KR20030084199A - A sewerage method using cultured nitrification microorganism by anaerobic or aerobic digestive fluid of sludge - Google Patents

Abstract

PURPOSE: An advanced wastewater treatment method using nitrifying bacteria is provided, which is characterized in that nitrifying bacteria are cultivated in extra anaerobic/aerobic sludge digestion chamber, and then nitrifying bacteria are supplied to anoxic tank or aeration tank in winter season so as to prevent the deterioration of wastewater treatment efficiency due to inactivation of nitrifying bacteria at low temperatures. CONSTITUTION: The advanced wastewater treatment method comprises the steps of returning excess sludge from a settling tank(4) to a digestion tank(5) where excess sludge is digested in anaerobic, anoxic or aerobic conditions so that cultivation liquid is obtained; cultivating such nitrifying bacteria as nitrosomonas and nitrobacter in a cultivation chamber(6); and supplying the nitrifying bacteria to an anoxic tank(2) or an aeration tank(3).

Description

A sewerage method using cultured nitrification microorganism by anaerobic or aerobic digestive fluid of sludge}

The present invention relates to a sewage treatment method for biologically removing nitrogen and phosphorus contained in sewage, and in particular, sludge in a separate culture tank in order to prevent the deterioration of sewage treatment efficiency due to the growth deterioration characteristics of nitrifying microorganisms in winter. The present invention relates to a method for advanced sewage treatment using nitrifying microorganisms cultured with anaerobic or aerobic digestion liquid of sludge which is supplied to an anoxic tank or aeration tank to increase the efficiency of sewage treatment during winter season.

If the sewage flows into a water supply source containing a large amount of nitrogen in the state where the sewage is not treated, odor occurs in the tap water, and when it enters the stream, it depletes the oxygen in the water, causing collective death of fish, eutrophication and red tide. It causes a lot of problems for the health of the people.

In accordance with the above-mentioned situation, environmental regulations are increasingly being strengthened in order to strengthen the water quality standards and meet the demand for a pleasant environment. Particularly, the standards for treating waste and sewage are being strengthened. It is a reality.

There are various ways to solve the above-mentioned pollution problems depending on the type of air pollution, land pollution, water pollution, etc. Among them, the sewage treatment method includes organic matter, nitrogen and phosphorus contained as pollutants in the sewage. To remove it.

The method for treating by microorganisms among the methods for treating sewage is well known in the art, and a conventional method for treating organic matter, nitrogen, and phosphorus contained as contaminants in sewage will be described with reference to FIG. 1.

In FIG. 1, in the anaerobic tank 1, a microorganism that accumulates phosphorus decomposes ATP (Adenosine TriPhosphate) to generate Adenosine DiPhosphate (ADP) while enzymatically absorbing phosphorus without releasing phosphorus in the process of using energy. Phosphorus polyphosphate (Poly-phosphate) or the like can not be produced in the aeration tank (3) does not occur excessive absorption of phosphorus.

The denitrification process occurs in the anoxic tank (2) that removes nitrogen, in which nitrate (NO _3- ) becomes nitrite (NO _2- ) and is finally reduced to nitrogen gas (N ₂ ) via nitrogen oxide (N ₂ O). As a process, denitrifying microorganisms are heterotrophic and some independent, including Pseudomonas, Micrococus, Archromobacter, Thiobaci llus and Bacillus species. Chemical nutrition bacteria. Denitrification bacteria are sufficiently present in the sewage treatment process, and denitrification is possible only if proper conditions are achieved. However, in winter, ammonia nitrogen is not sufficiently oxidized to nitrate nitrogen, so the nitrogen treatment efficiency is lowered.

In the aeration tank (3) where organic matters are removed and nitrified, aerobic mixing of wastewater, which is nutritionally balanced with microorganisms, causes various aerobic microorganisms to decompose organic pollutants in the wastewater and oxidize ammonia nitrogen. Floating particles of organic inorganic particles aggregate by microorganisms, and active sludge with good sedimentation is formed at this time.

