JP6055601B2 - Biological treatment apparatus for oil-containing wastewater and biological treatment method for oil-containing wastewater - Google Patents

Description

  The present invention relates to a biological treatment apparatus and a biological treatment method for fat and oil-containing wastewater.

  In biological treatment of wastewater containing a large amount of fats and oils such as wastewater from food factories, the fats and oils in the wastewater adhere to the biological sludge, the biological sludge activity is inhibited, and biological treatment becomes difficult. In general, when the concentration of fats and oils in the wastewater is 150 mg / L or more in terms of the concentration of the normal hexane extract, the activity of biological sludge is inhibited, and biological treatment may be difficult.

  Conventionally, as a method for preventing the inhibition of biological treatment by fats and oils, there is a method of removing fats and oils in advance by pressurized flotation before the biological treatment. Although the pressure flotation is an excellent method for removing oils and fats, the operation is complicated, and a large amount of flocculant is required, and the cost of the generated sludge is increased. Furthermore, the sludge containing fats and oils also causes bad odor.

  As another method for preventing the biological treatment from being inhibited by fats and oils, for example, Patent Documents 1 to 3 disclose a method of adding microorganisms and enzymes for decomposing fats and oils to the fat and oil-containing waste water. However, since the microorganisms that decompose fats and oils are difficult to separate, the processing cost becomes high. Moreover, the method of adding the enzyme which decomposes | disassembles fats and oils also increases a processing cost at the point which uses an enzyme formulation.

Japanese Patent Laid-Open No. 03-275195 JP 2006-142132 A JP 05-245479 A

  An object of the present invention is to provide a biological treatment apparatus and biological treatment method for fat and oil-containing wastewater that can efficiently biologically treat fat and oil in the fat and oil-containing wastewater.

Biological treatment apparatus of the fat-containing wastewater of the present invention includes: a tank unit at least having a first treatment tank and a second treatment tank for aerobic biological treatment of oil-containing waste water from a food factory, iron salt to said first treatment tank The heavy metal salt supplied to the first treatment tank is only the iron salt supplied by the iron salt supply means, and the iron salt supply means contains oil and fat. In the first treatment tank, the total amount of iron per unit volume of waste water is 1.0 × 10 ⁻³ or more in terms of the weight ratio of iron to the load of normal hexane extract material per unit volume of fat and oil containing waste water. It is a biological treatment device that supplies iron salts.

Moreover, this invention is the biological treatment method of the fat containing wastewater which carries out the aerobic biological treatment of the fat containing wastewater derived from a food factory by the processing tank unit which has a 1st processing tank and a 2nd processing tank, Comprising: Iron salt is added to the first treatment tank so that the total amount of iron per volume is 1.0 × 10 ⁻³ or more in terms of the weight ratio of iron to the load of normal hexane extract per unit volume of the same fat and oil-containing wastewater. The heavy metal salt supplied to the first treatment tank is only the iron salt .

  According to the present invention, fats and oils in fats and oils-containing wastewater can be efficiently biologically treated.

It is a schematic diagram which shows an example of a structure of the fat and oil containing waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of the structure of the fat-and-oils containing waste water treatment equipment which concerns on this embodiment. It is a figure which shows the result of the removal rate of the normal hexane extract in the weight ratio (iron / n-Hex ratio) of the iron per fat-containing waste water unit volume with respect to the load of the normal hexane extract per oil-containing waste water unit volume. .

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  Drawing 1 is a mimetic diagram showing an example of the composition of the oil-and-fat containing waste water treatment equipment concerning this embodiment. The oil-and-fat-containing wastewater treatment apparatus 1 shown in FIG. 1 includes a treatment tank unit having a first treatment tank 10 and a second treatment tank 12, and an iron salt supply device 14 as an example of iron salt supply means. A drainage introduction pipe 16 is connected to a drainage inlet (not shown) of the first treatment tank 10, and one end of a drainage discharge pipe 18 is connected to a drainage outlet (not shown) of the first treatment tank 10. The other end of the drainage discharge pipe 18 is connected to the drainage inlet (not shown) of 12, and the treated water discharge pipe 20 is connected to the treated water outlet (not shown) of the second treatment tank 12.

