JP2016221426A - Waste water treatment method and waste water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treatment method and a waste water treatment device where the collapse of granule sludge in a continuous biological treatment apparatus is suppressed, and high speed treatment is made possible.SOLUTION: Provided is a waste water treatment method comprising: a continuous type biological treatment step where, while continuously flowing waste water into a continuous type biological type treatment tank 10, the waste water is subjected to biological treatment by biological sludge; and a sludge feed step where granule sludge with a grain size of 200 μm or more is fed from a biological sludge feed line 28 to the continuous type biological treatment tank 10, and the BOD sludge load of the continuous type biological tank 10 in the continuous type biological treatment step lies in the range of 0.08 to 0.2 kgBOD/kgMLVSS/day.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment apparatus.

  Conventionally, an activated sludge method using assimilation and catabolism of microorganisms has been widely used for the purpose of treating organic substances contained in sewage, industrial wastewater, and the like. In the activated sludge method, sludge mainly consisting of microbial flocs and water to be treated are brought into contact with each other in the presence of dissolved oxygen to oxidize organic matter to carbon dioxide, and then in a sedimentation tank installed at the latter stage of the reaction tank. There is an aerobic activated sludge method in which sludge and treated water are separated to obtain treated water. This aerobic activated sludge method is widely used regardless of whether it is sewage or industrial wastewater because of its simple facility. However, since the aerobic activated sludge method uses floc-like bacteria and separates the treated water and sludge by gravity, the precipitation facility for separating the sludge and treated water becomes very large, resulting in a reaction There is a problem that it is difficult to keep the sludge concentration in the tank high. For example, in the biological treatment of sewage with low organic matter concentration in the wastewater, it is operated at about 150 to 200 mL / g as the value of SVI30, which is the sedimentation index of activated sludge, and in the worst case about 300 mL / g. In order to obtain the above, it is necessary to operate at a MLSS concentration in the tank of about 1000 to 2000 mg / L, and the space of the processing equipment has been increased at present.

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

  In recent years, treatment has been carried out using a semi-batch treatment device that allows wastewater to flow into the reaction tank intermittently, and the sedimentation time of biological sludge is shortened, so that it is not limited to anaerobic biological sludge. It has become clear that it is possible to form a biological sludge (hereinafter sometimes referred to as granular sludge) (see, for example, Patent Documents 1 to 4).

  Therefore, it is equipped with a continuous biological treatment device that treats wastewater by continuously flowing it in, and a semi-batch biological treatment device that generates aerobic granules, and aerobic granules are continuously fed from the semi-batch biological treatment device. A treatment apparatus that granulates biological sludge in a continuous biological treatment apparatus by supplying it to the biological treatment apparatus has been proposed (see, for example, Patent Documents 5 and 6).

International Publication No. 2004/024638 JP 2008-212878 A JP 2009-18263 A JP 2009-18264 A JP 2007-136367 A JP 2008-284427 A

  By the way, even if the granular sludge is supplied to the continuous reaction apparatus, if the supplied granular sludge collapses in the continuous biological treatment apparatus, it becomes difficult to maintain the sludge in the system. In some cases, it is difficult to maintain high-speed processing. In particular, when the BOD of the waste water flowing into the continuous biological treatment apparatus has a low concentration (for example, 200 mg BOD / L or less), there is a problem that it is difficult to maintain granular sludge.

  Accordingly, an object of the present invention is to provide a wastewater treatment method and a wastewater treatment apparatus that suppress the collapse of granular sludge in a continuous biological treatment apparatus and enable high-speed treatment.

  The wastewater treatment method of the present invention comprises a continuous biological treatment step of biologically treating the wastewater with biological sludge while allowing the wastewater to continuously flow into a continuous biological treatment tank, and granular sludge having a particle size of 200 μm or more. A sludge supply step for supplying to the continuous biological treatment tank, and a BOD sludge load of the continuous biological treatment tank in the continuous biological treatment step is in a range of 0.08 to 0.2 kgBOD / kgMLVSS / day. It is a certain wastewater treatment method.

  In the waste water treatment method, the continuous biological treatment tank is preferably composed of a plurality of reaction tanks.

  Further, in the wastewater treatment method, a sludge returning step of solid-liquid separating biological sludge from the biological treatment liquid treated in the continuous biological treatment step, and returning the biological sludge separated into the solid-liquid separation to the continuous biological treatment tank. A continuous organism obtained from the sum of the flow rate of waste water flowing into the continuous biological treatment tank and the flow rate of biological sludge returned to the continuous biological treatment tank, and the volume of the continuous biological treatment vessel The hydraulic residence time of the treatment tank is preferably in the range of 5 hours to 10 hours.

  In addition, in the wastewater treatment method, a semi-batch type biological process includes an inflow process for inflowing wastewater, a biological treatment process for biologically treating the wastewater with biological sludge, a sedimentation process for sedimenting the biological sludge, and a discharge process for discharging treated water. A semi-batch biological treatment process is performed repeatedly in a treatment tank to form granular sludge, and the granule sludge in the sludge supply process is a granule sludge formed in the semi-batch biological treatment process. It is preferable.

  Further, in the wastewater treatment method, the treated water discharge port of the semi-batch type reaction tank is provided above a drainage inlet, and the wastewater is allowed to flow into the semibatch type reaction tank from the drainage inlet. It is preferable to discharge the treated water from the treated water discharge port.

  Moreover, in the wastewater treatment method, in the inflow step of the semi-batch biological treatment process, it is preferable that a part of the wastewater supplied into the continuous biological treatment tank flows into the semi-batch biological treatment tank. .

  Moreover, the wastewater treatment apparatus of the present invention comprises a continuous biological treatment tank for biologically treating the wastewater with biological sludge while continuously flowing wastewater, and a granular sludge having a particle size of 200 μm or more. Sludge supply means for supplying to the treatment tank, wherein the continuous biological treatment tank has a BOD sludge load in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day.

  ADVANTAGE OF THE INVENTION According to this invention, even when BOD of the waste_water | drain which flows into a continuous type biological treatment apparatus is a low density | concentration, collapse of the granular sludge in a continuous type biological treatment apparatus is suppressed, and high-speed processing is enabled.

