JPH1147777A - Treatment of drainage by microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control temperature and pH conditions appropriately in a drainage treatment process by controlling the temperature of a drainage treatment system within a specified range and decomposing a surfactant by microorganisms. SOLUTION: The temperature of a kind of activated sludge which is a mixed microorganism group used in a usual drainage treatment system is controlled at 24-34 deg.C, and a surfactant containing a polyoxyethylene alkylphenyl ether which is used as a household detergent or an industrial surfactant is decomposed by microorganisms. As a result, activated sludge of this kind can demonstrate a high capacity for decomposing surfactants at pH 7.0-8.0. In this way, the maximum surfactant decomposing capacity of microorganisms can be maintained, and troubles such as a foaming phenomenon and the outflow of sludge can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating wastewater using microorganisms, and more particularly, to a method for treating wastewater containing a surfactant capable of efficiently decomposing a surfactant contained in the wastewater.

[0002]

2. Description of the Related Art Wastewater treatment methods utilizing microorganisms, such as activated sludge treatment, are widely used as one of various wastewater treatment methods. In the treatment of wastewater using these microorganisms, if the wastewater contains detergents or wetting agents used for domestic or industrial purposes, the foaming phenomenon of the wastewater treatment system This may cause sludge destruction and runoff. In conventional wastewater treatment using microorganisms, the control of decomposition conditions and the like is not usually performed, and the treatment performance fluctuates due to changes in the temperature, wastewater composition, and the like that fluctuate with the season, and foaming due to surfactants and the like. Trouble was likely to occur. Conventional wastewater treatment facilities have required large-scale wastewater treatment equipment to cope with such fluctuations in treatment performance.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the method for treating surfactant-containing wastewater using the above-mentioned microorganisms, and is affected by fluctuations in temperature and wastewater composition. It is an object of the present invention to provide a method for treating surfactant-containing wastewater using microorganisms, which can efficiently decompose a surfactant in a stable state without any problem.

[0004]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies on a method for treating surfactant-containing wastewater using microorganisms. It has been found that the surfactant can be efficiently decomposed by controlling the amount within such a range, and that the decomposition of the surfactant by microorganisms can be promoted by adding an appropriate decomposition accelerator. Thus, the present invention has been completed.

That is, the present invention relates to a wastewater treatment method for treating wastewater containing a surfactant using microorganisms.
(1) A wastewater treatment method using microorganisms, wherein the surfactant is decomposed by microorganisms while controlling the temperature conditions of the wastewater treatment system within a range of 24 to 34 ° C .;
A method for treating wastewater by microorganisms, wherein the surfactant is decomposed by microorganisms while controlling the H condition in the range of 6.5 to 8.5, and (3) the temperature condition of the wastewater treatment system is 24 to 34.
C. and controlling the pH condition in the range of 6.5 to 8.5 to decompose the surfactant by the microorganism, and (4) a wastewater treatment system. This is a method for treating wastewater with microorganisms, which comprises decomposing a surfactant with a microorganism by adding a decomposition accelerator composed of a structural analog of the surfactant.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The microorganism used in the method of the present invention is activated sludge used in ordinary wastewater treatment. According to the results of studies by the present inventors, these activated sludges exhibit a high decomposing ability for surfactants in a temperature range of 24 to 34 ° C, preferably 27 to 30 ° C. Therefore, in the method (1), the temperature condition of the wastewater treatment system is controlled in a temperature range of 24 to 34 ° C, preferably 27 to 30 ° C. As a result, the ability of microorganisms to decompose the surfactant is kept to a maximum, troubles such as a foaming phenomenon and sludge outflow can be avoided, and moreover, a stable treatment of the surfactant becomes possible. When the temperature is lower than 24 ° C. or higher than 34 ° C., the surfactant has a reduced ability to decompose.

Further, according to the results of the study by the present inventors,
These activated sludges exhibit a high ability to decompose surfactants when the pH is in the range of 6.5 to 8.5, preferably 7.0 to 8.0. Therefore, in the invention of the above (2), the pH of the wastewater treatment system is controlled in the range of 6.5 to 8.5, preferably 7.0 to 8.0. This keeps the surfactant's ability to decompose the surfactant to the maximum, avoids problems such as foaming phenomena and outflow of sludge, and further enables stable treatment of the surfactant. When the pH is lower than 6.5 or higher than 8.5, the decomposition ability of the surfactant is rapidly reduced. In the conventional wastewater treatment using activated sludge, the operating conditions may be around room temperature or around pH neutral depending on the external environment. However, control of decomposition conditions and the like has not usually been considered. In the present invention, by controlling these conditions within the above range, throughout the season,
Stable treatment became possible without being affected by fluctuations in wastewater composition.

