KR20110027457A - Method for treating wastewater using nitrification reaction in sequencing batch reactor - Google Patents

Abstract

PURPOSE: A wastewater treatment method using the wastewater nitrification method inside a continuous batch reactor is provided to reduce the carbon source cost and required energy for nitrifying ammonia into nitric acid. CONSTITUTION: A wastewater treatment method using the wastewater nitrification method inside a continuous batch reactor comprises the following steps: oxidizing ammonia nitrogen inside waste water using an inhibition action of a nitrite oxidizer; and controlling the pH inside the continuous batch reactor into 7~8, until the reaction metaphase of a nitrification process, to induce the inhibition of the nitrite oxidizer by free ammonia.

Description

Method for Treating Wastewater Using Nitrification Reaction in Sequencing Batch Reactor

The present invention relates to a wastewater treatment method using wastewater nitrification in a continuous batch reactor. More particularly, in the wastewater nitrification in a continuous batch reactor, nitrous acid produced by oxidation of the ammonia is not finally oxidized to nitric acid. In order to be denitrified in the state of nitrous acid, by adjusting the pH to inhibit the activity of the nitrite oxidizing bacteria by ammonia or nitrous acid, the waste water nitrification reaction in a continuous batch reactor, characterized in that oxidizing ammonia nitrogen to nitrite only It relates to a wastewater treatment method.

Much research and technology development has been attempted for efficient nitrogen removal of waste water. The background of such research and technology development is the premise that the effect of nitrogen on the global circulation, in addition to the bad environmental effects of nitrogen on the water system. Existing nitrification and denitrification processes for this circulation require a considerable amount of energy and organic compounds. Taking the balance of materials as a whole, globally, 3.73 kg of CO ₂ is generated in 1 kg of nitrogen cycle. Accumulation of global warming gases, CO ₂ , is inevitable. Therefore, attention and research are currently focused on more environmentally friendly or sustainable nitrogen removal method as an alternative to the conventional nitrogen removal method.

Specifically, this is a new microbial metabolism or process development that can reduce the energy required to give up in nitrification and reduce the amount of organic matter required in the denitrification process, in particular the nitrogen removal process through the new nitrogen conversion by microorganisms and Together, the research focuses on the development, deployment and combination of new reactors.

Most of the nitrogen in the waste water is in the form of ammonia (NH ₃ ), which requires a continuous process of nitrification and denitrification.

Ammonia oxidation
(Ammonia oxidizing bacteria)

350 kJ(2)NH ₄ ⁺ + 0.5 O ₂ → NH ₂ OH + H ⁺ (1)
_{NH 2 OH + O 2 → NO} 2 - + H 2 O + H + + 240

350 kJ (2) Nitrite oxidation
(Nitrite oxidizing bacteria) ^{_{NO 2 - + 0.5O 2 → NO}} 3 - + 65

90 kJ (3) Overall Nitrification ^{_{NH 4 + + 2O 2 → NO}} 3 - + H 2 O + 2H + (4)

The nitrification reaction of Table 1 shows that 1 mol of ammonia (NH ₃ ) is oxidized and 2 mol of oxygen (O ₂ ) is consumed to produce 2 mol of hydrogen ions (H ⁺ ). In terms of mass, it can be seen that 4.57 g of oxygen is required to oxidize 1 g of ammoniacal nitrogen. When oxidizing ammonia (NH ₃ ) to nitrous acid only, 1.5 mol of oxygen per 1 mol of ammonia (NH ₃ ) is required, and oxygen required (O ₂ ) is about 25 compared to oxidizing to nitrate. Decrease by% On the other hand, in case of denitrification, an electron donor is required, which is shown in Table 2 below.

Nitrite denitrification ^{_{6NO 2 - + 3CH 3 OH →}} 3N 2 + 3CO 2 + 3H 2 O + 6OH - (5) Nitrate denitrification ^{_{6NO 3 - + 5CH 3 OH →}} 3N2 + 5CO 2 + 7H 2 O + 6OH - (6)

In the denitrification reaction, 6 mol of nitrate nitrogen is reduced to nitrogen (N ₂ ) gas, and a total of 5 mol of CH ₃ OH is required, while 6 mol of nitrite nitrogen is reduced to nitrogen (N ₂ ) gas only. It can be seen that 3 mol of CH ₃ OH is required. In other words, nitrifying and denitrifying only ammonia nitrogen to nitrite nitrogen can reduce 2 mol of CH ₃ OH (40% of the total amount).

