WO2014045840A1

WO2014045840A1 - Water treatment system, filtration membrane module, and water treatment method

Info

Publication number: WO2014045840A1
Application number: PCT/JP2013/073320
Authority: WO
Inventors: 山本　和夫; チュン・チョン・ミン; 智宏飛野
Original assignee: 国立大学法人東京大学
Priority date: 2012-09-18
Filing date: 2013-08-30
Publication date: 2014-03-27

Abstract

In the present invention, an anode (42) is facially arranged at a first distance (1.5 cm) to one surface of a filtration membrane (24) so that untreated water flows in a satisfactory manner to the filtration membrane (24) when water is to be treated using aeration and filtration by the filtration membrane (24), a cathode (44) is arranged so as face the anode (42) at a second distance (3.0 cm) to the other surface of the filtration membrane (24), and a DC electric current is applied to the anode (42) and the cathode (44). The amount of organic matter that causes blockage of the filtration membrane (24) is thereby reduced, organic matter deposited on the surface of the filtration membrane (24) is also removed by oxidative decomposition, and an increase in the filtration resistance in the filtration membrane (24) can be inhibited. As a result, the frequency of washing the filtration membrane (24) can be reduced.

Description

Water treatment system, filtration membrane module, and water treatment method

The present invention relates to a water treatment system, a filtration membrane module, and a water treatment method, and more particularly, to a water treatment system that performs water treatment using aeration that promotes activation of aerobic microorganisms and filtration through a filtration membrane, and the water treatment system. The present invention relates to a filtration membrane module used and a water treatment method.

Conventionally, as this type of water treatment system, a biological treatment apparatus that obtains biological treatment water from wastewater by bringing the wastewater into contact with a base material on which microorganisms that decompose the waste contained in the wastewater are carried to decompose the waste, A membrane filtration device that permeates treated water through a filtration membrane and physically separates it into concentrated treated water containing filth contained in biological treated water and filtered water, and a solid liquid that separates the treated water containing concentrated treated water into solid and liquid A device including a separation device and a circulation device that circulates the separated water separated into the biological treatment device by the solid-liquid separation device has been proposed (for example, see Patent Document 1). In this system, the concentrated treated water separated by the membrane filtration device is taken out without staying in the membrane filtration device, so that the filtration membrane is not blocked.

JP 2011-140017 A

In the water treatment using biological treatment and filtration membrane as in the above-mentioned water treatment system, when filth deposits on the filtration membrane and the transmembrane pressure difference (pressure difference on both sides of the filtration membrane) increases, chemicals such as chlorine are removed. The filtration performance is recovered by washing the filtration membrane by backwashing or the like. Therefore, if the increase in transmembrane pressure difference can be suppressed, the frequency of cleaning the filtration membrane can be reduced, and the system can be reduced in size and efficiency.

The main purpose of the water treatment system, the filtration membrane module, and the water treatment method of the present invention is to suppress an increase in transmembrane pressure difference in the filtration membrane of the water treatment system.

The water treatment system, the filtration membrane module, and the water treatment method of the present invention employ the following means in order to achieve the main object described above.

The water treatment system of the present invention is
A water treatment system that performs water treatment using aeration that promotes activation of aerobic microorganisms and filtration through a filtration membrane,
An anode disposed in a plane so that at least a part of the upstream side of the filtration membrane allows flow of water to be treated before treatment by the filtration membrane to the filtration membrane;
A cathode disposed opposite the anode;
With
When water treatment is performed, a direct current is supplied to the anode and the cathode.
It is characterized by that.

In the water treatment system of the present invention, direct decomposition in which the organic substance is oxidatively decomposed on the surface of the anode and indirect decomposition in which an oxidative substance generated by oxidative decomposition or the like decomposes the organic substance are performed. By such direct decomposition and indirect decomposition of organic substances, the amount of deposition deposited on the filtration membrane can be reduced, and an increase in the transmembrane differential pressure as a pressure difference between both sides of the filtration membrane can be suppressed. As a result, the water treatment system can be reduced in size and efficiency. In addition, the anode does not need to be arrange | positioned planarly over the whole surface of the upstream of a filtration membrane, and may be arrange | positioned planarly in the part.

In such a water treatment system of the present invention, the cathode may be disposed so as to face the anode with the filtration membrane interposed therebetween. This is because the cathode only needs to be disposed opposite the anode. In this case, the anode is disposed on the filtration membrane with a distance in the range of 1.0 cm to 3.0 cm, and the cathode is disposed on the filtration membrane with a distance in the range of 1.0 cm to 5.0 cm. It can also be characterized by being arranged. These distances are compatible values. If the distance is too large, the voltage required to pass the current increases. If the distance is too small, deposits accumulate between the anode and the filtration membrane.

In the water treatment system of the present invention, a second filtration membrane having a coarser mesh than the filtration membrane is provided on the upstream side of the anode, and the cathode is provided with the second filtration membrane. It can also be characterized in that it is arranged upstream of the membrane. By providing the second filtration membrane having a coarser mesh than the filtration membrane in this way, a deposit having a large effective diameter can be deposited on the second filtration membrane, and the amount of deposition of the filtration membrane can be reduced. As a result, it is possible to suppress an increase in transmembrane pressure difference as a pressure difference between both sides of the filtration membrane. In addition, since the cathode is disposed so as to face the anode across the second filtration membrane, the anode and the cathode can be disposed over almost the entire surface of the filtration membrane, and the effect of oxidative decomposition of organic matter by the anode is filtered. It can be performed on the entire surface of the film.

In the water treatment system of the present invention having such a second filtration membrane, the second filtration membrane may be formed of a nonwoven fabric. The anode is disposed on the filtration membrane with a distance in the range of 1.0 cm to 3.0 cm, and the second filtration membrane is disposed on the anode with a distance in the range of 1.0 cm to 3.0 cm. The cathode may be disposed on the second filtration membrane with a distance within a range of 1.0 cm to 5.0 cm. These distances are compatible values. If the distance is too large, the voltage required to pass the current increases. If the distance is too small, deposits accumulate between the anode and the filtration membrane.

