KR102225883B1 - Partial Nitritation Methods of Sewage Using Autotrophic microorganism immobilized in Bead - Google Patents

Abstract

The present invention uses a carrier immobilized with nitric acid microorganisms to efficiently remove nitrogen components contained in urban sewage or sewage, and inhibits the activity of nitrite oxidizing microorganisms to maintain a high concentration of nitrite in the reaction tank. It relates to a partial nitrite oxidation method using a carrier on which nutrient microorganisms are immobilized, and more particularly, an agglomeration and precipitation step of separating the supernatant into sludge and supernatant after injecting a coagulant into sewage and an aerobic tank including a carrier immobilized with nitrifying microorganisms. It includes the step of supplying to and reacting for a predetermined time, wherein the nitrifying microorganism of the carrier accommodated in the aerobic tank maintains the activity of the ammonium oxidizing microorganism higher than that of the nitrite oxidizing microorganism. It's about how to get angry.

Description

Partial Nitritation Methods of Sewage Using Autotrophic microorganism immobilized in Bead}

The present invention uses a carrier immobilized with nitric acid microorganisms to efficiently remove nitrogen components contained in urban sewage or sewage, and inhibits the activity of nitrite oxidizing microorganisms to maintain a high concentration of nitrite in the reaction tank. It relates to a method for partial nitrite oxidation using a carrier on which nutrient microorganisms are immobilized.

When a large amount of nitrogen is introduced into the water system, it may be toxic to the aquatic environment, reduce residual DO in the water system, or cause eutrophication. In addition, when introduced during the chlorine disinfection process of the physicochemical method, it is necessary to maintain the nitrogen concentration in the water system at a low concentration because it causes secondary damage because it generates disinfection by-products.

As a method of removing such nitrogen, a biological process using a nitrification reaction and a denitrification reaction is widely used. The nitrogen removal reaction in a general biological process is performed by sequentially proceeding a nitrification reaction (Equations 1 and 2) under an aerobic condition and a denitrification reaction under an oxygen-free condition.

(1)

(One)

(2)

(2)

However, as can be seen from Equations 1 and 2 above, a large amount of oxygen is required to oxidize ammonia nitrogen, and the denitrification reaction of a biological process requires an organic carbon source as an electron donor of microorganisms for the reduction of nitric acid or nitrous acid. Therefore, the driving cost is inevitably increased.

In response to the problem of such a biological process, many studies have been conducted on a method of removing nitrogen using anaerobic ammonium oxidizing microorganisms. Anaerobic ammonium oxidizing microorganisms are ammonium (NH ₄ ⁺⁾ and nitrous acid under anaerobic conditions ^- the autotrophic micro-organisms for use in a substrate generate nitrogen _{(N 2) (NO 2)} . Anaerobic ammonium oxidizing microorganisms are ammonium (NH ₄ ⁺⁾ to the electron donor, nitrite (NO ₂ ^-) to with use as an electron acceptor, unlike the conventional biological processes do not require the addition of organic carbon sources, nitrification parts of ammonium nitrogen As compared with the conventional biological process, the amount of oxygen required for is also saved by about 60%, so there is an advantage in that aeration cost and carbon source supply cost can be reduced.

Further, anaerobic ammonium nitrogen removal processes using microorganisms is the maximum nitrogen oxide removal efficiency of 26 ~ 42 kg-N / m 3 -day to 0.3 kg-N / m ³ -day compared to the typical biological processes do not exceed the very efficient NO x removal great.

However, the above anaerobic ammonium oxidizing microorganisms exist in the form of Candidatus Brocadia, Candidatus Kuenenia, Candidatus Scalindua, Candidatus Anammoxoglobus, Candidatus Jettenia, etc. in the wastewater treatment process and the nitrogen circulation system of the natural system. In order for the nitrogen removal reaction by the anaerobic ammonium oxidizing microorganism to proceed to a certain level, it is necessary to effectively control the microorganisms lost from the reaction tank.

