JP3263292B2 - Septic tank and its operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a septic tank provided with a membrane separation device having a large number of filtration membranes arranged side by side and having a membrane separation tank provided with a diffuser tube below the filtration membrane, and its operation. About the method.

[0002]

2. Description of the Related Art Conventionally, this type of septic tank filters the water to be treated by the membrane separation device, and supplies air into the tank by supplying air from the diffuser pipe to form ammonium nitrogen or the like of the water to be treated. Function as a nitrification tank that promotes "nitrification" to convert nitric acid into nitrate nitrogen, and stop the air supply from the air diffuser to keep DO in the tank almost zero, thereby reducing nitric acid in the water to be treated. It has been operated to also function as a denitrification tank that performs `` denitrification '' to convert nitrogen to neutral nitrogen gas.In this case, only a membrane separation tank is used.
The biological treatment of nitrification and denitrification of the water to be treated was performed. In addition, during the nitrification, a filtration operation in which an operation state of collecting the filtrate from the filtration membrane and an operation stop state of stopping the collection of the filtrate are repeated. For this reason, the filtration membrane has a configuration in which the filtration membrane is washed by air supply only when the operation of the membrane separation device is stopped to stop the recovery of the filtrate (see FIGS. 3 and 4).

[0003]

In other words, according to the above-mentioned conventional septic tank, solid components such as sludge (hereinafter simply referred to as dirt) adhered to the surface of the filtration membrane in a state where filtration pressure is not applied to the filtration membrane. When it is easy to perform the cleaning, the air bubbles supplied from the air diffuser are made to collide with each other to peel off the solid components and perform cleaning. Therefore, during nitrification, the membrane surface of the filtration membrane has a configuration in which dirt is repeatedly adhered and peeled off. This phenomenon is called a fixing phenomenon), and the filtration capacity of the water to be treated in the membrane separation device gradually decreases, so that it becomes difficult to secure a sufficient amount of filtered water. In addition, if the operation state of recovering the filtrate from the filtration membrane during nitrification is secured for a long time in order to secure a sufficient amount of filtered water, the time ratio between the nitrification operation and the denitrification operation is almost constant depending on the microbial environment. However, it is necessary to shorten the time of the operation stop state in which the collection of the filtrate is relatively stopped, and as a result, it becomes impossible to sufficiently secure the time for cleaning the membrane surface. However, there is a situation in which dirt on the membrane surface becomes easier to fix even during nitrification, and again, the filtration capacity of the water to be treated of the membrane separation device gradually decreases, and a sufficient amount of filtered water can be secured. There was a risk of disappearing.

[0004] Accordingly, an object of the present invention is to provide a septic tank operation method and a septic tank which can easily secure a sufficient amount of filtered water in view of the above-mentioned circumstances.

[0005]

In order to achieve this object, a method of operating a septic tank according to the present invention is characterized in that a membrane separation device in which a large number of filtration membranes are juxtaposed is installed, and that the filtration membrane is provided below the filtration membrane. In a method for operating a purification tank having a membrane separation tank provided with a diffuser tube, a denitrification tank capable of advancing and returning water to be treated between the membrane separation tank and the membrane separation tank in advance is provided. A return path for providing a treated water supply device that constantly supplies treated water to the separation tank, and returning the treated water excessively supplied from the treated water supply device to the membrane separation tank to the denitrification tank. Is provided, and while constantly supplying air to the air diffuser, an operation state in which the filtrate is recovered from the filtration membrane, and a first step of repeating an operation stop state in which the filtration liquid is stopped, and an operation in the first step The filtration time is longer than the The second step of stopping the recovery of filtrate from the membrane is to be repeated alternately, and the characteristic configuration of the septic tank of the present invention is to install a membrane separation device in which many filtration membranes are juxtaposed, and In a purification tank in which a membrane separation tank provided with an aeration pipe is provided, a denitrification tank capable of advancing and returning water to be treated with the membrane separation tank is provided, and from the denitrification tank to the membrane separation tank, Providing a treated water supply device that constantly supplies treated water, and providing a return path for returning treated water excessively supplied from the treated water supply device to the membrane separation tank to the denitrification tank, While constantly supplying air to the air diffuser, the first step of repeating the operation state of collecting the filtrate from the filtration membrane and the operation stop state of stopping the collection of the filtrate, and the time of the operation stop state in the first step Filtrate from the filtration membrane The lies in the second step of stopping is provided a control device for alternating, the effects thereof are as follows.

