Removal of ozone from process streams using ultraviolet irradiation.

Abstract

A method is disclosed that includes providing an aqueous solution having dissolved carbon dioxide and dissolved ozone to a vessel, removing an amount of the dissolved carbon dioxide, and irradiating the wastewater with ultraviolet light to decompose an amount of the dissolved ozone. The method can include removing the dissolved carbon dioxide by controlling pH. The method can include removing the dissolved carbon dioxide by contact with a membrane degasser. A system is also disclosed that includes a channel fluidly connected to an aqueous solution source of the aqueous solution having dissolved carbon dioxide and dissolved ozone, a dissolved carbon dioxide removal subsystem, and an ultraviolet irradiation source. The dissolved carbon dioxide removal subsystem can include a pH adjuster source. The dissolved carbon dioxide removal subsystem can include a membrane degasser.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62 / 752,011, entitled "Removal of Ozone from Process Streams Using Ultraviolet Light and Caustic," filed October 29, 2018, which is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] FIELD OF THE INVENTION Aspects and embodiments disclosed herein relate generally to water treatment systems and methods, and more particularly to water treatment systems and methods for removing ozone. Summary of the Invention [Means for solving the problem]

[0003] According to one aspect, a method is provided that includes providing an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration to a vessel. The method can include removing an amount of dissolved carbon dioxide from the aqueous solution to produce a first effluent having a second dissolved carbon dioxide concentration lower than the first dissolved carbon dioxide concentration. The method can also include irradiating the first effluent with ultraviolet light at a dose effective to decompose a predetermined amount of dissolved ozone in the first effluent to produce a second effluent having a second dissolved ozone concentration lower than the first dissolved ozone concentration.

[0004] In some embodiments, removing the amount of dissolved carbon dioxide can include controlling the pH of the aqueous solution to a value effective to convert the amount of dissolved carbon dioxide to at least one of carbonate and bicarbonate.

[0005] The method can include controlling the pH of the aqueous solution to at least about 8. The method can include controlling the pH of the aqueous solution to between about 8.3 and 11.

[0006] In some embodiments, the method can further include measuring at least one of the pH of the aqueous solution and the pH of the first effluent, and adding a predetermined amount of acid or base in response to the measurement to control the pH of the aqueous solution.

[0007] In some embodiments, the first effluent may be substantially free of dissolved carbon dioxide.

[0008] In certain embodiments, removing an amount of dissolved carbon dioxide may include contacting the aqueous solution with a membrane degasser.

[0009] In some embodiments, the method can further include measuring at least one of the dissolved carbon dioxide concentration of the aqueous solution and the dissolved carbon dioxide concentration of the first wastewater. The method can further include controlling the dissolved carbon dioxide removal rate with the membrane degasser in response to the measurements. Controlling the removal rate can include at least one of adjusting the vacuum level of the membrane degasser, adjusting the sweep gas flow rate through the membrane degasser, and controlling the flow rate of the aqueous solution through the membrane degasser.

[0010] The first dissolved carbon dioxide concentration can be at least about 20 ppm.

[0011] The first dissolved ozone concentration can be at least about 30 ppm.

[0012] The second dissolved ozone concentration can be less than about 10 ppb.

[0013] The second dissolved ozone concentration can be less than about 2 ppb.

[0014] The second dissolved ozone concentration can be less than about 1 ppb.

[0015] The method can further include measuring at least one of the first dissolved ozone concentration and the second dissolved ozone concentration, and controlling at least one of the dose of ultraviolet radiation and the flow rate of at least one of the aqueous solution and the first wastewater in response to the measurements.

[0016] In some embodiments, the aqueous solution can include semiconductor manufacturing process water.

[0017] According to another aspect, a system is provided that includes a channel fluidly connectable to a source of an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration. The system can include a dissolved carbon dioxide removal subsystem fluidly connected to the channel and configured to remove an amount of dissolved carbon dioxide from the aqueous solution to produce a first effluent. The system can also include an ultraviolet radiation source disposed downstream from the dissolved carbon dioxide removal subsystem and configured to irradiate the first effluent to produce a second effluent.

[0018] In some embodiments, the dissolved carbon dioxide removal subsystem can include an adjuster source fluidly connected to the channel and configured to administer a pH adjuster to the aqueous solution to produce the first effluent.

[0019] The system may further include a mixer positioned downstream of the pH adjuster source and upstream of the ultraviolet radiation source.

[0020] The system can further include a pH sensing subsystem including an inlet pH sensor configured to detect a pH of the aqueous solution and an outlet pH sensor configured to detect a pH of at least one of the first effluent and the second effluent, The pH sensing subsystem can be configured to output a pH signal indicative of a measurement obtained by at least one of the inlet pH sensor and the outlet pH sensor.

[0021] In some embodiments, the dissolved carbon dioxide removal subsystem can include a membrane degasser fluidly connected to the channel.

[0022] The system may further comprise at least one of a vacuum pump and a sweep gas source associated with the membrane degasser.

[0023] The system can further include a dissolved carbon dioxide sensing subsystem including an inlet dissolved carbon dioxide sensor configured to detect a dissolved carbon dioxide concentration in the aqueous solution and an outlet dissolved carbon dioxide sensor configured to detect dissolved carbon dioxide in at least one of the first effluent and the second effluent. The dissolved carbon dioxide sensing subsystem can be configured to output a dissolved carbon dioxide signal indicative of a measurement obtained by at least one of the inlet dissolved carbon dioxide sensor and the outlet dissolved carbon dioxide sensor.

[0024] According to certain embodiments, the system may include a flow meter configured to measure a flow rate of at least one of the aqueous solution, the first effluent, and the second effluent, and the flow meter may be configured to output a flow rate signal indicative of a measurement obtained by the flow meter.

[0025] The system may further include a controller operably connected to the dissolved carbon dioxide removal subsystem and at least one of the pH sensing subsystem, the dissolved carbon dioxide sensing subsystem, and the flow meter. The controller may be configured to receive at least one of the pH signal, the dissolved carbon dioxide signal, and the flow rate signal, and to send a control signal to the dissolved carbon dioxide removal subsystem in response to the received signal.

[0026] The controller can be configured to direct the dissolved carbon dioxide removal subsystem to produce a first effluent that is substantially free of dissolved carbon dioxide.

[0027] The controller can be configured to send a control signal to the pH adjuster source, causing the pH adjuster source to dispense the pH adjuster into the aqueous solution in response to the control signal.

[0028] The system can further include at least one dissolved ozone sensor disposed downstream of the ultraviolet radiation source, the dissolved ozone sensor configured to measure a second dissolved ozone concentration in the second effluent and to output a dissolved ozone signal indicative of the measurement obtained by the dissolved ozone sensor.

[0029] The system may further include a controller operatively connected to the at least one dissolved ozone sensor. The controller may be configured to receive the dissolved ozone signal and send a control signal to at least one of the ultraviolet radiation source and the flow controller, such that the ultraviolet radiation source, in response to the control signal, irradiates the first wastewater with ultraviolet radiation at a dose effective to destroy a predetermined amount of dissolved ozone in the first wastewater.

[0030] The system may further include a controller operably connected to the at least one dissolved ozone sensor. The controller may be configured to receive the dissolved ozone signal and to send a control signal to the dissolved carbon dioxide removal subsystem to cause the dissolved carbon dioxide removal subsystem to remove an amount of dissolved carbon dioxide from the aqueous solution in response to the control signal.

[0031] The dissolved carbon dioxide removal subsystem can include a pH adjuster source fluidly connected to the channel and configured to administer a pH adjuster to the aqueous solution to produce the first effluent. The controller can be configured to send a control signal to the pH adjuster source, whereby the pH adjuster source administers the pH adjuster to the aqueous solution in response to the control signal.

[0032] In some embodiments, the aqueous solution source is associated with a semiconductor manufacturing system.

[0033] According to another aspect, a method is provided that includes providing an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration to a container; irradiating the aqueous solution with ultraviolet light at a dose effective to decompose a predetermined amount of dissolved ozone to produce a first effluent; and removing an amount of dissolved carbon dioxide from the first effluent to produce a second effluent having a second dissolved carbon dioxide concentration lower than the first dissolved carbon dioxide concentration and a second dissolved ozone concentration lower than the first dissolved ozone concentration.

