JP2002205077A - Method and apparatus for treating organic sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic dirty water, by which phosphorus can be recovered as valuable resources, in which difficult-to-dehydrate sludge to be obtained by flocculation and settlement is not produced and which is excellent in phosphorus removing speed and phosphorus removing effect. SOLUTION: This method for treating the organic dirty water comprises a step to flocculate/separate SS in the organic dirty water by adding a cationic or amphoteric macromolecular flocculating agent, a step to subject the separated SS to anaerobic digestion treatment, a phosphorus removing step to adsorb/remove phosphorus by adding fine particles of iron hydroxide and/or aluminum hydroxide and the macromolecular flocculating agent to the SS-removed organic water and making the organic water thus prepared pass upward through a slurry-blanketed flocculating and settling unit in which a fluidized bed is formed, a step to subject the phosphorus- adsorbed/removed treated water to biological treatment, a step to desorb the phosphorus adsorbed on the iron hydroxide or the aluminum hydroxide contained in the slurry discharged from the flocculating and settling unit by making the slurry alkaline and recycle the phosphorus-desorbed iron hydroxide or the aluminum hydroxide to the phosphorus removing step and a step to recover phosphorus as HAP or MAP from the liquid containing the desorbed phosphorus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method and apparatus for treating organic sewage, and more particularly to an excellent method for treating organic sewage, which sufficiently recovers phosphorus from organic sewage and generates little excess sludge. Related to the device.

[0002]

2. Description of the Related Art In many conventional organic wastewater treatment methods, organic wastewater is first flowed into a sedimentation basin, and suspended substances (SS) are settled and removed to some extent (about 40%). Many processing methods of processing are employed. The sludge initially settled in the sedimentation basin is supplied to the anaerobic digestion step, the digested sludge that has undergone the digestion treatment is subjected to dehydration treatment, and the obtained dewatered sludge is separately treated. In this conventional treatment method, as shown in FIG. 2, the organic sewage 1 is allowed to flow into the first sedimentation basin 23 without adding a coagulant and simply settled thereinto.
Is sent to an activated sludge aeration tank 25, and an inorganic coagulant 26 is added for biological treatment, and at the same time, the SS content is coagulated. The biologically treated water 27 from the activated sludge aeration tank 25 is sent to the final settling tank 28, and the supernatant water is obtained as the treated water 11. Most of the settled sludge in the final settling tank 28 is returned sludge 1
It is returned to the activated sludge aeration tank 25 as 2 and the remainder is sent to the dehydrator 30 as surplus sludge 29 and is discharged out of the system as a dewatered cake. The settled sludge 24 that has first settled in the settling basin 23 is subjected to anaerobic treatment in the anaerobic treatment tank 8. The liquid separated in the anaerobic treatment tank 8 is mixed with the organic wastewater 1 as a desorbing liquid 8b. The digested sludge 8c obtained in the anaerobic treatment tank 8 is sent to the dehydrator 13. In this method, since the SS removal rate of the first settling basin is only about 40%, the amount of sludge supplied to the anaerobic digestion process is very small.

[0003] However, in the above-mentioned conventional typical organic sewage treatment method, the following major problems still need to be solved. 1) Phosphorus cannot be recovered as a resource. 2) Since the amount of gas generated in the anaerobic digestion process is small, the amount of energy recovered is small. 3) A large amount of hardly dewaterable surplus sludge is generated from the activated sludge treatment process. 4) The low removal rate of phosphorus causes eutrophication of public water bodies such as rivers from which organic wastewater is discharged. 5) Phosphorus can be effectively removed by adding an inorganic flocculant such as ferric chloride and aluminum sulfate to the activated sludge aeration tank, but a large amount of hardly dewaterable inorganic sludge is generated and disposed of. Make it extremely difficult.

[0004] Among the phosphorus removal methods (phosphorus removal methods), a typical treatment method is an aggregation precipitation method. Conventional coagulation and precipitation methods use aluminum sulfate,
By adding an inorganic flocculant such as polyaluminum chloride, ferric chloride and polyferrous sulfate and stirring, a floc-like precipitate of aluminum phosphate or ferric phosphate is formed to remove phosphorus. is there. The coagulation-sedimentation method is simple in operation, excellent in maintenance and controllability, and highly practical, but the conventional coagulation-sedimentation method still has the following fatal drawbacks.

