JP2006095377A - Biological treatment method and apparatus for oil and fat-containing wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To purify oil and fat-containing wastewater with high efficiency and efficiently recover energy from organic components in the wastewater; to realize the stabilization of methane fermentation treatment, the improvement of treatment efficiency, the downsizing of a methane fermentation tank, the improvement of separation efficiency of oil and fat from the oil and fat-containing wastewater, the volume reduction of generated sludge, and the like. <P>SOLUTION: After the oil and fat-containing wastewater is coagulated in a coagulation reaction tank 2, it is subjected to pressure floatation treatment in an oil-water separation tank (a pressure floatation tank) 3. The water treated by pressure floatation is subjected to biological treatment in an acid production tank 4, a high-load anaerobic treatment tank 5, and an aerobic treatment tank 6, and then subjected to solid-liquid separation in a sedimentation pond 7. Pressure floatation sludge is subjected to methane fermentation treatment in the methane fermentation tank 8, and then dehydrated by a sludge dehydrator 9. Surplus anaerobic sludge and/or surplus aerobic sludge in the biological treatment processes are introduced into the methane fermentation tank 8. The surplus anaerobic sludge and surplus aerobic sludge in the biological treatment processes, and surplus digested sludge in the methane fermentation tank 8 are introduced into the coagulation reaction tank 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biological treatment method and treatment apparatus for oil-containing wastewater such as food factory wastewater, and in particular, oil is efficiently separated from oil-containing wastewater, and the oil-containing sludge after separation is decomposed by methane fermentation. Thus, the present invention relates to a biological treatment method and a treatment apparatus that purify oil-containing wastewater with high efficiency and promote reduction of excess sludge and energy recovery from organic components in the wastewater.

  When wastewater containing a large amount of fats and oils, such as food factory wastewater, is biologically treated, the oils and fats adhere to sludge microorganisms, leading to a reduction in processing capacity. In addition, a method of treating the separated liquid after separating the fats and oils by microbial treatment such as an activated sludge method and separately treating the fat and oil-containing sludges is employed. A large amount of aggregating agent is required to separate the oil and fat from the oil and fat-containing wastewater with a pressurized flotation device or the like. In addition, the separated oil-containing sludge is creamy and has poor handleability. For this reason, the oil-containing sludge is treated with an adsorbent to adsorb the oil on the adsorbent, and then dehydrated and discarded. At this time, since the oil-containing sludge contains undecomposed organic matter, generation of odor is also a problem. Further, the generated dewatered sludge is conventionally disposed of by landfill or incineration, but due to the generation of harmful substances at the time of incineration or the shortage of landfill sites, an increase in disposal cost is also a problem.

  On the other hand, there is a method in which a microorganism preparation is added to an adjustment tank or an aeration tank, and fat and oil decomposition is carried out in an aeration tank as a method of directly treating it in a wastewater treatment system without removing the oil and fat in the oil-containing wastewater. For example, Japanese Patent Application Laid-Open No. 6-246295 proposes a method of anaerobic treatment after adding lipase to oil-containing wastewater to decompose the oil. Here, as a function of lipase, an action of hydrolyzing fats and oils to glycerin and higher fatty acid by lipase and an action of converting the produced higher fatty acid to lower fatty acid by highly efficient β oxidation are known.

  In addition, a yeast treatment method is known as a method using a microorganism capable of efficiently decomposing fats and oils. Unlike the treatment with a microbial preparation, the yeast treatment method simply introduces the yeast at the time of start-up, and does not require a fixed-quantity injection device for the preparation or an oil-degrading bacterial culture tank. In addition, the yeast treatment method enables high-concentration wastewater treatment, and unlike the activated sludge method, decomposes organic matter and generates thermal energy, so that it is a system that generates less excess sludge.

