JPH0342019A - Membrane separation apparatus - Google Patents

Abstract

PURPOSE:To prevent the raw water flow passage of a membrane module from clogging in the recirculation of taken-out water by collecting efficiently the admixtures, such as an exfoliated matter, which are separated from the surface of separation membrane of a membrane module and flowed out into the taken- out water, and discharging them from a circulation water system. CONSTITUTION:The raw water in a raw water tank 1 is introduced into a raw water chamber of a membrane module 2, and the water taken out of the raw water chamber is returned to the raw water tank 1. In a flow passage 15 for the taken-out water, a solid-liquid separation unit 3, such as a screen, is provided to carry out the solid-liquid separation treatment. Thus, the admixtures, such as an exfoliated matter, which are separated from the surface of separation membrane of the membrane module and flowed out into the taken- out water are efficiently collected and discharged from the circulation system. As a result, the raw water passage of the membrane module is prevented from clogging when the taken-out water is recirculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a membrane separation device, and particularly to a membrane separation device that solves the problem of clogging of raw water flow paths in a membrane module.

[Prior Art] Membrane separation means such as microfiltration (MF) and ultrafiltration (UF) are used in various industrial fields as means for separating particulate matter and polymeric substances from various solutions.

These membrane separation means can be used in minutes! Various membrane modules equipped with III are used, but in many cases, in order to prevent blockage of the log flow path of the membrane module, a membrane module is installed on the raw water inlet side of the membrane module to remove impurities from the raw water. Normally, these screens or strainers are installed at the inlet of the membrane module, for example between the raw water pump outlet and the membrane module, or at the raw water intake section of the raw water tank (or circulation tank). It is said that

By the way, when membrane-separating particulate matter or polymeric substances from various solutions, in order to obtain a high passing water velocity, generally a circulation filtration method (cross-filtration method) in which concentrated water in a membrane module is circulated is used.
flow filtration method) is adopted. In this case, the amount of circulating water will be several times to several tens of times the actual amount of treated water. Therefore, if a strainer or the like is installed at the inlet of the membrane module, the amount of water that passes through is large, requiring a large separation area for the strainer, etc., and the treatment efficiency is extremely poor, and the frequency of cleaning of the strainer, etc. is extremely high. Therefore, it is not practical.

For this reason, at present, a method of arranging a strainer or the like exclusively at the raw water inlet of the raw water tank is adopted.

[Problems to be Solved by the Invention] When a strainer or the like is placed at the raw water inlet of the raw water tank, impurities in the raw water are removed. ) does not pass through, so it removes foreign matter such as exfoliated materials that occur in the circulation system that includes the membrane module, that is, exfoliated materials that separate from the membrane surface of the membrane module and flow into the taken water. Therefore, there is a problem in that the raw water flow path of the membrane module is blocked by foreign substances such as peeled substances generated from within the membrane module.

In particular, in order to maintain a high rate of water passing through the membrane module, backwashing is performed in which treated water and gas are flowed back from the treated water side to peel off gel-like substances and cake layers adhering to the separation membrane surface. In this case, the contaminants that flow out from inside the membrane module into the extracted water due to backwashing cannot be captured by the strainer at the raw water inlet, resulting in significant blockage of the raw water flow path.

Therefore, in order to peel off and remove the gel-like substance and cake layer that adhere to the separation membrane surface, physical means such as removing the membrane module and cleaning the separation membrane, or chemical means such as chemical cleaning are required. However, there were drawbacks such as poor work efficiency and high processing costs.

The present invention solves the above-mentioned conventional problems, and efficiently captures impurities such as detached substances that are separated from the separation membrane surface of the membrane module and flows into the extracted water, and discharges them from the circulating water system. An object of the present invention is to provide a membrane separation device that prevents clogging of the raw water flow path of a membrane module when water is recirculated.

