JP2012152708A - Flocculation magnetic separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculation magnetic separator capable of reducing a use amount of magnetic powder without using a chemical such as hydrochloric acid, and capable of reducing a recovered floc.SOLUTION: The flocculation magnetic separator includes a returning addition device 18 for sending the recovered floc discharged from a magnetic separator 16 back to a raw water feed pipe 12 in a position before a flocculant is added, in an upstream of a rapid stirring vessel 26. The recovered floc is returned to the raw water feed pipe 12, to be reutilized thereby without using the chemical such as hydrochloric acid. The magnetic powder contained in the recovered floc is also reutilized, and a use amount of new magnetic powder is reduced thereby.

Description

  The present invention relates to an aggregating magnetic separation device, and more particularly to an aggregating magnetic separation device that aggregates plankton and fungi contained in ballast water and separates them by magnetic force.

  In the Ballast Water Management Convention adopted by the International Maritime Organization (IMO) in 2004, plankton contained in ballast water is used to prevent disruption of the ecosystem and damage to the health caused by the movement and diffusion of microorganisms through the ballast water (seawater). And a device for removing or killing fungi and fungi is required to be mounted on a ship. At present, ballast water treatment technology combining various water treatment technologies such as chemical treatment using sodium hypochlorite, ozone treatment, ultraviolet irradiation, heat treatment, and magnetic separation is being promoted.

  The agglomeration magnetic separation device disclosed in Patent Document 1 adds magnetic powder and an aggregating agent to ballast water, which is raw water, and stirs this to generate a magnetic floc containing microorganisms and fungi in the ballast water. Is separated from the ballast water by a magnetic separation means, and relatively large solids (small fish or seaweed of several mm) that cannot be aggregated are collected by a drum type filter. According to this agglomeration magnetic separation device, the aggregating agent used is a highly safe one that is also used in tap water treatment, and it remains in the ballast water during drainage compared to treatment using chemicals such as chlorine. There is little risk of secondary contamination of the environment by chemicals and by-products. Moreover, since not only microorganisms and bacteria in the ballast water but also sand and mud can be coagulated and separated and removed at the same time, there is a secondary effect of preventing accumulation of sand and mud at the bottom of the ballast tank.

  By the way, in the agglomeration magnetic separation apparatus disclosed in Patent Document 1 and the like, it is a problem to reduce the amount of expensive magnetic powder used and to reduce the recovered recovered floc while maintaining the purification performance of ballast water. Has been raised.

  That is, in the aggregation magnetic separation apparatus, in the process of generating magnetic flocs, in order to embed the magnetic powder evenly in all the flocs as much as possible, the magnetic powder to be added has a very small particle size of about several microns, and Those with uniform particle diameter must be used.

  However, such a magnetic powder is very expensive and contributes to an increase in the running cost of the agglomerated magnetic separation apparatus. Therefore, it is desired to reduce the amount of magnetic powder used as much as possible. In addition, when aggregating magnetic separators are installed on ships, reducing the amount of magnetic powder used leads to downsizing of tanks that store magnetic powders, so the equipment can be installed in ships with limited equipment installation space. There are significant benefits. At the same time, the frequency of replenishment of magnetic powder into the ship can be reduced, reducing the burden on the crew.

  On the other hand, the recovered flock discharged from the magnetic separation means must be stored in a tank and disposed as industrial waste. In order to reduce the size of storage tanks, save space, and reduce industrial waste disposal costs, it is desired to reuse and reduce the recovered flock as much as possible.

  Therefore, in Patent Document 2, hydrochloric acid is added while stirring the recovered floc to decompose the polymer flocculant into oil and treated water-containing flocculant and magnetic powder, and the decomposed flocculant and magnetic powder. A magnetic separation and purification device is disclosed in which the water is returned to the raw water and reused.

JP-A-9-117618 JP 2006-718

  In Patent Document 2, hydrochloric acid is used to recycle magnetic powder. However, in order to use hydrochloric acid in a ship, it is necessary to install a treatment apparatus using hydrochloric acid, which is a strongly acidic substance, in the ship. What proves the safety and the certainty of the neutralization treatment of the substance to be treated must be submitted to the IMO, which requires a very complicated procedure.

  From such a background, as in Patent Document 1, in an agglomerated magnetic separation apparatus that physically removes microorganisms and fungi in ballast water, the agglomerated magnetic separation apparatus can reduce the amount of magnetic powder used and reduce the recovered flocs collected. Was desired.

  The problem of reducing the amount of magnetic powder used without using chemicals such as hydrochloric acid and reducing the recovered floc is not limited to ballast water, but is the raw water treated on land. It has similarly.

