JPH11137971A - Electric filter device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to remove the pollutant larger than membrane pore diameter and the decomposed components smaller than the membrane pore diameter by providing the water to be treated side of the device for filtering the polluting materials of the water to be treated by using the membrane with an electrochemical cell consisting of first and second electrodes facing each other and disposing a filter membrane on the filtrate side of the downstream. SOLUTION: The water to be treated is introduced from a water to be treated inlet 4 and is passed through the electrochemical cell comprising the electrodes 2, 3. The charge particles in the water to be treated are moved from the electrode 2 toward the electrode 3 by the voltage impression between the electrodes 2 and 3 to lower the charge particle concn. in the water to be treated. The water to be treated is thereafter filtered by the filter membrane 1 and the filtrate is discharged from a filtrate outlet 5 and the concd. water from a concd. water outlet 6. A target removal rate is calculated from the measured value of the materials to be removed of the water to be treated and the preset target value of the membrane filtrate and the impression electric power on the electrochemical cell is determined by using the target removal rate. The efficient filtration is made possible by controlling the impressed electric power on the electrodes 2, 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofiltration apparatus for all water treatments for separating and removing pollutants, particularly charged particles, molecules and ions contained in water, and a control method thereof.

[0002]

2. Description of the Related Art Water treatment methods using membranes are divided into (1) microfiltration method and
(2) Ultrafiltration, (3) Nanofiltration, and (4) Reverse osmosis, and smaller substances can be removed in the order of (1) to (4). First, the outline of these four film processing methods will be described.

(1) In the microfiltration method, the separated particle size is 0.01
Particles, suspended solids and bacteria in a solution of μm or more can be prevented, and the operation pressure is -600 kPa or more in the case of the suction method, and 200 kPa or less in the case of the pressurization method. (2) In the ultrafiltration method, a molecular weight of 1,000 to 300,00
Separation of colloidal substances and polymer substances in the solution of 0,
In the case of the suction method, the operation pressure is -600 kPa or more, and in the case of the pressurization method, the operation pressure is 300 kPa or less.

(3) In the nanofiltration method, low-molecular substances in a solution having a molecular weight of several hundred at the maximum can be separated, and the operating pressure of the pressurization method is 200 to 1500 kPa. (4) In the reverse osmosis method, salts, ions, and low molecular substances in a solution having a molecular weight of several tens can be separated, and the operating pressure of the pressurization method is 400 to 7000 kPa. The water treatment method using these membranes must be able to reliably remove suspended substances in the water to be treated, to be easily automated with few mechanically moving parts, to be able to save space, and to have a flocculant. There are many advantages, such as the ability to reduce the amount of used and shortening the construction period.

Next, there is an electrofiltration method in which a filtration membrane and an electrochemical cell are combined. In a general electrofiltration method, the treatment space for electrofiltration is separated by a filtration membrane, a second electrode is placed on the wall opposite to the filtration membrane on the side where the water to be treated flows, and the filtered water flows out through the filtration membrane. The first electrode is provided on the wall on the opposite side of the filtration membrane on the side, and filtration is performed in a state where power is supplied to the electrochemical cell including the pair of electrodes.

In the method described in JP-A-2-245209, the second electrode is the same as a general electrofiltration method, but is the first electrode on the same surface as the filtration membrane? , Or on the downstream side of the filtration membrane, that is, on the side of filtered water, and is a method of performing filtration with a structure that is installed integrally or in an overlapping manner. In this publication, filtration is performed with the above structure, and when a highly concentrated solution is concentrated, clogging of the filtration membrane is suppressed by hydrogen gas or oxygen gas bubbles generated by electrolysis of water. There is a feature.

[0007]

In order to remove dissolved components of rivers, lakes and marshes water and sewage secondary treatment water in water supply,
Among the water treatment methods using the membrane, (2) ultrafiltration and (3) nanofiltration are used depending on the membrane pore size and the size of the substance to be removed. However, these methods are 300-1
In order to obtain an operation pressure of about 500 kPa, pump equipment with large power is required, and there is a problem that running cost is increased. Therefore, space saving and power saving by improvement of filtration efficiency are required.