In such a water treatment system of the present invention, as the anode, iridium dioxide-coated titanium (Ti / IrO ₂ : titanium coated with iridium dioxide), ruthenium dioxide-coated titanium (Ti / RuO ₂ : titanium coated with ruthenium dioxide) Iridium dioxide / ruthenium dioxide coated titanium (Ti / (IrO ₂ + RuO ₂ ): titanium coated with a mixture of iridium dioxide and ruthenium dioxide), boron-doped diamond (BDD) Platinum (Pt), lead oxide (PbO ₂ ), or the like can be used. As the cathode, platinum-coated titanium (Ti / Pt: titanium coated with platinum), platinum (Pt), iron (Fe), aluminum (Al), carbon (C), titanium (Ti), or the like is used. be able to.

Further, in the water treatment system of the present invention, direct current supplied to the anode and cathode is preferably is adjusted to be in the range of ^{0.1mA / cm 2 ~ 0.8mA / cm} 2 as a current density . This is based on the fact that when the amount is less than 0.1 mA / cm ² , the amount of oxidative decomposition of the organic matter due to the electrode reaction becomes small, and when the amount exceeds 0.8 mA / cm ² , the activity of decomposing the organic matter by microorganisms decreases. Therefore, by setting the current density within the above-described range, water treatment can be efficiently performed by both the oxidative decomposition of the organic substance by the electrode reaction and the decomposition activity of the organic substance by the microorganism.

Furthermore, in the water treatment system of the present invention, the anode may be arranged in a plane by any one of a mesh, a lattice, and a plurality of rows. This is based on the need to pass non-filtered water through the filtration membrane.

The filtration membrane module of the present invention is
A filtration membrane module used in a water treatment system for water treatment using aeration that promotes activation of aerobic microorganisms,
A filtration membrane arranged to form a hollow portion for taking out the filtered water;
An anode disposed in a plane on at least a part of the outer peripheral side of the filtration membrane so that water to be treated before the filtration treatment can flow to the filtration membrane;
A cathode disposed opposite the anode;
It is a summary to provide.

In the filtration membrane module of the present invention, the filtration membrane is arranged so as to form a hollow part for taking out the filtered water, and the anode is treated water before the filtration treatment at least at a part of the outer peripheral side of the filtration membrane. Is arranged so that it can flow to the filter membrane, and the cathode is arranged to face the anode. Water treatment is performed by immersing such a filtration membrane module in water to be treated, performing aeration, supplying a direct current to the anode and the cathode, and taking out the treated water from the hollow portion. On the surface of the anode, direct decomposition that oxidizes and decomposes organic substances and indirect decomposition that oxidative substances generated by this oxidative decomposition and the like decompose organic substances are performed. An increase in transmembrane pressure difference as a pressure difference between both sides of the filtration membrane can be suppressed. As a result, efficiency in the water treatment of the filtration membrane module can be achieved. In addition, the anode should just be arrange | positioned in at least one part of the outer peripheral side of a filtration membrane, and does not need to be arrange | positioned planarly over the whole surface.

In such a filtration membrane module of the present invention, the cathode may be disposed on the outer peripheral side of the filtration membrane so as to sandwich the filtration membrane with the anode.

The filtration membrane module of the present invention further includes a second filtration membrane that is coarser than the filtration membrane and disposed on the outer peripheral side of the anode, and the cathode is disposed on the outer peripheral side of the second filtration membrane. It can also be. By providing the second filtration membrane having a coarser mesh than the filtration membrane in this way, a deposit having a large effective diameter can be deposited on the second filtration membrane, and the amount of deposition of the filtration membrane can be reduced. As a result, it is possible to suppress an increase in transmembrane pressure difference as a pressure difference between both sides of the filtration membrane.

Furthermore, in the membrane filter module of the present invention, as the anode, iridium dioxide-coated titanium (Ti / IrO ₂ ), ruthenium dioxide-coated titanium (Ti / RuO ₂ ), iridium dioxide / ruthenium dioxide mixed-coated titanium (Ti / (IrO ₂₎ + RuO ₂ ), boron-doped diamond (BDD), platinum (Pt), lead oxide (PbO ₂ ), platinum coated titanium (Ti / Pt), Platinum (Pt), iron (Fe), aluminum (Al), carbon (C), and titanium (Ti) can be used.

The water treatment method of the present invention comprises:
A water treatment method for water treatment using aeration that promotes activation of aerobic microorganisms and filtration through a filtration membrane,
An anode disposed in a plane so as to allow water to be treated to flow through the filtration membrane before treatment by the filtration membrane to at least a part of the upstream side of the filtration membrane during water treatment; to the the arrangement cathodes so as to face, applying a direct current in the range of ^{0.1mA / cm 2 ~ 0.8mA / cm} 2 as a current density,
It is characterized by that.

In the water treatment method of the present invention, direct decomposition in which organic substances are oxidatively decomposed on the surface of the anode and indirect decomposition in which oxidative substances generated by oxidative decomposition or the like decompose organic substances are performed. By such direct decomposition and indirect decomposition of the organic matter, the amount of deposition deposited on the filtration membrane can be reduced, and an increase in the transmembrane pressure difference can be suppressed. As a result, the water treatment system can be reduced in size and efficiency. In addition, the anode does not need to be arrange | positioned planarly over one surface side of the filtration membrane over the whole surface, and may be arrange | positioned planarly in the part.

