JP2020179340A - Operational method of organic wastewater treatment facility and organic wastewater treatment facility - Google Patents

Abstract

To provide an operational method of an organic wastewater treatment facility and the organic wastewater treatment facility, capable of reducing water content of an excess sludge in biological treatment for volume reduction, thereby reducing costs needed for final disposal of the excess sludge.SOLUTION: The operational method of the organic wastewater treatment facility containing a first biological treatment tank 1 to which an organic waste water flows and a second biological treatment tank 2 installed with a membrane separation apparatus 7 includes: a membrane separation step in which a tank liquid in the first biological treatment tank 1 is supplied to the second biological treatment tank 2, the tank liquid in the second biological treatment tank 2 is circulated to the first biological treatment tank 1, the tank liquid in the second biological treatment tank 2 is subjected to membrane separation with the membrane separation apparatus 7 to obtain a treated water, and the tank liquid in the second biological treatment tank 2 is discharged; and a membrane concentration step in which the tank liquid in the second biological treatment tank 2 is not circulated to the first biological treatment tank 1, the tank liquid in the second biological treatment tank 2 is subjected to membrane separation in the membrane separation apparatus 7 to obtain a treated water, and the tank liquid in the second biological treatment tank 2 is not discharged.SELECTED DRAWING: Figure 1

Description

The present invention relates to an operation method of an organic wastewater treatment facility and an organic wastewater treatment facility, and relates to a technique for disposing of excess sludge generated in the facility for treating organic wastewater.

Conventionally, there is an oxidation ditch method as one of the treatment methods for organic wastewater. For example, organic wastewater is stored for a long time in a water tank having a shape that circulates in a shallow water channel with organic wastewater of 2.5 m or less, and the organic wastewater is treated under aerobic conditions by stirring the water surface. It is a thing. Water tanks are used in small facilities because they require a large installation area for the amount of water flowing into the treatment facility.

Further, as a method for treating organic wastewater, there is a membrane separation activated sludge treatment method using a membrane separation device, and for example, there is one described in Patent Document 1.

This involves stirring and mixing the water to be treated and the mixed solution that is circulated and returned from the nitrification tank in the subsequent stage in an oxygen-free state in the denitrification tank in the first stage. Then, the mixed solution is suction-filtered by a membrane separation device immersed in a nitrification tank to obtain treated water.

Japanese Patent Application Laid-Open No. 07-68294

In organic wastewater treatment, microorganisms increase over time, so it is necessary to extract and dispose of excess microorganisms as excess sludge. When the excess sludge in the biological treatment tank is discharged and disposed of as it is, the capacity is too large and the treatment cost for transportation becomes high.

In order to reduce the capacity of excess sludge, it is common to discharge and dispose of excess sludge in a sludge treatment facility (dehydration facility) with the water content reduced to about 83%. However, if a sludge treatment facility is installed in a very small-scale wastewater treatment facility with a treatment capacity of several hundred m3 / day, the ratio of the construction cost to the amount of surplus sludge generated will increase, resulting in inefficient capital investment.

For this reason, in small-scale treatment facilities that perform oxidation ditch, it is common to carry out a concentration process that performs gravity precipitation concentration to reduce the volume of excess sludge to some extent without using a dehydration facility. is there. However, even if gravity sedimentation is concentrated, excess sludge can be concentrated only to a water content of about 99%, and as a result, the cost of carrying out vacuum for discharge and disposal increases. In addition, there is a problem that sludge putrefaction and odor are generated in the concentration process and the storage process.

The present invention solves the above problems, and is capable of reducing the water content of excess sludge in biological treatment to reduce its volume, and reducing the cost required for discharging and disposing of excess sludge. The purpose is to provide wastewater treatment equipment.

In order to solve the above problems, the method of operating the organic waste treatment facility of the present invention is an organic having a first biological treatment tank into which organic wastewater flows and a second biological treatment tank equipped with a membrane separation device. A method of operating a sex wastewater treatment facility, in which the liquid in the first biological treatment tank is supplied to the second biological treatment tank, and the liquid in the second biological treatment tank is supplied to the first biological treatment tank. A membrane separation step of circulating and separating the liquid in the tank of the second biological treatment tank with a membrane separation device to obtain treated water and discharging the liquid in the tank of the second biological treatment tank.
The liquid in the tank of the second biological treatment tank is not circulated to the first biological treatment tank, but the liquid in the tank of the second biological treatment tank is membrane-separated by a membrane separation device to obtain treated water, and the second organism is obtained. It is characterized by having a membrane concentration step that does not discharge the liquid in the treatment tank.

