KR20170119675A - Method and device for biologically treating organic wastewater - Google Patents

Abstract

A biological treatment method and apparatus for organic wastewater which can form a fixed bed without growing animalcules using a fixed bed carrier in a first biological treatment tank (dispersion bacterium) and can carry out a high load treatment of the dispersion bacterium without fear of operation failure Is provided. The organic wastewater is introduced into the first biological treatment tank 10 and subjected to biological treatment with bacteria to produce dispersed microorganisms and the first biological treatment water containing the dispersed bacteria from the first biological treatment tank 10 is subjected to the second biological treatment It is passed through the tank 20 for biological treatment. A plurality of sheet-like carriers are provided in the biological treatment tanks 10 and 20 so that their surface directions are perpendicular to each other to form fixed phases 11 and 21 and an acid quantity of 0.1 to 5 m < M2 - floor area / min.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for biological treatment of organic wastewater,

TECHNICAL FIELD The present invention relates to a biological treatment method and apparatus for organic wastewater which can be used for organic wastewater treatment in a wide concentration range including domestic wastewater, sewage, food factory or pulp mill, Wherein the first biological treatment water containing dispersed microorganisms from the first biological treatment tank is subjected to biological treatment with microorganisms after introducing organic wastewater into the first biological treatment tank, To a biological treatment method and apparatus for organic wastewater which is subjected to biological treatment by passing through a treatment tank.

Most of the organic matter is decomposed by the dispersible bacteria in the first biological treatment tank (dispersion tank) to produce dispersible bacteria, and after the second biological treatment tank (animal animal tank), the dispersed bacteria are pre- It is known to add and install a microorganism-retaining support 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 animalcules (Patent Documents 1 to 5).

When the fixed bed carrier is used in the animal animal tank, it is necessary to adjust the aeration condition in order to separate the animal animal and the excess sludge.

WO2012 / 124675 Japanese Patent Application Laid-Open No. 2013-121558 Japanese Patent Application Laid-Open No. 2013-141640 Japanese Patent Application Laid-Open No. 2007-050366 Japanese Laid-Open Patent Publication No. 05-068986

Since the dispersion tank is operated at a high load, when a fixed bed carrier is used, sludge is excessively attached, and floc bacteria and animalcules are produced in the dispersion tank. For this reason, conventionally, in a dispersing tank, a fluidized bed is treated as a microorganism-retaining carrier and treated at a high load.

In the case of a fluid phase, a screen for separating a carrier is required in the drainage section of the treatment tank. However, for the purpose of high load treatment, occurrence of filamentous bacteria and solidification of the oil The screen may be clogged. When a fluidized bed carrier is used, bubbles associate with each other due to collision between the bubbles and the carrier. Therefore, when a microbubble diffuser is used, the original dissolution efficiency may not be obtained.

An object of the present invention is to provide an organic waste water treatment apparatus capable of forming a fixed bed without growing animalcules even when a fixed bed carrier is used for the first biological treatment tank (dispersion tank) And an object thereof is to provide a biological treatment method and apparatus for biological treatment.

A biological treatment method for organic wastewater according to the present invention is a biological treatment method for organic wastewater, comprising two or more aerobic biological treatment tanks in series, introducing organic wastewater into the first biological treatment tank, Treating a first biological treatment water containing dispersed microorganisms in a biological treatment tank after the second biological treatment tank for biological treatment, characterized in that a plurality of sheet-like first supports Wherein the first stationary phase is formed so that the plane direction is perpendicular to the first stationary phase and is diffused from the lower side of the first stationary phase by an acid quantity of 0.1 to 5 m 3 -air / m 2 - floor area / min.

An apparatus for biological treatment of organic wastewater according to the present invention comprises an aerobic biological treatment tank having two or more tiers in series, introducing organic wastewater into the first biological treatment tank, biological treatment with bacteria to produce dispersed germs, Treating the first biological treatment water containing dispersed microorganisms in a biological treatment tank after the second biological treatment tank for biological treatment, characterized in that a plurality of sheet-like first supports And a diffusing means for diffusing the impurities from the lower part of the first stationary phase at an acid quantity of 0.1 to 5 m < 3 > -air / m2 - bottom area / min.

In an embodiment of the present invention, a plurality of sheet-like second carriers are provided in the second biological treatment tank so that their surface directions are perpendicular to each other to form a second stationary phase, and an acid quantity of 0.05 to 0.8 m & air / m < 2 > - floor area / min, and the amount of acid from below the first stationary phase is 1.5 to 3 times the amount of acid from below the second stationary phase.