It is a block diagram which shows the outline of a structure of the water treatment system 20 as 1st Example of this invention. It is a block diagram which shows the outline of a structure at the time of seeing from the left side surface in FIG. 1 centering on the filtration membrane 24 of the water treatment system 20 of 1st Example. It is explanatory drawing which shows typically the effect | action by the anode 42 in the water treatment system 20 of 1st Example with a comparative example. It is explanatory drawing which shows the item of the water treatment system of the experiment example in 1st Example as a list. It is explanatory drawing which shows the composition of the to-be-processed water in the experiment example in 1st Example as a table | surface. The relationship between the time and transmembrane differential pressure in the first example and the comparative example when water treatment is continued in the experimental example in the first example is shown. It is explanatory drawing which shows the washing | cleaning date in the experiment example with respect to a 1st Example and a comparative example, the total filtration resistance, the filtration resistance (%) recoverable by physical cleaning, and the filtration resistance (%) unrecoverable by physical cleaning as a list. . The amounts of the soluble extracellular polymer and the binding extracellular polymer in the cake layer deposited on the surface of the filtration membrane 24 during physical washing in the experimental example for the first example and the comparative example are shown as a list. It is explanatory drawing. It is explanatory drawing which shows the relationship between a current density and a substrate consumption rate. It is explanatory drawing which shows the relationship between a current density and ammonia consumption rate. It is a block diagram which shows the outline of a structure of the water treatment system 120 as 2nd Example. It is a block diagram which shows the outline of a structure of the filtration membrane module 123 used for the water treatment system 120 of 2nd Example. It is explanatory drawing which shows the item of the water treatment system of the experiment example in 2nd Example as a list. It is explanatory drawing which shows the composition of the to-be-processed water in the experiment example in 2nd Example as a table | surface. The structure of the type A filtration membrane module 123A and the type B filtration membrane module 123B used in the experimental example in the second embodiment is shown. It is explanatory drawing which shows the relationship between time when using a type A filtration membrane module 123A, and transmembrane pressure difference. The total filtration resistance of the experimental example in 2nd Example, the filtration resistance removable by physical washing | cleaning, and the filtration resistance not removed by physical washing | cleaning are shown. It is explanatory drawing which shows the relationship between time when using the membrane filter 123B of type B, and transmembrane differential pressure. It is a block diagram which shows an example of the filtration membrane module 223 of a modification. It is a block diagram which shows an example of the filtration membrane module 223 of a modification.

Next, modes for carrying out the present invention will be described using examples.

FIG. 1 is a configuration diagram showing an outline of the configuration of a water treatment system 20 as a first embodiment of the present invention, and FIG. 2 is a left side in FIG. 1 centering on a filtration membrane 24 of the water treatment system 20 of the first embodiment. It is a block diagram which shows the outline of a structure at the time of seeing from the surface. As shown in the drawing, the water treatment system 20 of the first embodiment includes a filtration membrane 24 that forms a hollow portion that is disposed in the treatment tank 22 and takes out the treated water, and a supply pump 26 that supplies the treated water to the treatment tank 22. One of the discharge pump 28 for discharging the treated water in the hollow portion formed in the filtration membrane 24, the aeration apparatus 30 arranged near the bottom of the treatment tank 22 to aerate the treated water, and one of the filtration membranes 24 The anode 42 disposed on the surface of the filter membrane 24 at a first distance (1.5 cm in the first embodiment) so that the water to be treated can be satisfactorily passed through the filter membrane 24, and the filter membrane 24. A cathode 44 arranged to face the anode 42 with a second distance (3.0 cm in the first embodiment) on the other side of the electrode, and a DC power supply 48 for supplying a DC current to the anode 42 and the cathode 44, The Obtain. The water treatment system 20 of the first embodiment includes various water quality sensors 52 that detect dissolved oxygen, pH, temperature, and the like of water to be treated, a water level sensor 54 that detects the water level of the treatment tank 22, and a filtration membrane 24. A pressure sensor 56 for detecting a transmembrane pressure difference as a pressure difference between both sides is attached.

In the first embodiment, the anode 42 is made of six anode plates 42a to 42f formed of iridium dioxide-coated titanium (Ti / IrO ₂ : titanium coated with iridium dioxide) and arranged in parallel in the horizontal direction. It is configured by being connected by a plurality of conductive connection lines 43. Therefore, the water to be treated can easily flow to the filtration membrane 24 through the space between the anode plates 42a to 42f. As the anode 42, not only iridium dioxide-coated titanium (Ti / IrO ₂ ) but also ruthenium dioxide-coated titanium (Ti / RuO ₂ : titanium coated with ruthenium dioxide) or iridium dioxide / ruthenium dioxide mixed-coated titanium (Ti / (IrO ₂ + RuO ₂ ): Titanium coated with a mixture of iridium dioxide and ruthenium dioxide), boron-doped diamond (BDD), platinum (Pt), lead oxide (PbO ₂ ), etc. Can be used. Among these, the chlorine generation efficiency at the anode is Ti / IrO ₂ > Ti / RuO ₂ ≈Ti / (IrO ₂ + RuO ₂ ) >>BDD> Pt.

In the first embodiment, the cathode 44 is formed of platinum-coated titanium (Ti / Pt: titanium coated with platinum) and has two

cathode plates

44a and 44b arranged in parallel in the horizontal direction. The plurality of connecting lines 45 are connected to each other. As the cathode 44, not only platinum-coated titanium (Ti / Pt) but also platinum (Pt), iron (Fe), aluminum (Al), carbon (C), titanium (Ti), and the like can be used.

In the water treatment system 20 of the first embodiment thus configured, the water to be treated is filtered with aeration by the aeration apparatus 30 and application of current to the anode 42 and the cathode 44. In FIG. 3, the effect | action by the anode 42 in the water treatment system 20 of 1st Example is typically shown with a comparative example. Here, as a comparative example, the anode 42 and the cathode 44 are removed from the water treatment system 20 of the first embodiment. Some of the organic matter in the water to be treated (for example, binding extracellular polymer) becomes a colloidal soluble organic matter due to hydrolysis, diffusion, etc. As shown in the comparative example, the film is deposited on the filtration membrane 24 to increase the transmembrane pressure difference. On the other hand, in the first embodiment, the organic matter is directly oxidatively decomposed on the electrode surface of the anode 42, and the organic matter is indirectly oxidatively decomposed by the oxidative substance generated by the electrode reaction of the anode 42. Organic matter adhering to the surface is also indirectly oxidized and decomposed. That is, in the first embodiment, the amount of organic matter that causes clogging of the filtration membrane 24 is reduced, and the organic matter adhering to the surface of the filtration membrane 24 is also oxidatively decomposed and removed. The rise can be suppressed. In addition, since colloidal soluble organic substances and solutes having an effective pore size less than that permeate the filtration membrane 24, it is possible to further suppress an increase in transmembrane pressure difference.

