JP2005046802A - Water treatment method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment method constituted so as to reduce cost and an installation area by directly supplying sewerage wastewater containing heavy metal ions to an RO membrane or an NF membrane or supplying the primarily treated water thereof to the membrane without performing treatment such as sedimentation and separation treatment or the like and enabling desired advanced treatment by a simple system, and an apparatus therefor. <P>SOLUTION: In the water treatment method and the apparatus therefor, wastewater containing heavy metal ions or the primarily treated water thereof is used as raw water and this raw water is directly supplied to an internal pressure type hollow fiber separation membrane comprising an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nano-filtration membrane to reduce the concentration of heavy metal ions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a water treatment method and apparatus, and more particularly, a water system that can reduce heavy metal ion concentration by direct treatment or primary treatment of sewage such as industrial wastewater and domestic wastewater and then advanced treatment with a simple system. The present invention relates to a processing method and apparatus.

Conventionally, in wastewater treatment, organic substances, nitrogen, phosphorus, etc. are treated by biological treatment such as the activated sludge method (primary treatment), and further, the concentration of pollutants is below the environmental regulation value by sedimentation and filtration, etc. Has been discharged as sewage. However, in recent years, reverse osmosis membranes (hereinafter sometimes abbreviated as RO membranes) and nanofiltration membranes (hereinafter referred to as NF membranes) are not discharged as sewage due to an increase in the amount of wastewater and strengthening of environmental regulations. In addition, there are increasing cases in which advanced treatment is performed using water and reused for toilet water, planting water, fish (breeding) water, and the like (for example, Patent Document 1). .
JP 2003-103297 A

  However, some heavy metal ions are taken into microorganisms and can be removed by sedimentation or filtration, but heavy metal ions dissolved in water cannot be removed by these methods. .

  As an advanced treatment, an RO membrane or an NF membrane is often used for the purpose of removing heavy metal ions in the sewage. This further installs an apparatus after the conventional biological treatment + precipitation separation or biological treatment + filtration, resulting in an increase in cost and installation area. However, when the RO membrane or NF membrane structure is a spiral type or external pressure type hollow fiber, omission of settling and filtration results in clogging of the raw water flow path, an increase in the water flow differential pressure, and further the membrane Damage to the processing equipment can occur. Therefore, as long as these types of separation membranes are used, it is difficult to omit the pretreatment for the purpose of removing turbidity from the advanced treatment.

  Therefore, in view of the above circumstances, the problem of the present invention is that it is possible to supply wastewater containing heavy metal ions directly to the RO membrane or NF membrane without performing treatment such as sedimentation separation directly or primary treatment water. Another object of the present invention is to provide a water treatment method and apparatus capable of reducing the installation area and performing a desired advanced treatment with a simple system.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, in particular, in treating primary treated water containing sewage containing heavy metal ions, an internal pressure type hollow fiber RO membrane or NF membrane is used. By using it, sedimentation separation and filtration can be omitted, and the system can be simplified. (2) Appropriate cleaning system piping configuration can easily eliminate turbidity. (3) Chemical solution The inventors have found that the amount of chemicals used can be reduced by devising the cleaning system, and (4) that the material containing the cellulose is preferable as the material of the membrane, and the present invention has been completed.

  That is, the water treatment method according to the present invention uses sewage containing heavy metal ions or primary treated water as raw water, and this raw water is directly composed of an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nanofiltration membrane. The method comprises supplying to an internal pressure type hollow fiber separation membrane to reduce the concentration of heavy metal ions. By using such an internal pressure type hollow fiber separation membrane, the raw water as the water to be treated is directly supplied to the internal pressure type hollow fiber separation membrane without carrying out the pretreatment for the purpose of turbidity as in the prior art, so that heavy metal ions are supplied. Therefore, the system can be simplified, the installation area can be reduced, and the cost can be reduced. In the present invention, the pretreatment for the purpose of turbidity omitted in this way means pretreatment for advanced treatment using RO membrane or NF membrane, which means coagulation sedimentation treatment, filtration treatment, membrane treatment, etc., simply removing coarse dust. Strainers installed for the purpose of doing this are not excluded. The raw water used in the present invention is not particularly limited as long as it is sewage containing heavy metal ions such as zinc, cadmium, palladium, arsenic, tin, or the primary treated water, and domestic wastewater and industrial wastewater are obtained by the activated sludge method. The treated water etc. which performed the biological treatment can be illustrated.

