JP2006007033A - Biological treatment tank for waste water and biologically treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological treatment tank for waste water, in which a circulating flow is formed without necessitating the supply of the power other than the power for prevention of the sedimentation of a microbe-fixed carrier and that for aeration from the outside and the microbe-fixed carrier or a suspended microbe is returned excellently and to provide a biologically treating method. <P>SOLUTION: A screen 12 for separating the microbe-fixed carrier and carrier intakes 13, 13a are arranged on the outflow side of the biological treatment tank in which the microbe-fixed carrier of a suspended state is incorporated. Circulation ducts are arranged for communicating these carrier intakes with the inflow side of the biological treatment tank. Ejector pipes 18, 18a are arranged on the inflow side of the biological treatment tank so that a flow of the microbe-fixed carrier from the outflow side to the inflow side is formed in each of circulation ducts 17, 17a by utilizing a water level difference between the biological treatment tank and a waste water tank arranged on the upstream side of the biological treatment tank, namely, by transforming the positional energy into the kinetic energy. As a result, since a sucking flow is formed on the inflow side even when external energy is not supplied, the water to be treated is mixed with the microbe-fixed carrier by the ejector effect and the circulating flow is formed, and the biological treatment can be effectively performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biological treatment tank for wastewater that biologically treats wastewater using a microorganism-immobilized carrier or floating microorganisms, and a biological treatment method for wastewater using this 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 the 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 fixed to the agitation and 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 Application Laid-Open Nos. 9-253589 and 7-163395, a driving device such as an air lift pump is installed to return the carrier to which the microorganisms are fixed and the suspended microorganisms to the treatment tank, After all, extra power is required. For this reason, there are problems from the viewpoint of equipment cost and energy consumption, such as the initial cost increases by newly installing these devices, and the running cost increases 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 treatment tank without the need for power supply other than the prevention of carrier sedimentation and aeration from the outside, so that the microorganism-fixed carrier or the suspended microorganisms can be returned well. A biological treatment tank and a biological treatment method are provided.

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

  That is, the biological treatment tank for wastewater according to claim 1 is a carrier separation tank installed on the outflow side of the water to be treated of the wastewater biological treatment tank containing the carrier in which microorganisms are fixed in a floating state, and does not have an opposing wall surface. A biological wastewater treatment tank comprising a screen, an intake port for the carrier disposed on the outflow side, and a circulation duct communicating from the intake port to the inflow side of the water to be treated in the treatment tank, the circulation duct Means for converting potential energy based on a difference in water level from the upstream side to the inflow side of the treatment tank into kinetic energy so as to form a flow of water to be treated containing the carrier from the outflow side to the inflow side. Is provided.

  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 biological treatment tank 1j on the upstream side 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 of the processing tank 1. In this way, the water to be treated 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 treatment tank 1. The return flow including the carrier A that has flowed through the circulation duct 4 to the inflow side of the treatment tank 1 is an ejector-type mixing region M formed by the action of the suction flow on the inflow side, that is, the ejector effect. It is mixed with water and sent to the reaction zone 5, and due to the mixing effect of the water to be treated and the carrier A in the ejector type mixing zone M, biological treatment of the water to be treated in the reaction zone 5 is effectively performed.

  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 treatment tank is generated. The ejector section cross-sectional area is designed according to 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.

  In the biological treatment tank for wastewater according to claim 2, a plurality of wastewater biological treatment tanks including a carrier in which microorganisms are fixed in a floating state are connected in series via a partition wall provided with a passage for water to be treated. Biological wastewater provided with a carrier separation screen installed on the outflow side of the biological treatment tank without an opposing wall surface and a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank Based on the difference in water level between the upstream side and the inflow side of the processing tank so as to form a flow of water to be treated containing the carrier from the outflow side to the inflow side in the circulation duct. Means for converting potential energy into kinetic energy is provided.

  In such an apparatus configuration, the water level difference Δh required to generate a suction flow by means for converting potential energy into kinetic energy on the inflow side of the most upstream treatment tank is equal to that of the most upstream treatment tank. Since it suffices if it can be secured between the upstream processing tank adjacent to the most upstream processing tank, the difference in the water level of the entire processing tank can be kept low. In addition, the screen may be provided only in the most downstream treatment tank, and the ejector mixing zone may be provided only on the inflow side of the most upstream treatment tank. Is simple and economical. Furthermore, since the carrier is returned from the most downstream processing tank to the most upstream processing tank by the circulation duct, uneven distribution of the carrier to the downstream processing tank is prevented.