Recently, by applying a comprehensive immobilization technique to bead activated sludge containing anaerobic ammonium oxidizing microorganisms, a technology for enriching anaerobic ammonium oxidizing microorganisms has been developed, and it is possible to retain a high concentration of anaerobic ammonium oxidizing microorganisms in a reaction tank for a long time. Was done.

However, when operating in the anaerobic ammonium oxidizing bacteria culture reactor immobilized on synthetic polymer (polyvinyl alcohol, PVA) for a long period of time, nitrogen gas generated in the beads was not properly discharged to the outside of the beads, resulting in a phenomenon in which the beads were expanded or destroyed.

In addition, the partial nitrite reaction used as a pretreatment concept in the nitrogen removal method using anaerobic ammonium oxidizing bacteria requires effective control of the dissolved oxygen concentration in the reaction tank, but the oxygen in the reaction tank is stably maintained due to changes in the activity of microorganisms and changes in the incoming water quality. In addition to being difficult to do, there is a problem in that it is difficult to maintain a high nitrite concentration.

Korean Patent Publication No. 2002-0072360 Korean Registered Patent Publication No. 1040518

In order to solve the above problems, an object of the present invention is to provide a partial nitrite oxidation method capable of maintaining a high nitrite nitrogen concentration in an aerobic tank so as to maximize the nitrogen removal effect by anaerobic ammonium oxidizing microorganisms.

In addition, an object of the present invention is to provide a method of manufacturing a carrier in which nitrifying microorganisms are immobilized.

The partial nitrite oxidation method using a carrier on which an autotrophic microorganism is immobilized according to the present invention for achieving the above object comprises: a coagulation sedimentation step of separating sludge and supernatant water after injecting a coagulant into sewage; And supplying the supernatant water to an aerobic tank including a carrier immobilized with nitrifying microorganisms and reacting for a predetermined time, wherein the nitrifying microorganisms of the carrier accommodated in the aerobic tank maintain higher activity of ammonium oxidizing microorganisms than nitrite oxidizing microorganisms. It is characterized.

In addition, in the partial nitridation method according to the present invention, the activity of the ammonium oxidizing microorganism is maintained higher than that of the nitrite oxidizing microorganism by exposing the carrier on which the nitrating microorganism is immobilized to a predetermined temperature for a predetermined time.

In addition, the predetermined temperature is preferably 55 ℃ to 65 ℃.

In addition, the predetermined time is preferably 15 minutes to 35 minutes.

In addition, it is preferable to maintain the dissolved oxygen in the aerobic tank at 2.0 mg/L to 3.0 mg/L.

In addition, in the partial nitridation method according to the present invention, the carrier on which the nitrifying microorganism is immobilized includes: preparing a PVA-alginate mixed solution in which PVA and alginate are mixed; Preparing a foaming-beading solution by mixing sludge containing nitrifying microorganisms and a foaming agent in the PVA-alginate mixed solution; And preparing a bead on which the sludge is immobilized by titrating the foaming-beading solution to a saturated boric acid solution containing calcium chloride.

In addition, the foaming agent is sodium hydrogen carbonate (NaHCO ₃ ), and the autotrophic microorganism is immobilized, characterized in that 0.3 to 1.2 parts by weight of sodium hydrogen carbonate (NaHCO _{3) in the foaming-beading solution is mixed with respect to 200 parts by weight of water.} It is preferable that it is a partial nitrite oxidation method using a prepared carrier.

According to the partial nitrite oxidation method using a carrier on which the autotrophic microorganisms are immobilized according to the present invention, there is an advantage in that the immobilization of ammonium oxidizing microorganisms is induced by controlling the content of the foaming agent in the carrier, and further, operation is possible without loss of the carrier for a long time.

Further, according to the partial nitrite oxidation method of the present invention, there is an advantage in that the concentration of nitrite nitrogen in the reaction tank can be maintained high by inducing the inhibition of the activity of oxidizing bacteria that oxidize nitrite to nitrate by exposing the carrier to a predetermined temperature.

