JP2009148710A - Treatment method of organic waste liquid and regenerated fuel charcoal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic wastewater treatment system capable of treating a large amount of organic wastewater using a small-sized biological treatment apparatus in order to eliminate the problem wherein, since an activated sludge method for converting BOD in wastewater to sludge is widely used in the treatment of organic wastewater and the treatment of excess sludge produced from a biological treatment process is difficult to become a large load, the organic wastewater is biologically treated at the present time under a condition of reducing the production amount of excess sludge and a wastewater treatment apparatus is made large-sized, and regenerated fuel charcoal. <P>SOLUTION: In this organic wastewater treatment method, the biological treatment apparatus is made small-sized by accelerating the propagation of sludge and enhancing a BOD removing ratio in the biological treatment process by connecting a regenerated fuel charcoal recovery process, which is constituted so that the excess sludge discharged from the biological treatment process is dried in the activated sludge method for treating organic wastewater and an iron oxide powder is added to and mixed with the dried excess sludge to mold and granulate the dried excess sludge and the granulated excess sludge is carbonized under heating, to the biological treatment process. The regenerated fuel charcoal is obtained using the organic wastewater treatment method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the activated sludge process for purifying organic wastewater, the present invention solves the problem of surplus sludge treatment, which was a heavy burden, by regenerating and recovering the surplus surplus sludge discharged from the biological treatment process into fuel coal. On the other hand, the present invention relates to an organic wastewater treatment system and regenerated fuel charcoal characterized in that the biological treatment apparatus is miniaturized by promoting the growth of sludge in the biological treatment process.

  For the treatment of organic wastewater, biological treatment methods that purify wastewater using microorganisms have been widely put into practical use. There are an aerobic treatment method using an aerobic microorganism and an anaerobic treatment method using an anaerobic microorganism. Both methods generate excess sludge. The present invention belongs to the former.

  The activated sludge method using aerobic microorganisms is as follows. That is, it can be defined as a treatment method in which floc-like biological growth bodies constantly circulate and come into contact with organic wastewater in the presence of oxygen (Non-patent Document 1). As described, the activated sludge method using aerobic active microorganisms refers to aerobic microorganisms that feed on wastewater (referred to as aeration) and eat soluble organic matter (referred to as BOD) in the wastewater as a nutrient source. When activated, microorganisms grow while eating BOD to become biological sludge. By circulating this biological sludge, BOD in wastewater is converted to sludge to purify wastewater, and surplus activated sludge is excess sludge. It is a method for treating organic wastewater to be removed.

  In order to increase wastewater treatment efficiency, according to FIG. 1 (Non-Patent Document 2), biological sludge is propagated using a logarithmic growth phase (ab in FIG. 1) in which the amount of sludge grows geometrically. It is necessary to maintain conditions that promote However, it is described that if the grown sludge is left as it is, it shifts to a decaying growth phase (b to c in FIG. 1) where the supply of usable biological sludge begins to run out, and sludge growth decreases. . Therefore, in order to maintain the logarithmic growth phase and promote the growth of biological sludge, it is necessary to quickly take out the excess surplus sludge from the system and treat it.

  However, “the surplus sludge consumes a great deal of labor and energy and is finally disposed of through concentration, dehydration, and incineration, but a shortage of final disposal sites is also a serious problem” (Non-Patent Document 3) ) As there is a problem in terms of environment and economy, such as a shortage of land for disposal of excess sludge, incineration facilities and their fuel costs, etc., there is no stopping at present, and attenuation that suppresses the growth of biological sludge Organic wastewater is being treated in the growth phase. As a result, the processing facilities are becoming larger.

  On the other hand, these surplus sludge treatment methods include a method of recycling for animal feed, agricultural fertilizer, and the like, a method of directly burning and treating solution or slurry sludge waste liquid (Non-patent Document 4), etc. There is a processing method. Further, as a method of utilizing the excess sludge to be discharged, there is a method of drying and fueling, steaming and charcoal, or dry distillation and gasification (Patent Document 1). However, it has not been solved yet to reduce the size of the wastewater treatment apparatus that is becoming larger or to efficiently treat and effectively utilize the excess surplus sludge generated in large quantities. There is a strong demand for the development of small-scale wastewater treatment equipment and the effective utilization of surplus breeding sludge.

