# US 2021/0239673 A1 · Apparatus for measuring water hardness using ion selective electrode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0239673 A1 - Document ID: US20210239673A1 - Status: Published application - Kind: A1 - Application number: 17/235,136 - Filed: 2021-04-20 - Published: 2021-08-05 - Earliest claimed: 2018-03-29 - Assignees: Ecowater Systems, Inc. - Applicants: Ecowater Systems LLC - Inventors: Malcolm Kahn; Robert Astle; Jeffrey Zimmerman; Ravi Meruva - Web page: https://patentgrep.com/patent/US20210239673A1 ## CPC - G01N 33/1853: {Hardness of water} - C02F 1/42: by ion-exchange (ion-exchange in general B01J) - G01N 27/333: Ion-selective electrodes or membranes (glass electrodes G01N27/36) - G01N 27/3335: {the membrane containing at least one organic component (G01N27/3271 takes precedence; aspects concerning the enzyme reagent in enzyme electrodes C12Q1/001)} - G01N 33/1813: {Specific cations in water, e.g. heavy metals} - G01N 33/1893: {using flow cells} - C02F 2209/055: Hardness - C02F 2303/16: Regeneration of sorbents, filters - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) ## Abstract An apparatus for determining total hardness in a fluid stream utilizing an ion exchange column in a monovalent cationic form having an inlet and an outlet, where one or more monovalent ion selective electrodes are positioned either at an inlet, outlet, or at both locations simultaneously. The monovalent cation selective electrodes are in electrical communication with one another, and in fluid communication with one or more valves incorporated within a fluid path in order to introduce feed water/softened water to the monovalent cation selective electrodes. Additionally, one blending valve may be incorporated in the ion exchange column to allow a fraction of the feed (hard) water to mix with a fraction of the softened water. In this manner, the blending valve may be utilized to adjust the hardness of the water at the output. ## Claims ### Claim 1 A cassette for measuring the total hardness in a fluid stream, comprising: a housing; an ion exchange column or vessel in a monovalent cationic form, the ion exchange column or vessel having an inlet and an outlet separately disposed and extending through the housing; and a monovalent cation selective electrode positioned within the housing at said inlet or said outlet, said monovalent cation selective electrode capable of measuring monovalent cation activity, quantity, or concentration in a fluid stream; wherein hard water flows through the housing via the inlet and outlet to be measured by the monovalent cation selective electrode. ### Claim 2 (depends on 1) The cassette of claim 1 wherein said monovalent cation selective electrode is coupled to a reference electrode. ### Claim 3 (depends on 1) The cassette of claim 1 wherein said monovalent cation selective electrode is configured to measure sodium ions (Na+). ### Claim 4 (depends on 1) The cassette of claim 1 including an internal filling solution within which said monovalent cation selective electrode is encased. ### Claim 5 (depends on 1) The cassette of claim 1 including an ion selective membrane shaped in tubular form to create a 360 degree engagement with a fluid sample flowing therethrough. ### Claim 6 An apparatus for determining hardness in water, said apparatus comprising: a first sodium ISE sensor coupled with a first reference electrode, said first sodium ISE sensor configured to receive hard water; a second sodium ISE sensor coupled with a second reference electrode, said second sodium ISE sensor in electrical communication with said first sodium ISE sensor, and configured to receive soft water; said first and second reference electrodes having a salt bridge therebetween; and at least one drain to receive outflow from effluent fluid from said first and second sodium ISE sensors. ### Claim 7 (depends on 6) The apparatus of claim 6 including; a valve disposed at an outflow path of said first sodium ISE sensor; and a drain in fluid communication with said valve. ### Claim 8 An apparatus for determining hardness in water, said apparatus comprising: a first sodium ISE sensor coupled with a first reference electrode, said first sodium ISE sensor configured to receive a standardized sodium solution; a second sodium ISE sensor coupled with a second reference electrode, said second sodium ISE sensor in electrical communication with said first sodium ISE sensor, and configured to receive hard water; said first and second reference electrodes having a salt bridge therebetween; a third sodium ISE sensor configured to receive soft water with exchanged sodium; and at least one drain to receive outflow from effluent fluid from said second and third sodium ISE sensors. ### Claim 9 An apparatus for measuring the total hardness in water of a water softener, comprising: a housing; an ion exchange column or vessel in a monovalent cationic form, the ion exchange column or vessel having an inlet and an outlet separately disposed and extending through the housing; a monovalent cation selective electrode positioned within the housing at said inlet or said outlet, said monovalent cation selective electrode capable of measuring monovalent cation activity, quantity, or concentration in the water; and a valve for receiving the water from said inlet and/or said outlet; wherein hard water flows through the water softener via the inlet and outlet to be measured by the monovalent cation selective electrode, and said electrode provides an electrical signal commensurate with the amount cation concentration measured at said inlet and at said outlet to provide for a differential measurement of these values in order to ascertain the amount of cation being generated by said softener. ### Claim 10 (depends on 9) The apparatus of claim 9 wherein said differential measurement relates to a remaining capacity of said softener to capture and/or exchange hardness ions. ### Claim 11 (depends on 9) The apparatus of claim 9 wherein said monovalent cation selective electrode is capable of measuring ionic species that will affect capacity of said softener, including iron that permanently exchanges in a cation resin bed in said softener. ### Claim 12 (depends on 9) The apparatus of claim 9 wherein the amount of cation concentration measured at said outlet is a measure of an amount of said cation in said water, such that said apparatus includes a bypass control to allow unsoftened water to be blended to reduce the amount of cation in the water, or to regulate the amount of hardness in the output.