JP2002018478A - Method for treating yeast waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating more efficiently and in more higher grade yeast waste liquid by further improving and developing a double phase type methane fermentation treatment which is traditionally known. SOLUTION: In a method wherein yeast waste liquid is treated by a double phase type methane fermentation treatment containing liquefaction treatment and gasification treatment, oxidization treatment is carried out before the double phase type methane fermentation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for treating a waste liquid containing yeast cells (hereinafter referred to as "yeast waste liquid").

[0002]

2. Description of the Related Art Yeast cells are used for brewing beer, sake, shochu, whiskey, wine, and industrial ethanol.
Alternatively, it is obtained as a by-product when producing a recombinant protein using yeast as a host. Some yeast cells are used as raw materials for pharmaceuticals, foods, feeds and the like, but the amount is limited, and excess yeast cells are discarded. Disposal methods include dumping into the ocean and incineration. However, due to problems such as environmental pollution and soaring treatment costs, search for more economical and efficient treatment methods has been awaited.

As a method for treating yeast waste liquid, a method using a two-phase methane fermentation method (JP-A-7-241593) and a method of liquefaction using a fixed-bed reactor (JP-A-9-150187). Etc. have been published.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for treating a yeast waste liquid more efficiently and highly by further improving and developing a conventionally known two-phase methane fermentation method. It is in.

[0005]

Means for Solving the Problems As a result of further studies in consideration of the above circumstances, the present inventors have found that by introducing an oxidation treatment as a pretreatment for two-phase methane fermentation, the organic substance volume load can be further reduced. It became possible to set higher. Further, if necessary, the function was further improved by introducing a deamination treatment as a pretreatment. Furthermore, by introducing a phosphorus removal treatment and / or a biological denitrification / nitrification treatment as a post-treatment of the two-phase methane fermentation, advanced treatment became possible. Finally, the present inventors have found that the yeast waste liquid can be treated more efficiently and more highly than the conventional method, and completed the present invention.

That is, the present invention provides 1) a method for treating a yeast waste liquid by a two-phase methane fermentation method including liquefaction treatment and gasification treatment, wherein the oxidation treatment is performed before the two-phase methane fermentation treatment. 2) In the above treatment method, the deamination treatment is further performed before the two-phase methane fermentation treatment. 3) In the treatment method, the phosphorus removal treatment and / or Or a biological denitrification / nitrification treatment method. The details will be described below.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The definitions of the abbreviations used in this specification are as follows. TVS (Total Volatile Soli)
d): Total volatile substance SS (Suspended Solid): Suspended substance VSS (Volatile Suspended So)
lid): Volatile floating substance MLVSS (Mixed Liquid Volati)
le Suspended Solid: Volatile suspended solids in the mixture TOC (Total Organic Carbo)
n): Soluble total organic carbon IC (Inorganic Carbon) VFA (Volatile Fatty Acid):
Volatile organic acids TS (Total Solid)

A. Yeast waste liquid The kind of yeast cells that can be treated in the present invention is not particularly limited, and can be appropriately used for recombinants to be developed in the future, in addition to those already described in known documents. Specific examples include the genera Saccharomyces, Pichia, Schizosaccharomyces, Kluyveromyces, Candida and Hansenula. In particular, in the present invention, G
418-sensitive strain Saccharomyces cerevisiae
e) AH22 strain (a, his4, leu2, can)
1), Pichia pasto (Pichia pasto)
ris) A recombinant (transformant) using GTS115 strain (his4) or the like as a host is preferably used.

[0009] These yeast cells are in the state of viable cells, or after being sterilized by a known method or a method analogous thereto, suspended in water or an appropriate aqueous solution, and treated by the following method. .

B. Oxidation Treatment Oxidation treatment is performed to increase the digestibility (particularly VSS digestibility) of yeast contained as a solid content in the waste liquid by oxidation in methane fermentation. Oxidation modes include ozone oxidation and Fenton oxidation.

