JP6630054B2 - Wastewater treatment method and wastewater treatment device - Google Patents

Description

  The present invention relates to a wastewater treatment method and a technology of a wastewater treatment device.

As a method for biologically treating wastewater containing organic substances and the like, an activated sludge method using an aggregate of microorganisms called floc (floating sludge) has been used. However, in the activated sludge method, when the floc is separated into treated water in the sedimentation basin, there is a problem that the surface area of the sedimentation basin must be extremely large because the floc, which is the suspended sludge, has a low sedimentation speed. There is. Further, the treatment speed of the activated sludge method depends on the sludge concentration in the tank, and the treatment speed can be increased by increasing the sludge concentration. However, the sludge concentration is increased from 1500 mg / L to 5000 mg / L at the highest. If it is about L, and if it is to be increased further, solid-liquid separation in the sedimentation basin becomes difficult, and the treatment may not be maintained. Therefore, the BOD treatment rate per tank volume in the conventional activated sludge method is about 0.2 to 0.8 kg / m ³ / day.

  In anaerobic biological treatment, it is common to utilize an aggregate (granular biological sludge) in which microorganisms called granules are densely aggregated and formed into granules. Granules have a very high sedimentation speed and a dense collection of microorganisms, so that the sludge concentration in the treatment tank can be increased, and high-speed treatment of wastewater can be realized. However, the anaerobic biological treatment has problems such as the limited number of wastewater to be treated and the necessity of maintaining the temperature of the treated water at 30 to 35 ° C as compared with the aerobic treatment (activated sludge method). May have. In addition, the anaerobic biological treatment alone has poor water quality, and when discharged into a river or the like, it may be necessary to separately perform an aerobic treatment such as an activated sludge method.

  In recent years, treatment is carried out using a semi-batch treatment device that intermittently flows wastewater into a reaction tank, and by further reducing the settling time of biological sludge, it is not limited to anaerobic biological sludge. It has become clear that sludge can be formed (hereinafter, may be referred to as granular sludge) (for example, see Patent Documents 1 to 4). In general, in a semi-batch processing apparatus, one reaction tank generally has four functions such as (1) inflow of wastewater, (2) biological treatment of wastewater, (3) sedimentation of biological sludge, and (4) discharge of treated water. Processing is performed by going through two steps.

  As described above, high-speed treatment can be achieved by granulating biological sludge, but when a semi-batch treatment device is used for large-scale wastewater treatment equipment such as sewage treatment, a huge wastewater storage tank is required. May need to be installed.

Therefore, a continuous biological treatment tank that continuously inflows wastewater and treats it, and a semi-batch biological treatment tank that generates aerobic granular sludge, is provided with aerobic granular sludge from the semi-batch biological treatment tank. There has been proposed a treatment apparatus for granulating biological sludge in a continuous biological treatment tank by supplying the sludge to the continuous biological treatment tank (for example, see Patent Documents 5 and 6). According to the devices of Patent Documents 5 and 6, the size of the sedimentation basin and the reaction tank can be reduced, and the BOD treatment rate per tank volume is set to 0.4 to 1.6 kg / m ³ / day, depending on the raw water concentration. It is possible to

WO 2004/024638 A JP 2008-212878 A JP 2009-18263 A JP 2009-18264 A JP 2007-136367 A JP 2008-284427 A

  However, in the treatment apparatuses of Patent Documents 5 and 6, further improvements in biological treatment speed, sedimentation of biological sludge, stability of biological treatment, and the like are required. In order to improve these characteristics, a continuous system is required. It is necessary to further increase the ratio of granule sludge in the biological sludge in the biological treatment tank.

  Therefore, an object of the present invention is to provide a wastewater treatment system in which wastewater is biologically treated with biological sludge while continuously flowing wastewater into a continuous biological treatment tank. The present invention provides a wastewater treatment method and a wastewater treatment device that can improve the ratio of wastewater.

In the wastewater treatment method of the present invention, the wastewater is biologically treated with biological sludge including granular sludge and suspended sludge while continuously flowing wastewater into a continuous biological treatment tank. A continuous biological treatment step of separating by solid-liquid separation means, and a first image containing a larger amount of the granular sludge than the floating sludge by applying a centrifugal force to the biological sludge separated into solid and liquid in the continuous biological treatment step. And a second fraction containing more suspended sludge than the granular sludge, and supplying the first fraction separated in the centrifugation step to the continuous biological treatment tank. comprising a sludge supplying step, wherein the granular sludge has a particle size of more than 200 [mu] m, the floating sludge have a particle size of less than 200 [mu] m, relative to the first fraction which is separated by the centrifugation step hand The ratio of granulated sludge having a particle size of 200 μm or more is 30% or more .

