WASTEWATER TREATMENT SYSTEM

• US 20130213895A1
• Filed: 02/21/2012
• Published: 08/22/2013
• Est. Priority Date: 02/21/2012
• Status: Active Grant

• Current Assignee: Denny Allen Criswell
• Original Assignee: Denny Allen Criswell
• Inventors: CRISWELL, Denny Allen
• Granted Patent: US 9,682,872 B2
• Time in Patent Office: Days
• US Class Current: 210/709
• CPC Class Codes: B01D 21/01 using flocculating agents for purifying water C02F1/52; for liquid radioactive waste G21F9/10
• CPC Class Codes: B01D 21/32 Density control of clear liquid or sediment, e.g. optical control ; Control of physical properties
• CPC Class Codes: B03D 1/028 Control and monitoring of flotation processes; computer models therefor
• CPC Class Codes: B03D 1/1431 Dissolved air flotation machines
• CPC Class Codes: C02F 1/008 Control or steering systems not provided for elsewhere in subclass C02F
• CPC Class Codes: C02F 1/24 by flotation C02F1/465 takes precedence
• CPC Class Codes: C02F 1/5209 Regulation methods for flocculation or precipitation
• CPC Class Codes: C02F 1/5245 using basic salts, e.g. of aluminium and iron
• CPC Class Codes: C02F 1/56 Macromolecular compounds
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2209/003 Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
• CPC Class Codes: C02F 2209/005 Processes using a programmable logic controller [PLC]
• CPC Class Codes: C02F 2209/006 comprising a software program or a logic diagram
• CPC Class Codes: C02F 2209/06 pH
• CPC Class Codes: C02F 2209/10 Solids, e.g. total solids [TS], total suspended solids [TSS] or volatile solids [VS]
• CPC Class Codes: C02F 2209/11 Turbidity
• CPC Class Codes: C02F 2209/40 Liquid flow rate

Abstract

A system for treating a wastewater stream produces an effluent having an acceptable level of turbidity. A PID controller is operatively coupled to at least one turbidity meter for monitoring turbidity of the effluent stream. A plurality of chemical treatment additive pumps are provided for adding a plurality of treatment chemicals to the wastewater stream in real time under supervision of the controller, and responsive to monitored turbidity.

Claims

1. A system for treating a wastewater stream to produce an effluent stream, comprising:

a plurality of pumps for supplying a plurality of chemical additives at variable flow rates to said wastewater stream at a plurality of points;

at least one total suspended solids sensor disposed in said wastewater stream downstream of said chemical additives for monitoring the clarity of said wastewater stream; and

a proportional-integral-derivative (PID) for monitoring said flow rate of said wastewater and varying the flow rates of said chemical additives proportionally based upon an algorithm employing each of a proportional term, a derivative term, wherein the PID is configured to set the derivative term for a rapid response dosing scheme, achieved with a predetermined gain in a derivative loop, without over dosing due to an over-shoot; and

an integral term, wherein the PID is configured to set the integral term to achieve a desired effluent quality, the value of which is pre-set, in the fastest time possible;

wherein, based upon turbidity measurements made by said at least one sensor, said controller continually and in real time makes chemical adjustments to the system to keep the effluent in a predetermined and set range.

2. The system of claim 1, comprising:

at least one coagulant pump having a variable flow rate for delivering a coagulant to said wastewater stream; and

at least one polymer pump having a variable flow rate for delivering a polymer to said wastewater stream.

3. The system of claim 1, comprising:

a second total suspended solids sensor disposed in said effluent stream for monitoring the clarity of said effluent.

4. The system of claim 3, comprising:

an output from said second total suspended solids sensor representative of effluent clarity operatively coupled to an input of said controller, wherein an output exceeding a predetermined threshold causes said controller to change the chemical dosing.

5. The system of claim 1, comprising:

a plurality of points of chemical injection through which said wastewater stream is passed, wherein said chemical additives are supplied to said system through said points of chemical injection.

6. The system of claim 5, wherein said first total suspended solids sensor is disposed downstream of a plurality of flocculent tubes.

7. The system of claim 1, comprising:

at least one pH meter in fluid communication with said wastewater stream having an output representative of the pH of said wastewater stream operatively coupled to said controller; and

at least one pH additive delivery pump for supplying an acidic or alkaline solution to said wastewater stream responsive to said pH meter.

8. The system of claim 1, comprising:

an automatic cleaning system for said sensor, comprising a clean water source, and a chemical addition system on a timer that interfaces with said PID.