  A biological treatment tank for wastewater according to claim 3 includes an intake of treated water provided on the outflow side of a wastewater biological treatment tank that contains floating microorganisms and does not include a carrier to which microorganisms are fixed, and the treatment from the intake A biological wastewater treatment tank having a circulation duct communicating with the inflow side of the water to be treated in the tank, wherein the microorganisms flow in the circulation duct from the outflow side to the inflow side. The inflow side is provided with means for converting potential energy based on the water level difference from the upstream side into kinetic energy.

  In this way, as described above (see FIG. 1), the biological treatment tank containing the microorganisms in a floating state without fixing the microorganisms to the carrier, the ejector-type mixing zone M is formed on the inflow side, and 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 a downflow containing floating microorganisms is formed on the outflow side where only the outlet is provided without installing the screen 7. Is done. By this downward flow, the biologically treated water passes through the outlet and flows toward the downstream treatment tank 1b without containing 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 of the treatment tank 1. Then, the return flow containing the floating microorganisms flowing in the circulation duct 4 to the upstream side of the treatment tank 1 is mixed with the water to be treated in the ejector-type mixing zone M on the inflow side, and sent to the reaction zone 5. Biological treatment of water to be treated in the reaction zone 5 is effectively performed.

  The biological wastewater treatment tank according to claim 4 includes a plurality of wastewater biological treatment tanks that contain floating microorganisms that do not include a carrier in which microorganisms are fixed and do not include a carrier in a floating state without being fixed to the carrier. Connected in series via a partition provided with a passage, and communicated with the treated water intake provided on the outflow side of the most downstream biological treatment tank, and from the intake to the treated water inflow side of the treatment tank A wastewater biological treatment tank having a circulation duct that is formed on the inflow side of the treatment tank so as to form a flow of treated water containing microorganisms from the outflow side to the inflow side in the circulation duct. Means is provided for converting potential energy based on the water level difference from the upstream side into kinetic energy.

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

  In the biological treatment tank for wastewater according to claim 5, the biological treatment tank at least the most downstream of the biological treatment tank for wastewater is a nitrification tank, and a biological treatment tank comprising a denitrification tank is provided upstream of the nitrification tank. It is characterized by.

  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.

  A biological wastewater treatment tank according to claim 6 is a separation means for separating the microorganisms and the treated water downstream of the wastewater treatment tank containing floating microorganisms, and an inlet for the separated microorganisms provided in the separation means A wastewater biological treatment tank provided with a circulation duct communicating from the intake to the inflow side of the water to be treated in the treatment tank, wherein the microorganism is separated from the separation means side to the inflow side in the circulation duct Means for converting potential energy based on a difference in water level from the upstream side to kinetic energy on the inflow side of the treatment tank so as to form a flow of

  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 the biological treatment tank for wastewater according to claim 7, the means for converting the potential energy into kinetic energy is an ejector pipe provided at a lower portion of the inflow side wall surface of the treatment tank, and the suction flow due to the effect of the ejector pipe Further, an ejector type mixing zone is formed in which the water to be treated flowing from the upstream side and the return flow of the carrier from the circulation duct are mixed.

  By doing so, the flow rate of the water to be treated flowing out from the inflow pipe into the treatment tank becomes larger than the case where the inlet is provided on the inflow side wall surface across the width of the treatment tank, and the suction flow described above. The water to be treated in the ejector type mixing zone and the carrier returned from the most downstream treatment tank through the circulation duct are more effectively mixed.

  The biological treatment tank for wastewater according to claim 8 is characterized in that an aeration apparatus is incorporated in an ejector-type mixing zone formed on the inflow side of the treatment tank.

  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.

  The biological treatment tank for wastewater according to claim 9 is characterized in that the ejector pipe is provided with a flow rate adjusting means.

  The flow rate in the circulation duct for returning the carrier is 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. Therefore, 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 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 for wastewater according to claim 10 is characterized in that the circulation duct is provided with a pipe for supplying treated water in an upstream water tank in which treated water and / or a carrier are not charged.