  In the water treatment method according to the present invention as described above, the concentration of the organic halogen compound contained in the permeate treated by the internal pressure type hollow fiber separation membrane is preferably 1% or less. By treating in this way, organic halogen compounds such as dioxins contained in the raw water can be significantly removed and reduced.

  Moreover, it is preferable to use what consists of a hydrophilic raw material for the said internal pressure type | mold hollow fiber separation membrane, and it is preferable to consist of a raw material containing a cellulosic material (for example, cellulose acetate) especially. By using a material made of such a hydrophilic material for the internal pressure type hollow fiber separation membrane, in particular, a cellulose-based material, the adhesion of contaminants to the membrane surface is particularly suppressed, and the decrease in flux is less likely to occur. The life of the processing equipment is increased and the intended purpose is achieved.

  Moreover, in the water treatment method according to the present invention, it is possible to efficiently recover the performance of the separation membrane by performing the following cleaning after performing the treatment for a predetermined period. That is, cleaning water is supplied to the raw water introduction pipe for introducing the raw water as described above into the internal pressure type hollow fiber separation membrane to wash at least the raw water introduction pipe, and the washed water is substantially removed from the internal pressure type hollow fiber separation membrane. The raw water introduction pipe can be passed through without being introduced into the yarn separation membrane, and discharged through a washing water drain pipe connected to the raw water introduction pipe. The turbidity accumulated in the raw water introduction pipe is washed away by the supplied washing water and removed, and the removed turbidity is discharged directly through the washing water drain pipe without flowing to the separation membrane side. The reattachment of the removed turbidity or the like to the separation membrane is prevented, and the amount of the chemical used when the separation membrane is washed with the chemical is greatly reduced.

  In the above washing, in addition to the raw water introduction pipe, the concentrated water outlet pipe from the membrane separation device can also be a washing target. In this case, the washing water is separated from the internal pressure type hollow fiber. What is necessary is just to set it as the structure provided with the water supply system for washing | cleaning which can be supplied also to the concentrated water outlet pipe from a membrane.

  Moreover, in the above washing | cleaning, after washing | cleaning by the said washing | cleaning water, a chemical | medical solution can be poured with respect to the said internal pressure type | mold hollow fiber separation membrane, and a separation membrane can be wash | cleaned. In this case, the chemical solution can be circulated and passed through and effectively used by washing the separation membrane. In particular, when a solid-liquid separation device is provided in the chemical solution circulation system, the chemical solution separated by the solid-liquid separation device can be efficiently reused for cleaning. In addition, when a chemical tank that stores the chemical separated by the solid-liquid separator is provided, the separated chemical can be reused for cleaning more efficiently. The solid-liquid separation device and the chemical tank can be shared, that is, one device can have both functions.

  In the above-described cleaning, independent of the cleaning of the raw water introduction pipe, when the chemical solution for cleaning the internal pressure type hollow fiber separation membrane is circulated and passed, the chemical solution used for cleaning is separated into solid and liquid. In addition, the separated chemical solution can be reused for cleaning. Also in this case, the separated chemical solution can be reused for cleaning after being stored in the chemical solution tank.

  The water treatment apparatus according to the present invention uses sewage containing heavy metal ions or its primary treated water as raw water, and this raw water is directly an internal pressure type comprising an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nanofiltration membrane. It is supplied to the hollow fiber separation membrane to reduce the concentration of heavy metal ions. In this case, the concentration of the organic halogen compound contained in the permeated water treated with the internal pressure type hollow fiber separation membrane is preferably 1% or less. Further, the internal pressure type hollow fiber separation membrane is preferably made of a hydrophilic material, particularly a material containing a cellulosic material. By using such a material, the adhesion of contaminants to the membrane surface is suppressed, and the flux of The decrease is less likely to occur.

