JP2010046602A - Method of treating oil-containing waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To treat oil-containing waste water containing animal and plant oil by combining biological treatment using microorganism and floatation separation using fine bubbles. <P>SOLUTION: The stable treatment extremely small in malodor is continuously carried out by combining activated sludge method and the solid-liquid separation by the floating separation using fine bubbles to attach flock containing actinomycete or other aerobic microbes to the fine bubbles to float it and separate it and returning the floated and separated froth to a biological reaction tank to hold the microorganism having high oil degradable property in the treatment system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of biologically treating oil-containing wastewater containing animal and vegetable oils using microorganisms.

  The conventional activated sludge method using the action of microorganisms mostly uses gravity sedimentation or membrane separation as a solid-liquid separation method for separating generated sludge from clean treated water (Patent Documents 1 and 2). , 3).

  In the case of solid-liquid separation by gravity sedimentation, if there is an inflow of oil or air bubbles adhering, sedimentation of the generated sludge is hindered, and the separation function is greatly reduced. The same applies when the microorganisms used in the activated sludge process discharge hydrophobic secretions. In such a state, the sludge settles slowly, the sedimented sludge does not become compact, and a phenomenon in which a hydrophobic substance floats on the water surface occurs. If sedimentation / sedimentation is not successful, the supernatant water not only becomes cloudy, but the floating microorganisms contained in the supernatant are discharged together with the supernatant water, so that the microorganisms cannot be retained in the system, and the processing is continued. There is a problem that becomes difficult.

  In the case of membrane separation, microorganisms exceeding the pore size do not flow out regardless of hydrophobicity or hydrophilicity. Therefore, the SS (floating matter amount) concentration in the treated water is low because it depends on the performance of the filtration membrane, but the presence of a substance with strong adhesiveness such as oil causes the membrane pores to be clogged by the substance. Therefore, there is a problem that continuous processing cannot be performed unless the filter membrane is periodically cleaned.

  By the way, many wastewater from food factories that produce bento lunches, side dishes, etc. contain oils such as animal and vegetable oils. As a method for removing oils from such oil-containing wastewater, the specific gravity difference between oil and moisture Although the method of physically removing the oil component that has floated by using this method has been implemented, the removal rate is poor because of the physical removal, and the wall of the treatment tank becomes sticky due to the oil as time passes. Moreover, a bad odor is generated by the oxidation of the oil.

There is also a method in which a chemical is added to the oil component floating on the upper layer of the wastewater to make it water-soluble and the oil component is chemically removed. Even when the oil is removed by either a physical or chemical method, this oil removal step is a pretreatment step that is unnecessary in the ordinary activated sludge method, and as a result, the treatment efficiency is also deteriorated.
JP 11-235599 A JP 2002-233890 A JP 2005-199167 A

  An object of the present invention is to enable treatment of oil-containing wastewater containing animal and vegetable oils or the like by combining biological treatment using microorganisms and flotation separation using fine bubbles.

  The invention of claim 1 for solving the above-mentioned problem is a method of biologically treating wastewater containing animal and vegetable oils using microorganisms, wherein the wastewater supplied to the aeration tank is treated with microorganisms mainly composed of actinomycetes. An aeration process in which air and water are stirred in the presence, and an animal and vegetable oil contained in the wastewater and organic matter are decomposed by the action of the microorganisms to generate sludge; and an intermediate treated water treated in the aeration process; A portion excluding the uppermost sludge layer and the uppermost layer by levitating the sludge containing the microorganisms by allowing it to stand in a floating separation tank in a mixed state with mixed water containing fine bubbles. A floating separation step for separating the treated water layer, and a treated water discharge step for discharging the treated water from the treated water layer to the outside after the sludge layer floats to the uppermost layer and becomes a compacted state. And included in the sludge layer A floating sludge returning step of returning at least a part of the sludge layer floating in the flotation separation tank to the aeration tank in order to repeatedly use microorganisms in animal and vegetable oils contained in wastewater and decomposition of organic matter. It is characterized by that.

