KR100971588B1 - Method for removing of nitrogen and perchlorate in waste water - Google Patents

Abstract

The present invention relates to a process for removing nitrogen and perchlorate from wastewater. The present invention comprises a first step of neutralizing the mixed waste water by mixing the raw waste water and waste isopropyl alcohol to be collected in the pH adjustment tank 30 and injecting an acidic or alkaline solution; A second step of injecting the wastewater in the first step into the anoxic tank 40 and removing nitrogen oxide and perchlorate from the wastewater using microorganisms; Wherein after step 2, the exemplary ammonium nitrogen increase in the residual organic matter and the second step to the removal of the waste water supplied to the nitrogen oxide and perchlorate aerobic tank 50 of nitrate to _{(NH 4 -N) (NO 3} -, a third step of oxidizing a) ^- NO _2; And a fourth step of discharging the wastewater of the aerobic tank 50 treated in the third step to the settling tank 60 to be returned to the second step or discharged to the outside. According to the present invention, it is possible to minimize the cost of removing nitrogen and perchlorate from the wastewater, as well as to reduce the cost of the biological treatment process using waste IPA, thereby removing the nitrogen and perchlorate from the wastewater more economically and efficiently. It has an effect.

Wastewater, Nitrogen, Perchlorate

Description

Method for removing of nitrogen and perchlorate in waste water

The present invention relates to a method for removing nitrogen and perchlorate from wastewater, and more particularly, to a method for removing nitrogen and perchlorate from wastewater for biological treatment of perchlorate in wastewater in which a large amount of nitrogen compounds are present.

Wastewater generated by domestic explosives industry, LCD manufacturing industry, etc. contains pollutants such as nitrogen compounds and perchlorate. Nitrogen in the wastewater adversely affects the ecosystem, such as eutrophication of seawater during discharge.

There are various methods of treating wastewater containing nitrogen, such as ammonia degassing, destruction point chlorination, ion exchange, etc., but biological nitrogen removal using microorganisms is mainly used for economical and technical limitations.

Algae cultivation, aquatic plant cultivation, nitriding by microorganisms are used for the biological nitrogen removal method, the reaction scheme is as follows.

Nitrification Process

NH ₄ ⁺ + 2O _{2 ^{→ NO 3 - + 2H + +}} H 2 O

Denitrification Process

^{_{2NO3 - + 5H 2 → N 2}} + 2OH- + 4H 2 0

As shown in the above scheme, the biological nitrogen removal method is treated in a two-step process in which the nitrogen component introduced into industrial wastewater is nitrified and denitrified. However, for the denitrification process, the process of returning a flow rate of about 3 to 7 times the original waste water is selected. Therefore, there is a problem in that the cost of power consumption is high and economically expensive, such as the injection of external carbon sources (hydrogen donors) such as methanol and waste alcohol.

In addition, perchlorate contained in wastewater is said to irritate human respiratory skin and to cause thyroid disorders in overexposure, which can cause various abnormalities in the body.

Perchlorate is an anionic inorganic substance called ClO ₄ ⁻ , in which one chlorine (Cl) atom and four oxygen (O) atoms are bonded. Perchlorate occurs naturally, but most are artificially manufactured for industrial use.

Therefore, extensive research is being conducted on the generation of perchlorate pollution and development of water and sewage treatment methods to include perchlorate as contaminants and to set new regulations and standards.

Perchlorate has high solubility and mobility in water but is chemically stable and does not easily decompose. Therefore, there is a limit to the removal of perchlorate contained in the waste water by chemical features.

As a method for removing pechlorate, ion exchange, membrane separation technology, electrodialysis, reduction technology using activated carbon, and the like are applied. However, this method does not completely remove the perchlorate contained in the actual waste water, there is a problem that requires periodic replacement due to the adsorption of activated carbon.

Accordingly, recently, a biological purification process for removing perchlorate has been applied. The reaction scheme of the pechlorate removal process is shown below.

