WO2015102997A1

WO2015102997A1 - Surface and space disinfection with composition including mixed oxidants

Info

Publication number: WO2015102997A1
Application number: PCT/US2014/071881
Authority: WO
Inventors: Jason E. PETERS; Dane H. MADSEN
Original assignee: Blue Earth Labs Llc
Priority date: 2013-12-30
Filing date: 2014-12-22
Publication date: 2015-07-09

Abstract

A disinfectant liquid includes a stabilized mixed oxidant solution produced by flowing a starting solution (e.g., salt brine, hypochlorous acid, and/or sodium hypochlorite) through a flow-through electrochemical module including first and second passages separated by an ion permeable membrane while electric power is applied between an anode and cathode in electrical communication with the first and second passages, respectively, followed by stabilization by elevating pH to yield a stabilized mixed oxidant solution. A disinfectant liquid may be vaporized and supplied to disinfect at least one surface, equipment, volume or enclosed space.

Description

SURFACE AND SPACE DISINFECTION

WITH COMPOSITON INCLUDING MIXED OXIDANTS

STATEMENT OF RELATED APPLICATION(S)

[0001] This application claims benefit of U.S. Provisional Patent Application No. Provisional Patent Application No. 61/921 ,578 filed on December 30, 2013.

TECHNICAL FIELD [0002] The present invention relates to methods and compositions for disinfecting surfaces, equipment, volumes, or enclosed spaces, and more specifically, to use of atomized or vaporized mists of disinfectant solutions for fumigation and sterilization.

BACKGROUND [0003] Sanitization and disinfection of enclosed spaces has become an issue of increasing importance due to potential presence of various pathogens including bacteria, viruses, mold, and mildew. Since most commercial or institutional structures and many residential structures are maintained in an effectively sealed condition (e.g., with processed air being recirculated), the ability to circulate fresh air may be limited. Additionally, certain vehicles such as airplanes, trains, and portions of cruise ships are sealed or effectively sealed against the environment during transit.

[0004] Some infectious agents, such as hepatitis virus, staph bacteria (including MRSA), Legionella genus bacteria (including L. pneumophila and L. longbeachae), and various spores, are known to survive in areas such as hospitals and other healthcare facilities, as well as in locations such as hotels, cruise ships, schools, locker rooms, and correctional facilities.

[0005] Other locations of concern for pathogenic contamination include vehicles such as emergency vehicles and public transit vehicles, which are seldom cleaned to a level sufficient to eradicate infectious agents. Such vehicles can include ambulances, EMS vehicles, police cars, fire rescue units, buses, trains, subway cars, boats, and taxis. [0006] Traditional methods of disinfecting surfaces involving application of biocide solutions have relied upon direct (e.g., directional) spray contact, which may be ineffective and/or impractical for penetrating hard-to-reach areas.

[0007] More recently, biocide vapor has been used for disinfecting spaces. One example of a conventional biocide that may be used for vapor disinfection is chlorine dioxide, which when arranged in a water solution is relatively less toxic than free chlorine and bleach solutions; however, chlorine dioxide is not very stable as a gas. Because of the instability of chlorine dioxide gas at relatively high concentrations, its use as a biocide has been problematic and less common in comparison to its use in liquid (solution) form.

[0008] U.S. Patent No. 7,264,773 discusses various difficulties associated with prior use of chlorine dioxide-based solutions (including distillation of chlorine dioxide gas during atomization of such solutions), and discloses that a stable aqueous solution of chlorine dioxide mist for sterilization may be obtained by separately generating a mist of chlorine dioxide (whether in aqueous or non-aqueous form) and a mist of water solvent, and then combining the two mists to form a homogenous mist with chlorine dioxide encapsulated in water. The homogeneous mist may be delivered by free or forced convection flow to a desired location for disinfection of a contaminated surface or volume.

[0009] Unfortunately, chlorine dioxide is generally not stable enough to be manufactured off-site and shipped to a point of use. Instead, it typically must be created at the point of use using a chemical generator of some sort. Off-gassing and atmospheric release of chlorine dioxide gas is problematic, particularly in indoor environments. Additionally, chlorine dioxide can be explosive at concentrations above about 10% by volume.

[0010] Certain subject matter disclosed herein relates to U.S. Patent No. 8,617,403 issued on December 31 , 2013, which is hereby incorporated by reference herein.

[0011] It would be desirable to provide improved compositions and methods for disinfecting surfaces, equipment, volumes, or enclosed spaces. Various compositions and methods disclosed herein address limitations associated with conventional compositions and methods. SUMMARY

[0012] Various aspects of the invention relate to production and use of disinfectant liquids that include mixed oxidant solutions exhibiting enhanced effectiveness and enhanced stability compared to prior solutions, with the resulting disinfectant liquids being useful for forming atomized or vaporized mists for disinfecting surfaces, equipment, volumes, or enclosed spaces.

[0013] In one aspect, the invention relates to a method for disinfecting at least one surface, equipment, volume, or enclosed space, the method comprising: vaporizing a disinfectant liquid including a mixed oxidant solution that comprises a plurality of different oxidants, wherein the mixed oxidant solution is produced by steps comprising (A) flowing at least one starting solution including at least one of salt brine, hypochlorous acid, and sodium hypochlorite through at least one flow-through electrochemical module comprising a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage, wherein a first solution or first portion of the at least one starting solution is flowed through the first passage to form an anolyte solution having an acidic pH, and a second solution or second portion of the at least one starting solution is simultaneously flowed through the second passage to form a catholyte solution having a basic pH, and (B) contacting the anolyte solution with a hydroxide solution to attain a pH value of at least about 9.0 to yield said mixed oxidant solution; and supplying an effective amount of the vaporized disinfectant liquid to the at least one surface, equipment, volume, or enclosed space for disinfection of the at least one surface, equipment, volume, or enclosed space.

[0014] In various aspects, the disinfectant liquid may include a supplemental biocide of oxidizing or non-oxidizing character.

[0015] In various aspects, the disinfectant liquid may comprise a total available chlorine value in a range of from 10 ppm to 600 ppm.

[0016] In various aspects, the mixed oxidant solution may comprises at least one of the following features: a total chlorine value of at least about 3,000 ppm; an oxidation- reduction potential (ORP) value in a range of from 600 mV to 800 mV; and a ratio of Na+ (in g/L according to Method EPA 300.0) to CI- (in g/L according to Method EPA 6010) of at least about 1 .5.

[0017] In another aspect, the invention relates to a disinfectant liquid suitable for disinfection of at least one surface, equipment, volume, or enclosed space, the disinfectant liquid comprising: a mixed oxidant solution comprising a plurality of different oxidants produced by a method comprising flowing at least one starting solution comprising at least one of salt brine, hypochlorous acid, and sodium hypochlorite through at least one flow-through electrochemical module comprising a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage, wherein a first solution or first portion of the at least one starting solution is flowed through the first passage to form an anolyte solution having an acidic pH, and a second solution or second portion of the at least one starting solution is simultaneously flowed through the second passage to form a catholyte solution having a basic pH; and contacting the anolyte solution with a hydroxide solution to attain a pH value of at least about 9.0 to yield said mixed oxidant solution; and at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water; wherein the disinfectant liquid comprises a total available chlorine value in a range of from 10 ppm to 600 ppm.

[0018] In another aspect, any of the foregoing aspects, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein.

[0019] Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a flow chart showing various stages involved in making a disinfectant liquid including a mixed oxidant solution component and optionally including at least one other component, according an embodiment of the present invention.

[0021] FIG. 2 is a simplified schematic cross-sectional view of a flow-through electrochemical module including flow chambers separated by an ion-permeable membrane and arranged to produce separate anolyte and catholyte streams by electrolysis of a salt brine solution, for producing a mixed oxidant solution of a disinfectant liquid according to the present invention.

[0022] FIG. 3 is a schematic diagram showing arrangement of a production system for mixed oxidant solution (as at least a component of a disinfectant liquid according to the present invention) including flow-through electrochemical modules and associated components.

[0023] FIG. 4 is a cross-sectional view of an exemplary flow-through electrochemical module such as may be used in the system of FIG. 3.

[0024] FIG. 5 is a line chart depicting total chlorine (ppm) versus time (days) for mixed oxidant solutions produced using the system of FIG. 3.

[0025] FIG. 6 is a table summarizing characteristics including total chlorine, pH, oxidation-reduction potential, conductivity, sodium ion concentration, chloride ion concentration, and sodium/chloride ion ratio for the following five products: (1 ) 12.5% hypochlorite bleach, (2) 6% hypochlorite bleach, (3) Clearitas® mixed oxidant solution, (4) Miox™ mixed oxidant solution, and (5) a stabilized mixed oxidant solution useful as at least a component of a disinfectant liquid according to embodiments of the present invention.

