KR20010011876A - Method and Apparatus of Nitrogen Removal from the Recycle Water in the Sewage Treatment Plant - Google Patents

Abstract

PURPOSE: A removal method of nitrogen of recycled flow in the wastewater treatment plants is provided. According to this method, Recycled flow is divided into supernatant of digestion, thickener effluent and filtrate by characteristic. Mixture of filtrate and supernatant of digestion being more concentrated nitrogen and a ratio of C/N lower than thickener effluent is flowed into the first reservoir (10), and ammonia of mixture is nitrified in an aeration tank (30), and nitrite and nitrate are denitrified in the first anaerobic tank (40) by using carbon source of thickener effluent which flowed into the first anaerobic tank (40). CONSTITUTION: The method and apparatus comprise of a first and a second reservoir (10)(20) for controlling flow rate and alkalinity respectively, a first aeration tank (30), a first anaerobic tank (40), a second aeration tank (40) for nitrification ammonia of thickener effluent, a second anaerobic tank (60) for denitrification residual nitrate and nitrite, and a sedimentation tank (70). Optionally, residual nitrogen and phosphorous are removed by chemical treatment therein.

Description

Nitrogen removal method and apparatus of sewage treatment plant effluent {Method and Apparatus of Nitrogen Removal from the Recycle Water in the Sewage Treatment Plant}

The present invention relates to a nitrogen removal method for a high concentration of nitrogen-containing reflux water and a device thereof, and in particular, the reflux water can be classified into a digestive supernatant, a concentrated supernatant, and a desorption filtrate according to the properties to remove nitrogen according to its generation amount and concentration characteristics. The present invention relates to a method for removing nitrogen from sewage treatment plant and its apparatus.

In general, the biological sewage treatment plant in Korea discharges the influent after the various suspended solids are precipitated in the primary sedimentation basin 100 through the aeration tank 200 and the secondary sedimentation basin 300.

Sludge treatment of the sewage treatment plant as described above, as shown in Figure 1, the sludge digestion unit 400, or the concentration tank 510 and dehydrator 520 of the concentration tank 410, digestion tank 420 and dehydrator 430. Sludge extinguishing treatment unit 500 of) is optionally provided in series. At this time, the digestive supernatant, the concentrated supernatant and the desorption filtrate, or the concentrated supernatant and the desorption filtrate generated in each sludge treatment process are mixed once, and the water treatment system through the primary sedimentation basin 100 or the sedimentation basin in the whole sewage treatment process. Is returned.

The domestic sewage treatment plant according to the presence or absence of the installation of the digester 420, the digester 420 in the manner of concentrated-digestion-dehydration, as shown in Table 1 when the sewage treatment plant responded to the survey below 80% of the large-scale treatment plant is provided, the small-scale treatment plant without digestion tank 420 in the concentrated-dehydration method is distributed to 20%, which will be described in more detail as follows.

Classification of Domestic Sewage Treatment Plants by Sludge Treatment System Digestion Sludge Treatment Method Longevity ratio(%) No digester Enrichment, Dehydration, Marine Dumping One 2.56 Thickening-dehydration 6 15.38 Thickening-Storage-Dehydration One 2.56 sub Total 8 20.50 With digester Concentration-digestion-dehydration 28 71.82 Concentration-Storage-Digestion-Digestion Sludge Concentration-Dewatering One 2.56 Concentration-digestion-digestion sludge concentration-dehydration One 2.56 Concentration-digestion-storage-dehydration One 2.56 sub Total 31 79.50 Sum 39 100.00

(39 responses from 85 domestic sewage treatment plants sent to survey)

The sludge treatment method of the domestic sewage treatment plant can be classified into seven types according to a series of sludge treatment unit processes such as concentration, storage, digestion, dewatering and disposal. As the most.

In addition, in the sludge treatment method of the domestic sewage treatment plant, the discharge pattern of the return water varies according to whether the digester 420 is installed or not, the amount of inflow load increase due to the return water derived from the field survey, the questionnaire and the mass balance calculation 2, BOD 10%, SS 31%, TN 21%, TP 22% in the case of a large-scale treatment plant, BOD 10% in the case of a small treatment plant without the digester 420 , SS 20%, TN 11%, and TP 21%.

Due to its characteristics, the return water is discharged from the sludge treatment system which is not operated continuously but is operated intermittently and periodically (such as waste sludge disposal and dehydrator operation), so the maximum flow rate and concentration at the time of return water generation are compared to the sewage inflow load of the water treatment process. In some cases, the increase in load may be more than 100%.