Ozone oxidation utilizes the oxidizing power of ozone. As the processing conditions, the amount of ozone added is 1 to 100 mg per liter of the processing solution, and the processing time is 20 to 180.
Min, the Fe ²⁺ concentration is 0.01 to 1 g / L, and the temperature is 15 to
About 100 ° C. is exemplified.

Fenton oxidation utilizes the strong oxidizing power of hydroxyl radicals generated by reacting Fe ²⁺ with hydrogen peroxide under acidic pH conditions. The treatment conditions were as follows: Fe ²⁺ concentration: 0.025 to 0.5 g / L; temperature: 50 to 105 ° C .; treatment time: 30 minutes to 2 hours; hydrogen peroxide concentration: 1 to 50 g / L; To 7.5, preferably about 3 to 4.5.

C. Two-phase methane fermentation (liquefaction treatment / gasification treatment) The two-phase methane fermentation method includes liquefaction treatment and gasification treatment, and a known method can be used. JP-A-7
See JP-A-241593 and JP-A-9-150187. Preferably, the liquefaction treatment is at a high temperature (50-60 ° C).
Degree), and gasification is performed at a medium temperature (about 30 to 40 ° C.). The gasification treatment is preferably performed by diluting the liquefied treatment water to about 2 to 10 times. It is more preferable to use a fixed bed reactor (UAFP) for both processes.

D. Other Waste Liquid Treatment Methods As a pretreatment for two-phase methane fermentation, examples of the method for treating yeast waste liquid include deamination treatment and the like in addition to the above oxidation treatment. These treatments are useful as pretreatments because they have the advantage that the organic substance volume load during the two-phase methane fermentation treatment can be set higher. Examples of the post-treatment of the two-phase methane fermentation include a phosphorus removal treatment and a biological denitrification / nitrification treatment.

A. Deamination treatment Deamination is performed to detoxify a thiourea-like substance when the waste liquid contains the substance. Specifically, the primary amine of the thiourea-like substance present in the waste liquid is deaminated by nitrous acid treatment. Processing conditions include p
H is about 2.5 to 4, preferably about 2.7 to 3. More preferably, the pH conditions are kept constant. Also,
The NO ₂ ^- concentration was 0.5 to 1 mole of the thiourea-like substance.
５5 mol, the temperature is 15４０40 ° C., and the treatment time is 5５〜60 minutes, preferably about 20〜60 minutes.

B. Phosphorus removal treatment This treatment involves phosphorus content in waste liquid, especially phosphate ions (P
O ₄ ^3- ) is removed. Specifically, by adding Mg ²⁺ , PO ₄ ^3- in the waste liquid is converted into NH ₄ MgPO ₄ (MA
P) is removed by precipitation. As the processing conditions, pH is from 8.3 to 9.2, Mg ²⁺ concentration PO ₄ ^3- 1
The temperature is 15 to 30 ° C., and the treatment time is about 10 minutes to 2 hours. Prior to this treatment, it is preferable to perform aeration for IC removal or decarboxylation.

C. Denitrified this process NO ₃ in the effluent ^- it is to remove ^- and NO _2. Specifically, it is performed by a biological denitrification treatment. The use of water obtained by diluting gasification-treated water by about 2 to 10 times is exemplified. pH is 6-9, preferably 7.4-8.2.
And the processing temperature is about 30 to 40 ° C.

D. Nitrification treatment This treatment nitrogen content in the effluent, in particular removing the NH ₄ ^+, NO ₃ ^-
Is generated. Specifically, it is performed by a biological nitrification treatment (mainly by the action of nitrifying bacteria). The use of water obtained by diluting gasification-treated water by about 2 to 10 times is exemplified. The pH is, for example, about 6 to 9, preferably about 7.4 to 8.2, and the treatment temperature is about 30 to 40 ° C.

[0019]

EXAMPLES The present invention will be described in more detail with reference to Examples and Experimental Examples, but the present invention is not limited thereto.

Reference Example Pichia pastoris (Pichia pastori)
s) The plasmid pMM042 for human serum albumin (HSA) expression was introduced into the GTS115 strain, and the transformant UH
G42-3 strain was obtained. See JP-A-4-299984.

