Method and apparatus for treating inorganic ion-containing water

Abstract

To provide a method and apparatus for treating water containing inorganic ions, capable of preventing an occurrence of pipe wear and pump blockages, reducing a frequency of disassembly, cleaning work and replacement of sludge return channels and accessories, and thereby stably treating water containing inorganic ions over the long term to produce high density sludge with excellent concentration and dehydration properties.SOLUTION: In a process to react treated inorganic ions in raw water with an insoluble matter generator in modified sludge to produce insoluble matter in a first reaction tank 1, react it with an inorganic coagulant in a second reaction tank 2, add a polymer coagulant in a coagulation tank 3 to aggregate, separate solid-liquid in a solid-liquid separation tank 4, return part of the separated sludge to a sludge reforming tank 5, and supply the returned sludge mixed with the insoluble matter generator to the first reaction tank 1, the flow velocity of the returned sludge in the sludge return channel L7 is controlled to be 1.2 to 1.5 m / sec, and the solids concentration of the returned sludge is controlled to be in the set area including the area selected from within 14 to 28% by weight.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for treating inorganic ion-containing water, in which inorganic ion-containing water is reacted with an insolubilizing agent to form insolubilized matter, and sludge containing the formed insolubilized matter is separated, in which a portion of the separated sludge is returned, and an insolubilizing agent is added to react with the inorganic ion-containing water. [Background technology]

[0002] High-density sludge (HDS) processes, such as alkaline sludge processes, are known as methods for treating wastewater containing inorganic ions such as metal ions, phosphate ions, and fluoride ions. In the HDS process, inorganic ion-containing water is reacted with an insolubilizing agent such as an alkali to produce insolubilized matter, and when the sludge containing the resulting insolubilized matter is separated, a portion of the separated sludge is returned to the treatment plant to which an insolubilizing agent is added, and the sludge is reacted with inorganic ion-containing water to produce high-density modified sludge, which is highly thickened and has excellent dewaterability.

[0003] Figure 2 is a flow diagram showing a conventional method and apparatus for treating inorganic ion-containing water using the HDS method described in Patent Document 1 (WO2011 / 115230) and elsewhere. In Figure 2, the conventional apparatus for treating inorganic ion-containing water includes a first reaction tank 1, a second reaction tank 2, a coagulation tank 3, a solid-liquid separation tank 4, and a sludge reforming tank 5. A raw water channel L1 for introducing inorganic ion-containing water to be treated is connected to the first reaction tank 1. The first reaction tank 1 is connected to the second reaction tank 2 via a channel L2. The second reaction tank 2 is connected to the coagulation tank 3 via a channel L3. The coagulation tank 3 is connected to the solid-liquid separation tank 4 via a channel L4. A treated water channel L5 connects the top of the solid-liquid separation tank 4 to the outside of the system, and a sludge discharge channel L6 with a pump P1 connects the bottom to the outside of the system. A sludge return line L7 equipped with a pump P2, a flow meter F, and a sludge concentration meter SS connects the bottom of the solid-liquid separation tank 4 to the sludge modification tank 5, and a modified sludge line L8 connects the sludge modification tank 5 to the first reaction tank 1. The sludge modification tank 5 is connected to an insolubilized material generating agent line L9. The first reaction tank 1 is equipped with a pH meter pH1 and is connected to a pH adjuster line L11. The second reaction tank 2 is equipped with a pH meter pH2 and is connected to a pH adjuster line L12 and a coagulant line L13. The coagulation tank 3 is equipped with a pH meter pH3 and is connected to a pH adjuster line L14 and a coagulant line L15. The sludge return line L7 is equipped with a flow meter F and a sludge concentration meter SS, and the sludge concentration meter SS is connected so that the amount of sludge returned to the sludge modification tank 5 by the pump P2 can be controlled based on the measured sludge concentration. The first reaction tank 1, the second reaction tank 2 and the flocculation tank 3 are provided with stirring devices, but these are not shown in the figure.

[0004] In the above system, raw water (water containing inorganic ions to be treated) is introduced into the first reaction tank 1 through raw water line L1. Modified sludge is then supplied to the first reaction tank 1 from the sludge modification tank 5 through the modified sludge line L8. A pH adjuster is supplied through the pH adjuster line L11 as needed to maintain a predetermined pH value measured by the pH meter pH1. This allows the inorganic ions in the raw water to react with the insolubilizer in the modified sludge, producing insolubilized materials. If the first reaction produces sludge with good separability and dewaterability, such as metal ions, the second reaction tank 2 and coagulation tank 3 can be omitted, and the reaction liquid can be sent directly to the solid-liquid separation tank 4 for solid-liquid separation. However, if the sludge produced is poorly separable and dewaterable, such as phosphate ions or fluoride ions, a pH adjuster is supplied through the pH adjuster line L12 and an inorganic coagulant, such as aluminum salt, is supplied through the coagulation line L13 to the second reaction tank 2. If necessary, a pH adjuster is supplied to the coagulation tank 3 via pH adjuster line L14, and a polymer coagulant is supplied via coagulant line L15 to carry out the coagulation reaction. It is possible to carry out either the reaction in the second reaction tank 2 or the reaction in the coagulation tank 3. The reaction liquid thus produced, which produces sludge with excellent separability and dewaterability, is sent directly to the solid-liquid separation tank 4 for solid-liquid separation. The separated liquid is discharged as treated water via treated water line L5, and a portion of the separated sludge is discharged as waste sludge via discharge line L6. A portion of the separated sludge is returned to the sludge reforming tank 5 via sludge return line L7 as returned sludge, and an insolubilizer is supplied via insolubilizer line L9 and mixed with the returned sludge for sludge reforming. The modified sludge is supplied to the first reaction tank 1 from the modified sludge line L8 and reacts with the raw water. At this time, the insolubilizing agent adsorbed to the concentrated sludge reacts with the inorganic ions to be treated in the raw water, producing insolubilized matter near the solids in the sludge, resulting in the growth of high-density sludge that is highly concentrated and has excellent dewaterability.