[0034] In some embodiments, removing the amount of dissolved carbon dioxide can include controlling the pH of the first effluent to a value effective to convert the amount of dissolved carbon dioxide to at least one of carbonate and bicarbonate.

[0035] In some embodiments, removing an amount of dissolved carbon dioxide can include contacting the first effluent with a membrane degasser.

[0036] According to yet another aspect, a system is provided that includes a channel fluidly connectable to a source of an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration; an ultraviolet irradiation source fluidly connected to the channel and configured to irradiate the aqueous solution to produce a first effluent; and a dissolved carbon dioxide removal subsystem positioned downstream of the ultraviolet irradiation source and configured to remove an amount of dissolved carbon dioxide from the first effluent to produce a second effluent.

[0037] In some embodiments, the dissolved carbon dioxide removal subsystem can include a pH adjuster source fluidly connected to the channel and configured to administer a pH adjuster to the first effluent to produce the second effluent.

[0038] In some embodiments, the dissolved carbon dioxide removal subsystem includes a membrane degasser fluidly connected to the channel.

[0039] The present disclosure contemplates all combinations of any one or more of the foregoing aspects and / or embodiments, as well as combinations with any one or more of the embodiments described in the detailed description and any examples. [Brief explanation of the drawings]

[0040] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures is represented by a like numeral. For clarity, not every element is labeled in every figure.

[0041] [Figure 1] 1 is a graph of the ultraviolet absorption spectrum of ozone. [Figure 2] 1 is a graph of the component ratios of carbon dioxide, bicarbonate, and carbonate aqueous solutions with varying pH values. [Figure 3A] FIG. 1 is a box plot diagram of a system for removing dissolved ozone from an aqueous solution containing dissolved carbon dioxide, according to one embodiment. [Figure 3B] FIG. 10 is a box plot diagram of an alternative system for removing dissolved ozone from an aqueous solution containing dissolved carbon dioxide, according to one embodiment. [Figure 4] FIG. 10 is a box plot diagram of an alternative system for removing dissolved ozone from an aqueous solution containing dissolved carbon dioxide, according to one embodiment. [Figure 5] FIG. 10 is a box plot diagram of an alternative system for removing dissolved ozone from an aqueous solution containing dissolved carbon dioxide, according to one embodiment. [Figure 6] 1 is a graph of dissolved ozone concentration versus time according to the operation of one embodiment. [Figure 7] 10 is a graph of dissolved ozone concentration versus time according to the operation of another embodiment. [Figure 8] 8A-8B are graphs of dissolved ozone concentration versus time according to the operation of another embodiment. [Figure 9] 10 is a graph of dissolved ozone concentration versus time according to the operation of another embodiment. [Figure 10] 10 is a graph of dissolved ozone concentration and sodium hydroxide pump speed versus time according to the operation of one embodiment. [Figure 11] 10 is a graph of dissolved ozone concentration and sodium hydroxide pump speed versus time according to the operation of another embodiment. [Figure 12A] 10 is a graph of dissolved ozone concentration versus time according to the operation of another embodiment. [Figure 12B] 10 is a graph of dissolved ozone concentration versus time according to the operation of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0042] Process water, such as semiconductor manufacturing process water, often contains residual chemicals from one or more manufacturing steps. For example, in the production of semiconductor-based materials such as silicon wafers, chemicals may be used to add or remove layers of material for cleaning or other purposes. The manufacturing process may include rotating semiconductor articles in a processing chamber. Liquid and gas phase chemicals are often sprayed or otherwise applied to the semiconductor products. After a period of time, the liquid processing chemicals are withdrawn, and the gases and / or vapors can be withdrawn or pumped out separately. The gases and / or vapors that meet environmental regulations can be exhausted from the processing chamber.

[0043] Certain processing steps use ultrapure water containing ozone, oxygen, and / or carbon dioxide to clean semiconductor wafers. Ozone is a strong oxidizing agent, even at low concentrations. Dissolved ozone in water can cause problems in other unit operations in semiconductor manufacturing systems, such as ion exchange resins and reverse osmosis membranes. Therefore, this process stream has traditionally been directed to waste treatment facilities.

[0044] In other manufacturing processes, ozone gas may be introduced into the processing chamber at intervals of 5 to 20 seconds, sometimes at high concentrations. Ozone and other gases, such as acid vapors, are traditionally removed from the processing chamber and vented to the atmosphere. However, ozone is a chemically reactive gas. At high concentrations, ozone gas can be toxic to humans. Exhaust gases containing ozone and acid vapors can be toxic and highly corrosive. Therefore, treatment of gas exhaust from the processing chamber may require special procedures. For example, components such as ducts and vents can contain or be made of polypropylene or other corrosion-resistant plastics and materials. Leak detectors can be used to detect leaks in pipes or ducts carrying exhaust gases. According to certain methods, exhaust gases can be scrubbed with water to form an aqueous solution containing dissolved ozone.

[0045] The systems and methods disclosed herein can be used for on-site treatment of wash or treated water containing dissolved ozone. In certain embodiments, the treated treated water can be recycled and reused at the facility, reducing the facility's water demand. In other embodiments, the treated treated water can be discharged. Generally, the treated treated water can meet environmental safety regulations for discharge.

[0046] In one particular embodiment, the source of the aqueous solution can be associated with a microelectronics manufacturing system or process. The source of the aqueous solution can be associated with a semiconductor manufacturing system or process. For example, the aqueous solution can be a solution used in the manufacture of semiconductor chips or wafers. As disclosed herein, semiconductor devices can include microprocessors, memory chips, and various other electronic devices that are typically manufactured from silicon or gallium arsenide wafers. Semiconductor devices manufactured from other suitable materials are within the scope of the present disclosure. Electronic products that include semiconductor devices include flat panel displays, fixed disk memories, thin film head device substrates, compact disk substrates, etc.

[0047] The source of the aqueous solution can include water containing at least about 20 ppb of total ionic impurities. In certain examples, the present disclosure may refer to semiconductor manufacturing systems. However, it should be noted that the systems and methods disclosed herein can similarly be used in connection with any aqueous solution containing dissolved ozone and dissolved carbon dioxide. For example, the source of the aqueous solution can be associated with water purification, nuclear power generation, microelectronics manufacturing, semiconductor manufacturing, food processing, textile manufacturing, papermaking and recycling, pharmaceutical manufacturing, chemical processing, and metal extraction systems or processes. The source of the aqueous solution can be associated with industrial applications, such as the removal of difficult organic contaminants from industrial wastewater. The source of the aqueous solution can be associated with wastewater and / or municipal water treatment. The source of the aqueous solution can be associated with activated sludge water treatment systems or processes. In general, the aqueous solution can be associated with systems or methods that contact water with ozone and carbon dioxide.

[0048] The systems and methods disclosed herein can include directing the aqueous solution to a vessel. The vessel can be any structure used to contain an aqueous solution. For example, the vessel can be or include a channel, container, vessel, holder, reactor, or any conduit usable in the methods disclosed herein.

[0049] One method for destroying dissolved ozone in an aqueous solution involves irradiating the solution with ultraviolet light. Briefly, under appropriate conditions, ultraviolet energy breaks one of the oxygen bonds in the ozone molecule. Thus, ultraviolet radiation can catalyze the breakdown of ozone into oxygen and water. UV radiation effective for decomposing ozone can have wavelengths as shown in the graph of FIG. 1. FIG. 1 is a graph of the ultraviolet absorption spectrum of ozone. UV radiation effective for decomposing ozone can have a wavelength between 200 and 280 nm. In certain embodiments, UV radiation effective for decomposing ozone can have a wavelength of approximately 254 nm.

[0050] The dose of UV radiation can be selected to decompose a predetermined amount of dissolved ozone in the aqueous solution. The dose can be controlled by controlling the UV radiation, the volume or area of ​​the exposed aqueous solution, and the duration of exposure. For a fixed volume vessel, the dose can be controlled by controlling the UV radiation or the flow rate of the aqueous solution through the UV radiation source. UV dose (μWs / cm 2 ) is the ultraviolet intensity (μW / cm 2 ) times the exposure time (seconds).