1 is a schematic configuration diagram of a wastewater treatment apparatus according to an embodiment of the present invention. It is a schematic diagram which shows an example of a structure of the granule formation tank used with the waste water treatment apparatus of FIG. It is a schematic block diagram of the waste water treatment apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the waste water treatment apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the waste water treatment apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the waste water treatment apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the waste water treatment apparatus which concerns on other embodiment of this invention. It is a schematic diagram which shows an example of a structure of the semibatch type biological treatment tank used for the waste water treatment apparatus shown in FIG. It is a figure which shows the particle size distribution of the seed sludge, the granular sludge formed in the semi-batch type biological treatment tank, and the sludge in the continuous biological treatment tank in the condition 6.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  In the present specification, “granule” refers to a self-granulated microorganism, and is not particularly limited. In a continuous biological treatment tank, which will be described later, organic components in the wastewater are oxidatively decomposed under aerobic conditions, and nitrogen compounds in the wastewater are nitrified or denitrified under aerobic conditions under aerobic conditions. Therefore, it is preferable that the granule sludge in this specification is comprised by the aerobic microorganism or the facultative anaerobic microorganism. Aerobic microorganisms are microorganisms that metabolize using molecular oxygen in the presence of dissolved oxygen, and facultative anaerobic microorganisms can use molecular oxygen, but molecular oxygen can also be used. It is a microorganism that can acquire energy by using bound oxygen such as nitric acid and nitrous acid even in the absence of oxygen, and these are distinguished from obligate anaerobic microorganisms such as methanogenic bacteria. Is done.

  In the present specification, the “continuous type” is a method for the batch type, and like the semi-batch type, the inflow of waste water, biological treatment, sedimentation of sludge, and discharge of treated water are repeated in one reaction tank. It is distinguished from batch processing. Further, in the present embodiment, the continuous type is not limited to a method in which drainage is continuously poured into the reaction tank and is operated, but the reaction is performed by a pump using a principle such as a reciprocating motion such as a diaphragm pump. The system may be operated by supplying wastewater to the tank, or a raw water tank is installed in front of the reaction tank, and the pump operation is controlled according to the water level of the raw water tank (when the water level is high). May be a simulated continuous water supply system that operates the pump and stops the pump when the water level is low) to supply waste water to the reaction tank.

  FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus according to an embodiment of the present invention. The waste water treatment apparatus 1 shown in FIG. 1 includes a waste water storage tank 16, a continuous biological treatment tank 10, a solid-liquid separation tank 14, and a granule formation tank 12.

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

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

  The continuous biological treatment tank 10 shown in FIG. 1 biologically treats wastewater that flows continuously, for example, under aerobic conditions and in the presence of biological sludge such as granules supplied from the granule formation tank 12. (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 from water containing biological sludge and treated water. For example, separation devices such as sedimentation separation, pressurized flotation, filtration, and membrane separation are used. Is mentioned.

  The granule formation tank 12 shown in FIG. 1 is an apparatus for forming granular sludge having a particle size of 200 μm or more while biologically treating waste water. Since the granule sludge supplied to the continuous biological treatment tank 10 is preferably composed of aerobic microorganisms or facultative anaerobic microorganisms, the granule formation tank 12 shown in FIG. It is preferable that the granular sludge can be formed while treating the wastewater under or under anoxic conditions.

  The drainage inflow line 20b and the second drainage inflow pump 32 shown in FIG. 1 function as devices for supplying drainage to the granule forming tank 12. In this embodiment, the drainage is supplied / stopped 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 the drainage is supplied / stopped by opening / closing the valve. May be performed.

  The biological sludge supply line 28 and the sludge supply pump 36 shown in FIG. 1 function as an apparatus that supplies the granular sludge formed by the granule formation tank 12 to the continuous biological treatment tank 10. In addition, you may install a valve | bulb etc. in the biological sludge supply line 28 suitably.

  The treated water discharge line 22b and the treated water discharge pump 34 shown in FIG. 1 function as a device that supplies the treated water in the granule formation tank 12 to the continuous biological treatment tank 10. In addition, you may install a valve | bulb etc. in the treated water discharge line 22b suitably.

  An example of the operation of the waste water treatment apparatus 1 shown in FIG. 1 will be described.

  The wastewater to be treated is, for example, wastewater containing biodegradable organic matter such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste and the like. In addition, when a biologically indegradable organic substance is contained in waste_water | drain, it is desirable to give a physicochemical process beforehand and to convert into a biodegradable substance.

  Before the wastewater containing organic matter is supplied to the continuous biological treatment tank 10, it is preferably sent to the wastewater storage tank 16 to stabilize the water quality of the wastewater. Note that the drainage storage tank 16 may be omitted when the quality of the drainage water is relatively stable or when the drainage inflow amount is large. Moreover, when the solid substance is contained in the waste_water | drain, it is preferable to remove a solid substance with a screen, a sedimentation basin, etc. before supplying to the waste_water | drain storage tank 16. FIG.

  The wastewater to be treated in the wastewater storage tank 16 is supplied to the continuous biological treatment tank 10 from the wastewater inflow line 20 a by the operation of the first wastewater inflow pump 30. Moreover, the waste water in the waste water storage tank 16 is supplied to the granule formation tank 12 from the waste water inflow line 20b by the operation of the second waste water inflow pump 32. In the granule formation tank 12, biological treatment of waste water is performed and granule sludge having a particle size of 200 μm or more is formed. Granule sludge formed in the granule formation tank 12 is supplied from the biological sludge supply line 28 to the continuous biological treatment tank 10 by the operation of the sludge supply pump 36. The treated water in the granule formation tank 12 is supplied to the continuous biological treatment tank 10 from the treated water discharge line 22b by the operation of the treated water discharge pump 34. And in the continuous biological treatment tank 10, the biological treatment of waste water is implemented by the biological sludge containing the said granule sludge, for example on aerobic conditions.

  The treated water treated in the continuous biological treatment tank 10 is supplied to the solid-liquid separation tank 14 from the waste water inflow line 20c, and the biological sludge is separated from the treated water. The sludge separated into solid and liquid is returned to the continuous biological treatment tank 10 from the sludge return line 24 by the operation of the sludge return pump 38. Further, when the valve 40 is opened, the solid-liquid separated sludge is discharged out of the system from the sludge discharge line 26. Furthermore, the treated water in the solid-liquid separation tank 14 is discharged out of the system from the treated water discharge line 22a.

  Below, the process conditions etc. of the waste water treatment apparatus 1 shown in FIG. 1 are demonstrated concretely.