By the way, methane fermentation, that is, anaerobic digestion, has many advantages such as stabilization of organic matter, sludge reduction, energy recovery, reduction of aeration cost, etc. It may be used for sludge treatment (Japanese Patent Laid-Open Nos. 57-117380 and 2001-321792). In particular, Japanese Patent Application Laid-Open No. 2001-321792 discloses a method of mixing excess sludge generated from a subsequent aerobic treatment tank with fat-containing wastewater as an efficient treatment method of fat-containing wastewater, and subjecting the wastewater to methane fermentation as it is. Has been proposed. Japanese Patent Application Laid-Open No. 2001-321792 describes that in this treatment, the treatment performance is improved by adding lipase, introducing a microorganism-supporting carrier, or adding microorganisms to alleviate inhibition of higher fatty acids.
JP-A-6-246295 JP-A-57-117380 JP 2001-321792 A

Although the method described in Japanese Patent Application Laid-Open No. 2001-321792 enables energy recovery from the organic matter in the fat and oil-containing wastewater, there are the following problems.
-Since the substrate thrown into the methane fermenter is not concentrated like pressurized flotation sludge, high-load operation cannot be performed (usually 3 kg-COD / m ³ / d or less).
・ Since wastewater treatment is performed at the same time, the required capacity of the methane fermentation tank increases.
-High load operation can be performed by introducing a microbial carrier, but in this case, clogging due to undegraded oil or higher fatty acid salt is likely to occur and the carrier is likely to float.
-In particular, since the above-mentioned problems are likely to occur in medium-temperature methane fermentation with slow oil decomposition, the temperature range of methane fermentation is limited to high temperature (45 to 75 ° C).

  The present invention solves the above-mentioned conventional problems, separates the fats and oils in the fat and oil-containing wastewater, and purifies the fat and oil-containing wastewater with high efficiency by applying methane fermentation to the decomposition of the fat and oil-containing sludge after separation, A method for efficiently recovering energy from organic components in wastewater, stabilizing methane fermentation treatment, improving treatment efficiency, downsizing the methane fermentation tank, improving the separation efficiency of fats and oils from wastewater containing fats and oils An object of the present invention is to provide a biological treatment method and a treatment apparatus for fat and oil-containing wastewater that can reduce the amount of sludge.

  As a result of studying the above problems, the present inventors first separated the oil-containing wastewater into oil and organic wastewater, the oil-containing sludge (oil-water separation sludge) was subjected to methane fermentation, and the oil-water separation liquid was subjected to an aerobic treatment. In this method, wastewater containing fats and oils is purified with high efficiency by circulating surplus sludge from biological treatment and digested sludge from methane fermentation to appropriate locations. In addition, energy is efficiently recovered from the organic components in the wastewater, and the methane fermentation treatment is stabilized, the treatment efficiency is improved, the methane fermentation tank is downsized, the oil separation efficiency from the oil-containing wastewater is improved, and the generated sludge The present inventors have found that the amount can be reduced and completed the present invention having the following gist.

  The biological treatment method for fat-and-oil-containing wastewater according to claim 1 includes an oil-water separation step for separating oil-and-water-containing wastewater into oil and water to obtain an oil-water separation sludge and a separated liquid, a methane fermentation step for subjecting the oil-water separation sludge to a methane fermentation treatment, In a biological treatment method for fat and oil-containing wastewater comprising a biological treatment step for aerobic treatment and / or high-load anaerobic treatment of a separated liquid, at least a part of surplus sludge generated in the biological treatment step is introduced into the methane fermentation step It is characterized by doing.

  The biological treatment method for fat and oil-containing wastewater according to claim 2 comprises: an oil-water separation step for separating oil-and-water wastewater into oil and water to obtain an oil-water separation sludge and a separated liquid; a methane fermentation step for subjecting the oil-water separation sludge to a methane fermentation treatment; In the biological treatment method for fat-containing wastewater comprising a biological treatment step for aerobic treatment and / or high-load anaerobic treatment of the separated liquid, the fat-containing wastewater introduced into the oil-water separation step is generated in the methane fermentation step. Digested sludge and / or at least part of surplus sludge generated in the biological treatment process is mixed.

  The biological treatment method for fat and oil-containing wastewater according to claim 3 is characterized in that, in claim 1 or 2, the operation conditions of the methane fermentation step are set to an in-tank sludge concentration of 20000 mg / L or more, SRT of 15 days or more, and HRT of 20 days or less. To do.

  The biological treatment method for fat and oil-containing wastewater according to claim 4 is the method according to claim 2 or 3, wherein the biological treatment step includes a high-load anaerobic treatment step, wherein the fat-containing wastewater is subjected to an acid fermentation treatment. And the treated water of the acid fermentation step is introduced into the oil / water separation step.