[0051] In some embodiments, the aqueous solution can contain at least 20 ppm, at least 25 ppm, at least 30 ppm, at least 40 ppm, or at least 50 ppm of dissolved ozone. The method can include controlling the dose of ultraviolet radiation to produce an irradiated wastewater having less than about 25 ppb, less than about 20 ppb, less than about 15 ppb, less than about 10 ppb, less than about 5 ppb, less than about 2 ppb, or less than about 1 ppb of dissolved ozone. Accordingly, the systems and methods disclosed herein can be configured to irradiate the aqueous solution with ultraviolet radiation at a dose effective to decompose at least 90%, at least 95%, at least 99%, at least 99.9%, or at least 99.99% of the dissolved ozone in the aqueous solution.

[0052] The methods disclosed herein can include measuring the concentration of dissolved ozone in the aqueous solution or the irradiated wastewater. The dose of ultraviolet radiation can be controlled in response to the measurement. For example, the dose or intensity of ultraviolet radiation can be increased in response to measuring dissolved ozone in the aqueous solution greater than an inlet threshold. The inlet threshold can be, for example, 20 ppm, 25 ppm, or 30 ppm. The dose or intensity of ultraviolet radiation can be increased in response to measuring dissolved ozone in the irradiated wastewater greater than a target threshold. The target threshold can be, for example, 2 ppb, 5 ppb, or 10 ppb. In some embodiments, the flow rate of the aqueous solution can be controlled in response to the dissolved ozone measurement. For example, the flow rate of the aqueous solution can be decreased in response to measuring dissolved ozone in the aqueous solution or in response to the irradiated wastewater being greater than an inlet or target threshold.

[0053] The method can include recirculating a quantity of the irradiated wastewater to a point upstream of the ultraviolet irradiation step. In particular, the method can include recirculating a quantity of the irradiated wastewater having a dissolved ozone concentration above a target threshold. In some embodiments, the method can include recirculating a quantity of the irradiated wastewater in response to a measurement of dissolved ozone in the irradiated wastewater that is outside an acceptable range of a target range. For example, the method can include recirculating a quantity of irradiated wastewater having a dissolved ozone concentration 10% above, 25% above, or 30% above the target threshold.

[0054] In some embodiments, the aqueous solution may contain dissolved carbon dioxide. Without wishing to be bound by theory, carbon dioxide may interfere with the removal of dissolved ozone by ultraviolet irradiation. Briefly, ultraviolet irradiation photochemically decomposes ozone according to the following reaction: O3+O→O2+O2 O3+hν→O2+O( 3 P) O3+hν→O2+O( 1 D)

[0055] The above reaction results in the formation of oxygen atoms in ground and excited states. In water, ultraviolet radiation can also generate hydroxyl radicals. Hydroxyl radicals typically react with ozone to form oxygen and water via the following reaction: OH· + O3 → O2 + HO2·

[0056] When dissolved carbon dioxide is present, it can react with hydroxyl radicals and inhibit the decomposition of ozone by the same radicals.

[0057] Thus, the systems and methods disclosed herein can include removing a quantity of dissolved carbon dioxide from an aqueous solution to produce wastewater having a lower concentration of dissolved carbon dioxide. The lower concentration of dissolved carbon dioxide can generally be sufficient to allow decomposition of dissolved ozone by irradiation with ultraviolet light without substantially interfering with the reaction. The systems and methods can then include irradiating the wastewater with ultraviolet light, as described above.

[0058] The above reactions generally occur at a slow rate. Therefore, according to other embodiments, the system and method can include irradiating the aqueous solution with ultraviolet light before removing the dissolved carbon dioxide. The dissolved carbon dioxide can then be removed to prevent substantial interference with the ozone depletion reaction. The dissolved carbon dioxide can be removed immediately after irradiation with ultraviolet light. In particular, the system and method can include removing the dissolved carbon dioxide before a significant amount of dissolved carbon dioxide interferes with the ozone depletion reaction. Thus, the method can include removing the dissolved carbon dioxide several seconds after irradiation with ultraviolet light (e.g., less than 30 seconds, less than 10 seconds, less than 5 seconds, less than 2 seconds, or less than 1 second after irradiation with ultraviolet light).

[0059] According to certain methods, dissolved carbon dioxide can be removed by controlling the pH of the aqueous solution. For example, the method can include controlling the pH to a value effective to convert the dissolved carbon dioxide to at least one of carbonate and bicarbonate. Dissolved carbon dioxide is generally in equilibrium with carbonic acid (H2CO3) according to the following equation: [ka]

[0060] Carbon dioxide, carbonic acid, and the deprotonated form bicarbonate (HCO3 - ) and carbonate (CO3 2- The relative concentrations of carbon dioxide and bicarbonate depend on the pH of the solution. Dissolved carbon dioxide can be removed from the solution by controlling the pH to a value effective to shift the equilibrium in favor of bicarbonate and carbonate. Figure 2 is a graph of the component ratios of carbon dioxide, bicarbonate, and carbonate aqueous solutions as the pH value is varied. The system and method can include controlling the pH to a value effective to shift the component ratio of dissolved carbon dioxide to less than 0.2, less than 0.15, less than 0.10, less than 0.05, or less than 0.01.

[0061] According to certain embodiments, the systems and methods disclosed herein can control the pH to greater than 7, greater than 7.5, or greater than 8. The systems and methods disclosed herein can control the pH to about 8.3 or greater, between about 8.3 and 11, at least about 9, or between about 9 and 11. Thus, the systems and methods disclosed herein can control the pH to produce wastewater with a dissolved carbon dioxide ratio value of less than 0.2, less than 0.15, less than 0.10, less than 0.05, or less than 0.01.

[0062] The systems and methods disclosed herein can include controlling pH by adding an acid or a base. Exemplary strong acids include hydrochloric acid (HCl), nitric acid (HNO), hydroiodic acid (HI), perchloric acid (HClO), and chloric acid (HClO). Exemplary weak acids include sulfurous acid (HSO), methanoic acid (HCOH), phosphoric acid (HPO), sulfurous acid (HNO), hydrofluoric acid (HF), and the conjugate acids of the bases described below. Exemplary strong bases that can be added include sodium hydroxide (NaOH), potassium hydroxide (KOH), barium hydroxide (Ba(OH)), cesium hydroxide (CsOH), strontium hydroxide (Sr(OH)), calcium hydroxide (Ca(OH)), lithium hydroxide (LiOH), and rubidium hydroxide (RbOH). Exemplary weak bases that can be added include ammonia (NH3), trimethylammonia (N(CH3)3), pyridine (C5H5N), ammonium hydroxide (NH4OH), and the conjugate bases of the above acids.

[0063] The method can include mixing an acid or a base with the aqueous solution. In some embodiments, the acid or base can be mixed with the aqueous solution to produce a substantially uniform pH-controlled effluent.

[0064] In another embodiment, the systems and methods disclosed herein can include removing the amount of dissolved carbon dioxide from an aqueous solution by contacting the solution with a membrane degasser. Briefly, the membrane degasser removes dissolved gas from a solution that contacts a hollow fiber membrane. Generally, the membrane degasser can operate in conjunction with a vacuum pump and a sweep gas. The sweep gas can be any inert gas. In certain embodiments, the sweep gas can be nitrogen. One exemplary membrane degasser that is effective in removing dissolved carbon dioxide is the Liqui-Cel® membrane degasser (distributed by 3M® Company, Maplewood, Minnesota).

[0065] The method may further include measuring the dissolved carbon dioxide concentration in the aqueous solution or wastewater. In response to the measurement, the method may include controlling the rate of dissolved carbon dioxide removal using a membrane degasser. The rate of dissolved carbon dioxide removal may be controlled by adjusting the vacuum level of the membrane degasser. For example, it may be controlled by adjusting the speed of a vacuum pump or by adjusting the setting of a vacuum relief valve. The rate of dissolved carbon dioxide removal may be controlled by adjusting the sweep gas flow rate through the membrane degasser. In another embodiment, the rate of dissolved carbon dioxide removal may be controlled by adjusting the flow rate of the aqueous solution through the membrane degasser.