  The present invention has been made in view of such circumstances, and it is possible to reduce the amount of magnetic powder used without using chemicals such as hydrochloric acid, and to provide an agglomerated magnetic separation apparatus that can reduce the recovered flocs recovered. Objective.

  In order to achieve the object, the present invention is connected to a raw water supply pipe for supplying raw water, and rapidly stirs the raw water to which the magnetic powder and the flocculant supplied from the magnetic powder supply means are added, A first agitation tank for generating magnetic micro flocs containing the magnetic powder, and raw water in which a polymer flocculant is added to the raw water containing the magnetic micro flocs flowing out of the first agitation tank; From the raw water including the second stirring tank for coarsening the magnetic micro flocs by stirring at a lower rotational speed than the stirring tank, and the coarse flocs flowing out from the second stirring tank, the coarsening Magnetic separation means for collecting flocs by magnetic force, and a position before the flocculant is added upstream of the first agitation tank with respect to the collected flocs collected by the magnetic separation means Providing cohesive magnetic separator, characterized in that it and a return adding means for adding to the raw water and returned to the raw water supply tube.

  According to the flocculation magnetic separation apparatus of the present invention, the return floc discharged from the magnetic separation means is returned upstream to the raw water supply pipe at a position before the flocculating agent is added on the upstream side of the first stirring tank. It has addition means. The recovered floc discharged from the magnetic separation means is once stored in the recovered floc receiving tank and then returned to the raw water supply pipe by the return adding means. That is, according to the present invention, since the magnetic powder in the recovered floc is reused, the amount of magnetic powder used can be reduced without using chemicals such as hydrochloric acid, and the recovered recovered floc can be reduced. In addition, the magnetic powder separation and extraction process is not necessary. The recovered flock that is not returned is overflowed as a surplus recovered flock from the recovered flock receiving tank and separately stored in the recovered flock storage tank.

  The present invention provides a concentration detection means for detecting a concentration of suspended solids in the raw water at a position before the magnetic powder, the flocculant, and the recovered floc are added, and a suspended substance detected by the concentration detection means. Control means for controlling the return amount of the recovered floc by the return addition means and the addition amount of the magnetic powder by the magnetic powder supply means based on the concentration and the preset maximum raw water suspended solid concentration. It is preferable to provide.

  The control means of the present invention is configured so that the recovery flocs by the return adding means are based on the suspended substance concentration detected by the concentration detecting means and the preset maximum raw water suspended substance concentration (design value of the coagulation magnetic separation device). And the amount of magnetic powder added by the magnetic powder supply means is controlled. As in the present invention, by detecting the concentration of suspended solids in raw water and confirming that the concentration of suspended solids is below the maximum concentration, the separation and extraction process becomes unnecessary. Can be reused. Moreover, since the magnetic powder contained in the recovered floc can be reused, the amount of new magnetic powder used can be reduced. Furthermore, the amount of recovered flocs caused by new magnetic powder can be reduced.

  According to the present invention, the control means returns the recovered flock by the return addition means when the suspended substance concentration detected by the concentration detection means is equal to the maximum raw water suspended substance concentration. The amount of the magnetic powder added by the magnetic powder supply means is controlled, and the return amount of the recovered flocs by the return addition means as the suspended substance concentration becomes lower than the maximum raw water suspended substance concentration. It is preferable to control so that the amount of magnetic powder added by the magnetic powder supply means is decreased. As a result, in the present invention, the throughput of the flocculating magnetic separation device is stabilized without being affected by the concentration of suspended solids in the raw water.

  By the way, in the said invention, when the suspended solid density | concentration of raw | natural water exceeds the maximum raw | natural water suspended solid density | concentration, a collection | recovery flock cannot be returned to a raw | natural water supply pipe | tube. Therefore, in order to return the recovered floc and reuse the magnetic powder in the recovered floc even in such a case, in the returning process, only the magnetic powder is extracted from the recovered floc and other suspended substance components Need to be removed.

  Therefore, according to the present invention, a magnetic powder extraction means is provided in a return pipeline between the return addition means and the raw water supply pipe, and the magnetic powder extraction means includes a crushing means for crushing the recovered flock by a shearing force. The extraction means for selectively extracting only the magnetic powder from the crushed recovered floc by magnetic force, and the return means for returning the extracted magnetic powder to the raw water supply pipe.

  According to the magnetic powder extraction means of the present invention, extraction of magnetic powder from the recovered floc and removal of other suspended substance components are performed in two steps.