W. W. ECKENFELDER, Jr D.C. J. et al. O'CONNR, Translated by Shigehisa Iwai, Biological Treatment of Wastewater, Corona, Inc. (Showa 45), p. 198 Same as above, page 15 Handa Hiroshi, Abe Masaki, Noda Yuki, Application Development of Magnetic Beads to Bio-Environmental Technology, CMC Publishing, (2006) 201 pages Pollution Prevention Technology and Regulations Editorial Committee, Fifth Amendment / Pollution Prevention Technology and Regulations [Water Quality], published by Japan Industrial Environment Management Association (1995) pp. 186-188 JP 2004-115576 A

  In an activated sludge process for treating organic wastewater, it is known that activating microorganisms to propagate activated sludge is essential for improving the efficiency of biological treatment. However, there is a contradiction that when activated sludge grows and surplus sludge increases, the activity of microorganisms decreases, so that the BOD treatment capacity also decreases. In order to solve this, it is necessary to take out the excess sludge from the system and dispose of it, and it is treated by methods such as incineration and landfill. However, these treatment methods cause secondary pollution such as a shortage of land to be discarded and environmental pollution due to bad odors, and thus have a difficult problem in terms of economy and environmental conservation. Therefore, in the decaying growth phase that suppresses the generation of excess sludge, it is unavoidable to increase the size of the treatment equipment because organic wastewater must be treated under conditions of low biological treatment efficiency. It is.

  Then, this invention makes it a subject to accelerate | stimulate the proliferation of the sludge in a biological treatment process, and to reduce a biological treatment apparatus, solving the problem of the treatment of the multiplication surplus sludge discharged | emitted from the biological treatment process of organic wastewater. .

  The technical problem can be achieved by the present invention as follows.

  The present invention that solves the above-mentioned problem is that, in the biological treatment process of organic waste water, the regenerated fuel coal recovery process for regenerating the surplus surplus sludge that has been propagated into fuel coal is connected to the biological treatment process, thereby An organic wastewater treatment method characterized by promoting growth and improving the BOD removal rate to downsize a biological treatment apparatus.

  Further, in the regenerated fuel charcoal recovery step, the excess sludge discharged from the biological treatment step is dried by heating at a temperature of 80 to 200 ° C., and the malodorous component in the sludge is decomposed and removed. A step of adding and mixing 0.5 to 5% by weight of iron oxide powder to the dried sludge, a step of granulating and / or molding the mixture obtained in the step, and a molded product obtained in the step Characterized in that it has a regenerated fuel coal recovery step comprising a step of recovering fuel coal with good combustibility in a high yield by heating at a temperature of 300 to 400 ° C. in a non-oxidizing atmosphere. To do.

  Moreover, the biological treatment process sets the biological sludge concentration to a logarithmic growth phase of 5000 to 10000 mg / L in terms of MLSS (an index representing the amount of microorganisms in wastewater), so that the BOD removal rate is 80% or more. And by setting the biological sludge concentration in the wastewater to a decaying growth phase with a MLSS concentration of 1000 to 3000 mg / L, the effluent water has a BOD removal rate of 98% or more with respect to the raw water. This is a method for treating organic wastewater comprising a biological treatment process in which a biological treatment facility is downsized by adopting a biological treatment process comprising two steps.

Further, the present invention provides an iron oxide powder to be added to the dried sludge in the regeneration fuel coal recovery step, such as hematite α-Fe ₂ O ₃ , magnetite Fe ₃ O ₄ , maghemite γ-Fe ₂ O ₃ , goethite α-FeOOH, One kind or two or more kinds selected from akagenite β-FeOOH and levitcrosite γ-FeOOH can be mixed and used.

  Moreover, this invention is the regenerated fuel charcoal obtained by the processing method of the said organic waste water, and the said regenerated fuel coal contains iron oxide.

  Since the activated sludge treatment system of the present invention recovers the generated surplus surplus sludge as regenerated fuel charcoal, the biological treatment is aerated in the logarithmic growth phase to promote sludge growth, and this step increases the BOD removal rate. The organic wastewater treatment device was solved while the excess sludge treatment problem was solved by aeration of the wastewater treated in step 1 in the decaying growth phase and purification of the BOD into effluent water of 20 mg / L or less. It can be downsized.

  On the other hand, the iron oxide powder added to the sludge increases the carbonization efficiency when the sludge is heated and carbonized and regenerated into fuel charcoal due to the redox catalytic action of the iron oxide, and the generated regenerated fuel containing iron oxide powder Since the combustion efficiency of charcoal is increased and complete combustion is performed at the time of combustion, there are effects such as exerting a safety and health effect that suppresses the generation of carbon monoxide.