In the operation method of the organic wastewater treatment facility of the present invention, the first biological treatment water tank has a tank capacity of 3 to 50 times the in-tank residence time of the second biological treatment water tank. It is characterized by.

The method of operating the organic wastewater treatment facility of the present invention is characterized in that a circular flow flows through the first biological treatment tank.

In the operation method of the organic wastewater treatment facility of the present invention, the membrane concentration step is characterized by operating with a permeation flux that is less than that of the permeation flux of the membrane separation device in the membrane separation step.

The method for operating an organic wastewater treatment facility of the present invention is characterized in that the first biological treatment tank is an oxygen-free tank and the second biological treatment tank is an aerobic tank.

In the organic waste treatment facility of the present invention, the first biological treatment tank into which the organic waste flows, the second biological treatment tank in which the membrane separation device is installed, and the liquid in the first biological treatment tank are the first. A supply channel for supplying to the biological treatment tank No. 2, a return passage for returning the liquid in the tank of the second biological treatment tank to the first biological treatment tank, a treatment water channel connected to the membrane separation device, and a second. It is equipped with a sludge discharge path for discharging sludge from the biological treatment tank and a control device having a plurality of operation modes, and the control device transfers the liquid in the tank of the first biological treatment tank to the second biological treatment tank by the supply path. A membrane separation operation mode in which the liquid in the tank is circulated from the second biological treatment tank to the first biological treatment tank by the return route, and the treated water separated by the membrane separation device is taken out of the system by the treatment water channel. Treatment in a state where the circulation of the liquid in the tank from the second biological treatment tank to the first biological treatment tank by the return route is stopped and the discharge of excess sludge from the second biological treatment tank by the sludge discharge passage is stopped. It is characterized by having a membrane concentration operation mode in which excess sludge in the second biological treatment tank is continuously taken out of the system by a water channel and concentrated by a membrane separator.

In the organic wastewater treatment facility of the present invention, the first biological treatment tank is characterized by having a tank capacity of 3 to 50 times the in-tank residence time of the second biological treatment tank. To do.

In the organic wastewater treatment facility of the present invention, the first biological treatment tank is characterized by having a circumferential flow path and having a circular flow generating means for generating a circular flow around the circular flow path in the middle of the circular flow path. And.

In the organic wastewater treatment facility of the present invention, the membrane separation device in the membrane concentration operation mode is operated with a permeation flux that is less than that of the permeation flux of the membrane separation device in the membrane separation operation mode.

The organic wastewater treatment facility of the present invention is characterized in that the first biological treatment tank is an oxygen-free tank and the second biological treatment tank is an aerobic tank.

According to the above invention, without adding a membrane separation device dedicated to concentration, biological treatment is performed in the membrane separation operation mode (membrane separation step) to treat the organic wastewater flowing into the system, and the membrane concentration operation is performed. In the mode (membrane concentration step), the activated sludge in the second biological treatment tank and the activated sludge flowing in from the first biological treatment tank are concentrated to reduce the water content, and the excess sludge discharged from the second biological treatment tank is discharged. Volume can be reduced. Therefore, the cost required for discharging and disposing of excess sludge can be reduced.

By increasing the tank capacity of the first biological treatment tank to a large capacity having a residence time in the tank 3 to 50 times that of the second biological treatment tank, a large amount of activated sludge can be discharged into the first biological treatment tank. Can be retained. In addition, since the effect of the organic wastewater newly flowing into the system on the sludge concentration of the first biological treatment tank is reduced, a flow rate adjusting tank is provided to allow the organic wastewater flowing into the first biological treatment tank to flow in. Even if the amount is not limited, the sludge concentration in the first biological treatment tank is stable in both the membrane separation operation mode (membrane separation step) and the membrane concentration operation mode (membrane concentration step), and the activated sludge has a constant sludge concentration. Can be stored in large quantities.

