JP2007050387A - Apparatus for treating organic waste liquor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating organic waste liquor in which phosphorus is prevented from being precipitated in a treatment tank for solubilizing sludge or in the succeeding pipelines or tanks. <P>SOLUTION: In the apparatus for treating organic waste liquor, organic waste liquor (raw water) is introduced into a biological treatment tank 1 to treat a BOD component aerobically or anaerobically/aerobically. The biologically treated water is introduced into a precipitation tank 2 and separated into supernatant water and waste sludge. The supernatant water is withdrawn to the outside as treated water. The excess sludge is introduced into a digestion tank 5 through a pipeline 4. The water permeated through a membrane 12 is introduced into a crystallization column 14 through a pipeline 13 to crystallize phosphorus. A part of the dephosphorized water is returned to the digestion tank 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic waste liquid treatment apparatus for biologically treating an organic waste liquid and dephosphorizing surplus sludge generated by the biological treatment.

  It is known to reduce the amount of sludge by solubilizing excess sludge generated when organic waste liquid is biologically treated by ozone treatment (for example, JP-A-6-206088, JP-A-8-299995, JP-A-11-10191, JP-A-11-57773).

JP-A-9-108699 discloses that organic sludge is digested in a digestion tank, and part of the sludge in the digestion tank is solubilized with ozone and returned to the digestion tank to reduce sludge. Further, it is described that the digested liquid discharged from the digester is subjected to solid-liquid separation, and the separated liquid is biologically nitrified and then dephosphorized.
JP-A-6-206088 JP-A-8-299995 JP-A-9-108699 JP-A-11-10191 JP-A-11-57773

  As described in JP-A-9-108699, after sludge is digested, a part of the digested liquid is subjected to solid-liquid separation, and the separated liquid is dephosphorized to reduce sludge and improve the quality of treated water ( In particular, the phosphorus concentration can be reduced).

  However, in this organic waste liquid treatment apparatus, phosphorus in the sludge is eluted as the sludge is reduced. As a result, the phosphorus concentration in the digestion tank rises, and phosphorus tends to accumulate in the digestion tank.

  The present invention relates to a biological treatment apparatus for organic waste liquid, surplus sludge treatment means for biologically digesting at least part of excess sludge discharged from the biological treatment apparatus and solubilizing digested sludge, and the excess sludge treatment. In an organic waste liquid treatment apparatus having a solid-liquid separation means for separating the liquid content of the means and a dephosphorization means for dephosphorizing the separated water from the solid-liquid separation means, phosphorus accumulation in the excess sludge treatment means is prevented. It is an object of the present invention to provide an organic waste liquid treatment apparatus.

  The organic waste liquid treatment apparatus according to claim 1 is a biological treatment apparatus for organic waste liquid and surplus sludge treatment for biologically digesting at least part of excess sludge discharged from the biological treatment apparatus and solubilizing the digested sludge. In an organic waste liquid treatment apparatus comprising: a solid-liquid separation means for separating the liquid content of the excess sludge treatment means; and a dephosphorization means for dephosphorizing separated water from the solid-liquid separation means And a return means for returning a part of the treated water from the waste sludge treatment means to the surplus sludge treatment means.

  The organic waste liquid treatment apparatus according to claim 2 is the organic waste liquid treatment apparatus according to claim 1, wherein the surplus sludge treatment means digests at least a part of the excess sludge, and at least a part of the digested sludge digested by the digestion means. And a circulating means for circulating the solubilized sludge solubilized by the solubilizing means to the digesting means.

  The organic waste liquid treatment apparatus according to claim 3 is the organic waste liquid treatment apparatus according to claim 1, wherein the excess sludge treatment means digests the solubilized sludge from the solubilization means and the solubilization means for solubilizing at least a part of the excess sludge. It comprises a digesting means to be treated and a circulating means for circulating digested sludge from the digesting means to the solubilizing means.

  The organic waste liquid treatment apparatus according to claim 4 is characterized in that, in any one of claims 1 to 3, the dephosphorization means is a crystallization dephosphorization means.

  According to the organic waste liquid treatment apparatus of the present invention, a part of the treated water after dephosphorization treatment is returned to the excess sludge treatment means, thereby reducing the phosphorus concentration in the water in the excess sludge treatment means, so that it is hardly soluble. Phosphate is dissolved, and accumulation of phosphorus in the excess sludge treatment means is prevented. Thereby, solubilization and digestion of sludge come to be performed efficiently.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a system diagram of an organic waste liquid treatment apparatus according to an embodiment.

