JPH09262599A - Dephosphorization apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover phosphorus from org. waste water without performing anaerobic digestion by providing a biological phosphorization tank and concentrating the excessive sludge from this treatment tank and discharging phosphorus from conc. sludge and precipitating magnesium ammonium phosphate from a phosphorus-containing soln. SOLUTION: Phosphorus-containing water is subjected to solid-liquid separation in a first sedimentation basin 1 and separated sludge is conc. in a gravity concn. tank 4 while separated water is returned to the first sedimentation basin 1. The separated water after solid-liquid separation is subjected to biological dephosphorization treatment in a biological dephosphorization treatment tank 2 to be supplied to a solid-liquid separation means 3 to separate phosphrus-containing sludge and a part of separated sludge is returned to the biological dephosphrization tank 2 as return sludge and excessive sludge is conc. by a concn. means 5. This conc. sludge is sent to an anaerobic tank 6 and the treated liquid of the anaerobic tank 6 is sent to a solid-liquid separation means 7 to be subjected to solid-liquid separation and separated water is supplied to a dephosphorization tank 8. A magnesium salt is added to the dephosphorization tank 8 to precipitate phosphorus as magnesium ammonium phosphate useful as fertilizer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dephosphorization apparatus,
Especially organic wastewater and dephosphorization process, useful magnesium ammonium phosphate as a fertilizer (MgNH ₄ PO ₄ · 6
H ₂ O. Hereinafter referred to as MAP. ) Is efficiently produced.

[0002]

2. Description of the Related Art MAP conventionally used effectively as fertilizer
Is manufactured by using excess sludge generated in the anaerobic and aerobic treatment processes such as sewage, night soil and waste water as a raw material. In particular,
It is manufactured by anaerobically digesting these excess sludges, then dehydrating and separating the undigested sludges, and adding magnesium salts to the separated liquid produced at that time. That is, when the excess sludge is digested in the anaerobic digestion tank, the excess sludge is digested and decomposed, and phosphorus in the sludge is released into the liquid. Therefore, since the separated liquid (digested desorbed liquid) obtained by separating undigested sludge from the digested liquid has a high phosphorus concentration and is suitable as a raw material for MAP, magnesium salt is added to this separated liquid to obtain MAP. To precipitate.

[0003]

The above-mentioned conventional method has the following problems because of anaerobic digestion.

A large anaerobic digester is required. It is difficult to dehydrate undigested sludge. The operation management of the anaerobic digestion tank is complicated.

The present invention solves the above-mentioned conventional problems, and efficiently recovers and concentrates phosphorus from organic wastewater without anaerobic digestion to efficiently produce MAP useful as a fertilizer. An object of the present invention is to provide a dephosphorization device capable of

[0006]

The dephosphorization device of the present invention comprises:
A biological dephosphorization treatment tank for biologically dephosphorizing phosphorus-containing water;
Concentrating means for concentrating excess sludge from the biological dephosphorization treatment tank, anaerobic tank for releasing phosphorus from the concentrated sludge concentrated by the concentrating means, and precipitation of magnesium ammonium phosphate from the phosphorus-containing liquid from the anaerobic tank It is characterized by comprising a dephosphorization tank for making it.

Excess sludge obtained by the biological dephosphorization treatment contains phosphorus at a high concentration. However, if an attempt is made to release phosphorus from this excess sludge directly in the anaerobic tank, the phosphorus concentration in the sludge will be insufficient, and phosphorus cannot be released efficiently. This excess sludge releases phosphorus to a high concentration in the anaerobic tank if it has been previously concentrated by the concentration means. Therefore, it is possible to efficiently generate MAP by treating phosphorus released in the anaerobic tank in the dephosphorization tank to precipitate MAP.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the dephosphorization apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the dephosphorization apparatus of the present invention.

In the dephosphorization apparatus of this embodiment, first,
The phosphorus-containing water is first subjected to solid-liquid separation in the settling tank 1, and then the separated water is subjected to biological dephosphorization treatment in the biological dephosphorization treatment tank 2. As the biological dephosphorization treatment tank 2, a general biological dephosphorization treatment tank having an anaerobic process and an aerobic process can be used.

The sludge first separated in the sedimentation tank 1 is
The water is concentrated in the gravity thickening tank 4 and the separated water is first returned to the settling tank 1. On the other hand, the concentrated sludge is sent to the anaerobic tank 6 in the subsequent stage.

The treated water in the biological dephosphorization treatment tank 2 is fed to a solid-liquid separation means (for example, a sedimentation tank) 3, sludge containing phosphorus is separated, and the separated water is discharged out of the system as treated water. . Further, part of the separated sludge is returned to the biological dephosphorization treatment tank 2 as return sludge, and excess sludge is sent to the concentration means 5.
It is concentrated.

