Method and system for treating wastewater by membrane filtration and electrochemical oxidation

Abstract

The wastewater treatment system includes a membrane filtration device that receives a stream of pretreated wastewater from a pretreatment unit and produces a waste stream, which is fed to an electrochemical oxidation reactor that produces a reactor effluent stream that is split into a recycled wastewater stream that is recycled back to an equalization tank and a reactor effluent stream that is discarded from the system. A target fraction ratio between the volume of the recycled wastewater stream and the volume of the reactor effluent stream is controlled based on a target total dissolved solids content in the wastewater being treated, an amount of regulated organic matter in the wastewater that is treated by the electrochemical oxidation reactor to increase the efficiency of the electrochemical oxidation reactor to a target value, and the composition of the wastewater that is discarded from the system.

Description

Technical Field

[0001] The present invention relates to a system and method for treating wastewater by membrane filtration assisted by electrochemical oxidation.

Background Art

[0002] Wastewater treatment systems are in high demand due to stricter wastewater treatment regulations, which require industrial facilities to remove recalcitrant water pollutants before discharge, and the current global shortage of clean water. Therefore, there is an increasing demand for cost-effective and sustainable wastewater treatment systems that minimize the addition of chemicals, do not generate secondary pollution, and minimize operation and maintenance requirements.

[0003] A preferred approach for treating recalcitrant wastewater is by electrochemical oxidation, which is a sustainable, safe, and efficient treatment solution for removing, for example, residual organic pollutants, dioxins, nitrogen species (e.g., ammonia), pharmaceuticals, pathogens, microorganisms, and other diverse pollutants. One approach for treating wastewater is by direct electrochemical oxidation of organic and / or inorganic pollutants, whereby such pollutants are directly oxidized on the anode surface. Another method is the indirect electrochemical oxidation of organic and / or inorganic pollutants via in-situ generation of chemical oxidation species (e.g., hydroxyl, chlorine, oxygen, or perchlorate radicals or compounds (e.g., hypochlorite, ozone, or hydrogen peroxide)). These chemical oxidation species are generated directly on the anode surface and then oxidize the pollutants in the wastewater solution.

[0004] In wastewater treatment systems using electrochemical oxidation, the anodic catalyst is selected from a group including platinum, tin oxide, antimonstin oxide, ruthenium oxide, iridium oxide, niobium-doped antimonstin oxide, graphite, and manganese oxide, or it can be a more expensive catalyst such as diamond or boron-doped diamond. Electrodes used in wastewater treatment are generally expensive, which can increase the overall system cost, especially in applications where large amounts of organic matter need to be removed.

[0005] Membrane filtration of wastewater is another known method for removing suspended and dissolved solids, organic matter, and other contaminants from wastewater that generates wastewater streams containing high concentrations of suspended and dissolved solids, organic matter, and other contaminants that require downstream treatment or disposal. Membrane filtration of wastewater may include reverse osmosis, ultrafiltration, nanofiltration, or microfiltration.

[0006] In the past, waste streams from membrane filtration systems were treated by electro-oxidation in an electrochemical reactor, as described above, to remove organic matter from the waste stream, and the treated wastewater from the electrochemical reactor was discarded.

[0007] For example, WO2011015556 describes a method for decomposing organic pollutants in industrial wastewater, in which the organic compounds in the wastewater are first concentrated in two stages by nanofiltration or ultrafiltration, then by reverse osmosis, and finally the waste stream is treated by electrolysis. When the concentration of pollutants (COD) in the wastewater exceeds a predetermined value, the waste stream from the reverse osmosis process is supplied to the electrolysis unit. This method attempts to improve the energy efficiency of the wastewater treatment system.

[0008] Similarly, KR101017006 describes a reverse osmosis concentrate treatment apparatus comprising a reverse osmosis concentrate tank for storing reverse osmosis concentrates generated during the treatment of livestock wastewater, from which the concentrates are supplied to a coagulation tank where organic matter is coagulated and removed, and then supplied to an electro-oxidation tank where the wastewater is treated by electrochemical oxidation to remove residual organic matter and ammonia nitrogen.

