JP2016150332A - Method and apparatus for biologically treating organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for biologically treating organic waste water, in each of which a fixed bed can be formed in a first biological treatment tank (a dispersed bacteria tank) by using a fixed bed carrier without growing microorganisms and high load treatment can be performed in the dispersed bacteria tank without worrying about operation failure.SOLUTION: The method for biologically treating organic waste water comprises the steps of: introducing the organic waste water into the first biological treatment tank 10; performing biological treatment on the introduced organic waste water while using bacteria to generate the dispersed bacteria; sending dispersed bacteria-containing first biologically-treated water to a second biological treatment tank 20 from the first biological treatment tank 10; and biologically treating the sent dispersed bacteria-containing first biologically-treated water in the second biological treatment tank. Each of the fixed beds 11, 21 is formed by arranging a plurality of sheet-shaped carriers in each of the first biological treatment tank 10 and the second biological treatment tank 20 so that the surface of the sheet-shaped carrier becomes vertical. Air is diffused from the bottom of the fixed bed 11 by 0.1-5 m/m(the bottom area)/minute.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biological treatment method and apparatus for organic wastewater that can be used for treatment of organic wastewater in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories, and in particular, two stages in series. The first aerobic biological treatment tank is provided, the organic waste water is introduced into the first biological treatment tank, and the bacteria are biologically treated to produce dispersed bacteria. The first biologically treated water containing the dispersed bacteria from the first biological treatment tank. The present invention relates to a biological treatment method and apparatus for organic wastewater that is passed through a biological treatment tank after the second biological treatment tank for biological treatment.

  In the first biological treatment tank (dispersed bacteria tank), most of the organic matter is decomposed by dispersible bacteria to produce dispersible bacteria. In biological treatment systems that prey on bacteria and reduce the amount of generated sludge, it is known to add and install a microorganism holding carrier in each biological treatment tank in order to stabilize the treatment. At this time, a fluidized bed is used for dispersible bacteria, and a fluidized bed carrier and a fixed bed carrier are used for minute animals (Patent Documents 1 to 5).

  When using a fixed bed carrier in a micro animal tank, it is necessary to adjust the aeration conditions in order to hold the micro animal and to remove excess sludge.

WO2012 / 124675 JP2013-121558A JP2013-141640A JP2007-050366 JP 05-068986 A

  Since the dispersed bacteria tank is operated at a high load, when a fixed bed carrier is used, sludge adheres excessively, and flocculent bacteria and micro animals are generated in the dispersed bacteria tank. For this reason, conventionally, in a dispersion bacterium tank, a fluidized bed is used as a microorganism-supporting carrier, so that the treatment is performed with a high load.

  In the case of a fluidized bed, a screen for separating the carrier is required in the drainage section of the treatment tank, but due to high load treatment, it is due to the generation of filamentous bacteria and solidification of oil (in the case of pH drop when oil-containing wastewater flows in) There is concern about screen blockage. In addition, when a fluidized bed carrier is used, the bubbles are associated by collision between the bubbles and the carrier. Therefore, when a fine bubble diffusing tube is used, the original dissolution efficiency may not be obtained.

  In the present invention, even when a fixed bed carrier is used in the first biological treatment tank (dispersed bacteria tank), a fixed bed can be formed without growing micro-animals, and there is no concern about the above-mentioned poor operation. It aims at providing the biological treatment method and apparatus of the organic waste water which can process a tank with high load.

The biological treatment method for organic wastewater of the present invention comprises two or more aerobic biological treatment tanks in series, introduces organic wastewater into the first biological treatment tank and biologically treats with bacteria to produce dispersed bacteria, In the biological treatment method for organic wastewater, the first biological treatment water containing the dispersal bacteria from the first biological treatment tank is passed through the biological treatment tanks after the second biological treatment tank for biological treatment. A plurality of sheet-like first carriers are installed such that the surface direction is a vertical direction to form a first fixed bed, and the amount of air diffused from below the first fixed bed is 0.1 to ⁵ m ³ -air / m ² −. Aeration is performed at the bottom area / min.

The organic wastewater biological treatment apparatus of the present invention comprises two or more aerobic biological treatment tanks in series, introduces organic wastewater into the first biological treatment tank, and biologically treats with bacteria to produce dispersed bacteria. In an organic wastewater biological treatment apparatus for conducting biological treatment by passing first biological treatment water containing dispersal bacteria from a first biological treatment tank to a biological treatment tank after the second biological treatment tank, A first fixed bed formed by installing a plurality of sheet-like first carriers so that the surface direction is vertical, and the amount of air diffused from below the first fixed bed is 0.1 to ⁵ m ³ -air / m. ^2—A diffuser for aeration at the bottom area / min.

In one aspect of the present invention, a plurality of sheet-like second carriers are installed in the second biological treatment tank so that the surface direction is a vertical direction to form a second fixed bed, and scattered from below the second fixed bed. Aeration amount is 0.05 to 0.8 m ³ -air / m ² -bottom area / min, and the amount of air diffused from below the first fixed bed is 1.5 of the amount of air diffused from below the second fixed bed. -3 times excess aeration.

