JP4438529B2 - Biological treatment tank and biological treatment method - Google Patents

Description

The present invention relates to a biological treatment tank that biologically treats water to be treated using a microorganism-immobilized carrier or floating microorganisms, and a biological treatment method using the biological treatment tank .

  As one of the new biological treatment methods for wastewater, a microorganism entrapping method has been developed in which microorganisms are fixed on a carrier and eutrophication components such as nitrogen and phosphorus are removed. In this method, as shown in FIG. 7, a pellet-shaped carrier A is generally charged into a treatment tank 31 filled with water to be treated such as waste water, and microorganisms for treating the waste water are fixed to the carrier A. The microorganisms in the treatment tank 31 are maintained at a high concentration (see Patent Document 1).

  In the treatment tank 31 shown in FIG. 7, an aeration device 32 communicating with an air supply source is disposed at the bottom, and a carrier separation device having a microorganism having an inclined screen 33 is disposed therein. Furthermore, a moving wall device in which an endless belt 36 is wound around pulleys 35, 35 a connected to the drive shaft of the motor 34 is provided substantially in parallel to the screen 33, and the carrier A is stirred. The clogging of the screen 33 is suppressed.

  When the water to be treated is stirred by air finely diffused from the aeration apparatus 32, oxygen is supplied to the microorganisms fixed to the carrier, and the water to be treated and the carrier A flow in a mixed state. Nitrogen in the treated water is biologically treated, and the treated water descends between the screen 33 and the opposed surface 36A of the belt 36 over the upper end of the moving wall device, passes through this screen, Drained from the outlet 38.

  In another example, as shown in FIG. 8, a sewage treatment system in which a baffle plate 42 having openings at the upper and lower portions is disposed, and a propeller-type stirrer 44 supported by a column 43 is disposed at the lower opening, respectively. A tank 41 is disclosed (see Patent Document 2). In this sewage treatment tank 41, by operating a propeller-type stirrer 44, the water to be treated that has flowed in from the inflow port 45 is vertically moved across the baffle plate 42 for each section divided by the baffle plate 42. Since the flow is formed, the carrier A is not distributed to the outlet 46 and is dispersed throughout the processing tank 41. Further, when the blower 47 is operated and diffused from the aeration device 48, a swirl flow is generated for each section divided by the baffle plate 42, and the water to be treated that has been sufficiently biologically treated is transferred to the screen. It flows out from the outlet 46 provided with.

  Furthermore, as an apparatus for separating the carrier attached to the screen, an apparatus for removing the carrier with a suction force by an underwater agitating and aeration device and a shearing force caused by a downward flow of the entire screen surface induced by a circulation pump has been developed (non-patent). Reference 1).

  On the other hand, in the wastewater treatment apparatus shown in FIG. 9, the treatment tank 51 for biologically treating the liquid to be treated (wastewater containing organic components) is biologically mixed with the biological carrier A and wastewater having a specific gravity smaller than that of the wastewater. A carrier separation unit 52 is provided at a terminal portion of the treatment tank 51 to separate the biological carrier A from the treatment liquid, and float and collect it. The treated water is discharged from the outlet 53 and settled in the sedimentation basin, and the biological carrier A floats and gathers at the upper part of the carrier separating unit 52 and is returned to the treatment tank 51 by a carrier driving device 54 such as an air lift pump (Patent Document). 3).

  Further, in the biological treatment apparatus shown in FIG. 10, the treatment tank includes a denitrification tank 62 and a nitrification tank 63, and includes a sedimentation tank 64 as a separation apparatus. In the treatment tank, microorganisms fixed on the carrier and non-fixed floating microorganisms coexist, and the treatment tank is gas-stirred using the blower 65 and the diffuser members 66 and 67 to remove nitrogen and nitrification reaction. By the treatment, the waste water 61 flowing into the treatment tank is purified to become treated water 68. The microorganisms become mud and settle in the sedimentation tank 64. The microorganism mud 69 is returned to the treatment tank by a return pump 70 such as an air lift pump (see Patent Document 4).

JP 2002-86177 A ([0006] to [0026]) JP-A-7-136679 ([0005] to [0015]) JP-A-9-253589 ([0018] to [0021]) Japanese Unexamined Patent Publication No. 7-163395 ([0009] to [0014]) Proceedings of the 36th Sewerage Research Conference (1999), P.577 to P.579

  However, in the apparatus (treatment tank) described in Japanese Patent Application Laid-Open No. 2002-86177 and Japanese Patent Application Laid-Open No. 7-136679, oxygen is supplied to the microorganisms agitated and fixed to the carrier necessary to prevent the carrier from settling. It is necessary to install a new device such as a moving wall device or a propeller type stirring device in order to require extra power more than the power required for aeration and to improve the return and dispersion of the carrier to the treatment tank. . In addition, in the apparatuses described in Japanese Patent Laid-Open Nos. 9-253589 and 7-163959, a driving device such as an air lift pump is installed to return the carrier to which the microorganisms are fixed and the floating microorganisms to the treatment tank, After all, extra power is required. For this reason, there is a problem from the viewpoint of equipment cost and energy consumption, such as the initial cost is increased by newly installing these devices, and the running cost is increased by operating and managing the devices. In addition, even when using an underwater aeration apparatus for the support | carrier separation described in the nonpatent literature 1, in addition to the power required for aeration, the stirring power by a circulation pump is required.

  In addition, when a power failure occurs, it takes several seconds to several tens of seconds until the emergency power supply is activated. Therefore, when a screen is used for separating the carrier, the carrier is removed from the screen during the power failure. If there is no flow of water to be treated to remove the clogging, the screen may be clogged instantly, and the sewage and the carrier may overflow from the treatment tank. In addition, a drive device such as an air lift pump is instantaneously stopped for returning the carrier and suspended microorganisms to the treatment layer, and in any case, the biological treatment is hindered.

Therefore, an object of the present invention is to form a circulation flow in the biological treatment tank without requiring power supply other than the carrier sedimentation prevention and aeration from the outside, and to return the microorganism-fixed carrier or the microorganisms in the floating state with good return. It is to provide a treatment tank and a biological treatment method.

  In order to solve the above problems, the present invention employs the following configuration.