Perchlorate Process

ClO ₄ ^- + 4H ₂ → Cl ^- + 4H ² O

The biological purification process for perchlorate requires a carbon source (hydrogen donor) as shown in Scheme 3. As a carbon source, acetic acid, ethanol, methanol, and the like are used, which also increases the operating cost of the perchlorate removal process as well as the nitrogen removal process.

In addition, since industrial wastewater generating a large amount of perchlorate contains nitrogen, it is urgent to prepare a method for simultaneously removing nitrogen and perchlorate.

The present invention is to solve the conventional problems as described above, the object of the present invention is to adopt a biological removal method that can remove the nitrogen compound and perchlorate at the same time, in the selection of the external carbon source while high organic matter and biodegradability It is to provide a nitrogen and perchlorate removal method of the waste water can also satisfy the economics.

The present invention is to solve the conventional problems as described above, the present invention is a first step of neutralizing the mixed wastewater by mixing the raw wastewater and waste isopropyl alcohol to be collected in a pH adjustment tank and injecting acidic or alkaline solution Wow; A second step of injecting the wastewater in the first step into an anoxic tank and removing nitrogen oxide and perchlorate from the wastewater using microorganisms; Wherein after step 2, the exemplary ammonium nitrogen increase in the residual organic matter and the second step by supplying the waste water to remove nitrogen oxides and perchlorate as the aerobic tank nitrate _{(NH 4 -N) (NO 3} -, NO 2 - Oxidizing with); And a fourth step of discharging the wastewater of the aerobic tank treated in the third step to a sedimentation tank to be returned to the second step or discharged to the outside.

The wastewater and waste isopropyl alcohol are mixed so that the ratio of chemical oxygen demand (COD, Chemical Oxygen Demand, mg / L, chromium method) / total nitrogen (T-N, mg / L) in the wastewater is between 10 and 20.

Wherein the microorganism is a precipitated sludge returned from the settling tank, the oxidation of nitrogen in the first step ^{_{4 (NO 2 -, NO 3}} -) , nitrogen gas converted to (N _2), and perchlorate (ClO4 ^-) a chlorine ion (Cl ^-) in Switch to remove

The dissolved oxygen concentration of the aerobic tank is maintained in the range of 2 ~ 5mg / L.

The concentration of microorganisms in the anaerobic and aerobic tanks is maintained at 3000 to 4000 mg / L.

The return rate of the settling sludge in the fourth step is 20 to 50% of the amount of wastewater flowing into the anoxic tank from the pH adjustment tank.

According to the present invention has the following effects.

First, the present invention can replace expensive methanol which is a basic carbon source by using waste IPA which is an economical carbon source to remove nitrogen and perchlorate.

Second, instead of using expensive methods such as ion exchange, activated carbon, reverse osmosis, etc. to remove perchlorate, the existing biological nitrogen removal process AO method is used and waste IPA is used to remove nitrogen and perchlorate. It will greatly contribute to pollution prevention.

That is, the cost of removing nitrogen and perchlorate in the wastewater can be minimized, and the waste IPA can be used to reduce the cost of biological treatment process, thereby removing the nitrogen and perchlorate in the wastewater more economically and efficiently.

Hereinafter, a preferred embodiment of the nitrogen and perchlorate removal method of the wastewater according to the present invention will be described in detail.

1 is a block diagram showing the nitrogen and perchlorate removal method of the wastewater according to the present invention, Figure 2 is a schematic configuration diagram showing a removal process for realizing the nitrogen and perchlorate removal method of the wastewater according to the present invention.

