JP6548937B2 - Waste water treatment method and waste water treatment apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a technique of waste water treatment and a waste water treatment apparatus.

As a method of biologically treating waste water containing organic matter and the like, an activated sludge method using an aggregate of microorganisms called floc (biological sludge) has been used. However, in the activated sludge method, when separating floc and treated water in the settling tank, the settling speed of the floc may be slow and the surface area of the settling tank must be very large. Moreover, the treatment rate of the activated sludge method depends on the sludge concentration in the tank, and the treatment rate can be increased by increasing the sludge concentration, but the sludge concentration is from 1500 mg / L to at most 5000 mg / L. When it is about L and it is going to increase more than that, solid-liquid separation in a sedimentation tank becomes difficult, and it may become impossible to maintain a process. Therefore, the BOD treatment rate per tank volume of 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 gathered and granulated. Granules have a very high sedimentation rate, and microorganisms are densely collected. Therefore, the sludge concentration in the treatment tank can be increased, and high-speed treatment of drainage can be realized. However, anaerobic biological treatment has problems such as limited drainage species to be treated compared with aerobic treatment (activated sludge method) and the necessity of maintaining treated water temperature at 30 to 35 ° C. May have. In addition, in the case of anaerobic biological treatment alone, the quality of treated water is poor, and it may be necessary to separately carry out aerobic treatment such as the activated sludge method when discharged to a river or the like.

  In recent years, treatment is carried out using a semi-batch treatment apparatus that intermittently discharges wastewater into the reaction tank, and further shortening of settling time of biological sludge is not limited to anaerobic biological sludge, and even aerobic biological sludge can be granulated. It has become clear that it is possible to form an activated biological sludge (hereinafter sometimes referred to as granular sludge) (see, for example, Patent Documents 1 to 4). In addition, in semi-batch type treatment equipment, generally, (1) inflow of drainage, (2) biological treatment of drainage, (3) sedimentation of biological sludge, (4) discharge of treated water in one reaction tank 4 The process is carried out by going through two steps.

  As mentioned above, high-speed treatment can be achieved by granulating biological sludge, but when semi-batch treatment equipment is used for large-scale drainage treatment equipment such as sewage treatment, for example, a huge drainage storage tank You may have to set up

Therefore, it is equipped with a continuous biological treatment device that allows wastewater to flow continuously and treated, and a semi-batch biological treatment tank that produces aerobic granular sludge, and aerobic granular sludge is treated from the semi-batch biological treatment tank. There has been proposed a treatment device for granulating biological sludge in a continuous biological treatment device by supplying the continuous biological treatment device (see, for example, Patent Documents 5 and 6). According to the apparatuses of Patent Documents 5 and 6, the sedimentation tank and the reaction tank can be miniaturized, and the BOD treatment rate per tank volume can be 0.4 to 1.6 kg / m ³ / day depending on the raw water concentration. It is possible.

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

  By the way, when it is going to draw out granular sludge generated in a semi-batch type biological treatment tank using a pump and supply it to a continuous biological treatment apparatus, stress such as shear force is applied to granular sludge, and continuous biological treatment Granule sludge may be destroyed before entering the device.

  Therefore, an object of the present invention is a waste water treatment method and waste water treatment capable of suppressing destruction of granular sludge when supplying granular sludge generated in a semi-batch biological treatment tank to a continuous biological treatment apparatus It is providing a device.

  The waste water treatment method of the present invention comprises a continuous biological treatment process of biological treatment of the waste water with biological sludge while continuously flowing the waste water into the continuous biological treatment tank, an inflow process of flowing the waste water, and aeration of the waste water. While repeating the biological treatment process of biological treatment with biological sludge, the sedimentation process of settling the biological sludge, the discharge process of discharging the treated water in the semi-batch biological treatment tank to form granular sludge A batch type biological treatment process, and a sludge supply process for supplying the granular sludge in the semi-batch biological treatment tank to the continuous biological treatment tank, in the sludge supply process, the semi-batch biological treatment At the liquid level in the tank, after the inflow process, the amount of granular sludge in the region from the liquid level before the biological treatment process to the liquid level increased by aeration in the biological treatment process Some and also a waste water treatment method for supplying the continuous biological treatment tank by gravity flow.

  In the waste water treatment method, it is preferable to adjust the ratio of the number of the sludge supply steps to the number of the biological treatment steps so that the MLSS concentration in the semi-batch biological treatment tank becomes a preset value. .

  In the waste water treatment method, it is preferable to adjust the supply time of the granular sludge in the sludge supply process so that the MLSS concentration in the semi-batch biological treatment tank becomes a preset value.