[0005] That is, floc-like precipitation of aluminum phosphate or ferric phosphate (referred to as sludge) generated in a large amount is extremely poor in sedimentation concentration and concentration dehydration. Such sludge with poor dehydration properties
It brings significant disadvantages in the treatment and disposal. For this reason, in recent years, adsorption dephosphorization and crystallization dephosphorization methods in which granular adsorbents are packed in columns and treated are being studied. All have the following drawbacks, and are evaluated as a technique that is considerably less practical than the coagulation sedimentation method. That is, 1. The price of the adsorbent (granular substances such as activated alumina, titanium oxide, and zirconium oxide) itself is expensive. 2. In the crystallization dephosphorization method, the process itself is complicated, for example, a decarboxylation step is required, and the activity of the phosphorus crystallization material is likely to be deteriorated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to completely solve the above-mentioned drawbacks recognized in the prior art. Specifically, all of the matters listed below are described. The aim is to provide new technologies that can be overcome. 1) Phosphorus can be recovered as a valuable resource. 2) No hard-to-concentrate and hard-to-dehydrate flocculated sludge is not generated. 3) The removal rate of phosphorus is high. 4) The phosphorus removal effect is excellent. 5) The recovery efficiency of phosphorus is excellent. 6) The amount of methane gas generated from the anaerobic digestion process increases. 7) Nitrification in the activated sludge treatment process proceeds. 8) The amount of excess activated sludge generated from the activated sludge treatment step can be reduced.

[0007]

Means for Solving the Problems In order to achieve the above object, as a result of diligent research on the above-mentioned matters, the present inventors have obtained the following findings and reached the present invention. That is, according to the study of the present inventors, ferric hydroxide and aluminum hydroxide (here, ferric hydroxide and aluminum hydroxide are used as a generic term including hydrated ferric oxide and hydrated aluminum oxide A) or a particle-containing slurry composed of a mixture thereof is prepared by the method described below, and the slurry is agglomerated with a polymer to form a fluidized bed (blanket).
It has been found that when organic sewage water is brought into contact with cationic polymer coagulation sedimentation water, phosphorus can be rapidly removed from raw water at a high removal rate. The present invention has been achieved based on various findings obtained from the above research results.

The present invention has solved the above-mentioned problems by the following means. (1) A cationic or amphoteric polymer flocculant is added to the organic wastewater to aggregate the SS in the organic wastewater, the SS aggregated by solid-liquid separation is removed, and the separated SS is subjected to anaerobic digestion treatment. On the other hand, iron hydroxide and / or aluminum hydroxide fine particles and a polymer flocculant are added to the organic wastewater from which the SS has been removed, and the flocculant is passed through a slurry blanket-type flocculating and settling apparatus in an upward flow. In the phosphorus removal step of forming a fluidized bed, phosphorus is adsorbed and removed, and then the treated water from which the phosphorus is adsorbed and removed is biologically treated, and the phosphorus-adsorbed iron hydroxide and / or aluminum hydroxide from the coagulation and sedimentation apparatus is used. Phosphorus is desorbed by making the contained slurry alkaline, phosphorus desorbed iron hydroxide and / or aluminum hydroxide are recycled to the phosphorus removing step, and phosphorus is desorbed from the phosphorus desorbing solution by hydroxyapa. Method of treating organic wastewater and recovering as site or magnesium apatite.

(2) The digested and desorbed liquid produced in the anaerobic digestion treatment of the separated SS is supplied to organic wastewater before the step of adding iron hydroxide and / or aluminum in the phosphorus removal step. The method for treating organic sewage according to (1) above. (3) A method for treating organic sewage, comprising supplying a dewatered separated solution of anaerobic digested sludge to organic sewage before the step of adding iron hydroxide and / or aluminum in the phosphorus removal step. (4) An organic sewage treatment method characterized in that a part of inflowing organic sewage or water treated by addition of a cationic or amphoteric polymer coagulant is separated and supplied to a biological process.

