KR101063828B1 - Method of wastewater treatment using an anaerobic reactor having a biological nitrification process connected a cation exchange membrane - Google Patents

Abstract

The present invention relates to an anaerobic tank having a nitrification tank connected by a cation exchange membrane and a wastewater treatment method using the same, and more particularly, to an anaerobic tank having a nitrification tank connected to a cation exchange membrane.

According to the present invention, wastewater containing a high concentration of organic matter and ammonia is transferred to the nitrification tank via a ion exchange membrane, and nitrates are transferred to the anaerobic tank, so that denitrification can occur simultaneously. Since the ion exchange membrane is regenerated, it is possible to simplify the process in the wastewater treatment and to reduce the treatment time, thereby making it useful for improving water quality.

Anaerobic Tank, Ammonia Wastewater, Cation Exchange Membrane

Description

Method of wastewater treatment using an anaerobic reactor having a biological nitrification process connected a cation exchange membrane}

The present invention relates to an anaerobic tank having a nitrification tank connected by a cation exchange membrane and a wastewater treatment method using the same.

In general, the decomposition process using anaerobic microorganisms refers to a process in which organic matters of contaminants are converted to carbon dioxide and methane by microorganisms in an oxygen-free environment.

In general, the nutrients contained in the waste water are inorganic elements, but when they enter rivers, coastal seas, lakes (lakes and reservoirs), algae grow and cause eutrophication. In the case of severe red tide due to abnormal growth of the algae, a bad smell caused by corruption occurs in the spoon, causing water pollution. Therefore, these nutrients must be removed before they enter a river or lake.

Wastewater containing high concentrations of organic matter and ammonia, such as livestock wastewater, is generally treated through anaerobic digestion tanks to induce residual organic matter removal and nitrification in aerobic aeration tanks, and to induce denitrification by returning. However, it is impossible to remove 100% of organic matter through anaerobic digestion, so an aerobic aeration tank must be installed at the rear of the anaerobic digester to oxidize the remaining organic matter. The residence time in the aerobic tank also increases because organic matter can be induced after nitrification. After nitrification, the treatment process becomes complicated because denitrification must be induced through internal transport. That is, the weakness of the existing technology is that the removal of organic matter is required, long residence time is required, and the entire process is complicated.

In Korea, most sewage treatment and livestock wastewater treatment methods rely on activated sludge method. Treatment with activated sludge can remove most suspended solids and organics, but only 20-40% of nutrients such as nitrogen and phosphorus. Processes for treating nutrients such as nitrogen and phosphorus include physical, chemical and biological treatments.

The physicochemical treatment methods include ammonia degassing, ion exchange using selective adsorption, precipitation of phosphorus using slaked lime and flocculant, and precipitation of struvite formation that simultaneously precipitates nitrogen and phosphorus. It is used.

However, the above-mentioned physical and chemical methods are disadvantageous in that they are sensitive to temperature and costly, and are difficult to operate due to the limited chemical and operating environment requirements. Is reluctant.

In the biological treatment method, in the case of nitrogen, nitrification (ie, ammonia is transformed into nitrate form) by nitrifying bacteria (ie, Nitrosomonas & Nitrobacter) under aerobic conditions, and ammonia nitrogen and organic nitrogen in the dissolved state are denitrified. Bacteria (ie, Pseudomonas, Paracoccus denitrifiers) are used as electron acceptors instead of oxygen in anoxic conditions, converted to nitrogen gas and released into the atmosphere (denitrification).

As a method for overcoming the wastewater treatment problem as described above may include the DEPHANOX process developed in Italy. In this process, anaerobic contacting tanks and separation tanks are used to adsorb organic matter in the anaerobic contacting tank, induce the release of phosphorus, separate organic matter and microorganisms adsorbed in the separation tank and enter the subsequent denitrification tank, Nitrogen compounds are nitrified in separate reactors and sent to subsequent denitrification tanks for denitrification by microorganisms that adsorb organic matter. That is, the DEPHANOX process is a process in which denitrification and nitrification are carried out in separate sludges and reactors, and the phosphorus is excessively ingested by microorganisms in a subsequent aerobic reactor.