<Processing conditions of continuous biological treatment tank 10>
The BOD load amount (BOD sludge load) in the waste water with respect to the sludge amount in the continuous biological treatment tank 10 is in the range of 0.08 to 0.2 kgBOD / kgMLVSS / day, and 0.1 to 0.18 kgBOD / kgMLVSS / More preferably in the range of days. When the BOD sludge load is smaller than 0.08 kgBOD / kgMLVSS / day, the disintegration rate of the granule sludge supplied from the granule formation tank 12 is high, and it becomes difficult to maintain the granule sludge. Also, if the BOD sludge load is greater than 0.2 kg BOD / kgMLVSS / day, the proportion of floc sludge will increase in addition to the granular sludge in the tank, and bulking (solid-liquid separation failure) may occur due to overload. Therefore, it becomes difficult to maintain high sedimentation properties. In general, when the BOD of the waste water flowing into the continuous biological treatment tank 10 is low, for example, 200 mg BOD / L or less, the granule sludge is significantly disintegrated, but the BOD sludge load is 0.08 to 0.2 kg BOD. By operating in the range of / kgMLVSS / day, the collapse of granules is suppressed, the sedimentation property of the sludge in the continuous biological treatment tank 10 is kept good, and the wastewater can be processed at high speed. In the present embodiment, even if the BOD concentration of the waste water flowing into the continuous biological treatment tank 10 is about 50 to 200 mg / L, the granule sludge is prevented from collapsing and the waste water can be processed at high speed.

  The BOD sludge load of the continuous biological treatment tank 10 includes the flow rate of the wastewater supplied to the continuous biological treatment tank 10, the amount of granular sludge passing through the biological sludge supply line 28, the amount of returned sludge passing through the sludge return line 24, etc. It is adjusted by. Specifically, from the BOD of the wastewater supplied to the continuous biological treatment tank 10 and the MLVSS in the continuous biological treatment tank 10, the BOD sludge load of the continuous biological treatment tank 10 satisfies the above range. The flow rate, granule sludge supply amount, return sludge amount, and excess sludge discharge amount are adjusted. The adjustment of the BOD sludge load is preferably performed by adjusting the flow rate of the wastewater supplied to the continuous biological treatment tank 10 from the viewpoint of ease of operation, but by adjusting the amount of sludge in the system You may go.

  The adjustment of the drainage flow rate, granule sludge, and return sludge amount may be performed by the operator adjusting the output of each pump, or each based on the BOD value and MLVSS value of the wastewater. The control may be performed by adjusting the output of each pump using a control device that controls the output of the pump. For example, the BOD of the wastewater supplied to the continuous biological treatment tank 10 may be measured by an operator according to an official method, or the BOD value may be estimated from a TOC or COD value measured daily. . The MLVSS in the continuous biological treatment tank 10 may be measured by an operator according to an official method, for example, or may be obtained from the value of the MLSS meter installed in the continuous biological treatment tank 10 and daily measurement. The average MLVSS / MLSS ratio may be estimated.

  The substantial hydraulic residence time (substantially HRT) in the continuous biological treatment tank 10 is preferably in the range of 5 hours to 10 hours, and more preferably in the range of 5 hours to 8 hours. Substantial HRT is the sum of the wastewater flow rate at which wastewater is introduced (in Fig. 1, the flow rate of wastewater through the drainage inflow line 20a) and the sludge flow rate by sludge circulation (in Fig. 1, the sludge flow rate through the sludge return line 24). The HRT calculated from the flow rate and the volume of the continuous biological treatment tank 10. When the substantial HRT exceeds 10 hours, the granular sludge may be easily disintegrated as compared with the case of the range of 5 hours to 10 hours. Moreover, when the residence time of the granular sludge in the continuous biological treatment tank 10 is less than 5 hours, the generation rate of floc sludge in the tank is larger than in the case of the range of 5 hours to 10 hours. It may become difficult to maintain granular sludge due to the concentration of organic matter in the tank.

  The MLSS concentration in the continuous biological treatment tank 10 is preferably maintained at 3000 mg / L or more, and more preferably maintained at 4000 mg / L or more. In activated sludge treatment when the organic matter concentration in the wastewater such as normal sewage is low, the MLSS concentration is usually maintained at about 1000 to 2000 mg / L due to the problem of sedimentation and separation of sludge. In the processing apparatus of the embodiment, even when the MLSS concentration is operated at 3000 mg / L or more, the sludge concentration in the system is kept high while maintaining the sludge with high sedimentation property, and the wastewater can be processed at high speed. As a result, the continuous biological treatment tank 10 can be greatly reduced in size, and the site area of the wastewater treatment facility can be saved and the equipment cost can be greatly reduced.

  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. When the pH value is out of the above range, it is preferable to adjust the pH using an acid or an alkali.

<Formation of granule sludge in the granule formation tank 12>
The waste water supplied to the granule forming tank 12 is not necessarily the same as the waste water supplied to the continuous biological treatment tank 10. For example, another system of waste water may be supplied to the granule forming tank 12. However, a part of the wastewater supplied to the continuous biological treatment tank 10 as in the wastewater treatment apparatus 1 shown in FIG. 1 in that a granular sludge having a microflora suitable for the wastewater to be treated is formed. It is preferable to form a granule by diverting the water into the granule forming tank 12 and utilizing the drainage.

  The granule sludge in the granule formation tank 12 is not limited to the form directly supplied to the continuous biological treatment tank 10. For example, when the sludge in the solid-liquid separation tank 14 is returned to the continuous biological treatment tank 10, the granular sludge in the granule formation tank 12 may be introduced into the solid-liquid separation tank 14, You may introduce into the sludge return line 24 for returning sludge from the liquid separation tank 14 to the continuous biological treatment tank 10. FIG. In any case, the granular sludge in the granule forming tank 12 may be supplied to the continuous biological treatment tank 10.

  For example, the treated water discharged from the granule formation tank 12 may be supplied to the continuous biological treatment tank 10, may be supplied to the solid-liquid separation tank 14, or discharged out of the system as the final treated water. However, in the case where components such as BOD and nitrogen compounds remain in the discharged water discharged from the granule formation tank 12, the continuous biological treatment tank 10 does not deteriorate the final treated water. Is preferably supplied.

  As the properties of the sludge in the granule forming tank 12, it is preferable that sludge having a particle size of 200 μm or more is present in a volume ratio of 50% or more, more preferably 85% or more. The particle size of the granular sludge and the volume distribution of each particle size are measured by, for example, a laser diffraction particle size distribution meter.