[0009] It is known that membrane filtration is used before electrochemical oxidation to concentrate organic matter from the wastewater to be treated in order to improve oxidation treatment efficiency, and then the amount of organic matter in the treated wastewater is reduced in the filtration stage of the electrochemical oxidation reactor to achieve safe discharge.

[0010] To achieve drinking water discharge levels, it is also known that wastewater is first treated by electrochemical oxidation to remove organic materials, and the effluent from the electrochemical oxidation process is further treated by membrane filtration processes such as reverse osmosis or electrodialysis to remove other dissolved solids.

[0011] Prior art literature describes electrochemical oxidation reactors as being designed to remove most organic contaminants from wastewater streams coming from membrane filtration systems, so that the treated wastewater streams from the membrane filtration system can be discharged into the environment. This involves having a sufficiently large electrode active region within the reactor to treat the wastewater to reduce the organic matter concentration to a level sufficient for discharge, and to allow the reactor to operate at higher current densities. This means that the cost of the system will be high due to the cost of the catalysts used in wastewater treatment and the power consumption.

[0012] Despite substantial advancements in the art, there remains a continuing need for more efficient and cost-effective methods for treating wastewater (particularly wastewater containing large amounts of organic matter) by using a combination of membrane filtration and electrochemical oxidation methods. The present invention addresses this need while providing additional advantages as disclosed herein. [Overview of the project]

[0013] The present invention relates to a wastewater treatment system, A first membrane filtration device receives a wastewater flow to be treated and generates a first waste flow and a first treated wastewater flow to be discarded from the system, The system includes an electrochemical oxidation reactor that receives a first waste stream from a first membrane filtration device, processes it to remove a portion of specific organic matter from the wastewater, and generates a reactor effluent stream. This section describes a wastewater treatment system in which the reactor outflow logistics are divided into a recirculated wastewater flow that is returned to the first membrane filtration unit for recycling and a reactor discharge flow that is discarded from the system.

[0014] In some embodiments, the wastewater stream to be treated is first supplied to a homogenization tank before being supplied to the membrane filtration device and then to a further treatment unit, or is supplied only to a pretreatment unit before being supplied to the membrane filtration device, and in these embodiments, the recirculated wastewater stream is returned to the homogenization tank and / or pretreatment unit before being supplied to the first membrane filtration device.

[0015] In a preferred embodiment, the first membrane filtration device is a reverse osmosis device.

[0016] In some embodiments, the system further comprises a second membrane filter that receives the wastewater stream to be treated before it is sent to the first membrane filter and generates a second treated wastewater stream to be supplied to the first membrane filter and a second waste stream to be supplied to an electrochemical oxidation reactor for further treatment.

[0017] In a preferred embodiment, the second membrane filtration device is an ultrafiltration device.

[0018] The first and / or second membrane filtration apparatus comprises a membrane selected to remove specific organic compounds, and the electrochemical oxidation reactor comprises at least one electrochemical cell having an electrode with a catalyst selected to remove specific organic compounds from wastewater.

[0019] In a preferred embodiment, the system further comprises control means for adjusting the volume of the reactor discharge flow and the volume of the recirculated wastewater flow by fractionation ratios that depend on a target total dissolved solids content in the wastewater flow to be treated, a target concentration of organic compounds in the wastewater to be treated, and / or the composition of the wastewater discharged from the system.

[0020] The target total dissolved solids content generally depends on the amount and type of inorganic compounds measured in the wastewater stream to be treated. The amount of inorganic compounds measured in the wastewater to be treated includes both desirable and undesirable amounts of inorganic compounds. Desired inorganic compounds in the wastewater to be treated include compounds that increase the conductivity of the wastewater, while undesirable inorganic compounds include scale-forming compounds or halides.

[0021] The fractionation ratio between the volume of the reactor discharge flow and the volume of the recirculated wastewater flow is determined based on the amount of regulated organic matter in the wastewater treated by the electrochemical oxidation reactor in order to increase the efficiency of the electrochemical oxidation reactor to a target value determined based on the rate of removal of pollutants and the amount of current and energy consumed to operate the electrochemical oxidation reactor.