Representative generation and water quality characteristics of the domestic sewage treatment plant return water generated in this way, as shown in Figure 3, will appear different depending on whether the digester 420 is installed. At this time, the influent sewage was assumed to be 104-113mg / L for BOD, 108-120mg / L for SS, 15-21mg / L for TN and 2.4-3.5mg / L for TP similar to the average water quality of domestic sewage.

However, despite the fact that the return water contains about 1 to 3% of the inflow flow, not only does it increase the inflow load by containing nitrogen (N) and organic matter, but also discharges it from the sludge treatment system that is operated intermittently without being operated continuously due to the generation characteristics. As a result, a shock load (shock load) due to a sudden inflow load has a problem that interferes with the normal nitrogen removal process.

In addition, the return water generated in each sludge treatment system discharges high concentration of ammonia nitrogen by short circuiting at impact load of sewage treatment plant, which not only deteriorates the water quality of nearby discharge water but also lowers the efficiency of initial settler. In order to increase the load of the subsequent process, there was also a problem of effluent from the primary sedimentation basin of higher concentration than the inflow source due to by-pass during rainfall.

In addition, since the soluble nitrogen cannot be removed by precipitation, an increase in the nitrogen load of a subsequent process due to the reflux water cannot be avoided without treating the nitrogen in the reflux water.

Therefore, to reduce the problems caused by the counterflow water, the method of reducing the counterflow water is used to improve the dewatering efficiency and the sludge concentration efficiency by the steam injection process, which will be described in more detail as follows.

First, a method of improving the sludge concentration and reducing the counterflow water is to inject a flocculant mixed with a cationic polymer into FeCl ₃ 18H ₂ O, or Al ₂ (SO ₄ ) ₃ 18H ₂ O in the concentration tank, Sludge uses 80 mg / L and 20 mg / L of polymer as Fe ⁺³ for primary sludge, and 50 mg / L and 10 mg / L as Fe ⁺³ for primary and secondary mixed sludge. I use it. At this time, the concentration time is 12 to 18 hours.

As shown in Table 2, as shown in Table 2, it can be seen that the concentration of SS and TP in the reflux water is reduced, as shown in Table 2 below.

Reflux concentration reduction effect by flocculant injection (Unit:%) Sludge SS NH ₄ ⁺ -N TP Mixed sludge 50.0 7.7 60.0 Secondary sludge 62.2 0.0 63.2

However, the method of reducing the water load by adding the flocculant as described above is not a fundamental prescription to prevent the increase of load due to the water and reduces the load so that the nitrogen concentration is relatively insignificant and the amount of sludge is reduced. There is a problem of increasing by 10.5-26.7%.

In addition, the method of reducing the load of the refluxed water not only increases the maintenance cost due to the chemical cost but also causes alkalinity to be consumed when the flocculant is used, which may adversely affect the process and cause secondary pollution.

On the other hand, the method of reducing the load of the return water by improving the dewatering efficiency by the steam injection uses a dehydration capacity evaluation method of WZS (Wedge Zone Simulator). At this time, the sludge to be tested is concentrated secondary sludge in the laboratory, concentrated mixed sludge, and sewage treatment plant sludge.

Item Thickened Secondary Sludge Concentrated mixed sludge Digestion Sludge Cake TS Concentration 107.9 109.1 106.8 Desorption amount 127.5 107.3 129.6 TS concentration of the desorption solution 78.4 93.3 77.1 NH ₄ ⁺ -N concentration of the desorption solution 119.2 116.7 111.1

As shown in Table 3, the method of treating the reflux water by improving the dehydration as described above, the water content of the digestion cake (CAKE): 75% to 73% was reduced, while the flow rate of the desorption liquid was about 30% In addition, the desorption ammonia nitrogen concentration had a problem of increasing about 17%.

In addition, the conventional method of reducing the load of the refluxed water is a method of simply reducing the load of the refluxed water as in the method of reducing the water discharge by the addition of the flocculant. There is a problem.

An object of the present invention is to solve the conventional problems as described above, in particular, to classify the reflux water into a digestive supernatant, a concentrated supernatant, and a desorption filtrate to remove nitrogen according to the amount and concentration characteristics thereof. The present invention provides a method and apparatus for removing nitrogen from sewage treatment plant.

In order to achieve the above object, the present invention provides a method for removing nitrogen from the sewage treatment plant and its apparatus for adjusting the desorption filtrate and digestive supernatant to the nitrogen concentration of the concentrated supernatant, and then inducing denitrification using its own organic matter in the concentrated supernatant. Characterized in that.

1 is a block diagram schematically showing a general sludge treatment system,

Figure 1A shows a large sewage treatment plant,

1B shows a small sewage treatment plant.