In one embodiment of the present invention, the distance between the supports of the first carrier or the second carrier is 1 to 10 cm, and the average cell diameter of the oxidative bubbles is 0.01 to 0.2 times the interval.

In one embodiment of the present invention, the first biological treatment tank is provided with a preliminary acidifier for adjusting the dissolved oxygen concentration other than below the first stationary phase, and the acid value of the acid from the lower side of the first stationary phase, Reduce skill.

In one embodiment of the present invention, the organic wastewater contains oil or has a high BOD of 300 to 10,000 mg / l.

In the present invention, a plurality of first carriers on a sheet in a first biological treatment tank are provided so that their surface directions are perpendicular to each other to form a first stationary phase, and an acid quantity of 0.1 to 5 m3-air / - the floor area / min. As a result of mass production from below the first stationary phase, the flow velocity of the surface of the carrier is increased, so that the animalcules do not grow on the carrier and the excessive adhesion of bacteria is prevented.

Therefore, in the present invention, the organic wastewater can be efficiently subjected to biological treatment without fear of operation failure even if the organic wastewater contains oil or the BOD is 300 to 10,000 mg / L at a high concentration.

The second stationary phase is formed in the second biological treatment tank and the amount of acid from the lower part of the first stationary phase is calculated from the lower part of the second stationary phase by the acid value of 0.05-0.8 m3-air / In the case of excessive aeration of 1.5 to 3 times the amount of acid from below, the biofilm is formed in the first carrier while the animalcules do not grow. In addition, the second carrier grows the animalcules.

By forming the first carrier or the second carrier such that the distance between the respective supports is 1 to 10 cm and the average cell diameter of the oxidative cells is 0.01 to 0.2 times the interval, air bubbles uniformly invade between the supports, Cleaning is promoted.

A preliminary acid generator for adjusting the concentration of dissolved oxygen is performed in the first biological treatment tank other than below the first stationary phase and the amount of acid in the preliminary acid generator is made smaller than the amount of acidic component in the acidic period from below the first stationary phase, 1 The inside of the stationary phase becomes upward flow.

1 is a flowchart showing a biological treatment method and apparatus for organic wastewater according to the embodiment.
2 is a flowchart showing a biological treatment method and apparatus for organic wastewater according to the embodiment.
3 is a flowchart showing a biological treatment method and apparatus for organic wastewater according to the embodiment.
4 is a flowchart showing a biological treatment method and apparatus for organic wastewater according to the embodiment.

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

1 is a flow chart showing a preferred embodiment of the method and apparatus of the present invention. In this flow, the organic wastewater is aerobically treated in the first biological treatment tank 10 to cultivate bacteria, and the first treated water from the first biological treatment tank 10 is treated in the second biological treatment tank 20, To feed the dispersed bacteria contained in the first treated water to the animal animal (protozoan animal, welfare animal) to feed the animal animal. In Fig. 1, the second treated water from the second biological treatment tank 20 is introduced into the sedimentation tank 30, subjected to solid-liquid separation, and the treated water is taken out of the system. And at least a part of the sludge settled in the settling tank (30) is returned to the second biological treatment tank (20).

The first biological treatment tank 10 and the second biological treatment tank 20 are provided with a plurality of sheet-like supports (first and second supports) so that their surface directions are perpendicular to each other, And the second fixed bed 21 are formed. And the air diffusers 12 and 22 are provided below the stationary phases 11 and 21, respectively.

By constituting the first stationary phase 11 as a sheet-like carrier, dispersed bacteria can be efficiently produced without being affected by fluctuation in the concentration of the organic wastewater.

By using the sheet-like carrier as the second carrier for forming the second fixed bed 21, the sludge with favorable solid-liquid separation can be formed by preferentially growing the filtrate-predominant small animal. Therefore, when the biological treatment water is subjected to solid-liquid separation using a membrane separation device, clogging of the separation membrane can be prevented, and membrane separation can be stably performed for a long period of time. In addition, when biological treatment water is subjected to coagulation treatment and sedimentation separation by a sedimentation tank or the like, the addition amount of the flocculant can be reduced, and stable sludge interface management can be performed even in the sedimentation tank of the sludge return type.

[Sheet-like carrier]

Preferred embodiments of the sheet-like carrier will be described. The sheet-like carrier is preferably a foam plastic. The foamed plastic carrier has a suitable bending property because it absorbs and expands in water, and may be appropriately shaken by the flow of water flowing into the bath or the upward flow caused by aeration to form a rocking stationary phase.

