Sewage and wastewater effluent treatment method

Abstract

According to the present disclosure, a sewage and wastewater effluent treatment method is provided. The method comprises the steps of: providing sewage and wastewater effluent; using a nanofilter (NF) to separate the sewage and wastewater effluent into NF concentrate and NF permeate; removing organic materials from the NF concentrate; introducing the NF permeate into reverse osmosis so as to separate same into reverse osmosis concentrate and deionized water; removing nitrogen from the reverse osmosis concentrate, the nitrogen removal step being performed by a biological or electrochemical method; and combining the NF concentrate that passed through the organic material removal step and the reverse osmosis concentrate that passed through nitrogen removal step. The method enables environmentally friendly and efficient treatment of sewage and wastewater effluent.

Description

Wastewater discharge treatment method

[0001] The present disclosure relates to a method for treating wastewater discharge.

[0002] The UN reports that 34.7% of the world's population faces water shortages, and projects that this figure will increase to 44.9% by 2050.

[0003] Water demand has been continuously increasing recently due to factors such as rapid industrial advancement, massive urbanization, and improvements in living standards.

[0004] However, Korea's water supply relies heavily on river water, and the supply of water resources through dam development is limited due to a shortage of suitable construction sites and social opposition.

[0005] Consequently, there are attempts to meet water demand by utilizing sewage. Sewage is generated on a large scale throughout the year, and when treated by recently introduced advanced treatment methods, the water quality is also satisfactory.

[0006] Furthermore, wastewater reuse is being actively encouraged as an alternative to resolve water supply shortages, as it can be treated to a level that meets discharge standards and reused in other processes after treatment near the point of generation can have positive economic, social, and environmental impacts.

[0007] For this reason, research and development on water treatment technologies capable of removing pollutants in water systems more efficiently and effectively are actively underway.

[0008] [Prior Art Literature]

[0009] [Patent Literature]

[0010] (Patent Document 1) KR 10-2021719 B1

[0011] The present disclosure can provide a wastewater effluent treatment method capable of effectively removing pollutants or organic matter from a water system without generating toxic by-products.

[0012] A wastewater effluent treatment method according to the present disclosure comprises: a step of providing wastewater effluent; a step of separating the wastewater effluent into nanofilter concentrate and nanofilter permeate using a nanofilter (NF); a step of removing organic matter from the nanofilter concentrate; a step of introducing the nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water; a step of removing nitrogen from the reverse osmosis concentrate, wherein the nitrogen removal step is performed by a biological or electrochemical method; and a step of combining the nanofilter concentrate after the organic matter removal step and the reverse osmosis concentrate after the nitrogen removal step.

[0013] In one embodiment, the nanofilter permeate may contain 10% or less of the weight of the polyvalent ions per unit volume relative to the weight of the polyvalent ions per unit volume contained in the initial wastewater discharge.

[0014] In one embodiment, the nanofilter concentrate may contain 20% or less of the weight of monovalent ions per unit volume relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step.

[0015] In one embodiment, the nanofilter concentrate may contain 20% or less of the weight of monovalent ions per unit volume relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step.

[0016] In one embodiment, the flow rate ratio of nanofilter permeate to nanofilter concentrate may be 5:1 to 20:1.

[0017] In one embodiment, the method may further include a step of pre-treating wastewater effluent before the wastewater effluent separation step.

[0018] In one embodiment, the pretreatment step may include a pH control process, a lime soda process, or a combination thereof.

[0019] In one embodiment, the method may further include a step of adding a separate salt to the wastewater effluent prior to the wastewater effluent separation step.

[0020] In one embodiment, the organic matter removal step can be performed by an advanced oxidation process.

[0021] In one embodiment, the advanced oxidation process may include a Fenton oxidation process, an ozone oxidation process, a UV oxidation process, a hydrogen peroxide oxidation process, a catalytic oxidation process, or a combination thereof.

[0022] In one embodiment, the biological nitrogen removal method may be carried out by Anammox denitrification, autotrophic denitrification, or a combination thereof.

[0023] In one embodiment, the method may further include a step of oxidizing chloride ions in reverse osmosis concentrate.

[0024] According to one embodiment of the present disclosure, environmentally friendly and efficient treatment of wastewater effluent is possible.

