JP5005165B2 - Water treatment method - Google Patents

Description

  The present invention relates to a water treatment method for efficiently treating raw water into water free of impurities.

  Water that does not contain impurities (pure water) is often used in semiconductor manufacturing, electronic component cleaning, medical device cleaning, and the like.

  Conventionally, as a water treatment method for treating raw water into water free of impurities, a reverse osmosis membrane is generally used, and the raw water is filtered through a reverse osmosis membrane, and a non-passivated metal body corrosion promoting component contained in the raw water or There is a method for removing other impurities.

  The reason why the reverse osmosis membrane is used for such water treatment is that the reverse osmosis membrane has a property of permeating the solvent but not allowing the solute to permeate. Using this property, the osmotic pressure of the water to be treated is higher. Processing is performed by applying pressure and selectively allowing only water as a solvent to pass through and filtering impurities in the water (for example, see Patent Document 1).

  In this water treatment, when the concentration of silica dissolved in the raw water is high, if the silica concentration of the water to be treated near the reverse osmosis membrane including the concentrated drainage generated in the reverse osmosis membrane exceeds the saturation concentration, Silica scale is deposited on the reverse osmosis membrane, and the reverse osmosis membrane is clogged. As a result, the recovery rate of treated water decreases. Precipitation of silica scale in the raw water is likely to occur when the silica concentration of the raw water exceeds the silica solubility of the raw water, that is, the silica saturation concentration, and the silica solubility in the raw water is directly proportional to the temperature of the raw water. The relationship is that the solubility increases as the temperature increases, and the solubility decreases as the temperature decreases.

Therefore, as a means for preventing clogging of the reverse osmosis membrane due to the silica scale deposited in the water to be treated in the vicinity of the reverse osmosis membrane where the silica concentration is high, the reverse osmosis membrane is periodically washed to wash the reverse osmosis membrane. Or, heat the treated water before sending it to the reverse osmosis membrane, increase the solubility of silica, or set the temperature of the treated water to a low temperature, and the silica concentration of the treated water depends on the set water temperature It is known to prevent clogging of the reverse osmosis membrane by suppressing the precipitation of silica scale in the water to be treated by operating so as not to exceed the solubility.
Japanese Patent Laid-Open No. 5-220480

  However, according to the water treatment method described above, clogging of the reverse osmosis membrane can be prevented, but a part of the chemical can be taken into the treated water by the means for supplying the chemical and washing the reverse osmosis membrane. If there is no special treatment for removing the chemicals when draining after using the treated water, it will be an environmental hazard. There was a problem that could cause contamination. Further, the means for heating the water to be treated before sending it to the reverse osmosis membrane has a problem that a water supply heating facility or the like is required and the cost is increased. Further, when the temperature of the water to be treated is set to a low temperature and the operation is performed such that the silica concentration of the water to be treated does not exceed the solubility due to the set water temperature, the recovery rate of the treated water is low, There was a problem that wasted money.

  Accordingly, the inventors of the present application have developed a water treatment method capable of suppressing precipitation of silica scale and ensuring a high recovery rate of treated water as a result of repeated research.

  That is, an object of the present invention is to provide a water treatment method for efficiently treating water to be treated into water free of impurities.

To achieve the above object, the water treatment method according to the invention of claim 1, wherein, after soft water treated water to be treated, filtered through a reverse osmosis membrane unit, predetermined intervals concentrated wastewater generated in the reverse osmosis membrane unit The predetermined interval for blowing the concentrated waste water is a predetermined time set based on the temperature of the water to be treated and the silica solubility of the water to be treated at that temperature. It is characterized by that.