The sheet-like carrier is preferably composed of a rectangular plate-like sheet or a short-sheet sheet. In general, fixtures are mounted on both short side portions (widthwise side edge portions) of the plate-like or short-handed desk carrier, and the sheet surfaces are set up in the tank upright so as to be in the depth direction of the tank. The fixing member is not limited to a metal, a cloth, or a plastic, and may be any member that can reinforce the fixing point with respect to tensile stress when the sheet-like carrier is fixed in the bath. It is preferable to fasten both short side portions of the sheet with a clamp or the like (an adhesive, a thread, a band, a fixing screw, a flat bar, etc.) after inserting the short side portions of the sheet between one or a plurality of fixing means.

The sheet-like carrier preferably has a large apparent surface area suitable for growth of bacteria, scattering and growth of animalcules.

The apparent surface area is the sum of the outermost surface area of the sheet not including the surface area of the foamed plastic sheet in the foamed cell. In the case of a rectangular sheet-shaped support having side lengths L ₁ , L ₂ and thickness d, the apparent surface area is expressed by (L ₁ × L ₂ × 2) + (L ₁ × d × 2) + (L ₂ × d × 2).

When the sheet-like carrier is in a rectangular shape, it is preferable that the long-side direction is provided so as to be 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 in the width direction orthogonal to the long side is 5 to 200 cm, Preferably 5 cm. In Applicability plane for article handling, biological treatment, L _2: length ratio of L _1, L _2: is preferably about _{1 ~ 80: L 1 = 1} . The second to fourth stages may be superposed in the height direction with L ₁ being 50 to 100 cm.

The length (L ₁ , L ₂ ) of the side of the sheet-like carrier influences the apparent surface area of the carrier, and this apparent surface area is preferable because the number of the bacteria (or animalcules) However, the length (L ₁ ) in the depth direction of the biological treatment tank forming the carrier is not particularly limited in that there is no influence on the fluidity of water because there is a flow due to aeration. It is preferable that the length (width) (L ₂ ) in the width direction affects the fluidity of water, and L ₂ is preferably 5 to 200 cm, particularly 5 to 100 cm, as described above. When the width of the biological treatment tank is large with respect to the width (L ₂ ) of the sheet-like support, it is preferable to increase the number of sheet-like supports formed in the biological treatment tank to prevent short-

If the thickness d of the carrier is excessively large, if the foamed plastic is used, the water permeability in the interior is lowered. Therefore, it is preferable that the thickness d of the sheet is made thin after securing the necessary strength, and it is preferable that the thickness d is 0.5 to 5 cm as described above.

In order to maintain microorganisms, it is preferable to have at least two planes with an apparent surface area of 500 cm 2 or more. That is, it is preferable that L ₁ × L ₂ is 500 cm 2 or more, preferably 1000 cm 2 or more. The upper limit of the apparent surface area is not particularly limited, but is usually 80000 cm 2 or less in order to satisfy the preferable lengths of L ₁ and L ₂ described above.

As the condition of the foamed cell of the foamed plastic sheet, it is preferable that the distribution of the foamed cells is uniform. It is preferable to control the number of foamed cells and the pore diameter of the foamed cell so that the sludge is easily adhered and easily peeled off. In particular, when the foamed cell is excessively large or the cell diameter is excessively large, It is preferable that the number of cells / 25 mm (the number of cells existing in the range of 25 mm) is 125/25 mm or less, particularly 100/25 mm or less since the mechanical strength becomes small. On the contrary, if the number of cells is too small or the cell diameter is excessively small, the function as a porous carrier can not be sufficiently obtained. In order to sufficiently exhibit the function of the porous carrier, Mm or more, particularly preferably 25/25 mm or more. The average pore diameter of the foamed cells is preferably in the range of 0.05 to 10 mm, particularly 0.25 to 1 mm, in order to realize such a number of foamed cells and good adhesion and peelability of the sludge.

With respect to the number of cells / 25 mm, the work of measuring the number of foamed cells crossing a straight line 25 mm in the longitudinal direction was performed for a plurality of points using the photograph of the sheet taken by a scanning electron microscope, The average value of the results can be calculated and obtained. The pore diameter of the foamed cell can be measured in the same manner.

The foamed plastic constituting such a sheet-like carrier is not particularly limited, but is preferably a flexible polyurethane foam in that it swells due to absorption and swings moderately in an upward flow caused by a water stream or aeration. The mechanical strength can be obtained by forming the sheet into a single, solid plate.