  The biological treatment apparatus for oil-containing wastewater according to claim 5 comprises oil-water separating means for separating oil-containing wastewater into oil-water to obtain oil-water separated sludge and a separated liquid, methane fermentation means for subjecting the oil-water separated sludge to methane fermentation, In a biological treatment apparatus for fat and oil-containing wastewater comprising a biological treatment means for aerobic treatment and / or high-load anaerobic treatment of a separated liquid, at least a part of surplus sludge generated in the biological treatment means is introduced into the methane fermentation means It is characterized by comprising sludge transfer means.

  The biological treatment apparatus for oil-containing wastewater according to claim 6 comprises oil-water separating means for separating oil-containing wastewater into oil-water to obtain oil-water separated sludge and a separated liquid, methane fermentation means for subjecting the oil-water separated sludge to methane fermentation, In a biological treatment apparatus for fat-containing wastewater comprising a biological treatment means for aerobic treatment and / or high-load anaerobic treatment of the separated liquid, digestion generated by the methane fermentation means in the fat-containing wastewater introduced into the oil-water separation means It has a sludge mixing means which mixes at least a part of sludge and / or surplus sludge generated in the biological treatment means.

  The biological treatment apparatus for fat and oil-containing wastewater according to claim 7 is the biological treatment apparatus according to claim 5 or 6, wherein the operation conditions of the methane fermentation means are: sludge concentration in the tank of 20000 mg / L or more, SRT (Solids Retention Time) 15 days or more, HRT (Hydric Retention Time) It is characterized by being 20 days or less.

  The biological treatment apparatus for fat and oil-containing wastewater according to claim 8 is the apparatus according to claim 6 or 7, wherein the biological treatment means includes high-load anaerobic treatment means, wherein the fat-containing wastewater is subjected to acid fermentation treatment. The treated water of the acid fermentation means is introduced into the oil / water separation means.

  According to the biological treatment method and treatment apparatus for fat and oil-containing wastewater of the present invention, the oil and fat-containing wastewater is purified with high efficiency, energy is efficiently recovered from the organic components in the wastewater, and methane fermentation treatment is stabilized and treated. It is possible to improve efficiency, downsize the methane fermenter, improve the separation efficiency of oil and fat from oil-containing wastewater, reduce the amount of generated sludge, reduce sludge disposal costs, reduce the processing facility site, and effectively use energy Energy saving can be achieved by this, which is extremely advantageous industrially.

  That is, according to the biological treatment method for fat-containing wastewater according to claim 1 and the biological treatment device for fat-containing wastewater according to claim 5, sludge is obtained by subjecting surplus sludge generated in the biological treatment of the oil-water separation liquid to methane fermentation treatment. In particular, when excessive sludge from high-load anaerobic treatment is introduced, high-concentration methanogenic bacteria can be inoculated, and methane fermentation treatment can be stabilized and highly efficient. Can be achieved.

  Moreover, according to the biological treatment method of the fat-containing wastewater of Claim 2, and the biological treatment apparatus of the fat-containing wastewater of Claim 6, the digestion sludge generated by methane fermentation and / or the surplus sludge generated in a biological treatment process are fat-containing. By mixing with wastewater, these sludges can function as fat and oil adsorbents, reducing the amount of flocculant used in the flocculant treatment prior to oil-water separation, or eliminating the need for flocculants. It is possible to reduce the amount of excess sludge generated.

  According to the biological treatment method for fat and oil-containing wastewater according to claim 3 and the biological treatment apparatus for fat and oil-containing wastewater according to claim 7, the methane fermentation tank can be downsized by high-load operation of the methane fermentation tank.

  According to the biological treatment method for fat and oil-containing wastewater according to claim 4 and the biological treatment device for fat and oil-containing wastewater according to claim 8, when the oil-water separation liquid of the fat-and-water wastewater is subjected to high-load anaerobic treatment, By maintaining the soluble COD concentration on the separation liquid side, stabilizing the high-load anaerobic treatment, and stabilizing the methane fermentation treatment by subjecting the oil-water separated sludge subjected to acid fermentation to methane fermentation In addition, the organic matter decomposition efficiency can be improved.

  Embodiments of the biological treatment method and treatment apparatus for fat and oil-containing wastewater of the present invention will be described below with reference to the drawings.

  1-4 is a systematic diagram showing an embodiment of a biological treatment method and treatment apparatus for fat and oil-containing wastewater of the present invention. 1-4, the same code | symbol is attached | subjected to the member which show | plays the same function.

