JP4375265B2 - Microbial acclimatization method and organic wastewater treatment method with acclimatized microorganisms - Google Patents

Description

  The present invention relates to a method for acclimatizing microorganisms in biological treatment of organic wastewater, and a method for treating organic wastewater with acclimatized microorganisms.

  Various treatment methods for domestic wastewater such as sewage and human waste, and wastewater containing organic matter discharged from manufacturing processes such as food processing factories and chemical industries have been proposed. Among them, the activated sludge method is mentioned as the most versatile method. In the activated sludge method, wastewater containing organic matter is supplied to a biological treatment tank where sludge, which is an aerobic microorganism, floats, and aerated with air, so that the organic matter in the wastewater is oxidatively decomposed by microorganisms that constitute the suspended sludge. It is a method to do.

  Many such microorganisms generally have a suitable growth temperature of 25 to 37 ° C. When the water temperature rises by 10 ° C, the activity of microorganisms increases about twice as high, so in the method of biologically treating organic matter contained in wastewater, the water temperature should be set higher from the viewpoint of the activity of microorganisms. Is advantageous. However, when the water temperature exceeds 40 ° C., the activity of the protein is significantly reduced due to the denaturation of the proteins constituting the microorganisms and the inactivation of the enzyme, and the quality of the treated water is deteriorated. The following operation is performed (see Non-Patent Document 1).

  In recent years, the temperature has risen due to the global warming phenomenon, and the temperature of the treated sludge facility has increased, especially in the summer. The temperature in the biological treatment tank rises remarkably due to the inflow of such high temperature waste water, sometimes the treatment water temperature exceeds 40 ° C, and the quality of the treatment water is remarkably deteriorated. There is. In general, a method of pouring a large amount of cooling water into an activated sludge tank to lower the temperature of the treated water and a method of cooling the influent wastewater to 40 ° C. or lower and supplying it to the biological treatment tank are disclosed. (For example, refer to Patent Document 1).

  Moreover, the method of maintaining the temperature in a biological treatment tank at 45 degreeC or more is disclosed in the aerobic biological treatment method of the waste_water | drain containing a soluble organic substance (refer patent document 2).

However, the above-described method has a problem that the treatment tank becomes large in order to inject a large amount of cooling water, and the cost for cooling or heating the treatment liquid in the inflow waste water or the biological treatment tank is high.
Even if the treatment liquid in the biological treatment tank exceeds 40 ° C and lower than 45 ° C, which is generally considered unfavorable for the growth of microorganisms, due to the rise in drainage temperature and temperature, it takes much equipment and operating costs. Therefore, a method capable of efficiently treating organic wastewater is desired.
“Activated sludge method and maintenance management” 5th edition, Industrial Water Research Committee, May 24, 1994, p59, p227 JP-A-8-155475 JP 2004-268023 A

  The object of the present invention is to efficiently treat organic wastewater without much equipment and operating costs even if it exceeds 40 ° C and lower than 45 ° C, which is generally considered undesirable for the growth of microorganisms. Provided are a method for acclimatizing microorganisms and a method for treating organic wastewater by the acclimatized microorganisms.

  Therefore, in view of such circumstances, the present inventor has conducted intensive studies on a method for efficiently decomposing organic matter contained in wastewater by microorganisms even in a temperature environment that is considered undesirable for the growth of microorganisms. By gradually exposing to a temperature environment of 40 ° C. or less and a temperature environment of more than 40 ° C. and less than 45 ° C., and then maintaining the temperature in the biological treatment tank above 40 ° C. and less than 45 ° C. The present inventors have found that organic substances contained in waste water having a temperature environment of 40 to 45 ° C. can be efficiently decomposed, and have led to the present invention.