Therefore, in the membrane concentration operation mode, a large amount of activated sludge can be supplied from the first biological treatment tank to the second biological treatment tank, and the activated sludge can be concentrated to a higher concentration.

In addition, by performing the membrane concentration operation mode for a long time while reducing the filtration rate (permeation flux) of the membrane separation device, activated sludge can be avoided while avoiding clogging of the filtration membrane without increasing the aeration intensity of the membrane separation device. Can be concentrated.

The liquid in the tank of the first biological treatment tank has the first biological treatment tank having a circular flow path and having a circular flow generating means for generating a circular flow around the circular flow path in the middle of the circular flow path. Can be homogenized and sludge concentration can be homogenized.

When the first biological treatment tank is an oxygen-free tank and the second biological treatment tank is an aerobic tank, a large amount of activated sludge is stored in a large-capacity oxygen-free tank in the membrane concentration operation mode. Even when the circulation of activated sludge from the aerobic tank to the oxygen-free tank is stopped, the sludge concentration in the oxygen-free tank can be maintained for a long time, so that the membrane concentration operation mode can be performed for a long time, and a large amount of high-concentration concentrated sludge is produced. Can be made into. In addition, by reducing the time constraint in the membrane concentration operation mode, the membrane concentration operation mode can be performed for a long time while the filtration rate (permeation flux) of the membrane separation device is reduced, and the aeration strength of the membrane separation device can be extended. Activated sludge can be concentrated while avoiding clogging of the filtration membrane without increasing the amount.

The oxygen-free tank has a circumferential flow path, and has a circular flow generating means for generating a circular flow around the circular flow path in the middle of the circular flow path and a circulation means with the aerobic tank. The liquid in the tank can be homogenized, the sludge concentration can be homogenized, and spoilage can be suppressed.

Schematic diagram showing an organic wastewater treatment facility according to an embodiment of the present invention. Schematic diagram showing an organic wastewater treatment facility according to another embodiment of the present invention. Schematic diagram showing the procedure for diverting a conventional oxidation ditch

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the organic wastewater treatment facility of the present embodiment includes an oxygen-free tank (cum-flow rate adjusting tank) 1 forming a first biological treatment tank and an aerobic tank 2 forming a second biological treatment tank. In the present invention, the first biological treatment tank is not limited to the oxygen-free tank 1, and the second biological treatment tank is not limited to the aerobic tank 2.

The oxygen-free tank 1 is a wastewater treatment facility having a sufficient flow rate adjusting function, and here, the existing oxidation ditch is diverted to the oxygen-free tank 1 and used. The method of diversion will be described later.

The oxygen-free tank 1 has a circulation flow path 3, and has a circulation flow generating means 5 for generating a circulation flow 4 circulating around the circulation flow path 3 in the middle of the circulation flow path 3. The circulating flow generating means 5 is composed of a stirring device, a pump device, and the like. A drainage inflow passage 6 through which organic wastewater newly flows is connected to the circulation flow path 3. Further, the oxygen-free tank 1 has a tank capacity of 3 to 50 times, preferably 5 to 30 times, more preferably 10 to 25 times the in-tank residence time of the aerobic tank 2.

The aerobic tank 2 includes a membrane separation device 7 and an MLSS densitometer (not shown). The membrane separation device 7 may be installed outside the tank, but here it is composed of an immersion type membrane separation device immersed in the tank. The aerobic tank 2 is anoxic in a supply path 8 for supplying the in-tank liquid of the anoxic tank 1 to the aerobic tank 2 and a return path 9 for returning the in-tank liquid of the aerobic tank 2 to the anoxic tank 1. It is connected to the tank 1. The supply path 8 has a pump 10 and the return path 9 has a valve 11.

Various filtration membranes such as a flat membrane and a tube membrane can be used for the membrane separation device 7, and a treatment water channel 12 for taking out the treated water that has passed through the filtration membrane is connected, and the treatment water channel 12 has a suction pump 13. ing. An air diffuser (not shown) is arranged below the casing 14 of the membrane separation device 7, and a blower 15 for supplying air is connected to the air diffuser. Further, a sludge discharge path 16 for discharging excess sludge is connected to the aerobic tank 2. The sludge discharge path 16 has a sludge pump 17 and is connected to the sludge treatment facility 18. In the present embodiment, the sludge discharge path 16 is connected to the sludge treatment facility 18, but the excess sludge taken out from the sludge discharge path 16 can be discharged by a vacuum truck or the like.

