TWI771476B - Processing device and processing method for silica-containing water - Google Patents

Abstract

An object of the invention is to provide a processing device and a processing method for processing a silica-containing water, which can reduce the amount of magnesium compound used during silica processing of the silica-containing water. A processing device 1 for silica-containing water comprises a reaction chamber 12 in which either a magnesium compound is added to the water to be treated which contains silica, or the magnesium contained in the water to be treated is used to insolubilize the silica at a pH of 10 or higher, a sedimentation tank 16 in which the obtained insolubilized matter undergoes a solid-liquid separation, and a return device which adds an acid to at least a portion of the sludge separated by the liquid-solid separation process and returns the resulting product to a stage prior to the sedimentation tank 16.

Description

Treatment device and treatment method of water containing silica

The present invention relates to a treatment device and a treatment method for water containing silicon dioxide.

In recent years, efforts have been made to reduce the amount of effluent discharged from factories, etc. as much as possible, and some methods have been adopted to reduce the amount of effluent by concentrating the effluent using reverse osmosis membranes, etc., and recovering permeable water. There is a tendency to improve the water recovery rate as much as possible. Among them, the concentrated water of reverse osmosis membrane is further processed by reverse osmosis membrane, or the method of concentration by evaporation concentration is implemented, and even almost all the water can be recovered. There are also more and more factories with Zero Liquid Discharge (ZLD) after solidifying impurities.

If the concentration ratio of the reverse osmosis membrane device and the evaporative concentration device is increased in this way, the risk of scaling (scaling) caused by the hardness components and silica in the discharge water will be correspondingly increased. If fouling occurs, the reverse osmosis membrane will be blocked and the permeable water will be reduced, or the heat transfer surface of evaporation and concentration will be covered with fouling and the heat transfer efficiency will be reduced.

Therefore, it is desirable to reduce the silica in the discharge water as much as possible before the reverse osmosis membrane treatment. As a method of treating wastewater containing silicon dioxide, a method of adding and removing magnesium salts under alkaline conditions as described in Patent Document 1 is known.

In the method for removing silicon dioxide using magnesium compounds such as magnesium salts, the amount of magnesium salts to be added must be several times to about ten times the concentration of silicon dioxide. subject. In addition, sometimes the treated water originally contains magnesium, but the magnesium contained in the treated water alone cannot reach the amount sufficient to remove the silicon dioxide in most cases. In this case, additional magnesium compounds must be added. , there are the same problems that the cost of chemicals and the amount of sludge generated increase. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 4-367783

[The problem to be solved by the invention]

The present invention aims to provide a treatment device and a treatment method for water containing silicon dioxide, which can reduce the amount of magnesium compounds used in the treatment of silicon dioxide in water containing silicon dioxide. [Means of Solving Problems]

The present invention relates to an apparatus for treating water containing silicon dioxide, comprising: a reaction tank for adding a magnesium compound to the water to be treated containing silicon dioxide, or using magnesium contained in the water to be treated to make the silicon dioxide more than pH 10 Insolubilization; solid-liquid separation means for solid-liquid separation of the obtained insoluble matter; and return means for adding acid to at least a part of the sludge separated by the solid-liquid separation and returning it to the solid-liquid separation means previous paragraph.

The present invention relates to an apparatus for treating water containing silicon dioxide, comprising: a reaction tank for adding a magnesium compound to the water to be treated containing silicon dioxide, or using magnesium contained in the water to be treated to make the silicon dioxide more than pH 10 insolubilization; first solid-liquid separation means for solid-liquid separation of the obtained insoluble matter; acid addition means for adding acid to at least a part of the sludge separated by the first solid-liquid separation means; second solid-liquid separation means for solid-liquid separation of the acid-added sludge; and a return means for returning at least a part of the second solid-liquid separation water separated by the second solid-liquid separation means to the first solid-liquid separation The front section of the component.

The present invention relates to a device for treating water containing silica, comprising: an insolubilizing member for adding a magnesium compound to water to be treated containing organic matter and silica, or for dissolving a magnesium compound at pH 10 or higher using magnesium contained in the water to be treated. Insolubilization of silicon oxide; membrane filtering means for subjecting the obtained insoluble matter to membrane filtration; backwashing means for backwashing the membrane filtering means; acid adding means for adding acid to at least a part of the discharged backwash discharge water; and backwashing The discharge water return means returns the backwash discharge water with added acid to the preceding stage of the membrane filter means.

The present invention relates to a device for treating water containing silica, comprising: an insolubilizing member for adding a magnesium compound to water to be treated containing organic matter and silica, or for dissolving a magnesium compound at pH 10 or higher using magnesium contained in the water to be treated. Insolubilization of silicon oxide; membrane filtration means for membrane filtration of the obtained insoluble matter; backwash means for backwashing the membrane filtration means; acid addition means for adding acid to at least a part of the discharged backwash discharge water; solid-liquid separation means for solid-liquid separation of the backwash discharge water with added acid; and a solid-liquid separation water return means for returning at least a part of the solid-liquid separation water obtained by separation by the solid-liquid separation means to the membrane filter means the preceding paragraph.

In the aforementioned treatment device for water containing silica, it is preferable to add the acid and adjust the pH to a range of 4 to 9.

The above-mentioned treatment device for water containing silicon dioxide preferably further includes a reverse osmosis membrane treatment device, in which the solid-liquid separation treatment water is passed through the reverse osmosis membrane at the rear stage of the solid-liquid separation member to obtain permeable water and concentrated water.

The above-mentioned treatment device for water containing silica is preferably further equipped with a reverse osmosis membrane treatment device, in which the membrane filtrate is passed through the reverse osmosis membrane in the latter stage of the membrane filtration member to obtain permeable water and concentrated water.

The invention relates to a method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing silicon dioxide, or using magnesium contained in the water to be treated to insolubilize the silicon dioxide at a pH above 10; A solid-liquid separation step for solid-liquid separation of the obtained insoluble matter; and a return step for adding acid to at least a part of the sludge separated by the solid-liquid separation, and returning it to the preceding stage of the solid-liquid separation step.

The invention relates to a method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing silicon dioxide, or using magnesium contained in the water to be treated to insolubilize the silicon dioxide at a pH above 10; In the first solid-liquid separation step, the obtained insoluble matter is subjected to solid-liquid separation; in the acid addition step, acid is added to at least a part of the sludge separated by the first solid-liquid separation step; and in the second solid-liquid separation step, The acid-added sludge is subjected to solid-liquid separation; and a return step is to return at least a part of the second solid-liquid separation water obtained by the second solid-liquid separation step to the waste water of the first solid-liquid separation step previous paragraph.

The present invention relates to a method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing organic matter and silicon dioxide, or using magnesium contained in the water to be treated to make the silicon dioxide more than pH 10 insolubilization; a membrane filtration step of subjecting the obtained insoluble matter to membrane filtration; a backwashing step of backwashing the membrane used in the membrane filtration step; an acid addition step of adding acid to at least a portion of the backwashing effluent discharged; and In the backwashing discharge water return step, the backwashing discharge water with added acid is returned to the previous stage of the membrane filtration step.

The present invention relates to a method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing organic matter and silicon dioxide, or using magnesium contained in the water to be treated to make the silicon dioxide more than pH 10 insolubilization; membrane filtration step, subjecting the obtained insoluble matter to membrane filtration; backwashing step, backwashing the membrane used in the membrane filtration step; acid adding step, adding acid to at least a part of the discharged backwashing water; solid A liquid-liquid separation step for solid-liquid separation of the backwash discharge water with added acid; and a solid-liquid separation water return step for returning at least a part of the solid-liquid separation water obtained by the solid-liquid separation step to the membrane The preceding paragraph of the filtering step.

In the above-mentioned treatment method of water containing silica, it is preferable to add the acid and adjust the pH to a range of 4-9.

The aforementioned method for treating water containing silicon dioxide preferably further includes: a reverse osmosis membrane treatment step, in the latter stage of the solid-liquid separation step, the solid-liquid separation treated water is passed through the reverse osmosis membrane to obtain permeable water and concentrated water.

The aforementioned method for treating water containing silicon dioxide preferably further includes: a reverse osmosis membrane treatment step, and in the latter stage of the membrane filtration step, the membrane filtrate is passed through the reverse osmosis membrane to obtain permeable water and concentrated water. [Effect of invention]

With the present invention, the amount of magnesium compound used can be reduced in the silica treatment of the silica-containing water.

Embodiments of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

The outline of the 1st example of the processing apparatus of the silica-containing water which concerns on embodiment of this invention is shown in FIG. 1, and the structure is demonstrated.

The treatment apparatus 1 for water containing silica includes: a reaction tank 12 for adding a magnesium compound to the water to be treated containing silica, or for insolubilizing the silica at pH 10 or more using magnesium contained in the water to be treated; a precipitation tank 16, as a solid-liquid separation member for solid-liquid separation of the obtained insoluble matter; and a sludge regeneration tank 18, for adding acid to at least a part of the sludge separated by the solid-liquid separation and returning it to the solid-liquid separation The member is the return member of the front stage of the sedimentation tank 16 . The treatment device 1 for water containing silica may further include: a water tank 10 to be treated for storing the water to be treated; and a polymer reaction tank 14 for adding a polymer flocculant to the reaction solution obtained in the reaction tank 12 to conduct agglomeration reaction.