1 is a graph of changes in dissolved oxygen depending on the depth of the carrier.
Figure 2 is a flow chart for explaining a method of manufacturing a carrier immobilized aerobic ammonium oxidizing microorganism of the present invention.
3 is an SEM photograph of the prepared beads.
4 is a result of the porosity of the prepared beads.
5 is a result of partial nitrite oxidation according to the amount of sodium hydrogen carbonate added.
6 is a result of partial nitrite oxidation according to the amount of sodium hydrogen carbonate added.
7 is a result of the activity of AOB and NOB according to the exposure temperature.
8 is a result of the activity of AOB and NOB according to the exposure time.
9 is a result of the activity of AOB and NOB according to the dissolved oxygen in the reaction tank.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

In the specification of the present invention, the oxidizing bacteria that oxidize ammonium to nitrite are referred to as AOB (ammonia oxidizing bacteria), and the oxidizing bacteria that oxidize nitrite to nitrate for partial nitrite are referred to as NOB (nitrite oxidizing bacteria).

The method for partial nitrite oxidation using a carrier immobilized with an autotrophic microorganism of the present invention comprises: a coagulation and precipitation step of separating into sludge and supernatant water after injecting a coagulant into sewage; And supplying the supernatant water to an aerobic tank including a carrier immobilized with nitrifying microorganisms and reacting for a predetermined time.

The partial nitrite oxidation method of the present invention including the above steps can be applied to a sewage treatment method including an oxygen-free reaction step, an aerobic reaction step, and a sludge transfer step after precipitation.

The coagulation sedimentation step is a step of injecting a coagulant after introducing sewage to be treated into a coagulation and sedimentation tank, and flocculating suspended substances, organic substances and phosphorus components contained in the sewage through rapid agitation and slow agitation. In the present invention, in order to minimize the supply of oxygen required for the growth of aerobic microorganisms and to minimize the inflow of organic matter that may inhibit the growth of anaerobic ammonium oxidizing microorganisms, the coagulation precipitation step is preceded.

Here, the coagulant may be a known coagulant such as iron salt-based or aluminum-based, but polyaluminumchloride (PAC) or polyaluminium chloride silicate (PACS), which can minimize the consumption of alkalinity, is used. desirable. These polyaluminum chloride or polysililicate aluminum are known coagulants, and their specific composition and manufacturing method will be omitted.

The supernatant obtained through the coagulation and precipitation step is supplied to an aerobic tank containing aerobic microorganisms (activated sludge) oxidizing organic matter and a carrier on which nitrifying microorganisms are immobilized and reacted for a predetermined time.

Specifically, in the aerobic tank, partial nitrite oxidation proceeds, and at the same time, organic matter contained in the supernatant is removed by aerobic microorganisms (activated sludge) that oxidize the organic matter. More specifically, the partial nitrite oxidation process is a step of oxidizing a part of ammonia nitrogen contained in the supernatant to nitrite nitrogen, and the reaction formula proceeds as shown in Equation (3) below.

(3)

(3)

In the partial nitrite oxidation step in the aerobic tank, it is preferable to oxidize about 50% of ammonia nitrogen in the supernatant in consideration of the growth and oxidation reaction of the anaerobic ammonium oxidizing microorganism located at the rear stage.

On the other hand, it is preferable that the nitrifying microorganism in the aerobic tank is immobilized on the carrier. As shown in Fig. 1, since dissolved oxygen decreases as it enters the carrier, even if the concentration of dissolved oxygen outside the carrier is out of the above range in the bulk state of the aerobic tank, it is required for partial nitrite oxidation inside the carrier on which the nitrifying bacteria are immobilized. possible to maintain a low dissolved oxygen concentration and, as a result of ammonium (NH ₄ ⁺⁾ and nitrous acid which is located at the rear end (NO ₂ ^-) and used as the substrate of the anaerobic ammonium oxidizing microorganisms in the anoxic tank to generate nitrogen (N ₂₎ You can maximize your activity.

The method for immobilizing the nitrifying microorganisms on the carrier as shown in FIG. 2 is a step of preparing a PVA-alginate mixed solution in which water, PVA and alginate are mixed, and sludge and hydrogen carbonate containing nitrifying microorganisms in the PVA-alginate mixed solution. Mixing sodium (NaHCO ₃ ) to prepare a foaming-beading solution, titrating the foaming-beading solution to a saturated boric acid solution containing calcium chloride to prepare sludge-immobilized beads, It may include the steps of immersing in a phosphoric acid solution to improve the mechanical strength of the beads and immersing the beads in distilled water to induce a swelling phenomenon of the beads.