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 in the case of the biological treatment tank in the return line) (i.e., the apparent surface area / the biological treatment tank volume ) Is in the range of 0.5 to 50 m ^-1 is preferable in carrying out efficient biological treatment with a carrier filling rate suitable for the load of the biological treatment tank.

A plurality of sheet-like supports are arranged in a vertical direction (a depth direction of the biological treatment tank, that is, a vertical direction) in a longitudinal direction thereof, and a sheet surface is uniform in a sheet- And are fixed to each other with a fastener or the like (an adhesive, a thread, a band, a fixing screw, a pipe, a metal rod or the like) through the fastener and arranged as a plurality of bodies, It is preferable that they are arranged in parallel with each other with a gap therebetween, and are fixed to each other through a fastener of each arrangement body by a catch so as to form a unit.

Thus, by arranging a plurality of sheet-like supports in parallel and forming them into a unit in a biological treatment tank, the sheet-like support can be easily formed in the biological treatment tank so as to have an optimum filling rate.

In the case where the carrier is not made into a unit, for example, a plurality of rod-shaped members are provided in a carrier mounting place in the tank, and the fasteners of the respective arrays are fastened to a plurality of rod-like members by a fastener (binding band, metal hook, piano wire, By fixing the sheet, the sheet can be placed in the biological treatment tank.

[Preferable Conditions for Biological Treatment of Organic Wastewater]

1, the raw water (organic wastewater) is introduced into the first biological treatment tank 10 and separated by dispersible bacteria (non-cohesive bacteria) to 70% or more of the organic component (soluble BOD), preferably 80 Or more, more preferably 85% or more. The pH of the first biological treatment tank 10 is set to 6 or more, preferably 8 or less. However, the pH may be 8 or more when the raw water contains a large amount of oil or when it is treated in the electronic industry drainage, liquid crystal drainage and solvent drainage.

The passage of water to the first biological treatment tank 10 is usually a one-over-type. The BOD volume load of the first biological treatment tank is set to 1 kg / m3 / d or more, for example, 1 to 20 kg / m3 / d, the HRT (raw water retention time) is 24 h or less, preferably 8 h or less, 0.5 to 8 h, it is possible to obtain treated water in which the dispersing bacteria are dominantly dominant. By shortening the HRT, it is possible to treat a drain with a low BOD concentration at a high load.

The first biological treatment tank may be a single stage, but a high load treatment with a BOD volume load of 5 kg / m3 / d or more can be achieved by using two or more sets of multi-stage structures.

By setting the filling rate of the sheet-like carrier to be added to the first biological treatment tank 10 to be 0.1% to 5%, preferably 0.2% to 2%, generation of dispersed bacteria susceptible to predation It becomes possible.

If there is no risk of obstructing the separation screen by the raw water or load, a fluidized bed carrier may be added in addition to the sheet-like carrier after the separation screen is provided in the first biological treatment tank 10. In this case, the shape of the fluidized-bed carrier may be any of spherical, pellet, hollow, filament, plate, and the like, and may have a diameter of about 0.1 to 10 mm. In addition, the material of the carrier may be any of natural materials, inorganic materials, polymer materials and the like, and a gel material may be used. However, when a fluidized bed carrier is used, bubbles are associated with each other due to contact with the carrier of the air bubble, which may lower the dissolution efficiency. When the filling rate of the carrier to be added to the first biological treatment tank is high, no dispersed microorganisms are produced, and the microorganisms adhere to the carrier or multiply. Thus, by setting the filling rate of the fluidized-bed carrier to be added to the first biological treatment tank to 20% or less, preferably 10% or less, it is possible to generate dispersed microorganisms which are easily affected by the concentration fluctuation and are predominant.

The first biological treatment tank 10 may have a dissolved oxygen (DO) concentration of 1 mg / L or less, preferably 0.5 mg / L or less, to inhibit the growth of marsupial bacteria.

When the soluble organic matter is completely decomposed in the first biological treatment tank 10, no flocs are formed in the second biological treatment tank, and nutrition for growing animalcules is insufficient, . Therefore, it is preferable that the decomposition ratio of the organic component in the first biological treatment tank is not 100% but 95% or less, preferably 85 to 90%.

The treated water (first biological treatment water) in the first biological treatment tank 10 is sent to the second biological treatment tank 20 in the subsequent stage, where oxidative decomposition of remaining organic components, And the excess sludge is reduced by the degradation and predation of the animalcules.

By forming the animal-animal support carrier in the second biological treatment tank 20, it is possible to efficiently feed the dispersed microorganisms and to maintain the retention amount in the tank of the sticky filtration predator type animal that contributes to the solid- Increase.