  In FIG. 1, raw water (oil-and-fat-containing wastewater) is introduced into a raw water storage tank 1 through a pipe 21, and introduced into a coagulation reaction tank 2 through a pipe 22 together with a desorption liquid of a sludge dehydrator 9 described later. In the agglomeration reaction tank 2, a polymer flocculant and an inorganic flocculant are added from the pipe 23, and the raw water is agglomerated. The agglomerated treated water is introduced into the oil / water separation tank (pressurized levitation tank) 3 through the pipe 24, and is floated and separated into the pressurized levitation sludge (oil-containing sludge) and the pressurized levitation treated water. The pressurized levitation treated water is introduced into the acid generation tank 4 through the pipe 25 and subjected to the acid fermentation treatment, and then introduced into the high-load anaerobic treatment tank 5 through the pipe 26 and subjected to a high-load anaerobic treatment. As this high load anaerobic treatment method, UASB method, anaerobic fluidized bed method and the like are effective. The biogas generated in the high load anaerobic treatment tank 5 is desulfurized in the desulfurization tower 10 from the pipe 27, and then sent to the energy utilization process such as gas power generation and boiler through the pipe 28, the gas holder 11 and the pipe 29. Be paid. Further, surplus sludge generated in the high-load anaerobic treatment tank 5 is fed to the methane fermentation tank 8 through the pipes 30 and 31. The treated water in the high-load anaerobic treatment tank 5 is introduced into the aerobic treatment tank 6 through the pipe 32 and subjected to aerobic treatment, and then introduced into the sedimentation tank 7 through the pipe 33 and separated into solid and liquid. The separated water in the sedimentation basin 7 is discharged out of the system as treated water from the pipe 34. A part of the separated sludge is returned to the aerobic treatment tank 6 through the pipes 35 and 35A, and the remaining part is fed to the methane fermentation tank 8 through the pipes 35, 35B and 31.

  The pressurized levitation sludge in the pressurized levitation tank 3 is supplied to the methane fermentation tank 8 through the pipe 36 and is subjected to methane fermentation treatment together with surplus sludge from the pipe 31 for biological treatment. The biogas generated in the methane fermentation in the methane fermentation tank 8 is desulfurized in the desulfurization tower 10 from the pipe 37 in the same manner as the biogas from the high-load anaerobic treatment tank 5, and then the gas holder 11 and the pipe 29 are connected. Then it is sent to the energy utilization process.

  Digested sludge in the methane fermentation tank 8 is fed from a pipe 38 to a sludge dewatering machine (or sludge concentrator) 9 for dehydration, and the dewatered cake is discharged out of the system through a pipe 39 and finally disposed of by landfill or incineration. The On the other hand, the desorbed liquid from the dehydrator 9 is returned to the raw water storage tank 1 through the pipe 40 and processed together with the raw water.

  In the treatment of FIG. 1, by introducing surplus sludge generated by biological treatment of pressurized floating treatment water into the methane fermentation tank 8, stabilization of methane fermentation and reduction of sludge can be achieved. When high-load anaerobic digestion is used for the treatment of floating treatment water, surplus anaerobic sludge is put into the methane fermentation tank 8 to inoculate high-concentration methanogenic bacteria, and methane fermentation in the methane fermentation tank 8 Stabilization and high efficiency can be achieved.

  In FIG. 2, surplus aerobic sludge from the pipe 35B and surplus anaerobic sludge from the pipe 30 are fed to the agglomeration reaction tank 2 instead of the methane fermentation tank 8, and surplus digested sludge is drawn from the methane fermentation tank 8. 1 is different from the process shown in FIG. 1 in that only the polymer flocculant is added to the agglomeration reaction tank 2 from the pipe 41 and no inorganic flocculant is added. Is done.

  In the process of FIG. 2, by mixing surplus sludge from the biological treatment and surplus digested sludge from the methane fermentation tank 8 in the agglomeration reaction tank 2, the oil in the raw water can be adsorbed to the biological sludge. That is, since this biological sludge functions as an oil and fat adsorbent, the required amount of inorganic flocculant added is greatly reduced, or floating separation without inorganic flocculant addition becomes possible.