The operation in the above configuration will be described below. In the oxygen-free tank 1, new organic wastewater flows into the circumferential flow path 3 from the drainage inflow passage 6, and the liquid in the tank in the flow path of the circular flow path 3 rides on the circular flow 4 generated by the circular flow generating means 5. The aerobic tank 2 and the oxygen-free tank 1 are circulated by the pump 10, the supply path 8, and the return path 9. Therefore, the liquid in the oxygen-free tank 1 can be homogenized, the sludge concentration can be homogenized, and putrefaction can be suppressed.
(Membrane separation operation mode)
In the membrane separation operation mode (membrane separation step), the liquid in the anoxic tank 1 is supplied to the aerobic tank 2 by the pump 10 of the supply path 8, and the aerobic tank 2 is sent to the oxygen-free tank 1 through the return path 9. The nitrification solution is circulated and biological nitrification denitrification treatment is performed to treat the organic wastewater flowing into the system. Since the oxygen-free tank 1 has a large capacity having a residence time in the tank 5 to 30 times that of the aerobic tank 2, the liquid in the tank of the aerobic tank 2 is sent to the oxygen-free tank 1 through the return path 9. Therefore, a large amount of activated sludge stays in the oxygen-free tank 1.

Further, in the membrane separation device 7, the air sent from the blower 15 is dispersed inside the casing 14, and a driving pressure is applied to the membrane separation device 7 by the suction pump 13, and the treated water separated by the membrane is discharged to the outside of the system by the treatment water channel 12. Take it out.

Then, at a systematically set timing, the mode shifts to the membrane concentration operation mode.
(Membrane concentration operation mode)
In the membrane concentration operation mode (membrane concentration step), the level switch or water level gauge installed in the aerobic tank 2 (the level switch or the water level gauge) is installed in the aerobic tank 2 in a state where the valve 11 is closed and the nitrifying liquid is not circulated from the aerobic tank 2 to the anoxic tank 1. The pump 10 is controlled by (not shown), and the liquid in the anoxic tank 1 is supplied to the aerobic tank 2 so that the membrane separation device 7 is not exposed on the water surface.

Then, in a state where the discharge of excess sludge from the aerobic tank 2 by the sludge discharge channel 16 is stopped, the excess sludge in the aerobic tank 2 is membrane-separated by continuing to take out the treated water through the treated water channel 12 to the outside of the system. Concentrate with device 7. At this time, the membrane separation device 7 operates with a permeation flux that is smaller than that of the permeation flux of the membrane separation device 7 in the membrane separation operation mode. After the MLSS concentration of the liquid in the tank measured by the MLSS meter of the aerobic tank 2 has increased to about 30,000 mg / l, which is the set concentration, the concentrated excess sludge of the aerobic tank 2 is passed through the sludge discharge channel 16. Pull out with pump 17.

In the present embodiment, the extracted excess sludge is sent directly to the sludge treatment facility 18, so that the sludge treatment facility 18 is operated in the membrane concentration operation mode in accordance with the operating time of the sludge dehydrator to extract the excess sludge. .. Alternatively, when treating at a separate facility, the concentrated excess sludge is vacuumed out.

If the MLSS concentration of the liquid in the tank exceeds the set concentration due to some trouble or the like and becomes an abnormal concentration, the membrane concentration operation mode is stopped, the valve 11 is opened, and the aerobic tank is provided by the return path 9. The circulation of the nitrifying liquid from 2 to the anoxic tank 1 is restarted, the sludge concentration in the aerobic tank 2 is reduced, and clogging of the filter membrane is prevented. It is also possible to predict and control the MLSS concentration of the aerobic tank 2 from the flow rate of the membrane filtration in the membrane concentration operation mode without providing the MLSS concentration meter.

It is also possible to input the scheduled extraction time of excess sludge to the control system and automatically switch to the membrane concentration operation mode.