Examples of the generation of the oxidative substance by the electrode reaction of the anode 42 include the following.
(1) Hydroxy radical (.OH)
(2) Hydrogen peroxide (H ₂ O ₂ )
(3) Ozone (O ₃ )
(4) Chlorine and hypochlorous acid (ion) (Cl ₂ , HClO, ClO ⁻ )

The reaction assumed at the anode 42 is as follows. In the following, “M” represents the metal forming the electrode, “R” represents the organic substance, and “Products” represents the product obtained by decomposing the organic substance.
(1) M + H ₂ O → M (• OH) + H ⁺ + e ⁻
(2) M (• OH) + R → M + Products
(3) M (.OH) → M + (1/2) O ₂ + H ⁺ + e ⁻
(4) 2M (.OH) → 2M + H ₂ O ₂
(5) OH → O + H ⁺ + e ⁻ + O ₂ → O ₃
(6) M + Cl ⁻ → M (· Cl) + e ⁻ , 2M (· Cl) → 2M + Cl ₂
(7) Cl ₂ + H ₂ O ← → HClO + Cl ⁻ + H ⁺
(8) HClO ← → ClO ⁻ + H ⁺

The cathode 44 undergoes the following electrode reaction.
(1) 2H ₂ O + 2e ⁻ → H ₂ + 2OH ⁻

Next, a specific experimental example by the water treatment system 20 of the first embodiment will be shown. The specifications of the water treatment system of the experimental example are shown in the specifications table of FIG. In the experimental example, as shown in FIG.
(1) The effective capacity of the treatment tank 22 is 5.5 (L).
(2) The membrane material of the filtration membrane 24 is made of polyvinylidene fluoride (PolyVinylidene DiFluoride: PVDF)
(3) The nominal pore diameter of the filtration membrane 24 is 0.4 (μm)
(4) Effective membrane area is 500 (cm ² )
(5) Average filtration flux is 0.35 (m ³ / m ² d) (7 minute on and 1 minute off interval)
(6) The aeration flow rate (aeration flow rate) by the aeration apparatus 30 is 2 (L / min).
(7) The hydraulic residence time in the treatment tank 22 is 8.7 (hr)
(8) Sludge residence time is 110 (day)

The composition of the water to be treated used in the experimental example is shown in FIG. The treated water is assumed to be industrial wastewater and has a higher salt concentration (NaCl) than general municipal sewage in order to increase the current density. The composition is shown below.
(1) Glucose is 300 (mg / L) as COD (Chemical Oxygen Demand)
(2) Yeast extract 40 (mg / L)
(3) 30 (mg / L) ammonium chloride (NH ₄ Cl) as nitrogen (N) of ammonium ion (NH ₄ ⁺ )
(4) Monopotassium phosphate (KH ₂ PO ₄ ) and dipotassium hydrogen phosphate (K ₂ HPO ₄ ) 5 (mg / L) as phosphorus (P) as phosphate ion (PO ₄ ⁻ )
(5) 355 (mg / L) of sodium chloride (NaCl) as chloride ion (Cl ⁻ )
(6) 14 (mg / L) of calcium chloride dihydrate (CaCl ₂ · 2H ₂ O)
(7) 36 (mg / L) potassium chloride (KCl)
(8) Magnesium sulfate heptahydrate (MgSO ₄ .7H ₂ O) 90 (mg / L)
(9) Sodium bicarbonate (NaHCO ₃ ) 126 (mg / L)
(10) 0.45 (mg / L) of iron (III) chloride hexahydrate (FeCl ₃ .6H ₂ O)
(11) 0.045 (mg / L) boric acid (H ₃ BO ₃ )
(12) 0.009 (mg / L) of copper sulfate pentahydrate (CuSO ₄ .5H ₂ O)
(13) 0.054 (mg / L) of potassium iodide (KI)
(14) 0.036 mg / L of manganese chloride dihydrate (MnCl ₂ .2H ₂ O)
(15) 0.018 (mg / L) sodium molybdate dihydrate (Na ₂ MoO ₄ .2H ₂ O)
(16) 0.003 (mg / L) of zinc sulfate heptahydrate (ZnSO ₄ .7H ₂ O)
(17) Cobalt chloride hexahydrate (CoCl ₂ .6H ₂ O) in 0.045 (mg / L)

FIG. 6 shows the relationship between time and transmembrane pressure difference in the first example and the comparative example when water treatment is continued in the experimental example. Here, the “transmembrane differential pressure” is a pressure difference between both sides of the filtration membrane 24, and means that the greater the transmembrane pressure difference, the greater the clogging of the membrane. In the figure, white circles (the upper part of the legend on the upper left in the figure) are comparative examples (those with neither an anode nor a cathode), and the black circles (the lower part of the legend on the upper left in the figure) are the anode 42 and cathode 44 in the first embodiment. When the current density of the current applied to is 0.4 (mA / cm ² ). In the figure, a downward triangle mark (middle of the legend on the upper left in the figure) is a reference example when no current is applied to the anode 42 and the cathode 44 in the first embodiment (current density is 0 (mA / cm ² )). ). Moreover, the downward arrow in the figure indicates that physical cleaning was performed by backwashing with tap water after removing the cake layer on the surface of the filtration membrane 24 with a brush. As shown in the figure, in the comparative example, physical cleaning is performed by increasing the transmembrane pressure difference five times in 14 days, 27 days, 33 days, 44 days, and 55 days in 57 days. In the reference example, physical cleaning is performed by increasing the transmembrane pressure difference five times on the 14th, 27th, 33rd, 44th, and 57th of 57 days. In the first embodiment, physical cleaning is performed by increasing the transmembrane pressure differential three times on the 16th, 36th, and 57th of 57 days. From this experimental example, by applying a current to the anode 42 and the cathode 44 of the water treatment system 20 of the first embodiment for water treatment, the frequency of physical cleaning is reduced to about 3/5 due to an increase in transmembrane pressure difference. I understand that you can. Date of physical cleaning in the experimental example for the first example and the comparative example, total filtration resistance, ratio of filtration resistance recoverable by physical cleaning (%), ratio of filtration resistance unrecoverable by physical cleaning (%) Is shown in FIG. As shown in the figure, the ratio (%) of the filtration resistance that cannot be recovered by physical cleaning in the first example is smaller than that in the comparative example. Thereby, it turns out that the cleaning effect of the physical cleaning when the water treatment system 20 of the first embodiment applies water to the anode 42 and the cathode 44 to perform the water treatment is better than that of the comparative example.

