JP2007244994A - Treatment method of digestion sludge and treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of digestion sludge and treatment equipment, capable of preventing scale deposition in a sludge-feeding pipe for feeding digestion sludge to a sludge treatment installation such as sludge fusion equipment by efficiently removing or recovering soluble phosphate ions of high concentration included in the digestion sludge in a short time as solid particles of ammonium magnesium phosphate (MAP) and reducing the soluble phosphate ions serving as a factor component for causing scaling. <P>SOLUTION: The treatment equipment of digestion sludge comprises: a reactor 21 provided with a digestion sludge injection pipe 24 for injecting the digestion sludge, a magnesium compound injection pipe 25, a gas blow pipe 26 for aeration, a MAP draw pipe 27 for drawing out the digestion sludge containing MAP particles and a treated sludge outflow pipe 28 for discharging the treated digestion sludge; a separator 22 which is connected to the MAP draw pipe 27 and separates the MAP particles from the digestion sludge; and a separated sludge return pipe 23 for returning the digestion sludge passing through the separator 22 to the reactor 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention removes soluble phosphate phosphorus from anaerobic digested sludge, and reduces soluble phosphate phosphorus, which is a scaling factor, to prevent scaling of magnesium ammonium phosphate and calcium phosphate compounds. The present invention relates to a digested sludge treatment method and treatment equipment.

Conventionally, when sludge generated from a sewage treatment facility is sent to a sludge treatment facility such as a sludge melting facility, phosphate ions (PO ₄ ³⁻ ), magnesium ions (Mg ²⁺ ), ammonium ions contained in the sludge (NH ₄ ⁺ ) produces magnesium ammonium phosphate (MgNH ₄ PO ₄ .6H ₂ O; hereinafter referred to as MAP) in the pipe, phosphate ion (PO ₄ ³⁻ ), calcium ion (Ca ²⁺ ). Reacts to form calcium phosphate compounds and precipitates on the inner wall of the pipe to form a scale, gradually reducing the diameter of the mud pipe, and in the worst case, the mud pipe may eventually be blocked. there were.

  When the mud is sent after the volume of sludge is reduced by the anaerobic digester, the concentration of each ion forming MAP is high, and the above tendency increases. In particular, along with the advanced treatment of sewage treatment facilities in recent years, sludge to which biological dephosphorization is applied has a high phosphate ion concentration discharged by anaerobic digestion, and there is a possibility that clogging of the mud pipe may be accelerated. It was.

  As a method to prevent clogging of the mud pipe, conventionally, a large amount of iron or aluminum inorganic flocculant is added, and the phosphate ion concentration in the digested sludge is reduced below the saturation concentration of MAP production, and MAP production reaction However, this method requires a large amount of flocculant, and the addition of a large amount of metal salt can lead to the use of refractory materials in the subsequent sludge treatment facility, particularly the sludge melting facility. The impact was a concern.

  As a method for solving such a problem, an aeration apparatus is provided upstream of a pipeline for transporting sludge, the sludge is aerated in advance with this aeration apparatus, the pH is increased by decarboxylation, and components that cause MAP are generated. A removal method (for example, see Patent Document 1) is known. However, in the method described here, usually, the digested sludge contains moles of phosphate ions greater than the number of moles of magnesium ions, and the MAP reaction is an equivalent reaction of magnesium ions and phosphate ions. A considerable amount of acid ions is expected to remain.

  A method of separating MAP particles generated in the above method with a centrifuge (for example, see Patent Document 2) is known. However, in this method as well, as described above, it is expected that a considerable amount of phosphate ions will remain because the magnesium ions previously contained in the digested sludge are used in the MAP reaction.

  Furthermore, a processing method and a processing apparatus (see, for example, Patent Document 3) are known in which a magnesium source is added to a digester and the generated MAP crystals are separated. However, in the method and apparatus described herein, adding a magnesium source directly into the digester may cause a MAP reaction in the digester and facilitate scaling of the MAP in the digester. . Once a failure due to scaling in the digester occurred, there was a major problem that the operation of the entire treatment facility was stopped.