  In one embodiment of the present invention, each carrier interval of the first carrier or the second carrier is 1 to 10 cm, and the aeration is performed so that the average bubble diameter of the aeration bubbles is 0.01 to 0.2 times the interval. .

  In one aspect of the present invention, a preliminary aeration for adjusting the dissolved oxygen concentration is performed in the first biological treatment tank other than the lower part of the first fixed bed, and the diffused air from the lower part of the first fixed bed is diffused. Reduce the amount of pre-air diffused air from the air volume.

  In one embodiment of the present invention, the organic waste water contains oil or has a high BOD concentration of 300 to 10,000 mg / L.

In the present invention, a plurality of sheet-like first carriers are installed in the first biological treatment tank so that the surface direction is a vertical direction to form a first fixed bed, and the amount of air diffused from below the first fixed bed is 0. Air is diffused at ^{1 to} 5 m ³ -air / m ² -bottom area / min. In this way, a large amount of air diffused from below the first fixed bed increases the flow velocity on the surface of the carrier, preventing micro-animals from growing on the carrier, and preventing excessive bacterial adhesion.

  Therefore, in this invention, even if organic wastewater contains an oil component or BOD is a high density | concentration of 300-10000 mg / L, organic wastewater can be biologically processed efficiently without fear of a malfunction.

A second fixed bed is formed in the second biological treatment tank, and the first fixed bed is diffused from below the second fixed bed with an air diffusion amount of 0.05 to 0.8 m ³ -air / m ² -bottom area / min. When the amount of air diffused from below the fixed bed is 1.5 to 3 times the amount of air diffused from below the second fixed bed, a biofilm is formed on the first carrier while preventing micro-animals from growing. . In addition, the second carrier can grow micro-animals.

  Each carrier interval of the first carrier or the second carrier is 1 to 10 cm, and by aeration so that the average bubble diameter of the aeration bubbles is 0.01 to 0.2 times the interval, Air bubbles uniformly intrude into the substrate to facilitate cleaning of the carrier surface.

  In the first biological treatment tank, a preliminary aeration for adjusting the dissolved oxygen concentration is performed at a place other than the lower part of the first fixed bed. By reducing the amount of diffused air, the inside of the first fixed bed becomes an upward flow.

It is a flowchart which shows the biological treatment method and apparatus of the organic waste_water | drain which concerns on embodiment. It is a flowchart which shows the biological treatment method and apparatus of the organic waste_water | drain which concerns on embodiment. It is a flowchart which shows the biological treatment method and apparatus of the organic waste_water | drain which concerns on embodiment. It is a flowchart which shows the biological treatment method and apparatus of the organic waste_water | drain which concerns on embodiment.

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

  FIG. 1 is a flowchart showing a preferred embodiment of the method and apparatus of the present invention. In this flow, the organic wastewater is treated aerobically in the first biological treatment tank 10 to culture bacteria, and the first treated water from the first biological treatment tank 10 is introduced into the second biological treatment tank 20. Then, the microanimals are preyed by causing the microanimals (protozoa, metazoans) to prey on the dispersal bacteria contained in the first treated water. In FIG. 1, the 2nd treated water from this 2nd biological treatment tank 20 is introduce | transduced into the precipitation tank 30, and it separates into solid and liquid, and takes out treated water out of the system. Further, at least a part of the sludge settled in the settling tank 30 is returned to the second biological treatment tank 20.

  In the first biological treatment tank 10 and the second biological treatment tank 20, a plurality of sheet-like carriers (first carrier, second carrier) are installed so that the surface direction is a vertical direction. 11 and the second fixed floor 21 are formed. Air diffusers 12 and 22 are installed below the fixed floors 11 and 21, respectively.

  By comprising the 1st fixed bed 11 with a sheet-like support | carrier, disperse bacteria produce | generate efficiently without being influenced by the density | concentration fluctuation | variation of organic waste water.

  By using a sheet-like carrier as the second carrier for forming the second fixed bed 21, it is possible to preferentially grow the filtration predation type micro-animal and to form sludge having good solid-liquid separation properties. For this reason, when biologically treated water is subjected to solid-liquid separation with a membrane separation device, clogging of the separation membrane can be prevented and membrane separation can be performed stably over a long period of time. In addition, when biologically treated water is agglomerated and settled and separated in a sedimentation tank, the amount of flocculant added can be reduced, and stable sludge interface management is also performed in a sludge return-type sedimentation tank. It becomes possible.

[Sheet carrier]
A preferred embodiment of the sheet-like carrier will be described. A sheet-like carrier is preferably made of foamed plastic. This foam plastic carrier absorbs water in water and expands, so it has moderate flexibility, and it swings moderately due to the flow of water flowing into the tank and the upward flow caused by aeration, forming a rocking fixed bed You can also

  The sheet-like carrier is preferably composed of a rectangular plate-like or strip-like sheet. In the normal case, a fixture is attached to each of the short side portions (edges in the short direction) of the plate-shaped or strip-shaped carrier, and the sheet surface is placed upright so that it is in the depth direction of the tank. The The fixing tool is not limited to a material such as metal, cloth, or plastic, and any material that can reinforce the fixing portion against tensile stress when the sheet-like carrier is fixed in the tank. In addition, in order to increase the mechanical strength, both short sides of the sheet are sandwiched between one or more fixing tools and then fixed with fasteners (adhesive, thread, band, fixing screw, flat bar, etc.). Is desirable.