In this way, by treating the water to be treated with soft water, hardness components such as calcium in the water to be treated are removed, and precipitation of scale due to the combination of the hardness components such as calcium and silica is prevented. The silica solubility of the water to be treated is increased, and the silica scale is prevented from being precipitated even in a state where the silica concentration of the water to be treated is high, and water treatment operation at a high silica concentration of the water to be treated becomes possible.
Furthermore, the treated water whose silica concentration has been increased by filtration through the reverse osmosis membrane part is periodically obtained by filtering the treated water subjected to the soft water treatment through the reverse osmosis membrane part and blowing the generated concentrated waste water at predetermined intervals. Since it flows to the drainage side of the concentrated drainage, an increase in the silica concentration of the water to be treated in the vicinity of the reverse osmosis membrane part will be suppressed, precipitation of silica scale is suppressed, and clogging of the reverse osmosis membrane part can be prevented, Long-term stable water treatment operation can be continued, and the recovery rate of treated water can be further improved .
The predetermined interval for blowing the concentrated wastewater is a predetermined time set based on the temperature of the treated water assumed in advance and the silica solubility of the treated water at that temperature. Concentrated wastewater can be blown at intervals necessary for the control, and blowout of more concentrated wastewater can be suppressed, silica scale precipitation can be effectively suppressed, clogging of the reverse osmosis membrane can be prevented, and the recovery rate of treated water Can be further improved and water supply can be saved.

The water treatment method according to the second aspect of the present invention is a water treatment method in which water to be treated is treated with soft water, filtered through a reverse osmosis membrane portion, and concentrated drainage generated in the reverse osmosis membrane portion is blown at predetermined intervals. The predetermined interval for blowing the concentrated drainage is set so as to detect the temperature of the water to be treated and to be long when the water temperature is high and short when the water temperature is low.

In this way, by treating the water to be treated with soft water, hardness components such as calcium in the water to be treated are removed, and precipitation of scale due to the combination of the hardness components such as calcium and silica is prevented. The silica solubility of the water to be treated is increased, and the silica scale is prevented from being precipitated even in a state where the silica concentration of the water to be treated is high, and water treatment operation at a high silica concentration of the water to be treated becomes possible.
Furthermore, the treated water whose silica concentration has been increased by filtration through the reverse osmosis membrane part is periodically obtained by filtering the treated water subjected to the soft water treatment through the reverse osmosis membrane part and blowing the generated concentrated waste water at predetermined intervals. Since it flows to the drainage side of the concentrated drainage, an increase in the silica concentration of the water to be treated in the vicinity of the reverse osmosis membrane part will be suppressed, precipitation of silica scale is suppressed, and clogging of the reverse osmosis membrane part can be prevented, Long-term stable water treatment operation can be continued, and the recovery rate of treated water can be further improved .
The predetermined interval for blowing the concentrated waste water is set so that the temperature of the water to be treated is detected and is long when the water temperature is high and short when the water temperature is low. The silica concentration of the water to be treated is close to the solubility of the water to be treated, the silica scale can be prevented from being precipitated in the water to be treated, and the reverse osmosis membrane can be prevented from being clogged. The treatment can be performed, the recovery rate of the treated water can be further improved, and the water supply can be saved.

In this way, by treating the water to be treated with soft water, hardness components such as calcium in the water to be treated are removed, and precipitation of scale due to the combination of the hardness components such as calcium and silica is prevented. The silica solubility of the water to be treated is increased, and the silica scale is prevented from being precipitated even in a state where the silica concentration of the water to be treated is high, and water treatment operation at a high silica concentration of the water to be treated becomes possible.
Furthermore, the treated water whose silica concentration has been increased by filtration through the reverse osmosis membrane part is periodically obtained by filtering the treated water subjected to the soft water treatment through the reverse osmosis membrane part and blowing the generated concentrated waste water at predetermined intervals. Since it flows to the drainage side of the concentrated drainage, an increase in the silica concentration of the water to be treated in the vicinity of the reverse osmosis membrane part will be suppressed, precipitation of silica scale is suppressed, and clogging of the reverse osmosis membrane part can be prevented, Long-term stable water treatment operation can be continued, and the recovery rate of treated water can be further improved .
The predetermined interval for blowing the concentrated drainage is set so as to detect the silica concentration of the water to be treated or the concentrated drainage sent to the reverse osmosis membrane part, and is short when the concentration is high and long when the concentration is low. Therefore, it is possible to operate the silica concentration of the water to be treated near the reverse osmosis membrane near the solubility of the water to be treated, thereby suppressing the precipitation of silica scale in the water to be treated, and clogging the reverse osmosis membrane. In addition, the water treatment can be performed more efficiently, the recovery rate of the treated water can be further improved, and the water supply can be saved.