The transformant is cultured under aeration and agitation, and after completion of the culture, 1 m ³ of a culture solution (100 k dry weight as cells)
g) was heat-treated at 68 ° C. for 30 minutes, diluted twice with distilled water, and 10 L of acetic acid was added. 5 m2 containing 50 mM sodium chloride in 2 m ³ of the pass fraction (including yeast cells) when recovering HSA using a stream line column
The solutions obtained by washing the column with 1.5 mM ³ of 0 mM acetate buffer (pH 4.5) were combined and used as yeast waste liquid in the following Examples and Experimental Examples. HSA using stream line
See JP-A-8-116985 for the purification of.

The composition of the obtained yeast waste liquid is shown in Table 1.

[0023]

[Table 1]

Example 1 The pH of a yeast waste solution was adjusted to 3, and sodium nitrite was added so that the NO ₂ ^- concentration was 1: 1.5 in molar ratio with respect to the thiourea-like substance in the waste solution. Allowed to react for minutes. After this deamination treatment, the fixed bed reactor (UAF)
Liquefaction treatment and gasification treatment (methane production reaction) were performed using P).

Liquefaction treatment: As a high-temperature digestive seed (anaerobic planting sludge), draw-and-fi using sewage mixed sludge under the conditions of an organic substance volume load of 3 g / L / day and 54 ° C.
The one that had been acclimated by the ll method was used.

A 0.78 L fixed bed reactor (UA)
FP), acclimated high-temperature digested seeds with MLVSS for 10
g / L. The carrier filled in the fixed-bed reactor was prepared by mixing rear pores (obtained by burning clay and pulverized) and pulverized high-density polyethylene at a ratio of 45:55, and firing the mixture at 100 to 230 ° C. to form a honeycomb structure. . The carrier has both a hydrophilic property (rear pore) and a hydrophobic property (high-density polyethylene), is very porous, and has a pore distribution of 20% of pores having a diameter of 1 to 2 mm and a pore distribution of 0.2%. 60% of 1-0.35mm pores,
The pores of 0.1 μm to 0.1 mm are 20%.

The liquid in the tank is 10.5 cm using a circulation pump.
/ Min circulation. The yeast waste liquid was continuously supplied by a supply pump. 0.8 L of the high-temperature digestive seed was added, and the solution in the tank was circulated overnight with a roller pump. The treatment temperature was 54 ° C., the organic substance volume load was 1 g / L / day for 8 days, and then 1.5 g / L
Liquefaction treatment was performed for 17 days at L / day.

Gasification treatment: Medium-temperature digested seeds (anaerobic planting sludge) are drawn-and-f using sewage mixed sludge under the conditions of an organic substance volume load of 1 g / L / day and 37 ° C.
The one acclimated by the ill system was used.

The same reactor as used in the liquefaction treatment was used. The temperature in the tank was maintained at about 37 ° C. 0.8 L of medium-temperature digestive seeds were added to this reactor, and during the acclimation period, glucose synthesis wastewater was supplied at 200 mL / day (0.5 g / L / day as an organic substance volume load). After that, the liquefied water was diluted 5 times, and the volume of the organic substance was reduced to 1 g / L.
/ Day (22 days) → 2g / L / day (18 days) → 4g /
L / day (18 days) → 6g / L / day (35 days) → 8g
/ L / day (15 days).

As a result, in the liquefaction treatment, a VSS digestibility of 70 to 80% was obtained at an organic substance volume load of 1.5 g / L / day. In addition, the gasification treatment of the treated water showed a good treatment result with a TOC removal rate of 70% even at a TOC volume load of 4 g / L / day.

