JP3698093B2 - Water treatment method and water treatment apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a water treatment method and a water treatment apparatus suitably used for purifying water such as rivers and lakes.
[0002]
[Prior art]
  Membrane separation technology is a technology used for solid-liquid separation, ion separation, gas separation, and the like, and has recently been used in various fields such as industrial water production and food, medicine, water purification, seawater desalination. Among them, nanofiltration membranes (NF membranes) and reverse osmosis membranes (RO membranes) are widely used as membranes that can produce high-quality water.
[0003]
  RO membranes and NF membranes are generally used in a cross-flow filtration system in which raw water is supplied along the membrane surface and permeate is passed in a direction perpendicular to the raw water, and a portion of the raw water supplied to the membrane module circulates. By applying a shearing force to the film surface, it is possible to suppress adhesion and deposition of fouling substances such as suspended substances and colloidal substances in the raw water. The water that has not permeated the membrane is called concentrated water, part of which is drained depending on the recovery rate of the water treatment device, and the rest is returned to the membrane supply water side.
[0004]
  It is important to set a high recovery rate from the viewpoint of water resources and water rights, and from the viewpoint of reducing the amount of wastewater (concentrated water) and downsizing the pretreatment and wastewater treatment processes. However, if the recovery rate is increased, the concentration ratio of each component is increased in accordance with the removal rate of the substance to be removed, and the load on the membrane is increased. In particular, fouling due to microorganisms, medium to high molecular humic acid, etc., and scales where calcium, magnesium, silica, etc. are deposited as calcium carbonate, magnesium hydroxide, calcium sulfate hydrate, silica and adhere to the membrane surface, are transmitted. A decrease in the amount of water, an increase in differential pressure, etc. may occur, making stable operation difficult. Depending on the quality of the water to be treated, a recovery rate of about 80% is considered the limit.
[0005]
  Concentrated water of membrane modules equipped with RO membranes and NF membranes contains a concentration of soluble components such as agricultural chemicals, trace amounts of harmful organic substances, and salts as regulated by the wastewater standards of the Water Pollution Control Law. However, the higher the recovery rate, the more often the wastewater standards of the Water Pollution Control Law are exceeded, and the concentrated water cannot be directly reused for some purpose or discharged directly into rivers. Therefore, a separate treatment is required for components that exceed wastewater standards. If the recovery rate is low, the scale of the wastewater treatment facility for discharge becomes large. For example, if the recovery rate is 80%, the amount of water produced is 10,000 m.³/ D is approximately 1,100m³/ D, which increases the processing cost.
[0006]
[Problems to be solved by the invention]
  The object of the present invention is to solve the above-mentioned conventional problems, and to increase the recovery rate, which has been limited to about 80%, in order to effectively use water resources, and to stably operate RO membranes and NF membranes. It is an object of the present invention to provide a water treatment method and a water treatment apparatus that can be used and can cope with measures for strengthening regulations on wastewater standards.
[0007]
[Means for Solving the Problems]
  In the present invention for achieving the above-mentioned object, the raw water is subjected to solid-liquid separation, and then the permeated water, concentrated water and the membrane module having a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane). The water treatment method for separating the water into the membrane module is operated so that the recovery rate is at least 90%, and at least a part of the concentrated water of the membrane module is softened.Law and existenceA water treatment method characterized in that it is treated with the machine removal method and refluxed to the raw water.The organic matter removal method includes an accelerated oxidation treatment for performing at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment.It is a feature.
[0008]
  At this time, that the softening treatment method includes ion exchange, the organic matter removal method,furtherIt is preferable to include activated carbon treatment.. SpiritIt is also preferable to perform solid-liquid separation using a tight filtration membrane (MF membrane) and / or an ultrafiltration membrane (UF membrane), or to add a flocculant to raw water before solid-liquid separation.
[0009]
  The present invention also provides a solid-liquid separation means for solid-liquid separation of raw water and a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (separated into permeated water and concentrated water). A water treatment comprising: a membrane module having an NF membrane; and a reflux means having an organic matter removing means and a softening treatment means for treating at least a part of the concentrated water of the membrane module and returning it to raw water apparatusThe reflux means includes an accelerated oxidation treatment means as an organic substance removal means, and the accelerated oxidation treatment means and the softening treatment means are arranged in this order.It is a characteristic.