[0066] In certain embodiments, the aqueous solution can contain at least about 10 ppm, at least about 15 ppm, at least about 20 ppm, at least about 25 ppm, at least about 30 ppm, at least about 40 ppm, or at least about 50 ppm of dissolved carbon dioxide. The dissolved carbon dioxide can be in the form of carbonic acid in equilibrium. The method can include removing the dissolved carbon dioxide to produce an effluent solution having less than about 25 ppb, less than about 20 ppb, less than about 15 ppb, less than about 10 ppb, less than about 5 ppb, less than about 2 ppb, or less than about 1 ppb. Thus, the systems and methods disclosed herein can be configured to remove at least 90%, at least 95%, at least 99%, at least 99.9%, or at least 99.99% of the dissolved carbon dioxide in the aqueous solution. In some embodiments, the method can include producing an effluent solution that is substantially free of dissolved carbon dioxide.

[0067] The method can further include measuring the concentration of dissolved carbon dioxide in the aqueous solution or wastewater. The rate of dissolved carbon dioxide removal can be controlled in response to the measurement. For example, the addition of a pH adjuster or the flow rate through a membrane degasser can be controlled in response to the measurement. The method can include recycling a volume of the wastewater or irradiated wastewater containing more than a threshold amount of dissolved carbon dioxide. For example, wastewater or irradiated wastewater exceeding a dissolved carbon dioxide component ratio of 0.2, 0.4, or 0.6 can be recycled for further treatment.

[0068] In certain embodiments, the method can include measuring the pH of the aqueous solution or wastewater. Thus, the addition of a pH adjuster can be controlled in response to the pH measurement. For example, the method can include adding a predetermined amount of acid or base to control the pH in response to the pH measurement.

[0069] The method can further include controlling the dose of ultraviolet radiation in response to measuring the dissolved carbon dioxide or pH of the aqueous solution or wastewater. In certain embodiments, the dose of ultraviolet radiation can be increased in response to the dissolved carbon dioxide being greater than a threshold amount or the pH being less than a threshold amount. Thus, in response to measuring the dissolved carbon dioxide or pH in the aqueous solution or wastewater, the ultraviolet radiation intensity can be increased or the flow rate can be decreased.

[0070] In some embodiments, the method can include measuring the temperature of the aqueous solution or wastewater. Temperature can affect the solubility of carbon dioxide in the aqueous solution and the equilibrium between dissolved carbon dioxide and carbonic acid. Simply put, carbon dioxide is more soluble at low temperatures. Therefore, the removal of dissolved carbon dioxide can be controlled in response to measuring the temperature of the aqueous solution or wastewater.

[0071] The method may further include measuring the flow rate of the aqueous solution or wastewater. As described above, the flow rate may affect the dose of ultraviolet radiation. Thus, the dose of ultraviolet radiation may be controlled in response to the flow rate measurement. For example, the ultraviolet radiation intensity may be increased in response to a larger flow rate measurement (e.g., greater than a threshold value). The ultraviolet radiation intensity may be decreased in response to a lower flow rate measurement (e.g., lower than a threshold value). The flow rate may also affect the removal of dissolved carbon dioxide from the aqueous solution. For example, the dose of a pH adjuster may be controlled in response to the flow rate measurement by administering a larger amount of pH adjuster in response to a larger flow rate measurement or a smaller amount of pH adjuster in response to a lower flow rate measurement. For a fixed-volume membrane degasser, the flow rate may affect the removal of dissolved carbon dioxide. In particular, the flow rate may be controlled in response to the dissolved carbon dioxide concentration in the aqueous solution.

[0072] According to certain aspects, systems capable of carrying out the methods disclosed herein are provided. Exemplary systems 1000 for decomposing dissolved ozone in an aqueous solution are shown as systems 1000A and 1000B in FIGS. 3A-3B , respectively. System 1000 generally includes a channel 100 fluidly connectable to an aqueous solution source 200, a dissolved carbon dioxide removal subsystem 300 fluidly connected to channel 100 and configured to remove a quantity of dissolved carbon dioxide, and an ultraviolet radiation source 400 configured to irradiate the wastewater, as described above. In system 1000A, ultraviolet radiation source 400 is disposed downstream of dissolved carbon dioxide removal subsystem 300. In system 1000B, ultraviolet radiation source 400 is disposed upstream of dissolved carbon dioxide removal subsystem 300. System 1000 can include a flow control device, such as a pump 120, configured to control the flow rate of aqueous solution 200 through channel 100. In other embodiments, the flow control device can include a flow control valve. The flow control valve can be configured to control the flow rate of the aqueous solution 200 through the channel 100 .

[0073] The aqueous solution source 200 can include processed water, demineralized water, filtered water, purified water, distilled water, deionized water, demineralized water, or highly pure water. Highly pure water includes water with very low levels of trace contaminants other than the aforementioned dissolved carbon dioxide and dissolved ozone. Trace contaminants can be measured in the parts per billion (ppb) or parts per trillion (ppt) concentration range. Trace contaminants can include volatile organic carbon, inorganic ions, organic compounds, bacteria and other microbial species, endotoxins and nucleases, particulate matter, and gases. Examples of highly pure water include ultrapure water and Grade 1-3 water established by the International Organization for Standardization (ISO) or Types I-IV water established by ASTM International. In some specific, non-limiting embodiments, ultrapure water has a resistivity of approximately 18.18 MΩ / cm at 25°C.

[0074] The channel 100 can be constructed or installed with materials that are resistant to oxidation and / or corrosion. For example, the channel 100 can be constructed or installed with materials including polyolefins (polyethylene, polypropylene, high density polyethylene (HDPE), low density polyethylene (LDPE), ultra-high molecular weight polymer (UHMW), polypropylene (PP)), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), or fluoroplastics or fluoropolymers (polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxyalkanes (PFA), polyvinylidene difluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene (ETFE), etc.).

[0075] The channels may be fluidly connectable to points of use 500. In certain embodiments, the aqueous solution source 200 is a semiconductor manufacturing system. In such embodiments, the points of use 500 may be associated with the semiconductor manufacturing system such that the treated aqueous solution can be reused by on-site unit operations. The aqueous solution source 200 and / or the points of use 500 may be associated with one or more of water purification, nuclear power generation, microelectronics manufacturing, semiconductor manufacturing, food processing, textile manufacturing, paper manufacturing and recycling, pharmaceutical manufacturing, chemical processing, and metal extraction systems or processes. The aqueous solution source 200 and / or the points of use 500 may be associated with one or more of industrial applications, wastewater and / or municipal water treatment applications, and activated sludge applications.

[0076] In some embodiments, system 1000 may be fluidly connectable to a post-treatment system upstream from point of use 500. For example, system 1000 may be fluidly connectable to one or more of a membrane filter system, a carbon filter system, an ion exchange system (including cation exchange beds, anion exchange beds, and / or mixed beds), an ultrafiltration system, and a reverse osmosis system. The post-treatment may be selected based on the target point of use 500 of the irradiated effluent.

[0077] In yet another embodiment, the treated aqueous solution may meet environmental discharge requirements. Thus, the point of use 500 may be an industrial or municipal drain.

[0078] The ultraviolet radiation source 400 can be configured to irradiate the aqueous solution with ultraviolet radiation at a dose effective to decompose a predetermined amount of dissolved ozone, as described above. The ultraviolet radiation source 400 can include an ultraviolet lamp configured to irradiate the solution with UVC light having a wavelength between 100 nm and 280 nm. In some embodiments, the ultraviolet radiation source 400 can be configured to irradiate the solution with light having a wavelength between 200 nm and 280 nm, e.g., about 254 nm.

[0079] The ultraviolet radiation source 400 is approximately 1000 mJ / cm 2 and 3000mJ / cm 2 For example, the ultraviolet radiation source 400 may be configured to irradiate the solution with ultraviolet light having an intensity between about 1000 mJ / cm 2 and about 1000 mJ / cm 2 . 2 , about 1500mJ / cm 2 , about 2000mJ / cm 2 , about 2500mJ / cm 2 , 3000mJ / cm 2 The UV radiation source 400 can be configured to irradiate the solution with UV radiation at an intensity that is dependent on the measured dissolved ozone concentration. The UV radiation source 400 can be configured to irradiate the solution with UV radiation at a variety of intensities. In some embodiments, as described above, the UV radiation source 400 can be configured to irradiate the solution with UV radiation at an intensity that is dependent on the measured dissolved ozone concentration.