  That is, in the conventional heating carbonization method, carbon dioxide gas is generated in the process of steaming and carbonizing excess sludge, so the production rate is low, and when the produced charcoal is burned, oxygen deficiency occurs, There was a problem that carbon monoxide gas was easily generated due to incomplete combustion. Therefore, the oxidation-reduction catalytic action of iron oxide powder, that is, when iron oxide is heated at a temperature of 300 ° C. or higher, when the atmosphere becomes a reducing atmosphere due to incomplete combustion gas, Fe (III) in the iron oxide is Fe When reduced to (II), the iron oxide releases oxygen and changes the atmosphere to an oxidizing atmosphere. Various studies were made focusing on the redox catalytic action in which Fe (II) was oxidized by oxygen to become Fe (III) again in an oxidizing atmosphere. As a result, when the sludge mixed with iron oxide powder is heated and carbonized at a temperature of 300 ° C. or higher, the production of carbon dioxide gas is suppressed, the production rate of charcoal is improved, and the produced iron oxide powder-containing coal is burned. The effect that it was good and incomplete combustion hardly occurred was confirmed.

  The configuration of the present invention will be described in more detail as follows.

  An embodiment of the present invention will be described with reference to FIG.

  FIG. 2 shows an organic waste liquid treatment system according to the present invention, wherein (I) is a biological treatment process, and comprises the primary treatment (A), secondary treatment (B), and tertiary treatment (C) steps. . (II) is a regenerated fuel coal recovery process for recovering and recovering excess surplus sludge discharged from the process (I) to fuel coal, and a thermal decomposition [HT1] process for drying and deodorization and deodorization of exhaust gas. A process consisting of a device [GT], a process [MIX] of adding iron oxide powder to dry sludge, a process [MOD] of granulating and molding the mixture, and a process of heating and carbonizing the molded product [HT2]. Consists of.

  First, the biological treatment process (I) will be described.

  First, in the biological treatment step (I), in the primary treatment step (A), solid waste mixed in the organic waste water W0 is separated from the primary treatment water W1 in the sedimentation tank D1, and the solid waste is separated from the waste storage tank ST1. The primary treated water W1 is transferred to the secondary treatment step (B) by a liquid feed pump.

  Next, in the secondary treatment step (B), the organic matter contained in the primary treated water W1 (hereinafter referred to as “BOD”) is eaten in the activated biological sludge by aeration in the aeration tank B1, BOD biosludge conversion is promoted and the biological sludge concentration is aerated in a logarithmic growth phase with MLSS concentration of 5000-10000 mg / L. The grown biological sludge slurry S1 flows into the sedimentation tank D2 through the communication pipe. In the sedimentation tank D2, the secondary treated water W2 is settled and separated into the biological sludge slurry S2, and the secondary treated water W2 flows into the tertiary treatment step (C) through the communication pipe.

  The reason why the biological sludge concentration is set to a high concentration of 5000 to 10,000 mg / L in terms of MLSS is to reduce the size of the waste liquid treatment apparatus by promoting the growth of biological sludge and increasing the BOD removal rate. When the MLSS concentration exceeds 10,000 mg / L, it becomes difficult to settle and separate the breeding sludge in the sedimentation tank. Less than 5000 mg / L is not preferable because the BOD removal rate is low. A preferred range is 5000 to 8000 mg / L.

  On the other hand, a portion of the surplus sludge slurry S2 that has settled and separated is transferred to the stabilization tank RC1, and the biological sludge that has been eaten and proliferated is made into a poor food state and reactivated. The reactivated biological sludge S3 is mixed with the primary treated water W1 and returned to the aeration tank B1, thereby maintaining the biological sludge concentration in the aeration tank B1 at a MLSS concentration of 5000 to 10000 mg / L. Further, the remaining surplus sludge slurry S2 is separated in the solid-liquid separation step PF, the waste liquid is returned to the primary treated water W1, and the paste surplus sludge is stored in the storage tank ST2.

  Furthermore, in the tertiary treatment step (C), the BOD remaining in the secondary treated water W2 is aerated in the aeration tank B2, and the biological sludge concentration is aerated in an attenuated growth phase with an MLSS concentration of 1000 to 3000 mg / L. The biological sludge slurry S4 propagated in the step is transferred to the sedimentation tank D3. In the settling tank D3, the purified waste water W3 and the biological sludge slurry S5 are settled and separated, and the purified waste water W3 is sterilized and discharged out of the system. A part of the slurry S5 is mixed with the secondary treated water W2. By returning to the aeration tank B2, the biological sludge concentration in the aeration tank B2 is maintained at a MLSS concentration of 2000 to 3000 mg / L. The remaining surplus sludge slurry S5 is transferred to the solid-liquid separation step PF of the secondary treatment step (B) for solid-liquid separation, and the waste liquid is returned to the primary treatment water W1, and the paste-like surplus sludge is stored. Store in tank ST2.