  The granule formation tank 12 is not particularly limited as long as it can form granule sludge having a particle size of 200 μm or more, but the granule sludge is an aerobic microorganism or facultative anaerobic. Since it is preferably constituted by microorganisms, it is preferable that the granular sludge can be formed while treating the waste water under aerobic conditions or oxygen-free conditions. The granule formation tank 12 is, for example, an upward flow type denitrification granule system (USB type denitrification device), a continuous water flow type granule formation system using a substrate concentration gradient (JP 2010-12404, JP 2010-29749, Japanese Patent Application Laid-Open No. 2010-42363), semi-batch biological treatment tanks, and the like. In consideration of the formation rate of granules, ease of management, etc., a semi-batch biological treatment tank is particularly desirable.

  Moreover, although the waste water treatment apparatus 1 of this embodiment is provided with the granule formation tank 12, it is not necessary to necessarily provide the granule formation tank 12. For example, in a separate wastewater treatment system, when granular sludge having a particle size of 200 μm or more is formed, the biological sludge is supplied so that the granular sludge is supplied to the continuous biological treatment tank 10. An apparatus (biological sludge supply line 28) may be installed.

  Below, an example of the granule formation tank 12 used with the waste water treatment apparatus of FIG. 1 is demonstrated.

  FIG. 2 is a schematic diagram showing an example of the configuration of a granule forming tank used in the waste water treatment apparatus of FIG. The granule formation tank 12 shown in FIG. 2 repeats four steps of (1) inflow of wastewater, (2) biological treatment of wastewater with biological sludge, (3) sedimentation of biological sludge, and (4) discharge of treated water. This is a semi-batch biological treatment tank that forms granular sludge (hereinafter referred to as a semi-batch biological treatment tank 12).

  The semi-batch biological treatment tank 12 shown in FIG. 2 includes a stirring device 48, an air pump 50, and an aeration device 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. In addition, the stirring device 48 has a structure in which a shaft attached to the motor rotates by driving the motor, and a stirring blade attached to the tip of the shaft rotates with the rotation of the shaft. The stirring device 48 is not limited to the above configuration. The semi-batch biological treatment tank 12 is provided with a drainage inlet 12a and a treated water outlet 12b, 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. Has been. The semi-batch biological treatment tank 12 is provided with a sludge outlet 12c, and a biological sludge supply line 28 is connected thereto.

  Below, an example of operation | movement of the semibatch type biological treatment tank 12 is demonstrated.

  The waste water in the waste water storage tank 16 shown in FIG. 1 is supplied from the waste water inflow line 20b to the semi-batch biological treatment tank 12 shown in FIG. 2 by the operation of the second waste water inflow pump 32 ((1) Inflow). The operation of the second drainage inflow pump 32 is stopped when a predetermined amount of wastewater is introduced into the semi-batch biological treatment tank 12. Next, air is introduced into the semi-batch biological treatment tank 12 from the diffuser 52 by the operation of the air pump 50, and the waste water in the semi-batch biological treatment tank 12 is stirred by the operation of the stirring device 48. The biological treatment of the wastewater is performed ((2) Wastewater biological treatment).

  After the biological treatment process of the wastewater is performed for a predetermined time, the operation of the air pump 50 and the stirring device 48 is stopped (end of the biological treatment). After completion of the biological treatment, the biological sludge in the semi-batch biological treatment tank 12 is allowed to settle for a predetermined time, and the biological sludge and treated water are separated in the semi-batch biological treatment tank 12 ((3) sedimentation of biological sludge). . Next, by the operation of the treated water discharge pump 34, the treated water in the semi-batch biological treatment tank 12 is discharged from the treated water discharge line 22b ((4) discharged treated water), and the continuous biological water is discharged from the treated water discharge line 22b. It is supplied to the treatment tank 10. And the biological sludge in the semi-batch type biological treatment tank 12 is granulated by repeating the steps (1) to (4), and granulated sludge is formed.

  The supply of granule sludge from the semi-batch biological treatment tank 12 may be performed in (2) wastewater biological treatment process, (3) biological sludge sedimentation process, or (4) treatment. You may perform in the discharge process of water. The granular sludge formed in the semi-batch biological treatment tank 12 is a sludge that has been self-granulated, for example, a biological sludge having an average particle diameter of 200 μm or more. In the present embodiment, whether or not granulated sludge has been formed is determined by measuring the particle size distribution of the sludge in the semi-batch biological treatment tank 12, and when the average particle size reaches 200 μm or more. It can be judged that le sludge has been formed. Alternatively, the SVI value is periodically measured by a sedimentation test of sludge in the semi-batch biological treatment tank 12, and the value of SVI5 calculated from the volume ratio after settling for 5 minutes is equal to or less than a predetermined value (for example, 80 mL / g or less). ), It may be determined that granule sludge has been formed (the lower the SVI value, the larger the average particle size, the better the granular sludge can be determined).

  The pH in the semi-batch biological treatment tank 12 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. 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 adjustment is performed in a state where the semi-batch biological treatment tank 12 is stirred rather than in a state where the pH value is appropriately measured. It is desirable to do. The dissolved oxygen (DO) in the semi-batch 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.

  If the reaction tank volume of the semi-batch biological treatment tank 12 is too small with respect to the volume of the continuous biological treatment tank 10, the increase in granules in the tank becomes slow, and it takes time to start up. . Therefore, it is preferable that it is 1/3 or less with respect to the volume of the continuous biological treatment tank 10, and it is more preferable that it is 1/5 or less.

  FIG. 3 is a schematic configuration diagram of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 2 shown in FIG. 3, the same code | symbol is attached | subjected about the structure similar to the waste water treatment apparatus 1 shown in FIG. 1, and the description is abbreviate | omitted. The waste water treatment apparatus 2 shown in FIG. 3 includes three continuous biological treatment tanks (10a, 10b, 10c). In the waste water treatment apparatus 2 shown in FIG. 3, one end of the biological sludge supply line 28 is connected to the sludge outlet of the granule formation tank 12, and the other end is connected to the sludge supply port of the continuous biological treatment tank 10b. One end of the treated water discharge line 22b is connected to the treated water outlet of the granule forming tank 12, and the other end is connected to the treated water inlet of the continuous biological treatment tank 10a.

  In a single continuous biological treatment tank, since the wastewater is in a completely mixed state, the organic matter concentration in the tank is constant, but as shown in FIG. 3, by installing a plurality of continuous biological treatment tanks, Since there is a difference in the organic matter concentration in each tank, compared to a single continuous biological treatment tank, it becomes easier for the microorganisms in the tank to form a satiety state and a starvation state, and the granule sludge is more collapsed. It is suppressed. In addition, by installing multiple continuous biological treatment tanks, it is possible to increase the proportion of granule sludge in the continuous biological treatment tank by growing microorganisms with the granular sludge present in the tank as the core. .

