KR20180116539A - Biological Treatment System And Method For Low Temperature Waste Water Using Electrochemical Stabilization Tank - Google Patents

Abstract

The present invention relates to an apparatus and a method to biologically treat low-temperature wastewater by using an electrochemical stabilization tank. In order to solve problems of a conventional biological treatment apparatus and a method thereof, which do not satisfy standards of discharged water due to degraded ammonia removal efficiency, provided is an electrochemical stabilization tank having a constant ammonia removal effect regardless of temperature and effectively controlling residual chlorine generated from an ammonia removing procedure, and thus, the present invention is capable of satisfying the standards and effectively conducting biological wastewater treatment regardless of temperature. Thus, the present invention is capable of replacing a conventional biological treatment method, in which ammonia removal efficiency must be maintained through repeated addition of nitrification bacteria in winter when a propagation rate of nitrification bacteria gets lower as the temperature of influent water gets lower.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrochemical stabilization tank,

The present invention relates to an apparatus and a method for biological treatment of low-temperature wastewater using an electrochemical stabilization tank.

Methods for removing nitrogen in wastewater include ion exchange methods, membrane methods, and biological treatment methods. Ion exchange method and membrane method is a treatment method which requires high cost in nitrogen treatment of wastewater. Biological treatment method is suitable for treatment of low concentration of nitrogen but there is a limit to high concentration of nitrogen treatment. Especially, there is toxic substance in wastewater, If the temperature is maintained at a low temperature, there is a drawback that the treatment efficiency is drastically reduced. Biological treatment methods in wastewater using nitrate bacteria have recently been widely used in sewage treatment plants. In the biological treatment apparatus, nitrate bacteria are present in the reaction tank, and the nitrification bacteria oxidize ammonia, ammonium ions and the like of the wastewater into nitrite or nitrate, and denitrify by the denitrifying microorganisms to remove nitrogen in the wastewater. In Korea, where the four seasons are clear and the mean temperature difference between winter and summer is very high, the number of days in which the average temperature falls below 10 ℃ increases in winter. Therefore, the average temperature of the wastewater flowing into the wastewater treatment plant in the winter season is 8 to 9 ° C. Since the biological treatment method is a step of discharging treated wastewater after a predetermined reaction time in a stepwise manner, a certain amount of nitrifying bacteria may be discharged in the wastewater treatment process. In such a situation, if the temperature of the inflow wastewater is maintained at a low temperature such as 8 to 9 占 폚, the rate of growth of nitrifying bacteria is slowed and the number of discharged nitrifying bacteria can not be canceled by the growth of nitrifying bacteria. Therefore, the biological treatment method can not secure the number of nitrifying bacteria necessary for the actual wastewater treatment in the winter season, so that the nitrification rate is drastically reduced. In order to overcome the above disadvantages, a method of supplying nitrification bacteria to the reaction vessel at regular intervals in the winter season is used. However, this method has an effect of increasing nitrification rate by increasing the number of nitrification bacteria temporarily, This is not a method of repetitive supply. Electrolysis is used to remove ammonia, turbidity, and biochemical oxygen demand (BOD). The removal of ammonia or ammonia nitrogen using the electrolysis is performed by two routes. The first path is direct oxidation and the second path is indirect oxidation. The direct oxidation method refers to a mechanism in which organic substances and nitrogen are removed by OH radicals generated in the oxidation electrode, and the indirect oxidation method is a method in which a chloride ion such as Cl ₂ , HOCl, and OCl ^- It means the mechanism by which ammonia is removed by chlorine. In the case of the indirect oxidation method, it is applied to the treatment of high concentration nitrogen wastewater, the nitrate, phosphorus, and chromaticity removal of livestock manure, the case where MgCl ₂ is added to the solid-liquid livestock manure to form struvite However, in all of the above cases, it has been found that there is a disadvantage in that the organic matter concentration of the treated water is high and the chlorine byproduct remains, which is inadequate to discharge the organic matter. Another example is the addition of NaCl to livestock manure to improve the electrical conductivity, thereby improving the removal efficiency of ammonia nitrogen. However, not only does the NaCl concentration in the treated water rise, but also the disadvantage of the indirect oxidation method is the formation of chlorine byproducts It has been confirmed that there is a disadvantage that it does not meet the criteria of effluent water.

The patent documents and references cited herein are hereby incorporated by reference to the same extent as if each reference was individually and clearly identified by reference.

Korean Patent No. 10-1392439

The present inventors have made efforts to solve the problem that ammonia treatment efficiency is lowered when the wastewater is introduced at a low temperature in the wastewater treatment using the biological treatment method of winter wastewater. As a result, the treatment efficiency of the ammonia decreased due to the temperature of the wastewater The present invention relates to an electrochemical stabilization tank capable of effectively removing residual chlorine generated from the ammonia removal reaction without using the electrolytic solution, and an electrolysis method of ammonia using the electrolytic stabilization tank. The present invention has been accomplished by developing a biological treatment device for low temperature wastewater.