The present invention is the first step of neutralizing the wastewater to the pH 6.5 ~ 8 range by mixing the raw waste water and the denitrification and perchlorate removal carbon source composition to a certain ratio to collect in a pH adjusting tank 30 and injecting an acidic or alkaline solution, A second step of removing nitrogen oxide and perchlorate from the waste water by injecting the waste water neutralized in the first step into the anoxic tank 40;

After the 2-step embodiment the ammonium nitrogen increase in NOx with the perchlorate is supplied to the removal of waste into aerobic tank 50, the residual organic matter and oxygen-free process to nitrate nitrogen _{(NH 4 -N) (NO 3} -, NO 2 - A third step of oxidizing), and a fourth step of discharging the wastewater of the aerobic tank 50 to the sedimentation tank 60 to be returned or discharged to the outside.

The present invention uses waste IPA (waste isopropyl alcohol) as the carbon source composition for denitrification and perchlorate removal. Waste IPA is a waste solution that is generated after cleaning or the like in the semiconductor and LCD manufacturing industries. This waste IPA has 250,000 ~ 300,000mg / L on the basis of COD chromium and contains other moisture, so it is effective as a carbon source composition. In addition, most waste IPAs are incinerated and effective in terms of cost.

Hereinafter, each step process will be described in detail.

1. First Step (Catching and pH Adjustment)

The raw waste water and the denitrification and perchlorate removal carbon source composition are supplied into the collection tank 10 and mixed at a constant ratio. Next, the prepared wastewater mixed at a predetermined ratio in the water collecting tank 10 is collected in the pH adjusting tank 30, and an acidic or alkaline solution is supplied so that the pH is in the range of 6.5-8.

In order to remove nitrogen oxide and perchlorate in the post-oxygen-free anoxic process, the ratio of chemical oxygen demand (mg / L, chromium method) / total nitrogen (T-N, mg / L) in the prepared wastewater must be at least 10.

This is because denitrification microorganisms grown in an oxygen-free tank first use nitrogen oxides (NO ₂ ⁻ , NO ₃ ⁻ ) and then reduce perchlorate (ClO 4 ⁻ ). Therefore, the concentration of total nitrogen (TN) of the influent is important for the complete removal of perchlorate.

In order to maintain this ratio, a carbon source composition for denitrification and perchlorate removal is introduced into the sump 10 where the raw waste water is collected. The above-described waste IPA is used as the carbon source composition for denitrification and perchlorate removal.

In addition, the ratio of chemical oxygen demand (mg / L, chromium method) / total nitrogen (T-N, mg / L) in the wastewater is preferably 20 or less. This is because the COD concentration of the effluent is increased, which may cause other pollution.

Sulfuric acid (H ₂ SO ₄ ) or sodium hydroxide (NaOH) may be used as an acidic or alkaline solution for adjusting the pH of the prepared wastewater, but is not limited thereto.

2. Second Step (Anoxic Process Step)

The prepared wastewater neutralized in the first step is injected into the anoxic tank 40 to remove nitrogen oxide and perchlorate in the wastewater.

That is, while the prepared waste water of neutral continuously into the anoxic nitrogen oxide by using a microorganism _{^{(NO 2 -, NO 3 -}} ) a perchlorate (ClO ₄ ^-) to nitrogen (N ₂₎ of chlorine (Cl ^-) ions decomposed to By removing it. At this time, the supply of microorganisms is to return the settling sludge generated in the settling tank 60 after the fourth step.

3. The third step (aerobic process step)

The ammonium nitrogen increase in the residual organic matter and oxygen-free process to supply the NOx perchlorate and the removed waste into aerobic tank (50) (NH ₄ -N) is oxidized into a nitrate nitrogen removal ^{_{(NO 3 - -, NO 2}} ) do. The aerobic process oxidizes ammonia nitrogen, which has been increased in the anoxic process, to nitrogen, by the injection of oxygen. The dissolved oxygen concentration in the aerobic tank 50 for removing residual organic matter and ammonia nitrogen is maintained between 2 and 5 mg / L.

Then, the concentration of microorganisms in the anaerobic tank and the aerobic tank is maintained at 3000 to 4000 mg / L. The microbial concentration regulates the return rate of the wastewater in the fourth step by maintaining the microbial amount appropriately.