In other words, in the second biological treatment tank 20, not only the filtrate-predation type animal that predates dispersed bacteria but also agglomerate-predator-type animal that can predominate the flocked sludge grows. In the latter, Therefore, in the case where the latter is prioritized, the sludge becomes swollen and swollen, and the finely divided flock pieces having poor solid-liquid separability become scattered sludge. Therefore, it is necessary to prevent the latter priority. The animalcules are fixed to the onion flocs and held in the system.

The sludge is drawn out of the second biological treatment tank 20 at a constant residence time. If the carrier is a particulate or angular fluidized bed, it can not be stably maintained at a high concentration due to a shearing force for flow, and the organic matter in the fluidized bed is completely treated, resulting in finer size of the ony frock and consequently clogging of the membrane . Therefore, the animalcules are stably maintained using the sheet-like carrier as the carrier formed in the second biological treatment tank.

The carrier filling rate for the second biological treatment tank 20 is preferably 0.5% or more, particularly 1 to 10% of the total volume of the second or later biological treatment tank for predation by the animalcules. With this filling rate, a carrier filling rate suitable for the load of the biological treatment tank is obtained, and efficient biological treatment can be performed. Here, the carrier filling rate refers to the ratio of the total apparent volume of the sheet to the total volume of the biological treatment tank. The apparent volume is the volume without considering the hole volume of the foam cell, and is calculated as (L ₁ · L ₂ · d).

In the second and subsequent biological treatment tanks, a large amount of footsteps for holding the animalcules are required. However, when the filling rate of the carrier excessively high, the lack of mixing in the tank and the decay of the sludge occur, Is preferably in the above range.

When sludge is transported in the second biological treatment tank 20 as shown in Fig. 1, it is preferable to regularly replace the sludge. That is, in order to filter animalcules and feces, the SRT (solids retention time) is preferably 60 days or less, more preferably 45 days or less, further preferably 10 days or more and 45 days or less And controls it constantly. However, when the sludge concentration (MLSS) in the second biological treatment tank 20 is 2000 mg / L or less, SRT may be 60 days. Here, the sludge concentration (MLSS) in the tank indicates the concentration of suspended sludge, and the sludge concentration in the sludge with carrier (sludge concentration) Are not included.

[Production capacity]

If no shear force is applied to the sheet-like carrier, excessive organ attachment of the sludge to the carrier or proliferation of animalcules other than the sticky filtration predominant type animal occurs. Excessive attachment of the sludge to the carrier leads to sludge decay, resulting in deterioration of the treated water quality and solid-liquid separability. In addition, in the second biological treatment tank, when animalcules other than the filtrate predator-type animalcules proliferate, various problems arise as described above. In order for the sheet-like carrier to function as a place for igniting the filtrate-type animalcules such as dispersed bacteria and nematode delodio rotifer, a suitable shearing force is applied to the sheet-like carrier to peel off sludge and animalcules attached to the surface of the carrier , It is necessary to discharge it into the suspended sludge. The attached sludge is replaced and the sludge is pulled out from the SRT in the previous stage, so that the animal animal phase in the tank is maintained well. For this purpose, it is preferable to provide a diffuser at the bottom of the sheet-like support in the biological treatment tank in which the sheet-like support is formed, and to apply appropriate acid to the sheet-like support in the water of the treated water by this diffuser Do.

The amount of acid in the first biological treatment tank 10 is preferably 0.1 to 5 m 3 -air / m 2 - area of carrier setting / min particularly 0.1 to 2 m 3 -air / m 2 - area of carrier setting / min. The amount of acid in the second biological treatment tank 20 is preferably 0.05 to 0.8 m 3 -air / m 2 in terms of the acid value, particularly 0.05 to 0.5 m 3 -air / m 2 in the carrier setting area / min, min.

The carrier mounting area corresponds to the apparent area of the projection surface of the stationary phase from above the biological treatment tank and corresponds to the bottom area of the unit surrounded by the outer periphery of the whole unit in which the sheet carrier is made into a plurality of unit units.

In the case of the carrier unit, when the distance between the sheet-like supports is smaller than the diameter of the bubble unit, the bubble does not fall out, and the cleaning effect is lost. If the interval is excessively wide, a downward flow is generated, and uniform carrier surface cleaning can not be performed. Therefore, in any of the first and second biological treatment tanks, the distance between the supports is set to 1 to 10 cm, the average bubble diameter of the oxidative bubbles is 0.01 to 0.2 times (preferably 0.02 to 0.1 times) . This makes it possible to perform stable cleaning. If the bubble diameter of the acid phase is too small, there is no peeling effect. If it is too large, the sticky filtrate type animalcules can not be retained. Therefore, the bubble diameter is preferably within the above range.