  The reason why the biological sludge concentration is set to a low concentration of 1000 to 3000 mg / L in the MLSS concentration in the aeration process in the decaying growth phase is to make the discharged water having a low BOD concentration in the waste water. If it exceeds 3000 mg / L, it is difficult to reduce the BOD concentration in the effluent water. If it is less than 1000 mg / L, the BOD removal rate is too low, so the purification of wastewater does not proceed. A preferred range is 1000 to 2000 mg / L.

  Next, the process (II) for recovering the surplus surplus sludge as regenerated fuel coal will be described.

  In the step (II) of recovering the surplus surplus sludge as regenerated fuel coal, the paste-like surplus sludge is taken out from the surplus sludge storage tank [ST2] in the biological treatment step (I), and the sealed drum provided with the exhaust pipe of the thermal decomposition step HT1 The container is put into a container, and the container is heated and dried at a temperature of 80 to 200 ° C. while rotating in an electric furnace. The malodorous component is decomposed and deodorized to produce dry sludge. The cracked gas is deodorized by the deodorizing device GT through the exhaust pipe and then released into the atmosphere.

  In the regenerated fuel charcoal recovery process of the present invention, the excess sludge discharged from the biological treatment process is heated at a temperature of 80 to 200 ° C. to dry the hydrous paste-like surplus sludge and to contain hydrogen sulfide contained in the sludge, This is for deodorizing treatment by decomposing malodorous components such as methyl sulfide, methyl mercaptan and ammonia. When the heating temperature is less than 80 ° C., the drying rate is slow and the decomposition of malodorous components is insufficient. When the temperature exceeds 200 ° C., the drying rate is large and the effect of decomposing the malodorous component is large, but it is not preferable because sludge gasification occurs. A preferable heating temperature is 100 to 180 ° C. The cracked gas is preferably treated using a deodorizing device.

  The deodorized and dried sludge obtained in the heating and deodorizing step is added with 0.5 to 5% by weight of iron oxide powder in the next mixing step MIX and mixed with a mix muller, a V-type mixer or the like.

In the present invention, the iron oxide powder is added to the dried sludge in order to efficiently recover the carbon component from the organic sludge and to improve the combustibility of the regenerated fuel coal. When the iron oxide powder added to the dried sludge is less than 0.5% by weight, the effect of the redox catalyst is reduced. If it exceeds 5.0% by weight, the redox catalyst effect is sufficient, but the purity of the regenerated coal is lowered, and the calorific value is reduced, which is not preferable. A preferable addition amount is 1.0 to 3.0% by weight. Examples of the iron oxide powder include hematite α-Fe ₂ O ₃ , magnetite Fe ₃ O ₄ , maghemite γ-Fe ₂ O ₃ , goethite α-FeOOH, akagenite β-FeOOH, levitcrosite γ-FeOOH, and the like, or 2 A mixture of seeds or more can be used.

  The mixture obtained in the mixing step is granulated and / or molded into a shape suitable for the use in the next molding step MOD using an extrusion molding machine, a compression molding machine or the like.

  In the present invention, the mixture of the dried sludge and the iron oxide powder is formed in order to obtain a uniform regenerated fuel char by performing carbonization uniformly during the heating carbonization, and to obtain an easy-to-use fuel char Because. In order to form a mixture of dried sludge and iron oxide powder, various shapes such as pellets, rods, plates, bean charcoal and briquettes can be used by using a molding machine such as a casting machine or extrusion machine. Can be molded. Moreover, a shaping | molding adjuvant can be used suitably.

  In the heating carbonization step HT2 for carbonizing the molded product obtained in the molding process, the molded product obtained in the step is heated to 300 to 400 ° C. in a non-oxidizing atmosphere using a heating furnace such as an electric furnace. The iron oxide-containing fuel charcoal is produced by heating at a temperature of, and after cooling to room temperature, the product is stored in the regenerated fuel charcoal storage tank ST3.

