JP2005137992A - Drainage treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drainage treatment apparatus which can improve a phosphorus removal effect by controlling the inflow of activated sludge into a dephosphorization means and maintain relatively strongly anaerobic condition required for phosphorus discharge by increasing sludge concentration in an anaerobic tank. <P>SOLUTION: The drainage treatment apparatus has the anaerobic tank 12 for anaerobically treating phosphorus-containing drainage with magnetic powder-containing activated sludge, and the dephosphorization means 17 for removing phosphorus from the anaerobically treated water drawn from the anaerobic tank 12. A magnetic separation means 16 for separating the magnetic powder-containing activated sludge and the anaerobically treated water is installed in the anaerobic tank. A passage 35 for supplying the separated anaerobically treated water to the dephosphorization means, a passage 38 for supplying the separated magnetic powder-containing activated sludge to the subsequent treatment tank, a passage 36 for returning dephosphorized water subjected to the dephosphorization treatment in the dephosphorization means to a treatment tank at the subsequent stage of the anaerobic tank, a separation means 18 for separating the magnetic powder-containing activated sludge from the activated sludge slurry flowing out from the subsequent treatment tank, and a passage 24 for returning the magnetic powder-containing activated sludge separated by the separation means to the anaerobic tank are installed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a wastewater treatment apparatus, and more specifically, efficiently removes phosphorus in a wastewater treatment apparatus that employs a biological dephosphorization method, and also useful phosphorus and ammonia in raw water for useful magnesium ammonium phosphate hexahydrate. The present invention relates to a wastewater treatment apparatus that can be effectively recovered as a product.

Solid-liquid separation that not only removes BOD contained in sewage and organic wastewater, but also performs solid-liquid separation of activated sludge extracted from the anaerobic tank at the latter stage of the anaerobic tank as a wastewater treatment device that removes nitrogen and phosphorus. There is known an apparatus provided with a dephosphorization means for adding a magnesium compound to a separation liquid of the solid-liquid separation means and removing ammonia and phosphorus in the separation liquid as magnesium ammonium phosphate hexahydrate. (For example, refer to Patent Document 1).
JP 2000-296399 A

  However, since the activated sludge in the anaerobic tank is finer than the activated sludge in the aerobic tank, it is difficult to perform effective solid-liquid separation by ordinary gravity sedimentation. In addition, in order to efficiently remove phosphorus, it is necessary to discharge sufficient phosphorus in an anaerobic tank. However, in the case of low-concentration drainage such as sewage, an anaerobic state necessary for discharging phosphorus is assumed. It was sometimes difficult to maintain.

  Therefore, the present invention can enhance the removal effect of phosphorus in the dephosphorization means by suppressing the inflow of activated sludge to the dephosphorization means, and can maintain a high sludge concentration in the anaerobic tank. An object of the present invention is to provide a wastewater treatment apparatus capable of maintaining the inside in a relatively strong anaerobic state necessary for discharging phosphorus.

  In order to achieve the above-mentioned object, the waste water treatment apparatus of the present invention comprises an anaerobic tank that performs anaerobic treatment of waste water containing phosphorus with magnetic powder-containing activated sludge to which magnetic powder is added, and an anaerobic treatment liquid extracted from the anaerobic tank. A wastewater treatment apparatus adopting a biological dephosphorization method comprising a dephosphorization means for removing phosphorus, wherein the activated sludge and the anaerobic treatment containing the magnetic powder in the activated sludge suspension are magnetically applied to the anaerobic tank. A path for supplying the separated anaerobic treatment liquid to the dephosphorization means, a path for supplying the separated magnetic powder-containing activated sludge to the treatment tank downstream of the anaerobic tank, and a dephosphorization. The path for returning the dephosphorization liquid after the dephosphorization treatment by means to the treatment tank downstream of the anaerobic tank, and the separation for separating the magnetic powder-containing activated sludge from the activated sludge suspension flowing out of the subsequent treatment tank Means and the separation means It is characterized in that the the magnetic powder-containing active sludge and a route for returning to the anaerobic tank.

