JP6715187B2 - Method and apparatus for treating oil-containing wastewater - Google Patents

Description

The present invention relates to a method and an apparatus for treating oil and fat-containing wastewater, and more particularly to a method and an apparatus for treating oil and fat-containing wastewater accompanied by biological treatment.

Wastewater from food factories, domestic wastewater, etc. contains a large amount of oil and fat.When such wastewater is discharged to the sewer pipeline, the solidified oil and fat adheres to the sewer pipeline, causing blockage of sewer pipes and oil balls. Various problems such as generation are caused due to the large amount of oil and fat in the wastewater.

Therefore, in general, wastewater such as domestic wastewater is subjected to biological treatment in a biological treatment facility to decompose organic substances containing oil and fat. However, if the oil content in the waste water is high, it takes a certain amount of time for the oil to be decomposed by the activated sludge, and if the biological treatment time is insufficient, the oil will remain in the treated water after the biological treatment. On the other hand, if the biological treatment takes time, the treatment efficiency decreases.

As a treatment method for such wastewater containing fats and oils, a technique described in Patent Document 1 is disclosed.

Specifically, in Patent Document 1, waste oil-containing wastewater is separated into oil and fat and separated water, and the separated water is subjected to biological treatment, and the oil and fat is separately aerobically decomposed using microorganisms. And a method for treating waste oil-containing wastewater, in which a microorganism-containing liquid obtained by this decomposition treatment is subjected to separated water or biological treatment.

According to the treatment method of Patent Document 1, since the separated water is separated from the fat and oil-containing wastewater, the contact efficiency between the fat and oil in the decomposition treatment and the microorganism decomposing the fat and oil is increased, and rapid decomposition of the fat and oil is expected. it can. In addition, since the microorganism-containing liquid after the decomposition treatment is subjected to the biological treatment, the decomposition of the oil and fat progresses further, and the treated water with a small amount of the oil and fat remaining after the biological treatment can be provided by the rapid treatment.

It is considered that an organic coagulant or an inorganic coagulant is optionally added to the oil/fat-containing wastewater to separate the oil/fat from the oil/fat-containing wastewater.

Non-Patent Document 1 discloses that iron strongly inhibits the reaction of lipase that catalyzes the decomposition reaction of fats and oils.

On the other hand, Patent Document 2 discloses a biological treatment apparatus that supplies an iron salt in the biological treatment process. Specifically, in Patent Document 2, in a biological treatment apparatus that performs biological treatment of oil-and-fat-containing wastewater in two treatment tanks arranged in series, an iron salt supply means for supplying iron salt to the first treatment tank. A biological treatment apparatus comprising is disclosed. According to this biological treatment device, the fats and oils in the wastewater are efficiently decomposed as compared with the case where the iron salt is not supplied to the first treatment tank.

JP-A-4-235799 JP, 2013-184093, A

Mieko Iwai, Lipase, The Basics and Applications, 168-173 (Koshobo)

However, the oil-and-fat-containing wastewater varies in its properties due to the operation status of facilities discharging the wastewater and the presence of foreign substances. According to the treatment method of Patent Document 1, the oil-and-fat-containing wastewater has different properties. In some cases, the proportion of fats and oils that can be separated in the separation step decreases. That is, the proportion of the oil/fat remaining in the separated water increases depending on the properties of the oil/fat-containing wastewater, which causes problems of prolonging the biological treatment time and decreasing the biological treatment efficiency.

The addition of various flocculants has been studied in order to reduce the proportion of oils and fats remaining in such separated water, but conventionally, iron salts were known to strongly inhibit the reaction of lipase, The use of iron salts as an inorganic flocculant for substances intended for reaction with lipases has never been tried.

Further, Patent Document 2 discloses that an iron salt is supplied to the biological treatment tank, but there is no description about using the iron salt as an aggregating agent for oil and fat.

The present invention has been made in view of the above problems, and its purpose is to be able to stably concentrate the fat and oil regardless of the properties of the fat and oil-containing wastewater, and the biological treatment of the concentrate after concentration. An object of the present invention is to provide a treatment method and a treatment device for oil-and-fat-containing wastewater that can enhance treatment efficiency.

The method for treating oil-and-fat-containing wastewater according to claim 1 for achieving the above-mentioned object is obtained by subjecting the oil-and-fat-containing wastewater to a concentration separation treatment for concentrating and separating an oil and fat component by adding an iron salt to the oil-and-fat wastewater. wherein the obtaining a biologically treated water of the biological treatment in facilities Succoth to concentrate.

According to this configuration, the iron salt added to the oil/fat-containing wastewater acts as an inorganic coagulant, and the oil/fat can be stably concentrated and separated regardless of the properties of the oil/fat-containing wastewater. Further, by subjecting the concentrate containing the iron salt to biological treatment, it is possible to improve the decomposition efficiency of the oil and fat component in the concentrate. The improvement of such decomposition efficiency has been conventionally considered that iron salts inhibit lipase activity, and lipase and/or synthetic reaction of fats and oils that promote hydrolysis of oils and fats in the presence of iron salts in biological treatment (of lipases). It is presumed that this is caused by the predominance of the lipase-producing microorganism that suppresses the (reverse reaction).

The invention according to claim 2 is the method for treating oil-and-fat-containing wastewater according to claim 1, wherein the biological treatment is performed under an anaerobic environment or a microaerobic environment, with anaerobic bacteria, facultative anaerobic bacteria, and microbes. Anaerobic treatment, which is a treatment that causes at least one action of decomposition, emulsification and dispersion by at least one microorganism selected from the group consisting of aerobic bacteria and aerobic bacteria, and a treated product obtained by the anaerobic treatment. And an aerobic treatment applied to.

According to this configuration, the concentrate obtained by the concentration and separation treatment in the presence of the iron salt is subjected to the anaerobic treatment prior to the aerobic treatment, so that the fat and oil concentrate is suddenly subjected to the aerobic treatment. It is possible to effectively decompose the fats and oils in the concentrate as compared with the case of performing.

The invention according to claim 3 is the method for treating oil and fat-containing wastewater according to claim 1 or 2, wherein the biological treatment is obtained by anaerobic treatment between the anaerobic treatment and the aerobic treatment. It is characterized in that the treated product includes a decomposing process in which the decomposing process is performed by a methanogen, and the aerobic process is performed on the decomposing product obtained by the decomposing process.

According to this configuration, the treated product obtained by the anaerobic treatment is decomposed by the methanogen, so that not only the low molecular weight of the organic substance but also the volatilization by the methane gasification is promoted. Therefore, the amount of organic substances to be treated in the aerobic treatment subsequent to the decomposition treatment by the methanogen can be greatly reduced. As a result, it is possible to more effectively decompose the oil and fat content in the concentrate.

The invention according to claim 4 is the method for treating oil-and-fat-containing wastewater according to any one of claims 1 to 3, wherein at least one of the oil-and-fat-containing wastewater and the concentrate is provided before the biological treatment. Finally, it is characterized by supplying an oil and fat decomposing preparation and/or an oil and fat decomposing microorganism.

According to this configuration, further oil and fat decomposing effect by the oil and fat decomposing preparation and/or the oil and fat decomposing microorganism can be obtained in the biological treatment, and the treatment efficiency of the biological treatment for the concentrate after the concentration and separation can be further enhanced.

The invention described in claim 5 is the apparatus of the fat-containing waste water, by introducing the iron salt to oil-containing waste water facilities concentrated separation process for concentration and separation of oils and fats, turned-concentration and separation to obtain a concentrate characterized in that it comprises means, and a biological treatment means for obtaining a biologically treated water in facilities Succoth the biological treatment in the concentrate.

According to this configuration, the iron salt added to the oil/fat-containing wastewater acts as an inorganic coagulant, and the oil/fat can be stably concentrated and separated regardless of the properties of the oil/fat-containing wastewater. Further, by subjecting the concentrate containing the iron salt to biological treatment, it is possible to improve the decomposition efficiency of the oil and fat component in the concentrate.
The invention according to claim 6 is the apparatus for treating oil and fat-containing wastewater according to claim 5, wherein the biological treatment means (80) decomposes the concentrate from the input/concentration separation means by a methanogen. An aerobic tank (38) including a decomposition treatment means (82) for applying the decomposition treatment product obtained by the decomposition treatment to obtain aerobic treatment water, and the aerobic treatment water as activated sludge. Activated sludge tank (42) for treating to obtain activated sludge treated water, settling tank (46) for precipitating the activated sludge treated water to obtain returned sludge and biological treated water, and the returned sludge to the aerobic tank And a sludge returning means (56) for supplying to the activated sludge tank.