  In FIG. 3, the digested sludge from the methane fermentation tank 8 is not sent to the agglomeration reaction tank 2, and the concentrated sludge from the sludge dehydrator 9 is returned to the methane fermentation tank 8 through the pipe 42. Unlike the above, the same processing is performed for others.

  In the process of FIG. 3, the digested sludge extracted from the methane fermentation tank 8 is dehydrated or concentrated by a sludge dewatering machine (or sludge concentrator) 9, and then part or all of the dehydrated sludge or concentrated sludge is returned to the methane fermentation tank 8. And the sludge density | concentration in the methane fermentation tank 8 is raised, and size reduction of the methane fermentation tank 8 by the high load driving | operation of the methane fermentation tank 8 is attained by lengthening SRT simultaneously. Thus, by returning the dehydrated or concentrated sludge, the operating conditions of the methane fermentation tank 8 are set to a sludge concentration in the tank of 20000 mg / L or more, preferably 20000 to 100,000 mg / L, and an SRT of 15 days or more, preferably 15 to 40 days, HRT can be 20 days or less, preferably 3 to 20 days.

  In FIG. 4, the acid generation tank 4 is provided in the preceding stage of the agglomeration reaction tank 2, and surplus aerobic sludge from the pipe 35 </ b> B and surplus anaerobic sludge from the pipe 30 are sent to the acid generation tank 4 instead of the aggregation reaction tank 2. 3 is different from the process shown in FIG. 3 in that the water in the raw water storage tank 1 is introduced into the acid generation tank 4 from the pipe 22A and introduced into the agglomeration reaction tank 2 through the pipe 22B. Is performed.

  In the process of FIG. 4, the methane fermentation tank 8 can be downsized by high-load operation of the methane fermentation tank 8 by returning the concentrated return sludge as in FIG. 3. Furthermore, by performing acid generation (acid fermentation) prior to flotation separation, it is possible to solubilize and organically oxidize fats and oils in raw water and SS derived from raw water, and then to adjust the soluble COD concentration of pressurized flotation treated water. Can be raised. In addition, since the pressurized flotation sludge is also subjected to acid fermentation in advance, it is possible to stabilize the treatment in the methane fermentation tank and improve the organic matter decomposition efficiency.

  That is, when the raw water containing a large amount of fats and oils is floated and separated, most of the organic components are transferred to the pressurized flotation sludge, making it difficult to apply the high load anaerobic treatment to the treatment of the pressurized flotation treatment water. In FIG. 4, by performing acid fermentation prior to flotation separation, this problem is solved and high load anaerobic treatment can be applied. In addition, you may perform an acid production | generation in the oil-water separation tank (pressurization levitation tank) 3. FIG.

  The process shown in FIGS. 1-4 is an example of embodiment of the biological treatment method and treatment apparatus of the fat-and-oils containing waste water of this invention, Comprising: This invention is limited to the process of illustration at all unless the summary is exceeded. It is not a thing. For example, the oil / water separation tank 3 is not limited to a pressurized flotation tank, and may be a precipitation tank if possible. Further, the biological treatment of the pressurized levitation treatment water is not limited to the combined use of the aerobic treatment and the high load anaerobic treatment, and only one of the treatments may be performed. Further, in FIG. 2, only digested sludge from methane fermentation may be returned to the agglomeration reaction tank 2, and surplus sludge from biological treatment of pressurized flotation treated water may be introduced into the methane fermentation tank 8. Of the surplus sludge from this biological treatment, surplus aerobic sludge from the sedimentation basin 7 is returned to the coagulation reaction tank 2, and surplus anaerobic sludge from the high-load anaerobic treatment tank 5 is introduced into the methane fermentation tank 8. Accordingly, as described above, the concentration of the methane-producing bacteria in the methane fermentation tank 8 can be increased. In addition, a part of the dewatered cake from the sludge dewatering machine 9 may be returned to the agglomeration reaction tank 2 together with or in place of the excessively digested sludge in the methane fermentation tank 8. In FIG. 3, a part of the concentrated return sludge from the sludge dehydrator 9 may be fed to the agglomeration reaction tank 2, and all of the concentrated return sludge is not the methane fermentation tank 8 but the agglomeration reaction tank 2. You may return it to Even in this case, as a result, the sludge concentration in the methane fermentation tank 8 can be increased and high-load operation can be performed. Similarly, in FIG. 4, a part of the concentrated return sludge from the sludge dehydrator 9 may be supplied to the acid generation tank 4, and the entire concentrated return sludge is not the methane fermentation tank 8 but the acid generation tank. 4 may be returned. Even in this case, as a result, the sludge concentration in the methane fermentation tank 8 can be increased and high-load operation can be performed.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
The following water quality food factory effluent (flow rate 430 m ³ / d) was treated as raw water by the method shown in FIG.
[Raw water quality]
BOD: 2300mg / L
SS: 653 mg / L
n-hexane extract: 170 mg / L

