Sewage reprocessing method at sewage treatment plant

Abstract

The present invention relates to a reprocessing technology for further purifying treated water discharged from a sewage treatment plant, and more specifically, to an improved sewage reprocessing method that simultaneously achieves the complete decomposition of residual organic matter and the inhibition of the reoxidation of nitrogen components by functionally linking an electrochemical oxidation process and an ion exchange process while controlling high concentrations of organic matter and nitrogen-based pollutants contained in the concentrated water generated in the reverse osmosis membrane process in stages, and by performing instantaneous heat treatment by high-frequency induction heating before final discharge.

Description

Technology Field

[0001] The present invention relates to a reprocessing technology for further purifying treated water discharged from a sewage treatment plant, and more specifically, to an improved sewage reprocessing method that simultaneously achieves the complete decomposition of residual organic matter and the inhibition of the reoxidation of nitrogen components by functionally linking an electrochemical oxidation process and an ion exchange process while controlling high concentrations of organic matter and nitrogen-based pollutants contained in the concentrated water generated in the reverse osmosis membrane process in stages, and by performing instantaneous heat treatment by high-frequency induction heating before final discharge. Background Technology

[0002] With the recent increase in demand for the reuse of treated wastewater, advanced treatment processes using reverse osmosis (RO) membranes are being widely applied.

[0003] While reverse osmosis membranes can effectively remove ionic substances and dissolved salts, the accumulation of these removed substances in the concentrate leads to a problem where the concentrations of COD, nitrogen, and recalcitrant organic matter in the concentrate increase rapidly.

[0004] If such concentrated water is treated simply by an ion exchange method, high-molecular organic matter is irreversibly adsorbed onto the resin surface, causing a rapid decrease in the resin's exchange capacity and a shortened regeneration cycle.

[0005] Furthermore, in conventional technology, a method was proposed to treat the regeneration waste liquid generated after ion exchange resin regeneration by electrolysis; however, since this is merely a post-treatment after contamination has already occurred, it is difficult to ensure the overall stability of the process.

[0006] Furthermore, even when high-temperature heating is performed prior to final discharge, if simple heating is carried out without oxygen control, there is a possibility that nitrogen components may be reoxidized into NOx, and there is a problem of accelerated corrosion and scale buildup inside the device in high-temperature and high-salinity environments. Prior art literature

[0007] Japanese Published Patent Application No. JP 2002-121012, Registered Patent Application No. 10-1279701, Registered Patent Application No. 10-1541101, Published Patent Application No. 10-2016-0121731 The problem to be solved

[0008] The present invention aims to provide a sewage retreatment method that solves the above-mentioned problems by controlling the organic structure of reverse osmosis concentrate in advance to suppress contamination of the ion exchange resin, sequentially linking electrochemical oxidation and ion exchange processes to induce a synergistic effect, and suppressing the reoxidation of nitrogen components through instantaneous high-temperature heating under oxygen-limited conditions while simultaneously completely removing bacteria and residual organic matter. means of solving the problem

[0009] The present invention, as a means to achieve the above-mentioned objective, comprises: a first step of primary filtration of influent wastewater using a screen; a second step of passing the treated water from the first step through a reverse osmosis membrane to remove ionic substances and generate concentrated water; and introducing the concentrated water into an electrolyzer to perform partial oxidation treatment, followed by passing it through an anion exchange resin to remove organic matter and nitrate ions (NO3 - A wastewater reprocessing method for a wastewater treatment plant is provided, characterized by comprising: a third step of removing ); a fourth step of mixing the treated water obtained from the third step with effluent; and a fifth step of introducing the mixed water into a high-frequency induction heating treatment pipe and performing instantaneous heat treatment at a temperature of 400 to 600°C for 1 to 5 seconds, wherein the treatment is performed under conditions where oxygen is limited to suppress the re-formation of oxides of residual nitrogen components. Effects of the invention

[0010] According to the present invention, an improved effect can be obtained by circulating indoor and outdoor air without opening the window through ventilation means provided on both sides of the window frame, thereby increasing ventilation efficiency. Specific details for implementing the invention

[0011] Hereinafter, preferred embodiments according to the present invention will be described in more detail.