[0005] Patent Document 2 (JP 5-57292 A) discloses a treatment method in which alkali is added to wastewater containing heavy metals to form insoluble matter, and when this is separated into treated water and sludge, the alkali is mixed with the returned sludge and added to the wastewater, so that the amount of solids in the returned sludge is 15 to 40 times the amount of insoluble matter formed from the wastewater (amount of SS generated). Here, R = (amount of solids in returned sludge) / (amount of SS generated) = (sludge concentration (g / L) × amount of returned sludge (1 / hr)) / (amount of solids generated (g / L) × amount of raw water (1 / hr)), and R is set to 15 to 40 times. This indicates that sludge is returned so that the amount of solids in the returned sludge is 15 to 40 times the amount of solids generated from the raw water being treated.

[0006] Patent Document 3 (JP 2010-234300 A) discloses a method for treating wastewater containing inorganic ions, in which an insoluble salt-forming agent is added to wastewater containing inorganic ions to precipitate insoluble salts, followed by solid-liquid separation to separate sludge containing insoluble salts from the treated water, with part of the separated sludge being used as returned sludge, the insoluble salt-forming agent being added to this returned sludge and added to the wastewater containing inorganic ions, and the remainder of the sludge being discharged as extracted sludge. In this method, the ratio of the flow rate of the returned sludge to the flow rate of the extracted sludge is set to a predetermined constant sludge return ratio so that the concentration of the returned sludge is 2 to 10% by weight, and it is said that this allows the sludge return ratio to naturally converge to an appropriate value even if the properties of the raw water change. Patent Document 3 states that if the sludge return ratio is not appropriately controlled in the HDS method, for example, if the sludge return ratio is excessively small, the dewaterability will deteriorate like that of normal flocculated sludge, and conversely, if the sludge return ratio is excessively high, fine flocs will be generated and the quality of the treated water will deteriorate.

[0007] However, in these conventional treatment methods, the amount of sludge returned from the solid-liquid separation tank is estimated based on the raw water and the insolubilization reaction, and the amount of sludge returned is determined based on this estimate. This results in a sludge concentration that is left to chance, resulting in the production of high-concentration sludge. This high concentration of returned sludge leads to pipe wear and pump blockages in the sludge return line L7. Because the sludge return line L7 returns sludge from a low position to a high position, it often includes elbows, bends, and other curved sections 7a and 7b, which often wear and block. This necessitates frequent disassembly, cleaning, and replacement of the sludge return line and accessories (valves, etc.), which poses a problem of impeding stable operation.

[0008] Patent Document 4 (JP 2006-167633 A) proposes a method for treating wastewater containing fluoride ions, in which a calcium compound is reacted with fluoride-ion-containing water to form calcium fluoride, and when the calcium compound is added to the returned sludge to cause the reaction, the sludge concentration of the resulting sludge is used as an indicator to keep the flow rate of the returned sludge constant and adjust the flow rate of the sludge discharged outside the system. Here, keeping the flow rate of the returned sludge constant means setting the flow rate of the returned sludge to 0.5 to 30%, preferably 1 to 10%, of the raw water flow rate. Therefore, the flow rate of the returned sludge will fluctuate depending on the fluctuation in the raw water flow rate, which, as in the above case, can cause pipe wear and pump blockage in the sludge circulation line. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2011 / 115230 [Patent Document 2] JP 5-57292 [Patent Document 3] Patent Publication No. 2010-234300 [Patent Document 4] Patent Publication No. 2006-167633 Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to solve the above-mentioned conventional problems by providing a method and apparatus for treating inorganic ion-containing water that can prevent the occurrence of pipe wear and pump blockage, reduce the frequency of disassembly, cleaning, and replacement of the sludge return line and accessories, and thereby enable stable treatment of inorganic ion-containing water over a long period of time to produce high-density sludge with excellent concentration and dewaterability. [Means for solving the problem]