The invention according to claim 7 is the apparatus for treating oil and fat-containing wastewater according to claim 5, wherein the biological treatment means is under anaerobic environment or microaerobic environment, and anaerobic bacteria, facultative anaerobic bacteria, Anaerobic treatment means for performing an anaerobic treatment, which is a treatment that causes at least one action of decomposition, emulsification and dispersion by at least one microorganism selected from the group consisting of microaerobic bacteria and aerobic bacteria, and the anaerobic Aerobic treatment means for applying aerobic treatment to the processed product obtained by the sexual treatment.

According to this configuration, the concentrate obtained by the concentration and separation treatment in the presence of the iron salt is subjected to the anaerobic treatment prior to the aerobic treatment, so that the fat and oil concentrate is suddenly subjected to the aerobic treatment. It is possible to effectively decompose the fats and oils in the concentrate as compared with the case of performing.

The invention according to claim 8 is the apparatus for treating oil-and-fat-containing wastewater according to claim 7 , which includes a decomposition treatment means for subjecting the treated matter obtained by the anaerobic treatment to decomposition treatment with methanogens, The aerobic treatment means is an aerobic treatment means for performing an aerobic treatment on the decomposition-treated product obtained by the decomposition treatment.

According to this configuration, the treated product obtained by the anaerobic treatment is decomposed by the methanogen, so that not only the low molecular weight of the organic substance but also the volatilization by the methane gasification is promoted. Therefore, the amount of organic substances to be treated in the aerobic treatment subsequent to the decomposition treatment by the methanogen can be greatly reduced. As a result, it is possible to more effectively decompose the oil and fat content in the concentrate.

The invention according to claim 9 is the treatment device for oil-and-fat-containing wastewater according to any one of claims 5 to 8 , wherein at least one of the oil-and-fat-containing wastewater and the concentrate is provided before the biological treatment. In addition, it is characterized by having a supply means for supplying an oil and fat decomposing preparation and/or an oil and fat decomposing microorganism.

According to this configuration, further oil and fat decomposing effect by the oil and fat decomposing preparation and/or the oil and fat decomposing microorganism can be obtained in the biological treatment, and the treatment efficiency of the biological treatment for the concentrate after the concentration and separation can be further enhanced.

According to the present invention, the iron salt added to the oil/fat-containing wastewater acts as an inorganic coagulant, and the oil/fat can be stably concentrated and separated regardless of the properties of the oil/fat-containing wastewater. Further, by subjecting the concentrate containing the iron salt to biological treatment, it is possible to improve the decomposition efficiency of the oil and fat component in the concentrate.

It is a schematic diagram of the processing apparatus 10 of the oil/fat-containing wastewater according to the first embodiment of the present invention. It is a figure which shows the biological treatment means 60 concerning the 1st modification of 1st Embodiment of this invention. It is a figure which shows the biological treatment means 80 concerning the 2nd modification of 1st Embodiment of this invention. It is a schematic diagram of the processing apparatus 70 of the oil-fat containing wastewater which concerns on 2nd Embodiment of this invention. It is a figure which shows the recovery rate of the oil component collect|recovered in the fat and oil concentrate from food factory wastewater. It is a figure which shows the result of the batch type biological treatment test of the fat-and-oil containing waste water (raw water) of the comparative example 4.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
A treatment method and a treatment apparatus for oil/fat-containing wastewater according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing a treatment device 10 for oil/fat-containing wastewater according to the present embodiment.

As shown in the figure, the treatment apparatus 10 for oil-and-fat-containing wastewater is configured to supply the oil-and-fat-containing wastewater 1 with the oil-and-fat-decomposing formulation 4 and/or the oil-and-fat-decomposing microorganisms 6, and the iron salt 2 into the oil and fat-containing wastewater 1. An input/concentration/separation unit 20 for performing a concentration/separation process, and a biological treatment unit 30 located downstream of the input/concentration/separation unit 20 for performing a biological treatment on the concentrate 22 obtained by the concentration/separation process. Prepare

The oil/fat-containing wastewater 1 means water containing an oil/fat in the present specification. Examples of the fat and oil include animal and vegetable fats and oils (triglyceride and partially decomposed products thereof). Specific examples include wastewater and domestic wastewater discharged from food factories and kitchens. The oil-and-fat-containing wastewater 1 may further contain components other than oil and fat components (for example, nitrogen components (ammonia nitrogen, organic nitrogen, etc.)).

In the present invention, the oil-and-fat-containing wastewater 1 may have a lower limit of hexane extract concentration of 30 mg/L, preferably 50 mg/L, more preferably 100 mg/L, and an upper limit of 50,000 mg/L, preferably 30. It may be 1,000 mg/L, more preferably 10,000 mg/L. Here, the hexane extract concentration of the oil/fat-containing wastewater 1 means the value obtained by measurement based on the factory wastewater test method (JIS K010224). In the following description, the hexane extract concentration means a value obtained by measuring by such a method.

In the present invention, the oil-and-fat-containing wastewater 1 that has been subjected to the pretreatment can be subjected to the concentration and separation treatment. Therefore, the oil-and-fat-containing wastewater 1 that has been subjected to pretreatment corresponds to the oil-and-fat-containing wastewater 1 in the present invention. Examples of the oil-and-fat-containing wastewater 1 in the present invention include, for example, pre-treatment of the oil-and-fat-containing wastewater 1 and dispersed water obtained by subjecting the oil-and-fat-containing wastewater 1 to a dispersion treatment.

The charging/concentrating/separating means 20 is provided upstream of the concentrating/separating means (concentrating/separating tank 24), which serves as a place for concentrating and separating the oil/fat in the oil/fat-containing wastewater 1, and the oil/fat-containing wastewater. 1 and a charging means 26 for charging the iron salt 2 therein.

The concentration/separation means may be any means as long as it is capable of concentrating and separating the oil/fat in the oil/fat-containing wastewater 1, and for example, existing flocculation/precipitation treatment, flocculation/pressure flotation treatment, flocculation/filtration treatment, etc. The concentration/separation means used in the solid-liquid separation method can be used.

The iron salt 2 is used as a flocculant added when the oil and fat are concentrated and separated. Examples of the iron salt 2 used include ferric chloride, polyiron, ferrous chloride, ferrous sulfate and the like, and preferably ferric chloride or polyiron. In the present invention, a cationic polymer or an anionic polymer can be used as the aggregation polymer. When the mass of the hexane extract contained in the fat and oil-containing wastewater 1 is 100, the amount of the iron salt 2 used is 10 to 500, preferably 50 to 300, as the mass of iron.

Note that it is not preferable to use PAC (polyaluminum chloride), which is a general coagulant, in the concentration treatment of the oil/fat-containing wastewater 1.

The oil and fat decomposing preparation 4 and/or the oil and fat degrading microorganisms 6 are additives that are supplied to at least one of the oil and fat-containing wastewater 1 and the concentrate 22 before the biological treatment described later, and by this supply, the biological treatment downstream. It is possible to obtain the effect of improving the oil/fat decomposition performance in.

The fat-and-oil-degrading microorganism 6 is exemplified by microorganisms such as Acinetobacter genus, Alcaligenes genus, Arthrobacter genus, Bacillus genus, Burkho1deria genus, Candida genus, Nocardia genus, Pseudomonas genus, and Rhodococcus genus such as Rhodococcus genus and other known microorganisms such as Rhodococcus. It is possible to use the returned sludge generated by the biological treatment of the oil/fat-containing wastewater 1, or the preparation obtained by subjecting the sludge to a treatment such as concentration and drying.

Assuming that the mass of the hexane extract contained in the fat/oil-containing wastewater 1 is 100, the amount of the fat/oil-decomposing microorganism 6 added is in the range of 10 to 300, preferably 30 to 100, as the dry mass of the microorganism.

There is no limitation on the oil/fat decomposition preparation 4 as long as it promotes the decomposition of oils/fats, and lipases that catalyze the hydrolysis of oils/fats, emulsifiers for enhancing the dispersibility of oils/fats, microbial preparations containing oil/fat-degrading microorganisms, etc. It is possible.

The concentrate 22 obtained by the concentration/separation means (concentration/separation tank 24) is subjected to biological treatment by the biological treatment means 30.

In the present embodiment, the biological treatment means 30 includes an anaerobic treatment means (anaerobic treatment tank 34) which is a place where the concentrate 22 is subjected to anaerobic treatment, and anaerobic treated water 36 obtained by the anaerobic treatment. Aerobic treatment means (aerobic tank 38) that is a place where aerobic treatment is performed on the above, and activated sludge treatment that is a further aerobic treatment for the aerobic treated water 40 obtained by the aerobic treatment. Aerobic treatment means (activated sludge treatment means 50) which is a place to be applied.