[0008] In the electrofiltration method using a combination of a filtration membrane and an electrochemical cell, when water to be treated containing Ca is filtered, if the first electrode on the membrane side is negatively charged, coagulation occurs in the filtered water. There is a problem that Ca precipitates and clear filtered water cannot be obtained. JP-A-2-245209
In the electrofiltration method of the publication, the first electrode described as “conductive sheet” in this publication, and the filtration membrane described as “porous or microporous”, the first electrode and the filtration membrane Are located on the same plane, or the first electrode has a structure in which the filtration membrane is on the filtered water side. In the case of such a structure, when the to-be-treated water containing Ca is filtered in a state where the first electrode is negative, Ca easily flows into the filtered water side through the membrane, and coagulation occurs. Another problem is that clear water cannot be obtained.

Furthermore, it is necessary to clarify a rational policy on a power control method for achieving a removal rate of a substance to be removed during an actual operation.

[0010]

In order to solve the above-mentioned problems, the present invention provides a device configuration for improving the performance of a membrane filtration system and an electric power for achieving a target removal rate of a substance to be removed. And a control method. First, in the method of improving the performance of the membrane filtration method, an electrochemical cell composed of a pair of electrodes is placed on the side of the water to be treated in order to allow the water to be treated to pass through the electrochemical cell and the membrane in this order, and the downstream side thereof. It is assumed that the apparatus has a configuration in which a filtration membrane is placed.

FIG. 1 shows a schematic diagram of the apparatus configuration of this filtration method. First, the water to be treated is introduced from the treated water inlet 4,
It passes through an electrochemical cell composed of a porous first electrode 2 and a second electrode 3. Thereafter, the water to be treated is the first electrode 2
Is filtered by the filtration membrane 1 in the vicinity of the filter water. Here, filtered water is sent out from the filtered water outlet 5, and unfiltered water is sent out from the concentrated water outlet 6.

The basic principle of this method is that, by applying a voltage between the electrodes, the charged particles in the water to be treated are moved by moving the charged particles in the water from the first electrode to the second electrode using electrophoresis as a driving force. This means that membrane filtration is performed after the reduction. As a result, the effect of removing charged particles is improved.
In addition, since the first electrode is located on the side of the water to be treated with respect to the filtration membrane, Ca that causes coagulation can be prevented from flowing into the side of the filtration water. With these two effects, it is possible to obtain clear filtered water, and the conventional problems can be solved.

Next, a power control method for achieving a target removal rate of a substance to be removed is described.
It is based on the finding that the removal rate of the substance to be removed is proportional to the square root of the power applied to the electrochemical cell through experiments. By utilizing this relationship, the removal rate is calculated from the measured value of the pollutant being treated by the water quality measurement device provided before passing through the electrochemical cell and the preset target value of the pollutant in the membrane filtration water. Is calculated from the relationship between the removal rate and the applied power, and the power applied to the first electrode and the second electrode is controlled. According to this method, rational control can be provided, and power saving during operation can be achieved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic diagram of an electrofiltration apparatus and a control method used to demonstrate the present invention. River water and lake water at five locations were used as the water to be treated. First, the water to be treated was injected into the water tank 8 to be treated, and was sent to the membrane filtration module 7 by the water pump 10 via the flowmeter 9. A ceramic membrane having a pore diameter of 0.2 μm is used for the filtration membrane 1, and an average pore diameter of 5 μm is used as the first electrode 2.
A platinum-plated titanium plate was used as the second electrode 3 using carbon porous material m.

Filtration was carried out in a state where power was supplied from a power source 12 with the first electrode 2 as a negative electrode and the second electrode 3 as a positive electrode. FIG. 3 shows the measurement results under these conditions. In this figure, the horizontal axis represents the square root of the applied power (W), and the vertical axis represents the removal rate measured by ultraviolet absorbance E260. Here, the E260 component is one of indexes indicating soluble organic substances such as humic acid and fulvic acid in river water and lake water. From the experimental results, it is usually 0.
E260, which is considered difficult to remove with a filtration membrane having a pore size of 2 μm
The components were confirmed to be removed by the apparatus of the present invention, and E2
The 60 rejection was found to increase in proportion to the square root of the applied power as shown.

