely anaerobic tank disposed in front of the reaction tank, and a part of the sludge separated in the final sedimentation tank is removed. After conducting the solubilization treatment in the sludge solubilization tank, a coagulant is added, and the mixture is led to the precipitation separation tank.The sludge separated by segregation and precipitation of phosphorus eluted from the sludge is discharged as excess sludge, and the separated liquid is completely removed. It is characterized by being returned to an anaerobic tank or a reaction tank.

In this method of treating sewage and sludge, the sludge separated in the final sedimentation tank is guided to the preceding completely anaerobic tank, so that the untreated components in the sludge can be completely treated by biological treatment again. It is possible to decompose sludge separated as a nutrient source for other microorganisms by solubilizing part of the sludge separated in the final sedimentation tank. Since only the sludge mainly composed of inorganic substances that did not exist, the volume was reduced to about 1/10 of the conventional sludge, and denitrification by biological treatment, and dephosphorization by treatment combining biological treatment and coagulant, Since it can be performed at the same time, advanced treatment of removing organic substances, denitrification, and dephosphorization can be performed together with sludge volume reduction.

In order to achieve the same object, the method for treating sewage and sludge according to the second aspect of the present invention is a biological treatment of organic sewage by sludge microorganisms in a reaction tank and solubilization of the sludge generated by the biological treatment. In the method of treating wastewater and sludge to be treated, separation of the treated water is performed by a membrane separation device disposed in the reaction tank, and the sludge in the reaction tank is returned to a completely anaerobic tank disposed in a preceding stage of the reaction tank, After a part of the sludge in the reaction tank is introduced into the sludge solubilization tank for solubilization, a flocculant is added, and the mixture is led to the sedimentation separation tank. It is characterized by discharging as sludge and returning the separated liquid to a completely anaerobic tank or a reaction tank.

In this method of treating sewage and sludge, a membrane separation device is provided in the reaction tank and the treated water subjected to solid-liquid separation is taken out, so that the sludge concentration in the reaction tank can be increased.
This makes it possible to perform treatment with activated sludge having a high concentration, so that the treatment time can be reduced, the amount of sludge generated can be reduced, and the installation space for the apparatus can be reduced, and Since the sludge that has been solubilized can be pulled out of the reaction tank, the concentration of the sludge to be solubilized is stable, and more stable solubilization can be performed. In addition, since the sludge in the reaction tank is led to the complete anaerobic tank in the preceding stage, the untreated components in the sludge can be completely treated by biological treatment again, and the sludge separated in the final sedimentation tank can be removed. By solubilizing the parts,
Since it is decomposed as a nutrient source for other microorganisms, the only sludge discharged out of the plant is coagulated sludge or non-solubilized inorganic-based sludge.
While the volume and volume can be reduced, denitrification by biological treatment, and dephosphorization by a combination of biological treatment and coagulant can be performed at the same time. Advanced treatment such as removal of organic matter, denitrification, and dephosphorization can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating sewage and sludge of the present invention will be described below with reference to the drawings.

FIG. 1 shows a processing flow chart of a first embodiment of the method for treating sewage and sludge of the present invention. The sewage A such as sewage containing organic matter, nitrogen, and phosphorus that flows into a sewage treatment facility, for example, a sewage treatment plant, is subjected to a pre-treatment facility 1 where sand and residue are removed in advance, and then a complete anaerobic tank 2 is further reacted. It is sent to the tank 3. Most of the phosphorus contained in the sewage A flowing into the treatment plant is in a water-soluble phosphate state, and is absorbed into the microorganisms by changing the activated sludge microorganism from a completely anaerobic state to an aerobic state, Biologically treated by activated sludge.