  In addition, the dephosphorization means may add a magnesium compound to the anaerobic treatment solution to remove ammonia and phosphorus in the anaerobic treatment solution as magnesium ammonium phosphate hexahydrate, or may contain phosphorus in the anaerobic treatment solution. Acid ions are crystallized and removed as hydroxyapatite phosphate on the surface of the seed crystal, the treatment tank after the anaerobic tank is an aerobic tank, or the treatment tank after the anaerobic tank is It has an oxygen-free tank and an aerobic tank connected to the subsequent stage of the oxygen-free tank, and has a path for circulating the activated sludge suspension in the aerobic tank to the oxygen-free tank. It is a feature.

  Furthermore, a second magnetic separation means for separating a part of the magnetic powder-containing activated sludge contained in the activated sludge suspension flowing out from the aerobic tank, which is a treatment tank subsequent to the anaerobic tank, from the liquid by magnetic force; The path for returning the magnetic powder activated sludge separated by the second magnetic separation means to the anaerobic tank and the remainder of the magnetic powder activated sludge in the activated sludge suspension flowing out from the second magnetic separation means are separated from the liquid. A solid-liquid separation means, a path for extracting treated water separated by the solid-liquid separation means, and a path for returning the magnetic powder activated sludge separated by the solid-liquid separation means to the anaerobic tank. In addition, the activated sludge separated by the second magnetic separation means and the solubilized / volume-reducing means for subjecting the activated sludge separated by the solid-liquid separation means to solubilization and volume reduction treatment are provided. It is characterized by.

  According to the waste water treatment apparatus of the present invention, the activated sludge in the activated sludge suspension in the anaerobic tank is forcibly separated by magnetic force, so that an anaerobic treatment liquid having a low activated sludge concentration is supplied to the phosphorus removing means. It is possible to improve the dephosphorization efficiency in the phosphorus removing means.

  FIG. 1 is a system diagram of a wastewater treatment apparatus showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of magnetic separation means. The wastewater treatment apparatus shown in the present embodiment includes a pressurized flotation separation apparatus 11 for separating and removing suspended components and foaming components in wastewater and sewage (raw water), and magnetic powder-containing activated sludge (hereinafter referred to as magnetic powder). The anaerobic tank 12, the anaerobic tank 13 and the aerobic tank 14 for water treatment, and the first magnetic provided on the water surface of the anaerobic tank 12. Separation means 16, dephosphorization means 17 for dephosphorizing the anaerobic treatment liquid separated by the first magnetic separation means 16, and magnetism contained in the activated sludge suspension flowing out from the aerobic tank 14 The second magnetic separation means 18 for separating a part of the powder-containing activated sludge from the liquid by magnetic force, the remainder of the magnetic powder-containing activated sludge in the activated sludge suspension flowing out from the second magnetic separation means 18 and the magnetic powder Activated sludge containing no And a settling tank 19 as a solid-liquid separation means for separating.

  In the second magnetic separation means 18 and the final sedimentation basin 19, a magnetic separation sludge return path 22 for extracting the magnetically separated activated sludge and the sedimented activated sludge to the sludge receiving tank 21 and returning them to the biological reaction tank 15, and A settling separation sludge return path 23 is provided. Further, in the sludge return path 24 between the sludge receiving tank 21 and the biological reaction tank 15, the solubilization / volume reduction means 25 for solubilizing and reducing the volume (sterilization) of activated sludge, and the pH of the return sludge are provided. An alkali addition tank 26 for adding an alkali for adjustment is provided. The final sedimentation basin 19 is provided with a treated water outflow passage 27 for extracting treated water from which activated sludge has been separated. The solubilizing / volume reducing means 25 includes the solubilizing / volume reducing means 25 and an alkali addition. A bypass path 28 for bypassing the tank 26 is provided.