A water treatment method according to a third aspect of the invention is characterized in that when the concentrated drainage generated in the reverse osmosis membrane part is blown according to the first or second aspect , the valve on the treated water side is closed. And

  In this way, all of the treated water flows to the drain side of the concentrated waste water, so that the silica concentration of the treated water can be lowered in a short time and the flow rate of the treated water flowing to the drain side of the concentrated waste water is high. Thus, the silica scale deposited on the reverse osmosis membrane portion by the flow pressure is peeled off from the reverse osmosis membrane portion, and the clogging of the reverse osmosis membrane portion can be eliminated at an early stage.

  According to the present invention, using a reverse osmosis membrane, in water treatment of filtering the treated water through the reverse osmosis membrane, it is possible to suppress silica scale precipitation in the treated water and prevent clogging of the reverse osmosis membrane part, A long-term stable water treatment operation can be continued, and the recovery rate of treated water can be improved.

  Hereinafter, the best mode for carrying out the water treatment method according to the present invention will be described.

(Embodiment 1)
In the water treatment method of this example, water to be treated was treated with soft water and then filtered through a reverse osmosis membrane portion.

  As described above, when the water to be treated is softened, hardness such as calcium in the water to be treated is removed. The hardness component such as calcium is a factor that promotes the generation of scale by combining with silica, and by removing the hardness component such as calcium in the treated water by the soft water treatment of the treated water, Generation of scale due to bonding between the hardness and silica is prevented. As a result, the silica solubility of the water to be treated is increased, and accordingly, precipitation of silica scale is suppressed even when the silica concentration of the water to be treated is high, and water treatment operation at a high silica concentration of the water to be treated is possible. Thereby, the recovery rate of treated water can be improved.

(Embodiment 2)
Water treatment method of this example, was filtered through a reverse osmosis membrane unit water to be treated, and the concentrated water discharge that occurs in the reverse osmosis membrane unit to blow at predetermined intervals.

Thus, when blown concentrated wastewater that occur in the reverse osmosis membrane unit, the drainage side of the concentrated waste water becomes negative, results the blown minute treatment water flows through the drainage side, the silica concentration in the vicinity of the reverse osmosis membrane unit The silica concentration of the to-be-processed water which becomes high falls. By blowing such concentrated waste water at predetermined intervals, the treated water whose silica concentration has been increased by filtration through the reverse osmosis membrane part periodically flows to the drain side of the concentrated waste water, so that the treated water near the reverse osmosis membrane part. Suppresses the increase in silica concentration, suppresses silica scale deposition, and even if silica scale is deposited, it flows to the drain side of the concentrated drainage, and the deposited silica scale is deposited on the reverse osmosis membrane. When it is, the silica scale deposited on the reverse osmosis membrane portion can be peeled off by the flow pressure flowing to the drainage side of the concentrated drainage and flowed to the drainage side. Thereby, clogging of the reverse osmosis membrane part can be prevented, a long-term stable water treatment operation can be continued, and the recovery rate of treated water can be improved.

  In the predetermined interval for blowing the concentrated waste water, the time for the silica concentration of the water to be treated to be saturated is obtained based on the temperature of the water to be preliminarily assumed and the silica solubility of the water to be treated at that temperature. And set a certain time.

  In this way, by setting the predetermined interval for blowing the concentrated waste water based on the temperature of the water to be treated that is assumed in advance and the silica solubility of the water to be treated at that temperature, the interval necessary for suppressing the precipitation of silica scale. In this case, it is possible to control the concentration of wastewater and to prevent the concentration of wastewater from blowing more than necessary, effectively suppressing silica scale deposition and preventing clogging of the reverse osmosis membrane, and further improving the recovery rate of treated water. Improvements can be made and water can be saved.