It is therefore an object of the present invention to provide a biological treatment apparatus for low temperature wastewater comprising an electrochemical stabilization tank, a primary clarifier, a bioreactor, or a secondary clarifier, And a method for biological treatment of low temperature wastewater using the biological treatment apparatus for low temperature wastewater.

Other objects and technical features of the present invention will be described in more detail with reference to the following detailed description, claims and drawings.

According to one aspect of the present invention, the present invention provides a process for the preparation of a low temperature wastewater comprising an electrochemical stabilization tank, a primary clarifier, a bioreactor, or a secondary clarifier. A biological treatment device for a biological sample is provided.

According to an embodiment of the present invention, the electrochemical stabilization tank is installed in front of the primary purification apparatus or at the back of the secondary purification apparatus to improve the nitrogen removal rate of the low-temperature wastewater treatment apparatus.

According to another embodiment of the present invention, the low-temperature wastewater has a temperature of 10 ° C or lower, and the electrochemical stabilization tank removes ammonia of the low-temperature wastewater by 70% or more using an electrolysis reaction, .

According to another embodiment of the present invention, when ammonia is removed from the low-temperature wastewater by the electrolysis reaction, powdered activated carbon is added to remove residual chlorine, and the powdered activated carbon has a ratio of 1: 3-5 By weight.

According to another aspect of the present invention, there is provided a method of biological treatment of cold wastewater comprising the steps of:

a) introducing cold wastewater into an electrochemical stabilization tank;

b) applying electricity to the low-temperature wastewater under the conditions of a voltage of 2-20 V and a current of 0.2-2 A to perform an electrolysis reaction for 2-5 hours;

c) adding powdered activated carbon to the low-temperature wastewater of b) and reacting for 2-3 hours to remove residual chlorine; And

d) performing a biological treatment by sequentially introducing cryogenic wastewater from which the residual chlorine of c) has been removed into a primary clarifier, a bioreactor, and a secondary purification device in sequence; And

e) removing the microorganisms by introducing the low-temperature wastewater subjected to the biological treatment of d) into a disinfection device.

According to another aspect of the present invention, the present invention provides a method for biological treatment of cold wastewater comprising the steps of:

a) subjecting the low temperature wastewater to sequential introduction into a primary clarifier, a bioreactor, and a secondary purification device to perform a biological treatment;

b) introducing the cold wastewater subjected to the biological treatment of a) into an electrochemical stabilization tank;

c) performing electrolysis reaction for 2-5 hours by applying electricity to the low temperature wastewater of b) under the condition of a voltage of 2-20 V and a current of 0.2-2A; And

d) adding powdered activated carbon to the electrolyzed low-temperature wastewater c), removing residual chlorine, and utilizing it as a conventional disinfection process.

The present invention relates to an apparatus and a method for biological treatment of low-temperature wastewater using an electrochemical stabilization tank. The present invention has the same ammonia removal effect regardless of temperature in order to solve the problems of the conventional biological treatment apparatus and method which can not meet the standard of the effluent water due to the ammonia removal efficiency lowered in treating the wastewater of low temperature in winter The present invention relates to a biological treatment apparatus and method for low-temperature wastewater that can effectively perform biological treatment of wastewater regardless of temperature and meet the criteria of effluent by introducing an electrochemical stabilization tank that effectively controls residual chlorine generated during ammonia removal process to provide. Therefore, the present invention can replace the conventional biological treatment method in which the ammonia removal efficiency of the wastewater must be maintained by repeated nitrification of nitrification bacteria in the case where the temperature of the influent water is lowered and the growth rate of the nitrifying bacteria is decreased as in winter .

Figure 1 schematically shows the configuration and reaction of the electrodes for electrolysis within an electrochemical stabilization tank.
2 schematically shows the configuration of a biological treatment apparatus to which the electrochemical stabilization tank of the present invention is applied.
FIG. 3 shows the change in the removal amount of ammonia nitrogen depending on the applied voltage. Panel A shows the removal of ammonia nitrogen; Panel B shows the change in free chlorine with removal of ammonia nitrogen; Panel C shows the change in bound chlorine (NH ₂ Cl) due to the removal of ammonia nitrogen; Panel D shows the change in bound chlorine (NHCl ₂ ) due to the removal of ammonia nitrogen.
Figure 4 shows the amount of ammonia remaining after the electrolysis reaction (panel A), the amount of free chlorine (HOCl) produced through electrolysis (panel B), the amount of bound chlorine NH ₂ Cl produced through electrolysis C) and the amount of bound chlorine NHCl ₂ produced through electrolysis (panel D).
FIG. 5 shows the pH change (panel A), the electrical conductivity change (panel B) and the amount of residual ammonia (panel C) of the wastewater after addition of the powdered activated carbon after the electrolysis reaction.
FIG. 6 is a graph showing the relationship between the amount of total chlorine (panel A), the amount of free chlorine (panel B), the amount of bound chlorine NH ₂ Cl (panel C) and the amount of bound chlorine NHCl ₂ in the wastewater reacted with powdered activated carbon after the electrolytic reaction (Panel D).