  Further, in the wastewater treatment method, a sludge return step of returning a part of the biological sludge solid-liquid separated in the continuous biological treatment step to the continuous biological treatment tank; An excess sludge discharge step of discharging the separated biological sludge as surplus sludge, wherein in the centrifugal separation step, the excess sludge discharged in the excess sludge discharge step is centrifuged to form the first sludge. It is preferable to separate the fraction from the second fraction.

In addition, the wastewater treatment apparatus of the present invention is a continuous biological treatment tank that biologically treats wastewater with biological sludge including granular sludge and suspended sludge while continuously flowing wastewater, and the biological sludge from the biological treatment liquid. A solid-liquid separation unit for solid-liquid separation of the granulated sludge from the suspended sludge by applying a centrifugal force to the biological sludge solid-liquid separated by the continuous biological treatment device. And a second fraction containing more suspended sludge than the granular sludge, and the first fraction separated by the centrifugal separator is separated by the continuous type. and a sludge supply means for supplying to the biological treatment tank wherein, the granular sludge has a particle size of more than 200 [mu] m, the floating sludge to have a particle size of less than 200 [mu] m, are separated in the centrifugal separation means No. The ratio of the granular sludge having a particle size of 200 μm or more to one fraction is 30% or more .

  According to the present invention, in wastewater treatment in which wastewater is biologically treated with biological sludge while continuously flowing wastewater into a continuous biological treatment tank, the ratio of granule sludge to biological sludge in the continuous biological treatment tank is Can be improved.

It is a mimetic diagram showing an example of the composition of the waste water treatment equipment concerning this embodiment. FIG. 2 is a schematic diagram illustrating an example of a configuration of a semi-batch biological treatment tank used in the wastewater treatment device in FIG. 1. It is a mimetic diagram showing other examples of the composition of the waste water treatment equipment concerning this embodiment. It is a mimetic diagram showing other examples of the composition of the waste water treatment equipment concerning this embodiment. It is a schematic diagram which shows an example of a structure of the semi-batch type biological treatment tank used for the wastewater treatment apparatus shown in FIG.

  Hereinafter, embodiments of the present invention will be described. Note that the present embodiment is an example of implementing the present invention, and the present invention is not limited to the present embodiment.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a wastewater treatment device according to the present embodiment. The wastewater treatment apparatus 1 shown in FIG. 1 includes a continuous biological treatment apparatus including a continuous biological treatment tank 10 and a solid-liquid separation tank 14, a semi-batch biological treatment tank 12, a wastewater storage tank 16, and a liquid cyclone 18. . In the present specification, the “continuous type” is a system for a batch type, in which inflow of wastewater, biological treatment, sedimentation of sludge, and discharge of treated water are repeatedly performed in a single reaction tank, as in a semi-batch type. This is distinguished from semi-batch processing. Further, in the present embodiment, the continuous type is not limited to a system in which drainage is continuously charged into the reaction tank to operate, and the reaction is performed by a pump using a principle such as a reciprocating motion of a diaphragm pump or the like. It may be a system that operates by supplying wastewater to the tank, or a raw water tank is installed in front of the reaction tank, and the operation-stop of the pump is controlled according to the water level of the raw water tank (when the water level is high, The pump may be operated, and if the water level is low, the pump may be stopped) to supply a waste water to the reaction tank.

  The wastewater treatment apparatus 1 shown in FIG. 1 includes wastewater inflow lines 20a, 20b, 20c, treated water discharge lines 22a, 22b, sludge supply line 24, sludge discharge lines 26a, 26b, and biological sludge discharge line 28. Further, the wastewater treatment device 1 shown in FIG. 1 includes a first wastewater inflow pump 30, a second wastewater inflow pump 32, a treated water discharge pump 34, a sludge discharge pump 36, and a sludge supply pump 38. The first drainage inflow pump 30 is installed in the drainage inflow line 20a, the second drainage inflow pump 32 is installed in the drainage inflow line 20b, the treated water discharge pump 34 is installed in the treated water discharge line 22b, and the sludge discharge pump 36 is installed. The sludge supply pump 38 is installed on the sludge supply line 24, and is installed on the biological sludge discharge line 28. Further, a valve 40 is provided in the sludge discharge line 26b.