  Alternatively, as the predetermined interval for blowing the concentrated waste water, the temperature of the water to be treated is detected, and the time when the silica concentration of the water to be treated is saturated becomes the limit. It is good to set as follows.

  In this way, the predetermined interval for blowing the concentrated drainage is set so that the temperature of the water to be treated is detected and is long when the water temperature is high and short when the water temperature is low. The silica concentration of the water to be treated is close to the solubility of the water to be treated, the silica scale can be prevented from being precipitated in the water to be treated, and the reverse osmosis membrane can be prevented from being clogged. The treatment can be performed, the recovery rate of the treated water can be further improved, and the water supply can be saved.

  Alternatively, as the predetermined interval for blowing the concentrated waste water, the silica concentration of the water to be treated sent to the reverse osmosis membrane part is detected, and the saturation concentration of the silica concentration of the water to be treated is limited, and when the concentration is high, it is short. If it is low, it should be set to be long.

  Thus, by detecting the silica concentration of the treated water sent to the reverse osmosis membrane part, the predetermined interval for blowing the concentrated drainage is set to be short when the concentration is high, and long when the concentration is low, It is possible to operate the silica concentration of the water to be treated near the reverse osmosis membrane near the solubility of the water to be treated, to suppress silica scale precipitation in the water to be treated, and to prevent clogging of the reverse osmosis membrane. In addition, the water treatment can be performed more efficiently, the recovery rate of the treated water can be further improved, and the water supply can be saved.

Further, in this example, when blown concentrated wastewater that occur to the reverse osmosis membrane unit may be performed by closing the valve of the processing water side.

  In this way, all of the treated water flows to the drain side of the concentrated waste water, so that the silica concentration of the treated water can be lowered in a short time and the flow rate of the treated water flowing to the drain side of the concentrated waste water is high. Thus, the silica scale deposited on the reverse osmosis membrane portion by the flow pressure is peeled off from the reverse osmosis membrane portion, and the clogging of the reverse osmosis membrane portion can be eliminated at an early stage. This method is effective when the silica concentration greatly exceeds the silica solubility and the silica scale is likely to precipitate, or when the silica scale is deposited on the reverse osmosis membrane portion and clogging starts.

(Embodiment 3)
Water treatment method of the present embodiment, after soft water treated water to be treated, filtered through a reverse osmosis membrane unit, and adapted to blow at predetermined intervals concentrated wastewater that occur in the reverse osmosis membrane unit.

  In this way, by treating the water to be treated with soft water, hardness components such as calcium in the water to be treated are removed, and precipitation of scale due to the combination of the hardness components such as calcium and silica is prevented. The silica solubility of the water to be treated is increased, and the silica scale is prevented from being precipitated even in a state where the silica concentration of the water to be treated is high, and water treatment operation at a high silica concentration of the water to be treated becomes possible.

  Furthermore, the treated water whose silica concentration has been increased by filtration through the reverse osmosis membrane part is periodically obtained by filtering the treated water subjected to the soft water treatment through the reverse osmosis membrane part and blowing the generated concentrated waste water at predetermined intervals. Since it flows to the drainage side of the concentrated wastewater, it suppresses the increase in the silica concentration of the water to be treated in the vicinity of the reverse osmosis membrane, suppresses silica scale precipitation, and even if silica scale is deposited, When the generated silica scale is deposited on the reverse osmosis membrane part, the silica scale deposited on the reverse osmosis membrane part is separated by the flow pressure flowing to the drain side of the concentrated waste water. This can prevent clogging of the reverse osmosis membrane part, and can continue to perform stable water treatment operation for a long period of time, thereby further improving the recovery rate of treated water. Can do.

  In the predetermined interval for blowing the concentrated waste water, as in the second embodiment, the temperature of the treated water assumed in advance and a fixed time set based on the silica solubility of the treated water at that temperature. Good.