[0022] In some embodiments, the fractionation ratio is adjusted to a constant value based on numerical modeling, while in other embodiments, the fractionation ratio is continuously adjusted based on a target total dissolved solids monitoring value in the wastewater stream to be treated, a target concentration of organic compounds in the wastewater stream to be treated, and the composition of the wastewater discharged from the system.

[0023] A wastewater treatment method by membrane filtration and electrochemical oxidation, The steps include supplying the wastewater to be treated to a membrane filtration device and disposing of the treated wastewater from the system, The steps include: supplying the waste flow from the membrane filtration system to an electrochemical oxidation reactor, processing the waste flow to remove only a portion of specific organic matter from it, generating a reactor effluent, and disposing of the reactor effluent from the electrochemical oxidation reactor; The steps include supplying a portion of the reactor outflow logistics to a membrane filtration system as recirculated wastewater, and disposing of the remainder of the reactor outflow logistics outside the system as reactor discharge, or merging it with the wastewater flow treated by the membrane filtration system and disposing of it outside the system, A method is further disclosed that includes controlling a fraction ratio between the volume of a recirculation wastewater stream from an electrochemical oxidation reactor to a membrane filtration device and the volume of a reactor effluent stream.

[0024] The fraction ratio between the volume of the recirculation wastewater stream from the electrochemical oxidation reactor to the membrane filtration device and the volume of the reactor effluent stream is controlled based on the target total dissolved solids in the wastewater stream to be treated, the target concentration of organic compounds in the wastewater to be treated, and the composition of the wastewater discharged from the system. As described above, the amount of inorganic substances measured in the wastewater to be treated includes the desired amount of inorganic substances and the undesired amount of inorganic substances. The desired inorganic substances in the wastewater to be treated include substances that increase the conductivity of the wastewater to be treated, and the undesired inorganic substances in the wastewater to be treated include scale-forming substances or halides.

[0025] In a preferred embodiment, the target concentration of the organic compound is increased to a target value determined based on the pollutant removal rate and the amount of current and energy consumed to operate the electrochemical oxidation reactor, in order to increase the efficiency of the electrochemical oxidation reactor, based on the amount of regulated organic substances in the wastewater treated by the electrochemical oxidation reactor.

[0026] The fraction ratio between the volume of the recirculation wastewater stream from the electrochemical oxidation reactor to the membrane filtration device and the volume of the reactor effluent stream can be adjusted to a constant value based on numerical modeling, or continuously adjusted based on the monitored value of the target total dissolved solids in the wastewater stream to be treated, the monitored value of the target concentration of organic compounds in the wastewater stream to be treated, and / or the monitored composition of the wastewater stream discharged from the system.

Brief Description of the Drawings

[0027] The drawings illustrate specific preferred embodiments of the present invention, but should not be considered as limiting the spirit or scope of the present invention in any way.

[0028] [Figure 1] FIG. 1 shows a schematic diagram of a first embodiment of a wastewater treatment system according to the present invention. [Figure 2]Figure 2 shows a schematic diagram of a second embodiment of the wastewater treatment system according to the present invention. [Figure 3] Figure 3 shows an example of data supporting how the fractionation ratio between the volume of the recirculated wastewater flow from the electrochemical oxidation reactor to the membrane filtration system and the volume of the reactor discharge flow can be selected according to the present invention. [Modes for carrying out the invention]

[0029] This explanation uses specific terminology, which is intended to be interpreted according to the definitions provided below. Furthermore, terms such as "a" and "comprises" are to be interpreted as open-ended.

[0030] A wastewater treatment system according to the first embodiment of the present invention is shown in Figure 1.

[0031] The electrochemical wastewater treatment system 100 comprises a homogenization tank 102, a pretreatment unit 104, a reverse osmosis device 106, and an electrochemical oxidation reactor 108.