The anaerobic treatment means is not particularly limited as long as it is a means that can perform the anaerobic treatment described later on the fat and oil concentrate 22 to obtain the anaerobic treated water 36. For example, the oil-fat concentrate is received in a closed container having anaerobic bacteria that live in an anaerobic environment, and the anaerobic bacteria act on this to discharge the anaerobic treated water.

Further, for example, a container having therein at least one selected from the group consisting of anaerobic bacteria, facultative anaerobic bacteria, microaerobic bacteria and aerobic bacteria that live in a microaerobic environment A substance that receives a substance inside and causes at least one selected from the group consisting of anaerobic bacterium, facultative anaerobic bacterium, microaerobic bacterium and aerobic bacterium to act thereon and discharge the anaerobic treated water 36 can be mentioned. .. Whatever container is used, it is preferable to have a device capable of stirring the inside.

As the anaerobic treatment means, it is possible to use an apparatus for performing conventionally known treatments such as an anaerobic fixed bed method, an anaerobic fluidized bed method, a UASB method and an EGSB method. However, as described later, since the anaerobic treatment in the present invention is processed under the condition that decomposition (methane fermentation) by methanogenic bacteria does not proceed in principle, auxiliary equipment such as a gas holder for storing methane gas and a desulfurization treatment device is not provided. You don't have to.

It is preferable that the anaerobic treatment means further comprises means capable of adjusting the pH, temperature, and redox potential of the concentrate 22 (in the case of using a reaction tank in the anaerobic treatment means). The pH and temperature can be adjusted by a known acid or alkali adding means or heating means. The redox potential can be adjusted by performing an anaerobic treatment while supplying an appropriate amount of oxygen to the fat and oil concentrate.

The anaerobic treated water 36 obtained in the anaerobic treatment means (anaerobic treatment tank 34) is transferred to the downstream aerobic treatment means (aerobic tank 38).

As the aerobic treatment means, conventionally known means used for aerobic biological treatment can be used. Specifically, it is a means capable of performing the treatment of receiving the anaerobic treated water 36 in the tank and performing aeration while stirring, and for example, a conventionally known floating organism treatment method (batch activated sludge method, continuous activated sludge method). Examples of aerobic treatment means used for carrying out a sludge method, a membrane separation activated sludge method, etc. and a biofilm treatment method (rotating disk method, aerobic filtration method, fluidized bed method, etc.). Further, the aerobic treatment means may store sludge (for example, activated sludge) therein, and in that case, it is preferable to have a configuration capable of discharging the sludge.

Further, the treatment device for oil-and-fat-containing wastewater may use two or more aerobic treatment means. For example, the first aerobic treatment means may perform the aerobic treatment, and the second aerobic treatment means may perform the aerobic treatment.

Furthermore, it is preferable that the aerobic treatment means includes a solid-liquid separation means. In this case, the sludge stored in the aerobic treatment means can be discharged quickly. Further, the aerobic treatment described later includes activated sludge treatment, and therefore the aerobic treatment means includes activated sludge treatment means.

Generally, the activated sludge treatment means includes an aeration tank and a sedimentation tank, and the flocs of the activated sludge transferred from the aeration tank where the activated sludge treatment is performed are separated by natural sedimentation in the sedimentation tank.

In the oil and fat-containing wastewater treatment device 10 according to the present embodiment, two aerobic treatment means for performing aerobic treatment, that is, the aerobic tank 38 and the activated sludge treatment means 50, are provided downstream of the anaerobic treatment means, respectively. They are arranged in series.

The activated sludge treatment means 50 is disposed in the activated sludge tank 42 (aeration tank) that is aerated and used as a place for aerobic treatment by the activated sludge, and the activated sludge transferred from the activated sludge tank 42 downstream of the activated sludge tank 42. And a settling tank 46 for separating the flocs of No. 1 by natural settling. The separated liquid separated from the flocs of the activated sludge in the settling tank 46 is finally discharged as the biologically treated water 32 from the treatment device 10 for the oil and fat-containing wastewater.

A method of treating oil-and-fat-containing wastewater using the treatment apparatus 10 for oil-and-fat-containing wastewater having the above configuration will be described below.

[1. Concentration separation treatment]
First, the oil and fat-containing wastewater 1 is supplied with the oil and fat decomposing preparation 4 and/or the oil and fat decomposing microorganisms 6 through the supplying means 15, the iron salt 2 is charged through the charging means 26 in the above amount, and the concentration and separation means is provided. In the (concentration separation tank 24), the oil and fat components are concentrated and separated.

There is no particular limitation on the order in which the oil and fat decomposing formulation 4 and/or the oil and fat decomposing microorganisms 6 and the iron salt 2 are added to the oil and fat containing wastewater 1, but the oil and fat decomposing formulation 4 and/or the oil and fat decomposing microorganisms 6 are added to the oil and fat containing wastewater 1. It is preferable to add and stir the iron salt 2 after the addition and agitation since the decomposition performance of the fat and oil component in the biological treatment described later is improved.

The hexane extract substance contained in the oil/fat concentrate 22 by the concentration and separation treatment is preferably concentrated 10 times or more, more preferably 40 to 50 times or more the concentration of the hexane extract substance in the oil/fat-containing wastewater 1. More preferably. When the concentration ratio of the concentrate 22 in the concentration treatment increases, the biological treatment of the concentrate 22 can be performed in a smaller amount as compared with the case where the concentrate having a smaller concentration ratio is biologically treated. When the extract material is biologically treated, the reaction time of the concentrate 22 in the biological treatment means 30 can be made longer than in the case where the concentrate having a small concentration ratio is biologically treated.

The fats and oils components generally exist as solids in the wastewater, and during biological treatment, the decomposition of the fats and oils progresses from the surface to the inside of the solids. Therefore, since the biological treatment time can be extended, the oil and fat components are decomposed, and the quality of the obtained biologically treated water is improved. That is, when the concentration ratio of the concentrate 22 in the concentration treatment is increased, the biological treatment time for the concentrate 22 can be made relatively long, which leads to an improvement in the water quality after the treatment.

It is generally said that when the hexane extraction concentration in the oil/fat-containing wastewater 1 is 150 mg/L or more, the activity of biological sludge is inhibited, but in the present invention, the concentration of the oil/fat having a hexane extraction concentration of 20,000 mg/L is concentrated. It was clarified that even a product could be processed satisfactorily without being affected by the inhibition.

By the concentration treatment, the oil/fat-containing wastewater 1 is separated into an oil/fat concentrate 22 and separated water 28, and the concentrate 22 is transferred to the biological treatment means 30 and subjected to biological treatment (above, concentration treatment).

[2. Biological treatment]
In the present invention, biological treatment includes both aerobic treatment and anaerobic treatment. In the method for treating oil-and-fat-containing wastewater of the present invention, the biological treatment includes a case where the aerobic treatment is performed after the anaerobic treatment or the aerobic treatment.

In the present embodiment, the biological treatment is performed by anaerobic treatment in the anaerobic treatment means (anaerobic tank 34) and then by two aerobic treatment means (aerobic tank 38 and activated sludge treatment means 50) arranged in series. Aerobic treatment once.

[2-1. Anaerobic treatment]
The concentrate 22 is transferred to an anaerobic treatment means (anaerobic tank 34) and subjected to anaerobic treatment.

Anaerobic treatment, in an anaerobic environment or a microaerobic environment, at least one selected from the group consisting of anaerobic bacteria, facultative anaerobic bacteria, microaerobic bacteria and aerobic bacteria, to fat and oil concentrate By acting on the contained fats and oils, it is mainly a process of promoting the emulsification and dispersion of fats and oils by metabolites such as biosurfactants produced by these bacteria, or hydrolyzing them with enzymes such as lipase. As a general rule, it means a treatment that does not generate methane gas due to decomposition by a methanogen that is an absolutely anaerobic bacterium. Therefore, the anaerobic treatment in the present invention is a treatment different from the conventional anaerobic digestion.

The anaerobic environment or the slightly aerobic environment refers to a state in which the dissolved oxygen concentration (DO) is 0 to 0.3 mg/L and the redox potential measured by a platinum electrode is +50 mV or less.

Conventional anaerobic digestion (anaerobic biological treatment) means a biological treatment method in which organic substances are decomposed into methane gas and carbon dioxide gas by the metabolic action of anaerobic bacteria growing in an anaerobic environment. In addition, it is considered that the decomposition route from the organic matter to methane gas is composed of three steps. Specifically, the first step of solubilizing and lowering the molecular weight of the organic matter by hydrolysis, and then the low molecular weight substance It is considered to be composed of three stages: a second stage for producing volatile fatty acids and alcohols by acid fermentation, and finally a third stage for producing methane gas from acetic acid or hydrogen and carbon dioxide.