  One end of the drainage inflow line 20a is connected to the drainage outlet of the drainage storage tank 16, and the other end is connected to the drainage inlet of the continuous biological treatment tank 10. One end of the drainage inflow line 20b is connected to a drainage outlet of the drainage storage tank 16, and the other end is connected to a drainage inlet of the semi-batch type biological treatment tank 12. One end of the drainage inflow line 20 c is connected to a drainage outlet of the continuous biological treatment tank 10, and the other end is connected to a drainage inlet of the solid-liquid separation tank 14. The treated water discharge line 22 a is connected to a treated water outlet of the solid-liquid separation tank 14. One end of the sludge discharge line 26a is connected to the sludge outlet of the solid-liquid separation tank 14, and the other end is connected to the sludge inlet of the liquid cyclone 18. One end of the sludge supply line 24 is connected to the sludge outlet of the liquid cyclone 18, and the other end is connected to the sludge inlet of the continuous biological treatment tank 10. The sludge discharge line 26b is connected to the sludge discharge line 26a. One end of the biological sludge discharge line 28 is connected to a sludge outlet of the semi-batch type biological treatment tank 12, and the other end is connected to a sludge supply port of the continuous biological treatment tank 10. One end of the treated water discharge line 22b is connected to the treated water outlet of the semi-batch biological treatment tank 12, and the other end is connected to the treated water inlet of the continuous biological treatment tank 10.

  FIG. 2 is a schematic diagram showing an example of a configuration of a semi-batch type biological treatment tank used in the wastewater treatment apparatus of FIG. In the semi-batch type biological treatment tank 12 shown in FIG. 2, four processes such as (1) inflow of wastewater, (2) biological treatment of wastewater with biological sludge, (3) sedimentation of biological sludge, and (4) discharge of treated water. Is repeated to form granular sludge. The semi-batch type biological treatment tank 12 shown in FIG. 2 includes a stirrer 48, an air pump 50, and an air diffuser 52. The air diffuser 52 is connected to the air pump 50, and the air supplied from the air pump 50 is supplied into the tank through the air diffuser 52. Further, the stirring device 48 has a structure in which the shaft attached to the motor rotates by driving the motor, and the stirring blade attached to the tip of the shaft rotates with the rotation of the shaft. Note that the stirring device 48 is not limited to the above configuration. A drainage inlet 12a and a treated water outlet 12b are provided in the semi-batch type biological treatment tank 12, a drainage inflow line 20b is connected to the drainage inlet 12a, and a treated water discharge line 22b is connected to the treated water outlet 12b. I have. The semi-batch type biological treatment tank 12 is provided with a sludge outlet 12c, and is connected to a biological sludge discharge line 28.

  The drainage inflow line 20b and the second drainage inflow pump 32 illustrated in FIG. 2 function as a semi-batch side drainage supply device that intermittently supplies waste water to the semi-batch type biological treatment tank 12. In the present embodiment, intermittent supply of drainage is performed by operating / stopping the second drainage inflow pump 32. For example, a valve or the like is installed in the drainage inflow line 20b, and intermittent supply of drainage is performed by opening and closing the valve. May be.

  The treated water discharge line 22b and the treated water discharge pump 34 illustrated in FIG. 2 function as a treated water supply device that supplies treated water to the continuous biological treatment tank 10. In addition, you may install a valve etc. in the treated water discharge line 22b suitably. In this embodiment, the treated water discharge line 22b is configured to be connected to the continuous biological treatment tank 10, but is not limited thereto, and is connected to the solid-liquid separation tank 14 and the treated water discharge line 22a. May be configured

  The biological sludge discharge line 28 and the sludge discharge pump 36 shown in FIG. 2 function as a sludge supply device that supplies the granular sludge to the continuous biological treatment tank 10. In addition, you may install a valve etc. in the biological sludge discharge line 28 suitably.

  The drainage inflow line 20a and the first drainage inflow pump 30 illustrated in FIG. 1 function as a continuous-side drainage supply device that supplies wastewater to the continuous biological treatment tank 10.

  The continuous biological treatment tank 10 shown in FIG. 1 is, for example, continuous under aerobic conditions in which wastewater is aerated by a diffuser or the like, and in the presence of biological sludge including floating sludge and granule sludge in the tank. The wastewater flowing into the wastewater is biologically treated (for example, the organic matter in the wastewater is oxidized to carbon dioxide).

  The solid-liquid separation tank 14 shown in FIG. 1 is a separation device for separating biological sludge and treated water from water containing biological sludge (biological treatment liquid), and includes, for example, sedimentation separation, pressure flotation, filtration, and membrane. Separation devices such as separation are exemplified.

  The liquid cyclone 18 shown in FIG. 1 has a cylindrical shape whose diameter gradually decreases as it goes downward. A sludge discharge line 26c is connected to the upper end of the liquid cyclone 18, and a sludge supply line 24 is connected to the lower end. It is connected.

  The liquid cyclone 18 shown in FIG. 1 exerts a centrifugal force on biological sludge including suspended sludge and granulated sludge, and includes a first fraction containing more granular sludge than suspended sludge and containing more suspended sludge than granulated sludge. It is a centrifugal separator for separating into a second fraction. In the present embodiment, the present invention is not limited to the hydrocyclone 18, but is a device capable of separating and concentrating granular sludge from the biological sludge by applying a centrifugal force to biological sludge including suspended sludge and granular sludge. For example, a centrifugal separator such as a separation plate type decanter, a straight body type, a horizontal type, a screen ball type, etc. may be used.