[0032] The wastewater stream 110 to be treated is supplied to a homogenization tank 102, and the effluent wastewater stream 112 from the homogenization tank is pretreated in a pretreatment unit 104. The pretreated wastewater stream 114 leaving the pretreatment unit 104 is supplied to a reverse osmosis unit 106. In the embodiment of the system shown in Figure 1, the membrane filtration unit is a reverse osmosis unit, but those skilled in the art will readily understand that other types of filtration devices can be used, including membranes that separate compounds by molecular size, charge, or other properties (e.g., nanofiltration membranes, microfiltration membranes, or ultrafiltration membranes). In the pretreatment unit, the wastewater is pretreated by adding solutions to increase the conductivity of the wastewater, solutions to control the pH of the wastewater, and / or solutions to prevent membrane fouling, such as descaling agents, dechlorinating agents, or biocides. The homogenization tank stores the wastewater to be treated and allows the system to pump up a certain amount of wastewater for further treatment in the membrane filtration unit and the electrochemical oxidation reactor.

[0033] The pre-treated wastewater stream 114 is treated in a reverse osmosis unit 106 by separating selected soluble and insoluble compounds, including organic compounds, to form a treated wastewater stream 116. The pore size and properties of the membrane are selected to retain the selected organic matter. The wastewater discharged from the reverse osmosis unit forms a reverse osmosis wastewater stream 118, which is fed into an electrochemical oxidation reactor 108, where it is electrochemically treated by electro-oxidation. The electrochemically treated wastewater exits the reactor to form a reactor outflow stream 120. The electrochemical oxidation reactor may comprise several electrochemical cells that can use different catalysts to remove specific contaminants in the wastewater (in particular, specific organic compounds in the wastewater).

[0034] A portion 122 of the reactor outflow logistics 120 forms a recirculating wastewater flow 122, which is returned to the homogenization tank, where it combines with the treated wastewater flow 110 and is then returned to the reverse osmosis device 106. Another portion of the reactor outflow logistics 120 forms a reactor discharge flow 124, which together forms a treated wastewater flow 126 that is mixed with the treated wastewater flow 116 and discharged from the system into the environment.

[0035] The primary objective of this application is not to remove all organic matter from the reverse osmosis wastewater stream, but rather to remove only a portion of the organic pollutants in the wastewater via electro-oxidation, thereby preventing excessive concentration of oxidative pollutants in the wastewater that is returned to the reverse osmosis unit 106 for recycling, and simultaneously controlling the total dissolved solids (TDS) concentration in the wastewater that is returned to the reverse osmosis unit and the electrochemical reactor for recycling. The TDS concentration is controlled to increase the conductivity of the wastewater to be treated, for example, by controlling the amount of sodium sulfate (Na2SO4), the amount of pH adjusting solution (e.g., sodium hydroxide (NaOH)), and / or the amount of scale inhibitor or biocide solution to maintain the state of the reverse osmosis unit membrane, and also to reduce the amount of undesirable inorganic dissolved solids in the wastewater to be treated (e.g., fluorides or those inorganic dissolved solids that increase the hardness of the wastewater). At the same time, the objective of this application is to improve the efficiency of the electrochemical oxidation reactor, which depends on the concentration of organic pollutants in the wastewater to be treated, as measured by the achieved pollutant removal rate and energy / current efficiency. This helps keep the cost of reactors low, as they require a smaller active area to process only a controlled amount of organic matter, while recycling some of the organic compounds back into the reverse osmosis unit.

[0036] This is achieved by controlling the fractionation ratio between the volume of the recirculated wastewater stream 122 and the volume of the reactor discharge stream 124, based on the composition of the wastewater to be treated, the target total dissolved solids content of the wastewater to be treated, the target concentration of organic compounds, more specifically, the concentration of organic compounds treated in the electrochemical oxidation reactor to achieve controlled reactor efficiency, and the acceptable composition of water discharged into the environment, respectively. The target total dissolved solids content in the wastewater to be treated includes desirable inorganic dissolved solids in the wastewater stream (e.g., sulfates or other compounds that increase the conductivity of the wastewater to be treated) and undesirable inorganic dissolved solids in the wastewater stream (e.g., scale-forming compounds, halides, compounds that increase wastewater hardness (e.g., fluorides)).

[0037] The volume of the recirculated wastewater flow 122 and the volume of the reactor discharge flow 124 are controlled by the above parameters through control means (not shown) including standard equipment such as controllers and valves for adjusting the flow of the reactor discharge flow and the recirculated wastewater flow.

