JP2001029994A - Membrane separation activated sludge process facility with flow control function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with flow control tank for coping with the fluctuation of the amount of sewage influent, by making the tank capacity of a denitrification tank consist of a reference capacity to keep a retention time in the tank, required for a biological reaction by activated sludge in the tank, and a buffer capacity to absorb the inflow fluctuation. SOLUTION: Separated water from an aeration grit tank 2, which receives raw water 1 flowing into a system, is made to overflow to a raw water pump tank 3, the sedimented grit is discharged to a sand elimination tank 4, and the separated water is returned to the aeration grit tank 2. A denitrification tank 6, to which sewage flows from the raw water pump tank 3 through a screen tank 5, has a tank capacity consisting of a reference capacity to keep a retention time in the tank, required for a biological reaction by activated sludge in the tank, and a buffer capacity to absorb the inflow fluctuation. When the amount of the sewage flowing into a system increases, the increment is absorbed by the buffer capacity of the denitrification tank 6, and a plurality of suction pumps in a suction pump device are operated at the same time and the flow rate is increased, thereby increasing the suction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological reaction tank of a water treatment facility employing a membrane separation activated sludge system, and has a flow control function for reducing the facility scale and improving the maintenance and management. Regarding processing equipment.

[0002]

2. Description of the Related Art Conventionally, in a water treatment facility of a membrane separation activated sludge system in which activated sludge in a reaction tank is separated by a submerged membrane, raw water flowing into the system is subjected to an aeration sand settling tank, a raw water pump tank,
The wastewater is guided to the flow control tank, the denitrification tank, and the nitrification tank sequentially for treatment, and discharged through the disinfection tank and the discharge pump tank.

The aeration sedimentation tank and the raw water pump tank remove sewage and sand from the raw water as pretreatment, and supply sewage from the raw water pump tank to the flow rate adjusting tank. The flow rate adjusting tank stores inflowing sewage and adjusts the amount of water supplied to the denitrification tank in a later process. The tank capacity is a residence time in the tank, for example, 6 to 7 hours. The denitrification tank and nitrification tank are for nitrifying and denitrifying wastewater by biological reaction with activated sludge. Circulates the internal solution at a volume of several times (5 times) the amount of treated water,
Activated sludge is separated by an immersion type membrane separation device immersed in a nitrification tank, and treated water is supplied to a disinfection tank. The tank capacity of the denitrification tank and the nitrification tank is a residence time in the tank, for example, 6 hours.

[0004]

However, in the case of a small-scale sewage treatment plant, the amount of inflow sewage varies greatly from day to day, and a flow control tank is indispensable for leveling the treatment load. However, the facility becomes large only in the space where the flow control tank is installed, and its existence is large in a small-scale sewage treatment facility.

It is necessary to stop the operation of the nitrification tank when replacing the membrane in the immersion type membrane separation apparatus or when checking the air diffuser arranged at the bottom of the tank. The present invention solves the above-described problems, and does not require a flow rate adjustment tank when dealing with fluctuations in the amount of inflowing sewage, without stopping the operation, and maintaining the immersion type membrane separation device and the aeration device of the nitrification tank. It is an object of the present invention to provide a membrane separation activated sludge treatment facility having a flow rate adjusting function capable of performing the following.

[0006]

According to a first aspect of the present invention, there is provided a membrane separation activated sludge treatment facility having a flow rate adjusting function, comprising: a denitrification tank into which pretreated wastewater flows; A nitrification tank into which the liquid in the tank flows, an immersion type membrane separator immersed in the nitrification tank, an air diffuser disposed below the immersion type membrane separator, and a denitrification tank for the liquid in the tank overflowing from the nitrification tank. And a return flow path for returning the denitrification tank,
The tank capacity consists of a reference capacity that can maintain the residence time in the tank required for biological reaction by activated sludge in the tank and a buffer capacity that absorbs fluctuations in the inflow of sewage, and has a circulating liquid pump device that sends sewage to the nitrification tank. The immersion type membrane separation device of the nitrification tank has a configuration including a filtration membrane means for filtering the liquid in the tank, and a suction pump apparatus capable of adjusting a suction amount of treated water sucked through the filtration membrane means.

[0007] With the above structure, the wastewater flowing into the system flows from the denitrification tank to the nitrification tank through the circulating fluid pump device, returns from the nitrification tank to the denitrification tank through the return flow path, and circulates in the system. I do. The sewage is nitrified and denitrified by the biological reaction of the activated sludge in the tank during a predetermined residence time in each tank.
On the other hand, the immersion type membrane separation device receives the suction pressure of the suction pump device to filter the liquid in the nitrification tank, and the suction pump device discharges the treated water out of the system.

When the flow rate of sewage flowing into the system increases, the increased amount is absorbed by the buffer capacity of the denitrification tank, and the suction amount of the suction pump device is increased. This makes it possible to absorb flow fluctuations of sewage by the action of the entire system without the need for a conventional flow control tank, and the buffer capacity provided in the denitrification tank is smaller than that of the conventional flow control tank. Can be reduced in installation space.