(5) A flocculation / separation tank for flocculating and separating SS in organic sewage by introducing organic sewage to which a cationic or amphoteric polymer flocculant is added, and the SS separated in the flocculation / separation tank.
Anaerobic digester for anaerobic digestion, iron hydroxide and / or aluminum hydroxide fine particles and a polymer flocculant are added to organic wastewater from which SS has been removed, and the mixture is introduced in an upward flow to flow the flocculated particles. A slurry blanket-type coagulation / sedimentation apparatus for forming a layer and adsorbing and removing phosphorus, a biological treatment apparatus for performing biological treatment by introducing treated water from which the phosphorus has been adsorbed and removed, and phosphorus-adsorbed iron hydroxide and / or water from the coagulation / sedimentation apparatus A phosphorus desorption device for debasing phosphorus by making the aluminum oxide-containing slurry alkaline, a circulation conduit for recycling phosphorus desorbed iron hydroxide and / or aluminum hydroxide from the phosphorus desorption device to the coagulation and sedimentation device, and a phosphorus desorption device. Organic having a phosphorus recovery device for recovering phosphorus as hydroxyapatite or magnesium apatite from a phosphorus desorption solution Sewage processing equipment.

The slurry of iron hydroxide and / or aluminum hydroxide used in the present invention can be prepared, for example, as follows. That is, an alkaline agent is added to an acidic solution of an iron salt and / or an aluminum salt to increase the pH value of the solution of the iron salt and the aluminum salt, and the resulting ferric hydroxide and aluminum hydroxide particles are formed. A method of preparing a slurry containing, or adding a magnesium-based or calcium-based alkaline agent to an acidic solution of an iron salt or an aluminum salt to increase the pH value of the solution of the iron salt or the aluminum salt, thereby forming water to be produced. A method of preparing a slurry having good sedimentation and concentration properties by using particles composed of ferric oxide and aluminum hydroxide is preferable.

In the conventional coagulation precipitation method, an inorganic coagulant such as ferric chloride, polyiron sulfate, aluminum sulfate, or polyaluminum chloride is directly added to phosphorus-containing water, for example, treated sewage water. By stirring, a floc-like precipitate of ferric phosphate or aluminum phosphate is rapidly formed. In this case, the following precipitation reaction,
In other _{^{words, M 3+ + PO 4 3- →}} MPO 4 ↓ ····· (1) M 3+ + 3OH - → M (OH) 3 ↓ ··· (2) ( in the above reaction formula, M ³⁺ is (Represents Fe ³⁺ or Al ³⁺ )
A precipitate formation reaction occurs and phosphorus is removed, and at the same time, MPO ₄ and M (O
H) There was the inconvenience that precipitation of ₃ was accompanied.

On the other hand, according to the present invention, since an alkaline agent is added to an acidic aqueous solution of an iron salt or an aluminum salt in advance, the reaction represented by the above reaction formula (2) is carried out in a tank for preparing a slurry. Since the process proceeds in an environment in which the environment changes from a low pH to a neutral pH, it is possible to reproducibly form a precipitate of M (OH) _{3 having} good sedimentation, concentration, and dehydration properties. As M other than NaOH
g (OH) ₂ , MgO, Ca (OH) ₂ , CaO, Ca
When an alkali such as CO ₃ is used, a precipitate of Mg (OH) _{3 having} better sedimentation, concentration, and dehydration properties can be generated. The adsorption rate of phosphorus by a slurry blanket formed by aggregating the ferric hydroxide slurry and aluminum hydroxide slurry of the present invention with a polymer flocculant is a granular phosphorus adsorbent such as activated alumina (particle diameter of about 3 to 5 mm). ) Is packed in a column, the phosphorus-containing water is passed through, and the rate of adsorbing phosphorus by the particulate phosphorus adsorbent is significantly higher.

[0014] When a polymer is added to the iron hydroxide fine particles of the present invention to form a slurry blanket layer and come into contact with raw water, the slurry concentration can be kept remarkably high at a large rising flow rate. The removal rate is significantly increased. A small amount of NaOH is added to the highly concentrated slurry in which phosphorus has been removed from the raw water to adjust the pH value to 11 or more (preferably pH 12 to 12.
In the case of (5), the adsorbed phosphorus is easily desorbed, so that the slurry can be easily regenerated and the regeneration cost is low.