  In the first step, the recovery flock is crushed by applying a physical force to the recovery flock. In the recovery floc, the magnetic powder and other suspended solids components are strongly aggregated by the inorganic flocculant and polymer flocculant, so an ultrasonic crusher, line mill, or ball mill is used to crush it. To do. As a result, the recovered floc is crushed only by physical force without using chemicals such as hydrochloric acid, so there is no risk of chemical leakage and high safety. In addition, the approval procedure of IMO is simplified for ship loading.

  In the second step, the magnetic powder is extracted from the crushed recovered floc and the other suspended solid components are removed by the magnetic force of the extraction means. Then, the extracted magnetic powder is returned to the raw water supply pipe by a return means. The recovered floc to be returned has high purity of the magnetic powder contained in the recovered floc since the suspended solid components other than the magnetic powder are removed. Therefore, even when the raw water suspended substance concentration is high, the recovered floc can be returned to the raw water supply pipe.

  According to the present invention, it is preferable that a return path of the recovery flock by the return addition means is provided with a sterilization means for sterilizing plankton and fungi contained in the recovery flock.

  When the agglomerated magnetic separation apparatus of the present invention is an apparatus for ballast water treatment installed in a ship, plankton and fungi contained in the recovered flock are sterilized by sterilization means and returned to the raw water supply pipe. It will not be a new load.

  According to the agglomeration magnetic separation apparatus of the present invention, the amount of magnetic powder used can be reduced without using chemicals such as hydrochloric acid, and the recovered recovered floc can be reduced.

Overall configuration diagram of agglomerated magnetic separation apparatus according to an embodiment FIG. 1 is a schematic block diagram of a basic type agglomerated magnetic separation apparatus in which a magnetic powder extraction device is removed from the agglomerated magnetic separation apparatus shown in FIG. Schematic block diagram of the agglomeration magnetic separation apparatus shown in FIG. The graph which showed the collection | recovery flock return rates in the aggregation magnetic separation apparatus shown in FIG. The graph which showed the collection | recovery flock return rates in the aggregation magnetic separation apparatus shown in FIG. Graph showing the relationship between magnetic powder addition concentration and floc removal rate Graph showing the relationship between raw water SS and recovered flock return rate

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an agglomerated magnetic separation apparatus according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of an agglomerated magnetic separation apparatus 10 according to an embodiment. This agglomeration magnetic separation apparatus 10 includes a raw water supply pipe 12, a flocculation apparatus 14, a magnetic separation apparatus (magnetic separation means) 16, a return addition apparatus (return addition means) 18, a magnetic powder extraction apparatus (magnetic powder extraction means) 20, a heating A sterilization device (sterilization means) 22 and a control unit 24 are provided.

  In addition, although the aggregation magnetic separation apparatus 10 of embodiment is equipped with the heat sterilization apparatus 22 for the apparatus for ballast water treatment installed in a ship, in the case of the aggregation magnetic separation apparatus installed on land The heat sterilizer 22 is not an essential component. Further, in the case of a device that directly returns the recovered floc recovered by the magnetic separation device 16 to the raw water supply pipe 12 by the return addition device 18, the magnetic powder extraction device 20 is not an essential configuration.

  The aggregating apparatus 14 includes a high-speed stirring tank (first stirring tank) 26 and a slow-speed stirring tank (second stirring tank) 28, and raw water (treated water: water to be treated) supplied through the raw water supply pipe 12. Magnetic micro flocs are generated from seawater. For this reason, the raw water supply pipe 12 is provided with a magnetic powder supply device (magnetic powder supply means) 30 and a flocculant addition device 32, and a pipe line 34 for feeding water from the high-speed stirring tank 26 to the slow-speed stirring tank 28. Is provided with a polymer flocculant addition device 36.

  The magnetic powder supply device 30 has a magnetic powder injection pump 38, and the amount of new magnetic powder added to the raw water supply pipe 12 is controlled by controlling the rotational speed of the magnetic powder injection pump 38 by the control unit 24. Is done.

  Further, an SS densitometer (which may be a turbidity meter) 40 for detecting the concentration of suspended solids (hereinafter referred to as SS (Suspended Solid)) is attached to the upstream side of the raw water supply pipe 12. The SS concentration information measured by the SS concentration meter 40 is output to the control unit 24, and the control unit 24 collects the rotational speed of the magnetic powder injection pump 38 and the return addition device 18 based on the SS concentration information. The number of rotations of the flock return pump 42 is controlled. As a result, new magnetic powder and recovered floc are added to the raw water flowing through the raw water supply pipe 12. In addition, the installation position of SS concentration meter 40 is not limited to the raw | natural water supply pipe | tube 12, What is necessary is just the position before the said magnetic powder, the said flocculant, and the said collection | recovery floc are added. For example, you may install in the tank which stores raw | natural water temporarily.