2 is a diagram schematically showing an increase in inflow load by a general return water,

2A shows a large sewage treatment plant,

2B shows a small sewage treatment plant.

Figure 3 shows the characteristics of the general return water,

3A shows a large sewage treatment plant,

3B shows a small sewage treatment plant.

4 is a block diagram schematically showing Embodiment 1 for removing nitrogen from sewage treatment plant effluent;

4A shows a large sewage treatment plant,

4B shows a small sewage treatment plant.

5 is a block diagram schematically showing a second embodiment for removing nitrogen from the sewage treatment plant effluent;

5A shows a large sewage treatment plant,

5B shows a small sewage treatment plant.

6 is a block diagram schematically showing a third embodiment for removing nitrogen from the sewage treatment plant effluent;

6A shows a large sewage treatment plant,

6B shows a small sewage treatment plant.

7 is a graph showing the inhibition (inhibition) to nitrification of the present invention,

Figure 7A shows the measurement results at 20 ℃,

7A shows the measurement results at 35 ° C.

Figure 8 is a graph showing the nitrogen behavior according to the SRT of the first aerobic oxidation tank of the present invention.

9 is a graph showing the nitrite oxidation rate according to the SRT change at 20 ℃ and 35 ℃.

<Explanation of symbols for main parts of drawing>

10: first storage tank 20: second storage tank

30,90: First aerobic reactor 40: First anoxic reactor

50: second aerobic reactor 60: second anoxic reactor

70: sedimentation tank

Hereinafter, with reference to the drawings according to the technical idea of the nitrogen removal method of the present invention sewage treatment plant and the apparatus configured as described above in detail as follows. 1 is a block diagram schematically showing a general sludge treatment system, FIG. 2 schematically shows an increase in inflow load due to a general return water, and FIG. 3 shows characteristics of a general return water, and FIGS. 4, 5 and 6 is a block diagram schematically showing Examples 1, 2 and 3 for nitrogen removal of sewage treatment plant, Figure 7 is a graph showing the inhibition (inhibition) to nitrification of the present invention, Figure 8 is the present invention Figure 1 is a graph showing the nitrogen behavior according to the SRT of the first aerobic oxidation tank, Figure 9 is a graph showing the nitrite oxidation rate according to the SRT changes at 20 ℃ and 35 ℃.

In the sewage treatment plant to which the present invention is applied, the concentration tanks 410 and 510, the digestion tank 420, and the dehydrator 430 and 520 are selectively provided in series to generate a desorption filtrate, a digestive supernatant, and a concentrated supernatant, respectively.

In the sewage treatment plant, the present invention provides first and second storage tanks (10, 20) for separately storing the desorption filtrate, the mixture of the desorption filtrate and the digestive supernatant, and the concentrated supernatant to adjust the load of the inflow amount and to adequately supplement the alkalinity. And a first aerobic reaction tank (30) for nitridizing the digestive supernatant and the desorption filtrate uniformly introduced by the first storage tank (10) to the nitrogen concentration of the concentrated supernatant, and the nitrous oxidation in the first aerobic reaction tank (30). Decomposition of organic matter using the first anoxic reaction tank 40 for denitrifying the influent using the own carbon source of the concentrated supernatant stored in the second storage tank 20 and the self carbon source of the concentrated supernatant in the first anoxic reaction tank 40 The second aerobic reaction for nitriding ammonia nitrogen not contained in the first aerobic reactor 30 as well as ammonia nitrogen contained in the concentrated supernatant. And a second anoxic reactor 60 for denitrifying the nitrous oxide influent by the external carbon source selectively administered in the second aerobic reactor 50, in the second anoxic reactor 60. Selective chemical treatment of the denitrified raw water is provided with a settling tank 70 for precipitating and removing some unremoved particulate nitrogen as well as phosphorus.

In addition, the present invention, the first and second storage tanks (10, 20) and the storage of the defoliation filtrate or the mixture and the concentrated supernatant of the digestive filtrate separately to adjust the load of the inflow amount and supplement the alkalinity appropriately, and the First aerobic reactor (30) for nitridizing the digestive supernatant and desorption filtrate constantly introduced into the first storage tank (10) to the nitrogen concentration of the concentrated supernatant, and the first aerobic nitrified in the first aerobic reactor (30) It is composed of a second aerobic reaction tank (50) for nitridizing the effluent of the reaction tank 30 with the concentrated supernatant stored in the second storage tank 20, the second aerobic nitrified in the second aerobic reactor (50) Selective chemical treatment of the effluent of the reaction tank 50 is provided with a precipitation tank 70 for precipitating and removing not only phosphorus but also some unremoved particulate nitrogen.