According to a second aspect of the present invention, there is provided a membrane separation activated sludge treatment facility having a flow rate adjusting function, wherein a nitrification tank is formed in a plurality of independent tanks, and an immersion type membrane separation device is immersed in each tank.
A suction pump device capable of selectively sucking the treated water of the immersion type membrane separation device of each tank body and adjusting the suction amount is provided. From the above configuration, when stopping the operation of the immersion type membrane separation device for maintenance,
The liquid supply to the tank in which the immersion type membrane separation device is arranged is stopped, the amount of liquid supply to the other tanks is increased, and the suction of the immersion type membrane separation device by the suction pump device is stopped. At the same time, the suction amount of the other tank body to the immersion type membrane separation device is increased. Thus, maintenance can be performed without stopping the operation of the nitrification tank.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The aeration and sedimentation tank 2 for receiving the raw water 1 such as sewage flowing into the system is for removing the residue and sand of the raw water as pretreatment, and the separated water overflows to the raw water pump tank 3 to remove the sediment. The water is discharged to the tank 4 and the separated water is returned to the aeration sand settling tank 2.

From the raw water pump tank 3 to the 2 mm screen tank 5
The denitrification tank 6 into which the sewage flows through is subjected to a denitrification treatment of the sewage by a biological reaction by activated sludge, and the liquid in the denitrification tank 6 is passed through a circulating liquid measuring tank 7 and a pair of 1 mm screens 8 to form a pair. The equal amount flows into the nitrification tank 9 respectively. Excess sludge in the denitrification tank 6 is discharged to the sludge concentration storage tank 10, and desorbed water from the sludge concentration storage tank 10 is returned to the raw water pump tank 3.

The nitrification tank 9 is for nitrifying sewage by biological reaction with activated sludge and returning the overflowing tank liquid to the denitrification tank 6 through the return flow path 11. The sludge water circulates at an amount of several times (five times) the amount of the treated water, and the treated water is supplied to the disinfecting tank 12 and the discharge pump 13.
Flows out of the system. As shown in FIG.
The tank capacity is composed of a reference capacity (for example, 6 hours) that can maintain the residence time in the tank required for biological reaction due to activated sludge in the tank (for example, 6 hours) and a buffer capacity (for example, 4 hours) that absorbs fluctuations in wastewater inflow, In the tank, there are provided a circulating liquid pump device 14 for sending sewage to the nitrification tank 9, a stirring device 15, and a sludge extraction pump 16 for taking out excess sludge. The circulating fluid pump device 14 includes two circulating pumps 14a and valves 14b arranged corresponding to the respective pumps. By stopping and starting the operation of each pump 14a, the circulating fluid measuring tank 7 and a pair of 1 mm screens are provided. The amount of liquid sent to the nitrification tank 9 through 8 is adjusted.

In each of the nitrification tanks 9, the immersion type membrane separation device 17 is immersed in an independent tank body.
An air diffuser 18 is arranged below 7. The immersion type membrane separation device 17 is, for example, a device in which a plurality of filtration membrane cartridges are arranged in parallel at a predetermined interval, and the aerated air ejected from the diffusion device 18 flows in a cross-flow along the membrane surface in a gas-liquid multiphase flow. To clean the membrane surface.

A suction pump device 19 for applying suction negative pressure to each of the membrane cartridges and extracting the treated water that has passed through the filtration membrane is connected to both immersion type membrane separation devices 17. The suction pump device 19 includes three suction pumps 19a,
Valve 19b and check valve 1 arranged before and after each pump
9c, by stopping and starting the operation of each pump 19a or controlling the discharge flow rate thereof, it is possible to selectively suction both immersion type membrane separation devices 17 with an arbitrary pump, and to suction the treated water. The amount is adjustable.

Each of the suction pumps 19a is capable of sucking treated water corresponding to the daily average amount of wastewater Q flowing into the system.
The amount of treated water can be adjusted within the range. In addition, each immersion type membrane separation device 17 has a filtration membrane area and a treatment capacity of the number of membrane cartridges capable of extracting treated water up to three times the daily average sewage amount Q. Hereinafter, the operation of the above configuration will be described. Raw water 1 that normally flows into the system
Flows into the denitrification tank 6 through the aeration sedimentation tank 2, the raw water pump tank 3, and the 2 mm screen tank 5, and the circulating liquid pump device 14
The circulating liquid pump 14a is operated to divide the fixed amount of the liquid in the tank through the circulating liquid measuring tank 7 and the pair of 1 mm screens 8 into equal amounts and flow into the respective nitrification tanks 9, respectively. It returns to the denitrification tank 6 through the return flow path 11 and circulates through the system.