  When a plurality of continuous biological treatment tanks are installed, the BOD sludge load of the entire continuous biological treatment tank may be in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day. That is, if the BOD sludge load of the entire continuous biological treatment tank is in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day, the BOD sludge load of each continuous biological treatment tank may not satisfy the above range. . When multiple continuous biological treatment tanks are installed, the BOD sludge load of the entire continuous biological treatment tank is set to a range of 0.08 to 0.2 kg BOD / kg MLVSS / day from the point of suppressing the collapse of the granular sludge, and It is preferable to lower the BOD sludge load of the tank as it goes from the front-stage continuous biological treatment tank to the subsequent-stage continuous biological treatment tank. At this time, the BOD sludge load of the front-stage continuous biological treatment tank is in the range of 0.24 to 0.6 kg BOD / kg MLVSS / day, and the BOD sludge load of the last-stage continuous biological treatment tank is 0.02 to 0.00. More preferably, the range is 05 kg BOD / kg MLVSS / day. In order to adjust the BOD sludge load in each water tank, it can be adjusted by dividing and introducing the waste water into each water tank and adjusting the inflow amount.

  FIG. 4 is a schematic configuration diagram of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 3 shown in FIG. 4, the same components as those in the waste water treatment apparatus 1 shown in FIG. The waste water treatment apparatus 3 shown in FIG. 4 is suitable for treatment of waste water mainly containing nitrogen compounds, and includes a continuous biological treatment tank in which the front stage is constituted by an anoxic tank 10d and the rear stage is constituted by an aeration tank 10e. . Here, the oxygen-free tank is a reaction tank in which oxygen-free conditions are maintained. The oxygen-free condition is that there is no dissolved oxygen in the wastewater, but there is nitrous acid or oxygen derived from nitric acid. It is a condition.

  In the continuous biological treatment tank shown in FIG. 4, nitrogen compounds and organic substances in the wastewater are treated by a circulating nitrification denitrification method. Specifically, in the subsequent aeration tank 10e, the nitrogen-containing substance in the waste water is oxidized to nitrite nitrogen or nitrate nitrogen under aerobic conditions. Then, the sludge mixed liquid containing nitrite nitrogen or nitrate nitrogen is supplied from the latter aeration tank 10e to the former anaerobic tank 10d by the circulation line 15 provided between the aeration tank 10e and the anaerobic tank 10d. The In the oxygen-free tank 10d, nitrite nitrogen or nitrate nitrogen is reduced to nitrogen gas under an oxygen-free condition.

  Granule sludge supplied to a continuous biological treatment tank has a large particle size, and therefore organic oxidizing bacteria and nitrifying bacteria may exist outside the sludge particles, and denitrifying bacteria may exist relatively inside the sludge particles. it can. Therefore, in a treatment apparatus using the anoxic tank 10d and the aeration tank 10e as a continuous biological treatment tank, by supplying granular sludge of 200 μm or more to the continuous biological treatment tank, nitrogen compounds and organic substances are fed by the granular sludge. It becomes possible to process efficiently. Also, by including an oxygen-free process in the continuous biological treatment tank, it is possible to maintain the denitrifying bacteria that make up the granular sludge in the granule and maintain the granules in the continuous biological treatment tank. It becomes. Then, granular sludge having a particle size of 200 μm or more is supplied to the continuous biological treatment tank composed of the anoxic tank 10d and the aeration tank 10e, and the BOD sludge load of the entire continuous biological treatment tank (the anoxic tank 10d and the aeration tank) is supplied. By making the total BOD load of the tank 10e) in the range of 0.08 to 0.2 kgBOD / kgMLVSS / day, it becomes possible to further suppress the collapse of the granule sludge, and the granule sludge is put in the tank. Can be maintained and grown. In particular, the BOD sludge load of the entire continuous biological treatment tank is in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day, and the BOD sludge load of the anoxic tank 10d is in the range of 0.16 to 0.6 kg BOD / kg MLVSS / day. More preferably.

  FIG. 5 is a schematic configuration diagram of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 4 shown in FIG. 5, the same components as those in the waste water treatment apparatus 1 shown in FIG. The waste water treatment apparatus 4 shown in FIG. 5 includes a continuous biological treatment tank configured by alternately arranging a plurality of oxygen-free tanks 10d and aeration tanks 10e. The continuous biological treatment tank shown in FIG. 5 is a system (step inflow type multistage nitrification denitrification method) in which a drainage inflow line 20a is connected to each anoxic tank 10d and the drainage is dispensed to each anoxic tank 10d. In each oxygen-free tank 10d and each aeration tank 10e, as described above, the nitrogen compound is nitrified and denitrified to become nitrogen gas.

  Granule sludge supplied to a continuous biological treatment tank has a large particle size, and therefore organic oxidizing bacteria and nitrifying bacteria may exist outside the sludge particles, and denitrifying bacteria may exist relatively inside the sludge particles. it can. Therefore, in a treatment apparatus using the anoxic tank 10d and the aeration tank 10e as a continuous biological treatment tank, by supplying granular sludge of 200 μm or more to the continuous biological treatment tank, nitrogen compounds and organic substances are fed by the granular sludge. It becomes possible to process efficiently. Also, by including an oxygen-free process in the continuous biological treatment tank, it is possible to maintain the denitrifying bacteria that make up the granular sludge in the granule and maintain the granules in the continuous biological treatment tank. It becomes. In the waste water treatment apparatus 4 shown in FIG. 5, the BOD sludge load of the whole continuous biological treatment tank (the total BOD sludge load of each anoxic tank 10d and each aeration tank 10e) is 0.08 to 0.2 kgBOD / kgMLVSS / A range of days. At this time, it is more preferable that the BOD sludge load of the oxygen-free tank 10d is in the range of 0.16 to 0.6 kg BOD / kg MLVSS / day.

  FIG. 6 is a schematic configuration diagram of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 5 shown in FIG. 6, the same code | symbol is attached | subjected about the structure similar to the waste water treatment apparatus 1 shown in FIG. 1, and the description is abbreviate | omitted. The waste water treatment apparatus 5 shown in FIG. 6 is suitable for treatment of waste water mainly containing phosphorus compounds, and includes a continuous biological treatment tank in which the front stage is constituted by an anaerobic tank 10f and the rear stage is constituted by an aeration tank 10e ( So-called AO method (Anaerobic-Oxic method) continuous biological treatment tank). In the continuous biological treatment tank shown in FIG. 6, the phosphorus compound and organic matter in the waste water are both treated by the AO method (Anaerobic-Oxic method). Here, the anaerobic tank is a reaction tank in which anaerobic conditions are maintained, and is a condition in which not only dissolved oxygen but also nitrous acid and nitric acid-derived oxygen do not exist in the waste water.