  In the water treatment apparatus according to the present invention, it is preferable to add a cleaning system. That is, the raw water introduction pipe that introduces the raw water into the internal pressure type hollow fiber separation membrane does not substantially introduce the cleaning water supplied to the raw water introduction pipe into the internal pressure type hollow fiber separation membrane. It is possible to adopt a structure in which a cleaning water drain pipe that passes through and discharges is connected. Further, a cleaning water supply system capable of supplying the cleaning water also to the concentrated water outlet pipe from the internal pressure type hollow fiber separation membrane may be provided.

  In addition, this cleaning system may employ a structure in which a chemical solution cleaning system is provided for passing the chemical solution through the internal pressure type hollow fiber separation membrane and cleaning the separation membrane. The chemical cleaning system can be configured as a circulation system. This chemical circulation system is preferably provided with a solid-liquid separator. The chemical solution circulation system having such a solid-liquid separation device may be provided independently of the above-described cleaning system for the raw water introduction pipe. Such a chemical solution circulation system may be provided with a chemical solution tank for storing the chemical solution separated by the solid-liquid separation device, or may have a structure in which the solid-liquid separation device and the chemical solution tank are shared.

  According to the water treatment method and apparatus according to the present invention, the raw water comprising the sewage containing heavy metal ions or the primary treated water is substantially directly subjected to the internal pressure type hollow fiber reverse osmosis membrane or the internal pressure type hollow fiber nanofiltration. It is supplied to an internal pressure type hollow fiber separation membrane consisting of a membrane to remove heavy metal ions. In such an internal pressure type hollow fiber separation membrane, the raw water flow path as in the case of a conventional spiral membrane module is used. Since the clogging is suppressed, it is possible to perform the removal treatment without performing the pretreatment for the purpose of removing turbidity as in the past, and the heavy metal ions contained in the raw water are efficiently used with a simplified system. In addition to being removed at a low cost, the entire system can be simplified, the installation area can be reduced, and the cost can be reduced. In particular, by using a hydrophilic material, especially a cellulose-based material, for the internal pressure type hollow fiber separation membrane, it is possible to perform a favorable treatment while suppressing a decrease in flux.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a water treatment apparatus according to an embodiment of the present invention. In FIG. 1, biological treatment is performed as water to be treated, and raw water 1 containing suspended substances and heavy metal ions is sent to a separation membrane module 4 via a raw water introduction pipe 3 by a pump 2. The separation membrane module 4 is an internal pressure type hollow fiber membrane module in which water to be treated is pressurized and supplied to the inside of the hollow fiber. The separation membrane module 4 includes an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber. An internal pressure type hollow fiber separation membrane 5 made of a nanofiltration membrane is provided. The raw water 1 supplied via the raw water introduction pipe 3 is substantially directly supplied to the internal pressure type hollow fiber separation membrane 5 (separation membrane element), and heavy metal ions are removed and reduced. In this embodiment, the raw water 1 is supplied to the inside of each internal pressure type hollow fiber separation membrane 5 via the introduction-side header 6 of the separation membrane module 4, and the water that has permeated through the hollow fiber membrane is permeated water 7 (treated water). The water condensed and passed through the hollow fiber membrane is taken out as concentrated water 10 via the outlet side header 8 and the concentrated water outlet pipe 9 of the separation membrane module 4. In this permeated water 7, the concentration of heavy metal ions is significantly reduced as compared with the raw water 1. At the same time, the organic halogen compound concentration is also reduced to, for example, 1% or less. Reference numeral 11 denotes an on-off valve for controlling the supply of the raw water 1, 12 denotes an on-off valve for controlling the delivery of the permeated water 7, and 13 denotes an on-off valve for controlling the delivery of the concentrated water 10. In the present embodiment, two separation membrane modules 4 are arranged side by side. However, a single unit may be provided, or three or more separation membrane modules 4 may be arranged side by side. What is necessary is just to determine the number of the separation membrane modules 4 in parallel according to the amount of water production required. When a plurality of juxtaposed pipes are provided, the raw water introduction pipe 3, the permeated water outlet pipe 8, and the concentrated water outlet pipe 10 may be provided as a common mother pipe form (inlet side mother pipe, outlet side mother pipe) as shown in the figure. . The raw water 1 is not particularly limited as long as it is sewage containing heavy metal ions or its primary water. In this embodiment, the separation membrane module 4 is shown in a vertical form (vertical arrangement form), but can also be in a horizontal form (horizontal arrangement form). Further, in the present embodiment, the separation membrane module 4 includes the introduction side header 6 and the outlet side header 8, but there are many separation membrane modules that do not include such a header, and such a header is not an essential configuration. Absent.