  This oil-containing wastewater has a relatively low oil concentration, and the composition ratio of sludge produced by the conventional method (pressurized flotation method + activated sludge method) shown in Comparative Example 1 described later is 3: 4 (pressurized flotation scum: surplus sludge) ) About water quality.

The specifications and processing conditions of each tank are as follows.
Acid production tank volume: 110 m ³
High-load anaerobic treatment tank volume: 210 m ³
Aerobic treatment tank volume: 150m ³
Methane fermentation tank volume: 45m ³

As a result, the amount of methane generated was 526 m ³ / d, the water content of the dehydrated cake was 85%, and the amount generated was 0.73 ton / d, which can be reduced by 84% compared to Comparative Example 1 described later. there were.

Comparative Example 1
Raw water similar to that treated in Example 1 was treated by the pressurized flotation method and the activated sludge method (activated sludge tank volume: 1010 m ³ ). That is, the raw water was subjected to pressure levitation treatment, the pressure levitation sludge was discharged, and the pressure levitation treatment water was subjected to activated sludge treatment.

  As a result, the amount of generated sludge was 4.67 ton / d.

Example 2
The following water quality food factory waste water (flow rate 352 m ³ / d) was treated as raw water by the method shown in FIG.
[Raw water quality]
BOD: 2840mg / L
SS: 1190mg / L
n-hexane extract: 959 mg / L

  This oil-containing wastewater has a relatively high oil concentration, and the composition ratio of sludge produced by the conventional method (pressurized flotation method + activated sludge method) shown in Comparative Example 2 described later is 4: 1 (pressurized flotation scum: surplus sludge) ) About water quality. Such waste water with a high oil concentration has a BOD of pressurized flotation treated water that is very low in the treatment shown in FIG.

The specifications and processing conditions of each tank are as follows.
Acid production tank volume: 88 m ³
High load anaerobic treatment tank volume: 130 m ³
Aerobic treatment tank volume: 88m ³
Methane fermenter volume: 67m ³

As a result, the amount of methane generated was 535 m ³ / d, the moisture content of the dehydrated cake was 85%, and the amount generated was 0.89 ton / d, which can be reduced by 83% compared to Comparative Example 2 described later. there were.

Comparative Example 2
Raw water similar to that treated in Example 2 was treated by the pressurized flotation method and the activated sludge method (activated sludge tank volume: 430 m ³ ). That is, the raw water was subjected to pressure levitation treatment, the pressure levitation sludge was discharged, and the pressure levitation treatment water was subjected to activated sludge treatment.

  As a result, the amount of generated sludge was 5.4 ton / d.

Example 3
Raw water similar to that treated in Example 1 was treated by the method shown in FIG. At this time, the composition of the pressurized floating sludge (28 m ³ / d) was as follows.
[Composition of pressurized floating sludge]
Total COD: 55000mg / L
Raw water derived SS: 12000mg / L
n-hexane extract: 11400 mg / L
Surplus sludge: 6600mg / L

  In this case, HRT and SRT of the methane fermentation tank, SS concentration in the tank, COD volume load, and the required methane fermentation tank volume are examined, and the concentrated sludge is not returned from the sludge dehydrator to the methane fermentation tank. In contrast, the results are shown in Table 1.

  Since all SRTs were set on the 15th in this treatment, the oil removal rate was 80%, the SS removal rate derived from raw water was 70%, and the excess sludge decomposition rate was 30%. No. that returned the concentrated sludge. In the system 1, the hardly decomposable components of excess sludge accumulated in the methane fermentation tank, and the anaerobic bacteria were adsorbed thereto, so that concentration could be easily performed. Moreover, even in sudden load fluctuations, stable treatment was maintained because the cells were maintained at a high concentration in the methane fermentation tank. No. which returned the concentrated sludge. In No. 1, no return is made. Compared with 2, the methane fermenter volume could be significantly reduced to about 1/4 by high-load operation of the methane fermenter.