[0025] FIG. 1 is a process flow diagram of a wastewater discharge treatment method according to one embodiment.

[0026] Figure 2 is a process flow diagram of a circulating nanofilter process according to one embodiment.

[0027] FIG. 3 is a process flow diagram of a wastewater discharge treatment method according to one embodiment.

[0028] Figure 4 is a graph showing the electrochemical nitrogen removal efficiency over time for reverse osmosis concentrate according to one embodiment.

[0029] The present disclosure will be described in detail below with reference to the attached drawings. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0030] According to the present disclosure, a method for treating wastewater effluent is provided, the method comprising: a step of providing wastewater effluent; a step of separating the wastewater effluent into nanofilter concentrate and nanofilter permeate using a nanofilter (NF); a step of removing organic matter from the nanofilter concentrate; a step of introducing the nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water; a step of removing nitrogen from the reverse osmosis concentrate, wherein the nitrogen removal step is performed by a biological or electrochemical method; and a step of combining the nanofilter concentrate after the organic matter removal step and the reverse osmosis concentrate after the nitrogen removal step. A schematic flow of the method is illustrated in FIG. 1.

[0031] The wastewater effluent provision step corresponds to the step of preparing the wastewater effluent to be treated. The aforementioned wastewater effluent contains chloride ions (Cl - ), ammonium ion (NH4 + ), nitrate ions (NO3 - Monovalent ions such as ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) and sulfate ions (SO4 2- It may contain various types of impurities such as multivalent ions, total organic carbon (TOC), ammonia, and inorganic contaminants. Wastewater effluent may also contain types of impurities other than those listed.

[0032] The step of separating wastewater effluent into nanofilter concentrate and nanofilter permeate using a nanofilter (NF) corresponds to a step of selectively separating ions and impurities contained in the wastewater effluent so that each wastewater effluent separated through the nanofilter is introduced into an appropriate water treatment stage according to the type of impurities contained therein. The nanofilter permeate separated in the above separation step has a higher concentration of monovalent ions compared to the monovalent ion concentration contained in the wastewater effluent and may contain trace amounts of polyvalent ions that were not separated in the separation step. Additionally, the nanofilter permeate has a higher ammonia concentration compared to the wastewater effluent. The nanofilter concentrate has higher concentrations of polyvalent ions and organic impurities compared to the wastewater effluent and may contain trace amounts of monovalent ions and trace amounts of ammonia that were not separated in the separation step. There are no limitations on the method of the above separation step as long as it can separate monovalent ions and ammonia from polyvalent ions and organic impurities. Furthermore, in the above separation step, inorganic carbon (IC) is mainly HCO3 - The nanofilter permeate can be separated into monovalent ions of the form. In one embodiment, the step of separating wastewater effluent into nanofilter concentrate and nanofilter permeate can be performed using a nanofilter membrane with high separation performance for monovalent and polyvalent ions, and can be carried out in a circulating or multi-stage process to achieve a desired level of ion and impurity separation. As shown in FIG. 2, the circulating process method is performed by introducing the nanofilter concentrate back into the separation stage using the nanofilter until the desired level of ion and impurity separation is achieved. The wastewater effluent separation stage using the nanofilter can lower the salt concentration in the reverse osmosis concentrate concentrated in the subsequent reverse osmosis stage, thereby reducing ecotoxicity caused by salt, which can improve the biological nitrogen removal efficiency of the reverse osmosis concentrate.

[0033] In one embodiment, the nanofilter permeate may contain 10% or less of the weight of polyvalent ions per unit volume relative to the weight of polyvalent ions per unit volume contained in the initial wastewater effluent. As described above, the nanofilter permeate contains monovalent ions at a concentration exceeding the concentration of monovalent ions contained in the wastewater effluent and may contain trace amounts of polyvalent ions that are not separated in the separation step. The trace amounts of polyvalent ions refer to polyvalent ions that are inevitably contained in the nanofilter permeate because the ion separation efficiency of the separation step is not 100% when a large amount of polyvalent ions is contained in the wastewater effluent. Among the polyvalent ions contained in the nanofilter permeate, calcium ions and magnesium ions may reduce the nitrogen removal performance during nitrogen removal in the reverse osmosis concentrate in the subsequent step. As described above, the nanofilter permeate contains only an unavoidable trace amount of polyvalent ions with a content of 10% or less relative to the weight of polyvalent ions per unit volume contained in the initial wastewater effluent, thereby preventing a decrease in nitrogen removal performance due to the presence of calcium and magnesium ions. In one embodiment, the nanofilter permeate may specifically contain polyvalent ions per unit volume of 0 to 10% or less, more specifically 0 to 7%, and even more specifically 0 to 5% relative to the weight of polyvalent ions per unit volume contained in the initial wastewater effluent.

