Method and apparatus for controlling concentration of water treatment chemicals

• US 7,105,095 B2
• Filed: 04/16/2004
• Issued: 09/12/2006
• Est. Priority Date: 04/17/2003
• Status: Expired due to Fees

• Current Assignee: Organo Corporation
• Original Assignee: Organo Corporation
• Inventors: Yoshikawa, Hiro, Wake, Toshiharu, Yamamura, Kiyotaka, Yano, Daisaku
• Primary Examiner(s): Hopkins, Robert A.
• Application Number:
  US10/826,675
• Publication Number:
  US 20040262233A1
• Time in Patent Office: 879 Days
• Field of Search: 210/745, 210/746, 210/739, 210/749, 210/143, 210/198.1, 436/55, 204/418
• US Class Current: 210/739
• CPC Class Codes: C02F 1/008 Control or steering systems not provided for elsewhere in subclass C02F
• CPC Class Codes: C02F 2103/023 Water in cooling circuits
• CPC Class Codes: C02F 2209/005 Processes using a programmable logic controller [PLC]
• CPC Class Codes: C02F 2209/02 Temperature
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B
• CPC Class Codes: G05D 11/138 by sensing the concentration of the mixture, e.g. measuring pH value
• CPC Class Codes: G05D 21/02 characterised by the use of electric means

Abstract

A water-soluble lithium salt is added as a tracer substance along with a water treatment chemical to water to be treated. The concentration of lithium ions is electrochemically or optically measured using a lithium ion sensitive substance, so as to perform concentration control of the water treatment chemical added to water to be treated. An ion selective electrode, ion selective field effect transistor, or ion optode may be employed to perform the electrochemical or optical measurement using a lithium ion sensitive substance.

Claims

1. A method for controlling concentration of a water treatment chemical, comprising

adding a water-soluble lithium salt as a tracer substance along with the water treatment chemical to water to be treated;

electrochemically or optically measuring concentration of lithium ions using a lithium ion sensitive substance; and

using the measured lithium ion concentration to control the concentration of the water treatment chemical added to the water to be treated.

2. A method as defined in claim 1, wherein the lithium ion concentration is measured by detecting a membrane potential indicated by a lithium ion electrode incorporating a sensitive membrane including the lithium ion sensitive substance.

3. A method as defined in claim 2, wherein the lithium ion sensitive substance is a compound denoted by chemical formula (1)

4. A method as defined in claim 2, wherein the lithium ion sensitive substance is a compound denoted by chemical formula (2)

5. A method as defined in claim 1, wherein the lithium ion concentration is measured by detecting a change in a value of current flowing in a field effect transistor incorporating the lithium ion sensitive substance.

6. A method as defined in claim 1, wherein the lithium ion concentration is measured by detecting an optical characteristic indicated by a membrane incorporating the lithium ion sensitive substance and a fluorescent or light-absorbing substance.

7. A method as defined in claim 1, wherein the water-soluble lithium salt is added so that the lithium ion concentration in the water to be treated is within the range of 0.01–

20 mg/liter.

8. An apparatus for controlling concentration of a water treatment chemical, comprising

a lithium ion sensitive substance placed in contact with water to be treated;

a transducer for converting a state of the sensitive substance into an electric or optical signal;

an arithmetic section for receiving the signal and calculating a concentration of the water treatment chemical; and

a control section for determining, based on the calculated water treatment chemical concentration, an amount of the water treatment chemical to be added to the water to be treated.

9. An apparatus as defined in claim 8, wherein

a sensitive membrane is formed including the lithium ion sensitive substance;

and

the sensitive membrane and the transducer constitute a lithium ion electrode.

10. An apparatus as defined in claim 9, wherein the lithium ion electrode includes a light-shielding cover which covers at least the sensitive membrane.

11. An apparatus as defined in claim 9, wherein lithium ion concentration within the water to be treated is measured by detecting a membrane potential indicated by the sensitive membrane.

12. An apparatus as defined in claim 8, wherein the lithium ion sensitive substance is a compound denoted by chemical formula (1)

13. An apparatus as defined in claim 8, wherein the lithium ion sensitive substance is a compound denoted by chemical formula (2)

14. An apparatus as defined in claim 8, wherein lithium ion concentration is measured by detecting a change in a value of current flowing in a field effect transistor incorporating the lithium ion sensitive substance.

15. An apparatus as defined in claim 8, wherein lithium ion concentration is measured by detecting an optical characteristic indicated by a membrane incorporating the lithium ion sensitive substance and a fluorescent or light-absorbing substance.