JP2951683B2 - Biological treatment of wastewater containing animal lipids - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for biologically treating animal lipid-containing wastewater, and more particularly to a method for reducing animal lipid in wastewater using microorganisms.

[Prior art] If wastewater containing a large amount of various organic substances is discharged directly into a river or the like, the pollution state of the river will be deteriorated. Therefore, wastewater containing a large amount of organic substances generally undergoes biological treatment represented by the activated sludge method.

However, wastewater generated from, for example, food processing factories or the food service industry contains extremely high concentrations of organic substances, and there are cases where conventional general polluted sludge methods cannot cope with them. Yes
58-8318, JP-B-57-12436, JP-B-56-52636, etc.).

As a result, organic substances such as proteins and saccharides can be relatively easily reduced even if they are present at a high concentration.

[Problems to be Solved by the Invention] However, biological treatment of wastewater containing a large amount of animal lipids has been extremely difficult.

That is, lipids are either mixed with water and emulsified in the wastewater, exist in colloidal form, or form oil balls.

However, bacteria appearing in activated sludge have weak enzyme activity to decompose and remove fats and oils, so fats and fats are more adsorbed,
Lipids are adsorbed around the activated sludge floc to form a film,
Oxygen is not transported into the floc, resulting in lack of oxygen.

For this reason, when the lipid content exists at a high concentration, for example, n
-When the hexane extract concentration is 200-500 mg / l, a fat / oil separation tank is provided, and when the hexane extract concentration is 500 mg / l or more, a pressurized flotation device is provided to remove lipids, followed by general biological treatment. It must be made.

As a result, the wastewater treatment process itself has become complicated, and various food industries and the like have had difficulty in treating wastewater containing a large amount of animal lipids.

Furthermore, in recent years, the enforcement order has been revised, and the treatment and disposal of sludge containing a large amount of separated fats has become a new major social problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to eliminate wastewater containing a large amount of animal lipids only by biological treatment without physical treatment such as an oil / fat separation tank or a pressure flotation device. An object of the present invention is to provide a biological treatment method for wastewater containing animal lipid which can be treated.

[Means for Solving the Problems] In order to achieve the above object, a biological treatment method for animal lipid-containing wastewater according to the present invention comprises a fat content of 200 mg / l or more which is detected as an n-hexane extractable substance. Animal lipid assimilating yeast belonging to the genus Trichosporone, which has a high glycerol ester hydrolase activity for decomposing animal lipids and a high enzyme activity for β-oxidation of decomposed fatty acids to wastewater containing animal lipids. And biologically treating the wastewater by assimilating animal lipids with the yeast.

Further, in the biological treatment method for animal lipid-containing wastewater according to the present invention, the animal lipid assimilating yeast belonging to the genus Trichosporon is a Trichosporone purulans.
sporon pullulans), Trichosporone Accelatum (T. acceleatum), Trichosporone fermentans (T. fermentans), Trichosporone merlioides (T. Merulioides), Trichosporone neofermentans (T. neofermentous), Trichosporone penicellatam (T. penicellatum), Trichosporone Cutanium (T.cutaneum), Trichosporone Capitatum (T.capitatum), Trichosporon Cericeum (T.ser)
iceum), Trichosporon brassicae (T. brassicae)
Preferably, the yeast is one or two or more yeasts selected from the group consisting of:

[Action] As described above, the biological treatment method of wastewater containing animal lipid according to the present invention involves adding one or more animal lipid-assimilating yeasts belonging to the genus Trichosporon. The yeast capable of assimilating lipid has a high activity of degrading animal lipids (glycerol ester hydrolase) and a series of enzymatic activities of β-oxidizing the produced fatty acids. Even if added, animal lipids are efficiently decomposed and removed, and there is no need to perform physical treatment in advance using an oil / fat separation tank or a pressure flotation device.

Here, the animal lipid assimilating yeast is obtained by separating and culturing yeast from wastewater containing a high concentration of lipids, and the bacterial species themselves are all known, but the inventors have found that animal lipid degradation is extremely high. It has been found that it has a removal ability.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

Example 1 Trichosporone pullulans (Trichospor) was used as an animal lipid to remove n-hexane extract from ham factory wastewater.
on pullulans).