  The sludge supply line 24 and the sludge supply pump 38 shown in FIG. 1 function as a sludge supply device that supplies the first fraction separated by the liquid cyclone 18 to the continuous biological treatment tank 10. In addition, you may install a valve etc. in the sludge supply line 24 suitably.

  In the present embodiment, for example, the above-described pumps need not always be installed as long as the apparatus configuration and the piping configuration are capable of feeding drainage, sludge, and the like passing through a line by gravity or an extrusion flow.

  An example of the operation of the wastewater treatment device 1 of the present embodiment will be described.

  In the wastewater storage tank 16 shown in FIG. 1, wastewater to be treated is stored. Examples of wastewater to be treated include wastewater from food processing factories, chemical factories, semiconductor factories, machinery factories, sewage, human waste, and river water. In addition, wastewater generally contains biodegradable organic substances and the like. In addition, when the organic matter which is hardly biodegradable is contained in the waste water, it is preferable to remove and carry out physicochemical treatment such as flotation separation, coagulation pressure flotation device and adsorption device in advance.

  First, the first wastewater inflow pump 30 is operated to supply the wastewater to be treated in the wastewater storage tank 16 from the wastewater inflow line 20a to the continuous biological treatment tank 10. Further, the sludge discharge pump 36 is operated to supply the granular sludge formed in the semi-batch type biological treatment tank 12 from the biological sludge discharge line 28 to the continuous biological treatment tank 10. The formation of granular sludge by the semi-batch type biological treatment tank 12 will be described later. In the continuous biological treatment tank 10, biological treatment of wastewater is performed under aerobic conditions by using biological sludge including suspended sludge and granular sludge in the tank. Here, the granular sludge is sludge that has undergone self-granulation, and is, for example, biological sludge having an average particle size of 200 μm or more or an SVI5 that is a sedimentation index of 80 mL / g or less. . In addition, suspended sludge is ordinary sludge in which self-granulation has not progressed. For example, sludge having an average particle size of less than 200 μm or SVI5 as a sedimentation index of 150 mL / g or more is used. It is.

  The biological treatment liquid treated in the continuous biological treatment tank 10 is supplied from the wastewater inflow line 20c to the solid-liquid separation tank 14 to separate biological sludge from the biological treatment liquid. The biological sludge separated in the solid-liquid separation tank 14 is supplied to the liquid cyclone 18 from a sludge discharge line 26a. The liquid cyclone 18 applies a centrifugal force to the biological sludge by the swirling flow, and a first fraction (granule-enriched sludge) containing more granular sludge than floating sludge, and a second fraction containing more suspended sludge than granular sludge. Separated into fractions (granule dilute sludge). The first fraction moves downward while rotating inside the hydrocyclone 18, is discharged from the sludge supply line 24, and is supplied to the continuous biological treatment tank 10 by the sludge supply pump 38. The second fraction overflows from the upper part of the hydrocyclone 18 and is discharged from the sludge discharge line 26c to the outside of the system. The treated water in the solid-liquid separation tank 14 is discharged from the treated water discharge line 22a to the outside of the system. In addition, the valve 40 provided in the sludge discharge line 26b may be opened to discharge a part of the biological sludge passing through the sludge discharge line 26a from the sludge discharge line 26b to the outside of the system.

  As described above, by supplying the first fraction obtained by concentrating the granular sludge with the liquid cyclone 18 to the continuous biological treatment tank 10, the granular sludge in the solid-liquid separation tank 14 is effectively used, and the continuous biological treatment tank 10 is used. It is possible to improve the granular sludge concentration in the treatment tank 10. In the present embodiment, of the biological sludge in the continuous biological treatment tank 10, for example, the ratio of the granular sludge having a particle size of 200 μm or more is set to 10% or more, preferably 30% or more, and the biological treatment is performed. It becomes possible. As a result, it is possible to improve the biological treatment speed, the sedimentation of biological sludge, the stability of biological treatment, and the like.

  Hereinafter, an example of a method of forming granular sludge using the semi-batch type biological treatment tank 12 will be described.

  First, the second wastewater inflow pump 32 is operated to supply the wastewater in the wastewater storage tank 16 from the wastewater inflow line 20b to the semi-batch biological treatment tank 12 ((1) inflow of wastewater). The wastewater is introduced into the semi-batch type biological treatment tank 12 until a predetermined amount is reached, and the second wastewater inflow pump 32 is stopped. Next, the air pump 50 is operated, air is introduced into the semi-batch biological treatment tank 12 from the air diffuser 52, and the stirring device 48 is operated to stir the wastewater in the semi-batch biological treatment tank 12. Then, biological treatment of wastewater is performed ((2) biological treatment of wastewater).