In the treatment device 1 for water containing silica in FIG. 1 , the outlet of the water tank 10 to be treated and the inlet of the reaction tank 12 are connected by a pipe 24 via a pump 20 . The outlet of the reaction tank 12 and the inlet of the polymer reaction tank 14 are connected by a pipe 26 . The outlet of the polymer reaction tank 14 and the inlet of the precipitation tank 16 are connected by a pipe 28 . The treated water piping 30 is connected to the solid-liquid separation liquid outlet of the sedimentation tank 16 . The sludge outlet at the bottom of the sedimentation tank 16 and the inlet of the sludge regeneration tank 18 are connected by a sludge return pipe 34 via the pump 22 . The sludge piping 32 is connected in the middle of the sludge return piping 34 . The outlet of the sludge regeneration tank 18 and the regeneration sludge inlet of the reaction tank 12 are connected by the regeneration sludge return piping 36 . A magnesium compound addition pipe 38 as a magnesium compound addition means, and a pH adjuster addition pipe 40 as a pH adjuster addition means are connected to the reaction tank 12, and a stirring device 46 provided with a stirring blade is provided as a stirring means. A polymer flocculant addition pipe 42 as a polymer flocculant addition means is connected to the polymer reaction tank 14, and a stirring device 48 provided with a stirring blade as a stirring means is provided. The acid addition piping 44 as an acid addition means is connected to the sludge regeneration tank 18, and the stirring apparatus 50 provided with stirring blades is provided as a stirring means. In the treatment apparatus 1 for water containing silica, the sludge regeneration tank 18, the acid addition pipe 44, the pump 22, the sludge return pipe 34, and the regenerated sludge return pipe 36 function as return means, and the return means The acid is added to at least a part of the sludge separated by the solid-liquid separation, and it is returned to the front stage of the sedimentation tank 16 which is a solid-liquid separation means.

The operation|movement of the processing method of the silica-containing water and the processing apparatus 1 of the silica-containing water of this embodiment is demonstrated.

The water containing silicon dioxide, which is the water to be treated, is stored in the treated water tank 10 as needed, and is transported to the reaction tank 12 by the pump 20 through the piping 24 . The amount of the magnesium compound to be added varies depending on the target silicon dioxide concentration of the treated water, etc., so it cannot be clearly defined. Taking a case where the silicon dioxide concentration of the treated water is 10 mg/L or less as an example, the description as follows. For example, when the pH of the water to be treated is 10 or more, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silica (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38 to insolubilize the silicon dioxide (insolubilization step). For example, when the pH of the water to be treated is less than 10, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silicon dioxide (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38, and the pH adjuster is added through the pH adjuster addition pipe 40 to adjust the pH of the water to be treated to 10 or more, and the silicon dioxide is insolubilized (insolubilized). step). For example, when the pH of the water to be treated is less than 10, and the content of magnesium in the water to be treated is 0.5 mol or more relative to the content of silica (1 mol), the water containing silica in the reaction tank 12 , adding a pH adjusting agent through the pH adjusting agent adding pipe 40 to adjust the pH of the water to be treated to 10 or more, and insolubilize the silica (insolubilization step). For example, when the pH of the water to be treated is 10 or more and the magnesium content in the treated water is 0.5 mol or more relative to the silica content (1 mol), the water is directly transferred to the next polymer reaction tank 14 . The reaction liquid may be stirred by the stirring device 46 in the reaction tank 12 .

The reaction liquid obtained in the insolubilization step is sent from the reaction tank 12 to the polymer reaction tank 14 via the piping 26 . In the polymer reaction tank 14, a polymer flocculating agent is added to the reaction liquid through the polymer flocculating agent addition pipe 42 as necessary, and a polymer flocculating reaction is performed (polymer flocculating step). In the polymer reaction tank 14 , the aggregated liquid may be stirred by the stirring device 48 .

The polymer flocculation liquid obtained in the polymer flocculation step is transported from the polymer reaction tank 14 to the precipitation tank 16 via the piping 28 . In the precipitation tank 16, the obtained insoluble matter is subjected to solid-liquid separation by natural sedimentation or the like (solid-liquid separation step).

The solid-liquid separation liquid obtained in the solid-liquid separation step is discharged from the sedimentation tank 16 through the treated water piping 30 as treated water.

At least a part of the sludge separated by the solid-liquid separation is sent to the sludge regeneration tank 18 through the sludge return pipe 34 by the pump 22 . In the sludge regeneration tank 18, acid is added to the sludge through the acid addition piping 44, and the sludge is regenerated. The regenerated sludge is returned to the reaction tank 12 in the preceding stage of the sedimentation tank 16 (solid-liquid separation step) through the regenerated sludge return pipe 36, that is, the return step. The portion of the sludge that has not been returned and regenerated is discharged from the sedimentation tank 16 through the sludge return piping 34 and the sludge piping 32 .

As described above, the method and apparatus for treating silica-containing water according to the present embodiment are performed by adding a magnesium compound to the silica-containing water or insolubilizing silica at pH 10 or more using magnesium contained in the water to be treated. In the solid-liquid separation treatment, acid is added to at least a part of the separated sludge, and this is returned to the previous stage of the solid-liquid separation step.

According to this method, the compound of magnesium and silica contained in the sludge can be dissolved by adding an acid to the sludge, and the magnesium can be dissolved in the form of ions. At this time, silica is also dissolved out at the same time, but the solubility of silica is usually low, so the part exceeding the solubility will gel and precipitate. Usually, the gelation of silica takes a long time (more than tens of hours), but according to this method, since silica is once solidified, it is considered that even a reaction time of about 30 minutes can make it fully gelled.

If the regenerated sludge is returned to the previous stage, the ionized magnesium can be reused as the magnesium compound of the silicon dioxide remover, and most of the silicon dioxide has been gelled and precipitated by itself, so it can be dissolved in solid-liquid The separation step separates it again and removes it as sludge.

Since the magnesium ion eluted from the compound of magnesium and silicon dioxide contained in the sludge can be reused as the magnesium compound of the silicon dioxide removing agent, the usage amount of the magnesium compound can be greatly reduced compared to the case where it is not reused. Thereby, the amount of generated sludge can be reduced. Sometimes even the magnesium that is originally contained in the water being treated can remove silica. In addition, since the eluted magnesium ions are reused, if the magnesium compound is used in the same degree as in the case where it is not reused, the content of silica in the treated water can be further reduced, and the treated water quality can be further improved. Therefore, when a processing apparatus such as a reverse osmosis membrane processing apparatus is further provided in the latter stage of the solid-liquid separation apparatus, the load can be reduced.

The outline of the 2nd example of the processing apparatus of the silica-containing water which concerns on embodiment of this invention is shown in FIG. 2, and the structure is demonstrated.

The treatment device 2 for water containing silica includes: a reaction tank 12 for adding a magnesium compound to the water to be treated containing silica, or for insolubilizing the silica at pH 10 or more using magnesium contained in the water to be treated; a precipitation tank 16. As the first solid-liquid separation means for solid-liquid separation of the obtained insoluble matter; the sludge regeneration tank 18 and the acid addition piping 44 are used as the first solid-liquid separation means for the separation of the sludge obtained by the sedimentation tank 16; Acid addition means for adding acid to at least a part of the sludge; a sludge separation tank 54 as a second solid-liquid separation means for solid-liquid separation of the acid-added sludge; and a solid-liquid separation water return pipe 66 as a At least a part of the second solid-liquid separation water obtained by separation in the sludge separation tank 54 , which is the second solid-liquid separation means, is returned to the return means in the preceding stage of the sedimentation tank 16 . The treatment device 2 for water containing silicon dioxide may further include: a treated water tank 10 for storing the treated water; a coagulation tank 52 for adding an inorganic coagulant to the reaction solution obtained in the reaction tank 12 to perform a coagulation reaction ; And a polymer reaction tank 14 for adding a polymer flocculating agent to carry out a polymer agglomeration reaction.

In the treatment device 2 of water containing silica in FIG. 2 , the outlet of the water tank 10 to be treated and the inlet of the water to be treated in the reaction tank 12 are connected by a pipe 24 via a pump 20 . The outlet of the reaction tank 12 and the inlet of the condensation tank 52 are connected by piping 58 . The outlet of the coagulation tank 52 and the inlet of the polymer reaction tank 14 are connected by a pipe 60 . The outlet of the polymer reaction tank 14 and the inlet of the precipitation tank 16 are connected by a pipe 62 . The treated water piping 30 is connected to the solid-liquid separation water outlet of the sedimentation tank 16 . The sludge outlet at the bottom of the sedimentation tank 16 and the inlet of the sludge regeneration tank 18 are connected by a sludge return pipe 34 via the pump 22 . The outlet of the sludge regeneration tank 18 and the inlet of the sludge separation tank 54 are connected by the regeneration sludge piping 64 . The solid-liquid separation water outlet of the sludge separation tank 54 and the solid-liquid separation water inlet of the reaction tank 12 are connected by a solid-liquid separation water return pipe 66 . A sludge pipe 68 is connected to the sludge outlet at the bottom of the sludge separation tank 54 via the pump 56 . The reaction tank 12 is connected with a magnesium compound addition pipe 38 as a magnesium compound addition means, and a pH adjuster addition pipe 40 as a pH adjuster addition means, and a stirring device 46 provided with a stirring blade as a stirring means is provided. The aggregation tank 52 is connected with an inorganic flocculant addition pipe 70 as an inorganic flocculant addition means, and a pH adjuster addition pipe 72 as a pH adjuster addition means, and a stirring device 74 provided with a stirring blade as a stirring means is provided. . The polymer reaction tank 14 is connected with a polymer flocculant addition pipe 42 as a polymer flocculant addition means, and is provided with a stirring device 48 provided with a stirring blade as a stirring means. The acid addition piping 44 as an acid addition means is connected to the sludge regeneration tank 18, and the stirring apparatus 50 provided with stirring blades is provided as a stirring means.

The operation|movement of the processing method of the silica-containing water and the operation|movement of the processing apparatus 2 of the silica-containing water concerning this embodiment is demonstrated.

The water containing silicon dioxide, which is the water to be treated, is stored in the treated water tank 10 as needed, and is transported to the reaction tank 12 by the pump 20 through the piping 24 . The amount of the magnesium compound to be added varies depending on the target silicon dioxide concentration of the treated water, etc., so it cannot be clearly defined. Taking a case where the silicon dioxide concentration of the treated water is 10 mg/L or less as an example, the description as follows. For example, when the pH of the water to be treated is 10 or more, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silica (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38 to insolubilize the silicon dioxide (insolubilization step). For example, when the pH of the water to be treated is less than 10, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silicon dioxide (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38, and the pH adjuster is added through the pH adjuster addition pipe 40 to adjust the pH of the water to be treated to 10 or more, and the silicon dioxide is insolubilized (insolubilized). step). For example, when the pH of the water to be treated is less than 10, and the content of magnesium in the water to be treated is 0.5 mol or more relative to the content of silica (1 mol), the water containing silica in the reaction tank 12 , adding a pH adjusting agent through the pH adjusting agent adding pipe 40 to adjust the pH of the water to be treated to 10 or more, and insolubilize the silica (insolubilization step). For example, when the pH of the water to be treated is 10 or more, and the magnesium content in the water to be treated is 0.5 mol or more with respect to the silica content (1 mol), it is directly sent to the next coagulation tank 52 . The reaction liquid may be stirred by the stirring device 46 in the reaction tank 12 .