That is, the present invention is to repeatedly expose microorganisms used when aerobically decomposing organic substances contained in wastewater to a temperature environment of 40 ° C. or less and a temperature environment of more than 40 ° C. and less than 45 ° C. It is a characteristic method of acclimatizing microorganisms.
In addition, when the organic matter contained in the wastewater is aerobically decomposed by microorganisms, the microorganisms are subjected to repeated exposure to a temperature environment of 40 ° C. or less and a temperature environment of more than 40 ° C. and less than 45 ° C. Next, the organic waste water treatment method is characterized in that the temperature in the biological treatment tank is maintained at a temperature higher than 40 ° C. and lower than 45 ° C.

  According to the method of the present invention, even in a temperature environment of 40 to 45 ° C., which is considered unfavorable for the growth of microorganisms, microorganisms capable of efficiently treating organic substances contained in wastewater can be obtained, Moreover, the organic substance contained in waste_water | drain can be efficiently processed using this microorganism in the temperature environment of 40-45 degreeC.

Hereinafter, the present invention will be described in detail.
Examples of the organic waste water in the present invention include waste water containing organic matter, such as domestic waste water such as sewage and human waste, waste water containing specific organic matter such as food processing factory and chemical industry. Although the kind of organic substance contained in this organic waste water is not specifically limited, Generally, easily decomposable organic substances such as carbohydrates, sugars, and organic acids are exemplified.

The microorganism used in the method of the present invention is not particularly limited as long as it is a microorganism that aerobically decomposes organic matter in wastewater, and is a microorganism used in a general activated sludge facility.
As described above, when the water temperature exceeds 40 ° C., the treatment activity of this microorganism is significantly reduced due to the denaturation of the protein constituting the microorganism and the deactivation of the enzyme.
In order to efficiently decompose organic matter in wastewater, the microorganism must be used even in a temperature environment exceeding 40 ° C. and less than 45 ° C., which is considered undesirable for the growth of microorganisms. It is necessary to adapt to medium and high temperature environment.

As a method of acclimatizing microorganisms to adapt microorganisms to medium-high temperature environments, generally, a method of gradually raising the temperature from a temperature environment suitable for growing microorganisms to a target medium-high temperature environment is used.
However, if the temperature is gradually raised from a suitable environment of microorganisms, when the temperature reaches a temperature exceeding 40 ° C., the microorganisms cannot adapt well to the new environment and the treatment activity decreases, and the quality of the treated water temporarily Gets worse. The deteriorated treated water quality gradually improves as the microorganisms adapt to the medium and high temperature environment, and the treated water quality is recovered. However, the treatment activity varies greatly and is not always a satisfactory method.

  Even if the treatment activity of microorganisms decreases and the quality of treated water deteriorates in the acclimatization process of microorganisms, if the treated water quality is lower than the wastewater regulation value of the activated sludge facility, it may be discharged as it is. If the quality of the treated water exceeds 50 ° C., the treated water is temporarily stored in a storage tank, and after the microorganisms have adapted to the temperature environment, the temporarily stored treated water is passed through the biological treatment tank for reprocessing. It can also be released. However, it is often difficult to install a sufficiently large storage tank due to cost or site constraints, and this method is sufficient even when there is not enough capacity for organic wastewater treatment. Can not.

In the present invention, microorganisms are acclimatized by repeatedly exposing them to a temperature environment of 40 ° C. or lower (hereinafter referred to as an intermediate temperature environment) and an intermediate temperature environment.
Organic wastewater can be treated efficiently by using microorganisms acclimatized in this manner and maintaining the inside of the biological treatment tank in a medium-high temperature environment.
The temperature difference between the medium temperature environment and the medium temperature environment is not particularly limited, but as the temperature difference is increased, the treatment activity of the microorganisms when exposed to the medium temperature environment tends to decrease, and usually about 10 ° C. or less is preferable. .

