JPH06292818A - Air closing preventive device for membrane filtration for waterworks - Google Patents

Abstract

PURPOSE:To prevent the decrease in an effective filtration area by generation of an air pool on a rear stage filter membrane primary side and to prevent the air closing of the pipeline of washing pipings at the time of back flow washing by automatically discharging the air bubbles generated from the water permeated through a front stage filter membrane to the outside of the system between the front stage filter membrane and the rear stage filter membrane. CONSTITUTION:The air bubbles are liable to be generated in the treated water of the front stage membrane as there is a rise of water temp. and a pressure difference arises at the time of passage through the membrane, because energy of cross flow is applied to raw water. The generated air bubbles are accumulated in the water flow route, and further, kept accumulation by flowing to the primary side in a rear stage membrane module 13. This air is, thereupon, expelled by an air vent valve 14 to prevent the decrease in the area of the rear stage membrane. The washing water is passed through a piping 17 from a washing water tank 19 and is pressurized by a washing pump 18 at the time of a back washing stage. A valve 11 is closed and a valve 12 held open and the air remaining on the secondary side of the front stage membrane module 6 is discharged from an air vent valve 9. The waste water of washing on the primary side of the front stage membrane module 6 is discharged from a drain pipe 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtering operation for waterworks utilizing a permeable membrane such as a microfiltration membrane and an ultrafiltration membrane.

[0002]

2. Description of the Related Art Heretofore, attempts have been made to perform a filtering operation for waterworks by using a filtration membrane such as a microfiltration membrane or an ultrafiltration membrane.

At this time, by arranging the filtration membranes in two stages in series, the effects of improving the quality of treated water and ensuring safety when the membrane is damaged are enhanced. By the way, if the post-stage membrane is a total filtration type, the energy efficiency is good, but bubbles are generated due to the pressure change of the pre-stage membrane filtration water, and air can be accumulated on the primary side of the post-stage total filtration membrane, which makes the post-stage filtration membrane effective. While reducing the membrane area, it hindered backwashing, which adversely affected filtration and backwashing.

[0004]

DISCLOSURE OF THE INVENTION In a membrane filtration device of a total volume filtration system composed of a membrane module case as a unit, the filtration membrane used for water supply cannot pass air unless it has a high pressure of several kg / cm ² or more. Therefore, the air contained in the supplied water and the air generated by the pressure change and the temperature change are accumulated on the primary side of the membrane module. Also, when the filtration membranes are installed in two stages in series and the post-filtration membrane is treated by the total filtration method, the bubbles generated from the pre-stage filtration water accumulate on the primary side of the post-filtration membrane module, and the filtration membrane area is reduced. Is causing. Further, when the air bubbles remain in the upstream pipe of the upstream filtration membrane, an air pool is generated during the upstream cleaning of the upstream filtration membrane, and a portion where the backwash water is not supplied is formed in the filtration membrane, resulting in poor cleaning.

[0005]

Means for Solving the Problems Here, the present invention provides a membrane filtration apparatus for waterworks in which filtration membranes such as microfiltration or ultrafiltration membranes are installed in series, and at least the latter-stage filtration membrane is a total-volume filtration system. After the filtration membrane filtration, the air bubbles generated from the upstream filtration membrane filtered water are automatically discharged to the outside of the system between the downstream filtration membrane, and the air is generated on the primary side of the downstream filtration membrane, and the effective filtration area. The present invention proposes an air blockage prevention device for membrane filtration for waterworks, which is characterized in that it prevents a decrease in water flow rate and prevents air blockage in a cleaning pipe path during backwashing.

[0006]

In general, in many cases, an air vent is attached to the casing of the membrane module, but it may be difficult to directly attach an automatic air vent valve or the like. Here, in the case of a cylindrical module such as a hollow fiber type, many of them have a shape in which both ends can be connected to a pipe, so an apparatus for removing air is connected to the connected pipe.

Since the specific gravity of air is lighter than that of water, it is easier to get rid of it by putting air vents near the module of the pipe connected to the membrane module and by installing an air vent at the top. Considering this, install the supply water supply pipe in the downward direction of the module. A float type air vent valve (small exhaust air amount), a quick intake / exhaust valve, an electric valve (large exhaust air amount), etc. are used for air venting.

[0008]

[Examples] This example is a case where a two-stage filtration membrane system is used, in which an air vent valve is installed in a device in which the former stage is a cross flow filtration by ultrafiltration and the latter stage is a total volume filtration by microfiltration. Is.

During the filtration process, the raw water pipe 1 receives the raw water from the water tank 2
Flow into. The front-stage membrane module 6 by the supply pump 3
Raw water is supplied to the water, and the cross flow returns to the water receiving tank 2 via the valve 7 and the pipe 8. The treated water filtered by the pre-stage membrane flows into the post-stage membrane module 13 after leaving the valve 11 open and the valve 12 closed via the pipe 10. The post-stage membrane-treated water flows into the washing water tank 19 via the pipe 15 and the flow meter 16, and is further distributed via the pipe 20.

Here, the treated water in the pre-stage membrane has bubbles because the water temperature rises because cross-flow energy is applied to the raw water and a pressure difference occurs when passing through the membrane. Cheap. The bubbles generated here accumulate in the flowing water path, and further continue to flow and accumulate in the primary side in the post-stage membrane module 13. Therefore, this air is removed by the air vent valve 14 to prevent a reduction in the area of the latter-stage membrane.

During the backwash process, the washing water tank 19 is connected to the pipe 17
Via the cleaning pump 18 and the valve 11 is closed,
The valve 12 is left open and flows into the anterior membrane module 6. Due to the pressure, the air remaining on the secondary side of the pre-stage membrane module 6 is discharged from the air vent valve 9. The cleaning drainage flowing out from the primary side of the upstream membrane module 6 is drained through the drain pipe 5 by opening the drain valve 4.

[0012] In this example, because of the two-stage treatment, there is almost no trapping of suspended matter in the post-filtration membrane. Therefore, the automatic cleaning mechanism for the latter filtration membrane is not incorporated.

[0013]

According to the above-mentioned device of the present invention, the air bubbles generated from the filtered water of the front stage filtration membrane are automatically discharged to the outside of the system, so that the air trap is generated on the primary side of the rear stage filtration membrane. And prevent the effective filtration area from decreasing,
It is possible to prevent air clogging in the cleaning piping path during backwashing.

[Brief description of drawings]

FIG. 1 is a system diagram of an apparatus according to the present invention.

[Explanation of Codes] 6 Front-stage membrane module 9 Air vent valve 13 Rear-stage membrane module 14 Air vent valve

Claims (1)

[Claims] 1. In a water supply membrane filtration device in which filtration membranes such as microfiltration membranes or ultrafiltration membranes are arranged in series, and at least the latter-stage filtration membrane is a total volume filtration system, after the first-stage filtration membrane filtration to the second-stage filtration membrane. In between, by automatically discharging the air bubbles generated from the upstream filtration membrane filtered water to the outside of the system, while preventing the occurrence of air pools on the primary side of the downstream filtration membrane and reducing the effective filtration area, An air blockage preventive device for membrane filtration for water supply, which is characterized by preventing air blockage in a cleaning pipe path during backwashing.