The sewage treated in the reaction tank 3 is sent to a final sedimentation tank 4 as a sludge mixture, where it is separated into solid and liquid, and the supernatant is overflowed as treated water B.
The sludge C which has been drained and precipitated by solid-liquid separation in the final sedimentation tank 4 is intermittently or continuously extracted by a sludge transfer pump 5 and returned to the complete anaerobic tank 2. The sludge C returned to the sludge is released from the sludge as phosphoric acid, which is taken up in the sludge microorganisms in the form of polyphosphoric acid, as a water-soluble phosphoric acid state. To rise. The released phosphoric acid is subjected to aeration in the reaction tank 3 in the subsequent stage to make it aerobic, thereby absorbing excessive phosphorus more than the microorganisms released. At this time, the phosphorus contained in the inflowing sewage is also reduced. Since it is taken up by microorganisms, it can be dephosphorized. Further, the nitrogen component mainly composed of ammonia nitrogen contained in the inflowing sewage is subjected to anaerobic aerobic operation in the reaction tank 3,
Alternatively, nitrification denitrification can be performed by dividing the reaction tank into an anaerobic tank and an aerobic tank, and circulating the mixed solution that has been nitrified from the aerobic tank to the anaerobic tank.

The settled sludge C in the final settling tank 4 is returned to the completely anaerobic tank 2 by a sludge transfer pump 5. Part of the returned sludge, usually 1/10 to 1/20 of the returned sludge
The degree is guided to the sludge solubilization tank 7 as needed, where the solubilization is performed. By performing the solubilization treatment, cell walls and cell membranes of the sludge microorganisms are destroyed, and components in the microorganisms are eluted, so that phosphorus in the body is also eluted into the solubilized sludge liquid. In the illustrated embodiment, the solubilization is performed by the solubilizer supplied from the solubilizer supply device 6. As a means for solubilizing the sludge, an oxidizing agent such as ozone or hydrogen peroxide or a combination thereof is added or supplied as a solubilizing agent, but in addition to this, it degrades the cell wall and cell membrane of microorganisms. A method of adding an enzyme or a microorganism that produces an enzyme, one kind of physical solubilization means such as pressure treatment or heat treatment, or a combination of two or more means can be used. Absent.

The solubilized sludge D solubilized in the sludge solubilization tank 7 is transferred to the sedimentation / separation tank 9, during which the coagulant is added or supplied from the coagulant supply device 8. The phosphorus is reacted with the metal salt to insolubilize it, and is precipitated as coagulated sludge in the sedimentation separation tank 9 together with other sludge mainly composed of inorganic substances. The settled sludge E settled in the settling tank 9 is discharged as surplus sludge by the sludge pump 12 and transferred to the sludge concentration storage tank 10. The sewage containing the solubilized organic matter is allowed to flow naturally or as a separated liquid G. Biological treatment is performed by withdrawing by a pump and returning to the complete anaerobic tank 2. Further, the separated liquid G can be returned to the reaction tank 3.

A small amount of excess sludge F concentrated and stored in the sludge concentrated storage tank 10 is periodically withdrawn and subjected to a treatment such as dehydration or carried out of the treatment plant by a vacuum truck or the like. Since a supernatant is formed, it is desirable to provide a pipe for returning the supernatant to the water treatment system. As described above, the sludge that increases in the reaction tank 3 is decomposed as a nutrient source of other microorganisms by the solubilization treatment, so that the sludge discharged out of the plant is agglomerated sludge or inorganic-sludge that is not solubilized. Therefore, in addition to about 1/10 of the conventional process, a process capable of denitrification and dephosphorization is possible.

Next, the operation of the method for treating sewage and sludge will be described. In the sludge sent to the sludge solubilization tank 7 by the sludge transfer pump 5, phosphorus taken into the body through the process of releasing phosphorus in the completely anaerobic tank 2 and excessively absorbing phosphorus in the reaction tank 3 is accumulated. ing.