On the other hand, since the anaerobic treatment in the present invention does not include the decomposition reaction (methane gas production reaction) corresponding to the third step in the conventional anaerobic digestion in principle, methane gas is not generated. Further, the present inventors presume that the decomposition reaction (acid fermentation) corresponding to the second stage is not substantially included. Furthermore, the decomposition reaction (hydrolysis) corresponding to the first step is significantly promoted by the addition of a high concentration iron salt.

It is known that iron strongly inhibits the reaction of lipase, which catalyzes the decomposition reaction of fats and oils, and therefore, there are almost no detailed research cases on fats and oils decomposition under the condition that a high concentration of iron salt is added. Was not known. In the present invention, as a result of a long-term biological treatment test using a high concentration of iron salt, hydrolysis of fats and oils is promoted at a high concentration of iron salt and/or a synthetic reaction of fats and oils that is a reverse reaction of lipase. It is presumed by the inventors that a phenomenon of being suppressed has appeared, and further, regarding the possibility that a lipase-producing microorganism having a property showing the above-mentioned phenomenon is dominated by the inventors, I'm estimating.

The anaerobic treatment in the present invention is, for example, a condition (at time, pH, at least one selected from the group consisting of anaerobic bacterium, facultative anaerobic bacterium, microaerobic bacterium and aerobic bacterium) acting on the oil and fat concentrate. The temperature can be adjusted by adjusting the temperature).

It is preferable to carry out the treatment under the following conditions, because emulsification of oils and fats by metabolites such as biosurfactants and decomposition by enzymes such as lipase tend to proceed.

In the anaerobic treatment, it is preferable that the lower limit of the time for allowing the fat and oil concentrate to act with at least one selected from the group consisting of anaerobic bacteria, facultative anaerobic bacteria, microaerobic bacteria and aerobic bacteria is 20 hours. It is more preferably 2 days and even more preferably 3 days. The upper limit of this time is preferably 15 days, and more preferably 10 days. The treatment time in the conventionally known anaerobic digestion is about 30 to 40 days, but the anaerobic treatment in the present invention can be made shorter because the reaction of methane fermentation is not performed.

The anaerobic treatment is preferably performed at a reaction pH of 7.2 or higher. The pH is preferably set to 11.0 or lower, and more preferably set to 8.8 or lower.

The anaerobic treatment is preferably performed at a reaction temperature of 20° C. or higher, more preferably 30° C. or higher. The temperature is preferably 58°C or lower, more preferably 47°C or lower.

When performing an anaerobic treatment by acting a microaerobic bacterium, an aerobic bacterium or a facultative anaerobic bacterium on a fat and oil concentrate, for example, different from the conventionally known aeration treatment, a limited oxygen supply to the fat and oil concentrate It is preferable to carry out. At this time, it is preferable to adjust so that the measured value of the redox potential is +50 mV or less, more preferably -50 mV or less, and further preferably -50 to -250 mV, and then perform the anaerobic treatment.

When anaerobic treatment is performed by causing anaerobic bacteria to act on the oil and fat concentrate, the anaerobic treatment is adjusted so that the measured value of the redox potential is preferably −200 mV or less, more preferably −300 mV or less. Shall be given.

In the present invention, the redox potential means a value obtained by measurement by the ORP electrode method using a platinum electrode (above, anaerobic treatment).

The anaerobic treated water 36 obtained by the anaerobic treatment in the anaerobic treatment means (anaerobic tank 34) is transferred to the downstream aerobic treatment means (aerobic tank 38) and subjected to aerobic treatment.

[2-2. Aerobic treatment]
In the present invention, the aerobic treatment means a treatment in which a microorganism mainly composed of aerobic bacteria living in an aerobic environment is caused to act on an oil and fat concentrate to decompose it.

The aerobic environment is an environment in which oxygen is supplied, and indicates a state in which the dissolved oxygen concentration (DO) is 0 mg/L or more.

As the aerobic treatment of the present invention, for example, a conventionally known aerobic biological treatment can be applied. Specifically, a treatment of receiving the oil/fat concentrate in a tank and aerating it with stirring is exemplified. More specifically, conventionally known floating organism treatment methods (batch activated sludge method, continuous activated sludge method, membrane separation activated sludge method, etc.) and biological membrane treatment methods (rotating disk method, aerobic filter method, Fluidized bed method, etc.) is exemplified.

Further, the aerobic treatment preferably includes a plurality of types of treatment. For example, it is preferable that the continuous activated sludge method is applied to the fat and oil concentrate, and then the fluidized bed method is applied. Moreover, it is preferable that the continuous activated sludge method is applied after aeration treatment of the fat and oil concentrate. Further, a denitrification step may be incorporated in the above process.

When the aerobic treatment includes a plurality of types of treatment, it is preferable to include a conventionally known activated sludge treatment as one of them. This is because in such a case, the cleanliness of the finally obtained aerobic treated water is further increased, and aerobic treated water having a hexane extract concentration that satisfies the sewage discharge standard value specified by the Sewerage Law is obtained.

The aerobic treatment in the present invention can be carried out, for example, by adjusting the conditions (time, pH, temperature, etc.) for causing aerobic bacteria and the like to act on the oil and fat concentrate.

In the aerobic treatment, the lower limit of the time for causing the aerobic bacteria and the like to act on the oil and fat concentrate is preferably 5 hours, more preferably 3 days, and further preferably 4 days. The upper limit of this time is preferably 14 days, more preferably 10 days. This is because aerobically treated water having a higher degree of cleanliness can be obtained when the time period for which the aerobic bacteria are allowed to act on the oil/fat concentrate is in such a range.

When two or more stages of aerobic treatment are performed, the total treatment time in each stage is equivalent to the time for allowing aerobic bacteria to act on the oil and fat concentrate as described above.

The aerobic treatment is preferably carried out at a pH of the oil/fat concentrate (the content of the tank when a reaction tank is used in the aerobic treatment) of 7.2 or more, and more preferably 7.5 or more. The pH is preferably set to 11.0 or lower, and more preferably set to 9.0 or lower. This is because aerobically treated water having a higher degree of cleanliness can be obtained by subjecting the oil/fat concentrate to an aerobic treatment in such a range of pH.

The aerobic treatment is preferably carried out at a temperature of the oil/fat concentrate (the contents of the tank when the reaction tank is used in the aerobic treatment) of 20° C. or higher, more preferably 39° C. or higher. The temperature is preferably 58° C. or lower, more preferably 48° C. or lower. This is because if the fat and oil concentrate is subjected to aerobic treatment at a temperature in such a range, a higher degree of cleanliness of aerobic treated water can be obtained.

The aerobic treatment is preferably carried out at a ratio of the mass of fats and oils in the fat and oil concentrate to the mass of nitrogen atoms (nitrogen atoms/fats and fats) of 0.05 or more, more preferably 0.1 to 0.5. preferable.

The aerobic treatment is preferably carried out with a ratio of the mass of fats and oils to the mass of phosphorus atoms (phosphorus/fats and fats) in the fat and oil concentrate of 0.01 or more, preferably 0.05 to 0.1.

It is preferable to supplement nutrients such as a nitrogen source during the aerobic treatment so that the mass ratio of the nitrogen, phosphorus and fats and oils is such.

The aerobic treatment is preferably carried out so that the dissolved oxygen content (DO) in the oil/fat concentrate (the content of the tank when a reaction tank is used in the aerobic treatment) is 1.0 mg/L or more, 2.0 mg /L or more is more preferable, and 3.0 mg/L or more is more preferable. This is because aerobic treated water with a higher degree of cleanliness can be obtained. The amount of dissolved oxygen can be measured with a conventionally known DO meter.

In the present embodiment, two types of aerobic treatment are included in each step. That is, after the aerobic treatment in the first aerobic treatment means (aerobic tank 38), the obtained aerobic treated water 40 is further treated in the second aerobic treatment means (activated sludge treatment means 50). Perform temper treatment.

After the second stage aerobic treatment, that is, the activated sludge treatment (aerobic treatment) in the activated sludge tank 42, the activated sludge treated water 44 containing the activated sludge is transferred to the settling tank 46 and spontaneously settles in the settling tank 46. Is separated into the biological treated water 32, the returned sludge 56 and the surplus sludge 52 (above, aerobic treatment).

The surplus sludge 52 merges with the biologically treated water 32 via the path 54 within an allowable range. The returned sludge 56 may be returned to the anaerobic treatment means (anaerobic tank 34) and/or the aerobic treatment means (aerobic tank 38, activated sludge tank 42, etc.) as shown in FIG. Thereby, the anaerobic treatment and/or the aerobic treatment is further promoted, and the treatment quality of the finally obtained biological treated water 32 is improved.