  Granules supplied to the continuous biological treatment tank have a large particle size, so that organic oxidizing bacteria are present outside the sludge particles, and phosphorus is metabolized inside the sludge particles under anaerobic and aerobic conditions. There can be bacteria that can be removed (phosphorus-accumulating bacteria). Therefore, in the processing apparatus using the anaerobic tank 10f and the aeration tank 10e as a continuous biological treatment tank, by supplying granular sludge of 200 μm or more to the continuous biological treatment tank, the phosphorus compound and the organic matter are efficiently used by the granular sludge. Can be processed automatically. In addition, by including anaerobic and aeration processes in the continuous biological treatment tank, the phosphorus accumulating bacteria present in the granular sludge are maintained in the granule, and the granules collapse in the continuous biological treatment tank. It becomes possible to maintain without making it. Then, granular sludge having a particle size of 200 μm or more is supplied to the continuous biological treatment tank composed of the anaerobic tank 10f and the aeration tank 10e, and the BOD sludge load of the entire continuous biological treatment tank (the anaerobic tank 10f and the aeration tank 10e). The total BOD load of 0.08 to 0.2 kg BOD / kg MLVSS / day makes it possible to further suppress the collapse of granule sludge, and maintain the granule sludge in the tank.・ It is also possible to train them. In particular, the BOD sludge load of the entire continuous biological treatment tank is in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day, and the BOD sludge load of the anaerobic tank 10f is in the range of 0.16 to 0.6 kg BOD / kg MLVSS / day. More preferably.

  Although the explanation in the figure is omitted, the continuous biological treatment tank shown in FIG. 6 has an anaerobic tank, an oxygen-free tank, and an aeration tank arranged in series, and the sludge mixed solution containing nitrate nitrogen in the aeration tank is anoxic. It may be a continuous biological treatment tank using a system circulating in a tank (so-called A2O method (Anaerobic-Anoxic-Oxic method)).

  FIG. 7 is a schematic configuration diagram of a wastewater treatment apparatus according to another embodiment of the present invention. In the waste water treatment apparatus 6 of FIG. 7, the same components as those of the waste water treatment apparatus 1 shown in FIG. The waste water treatment apparatus 6 shown in FIG. 7 includes a semi-batch biological treatment tank 17 as a granule formation tank. Moreover, in the waste water treatment apparatus 6 shown in FIG. 7, the waste water inflow pump 31 and the valve 44 are provided in the waste water inflow line 20a, and the valve 46 is provided in the waste water inflow line 20b. One end of the drainage inflow line 20 b is connected to the drainage inflow line 20 a between the drainage inflow pump 31 and the valve 44, and the other end is connected to the drainage inlet of the semi-batch biological treatment tank 17. 7 includes a sludge treated water supply line 58 for supplying treated water and granulated sludge discharged from the semi-batch biological treatment tank 17 to the continuous biological treatment tank 10. A valve 60 is provided in the sludge treated water supply line 58. The sludge treated water supply line 58 functions as a treated water supply device for supplying treated water discharged from the semi-batch biological treatment tank 17 to the continuous biological treatment tank 10 and granulated sludge to the continuous biological treatment tank 10. It functions as a sludge supply device.

  FIG. 8 is a schematic diagram showing an example of the configuration of a semi-batch biological treatment tank used in the wastewater treatment apparatus shown in FIG. In the semi-batch biological treatment tank 17 shown in FIG. 8, the same components as those in the semi-batch biological treatment tank 12 shown in FIG. In the semi-batch biological treatment tank 17 shown in FIG. 8, a treated water discharge port 12d for discharging treated water and granular sludge is provided, and one end of a sludge treated water supply line 58 is connected to the treated water discharge port 12d. Yes. The other end of the sludge treated water supply line 58 is connected to the continuous biological treatment tank 10. In the semi-batch biological treatment tank 17 shown in FIG. 8, the drainage inlet 12a into which wastewater flows is provided at a position lower than the treated water discharge port 12d.

  In the semi-batch biological treatment tank 17 shown in FIG. 8, the inflow of waste water and the discharge of treated water are performed simultaneously. That is, steps such as inflow of wastewater and discharge of treated water, biological treatment of a treatment target substance, and sedimentation of biological sludge are repeatedly performed. An example of the operation of the semi-batch biological treatment tank 17 shown in FIG. 8 will be described below together with the operation of the waste water treatment apparatus shown in FIG.

  First, the drainage inflow pump 31 is operated, the valve 44 is opened, and the wastewater to be treated in the drainage storage tank 16 is continuously supplied to the continuous biological treatment tank 10 from the drainage inflow line 20a. After the biological treatment of the wastewater is performed 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 17 is operated, the valve 46 and the valve 60 are opened, and the waste water is supplied to the semi-batch biological treatment tank 17 from the drainage inflow line 20b, and the semi-batch biological treatment tank 17 is provided. Treated water and granular sludge in the tank 17 are supplied to the continuous biological treatment tank 10 from the sludge treated water supply line 58 (inflow of wastewater / discharge of treated water). At this time, by operating the stirring device 48, the granular sludge in the semi-batch biological treatment tank 17 can be efficiently supplied from the sludge treated water supply line 58 to the continuous biological treatment tank 10. . And after the granular sludge which has a particle size of 200 micrometers or more among the biological sludge in the continuous biological treatment tank 10, the valve 46 and the valve 60 are closed. Next, in a state where the operation of the agitator 48 is maintained, the air pump 50 is operated, the supply of air into the semi-batch biological treatment tank 17 is started, and the biological treatment of the waste water is performed (biological treatment step). .

  After a predetermined time elapses, the operation of the air pump 50 is stopped, the supply of air is stopped, and the stirring device 48 is stopped (end of the biological treatment process). After the biological treatment is completed, the biological sludge in the semi-batch biological treatment tank 17 is allowed to settle for a predetermined time, thereby separating the biological sludge and the treated water in the semi-batch biological treatment tank 17 (sedimentation of biological sludge). And it again transfers to the inflow of wastewater / discharge process water.