  In this way, since the upstream water tank has a higher water level, a pump is not required, and the water to be treated can be introduced into the circulation duct to prevent the carrier from sinking or staying at the bottom of the duct. In this case, it is effective to supply a part of the treated water from the treatment tank to the circulation duct in order to prevent accumulation of sludge in the water to be treated introduced into the circulation duct for a long time. The upstream water tank includes both a waste water storage tank in which no carrier is introduced and the treatment tank in which the carrier is introduced.

  The biological treatment tank for wastewater according to claim 11 is characterized in that an air vent pipe is provided in the circulation duct of the treatment tank so that one end side communicates with the circulation duct and the other end side projects from the water surface in the treatment tank. And

  By so doing, 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 is not hindered.

  The biological treatment method for wastewater according to claim 12 is a wastewater biological treatment method in which wastewater is biologically treated using a carrier on which microorganisms are fixed. A wastewater biological treatment tank provided with a circulating duct communicating from the outflow side to the inflow side, provided with a carrier intake port separated by a screen not provided, to generate a suction flow of water to be treated on the inflow side, Due to the ejector effect due to this suction flow, a circulating flow is formed between the inflow side and the outflow side of the treatment tank to prevent the carrier from adhering to the screen, and the carrier is introduced through the circulation duct. It is characterized by being returned to the side and mixed with the water to be treated.

  The biological treatment method for wastewater according to claim 13 is a wastewater biological treatment method in which wastewater is biologically treated using a biological treatment tank that contains floating microorganisms and does not contain a carrier to which microorganisms are fixed. A circulation duct that communicates from the inlet of the water to be treated provided on the outflow side of the treatment tank to the inflow side of the treatment tank is provided, and a suction flow of the water to be treated is generated on the inflow side. The microorganisms are returned to the inflow side through a circulation duct and mixed with the water to be treated.

  The biological treatment method for wastewater according to claim 14 is a wastewater biological treatment method in which wastewater is biologically treated using a biological treatment tank containing floating microorganisms, and the microorganisms are disposed downstream of the biological treatment tank. Is provided with a separation means for separating water and treated water from the separation means, and a circulation duct communicating from the separation means to the inflow side of the water to be treated in the treatment tank is provided. A means for converting to energy is provided to generate a suction flow of water to be treated, and due to the ejector effect of this suction flow, the microorganisms are returned to the inflow side through the circulation duct and mixed with the water to be treated. It is characterized by.

  The biological treatment method for wastewater according to claim 15 is characterized in that the suction flow is generated using any one of the above-described wastewater biological treatment tanks.

  The biological treatment method for wastewater according to claim 16 is characterized in that the suction flow is formed by the difference in the level of the water to be treated between the wastewater biological treatment tanks.

  As described above, according to the present invention, due to the difference in water level between the upstream drainage biological treatment tank or the raw water tank on the inflow side of the wastewater biological treatment tank that performs the wastewater treatment using the carrier on which microorganisms are fixed or the floating microorganisms. A suction flow that draws in fluid around the treated water that has flowed in is generated, and an ejector-type mixing zone is formed on the inflow side of the treatment tank to form a circulation flow in the treatment tank. Even if energy is not supplied, the carrier or suspended microorganisms returned to the inflow side without settling and staying in the circulation duct and the water to be treated are mixed. Then, these mixed streams are supplied to the reaction zone of the treatment tank so that the distribution of carriers or suspended microorganisms in the treatment tank can be made uniform, biological treatment is effectively performed, and stirring power is also reduced. be able to. Further, since the carrier or floating microorganisms can be returned to the inflow side without requiring external energy, a circulation flow can be formed in the treatment tank even when a power failure occurs, and biological treatment can be continued.