As will be apparent from the specific embodiments of the present invention described below, the above-mentioned features make it possible to permanently remove and recover phosphorus from raw water containing phosphorus. Therefore, no sludge-like waste is generated in the coagulation sedimentation method from the step of the phosphorus removal method of the present invention, and
Replacement and replenishment of the phosphorus adsorbent becomes unnecessary. In addition, the concentration of phosphorus contained in the solid-liquid separation concentrated water obtained by the step of the phosphorus removal method of the present invention is extremely high, and furthermore, the purity is high. The phosphorus in the form of a phosphorus compound can be recovered very easily. Examples of the chemical method of phosphorus recovery that can be used therefor include a method of adding Ca (OH) ₂ and CaO and recovering as calcium phosphate precipitate.
A method of adding g ²⁺ and NH ₄ ⁺ to recover as ammonium ammonium phosphate (NH ₄ MgPO ₄ ).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIG. When a cationic polymer or amphoteric polymer 2 (anion and nonionic polymer are less effective) is added to an organic wastewater (for example, sewage) 1 flowing into a sewage treatment plant and stirred for several minutes in a stirring tank (not shown), Since SS in the organic sewage aggregates to form flocs having a large particle diameter, the floc is supplied to the aggregation separation tank 3 or a filtration tank filled with a coarse-grained filter medium,
By separating the flocculated floc, 95% or more of the SS of the organic wastewater 1 is removed, and the separated water 4 having an SS of several mg / liter or less flows out.

By such a turbidity treatment, organic SS in the organic sewage 1 is highly separated and removed, and the separated sludge 7 is supplied to an anaerobic digestion tank 8 to be subjected to methane fermentation to produce digested gas. The recovery amount of (methane gas) 8a can be twice or more as compared with the conventional organic sewage treatment method (FIG. 2). The treated water 4 of the coagulation / separation treatment with the cation or the amphoteric polymer 2 contains fine particles of iron hydroxide (aluminum hydroxide may be used, but for the sake of simplicity of description, it is represented by iron hydroxide in the following). (Polymer coagulant) is added and supplied to the slurry blanket type coagulation sedimentation apparatus 5. The iron hydroxide fine particles to be circulated from the sedimentation / separation unit 16 described later are added.

The polymer to be added is an anionic polymer,
Since the nonionic polymer has the greatest effect of aggregating iron hydroxide, it is preferable to use these, but it is no problem to use a cationic or amphoteric polymer. In the coagulation sedimentation apparatus, the iron hydroxide fine particles are strongly agglomerated by the addition of a polymer (arbitrary type), form pelletized flocs having extremely large sedimentation properties, and have a very high solids concentration (about 30 g / liter). To form a blanket (fluidized bed) of agglomerated particles of iron hydroxide. As a result, phosphate ions in the organic sewage are quickly adsorbed and removed by the iron hydroxide aggregated particles constituting the high-concentration blanket.
In the case of mg / liter, 90% or more of phosphorus is removed in a short time of 5 minutes through the blanket layer of the coagulation / sedimentation apparatus 5.

Next, the coagulated sedimentation treated water 6 from which phosphorus has been removed
Is supplied to a biological treatment tank (activated sludge treatment tank) 9 to biologically decompose and remove BOD, COD, nitrogen-containing compounds and the like in the treated water 6. At that time, since the treated water 6 contains BOD, COD, nitrogen-containing compounds, and the like in the effluent of the phosphorus removal step (the coagulation sedimentation apparatus 5), these are removed in the biological treatment tank 9. As the biological treatment step, any method such as an activated sludge treatment method and a biological nitrification denitrification method can be adopted. The biological treatment water 9a flows into the sedimentation tank 10 and flows out as the treated water 11 after sedimentation. The settled sludge is supplied to the coagulation settling water 6 as returned sludge 12 and circulated to the biological treatment tank 9. The anaerobic digester 8
The sludge 8c generated in the above is sent to the sludge dewatering machine 13, the dewatered cake 13a obtained by the sludge dewatering machine 13 is discharged to the outside, and the dewatered separated liquid 13b obtained there is supplied to the line of the treated water 4 in the coagulation separation step. Is done.

On the other hand, the slurry 14 of iron hydroxide to which phosphorus has been adsorbed in the coagulation and sedimentation apparatus 5 is appropriately discharged from the coagulation and sedimentation apparatus 5 to desorb phosphorus from the iron hydroxide particles.
That is, it is sent to the phosphorus attaching / detaching section 15. Phosphorous desorption part 15
In this case, for example, NaOH or the like (not limited) is added to the slurry 14 as the alkaline agent 18. When the alkaline slurry 18a to which the alkaline agent 18 is added stays in a stirring tank (not shown) for about 30 minutes, the adsorbed phosphorus is desorbed, and the phosphorus elutes to the liquid side.