[0026] FIG. 7 is a schematic diagram showing components of a subsystem arranged to receive a stream of a stabilized mixed oxidant solution component from the mixed oxidant solution production system of FIG. 3, and blend the mixed oxidant solution component with at least one additional component (e.g., at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water) to yield a disinfectant liquid according to an embodiment of the present invention.

[0027] FIG. 8 is a schematic diagram showing components of a system arranged to disinfect at least one surface, equipment, volume, or enclosed space by vaporizing a disinfectant liquid as disclosed herein and supplying an effective amount of the vaporized disinfectant liquid to the at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[0028] FIG. 9A is a line chart of luminometer relative light units (for detection of adenosine triphosphate (ATP)) versus concentration for five different doses of a first conventional disinfectant (including 25% gluteraldehyde and 12% quaternary ammonia) in 100 ml of dairy waste. [0029] FIG. 9B is a line chart of luminometer relative light units (for detection of ATP) versus concentration for five different doses of a second conventional disinfectant (including 12% gluteraldehyde and 3% quaternary ammonia) in 100 ml of dairy waste.

[0030] FIG. 9C is a line chart of luminometer relative light units (for detection of ATP) versus concentration for five different doses of a third conventional disinfectant (including 25% gluteraldehyde) in 100 ml of dairy waste.

[0031] FIG. 9D is a line chart of luminometer relative light units (for detection of ATP) versus concentration for five different doses of a fourth conventional disinfectant (5% chlorine dioxide produced from a mixture of Petrofid chlorite and hydrochloric acid in a 5:1 ratio) in 100 ml of dairy waste.

[0032] FIG. 9E is a line chart of luminometer relative light units (for detection of ATP) versus concentration for five different doses of a fifth conventional disinfectant (5.25% sodium hypochlorite (a/k/a liquid bleach)) in 100 ml of dairy waste.

[0033] FIG. 9F is a line chart of luminometer relative light units (for detection of ATP) versus concentration for five different doses of a disinfectant liquid according to one embodiment of the present invention (including 60% mixed oxidant solution blended with 40% hypochlorite solution to yield 5.25% sodium hypochlorite) in 100 ml of dairy waste.

[0034] FIG. 9G is a table embodying results of Free ATP and Total ATP measurements on 1 gallon per thousand treatments of 100 ml dairy waste after 22 hours of exposure to the disinfectants described in FIGS. 9A-9F.

DETAILED DESCRIPTION

[0035] Described herein are methods for making and using disinfectant liquids including a mixed oxidant solution component, and optionally including at least one of (a) deionized water, (b) an oxidizing biocide, and (c) a non-oxidizing biocide, that are particularly useful for vaporization and administration of the resulting vaporized disinfectant liquid to at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[0036] Disinfectant liquids as disclosed herein preferably include solutions in liquid form that are amenable to being produced at a centralized location, packaged in sealed containers (e.g., drums, tankers, totes, or the like) suitable for shipment to a point of use, and transported to a point of use, with sufficient stability and shelf life to permit the disinfectant liquids to be stored (if necessary) at the point of use, thereby eliminating any need for on-site generation of mixed oxidant chemistries. In certain embodiments, a mixed oxidant solution may be produced and packaged at a centralized location, transported to a point of use, and then blended with one or more additional components at the point of use to yield a disinfectant liquid useful for vaporization and administration of the resulting vaporized disinfectant liquid to at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[0037] In certain embodiments, at least one additional component of a liquid disinfectant solution includes deionized water.

[0038] In certain embodiments, at least one additional component of a liquid disinfectant solution includes an oxidizing biocide. Examples of oxidizing biocides include, but are not limited to, sodium hypochlorite, hydrogen peroxide, hypobromous acid, and chlorine dioxide. Other sources of chlorine ions and/or bromine ions may be used.

[0039] In certain embodiments, at least one additional component of a liquid disinfectant solution includes a non-oxidizing biocide. Examples of non-oxidizing biocides include, but are not limited to, glutaraldehyde, quaternary ammonia, and silver nitrate (or another source of silver ions).

[0040] In certain embodiments, a disinfectant liquid may comprise from 30% to 90% by volume mixed oxidant solution and comprise from 10% to 70% by volume of at least one other component disclosed herein (e.g., biocide and/or deionized water). In certain embodiments, a disinfectant liquid may comprise from 50% to 70% by volume mixed oxidant solution and comprise from 30% to 50% by volume of at least one other component disclosed herein. In certain embodiments, a disinfectant liquid may comprise from 55% to 65% by volume mixed oxidant solution and comprise from 35% to 45% by volume of at least one other component disclosed herein.

[0041] In certain embodiments, a disinfectant liquid may comprise a total available chlorine value in a range of at least 10 ppm, in a range of at least 100 ppm, in a range of from 10 ppm to 600 ppm, in a range of from 50 ppm to 600 ppm, in a range of from 50 ppm to 400 ppm, in a range of from 100 to 300 or in a range of from 100 ppm to 600 ppm.

[0042] In certain embodiments, a mixed oxidant solution useable as at least a component of a disinfectant liquid may comprises a pH of preferably at least about 12, more preferably at least about 12.5, still more preferably at least about 13, and still more preferably at least about 13.5.

[0043] A preferred mixed oxidant solution component exhibits enhanced effectiveness and enhanced stability compared to prior mixed oxidant solutions, including but not limited to RE-Ox® chemical solution described in U.S. Patent No. 8,366,939 and Clearitas® mixed oxidant solution commercialized by Blue Earth Labs, LLC (Las Vegas, Nevada, US) that are formed by electrolyzing a brine solution in a flow- through cathode chamber followed by electrolysis of the catholyte solution in a flow- through anode chamber. In contrast to prior mixed oxidant solutions, preferred mixed oxidant solution components described herein beneficially contain anolyte solution produced by flowing at least one starting solution (i.e., comprising at least one of salt brine, hypochlorous acid, and sodium hypochlorite) through an anode chamber without prior or subsequent transmission through a cathode chamber, wherein the resulting anolyte solution is immediately treated with a hydroxide solution to attain a mixed oxidant solution having a basic pH - preferably with a pH value of at least about 9.0, at least about 9.5, at least about 10.0, at least about 10.5, at least about 1 1 .0, at least about 1 1 .5, at least about 12.0, at least about 12.5, or at least about 13.0 - to yield the mixed oxidant solution. Elevated pH of the resulting mixed oxidant solution component has been found to significantly increase the effective shelf life of the component, even in the presence of high concentrations of mixed oxidants. The stabilized mixed oxidant solution component can be produced, blended with at least one other component (e.g., deionized water, an oxidizing biocide, and a non-oxidizing biocide) to form a disinfectant solution, either at a facility where the mixed oxidant solution is manufactured or proximate to a point of use. Either the mixed oxidant solution or the disinfectant solution may be packaged in at least one container (e.g., suitable for shipment), and delivered to a customer. Regardless of whether the at least one additional component is added at a point of mixed oxidant solution manufacture or at a point of use, any need to produce mixed oxidant solution at a point of use may be avoided.

[0044] Liquid disinfectants according to various embodiments include as components thereof a mixed oxidant solution (comprising a plurality of different oxidants) that may be produced from a starting solution comprising at least one of salt brine, hypochlorous acid, and sodium hypochlorite, with the mixed oxidant solution production including: flowing at least one starting solution through at least one flow-through electrochemical module comprising a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage, wherein a first solution or first portion of the at least one starting solution is flowed through the first passage to form an anolyte solution having an acidic pH, and a second solution or second portion of the at least one starting solution is simultaneously flowed through the second passage to form a catholyte solution having a basic pH; and contacting the anolyte solution with a hydroxide solution to attain a pH value of at least about 9.0 (or another desired pH value such as preferably at least about 10.0, preferably at least about 1 1 .0, preferably at least about 12.0, or preferably at least about 13.0) to yield said mixed oxidant solution.

[0045] The mixed oxidant solution component may be optionally combined with at least one other component to yield a liquid disinfectant. In certain embodiments, the at least one additional component may include at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water. In certain embodiments, the at least one additional component may comprise a source of chlorine ions. In certain embodiments, the additional component may comprise a sodium hypochlorite solution (including, but not limited to, sodium hypochlorite in a range of from 6% to 12.5%. Other biocides may be used, with solutions in certain embodiments comprising at least one source of chlorine ions. In certain embodiments, a biocide may comprise sodium hypochlorite in a range of from 4 wt.% to 7 wt.%. In certain embodiments, a biocide may comprises sodium hypochlorite in a range not exceeding 5.25%, thereby permitting the resulting disinfectant solution to be designated as non-hazardous and thereby eligible for shipping and containment methods suitable for non-hazardous agents.

[0046] Since the production and composition of the mixed oxidant solution component itself are novel (as disclosed in pending U.S. Patent Application No. 13/950,147, subsequently issued as U.S. Patent No. 8,617,403, which is hereby incorporated by reference herein), details of the mixed oxidant solution component and its production are described herein.