[0012] A wastewater retreatment method for a wastewater treatment plant according to the present invention comprises: a first step of primary filtration of influent wastewater using a screen; a second step of passing the treated water from the first step through a reverse osmosis membrane to remove ionic substances and generate concentrated water; and introducing the concentrated water into an electrolyzer to perform partial oxidation treatment, followed by passing it through an anion exchange resin to remove organic matter and nitrate ions (NO3 - A third step of removing ); a fourth step of mixing the treated water obtained from the third step with discharge water; and a fifth step of introducing the mixed water into a high-frequency induction heating treatment pipe and performing instantaneous heat treatment for 1 to 5 seconds in the range of 400 to 600°C, wherein the treatment is performed under conditions where oxygen is limited to suppress the re-formation of oxides of residual nitrogen components; are included.

[0013] More specifically, the present invention includes a first step of first filtering the influent wastewater using a screen.

[0014] In the first step above, a combination of a coarse screen and a fine screen is used to remove suspended solids and solid particles, thereby preventing membrane fouling and electrode surface fouling in the subsequent process.

[0015] Next, the treated water from the first step is passed through a reverse osmosis membrane to perform a second step in which ionic substances are removed and concentrated water is generated.

[0016] During this process, salts and nitrate ions move toward the concentrated water, and the organic matter concentration in the concentrated water also increases.

[0017] The present invention includes a third step of introducing such concentrated water into an electrolyzer first to perform partial oxidation treatment, rather than introducing it directly into an ion exchange resin.

[0018] At this time, the oxidation current density of the electrolytic cell is set to a range of 10 to 40 mA / cm².

[0019] The above range is not a simple numerical limitation, but a technical range for breaking down high-molecular-weight organic materials into low-molecular-weight compounds while preventing complete inorganicization.

[0020] If the current density is less than 10 mA / cm², the polymer chains are not sufficiently cut, which can lead to contamination of the resin surface. Conversely, if it exceeds 40 mA / cm², excessive oxide species are generated, increasing energy consumption and raising the risk of device corrosion.

[0021] Therefore, the present invention suppresses pore clogging of the resin and improves the exchange capacity retention rate through the above range.

[0022] The partially oxidized concentrated water is passed through a strong basic anion exchange resin having a macroreticular structure.

[0023] The macroreticular structure forms a developed porous network that can effectively remove low-molecular-weight organic matter and nitrate ions, and irreversible contamination is significantly reduced due to pre-oxidation.

[0024] The anion exchange resin used in the present invention is a strongly basic anion exchange resin having a macroreticular structure. It has a porous polymer matrix structure that is distinct from a simple gel-type resin and is selected to stably treat concentrated water containing high concentrations of organic matter and nitrogenous pollutants.

[0025] A macroreticular structure refers to a three-dimensional network structure that forms continuous macropores ranging in size from tens of nanometers to hundreds of nanometers inside.

[0026] This structure is formed in the following way.

[0027] For example, styrene and divinylbenzene (DVB) are copolymerized to form a cross-linked polymer matrix, and a porogen is added and then removed during the polymerization process to form a porous network. As a result, the resin has a high specific surface area (about 20 to 50 m² / g or more), a continuous and open pore structure, reduced internal diffusion resistance, and the ability to penetrate the solution into the pores, which implies a structural difference with significantly developed internal channels compared to gel-type resins.

[0028] Accordingly, the anion exchange resin is a strongly basic anion exchange resin having a macroreticular structure, and since it is a porous resin formed by introducing quaternary ammonium groups into a styrene-divinylbenzene copolymer matrix, it forms continuous macropores internally to reduce diffusion resistance and enables the selective removal of nitrate ions and low-molecular-weight organic matter. In particular, the present invention exhibits a functional interaction that is combined with a prior electro-oxidation treatment of concentrated water to suppress irreversible contamination of the resin surface and improve regeneration efficiency.

[0029] Afterward, the treated water that has gone through the aforementioned third stage undergoes a fourth stage in which it is mixed with the discharge water.

[0030] This mixture is adjusted by flow rate control to satisfy water quality standards.

[0031] Finally, the above-mentioned mixture is introduced into a high-frequency induction heating treatment tube and performs a fifth step in which it is instantaneously heated for 1 to 5 seconds in the range of 400 to 600°C.

[0032] The above heating is carried out under oxygen-limited conditions, thereby suppressing the re-oxidation of nitrogen components into NOx.