  The sheet-like carrier preferably has a large apparent surface area suitable for bacterial growth, egg laying and growth of micro animals.

The apparent surface area is the total surface area outside the surface of the foamed plastic sheet that does not include the surface area inside the foam cell. In the case of a rectangular sheet-like carrier having side lengths L ₁ and L ₂ and thickness d, the apparent surface area is (L ₁ × L ₂ × 2) + (L ₁ × d × 2) + (L ₂ × d × 2).

When the sheet-like carrier is rectangular, it is preferably installed so that the long side direction is the depth direction of the biological treatment tank. In this case, the length L ₁ of the long side of the sheet-like carrier is 100 to 400 cm, the length L ₂ of the short side perpendicular to the long side is 5 to 200 cm, and the thickness d is 0.5 to 5 cm is preferred. Moreover, handling properties, in terms of applicability to biological treatment _tank, L 2: length ratio of _{L 1 is, L 2: L 1 = 1} : is preferably about 1 to 80. Further, it may be repeated two to four stages in a height direction _{L 1} as 50 to 100 cm.

The side lengths L ₁ and L ₂ of the sheet-like carrier affect the apparent surface area of the carrier, and the larger the apparent surface area, the larger the number of bacteria (and minute animals) to be retained, which is preferable. However, the length L ₁ in the depth direction of the biological treatment tank in which the carrier is provided is not particularly limited because there is a flow due to aeration and the fluidity of water is not affected. The lateral direction length (width) _{L 2,} since the influence on the flowability of the water, _{L 2,} as described above, 5～200Cm, particularly preferably a 5 to 100 cm. Incidentally, the width L ₂ of the sheet-like carrier, in the case where the width of the biological treatment tank is large, it is preferable to prevent a short circuit current by increasing the number of sheet-like carrier provided in the biological treatment tank.

  On the other hand, if the thickness d of the carrier is too thick, when it is made of foamed plastic, the internal water permeability is lowered, so that the problem that the cells decay inside tends to occur. Therefore, the thickness d of the sheet is preferably reduced after securing the required strength, and is preferably 0.5 to 5 cm as described above.

In order to retain microorganisms, it is preferable to have at least two surfaces having an apparent surface area of 500 cm ² or more. That is, L ₁ × L ₂ is 500 cm ² or more, preferably 1000 cm ² or more. No particular limitation is imposed on the upper limit of the apparent surface area, in order to meet the suitable length of _L 1, _{L 2} described above, is usually 80000Cm ² below.

  As the conditions for the foamed cells of the foamed plastic sheet, those in which the distribution of the foamed cells is uniform are preferable. In addition, the number of foam cells and the pore diameter of the foam cells are preferably controlled to a value that allows sludge to adhere easily and easily peel off, and in particular, if there are too many foam cells or the cell diameter is too large, the sheet Therefore, it is preferable that the number of cells / 25 mm (the number of cells existing in the range of 25 mm length) is 125/25 mm or less, particularly 100/25 mm or less. Conversely, if the number of foamed cells is too small or the cell diameter is too small, the function as a porous carrier cannot be obtained sufficiently. / 25 mm is preferably 5 pieces / 25 mm or more, particularly preferably 25 pieces / 25 mm or more. Further, in order to realize such a number of foamed cells and to make the adhesion and peelability of sludge good, the average pore diameter of the foamed cells is in the range of 0.05 to 10 mm, particularly 0.25 to 1 mm. Preferably there is.

  For the number of cells / 25 mm, using a photograph of the sheet taken with a scanning electron microscope, the work of measuring the number of foamed cells intersecting the straight line 25 mm in the length direction was performed at a plurality of locations. An average value can be calculated and obtained. It can measure similarly about the hole diameter of a foaming cell.

  The foamed plastic composing such a sheet-shaped carrier is not particularly limited, but is preferably a flexible polyurethane foam because it expands due to water absorption and swings moderately in an upward flow due to water flow or aeration. . However, mechanical strength can also be obtained by using a hard plate-like sheet.

The sheet-like carrier has a ratio of the apparent surface area to the volume of the biological treatment tank (including the biological treatment tank if the return line has a biological treatment tank) relative to the volume of the biological treatment tank in which the sheet carrier is installed (that is, the apparent surface area). (Volume of biological treatment tank) is preferably 0.5 to 50 m ^{−1 in} terms of efficient biological treatment with a carrier filling rate suitable for the load of the biological treatment tank.

  A plurality of sheet-like carriers are arranged with the longitudinal direction thereof being the vertical direction (the depth direction of the biological treatment tank, that is, the vertical direction), and the sheet surfaces are aligned, with a slight gap between them. By fixing each other with a fastener (adhesive, thread, band, fixing screw, pipe, metal rod, etc.) via a fixing tool, an array body is formed. It is preferable to arrange them in parallel with a slight gap between them and to fix them by a fastener through the fixtures of each array to form a unit.