That is, the biological treatment tank according to claim 1 includes a carrier in which microorganisms are fixed in the treated water in a floating state, and the treated water containing the carrier separation screen and the carrier on the treated water outflow side in the tank. inlet and is provided with, comprising a circulation duct which communicates from the inlet in the tank to the treatment water inflow side of the tank, a biological treatment tank for treating water biologically, the An ejector pipe for converting the potential energy of the upstream tank treated water due to the difference in water level between the biological treatment tank and the upstream tank to a kinetic energy at the position of the circulating duct in the treated water inflow side. In the circulation duct, a flow of treated water containing a carrier is formed from the treated water outflow side in the tank to the treated water inflow side in the tank, and the flow of treated water and the tank from the upstream side are formed. ejector-type mixing for mixing the treated water flowing into the inner Band is characterized in that so as to be formed into treated water inflow side of the tank.

The biological treatment tanks are usually arranged in series, and treated water such as sewage is biologically treated, and the upstream treatment tank has a higher water level. For example, as shown in FIG. There is a water level difference Δh between treatment tanks. Due to this water level difference Δh, the water to be treated of the adjacent upstream treatment tank 1 j flows from the lower opening 3 provided on the inflow side wall surface 2 of the biological treatment tank 1. At that time, the potential energy of the upstream treatment tank 1 j is converted into kinetic energy when the treated water passes through the lower opening 3, and the momentum of the treated water draws the surrounding fluid in the treatment tank 1. A suction flow is formed.

In this way, when paying attention to the biological treatment tank 1, the flow path formed by the inflow side water suction flow is formed by the inflow side wall surface 2 and the partition plate T provided on the inflow side facing the lower opening 3. As a result, the ejector type mixing zone M is formed on the inflow side. And this to-be-processed water is biologically processed by mixing contact with the carrier A while being stirred by the underwater stirrer 6 in the reaction zone 5 formed by the outer wall surfaces 4a, 4b and 4c of the circulation duct 4, and the upper part on the outflow side. On the front side of the screen 7 provided on the bottom, a downward flow of the water to be treated mixed with the carrier A is formed. Due to this downward flow, the water to be treated which has been biologically treated without supplying external energy such as electric power passes through the screen 7 and flows out toward the treatment tank 1k on the downstream side, and also includes the carrier A. A part of the water is taken in from the intake 8 of the carrier A provided in front of the outflow side wall surface 2 a without providing a duct wall surface facing the front side of the screen 7, and becomes a return flow of the circulation duct 4. The carrier A can be flowed to the inflow side in the biological treatment tank 1. In this way, the treated water and the returned carrier A are mixed in the ejector-type mixing zone M formed on the inflow side, and a circulation flow is formed in the biological treatment tank 1. Then, the return flow including the carrier A that has flowed through the circulation duct 4 to the inflow side in the biological treatment tank 1 is an ejector-type mixing zone M formed by the action of the suction flow on the inflow side, that is, the ejector effect. It is mixed with the water to be treated and sent to the reaction zone 5, and the biological treatment of the water to be treated in the reaction zone 5 is effectively performed by the mixing effect of the water to be treated and the carrier A in the ejector type mixing zone M. It is. Further, by providing an ejector pipe at the position of the circulation duct 4 at the treated water inflow side in the tank, the flow speed of the treated water flowing out from the ejector pipe into the biological treatment tank is reduced to the width of the biological treatment tank on the inflow side wall surface. It is larger than the case where the inlet is provided over the area, and the above-described suction flow returns the treated water in the ejector type mixing zone and the treated water outflow side in the biological treatment tank through the circulation duct. Mixing with the carrier is effected more effectively.

The water level difference Δh is determined from the cross-sectional area of the lower opening 3, that is, the area of the ejector portion and the treatment flow rate of the water to be treated, so that a suction flow necessary for forming a circulation flow in the biological treatment tank is generated. The ejector section sectional area is designed in accordance with the flow rate of the treated water. Further, the water to be treated can be introduced in the lateral direction from the upstream treatment tank 1j to generate a suction flow.

The biological treatment tank according to claim 2 includes a carrier in which the treated water fixes microorganisms in a floating state, and the plurality of divided biological treatment tanks are connected in series via a partition wall provided with a passage for treated water. In addition, a screen for separating the carrier and an inlet for treated water containing the carrier are provided on the treated water outflow side in the most downstream divided biological treatment tank. A biological treatment tank comprising a circulation duct communicating with the treated water inflow side in the treatment tank and biologically treating the treated water , wherein the treated water in the uppermost divided biological treatment tank in the circulation duct An ejector pipe is provided at the inflow side position to convert the potential energy of the upstream tank treated water due to the difference in water level between the upstreammost divided biological treatment tank and the upstream tank into kinetic energy . The most downstream divided biological treatment A flow of treated water containing a carrier is formed from the treated water outflow side to the treated water inflow side in the uppermost stream divided biological treatment tank. An ejector type mixing zone for mixing the water to be treated flowing into the divided biological treatment tank is formed on the treated water inflow side in the uppermost stream divided biological treatment tank .

In such an apparatus configuration, the difference in water level Δh necessary for generating a suction flow by means for converting potential energy into kinetic energy on the inflow side in the most upstream divided biological treatment tank is the highest flow divided biological treatment. Since it is sufficient to ensure between the tank and the upstream processing tank adjacent to the most upstream divided biological treatment tank , the water level difference of the entire biological treatment tank can be suppressed low. Also, the screen may be provided only on the most downstream splitting biological treatment tank, the ejector mixing zone also, since it is sufficient to provide only the water to be treated inflow side of the most upstream splitting biological treatment tank, a plurality of split organism The apparatus configuration when the processing tanks are connected is simple and economical. Furthermore, since the carrier is returned from the most downstream divided biological treatment tank to the most upstream divided biological treatment tank by the circulation duct, uneven distribution of the carrier in the most downstream divided biological treatment tank is prevented.

The biological treatment tank according to claim 3 includes the treated water in a floating state without fixing the microorganisms to the carrier, the treated water outflow side in the tank is provided with an inlet for the treated water, A biological treatment tank for biologically treating the treated water from the intake port to the treated water inflow side in the tank , wherein the treated water inflow side in the tank in the circulation duct At the position, an ejector pipe for converting the potential energy of the upstream tank treated water due to the water level difference between the biological treatment tank and the upstream tank to kinetic energy is provided , and the covered duct in the tank is disposed in the circulation duct. A flow of treated water containing microorganisms is formed from the treated water outflow side to the treated water inflow side in the tank, and the treated water flow and the treated water flowing into the tank from the upstream side are mixed. is formed on the treated water inflow side of the ejector-type mixing zone is in the tank Characterized in that the so that.