  When intermediate treated water obtained by aerobic biotreatment of oil-containing wastewater in the aeration process is stored as it is in the sedimentation tank by the standard activated sludge method, many animal and vegetable oils such as lipase are present in the presence of sufficient oxygen. It is decomposed by microorganisms that secrete enzymes to form flocs, and these microorganisms grow by assimilating the substrate, but the flocs are poorly settled and remain floating in water, so that they are separated from the treated water. Is not done well. In this state, if the treated water is discharged, the microorganisms are also washed away, and microorganisms that contribute to the decomposition of animal and vegetable oils and other organic substances in the wastewater are no longer accumulated in the system, thus continuing the biological treatment with high treatment performance. It becomes difficult.

  In order to keep microorganisms capable of degrading animal and vegetable oils in the biological treatment system so that biological treatment with high treatment performance can be continued, the invention of claim 1 includes a decomposition component of animal and vegetable oils, and more than water. A floating separation method using fine bubbles is adopted as a solid-liquid separation method for separating activated sludge having a low specific gravity and treated water. The invention of claim 1 has a great feature in that the activated sludge method and the flotation separation method using fine bubbles are combined. That is, a contact aeration method in which a contact material is placed in an aeration tank and aerated to perform biological treatment, and a carrier method in which a carrier carrying microorganisms is flowed in water to perform biological treatment are compared with the activated sludge method. The density of organisms per unit volume is significantly low. Therefore, in the activated sludge method, if separation of activated sludge having buoyancy and treated water can be performed with high accuracy, treatment with higher efficiency than the contact aeration method and the carrier method described above becomes possible.

  Therefore, the invention of claim 1 attaches fine bubbles to floating activated sludge (floc) as a means for separating activated sludge (floc) containing a decomposition component of animal and vegetable oils and having floating properties and treated water. We adopted a method to ensure ascent by ascending. Thereby, if it is sedimentation separation, the flocs of the floating microorganisms that flow out together with the treated water are also floated on the upper part of the tank and can be separated from the treated water in the lower layer. That is, the activated sludge containing the microorganisms (floc) is stored in the floating separation tank in a mixed state with the intermediate treated water treated in the aeration step and the mixed water mixed with fine bubbles. ) Is levitated to separate the levitated sludge layer from the lower treated water layer, the treated water in the treated water layer is discharged out of the tank, and at least a part of the levitated sludge separated from the treated water is It is returned to the aeration tank, which is a treatment tank, and used for biological treatment of the next wastewater. By separating the activated sludge by attaching fine bubbles to the activated sludge having buoyancy, the separation accuracy between the treated water and the activated sludge containing microorganisms increases, so the SS concentration of the treated water decreases.

  In addition, certain actinomycetes with high oil content secretion secrete high molecular substances such as mycolic acid, and the high molecular substances have strong hydrophobicity and easily adhere to the outside of the cell wall. When fine bubbles are brought into contact with each other, the flocs containing actinomycetes are easily separated from the treated water and become floating sludge (floss). When this floss is returned to the aeration tank (biological reaction tank), it is possible to continue the biological treatment mainly composed of actinomycetes and other aerobic microorganisms. Undecomposed oil is taken into the floss side and returned to the bioreactor or discarded. In bioreactors, actinomycetes and other aerobic microorganisms with high oil resolution efficiently decompose oil, and the decomposition is an aerobic process performed in the presence of oxygen, so odor-causing substances are also adsorbed. Since it is decomposed, the original odor of the raw wastewater is greatly reduced in the biological reaction tank. Moreover, since the separated floss is also composed of aerobic organisms, almost no odor is emitted.

  The invention of claim 1 is a combination of the activated sludge method and solid-liquid separation by flotation separation using fine bubbles, and the flocs containing actinomycetes and other aerobic microorganisms are floated by attaching fine bubbles. Since the floss separated and floated is returned to the biological reaction tank, microorganisms having a high oil content can be retained in the treatment system, and stable treatment with very little odor can be continued.