[0010]
  Moreover, it is preferable that the organic substance removing means further includes an activated carbon treatment means, and the accelerated oxidation treatment means, the activated carbon treatment means, and the softening treatment means are arranged in this order.
[0011]
  Furthermore, a fresh water generation method using any one of the above methods or apparatuses is also a preferred embodiment.
[0012]
  The recovery rate in the present invention is the ratio of the membrane permeated water amount (b) to the water amount (a) obtained by subtracting the amount of concentrated water returned to the membrane feed water side from the amount of water supplied to the membrane module, as shown in the following formula, It is an index showing the quantitative processing efficiency in the separation method.
[0013]
[Expression 1]
[0014]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 shows an example of the flow of the water treatment apparatus of the present invention. This water treatment device includes a solid-liquid separation device 3 that separates the raw water 50 into a solid and a liquid, a reverse osmosis membrane (RO membrane) that separates the separated water 60 of the solid-liquid separation device 3 into permeated water 70 and concentrated water 80, and Organic membrane removing means (promoted oxidation treatment device 7, activated carbon treatment device 8) and softening that treat membrane module 6 having a nanofiltration membrane (NF membrane) and concentrated water 80 of membrane module 6 to return to raw water 50 And a reflux means 10 having a processing device 9. Further, on the upstream side of the solid-liquid separator 3, a tank 1 that temporarily stores the raw water 50 and a pressure pump 2 that pressurizes the water stored in the tank 1 and feeds the water to the solid-liquid separator 3 are provided. In addition, between the solid-liquid separation device 3 and the membrane module 6, the tank 4 storing the separation water 60 from the solid-liquid separation device 3 and the separation water 60 stored in the tank 4 are pressurized and supplied to the membrane module 6. And a pressurizing pump 5 is provided.
[0015]
  In this water treatment device, the raw water 50 stored in the tank 1 is sent to the solid-liquid separation device 3 by the pressurizing pump 2, and suspended solids are removed by the solid-liquid separation device 3. In the present invention, in order to prevent impurities such as turbidity, microorganisms, and organic matter contained in the raw water 50 from adhering to the surface of the RO membrane or NF membrane, the filtration differential pressure is rapidly increased. Separating and adjusting the FI (Fouling Index) value of the separated water 60 led to the RO membrane or NF membrane. The FI value is preferably 5 or less for spiral type modules and 4 or less for hollow fiber type modules. The FI value is also referred to as an SDI (Silt Density Index) value, which is a management index of impurities in the supply water (separated water 60) to the RO membrane or NF membrane, and is represented by the following equation.
[0016]
    FI = (1-T₀/ T₁₅) × 100/15
At this time, T₀Is the time required to initially filter 500 ml when the sample water is filtered under a pressure of 206 kPa using a 0.45 μm membrane filter.₁₅T₀Then, after filtering for 15 minutes in the same state, the time required to filter 500 ml of sample water again.
[0017]
  Examples of the solid-liquid separation device 3 include a filtration device that prevents leakage of suspended substances in raw water, such as sand filtration and a safety filter, but a microfiltration membrane (MF) having a pore diameter of 1 μm or less that prevents microorganisms from entering the membrane pores. Membrane) and ultrafiltration membrane (UF membrane) are preferably used alone or in combination.
[0018]
  When a separation membrane is used in the solid-liquid separation device 3, a flocculant can be added to the raw water for the purpose of improving the membrane permeation flux and the membrane differential pressure and improving the treatment capacity and stability by improving the quality of the treated water. The flocculant injection rate is such that the micro floc can be formed in a small amount so that the membrane can be separated as it is, or a sufficient flocculant is added for the agglomeration treatment and the floc floc is precipitated, and then the supernatant liquid is separated with a separation membrane. It may be processed.
[0019]
  Separation membranes such as MF membranes and UF membranes can improve the turbidity and can stably operate the NF membrane and the RO membrane for a longer period, as can be seen from the fact that the FI value of the separation water 60 can be brought close to 0.