  Although not shown in the figure, the first treatment tank 10 and the second treatment tank 12 include a heating device (heating means) such as an electric heater for heating the water temperature in the tank, and aeration for aeration in the tank. Device (aeration means), biologic addition device (biological product addition means) for adding biologics to the tank to control the biomass in the tank, acid or alkali in the tank to control the pH in the tank It is desirable that a pH adjusting device (pH adjusting means) or the like to which etc. are added is appropriately installed.

  The iron salt supply device 14 is not particularly limited as long as the iron salt can be supplied to the first treatment tank 10, but in this embodiment, the iron salt is filled, It is comprised from the storage tank 22 and the iron salt supply pipe 24 which can control the supply_amount | feed_rate of iron salt. The supply amount of iron salt may be controlled by installing a valve or a pump in the iron salt supply pipe 24. In the present embodiment, as shown in FIG. 1, one end of the iron salt supply pipe 24 is connected to an iron salt discharge port (not shown) of the storage tank 22, and the other end of the iron salt supply pipe 24 is the first treatment tank 10. However, the other end of the iron salt supply pipe 24 may not be directly connected to the first treatment tank 10 but may be connected to the drainage introduction pipe 16.

  Next, the operation of the fat and oil-containing wastewater treatment apparatus 1 according to this embodiment will be described.

  In the oil-containing wastewater treatment apparatus 1 according to the present embodiment, the oil-containing wastewater to be treated may be water of any origin, but as wastewater containing high-concentration oil, for example, kitchen wastewater, edible oil It is desirable to treat manufacturing plant wastewater, meat processing plant wastewater, confectionery manufacturing plant wastewater, etc. Moreover, many fats and oils-containing wastewater contains fats and oils and other BOD components. Here, the BOD component is a component such as organic matter that is decomposed by aerobic microorganisms such as activated sludge. Moreover, fats and oils are edible oil, animal and vegetable oil, etc.

  First, the fat and oil-containing wastewater is supplied to the first treatment tank 10 through the wastewater introduction pipe 16. In addition, in the case of drainage where oil film or oil droplets are conspicuous, it is preferable to add an emulsifier in advance to drainage before flowing into the first treatment tank 10. Then, the iron salt is supplied from the storage tank 22 through the iron salt supply pipe 24 to the first treatment tank 10. The iron salt may be supplied intermittently or continuously. In the 1st processing tank 10, in the presence of an iron salt, the oil-containing wastewater contacts with the oil-decomposing microorganism sludge (including biologics when the biologics are added to the first processing tank 10). To do. Thereby, in the 1st processing tank 10, the fats and oils in fat-containing waste water are mainly decomposed | disassembled. The iron salt supplied to the first treatment tank 10 is considered to have actions such as nutrient salts that promote the growth of oil-degrading microorganisms in the tank, oxidation catalysts that promote the decomposition of fats and oils, and the like. Therefore, compared with the case where the iron salt is supplied into the first treatment tank 10, it is suppressed that the activity of the oil-degrading microbial sludge by the fat is inhibited when the iron salt is supplied into the first treatment tank 10. It becomes possible to efficiently decompose the fats and oils in the waste water.

  Next, the wastewater treated in the first treatment tank 10 is supplied from the drainage discharge pipe 18 to the second treatment tank 12. In the 2nd processing tank 12, the waste_water | drain with which fats and oils were reduced, and biological sludge contact, and mainly the BOD component etc. in waste_water | drain are decomposed | disassembled. In this embodiment, since the fats and oils in waste_water | drain are decomposed | disassembled previously in the 1st processing tank 10, in the 2nd processing tank 12, it is suppressed that the activity of the microorganisms sludge by fats and oils is inhibited. As a result, the BOD component and the like can be efficiently decomposed (biological treatment). In addition, in the waste_water | drain supplied to the 2nd processing tank 12, since the case where the iron salt supplied to the 1st processing tank 10 remains is considered, it remains in the waste_water | drain also in the 2nd processing tank 12. FIG. It is inferred that fats and oils are also decomposed. And the waste water processed by the 2nd processing tank 12 is discharged | emitted out of the system from the treated water discharge pipe 20 as treated water.

  Below, an example of the treatment conditions of the biological treatment by a treatment tank unit, etc. are explained.

  Although the processing tank unit of this embodiment is the 2 tank structure of the 1st processing tank 10 and the 2nd processing tank 12, it is not limited to this tank structure, The tank structure of 3 tanks or more may be sufficient. . For example, when fat and oil-containing wastewater contains nitrogen compounds such as ammonia nitrogen in addition to fats and oils and BOD components, when the concentration of fats and oils and other substances is very high, three or more tanks A configuration is preferable.

