JPH03284396A - Device for treating organic waste water - Google Patents

Abstract

PURPOSE:To prevent the clogging of a filter member and to reduce the energy cost by providing an immersed membrane separator in which the negative- pressure side of a suction pump communicates with its suction side and a cross- flow membrane separator communicating with a treated water tank through a force-feed pump. CONSTITUTION:The immersed membrane separator 5 is placed in an aeration tank 4, and the cross-flow membrane separator 19 communicates with a biological reaction tank 1 through a circulating pipe 20. Accordingly, a liq. to be treated is concentrated in the immersed membrane separator in the aeration condition specified by the BOD concn. to such a sludge concn. that the filter membrane is not clogged, the deficiency in the concentration rate by the immersed membrane separator is made up with the cross-flow membrane separator, and the specified sludge concn. is finally attained. Consequently, clogging of the filter membrane in the immersed membrane separator is prevented, the quantitative load of the liq. to be treated on the cross-flow membrane separator is reduced, the output of the force-feed pump is lowered, and the energy cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for treating nitrogen-containing organic wastewater such as human waste and septic tank sludge.

Conventional technology Conventionally, treatment equipment for organic wastewater containing nitrogen, such as human waste and septic tank sludge, has been designed to perform cross-flow filtration by supplying the liquid to be treated at a high flow rate along the membrane surface of an ultrafiltration membrane. In some cases, an ultrafiltration membrane or a precision filtration membrane is immersed in a biological treatment tank, the membrane surface is cleaned by aeration and stirring, and then suction filtration is performed by negative pressure.

Problems to be Solved by the Invention However, in the above-mentioned cross-flow filtration, since the liquid to be treated is passed through at a high flow rate, there is a problem that a large amount of energy is consumed in the pressure pump and the like, resulting in high operating costs. In addition, in suction filtration using negative pressure, the permeation flux (Flux) is smaller than that in cross-flow filtration, so in order to secure the same permeation flow rate as cross-flow filtration, the membrane area increases and the equipment cost increases. There was a problem.

Furthermore, in suction filtration using negative pressure, the membrane surface is cleaned by aeration agitation to prevent clogging of the membrane surface, but with air agitation, the membrane surface flow velocity is 0.5 m/
Since the limit is about the diameter of a second, a cake layer tends to form on the membrane surface and there is a problem that the sludge concentration of the liquid to be treated cannot be increased.

Furthermore, if the amount of aerated air is too large, it exceeds the amount of oxygen required for the biological reaction in the biological treatment tank, resulting in the problem of adversely affecting the biological treatment.

The present invention solves the above problems, and aims to provide an organic wastewater treatment device that can compensate for the drawbacks of both immersion-type suction filtration and cross-flow filtration by using both methods.

Means for Solving the Problems In order to solve the above problems, the present invention provides a submerged membrane separator which is placed immersed in a treated water tank and whose negative pressure side communicates with the suction side of a suction pump, and a submerged membrane separator. An aeration device installed below the device, a cross-flow type membrane separator that communicates with the treated water tank via a pressure pump, and a circulation system in which one end communicates with the cross-flow membrane separator and the other end communicates with the treated water tank. The structure includes a pipe.

Further, a plurality of immersion type membrane separation devices are provided in the treated water tank, and a plurality of aeration devices are provided corresponding to each immersion type membrane separation device.

Effect With the above-mentioned configuration, the liquid to be treated that flows into the treated water tank is mixed with the activated sludge in the treated water tank, and the nitrifying bacteria, denitrifying bacteria, BOD oxidizing bacteria, etc.
OD is removed.

Then, the liquid to be treated in the treated water tank is suction-filtered by the submerged membrane separator under the negative pressure of the suction pump, and the permeate that passes through the filtration membrane of the submerged membrane separator is collected on the membrane surface of the filtration membrane. The activated sludge is separated into solid and liquid. In addition, the activated sludge collected on the membrane surface of the filtration membrane is washed by the upward stirring flow generated by the air ejected from the aeration device, and remains in the treated water tank.

Then, the liquid to be treated in the treated water tank is supplied to a cross-flow type membrane separation device by a pressure pump, and is cross-flow filtered by passing water along the membrane surface of the filtration membrane at a predetermined high flow rate. Solid-liquid separation is performed into permeated liquid and activated sludge whose permeation is blocked by a filtration membrane. Furthermore, the permeate that has permeated through the filtration membrane is extracted as treated water, and the activated sludge whose permeation is blocked by the filtration membrane is washed away by high-flow water and passes through the circulation pipe, where it is returned to the treatment water tank and the sludge and nitrification circulating liquid are returned. It will also be returned.