In addition, the present invention is the storage tank 80 and the storage tank 80 to adjust the load of the inflow amount and to adequately supplement the alkalinity by storing the deglyfil filtrate, or the mixed liquid and the concentrated supernatant of the digestion filtrate and the digestive supernatant together, and the storage tank 80 Consisting of the first aerobic reactor 90 to nitrate the concentrated supernatant, digestive supernatant and de-filtrating filtrate, which is constantly introduced, the inlet water nitridated in the first aerobic reactor 90 selectively chemically treated as well as phosphorus A settling tank 70 for precipitating and removing unremoved particulate nitrogen is provided.

In addition, the present invention is a portion of the effluent through the first and second aerobic reactors (30, 50, 90) to improve the nitrous oxidation efficiency of the water treatment process with the secondary sludge of the sewage treatment plant using the existing sludge returning facility It is returned to a separate aeration tank to supply nitrifying microorganisms.

In addition, the present invention operates hydraulic retention time (HRT) and sludge retention time (SRT) in the same manner, so that a separate transport facility is not required, thereby simplifying operation.

In the present invention, the sludge residence time (SRT) is 12 hours to 10 days.

In addition, the present invention is characterized by nitrous oxidation of a stripping filtrate containing a higher concentration of nitrogen than a concentrated supernatant and having a lower ratio of SCOD / NH ₄ ⁺ -N than a concentrated supernatant, or a mixed solution of a digestive supernatant and a stripping filtrate in an aerobic state. Denitrification using the carbon source of the concentrated supernatant introduced in the anoxic state, and the external carbon source in the anoxic state by nitriding not only the ammonia nitrogen of the concentrated supernatant from which organic matter decomposition occurred, but also the ammonia nitrogen not removed in the aerobic state. Denitrification by using, it will be described in more detail as follows.

After denitrification by the external carbon source, chemical precipitation is selectively performed to remove phosphorus as needed, and the effluent is discharged or returned to a sedimentation basin or primary sedimentation basin depending on the water quality.

Next will be described in more detail with reference to the embodiment of the present invention configured as described above. These examples are intended to illustrate the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not limited to these examples.

The abbreviation used in the present invention is as follows.

HRT: Hydraulic Retention time

BOD: Biological Oxygen Demand Biochemical Oxygen Demand

COD: Chemical Oxygen Demand

SS: Suspended Solid Suspended

TN: Total Nitrogen Total Nitrogen

TP: Total Phosphorus

FA: Free Ammonia Free Ammonia

FNA: Free Nitrous Acid

MLSS: Mixed Liquor Suspended Solid Activated Sludge Concentration

SDNR: Specific Denitrification Rate

SNR: Specific Nitrification Rate Specific Nitrification Rate

AUR: Ammonium Uptake Rate Ammonia Removal Rate

Figure 4 is a schematic diagram of a device for implementing the nitrogen removal method of the sewage treatment plant according to the present invention, 10 is the primary sedimentation basin, 20 is the secondary sedimentation basin, 30 and 90 is the first aerobic reactor, 40 is the first 1 anoxic reactor, 50 is a 2nd aerobic reactor, 60 is a 2nd oxygen-free reactor, and 70 is a precipitation tank.

First, the return water generated in the sludge treatment process of domestic sewage treatment plant will be described in detail as follows.

The increase in load due to the return water generated in the domestic sewage treatment plant is 50% to 75% of the inflow load increase in the large sewage treatment plant due to the digestion supernatant and the desorption filtrate. The increase in inflow load by the return water is about 75% of the increase in inflow load by the total return water. In other words, digestion and desorption liquids, which account for only 18% and 25% of the total amount of wreak water, account for about 75% of the total inflow load. 25% of the time. In this case, it can be seen that the concentrated supernatant has a relatively high SCOD / NH ₄ ⁺ -N ratio compared to the digestive supernatant and the desorption liquid.

On the other hand, in the case of the small-scale treatment plant without the digester 42, the concentrated supernatant having a large amount of generation takes up a considerable portion of the total inflow load increase due to the return water. In this case, the concentrated supernatant SCOD / NH4 ₊ ^- N non relatively high compared to the digestion supernatant and talriaek as in the large-scale sewage treatment plant.