  In the anaerobic tank 12 and the anaerobic tank 13, stirrers 31 and 32 are provided, and in the aerobic tank 14, an aeration tube 33 is provided. Further, a nitrification liquid circulation path 34 for circulating the activated sludge suspension (nitrification liquid) in the aerobic tank 13 to the anoxic tank 13 is provided between the anoxic tank 13 and the aerobic tank 14. . In the dephosphorization means 17, the anaerobic treatment liquid inflow path 35 to which the anaerobic treatment liquid separated by the first magnetic separation means 16 is supplied, and the dephosphorization treatment liquid after the dephosphorization treatment is returned and circulated to the anoxic tank 13. A dephosphorization liquid return path 36 and a phosphorus compound extraction path 37 for extracting the phosphorus compound recovered by the dephosphorization process are provided. The first magnetic separation means 16 is provided with an activated sludge path 38 for sending the separated magnetic powder-containing activated sludge to the anaerobic tank 13 at the subsequent stage.

  In order to make the activated sludge subjected to water treatment in the biological reaction tank 15 magnetically separable by the magnetic separation means 16, 18, magnetic powder is added and mixed in advance. It is necessary to keep it in a state of being adsorbed and held on the surface. As the magnetic powder to be used, an appropriate one can be selected. However, since magnetic powder having a size of 10 μm or more is too heavy for activated sludge, it is often separated from activated sludge by gravity. Smaller ones are preferred, and usually those in the range of 0.05 to 2 μm are optimal. Although it is possible to use ultrafine magnetic powder, it is not preferable because the cost of the magnetic powder increases.

  Further, the coercive force of the magnetic powder is suitably 0 to 200 Oe, and the magnetic powder having an excessively large coercive force has the disadvantage that it aggregates due to its own magnetic force and separates from the activated sludge and settles. Furthermore, in consideration of long-term use, it is preferable to use an oxide-based magnetic powder that hardly dissolves or deteriorates in water at room temperature. 0.1 to 1.0 μm, for example, about 0.4 μm of iron trioxide powder is optimal.

  If the concentration (addition amount) of the magnetic powder is too low, a strong magnet such as a superconducting magnet is required to separate the activated sludge. Conversely, if the concentration is too high, the cost of the magnetic powder will increase. The MLVSS of the activated sludge is preferably in a concentration range of 0.01 to 10 with respect to 1, and normally, it may be set to have a concentration similar to that of the activated sludge MLVSS.

  When such magnetic powder is put into the activated sludge suspension at an appropriate position in the biological reaction tank 15 or the like, it is immediately adsorbed and held by the activated sludge, and the magnetic powder-containing activated sludge attracted to the magnet Become. Since most or all of this magnetic powder-containing activated sludge circulates with the return sludge, the addition and mixing of the magnetic powder to the activated sludge suspension usually only needs to be performed once before starting the magnetic separation. However, it can be added as appropriate according to the situation of the water treatment facility. Also, when adding magnetic powder, add an appropriate amount of magnetic powder at appropriate intervals while circulating the activated sludge so that the magnetic powder is evenly adsorbed to the entire activated sludge circulating in the system. Is preferred.

  The aerated treated water and activated sludge treated in the aerobic tank 14 can be separated only by the second magnetic separation means 18, but in this embodiment, the second magnetic separation means 18 and the final sedimentation basin 19 are used. The separation process is performed in two stages. Therefore, it is not necessary for the second magnetic separation means 18 to magnetically separate the entire amount of the magnetic powder-containing activated sludge in the activated sludge suspension, depending on the concentration of the magnetic powder-containing activated sludge and the load of the final sedimentation basin 19. More than half of the activated sludge containing magnetic powder present in the liquid, that is, 50 to 99.5% may be separated. Also, in the first magnetic separation means 16, it is preferable that the activated sludge containing magnetic powder can be completely separated. However, since a small amount of activated sludge containing magnetic powder may flow into the dephosphorization means 17, What is necessary is just to be able to isolate | separate most magnetic powder containing activated sludge which exists in.