Further, as described above, the returned sludge 56 may be supplied to the oil/fat-containing wastewater 1 and the oil/fat concentrate 22 as the oil/fat-decomposing microorganism 6 before biological treatment.

When the separated water 28 separated by the concentration/separation means (concentration/separation tank 24) is aerobically treated by two or more aerobic treatment means as in the present embodiment, the final aerobic treatment means ( That is, in the present embodiment, it is preferable to supply the activated sludge to the activated sludge tank 42 in the activated sludge treatment means 50. Since the separated water 28 contains the oil and fat content that is not concentrated in the concentrated separation means (concentrated separation tank 24) and remains in the separated water 28, it is supplied to the last aerobic treatment means as described above. This is because oils and fats can also be decomposed.

Further, the separated water 28 may be supplied to the settling tank 46 downstream of the activated sludge tank 42 depending on the degree of oil and fat content remaining in the separated water 28.

In this embodiment, two aerobic treatment means (that is, the aerobic tank 38 and the activated sludge treatment means 50) are arranged in series as the aerobic treatment means in the biological treatment means, but the present invention is not limited to this. It is not something that will be done.

Hereinafter, a modified example of the aerobic treatment means (hereinafter, referred to as a first modified example) will be described with reference to FIG. 2, the same elements as those of the embodiment shown in FIG. 1 described above are designated by the same reference numerals, and the description thereof will be omitted. FIG. 2 is a schematic diagram showing the biological treatment means 60 according to the first modification.

As shown in the figure, the biological treatment means 60 according to the first modification includes an anaerobic treatment means (anaerobic tank 34), and one aerobic treatment means (aerobic tank 62) arranged downstream of the anaerobic treatment means. Have.

In the first modification, the aerobic tank 62, which is an aerobic treatment means, is partitioned by a partition part 62a into a front part 62b and a rear part 62c. Therefore, according to the aerobic treatment means (aerobic tank 62) according to the present modification, the front stage portion 62b performs the first stage aerobic treatment and the rear stage portion 62c performs the second stage aerobic treatment. Can be given. Therefore, by increasing the number of partition sections, it is possible to carry out a plurality of stages of aerobic treatment by one aerobic treatment means.

Further, in the above-described embodiment, the biological treatment means has a configuration including an anaerobic treatment means and an aerobic treatment means, but the present invention is not limited to this.

Hereinafter, a modified example of the biological treatment means (hereinafter referred to as a second modified example) will be described with reference to FIG. In FIG. 3, the same elements as those of the embodiment shown in FIG. 1 described above are designated by the same reference numerals, and the description thereof will be omitted. FIG. 3 is a schematic diagram showing the biological treatment means 80 according to the second modification.

In the biological treatment means 80 according to this modification, a methane fermentation tank 82 (decomposition treatment means) is provided downstream of the anaerobic tank 34 (anaerobic treatment means), and an aerobic tank 38 (first) is provided downstream of the methane fermentation tank 82. The aerobic treatment means) is different from the biological treatment means 30 of the first embodiment.

The methane fermentation tank 82 (decomposition treatment means) serves as a place for decomposing the anaerobic treated water 36 (treated product) obtained by the anaerobic treatment with a methanogen. As described above, the decomposition treatment with a methanogenic bacterium means a biological treatment that decomposes organic matter into methane gas and carbon dioxide by the metabolic action of the anaerobic bacterium growing in an anaerobic environment.

As the decomposition treatment means, similarly to the anaerobic treatment means, a conventionally known apparatus such as an anaerobic fixed bed method, an anaerobic fluidized bed method, a UASB method or an EGSB method can be used. Note that, unlike the above-described anaerobic treatment means, a gas holder for storing methane gas, ancillary equipment such as a desulfurization treatment device are required.

Further, the decomposing treatment by the methanogenic bacterium is a treatment involving the generation of methane gas accompanying the decomposition by the methanogenic bacterium, which is an absolutely anaerobic bacterium, and does not involve a methane gas producing reaction, and therefore, does not generate methane gas. Is a different process.

The difference between the anaerobic treatment in which methane gas is not generated and the treatment by the methanogen can be shown, for example, below. That is, the HRT (hydraulic retention time) of the anaerobic treatment is 20 hours to 10 days, while the HRT of the treatment with the methanogen is as long as 15 days to 30 days. This is because methanogens have a slow growth rate and require a long residence time.

The ORP of the anaerobic treatment is +50 to −300 mV, while the ORP of the treatment with the methanogen is small at −330 mV or less. This is because unlike methane fermentation, highly anaerobic conditions are not always essential in anaerobic treatment, and even if air flows into the tank within the above ORP range, it does not pose a problem.

According to this modification (second modification), the anaerobic treated water 36 after the anaerobic treatment is decomposed by the methanogen, so that not only the low molecular weight of the organic matter but also the methane gasification is caused. Volatilization is promoted. Therefore, the amount of organic substances to be treated in the aerobic treatment subsequent to the decomposition treatment by the methanogen can be greatly reduced.

As a result, the effect of greatly improving the decomposition rate of n-hexane in the biologically treated water after aerobic treatment is obtained.

(Second embodiment)
Next, with reference to FIG. 4, a second embodiment of the method and apparatus for treating oil-and-fat-containing wastewater will be described, focusing on the differences from the first embodiment. FIG. 4 is a schematic diagram of an oil and fat-containing wastewater treatment device 70 according to a second embodiment of the present invention. The same components as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

A treatment device 70 for oil-and-fat-containing wastewater according to the present embodiment includes a charging/concentrating/separating means 20 for charging the iron/fat 2 into the oil/fat-containing wastewater 1 to perform a concentration/separation process, and a downstream of the charging/concentrating/separating means 20. And a biological treatment means (a biological treatment tank 74) for biologically treating the concentrate 22 obtained by the concentration and separation treatment.

The charging/concentrating/separating means 20 is the same as that in the first embodiment, and therefore its explanation is omitted.

The biological treatment means 30 is an aerobic treatment means (biological treatment tank 74) which is a place for performing the aerobic treatment as described in the first embodiment, and performs one-step aerobic treatment. is there.

That is, in the present embodiment, compared to the first embodiment, there is no supply means for supplying the oil and fat decomposing preparation 4 and/or the oil and fat decomposing microorganisms 6, and one-step aerobic treatment as biological treatment. The difference is that only the processing is performed.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example 1]
Fig. 4 shows ferric chloride in food factory wastewater 1 (corresponding to fat/oil-containing wastewater 1) with BOD (biological oxygen demand) = 580 mg/L, SS = 408 mg/L, and hexane extractant = 400 mg/L. It was added at a concentration of 1 to 800 mg/L in terms of Fe and the pH was adjusted to 7.0. Then, anionic polymer (Ebagulose A-151, manufactured by Water Ing Co., Ltd.) was added at a concentration of 1 mg/L, and equal amounts of pressurized water pressurized to 4 kg/cm ² were mixed to carry out floating separation.

Next, the same flotation separation process was performed on the food factory wastewater 2 (corresponding to the oil and fat-containing wastewater 1) sampled at different times in the same procedure.

The values of BOD, SS, and hexane extract substance of food factory wastewater 1 and food factory wastewater 2 are almost the same. In addition, SS means a suspended substance and is one of the indicators of turbidity of water. Particles contained in water are filtered with a glass fiber filter paper or a MF membrane filter paper having a pore diameter of 1 μm, and the dry matter weight of the particles. (Mg/L).

[Comparative Example 1]
PAC (polyaluminum chloride) was used instead of ferric chloride, and the pressure levitation treatment was performed in the same manner as in Example 1 except for the above.

In Example 1 and Comparative Example 1, the amount of the hexane extract substance in the float-separated oil/fat concentrate was specified, and the recovery rate of the oil recovered in the oil/fat concentrate from the food factory wastewater 1 and 2 was calculated. .. Results are shown in FIG.

FIG. 5 is a graph in which the horizontal axis represents the amount of coagulant added to food factory wastewater (mg/L in terms of Fe and Al equivalents), and the vertical axis represents oil content recovery rate (%).

As shown in the figure, when ferric chloride was used as the coagulant, the oil and fat component contained in the wastewater could be stably separated and recovered regardless of the lot of the wastewater.

On the other hand, when PAC was used as the coagulant, the recovery of the oil and fat component from the food factory wastewater 1 was good, but the recovery rate of the oil and fat component from the food factory wastewater 2 deteriorated.

Therefore, it was confirmed that when the iron salt was added to the oil/fat-containing wastewater as an inorganic coagulant, the oil/fat could be stably concentrated and separated regardless of the properties of the oil/fat-containing wastewater.

[Example 2]
A mixture of commercially available mayonnaise and margarine at a mass ratio of 1:1 was used as an oil/fat raw material, and this was added to city water to adjust the hexane extract substance to 400 mg/L. I assumed.