[Other preferable flow]

In the second biological treatment tank 20, in order to utilize the function of the animalcules with a slower growth rate than that of bacteria and the autolysis of bacteria, it is necessary to use operating conditions and treatment devices in which the animalcules and bacteria stay in the system. 1, the activated sludge process for carrying out the sludge transport is adopted in the second biological treatment tank 20. In the case where the sludge transport is not carried out as shown in Fig. 2, it is preferable to increase the carrier filling rate Do. As shown in Fig. 3, the second biological treatment tank 20 may be a membrane-type activated sludge method having a membrane separation device 24. In this case, the membrane separation device may be any of the tank type (immersed type in biological treatment tank, biological treatment tank / membrane immersion set type) and tank type. By using the biological treatment tank / membrane immersion tank type or the bath tank type, it is possible to prevent the clogging of the membrane due to the dispersed bacteria having a slow predation upon high load. 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 form the air diffusing pipe 23 below the membrane separator 24. [

When the sheet-like carrier unit necessary for the second biological treatment tank can not be formed due to the restriction of the installation space, only the second biological treatment tank 20 is added with the fluidized bed support 25 as shown in Fig. 4, 26 may be provided. In this case, the shape of the fluidized-bed carrier 25 is arbitrary, such as spherical, pellet, hollow, scratched, plate-like, and any size with a diameter of about 0.1 to 10 mm. The material of the fluid phase carrier is arbitrary such as a natural material, an inorganic material, and a polymer material, and a gel material may be used. In addition, by keeping the filling rate of the fluidized bed carrier added to the second biological treatment tank at 10% or more, preferably 20 to 40%, it is possible to stably keep the animalcules.

When sedimentation or membrane separation facilities can be provided, the animalcules can be stably maintained by filling the fluidized bed carrier with 5% or more, preferably 5 to 10%, of the sludge sedimentation property and the membrane flux, .

Although not shown, a part of raw water, for example, about 5 to 50%, may be introduced directly after the second biological treatment tank without going through the first biological treatment tank. Thus, by introducing a part of the raw water directly after the second biological treatment tank, it is possible to avoid the shortage of the load of the second biological treatment tank when the source water is changed (when the load is lowered) It is possible to maintain the sludge load at a desired level.

Although not shown, a part of the sludge in the second biological treatment tank for holding the animalcules is withdrawn, treated in an anoxic tank, and transported, thereby further suppressing the proliferation of the aggregate predator-type animalcules in the animal animal- The filtrate-predation type small animal may be preferentially proliferated.

That is, the anaerobic tank is installed in this manner, and the sludge drawn from the second biological treatment tank is allowed to stay in the anoxic tank for a predetermined time, thereby inhibiting the proliferation of the animalcules of swimming ability, thereby stabilizing the biological phase. In this case, the animal-animal support carrier is formed in the second biological treatment tank, and the filtration-predominant type animalcules are maintained at a certain amount on the carrier side, so that the propagation of the filtration predator-type animalcules is not inhibited. The sludge which has been withdrawn from the second biological treatment tank and treated in the anoxic tank is returned to the second biological treatment tank.

The sludge withdrawn from the second biological treatment tank into the anoxic tank and the residence time of the sludge in the anoxic tank are appropriately determined according to the treatment conditions, but the withdrawal amount of the sludge is usually 1/30 times / day or more, The residence time of the sludge in the anoxic tank is preferably 0.5 hour or more.

In the anoxic tank, it is necessary to set the ORP to 0 mV or less in order to inhibit the growth of animalcules. Therefore, in the anoxic tank, it is preferable to perform only mechanical stirring without aerating. In order to accelerate the lowering of the ORP, the ORP may be lowered by passing the first biological treatment water or a part of the raw water through the acid generation reaction or the denitrification reaction.

In order to stably progress the ORP reduction (denitrification reaction, acid production reaction) in the anoxic tank, a carrier may be added to the anoxic tank. When the ORP in the anoxic tank is low, the decrease in the activity of the swimming microorganism is accelerated, so that the residence time of the second biological treatment zonicle in the anoxic tank can be shortened and the size of the anoxic tank can be reduced. The shape of the carrier to be added is arbitrary in the form of spheres, pellets, hollow spheres, and filaments in the case of a fluidized bed, and the diameter is arbitrarily set to a diameter of about 0.1 to 10 mm. A fixed bed may be used, and the shape of the carrier in this case is arbitrary such as mapped or plate-like. The material may be any of natural materials, inorganic materials, and polymer materials, and gel-like materials may be used.