To explain the above steps in more detail, first, a PVA-alginate mixed solution and sludge are prepared, respectively. The PVA-alginate mixed solution is a solution in which PVA (poly vinyl alcohol) and alginate are mixed in water, and a solution in which 10 to 20 parts by weight of PVA and 1 to 5 parts by weight of sodium alginate are mixed with respect to 100 parts by weight of water. Can be used. For uniform mixing of PVA and alginate, a process of dissolving the PVA-alginate mixed solution at 100° C. or higher for a certain period of time may be further performed.

The sludge refers to sludge containing nitrifying microorganisms, and it is preferable to use sludge of high concentration in order to improve the nitrous oxidation reaction, and sludge of high concentration can be prepared through gravity precipitation and centrifugation. In addition, it is possible to uniformize the size of microorganisms by filtering the sludge through a sieve of 100 to 1,000 μm.

Then, the PVA-alginate mixed solution and sludge are mixed. The PVA-alginate mixed solution and sludge may be mixed in a ratio of 1:0.8 to 1 by weight.

In a state in which the PVA-alginate mixture solution and sludge are mixed, more preferably, sodium hydrogen carbonate (NaHCO ₃ ) is additionally added to a blowing agent, and then mixed again. The sodium hydrogen carbonate (NaHCO ₃ ) is an inorganic blowing agent and is decomposed in an environment of pH 3-4 to generate _{carbon dioxide (CO 2 ). Carbon dioxide (CO 2} ) generated by the decomposition of sodium hydrogen carbonate (NaHCO ₃ ) serves to form pores in the beads during the bead formation process. In the following description, a mixed solution of PVA-alginate, sludge, and sodium hydrogen carbonate (NaHCO ₃ ) will be referred to as a “foaming-beading solution”. On the other hand, for the purpose of controlling the specific gravity of the beads, zeolite may be added and included in the foaming-beading solution.

In a state where the foaming-beading solution is prepared, the foaming-beading solution in a mucous state is titrated with a saturated boric acid (H ₃ BO _{3 ) solution containing calcium chloride (CaCl 2 ).} The calcium chloride (CaCl ₂ ) and saturated boric acid (H ₃ BO ₃ ) are crosslinking agents that make the foaming-beading solution into beads, and the calcium chloride serves as a crosslinking agent for alginate, and the saturated boric acid serves as a crosslinking agent for PVA. The saturated boric acid (H ₃ BO ₃ ) solution contains 0.5 to 1 parts by weight of calcium chloride (CaCl ₂ ) based on 100 parts by weight of water.

As the foaming-beading solution is titrated to a saturated boric acid (H ₃ BO _{3 ) solution containing calcium chloride (CaCl 2} ), PVA and alginate are crosslinked to form beads, and sludge is supported and immobilized in the beads.

In the process of forming such beads, sodium hydrogen carbonate (NaHCO ₃ ) contained in the foaming-beading solution is decomposed to generate carbon dioxide (CO _{2 ). Carbon dioxide (CO 2} ) generated by the decomposition of sodium hydrogen carbonate (NaHCO ₃ ) is discharged to the outside of the bead, and pores are formed inside the bead as _{carbon dioxide (CO 2} ) inside the bead is discharged to the outside of the bead.

Since the pores of the carrier formed through the above process act as a passage through which the bulk liquid, that is, the supernatant containing ammonia nitrogen, it is possible to keep the concentration of dissolved oxygen low inside the carrier.

In the foaming-beading solution, sodium hydrogen carbonate (NaHCO ₃ ) is preferably contained in an amount of 0.15 to 0.6 parts by weight, more preferably 0.15 to 0.3 parts by weight, based on 100 parts by weight of water. If the content of sodium hydrogen carbonate (NaHCO3) is less than 0.15 parts by weight, the diameter or porosity of the pores is too low to make it difficult for the bulk liquid to move to the inside of the beads. There may be a problem of spilling out of the carrier. In particular, when the concentration of dissolved oxygen in the bulk liquid is high, dissolved oxygen is kept high even inside the carrier, so that the nitrification reaction may proceed to the nitrification reaction.