FIG. 8 shows the amounts of the soluble extracellular polymer and the binding extracellular polymer in the cake layer deposited on the surface of the filtration membrane 24 in the physical cleaning of the experimental example for the first example and the comparative example. Shown as a list. In the first example, the amount of the soluble extracellular polymer is reduced as compared with the comparative example. This is because the amount of organic matter causing the clogging of the filtration membrane 24 is reduced due to the electrode reaction of the anode 42, the organic matter adhering to the surface of the filtration membrane 24 is indirectly removed by oxidative decomposition, the filtration membrane This is based on the fact that it is a colloidal soluble organic substance or solute having an effective pore size less than 24 that can pass through. Accordingly, it can be understood that an increase in filtration resistance can be suppressed by applying water to the anode 42 and the cathode 44 in the water treatment system 20 of the first embodiment to perform water treatment.

FIG. 9 is an explanatory diagram showing the relationship between current density and substrate consumption rate, and FIG. 10 is an explanatory diagram showing the relationship between current density and ammonia consumption rate. Here, “TOC” in the unit of substrate consumption rate means total organic carbon. In the figure, a circle indicates a state after energization for 6 hours, a downward triangle indicates a state after energization for 12 hours, and a square indicates a state after energization for 18 hours. Since the substrate consumption rate and the ammonia consumption rate indicate the activity of water treatment (biological treatment or microbial treatment) by microorganisms (aerobic microorganisms) contained in the water to be treated, the current density is 0.8 as shown in the figure. If it is (mA / cm ² ) or more, the activity due to microorganisms decreases. As a result, the current applied to the anode 42 and the cathode 44 of the water treatment system 20 of the first embodiment is within the range of 0.1 (mA / cm ² ) to 0.8 (mA / cm ² ) as the current density. In particular, it can be seen that the water treatment activity by microorganisms is desirably about 0.4 (mA / cm ² ), at which the activity does not decrease.

According to the water treatment system 20 of the first embodiment described above, when water treatment is performed using aeration and filtration by the filtration membrane 24, the first distance (first embodiment) is placed on one surface of the filtration membrane 24. Then, the anode 42 is arranged in a plane so that the flow of the water to be treated to the filtration membrane 24 can be satisfactorily performed with 1.5 cm), and the second distance (first implementation) is placed on the other surface of the filtration membrane 24. In the example, the cathode 44 is disposed so as to face the anode 42 at 3.0 cm), and a direct current is supplied to the anode 42 and the cathode 44, thereby causing the filtration membrane 24 to be blocked due to an electrode reaction or the like in the anode 42. It is possible to reduce the amount of organic matter and oxidatively decompose and remove organic matter adhering to the surface of the filtration membrane 24, thereby suppressing an increase in filtration resistance in the filtration membrane 24. As a result, compared with the comparative example, the frequency of performing the physical cleaning of the filtration membrane 24 can be reduced. Moreover, the direct current applied to the anode 42 and the cathode 44 is in the range of 0.1 (mA / cm ² ) to 0.8 (mA / cm ² ), more preferably 0.4 (mA / cm ² ). ² ) By setting before and after, it is possible to suppress a decrease in the activity of water treatment by microorganisms, so that the effect of water treatment by the electrode reaction of the anode 42 can be added to the effect of water treatment by microorganisms. As a result, the water treatment system 20 can be reduced in size and efficiency.

In the water treatment system 20 of the first embodiment, the anode 42 is arranged on one surface of the filtration membrane 24 with a first distance of 1.5 cm, but the distance between the filtration membrane 24 and the anode 42 is the same. Is not limited to 1.5 cm, as long as the anode 42 is not in contact with the cake layer deposited on the filtration membrane 24, and may be appropriately determined within a range of 1.0 cm to 3.0 cm, for example. In the water treatment system 20 of the first embodiment, the cathode 44 is disposed on the other surface of the filtration membrane 24 so as to face the anode 42 with a second distance of 3.0 cm. The distance from the cathode 44 is not limited to 3.0 cm, and may be determined as long as the filtration membrane 24 and the cathode 44 are not in contact with each other. For example, the distance may be appropriately determined within a range of 1.0 cm to 5.0 cm. .

In the water treatment system 20 of the first embodiment, six anode plates 42a to 42f are arranged at substantially equal intervals in the horizontal direction, and these are connected by a plurality of conductive connection lines 43 to constitute the anode 42. However, since the anode has only to be disposed so that the flow of the water to be treated to the filtration membrane 24 can be satisfactorily performed, the six anode plates 42a to 42f are substantially arranged in the vertical direction. The anodes may be arranged at equal intervals, the anodes may be configured in a mesh pattern, or the anodes may be configured in a grid pattern.

In the water treatment system 20 of the first embodiment, the anode 42 is disposed almost on the entire upstream side of the filtration membrane 24 and the cathode 44 is disposed on the downstream side of the filtration membrane 24 so as to face the anode 42. An anode may be arranged on a part of the upstream side of the membrane such as half or 1/4 of the area of the membrane from the lower side.

In the water treatment system 20 of the first embodiment, the filtration membrane module 23 is formed by the filtration membrane 24, the anode 42, and the cathode 44. That is, the filtration membrane module 23 has a filtration membrane 24 that forms a hollow portion for taking out treated water, and a surface of the filtration membrane 24 so that the water to be treated can be satisfactorily flowed to one side of the filtration membrane 24. And the cathode 44 disposed on the other surface of the filtration membrane 24 so as to face the anode 42.