The decomposition rate of a surfactant by microorganisms such as activated sludge can be promoted by adding a decomposition accelerator composed of a low molecular compound having a structure similar to the surfactant. Surfactants used for ordinary household and industrial purposes are a mixture of various types of surfactant components depending on the application, and the wastewater contains a wide variety of surfactants . Among these, it is known that a polyoxyethylene alkyl phenyl ether (APE) -based surfactant is most difficult to decompose. In the case of ordinary wastewater treatment, 2-oxygen having a similar structure to this APE-based surfactant is used. Phenoxyethanol, 3-phenyl-1-
It is effective to add at least one compound selected from propionic acid, 2-phenylethanol, 3-phenyl-1-propanol, polyethylene glycol and the like as a decomposition accelerator.

The amount of the decomposition accelerator to be added may be appropriately determined according to the properties of the waste water.
A few mol% is sufficient for E. The mechanism of promoting the surfactant decomposition reaction by the addition of these decomposition promoters is still unknown, but probably, the addition of a structural analog of the surfactant induces the production of an enzyme that degrades the surfactant, Along with this, it is considered that the surfactant-decomposing ability is promoted.

Hereinafter, the method of the present invention will be described more specifically with reference to examples. (Example 1) In this example, activated sludge which is a mixed microorganism group was used as a microorganism. As the surfactant to be decomposed, polyethoxyethylene alkyl phenyl ether (APE, which is used as a household detergent or an industrial surfactant, has 9 carbon atoms in the alkyl group and an average number of moles of the added ethylene oxide: 10)) was used. Here, the cultivation of the microorganisms was performed aseptically using a medium autoclaved as shown in Table 1. In this example, TOC (total organic carbon content) was used as an index of APE decomposition.

A concentrated solution of a mixed microorganism group which has been separately cultured (acclimated in a medium containing APE) is added in advance, and the protein concentration of the mixed microorganism group is set to 300 (microgram / gram).
20 ml of a fresh medium (shown in Table 1) prepared to give
H was kept constant at 7.0 (adjusted using NaOH), and each temperature condition (17 ° C., 22 ° C., 24 ° C., 27 ° C., 3
(0 ° C., 34 ° C., and 37 ° C.). These cultures are collected over time and the TOC of the supernatant after centrifugation is
Was measured to determine the amount of reduction in TOC. After the start of the degradation test, the average reduction rate of TOC (mg-TOC / liter / hr) from 4 hours to 24 hours was determined as A of the mixed microorganism group.
The PE decomposition rate was used. Note that the TOC in this embodiment is
Is derived from APE contained in the medium used.

FIG. 1 shows the obtained measurement results. Assuming that the APE decomposition rate at 27 ° C. was 1, the APE decomposition rate under each temperature condition was compared and evaluated. When the decomposition temperature condition was 24 to 34 ° C., especially around 27 to 30 ° C., the decomposition of APE was the most. It can be seen that when the rate is high and the temperature is less than 24 ° C. or exceeds 37 ° C., the decomposition ability is reduced.

(Example 2) In this example, activated sludge which is a mixed microorganism group was used as a microorganism. Also,
As a surfactant to be decomposed, a poly (ethylene glycol phenyl ether) (APE; alkyl group having 9 carbon atoms, average mole number of added ethylene oxide: 10) used as a household detergent or an industrial surfactant is used.
Was used. Here, the cultivation of the microorganisms was performed aseptically using a medium autoclaved as shown in Table 1. Also,
In this embodiment, TO index is used as an index of APE decomposition.
C (total organic carbon content) was used.

The fresh medium shown in Table 1 was prepared by using NaOH to each of the pH conditions (5, 6, 6.5, 7, 7,.
5, 8, 9 and 10). A concentrated solution of the mixed microorganism group separately cultured was added to the fresh medium under each of these pH conditions, and the protein concentration of the mixed microorganism group was adjusted to 300 (microgram / milliliter). 200 ml of the mixture was placed in an Erlenmeyer flask (500 ml), the temperature was 27 ° C., and the shaking speed was 100 rpm.
And cultured. These cultures are separated over time,
The TOC of the supernatant after centrifugation was measured to determine the amount of reduction in TOC. Average degradation rate of TOC (mg-TOC / liter / h) from 4 hours to 24 hours after the start of the decomposition test
r) was taken as the APE degradation rate of the mixed microorganism group. In addition, TOC in this Example is the AP contained in the medium used.
It is derived from E.