The heating method for changing the biological treatment tank from the medium temperature environment to the medium high temperature environment is not particularly limited. Usually, steam is blown directly into the inflow wastewater or the biological treatment tank, and the inflow wastewater and / or the organism. A method of indirectly heating the treated water in the treatment tank with a heat exchanger or the like can be mentioned.
In addition, the cooling method for changing from a medium to high temperature environment to a medium temperature environment is not particularly limited, but a method of supplying groundwater to a biological treatment tank and indirect wastewater and / or treated water in the biological treatment tank with a heat exchanger or the like. The method of cooling automatically is mentioned. Furthermore, the method of controlling the temperature in the biological treatment tank using the change in the temperature of daytime and nighttime is advantageous in terms of energy and is particularly preferably used.

  The time for maintaining in the medium temperature environment or medium temperature environment is not particularly limited, but is usually in the range of 1 minute to 3 days, preferably 1 to 24 hours. If the time for maintaining in the medium and high temperature environment is less than 1 minute, it is difficult to obtain the acclimatization effect to the medium and high temperature environment of the microorganism, and if it is more than 3 days, the treatment activity of the microorganism may be reduced. In addition, if the time for maintaining in the medium temperature environment is 3 days or more, it is difficult to obtain the acclimatization effect to the medium temperature environment of the microorganism, and if it is 1 minute or less, the treatment activity of the microorganism may be reduced.

  The number of repetitions of the medium temperature environment and the medium temperature environment is also not particularly limited, and is usually in the range of 1 to 30 times, preferably 1 to 10 times, although it varies depending on the time of holding in each temperature environment.

  Although it is not clear why microorganisms can be acclimatized without decreasing the treatment activity of microorganisms by sequentially exposing the microorganisms to an intermediate temperature environment and an intermediate high temperature environment, it is considered as follows. A microorganism is an aggregate of various microorganisms, and a microorganism having resistance to a medium temperature environment (hereinafter referred to as “medium temperature bacteria”) and a microorganism having resistance to a medium temperature environment (hereinafter referred to as “medium temperature bacteria”) coexist. In the middle temperature environment, mesophilic bacteria dominate, and in the middle temperature environment, mesophilic bacteria dominate. Since mesophilic bacteria are resistant to medium-high temperature environments for a short period of time, exposure to high-temperature environments for a short period of time and quick return to medium-temperature environments can cause mesophilic bacteria to die or decline much. Not maintained. On the other hand, when exposed to a medium-high temperature environment for a very short time, medium-high temperature bacteria grow or become activated. By repeating the medium temperature environment and the medium and high temperature environment sequentially, the medium and high temperature bacteria gradually become dominant without significantly changing the treatment activity.

  Examples of the water passing method when acclimatizing microorganisms include a batch method in which organic waste water is passed intermittently and a continuous method in which organic waste water is passed continuously.

  As a method for treating organic wastewater, a batch method in which the temperature in the biological treatment tank is maintained in a medium to high temperature environment, the organic wastewater is intermittently passed and biologically treated, and the organic wastewater is treated. A continuous method of biological treatment while continuously passing water is mentioned. Alternatively, a biological treatment method may be used in which the temperature in the biological treatment tank is repeatedly changed between an intermediate temperature environment and an intermediate temperature environment in order.

  In addition, during the acclimatization of microorganisms and / or the treatment period of organic wastewater, the pH in the biological treatment tank is not particularly limited as long as the microorganisms to be used can grow, but is usually in the range of 6 to 10, preferably 6 to 6. Nine ranges. If the treated water in the biological treatment tank exceeds the pH range, an alkali or acid is added as appropriate to bring the pH within the pH range. Examples of the alkali include sodium hydroxide and sodium carbonate. Examples of the acid include sulfuric acid.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