  Moreover, in this embodiment, although iron salt is supplied only to the 1st processing tank 10, you may supply iron salt also to the processing tank of the back | latter stage from the 1st processing tank 10. FIG.

Since the decomposition rate of fats and oils varies depending on the properties of the wastewater, the supply amount of iron salt to the first treatment tank 10 is set in consideration of the decomposition rate of fats and oils. Iron salt is added to the first treatment tank 10 so that the total amount of iron per volume is 1.0 × 10 ⁻³ or more in terms of the weight ratio of iron to the load of normal hexane extract per unit volume of the same fat and oil-containing wastewater. It is preferable to supply, and it is more preferable to supply iron salt to the 1st processing tank 10 so that it may become 2.0 * 10 < ^-3 > or more. When the total amount of iron per fat-containing wastewater unit volume after iron salt addition is less than 1.0 × 10 ^{−3 in} terms of the weight ratio of iron to the load of normal hexane extract per unit fat-containing wastewater unit volume, The iron salt does not sufficiently act as the nutrients described above or as an oxidation catalyst, and the oil and fat may not be decomposed efficiently. In this embodiment, during operation of the apparatus, the total amount of iron per unit volume of fat-containing wastewater is 1.0 × 10 ⁻³ or more in terms of the weight ratio of iron to the load of normal hexane extract per unit volume of fat-containing wastewater. However, from the viewpoint of processing costs, the upper limit of the total amount of iron per unit volume of fat-containing wastewater is 30 × by weight ratio to the load of normal hexane extract per unit volume of fat-containing wastewater. It is preferable to set it as 10 <^-3> or less. This is because the total amount of iron per unit volume of fat and oil containing wastewater is in the first treatment tank 10 so that the weight ratio with respect to the load amount of the normal hexane extract per unit volume of fat and oil containing wastewater exceeds 30 × 10 ^−3. Even when iron salt is supplied, the activity of the microbial sludge in the first treatment tank 10 is in the range of 1.0 × 10 ⁻³ or more and 30 × 10 ⁻³ or less in terms of the weight ratio with respect to the load amount of the normal hexane extract. This is because it is almost the same.

Here, the normal hexane extract substance is a component mainly composed of fats and oils extracted to the normal hexane side by mixing fat and oil-containing waste water and normal hexanes. The normal hexane extract material is charged with an appropriate amount of fat and oil-containing wastewater in the separatory funnel (about 200 to 1000 ml depending on the fat and oil content of the wastewater), and after dropping the methyl orange solution, the color of the solution changes to red. Hydrochloric acid was added dropwise until repeated, and 40 ml of normal hexane was added and shaken vigorously for 2 minutes twice. After separating only the normal hexane layer, filtration and dehydration were carried out. It is obtained by volatilization. The amount of iron salt supplied to the first treatment tank 10 is preferably calculated in advance as follows. For example, a normal hexane extract is obtained from a certain amount of oil-containing wastewater by the above method, and the weight of the obtained normal hexane extract is set as a load of the normal hexane extract in a certain amount. Next, the weight of iron in a certain amount is measured from a fixed amount of the same fat and oil-containing wastewater by a phenanthroline spectrophotometry method, an ICP emission spectrophotometry method or the like. Based on the measured weight of iron in the fat-containing wastewater and the load amount of the normal hexane extract material, the total amount of iron per fat-containing wastewater unit volume is the same as that of the normal hexane extract material per fat-containing wastewater unit volume. The amount of iron salt supplied to the first treatment tank 10 is calculated so that the weight ratio of iron to the load amount is in the range of 1.0 × 10 ^{−3 to} 30 × 10 ⁻³ .

  There is no restriction | limiting in particular as iron salt to add, Ferrous chloride, ferric chloride, poly ferric sulfate etc. can be used. These iron salts may be powder, slurry, solution, or the like.