  In the present invention, when the granulated product or molded product is heated and carbonized in a non-oxidizing atmosphere at a temperature of 300 to 400 ° C., the non-oxidizing atmosphere is caused by excess sludge burning. This is to prevent carbonation and efficiently carbonize. When the heating carbonization temperature is less than 300 ° C., the oxidation-reduction catalytic action of iron oxide hardly occurs. Moreover, when exceeding 400 degreeC, since gasification accelerates simultaneously with carbonization, it is not preferable. In addition, the heating carbonization apparatus uses a heating furnace in which the gas atmosphere in the furnace can be controlled, and in order to obtain a non-oxidizing atmosphere, a method using an inert gas such as nitrogen or a method in which mixing of air is cut off is used. Can be implemented.

  Next, the embodiment will be described in detail.

(I) Biological treatment process Water quality inspection of wastewater and treated water was carried out by the method described in “Sewage Test Method, Chapter 4 Activated Sludge Test” published by the Japan Sewage Association (1984).

  First, the conventional method in the wastewater treatment process of a legume processed food factory is shown.

<Comparative Example 1>
The organic wastewater discharged from the legume processed food factory has an average concentration of BOD of 1000 mg / L, the amount of drainage is 100 m ³ per day, and the total amount of BOD discharged is 100 kg per day.

Wastewater treatment process in the beans processed food plant, the volume consists of a settling tank in the aeration tank and 18m ³ of 250 meters ^3. First, waste water with a BOD concentration of 1000 mg / L was introduced into an aeration tank, and aerated in an attenuated growth phase with an MLSS concentration of 2000 mg / L. The BOD volume load at this time was 0.4 Kg / m ³ · day, and the BOD-MLSS load was 0.2 Kg / Kg · day. Slightly grown biological sludge slurry was transferred to a sedimentation tank through a communication pipe, where it settled and separated into purified waste water and biological sludge slurry. The separated purified wastewater was sterilized and released into the river, and excess sludge was taken out of the system and disposed of in landfills. The amount of excess sludge produced was 5 kg / day in terms of dry weight, and the BOD sludge conversion rate was 5%.

Moreover, the quality of the purified waste water was 98% in total BOD removal from the raw water, and the BOD concentration was 20 mg / L, which satisfied the discharged water standard. However, the aeration tank must use a large aeration tank having a volume of 250 m ³ that is 2.5 times the volume of wastewater having a daily volume of 100 m ³ . The reason is that surplus sludge was landfilled, so there was a problem with land shortage and environmental conservation, so it was necessary to suppress the generation of surplus breeding sludge, and the BOD sludge conversion rate was attenuated by 5%. It was because it aerated in the growth phase. The amount of surplus sludge produced was a small amount of 5 kg / day as a dry product.

Example 1
(I) Biological treatment process The bean processed food factory waste liquid of the comparative example 1 was refine | purified by the biological treatment process of (I) in FIG. 2 of this invention.
The waste water W0 having an average BOD concentration of 1000 mg / L is received in a sedimentation tank D1 having a volume of 18 m ^{3 in} the primary treatment step (A), and solid waste in the waste water W0 is settled and separated into the storage tank ST1, and the primary treatment water W1. Was a liquid feed pump, and transferred to the aeration tank B1 having a volume of the secondary treatment step (B) of 60 m ³ .

In the secondary treatment step (B), the primary treated water W1 with a BOD concentration of 1000 mg / L is received into the aeration tank B1, and aerated in a logarithmic growth phase with an MLSS concentration of 8000 mg / L to activate sludge. Increased the sludge conversion rate of BOD and propagated biological sludge. The BOD volumetric load at this time was 1.67 Kg / m ³ · day, and the BOD-MLSS load was 0.21 Kg / Kg · day. The grown biological sludge slurry S1 was transferred to a sedimentation tank D2 having a volume of 18 m ³ through a communication pipe. In the sedimentation tank D2, the secondary treated water W2 and the biological sludge slurry S2 were settled and separated, and the secondary treated water W2 was transferred to the aeration tank B2 having a volume of 60 m ^{3 in} the tertiary treatment step (C) through the communication pipe. The water quality of the secondary treated water W2 was a BOD of 200 mg / L (BOD removal rate was 80%).

On the other hand, the biological sludge slurry S2 separated and separated was transferred to a stabilization tank RC1 having a volume of 10 m ³ , and the appetite was reactivated by bringing the saturated biological sludge into a poor diet state. . The biological sludge S3 reactivated in this way was mixed with the primary treated water W1 and returned to the aeration tank B1, thereby maintaining the amount of microorganisms at a high activity with an MLSS concentration of 8000 mg / L. Further, the residue of the sludge slurry S2, that is, the generated surplus sludge was transferred to a solid-liquid separation step PF using a press filter and separated into solid and liquid. The wastewater was returned to the primary treated water W1, and the paste-like surplus sludge was collected in a surplus sludge storage tank ST2 having a volume of 20 m ³ . The amount of excess sludge generated was 27 kg / day in terms of dry weight, and the BOD sludge conversion rate was 27%.