However, despite these advantages of the DEPHANOX process, organic nitrogen and ammonia nitrogen flowing into the denitrification tank from the separation tank during the subsequent treatment in the nitrification tank are not sufficiently decomposed or nitrified and discharged, and only the single denitrification reactor following the nitrification tank is denitrified. Because it is made, there is a disadvantage that can not expect high nitrogen removal efficiency.

Accordingly, the present inventors minimize the reduction of nitrification efficiency by organic matter by separating ammonia from wastewater using a cation exchange membrane and supplying it to a biological nitrification tank for efficient nitrification of high concentration organic matter such as livestock wastewater and ammonia-containing wastewater. By developing a process to stably carry out nitrification by reducing the load primarily with a cation exchange membrane, it was confirmed that the ammonia removal rate using the same was 99% or more, and completed the present invention.

An object of the present invention is to provide an anaerobic tank having a nitrification tank connected by a cation exchange membrane.

In addition, another object of the present invention to provide a wastewater treatment method using the anaerobic tank.

In order to achieve the above object, the present invention is to prevent the nitrification is not inhibited due to the remaining of the organic matter, and to remove the organic matter through the anaerobic digestion and nitrification by separating and nitrifying the ammonia from the wastewater flowing into the anaerobic tank rather than after the anaerobic tank At the same time provide an inducible anaerobic tank.

The present invention also provides a wastewater treatment method using the anaerobic tank.

According to the present invention, wastewater containing a high concentration of organic matter and ammonia is transferred to the nitrification tank via a ion exchange membrane, and nitrates are transferred to the anaerobic tank, so that denitrification can occur simultaneously. Since the ion exchange membrane is regenerated, it is possible to simplify the process in the wastewater treatment and to reduce the treatment time, thereby making it useful for improving water quality.

Hereinafter, the present invention will be described in detail.

The present invention provides an anaerobic tank (2) having a nitrification tank (5) connected by a cation exchange membrane (1).

The schematic diagram of the anaerobic tank 2 which concerns on this invention is shown in FIG. As shown in FIG. 1, in the anaerobic tank 2 according to the present invention, when wastewater containing organic matter is introduced, organic matter is removed through hydrolysis, organic acid formation, and methane fermentation, and the cation exchange membrane is the anaerobic tank ( 2) Biological nitrification occurs in the nitrification tank containing the medium by separating ammonia generated from or contained in the wastewater containing the organic matter flowing into the nitrification tank (5) independently of the organic matter in the anaerobic tank (2). Is done.

The nitrification tank may remove ammonia introduced through the cation exchange membrane 1 through biological nitrification to generate nitrite or nitrate. Specifically, the biological nitrification reaction occurring in the nitrification tank 5 may be represented by the following Scheme 1.

NH ₄₊ + 1.5O ₂ ----> NO _2- + H ₂ O + 2H ⁺ ( Nitrosomonas ) (A)

NO _2- + 0.5 O ₂ ----> NO _3- ( Nitrobacter ) (B)

NH ₄₊ + NO _2- ----> N ₂ + 2H ₂ O (Anammox bacteria) (C)

NH ₄ ⁺ + 2H ₂ O ^{_{+ 6Fe 3+ ---> NO 2+ 6Fe}} 2+ + 8H + (Iron reducing bacteria) (D)

^{_{NO 2+ 2Fe 3+ + H 2 O}} ---> NO 3+ 2Fe 2+ + 2H + (Iron reducing bacteria) (E)

The reaction schemes (A) and (B) are reactions occurring when dissolved oxygen (DO) concentration is sufficiently maintained in the nitrification reaction. That is, when there is no organic substance and the concentration of ammonia is low, DO deficiency does not occur and oxidation of ammonia occurs smoothly. Reaction formula (C), (D), (E) has shown the oxidation reaction of ammonia which arises in the state in which oxygen supply is not smooth. In the case of general livestock wastewater, the concentration of ammonia is several thousand ppm, and as a result, the supply of oxygen into the wastewater is not smooth, and the reactions corresponding to the reactions (C) to (E), which are anaerobic reactions, mainly occur.