  In this way, by providing a unit in which a plurality of sheet-like carriers are arranged in parallel, the sheet-like carrier can be easily provided in the biological treatment tank so as to achieve an optimum filling rate. it can.

  If the carrier is not unitized, for example, a plurality of rod-like members are installed at the carrier installation location in the tank, and a plurality of rod-like members are fixed with fasteners (tie bands, metal hooks, piano wires, etc.) for each array. By fixing to a member, a sheet | seat can be installed in a biological treatment tank.

[Suitable conditions for biological treatment of organic wastewater]
In the embodiment of FIG. 1, raw water (organic wastewater) is introduced into the first biological treatment tank 10, and 70% or more, desirably 80%, of organic components (soluble BOD) due to dispersible bacteria (non-aggregating bacteria). More preferably, 85% or more is oxidatively decomposed. The pH of the first biological treatment tank 10 is 6 or more, preferably 8 or less. However, the pH may be 8 or more when raw oil contains a large amount of oil or when processing electronic industrial wastewater, liquid crystal wastewater, or solvent wastewater.

The water flow to the first biological treatment tank 10 is usually a transient type. The BOD volumetric load of the first biological treatment tank is 1 kg / m ³ / d or more, for example 1 to 20 kg / m ³ / d, HRT (raw water retention time) is 24 h or less, preferably 8 h or less, for example 0.5 to 8 h. By doing so, the treated water in which the dispersible bacteria are dominant can be obtained. Moreover, waste water with a low BOD concentration can be treated with a high load by shortening the HRT.

The first biological treatment tank may be a single stage, but a high-load treatment with a BOD volumetric load of 5 kg / m ³ / d or more is possible by adopting a multistage configuration of two or more tanks.

  The filling rate of the sheet-like carrier added to the first biological treatment tank 10 is 0.1% to 5%, preferably 0.2% to 2%. Can be generated.

  If there is no fear of clogging the separation screen due to the raw aqueous state or load, a fluidized bed carrier may be added in addition to the sheet carrier after the separation screen is installed in the first biological treatment tank 10. In that case, the shape of the fluidized bed carrier is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, a thread shape, a plate shape, etc., and the size is also arbitrary in a diameter of about 0.1 to 10 mm. Further, the material of the carrier is any material such as a natural material, an inorganic material, and a polymer material, and a gel material may be used. However, in the case of using a fluidized bed carrier, there is a possibility that bubbles are associated with each other due to contact with the carrier of the diffused bubbles and the dissolution efficiency is lowered. Moreover, when the filling rate of the support | carrier added to a 1st biological treatment tank is high, disperse bacteria do not produce | generate, but bacteria adhere to a support | carrier or a filamentous bacterium grows. Therefore, by setting the filling rate of the fluidized bed carrier added to the first biological treatment tank to 20% or less, preferably 10% or less, it is possible to produce dispersible bacteria that are easy to prey without being affected by concentration fluctuations.

  In addition, the first biological treatment tank 10 may suppress the growth of filamentous bacteria by setting the dissolved oxygen (DO) concentration to 1 mg / L or less, preferably 0.5 mg / L or less.

  In addition, when the dissolved organic matter is completely decomposed in the first biological treatment tank 10, flocs are not formed in the second biological treatment tank, and there is not enough nutrients for growing micro animals, and only sludge with low compactness is used. Becomes a biological treatment tank that has become dominant. Therefore, it is preferable that the decomposition rate of the organic component in the first biological treatment tank is not 100% but 95% or less, desirably 85 to 90%.

  The treated water (first biological treated water) in the first biological treatment tank 10 is passed through the second biological treatment tank 20 in the subsequent stage, where the remaining organic components are oxidatively decomposed and the dispersible bacteria are self-degraded. And reduce excess sludge by predation of micro-animals.

  By providing a micro-animal holding carrier in the second biological treatment tank 20, the inside of the fixed-feeding predation-type micro animal tank that efficiently eats the dispersal bacteria and contributes to the solid-liquid separation property of sludge and the quality of the treated water. Increase retention.

  That is, in the second biological treatment tank 20, not only the filtration predation type micro-animal that prey on the dispersal bacteria but also the aggregate predation type micro-animal that can prey on the flocs sludge, while the latter swims while flocating. When the latter is prioritized for predation, the sludge is eaten and roughened, resulting in sludge in which fine floc pieces with poor solid-liquid separation properties are scattered. Therefore, it is necessary to prevent the latter from being prioritized. Small animals stick to the sludge floc and remain in the system.

  The sludge is drawn out of the second biological treatment tank 20 with a certain residence time. If the carrier is a granular or square fluidized bed, not only can it not be stably maintained at a high concentration by the shearing force for fluidization, but also organic substances are completely processed in the fluidized bed, and sludge flocs are made finer. It leads to membrane blockage. Therefore, a micro animal is stably held using a sheet-like carrier as a carrier provided in the second biological treatment tank.

