KR20220151144A - Methods for treatment of refractory wastewater to simultaneously remove organic pollutants and ammonia nitrogen - Google Patents

Abstract

The present invention relates to a non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen. More specifically, the non-degradable wastewater treatment method comprises: an oxidizing agent introducing step of introducing a chlorine-based oxidizing agent into non-degradable wastewater; and an oxidizing agent activating step of activating the chlorine-based oxidizing agent introduced into the non-degradable wastewater through the oxidizing agent introducing step. The non-degradable wastewater treatment method performed through the steps simultaneously removes organic contaminants and ammonia nitrogen contained in non-degradable wastewater with high efficiency.

Description

Non-degradable wastewater treatment method that simultaneously removes organic contaminants and ammonia nitrogen

The present invention relates to a non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, and more particularly, to a method for treating organic pollutants (Total Organic Carbon, TOC) and ammonia nitrogen contained in non-degradable wastewater using a chlorine-based oxidizing agent. (Ammonia Nitrogen, NH ₃ -N) with high efficiency.

Ethanolamine [NH ₂ CH ₂ CH ₂ OH], which is used as a pH adjuster for secondary system water of nuclear power plants, has low volatility and high basicity compared to ammonia, a conventional pH adjuster, enabling pH adjustment with only a small amount of injection and corrosion control of devices It is a stable organic compound whose beneficial effect on the side has been verified. However, from an environmental point of view, ethanolamine contains organic carbon (C) and nitrogen (N) in its chemical formula [NH ₂ CH ₂ CH ₂ OH], which simultaneously increases the concentration of organic pollutants and ammonia nitrogen when introduced into the water system. It is a contaminant and is known as a difficult-to-decompose material that is difficult to remove with existing wastewater treatment facilities.

In order to remove these non-degradable contaminants, strong oxidizing agents such as hydroxyl radicals (OH·) and sulfate radicals (SO ₄ ^-· ) having high oxidation potential are required.

The oxidation potentials of representative oxidizing agents commonly used are shown in Table 1 below.

A representative method for generating hydroxyl radicals is the Fenton oxidation method. The Fenton oxidation method is a method of generating hydroxyl radicals by reacting divalent iron ions with hydrogen peroxide, and has disadvantages in that a large amount of sludge is generated due to iron ion implantation and economical efficiency is low because a large amount of expensive hydrogen peroxide is injected. In addition, it is possible to treat contaminants only under acidic conditions, so precise pH management is required.

Fe ²⁺ + H ₂ O ₂ → Fe ²⁺ + OH + OH ^- (1)

Sulfuric acid radicals can be generated by activating persulfate (S ₂ O ₈ ^2- and SO ₅ ^2- ) anions. _In order to activate _persulfuric acid, processes such as heating, ultraviolet irradiation, and metal catalyst injection are required _. (NH ₄ ) ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ) and potassium peroxymonosulfate (KHSO ₅ ) are relatively expensive oxidizing agents.

S ₂ O ₈ ^2- + heat → 2SO ₄ ^- (2)

S ₂ O ₈ ^2- + UV → SO ₄ ^- + SO ₄ ^2- (3)

S ₂ O ₈ ^2- + Fe ²⁺ → SO ₄ ^- + Fe ³⁺ + SO ₄ ^2- (4)

Chlorine-based oxidizing agent is a household sterilization disinfectant widely used worldwide, and is an oxidizing agent used for swimming pool disinfection and water treatment. It is also used in Breakpoint Chlorination, a representative wastewater treatment process that treats ammonia nitrogen contained in wastewater.

NH ₄ ⁺ + 1.5HOCl → 0.5N ₂ + 1.5H ₂ O + 2.5H ⁺ + 1.5Cl ^- (5)

Sodium hypochlorite is produced by electrolysis of salt (NaCl) or by reacting chlorine gas (Cl ₂ ) and caustic soda (NaOH) by a low-temperature cooling method.