  In the waste water treatment method, it is preferable to adjust the aeration amount in the biological treatment process during the sludge supply process such that the MLSS concentration in the semi-batch biological treatment tank becomes a preset value. .

  In the waste water treatment method, the position of granular sludge withdrawn from the semi-batch biological treatment tank is set between the regions so that the MLSS concentration in the semi-batch biological treatment tank becomes a preset value. It is preferable to adjust.

  Moreover, in the said waste water treatment method, it is preferable to implement the said discharge process, implementing the said inflow process in the said semi-batch type biological treatment process.

  In the waste water treatment apparatus according to the present invention, a continuous biological treatment tank for biological treatment of the waste water with biological sludge while flowing the waste water continuously, an inflow process for flowing the waste water, aeration of the waste water, A semi-batch type biological treatment tank for forming granular sludge, repeating the biological treatment process of biological treatment with sludge, the sedimentation process of settling the biological sludge, and the discharge process of discharging treated water, and the semi-batch biological organism And sludge supply means for supplying the granular sludge in the treatment tank to the continuous biological treatment tank, wherein the sludge supply means is provided after the inflow process at a liquid level in the semi-batch biological treatment tank. The continuous biological treatment under natural flow of at least a portion of the granular sludge in the region from the liquid level before the biological treatment step to the liquid level raised by aeration in the biological treatment step It is a flow path of natural flow method for feeding the.

  ADVANTAGE OF THE INVENTION According to this invention, when supplying the granular sludge produced | generated by the semi-batch-type biological treatment tank to a continuous-type biological treatment apparatus, it becomes possible to suppress destruction of granular sludge.

It is a schematic diagram which shows an example of a structure of the waste-water-treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows an example of a structure of the semi-batch type biological treatment tank used with the waste-water-treatment apparatus of FIG. It is a schematic diagram which shows another example of a structure of the semi-batch type biological treatment tank used by this embodiment. It is a schematic diagram which shows another example of a structure of the waste-water-treatment apparatus which concerns on 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 waste-water-treatment apparatus shown in FIG.

  Hereinafter, embodiments of the present invention will be described. In addition, this embodiment is an example which implements this invention, Comprising: This invention is not limited to this embodiment.

  FIG. 1: is a schematic diagram which shows an example of a structure of the waste-water-treatment apparatus which concerns on this embodiment. The waste water treatment apparatus 1 shown in FIG. 1 includes a continuous biological treatment tank 10, a semi-batch biological treatment tank 12, a solid-liquid separation tank 14, and a waste water storage tank 16. In the present specification, "continuous" is a system for batch system, and as in semi-batch system, inflow of wastewater, biological treatment, sedimentation of sludge, discharge of treated water is repeated in one reaction tank It is distinguished from semi-batch processing. Further, in the present embodiment, the continuous system is not limited to a system in which the reaction tank is continuously charged with drainage and operated, and a reaction using a pump such as a diaphragm pump using a principle such as reciprocating motion The system may be operated by supplying drainage to the tank for operation, etc. The original water tank is installed at the front stage of the reaction tank, and the operation-stop of the pump is controlled according to the water level of the original water tank (when the water level is high) The pump may be operated, and the pump may be stopped when the water level is low, and the reaction tank may be a simulated continuous water flow system or the like for supplying drainage.

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

  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. Further, 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 semi-batch type biological treatment tank 12. Further, 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 semi-batch type biological treatment 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 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 which shows an example of a structure of the semi-batch-type biological treatment tank used with the waste-water-treatment apparatus of FIG. In the semi-batch type biological treatment tank 12 shown in FIG. 2, (1) inflow of waste water, (2) biological treatment of waste water by biological sludge while aeration of waste water, (3) sedimentation of biological sludge, (4) treated water Granule sludge is formed by repeating four processes such as The semi-batch type biological treatment tank 12 shown in FIG. 2 includes an agitator 48, an air pump 50, and a diffuser 52. The aeration device 52 is connected to the air pump 50, and the air supplied from the air pump 50 is supplied into the tank through the aeration device 52. Further, the stirring device 48 has a structure in which a shaft attached to the motor is rotated by driving of the motor, and a stirring blade attached to the tip of the shaft is rotated along with the rotation of the shaft. In addition, the stirring apparatus 48 is not restrict | limited to the said structure. The semi-batch type biological treatment tank 12 is provided with a drainage inlet 12a and a treated water outlet 12b, a drainage inlet line 20b is connected to the drainage inlet 12a, and a treated water drainage line 22b is connected to the treated water outlet 12b. There is. Moreover, the sludge outlet 12 c is provided in the semi-batch type biological treatment tank 12. The sludge outlet 12c is disposed at the liquid level A in the semi-batch type biological treatment tank 12, and the biological sludge supply line 28 is connected to the sludge outlet 12c. Here, at the liquid level A in the semi-batch type biological treatment tank 12, after the inflow of the drainage of the above (1), the aeration of the drainage of the above (2) is started. (The process of (1) is started). Further, the liquid level B in the semi-batch type biological treatment tank 12 shown in FIG. 2 is the liquid level raised by the aeration in the biological treatment of the above (2).