The carrier filling rate with respect to the second biological treatment tank 20 is preferably 0.5% or more, particularly 1 to 10%, of the total volume of the second and subsequent biological treatment tank groups that prey on the minute animals. By setting it as this filling rate, it becomes a carrier filling rate suitable for the load of a biological treatment tank, and an efficient biological treatment can be performed. Here, the carrier filling rate represents the ratio of the total apparent volume of the sheet to the total volume of the biological treatment tank. The apparent volume is a volume that does not take into account the pore volume of the foam cell, and is calculated by (L ₁ × L ₂ × d).

  In biological treatment tanks in the second and subsequent stages, a large amount of scaffolding is required to maintain micro-animals, but if the carrier filling rate is excessively high, mixing in the tank and sludge decay will occur. The filling rate of the carrier is preferably within the above range.

  When sludge is returned as shown in FIG. 1 in the second biological treatment tank 20, it is preferable to periodically replace the tank sludge. That is, in order to thin out minute animals and feces, SRT (solid content residence time) is desirably controlled within a range of preferably 60 days or less, more preferably 45 days or less, and even more preferably 10 days or more and 45 days or less. However, when the sludge concentration (MLSS) in the second biological treatment tank 20 is 2000 mg / L or less, SRT> 60 days may be set. Here, SRT = (tank sludge concentration × aeration tank volume) ÷ (drawn sludge concentration × amount drawn per day), and the sludge concentration in the tank (MLSS) indicates the concentration of floating sludge, exclude.

[Aeration volume]
When no shearing force is applied to the sheet-like carrier, excessive long-term adhesion of sludge to the carrier and proliferation of micro animals other than the fixed filtration predation type micro-animal occurs. Excessive long-term adhesion of sludge to the carrier leads to sludge decay, and causes deterioration in the quality of treated water and solid-liquid separation. Moreover, when a micro animal other than the filtration predation type micro animal grows in the second biological treatment tank, various problems occur as described above. In order for the sheet-like carrier to function as a place for predominating filtration predatory type micro-animals such as dispersal bacteria, stag beetles and stag beetles, an appropriate shearing force is applied to the sheet-like carrier, and sludge adhering to the surface of the carrier, It is necessary to peel the minute animals and release them into the suspended sludge. The attached sludge is replaced, and the sludge is pulled out in the previous SRT, so that the fine fauna in the tank is maintained well. For this purpose, an air diffuser is provided below the sheet carrier in the biological treatment tank provided with the sheet carrier, and an appropriate air diffuser is supplied to the sheet carrier by the air diffuser during the passage of treated water. It is preferable to take care.

The amount of air diffused in the first biological treatment tank 10 is preferably 0.1-5 m ³ -air / m ² -carrier installation floor area / min, particularly 0.1-2 m ³ -air / m ² -carrier installation floor area / min. . The amount of air diffused in the second biological treatment tank 20 is, as the degree of air diffused, 0.05 to 0.8 m ³ -air / m ² -carrier installation floor area / min, particularly 0.05 to 0.5 m. ^3- air / m ² -carrier installation floor area / min is preferred.

  Here, the carrier installation floor area corresponds to the apparent area of the projection surface of the fixed floor from above the biological treatment tank, and the bottom area of the unit surrounded by the outer periphery of the entire unit obtained by unitizing a plurality of sheet-like carriers. It corresponds to.

  Further, in the carrier unit, when the interval between the sheet-like carriers is smaller than the aeration bubble diameter, the bubbles do not escape and the cleaning effect is lost. On the other hand, if the interval is too wide, a downward flow is generated and uniform carrier surface cleaning cannot be performed. Therefore, in both the first and second biological treatment tanks, the interval between the carriers is set to 1 to 10 cm, and the average bubble diameter of the diffused bubbles is 0.01 to 0.2 times the interval (preferably 0.02). It is preferable that the air is diffused so as to be -0.1 times. This enables stable cleaning. If the bubble size of the air diffuser is too small, there will be no peeling effect, and if it is too large, it will not be possible to hold the adherent filtration and predation type micro-animal.

[Other suitable flows]
In the second biological treatment tank 20, it is necessary to use an operation condition and a treatment apparatus that allow the minute animals and bacteria to stay in the system in order to use the action of minute animals having a slower growth rate than bacteria and the self-degradation of bacteria. . Therefore, in FIG. 1, the activated sludge method in which the sludge is returned is adopted for the second biological treatment tank 20, but the carrier filling rate is increased if the sludge return is not performed as shown in FIG. 2. It is desirable. Further, as shown in FIG. 3, the second biological treatment tank 20 may be a membrane activated sludge method having a membrane separation device 24. In this case, the membrane separation apparatus may be either an in-vessel type (an immersion type in a biological treatment tank, a separate biological treatment tank / membrane immersion tank type) or an external type. By using a separate biological treatment tank / membrane immersion tank type or an external tank type, it is possible to prevent clogging of the membrane due to dispersal bacteria whose predation was delayed at high loads. As the membrane of the membrane separation device 24, a UF membrane, an MF membrane, or the like can be used.

  It is preferable to provide a diffuser tube 23 below the membrane separator 24.