  Furthermore, a processing method and a processing apparatus (for example, refer to Patent Document 4) including a digestion tank and a MAP ripening tank capable of adding a magnesium source at a subsequent stage are known. However, since the method and apparatus described here are a method and apparatus for returning a liquid containing fine MAP to the digester, there is a risk of causing MAP accumulation or scaling in the digester. It was.

  On the other hand, conventionally, a method and an apparatus (for example, refer to Patent Document 5) are known in which a magnesium compound is added to wastewater containing ammonium ions and phosphate ions, and the wastewater is stirred by aeration to generate MAP solid particles. Yes.

Furthermore, an apparatus that collects fine MAP particles with a liquid cyclone (for example, see Patent Document 6) and an apparatus that efficiently collects generated MAP solid particles with a screen (for example, see Patent Document 7) are known. However, the devices described in these documents are intended for wastewater having a sludge concentration of several thousand mg / L or less, such as digested sludge dehydrated filtrate and human urine effluent, and sludge having a sludge concentration of about tens of thousands mg / L. There was no knowledge about the production and recovery of MAP at high sludge concentration.
JP 2000-271595 A JP 2001-162300 A Japanese Patent Laid-Open No. 2004-941 JP 2004-160300 A Japanese Patent No. 2578136 Japanese Patent No. 3681073 JP-A-9-117774

  The present invention removes or recovers high-concentration soluble phosphate ions contained in digested sludge as MAP solid particles efficiently and in a short time, and reduces soluble phosphate ions, which are factors that cause scaling. Thus, an object of the present invention is to provide a digested sludge treatment method and treatment equipment capable of preventing scale adhesion in a sludge pipe that sends digested sludge to a sludge treatment facility such as a sludge melting facility.

  As a result of intensive studies to solve such problems, the present inventors have applied soluble solubilized phosphate ions contained in digested sludge by applying the so-called MAP method to digested sludge having a high sludge concentration. The present inventors have found the fact that can be efficiently removed in a short time and can be recovered as MAP solid particles if necessary.

  That is, according to the first aspect of the present invention, digested sludge is supplied to a reaction tank, a magnesium compound is added to the reaction tank, and the inside of the reaction tank is aerated to thereby dissolve soluble phosphate phosphorus contained in the digested sludge. A digested sludge treatment method characterized by insolubilizing magnesium ammonium phosphate particles and then discharging the digested sludge containing magnesium ammonium phosphate particles from the reaction vessel.

  The second aspect of the present invention is to supply digested sludge to a reaction tank, add a magnesium compound to the reaction tank and aerate the inside of the reaction tank, thereby converting soluble phosphate phosphorus contained in the digested sludge into magnesium phosphate. A digested sludge treatment method characterized by obtaining digested sludge having a reduced concentration of soluble phosphate phosphorus by insolubilizing as ammonium particles and then removing magnesium ammonium phosphate particles from the digested sludge. To do.

  A third aspect of the present invention is a digested sludge injection tube for injecting digested sludge, a magnesium compound injection tube, a gas blowing tube for aeration, a drawing tube for extracting digested sludge containing magnesium ammonium phosphate particles, and a treatment A reaction tank provided with a treated sludge outflow pipe for discharging the digested sludge, a separation apparatus connected to the extraction pipe, for separating magnesium ammonium phosphate particles from the digested sludge, and the separation apparatus The digested sludge treatment facility is characterized by having a separated sludge return pipe for returning the digested sludge to the reaction tank, and preferably, the separation device is a screen. It is a treatment facility for digested sludge, and it is preferably connected to the treated sludge outflow pipe, and the fine magnesium phosphate ammonia discharged from this treated sludge outflow pipe. The digested sludge treatment facility is characterized in that a recovery device for recovering um particles is installed, and more preferably, the recovery device is a liquid cyclone. It is a processing facility.