  In this embodiment, since the waste water inlet 12a provided in the semi-batch biological treatment tank 17 is disposed at a position lower than the treated water discharge port 12d, the waste water flowing into the semi-batch biological treatment tank 17 is biologically treated. It is suppressed that it is discharged from the semi-batch biological treatment tank 17 without being carried out (shortcut of drainage). As a result, it becomes possible to efficiently form granular sludge in the semi-batch biological treatment tank 17. In addition, since the treated water in the semi-batch biological treatment tank 17 is discharged in a form that is pushed up by the inflowing wastewater, biological sludge with low sedimentation (such as sludge that is not granulated) is actively treated. It becomes possible to discharge outside. As a result, biological sludge having a high sedimentation property remains in the semi-batch biological treatment tank 17, so that the granular sludge can be formed more efficiently.

  In the formation of granular sludge in a semi-batch biological treatment tank, it is desirable to control the sedimentation time and appropriately control the wastewater inflow rate per batch. The settling time for stopping the agitation (including agitation by aeration) and settling the sludge is calculated from the distance from the water surface to the target sludge interface position and the sludge settling speed, for example, 4 min / m to 15 min / It is preferably set between m and more preferably set between 5 minutes / m and 10 minutes / m. Moreover, the wastewater inflow rate (ratio of inflow water to the effective volume during reaction) is preferably in the range of 20% to 120%, for example, and more preferably in the range of 40% to 120%. As sludge repeatedly experiences a state in which the concentration of organic matter, which is the treatment target substance, is very high (immediately after the inflow process, a satiety state) and a state in which the organic matter concentration is very low (the end of the biological treatment process, starvation state), Since granulation is considered to progress, the drainage inflow rate should be as high as possible from the viewpoint of forming granular sludge. On the other hand, the higher the drainage inflow rate, the more the inflow pump This increases the capacity and the cost. 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. When the wastewater inflow rate is high, the concentration of the discharged water from the semi-batch biological treatment tank may be poor, but since the discharged water is introduced into the continuous biological treatment tank, the final treated water concentration There is no concern of getting worse.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail more concretely, this invention is not limited to a following example.

(Example)
Using a wastewater treatment apparatus shown in FIG. 4 composed of a continuous biological treatment tank (114L), a granule formation tank (11L), and a solid-liquid separation tank, a biological treatment test of simulated wastewater was conducted. The simulated waste water used was mainly fish meat extract and peptone, and adjusted so that the BOD concentration was 80 to 120 mg / L and the total nitrogen concentration was 15 to 25 mg N / L.

  In a continuous biological treatment tank, a 13.6L oxygen-free tank, a 13.6L aerated tank, a 19L oxygen-free tank, a 19L oxygen-free tank, a 24.5L oxygen-free tank, and a 24.5L aerated tank are connected in series. The step inflow type multi-stage nitrification denitrification method (three stages) was used to treat organic matter and nitrogen components in the waste water by dispensing one third of the waste water into each oxygen-free tank. In the anaerobic tank, aeration was performed without aeration, and in the aeration tank, air aeration was performed using a diffuser so that the dissolved oxygen concentration was 1 to 5 mg / L. In the solid-liquid separation tank, the sludge mixture was separated into concentrated sludge and treated water by sedimentation separation, and the concentrated sludge was returned to the anaerobic tank at the front stage. As the granule formation tank, a semi-batch biological treatment tank shown in FIG. 2 was used. The treated water and granules from the granule formation tank were introduced into the anaerobic tank at the forefront of the continuous biological treatment tank.

  Adjustment of the BOD load in the continuous biological treatment tank was performed by adjusting the amount of inflow of waste water. The residence time including circulation was adjusted by adjusting the drainage flow rate calculated from the load and the circulation flow rate from the solid-liquid separation tank.

  The activated sludge collected from the sewage treatment plant was used as the seed sludge to be introduced into the continuous biological treatment tank. As the properties of the seed sludge, SVI was 200 mL / g, and the average particle size of the activated sludge was about 80 μm, and it was a sludge having a general sedimentation property.

  The semi-batch biological treatment tank formed granule sludge in advance using the simulated waste water before passing water through the continuous biological treatment tank. The formed granule sludge was a granular sludge having an average diameter of 340 μm and a volume ratio of 200 μm or more occupying 85%.

  In Table 1, each condition in the water flow test (MLSS in the continuous biological treatment tank, BOD sludge load and BOD volume load in the continuous biological treatment tank, substantial residence time (including circulation flow rate from the solid-liquid separation tank) The residence time))) and the SVI values of sludge after 50 days under various conditions were summarized.

  Under conditions 1 where MLSS was 1500 mg / L and BOD sludge load was 0.08 kg BOD / kg MLVSS / day, the supply of granule sludge from the semi-batch biological treatment tank and the flow of simulated waste water were started. SVI gradually decreased from the start of water flow, and decreased to about 150 mL / g on the 50th day. The residence time including circulation during this period was 10 to 14 hours. In addition, it is thought that the big improvement was not seen because the activated sludge of the seed sludge was not accustomed to the simulation drainage.

  Next, the load was reduced by reducing the inflow amount of the waste water, and the water flow test was performed under the condition 2 in which the BOD sludge load was 0.05 to 0.07 kg BOD / kg MLVSS / day. The substantial residence time was 10-12 hours. In the water flow test of Condition 2, the SVI of sludge in the continuous biological treatment tank increased with water flow and reached about 300 mL / g. When the sludge in the continuous biological treatment tank was observed with a microscope, no granules were found in the sludge. This is probably because the granule collapsed.

  Next, a water flow test was performed under the condition 3 in which the wastewater inflow amount was increased and the BOD sludge load was 0.12 to 0.18 kg BOD / kg MLVSS / day. The substantial residence time was about 8 to 10 hours. In the water flow test of Condition 3, the SVI of sludge in the continuous biological treatment tank rapidly decreased, and the SVI decreased to 100 mL / g in 15 days, and finally decreased to 60 mL / g. From this result, it can be said that the granular sludge is suppressed from being collapsed and the granular sludge having good sedimentation properties is maintained in the biological treatment tank.

  Next, while maintaining the BOD sludge load, a water flow test was performed under the condition 4 in which the residence time was 10 to 12 hours by dropping the sludge circulation flow rate. In the water flow test under condition 4, the SVI value of the sludge in the continuous biological treatment tank showed an upward trend, but it was stable at about 120 mL / g, and the granular sludge having relatively good sedimentation was maintained. It was done.