Meanwhile, as shown in FIG. 1, the removal of nitrogen through the nitrite pathway is referred to as a Sharon (single reactor system for high-rate ammonium removal over nitrite) process, which is a technique for oxidizing ammonia nitrogen to nitrite nitrogen and immediately denitrifying it. This term has the advantage of reducing oxygen and organic carbon required for nitrogen removal (EP 826,639). In order to achieve this, a method of increasing the temperature of the reactor to 25 to 40 ° C. and continuously operating it without sludge conveyance by the sedimentation basin is used to remove nitrite oxidizing bacteria having low specific growth rate from the reactor at high temperature. In this case, only ammonia oxides are distributed in the reactor without nitrite oxides, so that nitrous acid accumulates naturally. That is, the Sharon process uses nitrite oxidizing bacteria at a low specific growth rate at a high temperature, and excludes nitrite oxidizing bacteria from the reactor through temperature control in a continuous reactor, thereby oxidizing ammonia nitrogen to nitrite nitrogen to denitrification. It is a technique to do.

Accordingly, the present inventors have made diligent efforts to develop nitrite oxidizing bacteria in the reactor to oxidize ammonia nitrogen to nitrite nitrite and denitrify only. As a result, free ammonia or free nitrite selectively inhibits only nitrite oxidizing bacteria. In view of the above, in the process of wastewater nitrification in a continuous batch reactor, ammonia nitrogen is converted into nitrous acid only by inducing the inhibition of nitrous oxide by adjusting the pH according to the concentration of free ammonia as a substrate or free nitrite as a product. It was confirmed that it could be oxidized and denitrified, and the present invention was completed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wastewater treatment method using wastewater nitrification in a continuous batch reactor in which free ammonia is oxidized and denitrated only in the process of wastewater nitrification in a continuous batch reactor.

In order to achieve the above object, the present invention is a wastewater treatment method using the wastewater nitrification reaction in a continuous batch reactor, using ammonia nitrogen contained in the wastewater by inhibiting nitrite oxidizing bacteria by free ammonia or free nitrite Provided is a wastewater treatment method comprising oxidizing only with nitrous acid.

Wastewater treatment method according to the present invention can reduce the energy and carbon source costs required compared to the process of nitrifying ammonia to nitric acid to treat the wastewater, simplifying the process does not require a complicated process or a separate device when adjusting the pH Can be.

In one aspect, the present invention is a wastewater treatment method using the wastewater nitrification reaction in a continuous batch reactor, using ammonia nitrogen contained in the wastewater by inhibiting nitrite oxidizing bacteria by free ammonia or free nitrite The present invention relates to a wastewater treatment method characterized by oxidizing only with nitrous acid. At this time, the ammonia nitrogen is a concept including ammonia and ammonium.

The present invention utilizes the properties of nitrous oxide inhibiting bacteria of free ammonia and free nitrite and the characteristics of a continuous batch reactor in which the concentrations of substrate and product change over time.

In other words, in the nitrification of wastewater in a continuous batch reactor, the concentration of free ammonia as a substrate decreases with time, while the concentration of free nitrous acid as a product increases with time. Therefore, when the time corresponding to 1/2 of the total reaction time required for the nitrification reaction is referred to as the reaction medium, the free ammonia concentration from the start of the nitrification reaction to the reaction medium is determined by the concentration of free ammonia from the reaction medium to the end of the reaction. Relatively high. In addition, the free nitrite concentration from the start of the nitrification reaction to the middle stage of the reaction is relatively low compared to the concentration of free nitrite from the middle stage of the reaction to the end of the reaction. In order to maximize the nitrite oxidative inhibitory properties by the free ammonia from the start of the reaction in which the concentration of the free ammonia is relatively high during the nitrification process, the pH is adjusted to maintain the free ammonia at a high concentration. During the reaction, the pH of the wastewater is maintained so that the free nitrite is maintained at a high concentration in order to maximize the nitrite oxidative inhibitory properties by the free nitrite from the middle of the reaction to the end of the reaction, the concentration of free nitrite is relatively high during the nitrification process Adjust