  As described above, according to the present invention, a high concentration of soluble phosphate ions, which are components that cause scaling, can be efficiently removed and recovered as solid MAP particles in a short time from digested sludge. Scale adhesion in the sludge pipe sent to sludge treatment facilities such as sludge melting equipment can be prevented. The collected MAP particles can also be effectively used as a slow-acting chemical fertilizer that maintains the fertilization effect.

Embodiments of the present invention will be specifically described below with reference to the drawings.
The digested sludge that is the subject of the present invention contains phosphate ions and ammonium ions in addition to sludge insolubles, and those containing a high concentration of phosphate ions are particularly suitable. A typical example of such digested sludge is applied to reduce and stabilize the initial sedimentation basin sludge (raw sludge) and / or final sedimentation basin sludge (excess sludge) generated from a sewage treatment facility. Examples include digested sludge (anaerobic digested sludge) extracted from an anaerobic digester.

Next, the digested sludge treatment method of the present invention will be described with reference to the flow sheets of FIGS.
FIG. 1 shows a flow according to the first treatment method of the present invention, in which soluble phosphate phosphorus in digested sludge is insolubilized as MAP, and solid particles of MAP coexist in digested sludge. It is a flowchart of the method of mud feeding. First, the digested sludge 2 extracted from the anaerobic digester 1 is supplied to the reaction tank 3. While adding the magnesium compound 4 to this reaction tank 3, the inside of the reaction tank 3 is aerated by blowing in air 5. By these operations, the soluble phosphate phosphorus contained in the digested sludge 2 becomes insoluble MAP. Thereafter, the treated sludge 6 which is digested sludge containing MAP particles is discharged from the reaction tank 3 and sent to the next step 7 of the sludge treatment.

In the reaction tank 3, by adding a magnesium compound that is deficient in an amount equivalent to phosphate ions to phosphate ions and ammonium ions contained in a large amount in the digested sludge 2, the reaction formula (1) MAP is generated and grows into solid particles.
PO ₄ ³⁻ + NH ₄ ⁺ + Mg ²⁺ + 6H ₂ O → MgNH ₄ PO ₄ .6H ₂ O ↓ (MAP) (1)
In the reaction of formula (1), the higher the pH, the more the chemical equilibrium reaction moves to the right side, and the phosphorous phosphorus concentration in the digested sludge 2 decreases, so the addition of an alkaline agent such as caustic soda in the reaction tank 3 However, since the carbon dioxide in the digested sludge 2 is expelled by aeration in the reaction tank 3 and the pH rises as a result, it is not always necessary to adjust the pH. The optimum pH of the formula (1) is usually preferably in the range of 7.0 to 9.5, more preferably in the range of 7.5 to 9.0, and 8.0 to 8.5. The range of is most preferable.

  The magnesium compound 4 to be added is not particularly limited as long as it is a compound containing magnesium such as magnesium chloride or magnesium hydroxide, but it is an alkali agent itself, and it is preferable to use inexpensive magnesium hydroxide. The amount of magnesium added depends on the magnesium ion concentration contained in the digested sludge 2, but usually, the number of moles of magnesium is 0.8 to the number of moles of soluble phosphate phosphorus in the digested sludge 2. It is preferable to add so that it may become 2.5 times, Furthermore, the range of 0.9-2.0 times is preferable, The range of 1.0-1.5 times is the most preferable.

The aeration gas is not particularly limited as long as it is a gas having a low carbon dioxide content, but usually air may be used. Aeration amount, relative to the bottom area of the reaction tank 3, usually 5~100m ³ / ^{m 2} / range when, preferably 8~70m ³ / ^{m 2} / range when, more preferably 10 to 50 m ³ / A range of m ² / hour is most preferred.

  In the present invention, the reaction tank 3 is preferably stirred and mixed in order to advance the chemical reaction of the formula (1). Examples of the stirring method include, but are not limited to, the stirring method by aeration, the mechanical stirring method by rotating the stirring blade, the circulating mixing method by the pump in the reaction tank 3, and the like.