  Further, in the invention of claim 2, in the invention of claim 1, large internal bubbles are removed by guiding the intermediate treated water in the aeration tank in which sludge is generated by the aeration process to the deaeration tank and leaving it to stand. Later, it is characterized in that it is mixed with air-mixed water mixed with fine bubbles.

  In the state where the large bubbles generated inside are removed by the aeration process, the intermediate treated water and the mixed water mixed with the fine bubbles are mixed, so that the fine bubbles are easily held as they are. The total number of fine bubbles adhering to the flocs having floating properties can no longer be reduced, so that the floating properties of the flocs, and thus high separation between the flocs and the treated water can be maintained.

  Further, the invention of claim 3 is that in the invention of claim 1 or 2, the mixed water used in the floating separation step is circulated and used by the treated water separated in the floating separation step. It is a feature.

  According to the third aspect of the present invention, the sludge containing microorganisms is levitated and brought into a compacted state, whereby the uppermost sludge layer and the treated water of the portion excluding the uppermost layer are separated from each other. Since the treated water obtained in the floating separation process and discharged to the outside of the tank and discharged as it is is reused as the mixed water to be produced, the water for generating the mixed water is used as the mixed water. There is an advantage that is not necessary each time.

  The invention of claim 4 is characterized in that, in any of the inventions of claims 1 to 3, the SS concentration of treated water is adjusted by adjusting the amount of fine bubbles contained in the mixed water.

  According to the invention of claim 4, by adjusting the amount of fine bubbles contained in the mixed water, the amount of bubbles adhering to the suspended sludge is increased or decreased, and the buoyancy of the suspended sludge is changed. For example, when the amount of fine bubbles is reduced, floating sludge with a small amount of attached fine bubbles increases and remains suspended without being lifted or settles, so that the SS concentration of the treatment liquid increases. Therefore, the SS concentration of the treated water can be adjusted by adjusting the amount (ratio) of fine bubbles contained in the mixed water.

  The present invention is a combination of an activated sludge method and solid-liquid separation by flotation separation using fine bubbles, and the flocs containing actinomycetes and other aerobic microorganisms are separated by attaching fine bubbles to the surface. In addition, since the floss separated and floated is returned to the biological reaction tank, microorganisms with high oil content can be retained in the treatment system, and stable treatment with very little odor can be continued.

  Hereinafter, the present invention will be described in more detail with reference to the best mode.

FIG. 1 is an overall view of an apparatus for carrying out an oil-containing wastewater treatment method according to the present invention. While briefly explaining the overall configuration of an oil-containing wastewater treatment apparatus, FIG. explain. The aeration tank A is also referred to as a biological reaction tank. Air is blown into the tank from the aeration blower 1, and sewage containing animal and vegetable oils stored in the tank is agitated to generate sludge by the action of microorganisms. It functions as a “sewage adjustment reaction tank”. Nocardia, Enterobacter, Bacillus and the like are known as suitable microorganisms for degrading animal and vegetable oils by biological action. The aeration tank A of the embodiment is separated into a plurality of chambers (three chambers in the embodiment) by the partition wall 2, and the air supplied from the aeration blower 1 is treated sewage from an aerator 3 installed at the bottom of each chamber. The treated sewage is agitated while being supplied and floated. A predetermined flow gap 4 is formed between the lower end of each partition wall 2 and the bottom surface of the aeration tank A, and the sewage undiluted solution W ₁ supplied to a specific chamber passes through the flow gap 4 into each chamber. Supplied. Moreover, the air supplied from one common aeration blower 1 is branched and supplied to each chamber. Since the sewage undiluted solution W ₁ contains animal and vegetable oils, the generated sludge is a sludge mass (floc) that has a poor sedimentation property and remains floating. In FIG. 1, reference numeral 5 denotes an on-off valve provided in an air pipe for supplying air to each chamber.

