JPS63286749A - Method for measuring contamination index of membrane filter device - Google Patents

Abstract

PURPOSE:To exactly measure a contamination index by the flow rate of filtration when the water filtered by a filter membrane having excellent filter performance passes an ultrafilter membrane for testing and the flow rate of filtration at which test water passes the same filter membrane. CONSTITUTION:The filtered water as water to be treated is previously obtd. by using the filter membrane similar to the ultrafilter membrane 9 for testing or the filter membrane having the higher filter performance than the filter performance of the membrane 9. A brand new filter membrane 9 is then set to a measuring instrument and the filtered water which is previously obtd. is passed therethrough under a specified pressure. The filtered water 1 dropping from the outside of the membrane 9 is received in a measuring cylinder 12 and the flow rate A of filtration is measured from the volume of the filtered water within the specified period of time. The same pressure as the pressure applied to the water at the time of measuring the flow rate A is applied to the test water to be subjected to determination of the contamination index and is filtered by the filter membrane used for measurement of the flow rate A. The flow rater B of filtration of this time is measured. The membrane 9 is contaminated according to the content of the contaminating material in the test water. Since the flow rate B is inversely proportional to the content of the contaminating material in the test water, the contamination index of the test water is determined from the ratio between the flow rate B and the flow rate A.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is installed to obtain high purity water with extremely low particulate content, such as purified water for analysis, water for pharmaceuticals, or ultrapure water for cleaning semiconductors. , relates to a method for determining a contamination index of a membrane filtration device such as an ultrafiltration membrane device or a reverse osmosis membrane device.

<Conventional technology> Traditionally, water supply, industrial water, groundwater, river water, lake water,
Alternatively, various types of recovered water and the like are used as raw water and subjected to various treatment steps to obtain high-purity water with extremely low particulate content, such as ultrapure water for semiconductor cleaning. When obtaining such high-purity water, various membrane filtration devices depending on the purpose, such as microfiltration membranes, ultrafiltration membranes, and reverse osmosis membranes, are used during the treatment process to remove fine particles from the water to be treated. It is commonly used for. Reverse osmosis membranes were initially developed as permeable membranes to desalinate salts in water to be treated, but in recent years they have been installed at the end of the ultrapure water treatment process for semiconductor cleaning, for example, to remove salts from the water being treated. T, O, C (total organic carbon)
At the same time, it has been installed to remove microparticles such as various bacteria through permeation, and according to theory, permeation (
Permeation and filtration
), but since there is no difference in filtering out fine particles through a membrane, here, for convenience, a reverse osmosis membrane device is also treated as a membrane filtration device.

When such a membrane filtration device is used in a process, it is extremely important to know the contamination index for the filtration membrane of the water to be treated.

In other words, the type of filtration membrane to be used in a membrane filtration device can be determined from the contamination index, or the replacement period of the filtration membrane can be predicted, or the necessity of installing a pre-treatment device can be determined using the contamination index at the time of initial design. It is used to judge the quality of the pretreatment equipment, to use it as a clue to know the type of pretreatment equipment, or to manage the treatment performance of the pretreatment equipment by regularly knowing the contamination index of the water to be treated.

Conventional methods of measuring the pollution index include SDI value,
The MF value, FT value, SI value, etc. are used.

The SDI value is a contamination index determined from the flow rate when a sample water is filtered at a constant pressure using a 0.45 μm filter, and the MF value is a contamination index obtained by filtering a fixed amount of sample water using a 0.45 μm filter. The contamination index is determined from the filtration time when water is suction-filtered under a constant reduced pressure, and the contamination index is determined from the flow rate when the test water is filtered at a constant pressure using a filter with an FT value of 0.2 μm. The SL value is a contamination index determined from the flow rate when sample water is filtered at a constant pressure using a 0.8 μm filter.

<Problems to be Solved by the Invention> By the way, pure water for analysis, water for pharmaceuticals, ultrapure water for cleaning semiconductors, etc., can be obtained using various pretreatment equipment, such as a coagulation sedimentation equipment, a sand filtration equipment, and a two-bed In some cases, the water is processed through a three-column pure water production device, a mixed bed pure water production device, a precision filter, etc., and then processed with a membrane filtration device such as an ultrafiltration membrane device. It is difficult to measure contamination indicators of equipment using conventional SDI values, MF values, FT values, Sl values, etc.

This is because if the same raw water is treated with multiple lines of pretreatment equipment of exactly the same type, and these treated water is filtered as treated water through the same type of ultrafiltration membrane equipment, the ultrafiltration rate of each line will be Even if the FT value of the water to be treated in a filtration membrane device is exactly the same, a phenomenon often occurs in which the degree of increase in pressure loss in the ultrafiltration membrane device is completely different. Furthermore, F
Not only the T value, but also the SDI value, MF value, and Sl value,
This phenomenon also occurs.