  The drainage inflow line 20 b and the second drainage inflow pump 32 shown in FIG. 2 function as a semi-batch side drainage supply device that intermittently supplies the drainage to the semi-batch biological treatment tank 12. In the present embodiment, intermittent supply of drainage is performed by operation and stop of the second drainage inflow pump 32, but 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. It is good.

  The treated water discharge line 22 b and the treated water discharge pump 34 shown 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 the present embodiment, the treated water discharge line 22 b 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 or the treated water discharge line 22 a It is good also as composition

  The biological sludge supply line 28 shown in FIG. 2 is a natural flow of supplying granular sludge in the region from the liquid level A to the liquid level B in the semi-batch biological treatment tank 12 to the continuous biological treatment tank 10 under natural flow. It is a downflow piping. That is, the biological sludge supply line 28 is not provided with a pump for forcibly feeding granular sludge. And, in order to make the biological sludge supply line 28 the above-mentioned natural flow down method, the liquid level A in the semi-batch type biological treatment tank 12 is equal to or higher than the liquid level in the continuous biological treatment tank 10. The height position of each biological treatment tank may be adjusted or the inflow of drainage may be adjusted.

  In the present embodiment, at least a part of the granular sludge in the region from the liquid level A to the liquid level B in the semi-batch biological treatment tank 12 may be supplied to the continuous biological treatment tank under natural flow. Therefore, the sludge outlet 12c provided in the semi-batch biological treatment tank 12 is disposed in the region from the liquid level A to the liquid level B in the semi-batch biological treatment tank 12, and the biological sludge is supplied to the sludge outlet 12c. It is sufficient if the line 28 is connected.

  The drainage inflow line 20 a and the first drainage inflow pump 30 shown in FIG. 1 function as a continuous side drainage supply device that supplies drainage to the continuous biological treatment tank 10. Further, the continuous biological treatment tank 10 shown in FIG. 1 continuously flows, for example, under aerobic conditions and in the presence of biological sludge such as granules supplied from the semi-batch biological treatment tank 12. It is the biological treatment of the waste water (for example, the organic matter in the waste water is oxidized to carbon dioxide).

  The solid-liquid separation tank 14 of the present embodiment is a separation device for separating water containing biological sludge into biological sludge and treated water, and for example, separation devices such as sedimentation separation, pressure flotation, filtration, membrane separation, etc. Can be mentioned.

  An example of operation | movement of the waste water treatment apparatus 1 of this embodiment is demonstrated.

  In the drainage storage tank 16 shown in FIG. 1, drainage to be treated is stored. Waste water to be treated includes, for example, waste water from food processing plants, chemical plants, semiconductor plants, machine plants, sewage, manure, river water and the like. In addition, the waste water generally contains biodegradable organic matter and the like. In addition, when the organic matter of biodegradability is contained in the waste water, it is desirable to perform removal by physicochemical treatment such as flotation separation, flocculating pressure levitation device, adsorption device in advance.

  First, the first drainage inflow pump 30 is operated, and the wastewater to be treated in the drainage storage tank 16 is supplied to the continuous biological treatment tank 10 from the drainage inflow line 20 a. In the continuous biological treatment tank 10, biological treatment of waste water with biological sludge is performed under aerobic conditions. The treated water treated in the continuous biological treatment tank 10 is supplied from the drainage inflow line 20c to the solid-liquid separation tank 14 to separate the biological sludge from the treated water. The sludge return pump 38 is operated to return the solid-liquid separated sludge from the sludge return line 24 to the continuous biological treatment tank 10. Also, the valve 40 is opened to discharge the sludge solid-liquid separated from the sludge discharge line 26 out of the system. The treated water in the solid-liquid separation tank 14 is also discharged out of the system from the treated water discharge line 22a.