As shown in FIG. 1, sewage containing organic matter, nitrogen, and pollutants flows into the anaerobic tank 1, and the discharged water of the anaerobic tank 1 is an anaerobic tank 2, and the wastewater of the anaerobic tank 2 is the aeration tank 3. And the discharged water of the aeration tank 3 is sequentially introduced into the settling tank 4, and the remaining part is returned to the anoxic tank 2, and the biologically purified treated water from the settling tank 4. In addition to being discharged, the sludge is returned to the anaerobic tank 1 to treat sewage.

The anaerobic tank (1), and the microorganisms emits a, the anoxic tank (2), nitrate (NO ₃ -) in this and the denitrification is gasified to N ₂ by reaction with organic material, aerobic conditions in the aeration tank (3) by the action of nitrifying bacteria Ammonia (NH ₃ ) becomes NO ₃ and is returned to the oxygen-free tank 2. In addition, in the aeration tank (3), the discharge water flows from the anoxic tank (2), and the microorganisms contained therein excessively ingest phosphorus and decompose organic substances.

Next, in the settling tank 4, the discharged water discharged from the aeration tank 3 flows in and removes the solid matter in the influent water by solid-liquid separation.

The conventional method of biologically purifying sewage as described above is to control the growth conditions of microorganisms to treat contaminants such as biochemical oxygen demand (BOD), nitrogen, and phosphorus, which are biochemical oxygen demands. However, the specific growth rate of organotrophic bacteria, which are mainly involved in BOD removal, is about 30 to 60 day ^-1 , whereas the growth rate of nitrosomonas, nitrifying bacteria, is ¹ to 2 day ^-1 . Is very slow and affected by the water temperature, so in winter, when the water temperature is low, the nitrifying bacteria that have slow growth rate are washed out before they proliferate in the aeration tank (3), so that the nitrification bacteria in the aeration tank (3) cannot be maintained. There was a problem.

One way to prevent this phenomenon is to increase the sludge residence time (SRT) in the system. However, the method of increasing the residence time causes a problem in that the microorganisms that have excessively absorbed phosphorus in the aeration tank 3 stay in the system for a long time to release the phosphorus in the microorganism again.

The present invention has been invented to solve various problems and drawbacks of the conventional method for treating sewage by microorganisms.

An object of the present invention is to increase the efficiency of sewage treatment during the winter season by keeping the nitrification bacteria constant by supplying cultured nitrifiers in the winter when the nitrification bacteria number decreases in the aeration tank.

Another object of the present invention is to reduce the sludge waste by reducing the sludge to be used by cultivating the excess sludge to nitrate bacteria culture.

1 is a block diagram of a conventional sewage treatment system,

2 is a block diagram of a sewage treatment system employed as an embodiment of the present invention;

3 is a block diagram of a sewage treatment system adopted as another embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

1: anaerobic tank 2: anaerobic tank

3: aeration tank 4: sedimentation tank

5: digestion tank 6: nitrifying bacteria culture tank

7: dispensing tank

The present invention for achieving the above object is a microorganism as a method for decomposing the excess sludge, and supplying the nitrifying bacteria cultured using the decomposition liquid as a substrate to an anaerobic tank (2) or aeration tank (3) to prevent the decrease in sewage treatment efficiency. and the anaerobic tank (1) for emitting a person, nitrate (NO ₃ -) to the anoxic tank (2) for the reduction of a N ₂ gas, ammonia (NH ₃₎ by the action of nitrifying bacteria is oxidized to NO ₃ the anoxic tank (2 A) aeration tank (3), which is returned to the wastewater and microorganisms excessively ingest phosphorus, and decomposes organic substances, a sedimentation tank (4) for removing solid matter in the influent water by solid-liquid separation, and surplus discarded from the precipitation tank (4). In order to use sludge as a culture substrate for nitrifying bacteria, a digestion tank (5) which decomposes into anaerobic, aerobic or intermittent aeration is used, and a nitrifying bacteria culture tank (6) which cultures nitrifying bacteria using the decomposition solution as a substrate. do.