  It is preferable that the fat concentration in the fat-containing wastewater to be treated is in the range of 150 to 1000 mg / L in terms of the normal hexane extract substance concentration. If the normal hexane extractable substance concentration in the oil-containing wastewater is 1000 mg / L, the wastewater discharged from the first treatment tank 10 is biologically treated by adding iron salt to the first treatment tank 10. Can be reduced to, for example, less than 150 mg / L. By reducing the normal hexane extractable substance concentration in the wastewater in this way, in the second treatment tank 12 and subsequent stages in the latter stage, the inhibition of biological treatment by fats and oils is suppressed, and the fats and oils, BOD components, etc. are biologically treated efficiently. For example, the normal hexane extract substance concentration can be reduced to 30 mg / L or less, and the BOD component concentration can be reduced to 50 mg / L or less. Moreover, in the processing apparatus of the fat-and-oil containing waste water of this embodiment, since the pressurization flotation process for removing fats and oils is unnecessary beforehand, an installation can be simplified and processing cost can also be reduced. Furthermore, due to the action of nutrient salts of iron salts, oxidation catalysts, etc., expensive oil-degrading microorganisms and oil-degrading enzymes are not necessarily required for the decomposition of fats and oils, so that the processing cost can be further reduced.

  The growth of microorganisms in the first treatment tank 10 is easily affected by the pH in the tank. In particular, from the point that the growth of microorganisms is further improved in the presence of iron salt, the operation of neutralizing the final treated water and discharging it out of the system can be performed efficiently, and the like. It is preferable to adjust the pH within the range from weakly acidic to weakly alkaline, for example, preferably within the range of pH 6 to 9, and more preferably within the range of pH 6.5 to 7.5. In addition, the pH in the second treatment tank 12 also improves the growth of microorganisms, the point that the final treatment water can be efficiently neutralized and discharged out of the system, etc., for example, It is preferable to adjust to the range of pH 6-8, and it is preferable to adjust to the range of pH 6.5-7.5.

  The biological treatment in the first treatment tank 10 is preferably performed under aerobic conditions. An aeration apparatus is installed in the first treatment tank 10 so that the dissolved oxygen concentration in the first treatment tank 10 is 0.5 mg / L. It is preferable to supply oxygen so that it becomes the above, and it is more preferable to supply oxygen so that it may become 1.0 mg / L or more. The biological treatment after the second biological treatment tank 12 is also preferably performed under aerobic conditions, and an aeration apparatus is also installed in the treatment tank after the second treatment tank 12 so that the treatment after the second treatment tank 12 is performed. It is preferable to supply oxygen so that the dissolved oxygen concentration in the tank is 0.5 mg / L or more, and it is more preferable to supply oxygen so as to be 1.0 mg / L or more.

  Since the time required for the decomposition of fats and oils differs depending on the properties of the fat-containing wastewater, etc., the wastewater discharged from the first treatment tank 10 from the viewpoint of suppressing the inhibition of biological treatment by fats and oils in the second treatment tank 12 and later. It is preferable to set the residence time of the fat and oil-containing wastewater in the first treatment tank 10 so that the concentration of the normal hexane extractable substance in the first treatment tank 10 is 150 mg / L or less, for example, in the range of 6 hours to 48 hours. . When the normal hexane extractable substance concentration in the waste water discharged from the first treatment tank 10 is not reduced to, for example, 150 mg / L or less, it is preferable to add an iron salt to the second treatment tank 12 and the like at the subsequent stage. . In addition, from the viewpoint of appropriately biologically treating the BOD component in the wastewater, the wastewater in the treatment tanks after the second treatment tank 12 is adjusted so that the BOD component concentration in the finally obtained treated water is 50 mg / L or less. It is preferable to set the residence time, and for example, it is preferable to set the residence time in the range of 6 hours to 24 hours.

  From the viewpoint of maintaining the amount of microorganisms in the first treatment tank 10, it is preferable to put a commercially available microorganism preparation into the first treatment tank 10. In addition, in order to maintain the amount of microorganisms in the first treatment tank 10, a microorganism carrier such as a sponge carrier, a gel carrier, a hollow cylindrical simple substance, or a fibrous carrier is introduced into the first treatment tank 10 to introduce microorganisms. It is also preferable to use a method of immobilization. Similarly, in the treatment tanks after the second treatment tank 12, it is preferable to put a commercially available microbial preparation or microbial carrier.

  FIG. 2 is a schematic diagram illustrating another example of the configuration of the oil-and-fat-containing wastewater treatment apparatus according to the present embodiment. In the fat and oil-containing wastewater treatment apparatus 2 shown in FIG. 2, the same components as those in the fat and oil-containing wastewater treatment apparatus 1 shown in FIG.