  After performing the wastewater biological treatment process for a predetermined time, the air pump 50 and the stirring device 48 are stopped, and the biological treatment process ends. After the biological treatment is completed, the biological sludge in the semi-batch biological treatment tank 12 is settled for a predetermined time, and separated into biological sludge and treated water in the semi-batch biological treatment tank 12 ((3) Sedimentation of biological sludge). . Next, the treated water discharge pump 34 is operated, and the treated water in the semi-batch type biological treatment tank 12 is discharged from the treated water discharge line 22b ((4) discharge of treated water). It is supplied to the processing tank 10. Then, by repeating the steps (1) to (4), the biological sludge in the semi-batch type biological treatment tank 12 is granulated to form granule sludge.

  Then, the sludge discharge pump 36 is operated to supply the granular sludge formed in the semi-batch type biological treatment tank 12 from the biological sludge discharge line 28 to the continuous biological treatment tank 10. The supply of the granular sludge from the semi-batch type biological treatment tank 12 may be performed in (3) a biological sludge settling process, (2) a wastewater biological treatment process, or (4). ) It may be performed in a process of discharging treated water. Whether or not granule sludge is formed in the semi-batch type biological treatment tank 12 is determined, for example, by measuring SVI, which is an index of sludge settling property. Specifically, the SVI value is periodically measured by a sedimentation test of the sludge in the semi-batch type biological treatment tank 12, and the value of SVI5 calculated from the volume ratio after sedimentation for 5 minutes is equal to or less than a predetermined value (for example, 80 mL). / G or less), it can be determined that granule sludge has been formed. Alternatively, the particle size distribution of the sludge in the semi-batch type biological treatment tank 12 is measured, and when the average particle size becomes a predetermined value or more (for example, 200 μm or more), it is determined that the granular sludge has been formed. It is possible (the lower the SVI value and the larger the average particle size, the better the granular sludge can be determined).

  The MLSS concentration in the semi-batch type biological treatment tank 12 is desirably operated in the range of 2000 to 20000 mg / L. In order to maintain the soundness (sedimentation, activity, etc.) of the biological sludge, it is desirable to maintain an appropriate sludge load, preferably in the range of 0.05 to 0.60 kgBOD / MLSS / day, more preferably. It is desirable to pull out granular sludge from the inside of the tank so as to keep the range of 0.1 to 0.5 kg BOD / MLSS / day.

  In the formation of granular sludge in the semi-batch biological treatment tank 12, it is desirable to control the settling time and appropriately control the inflow rate of wastewater per batch. The settling time for stopping the stirring (including stirring by aeration) to settle the sludge is calculated from the distance from the water surface to the target sludge interface position and the settling speed of the sludge. For example, 4 minutes / m to 15 minutes / m, more preferably between 5 minutes / m and 10 minutes / m. Further, the drainage inflow rate (the ratio of inflow water to the effective volume at the time of reaction) is preferably, for example, in the range of 20% or more and 150% or less, and more preferably in the range of 40% or more and 120% or less. The sludge repeatedly experiences a state in which the concentration of the organic substance as a treatment target is very high (saturation immediately after the inflow process) and a state in which the concentration of the organic matter is extremely low (late stage of the biological treatment process, starvation). Since granulation is considered to progress, it is better to set the drainage inflow rate as high as possible from the viewpoint of forming granule sludge, but on the other hand, the higher the drainage inflow rate, the more the inflow pump And the cost increases. Therefore, the drainage inflow rate is preferably in the range of 40% or more and 120% or less in terms of formation of granule sludge and cost reduction.

  The pH in the semi-batch type biological treatment tank 12 is preferably adjusted to a range of 6 to 9, which is suitable for general biological treatment, and more preferably adjusted to a range of 6.5 to 7.5. When the pH value is out of the above range, it is preferable to adjust the pH using an acid or an alkali. When pH adjustment is performed in the semi-batch biological treatment tank 12, the pH is adjusted in a state where the semi-batch biological treatment tank 12 is being stirred, rather than in a state where the semi-batch biological treatment tank 12 is not stirred, in order to appropriately measure the pH value. It is desirable to do. The dissolved oxygen (DO) in the semi-batch type biological treatment tank 12 is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, which is suitable for general biological treatment.

