KR20100107752A - Method for removing of perchlorate ion and nitrate ion in underground water - Google Patents

Abstract

PURPOSE: A perchlorate ion of underground water and a method for eliminating the nitrate ion of the underground water for mixing the underground with carbon source are provided to efficiently remove the perchlorate ion. CONSTITUTION: A perchlorate ion and a method for eliminating the nitrate ion of the subsurface water(1) include as follows. A carbon source and a hydrogen donor are added in the polluted subsurface water. The activated charcoal is passed by the filter tub filtering the subsurface water. The carbon source is added so that it chemicals inside the subsurface water in which the carbon source is added for the value of oxygen demand.

Description

Method for removing of perchlorate ion and nitrate ion in underground water}

The present invention provides a perchlorate ion contained in the ground water (ClO ₄ ^-) and nitrate ion (NO ₃ ^-) relates to a method of removing, and more particularly for removing perchlorate ions and nitrate ions contained in the ground water to a biological It is about a method.

Wastewater generated in the explosives industry, LCD manufacturing industry, and the like contains a large number of pollutants such as perchlorate ions and nitrate ions. Such wastewater not only flows into rivers and seas, and acts as a source of pollution of river water or seawater, but also such groundwater directly penetrates the surface, or contaminated river water soaks into the surface and contaminates groundwater. As described above, when groundwater is contaminated with contaminants such as perchlorate ions and nitrate ions, the technology for treating such contaminants is very important industrially since it may cause a great disruption to the supply of industrial water.

Perchlorate ions are said to irritate human respiratory skin and cause thyroid disorders in overexposure, which can cause various abnormalities in the body. Perchlorate ions as combined chlorine (Cl) and one of four atoms of oxygen (O) atoms has the formula ClO ₄ ^- a. Perchlorate ions, although naturally occurring, are mostly derived from artificially manufactured perchlorates for industrial use. Therefore, extensive research is being conducted on the generation of perchlorate ion pollution and the development of constant and sewage treatment methods to include perchlorate ions in pollutants and to set new regulations and standards.

Perchlorate ions have high solubility and mobility in water but are chemically stable and do not readily decompose. Therefore, there is a limit in removing perchlorate ions contained in groundwater by chemical properties.

As a method for removing perchlorate ions, ion exchange, membrane separation technology, electrodialysis, reduction technology using activated carbon, and the like are applied. However, this method does not completely remove perchlorate ions contained in the actual groundwater, and when using activated carbon, there is a problem in that the activated carbon needs to be periodically replaced as the adsorption power is lowered.

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

^{_{ClO 4 - + 4H 2 → Cl}} - + 4H 2 O

Biological purification of perchlorate ions requires a carbon source (hydrogen donor) as shown in Scheme 1 above. As a carbon source, acetic acid, ethanol, methanol, etc. are generally used.

As a method of treating nitrate ions contained in groundwater, there are various methods such as ammonia degassing, destruction point chlorination, and ion exchange. However, biological nitrogen removal using microorganisms is mainly used for economical and technical limitations.

Algae culture, aquatic plant cultivation, microbial nitriding, etc. are used for the removal of biological nitrate ions.

^{_{2NO 3 - + 5H 2 → N}} 2 + 2OH- + 4H 2 0

Meanwhile, since industrial wastewater generating a large amount of perchlorate ions includes nitrate ions together, it is urgent to provide an efficient system capable of simultaneously removing perchlorate ions and nitrate ions. However, a system that can simultaneously remove perchlorate ions and nitrate ions has not been developed.

An object of the present invention is to provide a method for efficiently removing perchlorate ions and nitrate ions simultaneously from contaminated ground water by a simple method.

The present invention,

(a) adding and mixing a carbon source (hydrogen donor) to the contaminated groundwater;

(b) decomposing perchlorate ions and nitrate ions by supplying the mixture prepared in step (a) to a biofilm reactor including a carrier to which microorganisms for sewage treatment are attached; And

(C) it provides a method for removing perchlorate ions and nitrate ions of the ground water comprising the step of passing the ground water treated in step (b) through a filtration tank containing activated carbon.