[0034] In one embodiment, the nanofilter concentrate may contain 20% or less of the weight of monovalent ions per unit volume relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step. As previously mentioned, the nanofilter concentrate contains polyvalent ions at a concentration exceeding the concentration of polyvalent ions contained in the wastewater effluent, and may contain trace amounts of monovalent ions that are not separated in the separation step. The trace amounts of monovalent ions refer to the monovalent ions inevitably contained in the nanofilter concentrate because the ion separation efficiency of the separation step is not 100% when a large amount of monovalent ions is contained in the wastewater. The trace amounts of monovalent ions may include chloride ions. Chloride ions contained in the nanofilter concentrate can generate a large amount of chlorine byproducts during the removal of organic matter from the nanofilter concentrate in a subsequent step, and since these byproducts are toxic, they can have an adverse effect on the environment. Since the nanofilter concentrate contains only monovalent ions per unit volume of 20% or less relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation stage, it contains only unavoidable trace amounts of chloride ions, thereby minimizing the generation of chlorine byproducts during organic matter removal. In one embodiment, the nanofilter concentrate may specifically contain monovalent ions per unit volume of 0 to 20%, more specifically 0 to 15%, and even more specifically 0 to 10% relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation stage. In particular, in one embodiment, the nanofilter concentrate may contain 0 to 5% of chloride ions per unit volume relative to the weight of chloride ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step, and specifically, may contain 0 to 4%, more specifically 0 to 3% of chloride ions per unit volume relative to the weight of chloride ions per unit volume contained in the wastewater effluent prior to step b).

[0035] In one embodiment, the nanofilter concentrate may contain 200% to 2000% of the weight of polyvalent ions per unit volume relative to the weight of polyvalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step. The nanofilter concentrate contains polyvalent ions in a significantly concentrated amount compared to the wastewater effluent, and due to the concentrated polyvalent ion content, the removal efficiency and cost in the subsequent organic matter removal step can be significantly reduced. In one embodiment, the nanofilter concentrate may specifically contain 300% to 1500%, more specifically 500% to 1000% of the weight of polyvalent ions per unit volume relative to the weight of polyvalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation step.

[0036] In one embodiment, the flow rate ratio of nanofilter permeate to nanofilter concentrate may be 5:1 to 20:1. Since most of the polyvalent ions and organic pollutants contained in wastewater effluent are contained in the nanofilter concentrate, the lower the flow rate of the nanofilter concentrate, the higher the concentration of polyvalent ions and organic pollutants in the nanofilter concentrate. An increase in the concentration of polyvalent ions in the nanofilter concentrate can lead to an increase in the electrical conductivity of the nanofilter concentrate. This can increase process efficiency when the nanofilter concentrate is introduced into an electrochemical oxidation process of organic pollutants. Furthermore, since the advanced oxidation process can easily respond by changing the applied charge amount when the organic pollutant load increases, there is no need to invest additional costs in the advanced oxidation facility even if the concentration of pollutants in the nanofilter concentrate is increased as described above, and it is possible to target nanofilter concentrate with a wide range of pollutant concentrations.

[0037] In one embodiment, the method may further include a step of pre-treating the wastewater effluent before the wastewater effluent separation step. If the content of a specific ion in the wastewater effluent is excessively high, for example, if the concentration of monovalent anions in the wastewater effluent is higher than the concentration of monovalent cations, a large amount of monovalent anions may be contained in the nanofilter concentrate, which can generate unwanted by-products as described above. Conversely, if the concentration of monovalent cations in the wastewater effluent is higher than the concentration of monovalent anions, a large amount of monovalent cations may be contained in the nanofilter concentrate, which may require additional treatment to meet discharge standards. The pre-treatment step corresponds to a step of removing some of the ions with higher content from the wastewater effluent before the wastewater effluent separation step in order to prevent these problems when there is a difference in the content of monovalent cations and monovalent anions in the wastewater effluent. The above pretreatment step is not limited to any method as long as it can remove specific ions with high content from the wastewater effluent.