  Here, for example, triiron tetroxide can be suitably used as the magnetic powder, and water-soluble inorganic flocculants such as polyaluminum chloride, ferric chloride, and ferric sulfate are suitably used as the flocculant. Can do. Moreover, as a polymer flocculent, an anionic and nonionic thing can be used conveniently.

  The high-speed stirring tank 26 has a stirring blade (not shown) that rotates at high speed to stir the raw water, the magnetic powder added to the raw water, the flocculant, and the recovered floc. The raw water to which the magnetic powder, the flocculant, and the recovered floc are added is stirred at high speed by the stirring blade. Thereby, minute magnetic micro flocs having a size of about several tens of μm are generated in the high-speed stirring tank 26. When magnetic micro flocs are generated, microorganisms and fungi in the raw water are charged and are adsorbed with magnetic powder as nuclei and taken into the magnetic micro flocs.

  The slow stirring tank 28 is configured as a multistage continuous multistage stirring tank, and a stirring blade (not shown) is provided in each stage of the stirring tank. In the slow stirring tank 28 having such a configuration, the stirring speed is set to gradually decrease from the upstream stirring tank to the downstream stirring tank. Water to be treated containing magnetic micro flocs and a polymer flocculant added to the water to be treated are fed from the high speed stirring vessel 26 to the slow stirring vessel 28. For this reason, magnetic micro flocs grow and become coarse flocs (coarse flocs) by gradually performing low-speed stirring from the upstream stirring tank to the downstream stirring tank. Further, since the stirring speed is gradually reduced, there is little possibility that the coarse floc is destroyed by the collision of the respective stirring blades.

  The magnetic separation device 16 collects the coarse floc from the water to be treated. The magnetic separation device 16 includes a magnetic separation tank 44, a magnetic filter 46, a scraper (not shown), and a transfer device 48. Water to be treated containing coarsened floc is fed from the slow stirring tank 28 to the magnetic separation tank 44. The magnetic filter 46 is, for example, a body of a rotating drum, and at least a part of the magnetic filter 46 is immersed in the water to be treated in the magnetic separation tank 44 to collect coarse flocs floating in the magnetic separation tank 44 from the water to be treated. . The recovered coarse floc (recovered floc) is pulled up from the magnetic separation tank 44 by the rotation of the magnetic filter 46 and scraped off from the magnetic filter 46 by the scraper. Then, the recovered flock that has been scraped off is transferred to the recovery flock receiving tank 50 by a transfer device 48 such as a screw conveyor, and is temporarily stored therein.

  The collected flocks stored in the collected flock receiving tank 50 are sent to the heat sterilizer 22 by the pump 42. The heat sterilizer 22 kills microorganisms and fungi contained in the recovered flock by heat-treating the recovered flock. Since the recovered floc is in the form of a slurry, it is preferable to use a positive displacement pump such as a tube pump or a single screw pump as the pump 42. In addition, the temperature for killing fungi and the like by heating is 75 to 80 ° C., and the heating time is about 3 minutes.

  On the other hand, the magnetic powder extraction device 20 includes crushing devices (crushing means) 52 and 54 for crushing the recovered flocs by shear force, and an extraction device (extraction means) for selectively extracting magnetic powder from the crushed recovered flocks by magnetic force. 56 and a pump (return means) 58 for returning the extracted magnetic powder to the raw water supply pipe 12.

  That is, the agglomeration magnetic separation apparatus 10 shown in FIG. 1 has a configuration in which a heat sterilization apparatus 22 is provided on the upstream side and a magnetic powder extraction apparatus 20 is provided on the downstream side in the return path of the recovered floc by the return addition apparatus 18. It is.

  The crushing device 52 is a line mill that rotates a specially shaped stirring blade 60 at a high speed to generate a strong shearing force. The crushing device 54 immerses a rod-like vibrator 62 that vibrates at an ultrasonic frequency to immerse a liquid 64. It is an ultrasonic crusher (frequency about 20 kHz) that generates a shear force inside. In the embodiment, the two crushing devices 52 and 54 are installed, but any one crushing device may be installed. Moreover, you may use the ball mill 65 as a crushing apparatus.

  The recovered flocks crushed by the crushing devices 52 and 54 are supplied to the extraction device 56. The extraction device 56 extracts magnetic powder from the crushed recovery flock by magnetic force. As the extraction device 56, a device using a magnetic disk or a magnetic drum in which a permanent magnet is embedded is used. As a result, magnetic powder is extracted from the recovered floc, and SS substances other than the magnetic powder are discharged.

