JPH06277686A - Treatment capacity recovery method for active sludge tank - Google Patents

Abstract

PURPOSE:To recover the capacity in a period shorter than heretofore required when the drainage treatment capacity of an active sludge tank is lowered because of the variation in water quality. CONSTITUTION:A number of bacteria relating to the organic substance decomposition are separated from an active sludge tank representing good drainage treatment capacity, and the characteristics of the bacteria are confirmed and preserved. When the properties of active sludge is changed because the variation of water quality and the drainage treatment capacity is lowered, bacteria with which no resistance to the variation of water quality are selected out of the separated and preserved bacteria, and cultured in a perfect neutrified medium, anti proliferated bacteria are put into an active sludge tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an activated sludge tank used for the purification treatment of organic waste water, when the treatment capacity of the activated sludge tank decreases.
The present invention relates to a method for recovering normal processing capacity in a short time.

[0002]

2. Description of the Related Art The activated sludge method, which utilizes the decomposition of organic substances by aerobic microorganisms, is extremely effective for the purification of organic wastewater such as food factory wastewater, chemical factory wastewater, domestic wastewater, and municipal wastewater. Has been done. As is well known, in the activated sludge method, the wastewater to be treated is continuously flown into an activated sludge tank in which an appropriate amount of activated sludge is present, aeration is performed to supply oxygen, and organic matter is added to microorganisms in the activated sludge. Disassemble.

Although activated sludge also contains inorganic substances such as silicon,
Most are composed of many kinds of microorganisms and macromolecular compounds produced extracellularly by the microorganisms. Microorganisms are mainly bacteria, yeasts, molds, and protozoa, of which bacteria are actually involved in the decomposition of organic matter. Other microorganisms are thought to be organisms that either decompose excess organic matter or are symbiotic in the context of the food chain. The organic matter in the organic wastewater to be treated is partly CO ₂ , N ₂ ,
Inorganic substances such as H ₂ O are completely decomposed, and some of them are used for bacterial growth. Since the amount of activated sludge in the activated sludge tank gradually increases due to the grown bacteria and the polymer compound produced by it, excess activated sludge is appropriately taken out of the tank.

The ability of the activated sludge to decompose organic matter is not based on the action of a small number of microorganisms in the sludge, but is exerted by the involvement of an extremely large number of microorganisms in various aspects to decompose organic matter. is there. Therefore,
In an activated sludge tank that is stable and in good operating condition,
A microbial flora peculiar to the activated sludge tank is formed depending on the quality of effluent that constantly flows in (that is, the type of nutrient source for microorganisms). In this way, when the optimal activated sludge in terms of quality and quantity is not formed in the activated sludge tank, seed sludge is brought in from other activated sludge tanks as necessary and sufficient activated sludge is formed while inflowing wastewater. Wait to be done. This process, called acclimatization, usually requires about 30-180 days for a newly activated activated sludge tank.

The complex and delicate balance of bacterial flora in activated sludge, which exhibits good organic matter degrading, rests on the stability of the quality of the wastewater to be treated. If the fluctuation range of water quality is large, the wastewater treatment using activated sludge is hardly feasible. For example, when the pH of the wastewater to be treated drops sharply, the number of bacteria that cannot tolerate the change in pH is drastically reduced, and the decrease in the number of bacteria due to this is a slight amount of bacteria in sludge. The processing capacity of will be significantly reduced. Therefore, in the activated sludge method, by adjusting the tank before the activated sludge tank, the pH, BOD, inflow amount, etc. of the wastewater supplied to the activated sludge tank are adjusted,
Water quality fluctuations are kept within a certain allowable range. However, due to the nature of factory effluents and municipal sewage, it is unavoidable that there will be unpredictable large or sudden changes in water quality, and water quality control tanks may fail. An accident may occur in which wastewater of a water quality that is fatal to the bacteria inside flows into the treatment tank.