Next, the slurry 15a from which phosphorus has been eluted moves to the sedimentation / separation section 16, where the iron hydroxide 19 precipitates. The precipitated and separated iron hydroxide 19 is recycled and added to the treated water 4 in the coagulation / separation tank 3. In this recycling, the iron hydroxide 19 is again used as the iron hydroxide fine particles having a high phosphorus adsorption power. This is an alkaline aqueous solution containing sodium, and when Ca or Mg and ammonium ions are added thereto, it is crystallized and precipitated as calcium phosphate (HAP) or magnesium ammonium phosphate (MAP). By the above process, not only phosphorus is removed without generating coagulated sludge from organic wastewater permanently,
It becomes possible to continue to recover as phosphorus resources. From the phosphorus removal and recovery step of the present invention, in the coagulation sedimentation method, no unavoidable sludge is generated.

The alkaline agent added to release phosphorus from the iron hydroxide to which phosphorus has been adsorbed includes NaOH and KO.
H is preferable, and when Ca (OH) ₂ or CaO is used, it is not preferable because phosphorus becomes a solid phase as hydroxyapatite and calcium phosphate and precipitates, and a liquid containing phosphorus at a high concentration cannot be taken out. The above process makes it possible to permanently remove and recover phosphorus from phosphorus-containing organic wastewater. From the process of the present invention, no sludge-like waste is generated in the coagulation sedimentation method. There is no need to change the adsorbent.

[0023]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A test was conducted to apply the present invention to organic wastewater (sewage) having a concentration of 120 mg / L SS, 100 mg / L BOD, and 5.6 mg / L phosphorus. (SS Coagulation Separation) First, DAM-based cationic polymer (Evacloth C104G; EBARA product) was added to organic wastewater.
mg / liter and stirred for 2 minutes.
m large particle size floc is generated and the sedimentation speed is 250 m
A large sedimentability of m / min was obtained. The SS of the supernatant water after standing for 5 minutes was as small as 3.6 mg / liter, and 97% of the SS in the organic wastewater was removed. Since the SS phosphorus was removed, the phosphorus concentration was reduced to 3.2 mg / liter. When 3 mg / liter of the amphoteric polymer (Evacloth B304; Ebara product) was injected, flocs having a larger particle size were formed, and the sedimentation velocity was 340 mm / min. On the other hand, when the same treatment was performed by adding an anionic polymer and a nonionic polymer, formation of flocs was not recognized.

(Anaerobic digestion of settled sludge) When the settled sludge agglomerated with the above cationic polymer was digested anaerobically in 35 days at a medium temperature and digested for 30 days, the sludge digestibility was 6%.
5%, digestion gas generation amount is 620 slg / kg / SS
Liters. Therefore, 73 m ³ of digested gas could be recovered per 1000 m ^{3 of} organic wastewater. In the case of anaerobic digestion of the first sediment sludge in the conventional organic wastewater treatment, only 24 m ^{3 of} digestive gas can be recovered per 1000 m ^{3 of} organic waste water, so the amount of energy recovered from organic waste water is about three times. Increased.

(Step of Coagulation Precipitation / Phosphorus Removal) Next, the iron hydroxide fine particles were added to the above-mentioned cationic polymer coagulation separation water by 80 m.
g / l, and further, 1 mg / l of an anionic polymer (ebacrose A153) was added. Immediately, an ascending flow rate of 200 mm / mi was added to the blanket-type coagulation / sedimentation tank.
n in an upward flow. As a result, the iron hydroxide particles
Agglomerated strongly by polymer, high concentration (32g SS /
L) Agglomerated pellet-like particles formed in the blanket. Drive with the blanket layer height set to 1m,
The time for the raw water to pass through the blanket was set to 5 minutes.
As a result, when the phosphorus concentration of the effluent from the blanket layer was measured, the concentration was 0.13 to 0.21 mg / liter and the turbidity was 0.15, which was extremely low. Was removed at high speed and high altitude.

(Step of Desorbing Phosphorus) When the blanket height reached 1.2 m, the slurry in the blanket was discharged and returned to the blanket height of 1 m. Add 1500 mg / L of NaOH to the discharged slurry, and add pH12.
After adjusting to 2 and stirring for 1 hour, the precipitate was separated and, as a result, phosphorus was completely desorbed from the iron hydroxide. The phosphorus desorbed sediment slurry was recycled to raw water again and allowed to flow into the blanket. At this point, no fresh iron hydroxide was added.
The phosphorus concentration of the treated water is 0.11 to 0.23 mg / L, and even if recycled iron hydroxide is used,
It was confirmed that phosphorus in raw water was highly removed.