These phenomena clearly indicate that the water to be treated by the membrane filtration device contains pollutants that cannot be measured using conventional pollution indicators.

An object of the present invention is to provide a method that can accurately measure contamination indicators for a membrane filtration device even in relatively clear sample water that cannot be measured using conventional contamination indicators. That is.

Means for Solving Problems〉 The present invention provides an ultrafiltration membrane for testing using filtrated water from an ultrafiltration membrane similar to the ultrafiltration membrane for testing obtained in advance or from the ultrafiltration membrane for testing. The filtration flow rate A is measured when filtered water is passed through a filtration membrane with excellent filtration performance at a constant pressure, and then a certain amount of test water is passed through the test ultrafiltration membrane. The filtration flow rate B when the pollutant is filtered through the test ultrafiltration membrane, and then the filtrate water is passed through the test ultrafiltration membrane again at the same pressure as when the filtration flow rate A was measured. The present invention relates to a method for measuring a contamination index in a membrane filtration device, characterized in that the contamination index is determined using the filtration flow rate A and the filtration flow rate B.

In other words, 0.2μ used when measuring conventional contamination indicators.
Change to m ~ 0.8 μm filter, l/1 than that
Using a test ultrafiltration membrane with a pore size of 0 to 1/100, water that does not contain substances that substantially contaminate the ultrafiltration membrane is first passed through the ultrafiltration membrane at a constant pressure. Then, the filtration flow rate at that time is measured as a blank, and then a certain amount of test water is passed through the ultrafiltration membrane after measuring the blank, and the contaminants in the test water are captured by the filtration membrane,
Next, by filtering the same water under the same conditions as in the blank measurement described above and measuring the filtration flow rate at that time, it is possible to determine how much the ultrafiltration membrane is contaminated when the sample water is filtered. This is known from the filtration flow rate, and the contamination index is determined using both values of the filtration flow rate.

<Effect> The present invention will be explained in detail below for each measurement procedure.

FIG. 1 is an explanatory diagram showing the flow of an embodiment of the measuring device used in the present invention, and FIG. 2 is an enlarged partially cutaway sectional view of an ultrafiltration membrane for testing.

As shown in Figures 1 and 2, a sealable filtration tank 1 and a sealable test tank 2 are prepared, and valves 3 and 4 are provided at the lower parts of both tanks 1 and 2, respectively. One ends of the outflow pipes 5 and 6 are connected, the other ends of the outflow pipes 5 and 6 are communicated with each other, and one end of the merging pipe 7 is connected to the communication portion. In addition, an injection needle 8 having a diameter slightly larger than the inner diameter of the hollow fiber ultrafiltration membrane, which is the test ultrafiltration membrane 9, is attached to the other end of the confluence tube 7, and the injection needle 8 is inserted into the ultrafiltration membrane 9.
It is inserted into the hollow part of one end of the pipe to establish watertight communication.

Further, a wire-shaped seal plug lO having a diameter slightly larger than the inner diameter of the filtration membrane is inserted into the hollow portion at the other end of the filtration membrane 9 to close the hollow portion at the other end.

Further, a graduated cylinder 12 is installed below the filter membrane 9 to receive all the filtered water 11 dripping from the filter membrane.

A pressure indicator 13 is attached to the upper part of the filtered water tank 1 and the water test tank 2, respectively, and an inert gas inlet pipe 16 having valves 14 and 15 is connected to the upper part of both tanks 1 and 2, respectively.

Next, a procedure for measuring a contamination index in the present invention will be explained.

First, an ultrafiltration membrane similar to the test ultrafiltration membrane 9 used for measurement, or a filtration membrane with better filtration performance than the test ultrafiltration membrane 9, in other words, a filtration membrane with a filtration pore size larger than that of the ultrafiltration membrane 9. For example, pure water or the like is filtered in advance as water to be treated using a filtration membrane having a small filtration pore size to obtain filtrated water.

On the other hand, a new ultrafiltration membrane 9 for testing is set in the measuring device according to the flow shown in FIG.
is opened and a constant pressure is applied to the filtration tank 1 using an inert gas, such as nitrogen gas, and the filtered water in the filtration tank 1 is filtered by the test ultrafiltration membrane 9 using the pressure.

By receiving the filtered water 11 dripping from the outside of the test ultrafiltration membrane 9 into the graduated cylinder 12, the filtration flow rate A is measured from the amount of filtered water received by the graduated cylinder 12 within a certain period of time.