[Effects] In other words, a denitrification tank capable of advancing and returning water to be treated to and from the membrane separation tank is provided, and the water to be treated is constantly supplied from the denitrification tank to the membrane separation tank. Provided to be treated water supply device, if provided with a return path to return the treated water excessively supplied to the membrane separation tank from the treated water supply device to the denitrification tank, the treated water It can be treated in two chambers, a denitrification tank and the membrane separation tank,
The role of denitrification in the denitrification tank and the role of nitrification water treatment in the membrane separation tank can be shared. At this time, in the membrane separation tank, since the burden of performing denitrification is reduced, by performing a filtration operation that alternately repeats the first step and the second step, by constantly supplying air to the diffuser, In the first step, not only the operation stop state of stopping the recovery of the filtrate from the filtration membrane, but also the membrane surface of the membrane separation device can be washed in the second step. Therefore, in the first step, even if it is not possible to sufficiently remove the dirt on the membrane surface in the operation stop state of stopping the collection of the filtrate, and even if the dirt on the membrane surface becomes easy to fix gradually, the operation stop in the second step Since the membrane surface can be cleaned for a longer time than the state, even if the dirt gradually accumulates in the first step, it is easy to sufficiently remove the dirt in the second step, and the filtration capacity of the water to be treated of the membrane separation device is improved. Decreases,
The inconvenience that the amount of filtered water cannot be sufficiently secured is easily prevented. In addition, since the said 2nd process can allocate the period which carried out the denitrification in the conventional membrane separation tank, without compressing the time of the operating state which collects a filtrate from the filtration membrane in the said 1st process, rather, it is rather. In addition, the period in which denitrification is conventionally performed can be used in the above-mentioned operation state, and it is easy to sufficiently secure the amount of filtered water.

Further, if the septic tank for performing the above-described operation method is configured as described in claim 2, the operation for sufficiently securing the amount of filtered water can be easily performed, and the stable operation can be easily performed.

Accordingly, it is easy to secure a sufficient amount of filtered water, so that a large volume of water to be treated can be constantly treated even in a relatively small membrane separation tank having a small number of filtration membranes. It has become possible to provide a septic tank that is inexpensive but can handle large volumes.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a purification tank is provided by sequentially providing a flow rate adjusting tank N, a denitrification tank E1, a membrane separation tank E2, and a discharge pump tank T from the upstream side, and provided so as to transfer the water to be treated. .

The flow rate adjusting tank N receives raw water to be treated flowing into the septic tank from the inflow port I, precipitates and removes contaminants in the treated water, and is formed by anaerobic bacteria growing inside. A first pump P1 for transferring the water to be treated to the denitrification tank E1 is provided in a tank for temporarily storing the water to be treated while performing anaerobic treatment of the water to be treated. Even if there is no inflow of the water to be treated for a long time, the water to be treated is constantly transferred to the denitrification tank E1 so as not to hinder the water treatment in each of the subsequent water treatment tanks.

The denitrification tank E1 is provided with an inflow pipe A1 for inflowing the water to be treated from the flow rate adjusting tank N connected to the first pump P1 to constitute an inflow passage of the water to be treated. . A second pump P2 for transferring the water to be treated to the membrane separation tank E2 via the transfer pipe A2 is provided therein, and a stirring pump P4 for stirring and circulating the water to be treated in the tank is provided therein. is there.

The membrane separation tank E2 is provided with a membrane separation device M in which a number of flat membranes are arranged side by side.
Bubble is supplied to the membrane separation device M to prevent sludge from adhering excessively to the membrane surface, and the water to be treated is formed while forming a circulating flow in the membrane separation tank E2. And a water collecting pipe M1 is connected to each flat membrane of the membrane separation device M, and the filtered water from the water collecting pipe M1 is combined to form a membrane separation tank. An intake pipe M2 leading to the outside of E1 is connected to a discharge pump tank T adjacent to the membrane separation tank E2 below the water surface of the membrane separation tank E2. A return port A for returning the water to be treated excessively flowing from the denitrification tank E1 to the denitrification tank E1 is provided in a partition wall separating the denitrification tank E1.
3 is provided to constitute a return path for the water to be treated. In the membrane separation tank E2, aerobic treatment of the water to be treated with activated sludge is performed by aeration from the air diffuser, and the water to be treated is nitrified.

The intake pipe M2 is provided with a solenoid valve V on the side of the discharge pump tank T, and opens and closes the flow path of the intake pipe M2 in response to an open / close signal from a timer W. When the passage is in an open state, a filtration pressure is applied to the membrane separation device by a head difference between the membrane separation tank and the discharge pump tank T to perform a membrane separation operation in the membrane separation tank E2,
The membrane separation operation in the membrane separation tank E2 is stopped when the flow path of the intake pipe M2 is closed. The timer W
Is a first step of repeating the open state for 8 minutes and the closed state for 2 minutes 9 times (1.5 hours) with respect to the solenoid valve V, and the closed state for 3 minutes.
The second step, which is continued for 0 minutes, is alternately performed, and the air is diffused into the air diffuser D at all times (see FIG. 2). Accordingly, in the closed state of the electromagnetic valve V, the air bubbles collide with the filtration membrane without applying a filtration pressure to the filtration membrane, so that the membrane surface is efficiently cleaned. When the solenoid valve V is in the open state, the filtration operation when the solenoid valve V is in the open state removes solid components such as sludge attached to the membrane surface. The solid component which did not fall sufficiently was completely peeled off, and the structure was such that it was easy to secure a sufficient amount of filtered water when the next step was performed. Actually, conventionally, in the case where the repetitive operation of only the first step is performed at the time of the air diffusion operation of the air diffuser, the filtered water amount of the water to be treated is 0.65 m.
^When the flux was set to ³ / m ² / day, the fouling of the membrane surface gradually progressed. On the other hand, with the above configuration, even when the flux was set to about 0.70 m ³ / m ² / day, It can be expected that the stain hardly progresses.