(Biological treatment step) Next, the treated water from which phosphorus has been removed was allowed to flow into a standard activated sludge treatment facility. On this occasion,
In order to prevent the activated sludge from becoming phosphorus-deficient due to too little phosphorus, a portion of the cationic polymer coagulated sedimentation treated water is branched and allowed to flow into the activated sludge treatment aeration tank. It was adjusted to 3 mg / liter. As a result, the phosphorus in the activated sludge water was stably 0.1 mg / liter or less. Further, the amount of surplus activated sludge generated was very small, 22 g · ss / m ^{3 of} organic wastewater. (In the conventional organic wastewater treatment method, the amount of surplus activated sludge generated is 97 g · ss / m ^{3 of} organic wastewater.)

(Phosphorus recovery step) On the other hand, the slurry discharged from the phosphorus removal step is subjected to alkali treatment and then precipitated, and the supernatant has a very high phosphorus concentration of 1000 to 1200 mg / liter. It was highly concentrated, about 400 times. Add calcium chloride (C
a / PO ₄ ) The molar ratio was adjusted to 2 and the mixture was stirred for 5 minutes. As a result, a hydroxyapatite precipitate having a high value as a fertilizer raw material was quickly formed. The phosphorus concentration of the supernatant supernatant water is 0.3 mg / liter or less, and
% Could be recovered.

(Anaerobic digestion / elimination liquid) Next, in order to recover phosphorus in the anaerobic digestion / elimination liquid, the digestion / elimination liquid (phosphorus concentration 1) was used.
(53 mg / l) and a dewatered separation liquid (phosphorus concentration 126 mg / l) obtained by dewatering digested sludge with the sludge dewatering machine 13 were returned and mixed with the influent water at the previous stage of the cationic polymer coagulation separation step of the present invention. Was. In this case, since the phosphorus concentration of the inflow water in the phosphorus removal step was increased to 4.8 mg / liter, the amount of the added iron hydroxide fine particles was reduced to 110 m.
g / liter. No other changes were made. As a result, the phosphorus concentration in the effluent of the blanket layer was as high as 0.15 to 0.23 mg / liter, and phosphorus was highly removed. Therefore, it was confirmed that phosphorus resources can be effectively recovered not only from the organic wastewater system but also from the sludge system according to the present invention.

[0031]

Since the present invention is configured as described above, the following remarkable effects can be obtained. 1) Phosphorus recovery from organic sewage, which was impossible with conventional organic sewage treatment methods, can be realized with an extremely simple system. Phosphorus is a depleted resource worldwide, and Japan must import 100% of phosphate ore. Therefore, the significance of the present invention, which can recover a large amount of phosphorus, an essential element for crop harvesting, from organic wastewater is extremely large. is there. 2) In the method of the present invention, the greatest problem (removable inorganic hydroxide sludge) in removing phosphorus by the coagulation sedimentation method does not occur. Therefore, there is no need to treat and dispose sludge resulting from phosphorus removal. 3) Since the organic SS in the organic wastewater is highly separated and anaerobically digested, the amount of methane gas recovered from the organic wastewater is significantly increased.

4) Since the SS of the organic wastewater does not flow into the activated sludge treatment step, the amount of surplus activated sludge generated in the biological treatment step is significantly reduced as compared with the conventional case. As a result, the process of treating excess sludge is significantly improved. 5) In the phosphorus removal step, the running cost is lower than the conventional phosphorus removal method in which an expensive phosphorus adsorbent such as granular activated alumina is packed in a column and phosphorus-containing water is passed through to remove phosphorus. In addition, since the adsorption speed is extremely high, the apparatus is compact and the equipment cost is low. 6) Since the organic wastewater entering the phosphorus removal step has a high degree of SS removed in advance, the organic wastewater SS hardly flows into the phosphorus removal step using a fluidized bed. Hardly accumulates. Therefore,
Agglomerated particles of iron hydroxide or aluminum hydroxide in the fluidized bed are not contaminated by inert SS.

[Brief description of the drawings]

FIG. 1 is a diagram showing a treatment system of an organic wastewater treatment method of the present invention.