[0038] The volume control of the recirculated wastewater flow and reactor discharge flow can be performed at a fixed rate based on laboratory modeling using numerical models that utilize the composition of the wastewater to be treated and the characteristics of the reverse osmosis membrane and electrochemical oxidation reactor, or it can be performed continuously by monitoring the total amount of dissolved solids in the wastewater to be treated flow 110, the amount of organic compounds in the wastewater to be treated flow 110, the reverse osmosis waste flow 118, the electrochemical oxidation reactor 108, and the reactor discharge flow 120, and the composition of the wastewater discharged from the system.

[0039] By treating only a portion of the organic pollutants from wastewater in an electrochemical oxidation reactor and recycling a portion of the pH and conductivity control solution back into the treatment cycle, the overall system size can be reduced, while simultaneously achieving significant savings in terms of equipment costs and energy consumption.

[0040] The method for operating the system described above and illustrated in Figure 1 can be summarized as follows: The wastewater to be treated is supplied to the homogenization tank 102, the effluent wastewater stream 112 is supplied to the pretreatment unit 104, where it is treated, for example, to improve its conductivity or to add a solution to control the pH of the wastewater and / or a solution to prevent membrane fouling, as described above, and the pretreated wastewater stream 114 is supplied to a membrane filtration device (e.g., reverse osmosis device 106). The wastewater stream 118 is supplied to the electrochemical oxidation reactor 108, and the reactor effluent stream 120 is divided into a reactor discharge stream 124 and a recirculated wastewater stream 122 according to a controlled fractionation ratio determined according to one of the control methods described above. The reactor discharge stream 124 merges with the treated wastewater stream 116 coming out of the reverse osmosis device 106 to form a wastewater stream 126 that is discarded from the system.

[0041] A second embodiment of the present invention is shown in Figure 2. The electrochemical wastewater treatment system 200 of this second embodiment comprises a homogenization tank 202, a pretreatment unit 204, an ultrafiltration device 205, a reverse osmosis device 206, and an electrochemical oxidation reactor 208.

[0042] The wastewater stream 210 to be treated is supplied to a homogenization tank 202, and the wastewater stream 212 effluent from the homogenization tank is pretreated in a pretreatment unit 204. The pretreated wastewater stream 214 leaving the unit 204 is supplied to an ultrafiltration device 205, and the ultrafiltered wastewater stream 215 is supplied to a reverse osmosis device 206. Similar to the first embodiment, in the pretreatment unit, the wastewater is pretreated by adding a solution to increase the conductivity of the wastewater, a solution to control the pH of the wastewater, and / or a solution to prevent membrane fouling, such as a scale remover, dechlorinator, or biocide.

[0043] The pre-treated wastewater stream 214 is first treated in an ultrafiltration unit 205 to separate selected soluble and insoluble compounds, which may be the same as or different from those filtered by the reverse osmosis unit 206, which helps prevent fouling of the reverse osmosis unit 206. Those skilled in the art will readily understand that, instead of the ultrafiltration unit 205, or instead of the reverse osmosis unit 206, other membrane filtration devices such as another reverse osmosis unit, nanofiltration unit, or microfiltration or ultrafiltration unit may be used. The ultrafiltered water stream 215 is further treated in the reverse osmosis unit by separating selected soluble and insoluble compounds, including organic compounds, to form the treated wastewater stream 216. The wastewater discarded from the reverse osmosis unit forms the reverse osmosis waste stream 218, and the wastewater discarded from the ultrafiltration unit 205 forms the ultrafiltration waste stream 217. Both the ultrafiltration waste stream 217 and the reverse osmosis waste stream 218 are fed into an electrochemical oxidation reactor 208, where the wastewater is electrochemically treated by electro-oxidation, and the electrochemically treated wastewater exits the reactor to form a reactor outflow stream 220. The electrochemical oxidation reactor may comprise several electrochemical cells that can use different catalysts to remove specific contaminants in the wastewater (in particular, certain organic compounds in the wastewater). Similar to the first embodiment, the electrochemical oxidation reactor 208 processes only a controlled amount of organic matter from the wastewater to be treated, rather than the entire amount of organic matter, while returning some of the organic compounds to the reverse osmosis unit for recycling, thus reducing the required active area and resulting in significant cost savings for the system.