  As described above, even if the raw water 1 containing heavy metal ions is supplied directly to the internal pressure type hollow fiber separation membrane 5 without performing the pretreatment for the purpose of turbidity as in the prior art, the internal pressure type hollow fiber separation is performed. Occlusion of the membrane 5 with turbidity or the like is suppressed, and heavy metal ions contained in the raw water 1 are efficiently removed, and a desired reduction effect is obtained. The membrane material of the internal pressure type hollow fiber separation membrane 5 is preferably a hydrophilic material, particularly a material containing a cellulosic material. In recent years, the pressure of RO membranes and NF membranes has been reduced, and polyamide (PA) -based membranes are often used. However, PA membranes are vulnerable to dirt, and when used directly without any pretreatment, Various contaminants such as quality and humic substances adhere to the membrane surface and cause an early decrease in flux. On the other hand, this phenomenon is unlikely to occur in a cellulose-based film, and the decrease in flux is not observed. The reason for this is not clear, but is considered to be caused by a difference in zeta potential on the film surface, a difference in hydrophilicity, a difference in smoothness, and the like. That is, it is considered that the membrane material suitable for the present invention is required to have a zeta potential closer to minus, high hydrophilicity, and high smoothness. In this way, by using a highly hydrophilic membrane, in particular, a cellulose-based membrane, the raw water 1 is supplied substantially directly to the internal pressure type hollow fiber separation membrane 5 without performing a pretreatment for the purpose of turbidity removal. Thus, it is possible to perform heavy metal ion removal treatment. As a result, the entire system can be simplified, the installation area can be reduced, and the cost can be reduced.

  Furthermore, in this embodiment, a cleaning system for recovering the performance of the separation membrane module 4 after processing for a predetermined period is also provided. Connected to the raw water introduction pipe 3 is a washing water drain pipe 14 that drains the raw water introduction pipe 3 through the raw water introduction pipe 3 without substantially introducing the washing water supplied to the raw water introduction pipe 3 into the separation membrane module 4. Has been. In this embodiment, the raw water 1 is used as the cleaning water, and the raw water 1 as the cleaning water supplied by the pump 2 is passed through the raw water introduction pipe 3 by opening the on-off valve 15 to be passed through the raw water introduction pipe. After the inside of the pipe 3 is washed, it is discharged through the washing water drain pipe 14 together with the turbidity in the pipe removed by the washing. The washing waste water 16 may be appropriately discharged or the like, and may be discharged together with the concentrated water 10. In this embodiment, the raw water 1 is used as the cleaning water, but another cleaning water (for example, the permeated water 7) may be used. Further, although the cleaning water is supplied and discharged in the same direction as the flow direction of the raw water during the membrane separation process, it can be supplied so as to flow in the reverse direction in the raw water introduction pipe 3. For example, as shown by a two-dot chain line in FIG. 1, a cleaning water drain for connecting a cleaning water supply pipe 17 to the downstream side of the raw water introduction pipe 3 and discharging the cleaned water flowing in the reverse direction to the upstream side. A tube 18 can also be connected.