4. Fourth stage (sedimentation and return / discharge stage)

Waste water of the aerobic tank 50 is discharged to the settling tank 60 to be returned to the anoxic tank or discharged to the outside. The fourth step allows the untreated nitrogen nitrate and organics to be treated again in the aerobic process of the third step.

To this end, some of the contaminants finally remaining in the settling tank in the fourth step is returned to the anoxic process so that the removal of nitrogen is fed back.

That is, the settling tank 60 is installed to manage the last remaining pollutants within the emission standard. The return rate of the settling sludge in the settling tank is 20-50% of the amount of wastewater flowing from the pH adjustment tank into the anoxic tank. As a result of the experiment of the present invention, when the return rate is less than 20%, the nitrogen removal efficiency was low, and when it exceeds 50%, the nitrogen removal efficiency was high, but the process was lengthy, which was not preferable in terms of energy saving.

The total residence time of the wastewater consisting of the first to fourth stages is 24 hours or more, including the residence time of the anaerobic tank 40 and the aerobic tank 50.

The present invention is carried out by the AO method, and includes a waste IPA storage tank 20, a collecting tank 10, a pH adjusting tank 30, an oxygen-free tank 40, an aerobic tank 50, a precipitation tank 60. The AO method is a biological treatment method that removes nitrogen oxides and organic matters by using the returned microorganisms in the anoxic tank 40 and the aerobic tank 50.

The pH adjusting tank 30 is provided with an agitator 31 for quickly and evenly mixing the acid or alkaline solution and wastewater supplied therein, and an ion index meter 32 for measuring the pH of the wastewater.

The supply of the acidic or alkaline solution is connected to the acidic or alkaline solution tank 33 and the pH adjusting tank 30 to be arranged in the supply pipe 34 and the supply pipe 34, which is a transfer passage for the acidic or alkaline solution, and the ion index meter 32 By the control valve 35 which opens and closes the supply pipe 34 in accordance with the hydrogen ion index measured from).

In addition, a blower 51 for supplying oxygen is provided in the aeration tank 50, and agitators 11 and 41 are provided in the collection tank 10 and the oxygen-free tank 40, respectively.

In addition, the waste IPA storage tank 20 is connected to the sump tank 10, and the ratio of COD (chromium method) / total nitrogen (TN) (mg / mg) of the raw waste water prepared in the sump tank 10 becomes 10 or more. In order to provide waste IPA, a fixed quantity pump 21 is provided.

Hereinafter, the nitrogen and perchlorate removal method of the wastewater to help the understanding of the present invention will be described through the examples.

[Example]

LCD Manufacturing Process This is an example of treating a large amount of nitrogen compounds and perchlorate-containing wastewater in wastewater.

The characteristics of raw wastewater are pH 3.5 ~ 10.0, COD 200 ~ 300mg / L, total nitrogen 70 ~ 150mg / L, perchlorate 45 ~ 90mg / L, total phosphorus 2 ~ 5mg / L.

First, raw wastewater and waste IPA, a carbon source for denitrification and perchlorate removal, were introduced into the water collection tank 10 to maintain COD / total nitrogen consumption of 10 or more at a COD (chromium method) of 700 to 1500 mg / L and then adjust the pH (6.5 ~ 8.0) and introduced into an anaerobic tank 40 which is a biological treatment process.

At this time, in order to maintain the homogenization of the water quality and the COD / T-N (mg / mg) ratio of 10 or more, the retention time of the collection tank 10 is maintained for 1 day or more. Waste IPA input from the sump (10) is automatically supplied to the metering pump (21), for this condition to analyze the daily COD (chromium) and total nitrogen to maintain the ratio of 10 phases.

The temperature of the waste water in the anaerobic tank 40 was about 30 ~ 35 ℃, the amount of microorganism was maintained at 3,000mg / L ~ 4,000mg / L. In the aerobic tank 50, the dissolved oxygen concentration was maintained at 2 mg / L or more, and the amount returned to the anaerobic tank was maintained at 120% of the wastewater injection amount.