Thus, the microorganisms without fixing on a carrier, for the biological treatment tank containing in suspension, as described above (see FIG. 1), the ejector-type mixing zone M is formed in the tank inflow side, the In the reaction zone 5, the water to be treated is mixed and contacted with floating microorganisms while being stirred by the underwater stirrer 6, and the floating microorganisms are included on the outflow side in the tank where only the outflow port is provided without installing the screen 7. A downward flow is formed. By this downward flow, the biologically treated water passes through the outlet and flows toward the downstream treatment tank 1k without supplying external energy such as electric power, and contains floating microorganisms. A part of the water to be treated is taken in from the intake 8 provided on the outflow side, and becomes a return flow of the circulation duct 4 to allow the floating microorganisms to flow to the inflow side in the biological treatment tank 1. Then, the return flow containing the floating microorganisms flowing in the circulation duct 4 to the inflow side in the biological treatment tank 1 is mixed with the water to be treated in the ejector type mixing area M on the inflow side and sent to the reaction area 5. Thus, biological treatment of the water to be treated in the reaction zone 5 is effectively performed. In addition, the flow rate of the water to be treated flowing out from the ejector pipe into the biological treatment tank is larger than the case where an inlet is provided across the width of the biological treatment tank on the inflow side wall surface. The water to be treated in the mold mixing zone and the floating microorganisms returned from the treated water outflow side in the biological treatment tank through the circulation duct are more effectively mixed.

In the biological treatment tank according to claim 4, the water to be treated includes floating microorganisms without fixing the microorganisms to the carrier, and the plurality of divided biological treatment tanks are connected in series via a partition wall provided with a passage for the water to be treated. In addition, a treated water inlet is provided on the treated water outflow side in the most downstream divided biological treatment tank, and the treated water inflow side in the most upstream divided biological treatment tank is provided in the tank from the intake. A biological treatment tank having a circulation duct communicating with the biological treatment of the treated water, the uppermost flow division at the position of the treated water inflow side in the uppermost flow divided biological treatment tank in the circulation duct An ejector pipe is provided for converting the potential energy of the upstream tank treated water due to the water level difference between the biological treatment tank and the upstream tank to kinetic energy, and the inside of the most downstream divided biological treatment tank is in the circulation duct. From the outflow side of the treated water A flow of treated water containing microorganisms is formed on the treated water inflow side in the flow divided biological treatment tank, and the treated water flows into the uppermost flow divided biological treatment tank from the flow and upstream side of the treated water. An ejector type mixing zone for mixing water is formed on the treated water inflow side in the most upstream divided biological treatment tank .

In this way, as in the above-described case using a carrier, the apparatus configuration when a plurality of divided biological treatment tanks are connected becomes simple and economical. Furthermore, since the floating microorganisms are returned from the most downstream divided biological treatment tank to the most upstream divided biological treatment tank by the circulation duct, uneven distribution of the floating microorganisms in the most downstream divided biological treatment tank is prevented.

Biological treatment tank according to claim 5, in the biological treatment tank according to claim 4, wherein at least the most downstream splitting biological treatment tank is a nitrification tank, a division biological treatment tank made of denitrification reactor upstream of the nitrification tank It is provided.

  In the biological denitrification method in which denitrification is performed by biological treatment, a nitrification solution circulation type tank arrangement in which a nitrification tank is provided on the downstream side and a denitrification tank is provided on the upstream side, as opposed to the reaction sequence, is generally described later. Used. In this nitrification / denitrification process, it is necessary to return a large amount of water to be treated from the nitrification tank to the denitrification tank, but a circulating flow is formed in the biological treatment tank by the means for converting the above-mentioned potential energy into kinetic energy. The tank arrangement is possible without supplying external energy such as electric power.

The biological treatment tank which concerns on Claim 6 contains the to-be-processed water in a tank in the floating state, without fixing a microorganism to a support | carrier, and isolate | separates the microorganisms and the biologically treated treated water on the downstream side outside a tank. A biological treatment comprising a separation means, and a circulation duct that communicates from a microbial intake provided in the separation means to a treated water inflow side in the tank, and biologically treats the treated water. The position energy of the upstream tank treated water due to the difference in water level between the biological treatment tank and the upstream tank is converted into kinetic energy at the treated water inflow side position in the tank in the circulation duct. An ejector type for providing an ejector pipe for forming a flow of microorganisms separated from the separation means in the circulation duct and mixing the flow of microorganisms and water to be treated flowing into the tank from the upstream side treated in the mixing zone is in the tank Characterized in that so as to be formed on the inflow side.

In this way, microorganisms (sludge) and treated water are separated into solid and liquid, and sludge can be returned to the biological treatment tank and reused without supplying energy from the outside. In addition, the flow rate of the water to be treated flowing out from the ejector pipe into the biological treatment tank is larger than the case where an inlet is provided on the inflow side wall surface across the width of the biological treatment tank, The water to be treated in the ejector type mixing zone and the microorganisms (sludge) returned from the treated water outflow side in the tank through the circulation duct are more effectively mixed.

A biological treatment tank according to a seventh aspect is the biological treatment tank according to any one of the first to sixth aspects, wherein an aeration apparatus is incorporated in the ejector-type mixing zone .

  In this way, the air supplied to the ejector-type mixing zone by the aeration device exerts an air lift effect in addition to the original aeration action, so that even if the required water level difference Δh cannot be secured, the suction is performed. The suction force required to generate the flow can be supplemented, and the uniform mixing of the carrier and the suspended microorganisms is promoted.

A biological treatment tank according to an eighth aspect is the biological treatment tank according to any one of the first to seventh aspects, wherein the ejector pipe includes a flow rate adjusting means.

The flow velocity in the circulation duct must be 30 mm / s or less from the viewpoint of preventing pressure loss in the duct, and 10 cm / s or more from the viewpoint of preventing the carrier from sinking and staying in the duct. For this reason, it is usually at a low speed of 10 to 30 cm / s, and there is a risk that the inside of the circulation duct is blocked by foreign matters such as fibers in the drainage or a membrane secreted by microorganisms. When one of the ejector pipes is closed by the flow rate adjusting means, the flow of the closed circulation duct stops, so that the water level difference (Δh) on the inflow side of the biological treatment tank increases. Due to the increase in the water level difference (Δh), the amount of water to be treated flowing out from the other ejector pipe increases, and the flow velocity in the circulation duct increases accordingly. Removal is possible.

The biological treatment tank according to claim 9 is the biological treatment tank according to any one of claims 1 to 8, wherein one end side of the biological treatment tank communicates with the circulation duct, and the other end side protrudes from the water surface in the tank. It is characterized by providing an air vent pipe.

In this way, it is possible to prevent the accumulation of air in the circulation duct, so that the return flow smoothly flows and the return of the carrier or microorganisms is not hindered.