[0020]
  As membrane materials for UF membranes and MF membranes, cellulose acetate, polyacrylonitrile, polyethylene, polyethersulfone, polysulfone, polypropylene, polyvinylidene fluoride, ceramic, etc. can be applied.
  The membrane may have any shape such as a hollow fiber membrane, a tubular membrane, or a flat membrane. Here, the hollow fiber membrane is a tubular separation membrane having an outer diameter of less than 2 mm, and the tubular membrane is a tubular separation membrane having an outer diameter of 2 mm or more. The hollow fiber membrane can increase the effective membrane area per unit.
[0021]
  These UF membranes and MF membranes are modularized and used. The module should have a structure that is difficult to block by cells, such as (1) external pressure crossflow hollow fiber membrane module, (2) internal pressure crossflow hollow fiber membrane module with an inner diameter of 1 mm or more, etc. Is preferable because the film area is large.
[0022]
  In addition, there are a constant flow filtration operation and a constant pressure filtration operation as the operation method of the membrane device used for solid-liquid separation, but the constant flow filtration operation can obtain a constant processing amount and is easy to control the treatment process. Therefore, it is preferable.
[0023]
  The separated water 60 that has been treated by the solid-liquid separation device 3 and from which suspended substances have been removed is stored in the tank 4 and then pressurized and supplied to the membrane module 6 by the pressure pump 5, and the permeated water 70 and concentrated water. 80. At this time, the membrane module is operated so that the recovery rate is 90% or more.
[0024]
  The nanofiltration membrane and reverse osmosis membrane used in the membrane module 6 are as follows.
[0025]
  That is, the nanofiltration membrane (NF membrane: Nanofiltration Membrane) is mainly high in the removal performance of polyvalent ions such as medium to high molecular weight molecules, divalent ions, heavy metal ions of several hundred to several thousand or more, When used for drinking water production applications, trihalomethane precursors, agricultural chemicals, fulvic acid and the like can be mainly removed. Although the size of the removal target is located between the ultrafiltration membrane (UF membrane) and the reverse osmosis membrane (RO membrane), the desalination rate is 5% or more and less than 93% (evaluation condition NaCl concentration: 500-2, 000 mg / l, operating pressure: 0.5 to 1.5 MPa).
[0026]
  Examples of the film material include polyamide-based, polypiperazine amide-based, polyester amide-based, and water-soluble vinyl polymer crosslinked. In addition, the membrane structure has a dense layer on at least one side of the membrane, and has a fine pore with a gradually increasing pore size from the dense layer to the inside of the membrane or the other side. And a composite film having a very thin active layer formed of another material. Further, there are flat membranes, hollow fiber membranes, etc. as membrane forms, for example, the film thickness is in the range of 10 μm to 1 mm, and in the case of hollow fiber membranes, the outer diameter is in the range of 50 μm to 4 mm.
[0027]
  In addition, reverse osmosis membrane (RO membrane: Reverse Osmosis Membrane) removes monovalent ionic substances in addition to the removal target of NF membrane (mainly seawater desalination treatment, brine desalination, pure water production) And a desalting rate of 93% or more (evaluation conditions NaCl concentration: 500 to 2,000 mg / l, operating pressure: 0.5 to 3.0 MPa).
[0028]
  As the film material, polymer materials such as cellulose acetate, cellulose polymer, polyamide, and vinyl polymer can be used. Typical reverse osmosis membranes include cellulose acetate or polyamide asymmetric membranes and composite membranes having polyamide active layers. Among them, a cellulose acetate asymmetric membrane, a composite membrane having a polyamide-based active layer, and a composite membrane having an aromatic polyamide-based active layer, which have a high salt rejection performance, are preferred. In particular, an aromatic polyamide composite membrane has a high exclusion performance. And it is preferable because of its high water permeability. As the membrane structure, there are asymmetric membranes and composite membranes as with NF membranes, and there are flat membranes, hollow fiber membranes, etc., as with NF membranes. For example, film thickness ranges from 10 μm to 1 mm, hollow fiber membranes In this case, the outer diameter is in the range of 50 μm to 4 mm.