  In the present embodiment, (1) inflow of wastewater, (2) biological treatment of wastewater, (3) sedimentation of biological sludge, and (4) discharge of treated water are repeated to form semi-batch organisms that form granular sludge. Although the treatment tank 12 is used, it is not always necessary to use the semi-batch type biological treatment tank 12. In addition to the semi-batch type biological treatment tank 12, any device capable of forming granular sludge (granule sludge forming device) may be used. As such a device, for example, as described in JP-A-2011-56383, a nitrification unit and a denitrification unit (a first denitrification unit and a second denitrification unit) are provided as necessary. An apparatus that includes an oxidizing unit and the like, and that forms a granule by controlling the addition of a hydrogen donor to be added to the denitrifying unit, and the like. In addition, examples of an apparatus for forming granules by controlling the addition of a hydrogen donor include, for example, apparatuses described in JP 2010-29749 A, JP 2010-12404 A, and the like. . Since these devices enable the formation of granules by continuous treatment of wastewater, they may be applied to the continuous biological treatment tank 10 to form granules in the continuous biological treatment tank 10. Further, as another method of forming granules, a method of introducing anaerobic granules and the like can be mentioned.

  In addition, the wastewater treatment apparatus 1 of the present embodiment includes, for example, a granular sludge forming apparatus such as the semi-batch type biological treatment tank 12, but does not necessarily include the granular sludge forming apparatus. For example, when granular sludge is formed in another system of wastewater treatment system, the granular sludge may be charged in the continuous biological treatment tank 10 in advance at the time of starting wastewater treatment. Alternatively, a biological sludge supply device (biological sludge discharge line 28) may be installed so that the granular sludge formed by the wastewater treatment system of another system is continuously supplied to the continuous biological treatment tank 10. .

  In the continuous biological treatment tank 10, a form in which biological treatment is performed by a standard activated sludge method for treating organic substances and the like has been described as an example. However, the present invention is not limited to this. For example, A2O (Anaerobic-Anoxic-Oxic) is used. Process), AO (Anaerobic-Oxic Process) and other nutrient removal systems (systems with anoxic treatment and anaerobic treatment tanks), oxidation ditch method, step-flow type multi-stage activated sludge method, etc. for biological treatment. May be performed. Further, an apparatus for performing biological treatment in the presence of a carrier such as polyurethane, plastic, or resin may be used.

  The continuous biological treatment tank 10 is desirably operated, for example, at a sludge concentration in the tank of 1000 to 20,000 mg / L. In order to maintain the soundness (sedimentation, activity, etc.) of the biological sludge, the sludge load is preferably in the range of 0.05 to 0.6 kgBOD / MLSS / day, and 0.1 to 0.5 kgBOD. / MLSS / day is more preferably in the range.

  The pH in the continuous biological treatment tank 10 is preferably adjusted to a range of 6 to 9 suitable for general biological treatment, and more preferably adjusted to a range of 6.5 to 7.5. Further, the dissolved oxygen (DO) in the continuous biological treatment tank 10 is preferably 0.5 mg / L or more, and more preferably 1 mg / L or more, which is suitable for general biological treatment.

  The continuous biological treatment apparatus of the present embodiment is a form in which biological treatment and solid-liquid separation are performed in separate tanks, but is not limited thereto. For example, biological treatment and solid-liquid separation are performed in one tank. An immersion type membrane separation device may be used. The immersion type membrane separation device is composed of, for example, a continuous biological treatment tank and an immersion membrane module as a solid-liquid separation means installed in the continuous biological treatment tank.

  The ratio of granulated sludge to the first fraction (granule-concentrated sludge) separated by the hydrocyclone 18 is not particularly limited as long as it is higher than the ratio of suspended sludge to the first fraction, but the first fraction The ratio of the granular sludge to (granule-concentrated sludge) is preferably 10% or more, and more preferably 30% or more. The ratio of the granular sludge is measured by a laser type particle size distribution meter or the like.

  FIG. 3 is a schematic diagram illustrating another example of the configuration of the wastewater treatment device according to the present embodiment. In the wastewater treatment device 2 of FIG. 3, the same components as those of the wastewater treatment device 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The wastewater treatment device 2 shown in FIG. 3 includes a sludge return line 19 and surplus sludge discharge lines 21a and 21b. One end of the sludge return line 19 is connected to the solid-liquid separation tank 14, and the other end is connected to the continuous biological treatment tank 10. One end of the surplus sludge discharge line 21 a is connected to the sludge return line 19, and the other end is connected to the liquid cyclone 18. The surplus sludge discharge line 21b is connected to the surplus sludge discharge line 21a. In the wastewater treatment apparatus 2 shown in FIG. 3, one end of the sludge supply line 24 is connected to the liquid cyclone 18, and the other end is connected to the sludge return line 19.

  In the wastewater treatment apparatus 2 shown in FIG. 3, part of the biological sludge separated in the solid-liquid separation tank 14 is returned to the continuous biological treatment tank 10 through the sludge return line 19. Further, the remaining portion of the biological sludge is supplied as surplus sludge from the surplus sludge discharge line 21a to the liquid cyclone 18, and the first fraction (granule concentrated sludge) and the second fraction (granule Dilute sludge). The first fraction is supplied to the continuous biological treatment tank 10 via the sludge supply line 24 and the sludge return line 19, and the second fraction is discharged from the sludge discharge line 26c to the outside of the system. In addition, the valve 40 provided in the surplus sludge discharge line 21b may be opened to discharge a part of the surplus sludge passing through the surplus sludge discharge line 21a from the surplus sludge discharge line 21b to the outside of the system.