[0011] The present invention provides the following method and apparatus for treating water containing inorganic ions. (1) a reaction step in which inorganic ion-containing water is reacted with an insolubilizing agent to form an insolubilized substance; a solid-liquid separation step of separating the reaction liquid from the reaction step into sludge containing insoluble matter and treated water; A sludge returning step in which a portion of the separated sludge separated in the solid-liquid separation step is returned as returned sludge through a sludge returning line; a sludge modification step of adding an insolubilizing agent to the returned sludge to generate modified sludge, and supplying the modified sludge to a reaction step; The flow rate of the returned sludge in the sludge return line is 1.2 to 1.5 m / sec. The solids concentration of the returned sludge is controlled within a set range including a range selected from 14 to 28% by weight. A method for treating water containing inorganic ions, comprising: (2) The flow velocity of the pump suction pipe in the sludge return line is set to 1.2 to 1.5 m / sec. By adjusting the diameter of the pump discharge pipe to a maximum flow velocity of 1.5 m / sec, The flow rate of the returned sludge in the sludge return line is controlled to 1.2 to 1.5 m / sec. The method according to (1) above, characterized in that (3) A lower intermediate value LM and an upper intermediate value HM are set between the lower limit value L and the upper limit value H of the set range of the solid concentration of the returned sludge, When the solids concentration reaches the lower intermediate value LM, slow sludge discharge begins. When the solid concentration reaches the upper limit H, the system switches to high-speed sludge discharge. When the solids concentration reaches the upper intermediate value HM, high-speed sludge discharge is stopped and switched to low-speed sludge discharge. By stopping the slow sludge discharge when the solid concentration reaches the lower limit L, Control the solids concentration of the returned sludge within the set range. The method according to (1) or (2) above, (4) The method according to (3) above, wherein the high-speed sludge discharge is continuous sludge discharge and the low-speed sludge discharge is intermittent sludge discharge. (5) The method described in (3) above, characterized in that it includes a second reaction step between the reaction step and the solid-liquid separation step, in which an inorganic flocculant is added to the reaction liquid of the reaction step to cause a reaction, and / or a flocculation step in which a polymer flocculant is added to cause flocculation. (6) a reaction vessel in which the inorganic ion-containing water is reacted with an insolubilizing agent to form an insolubilized substance; a solid-liquid separation tank for separating the reaction liquid from the reaction process into sludge containing insoluble matter and treated water; A sludge return path for returning a portion of the separated sludge separated in the solid-liquid separation process as returned sludge; a sludge modification tank in which an insolubilizing agent is added to the returned sludge to form modified sludge, and the modified sludge is supplied to a reaction step; The flow rate of the returned sludge in the sludge return line is 1.2 to 1.5 m / sec. A control device is included that controls the solids concentration of the returned sludge to a set range including a range selected from 14 to 28% by weight. 1. A treatment device for inorganic ion-containing water. (7) The pump in the sludge return line has a flow velocity of 1.2 to 1.5 m / sec in the suction pipe. The diameter of the pump discharge pipe is such that the maximum flow velocity is 1.5 m / sec. The control device is configured to control the flow rate of the returned sludge in the sludge return path to 1.2 to 1.5 m / sec. The device according to (6) above. (8) The control device is A lower intermediate value LM and an upper intermediate value HM are set between the lower limit value L and the upper limit value H of the set range of solid concentration of the returned sludge, When the solids concentration reaches the lower intermediate value LM, slow sludge discharge begins. When the solid concentration reaches the upper limit H, the system switches to high-speed sludge discharge. When the solids concentration reaches the upper intermediate value HM, high-speed sludge discharge is stopped and switched to low-speed sludge discharge. By stopping the slow sludge discharge when the solid concentration reaches the lower limit L, The solids concentration of the returned sludge is controlled within a set range. The device according to (6) or (7) above. (9) The device according to (8) above, characterized in that the high-speed sludge discharge is continuous sludge discharge and the low-speed sludge discharge is intermittent sludge discharge. (10) The apparatus according to (8) above, characterized in that it comprises, between the reaction tank and the solid-liquid separation tank, a second reaction tank in which an inorganic flocculant is added to the reaction liquid in the reaction tank to cause a reaction, and / or a flocculation tank in which a polymer flocculant is added to cause flocculation.

[0012] The inorganic ion-containing water to be treated in the present invention is water containing inorganic ions that will produce insolubilized matter when reacted with an insolubilizing agent, and includes inorganic ion-containing water that has traditionally been treated by the HDS method. Examples of inorganic ions contained in such inorganic ion-containing water include metal ions, phosphate ions, fluoride ions, sulfate ions, sulfite ions, and carbonate ions. Examples of metal ions include Fe. 2+ , Fe 3+ , Cu 2+ , Mn 2+ , Cr 2+ , Co 2+ , Ni 2+ , Zn 2+ , Cd 2+ Heavy metal ions such as Mg 2+ , Al 3+ and other light metal ions.

[0013] Examples of insolubilizing agents that react with metal ions to produce insolubilized matter include alkaline agents such as sodium hydroxide, potassium hydroxide, and calcium hydroxide, and the reaction is an insolubilizing reaction through neutralization. Examples of insolubilizing agents for phosphate ions, fluoride ions, etc. include calcium salts such as calcium chloride and calcium hydroxide, and water-soluble calcium compounds such as hydroxides, and the reaction is an insolubilizing reaction through precipitation of insoluble calcium compounds.

[0014] The alkaline agent is added so that the pH in the reaction vessel is within a predetermined range. The suitable pH range varies depending on the metal species: pH 4 to 6 for Al, pH 5 to 7 for Cr, and pH 6 to 8 for Fe. 2+ pH 8-10 for Zn, pH 8-10 for Fe 3+ For , the pH is 4 to 5, and for Cu, the pH is 6 to 8. For other substances, the pH can be determined by an insolubilized matter formation test using a neutralization reaction.

[0015] Water-soluble calcium compounds such as calcium salts are added depending on the concentrations of phosphate ions, fluoride ions, etc. in the raw water, but are preferably added in slight excess. When treating phosphate ions, the amount of water-soluble calcium compound added is preferably 1x equivalent molar ratio + 20 to 200 mg / L as residual Ca. When treating fluoride ions, the amount of calcium salts added is preferably 1x equivalent molar ratio + 200 to 500 mg / L as residual Ca.

[0016] Any of nonionic, anionic, and cationic polymer flocculants can be used as the polymer flocculant. However, when the inorganic ion-containing wastewater is aluminum ion-containing wastewater, for example, nonionic and anionic polymer flocculants are effective as the polymer flocculant.

[0017] In the present invention, inorganic ion-containing water is treated by the HDS method, in which inorganic ion-containing water is reacted with an insolubilizing agent to form insolubilized matter, and sludge containing the formed insolubilized matter is separated. A portion of the separated sludge is returned, and an insolubilizing agent is added to the sludge to react with the inorganic ion-containing water. In this HDS method, the insolubilizing agent adsorbed on the concentrated returned sludge reacts with the inorganic ions to be treated in the raw water, forming insolubilized matter near the solid matter in the sludge, resulting in a high-density sludge that is highly concentrated and has excellent dewaterability.

[0018] The method for treating inorganic ion-containing water of the present invention is similar to conventional methods in that it includes a reaction step in which inorganic ion-containing water is reacted with an insolubilizing agent to produce insolubilized matter, a solid-liquid separation step in which the reaction liquid of the reaction step is separated into sludge containing insolubilized matter and treated water, a sludge return step in which a portion of the separated sludge separated in the solid-liquid separation step is returned as returned sludge through a sludge return line, and a sludge modification step in which an insolubilizing agent is added to the returned sludge to produce modified sludge and the modified sludge is supplied to the reaction step. However, the present invention is further configured to control the flow rate of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec and the solids concentration of the returned sludge to a set range selected from a range of 14 to 28 wt %.