2NaCl + 2H ₂ O → Cl ₂ + 2NaOH + H ₂ (6)

Cl ₂ + 2NaOH → NaOCl + NaCl + H ₂ O (7)

Generally, it is known that widely used chlorine-based oxidizing agents are not suitable for treating non-decomposable organic materials due to their low oxidizing power. However, the present inventors performed a number of experiments to increase the oxidizing power of the chlorine-based oxidizing agent, and through the experiments, as a method of activating the chlorine-based oxidizing agent, the present invention was completed by deriving a method of heating, ultraviolet irradiation, and catalyst input.

In general, chlorine-based oxidizing agents, especially sodium hypochlorite, are recommended to be stored at low temperatures and away from heat sources to maintain stability and oxidizing power. Korean Registered Patent No. 10-2058319 discloses that sodium hypochlorite is a chemically unstable substance and its concentration decreases depending on the storage period and temperature. Also, in the handbook of sodium hypochlorite from OxyChem, it is stated that the temperature affects the stability of the hypochlorous acid solution, and that the higher the temperature, the higher the decomposition rate, so keep the solution away from heat. The decomposition rate as a function of temperature has been recorded to decompose 5 times faster at 40°C than at 25°C for 15% sodium hypochlorite. European Union Regulation No. 528/2012, the half-life of sodium hypochlorite aqueous solution with an effective chlorine concentration of 10% (w/w) by temperature was 800 days at 15 ° C, 220 days at 25 ° C, 3.5 days at 60 ° C, and 0.079 days at 100 ° C. It is recorded that the stability decreases rapidly as .

In addition, a large amount of chlorine ions contained in the sodium hypochlorite solution is a causative material that causes metal corrosion and environmental pollution. Accordingly, low salt sodium hypochlorite products with reduced concentration of chlorine ions in sodium hypochlorite are being released. Low table salt sodium hypochlorite with reduced concentration of chlorine ions refers to those in which the sodium chloride content in sodium hypochlorite aqueous solution is 4.0% by weight or less. Korean Patent Laid-open Publication No. 10-2015-0076089 discloses sodium hypochlorite having a sodium hypochlorite concentration of 30 to 40% by mass, the concentration of chlorine ion is 1.5% by mass or less, and the concentration of sodium chloride is 5.0% by mass or less of sodium hypochlorite. The manufacturing method is described.

An object of the present invention is to provide a non-degradable wastewater treatment method for removing organic contaminants and ammonia nitrogen contained in non-degradable wastewater with high efficiency.

An object of the present invention is an oxidizing agent inputting step of introducing a chlorine-based oxidizing agent into non-degradable wastewater and an oxidizing agent activation step of activating the non-degradable wastewater into which the oxidizing agent is introduced through the oxidizing agent inputting step; This is achieved by providing a method for treating recalcitrant wastewater with simultaneous removal.

According to a preferred feature of the present invention, the step of introducing the oxidizing agent is made by adding 500 to 10,000 parts by weight of a chlorine-based oxidizing agent based on 100 parts by weight of organic contaminants contained in the recalcitrant wastewater.

According to a more preferred feature of the present invention, the step of introducing the oxidizing agent is made by adding 1000 to 7000 parts by weight of a chlorine-based oxidizing agent based on 100 parts by weight of organic contaminants contained in the recalcitrant wastewater.

According to a more preferred feature of the present invention, the oxidizing agent activation step is a reaction promoting step of maximizing the oxidation reaction by increasing the reaction rate of activating the chlorine-based oxidizing agent and converting it into activated radicals.

According to a more preferred feature of the present invention, the chlorine-based oxidizing agent is made of at least one selected from the group consisting of chlorine, hypochlorite, alkali metals and alkaline earth metals containing chlorine, and the hypochlorite is sodium hypochlorite, potassium hypochlorite and at least one selected from the group consisting of calcium hypochlorite.

According to a further preferred feature of the present invention, the chlorine-based oxidizing agent is that the content of the metal salt containing chlorine ions is 1 to 12% by weight.

According to a more preferred feature of the present invention, the oxidizing agent activation step is to consist of at least one selected from the group consisting of heating, ultraviolet irradiation and catalyst input.

According to a further preferred feature of the present invention, the catalyst is made of at least one selected from the group consisting of metal catalysts and chelate metal catalysts.