FIG. 2 shows the obtained measurement results. pH7.
Assuming that the APE decomposition rate at 5 is 1,
The APE decomposition rate under the conditions was compared and evaluated, and when the decomposition pH condition was 6.5 to 8.5, particularly 7.0 to 8.0, the APE decomposition rate was the fastest, and was less than 6.5 or It was found that when the ratio exceeded 8.5, the decomposition ability rapidly decreased.

Example 3 In this example, activated sludge, which is a mixed microorganism group, was used as a microorganism, and polyethoxyethylene alkyl phenyl ether (APE; the number of carbon atoms in the alkyl group: 9) was used as a surfactant to be decomposed. Average number of moles of added ethylene oxide: 10)) was used. For the determination of APE, tetrathiocyanocobalt (I
I) It was measured by an acid absorbance method (CTAS method) and a TOC method. This CTAS method is a method of extracting a complex of APE and ammonium tetrathiocyanocobaltate (II) with benzene, and is a method based on JIS K3363 (Testing method for biodegradability of synthetic detergent), This is a suitable method as an index of the foaming property of the surfactant. Also, T
The operating performance was evaluated with the OC removal rate as the APE removal rate.

Using activated sludge as a mixed microorganism group, a continuous culture apparatus having an aeration tank (2 liters) and a sedimentation tank (1.6 liters) was used, and the pH was 7.5 with the composition shown in Table 1. Using a medium adjusted to pH (using NaOH)
A day continuous APE degradation test was performed. Based on the results of Examples 1 and 2, the treatment temperature was 25 ° C., the pH was 7.5, and the air flow rate was 0.1 vvm (200 ml / mi).
n).

FIG. 3 shows the results of the continuous decomposition test. The APE volume load at the start of the decomposition test was 0.002 kg / m ³ /
The volume load was gradually increased. By the 15th day from the start of the test, the aeration tank foaming phenomenon was often observed.
The volume load was successfully increased at a rate of 04 kg / m ³ / day, and a volume load of 0.125 kg / m ³ / day was achieved in 30 days. During this period, the CTAS concentration was almost below the detection limit, and the APE removal rate was stable at around 80%. Thereafter, the volume load was reduced to 0.15 kg / m ³ / day.
When the concentration was increased (day 40), the CTAS concentration was increased, and a vigorous foaming phenomenon was observed. Thereafter, the volume load was set to 0.125 kg / m ³ / day,
When the decomposition test was continued for 2 weeks, the CTAS concentration was almost below the detection limit, and the APE removal rate was stable at around 80%.

As a result, in the APE continuous decomposition test for 60 days, 0.125 kg / m ³ / day (medium APE
Under the volume loading condition of 50 mg / liter), A
80% of PE could be removed. This indicates that stable and continuous surfactant treatment can be performed by controlling the temperature and pH of the wastewater treatment system to be suitable for the decomposition of the surfactant. In this example, when the APE volume load was increased to 0.15 kg / m ³ / day, the treatment capacity was reduced. However, in an actual surfactant treatment apparatus, a drainage flow control tank was provided. By adjusting the APE volume load to 0.125 kg / m ³ / day, stable processing performance can be obtained.

[0020]

[Table 1]

Example 4 In this example, surface-active sludge, which is a mixed microorganism group, was used as a microorganism, and polyethoxyethylene alkyl phenyl ether (APE; the number of carbon atoms in the alkyl group: 9 Average number of moles of added ethylene oxide: 10) was used. In addition, as a reaction promoting substance, 2-phenoxyethanol which is a structural analog of a hydrophilic region containing a benzene ring of APE was used. Here, the culture of the microorganisms was performed aseptically using a medium autoclaved as shown in Table 2. Further, in this example, the total amount of organic carbon (TO
C) was used as the APE concentration, and
The amount of PE reduction was defined as the amount of reduction.

200 ml of a fresh medium (shown in Table 2) prepared by adding a concentrated solution of the mixed microorganism group which has been separately cultured in advance and adjusting the mixed microorganism group to a protein concentration of 300 (microgram / milliliter). Into an Erlenmeyer flask (500 ml),
The pH was adjusted to 7.5 with NaOH, and a surfactant-like substance 2-phenoxyethanol (0.52 mg / L) was added as a decomposition accelerator to the mixture at a temperature of 27 ° C.
Shaking culture was performed at a shaking speed of 100 rpm for 1 hour. After culturing for 1 hour, a surfactant was added to each culture solution in the amount shown in Table 2, and shaking culture was further performed for 24 hours.