According to one aspect of the present invention there is provided a process for the preparation of low temperature wastewater comprising an electrochemical stabilization tank, a primary clarifier, a bioreactor, or a secondary clarifier, Thereby providing a biological treatment apparatus.

According to an embodiment of the present invention, the electrochemical stabilization tank is installed in front of the primary purification apparatus or at the back of the secondary purification apparatus to improve the nitrogen removal rate of the low-temperature wastewater treatment apparatus.

According to another embodiment of the present invention, the electrochemical stabilization tank comprises an oxidation electrode made of a material containing iron (Fe), titanium (Ti), platinum (Pt) or iridium (Ir) (Al), or copper (Cu), and a plurality of electrodes may be connected in series or in parallel to form a reactor.

When the wastewater flows into the electrochemical stabilization tank, electricity is supplied to the oxidation electrode and the reduction electrode to perform an electrolysis reaction on the wastewater. The electrolysis reaction can remove ammonia and organic substances present in the wastewater and reduce the turbidity of the wastewater. The mechanism by which ammonia is removed through the electrolysis reaction is performed by two routes. The pathway is a direct oxidation method and an indirect oxidation method. In the present invention, ammonia existing in wastewater is mainly removed by indirect oxidation. When the indirect oxidation process is performed, Cl ₂ is generated in the oxidation electrode having no reactivity, and the Cl ₂ is dissolved in water to be free chlorine (HOCl or OCl ^- ) (see Chemical Formula 1).

When the generated free chlorine reacts with the ammonia of the wastewater and is converted into nitrogen gas (N ₂ ) and treated, some of the nitrogen is nitrate nitrogen (NO ₃ -N), nitrite nitrogen (NO ₂ -N) (NH ₄ -N) (see Chemical Formula 2).

The reaction of free chlorine with ammonia is known to be very complex and not fully characterized. However, the synthesis of intermediate and final products depends on the pH of the reaction solution, the amount of chlorine introduced, and the contact time of chlorine and ammonia. In the case of ammonia nitrogen (NH ₃ -N) contained in the wastewater, chlorine or chlorine combined chlorine (NH ₂ Cl, NHCl ₂ and NCl ₃ ) is formed when the amount of chlorine corresponding to 5 times the ammonia nitrogen is added When more free chlorine is added, an oxidation reaction occurs in which the combined chlorine is converted into N ₂ gas. The formation of NH ₂ Cl corresponds to a basic reaction and can be expressed by the following formula (3).

The reaction rate constant for NCl ₃ is very small compared to the reaction rate constants for NHCl ₂ and NH ₂ Cl, but the production rate of NCl ₃ may be increased when the wastewater is below pH 3-4. However, if the pH of the wastewater is above 7 is basically the NH ₂ Cl is present in the main residual chlorine bonded in the pH 7 to pH 4 to increase the production of NHCl ₂ present in the residual primary NHCl _2-conjugated goat. Therefore, when the pH of the wastewater is kept over 4 and the electrolysis is performed after chlorine is added, free chlorine (HOCl) and bound chlorine (NH ₂ Cl and NHCl ₂ ) except NCl ₃ are present as the main residual chlorine . The HOCl, NH ₂ Cl and NHCl ₂ can be easily removed by the administration of activated carbon. However, NH ₂ Cl has a disadvantage in that NH ₃ Cl is partially re-substituted in the reaction with activated carbon. Therefore, it is necessary to control the reaction conditions of the wastewater.

According to one embodiment of the present invention, the low temperature wastewater of the present invention has a weakly acidic or neutral pH range. Therefore, the low temperature wastewater of the present invention has free chlorine (HOCl) and bound chlorine NHCl ₂ as the main chlorine remaining after the electrolysis reaction.