In the sludge solubilization tank 7, a solubilizing agent such as an oxidizing agent is injected by the solubilizing agent supplying device 6 in an amount corresponding to the amount of sludge. Cell membrane is destroyed. At this time, since the cytoplasm contained in the cells elutes, the accumulated phosphorus also elutes in the solution of the solubilized sludge D. By injecting a metal salt-based coagulant such as iron or aluminum before the solubilized sludge D is transferred to the sedimentation separation tank 9, phosphoric acid phosphorus reacts with metal ions and reacts with a phosphate compound. Become insoluble. At this time, in order to form a flocculated floc having good sedimentation property, it is preferable to mix the flocculant promptly and then perform gentle stirring. Is also good.

In the sedimentation separation tank 9, the condensed phosphorus precipitates together with the remaining inorganic-based sludge without being solubilized, and is transferred to the sludge concentration storage tank 10 by the sludge pump 12 as the sedimentation sludge E. . Since the sludge is gradually concentrated during the temporary storage in the sludge concentration storage tank 10, the upper supernatant liquid is sent to the completely anaerobic tank 2, and the concentrated sludge is subjected to treatment such as dehydration or vacuuming. Carry off the site by car.

On the other hand, in the water treatment system including the complete anaerobic tank 2 and the reaction tank 3, the incoming sewage A and the separated liquid G of the solubilized sludge are used.
With the biodegradation of the organic matter contained in the sludge, sludge microorganisms newly grow and the sludge concentration increases. Therefore, in order to solubilize a predetermined amount of sludge microorganisms and stabilize the sludge concentration, the sludge is drawn out in consideration of the solubilization efficiency, and a solubilization treatment is performed in the sludge solubilization tank 7 to reduce the sludge generated. It is necessary to balance the amount of sludge reduced by solubilization.
The amount of sludge to be solubilized varies depending on the solubilizing means used, but is usually set to 1 to 3 times the amount of sludge generated.

When nitrogen contained in the inflowing sewage, that is, ammonia nitrogen is used as a main component, the nitrogen component is oxidized to nitrate nitrogen by the action of nitrifying bacteria when the reaction tank 3 is brought into an aerobic state. For a single reactor,
By performing aeration intermittently and under anaerobic conditions, it is released into the atmosphere as nitrogen gas by the action of denitrifying bacteria,
Nitrate nitrogen is reduced to nitrogen gas and released into the atmosphere.

Further, the reaction tank 3 is divided into an aerobic tank and an anaerobic tank, and sewage is introduced into the anaerobic tank, and the nitrified liquid nitrified in the subsequent aerobic tank is circulated to the anaerobic tank as a sludge mixture. By configuring, it is possible to perform denitrification.

FIG. 2 shows a processing flow chart of a second embodiment of the method for treating sewage and sludge of the present invention. In this embodiment, a reaction tank 3 is used instead of the final precipitation tank 4 of the first embodiment.
A membrane separation device 11 is provided in the inside, and a method of taking out treated water B by a membrane such as a microfiltration membrane or an ultrafiltration membrane is adopted. Same as the example. By using the membrane separation device 11, the sludge concentration in the reaction tank 3 can be increased, so that the processing time can be further reduced as compared with the case of the first embodiment, thereby reducing the installation space. It is possible to make it smaller. However, in this embodiment, since the treatment is performed with high-concentration activated sludge using the membrane separation device 11, the amount of generated sludge is somewhat smaller than that of the ordinary activated sludge method. Therefore, it is necessary to set the amount of sludge to be solubilized in consideration of this.

In the processing flow of the first embodiment, when a part of the settled sludge in the final settling tank 4 is solubilized, the sludge concentration fluctuates somewhat. Since the sludge can be pulled out of the reaction tank 3,
The concentration of sludge to be solubilized is stable, and more stable solubilization can be performed.