A biological treatment method according to claim 10 is a biological treatment method using the biological treatment tank according to claim 1 or 2, wherein the biological treatment tank includes an amount of water to be treated when passing through the ejector pipe . A suction flow is generated by an ejector effect that draws fluid around the outflow side of the treated water toward the inflow side of the treated water in the biological treatment tank into the circulation duct, and the suction flow by the ejector effect causes a suction flow in the biological treatment tank. Forming a circulation flow between the treated water inflow side and the treated water outflow side to prevent the carrier from adhering to the screen, and the carrier in the biological treatment tank through the circulation duct . It returns to the to- be-processed water inflow side , It was made to mix with the to- be-processed water which flows in into a biological treatment tank from the upstream .

The biological treatment method according to claim 11 is a biological treatment method using the biological treatment tank according to any one of claims 3 to 5, and is based on the momentum of the water to be treated when passing through the ejector pipe. A suction flow is generated by the ejector effect that draws the fluid around the treated water outflow side in the biological treatment tank toward the treated water inflow side in the biological treatment tank into the circulation duct, and the suction flow by the ejector effect , said microorganism, back through said circulation duct to the treatment water inflow side of the biological treatment tank, to the upstream side, characterized in that so as to mix with the treated water flowing into the biological treatment tank.

A biological treatment method according to a twelfth aspect is the biological treatment method using the biological treatment tank according to the sixth aspect , wherein microorganisms from the separation means are obtained by the momentum of the water to be treated when passing through the ejector pipe. the toward treatment water inflow side of the biological treatment tank to generate a suction flow by ejector effect to draw in the circulating duct, the suction flow by the ejector effect, the microorganism, biological treatment tank through the circulation duct It returns to the to- be-processed water inflow side , and it mixes with the to- be-processed water which flows in into a biological treatment tank from the upstream .

As described above, according to the biological treatment tank or the biological treatment method of the present invention , when biologically treating water to be treated using a carrier or floating microorganisms in which microorganisms are immobilized , Of the biological treatment tank provided with a circulation duct communicating with the inflow side of the treated water , provided with an ejector pipe at the position of the treated water inflow side in the tank in the circulation duct , to be treated to flow into the biological treatment tank from the upstream side Due to the momentum of the water to be treated when water passes through the ejector pipe, a suction flow is generated by the ejector effect that draws the fluid around the treated water outflow side toward the treated water inflow side in the tank into the circulation duct. By this suction flow, a circulation flow is formed by a circulation duct between the treated water inflow side and the treated water outflow side in the biological treatment tank, and from the upstream side to the treated water inflow side in the tank. In the biological treatment tank Since so as to form an ejector type mixing zone for mixing the flow of the water to be treated from the circulation duct and the for-treatment water to enter, without supplying external energy such as electricity, settler through the circulation duct The carrier or suspended microorganism returned to the inflow side without staying and the water to be treated flowing into the biological treatment tank from the upstream side are mixed. Then, these mixed stream is fed to the reaction zone of the biological treatment tank, it is possible to make uniform the distribution of the carrier or suspended microorganisms in the biological treatment tank, biological treatment is effectively carried out, stirring power also You can save. Further, since the carrier or the floating microorganism can be returned to the inflow side without requiring external energy, a circulation flow can be formed in the biological treatment tank even when a power failure occurs, and the biological treatment can be continued.

  Embodiments of the present invention will be described below with reference to FIGS.

FIG. 2 is a perspective view showing the configuration of the biological treatment tank according to the first embodiment of the present invention. The biological treatment tank connects a plurality of divided biological treatment tanks, that is, three divided biological treatment tanks 1a, 1b, and 1c in series through partition walls 10 and 10a provided with passages 9 and 9a for water to be treated, respectively. This is a connected biological treatment tank. A carrier separation screen 12 is installed on the outflow side wall surface 11 of the most downstream divided biological treatment tank 1c without providing a duct wall surface facing the front side . On the both sides of the bottom of the most downstream divided biological treatment tank 1c, intakes 13 and 13a for taking in water to be treated containing a carrier (not shown) in which microorganisms are fixed are provided, and circulation ducts are provided from the intakes 13 and 13a. The main bodies 14 and 14a extend to the inflow side in the most upstream divided biological treatment tank 1a , and are connected to diffusers 16 and 16a extending upward along the inflow side wall surface 15 to form circulation ducts 17 and 17a. . The intake ports 13 and 13a have a cross-sectional area larger than that of the circulation duct bodies 14 and 14a so that the carrier can be easily taken in, and the diameter is gradually reduced from this end face so as to be integrated with the duct bodies 14 and 14a. Is formed. Ejector pipes 18 and 18a are inserted into the diffusers 16 and 16a, that is, the circulation ducts 17 and 17a extending upward, and the water to be treated flowing from the upstream side flows through the diffusers 16 and 16a. Valves 19 and 19a serving as flow rate adjusting means for the treated water to flow into are provided on the inlet side of the ejector pipes 18 and 18a. As the valves 19 and 19a, a gate valve, a butterfly valve, an eccentric casting valve, or the like can be used.

An aeration device (aeration device) for sending air from the blower can be provided on the inflow side in the most upstream divided biological treatment tank 1a. Further , as shown by a broken line, the middle of the circulation duct main body 14 is provided. Further, an air vent pipe 20 whose one end side communicates with the circulation duct main body 14 and whose other end side protrudes from the water surface in the treatment tank may be provided. This air vent pipe 20 can be provided in the same manner in the other circulation duct body 14a. A pellet-like carrier such as PEG (polyethylene glycol) to which microorganisms such as nitrate bacteria are fixed is placed in the uppermost divided biological treatment tank 1a, and sedimentation of the carrier is set in each divided biological treatment tank 1a, 1b, 1c. An underwater stirrer (not shown) is installed to prevent the above and promote uniform mixing.

  The first embodiment of the present invention is configured as described above, and the function thereof will be described below.

When water to be treated flows from a water tank in which no upstream carrier is introduced or an upstream biological treatment tank, the kinetic energy of the potential energy of the upstream water tank or treatment tank passes through the ejector pipes 18 and 18a. In accordance with the momentum of the water to be treated, a suction flow that draws the fluid around the intake ports 13 and 13a in the most downstream divided biological treatment tank 1c into the circulation duct bodies 14 and 14a is generated, and the ejector pipe 18 (18a) The diffuser 16 (16a) forms a kind of pump (ejector pump). The operation of such an ejector pump will be described below using a biological treatment tank model as shown in FIG.