Meanwhile, as described above, since sodium hydrogen carbonate (NaHCO ₃ ) is decomposed into carbon dioxide (CO ₂ ), the optimum pH is 3 to 4, so the saturated boric acid (H ₃ BO _{3 ) solution containing calcium chloride (CaCl 2} ) has a pH It should be adjusted to 3-4.

In the above, a method of forming pores in beads using sodium hydrogen carbonate (NaHCO ₃ ) has been described, but pores may also be formed using solid particles. That is, when the beads are completed in the state that the solid particles are included in the foam-beading solution, the solid particles are desorbed from the beads due to external physical impact of a certain strength as the solid particles do not form a chemical bond with PVA or alginate. This phenomenon occurs, and pores that spatially connect the inside and outside of the bead are formed in the area where the solid particles are detached. Here, the external physical impact of a certain strength may mean contact between the beads by the operation of the stirrer, or may mean an external physical impact to detach the solid particles from the beads.

The solid particles may be added to the foaming-beading solution, mixed, or premixed in a PVA-alginate mixed solution, and the solid particles are not particularly limited as long as they do not chemically react with PVA or alginate, but as an embodiment Activated carbon with a size of 10 μm to 1 mm or less can be used.

The beads made through the above processes may _{be immersed in a 0.5-1M phosphoric acid (KH 2} PO ₄ ) solution to further enhance the mechanical strength of the beads.

In addition, the prepared beads are washed 2-3 times with distilled water, and then immersed in distilled water to induce swelling, so that sodium hydrogen carbonate (NaHCO ₃ ) remaining in the beads and unreacted alginate are discharged to the outside of the beads. You can do more.

As described above, when the nitrifying microorganism is reacted in an aerobic tank containing a fixed carrier for a predetermined period of time, some of the ammonia nitrogen remains as it is, but some of the ammonia nitrogen is oxidized to nitrite nitrogen. This aerobic tank reaction solution is converted to nitrogen gas by being supplied to an oxygen-free tank in which anaerobic ammonium oxidizing microorganisms are immobilized on a carrier or floating (Equation 4).

(4)

(4)

Meanwhile, the present invention further includes maintaining high activity of ammonium oxidizing microorganisms, that is, AOB, so that a reaction in which ammonium is oxidized to nitrite can be performed relatively more than a reaction in which nitrite is oxidized to nitrate.

Specifically, the carrier on which the nitrifying microorganism is immobilized may be exposed under predetermined conditions, more specifically, 55°C to 65°C for 15 minutes to 35 minutes.

This is because when the exposure temperature is less than 55°C, the temperature is too low to lower the activity of NOB, and when it exceeds 65°C, AOB including NOB also loses its activity, making it difficult to expect sufficient nitrification.

In addition, if the exposure time is less than 15 minutes, the exposure time is too short to recover the activity of NOB quickly. On the contrary, if the exposure time exceeds 35 minutes, heating more than necessary is inefficient.

Hereinafter, the present invention will be described in more detail through experimental examples.

<Preparation example of carrier>

PVA-alginate mixture was prepared by mixing 15 g of PVA and 2 g of sodium alginate with 100 g of water, and then 2.0 g of nitrifying microorganisms (1.5 g to 2.5 g) and sludge containing 100 g of water were mixed in the PVA-alginate mixture solution. . Then, 0g, 0.3g, 0.60g, 1.2g, and 2.4g of sodium hydrogen carbonate (NaHCO ₃ ) were respectively added to the sludge-mixed PVA-alginate mixed solution to prepare a foam-beading solution. Then, each foam-beading solution was titrated with a saturated boric acid solution containing 0.5-1 g of calcium chloride based on 100 g of water to prepare beads, and the prepared beads were reacted with a 0.5 M phosphoric acid solution.