[0019] In the present invention, the term "a set range including a range selected from within 14 to 28 wt%" means that the set range is a range selected from the range of 14 to 28 wt%, for example, a range including 14 to 20 wt%, 18 to 25 wt%, or 20 to 28 wt%, and the solids concentration of the returned sludge is controlled within this set range. The range to be set is determined depending on the properties of the sludge to be generated. For example, in a system that produces heavy sludge with good separability, the set range can be a range including a low concentration range, while in a system that produces light sludge with poor separability, the set range can be a range including a high concentration range. The set range can be determined depending on the properties of the sludge to be generated. The set range may be a range that mainly includes "a range selected from within 14 to 28 wt%," or it may be a range that includes a range outside this range in addition to "a range selected from within 14 to 28 wt%," for example, a range below 14 wt% and / or a range above 28 wt%.

[0020] The inorganic ion-containing water treatment device of the present invention is similar to conventional devices in that it includes a reaction tank in which inorganic ion-containing water is reacted with an insolubilizing agent to produce insolubilized matter, a solid-liquid separation tank in which the reaction liquid of the reaction process is separated into sludge containing insolubilized matter and treated water, a sludge return line in which a portion of the separated sludge separated in the solid-liquid separation process is returned as returned sludge, and a sludge modification tank in which an insolubilizing agent is added to the returned sludge to produce modified sludge and the modified sludge is supplied to the reaction process.However, the present invention is further configured to include a control device that controls the flow rate of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec and the solids concentration of the returned sludge to a set range selected from a range of 14 to 28 wt%.

[0021] In the above-described inorganic ion-containing water treatment device of the present invention, the pump in the sludge return path preferably has a flow rate of 1.2 to 1.5 m / sec in the suction pipe, a diameter of the pump's discharge pipe is such that the maximum flow rate is 1.5 m / sec, and the control device is configured to control the flow rate of the returned sludge in the sludge return path to 1.2 to 1.5 m / sec. The control device is also preferably configured to set a lower intermediate value LM and an upper intermediate value HM between a lower limit L of 20% by weight and an upper limit H of 28% by weight for the solids concentration of the returned sludge, start low-speed sludge discharge when the solids concentration reaches the lower intermediate value LM, switch to high-speed sludge discharge when the solids concentration reaches the upper limit H, stop high-speed sludge discharge and switch to low-speed sludge discharge when the solids concentration reaches the upper intermediate value HM, and stop low-speed sludge discharge when the solids concentration reaches the lower limit L, thereby controlling the solids concentration of the returned sludge to 20 to 28% by weight. In this case, it is preferable that the high-speed sludge discharge is continuous and the low-speed sludge discharge is intermittent, but other modes are also possible. The flow rates of the continuous and intermittent sludge discharges are both arbitrary, and the time intervals between intermittent sludge discharges are also arbitrary. An example of intermittent sludge discharge is to withdraw the sludge for 10 minutes and then stop for 20 minutes, repeating this process.

[0022] In the above-mentioned inorganic ion-containing water treatment device, when treating raw water that produces sludge with poor separation and dewaterability, such as phosphate ions and fluoride ions, a second reaction tank in which an inorganic coagulant is added to the reaction liquid in the reaction tank to cause a reaction and / or a coagulation tank in which a polymer coagulant is added to cause coagulation can be provided between the reaction tank and the solid-liquid separation tank. In addition, in the above-mentioned treatment device, the sludge return path is configured to include bending parts such as elbows and bends in order to return sludge from a low position to a high position, and it is preferable that such bending parts have a radius of curvature of 1.5D or more (D is the outer diameter of the pipe), which further enhances the wear prevention effect at the bending parts.

[0023] In the apparatus for treating inorganic ion-containing water of the present invention, inorganic ion-containing water is treated by the treatment method of the present invention. That is, in a reaction tank, inorganic ion-containing water is reacted with an insolubilizing agent to form insolubilized matter, the reaction liquid of the reaction step is separated in a solid-liquid separation tank into sludge containing insolubilized matter and treated water, a portion of the separated sludge separated in the solid-liquid separation step is returned as returned sludge through a sludge return line, an insolubilizing agent is added to the returned sludge in a sludge modification tank to form modified sludge, and the modified sludge is supplied to the reaction step, thereby treating inorganic ion-containing water by the HDS method.

[0024] As mentioned above, in the conventional HDS process, the amount of sludge returned from the solid-liquid separation tank is estimated based on the raw water and the insolubilization reaction, and the amount of returned sludge is determined based on this estimated value. This leads to a tendency for the sludge concentration to increase, resulting in problems such as pipe wear and pump blockage in the sludge return line. To avoid this, the present invention controls the flow rate of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec. This prevents pipe wear and pump blockage in the sludge return line. If the flow rate of the returned sludge is less than 1.2 m / sec, blockage is likely to occur, while if the flow rate of the returned sludge is greater than 1.5 m / sec, pipe wear is likely to occur. While pipe wear and blockage vary slightly depending on the raw water quality, sludge properties, and pipe shape and size, practically, they can be prevented by controlling the flow rate of the returned sludge to 1.2 to 1.5 m / sec. In order to control the flow velocity of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec, the flow velocity of the pump suction pipe in the sludge return line can be set to 1.2 to 1.5 m / sec and the diameter of the pump discharge pipe can be adjusted so that the maximum flow velocity is 1.5 m / sec, thereby controlling the flow velocity of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec, but other means may also be used.