This culture solution was separated over time, and the TOC of the supernatant after centrifugation was measured to determine the amount of reduction in TOC. The TOC in this example is derived from APE contained in the medium used. Also, for comparison,
The test was also performed on a culture solution (control) to which no surfactant-like substance was added. The results are shown in FIG. From FIG. 4, the lag time at the start of APE degradation was eliminated in the cells cultured with the addition of 2-phenoxyethanol compared to the control cultured without the addition. In addition, the residual TOC concentration at the end of the culture was lower in the case of culturing with the addition of 2-phenoxyethanol than in the control.

From these results, it was observed that by adding 2-phenoxyethanol, the time from the addition of APE to the start of decomposition was shortened, and the decomposition rate was improved. In addition, the residual TOC concentration at the end of the culture was lower than that of the control, and the decomposition efficiency was improved. These facts indicate that the effect of the added 2-phenoxyethanol promoted the ability of the mixed microorganism group to degrade APE.

Example 5 Instead of 0.52 mg / liter of 2-phenoxyethanol as a decomposition accelerator, A
The procedure of Example 4 was repeated, except that 0.6 mg / liter of 3-phenyl-1-propionic acid, a structural analog of the hydrophobic region containing a benzene ring of PE, was added.
A decomposition test of PE was performed. The results are shown in FIG. 5 together with the test results for a culture solution (control) to which no surfactant analog was added for comparison. As shown in FIG. 5, the lag time at the start of APE degradation was eliminated in the cells cultured with the addition of 3-phenyl-1-propionic acid as compared with the control cultured without the addition. In addition, the residual TOC concentration at the end of the culture was lower in the case of culturing with the addition of 3-phenyl-1-propionic acid than in the control.

From these results, it was observed that by adding 3-phenyl-1-propionic acid, the time from the addition of APE to the start of decomposition was shortened, and the decomposition rate was improved. In addition, the residual TOC concentration at the end of the culture was lower than that of the control, and the decomposition efficiency was improved. These indicate that the effect of the added 3-phenyl-1-propionic acid promoted the APE-degrading ability of the mixed microorganism group.

[0027]

[Table 2]

[0028]

According to the method of the present invention, in a method of treating a surfactant-containing wastewater by utilizing microorganisms, the treatment temperature and / or pH are controlled within an appropriate range.
The surfactant can be efficiently decomposed in a stable state. Decomposition can be promoted by adding a low molecular weight compound having a structure similar to that of the surfactant to be decomposed as a decomposition accelerator.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a decomposition temperature and a decomposition rate of a surfactant in Example 1.

FIG. 2 is a graph showing a relationship between a decomposition pH and a decomposition rate of a surfactant in Example 2.

FIG. 3 is a graph showing the change over time in the CTAS concentration and APE removal rate of treated water in an APE continuous decomposition system in Example 3.

FIG. 4 shows T during culture of the degradation system to which 2-phenoxyethanol was added and the degradation system to which no 2-phenoxyethanol was added in Example 4.
5 is a graph showing a change over time in an OC concentration.

FIG. 5 is a graph showing the change over time in the TOC concentration in the culture medium of the decomposition system to which 3-phenyl-1-propionic acid was added in Example 5 and the decomposition system to which 3-phenyl-1-propionic acid was not added.

Claims (4)

[Claims] 1. A wastewater treatment method for treating wastewater containing a surfactant using a microorganism, wherein the surfactant is decomposed by the microorganism by controlling the temperature condition of the wastewater treatment system within a range of 24 to 34 ° C. A wastewater treatment method using microorganisms. 2. A wastewater treatment method for treating wastewater containing a surfactant using microorganisms, the method comprising:
A wastewater treatment method using microorganisms, wherein the surfactant is decomposed by microorganisms while controlling the H condition in a range of 6.5 to 8.5. 3. A wastewater treatment method for treating wastewater containing a surfactant using microorganisms, wherein the temperature condition of the wastewater treatment system is controlled in the range of 24 to 34 ° C. and the pH condition is 6.5 to 6.5. A wastewater treatment method using microorganisms, wherein the surfactant is decomposed by microorganisms while controlling the amount to 8.5. 4. A wastewater treatment method for treating wastewater containing a surfactant by utilizing a microorganism, wherein a decomposition accelerator comprising a structural analog of the surfactant is added to the wastewater treatment system to remove the surfactant from the microorganism. A wastewater treatment method using microorganisms, wherein the wastewater is treated by microorganisms.