[0029]
  Both the NF membrane and the RO membrane can be operated at a low pressure from the viewpoint of operation cost, but a composite membrane is preferable in consideration of the amount of water produced during low pressure operation. More preferably, it is a polyamide-based composite membrane. In the case of an NF membrane, a polypiperazine amide-based composite membrane is more suitable from the viewpoint of the amount of permeated water and chemical resistance.
[0030]
  And the membrane module 6 is modularized in order to actually use the above-mentioned NF membrane and RO membrane. In the case of flat membrane, spiral type, pleated type, plate-and-frame type, disk type disc type is stacked, and in the case of hollow fiber membrane, hollow fiber is bundled in U shape or I shape. Although there is a hollow fiber membrane type housed in a container, the present invention is not affected by the form of these modules.
[0031]
  In the present invention, either one of the RO membrane or the NF membrane may be used for the membrane module 6, or both may be used. These may be appropriately selected according to the supply water (separated water 60), the required water quality of the permeated water 70, and the purpose of use of the permeated water 70.
[0032]
  The membrane module 6 may be arranged in multiple stages so that the concentrated water from the preceding membrane module is processed by the subsequent membrane module 6. In this case, it should be noted that the concentration of calcium, magnesium, silica, etc. in the concentrated water of the subsequent RO membrane or NF membrane does not exceed the solubility.
[0033]
  The filtration pressure of the membrane module 6 is preferably set as appropriate within a range of about 0.5 to 3.0 MPa depending on the type of membrane supply water (separated water 60), the operation method, and the like. When treating fresh water such as river water and lake water, it can be filtered at a relatively low pressure because the osmotic pressure is low.
[0034]
  The water that has passed through the RO membrane and the NF membrane in such a membrane module 6 is taken out from the membrane module 6 as the permeated water 70. Since this permeated water is free of trihalomethane precursors, agricultural chemicals, heavy metal ions, etc., it is used as drinking water, industrial water, agricultural water or the like.
[0035]
  On the other hand, the concentrated water 80 is obtained by removing the organic matter provided in the reflux means 10 (accelerated oxidation treatment device 7, activated carbon treatment device 8) And softTreatment is performed by the softening treatment means (softening treatment device 9), and at least a part (the concentrated water 100 after the treatment by the softening treatment device 9) is returned to the raw water in the tank 1. Concentrated water that has not been refluxed to the raw water (a part of the concentrated water 90 that has been treated by the activated carbon treatment device 8) is discharged into nature as it is..The removal target of the organic substance removing means is mainly low-boiling organic chlorine compounds such as odor (mold odor), chromaticity, trihalomethane, trihalomethane precursor, agricultural chemical, anionic surfactant, phenols, and trichloroethylene. The removal target of the softening treatment means is calcium, magnesium, etc., which are scale components.
[0036]
  The present invention treats separated water 60 from which suspended substances have been removed by solid-liquid separation in advance with a membrane module 6 equipped with an RO membrane or NF membrane, and the concentrated water 80 obtained at that time is treated with an organic matter removing hand.Stepped and softSince it is processed by the chemical treatment means and again leads to solid-liquid separation, reverse osmosis separation, and nanofiltration, the recovery rate can be increased without reducing the water quality, and the membrane module is operated at a recovery rate of 90% or more. Can be operated stably.
[0037]
  As an organic substance removal means, accelerated oxidation treatment equipmentIn addition to 7,An activated carbon treatment apparatus 8 or the like can be used. In addition, as shown in FIG.7 can be used alone or activated with the accelerated oxidation treatment device 7Use both of the charcoal treatment equipment 8KakahaWhat is necessary is just to determine suitably according to the water quality of the concentrated water 80. FIG. When the concentration of the removal target in concentrated water is low, Accelerated oxidation treatment unit 7 singleIt can be used alone, but the concentration of each organic component in the concentrated water 80 is high.UrgeWhen it is difficult to remove the oxidative treatment alone, it is preferable to use both in combination. Concentrated water 80 contains organic chlorinated compounds such as dichloroethane, trichloroethylene, and tetrachloroethylene that are regulated by the drainage standards, pesticides such as simazine and thiuram, and biodegradable substances such as endocrine disrupting substances. In such a case, or when there is a possibility that it is contained, it is preferable to perform accelerated oxidation treatment.