  In this way, by setting the predetermined interval for blowing the concentrated waste water based on the temperature of the water to be treated that is assumed in advance and the silica solubility of the water to be treated at that temperature, the interval necessary for suppressing the precipitation of silica scale. In this case, it is possible to control the concentration of wastewater and to prevent the concentration of wastewater from blowing more than necessary, effectively suppressing silica scale deposition and preventing clogging of the reverse osmosis membrane, and further improving the recovery rate of treated water. Improvements can be made and water can be saved.

  Alternatively, as the predetermined interval for blowing the concentrated wastewater, as in the second embodiment, the predetermined interval for blowing the concentrated wastewater is detected when the temperature of the water to be treated is detected, and when the water temperature is high, it is long and low. Should be set to be shorter.

  In this way, by setting a predetermined interval for blowing concentrated wastewater, it is possible to operate the silica concentration of the water to be treated near the reverse osmosis membrane near the solubility of the water to be treated. Sedimentation of scale can be suppressed, clogging of the reverse osmosis membrane can be prevented, water treatment can be performed more efficiently, and the recovery rate of treated water can be further improved, thereby saving water supply. Can be achieved.

  Alternatively, as the predetermined interval for blowing the concentrated wastewater, as in the second embodiment, the predetermined interval for blowing the concentrated wastewater detects the silica concentration of the treated water sent to the reverse osmosis membrane part, It is better to set it to be short when the density is high and long when the density is low.

  By setting in this way, it is possible to operate the silica concentration of the water to be treated near the reverse osmosis membrane near the solubility of the water to be treated, thereby suppressing the precipitation of silica scale in the water to be treated, and reverse osmosis. Clogging of the membrane can be prevented and water treatment can be performed more efficiently, the recovery rate of treated water can be further improved, and water supply can be saved.

Further, in this embodiment, similarly to the second embodiment, when blown concentrated wastewater that occur to the reverse osmosis membrane unit may be performed by closing the valve of the processing water side.

  In this way, all of the treated water flows to the drain side of the concentrated waste water, so that the silica concentration of the treated water can be lowered in a short time and the flow rate of the treated water flowing to the drain side of the concentrated waste water is high. Thus, the silica scale deposited on the reverse osmosis membrane portion by the flow pressure is peeled off from the reverse osmosis membrane portion, and the clogging of the reverse osmosis membrane portion can be eliminated at an early stage. This method is effective when the silica concentration greatly exceeds the silica solubility and the silica scale is likely to precipitate, or when the silica scale is deposited on the reverse osmosis membrane portion and clogging starts.

Next, a specific embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view of a water treatment system showing an embodiment of the present invention.
The water treatment system shown in FIG. 1 removes impurities, etc. in the water to be treated, from the upstream side to the water supply line 1 for supplying the water to be treated, the soft water treatment unit 2, the filter 3 for removing dust and the like in the water to be treated. By permeating the reverse osmosis membrane part 4, the membrane type deaeration part 5 that deaerates using the gas permeable membrane that transmits the dissolved gas in the treated water treated by the reverse osmosis membrane part 4, and the membrane type deaeration part 5 A storage tank 6 for storing the obtained treated water is disposed in order, and further, a pump 7 that supplies the treated water to the reverse osmosis membrane unit 4 under pressure on the upstream side of the reverse osmosis membrane unit 4. Is arranged. The reverse osmosis membrane section 4 is connected to a concentrated drainage line 8 for draining concentrated drainage enriched with impurities. The drainage line 8a and the blow line 8b are branched into the concentrated drainage line 8. It is connected. Further, an on-off valve 9 is disposed in the treated water line 1a through which treated water treated by the reverse osmosis membrane section 4 flows, a drain valve 10a is disposed in the drain line 8a, and a blow valve is disposed in the blow line 8b. 10b is arranged.