  By introducing the raw water 1 as the cleaning water into the raw water introduction pipe 3, the turbidity or the like adhering to or accumulating in the raw water introduction pipe 3 is washed away and removed before the chemical solution cleaning described later, The removed turbidity and the like are discharged through the washing water drain pipe 14 together with the washed water. Since the introduction side of the separation membrane module 4, at least the inside of the raw water introduction pipe 3, is washed well in advance, the chemical solution to be circulated is not consumed for washing the raw water introduction pipe 3 at the time of the next chemical washing of the separation membrane As a result, the amount of the chemical used for cleaning the chemical of the separation membrane can be greatly reduced, and the cleaning cost can be greatly reduced. In addition, it is possible to shorten the time for cleaning the chemical solution of the separation membrane.

  Further, in this embodiment, the raw water 1 as cleaning water can be supplied to the outlet side mother pipe (concentrated water outlet pipe 9) side via the bypass pipe 19 and the on-off valves 20 and 21. By supplying cleaning water to the mother pipe, good pre-pipe cleaning can be performed on the outlet side as well. If the pipe cleaning on the outlet side is added, the amount of the chemical used for cleaning the separation membrane is further reduced.

  Cleaning of the separation membrane of the separation membrane module 4 is mainly performed with a chemical solution. In this embodiment, a chemical solution circulation system 24 having on-off valves 21, 22, and 23 is provided for the separation membrane module 4. The chemical solution to be used may be selected according to the type of the separation membrane of the separation membrane module 4 and the properties of the water to be treated, and is not particularly limited, but is not limited to organic acids such as oxalic acid and citric acid, nitric acid Examples include inorganic acids such as hydrochloric acid, alkalis such as caustic soda, sodium hypochlorite, hydrazine, surfactants and the like. When an organic acid is used, a preservative may be added to prevent corruption.

  The chemical solution circulation system 24 is provided with a solid-liquid separation device 25 and a chemical solution tank 26 for storing the chemical solution separated by the solid-liquid separation device 25. In the present embodiment, the solid-liquid separation device 25 is configured as a precipitation separation device, and the removed solids and the like from the separated separation membrane are extracted from the bottom of the precipitation tank 27 via the on-off valve 28 and separated. The resulting supernatant is recovered, for example, through the overflow weir 29 to the chemical tank 26 and reused for cleaning. By performing solid-liquid separation, the separated chemical solution is efficiently reused for cleaning, and the amount of the chemical solution used as a whole is further reduced accordingly. The solid-liquid separation device 25 and the chemical liquid tank 26 may be configured as a device that can be shared. The solid-liquid separation timing is not particularly limited, and examples include a timing for separation immediately after chemical solution cleaning, a timing for separation immediately before the next chemical solution cleaning, and the like. The method of solid-liquid separation is not particularly limited, and examples include filtration (membrane separation) and the like in addition to sedimentation separation as described above.

  As described above, the amount of the chemical solution consumed for cleaning the separation membrane is greatly reduced by the pre-cleaning of the piping with the cleaning water. Then, by reusing the chemical liquid by the chemical liquid circulation system 24 equipped with the solid-liquid separator 25, the amount of the chemical liquid used is further greatly reduced. Such a chemical liquid circulation system 24 has an effect of reducing the amount of chemical liquid used even when the pipe is not pre-cleaned with the above-described cleaning water, and the effect can be obtained only by this configuration.

  Moreover, in the said embodiment, although the several separation membrane module 4 was arrange | positioned in parallel, it is also possible to arrange | position in series, and it is also possible to supply permeated water of a front | former stage as treated water of a back | latter stage. When a plurality of modules are installed in series, the internal pressure type hollow fiber RO membrane or NF membrane as described above is included in the first stage, and polyamide (PA) is included in the second stage or the second and subsequent stages. It is even better to use a PA-based spiral RO membrane or NF membrane made of a material. As described above, the PA-based separation membrane is vulnerable to dirt, but the first-stage treatment eliminates the cause of contamination of the PA-based separation membrane, so it can be used in the second and subsequent stages. In the first stage, an internal pressure type hollow fiber is used in order to avoid clogging of the raw water flow path due to turbidity in the raw water. However, in this first stage, turbidity and the like are eliminated, so that two spiral elements are used. Can be used after the eye. By these, the merit in terms of water quality and cost can be expected rather than using the internal pressure type hollow fiber over a plurality of stages. In addition, considering that the preprocessing can be omitted, it is a very significant merit.