  The fat and oil-containing wastewater treatment apparatus 2 shown in FIG. 2 includes a treated water return pipe 26. One end of the treated water return pipe 26 is connected to the treated water discharge pipe 20, and the other end is connected to the drainage introduction pipe 16. Although not shown in the figure, one end of the treated water return pipe 26 may be connected to the drainage discharge pipe 18 and the other end may be connected to the drainage introduction pipe 16. In the present embodiment, the two-treatment tank configuration of the first treatment tank 10 and the second treatment tank 12 is taken as an example. For example, in the case of a three-tank construction, one end of the treated water return pipe 26 is discharged from the first treatment tank 10. Is connected to at least one of a pipe through which the waste water flows, a pipe through which the waste water discharged from the second treatment tank 12 flows, and a pipe through which the waste water discharged from the third treatment tank flows, and the other end is connected to the drain introduction pipe. 16 is connected. Further, in the present embodiment, the other end of the treated water return pipe 26 is connected to the drainage introduction pipe 16, but the configuration is not necessarily limited as long as the wastewater discharged from the second treated water can be returned to the first treated water. For example, the other end of the treated water return pipe 26 may be directly connected to the first treatment tank 10.

  Next, operation | movement of the fat and oil containing waste water treatment equipment 2 which concerns on this embodiment is demonstrated.

  In the first treatment tank 10, the oil-containing wastewater supplied from the drainage introduction pipe 16 and the oil-decomposing microorganism sludge are brought into contact with each other in the presence of the iron salt supplied from the iron salt supply pipe 24. Oils and fats in the wastewater are decomposed. The iron salt supplied to the first treatment tank 10 is considered to have actions such as nutrient salts that promote the growth of oil-degrading microorganisms in the tank, oxidation catalysts that promote the decomposition of fats and oils, and the like in the first treatment tank 10. Compared with the case where no iron salt is supplied, the oil and fat in the waste water can be efficiently decomposed. Next, the wastewater treated in the first treatment tank 10 is supplied from the drainage discharge pipe 18 to the second treatment tank 12. In the 2nd processing tank 12, the waste_water | drain with which fats and oils were reduced, and microbial sludge contact, and mainly the BOD component etc. in waste_water | drain are decomposed | disassembled. In this embodiment, since the fats and oils in waste water are decomposed | disassembled previously in the 1st processing tank 10, in the 2nd processing tank 12, it is suppressed that the activity of the microorganisms sludge by fats and oils is inhibited, and BOD component Etc. can be efficiently decomposed (biological treatment). In addition, in the waste_water | drain supplied to the 2nd processing tank 12, since the case where the iron salt supplied to the 1st processing tank 10 remains is considered, it remains in the waste_water | drain also in the 2nd processing tank 12. FIG. It is inferred that fats and oils are also decomposed.

  A part of the waste water treated by the second treatment tank 12 is discharged as final treated water from the treated water discharge pipe 20 to the outside of the system, and the remaining part is discharged from the treated water return pipe 26 through the drain introduction pipe 16 to the first. Returned to the treatment tank 10. Thus, a part of the wastewater treated in the second treatment tank 12 (if one end of the treated water return pipe 26 is connected to the drainage discharge pipe 18, the wastewater treated in the first treatment tank 10 is By returning a part) to the 1st processing tank 10, since fat and oil density | concentration can be reduced, the fats and oils in fat-and-oil containing wastewater can be decomposed | disassembled more efficiently.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
In Example 1, a first treatment tank having an effective volume of 2 L was prepared, and the effect of oil and fat decomposition in the fat and oil-containing wastewater when the amount of iron salt supplied to the first treatment tank was changed was tested. As the fat and oil-containing wastewater to be treated in Example 1, one obtained by adding commercially available mayonnaise to industrial water so that the concentration of normal hexane extract (n-Hex) was 800 mg / L was used. The industrial water contained 0.01 mg / L of iron, and iron / n-Hex was 0.13 × 10 ⁻⁴ . In addition, an aeration apparatus was installed in the first treatment tank so that the dissolved oxygen in the first treatment tank was about 1.0 mg / L. The temperature of the first treatment tank was 20 ° C., the pH was 7.0 to 7.5, and the residence time was 12 hours. Iron (II) sulfate heptahydrate was used as the iron salt supplied to the first treatment tank.