The wastewater is denitrified and denitrified by a biological reaction of the activated sludge in the denitrification tank 6 and the nitrification tank 9 during a predetermined residence time in the tank. On the other hand, the immersion type membrane separation device 17 receives a suction pressure by driving one suction pump 19a of the suction pump device 19 or simultaneously operating a plurality of suction pumps 19a and adjusting the flow rate thereof. The liquid in the nitrification tank 9 is filtered by the suction pump device 1
9 discharges the treated water out of the system.

When the flow rate of the sewage flowing into the system increases, the increased amount is absorbed by the buffer capacity of the denitrification tank 6, and the plurality of suction pumps 19a of the suction pump device 19 are simultaneously operated and the flow rate is increased. By doing so, the suction amount is increased. This eliminates the need for a flow rate adjusting tank having a tank capacity of 6 to 7 hours in the tank in the related art, and can absorb flow rate fluctuations of sewage by the action of the entire system. Also, the buffer capacity provided in the denitrification tank 6 is smaller than the conventional flow control tank capacity during the residence time in the tank.
It is time, and the installation space of the entire equipment can be reduced. The tank capacity of the denitrification tank 6 in the present embodiment is 6 hours + 4 hours as the residence time in the tank, and the tank capacity of the conventional flow control tank and the denitrification tank is 6 hours + 6 hours, and the ratio is 10 hours / 12. It becomes about 0.8 times in time.

When the operation of one immersion type membrane separation device 17 is stopped for maintenance, the liquid supply to the nitrification tank 9 in which the immersion type membrane separation device 17 is arranged is stopped,
Increase the amount of liquid sent to other tanks. Further, the suction pump device 19 stops the suction of the treatment water of the immersion type membrane separation device 17 and the immersion type membrane separation device 17 of another tank body.
Increase the amount of suction for. At this time, the immersion type membrane separation device 17 exhibits a treatment capacity twice as large as the daily average sewage volume Q for a maximum of 1.5 days (36 hours), or a treatment capacity three times the daily average sewage volume Q for a maximum of 24 hours. Therefore, maintenance such as replacement of the filtration membrane cartridge can be performed without stopping the operation of the nitrification tank 9.

[0019]

As described above, according to the present invention, when the amount of inflowing sewage increases, the increased amount is absorbed by the buffer capacity of the denitrification tank, and the suction amount of the suction pump device is increased, whereby the flow rate is increased. Without the need for an adjusting tank, fluctuations in the flow rate of sewage can be absorbed by the action of the entire system, and the installation space of the entire facility can be reduced. At the time of maintenance, the supply of liquid to one immersion type membrane separation device is stopped, the amount of liquid supply to the other tank is increased, and the suction of the immersion type membrane separation device by the suction pump device is stopped. The maintenance can be performed without stopping the operation of the nitrification tank by increasing the suction amount of the other tank body to the immersion type membrane separation device.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a membrane separation activated sludge treatment facility having a flow rate adjusting function according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a denitrification tank and a nitrification tank of the membrane separation activated sludge treatment facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water 2 Aeration sand tank 6 Denitrification tank 9 Nitrification tank 11 Return flow path 14 Circulating fluid pump device 14a Circulating fluid pump 17 Immersion type membrane separation device 18 Air diffuser 19 Suction pump device 19a Suction pump

Continued on the front page (72) Inventor Kenichi Kashimura 3-3-1 Nihombashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office (72) Inventor Buntaro Furuhata 3-1-1 Nihonbashi Muromachi, Chuo-ku, Tokyo Co., Ltd. Kubota Tokyo Head Office (72) Inventor Akira Ichihara 1-6-27 Konan, Minato-ku, Tokyo Inside Ebara Corporation Shinagawa Office (72) Inventor Miki Sakuno 1-6-27 Konan, Minato-ku, Tokyo Ebara Corporation F term in the Shinagawa office of the factory (reference) 4D006 GA02 KB22 KB23 KE01Q KE03Q PA02 PB08 PC62 4D040 BB52 BB91

Claims (2)

[Claims] 1. A denitrification tank into which pretreated wastewater flows, a nitrification tank into which a liquid in the denitrification tank flows, an immersion type membrane separation apparatus immersed in the nitrification tank, and a lower part of the immersion type membrane separation apparatus A degassing device, and a return flow path for returning the liquid in the tank overflowing from the nitrification tank to the denitrification tank.The denitrification tank has a tank capacity that reduces the residence time in the tank required for a biological reaction due to activated sludge in the tank. It has a circulating fluid pump device that sends sewage to the nitrification tank, consisting of a reference capacity that can be maintained and a buffer capacity that absorbs fluctuations in sewage inflow.The immersion type membrane separation device in the nitrification tank is a filtration membrane that filters the liquid in the tank. And a suction pump device capable of adjusting a suction amount of the treated water sucked through the filtration membrane means. 2. The nitrification tank is formed in a plurality of independent tank bodies,
The immersion type membrane separation device is immersed in each tank body, and a suction pump device capable of selectively suctioning the treatment water of the immersion type membrane separation device of each tank body and adjusting the suction amount is provided. A membrane separation activated sludge treatment facility having a flow rate adjusting function according to claim 1.