JPH04326927A - Membrane separator - Google Patents

Abstract

PURPOSE:To operate a membrane separator over a long period of time while keeping stable capacity by detecting clogging at an early stage before the fine flow paths of the solid-liquid separation membrane of the membrane separator is clogged with SS in raw water to remove clogging by simple washing. CONSTITUTION:In a membrane separator equipped with a raw water tank 5 a membrane module 1, a pump 5 passing the water in the raw water tank through the membrane module 1 and a circulation system 7 returning the conc. water discharged from the membrane module 1 to the raw water tank 5, a flow rate detection means is provided to the circulation system 7 and a controller subjecting the membrane module 1 to washing when the detection values of flow rate detection means 11, 12 become set values or less is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation device that performs solid-liquid separation using a membrane module equipped with a solid-liquid separation membrane such as a flat membrane type, tubular type UF membrane, or MF membrane.

0002

[Prior Art] A cross flow comprising a raw water tank, a membrane module, a pump for passing water from the raw water tank through the membrane module, and a circulation system that returns concentrated water discharged from the membrane module to the raw water tank. Membrane separation devices of this type are conventionally known. This membrane separation device has come to be used for solid-liquid separation of liquids with high MLSS, such as activated sludge mixed liquids and flocculation treated liquids.

[0003] The problem with solid-liquid separation of such a high MLSS liquid using a membrane separation method is that SS is deposited in the fine channels of the solid-liquid separation membrane through which water passes, clogging the channels. In the case of membrane separation equipment whose interior cannot be cleaned if it becomes clogged, the membrane module must be replaced with a new one, and in the case of membrane separation equipment whose interior can be cleaned, cleaning is required, but cleaning takes time and time. It takes a lot of work.

[0004] Therefore, before the flow path of the solid-liquid separation membrane becomes clogged with SS, it is necessary to detect at an early stage that the flow path is starting to be clogged with SS, and once detected, the operation is interrupted and cleaning water is passed through the membrane separation device. The solid-liquid separation membrane is regenerated by removing SS clogging the channel with water.

[0005]

[Problems to be Solved by the Invention] Early detection of flow path clogging by conventional SS is possible by
This is done by monitoring the inlet pressure or the amount of permeated water discharged from the membrane module.

[0006] However, even if the inlet pressure of raw water is monitored, in the case of a membrane separation device in which a plurality of membrane modules are installed together in a header pipe, the solid-liquid separation membrane of some membrane modules may become clogged. However, since the pressure increase is small, it cannot be detected reliably. In particular, when the pump for passing raw water through the membrane separation device is a centrifugal pump, the flow rate fluctuation is larger than the pressure fluctuation, so clogging cannot be detected early by monitoring the inlet pressure. In addition, even if the pump is a metering pump such as a snake pump, if the stator is worn, the flow rate fluctuation will be larger than the pressure fluctuation, just like in the case of a centrifugal pump, so early detection of clogging is also possible. cannot be done.

[0007]Furthermore, membrane contamination has a greater effect on fluctuations in the amount of permeated water discharged from the membrane module than clogging of the flow path, so even if the amount of permeated water decreases, It is not possible to distinguish between clogging of the flow path and membrane contamination, and it is not possible to accurately detect clogging of the flow path at an early stage. Since the permeated water is drained until just before the flow path of the solid-liquid separation membrane is blocked, it is difficult to detect early clogging of the flow path based on a decrease in the amount of permeated water.

[0008]

[Means for Solving the Problems] Therefore, the present invention makes it possible to detect clogging of the flow path of the solid-liquid separation membrane at an early stage by detecting the flow rate of concentrated water discharged by the membrane module and circulated to the raw water tank. In a membrane separation device comprising a raw water tank, a membrane module, a pump for passing water from the raw water tank through the membrane module, and a circulation system for returning concentrated water discharged from the membrane module to the raw water tank. , a flow rate detection means is provided in the circulation system, and a controller is provided which shifts to cleaning of the membrane module when the detected value of the flow rate detection means becomes less than a set value.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the illustrated embodiment, reference numeral 1 denotes a plurality of membrane modules arranged in parallel, and each membrane module is equipped with a solid-liquid separation membrane 2. The plurality of membrane modules 1, 1... are connected at one end in parallel to the water supply side header 3, and the circulation pump 4
By supplying the raw water in the raw water tank 5 to the header 3, the raw water is passed through each membrane module 1. and,
The water that permeated through the fine channels of the solid-liquid separation membrane 2 in each membrane module 1 is discharged from the permeated water discharge pipe 6, and the concentrated water that did not pass through the solid-liquid separation membrane leaves the membrane module 1 as a raw material. It is circulated to the water tank 5 by the circulation system 7. In this example, the circulatory system 7
consists of a header 8, a concentrated water discharge pipe 9 that connects each membrane module 1 and the header 8, and a return pipe 10 that connects the header and the raw water tank 5.