By performing this membrane concentration operation mode, it is possible to increase the amount of solid matter of the excess sludge in each operation of drawing out the excess sludge. Therefore, as in the conventional case, excess sludge can be sent to the sludge treatment facility 18 without going through a storage step such as gravity concentration, and sludge decay can be avoided.

Therefore, in the membrane concentration operation mode, the activated sludge flowing in from the aerobic tank 2 and the anoxic tank 1 is concentrated to reduce the water content, and the excess sludge discharged from the aerobic tank 2 is reduced in volume to reduce the excess sludge. The cost required for waste disposal can be reduced.

Further, since the oxygen-free tank 1 has a large capacity having a residence time of 24 hours or more, which is 3 to 50 times that of the aerobic tank 2, a large amount of activated sludge stays in the tank of the oxygen-free tank 1. .. Further, since the oxygen-free tank 1 has a large capacity, the influence of the organic wastewater newly flowing into the system on the sludge concentration of the oxygen-free tank 1 is reduced, so that the normal residence time in the tank is about 5 hours. A sufficient flow rate adjustment buffer can be secured without adjusting the inflow amount of the organic sludge flowing into the oxygen-free tank 1 by providing a flow rate adjustment tank having the above, and there is no case in either the membrane separation operation mode or the membrane concentration operation mode. The sludge concentration in the oxygen tank 1 is stable, and a large amount of activated sludge with a constant sludge concentration can be stored.

Therefore, a large amount of activated sludge can be supplied from the oxygen-free tank 1 to the aerobic tank 2 in the membrane concentration operation mode, and the activated sludge can be concentrated to a higher concentration.

Further, by storing a large amount of activated sludge in the large-capacity oxygen-free tank 1, even in a state where the circulation of activated sludge from the aerobic tank 2 to the oxygen-free tank 1 is stopped in the membrane concentration operation mode, oxygen-free for a long time. Since the sludge concentration in the tank 1 can be maintained, the membrane concentration operation mode can be performed for a long time, and a large amount of concentrated sludge with a high concentration can be produced. Further, by reducing the time constraint in the membrane concentration operation mode, the membrane concentration operation mode can be performed for a long time while the filtration rate (permeation flux) of the membrane separation device 7 is reduced, and the membrane separation device 7 can be operated for a long time. Activated sludge can be concentrated while avoiding clogging of the filtration membrane without increasing the aeration intensity of the air diffused by the air diffuser.

According to this embodiment, the membrane concentration can be performed only in a normal water treatment facility as compared with the case where a separate membrane concentration facility is installed, so that the facility construction cost can be suppressed.

In the present embodiment, the oxygen-free tank 1 has a large capacity, so that a separate flow rate adjusting tank is not provided. However, as shown in FIG. 2, the flow rate adjusting tank 51 is combined with the front stage of the oxygen-free tank 52, the large-capacity aerobic tank 53 is arranged after the oxygen-free tank 52, and the small capacity is arranged after the aerobic tank 53. In the configuration in which the membrane separation tank 54 is arranged, the air diffuser 55 is arranged in the aerobic tank 53, the blower 56 for supplying air is connected to the air diffuser 55, and the circulation pump 57 is provided in the return path 9. The present invention can also be carried out. In this case, the concentration efficiency is improved by reducing the capacity of the membrane separation tank 54.

As shown in FIG. 3, when the equipment 63 having the existing oxidation ditch 61 and the final settling basin 62 is diverted to the present invention, the operation of the oxidation ditch 61 is continued during the renovation. Then, an aerobic tank 2 provided with the membrane separation device 7 and an auxiliary machine unit 64 attached to the membrane separation device 7 are arranged beside the equipment 63. After the renovation, the oxidation ditch 61 is diverted to the oxygen-free tank 1 and the final settling basin 62 is used for the chemical washing facility 65. When operating the organic wastewater treatment facility of the present embodiment, the following It is possible to operate like this.
1. 1. The control system notifies the administrator by e-mail or the like when the concentrated sludge should be extracted from the operating status of the organic wastewater treatment facility.
2. Upon seeing the notification, the administrator inputs the scheduled time for the extraction work of the concentrated sludge into the control system.
3. 3. The control system back-calculates the scheduled start time of switching from the membrane separation operation mode to the membrane concentration operation mode based on the scheduled time input by the administrator and the current wastewater treatment status.
4. The control system automatically implements the membrane concentration operation mode at the scheduled start time.
5. If a system malfunction occurs and the membrane concentration operation mode is stopped, contact the administrator.