  Since the discharge amount of SS substances other than magnetic powder is about 0.2% of the processing amount of the agglomeration magnetic separation device 10, the extraction device 56 used here is smaller than the magnetic separation device 16 of the main configuration. Anything is fine. The recovered flocs after the magnetic powder extraction process are stored in a recovered floc storage tank (not shown) as a separate recovered floc, similar to the surplus recovered floc generated in the recovered flock receiving tank 50. Since the magnetic powder extracted by the magnetic force has a low water content and poor fluidity, the magnetic powder is supplied to the tank 68 in which fresh water 66 is stored, diluted in the tank 68, and then supplied to the raw water supply pipe 12 by the pump 58. Will be returned. Thereby, magnetic powder with high purity is added to the raw water flowing through the raw water supply pipe 12. The return position of the recovery floc to the raw water supply pipe 12 and the addition position of the magnetic powder are downstream of the SS concentration meter 40 and upstream of the high-speed stirring tank 26, and upstream of the position where the flocculant is added. On the side. The rotational speed of the pump 58 is controlled by the control unit 24 based on the SS concentration information measured by the SS densitometer 40.

  Next, the operation of the aggregation magnetic separation apparatus 10 configured as described above will be described.

  The schematic block diagram shown in FIG. 2 shows a basic type agglomerated magnetic separation device 10 in which the magnetic powder extraction device 20 is removed from the agglomerated magnetic separation device 10 shown in FIG. That is, the agglomeration magnetic separation device 10 of FIG. 2 is a form in which only the heat sterilization device 22 is provided in the return route of the recovered floc by the return addition device 18.

  According to the flocculating magnetic separation device 10 of FIG. 2, a return addition device 18 is provided for returning and adding the recovered floc discharged from the magnetic separation device 16 to the raw water supply pipe 12 at a position before the flocculating agent is added. Yes. The recovered floc discharged from the magnetic separation device 16 is temporarily stored in the recovered floc receiving tank 50 (see FIG. 1) and then returned to the raw water supply pipe 12 by the pump 42 of the return adding device 18. The recovered flock that is not returned is overflowed from the recovered flock receiving tank 50 as a surplus recovered flock and separately stored in the recovered flock storage tank.

  By returning the recovered floc to the raw water supply pipe 12 as described above, the recovered floc can be reused without using chemicals such as hydrochloric acid. Thereby, since the magnetic powder contained in the recovery floc can be reused, the amount of new magnetic powder used can be reduced. In addition, the amount of recovered flocs caused by new magnetic powder is also reduced.

  On the other hand, based on the SS concentration detected by the SS densitometer 40 and the preset maximum raw water SS concentration, the control unit 24 returns the recovered flock returned by the return adding device 18 and a new one by the magnetic powder supply device 30. Control the amount of magnetic powder added.

  That is, when the SS concentration detected by the SS densitometer 40 is equal to the maximum raw water SS concentration, the control unit 24 stops the return of the recovered floc by the return adding device 18 and the new product by the magnetic powder supply device 30. Control the amount of magnetic powder added. In addition, as the SS concentration becomes lower than the maximum raw water SS concentration, the control unit 24 increases the return amount of the recovered floc by the return addition device 18 and decreases the addition amount of the new magnetic powder by the magnetic powder supply device 30. To control.

  Thereby, according to the aggregation magnetic separation apparatus 10 of FIG. 2, processing capacity is stabilized, without being influenced by SS density | concentration of raw | natural water. Reference numeral 70 denotes a filter. The filter 70 separates the treated water and the cleaning waste water from the treated water separated by the magnetic separation device 16. The washing waste water is returned to the raw water supply pipe 12 via the pipe line 72.

  Next, a specific control method by the control unit 24 will be described.

  First, as a premise, the return amount of the recovered flock is controlled within a range of 0 to 100% of the recovered flock discharge amount by the control unit 24 controlling the rotation speed of the pump 42.

  The return amount of the recovered floc is controlled by the control unit 24 based on the SS concentration of the raw water detected by the SS densitometer 40 and a preset maximum raw water SS concentration.

  For example, it is assumed that the aggregation magnetic separation device 10 is designed with a maximum raw water SS concentration of 50 mg / L. At this time, when raw water having an SS concentration of 50 mg / L flows into the raw water supply pipe 12, when 100% of the recovered floc is returned, the SS equivalent to 50 mg / L contained in the recovered floc returns to the raw water. The SS concentration that flows in is 50 + 50 = 100 mg / L, which exceeds the maximum raw water SS concentration that is the capability of the flocculating magnetic separation apparatus 10.