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

  FIG. 2 shows the first embodiment. The biological treatment tank includes a plurality of biological treatment tanks, that is, three biological treatment tanks 1a, 1b, and 1c, and passages 9 and 9a for water to be treated. It is the connection type biological treatment tank connected in series via the partition 10 and 10a which were each provided. A carrier separation screen 12 is installed on the outflow side wall surface 11 of the biological treatment tank 1c without providing a duct wall surface facing the front side. On both sides of the bottom of the biological treatment tank 1c on the outflow side, intakes 13 and 13a for carriers (not shown) on which microorganisms are fixed are respectively provided. From these intakes 13 and 13a, the circulation duct bodies 14 and 14a are provided on the upstream side. Circulating ducts 17 and 17 a are formed by connecting to diffusers 16 and 16 a extending to the inflow side of the processing tank 1 a and extending upward along the inflow side wall surface 15. 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 inflowing water to be treated 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 of the biological treatment tank 1a. Also, as shown by a broken line, one end side is located in the middle of the circulation duct body 14. An air vent pipe 20 communicating with the circulation duct main body 14 and having the other end projecting 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. The biological treatment tank 1a is loaded with a pellet-like carrier such as PEG (polyethylene glycol) to which microorganisms such as nitrate bacteria are fixed. The treatment tanks 1a, 1b, and 1c are prevented from settling and uniformly mixed. An underwater stirrer (not shown) is installed to promote this.

  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. A suction flow that draws in the surrounding fluid in the biological treatment tank 1a is generated by the momentum of the water to be treated, and a kind of pump (ejector pump) is formed by the ejector pipe 18 (18a) and the diffuser 16 (16a). It is formed. The operation of such an ejector pump will be described below using a biological treatment tank model as shown in FIG.

ここに、Ａ：流路面積、Ｕ：流速、Ｐ：圧力、Ｌ：循環ダクト本体（返送管）の長さ、Ｄ：返送管径、ｇ：重力加速度、Δｈ：水位差、ρ：密度、η_D：ディフューザ回復率、λ：管摩擦係数、ζ：管曲がり係数、（添え字）０−１：上流側槽とエジェクタ設置槽（第１区画）間、１−２：第１区画と第２区画間、１：エジェクタ管、２：エジェクタ吸引側管、３：ディフューザ入口、４：ディフューザ出口、５：返送管（循環ダクト） In the biological treatment tank model shown in FIG. 3, the ejector nozzle (ejector pipe 18) and the diffuser 16 are installed in the inflow side treatment tank (first section), and the screen 7 is installed in the outflow side treatment tank. A return pipe 17b having a port 13 extends toward the inflow side treatment tank (second section) and is connected to the diffuser 16, and an ejector portion E is formed on the inflow side. 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), 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).

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 ejector installation tank (first section), 1-2: first section and first section Between two sections, 1: Ejector pipe, 2: Ejector suction side pipe, 3: Diffuser inlet, 4: Diffuser outlet, 5: Return pipe (circulation duct)

  The total pressure distribution and the return flow rate ratio in the treatment tank by the numerical analysis from the formulas (1) to (4) for the biological treatment tank including the three-stage treatment tanks 1a, 1b, and 1c shown in FIG. As a result, the suction flow is generated by the pressure decreasing from the intake port 13 (13a) to the ejector pipe 18 (18a), and the average pressure in the return pipe 17b (circulation duct) is an analysis example. Then, it was confirmed that the pressure was about 300 Pa lower than the pressure in the ejector installation tank (first section). In addition, 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 approximately 50 to 60%, and a required circulation flow is formed in the processing tank. In addition to the above numerical analysis, it was confirmed in a model water tank experiment.

  As confirmed from the analysis result, the water to be treated is taken into the circulation ducts 17 and 17a from the intake ports 13 and 13a through the intakes 13 and 13a by the action of the suction flow, that is, the ejector effect, and the inflow side treatment tank of the biological treatment tank. A circulating flow is formed between 1a and the outflow side treatment tank 1c, and the carrier on which the microorganisms are fixed is returned to the inflow side treatment tank 1a. In the ejector mixing zone M (see FIG. 1), the circulation ducts 17 and 17a are connected. Thus, the carrier returned to the inflow side and the water to be treated are mixed, and the distribution of the carrier in the treatment tank 1a can be made uniform. By this circulation flow, the water to be treated flows into the treatment tank 1b from the treatment tank 1a through the passage 9 together with the carrier, and further, the biological reaction in which the water to be treated containing this carrier flows into the treatment tank 1c through the passage 9a. In the treatment process, the carrier is prevented from being unevenly distributed and staying in the most downstream treatment tank 1c, and the carrier is separated from the screen 12 to prevent clogging, thereby effectively performing biological treatment of the water to be treated. be able to. 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 so that the flow from the ejector pipe 18 into the biological treatment tank 1a and the circulation duct 17 When the return flow 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 treatment tank 1a increases, and the flow velocity in the circulation duct 17a also increases due to the suction flow due to the ejector effect, so the inner surface of the circulation duct 17a. It is possible to remove foreign matters such as fibers adhering to the membrane and membranes secreted by microorganisms. The inner surface of the circulation duct 17 can be cleaned by the same operation. Furthermore, since the return flow of the carrier passes through the circulation ducts 17 and 17a, the air is exhausted from the air vent pipe 20 to the outside of the treatment tank, so that the occurrence of air accumulation can be prevented and the return flow smoothly flows and the carrier is returned. Is not disturbed.