A sludge mass (floc) is generated in the intermediate treated water (adjusted sewage) W ₂ containing animal and vegetable oils adjusted in the aeration tank A, but the sludge mass (floc) floats in water without settling. In addition, since the sewage is agitated by the air supplied from the aerator 3, the sewage contains large bubbles. In this state, the sewage is supplied to the floating separation tank C, and the fine air Even if microbubbles containing bubbles are supplied, the sludge mass (floc) floating in the sewage is decomposed into multiple small masses due to the presence of large air bubbles, and the sludge mass (floc) is levitated. In many cases, it is prevented from becoming floating sludge (floss) having an appropriate compaction property by being floated on the surface layer of the separation tank C and further compacted by another sludge mass (floc) that later floats.

Therefore, a certain amount of intermediate treated water W ₂ that is adjusted in the aeration tank A and in which the sludge mass (floc) is suspended in the water is temporarily stored in the deaeration tank B by the pump P _1, for a predetermined time (for example, 3 minutes), the large bubbles contained in the intermediate treated water W ₂ are levitated and released, thereby degassing the large bubbles from the adjusted sewage, and the adjusted sewage in this state contains fine bubbles. It produces “mixed water”. The water level of the intermediate treated water W ₂ supplied into the deaeration tank B is set to be equal to or slightly higher than the water level of the treated water stored in the floating separation tank C. The intermediate treatment water W ₂ is continuously supplied from the aeration tank A to the deaeration tank B, and the intermediate treatment water W ₂ of the deaeration tank B is supplied by the supply of the intermediate treatment water W ₂ from the aeration tank A. When the water level becomes higher than the upper end of the drain pipe 31 in the treated water discharge auxiliary tank 24 provided in the floating separation tank C, the intermediate treated water W ₂ in the deaeration tank B is part of the mixer 14. The mixed water described later is mixed and supplied into the floating separation tank C. That is, the flow of the intermediate treated water W ₂ from the deaeration tank B to the floating separation tank C depends only on the water level difference between both tanks B and C.

In the floating separation tank C, fine bubbles are mixed by the action of the fine bubbles by allowing the mixed water containing fine bubbles to flow into the intermediate treated water W ₂ deaerated in the degas tank B and storing it. The sludge mass (floc) floating in the intermediate treated water W ₂ is levitated to the upper layer, and the sludge mass (floc) levitated to the upper layer is pressurized from below by the sludge mass (floc) that later floats. An apparatus that separates sludge mass having buoyancy and treated water W ₃ by consolidating the sludge mass (floc) and storing treated water W ₃ in a portion other than the upper layer as floating sludge mass (floss) It is.

A degassing tank B and a pressurized mixed gas tank D are connected to the floating separation tank C via a pipe line. In the pressurized air / fuel tank D, a compressor 12 is connected to a tank 11, water is accommodated in most of the tank 11, and an upper layer portion is a space portion 13, and a compressor is placed in the upper layer space portion 13. By supplying the compressed air from 12, fine bubbles are taken into the water accommodated in the tank 11 to become “mixed water”. This “mixed water” is mixed with the intermediate treated water W ₂ flowing out from the deaeration tank B in the mixer 14, and the water level of the intermediate treated water W ₂ in the deaeration tank B rises to the floating separation tank C. By being relatively higher than the water level of the intermediate treated water W ₂ or the treated water W ₃ , it is supplied into the floating separation tank C.

In the floating separation tank C, the casing 22 is disposed in the center of the tank 21 in a submerged state, and the bottom center of the tank 21 is a deep bottom treated water outlet 23, and the treated water outlet 23 is The treated water discharge auxiliary tank 24 attached to the upper part of the tank 21 is communicated. The casing 22 is supplied from the deaeration tank B, guides the intermediate treated water W ₂ mixed with the mixed water supplied from the pressurized mixed tank D, and has a uniform upward flow in the tank 21. It is a member for making it. In a portion of the tank 21 that is different in phase along the circumferential direction from the treated water discharge auxiliary tank 24, a floating sludge mass (floss) that floats on the upper layer of the tank 21 is removed by a scraping plate 25 that is rotated by a motor M. A floss storage portion 26 for storing the scraped floss is provided.