Next, the water treatment system 120 of the second embodiment of the present invention will be described. FIG. 11 is a configuration diagram showing an outline of the configuration of the water treatment system 120 as the second embodiment, and FIG. 12 is a configuration showing an outline of the configuration of the filtration membrane module 123 used in the water treatment system 120 of the second embodiment. FIG. As shown in the drawing, the water treatment system 20 of the second embodiment is treated from a filtration membrane module 123 arranged in a treatment tank 122, a supply pump 126 for supplying treated water to the treatment tank 122, and a filtration membrane module 123. A discharge pump 128 that discharges water, an aeration device 130 that is disposed near the bottom of the treatment tank 122 and performs aeration on the water to be treated, and a DC power source 148 that supplies a DC current to the filtration membrane module 123 are provided. . In the water treatment system 120 of the second embodiment, various water quality sensors 152 that detect dissolved oxygen, pH, temperature, and the like of the water to be treated, a water level sensor 154 that detects the water level of the treatment tank 122, and a filtration membrane filtration membrane module A pressure sensor 156 for detecting a transmembrane pressure difference at 123 is attached.

As shown in FIG. 12, the filtration membrane module 123 includes two first filtration membranes 124 forming a hollow portion 124a, and the first filtration membrane 124 and a first distance (first In the second embodiment, the two anodes 142 are arranged so that the flow of the water to be treated to the first filtration membrane 124 can be satisfactorily performed at 1.5 cm) and on both outer sides of the two anodes 142. A second filtration membrane 125 arranged with a second distance (3 cm in the second embodiment) from the anode 142, and a second filtration membrane 125 and a third distance (second implementation) on both outer sides of the second filtration membrane 125. In the example, there are provided two cathodes 144 arranged in a plane so that the flow of the water to be treated to the second filtration membrane 125 can be performed satisfactorily at 3.0 cm). The discharge pump 128 discharges the treated water in the hollow portion 124a.

For example, a polyethylene membrane (PE) having a nominal pore diameter of 0.4 μm can be used for the first filtration membrane 124, and a nonwoven fabric having a coarser mesh than the first filtration membrane 124 can be used for the second filtration membrane 125. Here, the role of the second filtration membrane 125 is to suppress filtration clogging of the first filtration membrane 124 by removing relatively large suspended matters in the water to be treated. Therefore, the second filtration membrane 125 may be anything other than a nonwoven fabric, as long as it has a coarser mesh than the first filtration membrane 124.

Like the anode 42 of the first embodiment, the anode 142 is formed of iridium dioxide-coated titanium (Ti / IrO ₂ : titanium coated with iridium dioxide), and a plurality of anode plates arranged in parallel in the horizontal direction. Are connected by a plurality of conductive connection lines. As the anode 142, not only iridium dioxide-coated titanium (Ti / IrO ₂ ) but also ruthenium dioxide-coated titanium (Ti / RuO ₂ : titanium coated with ruthenium dioxide) or iridium dioxide / ruthenium dioxide mixed-coated titanium (Ti / (IrO ₂ + RuO ₂ ): Titanium coated with a mixture of iridium dioxide and ruthenium dioxide), boron-doped diamond (BDD), platinum (Pt), lead oxide (PbO ₂ ), etc. Can be used. Among these, the chlorine generation efficiency at the anode is Ti / IrO ₂ > Ti / RuO ₂ ≈Ti / (IrO ₂ + RuO ₂ ) >>BDD> Pt.

Similarly to the cathode 44 of the first embodiment, the cathode 144 is made of a plurality of cathode plates made of platinum-coated titanium (Ti / Pt: titanium coated with platinum) and arranged in parallel in the horizontal direction. It is comprised by connecting with the some connection line which has. As the cathode 144, not only platinum-coated titanium (Ti / Pt) but also platinum (Pt), iron (Fe), aluminum (Al), carbon (C), titanium (Ti), and the like can be used.

In the water treatment system 120 of the second embodiment thus configured, the water to be treated is filtered with aeration by the aeration apparatus 130 and application of current to the anode 142 and the cathode 144. Also in the second embodiment, as described with reference to FIG. 3, the organic matter is directly oxidatively decomposed on the electrode surface of the anode 142, and the organic matter is indirectly generated by the oxidative substance generated by the electrode reaction of the anode 142. The organic matter that has been oxidatively decomposed and adhered to the surface of the first filtration membrane 124 is also indirectly oxidatively decomposed. That is, also in the second embodiment, the amount of organic substances that cause clogging of the first filtration membrane 124 is reduced, and organic substances adhering to the surface of the first filtration membrane 124 are also oxidatively decomposed and removed, thereby suppressing an increase in transmembrane pressure difference. To do. In the second embodiment, since the second filtration membrane 125 having a coarser mesh than the first filtration membrane 124 is disposed on both outer sides of the first filtration membrane 124, the relatively large suspended matter in the treated water is second. Since it is captured by the filtration membrane 125, an increase in the transmembrane pressure difference of the first filtration membrane 124 can be suppressed.

The generation of an oxidative substance by the electrode reaction of the anode 142, the reaction assumed in the anode 142, the electrode reaction of the cathode 144, and the like are the same as those in the first embodiment, and these are described in detail.

Next, a specific experimental example using the water treatment system 120 of the second embodiment is shown. The specifications of the water treatment system of the experimental example are shown in the specification table of FIG. In the experimental example, as shown in FIG.
(1) The effective capacity of the treatment tank 122 is 13 (L)
(2) The first filtration membrane 124 is made of polyethylene.
(3) The nominal pore diameter of the first filtration membrane 124 is 0.4 (μm).
(4) The material of the second filtration membrane 125 is a nonwoven fabric. (5) The membrane area is 1 (m ² ) for the first filtration membrane 124 and 0.097 (m ² ) for the second filtration membrane 125.
(6) The applied current to the anode 142 and the cathode 144 is 5 (mA / cm ² ) (interval of 30 minutes on and 2 minutes 30 seconds off)
(7) The average filtration flux is 0.31 (m ³ / m ² d) for the first filtration membrane 124 and 3.17 (m ³ / m ² d) for the second filtration membrane 125.
(8) The areas of the anode 142 and the cathode 144 are both 50 (cm ² ).