The reaction liquid obtained in the insolubilization step is sent from the reaction tank 12 to the coagulation tank 52 through the piping 58 . In the agglomeration tank 52, an inorganic flocculant is added to the reaction liquid through the inorganic flocculating agent addition pipe 70 as needed, and a flocculation reaction is performed (aggregation step). In the aggregation tank 52, a pH adjuster may be added through the pH adjuster addition pipe 72 as needed. In the aggregation tank 52, the aggregating liquid may be stirred by the stirring device 74.

The coagulation reaction liquid obtained in the coagulation step is sent from the coagulation tank 52 to the polymer reaction tank 14 via the piping 60 . In the polymer reaction tank 14 , a polymer flocculating agent is added to the aggregation reaction liquid through the polymer flocculating agent addition pipe 42 as necessary to perform a polymer flocculating reaction (polymer flocculating step). In the polymer reaction tank 14, the aggregating reaction liquid may be stirred by the stirring device 48.

The polymer flocculation liquid obtained in the polymer flocculation step is transported from the polymer reaction tank 14 to the precipitation tank 16 through the piping 62 . In the precipitation tank 16, the obtained insoluble matter is subjected to solid-liquid separation by natural sedimentation or the like (first solid-liquid separation step).

The first solid-liquid separation water obtained in the first solid-liquid separation step is discharged from the sedimentation tank 16 through the treated water piping 30 as treated water.

At least a part of the sludge separated by the first solid-liquid separation is sent to the sludge regeneration tank 18 through the sludge return pipe 34 by the pump 22 . In the sludge regeneration tank 18, acid is added to the sludge through the acid addition piping 44 to regenerate the sludge (acid addition step).

The regenerated sludge is sent to the sludge separation tank 54 through the regenerated sludge piping 64 . In the sludge separation tank 54, the insoluble matter is subjected to solid-liquid separation by natural sedimentation or the like (second solid-liquid separation step).

The second solid-liquid separation water obtained in the second solid-liquid separation step is returned through the solid-liquid separation water return pipe 66 to the reaction tank 12 in the preceding stage of the sedimentation tank 16 (first solid-liquid separation step), that is, the return step. From the sludge separation tank 54 , the sludge separated by the second solid-liquid separation is discharged through the sludge piping 68 by the pump 56 .

As described above, the method and apparatus for treating silica-containing water according to the present embodiment are performed by adding a magnesium compound to the silica-containing water or insolubilizing silica at pH 10 or more using magnesium contained in the water to be treated. In the solid-liquid separation treatment (1st solid-liquid separation step), acid is added to at least a part of the sludge obtained by separation, the solid-liquid separation treatment is performed (2nd solid-liquid separation step), and the second solid-liquid separation obtained by separation is carried out. At least a part of the water is returned to the preceding stage of the first solid-liquid separation step.

According to this method, the compound of magnesium and silica contained in the sludge can be dissolved by adding an acid to the sludge, and the magnesium can be dissolved in the form of ions. At this time, silica is also dissolved at the same time, but the solubility of silica is usually low (for example, about 120 mg/L at pH 4~9, 25 ℃), so the part exceeding the solubility will gel and precipitate . Usually, the gelation of silica takes a long time (more than tens of hours), but according to this method, since silica is once solidified, it is considered that even a reaction time of about 30 minutes can make it fully gelled.

If the regenerated sludge obtained by regenerating in the acid addition step is directly returned to the previous stage of the first solid-liquid separation step, the ionized magnesium can be reused as the magnesium compound of the silica-based removing agent, and the two Most of the silicon oxide has been gelled and precipitated by itself, so it can be separated again in the sedimentation tank 16 and made into sludge to be removed. However, if the silica gelled separately is returned to the previous stage of the first solid-liquid separation step, it will be redissolved bit by bit. If it is a small amount, the influence is small, and as long as it is quickly turned into sludge in the sedimentation tank 16 and discharged to the outside of the system, there will be no problem. If the proportion of silicon oxide increases, the influence cannot be ignored. Furthermore, for example, if the treatment apparatus is temporarily stopped and the gelled silica remains in the system for a long time, the redissolution of the silica is accelerated, and the silica concentration of the treated water is observed to be greatly increased. Here, in the treatment method and treatment apparatus of the present embodiment, by subjecting the regenerated sludge obtained by regeneration in the acid addition step to solid-liquid separation (second solid-liquid separation treatment), it is possible to prevent gelling as much as possible. The dissolved silica is returned to the first stage of the first solid-liquid separation step, and the eluted magnesium (magnesium ion) is returned to the first stage of the first solid-liquid separation step to be reused, thereby reducing the amount of magnesium compound used. In addition, the silica concentration of the treated water can be reduced with a small addition amount of the magnesium compound.

In this way, the magnesium ion eluted from the compound of magnesium and silica contained in the sludge can be reused as the magnesium compound which is a silica removing agent, so that the magnesium compound can be greatly reduced compared to the case where it is not reused. usage. Thereby, the amount of generated sludge can be reduced. In some cases, even if the magnesium originally contained in the water to be treated can be used for the insolubilization of the silica, the silica can be removed. When the concentration of magnesium in the water to be treated is high relative to the concentration of silicon dioxide, the silicon dioxide can be removed even if no magnesium compound is newly added. In addition, since the eluted magnesium ions are reused, if the magnesium compound is used in the same degree as in the case where it is not reused, the content of silica in the treated water can be further reduced, and the treated water quality can be further improved. Therefore, when processing apparatuses, such as a reverse osmosis membrane processing apparatus, are further provided in the latter stage of a 1st solid-liquid separation apparatus, a load can be reduced.

In the sludge regeneration step of the treatment devices 1 and 2 of the water containing silicon dioxide, it is advisable to add acid and adjust the pH of the separated sludge to be in the range of 4 to 9. The amount of magnesium that can be regenerated depends on the amount of acid added to the sludge regeneration tank 18, with more magnesium being added the greater the amount of magnesium being regenerated. The solubility of silica is about 120 mg/L to 150 mg/L in the pH range of 4 to 9 at 25°C, so it is thought that the silica in excess of the solubility will gel and precipitate.

In the sludge regeneration step, when the pH is 9 or less, magnesium ions are eluted. Even if the pH is lower than 4, magnesium ions will dissolve, but the dissolved silica will become difficult to gel, so the preferred pH range is pH 4~9, more preferably 4~6.

As an acid used for sludge regeneration, hydrochloric acid, sulfuric acid, etc. are mentioned, for example. Among these, hydrochloric acid is preferred in consideration of the cost of medicines and the like.

The reaction temperature in the sludge regeneration step is not particularly limited, for example, it is in the range of 15°C to 30°C. The reaction time of the sludge regeneration step is not particularly limited, for example, it is in the range of 15 minutes to 120 minutes.

In terms of the circulation amount of the sludge returned to the previous stage of the solid-liquid separation step in the treatment device 1 for water containing silica, the amount of magnesium required for regeneration may be sufficiently circulated, and the water to be treated is preferred. The range of about 2~20% of the flow rate, more preferably the range of about 5~10%. If the circulating amount of sludge is less than 2% of the flow rate of the water to be treated, the amount of magnesium required for regeneration may not be sufficiently supplied; if it exceeds 20%, the flow rate of the water to be treated increases and The reaction time of each reaction tank is shortened, and the properties of silica may be deteriorated, and the cohesion may be deteriorated.

Regarding the circulation amount of the second solid-liquid separation water returned to the previous stage of the first solid-liquid separation step in the treatment device 2 for water containing silica, the amount of magnesium required for regeneration may be sufficiently circulated, Preferably, it is in the range of about 2 to 20% of the flow rate of the water to be treated, and more preferably in the range of about 5 to 10%. If the circulating volume of the second solid-liquid separation water is less than 2% of the flow rate of the water to be treated, the amount of magnesium required for regeneration may not be sufficiently supplied; if it exceeds 20%, the flow rate of the water to be treated As the size increases, the reaction time in each reaction tank is shortened, and the properties of silica may be deteriorated and the cohesion may be deteriorated.

When the concentration of the return sludge sent to the sludge regeneration tank 18 is high, the concentration in the sludge regeneration tank 18 increases, and the ratio of the gelatinized silica increases with respect to the amount of the eluted magnesium ions, and the regeneration is performed. Efficiency becomes good. The concentration of the returned sludge is, for example, in the range of 0.5 to 5.0%, preferably in the range of 1.0 to 3.0%.

In order to increase the sludge concentration, the above-mentioned polymer flocculation step using a polymer flocculant is preferably carried out.

In order to increase the sludge concentration and improve the solid-liquid separation of the regenerated sludge, at least one of the above-mentioned coagulation step using an inorganic coagulant and the above-mentioned polymer coagulation step using a polymer coagulant is preferably carried out By. In the treatment apparatus 1 of silica-containing water, the above-mentioned coagulation step using an inorganic coagulant may be performed in the preceding stage of the polymer coagulation step. In the treatment apparatus 2 of the water containing silica, the above-mentioned coagulation step using an inorganic coagulant can be omitted.

The return place of the regenerated sludge sent by the return means in the treatment apparatus 1 for silicon dioxide-containing water is not particularly limited as long as it is the first stage of the sedimentation tank 16 (solid-liquid separation step). For example, it is sufficient to return the regenerated sludge to at least one of the water tank 10 to be treated, the reaction tank 12, the polymer reaction tank 14, and the pipes 24, 26, and 28. However, by returning the sludge to the reaction tank 12, the reaction tank is The increase of magnesium ion concentration in 12 can promote the co-precipitation reaction of magnesium and silicon dioxide, so it is more ideal.

The return point of the second solid-liquid separation water sent by the return means in the silica-containing water treatment device 2 is not particularly limited as long as it is the first stage of the sedimentation tank 16 (first solid-liquid separation step). . For example, the recycled sludge may be returned to at least one of the water tank 10 to be treated, the reaction tank 12, the aggregation tank 52, the polymer reaction tank 14, the pipes 24, 58, 60, and 62. 12, the magnesium ion concentration in the reaction tank 12 will be increased, and the co-precipitation reaction of magnesium and silicon dioxide can be promoted, so it is ideal.