[0033] Since organic matter decomposition is insufficient below 400℃ and the possibility of nitrogen oxide generation increases when exceeding 600℃, the above range is technically meaningful.

[0034] In addition, in the present invention, a multi-layered protective coating layer is formed on the inner surface of the high-frequency induction heating treatment tube to simultaneously secure corrosion resistance, oxidation resistance, and antifouling properties.

[0035] The above protective coating layer is formed by coating with a coating composition consisting of 10 to 20 wt% fused silica powder, 5 to 15 wt% α-alumina (Al2O3) powder, 5 to 10 wt% FEP (fluorinated ethylene propylene), 5 to 10 wt% tetraethoxysilane (TEOS), and the remainder sodium silicate (Na2SiO3).

[0036] In this case, fused silica powder has an amorphous structure and a very low coefficient of thermal expansion, which suppresses crack formation during repeated high-temperature heating and contributes to improved heat resistance and stabilized thermal conductivity.

[0037] In addition, α-alumina (Al2O3) powder is added to suppress crack propagation in repeated heating environments due to its excellent thermal shock resistance, to ensure corrosion resistance in chloride ion environments, to increase high-temperature oxidation resistance, improve mechanical strength, and enhance wear resistance.

[0038] In addition, FEP (fluorinated ethylene propylene) has excellent chemical resistance, maintains stability in chlorine environments, and contributes to reducing surface energy, inhibiting scale adhesion, preventing sludge adhesion, and improving cleaning performance.

[0039] In addition, tetraethoxysilane (TEOS) forms a Si-O-Si network after hydrolysis, which improves water resistance and is effective in increasing adhesion, sealing micropores, and blocking moisture penetration.

[0040] In addition, sodium silicate (Na2SiO3) maintains a stable structure even at temperatures above 800°C, making it suitable for high-frequency instantaneous heating environments, buffering differences in thermal expansion coefficients, increasing bonding strength between the substrate and the coating layer, and improving thermal shock resistance.

[0041] Accordingly, the present invention enables the achievement of complex effects such as securing synergistic effects through process linkage, extending resin lifespan, suppressing nitrogen reoxidation, improving high-temperature corrosion resistance, and increasing antifouling properties and device lifespan.

Claims

Claim 1 delete Claim 2 A first step of primary filtration of influent wastewater using a screen; a second step of passing the treated water from the first step through a reverse osmosis membrane to remove ionic substances and generate concentrated water; introducing the concentrated water into an electrolyzer to perform partial oxidation treatment, and then passing it through an anion exchange resin to remove organic matter and nitrate ions (NO3 - A wastewater retreatment method for a sewage treatment plant, characterized by comprising: a third step of removing ); a fourth step of mixing the treated water obtained through the third step with effluent; and a fifth step of introducing the mixed water from the fourth step into a high-frequency induction heating treatment pipe and performing instantaneous heat treatment at a temperature range of 400 to 600°C for 1 to 5 seconds, wherein the treatment is performed under oxygen-limited conditions to suppress the re-formation of oxides of residual nitrogen components; wherein the oxidation current density of the electrolyzer is set in the range of 10 to 40 mA / cm² to degrade high-molecular organic matter while suppressing complete inorganicization, the anion exchange resin is a strongly basic resin having a macroreticular structure, the high-frequency induction heating treatment pipe is composed of a ceramic material and is formed to induce turbulence by forming a retention section inside, the macroreticular structure is a three-dimensional network structure forming continuous macropores ranging in size from tens of nanometers to hundreds of nanometers inside, and styrene and A method for reprocessing sewage at a sewage treatment plant, characterized by forming a cross-linked polymer matrix by copolymerizing divinylbenzene (DVB), adding a pore-forming agent (porogen), and removing it during the polymerization process, wherein a multilayer protective coating layer is formed on the inner surface of the high-frequency induction heating treatment tube to simultaneously secure corrosion resistance, oxidation resistance, and antifouling properties, and wherein the protective coating layer is formed by coating with a coating composition consisting of 10-20 wt% fused silica powder, 5-15 wt% α-alumina (Al2O3) powder, 5-10 wt% FEP (fluorinated ethylene propylene), 5-10 wt% tetraethoxysilane (TEOS), and the remainder sodium silicate (Na2SiO3).