Based on this finding, as shown in FIG. 2, an ultraviolet absorption spectrometer was installed in the water quality measuring device 13 to set a target removal rate for lake water, and the water quality was measured by the water quality measuring device 13. A signal of the density is transmitted to the calculator 14, and the output of the power supply 12 is controlled by the power controller 15 based on the signal to increase the removal rate by 10% at regular time intervals. FIG. 4 shows the relationship between the filtration time and the E260 removal rate. From this result, it can be seen that control on the target removal rate is effective using the fact that the E260 removal rate is proportional to the square root of the applied power. When a total organic carbon concentration meter, a turbidity meter, and a chemical oxygen demand meter are used as the water quality measurement device 13, the same results as in FIG. 4 are obtained.

In the above embodiment, the removal of dissolved components of river water, lake water, and sewage secondary water in drinking water has been described. However, water treatment using the electrochemical cell of the present invention is more extensive. Available in the field of water treatment. That is, not only the removal of substances having a negative charge in water such as humic acid or fulvic acid but also the removal of substances having a positive charge such as ammonia ions can be easily achieved by changing the polarity of the first electrode and the second electrode. This method can be applied to

[0018]

As described above, according to the present invention,
After placing the electrochemical cell by the first electrode and the second electrode facing the water to be treated, and a device configuration to place a filtration membrane on the side of the filtered water downstream thereof, after passing the water while the electrochemical cell is energized, Filtration made it possible to remove turbid matter larger than the membrane pore size and dissolved components smaller than the membrane pore size.

Further, a target removal rate is calculated from a measured value of the substance to be removed to be input to the membrane filtration device by the water quality measuring device and a preset target value of the membrane filtration water, and the target removal rate is calculated. Efficient filtration is achieved by determining the applied power using the relationship that the material removal rate is proportional to the square root of the applied power to the electrochemical cell and controlling the power applied to the first and second electrodes. Was made possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the electrofiltration method of the present invention.

FIG. 2 is a schematic diagram of the electrofiltration apparatus and control method of the present invention.

FIG. 3 is a graph showing experimental results of the applied power to the electrochemical cell and the E260 removal rate when using river water and lake water at five locations.

FIG. 4 shows the filtration time and E26 when the applied power is controlled so as to increase the target removal rate by 10% every 10 minutes.
The figure which shows the experimental result with 0 removal rate

[Explanation of symbols]

 1: filtration membrane 2: first electrode 3: second electrode 4: treated water inlet 5: filtered water outlet 6: concentrated water outlet 7: membrane filtration module 8: treated water tank 9: flow meter 10: treated water Pump 11: Filtration water tank 12: Power supply 13: Water quality measuring device 14: Operation unit 15: Power controller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuyuki Motoyama 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. No. 1 Fuji Electric Co., Ltd. (72) Inventor Ryutaro Takahashi No. 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Fuji Electric Co., Ltd.

Claims (4)

[Claims] An apparatus for filtering contaminants of water to be treated using a membrane, wherein the first electrode facing the side of the water to be treated is filtered in order to filter the water to be treated by the membrane after passing through the electrochemical cell. And an electrochemical cell comprising a second electrode and a filtration membrane downstream of the filtered water. 2. The apparatus according to claim 1, wherein one or both of the first electrode and the second electrode of the electrochemical cell are made of a metal mesh, a porous or fibrous activated carbon of carbon material, or a vapor-deposited or carbonized material. The electrofiltration device according to claim 1, wherein the electrofiltration device is calcined platinum or a platinum compound. 3. The apparatus according to claim 1, wherein a measured value of the pollutant during treatment by the water quality measuring device provided before passing through the electrochemical cell, and a preset target value of the pollutant in the membrane filtration water. To calculate the removal rate, calculate the applied power using the relationship that the calculated value of the removal rate is proportional to the square root of the applied power, and control the power applied to the first electrode and the second electrode. A method for controlling an electrofiltration device, comprising: 4. The method according to claim 3, wherein the measured value of the pollutant in the water quality measuring device is one of an ultraviolet absorbance meter, a total organic carbon concentration, a turbidity meter, and a chemical oxygen demand meter. 4. The method for controlling an electrofiltration device according to claim 3, wherein the measured value is a combination of a plurality of measured values.