<Example 1>

FIG. 3 is a SEM photograph of the prepared beads, and as shown in FIG. 5, in the case of a bead in which sodium hydrogen carbonate (NaHCO3) is not added (0g), pores are almost formed compared to the bead in which sodium hydrogencarbonate (NaHCO3) is added. It can be confirmed that it is not. In addition, as the amount of sodium hydrogen carbonate (NaHCO ₃ ) is increased, the size of the pores increases, and this result is consistent with the porosity measurement result shown in FIG. 5. Referring to FIG. 4, _{it can be seen that as the amount of sodium hydrogen carbonate (NaHCO 3} ) is increased, the porosity is also increased.

<Example 2>

FIG. 5 shows a bead (0 g) to which sodium hydrogen carbonate (NaHCO3) was not added and a bead (0.3g, 0.6g, 1.2) with different input rates to confirm the partial nitrite oxidation rate according to the amount of sodium hydrogencarbonate (NaHCO3) added. g) was prepared and put into an aerobic tank for an experiment.

3.5 mg/L, BOD 120.2

23.8 mg/L, COD 105.2

10.2 mg/L 및 SS 147.1

52.9 mg/L 였다.At this time, the representative pollutant of raw water is ammonia nitrogen concentration of 26.4

3.5 mg/L, BOD 120.2

23.8 mg/L, COD 105.2

10.2 mg/L and SS 147.1

It was 52.9 mg/L.

As can be seen from the results of FIG. 5, in the case of using the beads to which sodium hydrogen carbonate (NaHCO3) is not added, it is necessary to maintain the dissolved oxygen concentration at about 6.0 mg/L in order to achieve a nitrite oxidation rate of about 50%. On the other hand, about 4.5 mg/L for beads injected with 0.3 g of sodium hydrogen carbonate (NaHCO3), about 4.0 mg/L for 0.6 g and about 2.0 mg/L for 1.2 g, and adding sodium hydrogen carbonate (NaHCO3) It can be seen that it is possible to achieve the same nitrous oxide rate even if the concentration of dissolved oxygen is kept low.

<Example 3>

6 is a result of loss of microorganisms in the carrier according to the amount of sodium hydrogen carbonate (NaHCO3) added.

The contents of water, PVA, alginate, and microorganisms used in the carrier preparation process were 200g, 15g, 2g and 2g, respectively, and the _{addition amount of the foaming agent (NaHCO 3} ) was changed to 0.6g, 1.2g, and 2.4g to prepare a carrier.

After the carrier prepared at the above mixing ratio was filled with distilled water, beads were collected at regular intervals with stirring, and microorganisms discharged to the outside of the carrier were measured.

As can be seen from the results of FIG. 6, _{when 0.6 g of sodium hydrogen carbonate (NaHCO 3} ) was injected, the lost microorganisms were about 1.1%, and when 1.2 g was injected, 5.4%, indicating that the microorganisms were stably fixed in the carrier. I can confirm. On the other hand, _{when 2.4 g of sodium hydrogen carbonate (NaHCO 3} ) was injected, it was confirmed that up to 16% of microorganisms were lost.

<Example 4>

3.5 mg/L, BOD 60.9

10.1 mg/L, COD 85.2

10.5 mg/L 및 SS 45.0

5.9 mg/L였다.In order to lower the activity of NOB, which is a nitrite oxidizing microorganism, the carrier of the aerobic tank in which the nitrification reaction is in progress (water, PVA, alginate and microorganism contents are 200g, 15g, 2g and 2g, respectively, and sodium hydrogencarbonate content is 0.6g) to 50 It was exposed for 30 minutes at different temperatures, such as °C, 60 °C and 70 °C, and the results are shown in FIG. 7. At this time, the dissolved oxygen in the reaction tank was adjusted to maintain 2.0 ~ 2.5 mg/L. In addition, each 300 mL of the carrier in the reaction tank was taken and exposed to 2L distilled water at 50±2°C, 60±2°C, and 70±2°C for 30 minutes. During the exposure process, a temperature controller was used to maintain the temperature range so as not to exceed the above temperature range, and then, 300 mL of a carrier having different exposure conditions were each filled in three 1,000 mL reactors, and then operated in a continuous reaction process in the form of a CSTR. In all continuous experiments, the water temperature in the reaction tank was maintained at 30℃±2℃ through a constant temperature device, and the influent was G sewage treatment plant influent, and the representative pollutant was ammonia nitrogen concentration 26.4.