Therefore, in the submerged membrane separator, the liquid to be treated is concentrated to a sludge concentration that does not clog the filtration membrane under aeration conditions defined by the degree of BODm in the liquid to be treated,
The insufficiency of the concentration rate caused by the submerged membrane separator is compensated for by the cross-flow membrane separator, and a predetermined sludge concentration is finally achieved. This prevents clogging of the filtration membrane in the submerged membrane separator, reduces the quantitative load of the liquid to be treated on the cross-flow membrane separator, and lowers energy costs by reducing the output of the pressure pump. .

Then, by providing a plurality of submerged membrane separators and aeration devices, and adjusting the number of aeration devices and submerged membrane separators to be operated according to the flow rate of the liquid to be treated and the BOD concentration of the liquid to be treated, The amount of aerated air for the liquid to be treated can be adjusted as appropriate while maintaining the aeration intensity that prevents clogging of the filtration membrane of the membrane separation device.

EXAMPLE An example of the present invention will be described below based on the drawings. 1st
In the figure, a to-be-treated liquid supply pipe 3 for supplying a to-be-treated liquid 2 is connected to a biological reaction tank 1. (not shown), with impurities removed to the extent that they do not interfere with membrane separation. An aeration tank 4 is provided in communication with the biological reaction tank 1, and the biological reaction tank 1 and the aeration tank 4 constitute a treated water tank. Further, a submerged membrane separator 5 is disposed immersed inside the aeration tank 4, and the submerged membrane separator 5 has a plurality of membrane modules of 10 to 2.
They are arranged at intervals of about 0 mm, and each membrane module consists of a flat ultrafiltration membrane attached to a PvC or FRP filter plate.

A filtrate extraction pipe 7 is connected to the negative side of the submerged membrane separator 5, and a suction pump 8 is interposed in the middle of the filtrate extraction pipe 7. Further, an aeration device 8 is provided below the submerged membrane separator 5, and a blower IO is connected to the aeration device 9.

An excess sludge discharge pipe 11 communicates with the bottom of the aeration tank 4, and the excess sludge discharge pipe 11 communicates with a dehydrator 13 via a sludge pump 12. In addition, excess sludge discharge pipe 11
may be communicated in the middle of a circulation pipe, which will be described later, as shown by a broken line in the figure. Further, the dehydrator 13 is connected to a secondary treatment water tank 15 via a separated liquid pipe 14. Further, the aeration tank 4 communicates with a prescreen 17 via a liquid feed pump 16, and the prescreen 17 communicates with a cross-flow membrane separation device 13 via a pressure pump 18. still,
The pre-screen 17 is determined based on the pre-processing equipment, and is not necessarily necessary if the pre-processing accuracy is high.

Further, the cross-flow type membrane separation device 19 communicates with the biological reaction tank 1 via a circulation pipe 20, and the permeate side communicates with the secondary treatment water tank 15.

Hereinafter, the effects of the above configuration will be explained.

The liquid to be treated 2 flowing into the biological reaction tank 1 from the liquid to be treated supply pipe 3 is mixed with the activated sludge in the biological reaction tank 1 and then transferred to the aeration tank 4.
flows into. At this time, nitrogen and BOD are removed from the liquid to be treated 2 by nitrifying bacteria, denitrifying bacteria, BOD oxidizing bacteria, etc. that form activated sludge in the biological reaction tank 1 and the aeration tank 4.

Then, the liquid to be treated 2 in the aeration tank 4 is subjected to negative pressure from the suction pump 8 and is suction-filtered by the submerged membrane separator 5, and the permeated liquid and the membrane of the filtration membrane pass through the filtration membrane of the submerged membrane separator 5. The activated sludge is collected on the surface and separated into solid and liquid. In addition, the permeated liquid that has passed through the filtration membrane flows into the secondary treatment water tank 15 through the filtrate extraction pipe 7, and the activated sludge collected on the membrane surface of the filtration membrane is
The air is washed by the upward stirring flow generated by the air ejected from the aeration device 9, and remains in the aeration tank 4. The surplus sludge in the aeration tank 4 is then supplied by the sludge pump 12 to the dehydrator 13 through the surplus sludge discharge pipe 11, and the sludge concentration in the aeration tank 4 is maintained constant. Further, the separated liquid separated in the dehydrator 13 flows into the secondary treatment water tank I5.