  In the soft water treatment unit 2, a known soft water device using an ion exchange resin is used. Further, the reverse osmosis membrane portion 4 contains impurities (dissolved salt, silica, etc.) by utilizing the property that a reverse osmosis membrane (not shown) permeates the solvent but does not permeate the solute. A pressure higher than the osmotic pressure of the water to be treated is applied to selectively permeate and collect only water as a solvent. In the membrane type deaeration unit 5, a gas having a large number of the gas permeable membranes A permeable membrane module (not shown) and a water-sealed vacuum pump (not shown) for vacuuming the dissolved gas in the water to be treated through the gas permeable membrane module are provided.

  Furthermore, a temperature sensor 11 for detecting the temperature of the water to be treated is provided on the water supply line 1 on the upstream side of the reverse osmosis membrane portion 4. Similarly, a concentration measuring device 12 is provided on the water supply line 1 upstream of the reverse osmosis membrane portion 4 and in the vicinity of the reverse osmosis membrane portion 4 to detect the silica concentration in the water to be treated flowing through the portion.

  In addition, an inverter 13 connected to the pump 7 and capable of varying the rotational speed of the pump 7 according to an output frequency, and an interface to the temperature sensor 11, the concentration measuring device 12, the blow valve 10b, the on-off valve 9, and the inverter 13 are provided. And outputs a blow signal to the blow valve 10b arranged in the blow line 8b based on a temperature detection signal from the temperature sensor 11 or a silica concentration detection signal from the concentration measuring device 12, or blows to the blow valve 10b. An opening / closing command signal is output to the opening / closing valve 9 disposed in the treated water line 1a that outputs the command signal and flows the treated water treated by the reverse osmosis membrane unit 4, and the blow command signal to the blow valve 10b Based on this, a control unit 14 is provided for outputting a command signal to the inverter 13.

  The controller 14 has a temperature of the water to be treated, a silica solubility and a specific temperature of the water to be treated at the temperature, a silica solubility at the specific temperature, and a specific silica concentration at the specific temperature. The storage unit stores the silica precipitation time and the blow time for reducing the silica concentration of the water to be treated having a high concentration.

  Based on the signal from the temperature sensor 11, the interval time is set so that the silica concentration of the water to be treated reaches the saturation concentration, and is long when the water temperature is high and short when the water temperature is low. Based on the program that outputs the blow command signal to the valve 10b for a predetermined time at predetermined intervals and the signal from the concentration measuring device 12, the saturation concentration of the silica concentration of the water to be treated is limited, and when the concentration is high, it is short. When the time is low, the interval time is set to be long, and a program that outputs a blow command signal to the blow valve 10b for a predetermined time at a predetermined interval and a blow command to the blow valve 10b based on the blow command signal are selected. While outputting a signal, a program for outputting a close command signal to the on-off valve 9 disposed in the water supply line 1a through which the treated water treated by the reverse osmosis membrane section 4 flows. Eteiru.

  Furthermore, by selection, while outputting the blow command signal to the blow valve 10b based on the blow command signal, the command signal is output to the inverter 13, and the inverter 13 sets the rotation speed of the pump 7 to be treated water. A program for outputting a command signal for changing the supply amount to increase is provided.

  With the water treatment system configured as described above, the water treatment method according to the present invention is implemented as follows.

  The supplied treated water is subjected to soft water treatment in the soft water treatment unit 2 to remove hardness components such as calcium in the treated water, and the silica solubility in the treated water is increased in the treated water in the filter 3. Dust and the like are removed, and the water to be treated is pressurized by the pump 7 and supplied to the reverse osmosis membrane unit 4. The treated water that has passed through the reverse osmosis membrane unit 4 and from which impurities have been removed is deaerated by the membrane type deaeration unit 5 and stored in a storage tank 6 that stores the processed water.

  Then, in the course of the water treatment operation, the temperature of the water to be treated has decreased, and the temperature sensor 11 has detected that the silica concentration of the water to be treated has reached a temperature that exceeds the silica solubility of the treated water at that temperature. At this time, the control unit 14 outputs a blow signal to the blow valve 10b disposed in the blow line 8b based on the temperature detection signal from the temperature sensor 11, and opens and blows the blow valve 10b for a predetermined time. This operation is performed at predetermined intervals set by the program.