Therefore, in the flotation tank C, in a state in which admission water fine bubbles on the intermediate process water W ₂ are mixed it is mixed, the intermediate treatment water W ₂ in the portion of the cage body 22 of the flotation tank C The intermediate treated water W ₂ supplied and introduced into the enclosure 22 surrounded by the periphery rises as an upward flow. The buoyancy is increased by adhering fine bubbles to the activated sludge (lumps) existing in a floating state in the intermediate treated water W ₂ , and the buoyancy increases to the upper layer of the tank 21, and another activated sludge (lumps) below. ) Is activated from below, the activated sludge (lumps) that have floated first is compressed from below. On the other hand, specific actinomycetes with high oil content secretion secrete high molecular substances such as mycolic acid, and the high molecular substances have strong hydrophobicity and easily adhere to the outside of the cell wall. When fine bubbles are brought into contact with each other, the flocs containing actinomycetes are easily separated from the intermediate treated water W ₂ and become floating sludge (floss). Thus, the presence of fine bubbles in the intermediate treated water W ₂ increases the buoyancy of the activated sludge (lumps) suspended in water, and the specific actinomycetes with oil resolution are The activated sludge (lumps) of the intermediate treated water W ₂ is the upper layer of the tank 21 by synergistic with the biological reaction that flocs containing actinomycetes are easily separated from the intermediate treated water W ₂ by contacting with the intermediate treated water W _2. Therefore, the separability between the floating sludge mass (floss) floating on the upper layer portion of the tank 21 and the treated water W ₃ stored in a portion other than the upper layer portion of the tank 21 is enhanced. For this reason, the treated water W ₃ can be discharged in a clean state with a low SS concentration.

And since the treated water extraction part 23 of the bottom part of the tank 21 and the treated water discharge auxiliary tank 24 attached to the upper part of the said tank 21 are connected, most SS density | concentration stored by the said treated water extraction part 23 is connected. When the low treated water W ₃ is supplied to the treated water discharge auxiliary tank 24 and the water level in the auxiliary tank 24 tends to be higher than the upper end surface of the drainage tank 31 disposed in the auxiliary tank 24, The treated water W ₃ supplied into the auxiliary tank 24 from the treated water outlet 23 of the separation tank C is temporarily stored in the treated water monitoring tank E through the drain pipe 31 and then discharged as sewage. The processing water monitoring tank E is treated water discharged auxiliary tank is disposed at a position lower than the water level surface 24, treated water W ₃ is drained into the treated water monitoring tank E from treated water discharge auxiliary tank 24 by the water level difference Is done. On the other hand, the treated water outlet 23 at the bottom of the tank 21 and the tank 11 of the pressurized mixed tank D are communicated via a pipe line, and the treated water W ₃ in the tank 21 is acted on by the action of the pump P _2. Is supplied into the tank 11 of the pressurized mixed tank D and repeatedly used as mixed water in which fine bubbles are mixed. For this reason, there is an advantage that water for generating mixed air is not required each time because the treated water that is discharged out of the tank and discharged is reused.

The floating sludge mass (floss) that has floated on the upper layer of the tank 21 of the floating separation tank C is rotated by a scraping plate 25 that is rotated by a motor M, and a froth container 26 attached to the upper part of the tank 21. Is housed in. Here, a part of the stored floating sludge mass is returned to the aeration tank A, and microorganisms with high oil content are discharged to the outside for use in biological treatment of the next wastewater (sewage undiluted solution W ₁ ). Therefore, it is possible to continue the biological treatment mainly composed of actinomycetes and other aerobic microorganisms. In addition, the rest of the levitated sludge contained is discarded. Further, the undecomposed oil component is taken into the floating sludge lump side and returned to the aeration tank A or discarded together with the floating sludge lump.