The biological treatment method for removing ammonia present in wastewater is performed by cultivating nitrification bacteria in the reaction tank and nitrifying the ammonia of the introduced wastewater using nitrifying bacteria. For this purpose, nitrifiers must propagate at a rate higher than a certain level in the reaction tank. Otherwise, the number of nitrifying bacteria discharged together with the treated water during discharge can not be maintained and the nitrification rate is rapidly lowered. In the case of nitrification bacteria, when the temperature is lowered, the proliferation rate is lowered. If the temperature of the influent wastewater is maintained at 8-9 ° C as in winter, the nitrification rate of 25-27% Level. In order to solve this problem, conventionally, when biological treatment method is used in winter, nitrification bacteria are periodically injected into the reaction tank. According to an embodiment of the present invention, the electrochemical stabilization tank may be installed in front of or behind a conventional biological treatment tank to reduce the nitrification rate even when the temperature of the wastewater entering in winter is 10 ° C or lower. The present invention provides a biological treatment apparatus for low temperature wastewater. The electrochemical stabilization tank is provided with an electrode and performs an electrolytic reaction with the introduced wastewater. Therefore, ammonia is removed regardless of the temperature of the wastewater, thereby preserving the nitrification rate of the biological treatment apparatus which is decreased due to the temperature drop of the wastewater.

According to an embodiment of the present invention, the electrochemical stabilization tank removes ammonia of the low-temperature wastewater by 30% or more according to the discharge standard using the electrolysis reaction. The removal of ammonia carried out through the electrolysis reaction can be used to remove ammonia to a level that meets the discharge water criterion according to the change in efficiency of the biological treatment apparatus.

As described above, since the removal of ammonia through electrolysis of the present invention uses an indirect oxidation method, free chlorine and bonded chlorine are produced as reaction byproducts. The free and bound chlorine is toxic enough to be used in the disinfection of tap water and strict standards are applied for the discharge. Therefore, the free chlorine and the combined chlorine produced in the ammonia removal process must be removed before the discharge.

According to an embodiment of the present invention, the low temperature wastewater of the present invention may have a pH of 4-7, and free chlorine (HOCl) and binding chlorine (NHCl ₂ ) produced through the electrolysis reaction may be removed using powdered activated carbon .

The mechanism of removing free chlorine (HOCl) and bound chlorine (NH ₂ Cl and NHCl ₂ ) using the above powdered activated carbon is explained by the following chemical formulas 4 and 6. The reaction of the activated carbon to remove free chlorine (HOCl) is shown in the following chemical formula 4. The following C ^* means the carbon component of the activated carbon surface, and the following C ^* O is the surface oxide generated through the reaction, which lowers the adsorption ability of the activated carbon. When the free chlorine is effectively removed due to the introduction of the activated carbon, chlorination disinfection by-products produced by the free chlorine can be prevented from being present in the effluent.

Reaction of the activated carbon to remove chlorine bond NH ₂ Cl ₂ NHCl and which may be produced in the electrolytic reaction is described by the following chemical formula 5, and 6 below.

In the above formula (5), the reaction for removing the bound chlorine by activated carbon proceeds at 50:50 after an adaptation period of a predetermined time. According to the second reaction formula (5), the produced NH ₂ Cl reacts with activated carbon and is partially re-substituted with NH ₃ . However, as described above, if the pH of the wastewater is maintained in the neutral region, the main bound chlorine generated in the electrolysis reaction can be composed of NHCl ₂ . The combined chlorine NHCl ₂ reacts with activated carbon as shown in Formula 6 to be decomposed into nitrogen gas and chlorine ion, but is not replaced with NH ₃ . Therefore, if the pH of the wastewater is in a neutral range at the pH of the wastewater as in the embodiment of the present invention, the generation of NCl ₃ and NH ₂ Cl is suppressed, and the residual binding chlorine of the wastewater can be maintained as NHCl ₂ . Also, when the residual binding chlorine of the wastewater is maintained as NHCl ₂ as described above, there is an effect that partial reduction of ammonia removal efficiency due to NH ₃ replacement can be prevented.

In particular, the NHCl ₂ exhibits very fast reactivity (reactivity purity: NHCl ₂ >HOCl> OCl ^- > NH ₂ Cl). Therefore, when the type of combined chlorine is unified with NHCl ₂ through the control of the wastewater, ammonia removal efficiency is improved due to the rapid reactivity of NHCl ₂ .

According to an embodiment of the present invention, the powdered activated carbon is added at a weight ratio of 1: 3 to 5 relative to ammonia of the low-temperature wastewater.