Table 1 shows the analysis values of the wastewater, and FIG. 1 shows the removal characteristics.

The experimental conditions are as follows.

Sample sterilized drainage Bacterial cell addition 1 loop loop Culture method Shaking culture Sample volume 20ml / 50ml flask Temperature 20 ℃ pH unadjusted Culture days 5 days As is clear from Fig. 1, the n-hexane extract material
It is understood that good n-hexane extract material removal is performed in spite of 740 mg / l, and sufficient lipid reduction can be performed in practically 1 to 2 days.

FIG. 2 shows Trichospor
on pullulans), and shows the processing characteristics when n-hexane extract and SS load were changed by mass culture.

 The experimental conditions are as follows.

T.pullulans pH 5.0 Specimen Raw water Bacterial cell addition amount Incubation method with n-hexane extract material / SS loading Shaking culture Specimen filling method Fill and Draw method Specimen capacity 250ml / 500ml filled flask Temperature 20 ℃ Clear from Fig. 2 As described above, according to the method according to the present example, high-load operation is possible even with animal lipid-containing wastewater,
It is understood that the n-hexane extract / yeast load can be stably processed up to 1-4 kg n-hexane extract / kg yeast / day.

As described above, according to the treatment method of the present invention, by using a specific animal lipid assimilating yeast, wastewater containing animal lipid at a high concentration is directly subjected to biological treatment without physical treatment. Processing can be performed.

When these yeasts are used for wastewater treatment,
It is also preferable to use a flow sheet as shown in the figure to perform the pretreatment of the activated sludge method.

That is, in the figure, wastewater 10 is introduced into a solubilization digestion treatment step 12. In the solubilized digestion treatment step 12, the wastewater 10 is dissolved in the solubilized digestion tank at, for example, about 30 ° C. for about 24-48.
Hold in an anaerobic state for about an hour. As a result, the wastewater 10 undergoes temporary anaerobic decomposition to generate an organic acid. Also,
Decomposition of solid carbohydrates, proteins, lipids, etc. also occurs and is liquefied. Therefore, BOD increases and SS decreases.

Next, the treated water that has passed through the solubilized digestion treatment step 12 is introduced into the screen treatment step.

In this screen processing step 14, for example, the eye width is about 0.3 m
The treatment liquid is filtered by a fine screener of about m to separate undecomposed fiber components and other inorganic SS. Then, the screen residue is washed with treated water, dehydrated by a screw press, and the residue is removed. The residue may be removed by dehydration, but it is also possible to mix it with concentrated cells and use it as a fertilizer. Further, it is preferable to introduce the screw press separation liquid into the next yeast treatment step.

Next, the filtrate treated in the screen treatment step 14 is introduced into the yeast treatment step 16. In this yeast processing step 16,
The filtrate is introduced into a reaction vessel to which the yeast according to the present invention has been added, and fermentation is further maintained to be microaerobic by aeration.

At this time, if the pH of the filtrate is in the range of 2.5 to 7.5, fermentation is performed as it is. The BOD load is 15.0 kg / kg-SS · day or less, and there is no need to adjust the fermentation temperature because it is usually maintained by the heat of biological reaction. Then, at the beginning of operation, lipid-assimilating yeast is inoculated, but after that, it is returned. Next, the treatment solution after the yeast treatment step 16 is introduced into the centrifugation step 18.

In the centrifugation step 18, the treatment liquid is introduced into a centrifuge, and separated into concentrated cells and a supernatant.

At this time, since the particle size of the yeast floc is relatively large, about 3 mm to 5 mm, it can be effectively separated by a centrifugal separator, and can be sufficiently separated even by gravity sedimentation.

The isolated concentrated cells 20 have a water content of about 80 to 90%.
It shows a degree of glue.