Characteristics of effluent sources division flux BOD SS TN TP Thickener 0.68 53 to 2,320 347-12,300 72-446 27-115 Digester 0.22 240-1,010 525-23,000 280-958 134-207 dehydration 0.14 to 0.3 61-368 58-1,480 388-541 95-115 mix 1.04 to 1.2 89-1780 308-13,107 189-567 64 to 134

Example 1:

The first and second storage tanks 10 and 20 respectively store the stripping filtrate or the mixture of the stripping filtrate and the digestive supernatant and the concentrated supernatant separately to adjust the load of the inflow and settle and remove the suspended solids. At this time, the first storage tank 10 is lower than 7.14 required for nitrous oxidation due to the high concentration of the nitrate nitrogen flows in the inflow of the de-filtrate, or the desorbed filtrate and digestive supernatant, Alkalinity / The alkalinity is replenished by administering NaOH or NaHCO ₃ to control the NH ₄ ⁺ -N ratio to achieve proper nitrous oxidation.

In addition, the first aerobic reaction tank 30 causes the denitration filtrate, or the leaving filtrate and the digestive supernatant introduced from the first storage tank 10 to the nitrogen concentration of the concentrated supernatant to cause nitrous oxidation of ammonia nitrogen and decomposition of high concentration organic matter. to ammonia removal rate in the experiment with the water wake digestion supernatant of the sewage treatment plant is (AUR: ammonium uptake rate) value of each hour at 35 ℃ and ^{_{20 ℃ 9.3-16.3mgNH 4 + -N / L}} , 3.6-4.0mgNH 4 ⁺ -N / L. In addition, specific nitrification rate (SNR) was 1.9-20.3mgNH ₄ -N / gMv, 0.6mgNH ₄ -N / gMv per hour at 35 ℃ and 20 ℃, respectively. Consumption was similar for both 35 ℃ and 20 ℃ and averaged as 6.6mgAlkalinity / mgNH ₄ ⁺ -N.

In addition, the first anoxic reactor 40 denitrates nitrogen nitrated with nitrite nitrogen in the first aerobic reactor 30 using its own carbon source of the concentrated supernatant introduced from the second storage tank 20. At this time, the specific denitrification rate (SDNR) value was 3.35mgNO ₂ ^-- N / gMv and 2.37mgNO ₂ ^-- N / gMv per hour at 35 ℃ and 20 ℃, respectively. .

In addition, in the second aerobic reactor 50, the ammonia nitrogen contained in the concentrated supernatant in which organic matter decomposition occurred using the carbon source in the first anoxic reactor 40 and ammonia nitrogen not removed in the first aerobic reactor 30 Is oxidized with nitrous nitrogen. At this time, if necessary, the media may be selectively added to maintain stable nitrous oxidation. In general, when the media (media) can help the growth of slow growth microorganisms, various microbial species are clustered to be excellent in the ability to cope with temperature, pH fluctuations and impact loads and inflow of hardly decomposable substances. The use of media can be selectively determined according to the raw water to be processed and the operating conditions.

In addition, the second anoxic reactor 60 denitrates the nitrogen oxidized in the second aerobic reactor 50 using an external carbon source. The alkalinity recovery of denitrification was 3.16mgAlkalinity / mgNO ₂ ^-- N and 2.91mgAlkalinity / mgNO ₂ ^-- N at 35 ℃ and 20 ℃, respectively.

In addition, the sedimentation tank 70 is a main factor of the deterioration of phosphorus (phosphate) in addition to nitrogen, and selectively injects a chemical (Alum, Ferric Chloride, etc.) to remove it, precipitates the phosphorus and some unremoved particulate nitrogen, Remove it.

In the present invention, as a result of the study on the factors that induce nitrite oxidation, the biggest factor inducing nitrite oxidation to nitrite is Nitrobacter (NH ₃ ) due to the inhibition of nitrobacter (NH ₃ ) to free ammonia (NH ₃ ) This is because nitrification to ₃ ^-- N is suppressed and nitrous nitrogen (NO ₂ ^-- N) is accumulated. Therefore, by appropriately adjusting the SRT (or HRT) according to each temperature, it is possible to prevent Nitrobacter from complying with FA and induce stable nitrite oxidation. Therefore, in the case of the present method it can be applied not only 35 ℃ but also 20 ℃.

In the following, inhibition by FA causing nitrous oxidation and details thereof are described in more detail in the specification of the invention filed as the same as the present invention.

Figure 7 shows the experimental values of the laboratory in the graph proposed by Athonisen in 1976 to explain the inhibition on nitrification. As shown in the experimental results of the present invention, as shown in Figure 3, most appear in the region 2, FA causes the inhibition of Nitrobacter activity to accumulate nitrite nitrogen (NO ₂ ^-- N). In other words, the FA is an important factor for inducing nitrification by causing inhibition in Nitrobacter. In this case, region 1 represents inhibition against Nitrobacter and Nitrosomonas, region 2 represents inhibition to Nitrobacter, region 3 represents complete nitrification, and region 4 represents inhibition to Nitrobacter by FNA.