When wastewater of undesired water quality flows in and the bacterial flora of the activated sludge suddenly changes and the wastewater treatment capacity deteriorates, conventionally, the quality of the inflowing wastewater is quickly returned to within the control range and sometimes activated. After replacing all the sludge with that of other activated sludge tanks, I had no choice but to wait for the activated sludge to recover the conventional bacterial flora and amount by acclimation. However, in such a conventional method, it takes about one month or more long time for the activated sludge tank to recover its design capacity. In addition, in order to prevent a large economic loss due to such an accident and prevent the situation where untreated wastewater is discharged, many safety measures and backup facilities are required for wastewater treatment by the conventional activated sludge method. Met.

[0007] For the purpose of shortening the number of days required for acclimatization, it is necessary to add nutrients generally favored by bacteria such as glucose to the activated sludge tank because the nutrients are preferentially used by the bacterial group having the highest growth ability. Therefore, even if it is effective in recovering the amount of activated sludge, it brings about an undesirable change in terms of bacterial composition.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is, as described above, when the bacterial composition of activated sludge is changed due to a sudden accident and the treatment capacity of the activated sludge tank is remarkably reduced, it can be treated in a shorter period than before. It is to provide a way to recover in the meantime.

[0009]

The present invention succeeded in achieving the above-mentioned object, and when the wastewater treatment capacity of activated sludge is reduced due to the fluctuation of the water quality of the wastewater flowing into the activated sludge tank, the number of bacteria is changed due to the fluctuation of the water quality. The bacteria in the sludge that has been drastically reduced are rapidly proliferated by individual culture using a complete nutrient medium outside the activated sludge tank, and the number of days required for acclimatization is shortened by introducing it into the activated sludge tank. In advance, we collected activated sludge from an activated sludge tank that showed good wastewater treatment capacity, separated many bacteria involved in the decomposition of organic matter from the collected activated sludge, and confirmed the characteristics of those bacteria. It is something to save.

The method of the present invention will be described in detail below. As described above, a large number of bacteria are present in the activated sludge in the activated sludge tank, which has a good wastewater treatment capacity, and these bacteria are responsible for a plurality of processes of organic matter decomposition. For example, a protein becomes an N ₂ gasification from an amino acid via acetyl CoA, an organic acid, and NH ₄ ⁺ , or becomes an amino acid again to become a bacterial cell constituent component. Bacteria are involved.

In order to carry out the present invention, first, as many useful bacteria as possible are collected in each process of the above organic substance decomposition,
Furthermore, it is necessary to confirm the characteristics of each of the collected bacteria and divide them into groups. Specifically, a large number of pure strains, which are regarded as pure strains, are isolated from normal activated sludge according to a conventional method for separating bacteria, and their characteristics are examined. Identification of the bacterial species is unnecessary. For the characteristics of bacteria, for example, the following items are examined.

A. Presence or absence of decomposing ability for major organic matter in wastewater (this indicates whether the strain is a primary decomposer for organic matter in wastewater). B. Presence or absence of the ability to finally decompose organic matter into inorganic matter (CO ₂ , N _2, etc.) (this indicates whether or not the strain is the final decomposer for organic matter in wastewater). C. Presence or absence of ability to maintain preferable physical properties (floc forming property) of activated sludge (this makes it possible to determine not only mere organic matter decomposing ability but also flock forming ability for facilitating separation and discharge of treated liquid). D. Propagation speed in wastewater to be treated
It has a high ability to decompose, absorb, and use organic matter, and it is easy to see whether it tends to become priority bacteria in activated sludge). E. Abundance in activated sludge-forming bacteria (higher abundance does not necessarily mean higher resolution, but it has a great influence on the physical properties of activated sludge in some way).

The items to be emphasized are decided depending on the type of the activated sludge treatment method, the purpose of the treatment and the like. For example, in the case of an aerobic activated sludge tank which is not intended to remove nitrogen compounds, confirmation of the ability to decompose nitrogen compounds to N ₂ gas is not important, but the ability to decompose and remove carbohydrates is emphasized. From the above, it is possible to confirm in which of the many capabilities of activated sludge the bacteria are involved.