[0025] When the flow rate of returned sludge is controlled to 1.2 to 1.5 m / sec, the upper limit of the flow rate is limited to a low flow rate to prevent pipe wear. Therefore, if the sludge is returned at a low concentration (e.g., 2 to 10 wt % in Patent Document 3), as in conventional methods, the amount of sludge required for treatment may not be returned, which may adversely affect the treatment. To prevent this, the present invention is configured to control the solids concentration of the returned sludge to a set range selected from a range of 14 to 28 wt %, which is higher than conventional concentrations, so as to maintain a higher concentration than conventional concentrations. In the present invention, the solids concentration of the returned sludge is controlled to a higher concentration than conventional concentrations by controlling the amount of sludge extracted. Therefore, by returning sludge at a higher sludge concentration than conventional sludge, sludge accumulates in the system. This concentration is higher than the return sludge concentration controlled to 2 to 10 wt % in Patent Document 3, and this allows treatment to be carried out in a steady state. If the solids concentration of the returned sludge exceeds the upper limit of 28% by weight, the efficiency may decrease.

[0026] To control the solids concentration of the returned sludge within a set range, a lower intermediate value LM and an upper intermediate value HM are set between the lower limit L and the upper limit H of the set range. Slow-speed discharge is initiated when the solids concentration reaches the lower intermediate value LM and stopped when the solids concentration reaches the lower limit L. After slow-speed discharge is initiated when the solids concentration reaches the lower intermediate value LM, if the solids concentration reaches the upper limit H, high-speed discharge is switched to at that point. High-speed discharge is stopped and switched to low-speed discharge when the solids concentration reaches the upper intermediate value HM, and low-speed discharge is stopped when the solids concentration reaches the lower limit L. This allows the solids concentration of the returned sludge to be controlled within the set range. In this case, high-speed discharge at the upper limit H and the upper intermediate value HM rapidly reduces the solids concentration, and low-speed discharge between the lower intermediate value LM and the lower limit L slowly but accurately reduces the solids concentration. By using continuous sludge discharge for high-speed sludge discharge and intermittent sludge discharge for low-speed sludge discharge, efficient and accurate sludge discharge can be achieved by switching between high-speed and low-speed sludge discharge simply by controlling the sludge discharge time, without changing the pump drive conditions, etc. The lower mean value LM and upper mean value HM can be set arbitrarily, taking into consideration ease of control, accuracy, efficiency, etc.

[0027] In inorganic ion-containing water treatment where a high sludge concentration is returned, maintaining the treatment at a steady state requires the complete discharge of the sludge generated during the treatment. This is because, if the entire amount of sludge generated is not discharged, sludge will accumulate in the system. Therefore, to maintain the treatment at a steady state, it is effective to periodically discharge the sludge at a predetermined time, for example, about 2 minutes per hour. However, since it is difficult to accurately discharge the entire amount of sludge generated through periodic sludge discharge, it is preferable to discharge the sludge at a rate set lower than the amount of sludge generated, and to discharge any excess sludge that still accumulates despite such periodic sludge discharge by controlling the solids concentration of the returned sludge separately from the periodic sludge discharge. In this case, it is preferable to control the amount of returned sludge by a pump based on the fluctuating solids concentration of the returned sludge measured with a sludge concentration meter. To control the amount of returned sludge using a pump, precise control can be expected by providing separate pumps for the returned sludge and the discharged sludge and operating them separately. However, since the pump for discharging the sludge only operates for a short time, it is also possible to use one pump for both the returned sludge and the discharged sludge, and switch between the returned sludge and the discharged sludge by switching a valve.

[0028] In this way, by controlling the flow rate of the returned sludge in the sludge return line to 1.2 to 1.5 m / sec and the solids concentration of the returned sludge to 20 to 28% by weight, and by carrying out the process of reacting the inorganic ion-containing water with the insolubilization agent to generate insolubilized matter as described above, it is possible to prevent the occurrence of piping wear and pump blockage, reduce the frequency of disassembly, cleaning, and replacement of the sludge return line and accessories, and enable stable treatment of inorganic ion-containing water over a long period of time.

[0029] When sludge that is difficult to separate or dewater, such as phosphate ions or fluoride ions, is produced, a second reaction tank and / or coagulation tank can be provided between the reaction tank and the solid-liquid separation tank, and in the second reaction tank, an inorganic coagulant is added to the reaction liquid in the reaction tank as a second reaction step to cause a reaction, and in the coagulation tank, a polymer coagulant is added as a coagulation step to produce coagulated sludge through a coagulation reaction, and solid-liquid separation can be performed in the solid-liquid separation tank. Either the reaction in the second reaction tank or the reaction in the coagulation tank can be performed alone. [Effects of the Invention]

[0030] According to the present invention, in the method and apparatus for treating inorganic ion-containing water using the HDS method, it is possible to prevent the occurrence of pipe wear and pump blockage, and reduce the frequency of disassembly, cleaning, and replacement of the sludge return line and accessories, thereby achieving effects such as stable treatment of inorganic ion-containing water over a long period of time and producing high-density sludge with excellent concentration and dewaterability. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a flow diagram showing a method and apparatus for treating inorganic ion-containing water according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flow diagram showing a conventional method and apparatus for treating water containing inorganic ions. DETAILED DESCRIPTION OF THE INVENTION