  Various types of magnetic separation means 16 and 18 for separating the magnetic powder-containing activated sludge from the suspension can be used. For example, as shown in FIG. 2, a magnetic separation tank 43 having an inflow portion 41 and an outflow portion 42 of an activated sludge suspension, a rotating drum 44 having a magnet disposed on the outer peripheral surface, and magnetic powder adhered to the rotating drum 44. A magnetic separator provided with a scraper 46 that scrapes off the contained activated sludge 45 and a sludge collection trough 47 that collects the magnetic powder-containing activated sludge 45 scraped off by the scraper 46 can be used.

  The outflow portion 42 is connected to the anaerobic treatment liquid inflow path 35 in the first magnetic separation means 16, and is connected to the final sedimentation basin 19 in the subsequent stage in the second magnetic separation means 18. The sludge recovery trough 47 is connected to the activated sludge path 38 in the first magnetic separation means 16 and connected to the magnetic separation sludge return path 22 in the second magnetic separation means 18. A delivery pump is installed in each path as necessary, and a driving motor (not shown) is connected to the rotating drum 44.

  The magnet provided on the rotating drum 44 can be a special magnet such as a superconducting magnet or an electromagnet, but it is not necessary to separate all of the magnetic powder-containing activated sludge from the suspension. Permanent magnets that can be obtained at low cost, such as ferrite magnets, can be used. The arrangement of the magnetic poles on the drum peripheral surface is preferably in a state where N poles and S poles are alternately arranged at a magnetization interval of 2 to 20 mm. When this magnetization interval is narrowed, the saturated adhesion amount of the magnetic powder-containing activated sludge is reduced, and when the magnetization interval is widened, the adhesion force of the magnetic powder-containing activated sludge is weakened. The size (diameter and length) of the rotating drum 44 and the number of rotations during the magnetic separation process are arbitrary and can be selected according to the processing amount, taking into consideration the installation space, manufacturing cost, operating cost, etc. You only have to set it.

  Collection of the magnetic powder-containing activated sludge separated from the suspension by magnetic force can be performed by any method depending on the structure and shape of the magnet, and various shapes of magnets such as plates, disks, rods, etc. The sludge recovery means can be combined with the shape of these magnets, etc., but the magnetic powder-containing activated sludge 45 separated magnetically can be easily recovered in a continuous state by the combination of the rotating drum 44 and the scraper 46. Can do. In addition, by using a rotating drum-shaped magnet, the configuration of the apparatus can be simplified, the manufacturing cost of the magnetic separation apparatus can be reduced, and maintenance and inspection can be easily performed.

  Here, among the microorganisms constituting the activated sludge, most of the floc-forming bacteria that easily hold the magnetic powder are separated by the second magnetic separation means 18, but filamentous fungi and dispersibility that cannot hold the magnetic powder alone. Most of the microorganisms pass through the second magnetic separation means 18 and are settled and separated in the final sedimentation tank 19. Therefore, the activated sludge can be more reliably separated from the treated water by combining the second magnetic separation means 18 and the final sedimentation basin 19.

  On the other hand, since only the floc-forming bacteria separated and recovered by the magnetic separation means 18 are returned to the biological reaction tank 15, the activated sludge in the biological reaction tank 15 can be mainly composed of floc-forming bacteria. However, in this case, excess sludge is generated from the final sedimentation basin 19. In order to prevent the generation of this excess sludge, part or all of the returned sludge returned from the sludge receiving tank 21 to the biological reaction tank 15 is solubilized and reduced in volume according to the activated sludge concentration in the system. The activated sludge is solubilized and volume-reduced using ozone, chlorine, hydrogen peroxide, ultrasonic waves, or the like.

  Thereby, while the activated sludge density | concentration in a system can be maintained in a suitable range, the filamentous fungi etc. which are the causative bacteria of a bulking can be extinguished, and an excess sludge does not generate | occur | produce from the final sedimentation basin 19. The solubilization / volume reduction means 25 is installed in the sedimentation / separation sludge return path 23 so that the activated sludge is solubilized / volume-reduced only for the sedimentation / separation sludge separated in the final sedimentation basin 19. May be.