When the carrier is added to the anoxic tank, the filling rate is preferably 0.5 to 40%, though it differs depending on the type and material of the fluidized bed and fixed bed.

The above description shows an example of the embodiment of the present invention, and the present invention is not limited to what is shown at all. For example, the first biological treatment tank and the second biological treatment tank may each have a multi-stage structure of two or more stages, and therefore, in the present invention, the biological treatment tank may be provided in three or more stages. The solid-liquid separation of the biological treatment water is not limited to the membrane separation apparatus, but may be carried out by a sludge returning method using a sedimentation tank or by flocculation and sedimentation separation using a sedimentation tank after the single-sludge treatment, May be floating separation.

In any embodiment, according to the present invention, it is possible to achieve both improvement in the amount of sludge to be treated and improvement in the quality of treated water by stably maintaining the filtrate-predominant species animal in the second biological treatment tank. The biologically treated water after the second biological treatment tank is subjected to solid-liquid separation using a membrane separation device, thereby preventing clogging of the membrane of the membrane separation device and enabling stable high-load treatment. In addition, when the biological treatment water after the second biological treatment tank is subjected to coagulation sedimentation separation, the addition amount of the flocculant can be reduced, and in the sludge return type sedimentation tank, stable sludge interface management can be performed.

Example

[Example 1]

An organic wastewater treatment was carried out using an apparatus having a first biological treatment tank 10 and a second biological treatment tank 20 (provided with a UF membrane separation device 24) shown in FIG. As the organic wastewater (raw water), an aqueous solution containing an artificial substrate of COD _Cr : 1000 mg / l and BOD: 640 mg / l was prepared as a simulated drainage of the easily degradable carbohydrate drainage.

The treatment conditions of each biological treatment tank were as follows. The BOD volume load across the device was 0.73 kg-BOD / m3 / d, and the HRT throughout the device was 21 h.

≪ First biological treatment tank &

Capacity 105 ℓ

DO: 0.5 mg / l

BOD volume load: 3.85 kg-BOD / m3 / d

HRT: 4 h

pH: 7.0

<Second biological treatment tank>

Capacity 450 ℓ

DO: 4 mg / l

Solubility TOC sludge load: 0.01 kg - Solubility TOC / kg-MLSS / d

HRT: 17 h

pH: 7.0

SRT: 30 days

In the first and second biological treatment tanks, three lyophobic supports made of the following flexible polyurethane foams as the sheet-like supports were used for each biological treatment tank, and they were placed vertically (with the lengthwise direction of the support in the depth direction of the support) Whereby the first stationary phase 11 and the second stationary phase 21 were formed.

First carrier: 100 cm long x 7.1 cm wide x 1 cm thick The average pore diameter of the foamed cell 0.1 mm; the number of cells 50/25 mm

Second carrier: 100 cm long x 30 cm wide x 1 cm thick The average pore diameter of the foamed cell 0.1 mm; the number of cells 50/25 mm

The upper and lower ends of each sheet-like carrier were fixed to the frame, and the frame was fastened to the inner wall surfaces of the first and second biological treatment tanks. In this case, the apparent surface area (m 2) of the carrier / the volume of the biological treatment tank (m 3) = 12.3 (m ^-1 ), and the filling rate of the carrier was 6%.

The acid value is carried out from below each fixed bed of each biological treatment tank, and the acid quantity for the carrier is 2 m 3 -air / m 2 - carrier mounting area / min in the first biological treatment tank. In the second biological treatment tank, 0.67 m3-air / m &lt; 2 &gt;

As a result, the onyx flocculation and carrier 50 in the second biological treatment tank was preferentially filtered and the sludge conversion rate was 0.07 kg-MLSS / kg-COD _Cr .

The treated water (permeated water of membrane separation) had a soluble COD _Cr concentration of less than 20 mg / L, and maintained a good state at all times during the test period.

The intermembrane pressure difference of the membrane separation was scarcely increased and the stable flux could be maintained even if the chemical cleaning was not performed for one month or more. These results are shown in Table 1.

[Example 2]

The raw water was treated in the same manner as in Example 1 except that the carrier used was a plate made of polyethylene (the size was the same as in Example 1). The results are shown in Table 1.