The silica-containing water to be treated in the silica-containing water treatment apparatuses 1 and 2 is, for example, groundwater, industrial water, factory discharge water, and the like. The amount of silica in the silica-containing water is, for example, 10 to 400 mg/L. When the silica-containing water contains a hardness component, the amount of the calcium hardness component in the silica-containing water is, for example, 50 to 5000 mg-CaCO ₃ /L, and the amount of the magnesium hardness component is, for example, 10 to 1000 mg-Mg/L.

Examples of the magnesium compound used in the insolubilization step include inorganic salts of magnesium such as magnesium hydroxide (Mg(OH) ₂ ), magnesium chloride (MgCl ₂ ), and magnesium oxide (MgO). Among these, magnesium hydroxide is preferred in view of the cost of medicines and the like. When a substance that is poorly soluble in water, such as magnesium hydroxide or magnesium oxide, is used as the magnesium compound, a separate dissolving tank may be provided to dissolve the magnesium compound in water, etc., and then added to the reaction tank 12 or the sludge regeneration tank 18, in order to The magnesium compound is more soluble and should be added to the sludge regeneration tank 18 .

The amount of the magnesium compound added in the insolubilization step is preferably an amount in the range of 0.5 mol to 5.0 mol relative to the amount of silica (1 mol) in the silica-containing water that is the water to be treated. , more preferably an amount in the range of 1.0 mol to 2.5 mol. If the amount of the magnesium compound added in the insolubilization step is less than 0.5 mol relative to the amount of silica in the silica-containing water (1 mol), the insolubilization reaction may not proceed sufficiently. In some cases, if the amount exceeds 5.0 mol, it may become disadvantageous in terms of drug cost and the like.

When pH adjustment is performed in the insolubilization step, the pH in the reaction tank 12 is adjusted to 10 or more, preferably in the range of 10-12, more preferably in the range of 10-11. If the pH in the reaction tank 12 is less than 10, the insolubilization of magnesium will be insufficient, and the removability of silica will decrease; if it exceeds 12, the solubility of silica may increase and the removability of silica may decrease. Case.

Examples of the pH adjuster used for pH adjustment include acids such as hydrochloric acid and sulfuric acid, and alkaline agents such as sodium hydroxide.

When the silica-containing water contains a hardness component, at least one of an alkali agent and a carbonic acid compound may be added to the reaction tank 12, or another reaction tank (second reaction tank) may be installed in the front or rear of the reaction tank 12. At least one of an alkali agent and a carbonic acid compound is added thereto to insolubilize the hardness component, and it is removed by the above-mentioned solid-liquid separation step. The hardness component may be removed in the front stage of the reaction tank 12 using an ion exchange resin or the like.

As an alkali agent used for insolubilization of a hardness component, calcium hydroxide (Ca(OH) ₂ ), sodium hydroxide (NaOH), potassium hydroxide (KOH) etc. are mentioned, for example. Among these, calcium hydroxide and sodium hydroxide are preferred in consideration of the cost of medicines and the like. As a carbonic acid compound used for insolubilization of a hardness component, sodium carbonate ( _Na2CO3 ), sodium _{hydrogencarbonate} ( _NaHCO3 ), carbon dioxide gas, etc. are mentioned, for example. Among these, in consideration of the cost of medicines and the like, sodium carbonate is preferred.

The amount of alkali agent and carbonic acid compound added is preferably in the range of 1.0 mol to 1.2 mol, more preferably in the range of 1.0 mol to 1.1 mol, relative to the amount of hardness component (1 mol) in the water to be treated. If the amount of the alkali agent and carbonic acid compound added is less than 1.0 mol relative to the amount of the hardness component (1 mol) in the water to be treated, the insolubilization reaction may not proceed sufficiently; It will become disadvantageous in terms of drug costs, etc.

The reaction temperature in the insolubilization step is not particularly limited, but is, for example, in the range of 15°C to 30°C.

Examples of inorganic flocculants used in the coagulation step include iron-based inorganic flocculants such as iron(III) chloride and polyiron(III) sulfate; and aluminum-based inorganic flocculants such as aluminum sulfate and polyaluminum chloride (PAC). Wait.

The addition amount of the inorganic coagulant in the coagulation step is preferably in the range of 30-300 mg/L, more preferably in the range of 50-100 mg/L. If the addition amount of the inorganic coagulant in the coagulation step is less than 30 mg/L, the coagulation reaction may not proceed sufficiently;

The reaction temperature in the coagulation step is not particularly limited, but is, for example, in the range of 15°C to 30°C.

As a polymer flocculent used in a polymer flocculation process, polymer flocculants, such as acrylamide type|system|group and an acrylate type, are mentioned, for example. Among these, an acrylamide-based polymer flocculant is preferable in view of the cost of medicines and the like.

The amount of the polymer flocculant added in the polymer coagulation step is preferably in the range of 0.5 to 5.0 mg/L, more preferably in the range of 1 to 2 mg/L. If the amount of the polymer flocculant added in the polymer agglomeration step is less than 0.5 mg/L, the agglomeration reaction may not proceed sufficiently; if it is added excessively, it may be disadvantageous in terms of drug cost, etc. .

The reaction temperature in the polymer aggregation step is not particularly limited, but is, for example, in the range of 15°C to 30°C.

There is no solid-liquid separation step in the treatment device 1 for silica-containing water, or solid-liquid separation in the first solid-liquid separation step and the second solid-liquid separation step in the treatment device 2 for silica-containing water. Particularly limited, for example, a sedimentation tank utilizing natural sedimentation, and methods such as sand filtration, membrane filtration, and cyclone are also exemplified. Among these, a sedimentation tank utilizing natural sedimentation is preferable in consideration of equipment costs and the like.

Compared with the case where the regenerated sludge or the second solid-liquid separation water is not returned, the use of the magnesium compound can be reduced to, for example, about 1 by the treatment method and treatment apparatus 1 and 2 of the silica-containing water of the present embodiment. /2~0. In addition, the silica content in the treated water can be reduced to, for example, about 10 mg/L or less.

FIG. 3 shows a third example of the treatment apparatus for the silica-containing water according to the present embodiment.

The silicon dioxide-containing water treatment device 3 of FIG. 3 is provided with a reaction tank 12 for adding a magnesium compound to the water to be treated containing organic matter and silica, or for making the water to be treated with magnesium contained in the water to pH 10 or higher. An insolubilizing member for insolubilizing silicon oxide; a membrane filtration device 76 as a membrane filtration member for membrane filtration of the obtained insoluble matter; a pump 80 and a backwash water pipe 92 as a backwash for the membrane used in the membrane filtration device 76 Backwash means; sludge regeneration tank 18, acid addition pipe 44 as acid addition means for adding acid to at least a part of the discharged backwash discharge water; and regenerated sludge return pipe 90 as backwash discharge to which acid is added The water is returned to the backwash drain water return means in the preceding stage of the membrane filtration device 76 . The treatment device 3 for water containing silica may further include: a treated water tank 10 for storing the treated water; and a treatment water tank 78 for storing the treated water.

In the device 3 for treating water containing silica in FIG. 3 , the outlet of the water tank 10 to be treated and the inlet of the water to be treated in the reaction tank 12 are connected by a pipe 24 via a pump 20 . The outlet of the reaction tank 12 and the inlet of the membrane filtration device 76 are connected by a pipe 82 . The membrane filtrate outlet of the membrane filtration device 76 and the inlet of the treated water tank 78 are connected by a treated water pipe 84 . A treated water pipe 86 is connected to the treated water outlet of the treated water tank 78 . On the way between the backwash water outlet of the treatment water tank 78 and the treatment water pipe 84 , the backwash water pipe 92 is connected via the pump 80 . The backwash discharge water outlet of the membrane filtration device 76 and the inlet of the sludge regeneration tank 18 are connected by backwash discharge water piping 88 . The outlet of the sludge regeneration tank 18 and the regenerated sludge inlet of the reaction tank 12 are connected by the regenerated sludge return piping 90 . The reaction tank 12 is connected with a magnesium compound addition pipe 38 as a magnesium compound addition means, and a pH adjuster addition pipe 40 as a pH adjuster addition means, and a stirring device 46 provided with a stirring blade as a stirring means is provided. The acid addition piping 44 as an acid addition means is connected to the sludge regeneration tank 18, and the stirring apparatus 50 provided with stirring blades is provided as a stirring means.

In the treatment device 3 of the water containing silicon dioxide in FIG. 3, the water containing silicon dioxide containing organic matter and silicon dioxide, which is the water to be treated, is stored in the water tank 10 to be treated as needed, and the pump is used for pumping. 20 is transported to the reaction tank 12 via the piping 24 . The amount of the magnesium compound to be added varies depending on the target silicon dioxide concentration of the treated water, etc., so it cannot be clearly defined. Taking a case where the silicon dioxide concentration of the treated water is 10 mg/L or less as an example, the description as follows. For example, when the pH of the water to be treated is 10 or more, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silica (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38 to insolubilize the silicon dioxide (insolubilization step). For example, when the pH of the water to be treated is less than 10, and the water to be treated does not contain magnesium or the content of magnesium in the water to be treated is less than 0.5 mol relative to the content of silicon dioxide (1 mol), the reaction tank 12 In the water containing silicon dioxide, the magnesium compound is added through the magnesium compound addition pipe 38, and the pH adjuster is added through the pH adjuster addition pipe 40 to adjust the pH of the water to be treated to 10 or more, and the silicon dioxide is insolubilized (insolubilized). step). For example, when the pH of the water to be treated is less than 10, and the content of magnesium in the water to be treated is 0.5 mol or more relative to the content of silica (1 mol), the water containing silica in the reaction tank 12 , adding a pH adjusting agent through the pH adjusting agent adding pipe 40 to adjust the pH of the water to be treated to 10 or more, and insolubilize the silica (insolubilization step). For example, when the pH of the water to be treated is 10 or more, and the magnesium content in the water to be treated is 0.5 mol or more relative to the silica content (1 mol), it is directly sent to the next membrane filtration device 76 . The reaction liquid may be stirred by the stirring device 46 in the reaction tank 12 .