In the anaerobic tank 2 according to the present invention, the cation exchange membrane 1 not only selectively introduces ammonia from the anaerobic tank 2 into the nitrification tank 5, but also through the reaction schemes (3) to (5). The generated nitrite or nitrate is selectively passed through the anaerobic tank (2) to be removed by the denitrification reaction in the anaerobic tank (2).

In this case, the cation exchange membrane 1 may be used without particular limitation as long as it is advantageous for the permeation of monovalent cations such as ammonia and the separation of organic substances is limited.

Furthermore, denitrification and ammonia removal can be carried out simultaneously in the anaerobic tank 2 and the nitrification tank 5 connected thereto according to the present invention. As the cation exchange membrane provided in the present invention should maintain electrical neutrality when ammonia moves from the anaerobic tank (2) to the nitrification tank (5), the corresponding anions move to the anaerobic tank (2), and the nitrification tank (5). Nitrate, which is most widely distributed in), is also transferred to the anaerobic tank by concentration gradient. That is, since the nitrate generated in the nitrification tank 5 can be removed by moving to the anaerobic tank 2 through the cation exchange membrane, denitrification and ammonia removal can be performed simultaneously.

In addition, the present invention comprises the steps of introducing a wastewater containing a high concentration of organic matter and ammonia material into the anaerobic tank (step 1); Ammonia included in the high concentration organic material of step 1 or ammonia generated therefrom is transferred to the nitrification tank 5 through a cation exchange membrane and at the same time, the nitrite or nitrate generated in the nitrification tank 5 is transferred to the anaerobic tank 2. Step (step 2); And a denitrification reaction of nitrite or nitrate introduced into the anaerobic tank (2) and a removal reaction of ammonia introduced into the nitrification tank (5) are carried out simultaneously (step 3); wastewater treatment using the anaerobic tank (2) comprising Provide a method.

In the wastewater treatment method according to the present invention, step 1 is a step of introducing wastewater containing a high concentration of organic matter and ammonia into the anaerobic tank (2).

The waste water is preferably injected into the lower portion of the anaerobic tank (2).

In the wastewater treatment method according to the present invention, step 2 moves ammonia or ammonia generated from the high concentration organic matter of step 1 to the nitrification tank 5 through a cation exchange membrane and at the same time in the nitrification tank 5. The resulting nitrite or nitrate is transferred to the anaerobic tank (2).

In step 2, the cation exchange membrane provided in the present invention should maintain electrical neutrality when ammonia moves from the anaerobic tank (2) to the nitrification tank (5), so that the corresponding anions move to the anaerobic tank (2), Nitrate, which is most distributed in the nitrification tank (5), also moves to the anaerobic tank (2) by the concentration gradient. That is, since the nitrate generated in the nitrification tank 5 can be removed by moving to the anaerobic tank 2 through the cation exchange membrane, the ammonia contained in the high concentration organic matter or the ammonia generated therefrom is transferred to the nitrification tank 5 through the cation exchange membrane. At the same time, the nitrite or nitrate produced in the nitrification tank (5) can be moved to the anaerobic tank (2).

At this time, the nitrification tank 5 of step 2 is preferably adjusted to a pH of 6.5 to 8 in order to prevent the material exchange lowered due to the pH decrease.

In the wastewater treatment method according to the present invention, step 3 is a step in which the denitrification reaction of nitrite or nitrate introduced into the anaerobic tank 2 and the removal reaction of ammonia introduced into the nitrification tank 5 are performed simultaneously.

In step 3, the denitrification reaction for oxidizing the nitrite or nitrate transferred by step 2 to nitrogen gas and the ammonia removal reaction according to Scheme 1 may be simultaneously performed.

At this time, the nitrite or nitrate in the nitrification tank 5 may be produced by biological nitrification by nitrite bacteria or nitrate bacteria.

Furthermore, the wastewater treatment according to the invention can be carried out in a batch process or in a continuous process.

The wastewater treatment according to the above should be maintained in the electrical neutrality when the ammonia is moved from the anaerobic tank (2) to the nitrification tank (5), so that the corresponding anion is moved to the anaerobic tank (2), generated in the nitrification tank (5) Since the nitrate can be removed by denitrification by moving to the anaerobic tank 2 through the cation exchange membrane, wastewater treatment is possible without a separate internal conveying device, and the ammonia occupying the surface of the cation exchange membrane 1 is biologically nitrified. Can be continuously removed through a batch or continuous process can be performed without a separate cation exchange membrane (1) replacement process.