First, as a result of experiment of the digester supernatant at 35 ℃, the effect on the SRT in the inhibition of nitrous oxidation by FA is as follows. If the SRT is longer, as shown in FIG. 8, complete nitrification, not nitrification, occurs, in particular, optimal nitridation was observed in 2 to 4 days, and total nitrification was more than 6 to 8 days. Proceeded to. In this case, as shown in FIG. 9, the SRT which is completely nitrified instead of nitrous oxide is changed according to the temperature of the study, so that the SRT according to the temperature as well as the inhibition by FA in the present process using the biological nitrous oxide reaction. Control is an important process factor.

Example 2:

The return water flowing in accordance with the generation and concentration characteristics is nitridized in the first and second aerobic oxidation tanks 30 and 50. That is, in a large-scale sewage treatment plant, the digestive supernatant and the high-density filtrate having high concentration are nitridized to the nitrogen concentration of the concentrated supernatant in the first aerobic reaction tank 30 and concentrated again in the second aerobic reactor 50. Nitrify with supernatant. In the small sewage treatment plant, only the desorption filtrate is introduced into the first aerobic reaction tank 30, and the effluent is returned to the water treatment process (sedimentation basin or primary sedimentation basin) as returned water of the existing sewage treatment plant is returned. As shown in the calculation of the application example described below, if the BOD in the sewage treatment plant inflow sewage is 100 mg / L, the amount of BOD in the primary sedimentation basin is 1000 kg / d, which is sufficient to denitrate all the leachate after the nitrite oxidation.

In addition, the sedimentation tank 70 is a main factor of the deterioration of phosphorus (phosphate) in addition to nitrogen, and selectively injects a chemical (Alum, Ferric Chloride, etc.) to remove it, precipitates the phosphorus and some unremoved particulate nitrogen, Remove it.

Example 3:

The sludge treatment method stores the digested supernatant, desorption filtrate and concentrated supernatant of the relatively large sewage treatment plant consisting of concentrated-digestion-dehydration process together in the storage tank 80 and then nitrousizes in the first aerobic reactor 90 or sludge treatment. Only the desorption filtrate and the concentrated supernatant of the small-scale sewage treatment plant consisting of a concentration-dehydration process are stored in the storage tank 80, and then nitrite oxidation in the first aerobic reaction tank 90. The effluent is returned to the water treatment process (sedimentation or primary sedimentation basin) just as the return water from existing sewage treatment plants is returned. This is a suitable process when only a single reactor is required for the treatment of countercurrent due to the sewage treatment plant conditions.

In addition, the sedimentation tank 70 is a main factor of the deterioration of phosphorus (phosphate) in addition to nitrogen, and selectively injects a chemical (Alum, Ferric Chloride, etc.) to remove it, precipitates the phosphorus and some unremoved particulate nitrogen, Remove it.

Example 4:

In order to improve the nitrous oxidation efficiency of the water treatment process, a portion of the effluents passed through the first and second aerobic reactors 30, 50, and 90 of Examples 1 to 3 was discharged from the sewage treatment plant using the existing sludge return facility. It is also possible to improve the sewage treatment plant water treatment system so that nitrification is possible even in winter by supplying nitrification microorganisms by returning the sludge to the aeration tank.

Although the process of Examples 1 to 4 uses nitrous oxide as the main means, it can be driven even if complete nitrification occurs depending on the influent.

The following shows the design parameters of each reactor based on the experimental results.

1. Influent condition

The inlet flow rate of the sewage treatment plant 10,000m ³ / d, in which the mixed flow inlet of the inlet flow 120m ³ / d digestion supernatant and filtrate tally of the total number of wake 52m ³ / d, and the inlet flow rate of the concentrated supernatant 68m ³ / d. In this case, BOD, SS, TN, and NH ₄ ⁺ -N of the mixed solution and the concentrated supernatant of the digestive supernatant and the elimination filtrate are respectively as follows.