Biological treatment tank model shown in Figure 3, the diffuser 16 ejector nozzle (ejector tube 18) is installed in the inflow-side partition biological treatment tank (the first compartment), the screen on the outflow side dividing the biological treatment tank (second compartment) 7 is installed, and a return pipe 17b having an intake port 13 extends from the lower side thereof toward the inflow side divided biological treatment tank (first section) and is connected to the diffuser 16, and an ejector portion E is formed on the inflow side. Has been. The characteristics such as the total pressure distribution in the biological treatment tank and the return flow ratio (return flow rate in the circulation duct / flow rate in the ejector pipe) by the ejector part E, that is, the operation of the ejector pump, are stored in the momentum conservation formula (1) and diffuser pressure recovery. It can be obtained from the equation (2), the return pipe pressure loss equation (3), and the nozzle pressure loss equation (4).
(Equation 1)
A ₁ (ρU ₁ ² + P ₁ ) + A ₂ (ρU ₂ ² + P ₂ ) = A ₃ (ρU ₃ ² + P ₃ ) (1)
P ₃ = P ₄ −η _D 1 / 2ρ (U ₃ ² −U ₄ ² ) (2)
P ₄ = P ₂ + λ (L / D) 1 / 2ρU ₅ ² + ρgΔh _1-2 (3)
(1-ζ) 1 / 2ρU ₁ ² = ρgΔh _0-1 (4)
Here, A: flow path area, U: flow velocity, P: pressure, L: length of circulation duct body (return pipe), D: return pipe diameter, g: gravitational acceleration, Δh: water level difference, ρ: density, η _D : Diffuser recovery rate, λ: pipe friction coefficient, ζ: pipe bending coefficient, (subscript) 0-1: between upstream tank and inflow side divided biological treatment tank (first section), 1-2: first Between section and second section, 1: ejector pipe, 2: ejector suction side pipe, 3: diffuser inlet, 4: diffuser outlet, 5: return pipe (circulation duct)

The total pressure distribution in the divided biological treatment tank of the biological treatment tank composed of the divided biological treatment tanks 1a, 1b, and 1c shown in FIG. 2 by numerical analysis from the equations (1) to (4). As a result of obtaining the return flow rate ratio, the pressure drops from the intake port 13 (13a) to the ejector pipe 18 (18a) to generate a suction flow, and the average pressure in the return pipe 17b (circulation duct) In the analysis example, it was confirmed that the pressure was about 300 Pa lower than the pressure in the most upstream divided biological treatment tank (first section). Further, when the nozzle flow rate (discharge speed from the ejector pipes 18 and 18a) is in the range of 0.8 to 2.0 m / s, the return flow rate ratio is about 50 to 60%, and the necessary circulating flow is generated in the biological treatment tank. The formation was confirmed in the model water tank experiment together with the numerical analysis.

The analysis results as confirmed by the action of the suction flow, i.e. by ejector effect, the water to be treated from the inlet 13,13a are taken into the circulation duct 17,17a with a carrier, most upstream splitting organisms biological treatment tank A circulation flow is formed between the treatment tank 1a and the most downstream divided biological treatment tank 1c, and the carrier on which the microorganisms are fixed is returned to the most upstream divided biological treatment tank 1a, and in the ejector mixing zone M (see FIG. 1), The carrier returned to the inflow side through the circulation ducts 17 and 17a and the water to be treated are mixed, and the carrier distribution in the most upstream divided biological treatment tank 1a can be made uniform. By this circulating flow, the water to be treated flows together with the carrier from the uppermost divided biological treatment tank 1a through the passage port 9 into the next divided biological treatment tank 1b, and further, the water to be treated containing this carrier passes through the passage opening 9a. In the biological reaction treatment process that flows into the most downstream divided biological treatment tank 1c, the carrier is prevented from being unevenly distributed and staying in the lowest downstream divided biological treatment tank 1c, and the carrier is separated from the screen 12 to prevent clogging. Thus, biological treatment of the water to be treated can be performed effectively. Since external energy such as electric power is not required for returning the carrier, a circulation flow is formed even when a power failure occurs, and the biological reaction process can be continued without clogging the screen 12.

Further, by providing the valves 19 and 19a on the inlet side of the ejector pipes 18 and 18a, for example, the valve 19 is fully closed, and the flow from the ejector pipe 18 into the uppermost divided biological treatment tank 1a and the circulation duct 17 When the return flow inside is stopped, the water level difference at the inflow side wall surface 15 increases four times. As a result, the flow velocity from the ejector pipe 18a with the valve 19a open into the uppermost divided biological treatment tank 1a increases, and the flow velocity in the circulation duct 17a also increases due to the suction flow due to this ejector effect. Foreign matters such as fibers adhering to the inner surface of the duct 17a and a membrane secreted by microorganisms can be removed. The inner surface of the circulation duct 17 can be cleaned by the same operation. Further, since the return flow of the carrier passes through the circulation ducts 17 and 17a, it is exhausted from the air vent pipe 20 to the outside of the biological treatment tank, so that the occurrence of air pockets can be prevented and the return flow smoothly flows, Return is not hindered.

FIG. 4 is a perspective view showing a configuration of a biological treatment tank according to the second embodiment of the present invention. The biological treatment tank, the nitrification and denitrification process, a biological treatment tank for removing ammonia nitrogen in waste water biologically, denitrification 1d as the most upstream dividing the biological treatment tank from the inlet side of the drainage A nitrification tank 1e as an intermediate divided biological treatment tank and a nitrification tank 1f as a most downstream divided biological treatment tank are connected in series via partition walls 10 and 10a provided with passages 9 and 9a for treated water, respectively. An outflow port 21 of biologically treated water is formed at the upper part of the outflow side wall surface 11 of the most downstream nitrification tank 1f. On the inflow side of the nitrification tanks 1e and 1f, an aeration device (aeration device) (not shown) for sending air from the blower into the tank is provided. In the nitrification tanks 1e and 1f of the aerobic tank, nitrate bacteria and nitrite bacteria are not fixed to the carrier and work as floating microorganisms, and in the denitrification tank 1d of the anaerobic tank, denitrifying bacteria work as floating microorganisms. Similarly to the case of the first embodiment, intake sides 13 and 13a for water to be treated (nitrification liquid) nitrified in the nitrification process of the nitrification tanks 1e and 1f are provided on both sides of the bottom of the nitrification tank 1f, respectively. The circulation duct bodies 14 and 14a extend from the intakes 13 and 13a to the inflow side in the denitrification tank 1d of the biological treatment tank , and are connected to the diffusers 16 and 16a extending upward along the inflow side wall surface 15 to circulate. Ducts 17 and 17a are formed. The intake ports 13 and 13a have a cross-sectional area larger than the cross-sectional area of the circulation duct bodies 14 and 14a so that the water to be treated can be easily taken in. It is integrally formed. Ejector pipes 18 and 18a are inserted into the diffusers 16 and 16a, that is, the circulation ducts 17 and 17a extending upward, so that the water to be treated flowing from the upstream side flows through the diffusers 16 and 16a. Valves 19 and 19a serving as flow rate adjusting means for inflowing water to be treated are provided on the inlet side of the ejector pipes 18 and 18a. In addition, as shown in the first embodiment (see FIG. 2), one end side communicates with the circulation duct bodies 14 and 14a in the middle of the circulation duct bodies 14 and 14a, and the other end side is the water surface in the treatment tank. An air vent tube 20 (not shown on the duct main body 14a side) protruding from the above can also be provided. Each divided biological treatment tank 1d, 1e, 1f is provided with an underwater agitator (not shown). A precipitation tank (not shown) is installed on the outlet side of the outlet 21. In addition, floating microorganisms can be taken in from the intakes 13 and 13a and returned to the treatment tank on the inflow side to reuse the microorganisms.