[0044] A portion of the reactor outflow logistics 220 forms a recirculated wastewater flow 222, which is returned to a homogenization tank where it is mixed with the wastewater flow 210 to be treated, and then returned to the pretreatment unit 204, and further to the ultrafiltration unit 205 and reverse osmosis unit 206. Another portion of the reactor outflow logistics 220 forms a reactor discharge flow 224, which is mixed with the treated wastewater flow 216 and forms a treated wastewater flow 226 that is discarded from the system.

[0045] A method for controlling the fractionation ratio between the volume of the reactor discharge flow 224 and the volume of the recirculated wastewater flow 222 is performed in a manner similar to the control method applied in the first embodiment, based on the composition of the wastewater to be treated 210, the target total dissolved solids (TDS) in the wastewater to be treated flow 210, the target concentration of organic compounds treated in the electrochemical oxidation reactor 208 to achieve the controlled efficiency of the reactor, and the acceptable composition of the treated wastewater flow 226 discarded from the system, respectively. The target total dissolved solids (TDS) depends on the concentration of desirable inorganic dissolved solids (e.g., sulfates or other compounds that increase the conductivity of the wastewater to be treated) and the concentration of undesirable inorganic dissolved solids (e.g., scale-forming compounds, halides, compounds that increase the hardness of the wastewater (e.g., fluorides)) in the wastewater to be treated flow 210. This is done by controlling the fractionation ratio between the volume of the recirculated wastewater flow 122 and the volume of the reactor discharge flow 124, based on the composition of the wastewater to be treated.

[0046] The flow of the recirculated wastewater flow 222 and the reactor discharge flow 224 is controlled by control means (not shown) comprising a controller and flow valve, and can be done at a fixed rate based on calculations from a numerical model using the composition of the wastewater to be treated, as in the procedure described in the first embodiment, or continuously by monitoring the concentrations of these compounds in the system during operation.

[0047] The operation method of the system shown in Figure 2 can be summarized as follows: The wastewater to be treated stream 210 is supplied to the homogenization tank 202, the effluent wastewater stream 212 is supplied to the pretreatment unit 204, where it is treated to add solutions, for example, to improve its conductivity or to control the pH of the wastewater as described above and / or to prevent membrane fouling, the pretreated wastewater stream 214 is supplied to the first membrane filtration device, the ultrafiltration device 205, and the ultrafiltered wastewater stream 215 is further supplied to the second membrane filtration device, the reverse osmosis device 206. The ultrafiltered wastewater stream 217 and the reverse osmosis wastewater stream 218 are supplied to the electrochemical oxidation reactor 208, and the reactor effluent stream 220 is divided into the reactor discharge stream 224 and the recirculated wastewater stream 222 according to the controlled fraction ratio determined according to the control method described above. The reactor discharge flow 224 merges with the treated wastewater flow 216 coming out of the reverse osmosis unit 206 to form a treated wastewater flow 226 that is discarded from the system.

[0048] Figure 3 shows a graph illustrating how the fractionation ratio between the volume of the recirculated wastewater flow from the electrochemical oxidation reactor to the membrane filtration system and the volume of the reactor discharge flow depends on the composition of the wastewater to be treated, the target total dissolved solids content, and the acceptable composition of the wastewater to be discarded as described in the present invention.

[0049] Figure 3 was obtained based on the modeling and testing of wastewater in the system according to the present invention, using the following parameters. • COD of 300 mg / L, total dissolved solids (TDS) of 500 mg / L, and 10 m 3 A wastewater flow to be treated with a daily flow rate. • Reverse osmosis system with a 75% recovery rate. • Five sizes of electrochemical oxidation reactors with different removal rates of organic compounds ranging from 25% to 95% as measured in a system that does not recycle wastewater.