With such a configuration, the first pump P
In step 1, the water to be treated that has flowed into the flow rate control tank N is quantitatively flowed into the denitrification tank E1, and the inflow water is mixed and circulated with the nitrified water to be returned returned from the membrane separation tank E2. While being denitrified in the circulation of the water to be treated, it can be transferred to the membrane separation tank E2 by the second pump P2. Also,
The treated water transferred to the membrane separation tank E2 is set so that the average inflow amount of the treated water flowing into the flow rate adjusting tank N can be constantly subjected to membrane filtration. At this time, the transfer amount of the water to be treated by the second pump P2 is set to be about 5 times the average inflow amount, and the water to be treated that is about 4 times the average inflow amount is always in the membrane separation tank E2. , And circulates between the denitrification tank E1. As a result, the water to be treated has a low BOD value and a low acidity, is filtered by the membrane separation device M, and is transferred to the discharge pump tank T.

The discharge pump tank T comprises a disinfection tank Q1 and a storage tank Q2. The disinfection tank Q1 is provided with a treated water receiving container on a partition separating the membrane separation tank E2 and the discharge pump tank T. It is configured by providing a small hole in the wall surface,
The filtered water that has flowed into the disinfection tank Q1 flows into the storage tank Q2 after being disinfected. The storage tank Q2 is provided with a third pump P
3 is provided so that the filtered water is temporarily stored, then pumped up, and discharged from the discharge port Z to the outside of the septic tank through the discharge pipe A3. Thereby, the sterilized filtered water is discharged almost quantitatively outside the septic tank.

Another embodiment will be described below. In the above embodiment, the filtration of the water to be treated from the membrane separation device is naturally performed by the head difference, but a suction pump is provided to forcibly suction-filter the water to be treated from the membrane separation device. In such a case, a suction pump and a control device for turning on and off the suction pump are provided instead of the solenoid valve V and the timer W, and the suction pump is turned on and off. The said membrane separation tank E
2 and the membrane separation operation in the membrane separation tank E2 may be alternately repeated. That is, means for switching the filtration operation for collecting the filtrate, such as the timer W and the control device for turning on and off the above-described suction pump in the above embodiment, are collectively referred to as a control device.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a vertical side view of a septic tank.

FIG. 2 is a graph showing an operation method of the septic tank.

FIG. 3 is a graph showing a conventional method of operating a septic tank.

FIG. 4 is a vertical sectional side view of a conventional septic tank.

[Explanation of symbols]

 M Membrane separation device D Aeration tube E2 Membrane separation tank E1 Denitrification tank P2 Treated water supply device A3 Return path

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuyuki Honda 1 at 2, Takamatsu, Kosai-cho, Koga-gun, Koka-gun, Shiga Prefecture Inside the Kubota Shiga Plant (72) Katsumi Hamada 2, Takamatsu, Kosai-cho, Koga-gun, Shiga 1 Kubota Corporation Shiga Plant (56) References JP-A-9-206748 (JP, A) JP-A-3-232597 (JP, A) JP-A-4-7023 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) C02F 3 / 00,1 / 44 B01D 61 / 22,65 / 02

Claims (2)

(57) [Claims] 1. A purification tank having a membrane separation device (M) in which a large number of filtration membranes are juxtaposed and having a membrane separation tank (E2) provided with an air diffuser (D) below the filtration membrane. Operating method, wherein a denitrification tank (E1) capable of advancing and returning water to be treated to and from the membrane separation tank (E2) is provided in advance, and the denitrification tank (E
A treated water supply device (P2) for constantly supplying treated water from 1) to the membrane separation tank (E2) is provided, and excess water is supplied from the treated water supply device (P2) to the membrane separation tank (E2). A return path (A3) for returning the water to be treated supplied to the denitrification tank (E1) is provided, and air is constantly supplied to the air diffuser (D) and the filtrate is recovered from the filtration membrane. And a first step of repeating the operation stop state of stopping the filtrate collection, and a purification tank that alternately repeats the second step of stopping the filtrate collection from the filtration membrane for a longer time than the operation stop state in the first step. Driving method. 2. A clarification tank having a membrane separation device (M) in which a number of filtration membranes are juxtaposed and having a membrane separation tank (E2) provided with an air diffuser (D) below the filtration membrane. A denitrification tank (E1) capable of advancing and returning the water to be treated to and from the membrane separation tank (E2), and providing a steady state from the denitrification tank (E1) to the membrane separation tank (E2). A treatment water supply device (P2) for supplying the treatment water, and treating the treatment water excessively supplied from the treatment water supply device (P2) to the membrane separation tank (E2) in the denitrification tank. A return path (A3) for returning to (E1) is provided, and air is constantly supplied to the air diffuser (D), and an operation state of collecting the filtrate from the filtration membrane and an operation stop state of stopping the collection of the filtrate are repeated. The first step, and longer than the time of the operation stop state in the first step Septic from filtration membrane provided with the control device alternately repeating the second step of stopping the filtrate recovery (W).