[0047] In certain embodiments, at least one starting solution for producing a mixed oxidant solution comprises salt brine. In certain embodiments, at least one starting solution for producing a mixed oxidant solution comprises at least one of hypochlorous acid and sodium hypochlorite. [0048] In certain embodiments, catholyte solution produced by the at least one flow- through electrochemical module is discarded, preferably following partial or full neutralization by contacting the catholyte solution with an acid.

[0049] In certain embodiments, at least one flow-through electrochemical module useful for producing a mixed oxidant solution includes a centrally-arranged anode, a membrane surrounding the anode, a cathode surrounding the membrane, a first passage comprising an inner passage arranged between the anode and the membrane, and a second passage comprising an outer passage arranged between the membrane and the cathode. Electrochemical modules having different geometries and conformations may be used.

[0050] In certain embodiments, characteristics of the at least one starting solution, flow rate of the at least one starting solution, materials of construction of the at least one flow-through electrochemical module, dimensions of the at least one flow-through electrochemical module, number of the at least one flow-through electrochemical module, conformation of the at least one flow-through electrochemical module, and field density of the applied electric power are selected to yield a mixed oxidant solution having desired properties. Such properties may include one or more of the following: an oxidation-reduction potential (ORP) value in a range of from 500 mV to 900 mV (or in a range of from 600 mV to 900 mV, or in a range of from 600 mV to 800 mV); a ratio of Na+ (in g/L according to Method EPA 300.0) to CI- (in g/L according to Method EPA 6010) of at least about 1 .5; and total chlorine value of at least about 1000 ppm, at least about 3000 ppm, at least about 5000 ppm, in a range of from about 1 ,000 ppm to about 3,500 ppm, in a range of from about 1 ,000 ppm to about 6,000 ppm, or in a range of from about 3000 ppm to about 5000 ppm. In certain embodiments, multiple values in the foregoing ranges for ORP, Na+:CI-, and total CI (e.g., one value for ORP, another value for Na+:CI-, and/or another value for total CI) may be present in the same mixed oxidant solution.

[0051] Mixed oxidant solutions described herein as components of biocides may be beneficially used to reduce formation of, and/or remove, biofilm deposits as well as organic "glue" that holds such films together.

[0052] As illustrated in FIG. 1 , a system 100 for producing, transporting, and/or using a disinfectant solution as disclosed herein may involve multiple stages, including mixed oxidant solution production 101 (encompassing starting solution creation 102, starting solution supply 104, electrochemical processing 106, waste processing 108 (e.g., as applied to a catholyte stream), and stabilization 1 10 (e.g., as applied to an anolyte stream) to form a stabilized mixed oxidant solution) followed by blending 1 12 with at least one additional component (provided by supply 1 10) and output (preferably including packaging), transportation of the blended disinfectant liquid 1 14, and subsequent usage 1 16. In certain embodiments, one or more of the foregoing stages may be eliminated; two or more stages may be consolidated; and/or one or more additional stages may be added. For example, in certain embodiments, the mixed oxidant solution may be packaged alone and transported to a point of use, where it may optionally be combined (e.g., blended) with at least one additional component to yield a disinfectant liquid.

[0053] Continuing to refer to FIG. 1 , the starting solution creation stage 102 may include production of one or more starting solutions or precursors thereof. The starting solution supply stage 104 may include mixing and/or diluting starting solution precursors, and supplying the resulting one or more starting solutions to the electrochemical processing stage 106. The waste processing stage 108 may include neutralizing a basic catholyte stream produced by the electrochemical processing stage 106. The stabilization stage 1 10 may include elevating pH of an acidic anolyte stream produced by the electrochemical processing stage 106. The output/blending stage 1 12 may include venting, blending, and/or packaging steps. The transportation stage 1 14 may include transporting disinfectant liquid (including the mixed oxidant solution) to a point of use. The usage stage 1 16 may include vaporizing the disinfectant liquid, and supplying an effective amount of the vaporized disinfectant liquid to at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[0054] In certain embodiments, production of stabilized mixed oxidant solution may be conducted in a minimally conditioned or unconditioned environment temperature (approximately 75 °F., +/- 25°F.). In other embodiments, one or more stages (e.g., electrochemical processing 106, stabilization 1 10, output/storage 1 12, transportation 1 14, and/or usage may be performed in an air-conditioned or otherwise chilled environment.

[0055] Mixed oxidant solution components as described herein may be produced in one or more flow-through electrochemical modules. Within a flow-through electrochemical module, it is believed that a two-step oxidation process is performed. For example, if a NaCI (salt brine) solution is injected into a flow-through electrochemical module, the chloride ions are believed to undergo an initial oxidation step (e.g., to form hypochlorous acid and/or sodium hypochlorite), and the molecule(s) resulting from the initial oxidation step are believed to be further oxidized to generate the final molecule(s) of interest. Thus, if the starting solution includes hypochlorous acid and/or sodium hypochlorite in addition to or instead of salt brine, then the concentration of the final molecule(s) of interest may be enhanced.

[0056] Traditional methods for identifying and/or quantifying the specific oxidants contained in the stabilized mixed oxidant solutions (useful as components of biocides) described herein have not been successful, due at least in part to the fact that chlorine is a strong oxidant and interferes with measurement. With respect to the two streams produced by flow-through electrochemical modules as disclosed herein, the anolyte stream is believed to include two or more of the following: HOCI, CI0₂, 0₃, Cl₂, 0₂, OH⁰, and/or OH^* (as may be supplemented with hydroxide (e.g., NaOH) upon execution of the stabilization step), and the catholyte stream is believed to include two or more of the following: NaOCI, NaOH, H₂, and H₂0₂.

[0057] The starting solution creation stage 102 (for forming mixed oxidant solution) involves the creation of a solution comprising at least one of salt brine, hypochlorous acid, and sodium hypochlorite. If the starting solution comprises salt brine, such brine may be created by mixing water and any suitable one or more type of salt, resulting in dissolution of salt in water. In one embodiment, such salt may consist of or include 99.9% pure food high grade Morton® brand sodium chloride (NaCI). In other embodiments, various other types, brands, and grades of salt may be substitute. In certain embodiments, sodium chloride may be replaced or supplemented with one or more of sodium bromide, potassium chloride, potassium iodide, and calcium chloride. Substituting calcium chloride (CaCI₂) for some or all sodium chloride (NaCI) may be beneficial in certain embodiments, since the solubilized calcium ion is doubly charged in comparison to a singly charged sodium ion.

[0058] Water used to make salt brine may include municipal tap water; alternatively, highly mineralized, low mineralized, chlorinated, and/or chloraminated water may be used. In certain instances, conductivity of a salt brine solution may be in a range of from 5-50 millisiemens as measured with a conductivity meter. Salt brine solution may be subject to one or more filtering steps after creation (e.g., by flowing brine through a screen, sand bed, a diffusion bed, and/or other filtration media). Further details regarding creation of salt brine solutions are provided in U.S. Patent No. 8,366,939. [0059] In certain embodiments, a starting solution (for forming a mixed oxidant solution) may include at least one of hypochlorous acid and sodium hypochlorite, in combination with water and/or salt brine. Various methods for producing hypochlorous acid and sodium hypochlorite are known to those skilled in the art. In certain embodiments, hypochlorous acid and/or sodium hypochlorite may be manufactured at the same facility and/or in a substantially continuous process (i.e., without requiring intervening storage and/or transportation) for feeding such composition(s) to the electrochemical processing stage 106. In other embodiments, hypochlorous acid and/or sodium hypochlorite may be produced in a different facility and/or in a substantially discontinuous process relative to the electrochemical processing stage 106, whereby hypochlorous acid and/or sodium hypochlorite may be shipped to and/or stored in a facility prior to feeding of such composition(s) to the electrochemical processing stage 106.

[0060] The starting solution supply stage 104 may include blending and/or dilution of starting solution constituents. In certain embodiments, the starting solution creation stage 102 may include creation of a concentrated precursor solution that is subject to dilution with water and/or salt brine. In certain embodiments, hypochlorous acid and/or sodium hypochlorite may be blended with water and/or salt brine to form a starting solution. In certain embodiments, pH of a starting solution may be adjusted (e.g., raised or lowered) by addition of at least one acid or base. A suitable acid for addition to a starting solution may include HCI, and a suitable base for addition to a starting solution may include NaOH. Blending and/or dilution of constituents of a starting solution may be controlled responsive to one or more sensors, such as a pH sensor, a conductivity sensor, and/or one or more sensors arranged to sense chlorine content.

[0061] In certain embodiments, starting solution may be created and fed to the flow- through electrochemical processing stage 106 in a substantially continuous process (e.g., with minimal or no intervening storage). In other embodiments, one or more storage tanks may be arranged upstream of the electrochemical processing stage 106 in order to store starting solution.