  FIG. 4 shows a second embodiment. This biological treatment tank is a treatment tank for biologically removing ammonia nitrogen in wastewater by a nitrification / denitrification process. From the inflow side, the denitrification tank 1d, the nitrification tank 1e, and the nitrification tank 1f are connected in series via the partition walls 10 and 10a provided with the water treatment ports 9 and 9a, respectively, and the outflow side of the most downstream nitrification tank 1f On the upper surface of the wall surface 11, an outlet 21 for biologically treated water is formed. 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. As in the case of the first embodiment, intakes 13 and 13a for water to be treated (nitrification liquid) nitrified in the nitrification process of the treatment tanks 1e and 1f are provided on both sides of the bottom of the outflow side treatment tank 1f, respectively. The circulation duct bodies 14 and 14a extend from the intakes 13 and 13a to the inflow side of the treatment tank 1d on the upstream side of the biological treatment tank, and to the diffusers 16 and 16a extending upward along the inflow side wall surface 15 respectively. Circulation ducts 17 and 17a are formed by being connected. 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 processing 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 biological treatment tank 1d from the upstream water tank through the ejector pipes 18 and 18a and the diffusers 16 and 16a, the ammonia nitrogen component in the water to be treated is removed in the treatment tank 1d (denitrification tank). Does not change at all, 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.

  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. A suction flow that draws in the surrounding fluid in the treatment tank 1a is generated by the momentum of the water to be treated, which is converted into kinetic energy.

式（４）および式（５）におけるＨ₂は有機物の分解により供給されるもので、被処理水（原水）中のＢＯＤ成分がこの水素供与体にあたる。 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 between the inflow side treatment tank 1d and the outflow side treatment tank 1f of the biological treatment tank. A circulating flow is formed. 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. .

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 shows the third embodiment, and this biological treatment tank is composed of a plurality of biological treatment tanks, that is, three biological treatment tanks 1g, as in the first embodiment (see FIG. 2). This is a connected biological treatment tank in which 1h and 1i are connected in series via partition walls 10 and 10a provided with water treatment ports 9 and 9a, respectively. An outflow port 21 of biologically treated water is disposed at the upper part of the outflow side wall surface 11 of the most downstream treatment tank 1i. A settling tank 23 is provided for solid-liquid separation of the clear treated water and the microorganism group that have been treated automatically. A discharge pipe 24 is connected to the bottom of the sedimentation tank 23. The discharge pipe 24 branches to both sides of the biological treatment tank and rises to the height of the bottom of the treatment tank. It connects with the circulation duct main bodies 14 and 14a extended to 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 of the processing 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 processing tank 1g, 1h, 1i is provided with an underwater stirrer (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 biological treatment tanks 1g, 1h, 1i, the water to be treated is mixed and contacted with the aerobic microorganism group in the suspended state, and the BOD component in the water to be treated is oxidatively decomposed in the presence of dissolved oxygen. It 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 biological treatment tank 1g via the ejector pipes 18 and 18a and the diffusers 16 and 16a, the potential energy of the upstream water tank or the treatment tank passes through the ejector pipes 18 and 18a. When passing, it is converted into kinetic energy, and a suction flow that draws the surrounding fluid in the treatment tank 1g 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. A circulated flow including agglomerated microorganisms, that is, sludge, is formed between the settling tank 23 and the sludge is returned to the inflow side 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. 6A shows the biological treatment tank of the first and second embodiments. A trough 25 provided near the water level of the treatment tank instead of providing the circulation ducts 17 and 17a along the bottom of the treatment tank. , 25a and a circulation system composed of an ejector portion. This circulation system connects the diffusers 16, 16a in a lateral direction so as to face the downstream side of the treatment tank via a connecting pipe 26 directed downward from the troughs 25, 25a, and on the inlet side of the diffusers 16, 16a, The ejector tubes 18 and 18a are inserted. FIG. 6 (b) shows the inflow side main part of the biological treatment tank of another embodiment in which the troughs 25 and 25a are provided at both sides at a height near the water surface level, and are connected to the troughs 25 and 25a. Ejector pipes 18 and 18a are inserted into the entrance sides of the diffusers 16 and 16a. The open ends R of the troughs 25 and 25a reach the most downstream treatment tank (not shown) and serve as intakes for the carrier or treated water (nitrification liquid).