According to a more preferred feature of the present invention, the heating is to be performed at a temperature of 50 ° C. to a boiling point or less for 10 to 100 minutes.

According to a more preferred feature of the present invention, a pH adjustment step of adjusting the pH of the recalcitrant wastewater to 4 to 13 by adding a pH adjuster to the recalcitrant wastewater is further performed prior to the inputting of the oxidizing agent.

The non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen according to the present invention shows an excellent effect of simultaneously removing organic contaminants and ammonia nitrogen contained in non-degradable wastewater with high efficiency.

1 is a flowchart illustrating a method for treating recalcitrant wastewater for simultaneously removing organic contaminants and ammonia nitrogen according to an embodiment of the present invention.
2 is a flow chart showing a method for treating recalcitrant wastewater in which organic contaminants and ammonia nitrogen are simultaneously removed according to another embodiment of the present invention.
Figure 3 is a photograph showing the equipment used in the embodiment of the present invention taken.

Hereinafter, a preferred embodiment of the present invention and the physical properties of each component will be described in detail, but this is to be explained in detail so that a person having ordinary knowledge in the art to which the present invention belongs can easily practice the invention, This is not meant to limit the technical spirit and scope of the present invention.

The treatment method of non-degradable wastewater according to the present invention includes organic carbon (C) and nitrogen (N) in the chemical formula and contains ethanolamine, a non-degradable pollutant that simultaneously increases the concentration of organic contaminants and ammonia nitrogen. It consists of an oxidizing agent inputting step (S101) of introducing a chlorine-based oxidizing agent into the wastewater and an oxidizing agent activating step (S102) of activating the chlorine-based oxidizing agent introduced into the ethanolamine-containing recalcitrant wastewater through the oxidizing agent inputting step (S101).

The oxidizing agent input step (S101) is a step of injecting a chlorine-based oxidizing agent into the ethanolamine-containing non-decomposable wastewater, which is made by injecting 500 to 10,000 parts by weight of the chlorine-based oxidizing agent based on 100 parts by weight of organic contaminants in the ethanolamine-containing non-degradable wastewater. More preferably, 1000 to 7000 parts by weight of a chlorine-based oxidizing agent is added to 100 parts by weight of organic contaminants in non-degradable wastewater containing ethanolamine.

The chlorine-based oxidizing agent is composed of at least one selected from the group consisting of chlorine, hypochlorite, alkali metals and alkaline earth metals containing chlorine, and the hypochlorite is one selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite. It is preferable to consist of the above.

If the content of the chlorine-based oxidizing agent is less than 500 parts by weight, the effect of removing organic contaminants and ammonia nitrogen contained in the recalcitrant wastewater is reduced, and if the content of the chlorine-based oxidizing agent exceeds 10,000 parts by weight, the effect is not greatly improved. However, there is a problem that the non-decomposable wastewater is again contaminated with chlorine-based oxidizing agents.

In addition, the chlorine-based oxidizing agent is preferably used with a metal salt content of 1 to 12% by weight containing chlorine ions, and even if the content of metal salt containing chlorine ions exceeds 12% by weight, it does not matter. Considering the problems of device corrosion and environmental pollution caused by ions, it is more preferable to use those having a low content of chlorine ions.

The oxidizing agent activation step (S102) is a step of activating the chlorine-based oxidizing agent introduced into the recalcitrant wastewater through the oxidizing agent inputting step (S101), and heating and ultraviolet irradiation to the recalcitrant wastewater into which the oxidizing agent is introduced through the oxidizing agent inputting step (S101). And the oxidizing agent is activated by applying at least one selected from the activation method of adding the catalyst. At this time, the heating is preferably performed at a temperature of 50 ° C. to boiling point for 10 to 100 minutes, and the catalyst is a metal catalyst and It is preferably composed of at least one selected from the group consisting of chelate metal catalysts.