[0062] The starting solution supply stage 104 preferably includes pressurization of starting solution, such as with at least one pump or other suitable apparatus. In the electrochemical processing stage 106, the oxidation and/or reduction reactions may include production of gaseous by-products (e.g., hydrogen gas, oxygen gas, chlorine gas, and/or by-products of other oxidized species). Under low pressure conditions, these gaseous molecules may appear as bubbles that might interfere with fluid flow through gas flow passages and/or contact one or more electrodes within a flow-through electrochemical processing apparatus and therefore interfere with electron flow and redox reactions. In certain embodiments, the starting solution is pressurized to a level exceeding the partial pressure of at least one gas (and more preferably exceeding partial pressure of all gases) subject to being created in a flow-through electrochemical processing apparatus and associated downstream components, thereby inhibiting formation of bubbles. Partial pressure preferably exceeds at least one of hydrogen gas, oxygen gas, chlorine gas within a flow-through electrochemical processing apparatus as described herein. Pressure within a flow-through electrochemical processing apparatus may also be adjusted (e.g., using a pressure regulator or other pressure adjusting element(s)) to an appropriate level to adjust reaction kinetics within the apparatus. A bypass line may optionally be used to help adjust pressure before starting solution reaches a pressure regulator.

[0063] In certain embodiments, temperature of starting solution may be adjusted in the starting solution supply stage 104 and/or in the electrochemical processing stage 106 in order to enhance reaction kinetics. For example, temperature of starting solution and/or temperature within a flow-through electrochemical processing apparatus may be adjusted (e.g., increased) in order to enhance the likelihood of a particular oxidation reaction, and increase the concentration of one or more desired molecules of interest.

[0064] In the electrochemical processing stage 106, at least one starting solution may be flowed through an electrochemical module including a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage. In certain embodiments, composition and concentration of starting solution flowing through the first passage and the second passage may be substantially the same (e.g., with a first portion of a starting solution passing through the first passage, and a second portion of the starting solution passing through the first passage (wherein flow rate may be substantially the same or may be substantially different between the first passage and the second passage)). In other embodiments, at least one parameter of composition and concentration of starting solution may differ between the first passage and the second passage (e.g., with a first starting solution passing through the first passage, and with a second starting solution passing through the second passage), wherein flow rate may be substantially the same or may be substantially different between the first passage and the second passage. In certain embodiments, flow of starting solution through the anode chamber may be slower than flow rate through the cathode chamber, to permit longer residence time of starting solution (electrolyte) in the anode chamber and permit an increased number of oxidation reactions.

[0065] In certain embodiments, multiple flow-through electrochemical modules as described herein may be operated fluidically in parallel.

[0066] In certain embodiments, multiple flow-through electrochemical modules as described herein may be operated fluidically in series, with anolyte solution generated by a first module being used as a starting solution for at least the anode chamber of at least one downstream module, in order to promote an increased number of oxidation reactions.

[0067] In still further embodiments, multiple flow-through electrochemical modules as described herein may be operated fluidically in series-parallel. For example, one group of two or more modules may be arranged fluidically in series, and multiple series groups may further be arranged fluidically in parallel.

[0068] A simplified schematic cross-sectional view of a flow-through electrochemical module 225 suitable for producing a mixed oxidant solution (e.g., useful as a component of a liquid disinfectant) is shown in FIG. 2. The module includes a first flow-through chamber 236 comprising an anode 230, a second flow-through chamber 238 comprising a cathode 234, and a membrane (e.g., an ion-permeable membrane) 232 arranged between the first chamber 236 and the second chamber 238. The anode 230 and cathode 234 are in electrical communication with terminals 215A, 215B, respectively. In operation, a first starting solution or first starting solution portion is supplied to the first chamber 236 through a first chamber inlet port 221 A, and a second starting solution or second starting solution portion is supplied to the second chamber 234 through a second chamber inlet port 223A. Electric power is supplied across the anode 230 and cathode 234 to electrolyze the contents of the first chamber 236 and the second chamber 238, to yield an anolyte solution that exits the first chamber 236 through a first chamber outlet port 221 B, and to yield a catholyte solution that exits the second chamber 238 through a second chamber outlet port 223B.

[0069] In certain embodiments, an anode 230 may be formed of titanium coated with a material comprising iridium, rubidium, ruthenium, and tin. In one embodiment, the coating material includes iridium content of 48% - 24%, tin content of 40% - 54%, ruthenium content of 8% - 15%, and rubidium content of 4% - 7%. In other embodiments, the anode comprises a coating of platinum and iridium. The composition of the anode may be varied based on conductivity, durability, and cost considerations. In certain embodiments, coating materials provided by Siemens may be used.

[0070] In certain embodiments, a membrane 232 may comprise a ceramic material (e.g., including, but not limited to, glass bonded ceramic materials). In certain embodiments, the membrane 232 may comprise alumina. In other embodiments, the membrane may comprise a blend of alumina and zirconia materials. Various materials can also be used for the membrane 232 depending on considerations such as porosity, insulation characteristics, durability, and cost.

[0071] In certain embodiments, a cathode 234 may comprise titanium. In other embodiments, a cathode 234 may comprise different materials. The composition of the cathode may be varied based on conductivity, durability, and cost considerations.

[0072] Geometry and dimensions of the anode 230, cathode 234, membrane 232, and chambers 236, 238 may be varied in order to provide desired performance characteristics. In certain embodiments, anode, membrane, and cathode elements may be arranged as generally flat plates. In other embodiments, anode, membrane, and cathode elements may be arranged concentrically in a generally cylindrical apparatus (e.g., such as reactor cells made available by the VIIIMT Institute in Moscow, Russia. In certain embodiments, length of flow-through chambers may be adjusted (e.g., lengthened) and/or fluid flow rate may be adjusted (e.g., reduced) to increase residence time of starting solution in the chambers and increase the likelihood of contact of ions in solution with electrode (anode or cathode) surfaces for oxidation either once, twice, or three or more times. Anode and cathode surface areas may also be adjusted by altering geometry, size, and/or surface characteristics (e.g., texturing) in order to enhance likelihood of oxidation of ions once, twice, or three or more times.

[0073] In certain embodiments, power supply components and/or electrode materials may be adjusted to allow increased power to be supplied to a flow-through electrochemical module. In an electrochemical cell, the number of oxidizing events will be related to the voltage applied (to overcome the electrochemical potential of a given molecule or atom) and the amperage through the cell (more electrons are able to flow through the cell and perform redox reactions). A given oxidation/reduction reaction will be based on both the number of interactions between solubilized molecules/atoms with a given electrode surface and the availability of electrons from the power supply (amperage).

[0074] An exemplary flow-through electrochemical module 325 is illustrated in FIG. 4. The module 325 includes a center anode 330. A membrane 332 (e.g., ceramic membrane) having an annular shape surrounds the anode 330. Beyond the membrane 332, and forming an exterior portion of the electrochemical module 325, is the exterior cathode 334. The length of the center anode 330 may be greater than the exterior cathode 334, and the membrane 332 may also be also longer than the exterior cathode 334. A first (inside) passage 336 is arranged between the center anode 330 and the membrane 332. A second (outside) outside passage 338 is arranged between the membrane 332 and the exterior cathode 334.

[0075] At the ends of the module 325 are inside collectors 322A, 322B and outside collectors 324A, 324B, such as may be formed of polytetrafluoroethylene material or another fluoropolymer material, or may be formed of polyethylene with addition of antioxidant materials. The upstream inside collector 322A receives starting solution from an inlet port 321 A and leads into the first (inside) passage 336 that supplies anolyte solution to the downstream inside collector 322B and outlet port 321 B. In a corresponding manner, the upstream outside collector 324A receives starting solution from an inlet port 323A and leads into the second (outside) passage 338 that supplies catholyte solution to the downstream outside collector 324B and outlet port 323B. In one embodiment, each port 321 A, 321 B, 323A, 323B may have female 1/8 inch national pipe thread fittings; in other embodiments, other sizes and/or types of fittings may be used (including, but not limited to, hose barb fittings).

[0076] FIG. 3 is a schematic diagram showing arrangement of a mixed oxidant solution production system 300 including multiple flow-through electrochemical modules 325A-325B (each according to the module 325 illustrated in FIG. 4) and associated components. (The mixed oxidant solution production system 300 may be operated to perform the stages of electrochemical processing 106, waste processing 108, and stabilization 1 10 as depicted in FIG. 1 ). At least one starting solution source 301 (which may include a pressure regulator (not shown)) supplies starting solution through at least one feed valve 302 arranged to supply one or more starting solutions to starting solution supply headers 307, 309 and inlet pipes 31 1 , 313A. A first inlet pipe 31 1 is arranged to supply starting solution to a flow-through anode chamber 336, and a second inlet pipe is arranged to supply starting solution to a flow-through cathode chamber 338, wherein the anode chamber and cathode chamber are separated by a membrane 332. A power supply 308 is arranged to supply electrical direct current (DC) via terminals 315, 316 arranged to apply voltage between an anode in electrical communication with the anode chamber 336 and a cathode in electrical communication with the cathode chamber 338, to electrolyze starting solution present in the flow-through electrochemical module 325. Catholyte solution generated by the cathode chamber 338 flows to an outlet pipe 313B, catholyte header 319, and needle valve 360 for subsequent neutralization (i.e., by reducing pH). Anolyte solution generated by the anode chamber 336 flows to an outlet pipe 31 1 B, anolyte header 317, and three-way valve 340 for subsequent stabilization (i.e., by increasing pH). Catholyte solution generated by each module 325 has a basic pH (e.g., typically a pH value in a range of from 9 to 12), and anolyte solution generated by each module has an acidic pH (e.g., typically a pH value in a range of from 1 to 4).