FIG. 3 shows the results of the removal rate of normal hexane extractant in the weight ratio of iron per unit volume of fat-containing wastewater (iron / n-Hex ratio) to the load of normal hexane extractant per unit volume of fat-containing wastewater. FIG. As shown in FIG. 3, when the adjusted water to be treated was treated in the first treatment tank without adding an iron salt, the removal rate of the normal hexane extract was 0.65 kg / m ³ / day. On the other hand, when the iron salt is added and processed so that the iron / n-Hex ratio is 1.0 × 10 ⁻³ , the removal rate of the normal hexane extract is increased to 0.95 kg / m ³ / day, The effect of iron salt addition was recognized. Moreover, when the addition amount of iron salt is increased and the iron / n-Hex ratio is 2.0 × 10 ⁻³ , the removal rate of the normal hexane extractant increases to 1.4 kg / m ³ / day, Compared to the case without addition, the decomposition rate of the normal hexane extract increased more than twice. In addition, in the test by Example 1, the addition amount of iron salt was further increased, and the iron / n-Hex ratio was 4.0 × 10 ⁻³ , but the iron / n-Hex ratio was 2.0 × 10 ⁻³ . The removal rate of the normal hexane extract was almost the same as the case. Therefore, in order to promote the decomposition of fats and oils in the waste water, it is preferable to add an iron salt so that the iron / n-Hex ratio is 1.0 × 10 ⁻³ or more, and 2.0 × 10 ⁻³ or more. It was found that it is more preferable to add an iron salt so that

<Example 2>
Wastewater from a food factory and iron salt were put into a sealed screw mouth glass bottle, the gas phase was replaced with oxygen, and the fat and oil in the wastewater was decomposed. The amount of iron salt added to the sealed screw cap glass bottle was 25.3 × 10 ⁻³ in terms of iron / n-Hex ratio. The normal hexane density | concentration in the waste_water | drain before a process was 400 mg / L, and the iron / n-Hex ratio in the waste_water | drain before adding an iron salt was 0.7 * 10 < ^-3 >. The processing time of Example 2 was 18 hours. Table 1 summarizes the properties of waste water, treatment time, and normal hexane extractable substance concentration after treatment.

<Comparative example>
Wastewater from a food factory was put into a sealed screw mouth glass bottle, the gas phase was replaced with oxygen, and the oil and fat decomposition treatment in the wastewater was performed. The normal hexane density | concentration in the waste_water | drain before a process was 400 mg / L, and the iron / n-Hex ratio was 0.7 * 10 < ^-3 >. Moreover, the processing time of the comparative example was 18 hours. Table 1 summarizes the properties of waste water, treatment time, and normal hexane extractable substance concentration after treatment.

  As is apparent from Table 1, the decomposition rate of the normal hexane extract of Example 2 to which the iron salt was added was 1.4 compared with the decomposition rate of the normal hexane extract of the comparative example to which no iron salt was added. Doubled.

  DESCRIPTION OF SYMBOLS 1, 2 Oil-containing wastewater treatment apparatus, 10 1st treatment tank, 12 2nd treatment tank, 14 Iron salt supply apparatus, 16 Drainage introduction pipe, 18 Drainage discharge pipe, 20 Treated water discharge pipe, 22 Storage tank, 24 Iron salt Supply pipe, 26 treated water return pipe.

Claims (2)

A treatment tank unit having at least a first treatment tank and a second treatment tank for aerobic biological treatment of fat and oil-containing wastewater derived from a food factory ;
Iron salt supply means for supplying iron salt to the first treatment tank,
The heavy metal salt supplied to the first treatment tank is only the iron salt supplied by the iron salt supply means, and the iron salt supply means has the same total amount of iron per unit volume of oil-containing wastewater. Oil and fat content, wherein iron salt is supplied to the first treatment tank so that the weight ratio of iron to the load of normal hexane extract per unit volume of wastewater is 1.0 × 10 ⁻³ or more. Wastewater biological treatment equipment. It is a biological treatment method for fat and oil-containing wastewater for aerobic biological treatment of fat and oil-containing wastewater derived from a food factory by a treatment tank unit having at least a first treatment tank and a second treatment tank,
Said 1st process so that the total amount of iron per fat-containing drainage unit volume may become ^1.0x10-3 or more by weight ratio of iron with respect to the load of the normal hexane extract material per fat-containing wastewater unit volume. Supply iron salt to the tank ,
The biological treatment method of fat and oil-containing wastewater, wherein the heavy metal salt supplied to the first treatment tank is only the iron salt .

Images