[0050] Those skilled in the art will understand that the removal rate of an electrochemical oxidation reactor is based on the active region of each reactor; therefore, reactors that remove more organic compounds will have a larger active region, each with a larger electrolytic region coated with catalysts, and thus will be more expensive. This graph shows the COD (Chemical Oxygen Demand) (Elution COD) in treated wastewater streams discharged into the environment, which are obtained for several different-sized electrochemical oxidation reactors with different fractionation ratios (recycling rates) and different removal rates (25%, 50%, 70%, 85%, and 95%).

[0051] As can be seen in the graph shown in Figure 3, in this example, the wastewater flow discharged from the system must have an effluent COD (Chemical Oxygen Demand) of 100 mg / L, which represents the regulatory requirement imposed on the amount of pollutants in each treated wastewater flow 126 and 226 discharged into the environment. The 100 mg / L limit for effluent COD is indicated by line 300 in Figure 3.

[0052] Another constraint when selecting the recycling rate and the fractionation ratio between recycled and discharged wastewater is to prevent fouling of the membrane filtration system within the system. In this model of wastewater, if the recycling rate exceeds 90% (as shown by line 310 in the graph), fouling of the membrane filtration system and / or reactor will occur.

[0053] Based on the tests, a total dissolved solids (TDS) of 2,500 mg / L in the treated wastewater means that no electrolytes need to be added during treatment, and the tests showed that a recycling rate of over 25%, as shown in line 320, is sufficient to provide this required amount of TDS.

[0054] Based on these requirements, the areas on the graph delimited by lines 300, 310, and 320, indicated as "A," show that systems using reactors of size with a 70% removal rate require fractionation rates (recycling rates) of 40% to 90%. For reactors of size with 85% and 95% removal rates, fractionation rates (recycling rates) of 25% to 90% are used. According to the present invention, considerable savings can be achieved by using smaller reactors with smaller active regions, therefore, reactors of size with a 70% removal rate and a recycling rate of 40-90% are selected to operate this system.

[0055] Based on experiments conducted with a system operating according to the parameters shown in Figure 3, the fractionation ratio is selected within the range of 40% to 90%, based on the reactor size, which is determined by the amount of organic matter in the wastewater being treated, taking into account factors such as the required TDS, the necessary conductivity, and the amount of organic matter in the wastewater being treated, in order to prevent fouling of the membrane in the membrane filtration system and to provide the necessary conductivity and acceptable effluent COD.

[0056] Even though homogenization tanks are shown in all the figures presented herein, those skilled in the art will understand, based on the teachings of this disclosure, that homogenization tanks are not required in all embodiments.

[0057] Similarly, even if a pretreatment unit may be present in a preferred embodiment, those skilled in the art will understand that a pretreatment unit is not necessary in embodiments where the conductivity of the wastewater or film fouling is not a concern.

[0058] Even though all the diagrams show the reactor discharge from the electrochemical oxidation reactor coupled with the treated wastewater discharge from the reverse osmosis unit, a person skilled in the art will understand that the two flows (reactor discharge and treated wastewater from the reverse osmosis unit) can be discharged separately from the current system.

[0059] While specific elements, embodiments, and uses of the present invention have been illustrated and described, it will be understood that the present invention is not limited thereto, as modifications can be made by those skilled in the art without departing from the spirit and scope of this disclosure, particularly in light of the teachings set forth herein. Such modifications shall be deemed to fall within the scope of the claims appended herein.

Claims

1. A wastewater treatment system, (a) A first membrane filtration apparatus comprising a membrane selected for removing specific organic compounds, which receives a wastewater flow to be treated and generates a first wastewater flow and a first treated wastewater flow to be discarded from the system, (b) An electrochemical oxidation reactor that receives the first waste stream from the first membrane filtration device, processes it to remove a portion of specific organic matter from the wastewater stream to be treated, and generates a reactor outflow stream, wherein the reactor outflow stream is divided into a recirculated wastewater stream that is returned to the first membrane filtration device for recycling and a reactor discharge stream that is discarded from the system, (c) Control means for adjusting the volume of the reactor discharge flow and the volume of the recirculated wastewater flow by fractionation ratio, wherein the range of the fractionation ratio is: - The target total dissolved solids in the wastewater to be treated, which is determined based on the amount of undesirable inorganic compounds that prevent fouling of the membrane of the first membrane filtration device, and the amount of desirable inorganic compounds that increase the conductivity of the recirculated wastewater; - A target concentration of organic compounds in the wastewater flow to be treated, determined based on the size of the electrochemical oxidation reactor, which increases the efficiency of the electrochemical oxidation reactor to a target value determined based on the rate of removal of contaminants and the amount of current and energy consumed to operate the electrochemical oxidation reactor; - The permissible composition of the treated wastewater stream discharged into the environment from the aforementioned system and A wastewater treatment system comprising control means determined based on the above.