Further, 200 mg / L BOD remained in the secondary treated water W2 transferred to the tertiary treatment step (C). The secondary treated water W2 was aerated in an aeration tank B2 in an attenuated growth phase with an MLSS concentration of 2000 mg / L. At this time, the BOD volumetric load was 0.33 Kg / m ³ · day, and the BOD-MLSS load was 0.17 Kg / Kg · day. The biological sludge slurry S4 was transferred to a sedimentation tank D3 having a volume of 18 m ³ through a communication pipe. In the sedimentation tank D3, the purified waste water W3 and the biological sludge slurry S5 were settled and separated, and the purified waste water W3 was sterilized and then discharged out of the system. The water quality of this purified waste water W3 satisfied the discharge water standard with a BOD concentration of 20 mg / L. The BOD removal rate in the tertiary treatment step (C) was 90%, and the total BOD removal rate from the raw water was 98%.

  On the other hand, the biological sludge slurry S5 separated and separated was mixed with the secondary treated water W2 and returned to the aeration tank B2, whereby the amount of microorganisms was maintained at 2000 mg / L as the MLSS concentration. Moreover, the remainder of the sludge slurry S5, that is, the generated surplus sludge is transferred to the solid-liquid separation step PF of the secondary treatment step (B), separated into solid and liquid, and the wastewater is discharged from the secondary treatment step (B). It returned to the primary treated water W1, and the paste surplus sludge was collect | recovered by storage tank ST2. The amount of excess sludge generated was 1 kg / day in terms of dry weight, and the BOD sludge conversion rate was 5%. The total amount of excess sludge recovered in ST2 was 140 kg and the water content was 80%. This was a dry matter weight of 28 kg per day.

In the method of the present invention, a large amount of excess sludge was produced at a dry matter weight of 28 kg / day. The reason for this is that the regeneration fuel coal recovery process that regenerates surplus sludge into fuel coal is linked to the biological treatment process, which promotes the growth of sludge by aeration in a logarithmic growth phase with a large BOD sludge conversion rate. is there.
That is, the first aeration tank B1 is aerated in the logarithmic growth phase to remove BOD by 80% or more, and the second aeration tank B1 is aerated in the decaying growth phase, and the remaining 20% BOD is contained in the BOD. The amount was purified to waste water of 20 mg / L or less. As a result, the aeration tank was able to be reduced to 60 m ³ , which is about a quarter of the conventional 250 m ³ device.

(II) Process of regenerating surplus sludge into fuel coal The production rate of sludge regenerated coal was determined by measuring the weight change before and after the heat carbonization treatment. The standard for the amount of carbon in the sludge was 53% by weight calculated from the sludge composition formula C ₅ H ₇ NO ₂ as a standard. The ash was burned at a temperature of 800 ° C. for 3 hours and the remaining amount was measured. The ash content of the sludge was 21.5% by weight.

<Preliminary Experiment 1> About Sludge Drying and Deodorizing Treatment 1 kg of paste-like rate excess sludge was taken out from the excess sludge storage tank [ST2] in the organic wastewater treatment step (I) in FIG. Next, 100 g of sludge was taken in a heating sample pan, inserted into a tubular furnace, and heated. The state of exhaust gas odor generation with increasing temperature was observed. As a result, odorous gas began to be emitted from the heating temperature of around 80 ° C., generated vigorously between 130 ° C. and 170 ° C., and when it exceeded 200 ° C., generation of odor gas disappeared.

<Preliminary experiment 2> Heating carbonization conditions (no iron oxide powder) <2-1>
10 g of powder obtained by granulating sludge deodorized and dried at 150 ° C. into a granite granule was put in a crucible, covered, and heated at 200 ° C. using a muffle electric furnace while blocking air flow. It was heated for 3 hours, taken out into a desiccator and cooled. As a result of measuring the weight after cooling to room temperature, the weight of the produced charcoal was 9.1 g. Since the amount of carbon in 10 g of dried sludge is 53%, the amount of carbon is 5.3 g, and the amount of ash is 21.5%, which is 2.15 g. Therefore, when the weight after heating is 7.45 g in total, the carbonization rate is 100%. When the produced charcoal was 9.1 g, 1.65 g was uncarbonized and the carbonization rate was 69%.