When adding a magnesium compound to the water to be treated, the reaction tank 12 may be provided as shown in FIG. 3, or the reaction tank 12 may not be provided and an in-pipe mixer ( in-line mixer), etc. for pipeline injection.

The pH adjustment may be performed in the reaction tank 12 as shown in FIG. 3 , or a pH adjustment tank may be separately provided before or after the reaction tank 12 and the pH adjustment may be performed in the pH adjustment tank. That is, the magnesium compound may be added to the water to be treated to which the pH has been adjusted in advance, or the pH adjustment may be performed to the water to be treated to which the magnesium compound has been added.

Magnesium flocs are formed by adding a magnesium compound and under the alkaline condition of pH 10 or higher, the reaction time is preferably 1 to 15 minutes, for example, about 10 minutes and stirring is performed. In the magnesium floc, in addition to the magnesium silicate generated by the reaction of silicon dioxide and magnesium, at least a part of the organic matter contained in the treated water is also included. When using a membrane to remove insoluble silica, it is not necessary to settle it like agglomeration sedimentation, so the reaction time is short, even if the floc is small.

Then, the reaction liquid obtained in the insolubilization step is sent from the reaction tank 12 to the membrane filtration device 76 through the piping 82 . In the membrane filtration device 76, the insoluble matter obtained in the insolubilization step is subjected to membrane filtration (membrane filtration step). The membrane filtrate obtained in the membrane filtration step is stored in the treated water tank 78 through the treated water piping 84 from the membrane filtration device 76 as needed. At least a part of the membrane filtrate may be discharged through the treated water piping 86 as treated water.

After the membrane filtration device 76 performs the membrane filtration treatment for a predetermined period of time (for example, about once every 30 minutes to 1 hour), for example, at least a part of the membrane filtrate is reversed by the pump 80 from the downstream side of the membrane filtration device 76 . The washing water piping 92 and the treated water piping 84 are conveyed, and the membrane used in the membrane filtration step is backwashed (backwashing step). The backwash discharge water is discharged from the upstream side of the membrane filtration device 76 through the backwash discharge water piping 88 , and sent to the sludge regeneration tank 18 .

In the sludge regeneration tank 18, acid is added to the backwash discharge water containing sludge through the acid addition piping 44, and the sludge is regenerated (acid addition step). The backwashing discharge water containing the sludge regenerated by adding acid is returned to the reaction tank 12 in the preceding stage of the membrane filtration device 76 (membrane filtration step) through the regenerated sludge return pipe 90, that is, the backwashing discharge water returning step.

As described above, the method for treating silica-containing water and the treatment device 3 according to the present embodiment add a magnesium compound to the silica-containing water, or use magnesium contained in the water to be treated to insolubilize silica at pH 10 or higher. A membrane filtration treatment (membrane filtration step) is performed, the membrane used in the membrane filtration step is backwashed, an acid is added to at least a part of the discharged backwash effluent (acid addition step), and the acid-added backwash effluent is It is returned to the previous stage of the membrane filtration step (backwashing discharge water return step). By subjecting the magnesium flocs obtained in the insolubilization step to membrane filtration treatment, silica contained in the water to be treated can be removed. In addition, the clogging of the membrane filtration can be alleviated by incorporating into the magnesium flocculate an organic substance that tends to clog the membrane. According to this method, in the silica treatment of the silica-containing water containing organic matter and silica, silica can be removed in a stable operation state. By adding the magnesium compound to the silica-containing water, two effects can be obtained: silica can be removed; and the increase in the filtration resistance of the membrane filtration device 76 is suppressed to contribute to the stable operation of the membrane.

Moreover, according to this method, by adding an acid to sludge, the compound of magnesium and silicon dioxide contained in sludge can be melt|dissolved, and magnesium can be eluted in the form of an ion. At this time, silica is also dissolved out at the same time, but the solubility of silica is usually low, so the part exceeding the solubility will gel and precipitate. Usually, the gelation of silica takes a long time (more than tens of hours), but according to this method, since silica is once solidified, it is considered that even a reaction time of about 30 minutes can make it fully gelled.

If the regenerated sludge is returned to the first stage of the membrane filtration device 76 (membrane filtration step), the ionized magnesium can be reused as the magnesium compound of the silica-based removing agent, and most of the silica has been coagulated by itself. It gels and separates out, so it can be separated again in the membrane filtration step.

Since the magnesium ion eluted from the compound of magnesium and silicon dioxide contained in the sludge can be reused as the magnesium compound of the silicon dioxide removing agent, the usage amount of the magnesium compound can be greatly reduced compared to the case where it is not reused. Thereby, the amount of generated sludge can be reduced. Sometimes even the magnesium that is originally contained in the water being treated can remove silica. In addition, since the eluted magnesium ions are reused, if the magnesium compound is used in the same degree as in the case where it is not reused, the content of silica in the treated water can be further reduced, and the treated water quality can be further improved. Therefore, when a processing apparatus such as a reverse osmosis membrane processing apparatus is further provided in the latter stage of the membrane filtration apparatus, the load can be reduced.

FIG. 4 shows a fourth example of the apparatus for treating silica-containing water according to the present embodiment.

The silicon dioxide-containing water treatment device 4 of FIG. 4 is provided with a reaction tank 12 for adding a magnesium compound to the water to be treated containing organic matter and silica, or for making the water to pH 10 or more using magnesium contained in the water to be treated. An insolubilizing member for insolubilizing silicon oxide; a membrane filtration device 76 as a membrane filtration member for membrane filtration of the obtained insoluble matter; a pump 80 and a backwash water pipe 92 as a backwash for the membrane used in the membrane filtration device 76 Backwash means; sludge regeneration tank 18, acid addition piping 44 as acid addition means for adding acid to at least a part of the discharged backwash discharge water; sludge separation tank 54 as backwash discharge water to which acid is added A solid-liquid separation member for solid-liquid separation; and a solid-liquid separation water return pipe 96 for returning at least a part of the solid-liquid separation water obtained by the solid-liquid separation member, that is, the sludge separation tank 54, to the membrane filtration device 76. The solid-liquid separation water return member in the previous stage. The treatment device 4 for water containing silicon dioxide may further include: a treated water tank 10 for storing the treated water; and a treatment water tank 78 for storing the treated water.

In the device 4 for treating water containing silica in FIG. 4 , the outlet of the water tank 10 to be treated and the inlet of the water to be treated in the reaction tank 12 are connected by a pipe 24 via a pump 20 . The outlet of the reaction tank 12 and the inlet of the membrane filtration device 76 are connected by a pipe 82 . The membrane filtrate outlet of the membrane filtration device 76 and the inlet of the treated water tank 78 are connected by a treated water piping 84 . A treated water pipe 86 is connected to the treated water outlet of the treated water tank 78 . The backwash water outlet of the treatment water tank 78 and the treatment water piping 84 are connected by the backwash water piping 92 via the pump 80 in the middle. The backwash discharge water outlet of the membrane filtration device 76 and the inlet of the sludge regeneration tank 18 are connected by backwash discharge water piping 88 . The outlet of the sludge regeneration tank 18 and the inlet of the sludge separation tank 54 are connected by piping 94 . The solid-liquid separation water outlet of the sludge separation tank 54 and the solid-liquid separation water inlet of the reaction tank 12 are connected by a solid-liquid separation water return pipe 96 . A sludge pipe 68 is connected to the sludge outlet at the bottom of the sludge separation tank 54 via the pump 56 . The reaction tank 12 is connected with a magnesium compound addition pipe 38 as a magnesium compound addition means, and a pH adjuster addition pipe 40 as a pH adjuster addition means, and a stirring device 46 provided with a stirring blade as a stirring means is provided. The acid addition piping 44 as an acid addition means is connected to the sludge regeneration tank 18, and the stirring apparatus 50 provided with stirring blades is provided as a stirring means.

In the treatment device 4 of the water containing silicon dioxide in FIG. 4 , the water containing silicon dioxide containing organic matter and silicon dioxide, which is the water to be treated, is stored in the water tank 10 to be treated, and the pump 20 is used as needed. It is sent to the reaction tank 12 through the piping 24 . The insolubilization step is performed in the reaction tank 12 in the same manner as in the treatment device 3 of the silica-containing water in FIG. 3 .

Then, the reaction liquid obtained in the insolubilization step is sent from the reaction tank 12 to the membrane filtration device 76 through the piping 82 . In the membrane filtration device 76, the obtained insoluble matter is subjected to membrane filtration (membrane filtration step). The membrane filtrate obtained in the membrane filtration step is stored in the treated water tank 78 from the membrane filtration device 76 through the treated water piping 84 as needed. At least a part of the membrane filtrate may be discharged through the treated water piping 86 as treated water.

After the membrane filtration device 76 performs the membrane filtration treatment for a predetermined period of time (for example, once every 30 minutes to 1 hour), for example, at least a part of the membrane filtrate is passed from the downstream side of the membrane filtration device 76 through the backwashing water pipe using the pump 80 . 92. The treated water pipe 84 is transported, and the membrane used in the membrane filtration step is backwashed (backwashing step). The backwash discharge water is discharged from the upstream side of the membrane filtration device 76 through the backwash discharge water piping 88 , and sent to the sludge regeneration tank 18 .

In the sludge regeneration tank 18, acid is added to the backwash discharge water containing sludge through the acid addition piping 44, and the sludge is regenerated (acid addition step). The backwash discharge water containing the sludge regenerated by adding acid is sent to the sludge separation tank 54 through the piping 94 . In the sludge separation tank 54, the insoluble matter is subjected to solid-liquid separation by natural sedimentation or the like (solid-liquid separation step).

The solid-liquid separation water obtained in the solid-liquid separation step is returned through the solid-liquid separation water return pipe 96 to the reaction tank 12 in the front stage of the membrane filtration device 76 (membrane filtration step), that is, the solid-liquid separation water return step. The sludge separated by the solid-liquid separation is discharged from the sludge separation tank 54 by the pump 56 through the sludge piping 68 .