According to another aspect of the present invention, the present invention provides a method of biological treatment of cold wastewater comprising the steps of:

a) introducing cold wastewater into an electrochemical stabilization tank;

b) applying electricity to the low-temperature wastewater under the conditions of a voltage of 2-20 V and a current of 0.2-2 A to perform an electrolysis reaction for 2-5 hours;

c) adding powdered activated carbon to the low-temperature wastewater of b) and reacting for 2-3 hours to remove residual chlorine; And

d) performing a biological treatment by sequentially introducing cryogenic wastewater from which the residual chlorine of c) has been removed into a primary clarifier, a bioreactor, and a secondary purification device in sequence; And

e) introducing the low-temperature wastewater subjected to the biological treatment of d) into a disinfection device to remove microorganisms;

/ RTI > The method of claim 1,

The electrochemical treatment method can be applied with a neutral pH of 30 to 100 mg / L and a conductivity of 0.5 to 1.5 mS / cm. However, in the case of wastewater, the biological treatment method of the low temperature wastewater is electrochemically In order to improve the efficiency of the treatment method, the characteristics of the low temperature wastewater in step b) are maintained at pH neutral region, chlorine ion (Cl ^- ) concentration of 40-1000 mg / L or higher and electric conductivity of 0.5-3 mS / cm You can add a step. Maintaining the pH to be neutral is to maintain the main residual bound chlorine of the wastewater with NHCl ₂ to prevent reduction of ammonia removal efficiency due to NH ₃ replacement.

Maintaining the concentration of chlorine ions above 40 mg / L is to control the amount of free chlorine (HOCl) produced by electrolysis. If the concentration of chlorine ions is less than 40 mg / L, sufficient free chlorine is not produced, and ammonia removal efficiency may be lowered. If the concentration of chlorine ions exceeds 1,000 mg / L, excess free chlorine is produced, It may be necessary to take additional steps to remove it.

The electric conductivity is controlled by the ion concentration of the wastewater. If the conductivity is less than 0.5 mS / cm, the efficiency of electrolysis is lowered and the removal efficiency of ammonia is decreased.

If the electric voltage applied to the low-temperature wastewater in step b) is less than 2 V or less than 0.2 A, the efficiency of electrolysis is lowered and the removal efficiency of ammonia deteriorates. If the electric voltage exceeds 20 V or exceeds 2 A, The efficiency may increase but it is not economical.

When the powdered activated carbon is added to the electrolyzed low-temperature wastewater in the step c) and the reaction is carried out for less than 2 hours, there is a fear that the free chlorine and the bonding chlorine are not sufficiently removed by the activated carbon to form chlorine byproducts. Can be controlled to control the removal of chlorine.

In addition, when the electrochemical stabilization tank is installed at the rear end of the biological treatment apparatus to remove ammonia as described below, it can be used as a disinfection apparatus.

According to another aspect of the present invention, the present invention provides a method for biological treatment of cold wastewater comprising the steps of:

a) subjecting the low temperature wastewater to sequential introduction into a primary clarifier, a bioreactor, and a secondary purification device to perform a biological treatment;

b) introducing the cold wastewater subjected to the biological treatment of a) into an electrochemical stabilization tank;

c) performing electrolysis reaction for 2-5 hours by applying electricity to the low temperature wastewater of b) under the condition of a voltage of 2-20 V and a current of 0.2-2A; And

d) adding powdered activated carbon to the electrolyzed low temperature wastewater of c) and reacting for 2-3 hours to remove residual chlorine.

The electrochemical treatment method can be applied with a neutral pH of 30 to 100 mg / L and a conductivity of 0.5 to 1.5 mS / cm. However, in the case of wastewater, the biological treatment method of the low temperature wastewater is electrochemically In order to improve the efficiency of the treatment method, the characteristics of the low temperature wastewater in step b) are maintained at pH neutral region, chlorine ion (Cl ^- ) concentration of 40-1000 mg / L or higher and electric conductivity of 0.5-3 mS / cm You can add a step. Maintaining the pH to be neutral is to maintain the main residual bound chlorine of the wastewater with NHCl ₂ to prevent reduction of ammonia removal efficiency due to NH ₃ replacement.

Maintaining the concentration of chlorine ions above 40 mg / L is to control the amount of free chlorine (HOCl) produced by electrolysis. If the concentration of chlorine ions is less than 40 mg / L, sufficient free chlorine is not produced, and ammonia removal efficiency may be lowered. If the concentration of chlorine ions exceeds 1,000 mg / L, excess free chlorine is produced, It may be necessary to take additional steps to remove it.

The electric conductivity is controlled by the ion concentration of the wastewater. If the conductivity is less than 0.5 mS / cm, the efficiency of electrolysis is lowered and the removal efficiency of ammonia is decreased.

If the electric voltage applied to the low-temperature wastewater in c) is less than 2 V or less than 0.2 A, the efficiency of electrolysis is lowered and the removal efficiency of ammonia is lowered. If the electric voltage exceeds 20 V or exceeds 2 A, The efficiency may increase but it is not economical.