[3i! Means for Solving the Problems] The membrane separation device of the present invention is a membrane separation device in which raw water in a raw water tank is introduced into a raw water chamber of a membrane module, and water taken out from the raw water chamber is returned to the raw water tank. The present invention is characterized in that a solid-liquid separator is provided to enable solid-liquid separation treatment of the extracted water.

This solid-liquid separator is installed directly in the flow path of the extracted water,
The entire volume of the withdrawn water to be circulated may be passed through the solid-liquid separator, or it may be installed in a pipe branching from the flow path of the withdrawn water to separate the solid-liquid only when necessary, for example, during backwashing. Water may be allowed to flow through the device.

The solid-liquid separation device is not particularly limited, and any screen, strainer, etc. used in conventional membrane separation devices can be suitably employed.

[Function] In the membrane separation device of the present invention, since the solid-liquid separator is provided in the flow path of the water taken out of the membrane module, contaminants in the water taken out, such as exfoliated substances separated from the separation membrane surface of the membrane module, are removed. The substances are separated and removed in the solid-liquid separator before the extracted water returns to the raw water tank.

Therefore, impurities such as peeled substances generated from the membrane module are not reintroduced into the membrane module, and the raw water flow path of the membrane module is not clogged.

Moreover, the amount of water passed through this solid-liquid separator is a part of the amount of water sent from the raw water tank to the membrane module by the raw water pump, so compared to the case where a strainer etc. is installed at the inlet of the membrane module. , the load on the solid-liquid separator is small,
Less frequent cleaning is required, and processing efficiency is greatly improved.

〔Example] The present invention will be described in detail below with reference to the drawings.

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

The membrane separator shown in FIG.
This device circulates concentrated water (drawn water) to the raw water circulation tank 1, and a branch pipe (piping 15) is provided in the circulation flow path (piping 14) of this drawn water, and if necessary, the membrane module 2
The extracted water is passed through a solid-liquid separator (wedge wire type screen 3 in the figure) and returned to the raw water circulation tank 1.

That is, the membrane separator shown in FIG.
1. Concentration of the membrane module 2, which includes a raw water circulation tank 1, a feeding pipe 12 having a circulation pump P, a membrane module 2 equipped with a separation membrane 2a, a pipe 13 for discharging treated water from the membrane module 2, and a valve v1. Water (taken water) m-ring pipe 1
4 (14a.

14b), a pipe 15 (15a, 15b) equipped with a valve Vl branched from the circulation pipe 14 and a wedge wire type screen 3;

15c), it is mainly composed of a pipe 16 for supplying backwash water or backwash air (other gases may be used) from the treated water side of the membrane module 2. 17 is a pipe for draining mud from the screen 2.

In the membrane separation apparatus shown in FIG. 1, raw water such as a solution containing particulate matter or polymeric substances is supplied to a raw water circulation tank 1 from a pipe 11, and the raw water (circulated water) in the raw water circulation tank i is supplied to a circulation pump P. The raw water is supplied to the raw water chamber 2b of the membrane module 2 via the piping 12, and treated with the membrane component m. Then, the permeated water from the membrane module 2 is discharged as treated water from the pipe 13, while the concentrated water is extracted from the pipe 14a to the raw water circulation tank! At this time, if necessary, the valve Vl
, V2 is opened and closed, and all or part of the water taken out is transferred to pipe 1.
4b and then circulate it directly to the raw water circulation tank 1, or
The water is fed to the screen 3 through pipes 15a and 15b, treated with solid-liquid m, and then circulated to the raw water circulation tank 1 through pipe 15c. The solid content separated by the screen 3 is discharged from the pipe 17.

Next, a method for performing membrane separation using such a membrane separation apparatus will be described in more detail.

(i) First, when performing circulation filtration (cross flow [i) and backwashing, a method of performing backwashing by applying a backwashing pressure higher than the filtration pressure during filtration will be described.