  FIG. 2 shows a flow according to the second treatment method of the present invention. After the soluble phosphate phosphorus in the digested sludge is insolubilized as MAP in the same manner as in the first treatment method, It is a flowchart of the method of obtaining the digested sludge by which the density | concentration of soluble phosphorous phosphorus was reduced by removing the solid particle of MAP from digested sludge. The MAP generated in the reaction tank 3 is extracted from the MAP extraction tube 8 while being contained in the digested sludge 2 and supplied to the separation device 9. In the separator 9, the MAP particles 10 are removed from the digested sludge 2, and the digested sludge 11 from which the MAP particles 10 have been removed is returned to the reaction tank 3. The digested sludge 11 from which the MAP particles have been removed and the concentration of soluble phosphate phosphorus has been reduced is sent from the reaction tank 3 to the next process 7 of the treated sludge. In the second treatment method of the present invention, a collection device 12 for collecting fine MAP particles contained in the treated sludge is provided between the reaction tank 3 and the next step 7. The collected fine MAP particles are returned to the reaction vessel 3 through the return path 13. Reference numeral 14 denotes a recovery device processing sludge pipe between the recovery device 12 and the next step 7.

  The stirring method in the second treatment method of the present invention is not particularly limited, such as a mechanical stirring method by rotation of a stirring blade, a circulating mixing method by a pump in the reaction tank 3, and the like. In consideration of the reaction efficiency, a method of blowing and agitating aeration gas from the lower part of the reaction tank 3 as the air stirring type vertical double cylindrical reaction tank as will be described later is most preferable.

  In the present invention, the method for removing the MAP particles 10 from the digested sludge 2 is not particularly limited, such as a gravity sedimentation method using a specific gravity difference or a centrifugal separation method. The method of removing is most suitable.

  The MAP particles 10 removed by the separation device 9 are discharged from one end of the separation device 9, while the digested sludge 11 from which the MAP particles 10 have been removed and the concentration of soluble phosphorous phosphorus has been reduced passes through the separation sludge return pipe. 3 is returned.

  Next, the digested sludge treatment facility of the present invention will be described with reference to FIG. The treatment facility of the present invention mainly comprises a reaction tank 21, a separation device 22, and a separated sludge return pipe 23. In the reaction tank 21, a digested sludge injection pipe 24 for injecting digested sludge, a magnesium compound injection pipe 25 for supplying a magnesium compound, a gas blowing pipe 26 for aeration, and a digested sludge containing MAP solid particles. A MAP extraction pipe 27 and a treated sludge outflow pipe 28 are provided.

  The separation device 22 is connected to the reaction tank 21 via a MAP extraction pipe 27, and separates the MAP solid particles from the digested sludge containing the MAP solid particles extracted from the reaction tank 21. The digested sludge from which the MAP has been removed and the liquid containing fine MAP solid particles that could not be separated by the separation device 22 are returned to the reaction tank 21 through the separated sludge return pipe 23.

The reaction tank 21 in the treatment facility of the present invention is not particularly limited in form, but preferably an air stirring type vertical double cylindrical reaction tank as shown in FIG. 3 is used.
Next, the details of the air stirring type vertical double cylindrical reactor will be described with reference to FIG. The reaction tank 21 includes a reaction tank straight body part 29, a reaction tank cone part 30 positioned below the reaction tank straight part 29, and a reaction tank precipitation part located at an upper part of the reaction tank straight body part 29 and having a larger diameter than the reaction tank straight body part 29. The reaction vessel cylindrical body 32 is provided in the reaction vessel sedimentation portion 31 so as to form a slit at the intersection of the inclined portion and the reaction vessel straight body portion 29. The reaction tank second cylindrical body 33 is erected.