  The second embodiment of the present invention is configured as described above, and the function thereof will be described below.

When the water to be treated flows into the denitrification tank 1d of the biological treatment tank from the upstream water tank through the ejector pipes 18 and 18a and the diffusers 16 and 16a, what is the ammonia nitrogen component in the treated water to be removed in the denitrification tank 1d? It does not change, that is, does not cause a biological reaction, and flows into the nitrification tanks 1e and 1f through the passages 9 and 9a, respectively. In the nitrification tanks 1e and 1f, ammonia is oxidized into nitrous acid by the action of aerobic nitrite bacteria as shown in the formula (1). Next, the nitrous acid is oxidized by the action of an aerobic nitric acid bacterium as shown in the formula (2), and the formula (1) and the formula (2) are added to form a nitric acid as shown in the formula (3). become.
(Equation 2)
NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O (1)
NO ₂ ⁻ + 1 / 2O ₂ → NO ₃ (2)
NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺ (3)

As in the case of the first embodiment, when the water to be treated flows into the ejector pipes 18 and 18a from the upstream water tank, the potential energy of the upstream water tank passes through the ejector pipes 18 and 18a. The suction flow that draws the fluid around the intake ports 13 and 13a in the nitrification tank 1f into the circulation duct bodies 14 and 14a is generated by the kinetic energy converted into the kinetic energy.

By the action of this suction flow, that is, the ejector effect, the water to be treated is taken into the circulation ducts 14 and 14a from the intake ports 13 and 13a, and the denitrification tank 1d as the uppermost division biological treatment tank of the biological treatment tank and the most downstream division. A circulation flow is formed between the nitrification tank 1f as a biological treatment tank . By this circulation flow, the water to be treated (nitrification liquid) subjected to nitrification is returned to the denitrification tank 1d, and as shown in the formulas (4) and (5), nitric acid is reduced to nitrogen gas by the denitrification reaction. .
(Equation 3)
NO ₃ ⁻ +2 (H ₂ ) → 2NO ₂ ⁻ + 2H ₂ O (4)
2NO ₂ ⁻ +3 (H ₂ ) → N ₂ ↑ + 2OH ⁻ + 2H ₂ O (5)
H ₂ in the formulas (4) and (5) is supplied by the decomposition of the organic substance, and the BOD component in the treated water (raw water) corresponds to this hydrogen donor.

  As described above, in the nitrification / denitrification process, it is necessary to return a large amount of the water to be treated nitrified from the nitrification tank 1f to the denitrification tank 1d. Since the circulation flow is formed in the biological treatment tank by the suction flow by the ejector pipes 18 and 18a, the water to be treated that has been nitrified can be returned to the denitrification tank 1d without providing a return pump. Costs are reduced, and nitrification and denitrification can be continued even when a power failure occurs. In the biological treatment tank, a denitrification tank 1d is arranged in front of the nitrification tanks 1e and 1f, and is reverse to the reaction order. By circulating the nitrification liquid in such a tank arrangement, The BOD component in the treated water (raw water) can be used for the denitrification reaction, and there is an advantage that the BOD component added from the outside can be saved. For this reason, a nitrification liquid circulation type tank arrangement is often used. The nitrate bacteria, nitrite bacteria, and denitrifying bacteria are all contained in the water to be treated (raw water) and grow naturally in normal operation, so there is no need to supply them from the outside.

FIG. 5 is a perspective view showing a configuration of a biological treatment tank according to the third embodiment of the present invention. As in the first embodiment (see FIG. 2), this biological treatment tank includes a plurality of divided biological treatment tanks, that is, three divided biological treatment tanks 1g, 1h, and 1i, and a water treatment port 9, This is a connected biological treatment tank connected in series via partition walls 10 and 10a each provided with 9a. On the upper part of the outflow side wall surface 11 of the most downstream divided biological treatment tank 1i, an outlet 21 for biologically treated water is disposed, and on the outlet side of the outlet 21 via a flow path 22, A sedimentation tank 23 is installed as a separation means for separating the biologically treated clear treated water and the microorganism group into solid and liquid. At the bottom of the settling tank 23 is connected discharge pipe 24, the discharge pipe 24 is branched into both sides direction of the biological treatment tank, rising to the height of the bottom of the biological treatment tank, the most upstream splitting organisms from the bottom sides It connects with the circulation duct main bodies 14 and 14a extended to the processing tank 1g. The circulation duct bodies 14 and 14a are respectively connected to diffusers 16 and 16a extending upward along the inflow side wall surface 15 to form circulation ducts 17 and 17a. Ejector pipes 18 and 18a into which treated water from the upstream side flows are inserted into the diffusers 16 and 16a, and valves 19 and 19a for adjusting the flow rate of the treated water that flows in are provided on the inlet side. ing. Moreover, the aeration apparatus (aeration apparatus) for sending air from a blower can also be provided in the inflow side in the most upstream division | segmentation biological treatment tank 1g. Furthermore, an air vent pipe 20 (the duct body 14a side is not shown) can be provided in the middle of the circulation duct bodies 14 and 14a. Each divided biological treatment tank 1g, 1h, 1i is provided with an underwater agitator (not shown).

  The third embodiment of the present invention has the above configuration, and the function thereof will be described below.