Example 2 Initial pH 3 and no addition of Fe ²⁺ to the yeast waste liquid (Fe ²⁺ is present in the waste liquid at a concentration of 0.05 to 0.1 g / L; the same applies hereinafter). Hydrogen oxide concentration 5 g / L, 10
The Fenton oxidation treatment was performed at 5 ° C. for 1 hour.
Thereafter, a deamination treatment and a methane fermentation method were carried out according to Example 1. The organic substance volume load during the methane fermentation treatment was set at 18 days at 1.5 g / L / day → 20 days at 2 g / L / day → 40 days at 3 g / L / day. As a result, even at an organic substance volume load of 2 g / L / day, the VSS digestibility in the liquefaction treatment was 57%, and the VSS digestibility for waste yeast was 74%.

Example 3 The procedure of Example 2 was repeated except that the Fenton oxidation treatment was performed for 2 hours as the treatment time, and the liquefaction treatment was performed at an organic substance volume load of 5 g / L / day.

Example 4 According to the method of Example 2, the obtained gasified water was aerated for 6 hours to remove IC. The pH of the gasified water increased from 8.3 to 9.1 due to the aeration. Then 10600
× g, centrifugation was performed for 10 minutes, and 2
A 0% magnesium chloride solution was added at a molar ratio of Mg ²⁺ : PO ₄ ^3- of 1.5: 1, and stirred at room temperature for 1: 1.
The MAP method was performed by reacting for hours. After the reaction was completed, NH ₄ MgPO ₄ produced by centrifugation was separated.

Example 5 According to the method of Example 2, a denitrification tank and a nitrification tank as shown below were connected in series using the obtained 4-fold diluted solution of the gasification-treated water (diluted 20-fold in total). And subjected to biological denitrification / nitrification treatment.

Biological denitrification treatment: Denitrification tank is about 450 mL
Acrylic tower reactor (60 mm inner diameter)
X height 500 mm). The temperature was maintained at about 37 ° C. by passing constant temperature water through the water jacket. The liquid in the tank is a circulation pump (PERISTAPUMP SJ121
Circulation was performed at a circulation flow rate of 6 mL / min according to 1). The feed was stored in a refrigerator and continuously fed by a feed pump (same as above). The generated gas was collected in a gas holder through a vinyl tube, and the generated amount was measured.

Biological nitrification treatment: The nitrification tank was a 2.5 L reaction tank having a 1.6 L filling section, and a commercially available curler was cut in half as a filler (20 mm × 20 mm in diameter) and filled. The liquid in the tank was swirled by aeration at a flow rate of 2 L / min from a compressor through a ball filter.
The pH in the tank is 7.4 to 8.2 by a pH controller.
The temperature in the water tank was controlled to 30 ° C. by a heater. After aeration overnight, acclimation was performed by passing synthetic wastewater through, and a treatment test was performed.

Experimental Example 1 Various treatment conditions in Fenton oxidation were examined. Hydrogen peroxide concentration: Initial pH 4.5, Fe ²⁺ added 0.1 g /
Table 2 shows the relationship between the concentration of hydrogen peroxide and the VSS digestibility / chromaticity when the treatment was performed under the conditions of L, 105 ° C., and 2 hours.

[0038]

[Table 2]

Reaction temperature: Table 3 shows the relationship between the reaction temperature and the VSS digestibility when the treatment was performed under the conditions of initial pH 4.5, hydrogen peroxide concentration of 10 g / L, no addition of Fe ²⁺ , and 2 hours. .

[0040]

[Table 3]

PH: Table 4 shows the relationship between the initial pH and the VSS digestibility when the treatment was performed under the conditions of 10 g / L of hydrogen peroxide, no addition of Fe ²⁺ , and 105 ° C. for 2 hours.

[0042]

[Table 4]

Reaction time: initial pH 3, hydrogen peroxide 5 g /
Table 5 shows the relationship between the reaction time and the VSS digestibility when the treatment was performed under the conditions of L, Fe ²⁺ -free and 105 ° C.

[0044]

[Table 5]

Experimental Example 2 Various treatment conditions in deamination were examined. pH: p
30 ° C. for 30 minutes without controlling H, thiourea-like substance and N
Table 6 shows the relationship with the decomposition rate of the substance when the treatment was performed under the condition of a molar ratio of O ₂ ^- of 1: 2.