  The organic waste liquid (raw water) is introduced into the biological treatment tank 1, and the BOD component is treated aerobically or anaerobically / aerobically. In addition, this biological treatment tank 1 may be comprised so that a denitrification process may also be performed. This biologically treated water is introduced into the precipitation tank 2 and subjected to solid-liquid separation treatment. The supernatant water is taken out of the system as treated water.

  The settled sludge is taken out from the bottom of the settling tank 2, and a part thereof is returned to the biological treatment tank 1 through the sludge return pipe 3 as return sludge. The remaining surplus sludge is introduced into the digestion tank 5 through the pipe 4.

  The digestion tank 5 is provided with an air diffuser 6 and sludge is digested by aeration with air. In addition, a part of the digested sludge circulates through a circulation line composed of the pipe 7, the pump 8, the pipe 9, the ozone reaction tower 10, and the pipe 11, and ozone (or ozone-containing gas) is added to the pipe 9 in the middle. Digested sludge is solubilized. In addition, in this sludge digestion process, phosphorus elutes in water as sludge is reduced.

  A solid-liquid separation membrane 12 is provided in the digestion tank 5. As the membrane 12, for example, a nonwoven fabric, a woven fabric, a net, a UF (ultrafiltration) membrane, an MF (microfiltration) membrane, or the like can be used. The water that has permeated through the membrane 12 is introduced into the crystallization tower 14 through the pipe 13 and subjected to a crystallization process of phosphorus, and the crystallized phosphorus compound passes through the extraction pipe 14 a at the bottom of the crystallization tower 14. It is taken out. The dephosphorized water is introduced into the flow rate adjusting relay tank 15, a part thereof is returned to the biological treatment tank 1, and the remaining part is returned to the digestion tank 5 via the pipe 17 and the pump 18. The relay tank 15 may be omitted.

  Thus, since at least a part of the dephosphorized water is returned to the digestion tank 5, the digestion tank 5, the circulation pipes 7, 8, 11 and the pump 8, the inside of the stirring tank 10, the membrane 12, the pipe Phosphorus concentration in 13 etc. becomes low and accumulation of phosphorus is prevented.

  As the crystallization tower 14, a calcium phosphate reaction tower is suitable.

In the calcium phosphate reaction tower, alkali such as NaOH is injected so that the pH condition for precipitation of calcium phosphate, preferably pH 7.5 to 10, more preferably pH 8.5 to 9.5, and calcium phosphate is precipitated in the calcium phosphate precipitation column. Is insufficient, calcium compounds such as CaCl ₂ and Ca (OH) ₂ are added, and calcium phosphate is generated and precipitated by reaction with phosphorus in the liquid, thereby removing phosphorus in the liquid. In particular, phosphorus eluted in the digestion tank 5 is in the form of normal phosphoric acid that is advantageous for the production of calcium phosphate by undergoing biological treatment, and the calcium phosphate production reaction efficiency in the calcium phosphate reaction tower is high. It is possible to remove phosphorus.

  The phosphorus concentration in the effluent of the calcium phosphate reaction tower varies depending on the phosphorus concentration of the inflow water to the calcium phosphate reaction tower and the operating conditions of the crystallization tower, but in the embodiment of the present invention, the phosphorus concentration is about 10 to 100 mg / L. The liquid not returned to 5 is preferably returned to the biological treatment tank 1 for processing.

  In addition, the residence time of the calcium phosphate reaction tower is usually about 10 to 120 minutes, whereby calcium phosphate particles having a particle size of about 0.5 to 2 mm can be recovered. The calcium phosphate reaction tower may be either a fixed bed or a fluidized bed, but a fluidized bed can be preferably used.

  The biological treatment tank 1 may be aerobic or anaerobic. For example, the biological treatment tank 1 may be composed of only an aerobic aerobic tank or may be of an anaerobic / aerobic type.