[0038] In one embodiment, the pretreatment step may include a pH control process, a lime soda process, or a combination thereof. The pH control process increases the pH of the wastewater effluent, thereby increasing the Ca and Mg ions and NH4 in the wastewater effluent. + This is a process for removing [the substance]. Through this, the scale problem of the above method can be reduced, and the time required for ammonia post-treatment in subsequent steps can be reduced. The lime soda process is a process for removing multivalent ions, such as calcium ions and / or magnesium ions, present in wastewater effluent by adding sodium carbonate and sodium hydroxide to the wastewater effluent, stirring to induce a chemical reaction, and then separating and removing the resulting salts by precipitation.

[0039] In one embodiment, the method may further include a step of adding a separate salt to the wastewater effluent before the wastewater effluent separation step. As previously mentioned, if there is a difference in concentration between monovalent cations and monovalent anions in the wastewater effluent, the separation efficiency of monovalent and polyvalent ions in the nanofilter may decrease. To prevent this, a salt of monovalent cations and polyvalent anions, or a salt of polyvalent cations and monovalent anions, may be added to the wastewater effluent before the wastewater effluent separation step to balance the concentrations of monovalent cations and monovalent anions, and if necessary, the salt may be added to create an imbalance between monovalent cations and monovalent anions. For example, by adding salt, the concentration of monovalent cations in the wastewater effluent can be made higher than the concentration of monovalent anions. In this case, the concentration of monovalent anions entering the nanofilter permeate increases further, and the concentration of monovalent anions in the second treated water may be lower compared to when the balance of cations and anions in the wastewater effluent is maintained. This can reduce the generation of chlorine byproducts caused by the presence of chloride ions among monovalent anions during the oxidation of organic matter in the nanofilter concentrate.

[0040] The above method includes a step of removing organic matter from nanofilter concentrate. There are no limitations on the method of performing the organic matter removal step, as long as it can remove impurities such as organic matter within the nanofilter concentrate. For example, the organic matter removal step may be performed by removing organic matter by precipitation or by oxidizing it in any way. By removing organic matter from the nanofilter concentrate in the organic matter removal step, the nanofilter concentrate can have a water quality suitable for discharge. In addition, since the nanofilter concentrate does not contain monovalent ions, including chloride ions, except for unavoidable trace amounts, the generation of perchlorate caused by residual chloride ions during the oxidation of organic matter within the nanofilter concentrate can be prevented.

[0041] In one embodiment, the organic matter removal step may be performed by an advanced oxidation process. An advanced oxidation process is a process that generates radicals with strong oxidizing power, particularly hydroxyl radicals (·OH), to oxidize and decompose multivalent ion salts and organic impurities. According to the advanced oxidation process, almost all organic contaminants, including non-degradable organic contaminants that are difficult to remove by general physical and chemical treatments, can be removed. Furthermore, the advanced oxidation process using hydroxyl radicals has an additional advantage in that water is generated as a byproduct after the oxidation reaction, thereby preventing secondary pollution caused by the byproduct.

[0042] In one embodiment, the advanced oxidation process may be performed by an electrochemical oxidation process, a Fenton oxidation process, an ozone oxidation process, a UV oxidation process, an oxidation process using hydrogen peroxide, a catalytic oxidation process, or a combination thereof. The electrochemical oxidation process corresponds to a process of directly oxidizing contaminants at an electrode to which electricity is applied or indirectly oxidizing them by generating an oxidizing agent; the Fenton oxidation process corresponds to a process of removing organic contaminants by generating hydroxyl radicals through a catalytic reaction between organic matter and hydrogen peroxide; and the ozone oxidation process corresponds to a process of introducing ozone (O3) into the nanofilter concentrate and applying power to generate radicals, and oxidizing and decomposing organic matter in the nanofilter concentrate by utilizing the instability of the radicals. The UV oxidation process and the oxidation process using hydrogen peroxide correspond to processes of generating hydroxyl radicals by irradiating ozone with ultraviolet light or reacting it with hydrogen peroxide, thereby oxidizing and decomposing organic matter. The catalytic oxidation process corresponds to a process of directly oxidizing organic matter using a catalyst or indirectly oxidizing it through the generation of an oxidizing agent. Through the above process, organic matter in the nanofilter concentrate can be effectively removed. In particular, in the case of the electrochemical oxidation process, the high conductivity resulting from the high ion content of the nanofilter concentrate reduces the required voltage, which offers the advantage of lowering power costs.