As described above, only the supply of the intermediate treated water W ₂ from the aeration tank A to the deaeration tank B and the supply of the treated water W ₃ from the floating separation tank C to the pressurized mixed tank D are performed by a pump. However, the supply of the intermediate treated water W ₂ from the deaeration tank B to the floating separation tank C and the supply of the treated water W ₃ from the treated water discharge auxiliary tank 24 to the treated water monitoring tank E are both water level differences. It depends on. Therefore, after the intermediate treated water W ₂ is supplied from the aeration tank A to the deaeration tank B, the water level difference is all except for the supply of the treated water W ₃ from the floating separation tank C to the pressurized mixed gas tank D. Therefore, the intermediate treated water W ₂ or the treated water W ₃ flows.

  Further, the SS concentration of treated water can be adjusted by the amount (ratio) of fine bubbles contained in the mixed water. For example, if the amount of fine bubbles contained in the mixed water is reduced (squeezed), the amount of bubbles adhering to the floating sludge also decreases, resulting in an increase in the amount of air bubbles not adhering or a small amount of adhering floating sludge. As a result, the SS concentration of the treatment liquid becomes high because the liquid remains floating or settles. Therefore, the SS concentration of the treated water can be adjusted by adjusting the amount (ratio) of fine bubbles contained in the mixed water.

  Thus, the oil-containing wastewater treatment method according to the present invention is a combination of the activated sludge method and solid-liquid separation by flotation separation using fine bubbles, and includes flocs containing actinomycetes and other aerobic microorganisms. The structure is such that fine bubbles are attached and floated and separated, and the floss separated and floated is returned to the biological reaction tank, so that microorganisms with high oil content can be retained in the treatment system, and stable treatment with extremely low odor is possible. Can continue.

In the above embodiment, a part of the treated water W ₃ separated in the floating separation tank C is reused as mixed water, but all of the treated water W ₃ may be discharged into the sewage. .

1 is an overall view of an apparatus for carrying out an oil-containing wastewater treatment method according to the present invention.

Explanation of symbols

A: Aeration tank
B: Deaeration tank
C: Levitation separation tank
D: Pressurized mixed tank
W ₁ : Sewage concentrate
W ₂ : Intermediate treated water
W ₃ : treated water

Claims (4)

A method of biologically treating wastewater containing animal and vegetable oils using microorganisms,
The wastewater supplied to the aeration tank is stirred while blowing air in the presence of microorganisms mainly composed of actinomycetes, and the animal and vegetable oils and organic substances contained in the wastewater are decomposed by the action of the microorganisms to generate sludge. An aeration process;
The sludge containing the microorganisms is levitated by allowing the intermediate treated water treated in the aeration process and the mixed water mixed with fine bubbles to be mixed and stored in the floating separation tank and allowed to stand. A flotation separation step for separating the uppermost sludge layer and the treated water layer excluding the uppermost layer;
After the sludge layer rises to the uppermost layer and becomes a consolidated state, the treated water discharge step of discharging the treated water of the treated water layer out of the tank and discharging it,
Levitation for returning at least a part of the sludge layer floating in the flotation separation tank to the aeration tank in order to repeatedly use microorganisms contained in the sludge layer for the decomposition of animal and vegetable oils contained in wastewater and organic matter Sludge return process,
An oil-containing wastewater treatment method comprising:   The intermediate treated water in the aeration tank in which sludge is generated by the aeration process is guided to the deaeration tank and left to stand to remove large bubbles inside and then mixed with the mixed water mixed with fine bubbles. The oil-containing wastewater treatment method according to claim 1, wherein the oil-containing wastewater is treated.   The oil-containing wastewater treatment method according to claim 1 or 2, wherein the mixed water used in the floating separation step circulates and uses the treated water separated in the floating separation step.   The oil-containing wastewater treatment method according to any one of claims 1 to 3, wherein the SS concentration of the treated water is adjusted by adjusting the amount of fine bubbles contained in the mixed water.

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