The filtration flow rate A is the filtration flow rate when water is filtered without any contaminants attached to the membrane surface and without contaminating the membrane surface even during filtration, and corresponds to a so-called blank. Note that the pressure when measuring the filtration flow rate A varies depending on the pore size of the test ultrafiltration membrane 9 used, but for example, when using one with a molecular weight cut-off of around 10.000, 1 to 2 kgf/d is sufficient. , and a filtration time of about 5 minutes is sufficient.

Next, put the sample water to determine the contamination index into the test tank 2,
After sealing, valves 15 and 4 were opened to apply pressure to the test water tank 2 using nitrogen gas in the same way, and a certain amount of test water was used to measure the filtration flow rate A. filter.

By filtering the test water, the membrane surface becomes contaminated depending on the amount of contaminants in the test water.

Therefore, if the amount of contaminants contained in the sample water is relatively large, the amount of sample water to be filtered may be small, and if the amount of contaminants is relatively small, the amount of sample water to be filtered may be increased.

For example, as the test ultrafiltration membrane 9, the outer diameter is 1.21-1
Inner diameter 0.8 fin, length 200 crane, molecular weight cut off 13°000
When using a hollow fiber ultrafiltration membrane and using pure water obtained by treating city water with a sand filtration device and an ion exchange device as water test, the amount of water should be around 100 mJ.

After the sample water is filtered through such operations and the contaminants in the sample water are captured on the membrane surface, the valve 14.3 is opened under the same conditions as those used to measure the filtration flow rate A described above, and the filtration in the filtration water tank 1 is carried out. Water is filtered through the test ultrafiltration membrane 9, and the filtration flow rate B at that time is measured.

As is clear from the above explanation, the test ultrafiltration membrane 9 is contaminated depending on the amount of contaminants in the test water, so the filtration flow rate B is inversely proportional to the amount of contaminants in the test water. The contamination index of the sample water can be determined from the relationship between the filtration flow rate A measured as a blank and the filtration flow rate B after filtering a certain amount of sample water.

In addition, when measuring the filtration flow rate A and the filtration flow rate B, it is preferable that the filtration pressure be exactly the same and the filtration temperature also be the same. This is to eliminate errors caused by differences in water viscosity due to temperature differences, and by filtering at the same temperature, calculation of viscosity conversion of each filtration flow rate can be omitted.

The contamination index (Ul for convenience) in the present invention can also be displayed as UI-filtration flow rate A-filtration flow rate B. In this case, the larger the UI, the greater the amount of contaminants in the sample water.

However, as a UI, it is preferable to display the ratio between the filtration flow rate B and the filtration flow rate A, or the ratio according to equation (1) as a percentage.

When UI is calculated using equation (1), the larger the value, the smaller the amount of contaminants in the sample water. In other words, if the UI in (1) 2 is, for example, 100, it means that the filtration flow rate A and the filtration flow rate B are equal, and even if the sample water is filtered through the test ultrafiltration membrane, the ultrafiltration membrane will not be contaminated at all. This means that no contaminants are present in the sample water.

The ultrafiltration membrane for testing used in the present invention has a molecular weight cutoff of 3.
Preferably, an ultrafiltration membrane having a pore size in the range from .000 to 50.000 is used. In addition, the molecular weight cut-off is 3,00
If an ultrafiltration membrane with a small pore size of 0 or less is used, the filtration pressure will be too high, and the filtration tank 1 or the test tank 2 will become a pressure vessel with quite high pressure, which will not only increase the cost of the measuring device but also shorten the measurement time. This is not preferable as it becomes quite long, and if an ultrafiltration membrane with a large pore size with a molecular weight cutoff of 50,000 or more is used, relatively fine contaminants in the sample water will pass through the ultrafiltration membrane, resulting in measurement errors. is undesirable because it becomes large and there is no difference from the SDI value etc. using a conventional 0.2 to 0.45 μm filter.

It is usually preferable to use a test ultrafiltration membrane with a molecular weight cut-off of about 10,000.

The ultrafiltration membrane used for testing can be of any shape, such as hollow fiber, flat membrane, or tubular. It is preferable to use a thread-like material because the measuring device is simpler.

The present invention will be explained in detail below.

Example-1 A simple turbidity filtration device that filters raw water while adding aluminum sulfate as a flocculant, and 2 beds 3 at the rear stage.
Three types of pure water (I), (n), and (III) obtained from three lines of water treatment equipment equipped with tower-type pure water production equipment were used as test water, and the pollution index (SDI value) in accordance with the ASTM method was determined. )
and the contamination index (UI value) of the present invention were measured.

(1) Measuring method of SDI value by ASTM method 0.45μ
Using a test filter of 2. '1 kgr/c
o! The test water was filtered at a pressure of (30 psi), the time to obtain 250 ml of filtered water was measured, and this was measured at t.

