Method for automotive dose control of liquid treatment chemicals

• US 6,129,104 A
• Filed: 12/23/1998
• Issued: 10/10/2000
• Est. Priority Date: 12/23/1998
• Status: Expired due to Fees

• Current Assignee: Seven Trent Water Purification Incorporated Water Purification Solutions
• Original Assignee: Tetra Process Technologies Severn Trent Services Company
• Inventors: Bonazza, Joseph M., Ellard, Gregory A.
• Primary Examiner(s): Hepperle, Stephen M.
• Application Number:
  US09/219,946
• Time in Patent Office: 657 Days
• Field of Search: 137/3, 137/9, 137/93
• US Class Current: 137/3
• CPC Class Codes: C02F 2209/12 Volatile Fatty Acids (VFAs)
• CPC Class Codes: C02F 2209/15 N03-N
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: C02F 3/006 Regulation methods for biological treatment
• CPC Class Codes: C02F 3/305 characterised by the denitrification
• CPC Class Codes: G05D 21/02 characterised by the use of electric means
• CPC Class Codes: Y10T 137/0329 Mixing of plural fluids of diverse characteristics or conditions
• CPC Class Codes: Y10T 137/0363 For producing proportionate flow
• CPC Class Codes: Y10T 137/2509 By optical or chemical property

Abstract

A method for controlling the addition of liquid treatment chemicals by automatic dose control. The calculation of the amount of chemical to be dosed into the system combines signals from a liquid flow meter, an influent chemical concentration analyzer and/or an effluent chemical concentration analyzer. The signals are directed to a computerized chemical dose controller that analyzes and adjusts the data from the signals and generates an output signal that controls the chemical dosing mechanisms. For example, the automatic dose control method encompasses the ability to set maximum positive and negative limits of control action as well as the ability to automatically or manually control the reset period necessary to allow previous changes to propagate through the system and be displayed at the effluent sensor thereby improving the dosing of the chemical during treatment of a liquid, wastewater for example.

Claims

1. A method for automatic dose control of a liquid treatment chemical during a liquid treatment process within a treatment system, the system having an influent flow and an effluent flow, the method comprising:

a. measuring the liquid flow rate at a site wherein the site is selected from any one of a group of sites consisting of an influent flow site, an effluent flow site or a combination thereof, and generating a liquid flow rate signal from the measurement;

b. measuring the concentration of a chemical at a site wherein the site is an influent flow site, an effluent flow site or a combination thereof, and generating a chemical concentration signal from the measurement;

c. transmitting the signal generated from step (a) and the signal generated from step (b) to a chemical dosing controller;

d. automatically calculating the dosage of a chemical from signals supplied to the chemical dosing controller;

e. transmitting an output signal from the chemical dosing controller to a chemical feeding system, the output signal based on dosage calculated in step (d);

f. releasing the chemical from step d into influent flow in response to output signal of step (e); and

g. repeating steps (a)-(f) continuously during the liquid treatment process.

3. The method of claim 1 wherein the chemical in step (b) is the same chemical as in step (d).

4. The method of claim 1 wherein the chemical in step (b) is a different chemical from the chemical in step (d).

5. The method of claim 1 wherein the measurement of the liquid flow rate in step (a) and the concentration of the chemical in step (b) is performed continuously.

6. The method of claim 1 wherein the measurement of the liquid flow rate in step (a) is continuous and the measurement of the concentration of the chemical in step (b) is performed at intervals within a range of from a fraction of a second to approximately 15 minute intervals.

7. The method of claim 1 wherein the liquid of the liquid treatment process is water and the treatment process is a water treatment process.

2. A method for automatic dose control of a liquid treatment chemical during a liquid treatment process within a treatment system, the system having an influent flow and an effluent flow, the method comprising:

a. measuring the liquid flow rate through the treatment system and generating a liquid flow rate signal from the measurement and adjusting the liquid flow rate signal by a flow pace multiplier;

b. measuring the concentration of a chemical through the treatment system and generating a chemical concentration signal from the measurement;

c. transmitting the signal generated from step (a) and the signal generated from step (b) to a chemical dosing controller;

d. automatically calculating the dosage of a chemical from signals supplied to the chemical dosing controller;

e. transmitting an output signal from the chemical dosing controller to a chemical feeding system, the output signal based on dosage calculated in step (d);

f. releasing the chemical from step d into influent flow in response to output signal of step (e); and

g. repeating steps (a)-(f) continuously during the liquid treatment process.