[0080] The dissolved carbon dioxide removal subsystem 300 can be configured to remove an amount of dissolved carbon dioxide from the aqueous solution to produce a wastewater solution having a lower dissolved carbon dioxide concentration than the aqueous solution. In some embodiments, the dissolved carbon dioxide removal subsystem 300 can include a pH adjuster source fluidly connected to the channel 100. The pH adjuster source can be, for example, an acid or base source, as described above. The dissolved carbon dioxide removal subsystem 300 can further include a mixer disposed downstream of the pH adjuster source and configured to mix the aqueous solution with the pH adjuster. The mixer can be a static mixer or any structure or device capable of mixing the pH adjuster into the fluid. In particular, the mixer can be a structure or device configured to produce a substantially homogeneous mixture.

[0081] The carbon dioxide removal subsystem 300 may include a metering pump configured to add a predetermined amount of a pH adjuster to the channel 100. The metering pump may be configured to add the pH adjuster to the channel 100 at a variable flow rate. In some embodiments, as described above, the metering pump may be configured to add the pH adjuster to the aqueous solution flowing through the channel 100 at a concentration selected to control the pH of the solution. For example, the metering pump may be configured to add the pH adjuster to the aqueous solution at a concentration selected depending on the measured dissolved ozone concentration of the pH of the solution.

[0082] In certain embodiments, the dissolved carbon dioxide removal subsystem 300 can include a membrane degasser fluidly connected to the channel. The membrane degasser can be any membrane degasser configured to remove dissolved carbon dioxide. In some embodiments, the membrane degasser can include a medium in the form of a randomly packed medium or a fixed medium on a membrane. The medium can include polypropylene, polyvinylidene fluoride (PVDF), or any other medium suitable for removing dissolved carbon dioxide from an aqueous solution. The membrane degasser can be a gravity-flow membrane degasser. The dissolved carbon dioxide removal subsystem 300 can further include a vacuum pump for operation of the membrane degasser. The membrane degasser can be associated with a source of sweep gas. The source of sweep gas can be an inert gas, such as nitrogen.

[0083] The pump 120 can be configured to direct the aqueous solution 200 into the channel 100 and control the flow rate of the aqueous solution 200. In some embodiments, the flow rate can be controlled to be between 100 and 800 gallons per minute. For example, the flow rate can be controlled to be between 200 and 600 gallons per minute. The flow rate can be controlled to about 200 gallons per minute, about 300 gallons per minute, about 350 gallons per minute, about 400 gallons per minute, about 450 gallons per minute, about 500 gallons per minute, or about 600 gallons per minute. The pump 120 can be configured to deliver the aqueous solution 200 at a variable flow rate. In some embodiments, as described above, the pump 120 can be configured to deliver the aqueous solution 200 through the channel 100 at a selected flow rate to control the dose of UV radiation to the solution in response to the measured dissolved ozone concentration.

[0084] An exemplary system 2000 for decomposing dissolved ozone in an aqueous solution is shown in Figure 4. System 2000 includes the components of system 100 and further includes a dissolved carbon dioxide sensing subsystem including an inlet dissolved carbon dioxide sensor 320 and an outlet dissolved carbon dioxide sensor 325 configured to detect the concentration of dissolved carbon dioxide in at least one of the aqueous solution 200 and the wastewater downstream of the dissolved carbon dioxide removal subsystem 300. In certain embodiments, the dissolved carbon dioxide sensing subsystem can be a pH sensing subsystem including an inlet pH sensor 320 and an outlet pH sensor 325 configured to measure the pH of the solution or the wastewater.

[0085] The system 2000 includes a dissolved ozone sensor 420 disposed downstream of the ultraviolet irradiation source 400 configured to measure the dissolved ozone concentration in the irradiated effluent. The system can include more than one dissolved ozone sensor, for example, at least two dissolved ozone sensors disposed downstream of the ultraviolet irradiation source 400. In some embodiments, the system can include an inlet dissolved ozone sensor configured to measure the dissolved ozone concentration in the aqueous solution 200.

[0086] System 2000 includes a flow meter 720. Flow meter 720 can be configured to measure the flow rate of the solution moving through channel 100. System 2000 includes a temperature sensor 820. Temperature sensor 820 can be configured to measure the temperature of the solution moving through channel 100.

[0087] System 2000 further includes a controller 600 operably connected to dissolved carbon dioxide removal subsystem 300, ultraviolet irradiation source 400, and pump 120. Controller 600 can be configured to provide control signals to dissolved carbon dioxide removal subsystem 300, ultraviolet irradiation source 400, and pump 120. Note that the exemplary system can include one or more sensors that are not operated by the controller. The system can also include a controller operably connected to one or two of dissolved carbon dioxide removal subsystem 300, ultraviolet irradiation source 400, and pump 120.

[0088] At least one of the inlet dissolved carbon dioxide sensor 320 and the outlet dissolved carbon dioxide sensor 325 can be configured to output a dissolved carbon dioxide signal indicative of the measurement obtained by the respective dissolved carbon dioxide sensor. The dissolved carbon dioxide signal can be displayed on a display device. The dissolved carbon dioxide signal can be transmitted to a user. In some embodiments, the dissolved carbon dioxide signal can generate an alert to notify a user that the measured dissolved carbon dioxide value has exceeded a predetermined threshold. The dissolved carbon dioxide signal can be transmitted to the controller 600.

[0089] According to certain embodiments in which the dissolved carbon dioxide sensor is a pH sensor, at least one of the inlet pH sensor 320 and the outlet pH sensor 325 can be configured to output a pH signal indicative of the measurement obtained by the respective pH sensor. The pH signal can be displayed on a display device. The pH signal can be transmitted to a user. In some embodiments, the pH signal can generate an alert to notify a user that the measured pH value has exceeded a predetermined threshold. The pH signal can be transmitted to the controller 600.

[0090] The dissolved ozone sensor 420 can be configured to output a dissolved ozone signal indicative of the measurement obtained by the dissolved ozone sensor 420. The dissolved ozone signal can be displayed on a display device. The dissolved ozone signal can be transmitted to a user. In some embodiments, the dissolved ozone signal can generate an alert to notify a user that the measured dissolved ozone value has exceeded a predetermined threshold. The dissolved ozone signal can be transmitted to the controller 600.

[0091] The flow meter 720 can be configured to output a flow signal indicative of a measurement obtained by the flow meter 720. The temperature sensor 820 can be configured to output a temperature signal indicative of a measurement obtained by the temperature sensor 820. At least one of the flow signal and the temperature signal can be displayed on a display device. At least one of the temperature signal and the flow signal can be transmitted to a user. In some embodiments, the temperature signal and / or the flow signal can generate an alert to notify a user that a measurement has exceeded a predetermined threshold. The temperature signal and / or the flow signal can be transmitted to the controller 600.

[0092] The controller 600 may be operatively connected to one or more of the dissolved carbon dioxide sensing subsystem (320, 325) (including the pH sensing subsystem), the dissolved ozone sensor 420, the flow meter 720, and the temperature sensor 820. The system may be configured to receive input signals from one or more of the dissolved carbon dioxide sensing subsystem, the dissolved ozone sensor 420, the flow meter 720, and the temperature sensor 820. The controller 600 may be configured to generate control signals responsive to the input signals. Thus, the controller 600 may be configured to control the operation of one or more unit operations of the system 2000, as previously described herein.

[0093] In some embodiments, the controller 600 can be configured to instruct the dissolved carbon dioxide removal subsystem 300 to remove a predetermined amount of dissolved carbon dioxide from the aqueous solution. For example, the controller 600 can be configured to instruct the dissolved carbon dioxide removal subsystem 300 to produce an effluent solution that is substantially free of dissolved carbon dioxide. In some embodiments, the controller can be configured to send a control signal to the pH adjustment agent source to cause the pH adjustment agent source to dose the pH adjustment agent to the aqueous solution in response to a signal (e.g., a pH signal). The controller 600 can be configured to adjust the pH of the aqueous solution to between 8.0 and 11, or to a pH previously described.