At this time, when the heating is performed in the oxidizing agent activation step (S102), if the heating temperature is less than 50 ° C or the heating time is less than 10 minutes, the removal effect of organic contaminants contained in the recalcitrant wastewater is reduced, and the heating step (S103) If the temperature exceeds the boiling point or the heating time exceeds 100 minutes, the above effect is not greatly improved and is not desirable in terms of energy efficiency.

In addition, heating among the methods of activating the chlorine-based oxidizing agent in the oxidizing agent activation step (S102) is generally a cause of rapidly reducing the stability and oxidizing power of the chlorine-based oxidizing agent, but in this patent, organic contaminants and ammonia nitrogen in recalcitrant wastewater are removed. It is used as an activation method for chlorine-based oxidizing agents that simultaneously remove it.

Prior to the oxidizing agent input step (S101), a pH adjusting step (S100) of adjusting the pH of the recalcitrant wastewater to 4 to 13 by adding a pH adjuster to the recalcitrant wastewater may be further performed. As described above, the pH control step ( When the pH of the non-degradable wastewater is adjusted to 4 to 13 by introducing a pH adjuster through S100), the removal effect of organic contaminants and ammonia nitrogen contained in the non-degradable wastewater is further improved. However, it is preferable to determine whether to add the pH adjuster according to the on-site conditions of treating the non-degradable wastewater, the configuration of the treatment process, and the type of chlorine-based oxidizing agent used.

Hereinafter, a non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen according to the present invention and the effect of simultaneous removal of organic contaminants and ammonia nitrogen in non-degradable wastewater treated by the treatment method will be described with examples. do it with

As the non-degradable wastewater used in Examples and Comparative Examples, simulated wastewater prepared by mixing ethanolamine and deionized water was used, and sodium hypochlorite (NaOCl) was used as a chlorine-based oxidizing agent. Sulfuric acid (H ₂ SO ₄ ) and sodium hydroxide (NaOH) were used as pH adjusting agents for the prepared non-degradable wastewater. However, sulfuric acid and sodium hydroxide are not limited to pH adjusters of non-degradable wastewater. As shown in FIG. 3 below, this embodiment was carried out using a device equipped with a heating mantel capable of temperature control and stirring of the solution and a double-jacketed coil cooling tube capable of minimizing evaporation of the solution during heating. .

After the heating reaction was completed, the temperature of the solution was quenched by water cooling immediately to lower the temperature of the solution to room temperature to maintain the reaction time set during the experiment. Finally, the removal rate of organic contaminants and ammonia nitrogen was analyzed by TOC and TN concentrations before and after the introduction of the oxidizing agent. and confirmed.

<Example 1>

The pH was adjusted to 7 by adding a pH adjuster to the simulated wastewater prepared as described above. Next, sodium hypochlorite was added to the pH-adjusted wastewater. At this time, sodium hypochlorite was added in an amount of 2000 parts by weight relative to 100 parts by weight of organic pollutants (TOC) in simulated wastewater prepared with ethanolamine. 100 mL of the wastewater solution to which sodium hypochlorite was added was placed in a three-necked flask, inserted into a heating mantle, and then heated. The temperature of the solution was set to be 50 ℃, 70 ℃, 90 ℃, 100 ℃, and the temperature was maintained for 20 minutes after reaching the set temperature. After the completion of the heating reaction, the temperature was lowered to room temperature as described above, and then TOC and TN concentrations were analyzed.

<Comparative Example 1>

Proceed in the same manner as in Example 1, but sodium persulfate (Na ₂ S ₂ O ₈ ) was used instead of sodium hypochlorite as an oxidizing agent, compared to 100 parts by weight of organic pollutants (TOC) in simulated wastewater prepared with ethanolamine It was added so as to be 6000 parts by weight, and the temperature of the solution was set to 90 ° C. The TOC and TN concentrations of the treated water as described above were analyzed.

The test results of Example 1 and Comparative Example 1 are shown in Table 2 below.

As shown in Table 2, the results of Example 1 showed that the TOC removal rate increased significantly from 42% to 95% when the heating temperature was increased from 20 ° C to 100 ° C. Comparing the TOC removal rate result of Example 1 with Comparative Example 1, it was confirmed that the TOC removal rate was almost similar at a heating temperature of 90° C. or higher.