Next, for each bacterium, a resistance test against the water quality fluctuation of the wastewater to be treated is conducted. The test items are determined in consideration of the type of wastewater to be treated, the type of activated sludge treatment method, and the environment surrounding the facility. For example, confirm the following characteristics. a. Resistance to pH changes b. Resistance of treated wastewater to changes in BOD c. Resistance to accumulation of intermediate products of organic substance decomposition reaction (organic acid, NO ₂ ⁻ , NH ₄ ⁺ , P, etc.) in activated sludge tank d. Toxic substances for bacteria (organic solvents, surfactants,
Resistance to heavy metal ions, fats and oils) e. Resistance to temperature changes

Based on the characteristics confirmed as described above, all bacteria are first classified from the viewpoint of organic matter decomposition characteristics (primary classification), and each classified bacteria is further classified from the viewpoint of resistance to water quality fluctuation. (Secondary classification). The classified bacteria are stored in a state in which they can be cultivated at any time after confirming the medium and the culture conditions suitable for growing them.

If there is a large change in the quality of the wastewater to be treated that flows into the activated sludge tank and the activated sludge is damaged and the wastewater treatment capacity is significantly reduced, check the contents of the change in water quality immediately. (If the water quality remains out of the control range, eliminate the confirmed cause and stabilize the water quality.)

On the other hand, from the contents of the confirmed water quality fluctuations, it is possible to identify bacteria that are presumed to have been killed or the number of bacteria has been drastically reduced. Therefore, they are selected from the above-mentioned preserved strains (resistance as a criterion for secondary classification). Select by referring to the results of the sex test). Selection is performed for each group of strains in the primary classification. Then, the plurality of selected strains are individually cultured under a suitable culture condition using a suitable medium for them. Cultivation using a suitable medium and culture conditions for individual strains can grow up to about 1000 times the inoculum number in a short period of about 5 to 7 days in the case of organic matter-degrading bacteria that grow in a complete nutrient medium containing glucose. Can be made.

Once a sufficient number of bacteria has been obtained to restore the abundance ratio in normal activated sludge, the culture as it is or the bacterial cells separated from the culture are treated with the activated sludge tank in which the above-mentioned capacity deterioration has occurred. Throw in. The input amount is the amount necessary to restore the activated sludge of bacterial composition before the accident, the abundance of each bacterium in the isolate, the total number of heterotrophic bacteria in the activated sludge, and the death rate of heterotrophic bacteria due to the accident. (Measure separately)
It is desirable to make a decision taking into consideration the above, but the goal of shortening the acclimatization period can be achieved without rigorous calculation.
As a result, the bacterial composition of the activated sludge in the tank is almost restored to the state before the accident. Therefore, the effluent treatment capacity of the treatment tank can be completely restored by acclimation for a very short period thereafter.

[0019]

【Example】

Example 1 Protein-based food factory wastewater was treated, and two bench-scale batch-type activated sludge tanks (volume: 10 liters) were used to activate activated sludge 3000 mg MLSS / l, BOD-SS load 0.05 kg / kg-day, wastewater organic matter concentration. 1200 mg / l, pH
Aerobic treatment was carried out under the conditions of 6.8, and the BOD removal rate reached 95%.

A part of the activated sludge in this activated sludge tank was sampled, and bacteria were separated by the following procedure. First, the activated sludge is homogenized with a homogenizer, and the resulting activated sludge suspension is diluted with sterile physiological saline to prepare a diluted solution having a concentration of 5 steps within a range of 10 ⁴ to 10 ⁸ , and 1 ml of each diluted solution is used as waste water. Pour 10 ml of agar plate medium and incubate at 25 ° C for 3 to 10 days. The operation of isolating the expressed colonies daily and inoculating the standard agar medium is repeated several times. On the 10th day of culture, 109 colonies / plate of bacterial colonies were obtained on the 10 ^6- fold diluted waste water agar medium. From among these, cultures in which colonies were confirmed 3
A total of 67 colonies were randomly picked by using a random number table in four stages on the 5th, 7th and 10th days.
Each colony was replanted twice in a standard agar medium to obtain 67 strains of activated sludge-derived bacteria.