[0094] In some embodiments, controller 600 can be configured to send control signals to at least one of ultraviolet irradiation source 400, pump 120, and dissolved carbon dioxide removal subsystem 300. For example, controller 600 can be configured to cause ultraviolet irradiation source 400 to irradiate the solution with an amount of ultraviolet light effective to destroy a predetermined amount of dissolved ozone in the solution in response to a signal (e.g., a dissolved ozone signal). Controller 600 can instruct ultraviolet irradiation source 400 to adjust the ultraviolet light intensity or instruct pump 120 to adjust the flow rate in response to the dissolved ozone signal.

[0095] Additionally, controller 600 can be configured to cause dissolved carbon dioxide removal subsystem 300 to remove a predetermined amount of dissolved carbon dioxide in response to the dissolved ozone signal. For example, controller 600 can be configured to operate a membrane degasser (by adjusting a vacuum pump or sweep gas flow rate) in response to the dissolved ozone signal, or controller 600 can direct the administration of an amount of a pH adjuster to aqueous solution 200 in response to the dissolved ozone signal.

[0096] The controller 600 may be a computer or a mobile device. The controller 600 may include a touchpad or other operating interface. For example, the controller 600 may be operated via a keyboard, a touchscreen, a trackpad, and / or a mouse. The controller 600 may include one or more output devices, such as a display or a speaker. To generate the control signals, the controller 600 may include a system processor coupled to a memory device that stores data from at least one input value. The memory device may be an internal memory device, an external memory device, or a cloud-based memory device. The controller 600 may be configured to run software on an operating system known to those skilled in the art.

[0097] The controller 600 can be electrically connected to a power source. The controller 600 can be digitally connected to one or more unit operations as disclosed herein. The controller 600 can be connected to the unit operations via a wireless connection. For example, the controller 600 can be connected to the unit operations via wireless local area networking (WLAN) or ultra-high frequency (UHF) radio waves. The controller 600 can further be operatively connected to any pumps or valves in the system, for example, to enable the controller 600 to dispense solutions in the system as needed.

[0098] System 2000 further includes a recycle line 110 extending from a point downstream of ultraviolet irradiation source 400 to a point upstream of ultraviolet irradiation source 400 and to a point upstream of dissolved carbon dioxide removal subsystem 300. Controller 600 is configured to supply wastewater through recycle line 110 in response to the dissolved ozone signal. For example, controller 600 may be configured to supply wastewater having a concentration of dissolved ozone greater than a threshold concentration to a point upstream of dissolved ozone removal system 2000. Controller 600 may be configured to supply the wastewater to one or more valves (not shown) operably connected to the controller.

[0099] The system may include one or more additional valves, pumps, or channels configured to control the direction of aqueous solution or wastewater through the system, as described herein. [Example]

[0100] Example The function and advantages of these and other embodiments can be better understood from the following examples, which are intended to be illustrative in nature and are not to be construed as limiting the scope of the invention.

[0101] Example 1: Sodium hydroxide and ultraviolet irradiation Ultrapure water having 26 ppm dissolved carbon dioxide and 30 ppm dissolved carbon dioxide was treated using an experimental system 3000 as shown in Figure 5. The aqueous solution 200 was fed through the channel 100 at a flow rate of approximately 2 gallons per minute. The initial pH of the aqueous solution 200 was 4.7.

[0102] Dissolved carbon dioxide removal subsystem 300 included a sodium hydroxide source 310 as a pH adjuster and a static mixer 315 disposed downstream of sodium hydroxide source 310. A metering pump 330 was configured to introduce sodium hydroxide into channel 100. The system included an inlet pH sensor 320 and an outlet pH sensor 325 disposed downstream of dissolved carbon dioxide removal subsystem 300.

[0103] The ultraviolet radiation source 400 has a wavelength of 254 nm and an intensity of 2000 mJ / cm 2 The ultraviolet lamp was set to emit ultraviolet light of 1000 W. The system included a first dissolved oxygen sensor 420 and a second dissolved oxygen sensor 425 located downstream of the ultraviolet irradiation source 400.

[0104] The measured dissolved ozone concentrations are shown in the graphs of Figures 6 and 7. Briefly, Figure 6 is a graph of the dissolved ozone concentration (ppb) in the wastewater versus time (hours) as measured by two dissolved ozone sensors. Initially, despite UV irradiation activation, the dissolved ozone concentration peaked at approximately 120 ppb. Shortly after 1 hour, NaOH was continuously dosed to the solution at a concentration of approximately 10 ppb. The dissolved ozone concentration dropped to below 10 ppb. Shortly after 6 hours, the NaOH dosing was stopped. The dissolved ozone concentration rose to approximately 80 ppb.

[0105] Figure 7 is a graph of the dissolved ozone concentration (ppb) in the wastewater versus elapsed time (hours) as measured by two dissolved ozone sensors. The initial dissolved ozone concentration was measured at approximately 100 ppb by the first sensor and over 200 ppb by the second sensor. After 5 hours, the dissolved ozone concentration readings stabilized at 50 ppb and 100 ppb, respectively, as measured by the two sensors. Immediately after 5 hours, 3% NaOH was continuously dosed into the solution. The dissolved ozone concentration dropped below approximately 2 ppb.

[0106] Therefore, the removal of dissolved carbon dioxide increases the destruction of dissolved ozone by UV irradiation. The pH adjuster and UV irradiation have a synergistic effect on the removal of dissolved ozone. Using the systems and methods described herein, dissolved ozone concentrations in aqueous solutions can be reduced to 2 ppb or less.

[0107] 5 can be scaled up to commercially acceptable capacities. For example, the system 3000 can be scaled up to process 400 gallons per minute of aqueous solution.

[0108] Example 2: UV irradiation An experimental system similar to system 3000, but without the dissolved carbon dioxide removal subsystem 300 and pH sensors 320, 325, was used to supply feedwater with an initial dissolved ozone concentration of 30 ppm, a dissolved oxygen concentration of 50 ppm, and a dissolved carbon dioxide concentration of 26 ppm. The feedwater was supplied to channel 100 at a flow rate of 150-300 L / hour and a temperature of 25°C. 2.45 hours after supplying the feedwater to channel 100, it was irradiated with ultraviolet light.

[0109] The results are shown in the graphs in Figures 8A and 8B. Figure 8B shows the concentrations in Figure 8A with a different y-axis scale for clarity. As shown in the graph in Figure 8A, UV irradiation reduced the dissolved ozone concentration from 30 ppm to less than 1 ppm. As shown in the graph in Figure 8B, UV irradiation ultimately reduced the dissolved ozone concentration to 35 ppb. Therefore, UV irradiation can reduce the dissolved ozone concentration to 35 ppb.

[0110] Example 3: UV irradiation upstream of sodium hydroxide An experimental system similar to system 3000, but with ultraviolet light source 400 located upstream of dissolved carbon dioxide removal subsystem 300, was used to treat feedwater with an initial dissolved ozone concentration of 30 ppm, dissolved oxygen concentration of 50 ppm, and dissolved carbon dioxide concentration of 26 ppm. The feedwater was fed through channel 100 at a flow rate of approximately 300 L / hr and a temperature of 25°C. Ultraviolet light was applied. 1.3 hours after the feedwater was fed into channel 100, sodium hydroxide addition was initiated. The effluent pH was 7.9. 6.3 hours after the feedwater was directed into channel 100, sodium hydroxide addition was stopped.

[0111] The results are shown in the graph in Figure 9. As shown in Figure 9, after the addition of sodium hydroxide was started, the dissolved ozone concentration decreased from 90 ppb to 2.1 ppb. Also, after the addition of sodium hydroxide was stopped, the dissolved ozone concentration began to increase, as expected. Therefore, UV irradiation and increasing pH can reduce dissolved ozone to 2.1 ppb.

[0112] Example 4: Sodium hydroxide upstream of UV irradiation An experimental system similar to System 3000 was used to treat feedwater with an initial dissolved ozone concentration of 30 ppm, dissolved oxygen concentration of 50 ppm, and dissolved carbon dioxide concentration of 26 ppm. The feedwater was supplied to Channel 100 at a flow rate of approximately 150-270 L / h and a temperature of 25°C. Ultrapure water was initially run through the system under UV irradiation. Sodium hydroxide was added to stabilize the water pH.