The concentrated sludge obtained in the centrifugation step 18 is used as it is as a liquid fertilizer. Concentrated cells 20 have a protein content of 60
% (40-70%), and the vitamin content is 0.04% (0.03-
0.05%), it has almost the same value as a commercially available yeast extract, and can be used as a fertilizer or feed for mushroom cultivation.

Next, the separated liquid obtained in the centrifugation step 18 is introduced into the activated sludge treatment step 22.

In this activated sludge treatment step 22, the separated liquid is subjected to aerobic biological treatment in an activated sludge treatment tank. Here, aeration is performed intermittently, and the inside of the activated sludge treatment tank repeats anaerobic and aerobic, so that the denitrification treatment is also performed at the same time.

Further, the activated sludge treatment tank may be a contact aeration treatment tank in which a contact filter medium such as a corrugated sheet is filled and a circulating flow is generated in the tank by aeration. In the anaerobic step, the aeration may be stopped, stirring may be performed with another stirring device, or the amount of aerated air may be reduced.

Finally, the treated liquid after the activated sludge treatment is settled and then introduced into the sterilization step 24.

In this sterilization step 24, the treatment liquid is introduced into a chlorine disinfection tank and disinfected by the injected chlorine.

In addition, so that the residual chlorine of the processing solution is 1 mg / l or more,
Usually, it is preferable to inject about 15 mg-Cl / l of chlorine. Then, a part of the sterilized liquid 26 after the sterilization is returned to the yeast processing step 16. Since yeast is more resistant to chlorine and the like than bacteria, the above-described return suppresses the growth of bacteria during fermentation.

When the treatment with the lipid-assimilating yeast is used in place of the grease trap in this embodiment, the yeast itself may be immobilized on a filter medium or a structure with a polymer gel.

Further, it is also preferable that the spherical gel is formed by the entrapping and immobilizing method, and the resulting gel is packed in a container and used as a replaceable cartridge instead of the grease strap.

In addition, since the specific facilities designated by the water pollution method are often small-scale factories, it is also preferable to use unit products. In that case, it is possible to set the yeast which removes other substrates (for example, carbohydrates and proteins) together with the yeast which removes the n-hexane extract material on a filter medium or the like together in a yeast tank.

[Effects of the Invention] As described above, according to the biological treatment method for animal lipid-containing wastewater according to the present invention, the glycerol ester hydrolase activity for decomposing animal lipids is high, and the decomposed fatty acid is converted to β. Since the animal lipid assimilating yeast belonging to the genus Trichosporon having a high oxidizing enzyme activity is added, biological treatment can be performed on wastewater containing animal lipid at a high concentration.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a state of reducing animal lipid content by a method according to a first embodiment of the present invention, FIG. 2 is a comparison diagram of a treatment method according to FIG. 1 and a treatment characteristic by an activated sludge method, FIG. FIG. 2 is an explanatory diagram of a drainage process to which the treatment method according to the present invention is applied.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Norihisa Minegishi 454-1 Kaminami Enokicho, Takasaki City, Gunma Prefecture Japan Micro Biochemical Co., Ltd. (56) References JP-A-61-153197 (JP, A) JP-A-54-14154 (JP, A) JP-A-60-14996 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 3/34

Claims (2)

(57) [Claims] 1. An animal lipid-containing wastewater containing at least 200 mg / l of a fat detected as an n-hexane extractable substance, a fatty acid having a high glycerol ester hydrolase activity for decomposing animal lipids and a decomposed fatty acid. adding an animal lipid-assimilating yeast belonging to the genus Trichosporon having a high β-oxidizing enzyme activity, and subjecting the wastewater to biological treatment by assimilating animal lipids with the yeast. A biological treatment method for wastewater containing animal lipids. 2. The method according to claim 1, wherein the animal lipid-assimilating yeast belonging to the genus Trichosporon is Trichosporone prunus, Trichosporone accelitanum, Tricosporone fermentans, Trichosporone merlioides, Trichosporone neophormentans, Trichosporone. A biological treatment method for animal lipid-containing wastewater, which is one or more yeasts selected from peniceratam, trichosporone cutanium, trichosporone capitatam, trichosporone selyceum, and trichosporone brassicae.