As described above, the method for treating silica-containing water and the treatment device 4 according to the present embodiment add a magnesium compound to the silica-containing water, or use magnesium contained in the water to be treated to insolubilize the silica at a pH of 10 or higher. Membrane filtration treatment (membrane filtration step) is performed, the membrane used in the membrane filtration step is backwashed, acid is added to at least a part of the discharged backwash effluent (acid addition step), and solid-liquid separation treatment is performed (solid-liquid separation step) ), and at least a part of the solid-liquid separation water obtained by separation is returned to the preceding stage of the membrane filtration step (solid-liquid separation water returning step).

According to this method, the compound of magnesium and silica contained in the sludge can be dissolved by adding acid to the sludge, and the magnesium can be dissolved in the form of ions. At this time, silica is also dissolved at the same time, but the solubility of silica is usually low (for example, about 120 mg/L at pH 4~9, 25 ℃), so the part exceeding the solubility will gel and precipitate . Usually, the gelation of silica takes a long time (more than tens of hours), but according to this method, since silica is once solidified, it is considered that even a reaction time of about 30 minutes can make it fully gelled.

If the regenerated sludge obtained by regenerating in the acid addition step is directly returned to the previous stage of the membrane filtration step, the ionized magnesium can be reused as the magnesium compound of the silica-based removing agent, and the silica can be eliminated. Most of them have gelled and precipitated by themselves, so they can be separated again in the membrane filtration device 76 . However, if silica gelled separately is returned to the previous stage of the membrane filtration step, it will be redissolved bit by bit. If it is a small amount, the influence is small, and there is generally no problem as long as membrane filtration is performed in the membrane filtration device 76. However, if the ratio of silica gelled alone by regenerating a large amount of sludge increases, it will not be possible to ignore its impact. Also, for example, if the treatment device is temporarily stopped and the gelled silica remains in the system for a long time, it is sometimes observed that the redissolution of silica is accelerated, and the silica concentration of the treated water is greatly increased. Phenomenon. Here, in the treatment method and treatment apparatus 4 of the present embodiment, the regenerated sludge obtained by regenerating in the acid addition step is subjected to solid-liquid separation (solid-liquid separation treatment), so as to prevent gelation as much as possible. The silica is returned to the previous stage of the membrane filtration step, and the dissolved magnesium (magnesium ions) is returned to the previous stage of the membrane filtration step for reuse, which can reduce the amount of magnesium compounds used. In addition, the silica concentration of the treated water can be reduced with a small addition amount of the magnesium compound.

In this way, the magnesium ion eluted from the compound of magnesium and silica contained in the sludge can be reused as the magnesium compound which is a silica removing agent, so that the magnesium compound can be greatly reduced compared to the case where it is not reused. usage. Thereby, the amount of generated sludge can be reduced. In some cases, even if the magnesium originally contained in the water to be treated can be used for the insolubilization of the silica, the silica can be removed. When the concentration of magnesium in the water to be treated is high relative to the concentration of silicon dioxide, the silicon dioxide can be removed even if no magnesium compound is newly added. In addition, since the eluted magnesium ions are reused, if the magnesium compound is used in the same degree as in the case where it is not reused, the content of silica in the treated water can be further reduced, and the treated water quality can be further improved. Therefore, when a processing apparatus such as a reverse osmosis membrane processing apparatus is further provided in the latter stage of the membrane filtration apparatus 76, the load can be reduced.

In the acid addition step of the treatment devices 3 and 4 for the water containing silica, it is advisable to add acid and adjust the pH of the backwash discharge water to be in the range of 4 to 9. The amount of magnesium that can be regenerated depends on the amount of acid added to the sludge regeneration tank 18, with more magnesium being added the greater the amount of magnesium being regenerated. The solubility of silica is about 120 mg/L to 150 mg/L in the pH range of 4 to 9 and at 25°C, so it is thought that the silica that exceeds the solubility will gel and precipitate.

In the acid addition step, when the pH is 9 or less, magnesium ions are eluted. Even if the pH is lower than 4, magnesium ions will still dissolve, but the dissolved silica will become difficult to gel, so the preferred pH range is pH 4~9, more preferably 4~6.

As an acid used at the time of sludge regeneration, hydrochloric acid, a sulfuric acid, etc. are mentioned, for example. Among these, hydrochloric acid is preferred in consideration of the cost of medicines and the like.

The reaction temperature in the acid addition step is not particularly limited, but is, for example, in the range of 15°C to 30°C. The reaction time in the acid addition step is not particularly limited, but is, for example, in the range of 15 minutes to 120 minutes.

In terms of the circulating amount of backwashing discharge water returned to the previous stage of the membrane filtration step in the treatment device 3 for water containing silica, as long as the amount of magnesium required for regeneration is sufficiently circulated, it is preferable to be treated The range of about 2-20% of the flow rate of water, more preferably the range of about 5-10%. If the circulation volume of the backwash discharge water is less than 2% of the flow rate of the water to be treated, the amount of magnesium required for regeneration may not be sufficiently supplied; if it exceeds 20%, the flow rate of the water to be treated increases. The larger the size, the shorter the reaction time in each reaction tank, and the properties of silica may be deteriorated and the cohesion may be deteriorated.

In terms of the circulation amount of the solid-liquid separation water returned to the previous stage of the membrane filtration step in the treatment device 4 for water containing silica, as long as the amount of magnesium required for regeneration is sufficiently circulated, it is preferable to be treated The range of about 2-20% of the flow rate of water, more preferably the range of about 5-10%. If the circulation volume of the solid-liquid separation water is less than 2% of the flow rate of the water to be treated, the amount of magnesium required for regeneration may not be sufficiently supplied; if it exceeds 20%, the flow rate of the water to be treated increases. The larger the size, the shorter the reaction time in each reaction tank, and the properties of silica may be deteriorated and the cohesion may be deteriorated.

When the concentration of the sludge in the backwash discharge water sent to the sludge regeneration tank 18 is high, the concentration in the sludge regeneration tank 18 increases, and the amount of gelled silica is higher than the amount of the eluted magnesium ions. As the ratio increases, the regeneration efficiency becomes good. The concentration of the return sludge in the backwash discharge water is, for example, in the range of 0.5 to 5.0%, preferably in the range of 1.0 to 3.0%.

The return point of the regenerated sludge sent by the backwash discharge water return means in the silica-containing water treatment device 3 is not particularly limited as long as it is the first stage of the membrane filtration device 76 (membrane filtration step). For example, it is sufficient to return the regenerated sludge to at least one of the water tank 10 to be treated, the reaction tank 12, and the pipes 24 and 82. However, by returning the sludge to the reaction tank 12, the concentration of magnesium ions in the reaction tank 12 increases. It can promote the co-precipitation reaction of magnesium and silica, so it is ideal.

The return place of the solid-liquid separation water sent by the solid-liquid separation water return means in the silica-containing water treatment device 4 is not particularly limited as long as it is the first stage of the membrane filtration device 76 (membrane filtration step). . For example, it is sufficient to return the regenerated sludge to at least one of the water tank 10 to be treated, the reaction tank 12, and the pipes 24 and 82. However, by returning the sludge to the reaction tank 12, the concentration of magnesium ions in the reaction tank 12 increases. It can promote the co-precipitation reaction of magnesium and silica, so it is ideal.

Compared with the case where the regenerated sludge or solid-liquid separation water is not returned to the previous stage of the membrane filtration step, the use of the magnesium compound can be reduced by the treatment method and treatment devices 3 and 4 of the silica-containing water of the present embodiment. Reduce to, for example, about 1/2~0.

By means of the treatment method and treatment devices 3 and 4 of the silica-containing water of the present embodiment, the silica content in the treated water can be reduced to, for example, about 10 mg/L or less, and the organic matter content in the treated water can be reduced, for example, to about 10 mg/L or less. 1mg/L or less.

The silica-containing water to be treated in the silica-containing water treatment devices 3 and 4 is, for example, groundwater, industrial water, factory discharge water, and the like. The amount of silica in the silica-containing water is, for example, 10 to 400 mg/L. The amount of the organic matter in the silica-containing water is, for example, 1 to 10 mg/L. When the silica-containing water contains a hardness component, the amount of the calcium hardness component in the silica-containing water is, for example, 50 to 5000 mg-CaCO ₃ /L, and the amount of the magnesium hardness component is, for example, 10 to 1000 mg-Mg/L.

The membrane used in the membrane filtration step is, for example, at least one of a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane). The pore diameter of the microfiltration membrane is 0.1 μm or more and 10 μm or less, and the nominal pore diameter of the ultrafiltration membrane is 0.01 μm or more and less than 0.1 μm. Examples of the filter membrane include inorganic membranes such as ceramic membranes, and organic membranes such as PVDF (polyvinylidene fluoride), PES (polyether ash), PS (poly ash), and PTFE (polytetrafluoroethylene). In addition, with regard to the filter membrane, either an external pressure type or an internal pressure type may be used.

If necessary, the reaction liquid obtained in the insolubilization step may be subjected to a coagulation reaction by adding an inorganic flocculating agent to the reaction liquid, for example, in a coagulation tank before the membrane filtration step (coagulation step). A pH adjuster may also be added to the coagulation tank as needed. In the coagulation tank, the coagulation liquid can also be agitated by a stirring device.

If necessary, a polymer coagulation reaction may be performed by adding a polymer coagulation agent to the coagulation reaction liquid obtained in the coagulation step, for example, in a polymer reaction tank (polymer coagulation step). In the polymer reaction tank, the coagulation reaction liquid may be stirred by a stirring device.

The polymer aggregation solution obtained in the polymer aggregation step may be sent to the membrane filtration device 76, and the obtained insoluble matter may be subjected to membrane filtration in the membrane filtration device 76 (membrane filtration step).

The treatment method and treatment devices 1 and 2 of the silica-containing water according to the present embodiment are shown in Figs. 5 and 6, respectively. A reverse osmosis membrane treatment apparatus 100 is provided for passing solid-liquid separation treated water or first solid-liquid separation treated water (treated water) through a reverse osmosis membrane to obtain permeated water and concentrated water, and performs reverse osmosis membrane treatment.