9. The system of claim 1, wherein said PID is set to meet a performance, costing, or a combination of performance and costing objectives;

wherein said PID controller is set with a high gain for said proportional and integral terms to insure a quick and thorough response to an elevation in contamination in an effluent, providing an acceptable level of chemical over-shooting where compliance is required; and

wherein said PID is set with lower values for the proportional and integral terms and a higher gain for the derivative terms, providing a less responsive system that minimizes chemical over-shooting where maximum cost efficiency is required.

10. The system of claim 1, wherein gain for said integral term is set at a highest value possible for quickest system recovery to return water quality to an acceptable level for discharge in a shortest time possible;

wherein a large amount of variation in contaminant loading requires a higher gain in the integral term to accommodate loading swings; and

wherein a low amount of variation in contaminant loading requires a lower gain in the integral term.

11. The system of claim 1, wherein gain for the derivative term is set at a highest value possible to ensure a lowest chemical over-shoot;

wherein a small amount of variation in contaminant levels requires a higher gain value in the derivative term to provide small changes in chemical necessary dosages with a minimal amount of over-shooting; and

wherein a large amount of variation in levels of contamination requires a smaller gain in the derivative term to provide a quick recovery back to a desired set point;

wherein said set point is that which provides a desired water quality for a concentration of contaminants being treated.

12. A method for treating a wastewater stream to produce an effluent stream, comprising:

providing a plurality of pumps for supplying a plurality of chemical additives at variable flow rates to said wastewater stream at a plurality of points;

providing at least one total suspended solids sensor disposed in said wastewater stream downstream of said chemical additives for monitoring the clarity of said wastewater stream; and

using a proportional-integral-derivative (PID) for monitoring said flow rate of said wastewater and varying the flow rates of said chemical additives proportionally based upon an algorithm employing each of a proportional term, a derivative term, wherein the PID is configured to set the derivative term for a rapid response dosing scheme, achieved with a predetermined gain in a derivative loop, without over dosing due to an over-shoot; and

an integral term, wherein the PID is configured to set the integral term to achieve a desired effluent quality, the value of which is pre-set, in the fastest time possible;

wherein, based upon turbidity measurements made by said at least one sensor, said controller continually and in real time makes chemical adjustments to the system to keep the effluent in a predetermined and set range.

13. The method of claim 12, comprising:

providing at least one coagulant pump having a variable flow rate for delivering a coagulant to said wastewater stream; and

providing at least one polymer pump having a variable flow rate for delivering a polymer to said wastewater stream.

14. The method of claim 12, comprising:

providing a second total suspended solids sensor disposed in said effluent stream for monitoring the clarity of said effluent.

15. The method of claim 14, comprising:

providing an output from said second total suspended solids sensor representative of effluent clarity operatively coupled to an input of said controller, wherein an output exceeding a predetermined threshold causes said controller to change the chemical dosing.

16. The method of claim 12, comprising:

providing a plurality of points of chemical injection through which said wastewater stream is passed, wherein said chemical additives are supplied to said system through said points of chemical injection.

17. The method of claim 16, wherein said first total suspended solids sensor is disposed downstream of a plurality of flocculent tubes.

18. The method of claim 12, comprising:

providing at least one pH meter in fluid communication with said wastewater stream having an output representative of the pH of said wastewater stream operatively coupled to said controller; and

providing at least one pH additive delivery pump for supplying an acidic or alkaline solution to said wastewater stream responsive to said pH meter.

19. The method of claim 12, comprising:

providing an automatic cleaning system for said sensor, comprising a clean water source, and a chemical addition system on a timer that interfaces with said PID.

20. The method of claim 12, further comprising:

setting said PID to meet a performance, costing, or a combination of performance and costing objectives;

wherein said PID controller is set with a high gain for said proportional and integral terms to insure a quick and thorough response to an elevation in contamination in an effluent, providing an acceptable level of chemical over-shooting where compliance is required; and

wherein said PID is set with lower values for the proportional and integral terms and a higher gain for the derivative terms, providing a less responsive system that minimizes chemical over-shooting where maximum cost efficiency is required.

21. The method of claim 12, further comprising:

setting gain for said integral term at a highest value possible for quickest system recovery to return water quality to an acceptable level for discharge in a shortest time possible;

wherein a large amount of variation in contaminant loading requires a higher gain in the integral term to accommodate loading swings; and

wherein a low amount of variation in contaminant loading requires a lower gain in the integral term.

22. The method of claim 12, further comprising:

setting gain for the derivative term at a highest value possible to ensure a lowest chemical over-shoot;

wherein a small amount of variation in contaminant levels requires a higher gain value in the derivative term to provide small changes in chemical necessary dosages with a minimal amount of over-shooting; and

wherein a large amount of variation in levels of contamination requires a smaller gain in the derivative term to provide a quick recovery back to a desired set point;

wherein said set point is that which provides a desired water quality for a concentration of contaminants being treated.