(seconds). After measuring t, continue filtration and filter the test water for T minutes (time of 1+ is also included in the T minutes)
, measure the time to obtain 250ml of filtered water in the same way,
Let this be tz (seconds).

Using the 1+ (seconds), tz (seconds), and T (minutes), calculate the SDI value using the following calculation formula.

Each pure water measured with T as 15 minutes (1) (II)
The SDI values of (■) are shown in Table 1.

(2) Method for measuring Ul value according to the present invention Using a hollow fiber test ultrafiltration membrane with an inner diameter of 0.8 m, an outer diameter of 1.2 m, a length of 200 m, and a molecular weight cutoff of 13,000,
The ultrafiltration membrane was placed in a measuring device as shown in FIGS. 1 and 2. Next, filtered water obtained by previously filtering pure water with a module made by bundling a large number of ultrafiltration membranes identical to the ultrafiltration membrane for the test was put into a filtered water tank, and using nitrogen gas], Okg f / The filtered water is filtered at a pressure of crA, and the filtration flow rate A (m
β/m1n) was measured.

Next, after filtering 100 ml of test water through the test ultrafiltration membrane, the filtered water was filtered at exactly the same pressure and temperature as when the filtration flow rate A was measured, and the filtration flow rate B (m I
t7min) was measured.

Using the filtration flow rate A and the filtration flow rate B, I
Find the JI value.

Each pure water (I) (II) measured by such method
The Ul values of (III) are shown in Table 1.

Table 1 Example-2 The tJI values measured by the contamination index measuring method of the present invention shown in Example-1 (2) were 98.92.8, respectively.
The following experiment was conducted using four types of pure water of 4.76 (the SDI values of all pure waters are the same).

In other words, four types of pure water having different UI values are applied to four lines of ultrafiltration membrane devices using an internal pressure module with a filtration area of 0.2M using a large number of hollow fiber ultrafiltration membranes with a molecular fractionation of ff 113,000. Each was filtered for 3 months using crossflow.

The filtration pressure is I, Okg f/co! The amount of non-permeated water and the amount of permeated water at the initial stage are 5127H140, respectively.
~50m! /H.

The permeate flow rate at the initial stage of filtration and the permeate flow rate after three months under the same pressure were measured for each pure water, and the values are shown in Table 2.

Table 2 The clogging speed in Table 2 was calculated using the following formula.

<Effects> As is clear from the above examples, even if pure water shows exactly the same value when measured using the SDI value, which is a conventional pollution index, when measured using the method of measuring the pollution index of the present invention, it becomes clear. There is a difference. Therefore, the measuring method of the present invention can clearly identify contamination indicators that cannot be determined using conventional measuring methods.

Furthermore, as shown in Example 2, there is a clear correlation between the pollution index (Ul value) measured by the method of the present invention and the clogging rate of the ultrafiltration membrane device. By measuring , it is possible to effectively manage the operation of membrane filtration devices such as ultrafiltration membrane devices, as well as to determine the necessity of installing pre-treatment equipment, and to apply it to various uses. can.

[Brief explanation of the drawing]

Both Figures 1 and 2 are drawings showing embodiments of the present invention, Figure 1 is an explanatory diagram showing the flow of the measuring device used in the present invention, and Figure 2 is an ultrafiltration membrane for testing. FIG. ■...Filtering water tank 2...Testing tank 3.4.
... Valve 5.6 ... Outflow pipe 7 ... Merging pipe 8 ... Syringe needle 9 ... Ultrafiltration membrane for testing 1o ... Seal plug 11 ... Filtered water 1
2...Measured cylinder 13...Pressure indicator
14.15... Valve 16... Inert gas inflow pipe Figure 1

Claims (1)

[Scope of Claims] 1. The test ultrafiltration membrane contains filtrated water from an ultrafiltration membrane similar to the test ultrafiltration membrane obtained in advance or which has a better filtration performance than the test ultrafiltration membrane. Measure the filtration flow rate A when filtered water is passed through the filtration membrane at a constant pressure,
Subsequently, a certain amount of test water is passed through the test ultrafiltration membrane to filter out contaminants in the test water, and then the filtration flow rate A is applied to the test ultrafiltration membrane. A membrane filtration device characterized in that a filtration flow rate B is measured when the filtered water is passed through again at the same pressure as when it was measured, and a contamination index is determined using the filtration flow rate A and the filtration flow rate B. How to measure pollution indicators. 2. A method for measuring a contamination index in a membrane filtration device according to claim 1, wherein the contamination index is determined from the ratio of the filtration flow rate B and the filtration flow rate A. 3. A method for measuring a contamination index in a membrane filtration device according to claim 1 or 2, using a test ultrafiltration membrane having a pore size with a molecular weight cut-off of 3,000 to 50,000.