  On the other hand, when raw water having an SS concentration of 10 mg / L flows into the raw water supply pipe 12, there is a margin of 40 mg / L with respect to the maximum raw water SS concentration of 50 mg / L. There is no problem even if it is returned to the supply pipe 12.

  According to the trial calculation, in the case of the agglomeration magnetic separation apparatus 10 in FIG. 2, the raw water SS concentration (mg / L) (A), the returnable floc amount (the return rate of the recovered floc relative to the discharge amount) (B), and the new magnetism The relationship with the added amount of powder (mg / L) (C) is shown in the graph shown in FIG. The graph of FIG. 4 and Table 1 show the amount of recovered floc that can be returned when the design maximum raw water SS concentration is 50 mg / L.

  The vertical axis of the graph in FIG. 4 indicates the ratio of magnetic powder in the floc immediately before being fed to the magnetic separation device 16, and the horizontal axis indicates the return rate of the recovered floc with respect to the discharge amount. In order to effectively execute magnetic separation in the magnetic separation device 16, the lower limit value of the magnetic powder ratio in the floc is set to 31.6%, and the return rate of the recovered floc is set so that the magnetic powder ratio is higher than that. The amount of new magnetic powder added is determined.

  In the embodiment, the return rate of the recovered floc and the amount of new magnetic powder added are set so that the magnetic powder ratio in the flock is 31.6% of the lower limit. Specifically, as shown in Table 1, when the raw water SS concentration is 50 mg / L, the recovered floc is not returned and only new magnetic powder is added at 30 mg / L. The raw water SS concentration is detected by the SS densitometer 40, and the return amount of the recovered flock and the added amount of the new magnetic powder are controlled as shown in Table 1 according to the measurement result.

  When the agglomerated magnetic separation apparatus 10 is applied to ship ballast water treatment, the maximum raw water SS concentration is designed to be 50 mg / L according to IMO regulations. However, since the actual SS concentration of seawater is often less than 10 mg / L, the amount of new magnetic powder used can be reduced by returning the recovered floc to the raw water supply pipe 12 in this way. As a result, the necessary storage amount of new magnetic powder can be reduced, which is very advantageous in a ship where the installation space is limited. In the ballast water treatment, plankton and fungi (surviving individuals) are to be removed. Therefore, when returning the recovered flock to the raw water supply pipe 12, a heat sterilizer 22 is provided in the middle of the return pipe. Return them while killing plankton and fungi.

  On the other hand, the injection amount of the new magnetic powder is performed by the control unit 24 controlling the rotation speed of the pump 38. The control range is set to a range of 0 to 100% with the injection amount when the recovered floc is not returned to the raw water supply pipe 12 being 100% (30 mg / L). The injection amount of new magnetic powder is determined according to the return amount of the recovered floc. For example, when the recovery flock return amount is 50% of the discharge amount, 50% of the magnetic powder flowing into the high-speed stirring tank 26 is also returned, so the injection amount of the new magnetic powder may be about 50% (16 mg / L). . The return amount of the recovered floc is detected by a flow meter 74 installed in the return passage of the recovered floc, and the control unit 24 controls the number of revolutions of the pump 38 based on the measurement result. Control.

  Here, in the aggregation magnetic separation apparatus 10 of FIG. 2, when the raw water SS concentration exceeds the designed maximum raw water SS concentration, the recovered floc cannot be returned. Therefore, even in such a case, in order to return the recovered floc and reuse the magnetic powder in the recovered floc, in the returning process, only the magnetic powder is extracted from the recovered floc and other SS components are removed. There is a need to.

  The agglomerated magnetic separation device 10 of FIG. 3 is configured such that the magnetic powder extraction device 20 is disposed at the subsequent stage of the magnetic separation device 16 and the heat sterilization device 22 is disposed at the subsequent stage of the magnetic powder extraction device 20.

  That is, in the aggregated magnetic separation device 10 shown in FIG. 3, in the return route of the recovered floc by the return addition device 18, a magnetic powder extraction device 20 is provided on the upstream side, and a heat sterilization device 22 is provided on the downstream side. It is.

  In the magnetic powder extraction device 20, the extraction of the magnetic powder contained in the recovery flock and the removal of other SS components are performed in two steps in the recovery flock discharged from the magnetic separation device 16.