According to the method of the present invention, it is possible to efficiently remove perchlorate ions and nitrate ions simultaneously from contaminated groundwater by a simple method, thereby economically securing industrial water.

Hereinafter, a method of removing perchlorate ions and nitrate ions contained in the groundwater contaminated by the present invention will be described in detail.

1 shows a block diagram of a method for removing perchlorate ions and nitrate ions according to the present invention. As shown in Figure 1, the method of the present invention,

(a) adding and mixing a carbon source (hydrogen donor) to the contaminated groundwater;

(b) decomposing perchlorate ions and nitrate ions by supplying the mixture prepared in step (a) to a biofilm reactor including a carrier to which microorganisms for sewage treatment are attached; And

(c) passing the groundwater treated in step (b) through a filtration tank containing activated carbon, and including a filtration step.

Hereinafter, each step process will be described in detail.

(1) step (a): adding a carbon source (hydrogen donor)

Contaminated ground water and carbon sources are fed into the reservoir and mixed at a constant rate.

In order to remove perchlorate ion and nitrate ion at the same time in step (b), chemical oxygen demand (COD) / total nitrogen (mg / L) Carbon source should be added so that value of) is 5 ~ 10.

Because, for wastewater treatment microorganisms growing in a biofilm reactor is first night LES byte ions converted to ion (NO ₃ ^-) to and then switched to nitrogen (N ₂₎ gas perchlorate ion (ClO ₄ ^{- -),} chlorine (Cl) This is because if the above value is less than 5, it is difficult to completely remove perchlorate ions, and if it exceeds 10, the content of carbon source becomes high, which may cause other pollution. Ultimately, in order to treat contaminated groundwater and reuse it as industrial water, it is desirable to add a carbon source to minimize residual organic matter.

In order to maintain this value, a controlled dose of carbon source (hydrogen donor) is added to the reservoir where groundwater is collected.

In the present invention, at least one selected from the group consisting of acetate, ethanol and methanol can be used as the carbon source (hydrogen donor), and methanol is preferably used.

(2) (b) step: supplying groundwater to which the carbon source is added to the biofilm reactor to remove perchlorate ions and nitrate ions

The biofilm reactor uses a carrier having a microorganism for sewage treatment, and the carrier is 60-95% (v / v), more preferably 80% (v / v) of the internal volume of the biofilm reactor. It may be provided to occupy. When the carrier is included in less than 60% (v / v) of the internal volume of the biofilm reactor, the adhesion amount of the microorganisms for sewage treatment may be insufficient, if the carrier exceeds 95% (v / v) of the groundwater added carbon source Inflow and discharge may not be smooth.

The biofilm reactor is operated under anoxic conditions and not under aerobic conditions.

In the above, various kinds of carriers used in the art may be used, and for example, polypropylene-based plastic carriers may be used.

Microorganisms for sewage treatment in the above can be used to attach to the carrier in various ways used in this field. For example, it is possible to use microorganisms for sewage treatment attached to a carrier using sewage sludge. These microorganisms for sewage treatment convert nitrate ions (NO ₃ ⁻ ) to nitrogen (N ₂ ) gas and remove perchlorate ions (ClO ₄ ⁻ ) to chlorine (Cl ⁻ ) ions.

As illustrated above, when the sewage sludge is attached to the carrier using sewage sludge, the excess sewage microorganism not attached to the carrier may be discharged to the outside through an outlet provided at the bottom of the biofilm reactor. In addition, the microorganisms attached to the carrier and overgrown are preferably removed using compressed air of 20 to 25 psi every month.

It is preferable to maintain the concentration of the microorganisms for sewage treatment at 3000 to 4000 mg / L in order to sufficiently remove perchlorate ions and nitrate ions.