[0010] In the above device, when pressurized raw water passes through the fine channels of the solid-liquid separation membrane inside the membrane module,
Moisture permeates through the flow path of the membrane, and SS in the raw water is concentrated on the membrane surface and adheres to the membrane surface, forming a cake layer. If the amount of concentrated water circulated in the circulation system 7 from the membrane module to the raw water tank 5 (corresponding to the membrane surface flow rate of the solid-liquid separation membrane 2) is sufficient, the cake layer formation rate and cake peeling rate are balanced. , the thickness of the cake layer is constant. However, if the amount of circulating water decreases for some reason, the flow rate at the membrane surface also decreases, so the cake layer formation rate exceeds the cake peeling rate, the thickness of the cake layer increases, and the flow path of the solid-liquid separation membrane becomes narrower. A blockage occurs,
Eventually, the flow path becomes blocked.

Therefore, if the header 8 is not provided, a flow meter 11 is attached to each concentrated water discharge pipe 9 of each membrane module 1, and if the header 8 is provided, the flow meter 11 is installed to the concentrated water discharge pipe 9 from the header 8 to the raw water tank 5. A flow meter 12 is installed in the middle of the pipe 10. Of course, even when the header 8 is provided, a flow meter may be attached to each concentrated water discharge pipe 9.

[0012] When the circulation flow rate of concentrated water circulated from the membrane module 1 to the raw water tank 5 by the circulation system 7 is normally, for example, 1.5 to 3 m/S, the flow rate decreases by about 20% and the set value When it reaches 1.2 to 2.4 m/S,
After the flowmeters 11 and 12 send a signal to the alarm 13 to issue an alarm and stop the operation of the device, the pump 15 supplies the cleaning water (clean water) in the cleaning water tank 14 to the membrane module 1.
The solid-liquid separation membrane 2 is regenerated, the blockage is removed, and the operation is restarted. When a flow meter is attached to each concentrated water discharge pipe, the flow rate of each membrane is measured, so when the wash water is supplied to each module and the header 3 is installed, the flow rate of each membrane is measured. Supply wash water before. Note that the cleaning water may be supplied by a head instead of the pump 15.

[0013]

As described above, in the present invention, a flow rate detection means is provided in the circulation system 7 that circulates concentrated water from the membrane module 1 to the raw water tank 5, and by detecting the circulating flow rate of concentrated water, the solidification of the membrane module can be improved. It detects at an early stage that the channel of the liquid separation membrane 2 is clogged with SS, removes the blockage in the channel with washing water, and maintains the performance of the membrane separation device stably without clogging the channel of the solid-liquid separation membrane. , it becomes possible to drive for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of the membrane separation apparatus of the present invention.

[Explanation of symbols]

1 Membrane module 2 Solid-liquid separation membrane 3 Water supply side header 4 Circulation pump 5 Raw water tank 6 Permeated water discharge pipe 7 Circulatory system 8 Header 9 Concentrated water discharge pipe 10 Return pipe 11 Flowmeter 12 Flow meter 13 Alarm device 14 Washing water tank 15 Pump

Claims (1)

[Claims] 1. Membrane separation comprising a raw water tank, a membrane module, a pump for passing water from the raw water tank through the membrane module, and a circulation system for returning concentrated water discharged from the membrane module to the raw water tank. A membrane separation apparatus characterized in that the circulation system is provided with a flow rate detection means, and a controller is provided that shifts to cleaning the membrane module when the detected value of the flow rate detection means becomes equal to or less than a set value. Device.