  In the first step, the recovery flock is crushed by applying a physical force to the recovery flock. In the recovered floc, the magnetic powder and other SS components are strongly aggregated by the inorganic flocculant and the polymer flocculant, so that the line mill 52 and / or the ultrasonic crusher 54 as shown in FIG. Is used. It has been experimentally confirmed that the recovered floc is almost decomposed by the crushing process for several tens of seconds to several minutes by the line mill 52 and / or the ultrasonic crusher 54.

  Here, as disclosed in Patent Document 2, there is a method of adjusting the pH by using a chemical to promote the decomposition of the recovered flocs. However, particularly in the case of implementation in a ship, only the physical method is considered in consideration of IMO regulations. It is desirable to disassemble the recovered floc by

  In the second step, only magnetic powder is extracted from the crushed recovered floc by magnetic force. As the extraction device 56, a device using a magnetic disk or a magnetic drum in which a permanent magnet is embedded is used. The extracted magnetic powder is diluted with fresh water 66 and then returned to the raw water supply pipe 12 by a pump 58.

  Since the purity of the magnetic powder to be returned is improved by these two steps, the recovered floc can be returned even if the raw water SS concentration becomes high.

  According to a trial calculation when 30% of SS other than magnetic powder is separated from the recovered floc, in the case of the agglomerated magnetic separator 10 in FIG. 3, the concentration of raw water SS (mg / L) (A) and the amount of recovered floc that can be returned (discharge) The relationship between the recovered floc return rate (%) (B) and the amount of new magnetic powder added (mg / L) (C) is as shown in the graph of FIG.

  This makes it possible to increase the return rate of the recovered flocs according to the concentration of the raw water SS as compared with the aggregated magnetic separation device 10 shown in FIG. Less.

  Further, if 60% of the SS component other than the magnetic powder in the recovered floc can be separated and removed by the magnetic powder extraction device 20, when the raw water SS concentration is 50 mg / L, the recovered floc is equivalent to the raw water SS concentration of 20 mg / L, and the discharge amount 50% can be returned. When there are many cases where the raw water SS concentration exceeds the design maximum raw water SS concentration, or when it is desired to return more recovered flocks and reduce the amount of new magnetic powder used, it is desirable to install the magnetic powder extraction device 20. .

[Appendix]
"Explanation on the optimum value of the magnetic powder ratio in the magnetic coagulation floc"
Plankton and fungi are treated in ballast water treatment. On the other hand, when a ballast water treatment device is installed on a ship, a treatment performance confirmation test prescribed by the supervisory authority is required, and in that provision, suspended substances (SS) such as sand are contained in ballast water at a maximum of 50 mg / L. Even ballast water is required to be able to meet the ballast water discharge standards.

  Therefore, the inventors added mineral-based fine particles called kaolin to the test water as a simulated substance such as sand in a test for determining the agglomerated magnetic separation conditions for plankton and fungi. A specific test method will be described below.

  First, the above-mentioned kaolin is added to seawater containing plankton and fungi at a concentration of 50 mg / L, and an agglomeration test is performed using the addition rates of magnetic powder, inorganic flocculant and polymer flocculant as parameters (variables). The formation state of the aggregated floc is evaluated by visual observation or the like. After that, the seawater containing magnetic coagulation floc is passed through a water channel with permanent magnets, and the magnet is contacted and adsorbed for a predetermined time (several seconds), and the concentration of magnetic coagulation floc in the seawater coming out of the water channel is determined. Measure and evaluate its removal rate.

  As a result of the above test, it was revealed that plankton and fungi can be sufficiently aggregated under the conditions that the addition rate of polyaluminum chloride used as the inorganic flocculant is 5 mg Al / L and the addition rate of the polymer flocculant is 1 mg / L.

  Further, as shown in FIG. 6, the removal rate of the aggregated magnetic flocs increased with the addition rate of the magnetic powder, and the removal rate tended to reach a peak at an addition rate of 30 mg / L or more. From the viewpoint of processing cost, it is desirable that the addition rate of magnetic powder be as small as possible, so the addition rate of magnetic powder was 30 mg / L.

  The ratio of the magnetic powder in the magnetic coagulation floc in the case of the above-mentioned magnetic powder, inorganic coagulant and polymer coagulant addition rate can be calculated from the following formula.