[0023]

According to the method for treating wastewater and sludge of the first invention, the sludge separated in the final sedimentation tank is led to the complete anaerobic tank in the preceding stage, so that the untreated components in the sludge are re-used. Complete treatment can be performed by biological treatment, and sludge separated in the final sedimentation tank is solubilized to decompose as a nutrient source for other microorganisms. Is only the coagulated sludge and the sludge mainly composed of non-solubilized inorganic substances.
Since the volume can be reduced to about 10 and denitrification by biological treatment and dephosphorization by treatment combining biological treatment and coagulant can be performed at the same time, the volume of sludge can be reduced. Advanced treatments such as organic matter removal, denitrification, and dephosphorization can be performed. And since the sludge discharged out of the plant is only coagulated sludge and sludge mainly composed of non-solubilized inorganic substances, the volume is reduced to about 1/10 of the conventional sludge, and less land is required for landfill disposal. It does not cause problems such as anaerobic rot and odor.

According to the method for treating sewage and sludge of the second invention, a membrane separation device is provided in the reaction tank to take out the treated water subjected to solid-liquid separation. This makes it possible to perform treatment with activated sludge having a high concentration, thereby shortening the treatment time and reducing the amount of sludge generated, making it possible to reduce the installation space of the apparatus. In addition, since the homogenized sludge can be pulled out from the reaction tank, the concentration of the sludge to be solubilized is stable, and more stable solubilization can be performed. In addition, since the sludge in the reaction tank is led to the complete anaerobic tank in the preceding stage, the untreated components in the sludge can be completely treated by biological treatment again, and the sludge separated in the final sedimentation tank can be removed. By solubilizing the part, it is decomposed as a nutrient source of other microorganisms, so the only sludge to be discharged out of the plant is flocculated sludge and non-solubilized inorganic-based sludge only,
Since the volume can be reduced to about 1/10 of the conventional one, denitrification by biological treatment and dephosphorization by treatment combining biological treatment and coagulant can be performed at the same time. Advanced treatments such as removal of organic substances, denitrification, and dephosphorization can be performed together with the conversion. And since the sludge discharged out of the plant is only coagulated sludge and sludge mainly composed of non-solubilized inorganic substances, the volume is reduced to about 1/10 of the conventional sludge, and less land is required for landfill disposal. It does not cause problems such as anaerobic rot and odor.

[Brief description of the drawings]

FIG. 1 is a sewage treatment flow chart showing a first embodiment of a method for treating sewage and sludge of the present invention.

FIG. 2 is a sewage treatment flow chart showing a second embodiment of the method for treating sewage and sludge of the present invention.

[Description of Signs] A Wastewater flowing into sewage treatment plant B Solid-liquid separated treated water C Returned sludge D Solubilized sludge E Precipitated sludge F Excess sludge G Separation liquid 1 Pretreatment equipment 2 Complete anaerobic tank 3 Reaction tank 4 Final Sedimentation tank 5 Sludge transfer pump 6 Solubilizer supply device 7 Sludge solubilization tank 8 Coagulant supply device 9 Precipitation separation tank 10 Sludge concentration storage tank 11 Membrane separation device

Claims (2)

[Claims] 1. A method for treating sewage and sludge by subjecting organic sewage to biological treatment by sludge microorganisms in a reaction tank and solubilizing the sludge generated by the biological treatment. The sludge separated in the final sedimentation tank is returned to the tank, and a part of the sludge separated in the final sedimentation tank is guided to the sludge solubilization tank for solubilization treatment. A method for treating sewage and sludge, wherein the sludge that has been precipitated and separated by coagulation of phosphorus eluted from the sludge is discharged as surplus sludge, and the separated liquid is returned to a completely anaerobic tank or a reaction tank. 2. A method for treating sewage and sludge by subjecting organic sewage to biological treatment with sludge microorganisms in the reaction tank and solubilizing the sludge generated by the biological treatment. Separation of the treated water by the process, the sludge in the reaction tank is returned to the complete anaerobic tank installed in the previous stage of the reaction tank, and a part of the sludge in the reaction tank is led to the sludge solubilization tank to perform the solubilization treatment. After that, a flocculant was added, and the mixture was led to a sedimentation separation tank, and the sludge separated by segregation and precipitation of phosphorus eluted from the sludge was discharged as surplus sludge, and the separated liquid was returned to the complete anaerobic tank or the reaction tank. A method for treating sewage and sludge, characterized in that: