Apparatus for reducing ammonia nitrogen using electric deionization cell

Abstract

The present invention relates to an apparatus for reducing high-concentration ammonia nitrogen in digestion wastewater, generated during the anaerobic digestion of high-concentration organic waste, by using an electric deionization cell, and includes an electric deionization cell composed of a pair of cells formed by and in the order of: a cathode, a bipolar membrane (BP), an ion-exchange resin (resin wafer), a cation-exchange membrane (CEM), an anion exchange membrane (AEM), a bipolar membrane (BP), and an anode.

Description

Ammonia nitrogen reduction device using an electrodeionization cell

[0001] The present invention relates to an ammonia nitrogen reduction device using an electrodeionization cell, and more specifically, to a device for reducing high-concentration ammonia nitrogen in digester waste generated from anaerobic digestion of high-concentration organic waste using an electrodeionization cell.

[0002] With the increase in the amount of high-concentration organic waste (food waste, livestock manure, sewage sludge) and the potential for renewable energy, anaerobic digestion of these high-concentration organic wastes is being actively utilized as a means of reducing greenhouse gases and addressing climate change.

[0003] However, the digestion waste generated after anaerobic digestion contains a high concentration of ammonia nitrogen, and if the ammonia nitrogen is improperly treated and discharged into the water system, eutrophication occurs due to an increase in nitrogen concentration in surface water, and the ammonia nitrogen itself acts as a toxic substance to aquatic plants and animals.

[0004] Therefore, biologically and physically / chemically treating them and then discharging them is a very important task in wastewater treatment.

[0005] Biological nitrogen treatment involves converting ammonia nitrogen into nitrate through nitrification, which is then removed by denitrification into nitrogen gas. While this method has been relatively successful in sewage treatment, it suffers from the drawbacks of long treatment times, complex processes, and high sludge production. Furthermore, biological treatment alone is difficult to handle when high concentrations of ammonia nitrogen are present in water.

[0006] Electrochemical methods have recently received much attention as a method for removing ammonia nitrogen using physical and chemical treatment processes, but the nitrogen removal rate is still low.

[0007] Since ion exchange membranes accept or reject ions by establishing dilute and concentrate zones, processes using ion exchange membranes play an important role in water purification, ion removal, and concentration.

[0008] Figure 1 is a conceptual diagram of an electrodialysis process using an ion separation membrane.

[0009] Electrodialysis (ED) is a method in which a cation membrane that selectively allows only cations to pass through and an anion membrane that selectively allows only anions are arranged alternately in parallel, and when an electrode is placed at each end and electricity is passed through, cations in the solution pass through the cation membrane and move toward the cathode, but are blocked by the anion membrane.

[0010] Negative ions also behave in the opposite way, with ions removed from one space being concentrated in the adjacent space, resulting in concentrated and diluted salt solutions being filtered one by one to form sandwich-shaped cells, i.e., the space between the membranes.

[0011] In the electrodialysis device, the thickness of the separation membrane is approximately 0.5 mm, and the membranes are separated from each other by a porous space of approximately 1 mm, and the aqueous solution flows through the porous space.

[0012] Electrodialysis has the advantage of being able to separate unnecessary ions from an aqueous solution without producing residue and at low operating costs, but it has the inherent disadvantage of reducing cell efficiency by forming a high accumulated resistance within the cell due to concentration polarization when ions are separated from the supplied solution.

[0013] To overcome these shortcomings, solid conductive ion media are introduced into the dilution zone in the form of ion exchange resins, and by combining electrodialysis and ion exchange technologies, high-quality ion separation can be achieved with high energy efficiency.

[0014] Figure 2 shows the internal diagram of an electrodeionization cell.

[0015] Electrodeionization (EDI) is an application technology that combines electrodialysis and ion exchange, and has been used since the late 1950s for the purpose of minimizing the concentration polarization phenomenon that exists in the electrodialysis process.

[0016] The electrodeionization cell alternately places cation-exchange membranes (CEM) and anion-exchange membranes (AEM) between the anode and cathode to form dilution zones and concentration zones.

[0017] The ion exchanger charged in the dilution zone of the electrodeionization cell acts as a conductor due to the presence of functional groups that act as bridges between ion separation membranes, thereby canceling out the concentration polarization of electrodialysis (ED).

[0018] Resin Wafer Electrodeionization (RW-EDI), a porous ion-exchange resin used in the electrodeionization process, utilizes a resin wafer in wafer form to enhance electrical efficiency and separation efficiency due to the high surface area of ​​the resin wafer, which facilitates gas-liquid exchange. Figure 3 is a schematic diagram of the resin wafer in the electrodeionization cell.

[0019] [Prior Art Literature]

[0020] (Patent Document 1) Republic of Korea Patent Publication No. 10-1910211 (October 15, 2018)

[0021] (Patent Document 2) Republic of Korea Patent Publication No. 10-1443925 (September 17, 2014)

[0022] (Patent Document 3) Republic of Korea Patent Publication No. 10-0454093 (October 13, 2004)

[0023] The present invention provides an electrodeionization technology as a basic technology for treating digestion waste liquid generated at a biogasification site of high-concentration organic waste (food waste, livestock manure, sewage sludge) at low cost and high efficiency.

[0024] In addition, the present invention provides an electrodeionization technology as an element technology for reducing high-concentration ammonia nitrogen in high-concentration organic waste.

[0025] In addition, the present invention provides a digestion liquid treatment process capable of discharging digestion liquid generated from an anaerobic digestion facility for high-concentration organic waste at a level below the effluent water quality standard.

[0026] In order to achieve the above purpose, the present invention more specifically provides the following.

[0027] The present invention is an ammonia nitrogen reduction device using an electrodeionization cell capable of separating ammonia nitrogen in a high-concentration anaerobic digestion liquid generated after producing biogas using high-concentration organic waste, wherein the electrodeionization cell is composed of a pair of cells in the following order: a bipolar membrane (BP), an ion-exchange resin (Resin wafer), a cation-exchange membrane (CEM), an ion-exchange resin (Resin wafer), an anion-exchange membrane (AEM), a bipolar membrane (BP), and an anode, based on a cathode.

[0028] The above bipolar membrane (BP) is formed by sandwiching anion exchange layer and cation exchange layer materials together.

[0029] In the above deionization cell, hydrogen ions and electrons are generated at the anode, and hydroxide ions are generated at the cathode.

[0030] In the above-mentioned deionization cell, ammonium ions in the anaerobic digestion liquid pass through the cation exchange membrane and move to the cathode, and the ammonium ions that move to the cathode are converted into ammonia gas and separated due to an increase in pH caused by hydroxide ions.

[0031] The above ion exchange resin is made of a micro-network resin or gel resin having a porosity of 20 to 40% and a pore size of 50 to 400 ㎛, and is manufactured in the shape of a wafer.

[0032] In addition, the present invention provides an electrodeionization cell for reducing ammonia nitrogen, which is composed of a pair of cells in the order of a bipolar membrane (BP), an ion-exchange resin (Resin wafer), a cation-exchange membrane (CEM), an ion-exchange resin (Resin wafer), an anion-exchange membrane (AEM), a bipolar membrane (BP), and an anode based on a cathode, wherein hydrogen ions and electrons are generated at the anode, hydroxide ions are generated at the cathode, ammonium ions of anaerobic digestion liquid pass through the cation-exchange membrane (CEM) to move to the cathode, and the ammonium ions moved to the cathode are converted into ammonia gas and separated due to an increase in pH caused by the hydroxide ions.

[0033] The ammonia nitrogen reduction device using an electro-deionization cell according to the present invention has the effect of being able to treat digestion waste liquid generated at a biogasification site of high-concentration organic waste (food waste, livestock manure, sewage sludge) at low cost and high efficiency.

[0034] In addition, the ammonia nitrogen reduction device using the electrodeionization cell according to the present invention has the effect of providing an element technology for recovering high-concentration ammonia nitrogen from high-concentration organic waste.

[0035] In addition, the ammonia nitrogen reduction device using the electrodeionization cell according to the present invention has the effect of providing a digestion liquid treatment process capable of discharging the digestion liquid generated in an anaerobic digestion facility for high-concentration organic waste at a level below the effluent water quality standard.

[0036] Figure 1 is a conceptual diagram of an electrodialysis process using an ion separation membrane.

[0037] Figure 2 is a schematic diagram of an electrodeionization cell.

[0038] Figure 3 is a conceptual diagram of a resin wafer of an electrodeionization cell.

[0039] Figure 4 is a conceptual diagram of a nitrogen recovery-based anaerobic digestion liquid treatment system.

[0040] Figure 5 is a conceptual diagram of an ammonia nitrogen reduction device using an electrodeionization cell according to the present invention.

[0041] FIG. 6 is a view of an ammonia nitrogen reduction device consisting of a laboratory-scale single-cell electrodeionization device according to one embodiment of the present invention.

[0042] Figure 7 shows the module configuration of an electrodeionization single cell according to one embodiment of the present invention.

[0043] Fig. 8 is a photograph of a jig for manufacturing a gasket part for mounting an ion exchange resin according to one embodiment of the present invention.

[0044] Figures 9, 10, and 11 are configuration diagrams of a gasket component for mounting an ion exchange resin according to one embodiment of the present invention.

[0045] Fig. 12 is a photograph of a gasket component for mounting an ion exchange resin according to one embodiment of the present invention.

[0046] Fig. 13 is a photograph of an ion exchange resin manufactured using a jig according to one example of the present invention.

[0047] FIG. 14 is a photograph of a resin for mounting an electrodeionization single-cell module according to one embodiment of the present invention.

[0048] Hereinafter, specific details for implementing the present invention will be described with reference to the attached drawings. In describing the present invention, detailed descriptions of related known functions that are obvious to those skilled in the art and that may unnecessarily obscure the gist of the present invention will be omitted.

[0049] Figure 4 conceptually illustrates a nitrogen recovery-based anaerobic digestion liquid treatment system, in which high-concentration anaerobic digestion liquid generated after producing biogas using high-concentration organic waste is treated using a treatment device using an electrodeionization cell according to the present invention.

[0050] The present invention aims to treat high-concentration ammonia nitrogen in digester waste generated at a biogasification site of high-concentration organic waste (food waste, livestock manure, sewage sludge) at low cost and high efficiency using an electrodeionization cell.

[0051] Figure 5 is a conceptual diagram of an ammonia nitrogen reduction device using an electrodeionization cell according to the present invention.

[0052] The deionization cell according to the present invention is composed of one cell pair, which is composed of a bipolar membrane (BP), an ion-exchange resin (Resin wafer), a cation-exchange membrane (CEM), an ion-exchange resin (Resin wafer), an anion-exchange membrane (AEM), a bipolar membrane (BP), and an anode in that order, based on the cathode.

[0053] By repeatedly increasing the number of these cells, ion exchange efficiency and throughput can be increased in parallel.

[0054] A bipolar membrane (BP) is a membrane that sandwiches anion exchange layer and cation exchange layer materials, and does not allow any ions to pass through.

[0055] Instead, the bipolar membrane (BP) decomposes water to produce protons (H+) on the cation exchange layer side and hydroxide ions (OH-) on the anion exchange layer side.

[0056] According to Figure 5, protons (H+) are generated in the cation exchange layer of the bipolar membrane (BP) adjacent to the anode, so that the ion exchange resin on the anode side functions as an acidic chamber, and hydroxide ions (OH-) are generated in the anion exchange layer of the bipolar membrane (BP) adjacent to the cathode, so that the ion exchange resin on the cathode side functions as a basic chamber.

[0057] When feedstock containing a high concentration of ammonia nitrogen is introduced into an electrodeionization cell, ammonium ions pass through the cation exchange membrane and move to the cathode, and also, due to electrolysis, hydrogen ions and electrons are generated at the anode and hydroxide ions are generated at the cathode. The ammonium ions that move to the cathode are converted to ammonia gas due to the increase in pH caused by the hydroxide ions, so ammonia nitrogen can be separated.

[0058] In the electrodeionization cell according to the present invention, in order to maintain a stable fluid flow, the ion exchange resin between the bipolar membrane (BP) and the cationic membrane (CEM), and between the bipolar membrane (BP) and the anionic membrane (AEM) is manufactured in the shape of a wafer.

[0059] These wafer-shaped ion exchange resins (Resin-Wafer, RW) are made of porous macroreticular resin or gel resin, and have dimensions of approximately 170 mm in height, 110 mm in width, and 7 mm in thickness, and can have a porosity of 30 to 40% and a pore diameter of 200 to 300 μm.

[0060]

[0061] [Production example]

[0062] FIG. 6 is a view of an ammonia nitrogen reduction device composed of a laboratory-scale deionization single cell according to one embodiment of the present invention, FIG. 7 shows a module configuration of an deionization single cell according to one embodiment of the present invention, FIG. 8 is a photograph of a jig for manufacturing a gasket component for mounting an ion exchange resin according to one embodiment of the present invention, and FIGS. 9, 10, and 11 are configuration diagrams of a gasket component for mounting an ion exchange resin according to one embodiment of the present invention, respectively.

[0063] FIG. 12 is a photograph of a gasket component for mounting an ion exchange resin according to one embodiment of the present invention, FIG. 13 is a photograph of an ion exchange resin manufactured using a jig according to one embodiment of the present invention, and FIG. 14 is a photograph of a resin for mounting an electrodeionization single-cell module according to one embodiment of the present invention.

[0064] A single-cell deionization cell according to one embodiment of the present invention is composed of a pair of cells, each of which is composed of a bipolar membrane (BP), a resin-wafer (RW), a cationic membrane (CEM), a resin-wafer (RW), an anionic membrane (AEM), a bipolar membrane (BP), and an anode in that order, based on the cathode.

[0065]

[0066] [Experimental Example]

[0067] In order to analyze the efficiency, such as the ammonia nitrogen capture rate, according to the continuous operation of the deionization cell according to one embodiment of the present invention, the deionization cell manufactured as a single cell was used.

[0068] The specifications of the resin wafer (RW) mounted on the single electrodeionization cell are as shown in Table 1 below.

[0069] Size of resin wafer: Height 17.3 cm, width 11.3 cm, thickness 0.67 cm. Porosity of resin wafer: 30% of total volume. Pore size of resin wafer: 200~300 μm. Ionic conductivity of resin wafer: 3.0 mS (electrolyte: 500 ppm NaCl). Composition of resin wafer: Micro-network structure resin.

[0070] Other specifications and operating conditions of the single-cell electrodeionization cell are as shown in Table 2 below.

[0071] TAN concentration in the treated water (ppm) 3,500 Applied voltage (V) 4.0 Applied current (A) 2.0 Pump flow rate (RPM) 15

[0072] Here, TAN (Total Ammonia Nitrogen) represents total ammonia nitrogen.

[0073] The results of the operation test of the single-cell electrodeionization cell are shown in Table 3 below.

[0074] Before EDI application (total ammonia nitrogen) After EDI application (total ammonia nitrogen) Mean value (ppm) 3,515,156 Standard deviation (ppm) 8,610 Reduction rate (%) 95.6 Energy consumption (kWh / kg N) 7.14

[0075] While the technical concepts of the present invention have been described above, along with the accompanying drawings, they serve only as illustrative examples of preferred embodiments of the invention and are not intended to limit the scope of the invention. Furthermore, it is readily apparent that anyone skilled in the art will be able to make various modifications and imitations without departing from the scope of the technical concepts of the present invention.

[0076] The ammonia nitrogen reduction device using an electric deionization cell according to the present invention can provide a technology capable of treating digestion waste liquid generated at a biogasification site of high-concentration organic waste (food waste, livestock manure, sewage sludge) at low cost and high efficiency, and thus has very useful industrial applicability in the operation of a biogasification facility for high-concentration organic waste.

Claims

1. An ammonia nitrogen reduction device using an electric deionization cell capable of separating ammonia nitrogen from high-concentration anaerobic digestion fluid generated after producing biogas using high-concentration organic waste. The above electrodeionization cell is an ammonia nitrogen reduction device using an electrodeionization cell, which is composed of a pair of cells in the following order: a bipolar membrane (BP), an ion-exchange resin (Resin wafer), a cation-exchange membrane (CEM), an ion-exchange resin (Resin wafer), an anion-exchange membrane (AEM), a bipolar membrane (BP), and an anode, based on the cathode.

2. In paragraph 1, The above bipolar membrane (BP) is an ammonia nitrogen reduction device using an electrodeionization cell in which anion exchange layer and cation exchange layer materials are sandwiched together.

3. In paragraph 2, An ammonia nitrogen reduction device using an electrodeionization cell in which hydrogen ions and electrons are generated at the anode and hydroxide ions are generated at the cathode.

4. In paragraph 3, An ammonia nitrogen reduction device using an electrodeionization cell in which ammonium ions in anaerobic digestion fluid pass through a cation-exchange membrane (CEM) to move to the cathode, and the ammonium ions that move to the cathode are converted to ammonia gas and separated due to an increase in pH caused by hydroxide ions.

5. In paragraph 1, The above ion exchange resin is a micro-network resin or gel resin having a porosity of 20 to 40% and a pore size of 50 to 400 ㎛, and is an ammonia nitrogen reduction device using an electric deionization cell manufactured in the shape of a wafer.

6. An electrodeionization cell for reducing ammonia nitrogen, which is composed of a pair of cells in the order of a bipolar membrane (BP), anion-exchange resin (Resin wafer), a cation-exchange membrane (CEM), anion-exchange resin (Resin wafer), anion-exchange membrane (AEM), a bipolar membrane (BP), and an anode, wherein hydrogen ions and electrons are generated at the anode, hydroxide ions are generated at the cathode, and ammonium ions in the anaerobic digestion liquid pass through the cation-exchange membrane (CEM) to the cathode, and the ammonium ions moved to the cathode are converted into ammonia gas and separated due to an increase in pH caused by the hydroxide ions.

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