In the step (b), the groundwater to which the carbon source is added is introduced into the biofilm reactor, collected for about 1.5 to 2.5 hours, preferably about 2 hours, and then discharged to the next step.

(3) step (c): filtering using a filtration tank containing activated carbon

In order to treat groundwater contaminated by the method of the present invention and reuse it as industrial water, it is important to minimize residual contaminants such as organic matter remaining in the groundwater treated in steps (a) and (b). . Therefore, in this invention, the method of filtering by the filtration tank containing activated carbon is employ | adopted.

The contaminants filtered in the filtration tank containing the activated carbon are transferred to a wastewater treatment plant for treatment.

In the above, the activated carbon is backwashed once every month, which is advantageous for effectively removing contaminants such as residual organic matter.

In addition, the method of the present invention may further perform a filtration method generally used in this field in order to remove the remaining contaminants more cleanly apart from the filtration by the filtration tank including the activated carbon.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

Example 1 Purification of Groundwater Contaminated with Perchlorate and Nitrate Ions

Methanol as a carbon source (hydrogen donor) to a reservoir supplied with perchlorate ions and nitrate ions, and chemical oxygen demand (COD) in the groundwater with methanol (COD) / total nitrogen (mg / L) was added so that the value was 7 and mixed.

The mixture prepared in step (a) was supplied to a biofilm reactor including a carrier to which microorganisms for sewage treatment were attached, and stayed for 2 hours to remove perchlorate ions and nitrate ions.

The groundwater treated in step (b) was passed through a filtration tank containing activated carbon to remove residual contaminants such as residual carbon sources.

The results of the treatment of the contaminated groundwater are shown in Table 1 below.

Item Before treatment After treatment Perchlorate ion (ClO ₄ ^-) 50 ppb 0 ppb Nitrate ion (NO ₃ ^-) 15 ppm 0 ppm

(Unit: mg / L)

As confirmed in Table 1, when the groundwater contaminated with perchlorate ions and nitrate ions by the method of the present invention, it can be confirmed that the perchlorate ions and nitrate ions are completely removed by a simple method.

1 is a block diagram showing a method for removing nitrate ions and perchlorate ions from groundwater contaminated by the present invention.

Claims (6)

(a) adding and mixing a carbon source (hydrogen donor) to the contaminated groundwater; (b) decomposing perchlorate ions and nitrate ions by supplying the mixture prepared in step (a) to a biofilm reactor including a carrier to which microorganisms for sewage treatment are attached; And (C) a method for removing perchlorate ions and nitrate ions of ground water, comprising the step of passing the ground water treated in step (b) through a filtration tank containing activated carbon. The method of claim 1, wherein the carbon source in step (a), the chemical oxygen demand (COD, chemical oxygen demand, mg / L, chromium method) / total nitrogen (mg / L) value in the groundwater to which the carbon source is added 5 ~ Method for removing perchlorate ions and nitrate ions in groundwater, characterized in that added to 10. The method according to claim 1, wherein the carbon source in step (a) is a perchlorate ion and nitrate ion removal method of groundwater, characterized in that composed of one or more selected from the group consisting of acetate, ethanol and methanol. The method according to claim 1, wherein the microorganisms for sewage treatment in step (b) is attached to the carrier using sewage sludge, characterized in that the function of converting nitrate ions into nitrogen gas and decomposes perchlorate ions into chlorine ions. Method for removing perchlorate ions and nitrate ions in groundwater. The method for removing perchlorate ions and nitrate ions of groundwater, according to claim 4, wherein the concentration of the microorganisms for sewage treatment is maintained at 3000 to 4000 mg / L in the step (b). The method of claim 1, wherein in step (b), the carrier comprises 60-95% (v / v) of the internal volume of the biofilm reactor, and the method for removing perchlorate ions and nitrate ions in groundwater.

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