[0043] The above method includes a step of introducing nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water. In the wastewater effluent separation step, more than 80% of the water in the wastewater effluent flows into the nanofilter permeate. That is, after the wastewater effluent separation step, monovalent ions in the nanofilter permeate are concentrated compared to monovalent ions in the wastewater concentrate, but the degree of concentration is not significant. The reverse osmosis step is a step to further concentrate the monovalent ions in the nanofilter permeate. Specifically, the reverse osmosis step involves introducing the nanofilter permeate into a reverse osmosis membrane to separate deionized water that passes through the reverse osmosis membrane from reverse osmosis concentrate that does not pass through the reverse osmosis membrane. Conventional deionized water production involves two concentration steps; however, the above method can provide a cost advantage by replacing one of the concentration steps with an ion separation step using a nanofilter. In addition, in the above method, the organic oxidation efficiency can be increased by replacing one of the concentration steps with an ion separation step using a nanofilter. There is no restriction on the type of reverse osmosis process as long as it is a process capable of concentrating monovalent ions in the nanofilter permeate.

[0044] The above method includes the step of removing nitrogen from reverse osmosis concentrate. As previously mentioned, wastewater effluent contains a large amount of nitrate ions (NO3 - It contains ) and, if discharged without separate treatment, can cause environmental pollution due to toxicity. The above method can solve such problems by including a step of removing nitrogen from the reverse osmosis concentrate. Biological or electrochemical methods may be used as methods for removing nitrogen from the reverse osmosis concentrate. Biological nitrogen removal methods use nitrate (NO3 - ) or nitrite (NO2 -This corresponds to a microbial-based nitrogen removal process that reduces nitrogen in the form of ) into nitrogen gas (N2) under anaerobic conditions and releases it into the air. The electrochemical nitrogen removal method corresponds to a method in which reverse osmosis concentrate is introduced into a reactor comprising an anode and a cathode, and power is applied to convert nitrate or nitrite into ammonia gas (NH3) or nitrogen gas (N2) at the cathode. The above method can prevent a decrease in efficiency caused by the presence of calcium and magnesium ions in the nitrogen removal step by minimizing the calcium and magnesium ion content in the reverse osmosis concentrate introduced in the nitrogen removal step using a nanofilter as described above. Specifically, by minimizing calcium and magnesium ions in the reverse osmosis concentrate, a decrease in denitrification efficiency due to sludge aggregation during biological nitrogen removal can be prevented, and calcium and magnesium ions adsorbed on the electrode surface during electrochemical nitrogen removal can be prevented from inhibiting nitrate reduction.

[0045] In one embodiment, the biological nitrogen removal step may be performed by activated sludge denitrification, anaerobic digestion, A2O, trickling filter method, biofilm process, USAB process, or a combination thereof. Activated sludge denitrification is a denitrification method in which microorganisms within activated sludge reduce nitrates to nitrogen gas and release them into the atmosphere under anaerobic conditions, and anaerobic digestion includes a step of converting organic nitrogen into ammonia and subsequently removing ammoniacal nitrogen. A2O (Anaerobic-Anoxic-Oxic) is a method for removing total nitrogen and total phosphorus in the order of an anaerobic tank, anoxic tank, and aerobic tank. The trickling filter method is a method for inducing denitrification by microorganisms by treating wastewater by spraying it through filter media to which microorganisms are attached. The biofilm process is a method for treating wastewater through a biofilm to which microorganisms are attached to a fixed medium, and can perform oxidation of ammonia to nitrate outside the biofilm and denitrification of nitrates to nitrogen gas inside the biofilm. The UASB (Upflow Anaerobic Sludge Blanket) process is a method of performing denitrification by introducing wastewater upward into an anaerobic microbial layer (sludge blanket), which allows the sludge to be fixed to the blanket without floating.

