JPH07155758A - Waste water treating device - Google Patents

Abstract

PURPOSE:To obtain the discharged water quality always stabilized irrespective of change in flow rate of raw water by immersing a membrane separator attracted by a suction pump in a reaction tank, arranging a diffuser below it, and also inserting a membrane separator in an overflow line. CONSTITUTION:Waste water is allowed to flow from a waste water inflow port 8 into an aerator 1 equipped with a diffuser 7 at the lower part, where organic materials, etc., turning into BOD components and COD components and decomposed by decomposing force of active sludge. After a suction pump 6 is operated to filter the treated water through a membrane module 4, it is sent to a disinfecting tank 2. At this time, when the waste water of the set quantity or above is allowed to flow into the tank 2 from the waste water inflow port 8 caused by any reason, the treated water is allowed to flow out from an overflow line 3. At this time, the treated water is allowed to flow out through a membrane module 5 being a membrane separator inserted in the overflow line. In this way, the discharged water quality always stabilized irrespective of change in flow rate of waste water is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment device such as a septic tank (whether alone or in combination) and an industrial wastewater treatment device. In particular, it is effectively used for applications such as biological treatment and then solid-liquid separation, and is also effectively used in a small-scale apparatus having no flow rate adjusting tank.

[0002]

2. Description of the Related Art A conventional wastewater treatment apparatus utilizing biological treatment will be explained using an example of the simplest system.
It consisted of an aeration tank (activated sludge tank), a sedimentation tank, and a disinfection tank, and the fluid was moved to each tank by overflow. Therefore, even if the amount of raw water fluctuates temporarily, only the amount of discharged water fluctuates, and there were no accidents where raw water (sewage) overflowed from the aeration tank.

In recent years, for the purpose of improving the quality of discharged water and culturing sludge at a high density, a wastewater treatment device for solid-liquid separation using a microfiltration membrane or an ultrafiltration membrane has been studied. At that time, the membrane module is not a pressure filtration system generally used, but a so-called suction filtration system in which the module is immersed and the secondary side is sucked to collect the filtrate is often adopted. The basic system consists of an aeration tank (activated sludge tank and membrane immersion tank) and a disinfection tank.

The movement of the fluid from the aeration tank to the disinfection tank naturally takes place through a membrane, and a pump, a water level difference, etc. have been used as a driving force. The moving speed of the fluid from the aeration tank to the disinfection tank (permeation flux of the membrane) is often set at a constant speed in order to prevent sudden clogging of the membrane, and intermittent suction filtration in which suction is stopped is repeated. There is also. Therefore, the capacity of the aeration tank needs to be large enough to absorb the flow rate fluctuation. Alternatively, a flow rate adjusting tank was provided in front of the aeration tank to adjust the flow rate.

[0005]

However, in the above system, it cannot be denied that the installation space becomes large whether the aeration tank capacity is increased or the flow rate adjusting tank is installed. In addition, it cannot be said that a system with a large aeration tank capacity is safe against a temporary increase in raw water flow.

An object of the present invention is to provide a wastewater treatment system which performs solid-liquid separation while suction-filtering a constant flow rate through a membrane, and always obtains stable discharge water quality against fluctuations in the flow rate of raw water. It is to supply a wastewater treatment device that does not occupy an excessive space in terms of installation space.

[0007]

The gist of the present invention is as follows. (1) Reaction tank, membrane separation device A immersed in the reaction tank,
In a wastewater treatment device comprising a suction pump provided in communication with the membrane separation device A and an air diffuser arranged below the membrane separation device A, an overflow line is provided, and the membrane separation device B is provided in the line. Wastewater treatment equipment characterized by the presence of. (2) The device according to (1) above, wherein the membrane separation devices A and B use hollow fiber membranes.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic united configuration diagram showing an embodiment of the present invention. The wastewater treatment apparatus of the present invention comprises an aeration tank 1 also serving as a membrane immersion tank, a disinfection tank 2, an overflow line 3, a membrane module 4 immersed in a membrane immersion layer, a membrane module 5 attached to the overflow line, a suction pump 6, and aeration. It is composed of a device 7, a waste water inlet 8, and a treated water outlet 9.

With the above structure, the wastewater flowing into the aeration tank from the wastewater inlet 8 is decomposed by the decomposing power of the activated sludge in the aeration tank, such as the organic matter as the BOD component and the COD component. The MLSS (amount of suspended suspended solids in the mixed liquid of wastewater and activated sludge; mg / L) in the aeration tank depends on the concentration of organic substances in the wastewater, but is in the range of thousands to tens of thousands. As the material used for the aeration tank, known materials (FRP,
SUS etc.) can be used. As the capacity of the aeration tank, it is necessary to secure a capacity that does not fill the water under normal use.

By driving the suction pump 6, the treatment liquid in which organic substances and the like are biodegraded is filtered through the membrane module 4 and sent to the disinfection tank 2. At that time, substances larger than the pore diameter of the separation membrane used in the membrane module 4 are cut on the membrane surface. The pore size of the separation membrane is not particularly limited, but is preferably 0.2 μm or less in order to completely cut off bacteria and the like. The material of the separation membrane is not particularly limited, but when it is used in activated sludge, it is desirable that the material has strong microbial resistance. The shape of the membrane module is also not particularly limited.

When, for some reason, wastewater of a predetermined amount or more flows in from the wastewater inlet 8, the treated water flows out from the overflow line 3. Membrane module 5
The treatment liquid flows out through the. The pore size, material, etc. of the membrane used for the membrane module can be in the same range as above.

Regarding the membrane area, it is necessary to set a large membrane area because a large flow rate has to flow in a short time. The membrane modules 4 and 5 may have the same shape, different materials, different hole diameters, or the like.

The membrane module 4 is scrubbed and washed by the ascending stirring flow of air sent from the air diffuser 7, but the membrane module 5 is not washed and is heavily clogged. Therefore, the overflow line must be positioned as a safety device.

For these applications, the membrane module 4
It is preferable to use a hollow fiber membrane module because the membrane module 5 vibrates due to air diffusion and the membrane surface is washed well, and the membrane module 5 wants to obtain as much membrane area per volume as possible.

It is necessary to select an optimum range for the permeation flux and suction pressure of the membrane module 4 depending on the membrane module used, and if the suction pressure etc. is operated extremely high, the membrane surface will be blocked. In some cases, stable filtration may not be performed due to the progress. After the disinfection tank 2, the discharge is performed by overflow as in a normal wastewater treatment device.

[0016]

EFFECTS OF THE INVENTION According to the present invention, in a wastewater treatment system for performing solid-liquid separation while suction-filtering a constant flow rate through a membrane, a stable discharge water quality is always obtained even when the flow rate of raw water changes. Therefore, it is possible to supply a wastewater treatment device which does not occupy an excessive space in terms of installation space.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram showing a preferred embodiment of the present invention.

[Explanation of symbols]

 1 Aeration tank 2 Disinfection tank 3 Overflow line 4 Membrane module (for immersion in aeration tank) 5 Membrane module (for installation of overflow line) 6 Suction pump 7 Air diffuser 8 Waste water inlet 9 Treated water outlet 10 Blower

Claims (2)

[Claims] 1. A wastewater treatment apparatus comprising a reaction tank, a membrane separator A immersed in the reaction tank, a suction pump provided in communication with the membrane separator A, and an air diffuser arranged below the membrane separator A. 2. A wastewater treatment device having an overflow line and a membrane separator B existing in the line. 2. The device according to claim 1, wherein the membrane separation devices A and B utilize hollow fiber membranes.