  In the wastewater treatment apparatus 2 shown in FIG. 3, the first fraction obtained by concentrating the granular sludge by the liquid cyclone 18 is supplied to the continuous biological treatment tank 10. Therefore, the granular sludge in the solid-liquid separation tank 14 is effectively used. And the concentration of granular sludge in the continuous biological treatment tank 10 can be improved.

  FIG. 4 is a schematic diagram illustrating another example of the configuration of the wastewater treatment device according to the present embodiment. In the wastewater treatment device 3 of FIG. 4, the same components as those of the wastewater treatment device 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the wastewater treatment apparatus 3 shown in FIG. 4, a wastewater inflow pump 31 and a valve 44 are provided in the wastewater inflow line 20a, and a valve 46 is provided in the wastewater inflow line 20b. One end of the drainage inflow line 20b is connected to the drainage inflow line 20a between the drainage inflow pump 31 and the valve 44, and the other end is connected to the drainage inlet of the semi-batch type biological treatment tank 15. In addition, the wastewater treatment apparatus 3 shown in FIG. 4 includes a sludge treated water discharge line 58 that discharges treated water and granulated sludge discharged from the semi-batch type biological treatment tank 15 to the continuous biological treatment tank 10. A valve 60 is provided in the sludge treatment water discharge line 58.

  FIG. 5 is a schematic diagram showing an example of a configuration of a semi-batch type biological treatment tank used in the wastewater treatment device shown in FIG. In the semi-batch type biological treatment tank 15 shown in FIG. 5, the same components as those of the semi-batch type biological treatment tank 12 shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In the semi-batch biological treatment tank 15 shown in FIG. 5, a sludge treatment water outlet 12d for discharging treated water and granulated sludge is provided, and one end of a sludge treatment water discharge line 58 is connected to the sludge treatment water outlet 12d. I have. The other end of the sludge treatment water discharge line 58 is connected to the continuous biological treatment tank 10. In the semi-batch type biological treatment tank 15 shown in FIG. 5, the drainage inlet 12a into which the wastewater flows is provided at a position lower than the sludge treatment water outlet 12d.

  In the semi-batch type biological treatment tank 15 shown in FIG. 5, the inflow of wastewater and the discharge of treated water are performed simultaneously. That is, processes such as inflow of wastewater and discharge of treated water, biological treatment of a substance to be treated, and settling of biological sludge are repeatedly performed. An example of the operation of the semi-batch type biological treatment tank 15 shown in FIG. 5 will be described below together with the operation of the wastewater treatment device 2 shown in FIG.

  First, while operating the drainage inflow pump 31, the valve 44 is opened, and the wastewater to be treated in the wastewater storage tank 16 is continuously supplied from the wastewater inflow line 20a to the continuous biological treatment tank 10. After performing the biological treatment of the wastewater in the continuous biological treatment tank 10, the treated water is supplied to the solid-liquid separation tank 14 from the wastewater inflow line 20c. When the semi-batch biological treatment tank 15 is operated, the valve 46 and the valve 60 are opened, and wastewater is supplied from the drainage inflow line 20b to the semi-batch biological treatment tank 15, and the semi-batch biological treatment tank 15 is supplied. The treated water and granular sludge in 15 are supplied from the sludge treated water discharge line 58 to the continuous biological treatment tank 10 (inflow of wastewater / discharge of treated water). At this time, by operating the stirring device 48, it becomes possible to efficiently supply the granular sludge in the semi-batch type biological treatment tank 15 from the sludge treated water discharge line 58 to the continuous biological treatment tank 10. Then, while the valve 46 and the valve 60 are closed and the stirring device 48 is operated, the air pump 50 is operated to start supplying air into the semi-batch type biological treatment tank 15 and perform biological treatment of wastewater (biological treatment). Process).

  After a lapse of a predetermined time, the supply of air is stopped by stopping the operation of the air pump 50, and the biological treatment is ended by stopping the stirring device 48. After completion of the biological treatment, the biological sludge in the semi-batch biological treatment tank 15 is settled for a predetermined time, and separated into biological sludge and treated water in the semi-batch biological treatment tank 15 (sedimentation of biological sludge). Then, the process shifts again to the inflow of wastewater / discharge process water.