  The pressurized levitation separator 11 mixes the raw water flowing in from the raw water inflow path 51 and the pressurized air dissolved water supplied from the pressurized water path 52, introduces them into the tank, and generates from the pressurized air dissolved water. Floating matters, suspended components, and foaming components in raw water are lifted and separated by fine bubbles. Floating matters and suspended components in raw water adhere to fine bubbles generated from pressurized air-dissolved water. As a result, the apparent specific gravity is reduced and floats as flotation sludge (floss) on the tank upper part of the pressurized flotation separation device 11. At the same time, foaming components such as surfactants in the raw water are foamed by the fine bubbles and are formed in the upper part of the tank. Surface.

  The floss and foam that have floated to the upper part of the tank are scraped off by the scraper 53 or the like and extracted to the floating material collection path 54. In addition, the solid matter (primary sedimentation sludge) that has settled at the bottom of the pressurized flotation separation device 11 is extracted to the sediment collection path 55. Such a pressure levitation separation device 11 has a higher removal rate of suspended components than ordinary precipitation treatment, and also has foam components, oil, scum, etc., in addition to coarse suspended matter and threadlike suspended hair. This has the advantage that it can be removed almost completely in a short time.

  Further, the floss and solids separated by the pressurized flotation separation device 11 are introduced into the methane fermentation means 56 from the levitated substance recovery path 54 and the sediment recovery path 55 and subjected to methane fermentation treatment, followed by initial precipitation. After being introduced into the sludge solubilization / volume reduction treatment means 57 and subjected to the solubilization treatment and volume reduction treatment, the sludge is introduced into the biological reaction tank 15 through the initial sedimentation sludge path 58.

  In this way, by performing methane fermentation treatment with the methane fermentation means 56 on the floss and solid matter separated by the pressurized flotation separation device 11, it is possible to use primary sedimentation sludge with good fermentability as a raw material. While improving the efficiency of fermentation, the amount of excess sludge after methane fermentation can also be reduced. Further, the surplus sludge is subjected to solubilization and volume reduction treatment such as ozone treatment, alkali treatment and ultrasonic treatment by the solubilization / volume reduction treatment means 57, and then added to the biological reaction tank 15 to add the excess sludge. Although it is possible to eliminate the generation of excess sludge from the pressure levitation separation device 11, in this embodiment, a part of the initial settling sludge is branched to the dehydrator 59 and dehydrated, so that effective use of compost and the like is achieved. Or disposed of.

  In the previous stage of the pressurized flotation separation device 11, as a pretreatment facility for the inflow raw water, a raw water tank 63 having a screen 61 for removing coarse solids and a stirrer 62 for homogenizing the raw water, and a pH in the raw water An adjusting tank 66 having chemical tanks 64 and 65 for adding the adjusting agent and the flocculant is provided. In addition, a general thing can be used for a pH adjuster and a flocculant, and a suitable thing can be selected according to the property of raw | natural water, and it can also abbreviate | omit. The pressurized flotation separation device 11 includes a pressurization path 67 for extracting a part of the flotation separation water from the separation water outlet side, water added to the pressurization path 67 and pressurized by a pump and a compressor. An air dissolution tank 68 for generating the pressurized air dissolved water by mixing with the pressurized air is provided, and the pressurized air dissolved water generated in the air dissolution tank 68 passes through the pressurized water path 52 and enters the inflow path 51. It is formed to join the raw water.

  Furthermore, by combining such a pressurized flotation separation device 11 and the anaerobic tank 12, most of the foam components in the raw water can be removed by the pressurized flotation separation apparatus 11. Since the foam component remaining in the water can be removed by adsorbing the activated sludge (microbe floc) or decomposing it with the activated sludge, the foam component almost always flows into the aerobic tank 14 on the downstream side. Thus, it is possible to prevent the magnetic separation effect of the second magnetic separation means 18 from being impaired by foaming in the aerobic tank 14.