FIG. 2 is a diagram showing a treatment system of a conventional organic sewage treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic sewage 2 Cationic or amphoteric polymer 3 Flocculation separation tank 4 Flocculation separation treatment water 5 Flocculation sedimentation apparatus 6 Flocculation settling water 7 Separation sludge 8 Anaerobic digestion tank 8a Digestion gas 8b Digestion separation liquid 8c Digestion sludge 9 Activated sludge treatment Tank (biological treatment tank) 9a biological treatment water 10 sedimentation tank 11 treated water 12 return sludge 13 sludge dewatering machine 13a dehydration cake 13b dehydration separation liquid 14 iron hydroxide slurry 15 phosphorus desorption part 15a slurry 16 precipitation separation part 17 phosphorus recovery part 18 Alkaline agent 18a Alkaline slurry 19 Iron hydroxide 20 Separated water 21 Recovered phosphorus 22 Phosphorous recovered water 23 First sedimentation basin 24 Precipitated sludge 25 Activated sludge aeration tank 26 Inorganic coagulant 27 Biologically treated water 28 Final sedimentation basin 29 Excess sludge 30 Dehydrator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C02F 3/12 C02F 3/12 V 4G066 11/04 11/04 A F term (Reference) 4D015 BA05 BA19 BB05 BB08 BB12 CA18 DA04 DA13 DA16 DC06 DC07 DC08 EA14 EA32. GA25 GA34 GA37

Claims (5)

[Claims] 1. A cationic or amphoteric polymer flocculant is added to an organic wastewater to aggregate the SS in the organic wastewater, and the aggregated SS is removed by solid-liquid separation.
S is subjected to an anaerobic digestion treatment, while iron hydroxide and / or aluminum hydroxide fine particles and a polymer flocculant are added to the organic wastewater from which the SS has been removed, and the slurry is subjected to upward flow in a slurry blanket type flocculating and settling apparatus. In the phosphorus removal step of forming a fluidized bed of aggregated particles by passing through, phosphorus is adsorbed and removed, and then the treated water from which the phosphorus is adsorbed and removed is biologically treated, and the phosphorus adsorption and hydroxylation from the coagulation sedimentation apparatus The slurry containing iron and / or aluminum hydroxide is made alkaline to desorb phosphorus, and the phosphorus-desorbed iron hydroxide and / or aluminum hydroxide is recycled to the phosphorus removal step, and phosphorus is removed from the phosphorus desorbed solution as hydroxyapatite or magnesium apatite. A method for treating organic wastewater, comprising recovering the organic wastewater. 2. The method according to claim 1, wherein the digested and desorbed liquid produced in the anaerobic digestion treatment of the separated SS is supplied to organic wastewater before the step of adding iron hydroxide and / or aluminum hydroxide in the phosphorus removal step. Organic wastewater treatment method. 3. A process for treating organic sewage, comprising supplying a dewatered separated solution of anaerobic digested sludge to organic sewage before the step of adding iron hydroxide and / or aluminum hydroxide in the phosphorus removal step. Method. 4. A method for treating organic sewage, characterized in that a part of inflowing organic sewage or water treated by coagulation and separation with a cationic or amphoteric polymer flocculant is branched and supplied to a biological process. 5. An agglutination / separation tank for introducing and separating organic sewage to which a cationic or amphoteric polymer coagulant is added, and for aggregating and separating SS in the organic sewage; Anaerobic digester, adding iron hydroxide and / or aluminum hydroxide fine particles and a polymer flocculant to the organic wastewater from which SS has been removed and introducing the polymer flocculant in an upward flow to form a fluidized bed of the flocculated particles, A slurry blanket-type coagulation-sedimentation device for adsorbing and removing the water, a biological treatment device for introducing the treated water from which the phosphorus is adsorbed and removed, and a biological treatment device, and a slurry containing iron-adsorbed iron hydroxide and / or aluminum hydroxide from the coagulation-sedimentation device. A phosphorus desorption device for desorbing phosphorus by making it alkaline, a circulation conduit for recycling phosphorus desorbed iron hydroxide and / or aluminum hydroxide from the phosphorus desorption device to the coagulation and precipitation device, and An organic wastewater treatment device, comprising: a phosphorus recovery device that recovers phosphorus as hydroxyapatite or magnesium apatite from the phosphorus desorption solution from the phosphorus desorption device.