  In the above embodiment, the solid-liquid separation means uses a film 12 immersed in the digestion tank 5, but the solid-liquid separation means (solid-liquid separation tank 20) is a digestion tank as shown in FIG. It may be provided separately from 5. As described above, when the solid-liquid separation tank 20 is provided separately from the digestion tank 5, a part of the dephosphorized water is supplied to the solid-liquid separation tank 20 and / or the digestion tank 5 via the pipe 17 and the pump 18. Will be returned. In FIG. 2, the digested sludge is extracted from the solid-liquid separation tank 20 and solubilized in the ozone reaction tower 10, and then the digested sludge is returned to the digestion tank 5 again. The digested sludge may be circulated in the digester tank 5 and the digested sludge may be circulated in the digester tank 5 and the ozone reaction tower 10.

  Furthermore, in the said embodiment, although the excess sludge from the sedimentation tank 2 is introduce | transduced into the digestion tank 5 through the piping 4, you may pass through the ozone reaction tower 10 as shown in FIG.

  Other configurations in FIGS. 2 and 3 are the same as those in FIG. 1, and the same reference numerals denote the same parts.

  In the above embodiment, the digestion tank 5 is an aeration type, but may be an anaerobic type, an anaerobic / aerobic type, or the like.

  The solubilizing means may be an acid-alkali system other than the ozone oxidation system, a mill system, a heat treatment system, or the like.

  Hereinafter, examples and comparative examples will be described.

Example 1
Using an aeration type aerobic tank employing the oxidation ditch method, sewage was treated, and the generated excess sludge was treated by the excess sludge treatment means and the dephosphorization means shown in FIG. As the crystallization tower 14, a calcium phosphate reaction tower was used.

The specifications and operating conditions of each part were as follows.
Volume of raw water (primary sediment runoff): 2000 m ³ / day Capacity of biological treatment tank 1: 2000 m ³
MLSS concentration: 3000 mg / L
Digestion tank capacity: 400 m ³
Flow rate of pipe 7: 30 m ³ / day Ozone injection rate: 0.025 g-O ₃ / g-VSS
Capacity of calcium phosphate reaction tower: 3m ³
Water flow rate of calcium phosphate reaction tower: 80 m ³ / day Residence time of calcium phosphate reaction tower (HRT): 33 minutes Calcium phosphate reaction tower pH: 9.3
CaCl ₂ addition amount to calcium phosphate reaction tower: 800 mg / L
LV rise of calcium phosphate reaction tower: 40 m / Hr
Return ratio of dephosphorized water to digestion tank 5: 50%

  Table 1 shows the phosphorus concentration of the supernatant water (treated water) flowing out of the settling tank 2.

  In addition, Table 1 shows the phosphorus concentration, the phosphorus recovery amount, and the crystallization treatment amount of the influent water and the effluent water of the calcium phosphate reaction tower.

Comparative Example 1
In Example 1, the treatment was performed in the same manner except that the pump 18 was stopped and the total amount of dephosphorized water was sent to the biological treatment tank 1 and not returned to the digestion tank 5 at all. Table 1 shows the quality of the treated water obtained.

It is a systematic diagram of the organic waste liquid processing apparatus which concerns on embodiment. It is a systematic diagram of the organic waste liquid processing apparatus which concerns on another embodiment. It is a systematic diagram of the organic waste liquid processing apparatus which concerns on another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological treatment tank 2 Precipitation tank 5 Digestion tank 14 Crystallization tower 20 Solid-liquid separation tank

Claims (4)

Biological treatment apparatus for organic waste liquid, surplus sludge treatment means for biologically digesting at least part of excess sludge discharged from the biological treatment apparatus and solubilizing digested sludge, and liquid content of the excess sludge treatment means In an organic waste liquid treatment apparatus having a solid-liquid separation means for separating the water and a dephosphorization means for dephosphorizing the separated water from the solid-liquid separation means,
An organic waste liquid treatment apparatus comprising return means for returning a part of treated water from the dephosphorization apparatus to the excess sludge treatment means.   2. The surplus sludge treatment means according to claim 1, wherein digestion means for digesting at least a part of the excess sludge, solubilization means for solubilizing at least a part of the digested sludge digested by the digestion means, An organic waste liquid treatment apparatus comprising: a circulation means for circulating the solubilized sludge solubilized by the solubilization means to the digestion means.   The surplus sludge treatment means according to claim 1, the solubilization means for solubilizing at least a part of the excess sludge, the digestion means for digesting the solubilized sludge from the solubilization means, and the digestion means An organic waste liquid treatment apparatus comprising a circulation means for circulating the digested sludge to the solubilization means.   4. The organic waste liquid treatment apparatus according to claim 1, wherein the dephosphorization means is a crystallization dephosphorization means.

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