  When the semi-batch type biological treatment tank 12 is operated, the second drainage inflow pump 32 is operated to supply the wastewater to be treated in the drainage storage tank 16 from the drainage inflow line 20 b to the semi-batch biological treatment tank 12 ( (1) Inflow of drainage). The waste water is introduced into the semi-batch type biological treatment tank 12 until a predetermined amount is reached (the liquid level A shown in FIG. 2), and the second waste water inflow pump 32 is stopped. Next, the air pump 50 is operated, air is introduced from the air diffuser 52, and the supply of air into the semi-batch biological treatment tank 12 is started, and the agitator 48 is operated, the semi-batch biological treatment tank The biological treatment of the drainage is performed by stirring the drainage in 12 ((2) biological treatment of the drainage). In the biological treatment process for wastewater, biological sludge such as granular sludge in the semi-batch biological treatment tank 12 is dispersed, and the liquid level in the semi-batch biological treatment tank 12 is aerated as shown in FIG. It rises to the liquid level B shown in.

  After the biological treatment process of drainage is performed for a predetermined time, the air pump 50 and the stirring device 48 are stopped, and the biological treatment process is finished. 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 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 biological treatment tank 12 is discharged from the treated water discharge line 22 b ((4) discharge of treated water), and the biological organisms are continuously treated from the treated water discharge line 22 b. It supplies to the processing tank 10. And by repeating the process of (1)-(4), the biological sludge in semi-batch-type biological treatment tank 12 is granulated, and granular sludge is formed.

  Granule sludge formed in semi-batch type biological treatment tank 12 is sludge which self-granulation advanced, for example, the average particle diameter of sludge is 0.2 mm or more, or SVI5 which is a sedimentation index is 80 mL It is biological sludge below / g. Further, in the present embodiment, whether or not granular sludge is formed is determined, for example, by measuring SVI, which is a sedimentation index of sludge. Specifically, the SVI value is periodically measured by the 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 5 minutes sedimentation is equal to or less than a predetermined value (for example, 80 mL) It is possible to judge that granular sludge was formed at the stage when it became / g or less. Alternatively, the particle size distribution of the sludge in the semi-batch type biological treatment tank 12 is measured, and it is judged that the granular sludge is formed when the average particle size becomes equal to or more than a predetermined value (for example, 0.2 mm or more) (It can be judged that the lower the SVI value, the larger the average particle size, the better the granular sludge).

  In this embodiment, when granular sludge formed in the semi-batch biological treatment tank 12 is supplied to the continuous biological treatment tank 10, the liquid in the semi-batch biological treatment tank 12 is aerated by the biological treatment process of the wastewater. When the surface level rises to the liquid level B shown in FIG. 2, the valve 36 provided in the biological sludge supply line 28 is opened to allow the liquid level A in the semi-batch type biological treatment tank 12 to be liquid. At least a part of the granular sludge in the region up to the face B is supplied from the biological sludge supply line 28 to the continuous biological treatment tank 10 under natural flow. The biological sludge supply line 28 passes not only the granular sludge but also the treated water in the above region, the biological sludge which is not granulated, and the like. In addition, as long as at least a part of granular sludge in the above area is supplied to the continuous biological treatment tank 10 under natural flow, it is not necessary to install the valve 36, but the supply timing and amount of granular sludge are adjusted. It is preferable to install the valve 36 in that it can be done.

  As described above, in the present embodiment, the granular sludge in the semi-batch biological treatment tank 12 is supplied to the continuous biological treatment tank 10 by natural flow, compared to the case where it is forcibly supplied by a pump, The stress such as shear force applied to the granules is relieved and the collapse of the granular sludge is suppressed. Moreover, in the present embodiment, since the granular sludge supplied to the continuous biological treatment tank 10 is the granular sludge in the region from the liquid level A to the liquid level B in the semi-batch biological treatment tank 12, It is suppressed that the MLSS concentration in the semi-batch type biological treatment tank 12 is significantly reduced, and stable granule sludge formation and waste water treatment become possible. In the case of granular sludge in the region from liquid level A to liquid level B in the semi-batch biological treatment tank 12, the semi-batch biological treatment tank 12 is installed at a position higher than the continuous biological treatment tank 10. Since it becomes possible to supply to the continuous biological treatment tank 10 under natural flow, the cost of assembling the apparatus can be reduced. In addition, it is difficult to grasp the sludge concentration of concentrated sludge when extracting sludge in the sedimentation state under natural flow in the tank, and there is a risk that concentrated sludge may easily be accumulated in piping or waterways. It is possible to easily control the supply amount of granular sludge by supplying the dispersed sludge in the biological treatment process where the concentration of sludge can be easily grasped as in the embodiment, and the piping and waterway It also makes it possible to reduce the risk of blocking. In addition, when granular sludge is supplied to the continuous biological treatment tank 10 under natural flow, granular sludge is very likely to settle and is likely to deposit in the piping or waterway, so there is a risk of clogging of the piping or waterway. By setting the supply point of granular sludge above the liquid level A, it is possible to make the water level difference to the continuous biological treatment tank 10, and it becomes possible to reduce the risk of clogging of piping and waterways.