In the nitrification of the wastewater in the continuous batch reactor, the pH is adjusted from 7.0 to 8.0 after the start of the nitrification reaction in the continuous batch reactor to induce inhibition of nitrite oxidizing bacteria by the free ammonia to thereby ammonia nitrogen. It can only be oxidized to nitrous acid. In this case, when the pH is 7.0 to 8.0, it is possible to maintain a high concentration of free ammonia, it is possible to maximize the nitrite oxidizing bacteria inhibitory effect by the free ammonia. In addition, as the nitrification reaction proceeds, free nitrous acid starts to be produced over time, so the inhibitory action of the nitrite oxidizing bacteria by the free nitrite also becomes parallel. However, since free ammonia is maintained at a relatively high concentration in the entire nitrification process at pH 7.0-8.0, nitrite oxidative bacterium inhibition by free ammonia is superior to inhibition of nitrite oxidative bacteria by free nitrite.

In nitrification of the wastewater in the continuous batch reactor, the pH is adjusted to 6.0-7.0 after the middle stage of the nitrification reaction in the continuous batch reactor to induce the inhibition of nitrite oxidizing bacteria by the free nitrous acid to ammonia nitrogen It can only be oxidized to nitrous acid. In this case, when the pH is 6.0 ~ 7.0, it is possible to maintain a high concentration of free nitrous acid, it is possible to maximize the nitrite oxidizing bacteria inhibitory effect by the free nitrous acid. In addition, as the nitrification progresses, free ammonia decreases but remains partially before being completely removed, so that the inhibition effect of nitrite oxidizing bacteria by free ammonia is also parallel. However, since free nitrite is maintained at a relatively high concentration during the entire nitrification process at pH 6.0-7.0, nitrite oxidative bacteria inhibition by free nitrite is superior to inhibition of nitrite oxidative bacteria by free ammonia.

Nitrification of wastewater using a continuous batch reactor according to the present invention is different from the prior art Sharon process in that it uses free ammonia (NH ₃ ) and free nitrous acid (Free nitrous acid, HNO ₂ ). There is a difference. The above technique is mainly applied to a system with high ammonia nitrogen concentration. First of all, the high ammonia nitrogen concentration makes it easy to accumulate nitrite nitrogen and the high nitrogen concentration maximizes the reduction of oxygen and organic carbon source cost required for nitrification and denitrification. Because it becomes. Here, the ammonia (NH ₃ ) oxidizing bacterium is left intact, but only the nitrite (HNO ₂ ) oxidizing bacterium is deactivated. The free ammonia (NH ₃ ) is introduced into the sequencing batch reactor (SBR). ) And free nitrous acid (HNO ₂ ) formed later in the reaction.

This is not available in other continuous reactors and uses the characteristics of the batch reaction of the Sequencing Bach Reactor (SBR). Unlike the Plug Flow Reactor (PFR), SBR (Sequencing Bach Reactor) has the characteristics of a batch reactor, so the concentration of substrate or product changes over time. High and at the end of the reaction the product concentration is high.

In the present invention, to inhibit the nitrite oxidizing bacteria of the free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) and to maximize the effect of the Sequencing Bach Reactor (SBR) By using this property, ammonia (NH ₃ ) is oxidized to nitrite ions without being oxidized to nitrate ions.

Both free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) are toxic to nitrifying microorganisms, particularly nitrite oxidizing bacteria. Nitrosomonas is at a concentration 10~150 mg N / L of free ammonia _{(Free ammonia, NH 3),} Nitrobacter has been reported to receive inhibition at low concentrations of between 0.1~1.0 mg N / L (Anthonisen et al., J WPCF., 48: 835-852, 1976 ) . In addition, Nitrobacter was reported to be inhibited when the concentration of free nitrous acid (HNO ₂ ) was 0.22 to 2.8 mg N / L, and the concentration of free ammonia (NH ₃ ) was 1 to 5 mg N / L. L has been reported to inhibit Nitrobacter and not Nitrosomonas to accumulate nitrite nitrogen (Villaverde et al . Wat. Res., 34 (2): 602-610, 2000). It is possible to change the concentration of free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) according to the change of equilibrium even with slight pH change. Equation of equilibrium relationship of ammonia (NH ₃ ) or nitrous acid (HNO ₂ ), Free ammonia (NH ₃ ) or free nitrous acid (HNO ₂ ) is as follows.