When the sheet-like carrier unit necessary for the second biological treatment tank cannot be provided due to installation space restrictions, the fluidized bed carrier 25 is added only to the second biological treatment tank 20 and the separation screen 26 is installed as shown in FIG. It is also possible to use a one-time process. In that case, the shape of the fluidized bed carrier 25 is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, a thread shape, a plate shape, and the like, and the size is arbitrary in a diameter of about 0.1 to 10 mm. The material of the fluidized bed carrier may be any natural material, inorganic material, polymer material, etc., and a gel material may be used. Moreover, a micro animal can be stably maintained by making the filling rate of the fluidized bed carrier added to a 2nd biological treatment tank into 10% or more, desirably 20 to 40%.
In addition, when a sedimentation basin or a membrane separation facility can be installed, a minute animal can be stably maintained by filling a fluidized bed carrier with 5% or more, preferably about 5 to 10%. The membrane flux is lower than when the sheet-like carrier is installed.

  Although illustration is abbreviate | omitted, you may introduce | transduce a part of raw | natural water directly, for example about 5 to 50% directly after a 2nd biological treatment tank, without passing through a 1st biological treatment tank. In this way, by introducing a part of the raw water directly into the second biological treatment tank and beyond, an effect of avoiding a shortage of the load on the second biological treatment tank when the raw water fluctuates (when the load is reduced) is achieved. It is possible to maintain a preferable sludge load in the biological treatment after the eye.

  Although not shown in the drawings, a part of the sludge in the second biological treatment tank holding the micro-animal is extracted and treated in an oxygen-free tank, and then returned to return the aggregate predation type in the micro-animal holding biological treatment tank. It is also possible to preferentially proliferate the filtration and predation type micro animals by further suppressing the growth of the micro animals.

  That is, in this way, by providing an oxygen-free tank and retaining the sludge extracted from the second biological treatment tank for a predetermined time in this oxygen-free tank, Stabilize. In this case, the second biological treatment tank is provided with a micro-animal holding carrier, and since a fixed amount of the filter-predatory microanimal is held on the carrier side, the growth of the filter-predatory microanimal is inhibited. Absent. The sludge extracted from the second biological treatment tank and treated in the anoxic tank is returned to the second biological treatment tank.

  The amount of sludge withdrawn from the second biological treatment tank to the oxygen-free tank and the residence time of the sludge in the oxygen-free tank are appropriately determined according to the treatment status. It is preferable that the sludge residence time in the anoxic tank is 30 hours or more and 0.5 hours or more.

  In the anoxic tank, the ORP needs to be 0 mV or less in order to inhibit the growth of the minute animals. Therefore, it is desirable that only an agitation is performed in the anoxic tank without aeration. Moreover, in order to accelerate | stimulate the fall of ORP, a part of 1st biological treatment water and raw | natural water may be passed, and you may make it lower ORP by an acid production | generation reaction or a denitrification reaction.

  Moreover, in order to make ORP fall (denitrification reaction, acid production | generation reaction) lower in an oxygen-free tank stably, you may add a support | carrier to an oxygen-free tank. If the ORP in the anoxic tank is low, the decrease in the activity of the swimming micro-animal is promoted, so the residence time of the second biological treatment tank sludge in the anoxic tank can be shortened, and the anoxic tank can be downsized. it can. In the case of a fluidized bed, the shape of the carrier to be added is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape. A fixed bed may be used, and the shape of the carrier in that case is arbitrary such as a thread shape or a plate shape. Further, the material may be a natural material, an inorganic material, a polymer material or the like, and a gel material may be used.

  When adding a support | carrier to an oxygen-free tank, although the filling rate changes with the difference in the format and material of a fluid bed and a fixed bed, it is desirable to set it as 0.5 to 40%.

  The above description shows an example of the embodiment of the present invention, and the present invention is not limited to the illustrated one. For example, each of the first biological treatment tank and the second biological treatment tank may have a multi-stage configuration having two or more stages, and therefore, in the present invention, the biological treatment tank may be provided in three or more stages. In addition, solid-liquid separation of biologically treated water is not limited to a membrane separation device, and may be a sludge return method using a sedimentation basin, or a coagulation and sedimentation separation using a sedimentation tank after a transient treatment. The solid-liquid separation may be floating separation.

  In any aspect, according to the present invention, it is possible to achieve both the sludge reduction and the improvement of the quality of the treated water by stably maintaining the filtration predation type micro-animal in the second biological treatment tank. By performing solid-liquid separation of the biological treatment water after the second biological treatment tank with the membrane separation device, the membrane of the membrane separation device is prevented from being blocked, and stable high-load treatment is possible. Moreover, in the case of coagulating and separating the biologically treated water after the second biological treatment tank, the amount of the flocculant added can be reduced, and the sludge return type sedimentation tank performs stable sludge interface management. It becomes possible.

[Example 1]
Organic wastewater was treated using an apparatus having the first biological treatment tank 10 and the second biological treatment tank 20 (including the UF membrane separation device 24) shown in FIG. As the organic waste water (raw water), an aqueous solution containing an artificial substrate of COD _Cr : 1000 mg / L, BOD: 640 mg / L was prepared as a simulated waste water of easily degradable carbohydrate waste water.