[0046]

[Table 6]

PH control: The case where pH was controlled and the case where pH was not controlled were compared. Table 7 shows the relationship between the thiourea-like substance and the decomposition ratio of the thiourea-like substance when the treatment was performed at room temperature (16 ° C.) for 30 minutes at a molar ratio of thiourea-like substance to NO ₂ ⁻ of 1: 2.

[0048]

[Table 7]

The NO ₂ ^- amount: pH 3 to controls, room temperature (1
Table 8 shows the relationship with the decomposition rate of the thiourea-like substance when the treatment was performed under the conditions of 8 ° C.) for 30 minutes.

[0050]

[Table 8]

Experimental Example 3 The relationship between the molar ratio of Mg ²⁺ and PO ₄ ^{3- in} the phosphorus removal treatment (MAP method) and the phosphorus removal effect was examined. Room temperature, pH9.
The treatment was performed under the conditions of 1, 1 hour. Table 9 shows the results.

[0052]

[Table 9]

The values in parentheses in the table indicate the PO ₄ ³⁻ removal ratio%.

Experimental Example 4 Gasification-treated water was diluted 4 times (total 20 times dilution)
Using the resulting material, a biological denitrification / nitrification treatment was performed according to Example 5. Table 10 shows the results on the 10th day after the start of the treatment.

[0055]

[Table 10]

Since NH ₄ ⁺ was removed and NO ₃ ^- was produced, the inhibition of nitrifying bacteria was eliminated by the deamination of the thiourea-like substance, indicating that the treatment was performed stably. .

The following methods were used to analyze each substance in the examples and experimental examples. TOC and IC measured the supernatant liquid after centrifugation by an infrared gas analysis method using a total organic carbon meter. The pH was measured using a pH meter. VSS,
The SS was obtained by evaporating the precipitate after centrifugation to dryness, burning at 600 ° C., measuring the weight of each, and calculating from the weight difference. TVS and TS were directly evaporated to dryness without centrifugation, and the weight was determined in the same manner as in the measurement of VSS and SS. _{^{NO 2 -, NO 3 -,}} PO 4 3- is treated with an anion separation column and analyzed by conductivity detection. NH ₄ ⁺
The measurement was performed by an ammonium ion electrode method or a colorimetric method using a Nessler reagent. The chromaticity was measured by the platinum cobalt method. In addition, 1 ° chromaticity standard product is platinum
g and 0.5 mg of cobalt. Fe
Was measured by atomic absorption spectrometry. Thiourea like substances, starch indicator liquid, I ₂ solution was decolorized reaction mixture as obtained by the blue coloration with iodine starch reaction with NaN ₃ solution was determined by measuring the absorbance at 620 nm.

[0058]

According to the method of the present invention, by introducing an oxidation treatment and a deamination treatment as a pretreatment of a two-phase methane fermentation, it is possible to set a higher organic substance volume load. Advanced treatment became possible by introducing phosphorus removal treatment and biological denitrification / nitrification treatment as post-treatment of two-phase methane fermentation. That is, compared with the case where the conventional two-phase methane fermentation is carried out alone, it has become possible to treat the yeast waste liquid more efficiently and highly.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C02F 3/34 101 C02F 3/34 101A F-term (Reference) 4D038 AA08 AB12 AB48 BB19 4D040 AA02 AA04 AA12 AA23 BB02 BB13 4D050 AA12 AB06 BB02 BB09 CA17 CA20

Claims (3)

[Claims] 1. A method for treating a yeast waste liquid by a two-phase methane fermentation method including a liquefaction treatment and a gasification treatment, wherein the oxidation treatment is performed before the two-phase methane fermentation treatment. 2. The treatment method according to claim 1, wherein a deamination treatment is further performed before the two-phase methane fermentation treatment. 3. The treatment method according to claim 1, wherein a phosphorus removal treatment and / or a biological denitrification treatment / nitrification treatment is performed after the two-phase methane fermentation treatment.