[Comparative Example 1]

As the carrier, wefts of 5 cm were fixed to the warp yarns made of polyester having a length of 100 cm at intervals of 1 cm.

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

From Table 1, it was confirmed that it is preferable that the carrier is sheet-like (including plate-like).

[Comparative Example 2]

Raw water was treated in the same manner as in Example 1 except that the diffuser pipes (12, 22) were disposed at positions deviated from below the stationary phases (11, 21). The results are shown in Table 2.

As shown in Table 2, it was confirmed that the treatment was efficiently carried out by aeration from below the carrier.

[Comparative Examples 3 and 4]

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

It is confirmed from Table 3 that if the aeration amount of the second biological treatment tank 20 is less than 0.05 m 3 / m 2 / min, the treatment becomes difficult.

[Example 3, Comparative Examples 5 and 6]

The raw water was treated in the same manner as in Example 1 except that the aeration amount was changed (increased) as shown in Table 4. The results are shown in Table 4.

As shown in Table 4, it was confirmed that the aeration ratio (the aeration amount of the first biological treatment tank / the aeration amount of the second biological treatment tank) was preferably 1.5 to 3 times. In addition, in Comparative Example 6, the aeration ratio was three times, but since the amount of aeration in the first biological treatment tank was excessively large, the 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 intervals between the supports were changed as shown in Table 5. The results are shown in Table 5.

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

[Comparative Example 9]

The 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 cell diameter to the carrier spacing was preferably 0.2 or less.

From the above Examples and Comparative Examples, the following facts have been demonstrated.

(i) The carrier shape is preferably a sheet-like shape.

(ii) Aeration from below the carrier is necessary.

(iii) The aeration amount of the second biological treatment tank is preferably 1.5 to 3 times the aeration amount of the first biological treatment tank.

(iv) The distance between supports is preferably 1 to 10 cm.

(v) The bubble diameter is preferably 1/5 times or less the carrier interval.

While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various modifications are possible without departing from the spirit and scope of the invention.

This application is based on Japanese Patent Application No. 2015-030769 filed on February 19, 2015, the entirety of which is incorporated by reference.

10: First biological treatment tank
11:
12: The living organ
20: Second biological treatment tank
21: second stationary phase
22, 23:
25: fluidized bed carrier
26: Screen
30: Settling tank

Claims (6)

And an aerobic biological treatment tank having two or more tiers in series, wherein organic wastewater is introduced into the first biological treatment tank and subjected to biological treatment with bacteria to produce dispersed microorganisms, and the first biological treatment water In a biological treatment tank after the second biological treatment tank for biological treatment,
A plurality of first carriers on a sheet in a first biological treatment tank are provided so that their surface directions are perpendicular to each other to form a first fixed bed,
Wherein an acid value of 0.1 to 5 m &lt; 3 &gt; - air / m &lt; 2 &gt; - bottom area / min is produced from below the first stationary phase. The method according to claim 1,
A plurality of sheet-like second supports are provided in the second biological treatment tank so that their surface directions are perpendicular to each other to form a second fixed bed,
And an acid value of 0.05 to 0.8 m3-air / m &lt; 2 &gt; - bottom area / min from below the second stationary phase,
Wherein the amount of acid from the lower part of the first stationary phase is 1.5 to 3 times the amount of acid from below the second stationary phase. 3. The method according to claim 1 or 2,
Wherein the distance between the supports of the first carrier or the second carrier is 1 to 10 cm and the average cell diameter of the oxidative bubbles is 0.01 to 0.2 times the interval. 4. The method according to any one of claims 1 to 3,
A preliminary acid generator for adjusting the concentration of dissolved oxygen is performed in the first biological treatment tank other than below the first stationary phase so that the acid value of the preliminary acid generator is made smaller than the amount of acidity from below the first stationary phase. Methods for biological treatment of organic wastewater. 5. The method according to any one of claims 1 to 4,
Wherein the organic wastewater contains oil or has a BOD of 500 to 10,000 mg / l. And an aerobic biological treatment tank having two or more tiers in series, wherein organic wastewater is introduced into the first biological treatment tank and subjected to biological treatment with bacteria to produce dispersed microorganisms, and the first biological treatment water In a biological treatment tank after the second biological treatment tank for biological treatment,
A first fixed bed formed by arranging a plurality of first sheet-like supports in a first biological treatment tank so that their surface directions are perpendicular to each other,
And an acid generator means for generating an acid at an acid content of 0.1 to 5 m &lt; 3 &gt; -air / m &lt; 2 &gt; - bottom area / min from below the first stationary phase.

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