  In the semi-batch type biological treatment tank 12 shown in FIG. 2, as long as the biological treatment process of waste water is performed as long as the valve 36 installed in the biological sludge supply line 28 is opened, the liquid level A to the liquid level B At least a portion of the granular sludge in the region up to is supplied to the continuous biological treatment tank 10 from the biological sludge supply line 28. And, when granular sludge in the above region is supplied to the continuous biological treatment tank 10 every time the biological treatment process of waste water is performed, the MLSS concentration in the semi-batch biological treatment tank 12 tends to decrease, and granular sludge is easily May affect the formation of waste water and the efficiency of wastewater treatment. Therefore, it is preferable to adjust the number of times the granular sludge is supplied from the biological sludge supply line 28 to the continuous biological treatment tank 10 so that the MLSS concentration in the semi-batch biological treatment tank 12 becomes a preset value. For example, when the MLSS concentration in the semi-batch biological treatment tank 12 falls below a predetermined value, the number of times of supplying granular sludge is from every biological treatment process of drainage to a ratio of once in multiple biological treatment processes of drainage. Preferably, the opening timing of the valve 36 installed in the biological sludge supply line 28 is adjusted.

  Alternatively, the time for supplying granular sludge from the biological sludge supply line 28 to the continuous biological treatment tank 10 may be adjusted so that the MLSS concentration in the semi-batch biological treatment tank 12 becomes a preset value. For example, when the MLSS concentration in the semi-batch biological treatment tank 12 falls below a predetermined value, the open time of the valve 36 installed in the biological sludge supply line 28 is shortened, etc. It is preferable to adjust the supply time of granular sludge.

  Alternatively, the aeration amount in the biological treatment process of waste water may be adjusted so that the MLSS concentration in the semi-batch biological treatment tank 12 becomes a preset value. When the aeration amount is increased, the liquid level B in the semi-batch biological treatment tank 12 becomes higher, so the amount of granular sludge discharged from the semi-batch biological treatment tank 12 increases and the aeration amount is decreased. Since the liquid level B in the semi-batch biological treatment tank 12 is lowered, the amount of granular sludge discharged from the semi-batch biological treatment tank 12 is reduced. For example, when the MLSS concentration in the semi-batch biological treatment tank 12 falls below a predetermined value, the amount of air supplied from the aeration device 52 is suppressed, and the granular sludge from the semi-batch biological treatment tank 12 is It is preferable to adjust the amount of emissions.

  Alternatively, the granule withdrawn from the semi-batch biological treatment tank 12 in the region from the liquid level A to the liquid level B so that the MLSS concentration in the semi-batch biological treatment tank 12 becomes a preset value. The position of the sludge may be adjusted. The details will be described below.

  FIG. 3 is a schematic view showing another example of the configuration of the semi-batch type biological treatment tank used in the present embodiment. In the semi-batch type biological treatment tank 13 shown in FIG. 3, the same components as those of the semi-batch type biological treatment tank 12 shown in FIG. In the semi-batch type biological treatment tank 13 shown in FIG. 3, a plurality of sludge outlets (13a, 13b) are provided in the region from the liquid level A to the liquid level B in the semi-batch type biological treatment tank 13. The biological sludge supply lines (29a, 29b) are connected to each. In the semi-batch type biological treatment tank 13 shown in FIG. 3, the treated water discharge line 22 b is omitted.

  In the semi-batch type biological treatment tank 13 shown in FIG. 3, when the valve 36a of the biological sludge supply line 29a is opened, granular sludge in the area from the sludge outlet 13a to the liquid level B is discharged, and the biological sludge supply line When the valve 36b of 29b is opened, granular sludge in the region from the sludge outlet 13b to the liquid level B is discharged. That is, when the valve 36b of the biological sludge supply line 29b connected to the sludge outlet 13b higher than the sludge outlet 13a is opened, the granular sludge is discharged more than when the valve 36a of the biological sludge supply line 29a is opened. The amount decreases. For example, when the MLSS concentration in the semi-batch biological treatment tank 13 falls below a predetermined value, the valve 36 a of the biological sludge supply line 29 a is closed and the valve 36 b of the biological sludge supply line 29 b is opened. It is preferable to adjust the amount of granular sludge discharged from the treatment tank 13.

  It is desirable that the MLSS concentration of the semi-batch biological treatment tank 12 be operated in the range of 2000 to 20000 mg / L. Adjustment of the MLSS concentration is as described above. In addition, in order to maintain the soundness (sedimentation, activity, etc.) of biological sludge, it is desirable to maintain appropriate sludge load, preferably in the range of 0.05 to 0.60 kg BOD / MLSS / day, more preferably It is desirable to withdraw granular sludge from the tank so as to be maintained in the range of 0.1 to 0.5 kg BOD / MLSS / day.