Next, when a water flow test was conducted under the condition 5 with a BOD sludge load of about 0.08 to 0.1 kg BOD / kg MLVSS / day and a residence time of 5 to 8 hours, the SVI tends to decrease to 65 mL / g. It dropped to. During this period, an attempt was made to increase the sludge concentration and increase the load with the improvement of sedimentation. As a result, MLSS increased to 4500 mg / L, and BOD volume load increased to 0.4 kg BOD / m ³ / day.

Next, when a water flow test was conducted under conditions 6 in which MLSS was 4500 mg / L and BOD volumetric load was 0.4 kg BOD / m ³ / day, SVI could be stably operated while maintaining 90 mL / g. did it.

  FIG. 9 is a diagram showing the particle size distribution of seed sludge, granular sludge formed in a semi-batch biological treatment tank, and sludge in a continuous biological treatment tank under Condition 6. The seed sludge has an average particle size of about 80 μm, and the granular sludge formed in the semi-batch biological treatment tank was sludge having a particle size of 300 μm or more. Moreover, although the sludge in a continuous-type biological treatment tank in the conditions 6 has the sludge which has a particle size of about 80 micrometers, the sludge which has a particle size of about 300-500 micrometers was also confirmed. That is, it is considered that the granular sludge has a large particle size in the continuous biological treatment tank.

  During the water flow period of Conditions 1 to 6, the quality of the final treated water was 5 mg / L or less in BOD and 10 mg / L or less in TN concentration.

(Comparative example)
The water flow test was conducted under the condition that no granules were supplied from the semi-batch biological treatment tank to the continuous biological treatment tank. As the seed sludge, activated sludge collected from the sewage treatment plant was used in the same manner as in the example. As the properties of the seed sludge, SVI was 180 mL / g. Table 2 shows each condition in the water flow test (MLSS in the continuous biological treatment tank, BOD sludge load and BOD volume load in the continuous biological treatment tank, substantial residence time (including the circulation flow rate from the solid-liquid separation tank) Residence time)), and SVI values of sludge after 20 days after changing to each condition are summarized.

  First, a water flow test was performed under the condition 7 with a BOD sludge load of 0.06 to 0.08 kg BOD / kg MLVSS / day. As a result, the sedimentation property of the seed sludge gradually deteriorated and increased to 250 mL / g as SVI.

  Next, when a water flow test was conducted under the condition 8 in which the BOD sludge load was about 0.12 to 0.16 kg BOD / kg MLVSS / day, the sedimentation property showed an improvement trend, but it stagnated at 200 mL / g.

  Next, a water flow test was conducted under the condition 9 in which the BOD sludge load was about 0.08 to 0.1 kg BOD / kg MLVSS / day, but the sedimentation property was not changed and remained at 200 mL / g.

  In any period of conditions 7 to 9, the sedimentation property was not greatly improved. Therefore, the processing amount could not be increased by increasing the MLSS concentration.

  From the results of Examples and Comparative Examples, in a system for supplying granular sludge having a particle size of 200 μm or more to a continuous biological treatment tank, the value of BOD sludge load is 0.08 to 0.2 kg BOD / kg MLVSS / day. By operating in this way, it can be said that MLSS is 4000 mg / L or more and a high processing speed can be obtained while maintaining good sedimentation by suppressing the collapse of the granular sludge.

1-6 Wastewater treatment equipment, 10, 10a, 10b, 10c Continuous biological treatment tank, 10d Anoxic tank, 10e Aeration tank, 10f Anaerobic tank, 12 Granule formation tank or semi-batch biological treatment tank, 12a Drainage inlet 12b treated water outlet, 12c sludge outlet, 12d treated water outlet, 14 solid-liquid separation tank, 15 circulation line, 16 wastewater storage tank, 17 semi-batch biological treatment tank, 20a, 20b, 20c wastewater inflow line, 22a, 22b treated water discharge line, 24 sludge return line, 26 sludge discharge line, 28 biological sludge supply line, 30 first drainage inflow pump, 31 drainage inflow pump, 32 second drainage inflow pump, 34 treated water discharge pump, 36 sludge supply Pump, 38 Sludge return pump, 40, 44, 46, 60 Valve, 48 Stirrer, 50 Air pump, 52 Air diffuser, 58 Sludge Management water supply line.

Claims (7)

A continuous biological treatment process in which the wastewater is biologically treated with biological sludge while continuously flowing the wastewater into the continuous biological treatment tank;
A sludge supply step of supplying granular sludge having a particle size of 200 μm or more to the continuous biological treatment tank,
The waste water treatment method, wherein a BOD sludge load of the continuous biological treatment tank in the continuous biological treatment step is in a range of 0.08 to 0.2 kg BOD / kg MLVSS / day.   The waste water treatment method according to claim 1, wherein the continuous biological treatment tank is composed of a plurality of reaction tanks. Biological sludge is solid-liquid separated from the biological treatment liquid treated in the continuous biological treatment step, and the solid sludge separated biological sludge is returned to the continuous biological treatment tank.
Of the continuous biological treatment tank obtained from the sum of the flow rate of the wastewater flowing into the continuous biological treatment tank and the flow rate of the biological sludge returned to the continuous biological treatment tank and the volume of the continuous biological treatment tank. The waste water treatment method according to claim 1 or 2, wherein the hydraulic residence time is in the range of 5 hours to 10 hours.   An inflow process for introducing wastewater, a biological treatment process for biologically treating the wastewater with biological sludge, a sedimentation process for sedimenting the biological sludge, and a discharge process for discharging treated water are repeated in a semi-batch biological treatment tank, 2. A semi-batch biological treatment process for forming granular sludge, wherein the granule sludge in the sludge supply process is a granular sludge formed in the semi-batch biological treatment process. The waste water treatment method of any one of -3.   The treated water discharge port of the semi-batch type reaction tank is provided above the drainage inlet, and the treated water is introduced into the semibatch type reaction tank from the drainage inlet, thereby allowing the treated water to flow into the treated water discharge port. The wastewater treatment method according to claim 4, wherein the wastewater treatment method is performed.   6. The inflow process of the semi-batch biological treatment process, wherein a part of waste water supplied into the continuous biological treatment tank is allowed to flow into the semi-batch biological treatment tank. The described waste water treatment method. A continuous biological treatment tank for biologically treating the wastewater with biological sludge while allowing the wastewater to flow continuously;
A sludge supply means for supplying granular sludge having a particle size of 200 μm or more to the continuous biological treatment tank,
The BOD sludge load of the continuous biological treatment tank is in the range of 0.08 to 0.2 kg BOD / kg MLVSS / day.