3.5 mg/L, BOD 60.9

10.1 mg/L, COD 85.2

10.5 mg/L and SS 45.0

It was 5.9 mg/L.

As can be seen from FIG. 7, when exposed at 50±2° C. for 30 minutes, nitrate nitrogen was still high, so that the activity of NOB was not lowered. In the case of exposure at 70±2° C. for 30 minutes, not only nitrite nitrogen but also nitrate nitrogen is detected low, and it can be predicted that the activity of most nitrate oxidizing microorganisms is lowered.

On the other hand, in the case of exposure at 60±2° C. for 30 minutes, it can be seen that nitrite begins to accumulate after 12 days, and nitrite accumulates up to 18 mg/L in the reaction tank after 34 days of operation.

<Example 5>

For the same carrier as in Example 4, exposure times were differently exposed at a temperature of 60±2° C., such as 10 minutes, 20 minutes, and 30 minutes, and the results are shown in Fig. 8. At this time, the dissolved oxygen in the reaction tank is It was adjusted to maintain 2.0 ~ 2.5 mg/L.

As can be seen from FIG. 8, when exposed to 60±2° C. for 10 minutes, the activity of NOB is restored after about 10 days, and the accumulation of nitrate increases. On the other hand, when exposed to 60±2℃ for 20 minutes and 30 minutes, the activity of AOB is maintained, whereas the activity of NOB is maintained in a suppressed state, indicating that the nitrate concentration in the reaction tank is maintained at 2mg/L or less. have.

<Example 6>

After recovering the carrier to correspond to 40 v/v% from the aerobic reactor filled with the same carrier as in Example 4, it was exposed to a temperature of 60±2° C. for 20 minutes, and then supplied to the reactor again. At this time, the exposure interval was maintained once a day, and the dissolved oxygen in the reactor was set differently to 0.7 mg/L and 2.3 mg/L, and the operation was continued.

As can be seen from FIG. 9, it can be seen that it is possible to effectively suppress the accumulation of nitrate by maintaining the dissolved oxygen in the reaction tank at 2.0 mg/L or more.

As described above, although the present invention has been described by the limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those of ordinary skill in the art to which the present invention pertains. It goes without saying that various modifications and variations are possible within the equivalent range of the claims to be described.

Claims (8)

Coagulation sedimentation step of separating sludge and supernatant water after injecting a coagulant into sewage; And
Including the step of reacting for a predetermined time by supplying the supernatant water to an aerobic tank containing a carrier immobilized with nitrifying microorganisms,
In order to inhibit the activity of oxidizing bacteria (NOB) that oxidizes nitrite to nitrate and maintain the activity of oxidizing bacteria (AOB) that oxidizes ammonium to nitrite, the carrier on which the nitrifying microorganisms are immobilized is held at a water temperature of 60° C. for 20 minutes or more. Expose for 30 minutes,
Maintaining the dissolved oxygen in the aerobic tank at 2.0mg/L to 2.5mg/L,
The carrier on which the nitrifying microorganism is immobilized,
Preparing a PVA-alginate mixed solution in which PVA and alginate are mixed;
Preparing a foaming-beading solution by mixing sludge containing nitrifying microorganisms and a foaming agent in the PVA-alginate mixed solution; And
Partial nitrite oxidation method using a carrier immobilized with autotrophic microorganisms, characterized in that the foaming-beading solution is titrated with a saturated boric acid solution containing calcium chloride to prepare beads on which sludge is immobilized.
delete delete delete delete delete delete The method of claim 1,
The foaming agent is sodium hydrogen carbonate (NaHCO ₃ ), and the autotrophic microorganism is immobilized, characterized in that 0.3 to 1.2 parts by weight of sodium hydrogen carbonate (NaHCO _{3) in the foaming-beading solution is mixed with respect to 200 parts by weight of water.} Partial nitrite oxidation method using a carrier.

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