[0038]
  The accelerated oxidation treatment is called AOP (= Advanced Oxidation Processes) and is at least two selected from the group of ozone, ultraviolet rays, gamma rays, hydrogen peroxide, fluorine, sodium hypochlorite, chlorine, catalyst (photocatalyst, etc.), etc. Is used to generate hydroxy radicals (HO radicals) with high oxidizing power in water, and decompose organic substances by this oxidizing power. Since the HO radical has a very strong oxidizing power, it is effective in decomposing refractory organic substances such as organochlorine compounds and endocrine disrupting substances having a high binding force existing in water. These accelerated oxidation treatments do not generate secondary waste, and the effect treatment can be expected to have secondary effects such as deodorization, decolorization, and sterilization in addition to the decomposition of organic matter, and has an unprecedented feature. The combination of the accelerated oxidation treatment is preferably selected from the group of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment, and catalyst (photocatalyst) treatment in view of the influence on the environment. Further, it is preferable to generate more HO radicals that contribute to oxidative decomposition, and hydrogen peroxide and ultraviolet light, ozone and hydrogen peroxide, and ozone and ultraviolet light are more preferable. In addition, a combination of ozone, UV, and hydrogen peroxide is preferable because oxidative decomposition can be performed more efficiently.
[0039]
  On the other hand, activated carbon treatment adsorbs odor (mold odor), chromaticity, trihalomethane, trihalomethane precursors, agricultural chemicals, anionic surfactants, phenols, low-boiling organic chlorine compounds such as trichloroethylene, etc. remaining in the concentrated water. Remove. Activated carbon is a black, porous carbonaceous material made from wood (coconut shells, sawdust), coal, etc. as raw materials, and carbonized and activated. These raw materials, carbonization method and activation The adsorption characteristics differ depending on the method. The feature of activated carbon is that it has a large ability to remove organic substances dissolved in water, and unlike the case of chemical treatment, it does not leave a reaction product in the treated water.
[0040]
  Activated carbon having the property of adsorbing trace organic substances in gas and liquid is classified into powdered activated carbon, granular activated carbon, and fibrous activated carbon according to its shape. In the case of emergency or short-term use, powdered activated carbon treatment or fibrous activated carbon treatment is suitable, and for continuous or relatively long-term use, granular activated carbon treatment is more advantageous. Granular activated carbon is preferred. Of the granular activated carbon, woody coconut shell charcoal has many pores with a diameter of 3 nm or less and few large pores with a diameter of 30 nm or more. Therefore, low molecular weight substances are easily removed. On the other hand, coal systems exist widely from 3 nm to considerably large pores. Therefore, it is easy to remove a substance having a higher molecular weight. In the present invention, the activated carbon raw material is not limited, but the adsorptive capacity of the activated carbon varies depending on the coexisting organic matter and the amount thereof, so the physical properties, actual conditions, treatment effects, etc. of the substance to be removed in the concentrated water are tested in advance. It is preferable to conduct a thorough investigation including, and select the type of activated carbon.
[0041]
  Subsequently, the softening treatment device 9 prevents the scales of calcium carbonate, calcium sulfate, magnesium hydroxide, etc. from depositing on the membrane surface when the concentrated water 80 is refluxed and supplied to the membrane module 6 together with the raw water 50 again. For example, (1) injecting caustic soda into concentrated water 80 to bring the pH to about 10 is brought into contact with a fluid medium coated with calcium carbonate in a reaction tank, and calcium in the water is converted into calcium carbonate onto the fluid medium. A crystallization softening method for crystallization, (2) adding slaked lime, soda ash, caustic soda, etc. to increase the pH of the concentrated water 80 to increase the CaCO₃And Mg (OH)₂As described above, an alkali coagulation method excluding hardness components and (3) an ion exchange method using an ion exchange resin or the like are applied.