[0077] In one embodiment, ten groups of four flow-through electrochemical modules 325 (such the module 325 as illustrated in FIG. 4) may be employed, for a total of forty flow-through electrochemical modules. Each reactor cell 325 may receive 12 volts and 10 amps. Within each group, two of the four modules 325 may be wired electrically in parallel, with the two modules of each group being wired in series with another two modules in the group of four. FIG. 3 illustrates only two modules 325A-325B. In other embodiments different wiring configurations are employed, including all reactor modules 325 being operated electrically in series or in parallel.

[0078] A large number of modules 325 form a module bank that allows for the production of large quantities of mixed oxidant solution. With this number of modules 325, in one embodiment the pressure and aggregate flow rate of starting solution entering the modules may be adjusted to 5-10 psi and 1 -2 gal/minute. The number of modules used can be increased or decreased to meet production needs, and the pressure and/or flow rate of starting solution supplied to the module bank may be varied depending on factors including the number, size, and configuration of modules 325, the characteristics of the at least one starting solution, and the desired characteristics of the resulting anolyte solution.

[0079] The power supply 308 may comprise a linear unregulated unit (e.g., produced by Allen-Bradley), a linear regulated power supply, or an AC/DC/ AC/DC switching power supply. Multiple power supplies 308 can also be employed. The electric power to each module 325 from the power supply 308 can also be varied as needed. [0080] Continuing to refer to FIG. 3, the catholyte stream received from the outlet pipe 313B, catholyte header 319, and needle valve 360 flows past a pH meter 361 , a three-way valve 362, and a flow sensor 364 to reach a waste neutralization element 365 arranged to receive a flow of acid from an acid source 366 and an acid flow control valve 368. Various types of acid may be used, including but not limited to hydrochloric acid. Acid may be supplied to the neutralization element 365 (which may include a mixer, such as a flow-through mixer) responsive to signals from the pH meter 361 and flow sensor 364 to neutralize or at least partially neutralize the catholyte (e.g., preferably to a pH value in a range of from 7 to 9, or more preferably in a range of from 7 to 8) to permit disposal of the neutralized catholyte product (e.g., by directing such product to a sewer).

[0081] The anolyte stream received from the outlet pipe 31 1 B, anolyte header 317, and three-way valve 340 flows past a pH meter 341 then through a needle valve 342, a stabilization (e.g., base addition) element 344, a mixer 349, another pH meter 351 , and a flow meter 354 before flowing to an output stage 500. The stabilization element 344 is arranged to receive a flow of base (preferably one or more hydroxides, such as but not limited to sodium hydroxide, potassium hydroxide, and the like) from a base (e.g., hydroxide) source 346 and a base flow control valve 348. Base (e.g., hydroxide) may be supplied to the stabilization element 344 responsive to signals from one or both pH meters 341 , 351 and a flow sensor (not shown) to elevate pH of the anolyte from a starting acidic value (e.g., in a pH range of from 2 to about 4) to an elevated pH value in the basic range, (preferably a pH value of at least about 9.0, at least about 9.5, at least about 10.0, at least about 10.5, at least about 1 1 .0, at least about 1 1 .5, at least about 12.0, at least about 12.5, or at least about 13.0) - to yield the mixed oxidant solution.

[0082] The pH stabilization step is preferably performed a very short distance downstream of the flow-through electrochemical modules 325 to permit such stabilization to be performed immediately after anolyte production - thereby suppressing chlorine gas and minimizing degradation of mixed oxidants in the anolyte solution. Preferably, pH stabilization is performed on anolyte solution within less than about 5 seconds (more preferably within less than about 3 seconds) after anolyte exits the flow- through electrochemical modules 325.

[0083] FIG. 5 is a line chart depicting total chlorine (ppm) versus time (days) for mixed oxidant solutions produced using the system of FIG. 3. As shown in FIG. 5, chlorine content of an initially acidic anolyte solution having pH adjusted (e.g., with addition of sodium hydroxide) to a value of 7.73 degraded rapidly, from an initial chlorine value exceeding 4500 ppm to a value of approximately 1300 within 8 days. Increasing the pH of anolyte solutions resulted in enhanced stability, as shown in the data generated for pH-modified anolyte solutions having pH values of 9.1 , 10.04, 1 1 .05, and 12.09, respectively. At a pH value of 10.04, total chlorine content of a pH-modified anolyte solution diminished by less than about 10% (from a starting value of approximately 4700 ppm) after 28 days. At a pH value of 1 1 .05, total chlorine content of a pH-modified anolyte solution diminished by less than about 5% or less (from a starting value of approximately 4900 ppm) after 28 days At a pH value of 12.09, total chlorine content of a pH-modified anolyte solution was substantially unchanged after 28 days at a value of approximately 5000 ppm. FIG. 9 therefore shows that modifying pH of initially acidic anolyte to elevated pH (e.g., at least about 9.0, at least about 10.0, at least about 1 1 .0, at least about 12.0, or another intermediate value or value exceeding 12.0) beneficially improves stability of chlorine species in mixed oxidant solutions.

[0084] Referring back to FIG. 3, various elements of the system 300 may be automated and controlled via a controller 390. The flow-through electrochemical modules 325 may be periodically cleaned by suspending production of mixed oxidant solution, and circulating one or more solutions through the modules via recirculation lines 368, 369 and recirculation element 370. In certain embodiments, cleaning may involve three cycles: (a) an initial rinse cycle, (b) an acid rinse cycle, and (c) a final rinse cycle. Cleaning may be performed according to any suitable schedule, such as hourly, once every few hours, once per day, or any other suitable interval. Increased frequency of cleaning cycles is expected to enhance quality of the resulting mixed oxidant solution. An initial rinse cycle may last approximately 80 seconds, followed by an acid rinse cycle (e.g., using 0.1 to 5% hydrochloric acid (HCI)) that may last for approximately five minutes, followed by circulation of starting solution for approximately 160 seconds before the power supply 308 is reactivated for continued production of stabilized mixed oxidant solution. Timing and duration of cleaning cycles may depend on factors such as module size, flow rates, cleaning frequency, cleaning solution concentration, and desired results.

[0085] FIG. 6 is a table summarizing characteristics including total chlorine, pH, oxidation-reduction potential (ORP), conductivity, sodium ion concentration, chlorine ion concentration, and sodium/chloride ion ratio for the following five products: (1 ) 12.5% hypochlorite bleach, (2) 6% hypochlorite bleach, (3) Clearitas® mixed oxidant solution, (4) Miox™ mixed oxidant solution, and (5) a stabilized mixed oxidant solution (i.e., prior to combination with a disinfectant component to form a biocide) produced by a method as disclosed hereinabove. Various differences between the five compositions are apparent.

[0086] Relative to the stabilized mixed oxidant solution, both hypochlorite (liquid bleach) compositions have extremely high total chlorine (e.g., 37 to 90 times higher than the stabilized mixed oxidant solution), high pH, high conductivity (e.g., 7.5 times higher than the stabilized mixed oxidant solution), but lower ORP and lower ratio of sodium/chloride ion ratio. It is understood that hypochlorite (bleach) does not contain a significant number of mixed oxidants. The ability of hypochlorite to disrupt biofilms is more limited than that of the stabilized mixed oxidant solution. For example, in the context of water systems, Applicants have observed that hypochlorite (liquid bleach) has very limited ability to control deposits composed of both organic and inorganic constituents in water-containing conduits, in comparison to high efficacy in controlling deposits that is characteristic of the stabilized mixed oxidant solution.

[0087] Clearitas® mixed oxidant solution (previously sold as RE-Ox^® scale control additive) has been commercialized by the assignee of the present invention for a period of multiple years. Such solution may be produced substantially in accordance with the method described in U.S. Patent No. 8,366,939. Relative to the stabilized mixed oxidant solution, Clearitas® solution has significantly lower total chlorine (about 600 ppm versus 1550 ppm for the stabilized mixed oxidant solution), substantially lower conductivity, and substantially lower pH (i.e., 6.69 versus 9.12), but increased ORP and increased ratio of sodium/chloride ion ratio. Tests performed by the assignee of the present application confirm that a lower concentration of the stabilized mixed oxidant solution provides comparable scale control benefits to the use of Clearitas® solution at higher concentration, with the stabilized mixed oxidant solution further exhibiting significantly increased effective shelf life (e.g., on the order of at least 2-5 times greater than Clearitas® solution).