[0032] In Figure 1, the inorganic ion-containing water treatment system of this embodiment includes a first reaction tank 1, a second reaction tank 2, a coagulation tank 3, a solid-liquid separation tank 4, and a sludge reforming tank 5. These tanks are configured similarly to the conventional system shown in Figure 2, but the system shown in Figure 1 also includes a control device 6. A raw water channel L1 for introducing inorganic ion-containing water to be treated is connected to the first reaction tank 1. The first reaction tank 1 is connected to the second reaction tank 2 via a path L2. The second reaction tank 2 is connected to the coagulation tank 3 via a path L3. The coagulation tank 3 is connected to the solid-liquid separation tank 4 via a path L4. A treated water channel L5 connects to the outside of the system from the top of the solid-liquid separation tank 4, and a sludge discharge channel L6 with a pump P1 connects to the outside of the system from the bottom. A sludge return channel L7 with a pump P2, a flow meter F, and a sludge concentration meter SS connects to the sludge reforming tank 5 from the bottom. A modified sludge channel L8 connects to the first reaction tank 1 from the sludge reforming tank 5. The sludge reforming tank 5 is connected to an insolubilized material generating agent line L9. The first reaction tank 1 is equipped with a pH meter pH1 and is connected to a pH adjuster line L11. The second reaction tank 2 is equipped with a pH meter pH2 and is connected to a pH adjuster line L12 and a flocculant line L13. The coagulation tank 3 is equipped with a pH meter pH3 and is connected to a pH adjuster line L14 and a flocculant line L15. The sludge return line L7 is equipped with a flow meter F and a sludge concentration meter SS. Measurement signals from the flow meter F, sludge concentration meter SS, pH meter pH1, pH meter pH2, and pH meter pH3 are each input to a control device 6, which inputs control signals to pumps P1 and P2. This connection allows the sludge discharge by pump P1 and the sludge return to the sludge reforming tank 5 by pump P2 to be controlled based on the sludge concentration measured by the sludge concentration meter SS. The first reaction tank 1, the second reaction tank 2, and the coagulation tank 3 are equipped with agitators, but these are not shown. The sludge return path L7 is configured to include bent portions 7a, 7b such as elbows and bends in order to return sludge from a low position to a high position, and these bent portions 7a, 7b have a curvature radius of 1.5D or more (D is the outer diameter of the pipe).

[0033] In the above system, raw water (water containing inorganic ions to be treated) is introduced into the first reaction tank 1 through raw water conduit L1, and modified sludge is supplied from the sludge modification tank 5 through the modified sludge conduit L8 to the first reaction tank 1. The control device 6 controls the supply of pH adjuster through pH adjuster conduit L11 so that the pH measured by the pH meter pH1 is maintained at a predetermined value, causing the inorganic ions to react with the insolubilizer in the modified sludge to form insolubilized materials. If this first reaction produces sludge with good separability and dewaterability, such as metal ions, the second reaction tank 2 and coagulation tank 3 can be omitted, and the reaction liquid can be sent directly to the solid-liquid separation tank 4 for solid-liquid separation. However, when sludge containing phosphate ions, fluoride ions, or the like that is poorly separable and dewaterable is produced, a second reaction is carried out by supplying a pH adjuster through pH adjuster line L12 to the second reaction tank 2, controlling the supply of the pH adjuster through pH adjuster line L12 with the control device 6, and supplying an inorganic coagulant such as an aluminum salt through coagulant line L13. If necessary, a pH adjuster is further supplied through pH adjuster line L14 to the coagulation tank 3, controlling the supply of the pH adjuster through pH adjuster line L14 with the control device 6, and supplying a polymer coagulant through coagulant line L15 to carry out the coagulation reaction. It is possible to carry out either the reaction in the second reaction tank 2 or the reaction in the coagulation tank 3 alone.

[0034] The reaction liquid thus produced, which produces sludge with excellent separability and dewaterability, is sent directly to solid-liquid separation tank 4 for solid-liquid separation. The separated liquid is discharged as treated water through treatment water line L5, and a portion of the separated sludge is discharged as waste sludge through discharge line L6. A portion of the separated sludge is returned to sludge reforming tank 5 as returned sludge through sludge return line L7, and an insolubilizer is supplied through insolubilizer line L9 and mixed with the returned sludge for sludge reforming. The reformed sludge is supplied to first reaction tank 1 through reforming sludge line L8 and reacts with raw water. At this time, the insolubilizer adsorbed on the concentrated sludge reacts with the inorganic ions in the raw water, forming insolubilized matter near the solids in the sludge, resulting in a high-density sludge with excellent thickening properties and dewaterability.

[0035] In the above process, to prevent pipe wear and pump blockage, the flow velocity of the returned sludge in the sludge return line L7 is controlled to a set range including a range selected from 1.2 to 1.5 m / sec and the solids concentration of the returned sludge is controlled to a set range selected from a range of 14 to 28 wt%. In order to control the flow velocity of the returned sludge in the sludge return line L7 to 1.2 to 1.5 m / sec, the pump P2 in the sludge return line L7 has a suction piping flow velocity of 1.2 to 1.5 m / sec and a pump discharge pipe diameter that allows a maximum flow velocity of 1.5 m / sec, and the control device 6 controls the flow velocity of the returned sludge in the sludge return line L7 to 1.2 to 1.5 m / sec.

[0036] In order to maintain steady-state treatment in the above-mentioned equipment, it is necessary to discharge all of the sludge generated during treatment. For this reason, periodic sludge discharge is performed at a rate set to be less than the amount of sludge generated. For this reason, sludge discharge is performed periodically at a predetermined time, for example, about two minutes per hour, and sludge discharge is performed by pump P1 in response to a control signal from control device 6. The amount of sludge generated during treatment is calculated using the formula shown in Patent Document 2. Even with such periodic sludge discharge, excess sludge continues to be generated and accumulate, so control is exercised to discharge sludge in response to fluctuations in the solids concentration of the returned sludge, separate from the periodic sludge discharge.

[0037] In such a process, in order to control the solids concentration of the returned sludge to a set range including a range selected from 14 to 28% by weight, the control device 6 is configured to set a lower intermediate value LM and an upper intermediate value HM between the lower limit value L and the upper limit value H of the set range of the solids concentration of the returned sludge measured by the sludge concentration meter SS, and to start low-speed sludge discharge when the solids concentration reaches the lower intermediate value LM, switch to high-speed sludge discharge when the solids concentration reaches the upper limit value H, stop high-speed sludge discharge and switch to low-speed sludge discharge when the solids concentration reaches the upper intermediate value HM, and stop low-speed sludge discharge when the solids concentration reaches the lower limit value L.