When the powdered activated carbon is added to the electrolyzed low-temperature wastewater in the step d) and the reaction is carried out for less than 2 hours, there is a fear that the free chlorine and the bonding chlorine are not sufficiently removed by the activated carbon to form chlorine byproducts. Can be controlled to control the removal of chlorine.

Example

1. Removal of ammonia nitrogen in artificial wastewater by electrolysis

Using tap water, the concentration of ammonia nitrogen (NH ₃ ⁺ or NH ₄ ⁺ ) is 40 mg / L, which is the wastewater level; the pH is 7.2; The electrical conductivity is 1.6 mS / cm; Artificial wastewater containing no organic matter was prepared. The artificial wastewater was prepared in such a manner that the concentrations of chlorine ions were 0 mg / L (Comparative Example 1), 50 mg / L (Example 1), 100 mg / L (Example 2), 200 mg / Example 4). An anode made of Pt coated titanium and a cathode made of stainless steel were installed in the artificial wastewater. The electrolysis was performed by applying a voltage of 8 V DC for 10 hours.

Concentration of ammonia nitrogen Electrical conductivity Anode material / cathode material Concentration of chlorine ion Voltage Comparative Example 1 40 mg / L 1.6 mS / cm Platinum-coated titanium
/ Stainless Steel 0 mg / L 8V DC Example 1 40 mg / L 1.6 mS / cm Platinum-coated titanium
/ Stainless Steel 50 mg / L 8V DC Example 2 40 mg / L 1.6 mS / cm Platinum-coated titanium
/ Stainless Steel 100 mg / L 8V DC Example 3 40 mg / L 1.6 mS / cm Platinum-coated titanium
/ Stainless Steel 200mg / L 8V DC Example 4 40 mg / L 1.6 mS / cm Platinum-coated titanium
/ Stainless Steel 500 mg / L 8V DC

In the case of Example 4 in which the concentration of chlorine ions is 500 mg / L, electrolysis for 4 hours showed that 95% of the ammonia nitrogen was removed. When the electrolysis was performed for 6 hours, % Was removed (panel A of FIG. 3). On the contrary, in the case of Example 3 in which the concentration of chlorine ions is 200 mg / L, ammonia nitrogen was gradually removed according to the electrolysis time, and it was confirmed that 37.5% of ammonia nitrogen was removed when electrolysis was performed for 10 hours ; Example 2 in which the concentration of chlorine ions was 100 mg / L and the case of Example 1 in which the concentration of chlorine ions was 50 mg / L, showed that 20% and 10% of ammonia nitrogen was removed by electrolysis for 10 hours (See panel A in Fig. 3). Also did not remove all the ammonia nitrogen in the electrolysis for 10 hours In the case of artificial sewage (Comparative Example 1) that there is no chloride ions, which do not have the chloride ion present in the artificial wastewater is not Cl ₂ are generated from the anode which (HOCl or OCl ^- ), which is involved in the removal of ammonia nitrogen. In the electrolysis reaction, the removal rate of ammonia nitrogen depending on the concentration of chlorine ions is determined according to the concentration of Cl ₂ produced in the oxidation electrode. This is because the Cl ₂ is dissolved in water to produce free chlorine which participates in the ammonia nitrogen removal reaction. 3 shows that free chlorine is generated in proportion to the concentration of chlorine ions in Examples 1 to 4 during the time when ammonia nitrogen is removed through electrolysis. In the case of Example 4, since the removal of ammonia nitrogen was almost completed after 4 hours, the Cl ₂ produced from the oxidized electrode and the free chlorine generated by dissolving the Cl ₂ in water no longer participate in the removal reaction of ammonia nitrogen, It is confirmed that it is accumulated in the wastewater. Panels C and D in Fig. 3 show the results of binding chlorine generated by the electrolysis reaction. The combined chlorine means NH ₂ Cl (monochloramine), NHCl ₂ (dichloramine), or NCl ₃ (trichloramine). The combined chlorine is formed by the Cl ₂ produced in the oxidation electrode, which is dissolved in water to form HOCl, It is formed by reaction and has toxicity and should be removed for release. The NH ₂ Cl is formed by the reaction of ammonia with HOCl and the NHCl ₂ is formed by the reaction of NH ₂ Cl with HOCl. Therefore, NH ₂ Cl is generated in proportion to the ammonia removal reaction, and the production of NHCl ₂ is also increased in proportion to the formation of NH ₂ Cl. According to the panels C and D of FIG. 3, NH ₄ Cl and NHCl ₂ were most produced in Example 4 (chlorine ion concentration 500 mg / L) in which ammonia was most heavily used, It is confirmed that NH ₂ Cl and NHCl ₂ are not produced in Comparative Example 1 in which ammonia is not removed due to the absence of chlorine ions.