[0113] After 2.25 hours of supplying ultrapure water to channel 100, feed water was introduced into the system and the ultrapure water was stopped. The pH of the effluent was between 9 and 11. After 4 hours of supplying feed water to channel 100, the sodium hydroxide concentration was reduced. The low concentration of sodium hydroxide did not change the dissolved ozone concentration in the effluent.

[0114] The results are shown in the graph of Figure 10. As shown in the graph of Figure 10, the dissolved ozone concentration remained stable at about 2 ppb while adding sodium hydroxide at 50% metering pump 330 speed and 25% metering pump 330 speed. Therefore, reducing the sodium hydroxide dose at the test values ​​did not affect the dissolved ozone concentration in the effluent.

[0115] Example 5: Sodium hydroxide An experimental system similar to System 3000 but without the UV source 400 was used to treat feedwater with an initial dissolved ozone concentration of 30 ppm, dissolved oxygen concentration of 50 ppm, and dissolved carbon dioxide concentration of 26 ppm. The feedwater was fed through Channel 100 at a flow rate of approximately 150 L / h and a temperature of 25°C. Ultrapure water was initially run through the system under UV irradiation. Sodium hydroxide was dosed to stabilize the water pH.

[0116] After 0.5 hours of supplying ultrapure water to channel 100, feedwater was introduced into the system and the ultrapure water was stopped. The pH of the wastewater was between 9 and 11. After 1.3 hours of supplying feedwater to channel 100, the sodium hydroxide concentration was decreased. After 3 hours of supplying feedwater to channel 100, the sodium hydroxide concentration was increased. As the sodium hydroxide concentration decreased, the dissolved ozone concentration in the wastewater increased. After the high concentration sodium hydroxide was resumed, the dissolved ozone concentration in the wastewater decreased.

[0117] The results are shown in the graph of Figure 11. As shown in the graph of Figure 11, the dissolved ozone concentration varied significantly. The dissolved ozone concentration initially decreased to less than about 35 ppb at 100% metering pump 300 speed. The dissolved ozone concentration increased to about 50-70 ppb at 93% metering pump 330 speed. The dissolved ozone concentration decreased again to about 25 ppb (with a spike of about 50 ppb) at 99% metering pump 330 speed. Therefore, the reduction in sodium hydroxide dose in the test values ​​affected the dissolved ozone concentration in the wastewater when UV light was not irradiated.

[0118] Example 6: Membrane degassing and ultraviolet irradiation An experimental system similar to system 3000, but equipped with a membrane degasser and a vacuum pump as the dissolved carbon dioxide removal subsystem 300, was used to treat feedwater with an initial dissolved ozone concentration of 30 ppm, a dissolved oxygen concentration of 50 ppm, and a dissolved carbon dioxide concentration of 26 ppm. The experimental system included an additional UV irradiation source upstream 400 of the membrane degasser. The feedwater was supplied to channel 100 at a flow rate of approximately 240-300 L / h and a temperature of 25°C. The pH of the feedwater was 9. Ultrapure water was first exposed to UV light and flowed through the system.

[0119] After 0.75 hours of supplying ultrapure water to channel 100, feed water was introduced into the system and the ultrapure water was turned off.

[0120] The results are shown in the graph in Figure 12A. As shown in the graph in Figure 12A, the dissolved ozone concentration measurements remained stable at approximately less than 0.25 ppb. However, it should be noted that the dissolved ozone sensor 420 had a lower detection limit of 0.4 ppb. Therefore, the results of the experimental setup are equivocal. However, the removal of dissolved carbon dioxide by the membrane degasser was effective in significantly reducing the dissolved ozone concentration in the wastewater.

[0121] Example 7: Membrane Degassing, Ultraviolet Irradiation, and Sodium Hydroxide An experimental system similar to that of Example 6, but equipped with a sodium hydroxide source 310, a metering pump 330, and a static mixer 315 downstream of a second UV irradiation source 400, was used to treat intake water with an initial dissolved ozone concentration of 30 ppm, a dissolved oxygen concentration of 50 ppm, and a dissolved carbon dioxide concentration of 26 ppm. The experimental system included an additional UV irradiation source 400 upstream of the membrane degasser. Feedwater was supplied to the channel 100 at a flow rate of approximately 240-300 L / h and a temperature of 25°C. The pH of the feedwater was 9. Ultrapure water was first irradiated with UV light and then passed through the system.

[0122] After 0.8 hours of supplying ultrapure water to channel 100, the feed water was introduced into the system and the ultrapure water was turned off. After 3.7 hours of supplying the feed water through channel 100, the second ultraviolet radiation source 400 was turned off. After 4.9 hours of supplying the feed water to channel 100, sodium hydroxide was dosed. After 6.4 hours of supplying the feed water to channel 100, the sodium hydroxide was turned off.

[0123] The results are shown in the graph of FIG. 12B. As shown in the graph of FIG. 12B, the dissolved ozone concentrations generally ranged between 1 ppb and 0. As previously mentioned, the dissolved ozone sensor 420 has a lower detection limit of 0.4 ppb. Shutting off the second UV radiation source 400 had no effect on the dissolved ozone concentration in the wastewater. The addition of sodium hydroxide had little or no effect on the dissolved ozone concentration in the wastewater. Finally, stopping the sodium hydroxide had little or no effect on the dissolved ozone concentration in the wastewater. Removal of dissolved carbon dioxide using a membrane degasser and two UV radiation sources or the addition of sodium hydroxide offers no advantage over removal of dissolved ozone using a membrane degasser and a single UV radiation source.

[0124] The phraseology and terminology used herein are for purposes of description and should not be considered limiting. As used herein, the term "plurality" refers to two or more items or elements. The terms "comprising," "including," "carrying," "having," "containing," and "involving," whether in the description or claims, are open terms, i.e., mean "including, but not limited to." Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. With respect to the claims, only the prefix phrases "consisting of" and "consisting essentially of" are closed or semi-closed prefix phrases, respectively. The use of ordinal terms such as "first," "second," and "third" in the claims to modify claim elements does not, per se, imply a priority, seniority, or order of one claim element relative to another claim element, or the temporal order in which the actions of a method are performed, but is merely used as a label to distinguish one claim element having a particular name from another element having the same name (but using ordinal terms).

[0125] Having thus described several aspects of at least one embodiment, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Any feature described in any embodiment may be included in, or substituted for, any feature of any other embodiment. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

[0126] Those skilled in the art should understand that the parameters and configurations described herein are exemplary, and that the actual parameters and / or configurations will depend on the particular application in which the disclosed methods and materials are used. Those skilled in the art should also be able to recognize or ascertain using no more than routine experimentation equivalents to the specific embodiments disclosed.

Claims

1. providing an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration into a vessel; removing an amount of dissolved carbon dioxide from the aqueous solution to produce a first effluent having a second dissolved carbon dioxide concentration that is lower than the first dissolved carbon dioxide concentration; irradiating the first wastewater with ultraviolet light at a dose effective to decompose a predetermined amount of dissolved ozone in the first wastewater to produce a second wastewater having a second dissolved ozone concentration lower than the first dissolved ozone concentration; If the second dissolved ozone concentration is greater than a threshold amount, recirculating a quantity of the second effluent to a point upstream of the step of applying ultraviolet light; A method comprising:

2. 10. The method of claim 1, wherein removing the amount of dissolved carbon dioxide concentration comprises controlling a pH of the aqueous solution to a value effective to convert the amount of dissolved carbon dioxide to at least one of carbonate and bicarbonate.

3. 3. The method of claim 2, comprising controlling the pH of the aqueous solution to at least about 8.

4. 4. The method of claim 3, comprising controlling the pH of the aqueous solution to between about 8.3 and 11.

5. measuring at least one of the pH of the aqueous solution and the pH of the first effluent; 3. The method of claim 2, further comprising the step of adding a predetermined amount of acid or base in response to said measurement to control the pH of said aqueous solution.

6. 10. The method of claim 1, wherein the first wastewater is substantially free of dissolved carbon dioxide.

7. 10. The method of claim 1, wherein removing the amount of dissolved carbon dioxide comprises contacting the aqueous solution with a membrane degasser.

8. Measuring the concentration of dissolved carbon dioxide in the aqueous solution and the concentration of dissolved carbon dioxide in the first wastewater; 8. The method of claim 7, further comprising controlling the rate of removal of the quantity of dissolved carbon dioxide using the membrane degasser in response to the measurement by at least one of adjusting the vacuum level of the membrane degasser, adjusting a sweep gas flow rate through the membrane degasser, and controlling the flow rate of the aqueous solution through the membrane degasser.