As the concentration means 5, it is desirable that phosphorus is not released from the sludge because phosphorus recovery efficiency and MAP production efficiency are reduced if phosphorus is released from the sludge during concentration. For example, a pressure floating means that maintains aerobic property, or a centrifugal concentration or membrane concentration means that can perform concentration in a short time is suitable.

The sludge concentrated by the concentration means 5 is sent to the anaerobic tank 6 together with the concentrated sludge in the gravity concentration tank 4. As the anaerobic tank 6, any tank can be used as long as it does not become an aerobic condition. A closed stirring tank is most suitable as the anaerobic tank 6, but a normal storage tank may be used. When the anaerobic tank 6 is a concentrating (settling) tank, the solid-liquid separating means 7 in the latter stage can be omitted.

The residence time in the anaerobic tank 6 may be any time as long as phosphorus is sufficiently released from the concentrated sludge and is not particularly limited, but is preferably 1 day or more.

The treatment liquid in the anaerobic tank 6 is then fed to the solid-liquid separation means 7 and separated into solid and liquid. As the solid-liquid separating means 7, a means for aggregating with a polymer aggregating agent without using an inorganic aggregating agent and dehydrating with a belt press or a centrifugal separator is preferable.

The dehydrated cake obtained by the solid-liquid separation means is discharged out of the system.

On the other hand, the separated water is sent to the dephosphorization tank 8.
In the dephosphorization tank 8, magnesium salt is added and phosphorus is converted to M
Precipitates as AP. The magnesium salt is not particularly limited, and MgCl ₂ , Mg (OH) ₂ , MgSO
_4. Other seawater or the like can be used, and the addition amount thereof is preferably equimolar or more to the phosphorus in the separated water.

A granulation tank is used as the dephosphorization tank 8, and if necessary, an alkali is added and treated at a pH of 8 to 9 to precipitate granular MAP.
It is preferable because it facilitates the separation and recovery of the fertilizer and facilitates the handling as a fertilizer.

The MAP produced in the dephosphorization tank 8 is recovered and sent to the commercialization process as fertilizer. On the other hand, the separated water is first returned to the sedimentation tank.

In the present invention, examples of the phosphorus-containing water used for the biological dephosphorization treatment include sewage, night soil, organic waste water such as food waste water, and the like.

[0022]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 Excess sludge was drawn from a settling tank from an apparatus treating sewage by a biological dephosphorization method (anaerobic aerobic method). ML of this sludge
The SS concentration was 5200 mg / L, and the phosphorus content was 4.1% by weight based on MLSS.

500 mL of this sludge was added at 3000 rpm to 1
Centrifuged for minutes and concentrated. As a result, the MLSS concentration was 6.5% by weight. This concentrated sludge was left to stand in a 100 mL graduated cylinder for 24 hours. As a result, 1310 mg / L of phosphorus was released in the liquid. After adding 3.0% by weight of a cationic polymer (“Cliffix CP-604” manufactured by Kurita Water Industries Ltd.) to this liquid and stirring, N
o. It was filtered with 5A filter paper. 1280 in the resulting filtrate
It contained mg / L of phosphorus.

Magnesium sulfate was added to this filtrate at 10000
The pH was adjusted to 8.5 with sodium hydroxide, and the mixture was stirred slowly for 4 hours. as a result,
It was possible to recover 0.9 g of MAP.

Comparative Example 1 When the same treatment as in Example 1 was carried out except that the excess sludge was not concentrated, the recovered amount of MAP was 0.06 g.

[0027]

As described in detail above, according to the dephosphorization apparatus of the present invention, phosphorus is efficiently recovered and concentrated from organic wastewater without anaerobic digestion, and MA useful as a fertilizer is obtained.
P can be produced efficiently.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a dephosphorization apparatus of the present invention.

[Explanation of symbols]

 1 First settling tank 2 Biological dephosphorization treatment tank 3 Solid-liquid separation means 4 Gravity concentration tank 5 Concentration means 6 Anaerobic tank 7 Solid-liquid separation means 8 Dephosphorization tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Oyama 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A biological dephosphorization treatment tank for subjecting phosphorus-containing water to biological dephosphorization treatment, a concentration means for concentrating excess sludge from the biological dephosphorization treatment tank, and phosphorus from the concentrated sludge concentrated by the concentration means. A dephosphorization apparatus comprising: an anaerobic tank for discharging and a dephosphorization tank for precipitating magnesium ammonium phosphate from a phosphorus-containing liquid from the anaerobic tank.