The present invention is provided with an anaerobic tank (1), an anaerobic tank (2), aeration tank (3) and sedimentation tank (4) in the sewage treatment method for biologically purifying sewage, the excess sludge disposed from the sedimentation tank (4) Dissolving with anaerobic, aerobic or intermittent aeration in a digestion tank (5) for use as a culture substrate of nitrifying bacteria; Culturing the nitrifying bacteria using the digestion solution as a substrate in the nitrifying bacteria culture tank 6; The nitrifying bacteria cultured in the nitrifying bacteria culture tank 6 are introduced into the anoxic tank 2 or the aeration tank 3 to cultivate the nitrifying bacteria in a separate culture tank and continuously supply them.

The amount of excess sludge in the digestion tank 5 is 1 to 3% of the amount of inflow sewage, and is used as a substrate for nitrifying culture by decomposing the sludge at an anaerobic, aerobic or intermittent aeration at a temperature of 25 to 50 ° C. The retention period of the culture solution is 1 to 3 days.

In addition, the residence period of the sludge in the nitrifying bacteria culture tank 6 is 3 to 6 days, and oxygen is supplied to the nitrifying bacteria culture tank 6 by performing continuous aeration or intermittent aeration, which is obtained from the decomposition tank 5. The ammonia nitrogen generated in the sludge decomposition solution is used to multiply nitrifying microorganisms such as nitrosomonas and nitrobacter and feed them to the anoxic tank 2 or the aeration tank 3.

Hereinafter, a method of supplying nitrifying bacteria cultured with the sludge digestion solution of the present invention to an anoxic tank (2) or an aeration tank (3) to prevent a decrease in sewage treatment efficiency will be described in detail with reference to the accompanying drawings.

2 is a configuration diagram of a sewage treatment system employed as an embodiment in the present invention. First, the digestion tank 5 and the culture tank 6 will be described.

<Decomposition tank>

The decomposition tank 5 obtains a decomposition solution for using the excess sludge discarded from the precipitation tank 4 as a culture substrate of the nitrifying bacteria, the characteristics of which are as follows.

1) In order to maintain the decomposition temperature of sludge in a decomposition tank 25-50 degreeC, the exterior of the decomposition tank 5 shall be heat-insulated.

If the sludge decomposition temperature is lower than 25 ℃, the sludge is hardly decomposed, so that it is not possible to obtain a decomposition solution suitable for cultivation of nitrifying bacteria. If it is higher than 50 ℃, COD, BOD, and ammonia nitrogen (NH ₃ -N) Since the concentration is high and not suitable for culturing nitrifying bacteria, the decomposition temperature of the sludge in the decomposition tank 5 is preferably 25 to 50 ° C.

2) The amount of excess sludge to be added to the digestion tank 5 is 1 to 3% of the amount of sewage inflow, which produces a decomposition solution capable of cultivating an appropriate amount of nitrifying bacteria, and also reduces the amount of sludge that is disposed of as a result of sludge treatment. To save.

3) The digestion tank 5 is operated by intermittent aeration method which repeats anaerobic, exhalation or aeration and stop, and the sludge residence time in the digestion tank 5 is 1-3 days.

4) In the digestion tank (5), ammonia nitrogen (NH ₃ -N) and BOD components are eluted from the introduced sludge. Ammonia nitrogen (NH ₃ -N) is used for the growth of nitrifiers in the nitrifier culture tank (6). The BOD component is used as a carbon source in the denitrification reaction in the anoxic tank (2).

<Nitric Oxide Bacteria Culture Tank>

In the nitrifying bacteria culture tank 6, the nitrifying bacteria are cultured using ammonia nitrogen (NH ₃ -N) contained in the decomposition solution as an energy source, and the characteristics thereof are as follows.

1) Nitrifying microorganisms such as Nitrosomonas and Nitrobactor are aerobic microorganisms, and thus aeration or intermittent aeration is performed to supply oxygen.

2) Nitrifying bacteria have a slow growth rate, so if the sludge stays less than 3 days, nitrifying bacteria of the required number of bacteria are not cultured, and if it exceeds 6 days, the microorganisms that excessively absorb phosphorus in the aeration tank (3) are microorganisms. Since the phosphorus inside is not released, the residence period of the sludge in the nitrifying culture medium 6 is 3 to 6 days.