9. 10. The method of claim 1, wherein the first dissolved carbon dioxide concentration is at least about 20 ppm.

10. 10. The method of claim 1, wherein the first dissolved ozone concentration is at least about 30 ppm.

11. 11. The method of claim 10, wherein the second dissolved ozone concentration is less than about 10 ppb.

12. 12. The method of claim 11, wherein the second dissolved ozone concentration is less than about 2 ppb.

13. 13. The method of claim 12, wherein the second dissolved ozone concentration is less than about 1 ppb.

14. measuring at least one of the first dissolved ozone concentration and the second dissolved ozone concentration; 10. The method of claim 1, further comprising controlling at least one of the dose of the ultraviolet radiation and a flow rate of at least one of the aqueous solution and the first wastewater in response to the measurement.

15. The method of claim 1 , wherein the aqueous solution comprises semiconductor manufacturing process water.

16. a channel fluidly connected to an aqueous solution source of an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration; a dissolved carbon dioxide removal subsystem fluidly connected to the channel and configured to remove an amount of dissolved carbon dioxide from the aqueous solution to produce a first effluent; an ultraviolet radiation source disposed downstream of the dissolved carbon dioxide removal subsystem and configured to irradiate the first effluent with ultraviolet light to produce a second effluent; a recycle line for recirculating a quantity of the second wastewater from a point downstream of the ultraviolet radiation source to a point upstream of the ultraviolet radiation source; at least one dissolved ozone sensor disposed downstream of the ultraviolet radiation source and configured to measure a second dissolved ozone concentration in the second wastewater; a controller operably connected to the at least one dissolved ozone sensor; wherein the controller is configured to supply the second wastewater to the recycle line when the second dissolved ozone concentration in the second wastewater is greater than a threshold concentration.

17. 17. The system of claim 16, wherein the dissolved carbon dioxide removal subsystem comprises a pH adjuster source fluidly connected to the channel and configured to administer a pH adjuster to the aqueous solution to produce the first effluent.

18. 20. The system of claim 17, further comprising a mixer positioned downstream of the pH adjuster source and upstream of the ultraviolet radiation source.

19. a pH sensing subsystem comprising an inlet pH sensor configured to detect a pH of the aqueous solution and an outlet pH sensor configured to detect a pH of at least one of the first effluent and the second effluent; 20. The system of claim 17, wherein the pH sensing subsystem is configured to output a pH signal indicative of a measurement obtained by at least one of the inlet pH sensor and the outlet pH sensor.

20. 17. The system of claim 16, wherein the dissolved carbon dioxide removal subsystem comprises a membrane degasser fluidly connected to the channel.

21. 21. The system of claim 20, wherein the dissolved carbon dioxide removal subsystem comprises at least one of a vacuum pump and a sweep gas source associated with the membrane degasser.

22. a dissolved carbon dioxide sensing subsystem comprising an inlet dissolved carbon dioxide sensor configured to detect a dissolved carbon dioxide concentration in the aqueous solution and an outlet dissolved carbon dioxide sensor configured to detect dissolved carbon dioxide in at least one of the first effluent and the second effluent; 20. The system of claim 19, wherein the dissolved carbon dioxide sensing subsystem is configured to output a dissolved carbon dioxide signal indicative of a measurement obtained by at least one of the inlet dissolved carbon dioxide sensor and the outlet dissolved carbon dioxide sensor.

23. 23. The system of claim 22, further comprising a flow meter configured to measure a flow rate of at least one of the aqueous solution, the first wastewater, and the second wastewater, the flow meter configured to output a flow rate signal indicative of the measurement obtained by the flow meter.

24. the controller operably connected to the dissolved carbon dioxide removal subsystem and at least one of the pH sensing subsystem, the dissolved carbon dioxide sensing subsystem, and the flow meter; 24. The system of claim 23, wherein the controller is configured to receive at least one of the pH signal, the dissolved carbon dioxide signal, and the flow rate signal and to send a control signal to the dissolved carbon dioxide removal subsystem in response to the received signal.

25. 25. The system of claim 24, wherein the controller is configured to direct the dissolved carbon dioxide removal subsystem to produce the first effluent that is substantially free of dissolved carbon dioxide.

26. 25. The system of claim 24, wherein the controller is configured to send the control signal to the pH adjuster source, whereby in response to the control signal, the pH adjuster source dispenses the pH adjuster into the aqueous solution.

27. 27. The system of claim 26, wherein the controller is configured to adjust the pH of the aqueous solution to between about 8.0 and 11.

28. 17. The system of claim 16, wherein the at least one dissolved ozone sensor is configured to output a dissolved ozone signal indicative of a measurement obtained by the dissolved ozone sensor.

29. The system described in Claim 28, wherein the controller is configured to receive the dissolved ozone signal and send a control signal to at least one of the ultraviolet irradiation source and the flow control device, thereby causing the ultraviolet irradiation source to irradiate the first wastewater with ultraviolet light at a dose effective to destroy a predetermined amount of dissolved ozone in the first wastewater in response to the control signal.

30. The system described in claim 28, wherein the controller is configured to receive the dissolved ozone signal and send a control signal to at least one of the ultraviolet irradiation source and the flow control device, thereby causing the dissolved carbon dioxide removal subsystem to remove the amount of dissolved carbon dioxide from the aqueous solution in response to the control signal.

31. the dissolved carbon dioxide removal subsystem comprises a pH adjuster source fluidly connected to the channel, the pH adjuster source dispensing a pH adjuster into the aqueous solution to produce the first effluent; 31. The system of claim 30, wherein the controller is configured to send the control signal to the pH adjuster source, whereby in response to the control signal, the pH adjuster source dispenses the pH adjuster into the aqueous solution.

32. 32. The system of claim 31, wherein the pH adjuster source is associated with a semiconductor manufacturing system.

33. providing an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration into a vessel; irradiating the aqueous solution with ultraviolet light at a dose effective to destroy a predetermined amount of dissolved ozone in the aqueous solution to produce a first effluent; removing an amount of dissolved carbon dioxide from the first wastewater to produce a second wastewater having a second dissolved carbon dioxide concentration lower than the first dissolved carbon dioxide concentration and a second dissolved ozone concentration lower than the first dissolved ozone concentration; If the second dissolved ozone concentration is greater than a threshold amount, recirculating a quantity of the second effluent to a point upstream of the step of applying ultraviolet light; A method comprising:

34. 34. The method of claim 33, wherein removing the amount of dissolved carbon dioxide comprises controlling a pH of the first effluent to a value effective to convert the amount of dissolved carbon dioxide to at least one of carbonate and bicarbonate.

35. 34. The method of claim 33, wherein removing the amount of dissolved carbon dioxide comprises contacting the first effluent with a membrane degasser.

36. a channel fluidly connected to an aqueous solution source of an aqueous solution having a first dissolved carbon dioxide concentration and a first dissolved ozone concentration; an ultraviolet radiation source fluidly connected to the channel and configured to irradiate the aqueous solution with ultraviolet light to produce a first effluent; a dissolved carbon dioxide removal subsystem disposed downstream of the ultraviolet irradiation source and configured to remove a quantity of dissolved carbon dioxide from the first effluent to produce a second effluent; a recycle line for recirculating a quantity of the second wastewater from a point downstream of the ultraviolet radiation source to a point upstream of the ultraviolet radiation source; at least one dissolved ozone sensor disposed downstream of the ultraviolet radiation source and configured to measure a second dissolved ozone concentration in the second wastewater; a controller operably connected to the at least one dissolved ozone sensor; wherein the controller is configured to supply the second wastewater to the recycle line when a second dissolved ozone concentration in the second wastewater is greater than a threshold concentration.

37. 37. The system of claim 36, wherein the dissolved carbon dioxide removal subsystem comprises a pH adjuster source fluidly connected to the channel and configured to administer a pH adjuster to the first effluent to produce the second effluent.

38. 37. The system of claim 36, wherein the dissolved carbon dioxide removal subsystem comprises a membrane degasser fluidly connected to the channel.

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