  In other words, when aiming for further advanced treatment, a multi-stage treatment of two or more stages is performed, the waste water containing heavy metal ions or the primary treated water is used as raw water, and this raw water is directly used as an internal pressure type hollow as the first stage treatment. Supply to an internal pressure type hollow fiber separation membrane consisting of a yarn reverse osmosis membrane or an internal pressure type hollow fiber nanofiltration membrane to reduce the concentration of heavy metal ions. In the second and subsequent stages, the permeated water in the previous stage is treated. For example, water is supplied to a separation membrane of a form other than the internal pressure type hollow fiber separation membrane (for example, a reverse osmosis membrane or a nanofiltration membrane such as a spiral type or a flat membrane type) to perform further advanced treatment. The configuration of the water treatment method and apparatus can be adopted.

The example illustrated below shows one embodiment of the invention and does not limit the content of the invention.
(Example 1)
Using the primary treatment water of industrial wastewater as raw water, using the flow shown in FIG. 1, water was passed through the internal pressure type hollow fiber NF membrane module according to the present invention, and a test for 1500 hours was performed. As the membrane module, NF50 manufactured by Norit was used. The recovery rate was 50%.

(Comparative Example 1)
A similar test was performed using a spiral NF membrane module instead of the membrane module used in Example 1. As the membrane module, NTR-7250 manufactured by Nitto Denko Corporation was used. The recovery rate was 50%.

(Comparative Example 2)
A similar test was performed using an internal pressure type hollow fiber MF membrane module instead of the membrane module used in Example 1. As the membrane module, Microza USV-3003 manufactured by Asahi Kasei Co., Ltd., which is an external pressure type hollow fiber membrane, was used for internal pressure. The recovery rate was 50%.

  Table 1 shows the quality of the raw water used, and Table 2 shows the test results.

  In Comparative Example 1, the operation was stopped because the allowable water flow differential pressure was exceeded before reaching 1500 hours. In Comparative Example 2, it is possible to maintain a high flux, but there is no ability to remove dissolved Cd and Cr. On the other hand, in Example 1, it was possible to maintain a stable flux, and it was also possible to remove dissolved Cd and Cr. Dioxins could be suitably removed in Example 1. On the other hand, in Comparative Example 2, although the removal capability at the initial stage of operation is low and the fouling occurs with time, the removal capability is improved, but the removal capability is insufficient. Further, although data is not shown, the removal capability is lowered again after the film is washed. In addition, the film | membrane used in Example 1 this time was a polyamide-type raw material. Although it is a test stage using a flat membrane, it is presumed that the flux can be kept constant even if the cellulosic material is operated for a longer time.

  The water treatment method and apparatus according to the present invention are particularly suitable for a system that is required to perform a desired removal treatment on raw water containing heavy metal ions while greatly simplifying the pretreatment for turbidity. .

It is a schematic equipment system diagram of the water treatment equipment concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water 2 Pump 3 Raw water introduction pipe 4 Separation membrane module 5 Internal pressure type hollow fiber separation membrane 6 Introduction side header 7 Permeated water 8 Outlet side header 9 Concentrated water outlet pipe (outlet side main pipe)
DESCRIPTION OF SYMBOLS 10 Concentrated water 11, 12, 13, 15, 20, 21, 22, 23, 28 On-off valve 14 Washing water drain pipe 16 Washing drain 17 Washing water supply pipe 18 Washing water drain pipe 19 Bypass pipe 24 Chemical solution circulation system 25 Solid-liquid separation Equipment 26 Chemical tank 27 Precipitation tank 29 Overflow weir

Claims (22)