  In addition to the above, in the course of the water treatment operation, the silica concentration of the water to be treated is increased, and the concentration measuring device 12 detects that the silica concentration has exceeded the silica solubility of the water to be treated. Then, the control unit 14 outputs a blow signal to the blow valve 10b arranged in the concentrated drainage line 8 based on the silica concentration detection signal from the concentration measuring device 12, and opens the blow valve 10b for a predetermined time. To do. This operation is performed at predetermined intervals set by the program.

  The operator selects either the temperature detection signal from the temperature sensor 11 or the silica concentration detection signal from the concentration measuring device 12 as the one that outputs a blow signal to the blow valve 10b disposed in the blow line 8b. Is done.

  By doing in this way, since the to-be-processed water with which the silica density | concentration became high by filtration by the reverse osmosis membrane part 4 flows to the side which drains concentrated waste water regularly, the silica of to-be-processed water in the reverse osmosis membrane part 4 vicinity. The increase in concentration is suppressed, and the precipitation of silica scale is suppressed, whereby clogging of the reverse osmosis membrane portion 4 can be prevented, and stable water treatment operation can be continuously performed for a long time. The recovery rate can be further improved.

  When the blow valve 10b is opened for a predetermined time and concentrated drainage is blown, the reverse osmosis membrane unit 4 performs processing while outputting a blow command signal to the blow valve 10b based on the blow command signal. A close command signal can be output to the on-off valve 9 disposed in the treated water line 1a through which the treated water flows.

  In this way, since all the water to be treated flows to the blow line 8b, the silica concentration of the water to be treated can be lowered in a short time, and the flow rate of the water to be treated flowing to the blow line 8b is increased. The silica scale deposited on the reverse osmosis membrane part 4 due to the pressure is peeled off from the reverse osmosis membrane part 4, so that the clogging of the reverse osmosis membrane part 4 can be eliminated at an early stage. This method is effective when the silica concentration greatly exceeds the silica solubility and the silica scale is likely to precipitate, or when the silica scale is deposited on the reverse osmosis membrane portion 4 and clogging starts.

  Further, by selection, while outputting the blow command signal to the blow valve 10b based on the blow command signal, the command signal is output to the inverter 13, and the rotation speed of the pump 7 is adjusted by the inverter 13 to the water to be treated. A command signal for changing the supply amount to be increased can be output.

  If it does in this way, the flow volume of the to-be-processed water which permeate | transmits the reverse osmosis membrane part 4 will be the same as before blow, and can maintain the quantification of treated water.

The schematic explanatory drawing of the water treatment system which enforces the water treatment method concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Soft water processing part 4 Reverse osmosis membrane part 7 Pump 8 Concentration drainage line 8a Drainage line 8b Blow line 9 Open / close valve 10a Drain valve 10b Blow valve 11 Temperature sensor 12 Concentration measuring device 13 Inverter 14 Control part

Claims (3)

After water to be treated is treated with soft water, it is filtered through a reverse osmosis membrane part, and is a water treatment method for blowing concentrated wastewater generated in the reverse osmosis membrane part at predetermined intervals,
The water treatment method according to claim 1, wherein the predetermined interval for blowing the concentrated waste water is a predetermined time set based on a temperature of the water to be treated which is assumed in advance and a silica solubility of the water to be treated at the temperature. After water to be treated is treated with soft water, it is filtered through a reverse osmosis membrane part, and is a water treatment method for blowing concentrated wastewater generated in the reverse osmosis membrane part at predetermined intervals,
The water treatment method is characterized in that the predetermined interval for blowing the concentrated waste water is set so as to detect the temperature of the water to be treated and to be long when the water temperature is high and short when the water temperature is low. The water treatment method according to claim 1 or 2, wherein when the concentrated drainage generated in the reverse osmosis membrane part is blown, the valve on the treated water side is closed .

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