And ferric chloride is 1 mg/L (Condition (1)), 20 mg/L (Condition (2)), 100 mg/L (Condition (3)) in terms of iron with respect to the oil and fat-containing wastewater (raw water). , 400 mg/L (condition (4)), 800 mg/L (condition (5)), and concentrated and separated 40 times to obtain a fat and oil concentrate (equivalent to concentrate 22). Assuming a case, ferric chloride in city water is converted into iron at 40 mg/L (condition (1)), 800 mg/L (condition (2)), 4,000 mg/L (condition (3)), 16 2,000 mg/L (Condition (4)) and 32,000 mg/L (Condition (5)), respectively, and each of the above-mentioned fats and oils raw material was adjusted so that the hexane extraction substance concentration became 16,000 mg/L. What was added was the supposed concentrate of oil and fat.

Next, for the concentrate of conditions (1) to (5), a 2 L reaction vessel is prepared as a one-step biological treatment means (corresponding to biological treatment tank 74), and the reaction conditions are 37° C. and pH 7.5. .About.8.2, dissolved oxygen concentration 1.0 mg/L, and residence time 320 hours were set, and continuous biological treatment (aerobic treatment) test of the concentrates of the conditions (1) to (5) was conducted.

[Comparative example 2]
A liquid assumed to be raw water of oil-and-fat-containing wastewater in Example 2 (that is, a mixture of commercially available mayonnaise and margarine at a mass ratio of 1:1 was used as an oil and fat raw material, and this was added to city water to obtain 400 mg of a hexane extraction substance. /L)), ferric chloride was added at a concentration of 1 mg/L in terms of iron.

For such raw water, a 2 L reaction vessel was prepared as one-stage biological treatment means (corresponding to biological treatment tank 74), reaction conditions were 37° C., pH 7.5 to 8.2, and dissolved oxygen concentration 1.0 mg/L. A continuous biological treatment (aerobic treatment) test was conducted with a residence time of 8 hours.

The residence time was set to 8 hours because the concentrate of Example 2 had a hexane extractant concentration of 16,000 mg/L, whereas the raw water of Comparative Example 2 had a hexane extractant concentration of 400 mg/L of 1/40. Therefore, the reaction time of Comparative Example 2 is set to 8 hours, which is 1/40 of that of Example 2.

The results are shown in Table 1.

※1：比較例２にいう原水のヘキサン抽出物質濃度を示す。
※2：実施例２の条件(1)〜(5)の４０倍濃縮を想定した濃縮物のヘキサン抽出物質濃度を示す。
※3：比較例２においては、直接添加した鉄塩のＦｅ換算量であり、実施例２(1)〜(5)においては、濃縮物を原水レベルまで希釈（４０倍希釈）したと想定した場合の鉄塩のＦｅ換算量を示す。
※4：原水ｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）に対する、原水レベルまで濃縮物を希釈（４０倍希釈）したと想定した場合の鉄塩のＦｅ換算量の比を示す。すなわち、原水あたりのｎ−Ｈｅｘ量に対する添加された鉄塩のＦｅ換算量の比である。
※5：生物処理試験後の生物処理水のヘキサン抽出物質濃度を示す。
※6：比較例２においては、原水ｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）と生物処理水のｎ−Ｈｅｘ濃度との差分から算出されるヘキサン抽出物質の分解率であり、実施例２(1)〜(5)においては、原水ｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）（４００ｍｇ／Ｌ）と生物処理水のｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）を４０で除した値との差分から算出されるヘキサン抽出物質の分解率を示す。

*1: Indicates the concentration of the hexane extracted substance in the raw water referred to in Comparative Example 2.
*2: Indicates the concentration of hexane-extracted substance in the concentrate, which is assumed to be 40 times concentrated under the conditions (1) to (5) of Example 2.
*3: In Comparative Example 2, it is the Fe-equivalent amount of the iron salt added directly, and in Examples 2 (1) to (5), it was assumed that the concentrate was diluted to the raw water level (40-fold dilution). The Fe conversion amount of the iron salt in this case is shown.
*4: Indicates the ratio of the Fe-equivalent amount of the iron salt to the raw water n-Hex concentration (mg/L), assuming that the concentrate was diluted to the raw water level (40-fold dilution). That is, it is the ratio of the Fe-equivalent amount of the added iron salt to the amount of n-Hex per raw water.
*5: Indicates the hexane extractable substance concentration of biologically treated water after the biological treatment test.
*6: In Comparative Example 2, it is the decomposition rate of the hexane extract substance calculated from the difference between the n-Hex concentration (mg/L) of the raw water and the n-Hex concentration of the biologically treated water, and Example 2(1) In (5), hexane calculated from the difference between the raw water n-Hex concentration (mg/L) (400 mg/L) and the biological treated water n-Hex concentration (mg/L) divided by 40. The decomposition rate of the extracted substance is shown.

As shown in Table 1, the condition (1) of Comparative Example 2 and Example 2 is that biological treatment was carried out under the condition that the iron addition amount (Fe equivalent amount) per oil component contained in raw water was the same, Under the condition (1) of Example 2 in which the fat and oil component was concentrated and separated, the decomposition rate of the fat and oil component was improved by 10% as compared with Comparative Example 2.

Even if the liquid has the same amount of the hexane extract substance, the liquid having a low concentration of the hexane extract substance has a large volume. Therefore, when biological treatment is performed at the same time in a tank having a constant volume, a liquid having a large volume (that is, a liquid having a low hexane extraction concentration) has a short residence time in the biological treatment tank and a liquid having a small volume (that is, A liquid with a high concentration of hexane extractable substance) can have a long residence time in the biological treatment tank.

Further, as described above, the oil and fat component generally exists as a solid in the liquid, and during the biological treatment, the oil and fat component proceeds from the surface of the solid to the inside thereof. Therefore, the ability to take a long time for biological treatment leads to the progress of decomposition of fats and oils, which leads to an improvement in the quality of biological treatment water obtained.

That is, in the condition (1) of Example 2, the residence time of the oil and fat component is longer than that of Comparative Example 2, so that the decomposition is further advanced and the purification of the biologically treated water is further advanced.

Furthermore, according to Table 1, the value of the ratio of (B)/(A), that is, the "total amount of iron per unit volume of oil-and-fat-containing wastewater (see paragraph [0024])" in Patent Document 2 is the same. The weight ratio of iron to the load amount of the normal hexane extract material per unit volume of oil-and-fat-containing wastewater (see the same paragraph) is a very large value of 0.0025 to 2, and the inventors Under the conditions (1) to (5) of No. 2, it was found that the treated water quality of the biological treated water becomes better as the added amount of the iron salt is increased.

This result indicates that the total amount of iron per unit volume of oil-and-fat-containing wastewater of Patent Document 2 is more than 30×10 ⁻³ in terms of weight ratio to the load amount of the normal hexane extract substance per unit volume of the same oil-and-fat-containing wastewater. It is supplied iron salts to the first treatment tank 10, activity of microbial sludge in the first treatment tank 10, in a weight ratio to the load of normal hexane extract 1.0 × 10 ^-3 or more 30 × 10 ^- The result is almost the same as the case of ³ or less (the same paragraph)", which is a different result.

That is, even when the mass ratio of iron salt to the amount of normal hexane extract per raw water (Fe equivalent) exceeds 1.0×10 ⁻³ , when biological treatment is performed, the total amount of iron increases with increase. It was found that the decomposition efficiency of fats and oils was improved.

[Example 3]
A mixture of commercially available mayonnaise and margarine at a mass ratio of 1:1 was used as an oil/fat raw material, and this was added to city water to adjust the hexane extract substance to 400 mg/L. I assumed.

Ferric chloride was added to the oil-containing wastewater (raw water) so as to be 400 mg/L in terms of iron, and concentrated and separated 40 times to obtain a concentrate. Was added at a concentration of 16,000 mg/L in terms of iron, and the above oil/fat raw material was added so that the hexane extract substance concentration was 16,000 mg/L. 6)).

In addition, it is assumed that the fat-degrading microorganisms are added at a concentration of 200 mg-SS/L per fat/oil-containing wastewater (raw water), which is a concentrate having the same iron content, the same fat/oil content, and the same concentration ratio as those in the condition (6). Then, ferric chloride in city water at a concentration of 16,000 mg/L in terms of iron and the above oil/fat raw material as a hexane extract substance at a concentration of 16,000 mg/L were obtained under the conditions (4) of Example 2. The sludge of the biological treatment tank was added at a concentration of 8,000-SS/L to obtain a fat and oil concentrate (condition (7)).