  In the formation of granular sludge in the semi-batch type biological treatment tank 12, it is desirable to appropriately control the settling time and the inflow rate of drainage per batch. The settling time for stopping agitation (including agitation by aeration) and settling sludge is calculated from the distance from the water surface to the bottom of the tank and the settling velocity of sludge, for example, between 4 minutes / m to 15 minutes / m It is preferably set, and more preferably set between 5 minutes / m and 10 minutes / m. The inflow rate of drainage (the ratio of influent water to the effective volume at the time of reaction) is, for example, preferably in the range of 20% to 120%, and more preferably in the range of 40% to 120%. The sludge repeatedly experiences a state in which the organic substance concentration to be treated is very high (immediately after the inflow process, in a state of satiation) and in a state where the organic substance concentration is very low (in the final stage of the biological treatment process, in a starvation state). Since it is thought that granulation will progress, it is better to take the drainage inflow rate as high as possible from the viewpoint of forming granular sludge, but on the other hand, the higher the drainage inflow rate, the more inflow pump Capacity increases and costs increase. Therefore, in terms of formation of granular sludge and cost reduction, the inflow rate of drainage is preferably in the range of 40% to 120%.

  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, pH adjustment is preferably performed using an acid or an alkali. When pH adjustment is carried out in the semi-batch type biological treatment tank 12, the pH adjustment is carried out in a state where the semi-batch type biological treatment tank 12 is stirred from the state where the semi-batch type biological treatment tank 12 is not stirred. 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 suitable for general biological treatment, and more preferably 1 mg / L or more.

  In the continuous biological treatment tank 10, the embodiment in which the biological treatment is performed by the standard activated sludge method in which organic matter or the like is treated has been described as an example, but is not limited thereto. For example, A2O (Anaerobic-Anoxic-Oxic) Nutrient removal systems (systems that install an anoxic treatment tank and an anaerobic treatment tank) such as A process (Process) and AO (Anaerobic-Oxic Process), oxidation ditch method, biological treatment by systems such as step flow type multistage activated sludge method It may be a device that In addition, it may be an apparatus that performs biological treatment in the presence of a carrier such as polyurethane, plastic, or resin.

  The continuous biological treatment tank 10 is preferably operated, for example, in the range of 2000 to 20000 mg / L of sludge concentration in the tank. Moreover, in order to maintain the soundness (sedimentation, activity, etc.) of biological sludge, the sludge load is preferably in the range of 0.05 to 0.6 kg BOD / MLSS / day, and 0.1 to 0.5 kg BOD More preferably, it is in the range of / MLSS / day.

  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. The dissolved oxygen (DO) in the continuous biological treatment tank 10 is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, which is suitable for general biological treatment.

  In the waste water treatment apparatus 1, although the form provided with the solid-liquid separation tank 14 was demonstrated to the example, the solid-liquid separation tank 14 does not necessarily need to be provided. However, the waste water treatment apparatus 1 is a solid-liquid separation tank that separates biological sludge from treated water discharged from the continuous biological treatment tank 10 in terms of, for example, circulating granular sludge to improve waste water treatment efficiency. And a sludge return line 24 for returning biological sludge (including granular sludge) discharged from the solid-liquid separation tank 14 to the continuous biological treatment tank 10.

  FIG. 4 is a schematic view showing another example of the configuration of the wastewater treatment device according to the present embodiment. In the waste water treatment apparatus 2 of FIG. 4, 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. In the drainage processing apparatus 2 shown in FIG. 4, the drainage inflow pump 31 and the valve 44 are provided in the drainage inflow line 20a, and the valve 46 is provided in the drainage 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 type biological treatment tank 15. Further, the waste water treatment apparatus 2 shown in FIG. 4 is provided with a sludge treated water supply line 58 for supplying treated water and granular sludge discharged from the semi-batch type biological treatment tank 15 to the continuous biological treatment tank 10. The sludge treatment water supply line 58 is provided with a third valve 60. The sludge treatment water supply line 58 has a function as a treated water supply device for supplying treated water discharged from the semi-batch type biological treatment tank 15 to the continuous biological treatment tank 10 and a granular sludge into the continuous biological treatment tank 10 It has a function as a biological sludge supply device to supply.