  The raw water flowing into the wastewater treatment apparatus formed in this way flows into the anaerobic tank 12 of the biological reaction tank 15 via the pressurized flotation separation apparatus 11 and circulates from the sludge return path 24 (activated sludge containing magnetic powder). And it will be in the state mixed with the primary sedimentation sludge from the primary sedimentation sludge path | route 58. FIG. By the anaerobic treatment in the anaerobic tank 12, the phosphorus accumulating bacteria in the activated sludge discharges the phosphorus taken in the aerobic tank 14 into the anaerobic tank 12, and the phosphorus concentration in the activated sludge suspension in the anaerobic tank 12 increases. To do. The activated sludge suspension is separated from the magnetic powder-containing activated sludge by the first magnetic separation means 16 and introduced into the dephosphorization means 17 as an anaerobic treatment liquid containing phosphorus at a high concentration, and a predetermined dephosphorization operation is performed. .

An appropriate dephosphorization method can be applied to the dephosphorization means 17, and a MAP method or a crystallization method can be employed. For example, in the MAP method, ammonium ions contained in an anaerobic treatment liquid, phosphate ions released from activated sludge, and magnesium ions from a magnesium compound to which a necessary amount is added are reacted at a predetermined pH. Produces crystalline ammonium ammonium phosphate hexahydrate (MAP: Strabite: MgNH ₄ PO ₄ .6H ₂ O), which is separated and recovered. The collected MAP can be used, for example, as a slow-acting fertilizer, and can be effectively recycled as a fertilizer containing the three major nutrients of plants by mixing with potassium salts and processing such as granulation. it can. In the crystallization method, phosphate ions contained in the anaerobic treatment liquid are crystallized as phosphate hydroxyapatite (HAP: Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ ) in a seed crystal such as calcium silicate hydrate. By analyzing, phosphorus is collected, and this can be used as it is as a fertilizer. The dephosphorization solution from which phosphorus has been removed by the dephosphorization means 17 is returned to the oxygen-free tank 13 and reprocessed.

  In addition, the organic matter in the raw water is purified by being sequentially treated with activated sludge in the anaerobic tank 12, the oxygen-free tank 13, and the aerobic tank 14, and the activated sludge ingests phosphorus in the aerobic tank 14. Underwater phosphorus is removed. Further, by circulating the nitrification liquid from the aerobic tank 14 to the oxygen-free tank 13, nitrogen in the raw water is also removed in the oxygen-free tank 13. The activated sludge suspension after the aeration treatment in the aerobic tank 14 flows into the second magnetic separation means 18, and a part of the magnetic powder-containing activated sludge in the suspension is magnetically separated.

  The amount of activated sludge separated in the second magnetic separation means 18 is set according to the balance between the activated sludge growth and auto-oxidation in the biological reaction tank 15 and the load of the final sedimentation basin 19. Usually, it is preferable that the activated sludge concentration in the activated sludge suspension flowing into the final sedimentation basin 19 is set to 3000 mg / L or less, preferably 2000 mg / L or less, particularly 1500 mg / L or less.

  Generally, the BOD concentration of sewage flowing into the sewage treatment plant is about 100 to 200 mg / L. In the aerobic tank 14 under this load condition, when the activated sludge concentration is in the range of 5000 to 10000 mg / L, the activated sludge is balanced with the self-oxidation, and the surplus sludge is hardly generated. Therefore, by separating 80% of the activated sludge by the second magnetic separation means 18, the activated sludge concentration flowing into the final sedimentation basin 19 can be 1000 to 2000 mg / L. Within this activated sludge concentration range, it is possible to perform sufficient sedimentation separation in the final sedimentation basin 19.

  At this time, even if the entire amount of the activated sludge separated by the second magnetic separation means 18 and the final sedimentation basin 19 is returned to the biological reaction tank 15, in the normal conditions, the growth of the activated sludge itself and auto-oxidation are reduced. Since the increase in the activated sludge concentration is automatically stopped by the balance, the maintenance and management of the activated sludge concentration can be made unnecessary. At this time, the activated sludge concentration in the equilibrium state naturally fluctuates with the load variation, but the activity in the second magnetic separation means 18 does not exceed the allowable sludge concentration in the final sedimentation basin 19 even at the maximum load. By setting the amount of sludge separation, water treatment can be continued in a state where the activated sludge concentration is high regardless of load fluctuations.