[0042]
  The crystallization softening method has the advantage that the facility is relatively compact, magnesium cannot be removed but calcium can be removed, and sludge treatment is not required. However, since the pH value of the reaction tank effluent becomes high, equipment for pH adjustment is required. Moreover, since the size of the fluid medium in the reaction tank changes due to crystallization of calcium carbonate and the removal efficiency is lowered, the fluid medium must be periodically discharged and replenished. The alkali coagulation method can simultaneously remove turbidity, heavy metal ions and the like other than the hardness component. However, in order to remove magnesium, it is necessary to increase the pH value to about 11, and sludge treatment is required. The ion exchange method is an operation in which ions are reversibly exchanged between a solid and a liquid without causing a major change in the main component of the solid component, and is relatively easy to maintain. In water treatment in which calcium and magnesium cations are to be removed, a cation exchange resin is used.
[0043]
  The most common ion exchange resin is based on styrene-divinylbenzene (DVB) addition copolymer, and the structure has various ionic group groups. Decide. Cation exchange resins include strong acid cation exchange resins and weak acid cation exchange resins. The strong acid cation exchange resin is a cation exchange resin having a strong electrolyte such as a sulfonic acid group, and works in the entire pH range and has an ability to decompose a neutral salt. The weakly acidic cation exchange resin is a cation exchange resin having a carboxyl group, and the effective pH range showing ion exchange is 4 to 14. Both are applicable in the present invention.
[0044]
  As the ion exchange resin, a fixed bed adsorbing apparatus in which a resin having an effective diameter of about 0.5 mm is filled to about several tens of cm is common. Since a solution of several percent or more of salt, sulfuric acid, hydrochloric acid or the like is used for regeneration of the ion exchange resin, the material of the apparatus must be corrosion resistant.
[0045]
  The ion exchange process is performed using SV (Space Velocity, 1 / h) = flow rate (m³/ H) / filled resin amount (m³) Is preferably within a range of 10 to 30 (1 / h).
[0046]
  In addition, when the removal performance of the hardness component by the ion exchange method is extremely high, the ion exchange treatment is performed to such an extent that calcium-derived scale is not generated after ion exchange treatment of a part of the concentrated water after the NF membrane or RO membrane treatment. What is necessary is just to mix with the concentrated water which was not done and to return as treated water.
[0047]
  Moreover, when the suspended water is contained in the concentrated water subjected to the ion exchange treatment, the ion exchange resin is contaminated by the suspended material, and the hardness component removal performance is lowered. In addition, since the effective diameter of an ion exchange resin is generally around 0.5 mm, suspended substances are trapped in the resin layer, so that the loss head is increased and the amount of treated water is reduced. However, in the present invention, the raw water 50 is solid-liquid separated at the front stage of the membrane module 6 and the suspended substances are removed, so this problem does not occur.
[0048]
  In the present invention, the order of organic substance removal and softening treatment is not particularly limited. However, when the accelerated oxidation treatment device 7, activated carbon treatment device 8 and softening treatment device 9 are used, the accelerated oxidation treatment is performed with the concentration of organic matter in water. The higher the value, the higher the oxidative decomposition efficiency of organic substances by HO radicals, and the softening treatment cannot continue effective treatment because the surface of the ion exchanger is quickly contaminated and deteriorated when minute organic substances are present in the water. Therefore, as shown in FIG. 1, it is preferable to provide in the order of the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9..
[0049]
  It is shown for comparison with the present invention.FIG. 2 is a mode in which the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 are not provided in the water treatment device of FIG. About others, it is the same as the water treatment apparatus of FIG.Also shown for comparison with the present invention.FIG. 3 is a mode in which the softening device 9 is not provided in the water treatment device of FIG. About others, it is the same as the water treatment apparatus of FIG.
[0050]
【Example】
  <Example 1>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was river water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0051]
  The separated water 60 treated by the solid-liquid separation device 3 is stored in the tank 4 and then passed through the pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). The membrane module 6 was processed. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0052]
  And the whole quantity of the concentrated water 80 discharged | emitted by the membrane module 6 was processed with the accelerated oxidation processing apparatus 7 which consists of ozone and an ultraviolet-ray. The accelerated oxidation treatment apparatus 7 has three low-pressure mercury lamps 15W arranged in a small reaction tank, irradiates the concentrated water with ultraviolet rays, and generates and injects ozone at 10 mg / l.