H ⁺ + OH ^- ↔ NH ₃ + H ₂ O ...... ammonia equilibrium

H ⁺ + NO ₂ ^- ↔ HNO ₂ ... nitrous acid equilibrium

NH ₃ -N (mg / L) = NH ₄ ⁺ -N (mg / L) × 10 ^pH / (K _a / K _w + 10 ^pH )

_{HNO 2 -N (㎎ / ℓ)} = NO 2 - -N (㎎ / ℓ) / (K b / K w × 10 pH)

K _a , K _b = The ionization constant of the ammonia and nitrous acid equilibrium equation

K _w = The ionization constant of water

K _a / K _w = e ^{(6334/273 + ° C)} , K _b / K _w = e ^{(-2300 / 273 + ° C)}

Therefore, the concentrations of free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) are particularly sensitive to pH in addition to ammonium and nitrite ions. Sequencing Bach Reactor (SBR) is used to maintain high concentration of free nitrous acid (HNO ₂ ) in the low pH range by increasing the concentration of NH ₃ ) and preventing the decrease of pH due to nitrification in the latter part of the reaction. ) Continually inhibit nitrite oxidizing bacteria so that they are dilution out from the reactor.

In the present invention, the pH may be controlled by bicarbonate or alkaline (caustic soda or lime), but is not limited thereto.

In the present invention, the pH of the wastewater in the continuous batch reactor may be detected by a pH sensor or the like, but is not limited thereto.

In the present invention, the waste water may be characterized in that it is introduced into the continuous batch reactor under anoxic conditions or aerobic conditions. When simultaneously with denitrification and nitrification in the reactor, the wastewater may be introduced into anoxic conditions, and when nitrification is mainly performed in the reactor, the wastewater may be introduced into aerobic conditions.

The wastewater treatment method according to the present invention can save 25% of the amount of air required for nitrification and 40% of the carbon source, an electron donor required for denitrification, compared to the conventional method of oxidizing and removing ammonia with nitric acid. Very economical in processing. In addition, pH control does not require a separate device or complicated process can simplify the process.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as being limited by these examples.

Example 1 Nitrification of Wastewater Using a Continuous Batch Reactor

Wastewater containing ammonia (NH ₃ ) was introduced into a sequencing Bach Reactor (SBR) and nitrified to accumulate nitrous acid (FIG. 2). Continuous batch reactor operating conditions were as shown in Table 3 and the composition of the wastewater used in the experiment was as shown in Table 4. Nitrifying microorganisms were collected and inoculated from sludge sludge collection tanks in Chuncheon-si.

Continuous Batch Reactor Operation Procedure Operating conditions
Operation time Fill
Aeration
Setting
Draw
Total 2 min
180 ~ 300 min
4 min
5 min
180 min DO> 1.8 mg / l
MLSS 2500-300 mg / l
Air Flow> 3ℓ / min
pH 7.0 to 7.6

ingredient Concentration (mg / l) (NH ₄ ) ₂ SO ₄ 200 to 1,000
MgSO _{4 7} H ₂ O 30 KCl 35 NaHPO ₄ · 12H ₂ O 29 CaCl ₂ · 2H ₂ O 16 KH ₂ PO ₄ 45 FeCl ₃ · 6H ₂ O 10

As a result of water analysis after about 70 days after the operation of the reactor, as shown in FIG. 3, during 160 minutes of ammonia (NH ₃ ) oxidation, ammonia (NH ₃ ) was completely oxidized and no nitrate nitrogen was detected. Nitrate nitrogen was not detected even under aerobic conditions of 20 minutes. Instead, nitrite ions were increased to confirm that the oxidized ammonia (NH ₃ ) was almost converted to nitrite (HNO ₂ ). Therefore, 100% of ammonia (NH ₃ ) was removed, and about 99% of the totally oxidized ammonia (NH ₃ ) was confirmed to be converted to nitrous acid (HNO ₂ ). According to the prior art, inhibition of free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) is reported to be more sensitive to nitrite oxidizing bacteria than ammonia (NH ₃ ) oxidizing bacteria.

In this experiment, in order to maximize the inhibitory effect of free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ), the amount of bicarbonate added to maintain alkalinity was adjusted. PH was maintained in the range of 6.5 to 7.5 after the reaction medium in the range of 7.0 ~ 8.0. In this way, the chemical equilibrium was maintained to increase the concentration of free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ), and the inhibitory effect was increased.