The composition of the water to be treated used in the experimental example is shown in FIG. The treated water was assumed to be general sewage. The composition is shown below.
(1) Glucose is 100 (mg / L) as COD (Chemical Oxygen Demand)
(2) 10 (mg / L) ammonium chloride (NH ₄ Cl) as ammonium ion (NH ₄ ⁺ ) nitrogen (N)
(3) Monopotassium phosphate (KH ₂ PO ₄ ) and dipotassium hydrogen phosphate (K ₂ HPO ₄ ) 2 (mg / L) as phosphorus (P) as phosphate ion (PO ₄ ⁻ )
(4) Sodium chloride (NaCl) as chloride ion (Cl ⁻ ) 118 (mg / L)

FIG. 15 shows configurations of a type A filtration membrane module 123A and a type B filtration membrane module 123B used in the experimental example. As shown in the figure, in the type A filtration membrane module 123A, the anode 142 and the cathode 144 are arranged below the module, and in the type B filtration membrane module 123B, the anode 142 and the cathode 144 are arranged in the center of the module. ing.

FIG. 16 shows the relationship between time and transmembrane pressure difference when using a type A filtration membrane module 123A. Here, the “transmembrane differential pressure” is a pressure difference between the hollow portion 124a of the filtration membrane module 123A and the processing tank 122, and means that the membrane clogging is larger as the transmembrane differential pressure is larger. In the figure, a white circle mark (upper part of the legend on the upper left in the figure) is a current applied using a type A filtration membrane module 123A, and a white triangle mark (middle part of the legend on the upper left in the figure) indicates a type A filtration. The membrane module 123A was used but no current was applied, and the white square mark (lower part of the legend on the upper left in the figure) is only the first filtration membrane 124 that does not include the second filtration membrane 125, the anode 142, and the cathode 144. It is a comparative example using the filtration membrane module of. As shown in the figure, the transmembrane differential pressure is smaller when the type A filtration membrane module 123A is used even when no current is applied as compared with the comparative example. However, when the current is applied, the transmembrane differential pressure is further increased. You can see that is getting smaller. FIG. 17 shows the total filtration resistance of the experimental example, the filtration resistance that can be removed by physical washing, and the filtration resistance that is not removed by physical washing. Compared with the comparative example, the filtration resistance that is not removed by physical cleaning is smaller when the type A filtration membrane module 123A is used even when no current is applied, but it is not further removed by physical cleaning when the current is applied. Filtration resistance is low. Thereby, it turns out that the effect of the physical washing | cleaning at the time of water-processing using the type A filtration membrane module 123A to which the electric current was applied may be better than the comparative example and the case where no electric current is applied.

FIG. 18 shows the relationship between time and transmembrane pressure difference when a type B filtration membrane module 123B is used. In the figure, a white circle mark (upper part of the legend on the upper left in the figure) is a current applied using a type B filtration membrane module 123B, and a white triangle mark (middle part of the legend on the upper left in the figure) indicates a type B filtration. The membrane module 123B was used but no current was applied, and the white square mark (lower part of the legend at the upper left in the figure) is only the first filtration membrane 124 that does not include the second filtration membrane 125, the anode 142, and the cathode 144. It is a comparative example using the filtration membrane module of. As shown in the figure, the transmembrane differential pressure is smaller when the type B filtration membrane module 123B is used even when no current is applied as compared with the comparative example. However, when the current is applied, the transmembrane differential pressure is further increased. You can see that is getting smaller.

According to the water treatment system 120 of the second embodiment described above, by applying a direct current to the anode 142 and the cathode 144 using the filtration membrane module 123 with aeration, the electrode reaction at the anode 142 and the like are performed. The amount of organic matter that causes clogging of the first filtration membrane 124 can be reduced, and the organic matter adhering to the surface of the first filtration membrane 124 can be oxidatively decomposed and removed, thereby suppressing an increase in filtration resistance in the first filtration membrane 124. As a result, the frequency of performing physical cleaning can be reduced as compared with the comparative example. In addition, by disposing the second filtration membrane 125 on both outer sides (upstream side) of the first filtration membrane 124, relatively large suspended matters in the water to be treated are removed, so that the filtration resistance of the first filtration membrane 124 is increased. Can be further suppressed. Of course, the direct current applied to the anode 142 and the cathode 144 is a current density in the range of 0.1 (mA / cm ² ) to 0.8 (mA / cm ² ), more preferably 0.4 (mA / cm ² ). ² ) Since the decrease in the activity of water treatment by microorganisms can be suppressed by setting the front and back, the effect of water treatment by the electrode reaction of the anode 42 can be added to the effect of water treatment by microorganisms. As a result, the water treatment system 120 can be reduced in size and efficiency.

In the water treatment system 120 of the second embodiment, the anode 142 is disposed with a first distance of 1.5 cm from the first filtration membrane 124. However, the distance between the first filtration membrane 24 and the anode 142 is 1. The thickness is not limited to 5 cm, and may be determined as long as the anode 142 is not in contact with the cake layer deposited on the first filter membrane 124. For example, the thickness may be appropriately determined within a range of 1.0 cm to 3.0 cm. In the water treatment system 120 of the second embodiment, the second filtration membrane 125 is arranged with a second distance of 3.0 cm from the anode 142, but the distance between the anode 142 and the second filtration membrane 125 is as follows. The thickness is not limited to 3.0 cm, and may be determined as long as the anode 142 and the second filtration membrane 125 are not in contact with each other. For example, the thickness may be appropriately determined within a range of 1.0 cm to 5.0 cm. Furthermore, in the water treatment system 120 according to the second embodiment, the cathode 144 is disposed with a third distance of 3.0 cm from the second filtration membrane 125, but the distance between the second filtration membrane 125 and the cathode 144 is 3. The thickness is not limited to 0.0 cm, and may be determined as long as the second filtration membrane 125 and the cathode 144 are not in contact with each other, and may be appropriately determined within a range of 1.0 cm to 5.0 cm, for example.