[0038] In this control by the control device 6, to control the solids concentration of the returned sludge within a set range, low-speed discharge by the pump P1 is initiated when the solids concentration of the returned sludge measured by the sludge concentration meter SS reaches a lower intermediate value LM, and low-speed discharge is stopped when the solids concentration reaches a lower limit value L. After low-speed discharge by the pump P1 is initiated when the solids concentration reaches the lower intermediate value LM, if the solids concentration reaches an upper limit value H, high-speed discharge is switched to low-speed discharge at that point. When the solids concentration reaches an upper intermediate value HM, high-speed discharge is stopped and switched to low-speed discharge. In this state, low-speed discharge is stopped when the solids concentration reaches the lower limit value L. This allows the solids concentration of the returned sludge to be controlled within a set range. In this case, high-speed discharge between the upper limit value H and the upper intermediate value HM rapidly reduces the solids concentration, and low-speed discharge between the lower intermediate value LM and the lower limit value L slowly but accurately reduces the solids concentration. By using continuous sludge discharge by pump P1 for high-speed sludge discharge and intermittent sludge discharge by pump P1 for low-speed sludge discharge, it is possible to switch between high-speed and low-speed sludge discharge simply by controlling the sludge discharge time, without changing the drive conditions of pump P1, thereby achieving efficient and accurate sludge discharge. The lower mean value LM and upper mean value HM can be set arbitrarily taking into consideration ease of control, accuracy, efficiency, etc., but as an example, the lower mean value LM can be set to 22% by weight and the upper mean value HM to 24% by weight. The time interval for intermittent sludge discharge can also be set arbitrarily, but intermittent sludge discharge is typically performed by repeatedly withdrawing sludge for 10 minutes and stopping for 20 minutes.

[0039] In this way, by controlling the flow rate of the returned sludge in the sludge return line L7 to 1.2 to 1.5 m / sec and the solids concentration of the returned sludge measured by the sludge concentration meter SS to a set range including a range selected from 20 to 28% by weight, and performing the process of reacting inorganic ion-containing water with an insolubilization agent to generate insolubilized matter as described above, it is possible to prevent pipe wear and pump blockage, and reduce the frequency of disassembly, cleaning, and replacement of the sludge return line and accessories.This allows for stable treatment of inorganic ion-containing water over a long period of time, producing high-density sludge with excellent concentration and dewaterability.

[0040] In Figure 1, in order to control the amount of returned sludge by pump, separate pumps P1 for sludge discharge and P2 for sludge return are provided and operated separately, but if the operating time of sludge discharge pump P1 is short, one pump can be used for both return sludge and sludge discharge, and the return sludge and discharge can be switched by switching a valve. In this case, valves can be provided in sludge discharge line L6 and sludge return line L7, and the return sludge and discharge can be switched by switching them, but a three-way valve can also be provided at the branch point to switch between return sludge and discharge. [Example]

[0041] [Comparative Example 1] Using the apparatus shown in Figure 1, inorganic ion-containing water containing 1,000 to 10,000 mg / L of fluoride ions was treated. Raw water and HDS sludge were supplied to the first reaction tank 1, and slaked lime was added as a pH adjuster if necessary. The fluoride ions in the raw water reacted with the insolubilizer in the modified sludge to form insolubilized matter. Slaked lime was added as a pH adjuster in the second reaction tank 2 to carry out a second reaction. A polymer flocculant was added in the coagulation tank 3 to carry out a coagulation reaction, followed by solid-liquid separation in the solid-liquid separation tank 4. A portion of the separated sludge from the solid-liquid separation tank 4 was returned to the sludge modification tank 5 via the sludge return line L7. Slaked lime was added as an insolubilizer via the insolubilizer line L9. The sludge was mixed with the returned sludge for sludge modification, and the resulting mixture was then supplied to the first reaction tank 1 to react with the raw water. In this treatment, the return sludge concentration was controlled to approximately 20% by weight, and the return sludge flow rate (flow rate at the pump P2 outlet) was controlled to 1.6 to 1.8 m / sec. However, due to blockage and wear, the valves needed to be replaced every 3 to 4 months, and the piping needed to be replaced every 6 months to 1 year.

[0042] [Example 1] In Comparative Example 1, the solids concentration of the returned sludge was set to 20 to 28 wt%, and a lower intermediate value LM of 22 wt% and an upper intermediate value HM of 24 wt% were set between the lower limit L of 20 wt% and the upper limit H of 28 wt%. Slow-speed sludge discharge was started when the solids concentration reached the lower intermediate value LM, and stopped when the solids concentration reached the lower limit L. After starting slow-speed sludge discharge when the solids concentration reached the lower intermediate value LM, if the solids concentration reached the upper limit H, high-speed sludge discharge was switched to at that stage. When the solids concentration reached the upper intermediate value HM, high-speed sludge discharge was stopped and switched to low-speed sludge discharge. In this state, low-speed sludge discharge was stopped when the solids concentration reached the lower limit L. By controlling the returned sludge concentration to approximately 20 to 28 wt%, which is near the set range, and controlling the return sludge flow rate (pump outlet flow rate) to 1.25 m / sec, there was no need to replace valves or piping due to blockage or wear for five years.