In this case, the continuous process may be operated by sedimenting the sludge of the nitrification tank 5, removing the supernatant and injecting fresh medium, and the medium used is nutrients other than ammonia. , Minerals, sodium bicarbonate or mixtures thereof, and the pH is preferably 7-8.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Comparative Example Ammonia Concentration Gradient Through Cation Exchange Membrane

In order to determine the amount of ions through the cation exchange membrane of ammonia ions, NH ₄ Cl was dissolved in distilled water in an anaerobic tank to adjust the ammonia concentration to 1400 mg N / L. 2 is shown.

As shown in Figure 2, despite the presence of about 950 mg N / L of ammonia in the anaerobic tank it can be seen that in the nitrification tank is maintained at a concentration of about 73 mg N / L, ammonia by concentration gradient alone in the absence of a biological reaction It is confirmed that there is a limit to moving. This is because the surface of the cation exchange membrane is occupied by ammonia ions and the ion exchange ability is inhibited, so that the movement of ammonia by a simple concentration gradient is limited by the physicochemical resistance generated by the cation exchange membrane.

Example 1 Wastewater Treatment by Batch Process

Wastewater was introduced into an anaerobic tank, and CMX was used in NEOSEPTA membrane of Astom of Japan as a cation exchange membrane, the medium was added to the nitrification tank, and the operation was performed to measure the ammonia concentrations of the anaerobic tank and the nitrification tank according to the operation time. The nitrate or nitrite concentrations in the nitrification baths were measured and shown in FIGS. 4 and 5, respectively.

As shown in FIG. 3, when the ammonia is continuously removed from the nitrification tank by the biological nitrification reaction, it can be seen that the concentration of ammonia in the anaerobic tank is close to 0 mg N / L. That is, when continuous removal of ammonia is made in the nitrification tank, anion is generated to form a favorable condition for the movement of ammonia and the concentration of ammonia is kept low, thereby confirming that nitrification can be efficiently separated and ammonia.

As shown in Fig. 4 or 5, biological nitrification can be seen by the detection of nitrite and nitrate detected in the nitrification tank. However, the initial concentration of ammonia was 700 mg N / L, whereas the concentrations of nitrite and nitrate were higher. This may be due to the ammonia produced by the decomposition of organic matter contained in the sludge planted in the initial nitrification tank. In addition, as nitrite and nitrate were detected in the anaerobic tank, ammonia was moved through the cation exchange membrane, and nitrite and nitrate, which are anions in the nitrification tank, were confirmed to move to the anaerobic tank. It can be seen that the nitrite and nitrate generated in the nitrification tank can be removed through the denitrification process by moving to the anaerobic tank by ion exchange without separate transport.

<Example 2> Wastewater treatment 1 through the continuous

Artificial wastewater with an ammonia concentration of 10 mM (140 mg N / L) was prepared, and the hydrodynamic retention time (HRT) was set to 5 days in the anaerobic tank so that the volume load of the anaerobic tank was 0.03 kg N / m ³ /. Operation was adjusted to d. Since nitrification induced only nitrification, the sludge was settled every 5 days for 1 hour without additional internal transport, inflow and outflow, and then the supernatant was removed and replaced with fresh medium. At this time, nutrients and minerals except ammonia needed for the growth of nitrifying microorganisms and 1 g / L of NaHCO ₃ were included and the pH was adjusted to 7.4 using phosphate. The pH of the anaerobic influent was adjusted to around 7.0, and the nitrification tank was operated to adjust to around pH 7.4 using 1.0 N NaOH solution due to the decrease in pH due to nitrification. Dissolved oxygen (DO) was maintained at about 1.4 mg / L. The ammonia concentration change in the influent, anaerobic tank and nitrification tank during the operation was measured in FIG. 6, the nitrate concentrations in the anaerobic tank and nitrification tank were measured in FIG. 7, and the pH in the influent, anaerobic tank and nitrification tank was measured and shown in FIG. 8.