In the treatment device 5 for water containing silica in FIG. 5 , the solid-liquid separation treated water (treated water) obtained in the precipitation tank 16 (solid-liquid separation step) is passed into the reverse osmosis membrane treatment device 100 for reverse osmosis. membrane to obtain permeable water and concentrated water (reverse osmosis membrane treatment step). The permeable water is discharged through the permeable water pipe 102 , and the concentrated water is discharged through the concentrated water pipe 104 . Since the content of silicon dioxide in the treated water (treated water) for solid-liquid separation has been reduced, it is possible to suppress the occurrence of fouling caused by silicon dioxide in the reverse osmosis membrane treatment device, and to suppress the clogging of the reverse osmosis membrane.

In the treatment device 6 of the water containing silica in FIG. 6 , the first solid-liquid separation treated water (treated water) obtained in the precipitation tank 16 (first solid-liquid separation step) is passed into the reverse osmosis membrane treatment device 100 The reverse osmosis membrane in the medium is used to obtain permeable water and concentrated water (reverse osmosis membrane treatment step). The permeable water is discharged through the permeable water pipe 102 , and the concentrated water is discharged through the concentrated water pipe 104 . Since the content of silica in the first solid-liquid separation treatment water (treated water) has been reduced, it is possible to suppress the occurrence of fouling caused by silica in the reverse osmosis membrane treatment device, etc. blocked.

The treatment method and treatment devices 3 and 4 of the silica-containing water according to the present embodiment are shown in Figs. 7 and 8, respectively. It is preferable that the membrane filtration device 76 (membrane filtration step) is further equipped with a membrane filtration solution (treatment step) in the latter stage. water) is passed through the reverse osmosis membrane to obtain the reverse osmosis membrane treatment device 100 of permeated water and concentrated water, and the reverse osmosis membrane treatment is performed.

In the treatment devices 7 and 8 of the silica-containing water shown in Figs. 7 and 8, the membrane filtrate (treated water) obtained in the membrane filtration device 76 (membrane filtration step) is stored in the treated water pipe 84 as necessary in the treatment water pipe 84. In the treated water tank 78 , the treated water is sent to the reverse osmosis membrane treatment apparatus 100 through the treated water piping 86 . This is passed through the reverse osmosis membrane in the reverse osmosis membrane processing apparatus 100 to obtain permeable water and concentrated water (reverse osmosis membrane processing step). The permeable water is discharged through the permeable water pipe 102 , and the concentrated water is discharged through the concentrated water pipe 104 . Since the silica content of the membrane filtrate (treated water) has been reduced, even if the water recovery rate of the reverse osmosis membrane treatment device 100 is improved, the silica fouling on the concentration side of the reverse osmosis membrane will still be reduced. risk.

When the water to be treated contains calcium and other hardness components, the pH can be lowered to, for example, 4 to 7 and the Langelier's index is less than 0 by passing between the membrane filtration device 76 and the reverse osmosis membrane treatment device 100. A pH adjuster is added to reduce the risk of fouling such as calcium carbonate.

The permeated water of the reverse osmosis membrane treatment device 100 can also be reused for the make-up water of the cooling tower, the production water, and the like. [Example]

The following examples and comparative examples are given to describe the present invention more specifically and in detail, but the present invention is not limited to the following examples.

<Example 1> The influence of pH of sludge regeneration was confirmed by the jar test.

(Water to be treated) Water to be treated: RO concentrated water of pure water production line (containing silica) SiO ₂ =95.7mg/L

(Sludge production method) 200 mg-Mg/L of magnesium chloride (MgCl ₂ ) aqueous solution as a magnesium compound was added to 50 L of water to be treated. Sodium hydroxide (NaOH) as a pH adjuster was added to adjust the pH to 11.0, and the reaction was performed for 30 minutes. 2 mg/L of Orfloc M-4216 (manufactured by Orujano Co., Ltd.) was added as a polymer flocculant. After standing and settling, the supernatant was removed and concentrated to 4.4 L. The amounts of Mg and SiO ₂ were determined for the supernatant. After a part of the concentrated sludge was dehydrated by centrifugation, hydrochloric acid (HCl) was added to dissolve it, and the amounts of Mg and SiO ₂ in the sludge were measured. The results are shown in Table 1.

In addition, the amount of Mg in water and sludge was measured using an ion chromatography apparatus (761 Compact, manufactured by Metrohm). The amount of SiO ₂ in water and sludge was measured by JIS K 0101 molybdenum blue absorptiometry using an absorptiophotometer (U-2900, manufactured by Hitachi, Ltd.).

[Table 1] Sludge properties

(Sludge regeneration test) To 100 mL of concentrated sludge, hydrochloric acid (HCl) as an acid was added, it adjusted to each pH (pH3-10) shown in Table 2, and it was made to react for 30 minutes. After filtering with filter paper (5C), the amounts of Mg and SiO ₂ in the filtrate were measured. After the sludge was dewatered by suction filtration, it was dried at 105° C. for 2 hours. The obtained dried product was added to 100 mL of pure water again, and hydrochloric acid (HCl) was added to dissolve it, and the amounts of Mg and SiO ₂ in the sludge were measured. The results are shown in Table 2 and FIG. 9 . Figure 9 is a graph showing dissolved Mg concentration (mg/L) or _SiO2 concentration (mg/L) versus sludge regeneration pH.

[Table 2] Sludge regeneration test results

When the pH at the time of sludge regeneration is lowered, Mg ions are eluted. This Mg ion can be utilized as a _SiO2 remover. On the other hand, SiO ₂ also dissolves, but in the range of pH 4 to 9, the amount of dissolution is small, which is near the solubility. The portion detected in excess of the solubility was considered to be a portion (pH 3) that was not gelled due to insufficient reaction time. In the case of pH 9, SiO ₂ hardly dissolves.

<Example 2, Comparative Example 1> (Continuous water-passing test) For confirmation, a water-passing test was carried out using the experimental facility of the flow shown in FIG. 10 . In Comparative Example 1, the sludge was circulated, but acid (hydrochloric acid) was not added to the sludge regeneration tank.

(Water to be treated) Water to be treated: RO concentrated water of pure water production line (containing silicon dioxide) SiO ₂ =95.7mg/L

Water was passed through the reaction tank at a flow rate of 10 L/h of water to be treated. In the reaction tank, sodium hydroxide (NaOH) as a pH adjuster was added to adjust to pH 10.8 to 11.0, and magnesium chloride (MgCl ₂ ) 12.5 to 200 mg-Mg/L was added as a magnesium compound. In the polymer reaction tank, 2 mg/L of Orfloc M-4216 (manufactured by Oruganao Co., Ltd.) was added as a polymer flocculant. Solid-liquid separation is performed using a sedimentation tank as a solid-liquid separation device. The sludge after precipitation is returned to the sludge regeneration tank at 10% of the flow rate of the treated water (about 1 L/h), and hydrochloric acid (HCl) as an acid is added to the sludge regeneration tank to adjust to pH 7 or pH 9. The regenerated sludge after regeneration is returned to the reaction tank. The SiO ₂ concentration of the treated water was measured 8 hours after the start of water flow. The results are shown in FIG. 11 . FIG. 11 is a graph showing the addition amount (mg-Mg/L) of Mg (new product) to the SiO ₂ concentration (mg/L) in Example 2 and Comparative Example 1. FIG.

In Example 2, by carrying out the regeneration of the sludge, even if the addition amount of the magnesium compound (magnesium chloride) was small, the _SiO2 concentration of the treated water was reduced. The lower the regeneration pH, the greater the effect. In Comparative Example 1, since regeneration of the sludge was not performed, the addition amount of the magnesium compound (magnesium chloride) was increased.

<Example 3, Comparative Example 2> (Continuous water-passing test) For confirmation, a water-passing test was performed using the experimental equipment of the flow shown in FIG. 2 . In Comparative Example 2, the sludge was circulated, but acid (hydrochloric acid) was not added to the sludge regeneration tank, and the experiment was conducted by bypassing the sludge separation tank.

(Water to be treated) Water to be treated: RO concentrated water of pure water production line (containing silicon dioxide) SiO ₂ =100mg/L

Water was passed to the reaction tank (17 L) at a flow rate of 100 L/h of water to be treated. In the reaction tank, sodium hydroxide (NaOH) as a pH adjuster was added to adjust to pH 10.8 to 11.0, and 50 mg-Mg/L of magnesium chloride (MgCl ₂ ) as a magnesium compound was added. In a coagulation tank (17 L), 100 mg/L of a 35 wt% ferric (III) chloride (FeCl ₃ ) aqueous solution as an inorganic coagulant was added, and sodium hydroxide was added as a pH adjuster to adjust the pH to 10.8 to 11.0. In the polymer reaction tank (17 L), 2 mg/L of Orfloc OA-3H (manufactured by Oruganao Co., Ltd.) was added as a polymer flocculant. The solid-liquid separation was performed using the sedimentation tank as the first solid-liquid separation device. The sludge after precipitation is returned to the sludge regeneration tank (5L) at 10% by volume (about 10L/h) of the flow rate of the treated water, and hydrochloric acid (HCl) as an acid is added to the sludge regeneration tank to adjust the pH to 5 . After the regenerated sludge was subjected to solid-liquid separation in the sludge separation tank, the supernatant liquid (second solid-liquid separation water) was returned to the reaction tank. The SiO ₂ concentration of the treated water was measured 24 hours after the start of water flow. The results are shown in FIG. 12 . FIG. 12 is a graph showing the addition amount (mg-Mg/L) of Mg (new product) to the SiO ₂ concentration (mg/L) in Example 3 and Comparative Example 2. FIG.

In addition, Table 3 shows the SiO ₂ concentration of the treated water after 24 hours in Example 3 and Comparative Example 2, and the SiO ₂ concentration of the treated water after the experimental apparatus was stopped for 2 hours and operated again.

[table 3]

As shown in FIG. 12 , in Example 3, the regeneration of the sludge by the acid and the second solid-liquid separation treatment were carried out, and at least a part of the second solid-liquid separation water was returned to the first stage of the first solid-liquid separation. , even if the amount of magnesium compound (magnesium chloride) added is smaller than that of Comparative Example 2, the SiO ₂ concentration in the treated water is still reduced. In Comparative Example 2, since the regeneration of the sludge was not performed, the addition amount of the magnesium compound (magnesium chloride) was increased.