As a biological treatment tank, a 0.6-liter reaction vessel and a 1.4-liter reaction vessel were prepared and used in order for anaerobic treatment (anaerobic treatment means), one-stage aerobic treatment aerobic treatment tank (late treatment). Means). The reaction conditions of the anaerobic tank are set at 37° C., pH 7.5 to 8.5, and the residence time is 96 hours, and the reaction conditions of the aerobic tank are 37° C., pH 7.5 to 8.2, and dissolved oxygen concentration 1.0 mg/ A continuous treatment test of the oil/fat concentrate was conducted under the conditions of L and residence time of 224 hours.

[Comparative Example 3]
The iron salt used when adjusting the oil/fat concentrate of Example 3 was changed to PAC, and the concentration of PAC added was 400 mg/L in terms of Al per oil/fat-containing wastewater (raw water), and concentrated 40 times. Assuming a case where the concentrate is separated to obtain a concentrate, ferric chloride added to city water at a concentration of 16,000 mg/L in terms of iron is assumed to be a fat concentrate (comparative example 3). And

Other conditions were adjusted in the same manner as the procedure for adjusting the oil/fat concentrate described in the condition (6) of Example 3 to adjust the oil/fat concentrate. With respect to the fat and oil concentrate of Comparative Example 3, the same biological treatment test as in Example 3 was performed.

Table 2 shows the test conditions of Example 3 and Comparative Example 3, and Table 3 shows the results of the biological treatment tests of Example 3 and Comparative Example 3.

※7：油脂含有排水（原水）のヘキサン抽出物濃度を示す。
※8：４０倍濃縮を想定した油脂濃縮物のヘキサン抽出物質濃度を示す。
※9：油脂濃縮物を４０倍希釈した場合の鉄塩のＦｅ換算量を示す。
※10：油脂濃縮物を４０倍希釈した場合のＰＡＣのＡｌ換算量を示す。
※11：嫌気槽での嫌気性処理により得られた嫌気処理水のヘキサン抽出物濃度を示す。
※12：嫌気処理水に対して好気槽にて好気性処理を施し、得られた生物処理水のヘキサン抽出物濃度を示す。
※13：油脂含有排水（原水）ｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）と生物処理水のｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）を４０で除した値との差分から算出されるヘキサン抽出物質の分解率を示す。

*7: Indicates the hexane extract concentration of oil-containing wastewater (raw water).
*8: Indicates the concentration of hexane-extracted substances in oil and fat concentrates assuming 40-fold concentration.
*9: Indicates the Fe equivalent of the iron salt when the fat and oil concentrate is diluted 40 times.
*10: Indicates the amount of PAC converted to Al when the fat and oil concentrate is diluted 40 times.
*11: Indicates the hexane extract concentration of anaerobic treated water obtained by anaerobic treatment in an anaerobic tank.
*12: Indicates the hexane extract concentration of biologically treated water obtained by subjecting anaerobic treated water to aerobic treatment in an aerobic tank.
*13: Decomposition of hexane extracted substance calculated from the difference between the n-Hex concentration (mg/L) of oil-containing wastewater (raw water) and the n-Hex concentration (mg/L) of biologically treated water divided by 40. Indicates the rate.

As can be understood from the comparison between Table 1 and Table 3, in Example 3-(6) as compared with Example 2-(4), when the anaerobic treatment was introduced in the first half of the biological treatment, the decomposition rate of oil and fat components was increased. Could be improved by 2%.

In addition, in Example 2-(4), although not shown in the table, there were occasional problems such as undecomposed oil floating on the upper part of the aerobic tank during the biological treatment and generation of fat and oil residues. However, in Example 3-(6), it was possible to show that the introduction of the anaerobic treatment enables stable treatment without the generation of oil and fat residues.

Conventionally, when the concentrated oil and fat component is directly subjected to aeration treatment (aerobic treatment) as in the prior art of Patent Document 1, undecomposed oil and fat causes fat and oil residues in the process of treatment due to such aeration treatment. There was a defect of forming. An example of such an oil/fat residue is an oil ball, and the oil/fat residue is difficult to decompose, so that the decomposition treatment takes a very long time. According to the present invention, the anaerobic treatment is performed on the oil/fat concentrate prior to the aerobic treatment, so that the concentration of the oil/fat concentrate in the concentrate is increased as compared to the case where the oil/fat concentrate is suddenly subjected to the aerobic treatment. The oil and fat content can be effectively decomposed.

Further, comparing Example 3-(6) with Example 3-(7), by adding the sludge acclimatized in the biological treatment tank as an oil-degrading microorganism at the time of adjusting the oil-fat concentrate, the decomposition of the oil-fat component is performed. The rate could be improved by 7% (see Table 3). That is, in the biological treatment, a further oil-degrading effect by the oil-degrading microorganisms was obtained, and the treatment efficiency of the biological treatment on the concentrate after concentration and separation could be further enhanced.

In addition, comparison between Example 3-(7) and Comparative Example 3 shows that when the coagulant is changed from iron to PAC, the decomposition rate of oil and fat components is reduced by 23%.

Hereinafter, in a continuous biological treatment test carried out in the categories of Comparative Example 3 and Example 3-(7), the fat and oil concentrate collected from the anaerobic tank (anaerobic treatment means) of the biological treatment means was analyzed by thin layer chromatography. The results of composition analysis are shown in Table 4.

As shown in Table 4, in the comparative example, the proportion of undegraded oil, triglycerol, in the total oil and fat component was 46.9%, whereas in the example, the proportion of triglycerol in the total oil and fat component was high. Was as small as 2.0%, indicating that the hydrolysis was accelerated. Thus, it was shown that the use of the iron salt as the coagulant used in the separation and concentration of fats and oils promotes the hydrolysis of fats and oils in the biological treatment process and improves the degradation rate of fats and oils.

[Comparative Example 4]
A mixture of commercially available mayonnaise and margarine in a mass ratio of 1:1 was used as an oil/fat raw material, and this was added to city water to adjust the hexane extract substance to 500 mg/L. I assumed.

Ferric chloride was added to the fat-and-oil-containing wastewater (raw water) at a concentration of 1 mg/L in terms of iron, and biological treatment was performed as it was. That is, Comparative Example 4 assumes the case where the fat and oil are not concentrated and separated by adding the iron salt, and the iron salt is added only to the biological treatment step as in Patent Document 2.

As a biological treatment tank used for biological treatment, a 2 L reaction vessel was prepared, and the reaction conditions were set at 37° C., pH 7.5 to 8.2, dissolved oxygen concentration 1.0 mg/L, initial sludge concentration 5,000 mg/L. The batch treatment test of raw water was conducted.

Results are shown in FIG. FIG. 6 is a diagram showing the results of a batch-type biological treatment test of the oil/fat-containing wastewater (raw water) of Comparative Example 4. As shown in the figure, in 6 hours after the start of the test, 68% of the oil/fat component contained at the start of the test was rapidly decomposed, and then the decomposition rate of the oil/fat component was remarkably slowed, and at the end of the treatment test of 84 hours. Then, the oil component corresponding to 10% of the initial charge remained. As described above, in the biological treatment of unconcentrated oil-and-fat-containing wastewater (raw water), even if iron was added, the decomposition rate of the oil and fat components decreased in the middle and latter half of the biological treatment.

This is because under aerobic biological treatment conditions, a part of the fats and oils to be decomposed forms a fat and oil residue due to aerobic treatment (aeration treatment), and the fat and oil residue is in the middle stage of the biological treatment. It can be seen that even in the latter half, it remained without being decomposed.

[Example 4]
A mixture of commercially available mayonnaise and margarine in a mass ratio of 1:1 was used as an oil/fat raw material, and this was added to city water to adjust the hexane extract substance to 400 mg/L. I assumed.

Oil-decomposing microorganisms were added to the oil-containing wastewater (raw water) at a concentration of 200 mg-SS/L, and ferric chloride was further added so as to be 400 mg/L in terms of iron. Assuming that a product is obtained, the sludge and ferric chloride in the biological treatment tank obtained under the condition (4) of Example 2 are 8,000-SS/L and 16,000 mg in terms of iron in city water, respectively. What was added at a concentration of /L, and the above-mentioned oil and fat raw material was added so that the hexane extract substance concentration would be 16,000 mg/L was used as an assumed oil and fat concentrate.

As a biological treatment tank, 0.6 L, 3.0 L, and 1.0 L reaction vessels were prepared, and an anaerobic tank (anaerobic treatment means) used for anaerobic treatment and a methane fermentation tank used for decomposition treatment by methanogens ( The decomposition treatment means) and an aerobic tank (aerobic treatment means) used for one-step aerobic treatment. The reaction conditions of the anaerobic tank are set to 45° C., pH 7.5 to 8.5, and the retention time is 96 hours, and the reaction conditions of the methane fermentation tank are set to 55° C., pH 7.0 to 8.0, and the retention time is 360 hours. The continuous treatment test of the fat and oil concentrate was conducted under the conditions of the aerobic tank at 50 to 55° C., pH of 7.5 to 8.2, dissolved oxygen concentration of 1.0 mg/L, and residence time of 120 hours.