3) In order for the effluent from the nitrifying bacteria culture tank 6 not to affect the water quality of the sewage treatment plant effluent, the flow rate of the nitrifying bacteria culture tank 6 is 1 to 3% of the inflow flow.

In general, in the sewage treatment system, the temperature of influent sewage is lowered to 8 ~ 9 ℃ during the winter season. Then, the aeration tank 3 of the conventional sewage treatment system shown in FIG. 1 will have a low water temperature of about 10 to 15 ° C.

As such, when the water temperature decreases, the number of nitrifying bacteria decreases due to the growth of nitrifying bacteria in the aeration tank 3, and thus it is difficult to maintain the removal efficiency of nitrogen contained in the sewage during the winter season.

As described above, when the temperature of the sewage is lowered in winter, the number of nitrifying bacteria decreases due to the decrease in the growth of the nitrifying bacteria in the aeration tank 3, and the nitrogen removal efficiency is lowered. And nitrifying bacteria through the nitrifying culture medium (6).

That is, excess sludge discarded from the settling tank 4 is introduced into the decomposition tank 5 to obtain sludge decomposition liquid through anaerobic, aerobic or intermittent aeration, and the residence time of the sludge in the decomposition tank 5 is 1 to 3 days. do. If the residence time is less than 1 day, sufficient decomposition solution cannot be obtained, which is required for nitrifying bacteria culture. If it exceeds 3 days, the concentration of COD, BOD, and ammonia nitrogen (NH ₃ -N) in the decomposition solution is high. Not suitable for cultivation

After culturing the nitrifying bacteria using the digestion solution as the substrate in the nitrifying bacteria culture tank 6, the cultured nitrifying bacteria are introduced into the anoxic tank 2 or the aeration tank 3.

FIG. 3 is a schematic diagram of a sewage treatment system employed as another embodiment of the present invention, compared to the embodiment shown in FIG. 2, in the embodiment of FIG. 6) is different in that it further comprises a distribution tank (7) for distributing and supplying, and thus, by dispensing the distribution tank (7) to distribute the excess sludge to the digestion tank (5) and nitrifying bacteria culture tank (6) It is to increase the culture efficiency of the nitrifying bacteria, and elsewhere the same as in the embodiment of Figure 2, the description thereof will be omitted.

The degree of culture of nitrifying bacteria can be confirmed by measuring the activity of nitrifying bacteria, the principle of which is as follows.

The reaction in which ammonia in water is oxidized to nitrous acid and nitrous acid to nitrate is called nitrification. The bacterium that catalyzes these two reactions is nitrifying bacteria. Therefore, the activity of nitrifying bacteria is the activity of nitrifying bacteria how fast ammonia is converted to nitrous acid and nitric acid, and the nitrifying bacteria activity can be easily measured because the nitrifying bacteria activity is generally proportional to the number of nitrifying bacteria in the sample. By measuring and analyzing, the culture degree of nitrifying bacteria can be known.

Comparative Example 1

The activity of the nitrifying bacteria in the sewage treatment method for carrying out the method of the present invention and the conventional sewage treatment method was measured and shown in Table 1 below. In the present invention, the activity of nitrifying bacteria was used as a control, and in the present invention, the activity of nitrifying bacteria in the aeration tank 3 and the nitrifying bacteria culture tank 6 was measured.

The activity of nitrifying bacteria is a measure of how many micrograms of ammonia is changed to nitrous acid during 1 hour.

Therefore, the measuring method is to mix a sample containing nitric oxide in a solution containing a certain concentration (50mg / ℓ), and supply the reaction by shaking with a shaker incubator at a constant temperature of 25 ℃ and then reacted with a filtration device The activity was calculated by filtering the concentration of nitrous acid produced in ammonia at 11 ± 1.5 ℃. Measurement of the concentration of nitrous acid was measured with an absorbance meter.

In the measurement, the degree of change from nitrous acid to nitric acid was not measured separately because the rate limiting reaction in nitrification was oxidation from ammonia to nitrous acid. That is, when ammonia is oxidized to nitrous acid, oxidation of nitrous acid to nitric acid is easy and quick.