  The inclination angle of the reaction tank precipitation section 31 and the inclination angle of the reaction tank cone section 30 are not particularly limited, but in consideration of smooth sliding of solid particles, an inclination angle of 45 degrees or more is preferable, and more preferably 60 degrees or more is preferable. The ratio of the diameter of the reaction tank second cylindrical body 33 to the diameter of the reaction tank straight body portion 29 (reaction tank second cylinder diameter / reaction tank straight body diameter) is usually 0.2 to 0.8. Is preferably designed to be in the range of 0.3 to 0.7, more preferably in the range of 0.3 to 0.7, and most preferably in the range of 0.4 to 0.6.

  The ratio (reaction tank height / reaction tank straight body diameter) between the height of the reaction tank 21 (height of the reaction tank straight body 29 + the height of the precipitation part 31) and the diameter of the reaction tank straight body 29 In general, it is preferably designed to be in the range of 2 to 7, more preferably in the range of 2.5 to 6, and most preferably in the range of 3 to 5.

In the present invention, when the above-described air-stirring vertical double cylindrical reaction tank is used as the reaction tank 21, the digested sludge is supplied into the reaction tank second cylindrical body 33 through the digested sludge injection pipe 24. As the digested sludge supply amount, the sludge residence time in the reaction tank reaction part volume (volume of the part formed by the reaction tank straight body part 29 + part of the volume formed by the reaction tank cylindrical body 32) is usually 5 to 5. The range is preferably set to 90 minutes, more preferably 10 to 60 minutes, and most preferably 15 to 40 minutes. The water area load of the gravity sedimentation portion of the solid particles formed inside the reactor sedimentation section 31 and outside the reactor cylinder 32 is usually in the range of 5 to 60 m ³ / m ² / day with respect to the digested sludge injection amount. The range is preferably 6 to 50 m ³ / m ² / day, and more preferably 8 to 40 m ³ / m ² / day.

The aeration gas is blown into the reaction tank 21 from the gas blowing pipe 26. Air volume supplied from the gas injection tube 26, with respect to the cross-sectional area of the reaction vessel straight body portion 29, usually 5~100m ³ / ^{m 2} / range of time, preferably 8~70m ³ / ^{m 2} / time The range is more preferably 10 to 50 m ³ / m ² / hour.

  In the reaction vessel 21, MAP crystals are generated and grown to form solid particles. The MAP solid particles are settled and separated by the reaction tank settling portion 31, and the set and separated MAP is between the intersection of the inclined portion of the reaction tank settling portion 31 and the MAP reaction tank straight body portion 29 and the reaction tank cylindrical body 32. It passes through the formed slit and slides into the reaction vessel 21.

  On the other hand, the digested sludge in which the MAP that did not settle and the phosphoric acid phosphorus concentration decreased overflowed the V notch installed in the outflow trough surrounding the outside of the reaction tank settling portion 31 and recovered from the treated sludge outflow pipe 28 through the recovery device 34. Supplied to.

  The MAP particles accumulated in the reaction vessel 21 are supplied to the separation device 22 through the MAP extraction tube 27 by opening the MAP extraction valve 35 connected to the bottom of the reaction vessel cone 30 at intervals of 3 days to 2 weeks.

In the present invention, the reaction tank 21 may be filled with MAP seed crystals, and in that case, MAP particles having a large particle diameter can be obtained within a few days.
Separation device 22 separates MAP particles from a mixture of digested sludge and MAP particles extracted from the inside of reaction vessel 21, and is not particularly limited, such as a gravity sedimentation method using a specific gravity difference or a centrifugal separation method. However, a method of separating by a screen having a specified mesh width is most suitable.

  The MAP particles and the digested sludge accumulated in the reaction tank 21 are supplied to the separation device 22 by a MAP extraction pump 36 connected to the MAP extraction pipe 27. Separation device 22 is constituted by a screen, and the prescribed mesh width of the screen is usually in the range of 0.1 to 2 mm, preferably 0.15 to 1.5 mm, more preferably 0.2 to 1.0 mm. To do. A screen composed of a wedge wire having a trapezoidal cross section is effective in preventing clogging, and the screen may be either flat or cylindrical. A so-called trommel-shaped one in which the mixture to be separated is further supplied, the cylindrical body is rotated about 10 to 60 revolutions per minute, and washed with washing water is most suitable.