In addition, comparing the TN removal rate, the TN removal rate of Comparative Example 1 was about 11%, and ammonia nitrogen was hardly removed, whereas the TN removal rate of Example 1 was about 74% at 20 ° C. and at a temperature of 50 ° C. or higher It showed a high ammonia nitrogen removal rate of 84% on average. This means that ammonia nitrogen contained in the wastewater is removed with high efficiency in a short time at the same time as sodium hypochlorite is introduced.

As a result, Example 1 showed excellent TOC and TN removal rates.

<Example 2>

A pH adjusting agent was added to the simulated wastewater prepared as described above to adjust the pH to 7, and then sodium hypochlorite was added to the pH-adjusted wastewater. However, the amount of sodium hypochlorite added was 1500, 2000, 2500, and 3000 parts by weight, respectively, relative to 100 parts by weight of organic pollutants (TOC) in simulated wastewater prepared with ethanolamine. 100 mL of the wastewater solution to which sodium hypochlorite was added was placed in a three-necked flask, inserted into a heating mantle, and then heated. The temperature of the solution was set to 90 °C, and the temperature was maintained for 20 minutes after reaching the set temperature. After the completion of the heating reaction, the temperature was lowered to room temperature as described above, and then TOC and TN concentrations were analyzed. The results of Example 2 are shown in Table 3.

As shown in Table 3, in the results of Example 2, the TOC removal rate tended to increase as the input amount of the oxidizing agent compared to the organic pollutants in the wastewater increased. However, from 2000 parts by weight (20 times) or more of the amount of the oxidizing agent, the increase in the TOC removal rate was found to be low. The average TN removal rate was 84.89%, showing a similar removal rate regardless of the increase in the amount of oxidizing agent.

Therefore, the non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen according to the present invention exhibits an effect of simultaneously removing organic contaminants and ammonia nitrogen contained in non-degradable wastewater with high efficiency.

S100; pH adjustment step
S101; Oxidant input step
S102; Oxidant activation step

Claims (10)

An oxidizing agent inputting step of injecting a chlorine-based oxidizing agent into the recalcitrant wastewater; and
An oxidizing agent activation step of activating the chlorine-based oxidizing agent introduced into the recalcitrant wastewater through the oxidizing agent input step; a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen.
According to claim 1,
The oxidizing agent input step is a non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that by adding 500 to 10,000 parts by weight of a chlorine-based oxidizing agent based on 100 parts by weight of organic contaminants contained in the non-degradable wastewater.
According to claim 2,
The oxidizing agent input step is a non-degradable wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that by adding 1000 to 7000 parts by weight of a chlorine-based oxidizing agent based on 100 parts by weight of organic contaminants contained in the non-degradable wastewater.
According to any one of claims 1 to 3,
The chlorine-based oxidizing agent is composed of at least one selected from the group consisting of chlorine, hypochlorite, alkali metals and alkaline earth metals including chlorine,
The hypochlorite is a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that consisting of at least one selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite.
According to claim 1,
The chlorine-based oxidizing agent is a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that the content of metal salt containing chlorine ions is 1 to 12% by weight.
According to claim 1,
The oxidizing agent activation step is a reaction promoting step of maximizing the oxidation reaction by increasing the reaction rate of activating the chlorine-based oxidizing agent and converting it into activated radicals.
According to claim 6,
The oxidizer activation step is a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that consisting of at least one selected from the group consisting of heating, ultraviolet irradiation and catalyst input.
According to claim 7,
The heating is a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that for 10 to 100 minutes at a temperature of 50 ℃ to boiling point (Boiling point).
According to claim 7,
The catalyst is a recalcitrant wastewater treatment method for simultaneously removing organic contaminants and ammonia nitrogen, characterized in that consisting of at least one selected from the group consisting of a metal catalyst and a chelate metal catalyst.
According to claim 1,
Prior to the oxidizing agent input step, a pH adjusting step of adjusting the pH of the non-degradable wastewater to 4 to 13 by adding a pH adjuster to the non-degradable wastewater is further performed. Degradable wastewater treatment methods.

Images