Comparative Example 1
A schematic diagram of the processing apparatus used is shown in FIG. A partition plate 5 is provided inside the aeration tank 1, and an air supply pipe 3 is inserted into the bottom of the aeration tank from the top. Waste water A is introduced from the top into the aeration tank 1 containing activated sludge from the waste water introduction pipe 2, supplied with air B from the air supply pipe 3, processed while circulating through the aerobic treatment section 11, and the solid-liquid separation section 12. Then, activated sludge is settled and separated, and the treated water C is discharged from the treated water discharge pipe 4.
Activated sludge [MLSS concentration 6700 mg / L] from a chemical factory was put into an aeration tank with an internal volume of 1 L. Then, while supplying air at 0.5 L / min, acetic acid 1.32 g / L, ammonium sulfate 1.29 g / L, sodium carbonate 1.25 g / L, phosphoric acid 0.11 g / L, and calcium chloride (2 Water salt) Synthetic waste water containing 0.70 g / L was introduced under the condition of 4 ml / min.
After carrying out the treatment for 3 days while maintaining the temperature in the aeration tank at about 32 ° C., the microorganisms were habituated while increasing the temperature every 1-2 ° C. every 3-7 days.
During the acclimatization period, the sludge was appropriately extracted and the MLSS concentration was adjusted to a range of about 6000 to 10000 mg / L.
During the acclimatization period, the TOC (total organic carbon) concentration of the synthetic waste water and the treatment liquid was measured to determine the TOC removal rate. The results are shown in FIG.
When the treated water reached a temperature environment exceeding 40 ° C., a decrease in the TOC removal rate was observed, but it recovered thereafter, but the fluctuation is large.

Example 1
The same aeration tank as used in Comparative Example 1 was used, activated sludge from a chemical factory was introduced, and synthetic wastewater was introduced while supplying air in the same manner as Comparative Example 1.
For acclimatization of microorganisms, as shown in FIG. 3, the medium temperature environment and the medium temperature environment were repeated seven times about every 24 hours, and then maintained in the medium temperature environment. The TOC removal rate is shown in FIG.
When the microorganisms were first exposed to a medium to high temperature environment, the TOC removal rate decreased slightly but recovered immediately. During the subsequent acclimatization period and treatment period, the TOC removal rate was always at a high level, and the fluctuation was small.

Example 2
The same aeration tank as used in Comparative Example 1 was used, activated sludge from a chemical factory was introduced, and synthetic wastewater was introduced while supplying air in the same manner as Comparative Example 1.
As shown in FIG. 4, the acclimatization of microorganisms is repeated three times with a medium temperature environment holding time of about 16 to 14 hours and a medium temperature environment temperature holding time of about 8 to 10 hours. We extended and shortened the holding time of the medium temperature environment, and then maintained the medium temperature environment. The TOC removal rate is shown in FIG.
During the acclimation period and the treatment period of the microorganism, the TOC removal rate was always at a high level, and the fluctuation was small.

It is a schematic diagram of the processing apparatus used in the Example. It is a figure which shows the result of the comparative example 1. It is a figure which shows the result of Example 1. It is a figure which shows the result of Example 2.

Explanation of symbols

1 Aeration tank
2 Drainage introduction pipe 3 Air supply pipe 4 Treated water discharge pipe 5 Partition plate
11 Aerobic processing department
12 Solid-liquid separation part A Wastewater B Air C Treated water

Claims (4)

  Microorganisms used for aerobically decomposing organic substances contained in wastewater are repeatedly exposed to a temperature environment of 40 ° C. or less and a temperature environment of more than 40 ° C. and less than 45 ° C. How to acclimatize.   The method for acclimatizing a microorganism according to claim 1, wherein the time of exposure to a temperature environment of 40 ° C or less and a temperature environment exceeding 40 ° C and less than 45 ° C is 1 minute to 3 days, respectively, and the number of repetitions is 1 to 30 times.   When organic matter contained in wastewater is aerobically decomposed by microorganisms, microorganisms are subjected to repeated exposure to a temperature environment of 40 ° C. or less and a temperature environment of more than 40 ° C. and less than 45 ° C. A method for treating organic wastewater, characterized in that the temperature in the treatment tank is kept above 40 ° C and below 45 ° C. The method for treating organic waste water according to claim 3, wherein the time of exposure to a temperature environment of 40 ° C or less and a temperature environment exceeding 40 ° C and less than 45 ° C is 1 minute to 3 days, respectively, and the number of repetitions is 1 to 30 times.