  FIG. 5: is a schematic diagram which shows an example of a structure of the semi-batch-type biological treatment tank used for the waste-water-treatment apparatus 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. In the semi-batch type biological treatment tank 15 shown in FIG. 5, a sludge treated water outlet 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 sludge treated water outlet 12d. There is. The other end of the sludge treatment water supply line 58 is connected to the continuous biological treatment tank 10. In the present embodiment, the sludge treated water outlet 12 d may be disposed in the region from the liquid level A to the liquid level B, and the sludge treated water supply line 58 may be connected to the sludge treated water outlet 12 d. Moreover, in the semi-batch type biological treatment tank 15 shown in FIG. 4, the drainage inlet 12a into which the drainage flows is provided at a position lower than the sludge treated water outlet 12d.

  In the semi-batch type biological treatment tank 15 shown in FIG. 5, the inflow of drainage and the discharge of treated water are simultaneously performed. That is, steps such as inflow of drainage 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 waste water treatment apparatus 2 shown in FIG.

  First, the drainage inflow pump 31 is operated, the valve 44 is opened, and the drainage to be treated in the drainage storage tank 16 is continuously supplied to the continuous biological treatment tank 10 from the drainage inflow line 20 a. After biological treatment of waste water is performed in the continuous biological treatment tank 10, treated water is supplied to the solid-liquid separation tank 14 from the waste water inflow line 20c. Then, when the semi-batch type biological treatment tank 15 is operated, the valve 46 and the third valve 60 are opened, and the waste water is supplied from the drainage inflow line 20 b to the semi-batch type biological treatment tank 15. The treated water in the treatment tank 15 is supplied to the continuous biological treatment tank 10 from the sludge treated water supply line 58 (inflow of drainage / discharge of treated water). After supplying a predetermined amount of treated water to the continuous biological treatment tank 10, the valve 46 and the third valve 60 are closed. At this time, the opening and closing of the valve 46 and the third valve 60 are adjusted so that the liquid level of the waste water in the semi-batch type biological treatment tank 15 becomes the liquid level A shown in FIG. Next, the stirring device 48 and the air pump 50 are operated to start the supply of air into the semi-batch biological treatment tank 15 to perform biological treatment of the drainage (biological treatment process). At this time, the liquid level in the semi-batch type biological treatment tank 15 is raised to the liquid level B shown in FIG. 5 by aeration, so by opening the third valve 60, the semi-batch type biological treatment is performed. Granule sludge in the region from the liquid level A to the liquid level B in the tank 15 can be supplied from the sludge treatment water supply line 58 to the continuous biological treatment tank 10 under natural flow.

  After a predetermined time has elapsed, the operation of the air pump 50 is stopped to stop the supply of air, and the stirring device 48 is stopped to terminate the biological treatment. After completion of the biological treatment, the biological sludge in the semi-batch biological treatment tank 15 is allowed to settle for a predetermined time, and separated into biological sludge and treated water in the semi-batch biological treatment tank 15 (sedimentation of biological sludge). And it transfers to the discharge process of the inflow / treated water of drainage again.

  In the present embodiment, the drainage inlet 12a provided in the semi-batch biological treatment tank 15 is disposed at a position lower than the sludge treated water outlet 12d, so the wastewater flowing into the semi-batch biological treatment tank 15 is subjected to biological treatment It is suppressed that it discharges | emits from the semi-batch-type biological treatment tank 15 (short-cut of drainage). As a result, it is possible to efficiently form granular sludge in the semi-batch type biological treatment tank 15. In addition, the treated water in the semi-batch type biological treatment tank 15 is discharged in a form that is pushed up by the inflowing wastewater, so it is possible to actively use biological sludge (such as non-granulated sludge) with low settling ability. It can be discharged outside. As a result, biological sludge having high sedimentation property remains in the semi-batch type biological treatment tank 15, so that granular sludge can be formed more efficiently.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

In the example, treatment of sewage was carried out under the following conditions using a semi-batch type biological treatment tank shown in FIG. In the example, a sludge treatment water discharge line is installed at a height of 3000 mm from the bottom of the tank using a semi-batch type biological treatment tank of 683 mm wide × 683 mm long × 4000 mm high, and the bottom of the tank (100 mm higher than the bottom Installed a drainage inflow line (tank effective volume: 1.4 m ³ ). Two storage tanks (storage tanks 1 and 2) were installed on the discharge side of the sludge treatment water discharge line. Sewage was used for the supplied drainage.