As a result of operating the reactor under the condition that the nitrite oxidizing bacteria were continuously inhibited, free ammonia (NH ₃ ) initially inhibited the nitrite oxidizing bacteria, and after the inhibition of free ammonia (NH ₃ ) was completed, Free nitrous acid (HNO ₂ ) was found to inhibit nitrite oxidizing bacteria. As described above, due to the continuous inhibition of nitrite oxidizing bacteria, the nitrite oxidizing bacteria was found to be washed out.

Experimental Example 1. Confirmation of distribution of nitrifying microorganisms

The microorganisms were collected from the continuous batch reactor in which the nitrification process of Example 1 was completed, and subjected to Fluorescent in situ Hybridization (FISH), and observed by Confocal Laser Scanning Microscopy (CLSM) to confirm the distribution of nitrifying microorganisms. Representative microorganisms of ammonia oxidizing bacteria are Nitrosomonas spp. And Nitrosospira spp. , Nitrobacter spp. And genus Nitrospira were analyzed. The quantitative analysis of microorganisms is an image analyzer. The data obtained by quantitatively analyzing 10 or more FISH images is analyzed using SPSS V12, a data statistics analysis program, with the minimum, maximum, average, and standard error of the mean and 95% of the mean. The confidence range was obtained to determine the quantitative% for each microorganism.

Table 5 shows the average of each microorganism using SPSS V12, which is a numerical program for analyzing the data of 10 FISH images observed by FISH / CLSM with an image analyzer to quantify the cluster distribution of microorganisms in a continuous batch reactor. And the standard error of the mean, 95% confidence range. The quantification data of the microorganisms were within the standard error range with an average within the 95% confidence interval. As a result of continuously inhibiting nitrite oxidizing bacteria and washing out, ammonia oxidizing bacteria accounted for 99%, and nitrite oxidizing bacteria were hardly detected.

Sample #
Ammonia Oxidizing Bacteria Nitrite oxidizing bacteria Nitrosomonas spp. Nitrosospira spp. Nitrobacter spp. genus Nitrospira One
2
3
4
5
6
7
8
9
10 34.78
29.98
31.15
30.94
32.31
34.12
34.18
35.01
29.83
35.41 5.54
5.21
5.31
4.56
5.80
5.43
5.32
5.18
5.60
5.67 0.44
0.39
0.45
0.49
0.52
0.46
0.52
0.49
0.47
0.39 ND *
ND
ND
ND
ND
ND
ND
ND
ND
ND Minimum value
Value 29.83
35.41 4.56
5.80 0.39
0.52 -
- Average 32.8 5.4 0.46 - 95% of average
Confidence interval 31.22-34.32 5.11 ~ 5.61 0.42-0.50 - Standard error of the mean 0.68 0.11 0.01 -

* N.D. not detected

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Figure 1 shows an overall schematic of selective nitrification and denitrification by nitrite according to the present invention.

2 is a view showing a continuous batch reactor used for nitrogen removal according to the present invention.

3 is a graph showing the nitrous oxide inhibiting section by the nitrogen component concentration change and free ammonia (NH ₃ ) and free nitrous acid (HNO ₂ ) in the nitrification step in the continuous batch reactor according to the present invention {●: NH ₄ ⁺ -N, ○: NO ₂ ^-- N, ▼: NO ₃ ^-- N, ◆: Total-N, ■: Free ammonia (NH ₃ ), ▲: Free nitrous acid (Free nitrous acid, HNO ₂ )}.

Claims (4)

In the wastewater treatment method using wastewater nitrification in a continuous batch reactor, A wastewater treatment method comprising oxidizing ammonia nitrogen contained in wastewater to nitrous acid only by using the inhibitory effect of nitrite oxidizing bacteria by free ammonia or free nitrite. The method of claim 1, wherein from the start of nitrification in the continuous batch reactor, the pH is adjusted to 7.0 to 8.0 to induce inhibition of nitrite oxidizing bacteria by the free ammonia to oxidize only ammonia nitrogen to nitrite. Wastewater treatment method characterized in that. The method according to claim 1, wherein the pH is adjusted to 6.0 to 7.0 after the intermediate nitrification reaction in the continuous batch reactor to induce inhibition of nitrite oxidizing bacteria by nitrous acid to oxidize ammonia nitrogen to nitrite only. Wastewater treatment method. The method of claim 1, wherein the pH is controlled by bicarbonate or an alkaline agent.

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