In the water treatment system 120 of the second embodiment, the anode 142 is configured by arranging a plurality of anode plates at substantially equal intervals in the horizontal direction and connecting them with a plurality of conductive connection lines. The anode is only required to be disposed in a plane so that the flow of the water to be treated to the first filtration membrane 124 can be satisfactorily performed. Therefore, a plurality of anode plates are disposed at substantially equal intervals in the vertical direction. Alternatively, the anode may be configured in a mesh pattern, or the anode may be configured in a grid pattern.

In the water treatment system 120 according to the second embodiment, the anode 142 and the cathode 144 are disposed below and in the center of the first filtration membrane 124. However, the anode and the cathode are disposed on the entire surface of the first filtration membrane 124. It may be a thing.

FIG. 19 is a block diagram showing an outline of the configuration of a modified membrane membrane module 223, and FIG. 20 is a cross-sectional view taken along the line AA in FIG. In the water treatment system 120 of the second embodiment, as the filtration membrane module 123, the two first filtration membranes 124 are arranged so as to face each other so that a flat hollow portion 124a is formed, and two outer sides of the two first filtration membranes 124 are arranged. The anode 142, the two second filtration membranes 125, and the two cathodes 144 are arranged in this order. However, as shown in the filtration membrane module 223 of the modified example of FIGS. A plurality of membrane tubes 224 may be arranged, and two anodes 242, two second filtration membranes 225, and two cathodes 244 may be arranged in that order on both outer sides thereof. When a plurality of filtration membrane tubes 224 are used as described above, the anode, the second filtration membrane, and the cathode may be arranged in a ring shape.

As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

The present invention can be used in the water treatment industry in the manufacturing industry of water treatment systems and filtration membrane modules and in water treatment facilities such as sewage treatment and wastewater treatment.

Claims

A water treatment system that performs water treatment using aeration that promotes activation of aerobic microorganisms and filtration through a filtration membrane,
An anode disposed in a plane so that at least a part of the upstream side of the filtration membrane allows flow of water to be treated before treatment by the filtration membrane to the filtration membrane;
A cathode disposed opposite the anode;
With
When water treatment is performed, a direct current is supplied to the anode and the cathode.
A water treatment system characterized by that.
The water treatment system according to claim 1,
The cathode is arranged to face the anode across the filtration membrane,
A water treatment system characterized by that.
The water treatment system according to claim 2,
The anode is disposed on the filtration membrane with a distance within a range of 1.0 cm to 3.0 cm,
The cathode is disposed on the filtration membrane with a distance within a range of 1.0 cm to 5.0 cm.
A water treatment system characterized by that.
The water treatment system according to claim 1,
A second filtration membrane having a coarser mesh than the filtration membrane disposed substantially parallel to the filtration membrane on the upstream side of the anode;
The cathode is disposed upstream of the second filtration membrane;
A water treatment system characterized by that.
The water treatment system according to claim 4,
The second filtration membrane is formed of a nonwoven fabric,
A water treatment system characterized by that.
The water treatment system according to claim 4 or 5,
The anode is disposed on the filtration membrane with a distance within a range of 1.0 cm to 3.0 cm,
The second filtration membrane is disposed on the anode with a distance within a range of 1.0 cm to 3.0 cm,
The cathode is disposed on the second filtration membrane with a distance within a range of 1.0 cm to 5.0 cm.
A water treatment system characterized by that.
The water treatment system according to any one of claims 1 to 6,
The anode includes iridium dioxide-coated titanium (Ti / IrO 2 ), ruthenium dioxide-coated titanium (Ti / RuO 2 ), iridium dioxide-ruthenium dioxide mixed-coated titanium (Ti / (IrO 2 + RuO 2 ), boron-doped diamond ( BDD: Boron-doped diamond), platinum (Pt), lead oxide (PbO 2 )
The cathode is formed of any one of platinum-coated titanium (Ti / Pt), platinum (Pt), iron (Fe), aluminum (Al), carbon (C), and titanium (Ti).
A water treatment system characterized by that.
A water treatment system according to any one of claims 1 to 7,
DC current supplied to the anode and the cathode is adjusted to be within a range of 0.1mA / cm 2 ~ 0.8mA / cm 2 as a current density,
A water treatment system characterized by that.
A water treatment system according to any one of claims 1 to 8,
The anode is arranged in a plane as one of a mesh, a grid, and a plurality of rows.
A water treatment system characterized by that.
A filtration membrane module used in a water treatment system for water treatment using aeration that promotes activation of aerobic microorganisms,
A filtration membrane arranged to form a hollow portion for taking out the filtered water;
An anode disposed in a plane on at least a part of the outer peripheral side of the filtration membrane so that water to be treated before the filtration treatment can flow to the filtration membrane;
A cathode disposed opposite the anode;
A membrane filter module.
The filtration membrane module according to claim 10,
The cathode is disposed so that the filtration membrane is sandwiched between the anode and the anode on the outer peripheral side of the filtration membrane.
A filtration membrane module.
The filtration membrane module according to claim 10,
A second filtration membrane having a coarser mesh than the filtration membrane and disposed on the outer peripheral side of the anode;
The cathode is disposed on the outer peripheral side of the second filtration membrane,
A filtration membrane module.
The filtration membrane module according to any one of claims 10 to 12,
The anode includes iridium dioxide-coated titanium (Ti / IrO 2 ), ruthenium dioxide-coated titanium (Ti / RuO 2 ), iridium dioxide-ruthenium dioxide mixed-coated titanium (Ti / (IrO 2 + RuO 2 ), boron-doped diamond ( BDD: Boron-doped diamond), platinum (Pt), lead oxide (PbO 2 )
The cathode is formed of any one of platinum-coated titanium (Ti / Pt), platinum (Pt), iron (Fe), aluminum (Al), carbon (C), and titanium (Ti).
A filtration membrane module.
A water treatment method for water treatment using aeration that promotes activation of aerobic microorganisms and filtration through a filtration membrane,
An anode disposed in a plane so as to allow water to be treated to flow through the filtration membrane before treatment by the filtration membrane to at least a part of the upstream side of the filtration membrane during water treatment; to the the arrangement cathodes so as to face, applying a direct current in the range of 0.1mA / cm 2 ~ 0.8mA / cm 2 as a current density,
A water treatment method characterized by the above.