The concentration of treated water after 28 hours of anoxic and aerobic baths is shown in Table 1.

(Unit: mg / L) Item pH Total nitrogen COD (chrome) A total person Perchlorate Pharmaceutical Wastewater 6.5-8.0 70-100 700-1500 2 ~ 5 45-90 Anaerobic 6.8 ~ 7.6 20-30 100-200 1-3 Not Detected Sedimentation tank 6.5 ~ 7.3 10-20 50-100 0.1 ~ 1 Not Detected

As a result of the removal test of biological nitrogen and perchlorate using the waste IPA carbon source of Table 1, it can be seen that perchlorate is contained in the raw wastewater, but perchlorate is not detected in the anoxic tank.

In addition, it can be seen that the amount of total nitrogen (N), total phosphorus (P), chromium (Cr) is also reduced from the oxygen-free tank to the precipitation tank. Therefore, it can be inferred that organic matter and nitrogen can be reduced to the maximum through the process of returning from the precipitation tank to the anoxic tank.

Within the scope of the basic technical idea of the present invention, many other modifications are possible to those skilled in the art, and the scope of the present invention should be interpreted based on the appended claims. will be.

1 is a block diagram showing a nitrogen and perchlorate removal method of the wastewater according to the present invention.

Figure 2 is a schematic diagram of a process for realizing the nitrogen and perchlorate removal method of the wastewater according to the present invention.

Explanation of symbols on the main parts of the drawings

10: water tank 11: stirrer

20: waste IPA storage 21: metering pump

30: pH adjustment tank 31: Agitator

32: ion index meter 33: solution tank

34: supply pipe 35: control valve

40: Anaerobic tank 41: Agitator

50: Unit 51: Blower

60: sedimentation tank

Claims (6)

A first step of neutralizing the mixed wastewater by mixing the raw wastewater with waste isopropyl alcohol and collecting them in a pH adjusting tank and injecting an acidic or alkaline solution; A second step of injecting the wastewater in the first step into an anoxic tank and removing nitrogen oxide and perchlorate from the wastewater using microorganisms; Wherein after step 2, the exemplary ammonium nitrogen increase in the residual organic matter and the second step by supplying the waste water to remove nitrogen oxides and perchlorate as the aerobic tank nitrate _{(NH 4 -N) (NO 3} -, NO 2 - Oxidizing with); And a fourth step of discharging the wastewater of the aerobic tank treated in the third step to the sedimentation tank and returning it to the second step or discharging it to the outside. In the second step, Wherein the microorganism is a precipitated sludge returned from the settling tank, the oxidation of nitrogen in the first step ^{_{4 (NO 2 -, NO 3}} -) , nitrogen gas converted to (N _2), and perchlorate (ClO4 ^-) a chlorine ion (Cl ^-) in Nitrogen and perchlorate removal method of wastewater, characterized in that the conversion by removing. The method according to claim 1, In the first step The wastewater and waste isopropyl alcohol are mixed so that the ratio of chemical oxygen demand (COD, Chemical Oxygen Demand, mg / L, chromium method) / total nitrogen (TN, mg / L) in the wastewater is between 10 and 20. Nitrogen and perchlorate removal method of wastewater. delete The method according to claim 1, In the third step, Dissolved oxygen concentration of the aerobic tank is a nitrogen and perchlorate removal method of the waste water, characterized in that maintained in the range 2 ~ 5mg / L. The method according to claim 1 or 2 or 4, In the second step and the third step, Nitrogen and perchlorate removal method of the waste water, characterized in that to maintain the microbial concentration of the anoxic tank and aerobic tank at 3000 ~ 4000mg / L. The method according to claim 5, The return rate of the precipitated sludge in the fourth step is nitrogen and perchlorate removal method of the wastewater, characterized in that 20 to 50% of the amount of wastewater flowing into the anoxic tank from the pH adjustment tank.

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