[0046] In one embodiment, the method may further include a step of oxidizing chloride ions in the reverse osmosis concentrate. As described above, the electrochemical nitrogen removal method can remove only nitrogen in the form of nitrate or nitrite, so that ammoniacal nitrogen (NH3 or NH4) in the reverse osmosis concentrate +If present, it may remain in the reverse osmosis concentrate even after the nitrogen removal step. Such ammonia nitrogen is highly toxic and can cause water pollution and eutrophication upon discharge. As illustrated in Fig. 3, when a chlorine oxidation step is applied to the reverse osmosis concentrate, the ammonia nitrogen is oxidized and removed in the form of salts, thereby preventing water pollution and eutrophication caused by ammonia nitrogen. Specifically, ammonia nitrogen can be removed in gaseous form by being oxidized by hypochlorous acid generated during chlorine oxidation. If the chlorine concentration in the reverse osmosis concentrate is low, the chlorine oxidation step may be performed after adding additional chloride ions to the reverse osmosis concentrate. The chlorine oxidation step may be performed after the electrochemical nitrogen removal step or simultaneously with the electrochemical nitrogen removal step, and preferably, it may be performed in the same reactor as the electrochemical nitrogen removal step to provide advantages in terms of process efficiency.

[0047] The above method includes a step of combining the nanofilter concentrate after the organic matter removal step and the reverse osmosis concentrate after the nitrogen removal step. As previously mentioned, in the wastewater effluent separation step using a nanofilter, trace amounts of ammoniacal nitrogen that were not fully separated may remain in the nanofilter concentrate. By mixing the nanofilter concentrate after the organic matter removal step with the reverse osmosis concentrate after the nitrogen removal step, the trace amounts of ammoniacal nitrogen remaining in the nanofilter concentrate can be oxidized by reacting with chloride ions remaining in the reverse osmosis concentrate after being separated into nanofilter permeate during ion separation using a nanofilter, and / or with hypochlorous acid generated by the oxidation of chloride ions added to the reverse osmosis concentrate during the chlorine oxidation step. Through the above reaction, the ammoniacal nitrogen content in the combined concentrate can be reduced. A process flow diagram of the method for removing pollutants from wastewater including the above step is shown in FIG. 3.

[0048] Preferred embodiments are provided below to aid in understanding the present disclosure, but the following embodiments are provided merely to facilitate a better understanding of the present disclosure and are not intended to limit the present disclosure.

[0049] Experimental Example 1

[0050] As illustrated in FIG. 1, the process is configured to include: a step of providing wastewater effluent; a step of separating the wastewater effluent using a nanofilter into nanofilter permeate containing monovalent ions, ammonia, and nitrates, and nanofilter concentrate containing polyvalent ions and organic impurities; a step of removing organic matter from the nanofilter concentrate; a step of introducing the nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water; a step of introducing the reverse osmosis concentrate into an electrochemical nitrogen removal process; and a step of combining the nanofilter concentrate after the organic matter removal step and the reverse osmosis concentrate after the electrochemical nitrogen removal step.

[0051] The aforementioned wastewater effluent was from the wastewater treatment plant of SK Energy's refining and petrochemical business, and the nanofilter used in the wastewater effluent separation stage was an NE8040-40 membrane nanofilter. The nanofilter had a recovery rate of 90%, a pressure of 20 bar, and 1.6 m 3 It was operated under process conditions of an hourly processing flow rate of 1 / h. The organic matter removal step was performed in a reactor equipped with ATO (antimony-doped tin oxide) as the anode and titanium (Ti) as the cathode, with an electrode area of ​​1,500 cm². 2 , the applied current density is 10 mA / cm² 2 The reaction volume was 250 L, and the distance between each electrode was 3 mm. The reverse osmosis step was performed using an RE8040-BE reverse osmosis membrane, and the process conditions were a recovery rate of 87.5%, a pressure of 20 bar, and 1.6 m 3It was performed with an hourly processing flow rate of 1 / h. The nitrogen removal step was carried out in a reactor equipped with a Dimensionally Stable Anode (DSA) as the anode and silver (Ag) as the cathode, with an electrode area of ​​1,500 cm². 2 , the applied current density is 10 mA / cm² 2 The reaction volume was 280 L, and the distance between each electrode was 3 mm.