2. Removal of ammonia nitrogen and residual chlorine according to applied voltage during electrolysis

pH 7.2; An electrical conductivity of 0.65 mS / cm; The concentration of ammonia is 40 mg / L; The amount of ammonia nitrogen and residual chlorine was measured by applying applied voltage to the artificial wastewater with a chlorine ion concentration of 80 mg / L. 4 is a graph showing the results of the comparison between the results of Comparative Example 2 in which electrolysis was not performed on the above-mentioned wastewater, Example 5 in which electrolysis was performed at 5 V (0.5 A) for 2, 4, 6, 8, Example 6 in which electrolysis was performed for 2, 4, 6, 8, and 10 hours with the electrolytic solution (1A), electrolysis was performed for 2, 4, 6, 8, and 10 hours with 15V 7, and 20V (20A) for 2, 4, 6, 8, and 10 hours. As a result of the treatment, it was confirmed that the amount of ammonia removal in the wastewater was proportional to the intensity of the applied voltage (see panel A of FIG. 4). It was also confirmed that the amounts of free chlorine (HOCl) and bound chlorine (NH ₂ Cl, and NHCl ₂ ) generated due to the removal of ammonia nitrogen were also increased (see panels B, C, and D of FIG. 4).

Concentration of ammonia nitrogen Electrical conductivity Anode material / cathode material Concentration of chlorine ion Voltage / Current Comparative Example 2 40 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 80 mg / L 0V / 0A Example 5 40 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 80 mg / L 5V / 0.5A Example 6 40 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 80 mg / L 10V / 1A Example 7 40 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 80 mg / L 15V / 1.5A Example 8 40 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 80 mg / L 20V / 2A

3. Removal of ammonia nitrogen and residual chlorine by electrolysis and powdered activated carbon

The wastewater was collected from the wastewater treatment plant in Chuncheon City in order to confirm ammonia nitrogen and residual chlorine removal by electrolysis and powdered activated carbon. An electrical conductivity of 0.65 mS / cm; The concentration of ammonia is 37.5 mg / L; The concentration of chlorine ions was 50 mg / L. A positive electrode made of titanium coated with platinum and a negative electrode made of stainless steel were attached to the wastewater, and a voltage of 8 V and a current of 0.8 A were applied to perform electrolysis for 4 hours. After 4 hours of electrolysis, the pH of the activated carbon was changed with time (Comparative Example 3), 5 mg / L (Example 9) and 10 mg / L (Example 10) ), The change in electrical conductivity (panel B in FIG. 5) and the degree of ammonia removal (panel C in FIG. 5) were measured and the concentration of total free chlorine B), the concentration of NH ₂ Cl (panel C in FIG. 6) and the concentration of NHCl ₂ (panel D in FIG. 6).

Concentration of ammonia nitrogen Electrical conductivity Anode material / cathode material Concentration of chlorine ion Voltage / Current Powder activated carbon Comparative Example 3 37.5 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 50 mg / L 8V /
0.8A 0 ppm Example 9 37.5 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 50 mg / L 8V /
0.8A 5 ppm Example 10 37.5 mg / L 0.65 mS / cm Platinum-coated titanium
/ Stainless Steel 50 mg / L 8V /
0.8A 10ppm

When the powdered activated carbon was added to the wastewater after electrolysis for 4 hours, it was confirmed that the pH change was insignificant in all the examples, and the electric conductivity and the ammonia removal amount were also insignificantly changed (see FIG. 5). However, it was confirmed that the amount of residual chlorine produced through electrolysis differs depending on the amount of powdery activated carbon added (see FIG. 6). The free chlorine (HOCl) is a necessary component for the removal of ammonia or, if it is present in the treated water after the ammonia removal reaction is not performed, it reacts with the humus during the subsequent process to produce disinfection by products (DBP) But it must also be removed because it can affect subsequent bioprocessing. In the case of bound chlorine (NH ₂ Cl, and NHCl ₂ ), it is also necessary to adjust the chlorine concentration in the treated water to meet the water quality standard of effluent water. In the case of Comparative Example 3 in which powdered activated carbon was not added, the amount of total residual chlorine gradually decreased after 4 hours from the electrolysis to 5 hours after the reaction (after 8 hours), but it was not decreased any more after that . This reduction was judged to be due to the fact that the free chlorine (HOCl) produced by the electrolysis reaction was subjected to a reaction to convert the residual chlorine (NH ₂ Cl, and NHCl ₂ ) to N ₂ (see panel A of FIG. 6) . On the contrary, in the case of Example 9 (5 ppm of powdered activated carbon) and Example 10 (10 ppm of powdered activated carbon) in which powdered activated carbon was added, the concentration of total residual chlorine decreased suddenly from 1 hour (5 hours elapsed) And it was confirmed that the removal rate of residual chlorine was faster as the added amount of powdered activated carbon was larger (see panel A of FIG. 6). The results were found to show the same tendency as the effect of powdered activated carbon on free chlorine (HOCl) and bound chlorine (NH ₂ Cl, and NHCl ₂ ) (see panels B, C and D in FIG. 6). The exemplary nitrite nitrogen (NO ₂ N) and nitrate nitrogen (NO ₃ N) resulting the nitrite nitrogen (NO ₂ N) confirm the residual whether and nitrate nitrogen (NO ₃ N) for example it is confirmed does not exist .