[0053]
  The concentrated water treated with the accelerated oxidation treatment device 7 was treated with the activated carbon treatment device 8. The activated carbon treatment device 8 was fixed bed granular activated carbon, and the raw material of the activated carbon was coconut shell. The operating conditions were LV: 100 m / d and filter layer thickness: 2.5 m / d. 20% of the concentrated water 90 treated with the activated carbon treatment device 8 was drained, and 80% was allowed to flow into the softening treatment device 9.
[0054]
  The softening treatment apparatus 9 performed ion exchange treatment and used a cation exchange resin having a sulfonic acid group. The water flow rate was SV = 20 (1 / h). The concentrated water 100 treated by the softening device 9 was returned to the tank 1 and mixed with raw water.
[0055]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but was stable at 0.42 MPa even after 3000 hours had elapsed since the start of operation.
[0056]
  Also, raw water 50 ((1)), separated water 60 ((2)) of the solid-liquid separator 3, permeated water 70 ((3)) of the membrane module 6, concentrated water 80 ((4)) of the membrane module 6, Table 1 shows the average water quality of the concentrated water 90 ((5)) treated with the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 and the concentrated water 100 ((6)) treated with the softening treatment device 9. The average water quality is the average of the results measured for one year at a frequency of once a day.
[0057]
[Table 1]
[0058]
  As a result of the above water treatment, the permeated water 70 ((3)) of the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 satisfied the drainage standard in the Water Pollution Control Law.
[0059]
  <Comparative Example 1>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was the same river water as in Example 1. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0060]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0061]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0062]
  As a result, the operating pressure of the NF film immediately after the start of operation was 0.35 MPa, but after 700 hours had elapsed from the start of operation, it reached 1.7 MPa, and chemical cleaning had to be performed.
[0063]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 2 shows the average water quality of 4)).
[0064]
[Table 2]
[0065]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. However, the concentrated water 80 ((4)) of the membrane module 6 did not satisfy the drainage standards in the Water Pollution Control Law for simazine and thiuram.
[0066]
  <Comparative example2>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was groundwater. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0067]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0068]
  The concentrated water 80 of the membrane module 6 was not treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8, but 20% of the concentrated water 80 was drained and the remaining 80% was allowed to flow into the softening treatment device 9. The softening treatment apparatus 9 performed ion exchange treatment and used a cation exchange resin having a sulfonic acid group. The water flow rate was SV = 20 (1 / h). The concentrated water 100 treated by the softening device 9 was returned to the tank 1 and mixed with raw water.
[0069]
  As a result, although the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, it was stable at 0.63 MPa even after 3000 hours had elapsed from the start of operation, and it was not yet time for chemical cleaning.
[0070]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 3 shows the average water quality of the concentrated water 100 ((6)) treated by the softening device 9).
[0071]
[Table 3]
[0072]
  As a result of the above water treatment, the permeated water 70 ((3)) of the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 80 ((4)) of the membrane module 6 satisfied the drainage standard in the Water Pollution Control Law.
[0073]
  <Comparative example3>
  The membrane filtration apparatus which carried out the operation is shown in FIG. Raw waterComparative exampleThe same groundwater as 2. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0074]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0075]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0076]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but reached 700 MPa after 700 hours from the start of operation, and chemical cleaning had to be performed.
[0077]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 4 shows the average water quality of 4)).
[0078]
[Table 4]
[0079]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 80 ((4)) of the membrane module 6 satisfied the drainage standard in the Water Pollution Control Law.
[0080]
  <Comparative Example 4>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was lake water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0081]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0082]
  And the concentrated water whole quantity 80 discharged | emitted by the membrane module 6 was processed with the accelerated oxidation processing apparatus 7 which consists of ozone and UV. The accelerated oxidation treatment apparatus 7 has three low-pressure mercury lamps 15W arranged in a small reaction tank, irradiates the concentrated water with UV, and generates and injects ozone at 10 mg / l.
[0083]
  The concentrated water treated with the accelerated oxidation treatment device 7 was treated with the activated carbon treatment device 8. The activated carbon treatment device 8 was fixed bed granular activated carbon, and the raw material of the activated carbon was coconut shell. The operating conditions were LV: 100 m / d and filter layer thickness: 2.5 m / d. 20% of the concentrated water 90 treated with the activated carbon treatment device 8 was drained, and 80% was returned to the tank 1 without being treated with the softening treatment device 9 and mixed with raw water.