[0052] The pH, ion conductivity, organic matter, and ion concentration of the wastewater effluent (Feed) before being fed into the above process, and the feed after each process step, were as shown in Table 1 below. The data in Table 1 were analyzed by the SK Innovation Analysis Center, which is a KOLAS accredited testing laboratory in accordance with KS Q ISO / IEC 17025.

[0053]

[0054] Referring to Table 1, TOC and Ca by nanofilter 2+ , Mg 2+ , SO4 2- It can be confirmed that multivalent ions such as [the above] are concentrated in the nanofilter concentrate, and that the nanofilter permeate does not contain TOC and multivalent ions except for unavoidable trace amounts.

[0055] As a result of ion separation by the nanofilter described above, the reverse osmosis concentrate contains polyvalent ions, particularly Ca 2+ , and Mg 2+ It can be confirmed that it contains almost nothing.

[0056] Meanwhile, nanofilter concentrate is rich in TOC and polyvalent ions, whereas Cl - Since the content of monovalent ions, including [unclear], is low, it can be inferred that toxic chlorine byproducts will not be formed when organic matter is removed from the nanofilter concentrate by advanced oxidation.

[0057] Experimental Example 2

[0058] The process is configured to include: a step of providing wastewater effluent; a step of separating the wastewater effluent into nanofilter permeate containing monovalent ions and ammonia, and nanofilter concentrate containing polyvalent ions and organic impurities using a nanofilter; a step of removing organic matter from the nanofilter concentrate; a step of introducing the nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water; a step of introducing the reverse osmosis concentrate into biological nitrogen removal; and a step of combining the nanofilter concentrate after the organic matter removal step and the reverse osmosis concentrate after the electrochemical nitrogen removal step.

[0059] The aforementioned wastewater effluent was from the wastewater treatment plant of SK Energy's refining and petrochemical business, and the nanofilter used in the wastewater effluent separation stage was an NE8040-40 membrane nanofilter. The nanofilter had a recovery rate of 90%, a pressure of 20 bar, and 1.6 m 3 It was operated under process conditions of an hourly processing flow rate of 1 / h. The organic matter removal step was performed in a reactor equipped with BDD (Boron-doped Diamond) as the anode and SUS (Stainless Steel) as the cathode, with an electrode area of ​​15 cm². 2 , the applied current density is 30 mA / cm² 2 The reaction volume was 800 mL, and the distance between each electrode was 5 mm. The reverse osmosis step was performed using a TM720D-400 reverse osmosis membrane, and the process conditions were a recovery rate of 87.5%, a pressure of 20 bar, and 1.6 m 3The process was performed with an hourly treatment flow rate of 1 / h. The nitrogen removal step was carried out by activated sludge denitrification, and the sludge used was activated sludge obtained from SK Energy Water Management Center No. 1. Trace amounts of minerals (Ca, Mg, Fe, etc.) and methanol were supplied as nutrients to the sludge, and the reaction volume was controlled to 1.5 L. The aeration conditions were a DO (dissolved oxygen) of 10 ppm and a MLSS (Mixed Liquor Suspended Solids) of 4000 ppm.

[0060] The pH, ion conductivity, organic matter, and ion concentration of the wastewater effluent (Feed) before being fed into the above process, and the feed after steps a) to f), were as shown in Table 2 below. The data in Table 2 were analyzed at the SK Innovation Analysis Center, which is a KOLAS accredited testing laboratory in accordance with KS Q ISO / IEC 17025.

[0061]

[0062] From Table 2, it can be confirmed that organic matter can be removed without generating chlorine byproducts by separating organic matter and monovalent ions, particularly chloride ions, using a nanofilter and removing organic matter. In addition, it can be confirmed that the total nitrogen content in the nanofilter permeate can be significantly reduced through biological denitrification following reverse osmosis concentration of the nanofilter permeate.

[0063] Experimental Example 3

[0064] Electrochemical nitrogen removal was performed on reverse osmosis concentrate having the characteristics shown in Table 3 below under the same process conditions as in Experimental Example 1.