[0043] [Example 2] In Example 1, inorganic ion-containing water containing 1,000 to 10,000 mg / L of metal ions was treated using the apparatus shown in Figure 1, omitting the second reaction tank 2 and coagulation tank 3. HDS sludge was supplied to the first reaction tank 1 as raw water and modified sludge, and slaked lime was added as a pH adjuster, if necessary, to allow the fluoride ions in the raw water to react with the insolubilization agent in the modified sludge to produce insolubilized matter. The solids concentration of the returned sludge was set to a range of 14 to 20 wt%, with a lower intermediate value LM of 16 wt% and an upper intermediate value HM of 18 wt% set between the lower limit L of 14 wt% and the upper limit H of 20 wt%. Slow-rate sludge discharge was initiated when the solids concentration reached the lower intermediate value LM, and stopped when the solids concentration reached the lower limit L. When the solids concentration reaches the lower intermediate value LM, low-speed sludge discharge is started. When the solids concentration reaches the upper limit value H, high-speed sludge discharge is switched to at that point. When the solids concentration reaches the upper intermediate value HM, high-speed sludge discharge is stopped and the system switches to low-speed sludge discharge. When the solids concentration reaches the lower limit value L in this state, low-speed sludge discharge is stopped. By doing this, the return sludge concentration can be controlled to approximately 14 to 20% by weight, near the set range, and the return sludge flow rate (pump outlet flow rate) can be controlled to 1.25 m / sec. No valves or piping needed to be replaced due to blockage or wear for five years. [Industrial Applicability]

[0044] The present invention can be used in a method and apparatus for treating inorganic ion-containing water, in which inorganic ion-containing water is reacted with an insolubilizing agent to form insolubilized matter, and sludge containing the formed insolubilized matter is separated, in which a portion of the separated sludge is returned, and an insolubilizing agent is added to react with the inorganic ion-containing water. [Explanation of symbols]

[0045] 1 1st reaction tank, 2 2nd reaction tank, 3 flocculation tank, 4 solid-liquid separation tank, 5 sludge reforming tank, 6 control device, 7a, 7b bending section, P1, P2 pump, pH1, pH2, pH3 pH meter, F flow meter, SS sludge concentration meter.

Claims

1. a reaction step of reacting inorganic ion-containing water with an insolubilizing agent to form an insolubilized substance; a solid-liquid separation step of separating the reaction liquid from the reaction step into sludge containing insoluble matter and treated water; A sludge returning step in which a portion of the separated sludge separated in the solid-liquid separation step is returned as returned sludge through a sludge returning line; a sludge modification step of adding an insolubilizing agent to the returned sludge to generate modified sludge, and supplying the modified sludge to a reaction step; The flow rate of the returned sludge in the sludge return line is 1.2 to 1.5 m / sec. The solid concentration of the returned sludge is controlled to a set range including a range selected from 14 to 28% by weight. A method for treating water containing inorganic ions, comprising:

2. The flow velocity of the pump suction pipe in the sludge return line is set to 1.2 to 1.5 m / sec, By setting the diameter of the pump discharge pipe so that the maximum flow velocity is 1.5 m / sec, The flow rate of the returned sludge in the sludge return line is controlled to 1.2 to 1.5 m / sec.

2. The method of claim 1 .

3. A lower intermediate value LM and an upper intermediate value HM are set between the lower limit value L and the upper limit value H of the set range of the solid concentration of the returned sludge, When the solid concentration reaches the lower intermediate value LM, low-speed sludge discharge begins. When the solid concentration reaches the upper limit H, the system switches to high-speed sludge discharge. When the solids concentration reaches the upper intermediate value HM, the high-speed sludge discharge is stopped and switched to the low-speed sludge discharge. By stopping the slow sludge discharge when the solid concentration reaches the lower limit L, Control the solids concentration of the returned sludge within the set range.

3. The method according to claim 1 or 2.

4. 4. The method according to claim 3, wherein the high-speed sludge discharge is continuous sludge discharge and the low-speed sludge discharge is intermittent sludge discharge.

5. The method according to claim 3, characterized in that, between the reaction step and the solid-liquid separation step, a second reaction step is included in which an inorganic flocculant is added to the reaction liquid of the reaction step to cause a reaction, and / or a flocculation step is included in which a polymer flocculant is added to cause flocculation.

6. a reaction vessel in which inorganic ion-containing water is reacted with an insolubilizing agent to form an insolubilized substance; a solid-liquid separation tank for separating the reaction liquid from the reaction process into sludge containing insoluble matter and treated water; A sludge return path for returning a portion of the separated sludge separated in the solid-liquid separation process as returned sludge; a sludge modification tank in which an insolubilizing agent is added to the returned sludge to form modified sludge, and the modified sludge is supplied to a reaction step; The flow rate of the returned sludge in the sludge return line is 1.2 to 1.5 m / sec. A control device is included that controls the solid concentration of the returned sludge to a set range including a range selected from 14 to 28% by weight.

1. A treatment device for inorganic ion-containing water.

7. The pump in the sludge return line has a flow rate of 1.2 to 1.5 m / sec in the suction pipe, The diameter of the pump discharge pipe is such that the maximum flow rate is 1.5 m / sec. The control device is configured to control the flow rate of the returned sludge in the sludge return path to 1.2 to 1.5 m / sec.

7. The device of claim 6.

8. The control device A lower intermediate value LM and an upper intermediate value HM are set between the lower limit value L and the upper limit value H of the set range of the solid concentration of the returned sludge, When the solid concentration reaches the lower intermediate value LM, low-speed sludge discharge begins. When the solid concentration reaches the upper limit H, the system switches to high-speed sludge discharge. When the solids concentration reaches the upper intermediate value HM, the high-speed sludge discharge is stopped and switched to the low-speed sludge discharge. By stopping the slow sludge discharge when the solid concentration reaches the lower limit L, The solids concentration of the returned sludge is controlled within a set range.

8. The device according to claim 6 or 7.

9. 9. The apparatus according to claim 8, wherein the high-speed sludge discharge is continuous sludge discharge and the low-speed sludge discharge is intermittent sludge discharge.

10. The apparatus according to claim 8, further comprising, between the reaction tank and the solid-liquid separation tank, a second reaction tank in which an inorganic flocculant is added to the reaction liquid in the reaction tank to cause a reaction, and / or a flocculation tank in which a polymer flocculant is added to cause flocculation.

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