The liquid to be treated 2 in the aeration tank 4 is sent to a pre-screen 17 by a liquid feed pump 16 to remove impurities, and then is fed to a cross-flow type membrane separator 19 by a pressure feed pump 18. Further, the water to be treated supplied to the cross-flow type membrane separation device 19 is cross-flow filtered by passing water along the membrane surface of the filtration membrane at a predetermined high flow rate, and the water is mixed with the permeate passing through the filtration membrane. It is separated into solid-liquid and activated sludge whose permeation is blocked by a filtration membrane. Furthermore, the permeate that has passed through the filtration membrane is extracted as treated water to the secondary treatment tank ■5.
The activated sludge that is supplied to the biological reaction tank 1 and whose permeation is blocked by the filter membrane is washed away by high-flow water, passes through the circulation pipe 20, and is returned to the biological reaction tank 1, serving as return sludge and nitrification circulating liquid.

Therefore, in the immersed membrane separator 4, the liquid to be treated 2 is concentrated to a sludge concentration that does not clog the filtration membrane under the aeration conditions defined by the BOD concentration of the liquid to be treated 2, and the immersed membrane separator The lack of concentration ratio due to 4 is compensated for by the cross-flow type membrane separator 19, and a predetermined sludge concentration is finally achieved. Therefore, clogging of the filtration membrane in the submerged membrane separator 4 is prevented, and the quantitative load of the liquid to be treated 2 on the cross-flow membrane separator 19 is reduced. Costs go down.

Note that the immersed membrane separator 5 may be placed in the biological reaction tank 1, but in order to improve the water quality level, the immersed membrane separator 5 is placed inside the independent aeration tank 4 as in this embodiment. It is better to place

As shown in FIG. A valve 21 is installed, and a second valve is installed between each aeration device 9 and the blower 10.
A configuration may be adopted in which an on-off valve 22 is provided, and in this configuration, the first on-off valve 21 and the second on-off valve 22 are operated according to the flow rate of the liquid to be treated 2 and the BOD concentration of the liquid to be treated 2. By adjusting the quantity of the aeration device 9 and submerged membrane separator 5 to be operated, the amount of aerated air for the liquid to be treated 2 can be controlled while maintaining the aeration intensity that prevents clogging of the filtration membrane of the submerged membrane separator 5. It can be adjusted as appropriate.

Effects of the Invention As described above, according to the present invention, a submerged membrane separator and a cross-flow membrane separator are used in combination, and the cross-flow membrane separator compensates for the lack of concentration caused by the submerged membrane separator. By finally achieving a predetermined sludge concentration, the sludge concentration in the treated liquid is adjusted to such a level that the filtration membrane does not become clogged under the aeration conditions specified by the BOD concentration in the treated liquid. It is possible to prevent clogging of the filtration membrane of the submerged membrane separator. In addition, by concentrating the liquid to be treated to a certain extent using the submerged membrane separator, the quantitative load of the liquid to be treated on the cross-flow membrane separator is reduced, reducing the output of the pressure pump and reducing energy costs. can be achieved.

In addition, by providing a plurality of submerged membrane separators and aeration devices, the number of aeration devices and submerged membrane separators to be operated can be adjusted to prevent clogging of the filtration membrane of the submerged membrane separator. The amount of aerated air for the liquid to be treated can be adjusted as appropriate while maintaining the strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, and FIG. 2 is a layout diagram of a submerged membrane separation apparatus showing another embodiment of the present invention. 1... Biological reaction tank, 4... Aeration tank, 5... Immersion type membrane separation device, 19... Cross flow type membrane separation device.

Claims (1)

[Scope of Claims] 1. An immersed membrane separator that is immersed in a treated water tank and whose negative pressure side communicates with the suction side of a suction pump; and an aeration device provided below the immersed membrane separator. , a cross-flow membrane separation device that communicates with the treated water tank via a pressure pump;
1. An organic wastewater treatment device comprising a circulation pipe having one end communicating with a cross-flow type membrane separation device and the other end communicating with a treated water tank. 2. The organic wastewater treatment apparatus according to claim 1, wherein a plurality of immersion type membrane separation devices are provided in the treated water tank, and a plurality of aeration devices are provided corresponding to each immersion type membrane separation device.