[0088] Miox™ mixed oxidant solution is typically generated at a point of use through operation of an on-site mixed oxidant production apparatus commercially available from Miox Corporation (Albuquerque, New Mexico, USA). A two-month old refrigerated sample of a mixed oxidant solution produced by a Miox mixed oxidant production apparatus (believed to have embodied an oxidant solution production method according to at least one of U.S. Patent Nos. 5,316,740 and U.S. 7,922,890) was analyzed as the basis for comparison. Relative to the stabilized mixed oxidant solution described previously herein, the Miox™ mixed oxidant solution has higher total chlorine (about 3780 versus 1550 ppm for Applicants' stabilized mixed oxidant solution), lower pH (about 9.12 versus about 10.46), higher ORP, higher conductivity, and similar sodium/chloride ion ratio.

[0089] FIG. 7 is a schematic diagram showing components of a subsystem 500 arranged to receive a stabilized mixed oxidant solution from the production system 300 of FIG. 3, and optionally blend the mixed oxidant solution component with at least one additional component (e.g., at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water) to yield a disinfectant liquid according to an embodiment of the present invention. After passage through the pH sensor 351 and flow sensor 354, a stabilized mixed oxidant solution may flow past a vent line 502 to vent any gas produced during the process. The stabilized mixed oxidant solution 350 enter a holding tank 510, where it may be monitored for quality (e.g., to confirm that the pH value desirably is at least about 9.0, at least about 9.5, at least about 10.0, at least about 10.5, at least about 1 1 .0, at least about 1 1 .5, at least about 12.0, at least about 12.5, or at least about 13.0. Titration may also be conducted (e.g., using a Hach digital titrator Method 8209 (Hach Co., Loveland, CO)) to measure the total chlorine content, to preferably yield a total chlorine value of preferably at least about 1000 ppm, or preferably at least about 2000 ppm, or preferably at least about 3000 ppm, or preferably at least about 4000 ppm, or preferably at least about 5000 ppm. In certain embodiments, the total chlorine value of the stabilized mixed oxidant solution may desirably be in a range of from about 1000 ppm to about 3500 ppm.

[0090] In certain embodiments, the stabilized mixed oxidant solution 350 may be pumped (using pump 515) to an insulated storage tank 520, wherein insulation 522 helps keep the temperature of the solution 350 consistent. A desired temperature for the solution is in a range of from 50 °F-80°F. Degradation of the mixed oxidant solution 350 depends on temperature and time, with degradation being more rapid at high temperatures (and particularly in direct sunlight). Reducing solution temperature may enhance shelf life. The anolyte solution exiting the flow-through electrochemical modules may have a temperature of approximately 100^QF. Chilling the mixed oxidant solution immediately after stabilization is believed to permit further enhanced shelf life. The storage tank 520 may optionally be refrigerated, such as by using a fluoroplastic heat exchanger constructed utilizing polyvinylidene fluoride and/or polytetrafluoroethylene materials. [0091] In certain embodiments, the stabilized mixed oxidant solution may be packaged alone in one or more containers and transported to a point of use, where it may be used for disinfection either alone or combined with one or more components (e.g., at least one of deionized water, an oxidizing biocide, and a non-oxidizing biocide).

[0092] In certain embodiments, the stabilized mixed oxidant solution may be combined with one or more components (e.g., at least one of deionized water, an oxidizing biocide, and a non-oxidizing biocide), with the resulting blended solution subject to being packaged in one or more containers and transported to a point of use. An embodiment showing the blending of stabilized mixed oxidant solution with one or more other components is shown in FIG. 7. In particular, from the storage tank 520, the stabilized mixed oxidant solution may be pumped (using pump 525) through a first flow regulating device (e.g., mass flow controller) 527 to a mixer 540, which is further arranged to receive a stream of at least one additional component 531 supplied from a component tank 530, a pump 535, and a second flow regulating device (e.g., mass flow controller) 537. Any suitable type of mixer 540 may be use, with certain embodiments preferably embodying one or more static mixer or other flow-through mixing elements to blend the mixed oxidant solution component 350 and the at least one additional component 531 to yield a disinfectant solution. The at least one additional component may include at least one of (or at least two of, or all three of) (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water. At least one sensor 542 may be arranged at or downstream of the mixer(s) 540 to sense one or more properties of the disinfectant liquid (e.g., flow rate, pH, conductivity, chlorine content, temperature, etc.). In certain embodiments, flow of the mixed oxidant solution component 350 and/or the at least one additional component 531 through the flow regulating devices 527, 537 may be controlled responsive to output signals of the at least one sensor 542. Downstream of the at least one sensor 542, the at disinfectant liquid into at least one container 545 (such as totes, barrels, tanks, or the like) that may be subsequently sealed and suitable for transport to a point of use. Suitable materials for packaging and handling disinfectant liquids as disclosed herein may include fluoroplastics, PVC, and polyethylene.

[0093] Following packaging of disinfectant liquid in one or more containers 545, such liquid is ready for the transportation 548 to a customer / point of use 550. In certain embodiments, a customer may supply the disinfectant liquid to one or more vaporizers to supply vapor for disinfection of at least one surface, equipment, volume, or enclosed space according to methods disclosed herein. [0094] The term "vapor" as used herein refers to a substance including small droplets liquid mixed with (or otherwise suspended in) air or gas, and encompasses the terms "fog" or "mist".

[0095] In certain embodiments, at least one surface, equipment, volume, or enclosed space may be disinfected by vaporizing a disinfectant liquid as described herein (e.g., including a mixed oxidant solution, and optionally including at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water), and supplying an effective amount of the resulting vaporized disinfectant liquid to the at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[0096] In certain embodiments, the disinfectant liquid may have a pH in a range of from about 7 to about 10. In certain embodiments, disinfectant solution may be diluted (e.g., with deionized water) to yield total available chlorine in a range of 600 ppm to 100 ppm, or 600 ppm to 10 ppm (measurable by either titration or estimated with DPD methods). Any subranges of the foregoing ranges as disclosed herein may alternatively be used.

[0097] In certain embodiments, at least one surface, equipment, volume, or enclosed space should be thoroughly cleaned with conventional means prior to supplying vaporized disinfectant liquid thereto, in order to reduce potential for a barrier preventing the vaporized disinfectant from acting directly on one or more surfaces to be cleaned.

[0098] In certain embodiments, a disinfectant liquid may be vaporized by traditional industrial nozzle-based fogging equipment (e.g., which may provide a vapor or mist having an average droplet size (or diameter) in a range of from 7 to 30 microns). In certain embodiments, alternative fogging devices using ultrasonic pressure waves may be used to generate vapor or mist having a smaller average droplet size or diameter (e.g., in a range of at least about 1 -2 microns). In certain embodiments, vaporization may generate droplets of disinfectant liquid having an average droplet size in a range of from 2 to 30 microns, or in a range of from 2 to 6 microns.

[0099] In certain embodiments, a vapor or fog may be generated and continuously supplied to at least one surface, equipment, volume, or enclosed space until all target surfaces thereof have a coating (e.g., at least 1 micron thickness, at least 2 micron thickness, from 1 to 6 micron thickness, from 2 to 6 micron thickness, or any other suitable thickness) coating of disinfectant solution. In an average sized hospital room, depending on the output of the vaporizer, suitably thick and uniform coating of surfaces with vaporized disinfectant solution may be completed in a time of approximately 10 to 20 minutes (or a period of at least 10 minutes). Other durations of supplying vaporized disinfectant liquid to at least one surface, equipment, volume, or enclosed space may be used. To enhance coverage and efficiency of applied vapor, in certain embodiments a vapor delivery device can be moved within or though the space during delivery, and/or multiple vapor delivery devices (or units) may be employed. To enhance circulation, in certain embodiments an air moving apparatus (e.g., fan, blower educator, or similar device) may be used to circulate air and/or vapor during (and/or after) a vapor supplying step. In certain embodiments, air (and/or vapor) may be circulated on, over, or through the at least one surface, equipment, volume, or enclosed space during or after said supplying of vaporized disinfectant liquid.

[00100] In certain embodiments, at least one surface, equipment, volume, or enclosed space to be disinfected should have an ambient temperature above freezing, and more preferably in a range of from 50 to 100 degrees F.

[00101 ] In certain embodiments, HVAC equipment in fluid communication with a space or volume to be disinfected may be deactivated or blocked (e.g., by covering or otherwise sealing air registers and return air orifices in fluid communication with the space or volume) to prevent dilution or leakage of vaporized disinfectant liquid into one or more adjacent spaces.