2. The system according to claim 1, further comprising a second membrane filtration device that receives the wastewater flow to be treated before it is sent to the first membrane filtration device and generates a second treated wastewater flow to be supplied to the first membrane filtration device and a second waste flow to be supplied to the electrochemical oxidation reactor for further treatment.

3. The system according to claim 2, wherein the second membrane filtration apparatus comprises a membrane selected to remove a specific organic compound.

4. The system according to claim 1, wherein the undesirable inorganic substance in the wastewater flow to be treated includes a scale-forming compound or a halide.

5. The system according to claim 1, wherein the fractionation ratio is adjusted to a constant value based on modeling.

6. The system according to claim 1, wherein the fractionation ratio is continuously adjusted based on a monitored value for the total amount of dissolved solids in the wastewater stream to be treated, a monitored value for the concentration of organic compounds in the wastewater stream to be treated, and / or a monitored value for the composition of the treated wastewater stream discarded from the system.

7. The system according to claim 1, wherein the wastewater flow to be treated is first supplied to a homogenization tank before being supplied to the first membrane filtration device, or is supplied to the first homogenization tank before being supplied to the first membrane filtration device and then supplied to a pretreatment unit.

8. A wastewater treatment method by membrane filtration and electrochemical oxidation, (a) A step of supplying the wastewater stream to be treated to a membrane filtration device equipped with a membrane selected to remove specific organic compounds, and disposing of the wastewater stream treated by the membrane filtration device from the system, (b) The steps of supplying the waste flow from the membrane filtration device to an electrochemical oxidation reactor, processing the waste flow to remove only a portion of specific organic matter from it, generating a reactor outflow flow, and disposing of the reactor outflow flow from the electrochemical oxidation reactor, (c) A step of supplying a portion of the reactor outflow logistics as a recirculated wastewater stream to the membrane filtration device, and discarding the remainder of the reactor outflow logistics as a reactor discharge stream outside the system, or merging it with the wastewater stream treated by the membrane filtration device and discarding it outside the system, (d) A step of controlling the volume of the recirculated wastewater flow from the electrochemical oxidation reactor to the membrane filtration device and the volume of the reactor discharge flow by a fractionation ratio, wherein the range of the fractionation ratio is: - The target total dissolved solids in the wastewater to be treated, which is determined based on the amount of undesirable inorganic compounds that prevent fouling of the membrane of the membrane filtration device, and the amount of desirable inorganic compounds that increase the conductivity of the recirculated wastewater; - A target concentration of organic compounds in the wastewater flow to be treated, determined based on the size of the electrochemical oxidation reactor, which increases the efficiency of the electrochemical oxidation reactor to a target value determined based on the rate of removal of contaminants and the amount of current and energy consumed to operate the electrochemical oxidation reactor; - The permissible composition of the treated wastewater stream discharged into the environment from the aforementioned system and A method comprising steps based on the above.

9. The method according to claim 8, wherein the undesirable inorganic substance in the wastewater flow to be treated includes a scale-forming substance or a halide.

10. The method according to claim 8, wherein the fractionation ratio is adjusted to a constant value based on modeling.

11. The method according to claim 8, wherein the fractionation ratio is continuously adjusted based on a monitored value for the total dissolved solids content in the wastewater stream to be treated, a monitored value for the concentration of organic compounds in the wastewater stream to be treated, and / or a monitored value for the composition of the treated wastewater stream discarded from the system.

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