  The MAP particles 37 separated by the separation device 22 are discharged from one end of the separation device 22. On the other hand, the digested sludge and fine MAP particles that have passed through the separation device 22 are returned to the reaction tank 21 by the separated sludge transfer pump 38.

  In the treatment facility of the present invention, preferably, in order to collect fine MAP solid particles flowing out from the reaction tank 21, a recovery device 34 is connected to the treatment sludge outflow pipe 28. The fine MAP solid particles recovered by the recovery device 34 are returned to the reaction vessel 21 through the recovery MAP return pipe 39.

  The recovery device 34 is not particularly limited, such as a screen separation method or a centrifugal separation method, but a liquid cyclone utilizing a specific gravity difference between digested sludge and MAP particles (true specific gravity 1.72) is most suitable.

  The treated sludge outflow pipe 28 is connected to the recovery device relay tank 40, temporarily stored, and supplied by the recovery device raw sludge supply pump 41 in the direction of the straight section of the recovery device 34. When the pressure on the upstream side of the recovery device 34 is sufficiently high, the recovery device relay tank 40 and the recovery device raw sludge supply pump 41 are not necessary. However, in order to obtain a sufficient supply speed, the recovery device 34 is usually used. Considering the pressure loss, pumping by a pump is required.

  The supply amount to the recovery device 34 is such that the inlet flow velocity of the recovery device 34 is usually in the range of 1 to 20 m / sec, preferably 2 to 10 m / sec, more preferably 3 to 8 m / sec. The mixture of digested sludge and fine MAP particles supplied to the recovery device 34 becomes a rotational flow along the peripheral wall of the recovery device 34 and is given a shearing force associated with a velocity gradient. The MAP particles having a large specific gravity reach the bottom, and are returned to the reaction tank 21 via the recovery MAP return pipe 39 by the recovery MAP return pump 42. The return amount is usually in the range of 1 to 30%, preferably 2 to 20%, more preferably 3 to 10% with respect to the supply amount to the recovery device 34. On the other hand, the treated sludge from which most of the MAP particles have been collected rises in a vortex state near the center of the collection device 34, and the above-mentioned figure of the sludge treatment from the collection device treatment sludge pipe 43 connected to the upper part of the collection device 34. 1 and the next step 7 described in FIG.

Next, the present invention will be specifically described with reference to examples.
Example 1
The diameter of the straight body part of the reaction tank is 300 mm, the diameter of the sedimentation part is 600 mm, the total height of the straight body part, the sedimentation part and the lower cone part is 1510 mm, and the total volume is 160 liters. A cylindrical body is installed so as to form a slit at the intersection with the inclined portion, and a second cylindrical body having a diameter of 155 mm is installed so that the upper end is located above the slit, pH 7.8, phosphate state Digested sludge containing a phosphorus concentration of 150 mg / liter, a sludge concentration of 26000 mg / liter, and an ammoniacal nitrogen concentration of 1000 mg / liter is continuously supplied at a flow rate of 5 m ³ / day, and continuously from the bottom of the MAP reactor at 40 liters / minute. A 5% magnesium hydroxide slurry was continuously added so that the molar ratio of the phosphoric acid phosphorus concentration was 150 mg / liter. The paper was.

A mixture of digested sludge and fine MAP particles overflowing from the sedimentation part of the MAP reaction tank is stored in a relay tank having a diameter of 1030 mm, a total height of 1150 mm, and an effective capacity of 520 liters. The mixture was constantly stirred at a speed of 120 revolutions per minute. The hydrocyclone raw sludge supply pump is activated by a level switch installed in the relay tank, and the flow rate is 6.8 m at a recovery hydrocyclone with a straight barrel diameter of 115 mm and a total cone height of 550 mm with a flow rate of 120 m ³ / day. Per second. The digested sludge containing a large amount of fine MAP particles recovered by the liquid cyclone was continuously returned to the MAP reaction tank at a flow rate of 6 m ³ / day by the MAP return pump.