TABLE 1

Nitric Oxide Activity of the Method of the Present Invention and the Conventional Method

division Nitrifier Activity (㎍ / mL / hr) Rate (Control Base) Control (A ² / O method) 5.3 to 5.5 One Invention Nitrifying bacteria culture tank 15.5-16.7 3 to 4 Aeration tank 6.48-8.9 1.1 to 1.7

In the control method of the conventional method as shown in Table 1, the activity of the nitrifying bacteria was measured in 5.3 ~ 5.5 (㎍ / ㎖ / hr) in the aeration tank (3) while the activity of the nitrifying bacteria in the method of the present invention cultured nitrifying bacteria Nitrification occurred in the sewage treatment process during the winter season by the method of the present invention, which was higher than the control group at 15.5-16.7 (㎍ / ml / hr) in the tank (6) and 6.48∼8.9 (µg / ml / hr) in the aeration tank (3). It can be seen that the decrease in the number of bacteria can be compensated for.

Comparative Example 2

The nitrified bacteria water in the sewage treatment method according to the present invention and the conventional sewage treatment method were measured when the water temperature was 10 to 13 ° C and are shown in Table 2 below. Using the conventional case as a control, the number of nitrifying bacteria in the aeration tank 3 during each treatment step was measured. As described above, during the winter season when the water temperature is low, the growth rate of the nitrifying bacteria is very slow, and then outwards before the growth in the aeration tank (3), the number of nitrifying bacteria in the aeration tank (3) is reduced, and thus ammonia nitrogen Since nitrification is not carried out, the number of nitrifiers in the aeration tank 3 is a very important indicator. Nitrogenated bacterial count was measured by MPN method of water pollution process test method.

TABLE 2

Nitric Oxide Bacteria in Aeration Tanks of the Method of the Present Invention and the Conventional Method

※ Figure 2 shows log values.

division Nitrifying bacteria count (MPN / 100ml) Control (A2 / O process) 2,300,000 ± 150,000 The present invention 46,000,000 ± 1,000,000

As shown in Table 2, in the present invention, the number of nitrifying bacteria in the aeration tank was found to be about 20 times higher than that of the control method. Therefore, when adopting the sewage treatment method according to the method of the present invention it can be seen that the nitrification bacteria in the aeration tank (3) can be maintained much more than the conventional treatment method can improve the nitrogen removal efficiency.

Comparative Example 3

The water quality of the treated water in the sewage treatment method according to the method of the present invention and the conventional sewage treatment method is shown in Table 3 below. Using the conventional case as a control, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), total nitrogen (TN) and total phosphorus (TP) were measured according to the water pollution process test method. Comparative analysis.

TABLE 3

Comparison of Water Quality of Sewage Treatment Water

※ ± indicates standard deviation.

BOD (mg / l) COD (mg / L) SS (mg / l) T-N (mg / L) T-P (mg / l) 109 ± 35 64 ± 5 96 ± 43 32 ± 3 3.8 ± 1.6 Control tool (A2 / O method) Concentration 13 ± 5 17 ± 6 7 ± 3 20 ± 7 1.6 ± 1.2 % Removal 87 ± 6 73 ± 11 92 ± 5 37 ± 22 50 ± 13 Invention Concentration 10 ± 4 13 ± 5 6 ± 3 11 ± 3 1.0 ± 0.4 % Removal 92 ± 5 83 ± 8 94 ± 3 65 ± 10 73 ± 6

As can be seen from Table 3, the biochemical oxygen demand (BOD), the chemical oxygen demand (COD), the suspended solids amount (SS), the total nitrogen amount (TN), and the total phosphorus amount (TP) are respectively higher than those of the conventional method. The concentration of the method was lowered by 3 ± 1, 4 ± 1, 1 ± 0, 9 ± 4, 0.6 ± 0.8, and the present invention showed that the sewage treatment capacity was significantly improved over the conventional method.

Next, the measured water quality values of the treated water in the method of the present invention shown in Table 3 were compared with the water quality standards of the sewage treatment plant effluent prescribed by the Water Quality Preservation Act shown in Table 4 below.