In each of the divided biological treatment tanks 1g, 1h, and 1i, the water to be treated is brought into contact with the suspended aerobic microorganism group, and the BOD component in the water to be treated is oxidized and decomposed in the presence of dissolved oxygen. Flows into the sedimentation tank 23 from the outlet 21 through the flow path 22. In the sedimentation tank 23, the microorganism group aggregates and settles, and is separated from the supernatant treated water by solid-liquid separation. On the other hand, when the water to be treated flows from the upstream water tank into the most upstream divided biological treatment tank 1g through the ejector pipes 18 and 18a and the diffusers 16 and 16a, the potential energy of the upstream water tank or the treatment tank is changed to the ejector pipe 18. , 18a is converted into kinetic energy, and a suction flow that draws a group of microorganisms from the bottom of the sedimentation tank 23 into the circulation duct bodies 14, 14a is generated by the momentum of the water to be treated.

Due to the action of this suction flow, that is, the ejector effect, the settled microorganism group passes through the discharge pipe 24 from the bottom of the sedimentation tank 23 and is taken into the circulation ducts 17 and 17a via the rising part 24a, and the most upstream divided biological treatment tank 1g. A circulated flow containing a group of microorganisms, that is, sludge, is formed between the slag and the sedimentation tank 23, and the sludge is returned to the most upstream divided biological treatment tank 1g. The returned sludge functions to remove the BOD component of the water to be treated again in the biological treatment tank. Thus, a circulation flow is formed by the suction flow by the ejector pipes 18 and 18a, and sludge is returned to the inflow side from the sedimentation tank 23 without providing a return pump. Costs and energy costs are saved, and nitrification / denitrification can be continued even when a power failure occurs.

FIG. 6 is a perspective view showing a circulation system in place of the circulation duct and the ejector pipe in the biological treatment tank shown in FIGS. 2 and 4, and (a) is an enlarged perspective view showing the circulation system composed of a trough and an ejector. The (b) is a perspective view which shows the principal part of the biological treatment tank provided with the circulation system shown to (a). As shown in FIG. 6 (a), this circulation system connects the diffusers 16, 16a laterally so as to face the downstream side of the processing tank through the connecting pipes 26 extending downward from the troughs 25, 25a. The ejector tubes 18 and 18a are inserted into the entrance sides of the diffusers 16 and 16a. As shown in FIG. 6 (b), the troughs 25, 25a are provided on both sides of the tank at a height near the water surface level, and ejectors are disposed on the entry side of the diffusers 16, 16a connected to the troughs 25, 25a. Tubes 18 and 18a are inserted. The open ends R of the troughs 25 and 25a reach the most downstream divided biological treatment tank (not shown) and serve as intakes for the carrier or treated water (nitrification liquid).

Dividing the biological treatment tank 1a of 3 sections shown in FIG. 2, 1b, the numerical results of the foregoing for biological treatment tank made of 1c, the average pressure in the circulation duct 17, 17a (return pipe) is most upstream splitting organisms Since the pressure is about 300 Pa lower than the pressure in the processing tank 1a (first section), as shown in FIG. 6B, when troughs 25 and 25a are provided as return pipes, the water level in the trough is in the surrounding tank. It is about 30 mm lower than the water level. For this reason, carrier or treated water flows from the open end R (see FIG. 6 (a)) of the troughs 25, 25a corresponding to the intake port 13 (13a) of the most downstream divided biological treatment tank, and the inflow side treatment is performed. A circulating flow toward the tank is formed. As described above, when a trough having an open top as a circulation duct is provided in the vicinity of the water surface level, maintenance against duct clogging and dirt is greatly improved.

  In the first to third embodiments and the other embodiments described above, the circulation ducts 17, 17a or troughs 25, 25a are two in total along the bottom side of the biological treatment tank or near the water surface level. In addition, a plurality of more than that can be provided, and thus the plurality of ejector tubes can also be provided. In addition, the total cross-sectional area of the ejector pipe is the energy shown in the equations (1) to (4) so as to ensure a water level difference from the upstream side necessary for the circulation flow to occur in the biological treatment tank. And considering the pressure balance, it can be designed corresponding to the flow rate of the water to be treated.

This invention is an economical biological treatment tank that does not require external energy such as electric power for returning microorganism support, sludge, and circulating nitrification liquid in nitrification / denitrogenation process, etc. Can be used to build

It is explanatory drawing about the suction flow in the biological treatment tank by this invention . It is a perspective view which shows the structure of the biological treatment tank by the 1st Embodiment of this invention . It is explanatory drawing which modeled the biological treatment tank by the 1st Embodiment of this invention . It is a perspective view which shows the structure of the biological treatment tank by the 2nd Embodiment of this invention . It is a perspective view which shows the structure of the biological treatment tank by the 3rd Embodiment of this invention . FIG. 5 is a perspective view showing a circulation system in place of the circulation duct and the ejector pipe in the biological treatment tank shown in FIGS. 2 and 4, wherein (a) is an enlarged perspective view showing the circulation system composed of a trough and an ejector, (b). FIG. 3 is a perspective view showing a main part of a biological treatment tank provided with the circulation system shown in FIG. It is sectional drawing which shows the biological treatment tank of an example of a prior art . It is sectional drawing which shows the biological treatment tank of the other example of a prior art . It is sectional drawing which shows the biological treatment tank of the other example of a prior art . It is sectional drawing which shows the biological treatment tank of the other example of a prior art .

DESCRIPTION OF SYMBOLS 1 ... Biological treatment tank 1a-1i ... Division | segmentation biological treatment tank 2, 15 ... Inflow side wall surface 2a, 11 ... Outflow side wall surface 3 ... Lower opening 4, 17, 17a ... Circulation duct 4a, 4b ... Outer wall surface 5 ... Reaction zone 6 ... underwater agitator 7, 12 ... screen 8, 13, 13a ... intake port 9, 9a ... passage port 10, 10a ... partition wall 14, 14a ... circulation duct body 16, 16a ... diffuser 17b ... return pipe 18, 18a ... ejector pipe 19 , 19a ... Valve 20 ... Air vent pipe 21 ... Outlet 22 ... Flow path 23 ... Precipitation tank 24 ... Discharge pipe 24a ... Rising part 25, 25a ... Trough 26 ... Connecting pipe

Claims (12)