<2-2>
In the same manner as in 2-1, the sludge was heated at a temperature of 200 ° C. for 24 hours. The remaining amount was 8.55 g. This was ungenerated charcoal, and carbonization was insufficient at a heating temperature of 200 ° C.
<2-3>
The sludge was heated and carbonized in the same manner as in 2-1, except that the heating temperature was 250 ° C. and the heating time was changed. The remaining amount is 7.88 g (carbonization rate 92%) when the heating time is 3 hours, 7.65 g (carbonization rate 96%) when the heating time is 6 hours, and the carbonation rate is 98% after 8 hours. there were.
<2-4>
The sludge was heated and carbonized in the same manner as in 2-1, except that the heating temperature was 300 ° C. and the heating time was changed. The remaining amount was 7.26 g when the heating time was 1 hour, which was partially gasified, suggesting that the carbonization of the sludge was completed within 1 hour. Moreover, when heated at a temperature higher than this, gasification of sludge was further promoted.

<Preliminary experiment 3> Additives and heating carbonization conditions <3-1>
3% by weight of iron oxide (goethite) powder having a specific surface area of 80 m ² / g was added to and mixed with dried sludge that had been deodorized by heating at 150 ° C., and granulated into a granite granule. 10 g of this granulated powder was put in a crucible, covered, and heated at 300 ° C. using a muffle electric furnace while blocking air from flowing. After heating for 3 hours, it was taken out into a desiccator and cooled. As a result of measuring the weight after cooling to room temperature, it was 7.85 g. Since 10 g of dried sludge contains 3% iron oxide, the net amount of sludge is 9.7 g. Since the carbon content is 53%, the carbon content is 5.14 g, and the ash content is 21.5%, which is 2.13 g. Therefore, when the weight after heating is 7.27 g in total, the carbonization rate is 100%. Therefore, when the produced | generated charcoal was 7.85g, 0.58g was an ungenerated | generated charcoal and the carbonization rate was 89%. When the heating time was 4 hours, the carbonization rate of the sludge was 98%.
<3-2>
The sludge was heated and carbonized in the same manner as in 3-1, except that the heating temperature was 350 ° C. and the heating time was changed. The residual amount was 7.66 g (carbonization rate 92%) when the heating time was 1 hour, and 7.32 g (carbonization rate 99%) when the heating time was 3 hours. The remaining amount when the heating time was 4 hours was 7.08 g, and it was confirmed that it was partially gasified.
<3-3>
The sludge was heated and carbonized in the same manner as in the above 3-1 except that iron oxide (magnetite) powder having a specific surface area of 28 m ² / g was used and the addition amount was 1 wt%. When the heating time was 3 hours, the carbonization rate of the sludge was 98%.

  From the results of Preliminary Experiment 2 and Preliminary Experiment 3, it has been found that when iron oxide powder is added to the dried sludge, heating carbonization can be promoted without gasifying the carbon component in the sludge.

Example 2
In FIG. 2, 140 kg of paste-like surplus sludge is taken out from the surplus sludge storage tank [ST2] in the organic wastewater treatment step (I) and put into a 500 L rotary drum container equipped with an exhaust pipe in the thermal decomposition step HT1. The container was dried and deodorized by heating to a temperature of 150 ° C. while rotating in an electric furnace. 28 kg of deodorized dry product was obtained. The generated odorous gas was processed by a deodorizer GT and released to the atmosphere. A deodorizing device “Bioforest” manufactured by Fuji Kasui Kogyo Co., Ltd. was used as the deodorizing device.

Next, in the mixing step MIX, 560 g (2% by weight) of iron oxide (goethite) powder having a specific surface area of 80 m ² / g is added to 28 kg of the dried deodorized sludge obtained in the above step and mixed with a mix muller. After mixing uniformly, the mixture was stirred and mixed while adding a small amount of water, and granulated to 0.5 mmΦ. This granulated product was formed into a 10 mm × 10 mm × 100 mm rod shape by an extrusion molding machine in the molding step MOD.

  After drying the molded product obtained in the above step, in the heating carbonization step HT2, 40 pieces of molded products are put in one koji bowl using a square-shaped koji bowl (120W x 120D x 50Hmm) made of alumina, Using a stationary electric furnace with an internal volume of 36 liters and internal dimensions (300W x 600D x 200Hmm), the koji bowls are stacked in three stages, a total of 24 bowls are inserted in 4 rows and 2 rows, and the interior of the furnace is A non-oxidizing atmosphere in which the circulation of the outside air was blocked, heated at a temperature of 350 ° C. for 3 hours, cooled to room temperature, and taken out from the furnace. This operation was performed 6 times to heat and carbonize the entire molded product. The black product was iron oxide-containing regenerated fuel coal, the total weight of the product was 14.5 kg, and the carbonization rate of sludge was 98%. In addition, the iron oxide-containing regenerated fuel charcoal had good ignitability, burned smokelessly and odorlessly, and combustibility was good.