The treatment conditions for each biological treatment tank were as follows. The BOD volumetric load in the entire apparatus was 0.73 kg-BOD / m ³ / d, and the HRT in the entire apparatus was 21 h.
<First biological treatment tank>
105L capacity
DO: 0.5 mg / L
BOD volumetric load: 3.85 kg-BOD / m3 / d
HRT: 4h
pH: 7.0
<Second biological treatment tank>
450L capacity
DO: 4 mg / L
Dissolvable TOC sludge load: 0.01 kg-soluble TOC / kg-MLSS / d
HRT: 17h
pH: 7.0
SRT: 30 days

  Three swingable carriers made of the following flexible polyurethane foam are used as sheet-like carriers in the first and second biological treatment tanks for each biological treatment tank, and are placed vertically in the tank (the longitudinal direction of the carrier is the depth direction of the tank). As a result, the first fixed bed 11 and the second fixed bed 21 were formed.

First carrier: length 100 cm × width 7.1 cm × thickness 1 cm; average pore diameter of foamed cells 0.1 mm; number of cells 50/25 mm
Second carrier: length 100 cm × width 30 cm × thickness 1 cm; average pore diameter of foamed cell 0.1 mm; number of cells 50/25 mm
The upper and lower ends of each sheet-like carrier were fixed to a frame, and the frame was fixed to the inner wall surfaces of the first and second biological treatment tanks. At this time, the apparent surface area of the carrier (m ² ) / biological treatment tank volume (m ³ ) = 12.3 (m ⁻¹ ), and the carrier filling rate was 6%.

Aeration is performed from below the fixed beds of each biological treatment tank, and the amount of diffusion to the carrier is 2 m ³ -air / m ² -carrier installation floor area / min in the first biological treatment tank. In the 2nd biological treatment tank, it was set to 0.67m < ³ > -air / m < ² > -carrier installation floor area / min.

As a result, the sludge floc in the second biological treatment tank and the carrier 50 are preferentially fixed filter predation type micro-animals (Villus elegans, scallop), and the sludge conversion rate is 0.07 kg-MLSS / kg-COD _Cr. It was.

The quality of the treated water (permeated water for membrane separation) was always in good condition throughout the test period with a soluble COD _Cr concentration of less than 20 mg / L.

  Moreover, there was almost no increase in the transmembrane pressure difference during membrane separation, and a stable flux could be maintained without chemical cleaning for one month or longer. These results are shown in Table 1.

[Example 2]
Raw water was treated in the same manner as in Example 1 except that a polyethylene plate-like material (size is the same as in Example 1) was used. The results are shown in Table 1.

[Comparative Example 1]
As a carrier, two 5 cm weft yarns were fixed at intervals of 1 cm to 100 cm long polyester warp yarns.

  Raw water was treated in the same manner as in Example 1 except that six of these string-like materials were used. The results are shown in Table 1.

  From Table 1, it was recognized that the carrier is preferably in the form of a sheet (including a plate).

[Comparative Example 2]
Raw water was treated in the same manner as in Example 1 except that the air diffusers 12 and 22 were arranged at positions deviating from below the fixed beds 11 and 21. The results are shown in Table 2.

  As shown in Table 2, it was confirmed that the treatment was efficiently performed by explosion from below the carrier.

[Comparative Examples 3 and 4]
Raw water was treated in the same manner as in Example 1 except that the amount of aeration in the first biological treatment tank 10 and the second biological treatment tank 20 was reduced as shown in Table 3. The results are shown in Table 3.

From Table 3, when the aeration amount of the 2nd biological treatment tank 20 was less than 0.05 m < ³ > / m < ² > / min, it was recognized that a process becomes difficult.

[Example 3, Comparative Examples 5 and 6]
Raw water was treated in the same manner as in Example 1 except that the amount of aeration was changed (increased) as shown in Table 4. The results are shown in Table 4.

  As shown in Table 4, it was recognized that the aeration ratio (aeration amount of the first biological treatment tank / aeration amount of the second biological treatment tank) is preferably 1.5 to 3 times. In Comparative Example 6, the aeration rate ratio was three times, but since the aeration rate in the first biological treatment tank was too large, sludge did not adhere to the first fixed bed, and the treatment was difficult.

[Examples 4 and 5, Comparative Examples 7 and 8]
Raw water was treated in the same manner as in Example 1 except that the interval between the carriers was as shown in Table 5. The results are shown in Table 5.

  As shown in Table 5, it was confirmed that the carrier spacing is preferably 1 to 10 cm.

[Comparative Example 9]
Raw water was treated in the same manner as in Example 1 except that the bubble diameter was increased to 5 mm. The results are shown in Table 6.

  As shown in Table 6, it was confirmed that the ratio of the bubble diameter to the carrier interval is preferably 0.2 or less.

From the above examples and comparative examples, the following matters were proved.
(i) The carrier shape is preferably a sheet shape.
(ii) Aeration from below the carrier is required.
(iii) The amount of aeration in the second biological treatment tank is preferably 1.5 to 3 times the amount of aeration in the first biological treatment tank.
(iv) The carrier interval is preferably 1 to 10 cm.
(v) The bubble diameter is preferably 1/5 times or less of the carrier interval.