It is a systematic diagram which shows embodiment of the biological treatment method and processing apparatus of the fat-and-oil containing waste water of this invention. It is a systematic diagram which shows other embodiment of the biological treatment method and processing apparatus of the fat-and-oil containing waste water of this invention. It is a systematic diagram which shows another embodiment of the biological treatment method and processing apparatus of the fat and oil containing waste water of this invention. It is a systematic diagram which shows another embodiment of the biological treatment method and processing apparatus of the fat and oil containing waste water of this invention.

Explanation of symbols

1 Raw water storage tank 2 Coagulation reaction tank 3 Oil / water separation tank (pressurization flotation tank)
4 Acid generation tank 5 High load anaerobic treatment tank 6 Aerobic treatment tank 7 Sedimentation tank 8 Methane fermentation tank 9 Sludge dehydrator 10 Desulfurization tower 11 Gas holder

Claims (8)

An oil / water separation step for separating oil / water containing wastewater to obtain oil / water separation sludge and a separated liquid;
A methane fermentation process in which the oil-water separated sludge is subjected to a methane fermentation treatment;
In the biological treatment method of fat and oil-containing wastewater comprising a biological treatment step of aerobic treatment and / or high-load anaerobic treatment of the separated liquid,
A biological treatment method for fat and oil-containing wastewater, wherein at least a part of surplus sludge generated in the biological treatment step is introduced into the methane fermentation step. An oil / water separation step for separating oil / water containing wastewater to obtain oil / water separation sludge and a separated liquid;
A methane fermentation process in which the oil-water separated sludge is subjected to a methane fermentation treatment;
In the biological treatment method of fat and oil-containing wastewater comprising a biological treatment step of aerobic treatment and / or high-load anaerobic treatment of the separated liquid,
Oil and fat-containing wastewater introduced into the oil / water separation step is mixed with at least part of digested sludge and / or surplus sludge generated in the biological treatment step generated in the methane fermentation step. Biological treatment method.   The biological treatment method for fat and oil-containing wastewater according to claim 1 or 2, wherein the operating conditions of the methane fermentation step are an in-tank sludge concentration of 20000 mg / L or more, an SRT of 15 days or more, and an HRT of 20 days or less.   4. The method according to claim 2, wherein the biological treatment step includes a high-load anaerobic treatment step, and includes an acid fermentation step of subjecting the oil-containing wastewater to an acid fermentation treatment, and the treated water of the acid fermentation step is A biological treatment method for fat and oil-containing wastewater, which is introduced into an oil / water separation step. Oil / water separation means for separating oil / water containing oil / water to obtain oil / water separation sludge and separated liquid;
Methane fermentation means for methane fermentation treatment of the oil-water separated sludge;
In a biological treatment apparatus for fat-containing wastewater, comprising biological treatment means for aerobic treatment and / or high-load anaerobic treatment of the separated liquid,
A biological treatment apparatus for fat and oil-containing wastewater, comprising a sludge transfer means for introducing at least a part of surplus sludge generated by the biological treatment means into the methane fermentation means. Oil / water separation means for separating oil / water containing oil / water to obtain oil / water separation sludge and separated liquid;
Methane fermentation means for methane fermentation treatment of the oil-water separated sludge;
In a biological treatment apparatus for fat-containing wastewater, comprising biological treatment means for aerobic treatment and / or high-load anaerobic treatment of the separated liquid,
The oil-containing wastewater introduced into the oil / water separation means has a sludge mixing means for mixing digested sludge generated by the methane fermentation means and / or surplus sludge generated by the biological treatment means. Biological treatment equipment for oil-containing wastewater.   The biological treatment apparatus for fat and oil-containing wastewater according to claim 5 or 6, wherein operating conditions of the methane fermentation means are in-tank sludge concentration of 20000 mg / L or more, SRT of 15 days or more, and HRT of 20 days or less.   In Claim 6 or 7, The said biological treatment means is an apparatus containing a high load anaerobic treatment means, Comprising: It has an acid fermentation means which carries out the acid fermentation process of the said fat-and-oils containing waste_water | drain, The treated water of this acid fermentation means is the said A biological treatment apparatus for fat and oil-containing wastewater, which is introduced into an oil-water separation means.

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