Sewage treatment plant inflow: 10,000m ³ / d

Digestive Supernatant + Tally Filtrate: 10,000m ³ / d × 0.0052 = 52m ³ / d

Concentrated Supernatant Flow: 10,000m ³ / d × 0.0068 = 68m ³ / d

Total return water inflow: 120m ³ / d

Digestive Supernatant + Tally Filtrate Influx BOD: 1,120mg / L

Inflow SS: 4,050mg / L (VSS / TSS = 0.5)

Influx TN: 550mg / L

Inlet NH ₄ ⁺ -N: 440 mg / L

Inflow TP: 110mg / L

Concentrated supernatant inlet BOD: 860mg / L

Inflow SS: 1830 mg / L (VSS / TSS = 0.6)

Inflow TN: 150mg / L

Inflow NH ₄ ⁺ -N: 115 mg / L

Inflow TP: 30mg / L

2. First aerobic reactor

Digestive supernatant 0.43Q (52m ³ / d) is introduced at the total influent flow rate of 120m ³ / d, and the BOD: N: P ratio is 100: 5: 1 in cell synthesis, so the inlet BOD amount is 1120 at the concentration of nitrogen. 56 mg / L, and the phosphorus concentration is 11.2 mg / L. Therefore, pure nitrification target nitrogen is 20 kg.

Fire extinguishing fluid 0.43Q inflow (52m ³ / d)

Cell Synthesis BOD: N: P = 100: 5: 1 = 1120: N: P

N synthesis = 56 mg / L, P synthesis = 11.2 mg / L

Nitrification Target N = (440-56) = 384mg / L ⇒384mg / L * 52m ³ = 20kg

HRT = 4day ⇒ (208m ³ )

NH ₄ -N _eff = 384 mg / L * 20% = 77 mg / L

3. First anoxic reactor

The pure denitrification target nitrogen is the total amount of reflux inflow of 120 m ³ / d of 0.43Q (52m ³ ) of digestive supernatant introduced through the first aerobic reactor and 0.57Q (68m ³ ) of concentrated supernatant flowing from the second storage tank 20. 16 kg.

0.57Q (68m ³⁾ and concentrated supernatant + 0.43Q (52m ³⁾ the aerobic reactor effluent = 120m ³ flows

Nitrogen to be denitrated = (384-77) = 307mg / L ⇒ 307mg / L * 52m ³ = 16kg

(16kg / 120m3 = 133mg / L)

HRT = 0.6day⇒ 1day (V = 120m ³ )

Inflow BOD = 860mg / L * 68m ³ = 59kg BOD

(Assuming no BOD can be used for denitrification in the effluent of the first aerobic reactor)

NH ₄ -N _eff = = 99mg / L

BOD _eff = = 225 mg / L

4. The second aerobic reactor

HRT = 1.03day ⇒ 1 day (V = 120m ³ )

NH ₄ -N _eff = 99 * 10% = 9.9 mg / L

5. Second anoxic reactor

Nitrogen to be denitrated = (100-10) = 90mg / L ⇒ 90mg / L * 120m ³ = 10.8kg

HRT = 0.3day⇒ 0.4day (V = 48m ³ )

6. Precipitation Tank

Selective administration of Alum, Ferric Chloride, etc. to the reactor or the flow path of the reactor is carried out to precipitate and remove some of the unremoved nitrogen as well as phosphorus.

Cell synthesis amount = 9.8 mg / L

Sedimentation target = 64-9.8 = 54.2mg / L ⇒ 54.2mg / L * 120m3 = 6.5kg

Chemical requirement = 0.35kgFe ³⁺ / kgP _removed * 6.5kgP = 2.285kg Fe ³⁺

HRT = 6 hours

7. Final discharge water quality

The concentration of the treated water discharged from the settling tank 70 is shown as follows.

BOD _eff = 100mg / L or less

TN _eff = 30 mg / L

TP _eff = 4 or less

SS _eff = 100 or less

Total residence time = storage tank (1 day) + first oxidation tank (1.75 days) + denitrification tank (1 day) + second oxidation tank (1 day) + denitrification tank (0.4 days) + precipitation (0.25 days) = 5.4 days

Therefore, the nitrite oxidation rate and the BOD removal rate of the large-scale sewage treatment plant of concentrated-digestion-dehydration are 70-90% and 60-90%, respectively, through the reverse water treatment process as described above. The nitrite oxidation rate and BOD removal rate can be obtained from 50 to 70% and from 50 to 80%.

As described above, the method and apparatus for removing nitrogen from sewage treatment plant of the present invention are selectively separated and treated by appropriately using the generation and concentration characteristics of the concentrated supernatant, the digestive supernatant and the desorption filtrate constituting the sewage treatment plant. In addition to stable water treatment of the countercurrent, there is an effect to improve the treatment efficiency.

In addition, the present invention is to prevent the increase of load due to the return of the water ultimately has the effect of improving the expansion effect of the existing treatment plant.

In addition, the present invention will not only reduce the influence of the water treatment system by the return water, but also improve the nitrogen removal capacity of the sewage treatment plant in winter.