[00102] In other embodiments, HVAC equipment (i.e., a recirculatory heating or cooling system) may be intentionally operated while vaporized disinfectant liquid is supplied to at least one surface, equipment, volume, or enclosed space, with the HVAC equipment being useful to circulate vaporized disinfectant liquid. In certain embodiments, the recirculatory heating or cooling system includes or consists of a premises HVAC system. In certain embodiments, any air filtering device associated with the HVAC equipment should be removed prior to the supplying of vaporized disinfectant liquid to prevent disinfectant vapor from being captured by the air filtering device.

[00103] In certain embodiments, HVAC equipment associated with the at least one surface, equipment, volume, or enclosed space may be cleaned (e.g., physically cleaned) prior to administration of vaporized liquid disinfectant in order to enhance effectiveness of the vaporized liquid disinfectant treatment.

[00104] In certain embodiments, HVAC equipment (including interior surfaces thereof) may constitute the equipment being disinfected with administration of vaporized liquid disinfectant. In certain embodiments, HVAC equipment may be operated in air conditioning mode while vaporized liquid disinfectant is supplied in fluid communication with at least one return air duct of the HVAC system to cause vaporized liquid disinfectant to condense on surfaces of a condensing heat exchanger associated with the HVAC system, thereby promoting disinfection of such heat exchanger surfaces. In certain embodiments, HVAC equipment may be operated solely in a fan mode (i.e., without activation of system heating or cooling functions) while vaporized liquid disinfectant is supplied in fluid communication with at least one return air duct of the HVAC system.

[00105] In certain embodiments, at least one vaporizing apparatus configured to vaporize liquid disinfectant may be operated on a timer and/or remotely, to permit vaporized liquid disinfectant to be supplied to at least one surface, equipment, volume, or enclosed space for a specified time, and to permit the supply of vaporized liquid disinfectant to be stopped and remain off for a desired period of time (e.g., a waiting period) to permit vaporized disinfectant liquid to settle on surfaces and/or dissipate prior to re-entry of occupants into a treated space. In certain embodiments, a desirable waiting period may be in a range of from 1 to 4 hours. A treated space may be generally considered safe to re-enter when airborne concentration of liquid disinfectant vapor is below 1 ppm. In certain embodiments, one or more sensors may be arranged in or proximate to a space to be disinfected to permit conditions in the space to be monitored, and to provide indication of when the space may be safely re-entered.

[00106] In certain embodiments, at least one neutralizing agent may be supplied (e.g., in vapor form) to at least one surface, equipment, volume, or enclosed space within a predetermined time after vaporized disinfectant liquid is supplied, in order to neutralize or otherwise break down any residual disinfectant liquid remaining on surfaces thereof. In certain embodiments, a neutralizing agent may comprise (or may consist of) ascorbic acid. Other neutralizing agents may be used. In certain embodiments, a second vaporizing unit may be employed to initiate dispersal of at least one neutralizing agent a predetermined time after application of the vaporized liquid disinfectant. The at least one neutralizing agent may be employed to reduce or mitigate potentially undesired oxidizing effects on sensitive materials in the space being treated, and/or to assist in returning the space to normal condition.

[00107] In certain embodiments, a space subjected to disinfection with a vaporized liquid disinfectant as disclosed herein may be tested thereafter to determine whether the disinfection treatment was successful, or whether one or more additional treatments may be necessary. For example, in a hospital setting follow-up testing may be employed to provide added protection when sterility of an environment may be in question - such as after the discharge of one or more patients under contact precautions, when an outbreak is determined to be due to environmental contamination, or in any context in which hospital management considers it necessary to return a room or other space to a disinfected condition. A need for initial vapor disinfection treatment or additional vapor disinfection treatment may be determined by testing aerobic colony counts from samples collected from high touch sites (e.g., bedside rail, over-bed table, TV remote, bed remote, bathroom grab bar, toilet seat, or other surfaces). Comparison of initial aerobic colony counts and subsequent colony counts may also be used to evaluate efficacy of one or more vapor disinfection treatment cycles. Similar procedures may be employed in settings such as hotels, correctional facilities, and the like.

[00108] FIG. 8 is a schematic diagram showing components of a system 600 arranged to disinfect at least one surface, equipment, volume, or enclosed space by vaporizing a disinfectant liquid as disclosed herein and supplying an effective amount of the vaporized disinfectant liquid for disinfection of the at least one surface, equipment, volume, or enclosed space. The system 600 is specifically arranged to treat two rooms 61 OA, 610B in fluid communication with a premises HVAC system 640. Each room 61 OA, 610B includes interior surfaces 61 1 A, 61 1 B and an interior volume 612A, 612B in fluid communication with a return air duct 641 A, 641 B and air supply ducts (air registers) 649A1 , 649A2, 649B1 , 649B2. Each return air duct 641 A, 641 B connects to a plenum 643 arranged to route air to a blower 644 and a downstream heat exchanger element 645. A header duct 646 receives heated or cooled air from the heat exchange element 645 and conveys air to downstream ducts 648A, 648B arranged to supply conditioned (i.e., heated or cooled) air through the registers 649A1 , 649A2 to the rooms 612A, 612B.

[00109] As shown in FIG. 8, each room 612A, 612B includes a first vapor generating element 621 A, 621 B and a second vapor generating element 622A, 622B, each arranged to receive liquid from at least one associated chemical supply element 623A, 623B, 624A, 624B. Each vapor generating element 621 A, 621 B, 622A, 622B is arranged to discharge a vapor stream 625A, 625B, 626A, 626B into the volume 612A, 612B of the respective room 61 OA, 610B. Each room 612A, 612B further includes an air circulating apparatus 628A, 628B and at least one sensor 629A, 629B that may be arranged to sense one or more conditions within the respective room (e.g., to determine when it is safe to re-enter the rooms 61 OA, 61 OB). A controller 650 may be arranged control and/or receive inputs from the foregoing elements.

[00110] In certain embodiments, each vapor generating element 621 A, 621 B, 622A, 622B may be arranged to supply disinfectant vapor into the respective rooms 61 OA, 610B. In other embodiments, a first vapor generating element 621 A, 621 B in each room 61 OA, 61 OB may be arranged to generate vaporized liquid disinfectant, and a second vapor generating element in each room 61 OA, 61 OB may be arranged to generate at least one vaporized neutralizing agent to be supplied to the respective room 61 OA, 61 OB starting a specified time after the termination of supply of vaporized liquid disinfectant.

[00111 ] In certain embodiments, vaporized liquid disinfectant may be supplied to the rooms 61 OA, 61 OB while the HVAC system 640 is operated to recirculate air (and vapor) in the rooms 61 OA, 61 OB. In other embodiments, vaporized liquid disinfectant (or neutralizing agent) may be supplied to the rooms while the HVAC is not operated (and/or when the return air ducts 641 A, 641 B and air supply registers 649A1 , 649A2, 649B1 , 649B2 are blocked). In certain embodiments, the air circulating apparatuses 628A, 628B may be operated while vaporized liquid disinfectant (or while neutralizing agent) is supplied to the rooms 61 OA, 61 OB. During operation, an effective amount of vaporized disinfectant liquid is supplied to the rooms 61 OA, 61 OB for disinfection of the interior surfaces 61 1 A, 61 1 B and volumes 612A, 612B as well as any contents thereof. It is therefore apparent that the vapor disinfection system 600 may be used to disinfect the rooms 61 OA, 61 OB and/or ducts and equipment of the HVAC system 640.

[00112] Although the embodiment shown in FIG. 8 relates primarily to premises disinfection (e.g., of a residential, commercial, or institutional structure), it is to be appreciated that substantially the same system and method steps may be used to disinfect vehicles (e.g., airplanes, trains, cruise ships, emergency vehicles) of any desired type.

[00113] FIGS. 9A-9E embody line charts of luminometer relative light units (RLU) (for detection of adenosine triphosphate (ATP)) versus concentration for five different conventional disinfectants as applied to dairy waste, and FIG. 9F provides a similar line chart for a disinfectant solution as disclosed herein (including 60% mixed oxidant solution produced by a method disclosed above, blended with 40% hypochlorite solution to yield 5.25% sodium hypochlorite content in the disinfectant liquid). Each disinfectant was dosed into 100 ml of dairy waste at different dosages and allowed to sit for three minutes prior to testing ATP. The testing sequence in each instance was: Total ATP, Free ATP, Duplicate Total ATP, and Duplicate Free ATP. All four tests were performed within three minutes after the above-mentioned three minute holding time. The averages were then plotted against control values (of 9420 Total ATP, and 6741 Free ATP).