Next, the following tests were carried out for each strain,
8 strains were selected based on the number of days of colony development and the results of characterization tests.
The strains were divided into groups, and the strains in each group were ranked in three stages based on pH resistance. Colony expression day Gram stainability Cytochrome oxidase test Catalase test Sugar degradation test (OF test and glucose, agar,
Starch, cellulose, glycerol) Proteolytic test (peptone, collagen, casein, liver extract, myocardial extract)

Degradation test for specific substances (raw water medium and raw material extract in food factory processes) Cell morphology microscopy (check for the presence of structures that cause floc formation) Nitrate reduction test pH resistance test (7. Prepare a wastewater whose pH is adjusted stepwise in the range of 2 to 4.4, and inoculate this with the same amount of bacterial cells.
Incubate with shaking at 5 ° C for 3 to 7 days. During this period, the remaining amount of decomposed organic matter is quantified daily. Thereafter, all strains were freeze-dried or were preserved as inoculum by repeated low temperature storage and subculture.

On the other hand, in the above two activated sludge tanks in operation,
Assuming an accident in the former pH adjusting tank, waste water of pH 4.0 was supplied for 2 hours. As a result, the pH in the tank was lowered from 6.8 to 4.4. The pH of the waste water supplied was returned to 6.8 and the operation was restarted, but the BOD removal rate had dropped to 66%. After this, one of the two activated sludge tanks continued to be acclimatized as usual, expecting natural recovery for comparison.

For another activated sludge tank, an attempt was made to recover the treatment capacity according to the present invention. That is, from the above-mentioned preserved strains, a group of bacteria belonging to the weakest group of pH resistance was selected, and from them, the organic matter in wastewater was highly decomposable, and cytochrome oxidase / catalase positive (oxygen was used to obtain energy. It shows that there is a cytochrome enzyme for this and catalase that decomposes toxic substances produced in the oxygen utilization system, which means that it has the ability to aerobically decompose organic substances to carbon dioxide gas.)
And from the group within 3 days of colony expression,
2 strains of morphologically different Gram-negative bacilli, 2 strains of morphologically different gram-negative bacilli from a group with the same properties and colony expression days of 3 days or more but less than 5 days Choose one strain from the bacterial group, which accounts for about 36% of the strains, a total of 5 strains, and select them from peptone 0.5
%, Yeast extract 0.25%, glucose 0.1%, pH 7.
It was cultured in 0 liquid medium for 7 days. Next, each culture solution is centrifuged to collect the bacterial cells, and the amount of them is measured to restore the activated sludge to a bacterial composition similar to that of the activated sludge before pH reduction. I put it in. The required input amount is the ratio of each bacterium in 67 strains of bacteria isolated from the activated sludge, the number of heterotrophic bacteria in the activated sludge (1.09 × 10 ⁸ cells / ml), and a separate confirmation. It was calculated from the killed heterotrophic bacteria (37%).

Two days after the culture strain was added and the operation was restarted, the BOD removal rate recovered to 93%, and the total number of days required for recovery was 9 days. On the other hand, another activated sludge tank, which was expected to recover the treatment capacity by mere acclimatization, had a BOD removal rate of 9
It took 35 days to recover to 3%.

[0026]

Industrial Applicability As described above, according to the present invention, the bacteria whose number of bacteria has been reduced due to water quality fluctuations are rapidly proliferated in a culture device different from the activated sludge tank and are introduced into the activated sludge tank. Along with this, it is possible to recover the lowered treatment capacity of the activated sludge tank in a much shorter time than before.

Claims (1)

[Claims] 1. An activated sludge is collected from an activated sludge tank showing good wastewater treatment capacity, a large number of bacteria involved in the decomposition of organic matter are separated from the collected activated sludge, and the characteristics of those bacteria are confirmed. And, when the activated sludge is deteriorated due to the water quality fluctuation of the wastewater flowing into the activated sludge tank and the wastewater treatment capacity is reduced, there is no resistance to the water quality fluctuation among the isolated and preserved bacteria. A method for recovering the treatment capacity of an activated sludge tank, which comprises selecting a confirmed bacterium, culturing it in a complete nutrient medium, and introducing the grown bacterial cells into the activated sludge tank for acclimatization.