Claims (8)

In the sewage treatment plant in which the tally filtrate, the digestive supernatant and the concentrated supernatant are generated, Denitrification filtrate containing a higher concentration of nitrogen than the concentrated supernatant and having a lower SCOD / NH ₄ ⁺ -N ratio than the concentrated supernatant, or a mixture of digestive supernatant and the denitrified filtrate, was nitred to the nitrogen concentration of the concentrated supernatant in an aerobic state and introduced in anoxic state Denitrification by using the carbon source of the concentrated supernatant, which is denitrified by the ammonia nitrogen not removed in the aerobic state as well as ammonia nitrogen of the concentrated supernatant in which organic matter decomposition has occurred, and denitrification using an external carbon source in anoxic state. Nitrogen removal method of the sewage treatment plant characterized in that. The method of claim 1, After denitrification by the external carbon source, selectively settling the chemical so as to remove the phosphorus if necessary, and the effluent is discharged according to the water quality, or sewage, characterized in that returned to the sedimentation basin or primary sedimentation basin of the sewage treatment plant Nitrogen removal from treatment plant return water. In the sewage treatment plant in which the concentration tanks 410, 510, the digestion tank 420, and the dehydrator 430, 520 are selectively provided in series to generate a desorption filtrate, a digestive supernatant and a concentrated supernatant, respectively, First and second storage tanks (10, 20) for separately storing the desorption filtrate, the mixture of the desorption filtrate and the digestive supernatant, and the concentrated supernatant to adjust the load of the inflow amount and to adequately supplement the alkalinity; A first aerobic reactor (30) for nitrous oxidation of the digestive supernatant and the desorption filtrate uniformly introduced by the first storage tank (10) to the nitrogen concentration of the concentrated supernatant; A first anoxic reactor 40 for denitrifying the influent water nitridated in the first aerobic reactor 30 using its own carbon source of the concentrated supernatant stored in the second reservoir 20; An agent for nitridizing ammonia nitrogen not removed in the first aerobic reactor 30 as well as ammonia nitrogen contained in the concentrated supernatant in which organic matter decomposition occurs using the self-carbon source of the concentrated supernatant in the first anoxic reactor 40. An aerobic reactor (50); Nitrogen removal apparatus for sewage treatment plant return water, characterized in that it comprises a second anoxic reaction tank (60) for denitrifying by the external carbon source to be selectively administered nitrous oxide inlet water in the second aerobic reactor (50). In the sewage treatment plant in which the concentration tanks 410, 510, the digestion tank 420, and the dehydrator 430, 520 are selectively provided in series to generate a desorption filtrate, a digestive supernatant and a concentrated supernatant, respectively, First and second storage tanks (10, 20) for separately storing the desorption filtrate, the mixture of the desorption filtrate and the digestive supernatant, and the concentrated supernatant to adjust the load of the inflow amount and to adequately supplement the alkalinity; A first aerobic reactor (30) for nitrous oxidation of the digestive supernatant and the desorption filtrate uniformly introduced by the first storage tank (10) to the nitrogen concentration of the concentrated supernatant; And a second aerobic reactor (50) for denitrifying the influent water nitridated in the first aerobic reactor (30) using its own carbon source of the concentrated supernatant stored in the second reservoir (20). Nitrogen removal device of sewage treatment plant. In the sewage treatment plant in which the concentration tanks 410, 510, the digestion tank 420, and the dehydrator 430, 520 are selectively provided in series to generate a desorption filtrate, a digestive supernatant and a concentrated supernatant, respectively, A storage tank 80 for storing the desorption filtrate, or the desorption filtrate, the digestive supernatant and the concentrated supernatant together to adjust the load of the inflow amount and to adequately supplement the alkalinity; Nitrogen removal apparatus for sewage treatment plant semi-reduced water, characterized in that it comprises a first aerobic reaction tank (90) for nitridizing the concentrated supernatant, digestive supernatant and desorption filtrate constantly introduced by the storage tank (80). The method according to claim 3 to 5, Part of the effluent from the first and second aerobic reactors (30, 50, 90) is returned to a separate aeration tank along with the secondary sludge in the sewage treatment plant to improve the nitrous oxidation efficiency of the water treatment process. Nitrogen removal device of sewage treatment plant, characterized in that to supply nitrifying microorganisms. The method according to claim 3 to 5, A nitrogen removal apparatus for sewage treatment plant return water, characterized in that a sedimentation tank (70) is provided for selectively removing chemically treating influent water which is nitridated, as well as phosphorus as well as some unremoved particulate nitrogen. The method according to claim 3 to 5, A nitrogen removal apparatus for sewage treatment returning water, characterized in that the hydraulic retention time (HRT) is set to be equal to the sludge residence time (SRT) with 12 hours to 10 days depending on the influent.