[0065]

[0066] 25 ppm and 50 ppm of Ca in the same reverse osmosis concentrate 2+ (CaCl2) and Mg 2+After adding (MgCl2) ions, electrochemical nitrogen removal was performed under the same process conditions as in Experimental Example 1.

[0067] The results of measuring the total nitrogen removal efficiency over time for each reverse osmosis concentrate were as shown in Figure 4.

[0068] Referring to Figure 4, it was confirmed that the electrochemical total nitrogen removal efficiency for reverse osmosis concentrate without external addition of Ca and Mg ions remained at a level of about 65 to 70%, whereas when 25 ppm of Ca and Mg ions were externally added, the electrochemical total nitrogen removal efficiency decreased to about 21 to 29%. When 50 ppm of Ca and Mg ions were externally added, the electrochemical total nitrogen removal efficiency decreased further to about 5 to 21%.

[0069] From this, it can be inferred that as the Ca and Mg ion content in the reverse osmosis concentrate increases, the electrochemical nitrogen removal efficiency tends to decrease.

[0070] In addition, in Experimental Example 1, since Ca and Mg ions were separated so as not to be contained in the reverse osmosis concentrate through a nanofilter, it can be inferred that a high electrochemical total nitrogen removal rate of about 85% as described in Table 1 could be achieved.

[0071] The present disclosure has been described in detail through specific embodiments. The embodiments are intended to specifically illustrate the present disclosure and are not limited thereto. It will be apparent that modifications or improvements can be made by those skilled in the art within the technical scope of the present disclosure. All simple modifications or alterations of the present disclosure fall within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be clarified by the appended claims.

Claims

1. Wastewater discharge supply stage; A step of separating wastewater effluent into nanofilter concentrate and nanofilter permeate using a nanofilter (NF); Step of removing organic matter from nanofilter concentrate; A step of introducing nanofilter permeate into a reverse osmosis process to separate it into reverse osmosis concentrate and deionized water; A step of removing nitrogen from reverse osmosis concentrate, the nitrogen removal step is performed by a biological or electrochemical method; and A wastewater effluent treatment method comprising the step of combining nanofilter concentrate after an organic matter removal step and reverse osmosis concentrate after a nitrogen removal step.

2. In Claim 1, A wastewater effluent treatment method in which the nanofilter permeate contains 10% or less of the weight of polyvalent ions per unit volume relative to the weight of polyvalent ions per unit volume contained in the initial wastewater effluent.

3. In Claim 1, A wastewater effluent treatment method in which the nanofilter concentrate contains 20% or less of the weight of monovalent ions per unit volume relative to the weight of monovalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation stage.

4. In Claim 1, A wastewater effluent treatment method comprising nanofilter concentrate containing 200% to 2000% of polyvalent ions per unit volume relative to the weight of polyvalent ions per unit volume contained in the wastewater effluent prior to the wastewater effluent separation stage.

5. In Claim 1, A wastewater effluent treatment method in which the flow rate ratio of nanofilter permeate to nanofilter concentrate is 5:1 to 20:

1.

6. In Claim 1, The above method is a wastewater treatment method that further includes a step of pre-treating wastewater effluent before a wastewater effluent separation step.

7. In Claim 6, A wastewater effluent treatment method comprising a pretreatment step including a pH control process, a lime soda process, or a combination thereof.

8. In Claim 1, The above method is a wastewater treatment method that further includes a step of adding a separate salt to the wastewater effluent prior to the wastewater effluent separation step.

9. In Claim 1, A wastewater effluent treatment method in which the organic matter removal step is performed by an advanced oxidation process.

10. In Claim 9, A wastewater effluent treatment method comprising an advanced oxidation process including a Fenton oxidation process, an ozone oxidation process, a UV oxidation process, a hydrogen peroxide oxidation process, a catalytic oxidation process, or a combination thereof.

11. In Claim 1, A wastewater effluent treatment method in which biological nitrogen removal is performed by activated sludge denitrification, anaerobic digestion, A2O, trickling filter method, biofilm process, USAB process, or a combination thereof.

12. In Claim 1, The above method is a wastewater effluent treatment method further comprising the step of oxidizing chloride ions in reverse osmosis concentrate.

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