As shown in Table 3, in Example 3, even if the treatment apparatus was temporarily stopped, the silica concentration of the treated water hardly changed. In Comparative Example 2, when the treatment apparatus was temporarily stopped, the silica concentration of the treated water increased significantly.

As described above, by means of the apparatus and method of the embodiments, the amount of magnesium compounds used in the silica-containing water-containing silica treatment can be reduced.

1‧‧‧Apparatus for treating water containing silica 2‧‧‧Apparatus for treating water containing silica 3‧‧‧Apparatus for treating water containing silica 4‧‧‧Apparatus for treating water containing silica Treatment device 5‧‧‧Treatment device for silica-containing water 6‧‧‧Treatment device for silica-containing water 7‧‧‧Treatment device for silica-containing water 8‧‧‧Silicon dioxide-containing water Water treatment device 10‧‧‧Water tank to be treated 12‧‧‧Reaction tank 14‧‧‧Polymer reaction tank 16‧‧‧Sedimentation tank 18‧‧‧Sludge regeneration tank 20‧‧‧Pump22‧‧‧Pump Pu 24‧‧‧Piping 26‧‧‧Piping 28‧‧‧Piping 30‧‧‧Treatment water piping 32‧‧‧Sludge piping 34‧‧‧Sludge return piping 36‧‧‧Reclaimed sludge return piping 38‧‧ ‧Magnesium compound addition piping 40‧‧‧pH adjuster addition piping 42‧‧‧polymer flocculant addition piping 44‧‧‧acid addition piping 46‧‧‧stirrer 48‧‧‧stirrer 50‧‧‧stirring unit 52 ‧‧‧Coagulation tank 54‧‧‧Sludge separation tank 56‧‧‧Pump 58‧‧‧Piping 60‧‧‧Piping 62‧‧‧Piping 64‧‧‧Piping for regeneration sludge 66‧‧‧Solid-liquid separation water Return piping 68‧‧‧Sludge piping 70‧‧‧Inorganic flocculating agent adding piping 72‧‧‧pH adjusting agent adding piping 74‧‧‧Agitating device 76‧‧‧Membrane filtration device 78‧‧‧Treatment water tank 80‧‧‧ Pump 82‧‧‧Piping 84‧‧‧Treatment water piping 86‧‧‧Treatment water piping 88‧‧‧Backwashing drainage water piping 90‧‧‧Recycled sludge return piping 92‧‧‧Backwashing water piping 94‧‧ ‧Piping 96‧‧‧Solid-liquid separation water return piping 100‧‧‧Reverse osmosis membrane treatment device 102‧‧‧Permeable water piping 104‧‧‧Concentrated water piping

Fig. 1 is a schematic configuration diagram showing a first example of a treatment apparatus for silica-containing water according to an embodiment of the present invention. Fig. 2 is a schematic configuration diagram showing a second example of the treatment apparatus for silica-containing water according to the embodiment of the present invention. Fig. 3 is a schematic configuration diagram showing a third example of the treatment apparatus for silica-containing water according to the embodiment of the present invention. 4] It is a schematic block diagram which shows the 4th example of the processing apparatus of the silica-containing water which concerns on embodiment of this invention. [ Fig. 5] Fig. 5 is a schematic configuration diagram showing a fifth example of an apparatus for treating silica-containing water according to an embodiment of the present invention. Fig. 6 is a schematic configuration diagram showing a sixth example of the treatment apparatus for silica-containing water according to the embodiment of the present invention. Fig. 7 is a schematic configuration diagram showing a seventh example of the treatment apparatus for silica-containing water according to the embodiment of the present invention. Fig. 8 is a schematic configuration diagram showing an eighth example of the treatment apparatus for silica-containing water according to the embodiment of the present invention. 9 is a graph showing the effect of the dissolved Mg concentration (mg/L) or the SiO ₂ concentration (mg/L) on the sludge regeneration pH in Example 1. [ FIG. 10 is a schematic configuration diagram showing a processing apparatus used in Example 2. FIG. 11 is a graph showing the addition amount (mg-Mg/L) of Mg (new product) with respect to the SiO ₂ concentration (mg/L) in Example 2 and Comparative Example 1. FIG. 12 is a graph showing the SiO ₂ concentration (mg/L) of the treated water in Example 3 and Comparative Example 2 with respect to the addition amount (mg-Mg/L) of Mg (new product).

Claims (12)

A device for treating water containing silicon dioxide, comprising: a reaction tank for adding a magnesium compound to the water to be treated containing silicon dioxide, or to insolubilize the silicon dioxide by using the magnesium contained in the water to be treated at a pH of 10 or higher; Liquid separation means for solid-liquid separation of the obtained insoluble matter; and return means for adding acid to at least a part of the sludge separated by the solid-liquid separation, and adjusting the pH of the separated sludge to be between 4 and 6 range and return it to the front section of the solid-liquid separation member. A device for treating water containing silicon dioxide, comprising: a reaction tank for adding a magnesium compound to water to be treated containing silicon dioxide, or for insolubilizing silicon dioxide at pH 10 or more using magnesium contained in the water to be treated; 1 solid-liquid separation means for solid-liquid separation of the obtained insoluble matter; acid addition means for adding acid to at least a part of the sludge separated by the first solid-liquid separation means, and pH of the separated sludge Adjusted to the range of 4 to 6; the second solid-liquid separation means, for solid-liquid separation of the acid-added sludge; and the return means for the second solid-liquid separation obtained by the second solid-liquid separation means At least a part of the separated water is returned to the preceding stage of the first solid-liquid separation means. An apparatus for treating water containing silica, comprising: an insolubilizing member for adding a magnesium compound to water to be treated containing organic matter and silica, or for insolubilizing silica at pH 10 or more using magnesium contained in the water to be treated ; Membrane filtration means for membrane filtration of the obtained insoluble matter; backwash means for backwashing the membrane filtration means; acid addition means for adding acid to at least a part of the discharged backwash discharge water, and the backwash discharge water is The pH is adjusted to the range of 4 to 6; and the backwash discharge water return member is backwashed and the backwash discharge water with added acid is returned to the front stage of the membrane filtration member. An apparatus for treating water containing silica, comprising: an insolubilizing member for adding a magnesium compound to water to be treated containing organic matter and silica, or for insolubilizing silica at pH 10 or more using magnesium contained in the water to be treated ; Membrane filtration member, the obtained insoluble matter is subjected to membrane filtration; Backwash member, backwash the membrane filtration member; Acid addition member, for at least a part of the discharged backwash discharge water, add acid, this backwash discharge water The pH of the water is adjusted to the range of 4 to 6; the solid-liquid separation means, the backwash discharge water with added acid is subjected to solid-liquid separation; and the solid-liquid separation water return means, which is separated by the solid-liquid separation means. At least a part of the solid-liquid separation water is returned to the preceding stage of the membrane filtration member. The treatment device for water containing silica according to claim 1 or 2 of the scope of the patent application further comprises: a reverse osmosis membrane treatment device, in which the solid-liquid separation treatment water is passed through the reverse osmosis membrane at the rear stage of the solid-liquid separation member. Obtain permeable water and concentrated water. For example, the treatment device for water containing silicon dioxide according to the 3rd or 4th item of the patent application scope further has: In the reverse osmosis membrane treatment device, the membrane filtrate is passed through the reverse osmosis membrane in the latter stage of the membrane filtration member to obtain permeable water and concentrated water. A method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the treated water containing silicon dioxide, or using magnesium contained in the treated water to insolubilize the silicon dioxide at a pH above 10; solid-liquid separation step, the obtained insoluble matter is subjected to solid-liquid separation; and the return step is to add acid to at least a part of the sludge separated by the solid-liquid separation, and adjust the pH of the separated sludge to a range of 4 to 6, And return it to the previous stage of the solid-liquid separation step. A method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing silicon dioxide, or using magnesium contained in the water to be treated to insolubilize the silicon dioxide at a pH above 10; a liquid separation step for solid-liquid separation of the obtained insoluble matter; an acid addition step for adding acid to at least a part of the sludge separated by the first solid-liquid separation step to adjust the pH of the separated sludge to The range of 4 to 6; the second solid-liquid separation step, the solid-liquid separation of the acid-added sludge; and the return step, the second solid-liquid separation water obtained by the second solid-liquid separation step. At least a part of it is returned to the preceding stage of the first solid-liquid separation step. A method for treating water containing silica, comprising: In the insolubilization step, a magnesium compound is added to the treated water containing organic matter and silica, or the silica is insolubilized by using the magnesium contained in the treated water at a pH above 10; the membrane filtration step is to perform membrane filtration on the obtained insoluble matter; washing step, backwashing the membrane used in the membrane filtration step; acid adding step, adding acid to at least a part of the backwashing discharge water discharged, and adjusting the pH of the backwashing discharge water to a range of 4 to 6; and In the backwashing discharge water return step, the backwashing discharge water with added acid is returned to the previous stage of the membrane filtration step. A method for treating water containing silicon dioxide, comprising: an insolubilization step, adding a magnesium compound to the water to be treated containing organic matter and silicon dioxide, or using magnesium contained in the water to be treated to insolubilize the silicon dioxide at a pH above 10; a membrane Filtration step, subjecting the obtained insoluble matter to membrane filtration; backwashing step, performing backwashing on the membrane used in the membrane filtration step; acid adding step, adding acid to at least a part of the discharged backwashing discharge water, and backwashing the backwash The pH of the discharge water is adjusted to be in the range of 4 to 6; the solid-liquid separation step, the backwash discharge water with added acid is subjected to solid-liquid separation; and the solid-liquid separation water return step, which will be separated by the solid-liquid separation step. At least a part of the obtained solid-liquid separation water is returned to the preceding stage of the membrane filtration step. For example, the method for treating silica-containing water as claimed in claim 7 or 8 of the scope of the patent application further comprises: a reverse osmosis membrane treatment step, in which the solid-liquid separation treated water is passed into the reverse osmosis membrane in the latter stage of the solid-liquid separation step to Obtain permeable water and concentrated water. For example, the method for treating silica-containing water as claimed in item 9 or 10 of the scope of the patent application further comprises: a reverse osmosis membrane treatment step, in the latter stage of the membrane filtration step, the membrane filtrate is passed through the reverse osmosis membrane to obtain permeation water and concentrated water.

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