Magnetic powder ratio (%) in magnetic coagulation floc = (magnetic powder addition rate) / (kaolin addition rate + magnetic powder addition rate + inorganic flocculant addition rate + polymer flocculant addition rate) × 100 (Equation 1)
Here, magnetic powder addition rate = 30 mg / L, kaolin addition rate = 50 mg / L, inorganic flocculant addition rate = 5 × (78/27) = 14.4 mg / L, polymer flocculant addition rate = 1 mg / L It is. In addition, since the polyaluminum chloride added as an inorganic flocculant exists as aluminum hydroxide (Al (OH) ₃ ) in the magnetic flocculent floc, the molecular weight of Al (OH) ₃ is 78 as a coefficient with an addition rate of 5 mg Al / L. / Al molecular weight 27 is multiplied.
Substituting each numerical value into (Equation 1),
Magnetic powder ratio in magnetic coagulation floc (%) = 30 / (50 + 30 + 14.4 + 1) = 31.4 (%)
It becomes. The inventors have determined that this magnetic powder ratio is an optimal value that can minimize the processing cost while ensuring the removal rate of the magnetic aggregate flocs.

  In reusing the magnetic powder, it is necessary to configure the processing flow so as not to fall below the magnetic powder ratio in order to secure the removal rate of the magnetic aggregate floc and maintain the processing performance.

  Moreover, the graph of FIG. 7 has shown the collection | recovery flock return rate with respect to raw | natural water SS (mg / L). The recovery flock return rate is set based on this graph.

  DESCRIPTION OF SYMBOLS 10 ... Aggregation magnetic separation apparatus, 12 ... Raw water supply pipe, 14 ... Aggregation apparatus, 16 ... Magnetic separation apparatus, 18 ... Return addition apparatus, 20 ... Magnetic powder extraction apparatus, 22 ... Heat sterilization apparatus, 24 ... Control part, 26 ... High-speed stirring tank 28 ... Slow stirring tank 30 ... Magnetic powder supply device 32 ... Coagulant adding device 34 ... Pipe line 36 ... Polymer flocculant adding device 38 ... Magnetic powder injection pump 40 ... SS Densitometer 42 ... Recovery flock return pump 44 ... Magnetic separation tank 46 ... Magnetic filter 48 ... Transfer device 50 ... Recovery flock receiving tank 52 ... Crushing device (line mill) 54 ... Crushing device (ultrasonic crusher) ), 56 ... extraction device, 58 ... pump, 60 ... stirring blade, 62 ... vibrator, 64 ... liquid, 66 ... clear water, 68 ... tank, 70 ... filter, 72 ... pipe, 74 ... flow meter

Claims (5)

A magnetic micro floc containing the magnetic powder is generated by rapidly stirring the raw water to which the magnetic powder supplied from the magnetic powder supply means and the flocculant are added, connected to the raw water supply pipe for supplying the raw water. 1 stirring tank,
The magnetic micro floc is obtained by stirring raw water in which a polymer flocculant is added to the raw water containing the magnetic micro floc flowing out from the first stirring tank at a rotation speed slower than that of the first stirring tank. A second agitation tank for coarsening,
Magnetic separation means for recovering the coarse floc by magnetic force from the raw water containing the coarse floc flowing out of the second stirring tank;
The return flocs collected by the magnetic separation means are returned to the raw water supply pipe and added to the raw water at a position before the flocculant is added on the upstream side of the first stirring tank. Means,
An agglomeration magnetic separation device comprising: Concentration detecting means for detecting the concentration of suspended solids in the raw water at a position before the magnetic powder, the flocculant, and the recovered floc are added;
Based on the suspended substance concentration detected by the concentration detecting means and the preset maximum raw water suspended substance concentration, the return amount of the recovered floc by the return adding means, and the magnetic powder by the magnetic powder supplying means Control means for controlling the addition amount of
The aggregation magnetic separation apparatus according to claim 1, comprising: The control means includes
When the suspended substance concentration detected by the concentration detection means is equal to the maximum raw water suspended substance concentration, the return of the recovered floc by the return addition means is stopped, and the magnetic powder supply means The amount of magnetic powder added is controlled, and as the suspended solid concentration becomes lower than the maximum raw water suspended solid concentration, the return amount of the recovered floc by the return adding means is increased, and the magnetic powder supply means The agglomerated magnetic separation device according to claim 2, which is controlled so as to reduce the amount of magnetic powder added. The return pipeline between the return addition means and the raw water supply pipe is provided with magnetic powder extraction means,
The magnetic powder extraction means includes a crushing means for crushing the recovered flocs by a shearing force, an extracting means for selectively extracting only the magnetic powder from the crushed recovered flocks by a magnetic force, and the extracted magnetic powders as the raw water. The agglomerated magnetic separation device according to claim 1, 2 or 3, further comprising a return means for returning to the supply pipe.   The aggregation magnetic separation apparatus according to claim 4, wherein a sterilization unit for sterilizing plankton and fungi contained in the recovery flock is provided in a return path of the recovery flock by the return addition unit.

Images