  In the present embodiment, since the drainage inlet 12a provided in the semi-batch type biological treatment tank 15 is disposed at a position lower than the sludge treatment water outlet 12d, the wastewater flowing into the semi-batch type biological treatment tank 15 is biologically treated. Without being discharged from the semi-batch type biological treatment tank 15 (shortcut of drainage). As a result, granule sludge can be efficiently formed in the semi-batch type biological treatment tank 15. Further, the treated water in the semi-batch type biological treatment tank 15 is discharged in a form pushed up by the inflowing wastewater, so that the biological sludge having low sedimentation property (sludge not granulated, etc.) is actively collected. It can be discharged outside. As a result, biological sediment with high sedimentation remains in the semi-batch type biological treatment tank 15, so that granule sludge can be formed more efficiently.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

  In the embodiment, using a continuous biological treatment tank charged with granulated sludge and suspended sludge, biological treatment is performed on wastewater simulating industrial wastewater. separated. The biological sludge is charged into a liquid cyclone (T-80, manufactured by Murata Industries Co., Ltd.), centrifuged, and the sludge discharged from the lower part of the liquid cyclone (first fraction) and the sludge discharged from the upper part (No. 1). 2 fractions) were collected. The ratio of granular sludge to each sludge was measured by a laser type particle size distribution meter. As a result, in the first fraction, the granular sludge having a particle size of 200 μm or more was 56% of the total amount of the sludge in the first fraction. In the second fraction, the granular sludge having a particle size of 200 μm or more was 4% of the total amount of the second fraction.

  From this result, it is possible to increase the ratio of granule sludge in the biological sludge in the continuous biological treatment tank by supplying the sludge of the first fraction separated by the liquid cyclone to the continuous biological treatment tank. It can be said that

1-3 wastewater treatment equipment, 10 continuous biological treatment tanks, 12,15 semi-batch biological treatment tanks, 12a wastewater inlet, 12b treated water outlet, 12c sludge outlet, 12d sludge treated water outlet, 14 solid-liquid separation tank, 16 Wastewater storage tank, 18 liquid cyclone, 19 sludge return line, 20a, 20b, 20c wastewater inflow line, 21a, 21b excess sludge discharge line, 22a, 22b treated water discharge line, 24 sludge supply line, 26a, 26b, 26c sludge discharge Line, 28 biological sludge discharge line, 30 first drainage inflow pump, 31 second wastewater inflow pump, 32 second wastewater inflow pump, 34 treated water discharge pump, 36 sludge discharge pump, 38 sludge supply pump, 40, 44, 46, 60 Valve, 48 stirrer, 50 air pump, 52 diffuser, 58 sludge treated water discharge line.

Claims (3)

While continuously draining the wastewater into the continuous biological treatment tank, the wastewater is biologically treated with biological sludge including granular sludge and suspended sludge, and then the biological sludge is separated from the biological treatment liquid by solid-liquid separation means. Type biological treatment process,
A centrifugal force is applied to the biological sludge that has been solid-liquid separated in the continuous biological treatment step, a first fraction containing more granular sludge than the floating sludge, and containing more floating sludge than the granular sludge. A centrifugation step of separating into a second fraction,
A sludge supply step of supplying the first fraction separated in the centrifugation step to the continuous biological treatment tank,
The granular sludge may have a particle size of more than 200 [mu] m, the floating sludge have a particle size of less than 200 [mu] m,
The wastewater treatment method according to claim 1, wherein the ratio of the granular sludge having a particle size of 200 µm or more to the first fraction separated in the centrifugation step is 30% or more . A sludge return step of returning a portion of the biological sludge solid-liquid separated in the continuous biological treatment step to the continuous biological treatment tank,
An excess sludge discharge step of discharging the remaining part of the biological sludge solid-liquid separated in the continuous biological treatment step as excess sludge,
The centrifugal separation step, wherein the excess sludge discharged in the excess sludge discharge step is centrifuged and separated into the first fraction and the second fraction. Wastewater treatment method. A continuous biological treatment tank for biologically treating the wastewater with biological sludge including granular sludge and suspended sludge while continuously flowing wastewater, and a solid-liquid separation unit for solid-liquid separating the biological sludge from the biological treatment liquid. A continuous biological treatment apparatus comprising:
A centrifugal force is applied to the biological sludge that has been solid-liquid separated by the continuous biological treatment apparatus, and a first fraction containing more granular sludge than the suspended sludge, and containing more suspended sludge than the granular sludge. Centrifugal separation means for separating into a second fraction,
Sludge supply means for supplying the first fraction separated by the centrifugal separation means to the continuous biological treatment tank,
The granular sludge may have a particle size of more than 200 [mu] m, the floating sludge have a particle size of less than 200 [mu] m,
The wastewater treatment apparatus according to claim 1, wherein the ratio of the granular sludge having a particle size of 200 µm or more to the first fraction separated by the centrifugal means is 30% or more .

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