[00114] FIG. 9A is a line chart of RLU versus concentration for five different doses of a disinfectant including 25% gluteraldehyde and 12% quaternary ammonia. FIG. 9B is a line chart of RLU versus concentration for five different doses of a disinfectant including 12% gluteraldehyde and 3% quaternary ammonia). FIG. 9C is a line chart of RLU versus concentration for five different doses of a disinfectant including 25% gluteraldehyde). FIG. 9D is a line chart of RLU versus concentration for five different doses of a disinfectant including 5% chlorine dioxide produced from a mixture of Petrofid chlorite and hydrochloric acid in a 5:1 ratio). FIG. 9E is a line chart of RLU versus concentration for five different doses of a disinfectant including 5.25% sodium hypochlorite (a/k/a liquid bleach)). FIG. 9F is a line chart of RLU versus concentration for five different doses of a disinfectant liquid according to an embodiment of the present invention (including 60% mixed oxidant solution blended with 40% hypochlorite solution to yield 5.25% sodium hypochlorite).

[00115] After 22 hours, the Free and Total ATP was again measured on the 1 gallon per thousand treatments to illustrate the effect of disinfectant on ATP over time. Results of such measurements (for the disinfectants described above in connection with FIGS. 9A-9F) are contained in FIG. 9G. FIGS. 9A-9G demonstrate the relative and absolute efficacy of Applicant's disinfectant liquid in controlling a broad spectral of bacteria. Notably, Applicant's disinfectant liquid (described in connection with FIG. 9F) performed markedly better than each of 5% chlorine dioxide (of FIG. 9D) and 5.25% sodium hypochlorite (of FIG. 9F) with respect to both average total ATP and free total ATP, but without the toxicity associated with gluteraldehyde and/or quaternary ammonia (contained in the disinfectants described in connection with FIGS. 9A-9C).

[00116] Novel compositions and methods utilizing disinfectant liquids including mixed oxidant solutions for disinfecting at least one surface, equipment, volume, or enclosed space by vaporization of such have been disclosed herein, with particular utility for vaporizing the disinfectant liquids and supplying vaporized disinfectant liquid to the at least one surface, equipment, volume, or enclosed space for disinfection thereof.

[00117] Embodiments as disclosed herein may provide beneficial technical effects including enhanced disinfection treatment, extended effective shelf life, and elimination of need for on-site generation of mixed oxidant solutions. In certain embodiments, use of hazardous chemicals may be reduced or avoided altogether.

[00118] While the invention has been described herein in reference to specific aspects, features and illustrative embodiments of the invention, it will be appreciated that the utility of the invention is not thus limited, but rather extends to and encompasses numerous other variations, modifications and alternative embodiments, as will suggest themselves to those of ordinary skill in the field of the present invention, based on the disclosure herein. Various combinations and sub-combinations of the structures described herein are contemplated and will be apparent to a skilled person having knowledge of this disclosure. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein. Correspondingly, the invention as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its scope and including equivalents of the claims.

Claims

CLAIMS What is claimed is:

1 . A method for disinfecting at least one surface, equipment, volume, or enclosed space, the method comprising:

vaporizing a disinfectant liquid including a mixed oxidant solution that comprises a plurality of different oxidants, wherein the mixed oxidant solution is produced by steps comprising (A) flowing at least one starting solution including at least one of salt brine, hypochlorous acid, and sodium hypochlorite through at least one flow-through electrochemical module comprising a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage, wherein a first solution or first portion of the at least one starting solution is flowed through the first passage to form an anolyte solution having an acidic pH, and a second solution or second portion of the at least one starting solution is simultaneously flowed through the second passage to form a catholyte solution having a basic pH, and (B) contacting the anolyte solution with a hydroxide solution to attain a pH value of at least about 9.0 to yield said mixed oxidant solution; and

supplying an effective amount of the vaporized disinfectant liquid to the at least one surface, equipment, volume, or enclosed space for disinfection of the at least one surface, equipment, volume, or enclosed space.

2. The method according to claim 1 , wherein the disinfectant liquid includes deionized water, and the method further comprises diluting the mixed oxidant solution with water prior to said vaporizing.

3. The method according to claim 1 , wherein the disinfectant liquid further includes an oxidizing biocide.

4. The method according to claim 3, wherein the oxidizing biocide includes at least one of sodium hypochlorite, hydrogen peroxide, hypobromous acid, and chlorine dioxide.

5. The method according to claim 1 , wherein the disinfectant liquid further includes a non-oxidizing biocide.

6. The method according to claim 5, wherein the non-oxidizing biocide includes at least one of glutaraldehyde, quaternary ammonia, and silver nitrate.

7. The method according to claim 1 , wherein the disinfectant liquid comprises a total available chlorine value in a range of from 10 ppm to 600 ppm.

8. The method according to any one of claims 1 to 7, wherein said vaporizing generates droplets of disinfectant liquid having an average droplet size in a range of from 2 to 30 microns.

9. The method according to any one of claims 1 to 7, wherein said vaporizing generates droplets of disinfectant liquid having an average droplet size in a range of from 2 to 6 microns.

10. The method according to any one of claims 1 to 7, wherein said supplying of vaporized disinfectant liquid is performed until the at least one surface, equipment, volume, or enclosed space includes a surface coating of at least 2 microns of disinfectant liquid.

1 1 . The method according to any one of claims 1 to 7, wherein said supplying of vaporized disinfectant liquid is performed for a period of at least 10 minutes.

12. The method according to any one of claims 1 to 7, further comprising circulating air on, over, or through the at least one surface, equipment, volume, or enclosed space during said supplying of vaporized disinfectant liquid.

13. The method according to any one of claims 1 to 7, further comprising operating a recirculatory heating or cooling system associated with the at least one surface, equipment, volume, or enclosed space during said supplying of vaporized disinfectant liquid.

14. The method according to any one of claims 1 to 7, wherein the recirculatory heating or cooling system comprises a premises HVAC system.

15. The method according to any one of claims 1 to 7, further comprising: after said supplying of vaporized disinfectant liquid, waiting a predetermined period and then supplying an effective amount of vaporized neutralizing agent liquid to the at least one surface, equipment, volume, or enclosed space to substantially neutralize any deposited disinfectant liquid.

16. The method according to claim 15, wherein the neutralizing agent comprises ascorbic acid.

17. The method according to any one of claims 1 to 7, wherein said vaporizing of disinfectant liquid comprises use of an ultrasonic vaporizing apparatus.

18. The method according to any one of claims 1 to 7, wherein the mixed oxidant solution comprises at least one of the following features (a) to (c): (a) a total chlorine value of at least about 3,000 ppm; (b) an oxidation-reduction potential (ORP) value in a range of from 600 mV to 800 mV; and (c) a ratio of Na+ (in g/L according to Method EPA 300.0) to CI- (in g/L according to Method EPA 6010) of at least about 1 .5.

19. The method according to any one of claims 1 to 7, wherein the disinfectant solution comprises a pH in a range of from 7 to 10.

20. A disinfectant liquid suitable for disinfection of at least one surface, equipment, volume, or enclosed space, the disinfectant liquid comprising:

a mixed oxidant solution comprising a plurality of different oxidants produced by a method comprising flowing at least one starting solution comprising at least one of salt brine, hypochlorous acid, and sodium hypochlorite through at least one flow-through electrochemical module comprising a first passage and a second passage separated by an ion permeable membrane while electric power is applied between (i) an anode in electrical communication with the first passage and (ii) a cathode in electrical communication with the second passage, wherein a first solution or first portion of the at least one starting solution is flowed through the first passage to form an anolyte solution having an acidic pH, and a second solution or second portion of the at least one starting solution is simultaneously flowed through the second passage to form a catholyte solution having a basic pH; and contacting the anolyte solution with a hydroxide solution to attain a pH value of at least about 9.0 to yield said mixed oxidant solution; and

at least one of (a) an oxidizing biocide, (b) a non-oxidizing biocide, and (c) deionized water;

wherein the disinfectant liquid comprises a total available chlorine value in a range of from 10 ppm to 600 ppm.

21 . A disinfectant liquid according to claim 20, comprising an oxidizing biocide.

22. A disinfectant liquid according to claim 21 , wherein the oxidizing biocide includes at least one of sodium hypochlorite and hydrogen peroxide.

23. A disinfectant liquid according to claim 21 , wherein the oxidizing biocide includes at least one of hypobromous acid and chlorine dioxide.

24. A disinfectant liquid according to claim 21 , comprising a non-oxidizing biocide.

25. A disinfectant liquid according to claim 24, wherein the non-oxidizing biocide includes at least one of glutaraldehyde and quaternary ammonia.

26. A disinfectant liquid according to claim 25, wherein the non-oxidizing biocide includes silver nitrate.

27. A disinfectant liquid according to claim 20, comprising deionized water.

28. A disinfectant liquid according to any one of claims 20 to 27, wherein the mixed oxidant solution comprises at least one of the following features (a) to (c): (a) a total chlorine value of at least about 3,000 ppm; (b) an oxidation-reduction potential (ORP) value in a range of from 600 mV to 800 mV; and (c) a ratio of Na+ (in g/L according to Method EPA 300.0) to CI- (in g/L according to Method EPA 6010) of at least about 1 .5.

29. A disinfectant liquid according to any one of claims 20 to 27, comprising a total available chlorine value in a range of from 100 ppm to 600 ppm.