  In the biological treatment method of organic wastewater, the present invention is a heavy burden on the treatment of the generated excess sludge, but the excess sludge is made combustible by adding iron oxide powder to the excess sludge and carbonizing it by heating. It could be recovered and recovered into an excellent iron oxide-containing fuel coal. In addition, since the biological treatment conditions are implemented in the attenuated growth phase in order to reduce the load of surplus sludge treatment, the biological treatment equipment has been enlarged. However, by connecting the recycled fuel coal recovery process to the biological treatment process, Since the conditions were the logarithmic growth phase, the BOD removal rate was increased, and the biological treatment apparatus could be miniaturized, it can be easily implemented as an environment-friendly system that is excellent in economic efficiency. Furthermore, since iron oxide powder added to sludge has a redox catalytic action, when the sludge is heated and carbonized to be regenerated into fuel coal, the carbonization efficiency is high and the yield is high. When burning iron powder-containing regenerative fuel charcoal, combustion efficiency is good and complete combustion is achieved, so that it is excellent in combustibility such as suppressing the generation of carbon monoxide and exhibiting health and safety effects. For this reason, the present invention can be implemented in accordance with the demands of the times from the present background where the problem of depletion of energy resources is screamed.

Relationship between BOD removal and sludge growth Process flow diagram of the method of the present invention

Explanation of symbols

FIG.
a-b logarithmic growth phase region b-c decaying growth phase region
(I) Organic wastewater treatment process (A) Primary treatment process W0 Organic wastewater D1 Primary sedimentation tank ST1 Solid waste storage tank in W0 (B) Secondary treatment process W1 Primary treatment water B1 Aeration treatment tank S1 Proliferation biological sludge slurry D2 Secondary sedimentation tank S2 Surplus sludge slurry RC1 Stabilization tank S3 Reactivated sludge PF Solid-liquid separator ST2 Surplus sludge storage tank (C) Tertiary treatment process W2 Secondary treatment water B2 Aeration treatment tank S4 Proliferation biological sludge slurry D3 Tertiary Precipitation tank W3 Purified wastewater S5 Surplus sludge slurry (II) Regenerated fuel coal recovery process HT1 Thermal decomposition process GT Deodorizer MIX Mixing process MOD Molding process HT2 Heated carbonization process ST3 Regenerated fuel coal storage tank

Claims (6)

A method for treating organic wastewater, characterized in that, in a biological treatment process for organic wastewater, a regenerated fuel coal recovery process for regenerating the surplus surplus that has been propagated into fuel coal is connected to the biological treatment process. In the regenerated fuel charcoal recovery step, the excess sludge is heated and dried in a temperature range of 80 to 200 ° C. to decompose and remove malodorous components in the sludge, and the dried sludge obtained in the step is 0.5 to 5 wt. % Of iron oxide powder, a step of granulating and / or molding the mixture obtained in the step, and a molded product obtained in the step in a non-oxidizing atmosphere at 300 to 400 ° C. The method for treating organic wastewater according to claim 1, comprising a step of carbonizing by heating in a temperature range of The biological treatment step is a step of setting the biological sludge concentration to a logarithmic growth phase with an MLSS concentration of 5000 to 10000 mg / L so that the BOD removal rate is 80% or more of wastewater, The biological sludge concentration is an attenuation growth phase with an MLSS concentration of 1000 to 3000 mg / L, which is a two-stage process that makes the BOD removal rate 98% or more of the raw water. The method for treating organic wastewater according to claim 1 or 2 In the regenerated fuel coal recovery step, iron oxide powder added to the dried sludge is hematite α-Fe ₂ O ₃ , maghemite γ-Fe ₂ O ₃ , magnetite Fe ₃ O ₄ , goethite α-FeOOH, acagenite β-FeOOH, 3. The method for treating organic wastewater according to claim 2, wherein any one or more of rapid crosite γ-FeOOH is used. Regenerated fuel coal obtained by the method for treating organic wastewater according to any one of claims 1 to 4. The regenerated fuel coal according to claim 6, wherein the regenerated fuel coal contains iron oxide.