  By maintaining the activated sludge concentration in a sufficiently high state in this way, the intake of phosphorus in the aerobic tank 14 and the discharge of phosphorus in the anaerobic tank 12 can be performed with high efficiency. In particular, the activated sludge concentration is increased. Since it can do, even when processing low concentration drainage like sewage, it becomes easy to maintain the comparatively strong anaerobic state required for the discharge of the phosphorus in the anaerobic tank 12, and an effective dephosphorization process can be performed.

  Furthermore, by separating most of the activated sludge with the second magnetic separation means 18, it is possible to prevent the final sedimentation basin 19 from exceeding the allowable sludge concentration even if the activated sludge concentration in the biological reaction tank 15 increases to some extent. Further, negative emission in which excess sludge from the outside is introduced into the biological reaction tank 15 and auto-oxidized is also possible. Further, even when the amount of water flowing into the final sedimentation basin 19 increases due to the inflow of rainwater, the activated sludge that has captured the magnetic powder has a higher specific gravity and better sedimentation than ordinary activated sludge. Thus, since floc-forming bacteria can be preferentially grown, sufficient sedimentation separation can be performed in the final sedimentation basin 19. For example, if the capacity of the second magnetic separation means 18 is set so that the MLVSS concentration flowing into the final sedimentation basin 19 is about 1000 mg / L even when the flow rate is increased by rainwater, it is usually set to about 3 to 4 hours. Even if the residence time of the final sedimentation basin 19 is about half, adverse effects on sedimentation separation can be almost eliminated.

  In addition, since the second magnetic separation means 18 does not need to separate the entire amount of the magnetic powder-containing activated sludge, the required amount of activated sludge can be separated in a very short time. Even when the separation / removal rate is 99.5%, the magnetic separation can be performed in several seconds to several tens of seconds, so that the treatment can be performed in a volume of about 1/100 to 1/10000 of the volume of the final sedimentation tank 18. Therefore, the second magnetic separation means 18 may be inserted between the biological reaction tank 15 and the final sedimentation basin 19 in the existing water treatment facility. Since it can be installed in the inflow section with small modifications, it can be easily applied not only to new water treatment facilities but also to existing water treatment facilities. Similarly, the first magnetic separation means 16 can also be installed at an arbitrary position.

  In the present embodiment, the final sedimentation basin 19 that settles and separates activated sludge by gravity is exemplified as the solid-liquid separation means subsequent to the second magnetic separation means, but even when membrane separation is adopted as the solid-liquid separation means. Further, since clogging of the membrane can be suppressed and the interval between cleaning operations can be made wider than before, the lifetime of the membrane can be increased, and the cost for membrane separation can be reduced. Furthermore, when it is not necessary to remove nitrogen in the wastewater treatment, the oxygen-free tank 13 can be omitted. In this case, the dephosphorization solution from the dephosphorization means 17 may be sent to the aerobic tank 14.

  The waste water treatment apparatus of the present invention can be suitably used for the purpose of recovering phosphorus as a useful substance from waste water containing phosphorus.