  From the above-mentioned numerical analysis results for the biological treatment tank composed of the three-section treatment tanks 1a, 1b and 1c shown in FIG. 2, the average pressure in the circulation ducts 17 and 17a (return pipe) is the ejector installation treatment tank 1a ( As shown in FIG. 6 (b), when troughs 25 and 25a are provided as return pipes, the water level in the trough is 30 mm higher than the water level in the surrounding tank. The level is lowered. For this reason, carrier or treated water flows into the inflow side treatment tank from the open end R (see FIG. 6 (a)) of the troughs 25, 25a corresponding to the inlet 13 (13a) of the outflow side treatment tank. A circulating flow 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

Explanatory drawing about the attraction | suction flow in the biological treatment tank of the waste_water | drain of embodiment of this invention The perspective view of the biological treatment tank of the drainage of a 1st embodiment It is explanatory drawing which modeled the biological treatment tank of 1st Embodiment. The perspective view of the biological treatment tank of the drainage of a 2nd embodiment The perspective view of the biological treatment tank of the drainage of a 3rd embodiment (A) Enlarged perspective view of trough and ejector provided in a biological treatment tank of another embodiment (b) Biological treatment tank of another embodiment incorporating (a) Sectional view of biological wastewater treatment tank Cross section of other prior art wastewater biological treatment tank Cross section of other prior art wastewater biological treatment tank Cross section of other prior art wastewater biological treatment tank

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a-1k ... 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 stirrer 7, 12 ... Screen 8, 13, 13a ... Intake port 9, 9a ... Pass-through port 10, 10a ... Partition wall 14, 14a ... Circulating 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 (16)