The process (process 1) of discharging the treated water in the tank from the sludge treated water discharge line to the storage tank 1 was performed for 90 minutes while sewage was introduced into the semi-batch type biological treatment tank from the drainage inflow line. The amount of sewage introduced and the amount of treated water discharged were adjusted so that the liquid level of the waste water in the semi-batch type biological treatment tank after the process became a height of 3000 mm from the bottom of the tank. Next, air was supplied at a feed rate of 10 m ³ / h by an aeration apparatus installed in a semi-batch biological treatment tank. Due to the air supply, the liquid level of the drainage in the semi-batch type biological treatment tank is raised, and the granular sludge (including treated water) is supplied to the storage tank 2 under natural flow from the sludge treated water discharge line. did. After conducting the biological treatment process of the waste water by air supply for 240 minutes (after process 2), the aeration apparatus was stopped and the sedimentation process of the sludge in a tank was performed for 30 minutes (process 3). The cycle of steps 1 to 3 was repeated (4 cycles / day).

  The granules (including the treated water) accumulated in the reservoir 2 in one cycle of steps 1 to 3 were about 36 liters. In addition, about 10% of the amount of sludge in the semi-batch biological treatment tank was withdrawn from the semi-batch biological treatment tank in one day.

  Moreover, when the particle size distribution of the granular sludge in a semi-batch type biological treatment tank and the granular sludge in the storage tank 2 was measured with a laser diffraction type particle size distribution meter, both had an average diameter of about 200 micrometers. That is, it was confirmed that the granule sludge was not broken when the granules in the semi-batch type biological treatment tank were supplied to the storage tank.

1, 2 Wastewater treatment equipment, 10 Continuous biological treatment tank, 12, 13, 15 semi-batch biological treatment tank, 12a drainage inlet, 12b treated water outlet, 12c, 13a, 13b sludge outlet, 12d sludge treated water outlet, 14 Solid-liquid separation tank, 16 drainage storage tank, 20a, 20b, 20c drainage inflow line, 22a, 22b treated water discharge line, 24 sludge return line, 26 sludge discharge line, 28, 29a, 29b biological sludge supply line, 30 1st Drainage inflow pump, 31 drainage inflow pump, 32 second drainage inflow pump, 34 treated water discharge pump, 36, 36a, 36b, 40, 44, 46, 60 valves, 38 sludge return pump, 48 stirring device, 50 air pump, 52 Aeration system, 58 sludge treatment water supply line.

Claims (7)

A continuous biological treatment process in which the waste water is treated with biological sludge while continuously flowing the waste water into the continuous biological treatment tank;
The semi-batch type biological treatment tank, inflow process of inflowing waste water, biological treatment process of biological treatment with biological sludge while aeration of the waste water, sedimentation process of settling the biological sludge, discharge process of discharging treated water A semi-batch biological treatment process which is repeated to form granular sludge,
A sludge supply step of supplying the granular sludge in the semi-batch biological treatment tank to the continuous biological treatment tank;
In the sludge supply step, after the inflow step at the liquid level in the semi-batch biological treatment tank, from the liquid level before the biological treatment step to the liquid level increased by aeration in the biological treatment step The waste water treatment method characterized by supplying at least one copy of said granular sludge of a field to said continuous biological treatment tank under natural flow.   The method is characterized in that the ratio of the number of sludge supply steps to the number of biological treatment steps is adjusted so that the MLSS concentration in the semi-batch type biological treatment tank becomes a preset value. The wastewater treatment method described in.   The waste water treatment method according to claim 1, wherein the supply time of the granular sludge in the sludge supply step is adjusted so that the MLSS concentration in the semi-batch type biological treatment tank becomes a preset value. .   The said aeration amount in the said biological treatment process is adjusted during the said sludge supply process, so that the MLSS density | concentration in the said semi-batch-type biological treatment tank becomes a preset value, The said Claim 1 characterized by the above-mentioned. Wastewater treatment method.   The position of granular sludge withdrawn from the semi-batch biological treatment tank is adjusted between the regions so that the MLSS concentration in the semi-batch biological treatment tank becomes a preset value. The waste-water-treatment method of claim 1.   The waste water treatment method according to any one of claims 1 to 5, wherein in the semi-batch type biological treatment step, the discharging step is performed while the inflow step is performed. A continuous biological treatment tank for biological treatment of the waste water with biological sludge while continuously discharging the waste water;
The granular sludge is repeatedly performed by an inflow process of inflowing drainage, a biological treatment process of biological treatment with biological sludge while aeration the drainage, a sedimentation process of settling the biological sludge, and a discharge process of discharging treated water. A semi-batch biological treatment tank to be formed,
Sludge supplying means for supplying the granular sludge in the semi-batch biological treatment tank to the continuous biological treatment tank;
The sludge supply means is from the liquid level before the biological treatment process to the liquid level raised by aeration in the biological treatment process after the inflow process at the liquid level in the semi-batch biological treatment tank. It is a natural flow down type flow path which supplies at least one copy of said granular sludge of a field to said continuous biological treatment tank under natural flow, The waste water treatment equipment characterized by the above-mentioned.

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