It is a systematic diagram of the waste water treatment equipment showing an example of the present invention. It is sectional drawing which shows an example of a magnetic separation means.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Pressure floating separator, 12 ... Anaerobic tank, 13 ... Anoxic tank, 14 ... Aerobic tank, 15 ... Biological reaction tank, 16 ... 1st magnetic separation means, 17 ... Dephosphorization means, 18 ... 2nd magnetism Separation means, 19 ... final sedimentation basin, 21 ... sludge receiving tank, 22 ... magnetic separation sludge return path, 23 ... sedimentation separation sludge return path, 24 ... sludge return path, 25 ... solubilization / volume reduction means, 26 ... alkali addition Tank, 27 ... treated water outflow route, 28 ... bypass route, 31, 32 ... stirrer, 33 ... diffuser tube, 34 ... nitrification solution circulation route, 35 ... anaerobic treatment solution inflow route, 36 ... dephosphorization treatment solution return route, 37 ... Phosphorus compound extraction path, 38 ... Activated sludge path, 41 ... Inflow part, 42 ... Outflow part, 43 ... Magnetic separation tank, 44 ... Rotating drum, 45 ... Magnetic powder containing activated sludge, 46 ... Scraper, 47 ... Sludge Recovery trough, 51 ... Raw water inflow path, 52 ... Pressurized water path, 53 ... scraper, 54 ... floated material recovery path, 55 ... sediment recovery path, 56 ... methane fermentation means, 57 ... solubilization / volume reduction processing means, 58 ... first sedimentation sludge path, 59 ... Dehydrator, 61 ... screen, 62 ... stirrer, 63 ... raw water tank, 64, 65 ... chemical tank, 66 ... adjustment tank, 67 ... pressure path, 68 ... air dissolution tank

Claims (7)

  Biological desorption provided with an anaerobic tank in which wastewater containing phosphorus is anaerobically treated with magnetic powder-containing activated sludge to which magnetic powder is added, and a dephosphorization means for removing phosphorus from the anaerobic liquid extracted from the anaerobic tank. A wastewater treatment apparatus employing a phosphorus method, wherein the anaerobic tank is provided with magnetic separation means for separating the magnetic powder-containing activated sludge and the anaerobic treatment liquid in the activated sludge suspension by magnetic force, and the separated anaerobic A path for supplying the treatment liquid to the dephosphorization means, a path for supplying the separated magnetic powder-containing activated sludge to the treatment tank downstream of the anaerobic tank, and a dephosphorization liquid after dephosphorization treatment by the dephosphorization means are anaerobic A path for returning to the treatment tank at the rear stage of the tank, a separation means for separating the magnetic powder-containing activated sludge from the activated sludge suspension flowing out of the latter-stage treatment tank, and a magnetic powder-containing activated sludge separated by the separation means. Return to the anaerobic tank Wastewater treatment apparatus characterized by comprising and.   The waste water treatment apparatus according to claim 1, wherein the dephosphorization means removes ammonia and phosphorus in the anaerobic treatment liquid as magnesium ammonium phosphate hexahydrate by adding a magnesium compound to the anaerobic treatment liquid. .   The waste water treatment apparatus according to claim 1, wherein the dephosphorization means removes phosphate ions in the anaerobic treatment liquid by crystallization on the surface of seed crystals as phosphate hydroxyapatite.   The waste water treatment apparatus according to claim 1, wherein the treatment tank downstream of the anaerobic tank is an aerobic tank.   The treatment tank subsequent to the anaerobic tank has an oxygen-free tank and an aerobic tank connected to the latter stage of the oxygen-free tank, and the activated sludge suspension in the aerobic tank is circulated to the oxygen-free tank. The wastewater treatment apparatus according to claim 1, further comprising a path.   A second magnetic separation means for separating a part of the magnetic powder-containing activated sludge contained in the activated sludge suspension flowing out from the aerobic tank from the liquid by magnetic force, and a magnetic material separated by the second magnetic separation means. A path for returning the powder activated sludge to the anaerobic tank, a solid-liquid separation means for separating the remainder of the magnetic powder activated sludge in the activated sludge suspension flowing out of the second magnetic separation means from the liquid, and the solid-liquid The waste water according to claim 4 or 5, comprising a path for extracting treated water separated by the separation means and a path for returning the magnetic powder activated sludge separated by the solid-liquid separation means to the anaerobic tank. Processing equipment.   The activated sludge separated by the second magnetic separation means and the solubilization / volume reduction means for subjecting the activated sludge separated by the solid-liquid separation means to solubilization and volume reduction treatment are provided. Item 7. A wastewater treatment apparatus according to item 6.

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