DESCRIPTION OF SYMBOLS 10 1st biological treatment tank 11 1st fixed bed 12 Aeration pipe 20 2nd biological treatment tank 21 2nd fixed bed 22,23 Aeration pipe 25 Fluidized bed support | carrier 26 Screen 30 Settling tank

The biological treatment method for organic wastewater of the present invention comprises two or more aerobic biological treatment tanks in series, introduces organic wastewater into the first biological treatment tank and biologically treats with bacteria to produce dispersed bacteria, In the biological treatment method for organic wastewater, the first biological treatment water containing the dispersal bacteria from the first biological treatment tank is passed through the biological treatment tanks after the second biological treatment tank for biological treatment. , a plurality of the sheet-like first carrier to form a first fixed bed to installation, aeration amount from below the first fixed bed 0.1~5m ³ -air / ^{m 2} - at a carrier installation footprint / min A method for biological treatment of diffused organic wastewater, wherein the plurality of sheet-like first carriers are made of foamed plastic, and the sheet surfaces of the plurality of sheet-like first carriers are deep in the depth of the first biological treatment tank. Standing upright so as to be in the vertical direction, they are arranged in parallel with an interval of 1-10 cm between them. It is characterized in that that.

The organic wastewater biological treatment apparatus of the present invention comprises two or more aerobic biological treatment tanks in series, introduces organic wastewater into the first biological treatment tank, and biologically treats with bacteria to produce dispersed bacteria. In an organic wastewater biological treatment apparatus for conducting biological treatment by passing first biological treatment water containing dispersal bacteria from a first biological treatment tank to a biological treatment tank after the second biological treatment tank, a first fixed bed formed by installation multiple sheet first carrier, aeration amount 0.1~5m from below the first fixed bed ^{3 -air} / ^{m 2} - carrier installation footprint / min An organic wastewater biological treatment apparatus comprising: a plurality of sheet-like first carriers made of foamed plastic; and the plurality of sheet-like first carriers having a sheet surface Stand upright in the depth direction of the first biological treatment tank and 1-10 cm between them It is characterized by being arranged in parallel with an interval of .

In one aspect of the present invention, in the second biological treatment tank, a sheet-like second carrier made of a plurality of foamed plastics is placed upright so that the sheet surface is in the depth direction of the second biological treatment tank. Are arranged in parallel at an interval of 1 to 10 cm to form a second fixed bed, and the amount of air diffused from the lower side of the second fixed bed is 0.05 to 0.8 m ³ -air / m ² -carrier installation bottom area / Air is diffused at min, and the amount of air diffused from below the first fixed bed is 1.5 to 3 times the amount of air diffused from below the second fixed bed.

In one aspect of the present invention, average cell diameter of diffusing air bubbles are air diffuser so that 0.01 to 0.2 times the distance between carrier.

Claims (6)

A first or more aerobic biological treatment tank having two or more stages in series is provided, organic wastewater is introduced into the first biological treatment tank, and biological treatment is performed with bacteria to produce dispersed bacteria. In the biological treatment method for organic wastewater, the biological treatment water is passed through a biological treatment tank after the second biological treatment tank and biologically treated.
A first fixed bed is formed by installing a plurality of sheet-like first carriers in the first biological treatment tank so that the surface direction is vertical.
A biological treatment method for organic waste water, wherein air is diffused from below the first fixed bed at an amount of air diffused from 0.1 to ⁵ m ³ -air / m ² -bottom area / min. In claim 1,
A plurality of sheet-like second carriers are installed in the second biological treatment tank so that the surface direction is a vertical direction to form a second fixed bed,
Air is diffused from the lower side of the second fixed bed at an air amount of 0.05 to 0.8 m ³ -air / m ² -bottom area / min,
A biological treatment method for organic waste water, wherein the amount of air diffused from below the first fixed bed is 1.5 to 3 times the amount of air diffused from below the second fixed bed.   3. The air diffuser according to claim 1 or 2, wherein each carrier interval of the first carrier or the second carrier is 1 to 10 cm, and an average bubble diameter of the diffused bubbles is 0.01 to 0.2 times the interval. A method for biological treatment of organic wastewater.   In any 1 item | term of Claim 1 thru | or 3, in the 1st biological treatment tank, the preliminary aeration for adjustment of a dissolved oxygen concentration is performed also except the lower part of a 1st fixed bed, and the amount of diffused of a preliminary | backup aeration The biological treatment method of the organic waste water characterized by making smaller than the amount of aeration from the downward direction of a 1st fixed bed.   5. The biological treatment method for organic wastewater according to any one of claims 1 to 4, wherein the organic wastewater contains oil or has a BOD of 500 to 10000 mg / L. A first or more aerobic biological treatment tank having two or more stages in series is provided, organic wastewater is introduced into the first biological treatment tank, and biological treatment is performed with bacteria to produce dispersed bacteria. In the biological treatment apparatus for organic wastewater, the biological treatment water is passed through the biological treatment tank after the second biological treatment tank and biologically treated.
A first fixed bed formed by installing a plurality of sheet-like first carriers in the first biological treatment tank so that the surface direction is vertical;
An organic wastewater biological treatment apparatus comprising: a diffuser for aeration at a diffusion amount of 0.1 to ⁵ m ³ -air / m ² -bottom area / min from below the first fixed bed.

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