Therefore, even in a facility where a manager is not resident, the concentrated sludge extraction work can be smoothly carried out without the manager performing operations or calculations.

1 Anoxic tank 2 Aerobic tank 3 Circular flow path 4 Circulation flow 5 Circulation flow generation means 6 Drainage inflow path 7 Membrane separation device 8 Supply path 9 Return path 10 Pump 11 Valve 12 Treatment water channel 13 Suction pump 14 Casing 15 Blower 16 Sludge drainage channel

Claims (10)

It is a method of operating an organic wastewater treatment facility having a first biological treatment tank into which organic wastewater flows in and a second biological treatment tank equipped with a membrane separation device.
The liquid in the tank of the first biological treatment tank is supplied to the second biological treatment tank, the liquid in the tank of the second biological treatment tank is circulated to the first biological treatment tank, and the tank of the second biological treatment tank is used. A membrane separation step in which the internal liquid is separated by a membrane separation device to obtain treated water and the liquid in the second biological treatment tank is discharged.
The liquid in the tank of the second biological treatment tank is not circulated to the first biological treatment tank, but the liquid in the tank of the second biological treatment tank is membrane-separated by a membrane separation device to obtain treated water, and the second organism is obtained. A method of operating an organic wastewater treatment facility, which comprises a membrane concentration step that does not discharge the liquid in the treatment tank. The organic wastewater according to claim 1, wherein the first biological treatment water tank has a tank capacity of 3 to 50 times the in-tank residence time of the second biological treatment water tank. How to operate the processing equipment. The method for operating an organic wastewater treatment facility according to claim 1 or 2, wherein a circular flow flows through the first biological treatment tank. The organic wastewater treatment facility according to any one of claims 1 to 3, wherein in the membrane concentration step, the operation is performed with a permeation flux that is less than that of the permeation flux of the membrane separation device in the membrane separation step. how to drive. The operation of the organic wastewater treatment facility according to any one of claims 1 to 4, wherein the first biological treatment tank is an oxygen-free tank and the second biological treatment tank is an aerobic tank. Method. A first biological treatment tank into which organic wastewater flows, a second biological treatment tank equipped with a membrane separation device, and a supply of liquid in the first biological treatment tank to a second biological treatment tank. A passage, a return passage for returning the liquid in the second biological treatment tank to the first biological treatment tank, a treatment water channel connected to the membrane separation device, and a sludge discharge for discharging sludge from the second biological treatment tank. Equipped with a road and a control device with multiple operation modes
The control device supplies the liquid in the tank of the first biological treatment tank to the second biological treatment tank by the supply path, and supplies the liquid in the tank from the second biological treatment tank to the first biological treatment tank by the return path. A membrane separation operation mode in which the treated water that circulates and is separated by the membrane separation device is taken out of the system through the treatment channel.
Treatment in a state where the circulation of the liquid in the tank from the second biological treatment tank to the first biological treatment tank by the return path is stopped and the discharge of excess sludge from the second biological treatment tank by the sludge discharge path is stopped. An organic wastewater treatment facility having a membrane concentration operation mode in which excess sludge in a second biological treatment tank is continuously taken out of the system by a water channel and concentrated by a membrane separation device. The organic wastewater according to claim 6, wherein the first biological treatment tank has a tank capacity of 3 to 50 times the residence time in the tank of the second biological treatment tank. Processing equipment. The first biological treatment tank has a circular flow path, and has a circular flow generating means for generating a circular flow around the circular flow path in the middle of the circular flow path, according to claim 6 or 7. Described organic waste treatment equipment. The invention according to any one of claims 6 to 8, wherein in the membrane concentration operation mode, the membrane separation device operates with a permeation flux that is smaller than that of the permeation flux of the membrane separation device in the membrane separation operation mode. Organic wastewater treatment equipment. The organic wastewater treatment facility according to any one of claims 6 to 9, wherein the first biological treatment tank is an oxygen-free tank and the second biological treatment tank is an aerobic tank.

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