[0084]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but it remained stable at 0.83 MPa even after 3000 hours had elapsed from the start of operation, and it was not yet time for chemical cleaning.
[0085]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 5 shows the average water quality of the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8).
[0086]
[Table 5]
[0087]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 satisfied the drainage standard in the Water Pollution Control Law.
[0088]
  <Comparative example5>
  The membrane filtration apparatus which carried out the operation is shown in FIG. Raw waterComparative Example 4The same lake water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0089]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0090]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0091]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa. However, after 700 hours had elapsed from the start of operation, it reached 1.8 MPa, and chemical cleaning had to be performed.
[0092]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 6 shows the average water quality of 4)).
[0093]
[Table 6]
[0094]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. However, the concentrated water 80 ((4)) of the membrane module 6 did not satisfy the drainage standards in the Water Pollution Control Law for simazine and thiuram.
[0095]
【The invention's effect】
  In the present invention, the concentrated water of a reverse osmosis filtration (RO) membrane and / or a nanofiltration membrane (NF membrane) that has been solid-liquid separated in advance is subjected to a softening treatment method andAnd an accelerated oxidation treatment that includes at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment.By treating with the machine removal method, fouling and scale can be suppressed even in high recovery rate operation, and the concentrated water can be reduced below the drainage standard value, so that it can be discharged as it is.
[Brief description of the drawings]
FIG. 1 is a flowchart showing one embodiment of a water treatment apparatus of the present invention.
[Figure 2]Of the water treatment apparatus of Comparative Example 2It is a flowchart which shows an embodiment.
[Fig. 3]Comparative Example 4Water treatment equipmentThe fruitIt is a flowchart which shows an embodiment.
[Fig. 4]Comparative Examples 1, 3, 5It is a flowchart which shows the aspect of this water treatment apparatus.
[Explanation of symbols]
1, 4: Tank
2, 5: Pressurizing pump
    3: Solid-liquid separator
    6: Membrane module
    7: Accelerated oxidation treatment equipment
    8: Activated carbon treatment equipment
    9: Softening device
  10: Recirculation means
  50: Raw water
  60: Separation water of the solid-liquid separator 3
  70: Permeated water of membrane module 6
  80: Concentrated water of the membrane module 6
  90: Concentrated water treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8
100: Concentrated water treated by the softening treatment device 9

Claims (8)

1. A water treatment method in which raw water is separated into solid and liquid and then separated into permeate and concentrated water by a membrane module equipped with a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane), and the recovery rate there as well as operation to be at least 90%, a water treatment method characterized by processing the at least part of the concentrated water of the membrane module in the softening treatment and organic matter removal method is refluxed in raw water The water treatment method is characterized in that the organic substance removal method includes an accelerated oxidation treatment in which at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment are performed .
2. The water treatment method according to claim 1, wherein the softening treatment method includes ion exchange.
3. The water treatment method according to claim 1 or 2, wherein the organic substance removal method further includes activated carbon treatment.
4. The water treatment method according to any one of claims 1 to 3 , wherein solid-liquid separation is performed using a microfiltration membrane (MF membrane) and / or an ultrafiltration membrane (UF membrane).
5. Adding a coagulant to the raw water in front of the solid-liquid separation, water treatment method according to any one of claims 1-5.
6. A membrane having a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane) that separates the raw water into solid-liquid separation means and the treated water of the solid-liquid separation means into permeated water and concentrated water. A water treatment apparatus comprising: a module; and a reflux means having an organic substance removing means and a softening treatment means for treating at least a part of the concentrated water of the membrane module and returning it to raw water , The reflux means comprises an accelerated oxidation treatment means as the organic substance removal means, and the accelerated oxidation treatment means and the softening treatment means are arranged in this order .
7. 7. The water according to claim 6, wherein the organic matter removing means further comprises an activated carbon treatment means, and the accelerated oxidation treatment means, the activated carbon treatment means, and the softening treatment means are arranged in this order. Processing method.
8. A fresh water generation method using the method according to any one of claims 1 to 5 , or the device according to claim 6 or 7 .

Images