[Example 5]
The same test as in Example 4 was performed except that the anaerobic treatment was not performed.

That is, 3.0 L and 1.0 L reaction vessels were prepared as biological treatment tanks, and were sequentially used as a methane fermentation tank (decomposition treatment means) and an aerobic tank (aerobic treatment means) used for one-step aerobic treatment. .. The reaction conditions of the methane fermentation tank are 55° C., pH 7.0 to 8.0, and the residence time is 456 hours. The reaction conditions of the aerobic tank are 50 to 55° C., pH 7.5 to 8.2, and dissolved oxygen concentration 1 A continuous treatment test of the oil/fat concentrate was conducted under the settings of 0.0 mg/L and a residence time of 120 hours.

The residence time in the methane fermentation tank was set to 456 hours in order to match the total biological treatment time with the conditions of Example 4. Other conditions were the same as in Example 4.

[Comparative Example 5]
The same test as in Example 4 was performed except that PAC was used instead of ferric chloride.

That is, the sludge of the biological treatment tank obtained under the condition (4) of Example 2 was added to city water at a concentration of 8,000-SS/L, and PAC was added at a concentration of 16,000 mg/L on a product basis. Then, the above-mentioned fat and oil raw material was added so that the hexane extract substance concentration would be 16,000 mg/L, and used as a fat and oil concentrate in the test. Other conditions were the same as in Example 4.

In Examples 4 to 5 and Comparative Example 5, after the water quality of the treated water is stabilized, the anaerobic treated water after the anaerobic treatment, the decomposed treated water after the decomposition treatment by the methanogen and the biological treated water after the aerobic treatment. The hexane extract substance concentration was measured, and the decomposition rate of the hexane extract substance (n-Hex decomposition rate) was calculated.

Table 5 shows the test conditions of Examples 4 to 5 and Comparative Example 5, and Table 6 shows the results of the continuous treatment tests of Examples 4 to 5 and Comparative Example 5.

※14：実施例２の条件（４）で得られた生物処理槽の汚泥を示す。

*14: Indicates the sludge in the biological treatment tank obtained under the condition (4) of Example 2.

※15：油脂含有排水（原水）ｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）と嫌気処理水、分解処理水、生物処理水のそれぞれのｎ−Ｈｅｘ濃度（ｍｇ／Ｌ）を４０で除した値との差分から算出されるヘキサン抽出物質の分解率を示す。
※16：ＰＡＣ等の従来の無機凝集剤で回収した油脂濃縮物において、油脂成分が密に固まった粒状物を形成し、生物処理における反応性が著しく低下する結果、そのまま粒状物の形状で処理水に分散した状態をいう。

*15: Of oil-containing wastewater (raw water) n-Hex concentration (mg/L) and anaerobic treated water, decomposed treated water, biological treated water n-Hex concentration (mg/L) divided by 40 The decomposition rate of the hexane extract substance calculated from the difference is shown.
*16: In the oil/fat concentrate collected with a conventional inorganic coagulant such as PAC, the oil/fat components are densely solidified to form granules, and the reactivity in biological treatment is significantly reduced. The state of being dispersed in water.

As shown in Example 4 of Table 5 and Table 6, the anaerobic treatment as a biological treatment and the one obtained by adding a fat-degrading microorganism and an iron salt to a fat-containing wastewater (raw water) were used. When the methane fermentation treatment (decomposition treatment) was performed during the aerobic treatment, the biologically treated water after the aerobic treatment showed a high hexane extract substance decomposition rate of 95%.

Further, as shown in Example 5, even when the methane fermentation treatment (decomposition treatment) was introduced into the biological treatment, the decomposition rate of the hexane extract substance of the biological treated water was 76 when the anaerobic treatment was not performed. %, which is lower than that of Example 4.

Furthermore, when conventional anaerobic digestion (decomposition treatment by methanogenic bacteria) and aerobic treatment were performed without performing anaerobic treatment, symptoms of anaerobic digestion inhibition were observed.

Further, as shown in Comparative Example 5, even when the conventional anaerobic digestion (decomposition treatment by methanogens) is performed in addition to the anaerobic treatment, if the iron salt is not added, biological treatment is performed. The decomposition rate of the hexane-extracted substance in water was 70%, which was lower than that in Example 4. Furthermore, in Comparative Example 5 in which PAC was added instead of Fe as the aggregating agent, the dispersion of fats and oils in the biologically treated water was worse than in Example 4.

1 Oil-and-fat-containing wastewater 2 Iron salt 4 Oil-and-fat decomposition preparation 6 Oil-and-fat-degrading microorganisms 10, 70 Oil-and-fat-containing wastewater treatment equipment 15 Supply means 20 Input/concentration separation means 22 Concentrate 24 Concentration separation tank (concentration separation means)
26 input means 30, 80 biological treatment means 34 anaerobic tank (anaerobic treatment means)
38, 62 Aerobic tank (aerobic treatment means)
50 Activated sludge treatment means (aerobic treatment means)
74 Biological treatment tank (biological treatment means)
82 Methane fermentation tank (decomposition processing means)

Claims (3)

A method for treating fat/oil-containing wastewater, in which iron salt is added to fat/oil-containing wastewater to perform concentration/separation treatment for concentrating/separating oil/fat components, and biological treatment is performed by subjecting the concentrate obtained by the concentration/separation treatment to biological treatment And
The biological treatment is
At least one of decomposition, emulsification and dispersion by at least one microorganism selected from the group consisting of anaerobic bacteria, facultative anaerobic bacteria, microaerobic bacteria and aerobic bacteria under an anaerobic environment or a microaerobic environment. One process der to the action of is, the anaerobic treatment of degradation by methanogenic bacteria are treated with conditions that do not proceed,
Aerobic treatment applied to the treated product obtained from the anaerobic treatment, only including,
A method for treating fat/oil-containing wastewater, which comprises supplying a fat/oil-decomposing preparation and/or a fat/oil-degrading microorganism to at least one of the fat/oil-containing wastewater and the concentrate before the biological treatment. A treatment device for wastewater containing oil and fat,
An input/concentration/separation means for performing a concentration/separation process in which an iron salt is added to the oil/fat-containing wastewater to concentrate/separate the oil/fat, to obtain a concentrate.
E Bei and a biological treatment means for obtaining a biologically treated water by applying biological treatment in the concentrate,
The biological treatment hand stage,
An anaerobic tank for treating the concentrate from the charging/concentrating/separating means under conditions where decomposition by methanogens does not proceed ,
An aerobic tank for aerobically treating the decomposed product obtained by the treatment under the condition that the decomposition by the methanogen does not progress, and obtaining aerobically treated water,
An activated sludge tank for treating the aerobic treated water with activated sludge to obtain activated sludge treated water,
The activated sludge treated water is subjected to a precipitation treatment, and a settling tank for obtaining returned sludge and biologically treated water by separating the flocs of the activated sludge transferred from the activated sludge tank by natural sedimentation ,
Prior to the biological treatment, a supply means for supplying an oil and fat-containing wastewater and at least one of the concentrate with an oil and fat decomposing formulation and/or an oil and fat decomposing microorganism,
The return sludge, and the oil degrading microorganisms as the oil-containing wastewater before biological treatment, the concentrate, the sludge return hand stage supplies the aerobic tank and the activated sludge tank,
An apparatus for treating wastewater containing oil and fat, comprising: A treatment device for wastewater containing oil and fat,
An input/concentration/separation means for performing a concentration/separation process in which an iron salt is added to the oil/fat-containing wastewater to concentrate/separate the oil/fat, to obtain a concentrate.
Biological treatment means for obtaining biologically treated water by subjecting the concentrate to biological treatment ,
The biological treatment means,
At least one of decomposition, emulsification and dispersion by at least one microorganism selected from the group consisting of anaerobic bacteria, facultative anaerobic bacteria, microaerobic bacteria and aerobic bacteria under an anaerobic environment or a microaerobic environment. One process der to the action of is, the anaerobic treatment means for performing anaerobic treatment of degradation by methanogenic bacteria are treated with conditions that do not proceed,
Anda aerobic processing means for performing aerobic treatment process product obtained in the anaerobic treatment,
Furthermore, prior to the biological treatment, at least one of the fat-and-oil-containing wastewater and the concentrate has a supply means for supplying a fat-and-oil-decomposing formulation and/or a fat-and-oil-degrading microorganism, Processing equipment.

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