Backwash water or air (gas) is supplied from the pipe 16 to the membrane module 2.
When introducing the water in-house and applying pressure to the separation membrane 2a to perform backwashing, the valve vI is closed, the valve v2 is opened, and the water taken out from the membrane module 2 is passed through the screen 3c through the pipes 14a, 15a, and 15b. After that, the raw water is returned to the raw water circulation tank 1 through the pipe 15c. The separated substances that have separated from the separation membrane 2a and flowed into the taken water due to backwashing are removed in the screen 3. When backwashing is not performed, C opens valve V;
2 is closed, the water taken out from the membrane module 2 is taken out through the piping 14a,
Raw water circulation tank l without solid-liquid content m treatment from 14b
Return to

(il) When cross-flow filtration and backwashing are performed, a method for stopping filtration and backwashing will be explained below.

Stop filtration and backwash water or air (gas) from piping 16.
is introduced into the membrane module 2 to apply pressure to the separation membrane 2a to perform backwashing and restart filtration after backwashing. Only during the period when the detached peeled matter is flowing out, valve Vl is closed and valve ■2 is opened, and the water taken out from the membrane module 2 is transferred to the pipes 14a, 15a, 15b, the screen 3, and the pipe 15c.
During other filtration, such as passing water through the tank and returning it to the raw water circulation tank 1 after processing the solid-liquid content m, valve V+ is opened and valve V2 is
is closed, and the water taken out of the membrane module 2 is returned to the raw water circulation tank 1 as it is.

(Ili) A method of alternately performing dead end filtration and circulation filtration (cross flow filtration) will be described below.

During total filtration when all circulation lines are closed, part of the gel-like substance or cake-like substance deposited on the surface of the separation membrane 28 is removed during circulation filtration, so valve v1 is closed during circulation filtration.
is closed, valve v2 is opened, and the water taken out from the membrane module 2 is passed through the pipes 14a, 15a, 15b, the screen 3, and the pipe 15c, and after being treated with the solid-liquid component 11, it is returned to the raw water circulation tank 1. In order to increase the stripping effect during this circulation filtration, backwashing water or air (gas) may be introduced from the pipe 16 to perform backwashing.

In this method of alternately performing total filtration and circulation filtration, as shown in Figure 1C, there is no need to provide a pipe with a screen branching from the circulation line, and solid-liquid liquid such as a screen is directly connected to the flow path of the taken water. It may also be equipped with a separation device.

In any of the cases (i) to (iii) above, according to the membrane separation device of the present invention, the separated material that has separated from the separation membrane of the membrane module and flowed into the taken water is solidified before being returned to the raw water circulation tank. Since it can be removed by the liquid separator, this peeled material will not be guided to the membrane module again and cause blockage of the raw water supply line. Since the amount of water flowing is a part of the amount of water introduced into the membrane module, the load is smaller and the frequency of cleaning is reduced compared to when a solid-liquid separation device such as a strainer is provided on the inlet side of the membrane module.

[Effects of the Invention] As described in detail above, according to the membrane separation apparatus of the present invention, the flow path is created by contaminants such as membrane peeled substances that are separated from the separation membrane of the membrane module, flowed out into the taken-out water, and circulated. Blockage is prevented. Furthermore, the load on the solid-liquid separator used is reduced compared to conventional ones, and maintenance such as cleaning is also reduced.

Therefore, according to the membrane separation apparatus C of the present invention, it is possible to perform stable and efficient membrane separation treatment in continuous treatment for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the membrane separation apparatus of the present invention. l... Raw water circulation tank, 2... Membrane module,
3...Screen, P...Circulation pump.

Claims (1)

[Claims] (1) In a membrane separation device in which raw water in a raw water tank is introduced into the raw water chamber of a membrane module, and the water taken out from the raw water chamber is returned to the raw water tank, the taken water can be solid-liquid separated to enable solid-liquid separation treatment. A membrane separation device characterized by being provided with a device.