8. A method for automatic dose control of nitrate-nitrogen during a water treatment process within a denitrification treatment system using a chemical source of organic carbon as the feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. measuring the water flow rate at a site wherein the site is selected from any one of a group of sites consisting of an influent flow site, an effluent flow site or a combination thereof and generating a water flow rate signal from the measurement;

b. measuring the concentration of a chemical at a site wherein the site is an influent flow site, an effluent flow site or a combination thereof, and generating a chemical concentration signal from the measurement;

c. transmitting the signal generated from step (a) and the signal generated from step (b) to a chemical dosing controller;

d. automatically adjusting the nitrate/nitrogen signal by at least one adjustable dose factor;

e. automatically calculating the dosage of the feed chemical from adjusted signals supplied to chemical dosing controller;

f. transmitting an output signal from the chemical dosing controller to a chemical feeding system, the output signal based on dosage calculated in step (e);

g. releasing the feed chemical into the influent flow in response to the output signal of step (f); and

h. repeating steps (a)-(g) continuously during the denitrification process.

9. The method of claim 8 wherein the feed chemical is selected from the group consisting of alcohol and volatile fatty acid.

10. The method of claim 9 wherein the feed chemical is methanol.

12. The method of claim 8 wherein a setpoint for effluent nitrate-nitrogen is selected, an effluent flow concentration signal is generated from the measurement of concentration of nitrate-nitrogen in the effluent flow and the concentration signal is transmitted to the chemical dosing controller.

13. The method of claim 12 wherein the difference between the effluent concentration of nitrate-nitrogen and the setpoint is calculated to generate a control response, the control response is adjusted by one or more sensitivity factors and the adjusted control response is automatically incorporated into the calculation for the dosage of the feed chemical.

11. A method for automatic dose control of nitrate-nitrogen during a water treatment process within a denitrification treatment system using a chemical source of organic carbon as the feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. measuring the water flow rate at a site wherein the site is an influent flow site, an effluent flow site or a combination thereof and generating a water flow rate signal from the measurement;

b. measuring the concentration of a chemical at a site wherein the site is selected from any one of a group of sites consisting of an influent flow site, an effluent flow site or a combination thereof, and generating a chemical concentration signal from the measurement;

c. transmitting the signal generated from step (a) and the signal generated from step (b) to a chemical dosing controller wherein the water flow rate signal of step (a) is automatically adjusted by a flow pace multiplier;

d. automatically adjusting the nitrate/nitrogen signal by at least one adjustable dose factor;

e. automatically calculating the dosage of the feed chemical from adjusted signals supplied to chemical dosing controller;

f. transmitting an output signal from the chemical dosing controller to a chemical feeding system, the output signal based on dosage calculated in step (e);

g. releasing the feed chemical into the influent flow in response to the output signal of step (f); and

h. repeating steps (a)-(g) continuously during the denitrification process.

14. A method for automatic dose control of nitrate-nitrogen during a water treatment process within a denitrification treatment system using a chemical source of organic carbon as the feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. measuring the water flow rate through the treatment system and generating a water flow rate signal from the measurement;

b. measuring the concentration of a chemical at a site wherein the site is an effluent flow site, selecting a setpoint for effluent nitrate-nitrogen and generating an effluent flow concentration signal from the measurement of concentration of nitrate-nitrogen in the effluent flow;

c. transmitting the signal generated from step (a) and the signal generated from step (b) to a chemical dosing controller;

d. calculating the difference between the effluent concentration of nitrate-nitrogen and the setpoint to generate a control response, adjusting the control response by one or more sensitivity factors and automatically incorporating the adjusted control response into the calculation for the dosage of the feed chemical wherein the dosage is used to generate a modified output sign which is transmitted from the chemical dosing controller to the chemical feeding system;

e. releasing the feed chemical into the influent flow in response to the output signal of step (f); and

h. repeating steps (a)-(e) continuously during the denitrification process.

15. The method of claim 14 wherein the modified output signal from the chemical dosing controller to the chemical feeding system is transmitted after a reset time.

16. The method of claim 15 wherein the reset time is input manually.

17. The method of claim 15 wherein the reset time is an automatically calculated variable based on the hydraulic residence time through the process and the process reaction time.

18. The method of claim 14 wherein the nitrate-nitrogen signal is automatically adjusted by at least one adjustable dose factor.