TABLE 4

Water quality standard list of sewage treatment plant discharged water

BOD (mg / l) COD (mg / L) SS (mg / l) T-N (mg / L) T-P (mg / l) Sewage Terminal Treatment Facility Special Measures Area and Jamsil Underwater Area Within 10 Within 40 Within 10 Within 20 Within 2 Other Area Within 20 Within 40 Within 20 Within 60 Within 8 Within 30 Within 40 Within 30 Within 60 Within 8

In the present invention, the concentration of biochemical oxygen demand (BOD) of the treated water is 10 ± 4, except for the standard deviation, which is within the range of 10 or less in the special measures area and Jamsil submerged area where the minimum concentration is required according to the standard of water quality. The concentrations of the remaining chemical oxygen demand (COD), suspended solids (SS), total nitrogen (TN) and total phosphorus (TP) are significantly lower than the water quality standards of the sewage treatment plant effluent. It has been confirmed that the water quality of the treated water can be improved when employed in the treatment plant.

As described above, the present invention provides an anaerobic tank or nitrifier cultured by separately installing a nitrifier for culturing nitrifier bacteria using the digestion tank for dissolving excess sludge and using it as a substrate for culturing nitrifying bacteria. Since it is supplied to the aeration tank, nitrification is possible even if the sludge residence time (SRT) in the system is short. Sewage treatment is possible with the discharge below the allowable standard value.

And packaging the decomposition tank and the nitrifying bacteria culture tank employing the method of the present invention when installed in all existing sewage treatment plants has the effect of improving the water quality of the treated water with a simple facility supplement.

In addition, the present invention has the advantage of reducing the sludge treatment cost by reducing the sludge to be discarded by using the decomposed excess sludge to nitrate bacteria culture.

Claims (4)

In the anaerobic tank (1), microorganisms release phosphorus, and in the anoxic tank (2), nitrates (NO _3- ) are reacted with organic matter to denitrate with N ₂ gas, and in the aeration tank (3), ammonia (NH ₃ ) In the sewage treatment method for biologically treating the sewage to remove the solid matter in the influent by separating the influent from the settling tank (4) by oxidizing to NO ₃ and returned to the anoxic tank (2), the sedimentation tank ( Dissolving the excess sludge discarded from 4) as anaerobic, aerobic or intermittent aeration in the digestion tank 5 to use as a culture substrate of the nitrifying bacteria; Culturing the nitrifying bacteria using the digestion solution as a substrate in the nitrifying bacteria culture tank 6; Sludge of the nitrifying bacteria cultured in the nitrifying bacteria culture tank (6) comprising the step of injecting into the anoxic tank (2) or aeration tank (3) to cultivate the nitrifying bacteria in a separate culture tank to continuously supply Sewage treatment method using nitrifying microorganisms cultured with anaerobic or aerobic digestion. The apparatus of claim 1, further comprising a dispensing tank (7), wherein 30 to 70% of the total sludge flowing into the dispensing tank (7) is in the digestion tank (5), and 30 to 70% in the nitrifying culture medium (6). Sewage advanced treatment method using nitrified microorganisms cultured with anaerobic or aerobic digestion of sludge, characterized in that the input to distribute. 3. The sludge according to claim 1 or 2, wherein the amount of excess sludge in the decomposition tank 5 is 1 to 3% of the amount of inflow sewage, and the sludge is subjected to anaerobic, aerobic, or intermittent aeration at a temperature of 25 to 50 ° C. Decomposition to obtain a culture medium used as a substrate for nitrifying bacteria culture, and to reduce the sludge discarded with a sludge retention period of 1 to 3 days, sewage altitude treatment using nitrified microorganisms cultured with anaerobic or aerobic digestion of sludge Way. The oxygen supply is carried out according to claim 1 or 2, wherein the sludge retention period in the nitrifying bacteria culture tank 6 is 3 to 6 days, and continuous aeration or intermittent aeration is performed. Sewage advanced treatment method using nitrified microorganisms cultured with anaerobic or aerobic digestion of sludge.