The above operation was continued for one week, and MAP particles and digested sludge inside the reaction tank were continuously discharged from the lower part of the MAP reaction tank to a wedge wire screen having a 350 mm square and an opening of 0.3 mm.
By the above method, the treatment sludge of the recovery liquid cyclone was raised to about pH 8.3, and the phosphate phosphorus concentration was lowered to 20 mg / liter or less. The MAP particles could be recovered by the MAP separation screen.

Although the operation was continued for 6 months under the above conditions, no scaling occurred on the surface of the stirring blade installed in the relay tank.
Comparative Example 1
The result of continuously supplying the same digested sludge used in Example 1 to a relay tank similar to the above at a flow rate of 5 m ³ / day, stirring under the same conditions as described above, and continuing operation for 6 months A gray scale having a thickness of about 5 mm was generated on the surface of the stirring blade, and as a result of analysis, it was found that most of the scale was MAP.

It is a flow sheet figure showing an example of a processing method of digested sludge of the present invention. It is a flow sheet figure which shows the other example of the processing method of the digested sludge of this invention. It is the schematic which shows an example of the processing equipment of the digested sludge of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anaerobic digestion tank 2 Digested sludge 3 Reaction tank 4 Magnesium compound 5 Air 6 Processed sludge 7 Next process 8 MAP extraction pipe 9 Separation apparatus 10 MAP particle 11 Digested sludge 12 Recovery apparatus 13 Return path 14 Recovery apparatus treatment sludge pipe 21 Reaction tank 22 Separation device 23 Separation sludge return pipe 24 Digested sludge injection pipe 25 Magnesium compound injection pipe 26 Gas blowing pipe 27 MAP extraction pipe 28 Treatment sludge outflow pipe 29 Reaction tank straight body section 30 Reaction tank cone section 31 Reaction tank precipitation section 32 Reaction tank Cylindrical body 33 Reaction tank second cylindrical body 34 Recovery device 35 MAP extraction valve 36 MAP extraction pump 37 MAP particle 38 Separation sludge transfer pump 39 Recovery MAP return pipe 40 Recovery device relay tank 41 Recovery device raw sludge supply pump 42 Recovery MAP return pump 43 Recovery equipment treatment sludge pipe

Claims (6)

The digested sludge is supplied to the reaction tank, and the magnesium compound is added to the reaction tank and the inside of the reaction tank is aerated to insolubilize the soluble phosphate phosphorus contained in the digested sludge as magnesium ammonium phosphate particles, and then The digested sludge containing magnesium ammonium phosphate particles is discharged from the reaction tank. The digested sludge is supplied to the reaction tank, and the magnesium compound is added to the reaction tank and the inside of the reaction tank is aerated to insolubilize the soluble phosphate phosphorus contained in the digested sludge as magnesium ammonium phosphate particles, and then A method for treating digested sludge, characterized in that digested sludge having a reduced concentration of soluble phosphate phosphorus is obtained by removing magnesium ammonium phosphate particles from the digested sludge. Digested sludge injection pipe for injecting digested sludge, magnesium compound injection pipe, gas blowing pipe for aeration, extraction pipe for extracting digested sludge containing magnesium ammonium phosphate particles, and discharging processed digested sludge A reaction tank equipped with a treated sludge outflow pipe, a separation apparatus connected to the extraction pipe for separating magnesium ammonium phosphate particles from the digested sludge, and the digested sludge passed through this separation apparatus is returned to the reaction tank A digested sludge treatment facility characterized by having a separated sludge return pipe for the purpose. 4. The digested sludge treatment facility according to claim 3, wherein the separation device is a screen. The digested sludge according to claim 3 or 4, further comprising a recovery device connected to the treated sludge outflow pipe for collecting fine magnesium ammonium phosphate particles flowing out from the treated sludge outflow pipe. Processing equipment. 6. The digested sludge treatment facility according to claim 5, wherein the recovery device is a hydrocyclone.

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