The treated water includes a carrier in which microorganisms are fixed in a floating state, and a screen for separating the carrier and an inlet for treated water containing the carrier are provided on the treated water outflow side in the tank. A biological treatment tank comprising a circulation duct communicating from the intake to the treated water inflow side in the tank, and biologically treating the treated water ,
An ejector pipe for converting the potential energy of the upstream tank treated water due to the difference in water level between the biological treatment tank and the upstream tank to kinetic energy at the position of the circulating duct in the treated water inflow side. Providing a flow of treated water containing a carrier from the treated water outflow side in the tank to the treated water inflow side in the tank in the circulation duct, and from the upstream side of the treated water flow A biological treatment tank , characterized in that an ejector-type mixing zone for mixing the treated water flowing into the tank is formed on the treated water inflow side in the tank . The treated water includes a carrier in which microorganisms are fixed in a floating state, and a plurality of divided biological treatment tanks are connected in series via a partition wall provided with a passage portion of the treated water, and in the most downstream divided biological treatment tank A screen for separating the carrier and an intake of treated water containing the carrier are provided on the treated water outflow side, and the intake is provided in the tank from the intake to the treated water inflow side in the uppermost divided biological treatment tank. A biological treatment tank having a circulation duct communicating therewith and biologically treating the water to be treated ;
The position energy of the upstream side tank treated water due to the difference in water level between the upstreammost divided biological treatment tank and the upstream tank is moved to the treated water inflow side position in the uppermost stream divided biological treatment tank in the circulation duct. An ejector pipe for converting to energy is provided, and a carrier is included in the circulation duct from the treated water outflow side in the most downstream divided biological treatment tank to the treated water inflow side in the uppermost divided biological treatment tank. An ejector type mixing zone that forms a flow of water to be treated and mixes the flow of water to be treated and the water to be treated flowing from the upstream side into the most upstream divided biological treatment tank includes the uppermost flow divided biological treatment. A biological treatment tank characterized by being formed on the treated water inflow side in the tank . The treated water contains microorganisms in a floating state without fixing them to the carrier, and an inlet for treated water is provided on the treated water outflow side in the tank. A biological treatment tank having a circulation duct communicating with the water inflow side and biologically treating the water to be treated ,
An ejector pipe for converting the potential energy of the upstream tank treated water due to the difference in water level between the biological treatment tank and the upstream tank to kinetic energy at the position of the circulating duct in the treated water inflow side. And forming a flow of treated water containing microorganisms from the treated water outflow side in the tank to the treated water inflow side in the tank in the circulation duct, and from the upstream of the treated water flow A biological treatment tank , characterized in that an ejector-type mixing zone for mixing the treated water flowing into the tank is formed on the treated water inflow side in the tank . The treated water contains microorganisms in a floating state without being fixed to the carrier, and a plurality of divided biological treatment tanks are connected in series via a partition wall provided with a passage for treated water, and the most downstream divided biological treatment tank A treated water inlet is provided on the treated water outflow side, and a circulation duct is provided in the tank to communicate from the intake to the treated water inflow side in the most upstream divided biological treatment tank. A biological treatment tank for biologically treating water ,
The position energy of the upstream side tank treated water due to the difference in water level between the upstreammost divided biological treatment tank and the upstream tank is moved to the treated water inflow side position in the uppermost stream divided biological treatment tank in the circulation duct. An ejector pipe for converting to energy is provided, and microorganisms are contained in the circulation duct from the treated water outflow side in the most downstream divided biological treatment tank to the treated water inflow side in the uppermost divided biological treatment tank. An ejector type mixing zone that forms a flow of water to be treated and mixes the flow of water to be treated and the water to be treated flowing from the upstream side into the most upstream divided biological treatment tank includes the uppermost flow divided biological treatment. A biological treatment tank characterized by being formed on the treated water inflow side in the tank . At least the most downstream splitting biological treatment tank is nitrification tank, biological treatment tank according to claim 4, characterized in that a dividing biological treatment tank made of denitrification reactor upstream of the nitrification tank. The treated water in the tank contains microorganisms in a floating state without fixing them to the carrier, and is equipped with a separating means for separating the microorganisms and the biologically treated treated water on the downstream side outside the tank. A biological treatment tank for biologically treating the water to be treated, comprising a circulation duct communicating with the treated water inflow side in the tank from the microorganism inlet provided in the separation means ;
An ejector pipe for converting the potential energy of the upstream tank treated water due to the difference in water level between the biological treatment tank and the upstream tank to kinetic energy at the position of the circulating duct in the treated water inflow side. An ejector-type mixing zone for forming a flow of microorganisms separated from the separation means in the circulation duct and mixing the flow of microorganisms and water to be treated flowing from the upstream side into the tank. A biological treatment tank formed on the inflow side of water to be treated . The biological treatment tank according to any one of claims 1 to 6, wherein an aeration apparatus is incorporated in the ejector-type mixing area . Biological treatment tank according to any one of 7 to claim 1, characterized in that the ejector tube is provided with a flow regulating means. The biological treatment tank according to any one of claims 1 to 8, wherein an air vent pipe is provided in the circulation duct so that one end side communicates with the circulation duct and the other end side protrudes from the water surface in the tank . It is a biological treatment method using the biological treatment tank of Claim 1 or 2, Comprising: The fluid around the to-be-processed water outflow side in a biological treatment tank by the momentum of the to-be-processed water at the time of passing the said ejector pipe | tube. the generate a suction flow by ejector effect to draw in the circulating duct toward the treatment water inflow side of the biological treatment tank, the suction flow by the ejector effect, the treatment water inflow side and treated water biological treatment tank between the outlet side to form a circulating flow to prevent adhesion of the carrier to the screen, and the carrier, back through the circulation duct to the treatment water inflow side of the biological treatment tank, the upstream side A biological treatment method characterized in that it is mixed with water to be treated flowing into the biological treatment tank . It is a biological treatment method using the biological treatment tank of any one of Claims 3-5, Comprising: Outflow of the to-be-processed water in a biological treatment tank by the momentum of the to-be-processed water at the time of passing the said ejector pipe | tube towards the fluid around the sides to the treatment water inflow side of the biological treatment tank to generate a suction flow by ejector effect to draw in the circulating duct, the suction flow by the ejector effect, the microorganism through the circulation duct The biological treatment method is characterized in that it is returned to the treated water inflow side in the biological treatment tank and mixed with the treated water flowing into the biological treatment tank from the upstream side . It is a biological treatment method using the biological treatment tank of Claim 6, Comprising: The microorganisms from the said isolation | separation means flow into the to-be-processed water in a biological treatment tank by the momentum of the to-be-processed water at the time of passing the said ejector pipe | tube. to generate a suction flow by ejector effect to draw in the circulating duct toward the side, the suction flow by the ejector effect, the microorganism, back through the circulation duct to the treatment water inflow side of the biological treatment tank, upstream A biological treatment method characterized by mixing with water to be treated flowing into a biological treatment tank from the side .

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