19. A method for automatic dose control of nitrate-nitrogen during a water treatment process within a denitrification treatment system using a chemical source of organic carbon as the feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. selecting a setpoint for effluent nitrate-nitrogen;

b. measuring the water flow rate at an effluent flow site, and generating a water flow rate signal from the measurement;

c. measuring the concentration of nitrate-nitrogen in the effluent flow and generating a chemical concentration signal from the measurement;

d. transmitting the signal generated from step (b) and the signal generated from step (c) to a chemical dosing controller;

e. calculating the difference between the effluent concentration of nitrate-nitrogen and the setpoint to generate a control response;

f. adjusting the control response by one or more sensitivity factors;

g. automatically calculating the dosage of the feed chemical from the control response;

h. transmitting output signal from chemical dosing controller to the chemical feeding system, the output signal based on dosage calculated in step (g);

i. releasing the feed chemical into influent flow in response to output signal of step (h); and

j. repeating steps (a)-(i) continuously during the denitrification process.

20. The method of claim 19 wherein the concentration of nitrate-nitrogen is measured in both the influent flow and the effluent flow.

21. The method of claim 20 wherein the concentration of the of nitrate-nitrogen in the influent flow is measured and an influent flow concentration signal is generated and transmitted to the chemical dosing controller.

22. A method for automatic dose control of nitrate-nitrogen during a water treatment process within a denitrification treatment system using a chemical source of organic carbon as the feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. selecting a setpoint for effluent nitrate-nitrogen;

b. measuring the water flow rate through the treatment system and generating a water flow rate signal from the measurement, wherein the water flow rate signal is adjusted by a flow pace multiplier;

c. measuring the concentration of nitrate-nitrogen at an effluent flow site and generating a chemical concentration signal from the measurement;

d. transmitting the signal generated from step (b) and the signal generated from step (c) to a chemical dosing controller;

e. calculating the difference between the effluent concentration of nitrate-nitrogen and the setpoint to generate a control response;

f. adjusting the control response by one or more sensitivity factors;

g. automatically calculating the dosage of the feed chemical from the control response;

h. transmitting output signal from chemical dosing controller to the chemical feeding system, the output signal based on dosage calculated in step (g);

i. releasing the feed chemical into influent flow in response to output signal of step (h); and

j. repeating steps (a)-(i) continuously during the denitrification process.

23. The method of claim 22 wherein the calculation of a n output signal from the chemical dosing controller to the chemical feeding system is based on water flow rate, concentration of nitrate-nitrogen in the influent flow and concentration of nitrate-nitrogen in the effluent flow.

24. The method of claim 22 wherein the calculation of succeeding control responses in step (e) is performed after a reset time.

25. The method of claim 24 wherein the reset time is input manually.

26. The method of claim 24 wherein the reset time is an automatically calculated variable based on the hydraulic residence time through the process and the process reaction time.

27. The method of claim 24 wherein a derivative control response is generated to counteract rapid rates of change towards or away from the setpoint.

28. The method of claim 27 wherein a derivative control response is generated by determining a first effluent concentration prior to the reset time, a second effluent concentration is measured at the reset time, comparing the first effluent concentration to the second effluent concentration and adjusting the control response accordingly.

29. A method for automatic dose control of a liquid treatment chemical during a treatment process within a liquid treatment system using a feed chemical, the system having an influent flow and an effluent flow, the method comprising:

a. selecting a setpoint for a chemical in the effluent flow;

b. measuring the liquid flow rate through the treatment system and generating a liquid flow rate signal from the measurement;

c. measuring the concentration of the chemical of step (a) in the influent flow and generating an influent chemical concentration signal from the measurement;

d. measuring the concentration of the chemical of step (a) in the effluent flow and generating an effluent chemical concentration signal from the measurement;

e. transmitting the signal generated from step (b) to a chemical dosing controller and generating a primary control response;

f. adjusting the primary control response by a flow pace modifier;

g. transmitting the signal generated from step (c) to a chemical dosing controller and generating a secondary control response;

h. adjusting the secondary control response by an adjustable dose factor;

i. transmitting the signal from step (d) to the chemical dosing controller and calculating the difference between the effluent chemical concentration and the setpoint to generate a tertiary control response;

j. adjusting the tertiary control response by one or more sensitivity factors;

k. continuously calculating the dosage of the feed chemical from the primary control response and secondary control response while incorporating the tertiary control response from step (f) after a reset period;

l. transmitting an output signal from chemical dosing controller to a chemical feeding system, the output signal based on dosage calculated in step (k);

m. releasing a feed chemical into influent flow in response to output signal of step (l); and

n. repeating steps (a)-(m) continuously during the treatment process.

30. The method of claim 29 wherein the chemical in step (a) is the same chemical as in step (m).

31. The method of claim 29 wherein the chemical in step (a) is a different chemical from the chemical in step (m).

32. The method of claim 29 wherein the reset time is input manually.

33. The method of claim 29 wherein the reset time is an automatically calculated variable based on the hydraulic residence time through the process and the process reaction time.