4. Electrolysis reaction and application of wastewater treatment method using activated carbon powder

According to the above results, since the degree of removal of ammonia nitrogen present in the wastewater is proportional to the intensity of the applied voltage, it is confirmed that the ammonia nitrogen can be effectively removed by performing electrolysis according to the amount of ammonia nitrogen present in the wastewater And it was confirmed that free chlorine and binding chlorine generated in the ammonia nitrogen removal process can be effectively removed by adding powdered activated carbon.

Therefore, in order to solve the problem that the removal efficiency of ammonia nitrogen is lowered due to the low-temperature influent sewage in winter in the conventional biological treatment method for removing ammonia nitrogen present in wastewater, the same ammonia nitrogen It is possible to reduce the concentration of free chlorine and bound chlorine by using powdered activated carbon having the effect of removing the ammonia nitrogen of the present invention, It can be solved.

The specific embodiments described herein are representative of preferred embodiments or examples of the present invention, and thus the scope of the present invention is not limited thereto. It will be apparent to those skilled in the art that modifications and other uses of the invention do not depart from the scope of the invention described in the claims.

Claims (9)

A biological treatment device for low temperature wastewater comprising an electrochemical stabilization tank, a primary clarifier, a bioreactor, or a secondary clarifier.

The biological treatment apparatus for low-temperature wastewater according to claim 1, wherein the electrochemical stabilization tank is installed in front of the primary purification apparatus or installed behind the secondary purification apparatus to improve the nitrification rate of the low-temperature wastewater treatment apparatus.
The electrochemical stabilization tank according to claim 1, wherein the electrochemical stabilization tank comprises an oxidation electrode made of a material containing iron (Fe), titanium (Ti), platinum (Pt) or iridium (Ir) , Or copper (Cu), characterized in that the electrodes are connected in series or in parallel, and the low-temperature wastewater biological treatment apparatus is characterized in that the electrodes are connected in series or in parallel.
The biological treatment apparatus for low-temperature wastewater according to claim 1, wherein the electrochemical stabilization tank removes ammonia of the low-temperature wastewater by an electrolysis reaction in an amount of 30% or more in accordance with a discharge standard.
5. The biological treatment apparatus for low-temperature wastewater according to claim 4, wherein residual chlorine is removed by adding powdered activated carbon when ammonia is removed from the low-temperature wastewater by the electrolysis reaction.
[6] The biological treatment apparatus for low-temperature wastewater according to claim 5, wherein the powdered activated carbon is added at a weight ratio of 1: 3-5 to ammonia of the low-temperature wastewater.
The method of claim 5, wherein the residual chlorine free chlorine (HOCl), and coupling a low temperature chlorine biological processing apparatus for sewage, characterized in that _{(NHCl 2, NH 2 Cl)} .
a) introducing cold wastewater into an electrochemical stabilization tank;
b) applying electricity to the low-temperature wastewater under the conditions of a voltage of 2-20 V and a current of 0.2-2 A to perform an electrolysis reaction for 2-5 hours;
c) adding powdered activated carbon to the low-temperature wastewater of b) and reacting for 2-3 hours to remove residual chlorine; And
d) performing a biological treatment by sequentially introducing cryogenic wastewater from which the residual chlorine of c) has been removed into a primary clarifier, a bioreactor, and a secondary purification device in sequence; And
e) introducing the low-temperature wastewater subjected to the biological treatment of d) into a disinfection device to remove microorganisms;
/ RTI > The method of claim 1,
a) subjecting the low temperature wastewater to sequential introduction into a primary clarifier, a bioreactor, and a secondary purification device to perform a biological treatment;
b) introducing the cold wastewater subjected to the biological treatment of a) into an electrochemical stabilization tank;
c) performing electrolysis reaction for 2-5 hours by applying electricity to the low temperature wastewater of b) under the condition of a voltage of 2-20 V and a current of 0.2-2A; And
d) adding powdered activated carbon to the electrolyzed low temperature wastewater of c) and reacting for 2-3 hours to remove residual chlorine;
/ RTI > The method of claim 1,

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