As shown in Figure 6, the ammonia concentration of the influent is about 130 mgN / L, while ammonia is continuously introduced into the anaerobic tank, the ammonia concentration in the anaerobic tank is reduced to 0 mgN / L in 3 days, and continuously maintained. In addition, the ammonia concentration in the nitrification tank was reduced to 0 mgN / L in one day so that the nitrification rate of ammonia was more than 99%,

As shown in Fig. 7, no accumulation of nitrite nitrogen was found in the nitrification tank and the anaerobic tank. In the case of nitrates, the medium decreases and then rises again every five days as the medium of nitric oxide is replaced. As in the batch experiment, the ammonia introduced into the anaerobic tank was found to be oxidized by migrating more than 99% to the nitrification tank. When fresh media were injected after sludge settling, the mixed liquor suspended solids (MLSS) ranged from 750 to 770 mg / L.

As shown in FIG. 8, 1.0 N NaOH solution was consumed at 1 mL / L to maintain the pH of the nitrification tank at around 7.4. Since nitrates and nitrites are transferred to anaerobic tanks, induction of denitrification using organic materials in livestock wastewater in anaerobic tanks will reduce the amount of base required in nitrification tanks due to the alkalinity generated during heterotrophic denitrification. do.

<Example 3> Wastewater treatment 2 through the continuous

The load of ammonia (0.06 kg N / m ³ / d) was doubled and operated in the same manner as in Example 2, and then the ammonia concentration change of the influent anaerobic tank nitrification tank according to the operating time is shown in Fig. 9. 10 is shown.

As shown in FIG. 9, as the ammonia concentration was increased, the dissolved oxygen concentration was maintained at a low level of about 0.6 mg / L, but it was confirmed that the nitrification rate was 99% or higher as in Example 2.

As shown in FIG. 10, as the load increased, the amount of ammonia nitrified also increased, and the pH lowering of the nitrification tank was more severe. Therefore, the injection amount of 1.0 N NaOH averaged 2.5 mL / L, and MLSS was maintained at about 755 ~ 768 mg / L did not show an increased value. This is because the amount of aeration was fixed and the amount of NaHCO _{3 was also} the same, which is because the growth of the microorganism was limited by the concentration of the carbon source.

1 is a process schematic diagram of an embodiment according to the present invention;

2 is a graph showing ammonia migration tendency according to Comparative Example 1;

3 is a graph showing the ammonia concentration tendency of one embodiment according to the present invention;

4 is a graph showing the nitrate concentration trend of one embodiment according to the present invention;

5 is a graph showing the nitrite concentration trend of one embodiment according to the present invention;

6 is a graph showing the ammonia concentration tendency of one embodiment according to the present invention;

7 is a graph showing the nitrate concentration trend of one embodiment according to the present invention;

8 is a graph showing the pH trend of one embodiment according to the present invention;

9 is a graph showing the ammonia concentration tendency of one embodiment according to the present invention; And

Figure 10 is a graph showing the pH trend of one embodiment according to the present invention.

DESCRIPTION OF REFERENCE NUMERALS

1: cation exchange membrane 2: anaerobic tank

3: acid engine 4: aeration

5: nitrification tank

Claims (5)

An anaerobic tank having a nitrification tank connected to a cation exchange membrane, wherein the cation exchange membrane selectively passes ammonia generated from or contained in the wastewater containing organic matter introduced into the anaerobic tank to the nitrification tank. delete The anaerobic tank according to claim 1, wherein the cation exchange membrane selectively passes nitrite or nitrate generated in the nitrification tank to the anaerobic tank. The denitrification reaction of nitrite or nitrate flowing through the cation exchange membrane is performed in the anaerobic tank, and the ammonia removal reaction is performed in the nitrification tank, wherein the denitrification reaction and the ammonia removal reaction are simultaneously performed. Anaerobic tank. Introducing wastewater containing a high concentration of organic matter and ammonia into the anaerobic tank (step 1); Moving ammonia or ammonia generated from the high concentration organic material of step 1 to the nitrification tank through a cation exchange membrane and simultaneously transferring nitrite or nitrate generated in the nitrification tank to an anaerobic tank (step 2); And The denitrification reaction of nitrite or nitrate introduced into the anaerobic tank and the removal reaction of ammonia introduced into the nitrification tank are simultaneously performed (step 3).

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