A screen for separating the carrier, which is not provided with an opposing wall surface, installed on the outflow side of the treated water in the wastewater biological treatment tank containing the carrier in which the microorganisms are fixed in a floating state;
An inlet for the carrier disposed on the outflow side;
A wastewater biological treatment tank having a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank,
In order to form a flow of water to be treated containing the carrier from the outflow side to the inflow side in the circulation duct, the potential energy based on the water level difference from the upstream side is converted into kinetic energy on the inflow side of the treatment tank. A biological wastewater treatment tank characterized by providing means for conversion. A plurality of wastewater biological treatment tanks containing a carrier in which microorganisms are fixed in a floating state are connected in series via a partition wall provided with a passage for treated water, and are installed on the outflow side of the most downstream biological treatment tank. A screen for separating the carrier not provided with a wall surface,
A wastewater biological treatment tank having a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank,
In order to form a flow of water to be treated containing the carrier from the outflow side to the inflow side in the circulation duct, the potential energy based on the water level difference from the upstream side is converted into kinetic energy on the inflow side of the treatment tank. A biological wastewater treatment tank characterized by providing means for conversion. An intake of water to be treated provided on the outflow side of a wastewater treatment tank that contains floating microorganisms and does not contain a carrier to which microorganisms are fixed;
A wastewater biological treatment tank having a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank,
Converts potential energy based on the difference in water level from the upstream side to the inflow side of the treatment tank into kinetic energy so as to form a flow of treated water containing microorganisms from the outflow side to the inflow side in the circulation duct. A biological treatment tank for wastewater, characterized in that means are provided. A plurality of wastewater biological treatment tanks that contain floating microorganisms and do not contain a carrier to which microorganisms are fixed are connected in series via a partition wall having a passage for water to be treated, and are connected to the outflow side of the most downstream biological treatment tank. An inlet for the treated water,
A wastewater biological treatment tank having a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank,
Converts potential energy based on the difference in water level from the upstream side to the inflow side of the treatment tank into kinetic energy so as to form a flow of treated water containing microorganisms from the outflow side to the inflow side in the circulation duct. A biological treatment tank for wastewater, characterized in that means are provided.   5. The wastewater treatment tank according to claim 4, wherein at least the most downstream biological treatment tank of the wastewater biological treatment tank is a nitrification tank, and a biological treatment tank including a denitrification tank is provided upstream of the nitrification tank. Biological treatment tank. Separation means for separating the microorganisms and treated water downstream of a wastewater treatment tank containing floating microorganisms;
An inlet for separated microorganisms provided in the separating means;
A wastewater biological treatment tank having a circulation duct communicating from the intake to the inflow side of the treated water in the treatment tank,
The potential energy based on the water level difference from the upstream side is converted into kinetic energy on the inflow side of the treatment tank so as to form a flow of microorganisms separated from the separation means side to the inflow side in the circulation duct. A biological treatment tank for wastewater, characterized by providing means.   The means for converting the potential energy into kinetic energy is an ejector pipe provided at the lower part of the inflow side wall surface of the treatment tank, and the water to be treated and the circulation duct flowing from the upstream side by the suction flow due to the effect of the ejector pipe The biological treatment tank for wastewater according to any one of claims 1 to 6, wherein an ejector-type mixing zone is formed for mixing the carrier and / or the return flow of suspended microorganisms.   The wastewater biological treatment tank according to any one of claims 1 to 7, wherein an aeration apparatus is incorporated in an ejector-type mixing zone formed on the inflow side of the treatment tank.   The wastewater biological treatment tank according to claim 7 or 8, wherein the ejector pipe is provided with a flow rate adjusting means.   The drainage pipe according to any one of claims 1 to 9, wherein a pipe for supplying treated water in an upstream water tank in which treated water and / or a carrier is not introduced is provided in the circulation duct. Biological treatment tank.   11. The air duct according to claim 1, wherein an air vent pipe is provided in the circulation duct of the treatment tank so that one end side thereof communicates with the circulation duct and the other end side projects from a water surface in the treatment tank. Biological wastewater treatment tank.   A wastewater biological treatment method in which wastewater is biologically treated using a carrier on which microorganisms are fixed, and the carrier intake port separated by a screen that is installed on the outflow side of the water to be treated and does not have an opposing wall surface A wastewater biological treatment tank provided with a circulation duct communicating from the outflow side to the inflow side, generating a suction flow of water to be treated on the inflow side, and an inflow of the treatment tank by an ejector effect by the suction flow A circulation flow is formed between the side and the outflow side to prevent the carrier from adhering to the screen, and the carrier is returned to the inflow side through the circulation duct and mixed with the water to be treated. A biological treatment method for wastewater.   A wastewater biological treatment method that biologically treats wastewater using a biological treatment tank that contains floating microorganisms and does not contain a carrier to which microorganisms are fixed, wherein the treated water provided on the outflow side of the biological treatment tank A circulation duct communicating from the intake port to the inflow side of the treatment tank is provided, and a suction flow of water to be treated is generated on the inflow side. Due to the ejector effect of the suction flow, the microorganisms are sent to the inflow side through the circulation duct. A wastewater biological treatment method characterized by being returned and mixed with water to be treated.   A biological wastewater treatment method that biologically treats wastewater using a biological treatment tank containing floating microorganisms, provided with a separation means for separating the microorganisms and treated water downstream of the biological treatment tank, A circulation duct that communicates from the separation means to the inflow side of the water to be treated in the treatment tank is provided, and a means for converting potential energy based on a water level difference from the upstream side to kinetic energy is provided on the inflow side. A wastewater biological treatment method characterized in that a suction flow is generated, and the microorganisms are returned to the inflow side via a circulation duct and mixed with water to be treated by an ejector effect by the suction flow.   The wastewater biological treatment method according to any one of claims 12 to 14, wherein the suction flow is generated using the wastewater biological treatment tank according to any one of claims 1 to 11. .   The biological treatment method for wastewater according to any one of claims 12 to 15, wherein the suction flow is formed by a difference in water level of water to be treated between wastewater biological treatment tanks.

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