  Wastewater containing heavy metal ions or its primary treated water is used as raw water, and this raw water is directly supplied to an internal pressure type hollow fiber separation membrane consisting of an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nanofiltration membrane to produce heavy metal. A water treatment method characterized by reducing the concentration of ions.   The water treatment method according to claim 1, wherein the concentration of the organic halogen compound contained in the permeate treated by the internal pressure type hollow fiber separation membrane is 1% or less.   The water treatment method according to claim 1 or 2, wherein the internal pressure type hollow fiber separation membrane is made of a hydrophilic material.   The water treatment method according to claim 3, wherein the hydrophilic material is made of a material containing a cellulosic material.   The cleaning water is supplied to the raw water introduction pipe for introducing the raw water into the internal pressure type hollow fiber separation membrane to wash at least the raw water introduction pipe, and the washed water is substantially supplied to the internal pressure type hollow fiber separation membrane. The water treatment method according to any one of claims 1 to 4, wherein the raw water introduction pipe is allowed to pass through without being introduced, and is discharged through a cleaning water drain pipe connected to the raw water introduction pipe.   6. The water treatment method according to claim 5, wherein the cleaning water is also supplied to a concentrated water outlet pipe from the internal pressure type hollow fiber separation membrane to wash at least the concentrated water outlet pipe.   The water treatment method according to claim 5 or 6, wherein after the washing with the washing water, the separation membrane is washed by passing a chemical solution through the internal pressure type hollow fiber separation membrane.   The water treatment method according to claim 7, wherein the chemical solution is circulated and passed.   The water treatment method according to claim 8, wherein the chemical solution used for cleaning is separated into solid and liquid, and the separated chemical solution is reused for cleaning.   The circulating chemical solution for washing the internal pressure type hollow fiber separation membrane is subjected to solid-liquid separation of the chemical solution used for washing, and the separated chemical solution is reused for washing. The water treatment method according to any one of the above.   The water treatment method according to claim 9 or 10, wherein the separated chemical solution is stored in a chemical solution tank and reused for cleaning.   Wastewater containing heavy metal ions or its primary treated water is used as raw water, and this raw water is directly supplied to an internal pressure type hollow fiber separation membrane consisting of an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nanofiltration membrane to produce heavy metal. A water treatment apparatus characterized by reducing ion concentration.   The water treatment device according to claim 12, wherein the concentration of the organic halogen compound contained in the permeated water treated by the internal pressure type hollow fiber separation membrane is 1% or less.   The water treatment device according to claim 12 or 13, wherein the internal pressure type hollow fiber separation membrane is made of a hydrophilic material.   The water treatment apparatus according to claim 14, wherein the hydrophilic material is made of a material containing a cellulosic material.   The raw water introduction pipe for introducing the raw water into the internal pressure type hollow fiber separation membrane passes through the raw water introduction pipe without substantially introducing the cleaning water supplied to the raw water introduction pipe into the internal pressure type hollow fiber separation membrane. The water treatment apparatus according to any one of claims 12 to 15, to which a cleaning water drain pipe for discharging the liquid is connected.   The water treatment apparatus according to claim 16, further comprising a cleaning water supply system capable of supplying the cleaning water to the concentrated water outlet pipe from the internal pressure type hollow fiber separation membrane.   The water treatment device according to claim 16 or 17, wherein a chemical solution cleaning system is provided for passing the chemical solution through the internal pressure type hollow fiber separation membrane and cleaning the separation membrane.   The water treatment apparatus according to claim 18, wherein the chemical cleaning system is configured as a circulation system.   The water treatment device according to claim 19, wherein a solid-liquid separation device is provided in the chemical solution circulation system.   A chemical solution circulation system for circulating a chemical solution through the chemical solution through the internal pressure type hollow fiber separation membrane and washing, and a solid-liquid separation device is provided in the chemical solution circulation system. The water treatment apparatus in any one of.   The water treatment device according to claim 20 or 21, wherein the chemical solution circulation system is provided with a chemical solution tank that stores the chemical solution separated by the solid-liquid separation device.

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