Chemical injection and control system and method for controlling chloramines

1. A method of automatically controlling chloramine concentration in a body of water contained in a reservoir, the method comprising:

a) determining residual chloramine concentration in a first water sample obtained from the body of water;

b) automatically engaging a supply of chlorine to add chlorine to the body of water when:

i) the residual chloramine concentration in the first water sample is determined to be below a pre-determined residual chloramine concentration set-point; or

ii) the residual chloramine concentration in the first water sample is determined to be below a first chloramine concentration percentage of a pre-determined residual chloramine concentration set-point;

c) determining residual chloramine concentration in a second water sample obtained from the body of water after step b); and

d) automatically engaging a supply of ammonia and the supply of chlorine to add both ammonia and chlorine to the body of water if:

i) the residual chloramine concentration in the second water sample is determined to be below the residual chloramine concentration in the first water sample; or

ii) the residual chloramine concentration in the second water sample is determined to be below a second chloramine concentration percentage of the pre-determined residual chloramine concentration set-point,

wherein steps a) through d) form at least a portion of a first water treatment cycle, and wherein the method comprises a subsequent water treatment cycle that is different from the first water treatment cycle,

wherein a controller, in operable communication with an analyzer and one or more computer-readable storage mediums containing programming instructions, automatically executes steps a)-d) of the first water treatment cycle and the steps in the subsequent water treatment cycle that is different from the first water treatment cycle, and

wherein the programming instructions comprise algorithm X or algorithm XI for causing the controller to add chlorine and ammonia in the subsequent water treatment cycle:

Algorithm X: y′<x′=add chlorine and ammonia, where y′ is the residual chloramine concentration determined in the first water sample of the subsequent treatment cycle and x′ is the residual chloramine concentration set-point; or

Algorithm XI: y′<[(a′)(x′)]=add chlorine and ammonia, where y′ is the residual chloramine concentration determined in the first water sample of the subsequent treatment cycle, a′ is a percentage selected within a range of 99% to 80%, and x′ is the residual chloramine concentration set-point.

2. The method of claim 1 , wherein after the first treatment cycle is completed, the method comprises engaging only a supply of chlorine, or engaging only a supply of both chlorine and ammonia together, to reestablish a predetermined chloramine concentration level in the subsequent water treatment cycle.

3. The method of claim 1 , wherein after the first water treatment cycle is completed the method comprises engaging a supply of both chlorine and ammonia to the body of water at a weight ratio of chlorine to ammonia of 5:1 or less in the subsequent water treatment cycle when the residual chloramine concentration in a water sample is determined to be below the predetermined chloramine concentration level.

4. The method of claim 1 , wherein the supply of chlorine is added to the body of water in step b) when (i) the residual chloramine concentration in the first water sample is determined to be below the pre-determined residual chloramine concentration set-point, and

wherein the supply of chlorine and the supply of ammonia are both added to the body of water in step d) when (i) the residual chloramine concentration in the second water sample is determined to be below the residual chloramine concentration in the first water sample.

5. The method of claim 1 , wherein the supply of chlorine is added to the body of water in step b) when (i) the residual chloramine concentration in the first water sample is determined to be below the pre-determined residual chloramine concentration set-point, and

wherein the supply of chlorine and the supply of ammonia are both added to the body of water in step d) when (ii) the residual chloramine concentration in the second water sample is determined to be below the second chloramine concentration percentage of the pre-determined residual chloramine concentration set-point.

6. The method of claim 1 , wherein the supply of chlorine is added to the body of water in step b) when (ii) the residual chloramine concentration in the first water sample is determined to be below the first chloramine concentration percentage of the pre-determined residual chloramine concentration set-point, and

wherein the supply of chlorine and the supply of ammonia are both added to the body of water in step d) when (i) the residual chloramine concentration in the second water sample is determined to be below the residual chloramine concentration in the first water sample.

7. The method of claim 1 , wherein the supply of chlorine is added to the body of water in step b) when (ii) the residual chloramine concentration in the first water sample is determined to be below the first chloramine concentration percentage of the pre-determined residual chloramine concentration set-point, and

wherein the supply of chlorine and the supply of ammonia are both added to the body of water in step d) when (ii) the residual chloramine concentration in the second water sample is determined to be below the second chloramine concentration percentage of the pre-determined residual chloramine concentration set-point.

8. The method of claim 1 , wherein, if the residual chloramine concentration in the second water sample is determined to be at or above the residual chloramine concentration in the first water sample but below the pre-determined residual chloramine concentration set-point, the addition of chlorine only to the body of water is maintained.

9. The method of claim 1 , wherein, if the residual chloramine concentration in the second water sample is determined to be at or above the pre-determined residual chloramine concentration set-point, the supply of chlorine to the body of water is stopped.

10. The method of claim 1 , wherein the supply of chlorine and the supply of ammonia are added to the body of water during step d) until a subsequently obtained water sample is determined to be at or above the pre-determined residual chloramine concentration set-point.

11. The method of claim 1 , wherein at least one of the first chloramine concentration percentage and the second chloramine concentration percentage is a percentage selected within a range of about 99% to about 80% of the pre-determined residual chloramine concentration set-point, provided that the first chloramine concentration percentage is higher than the second chloramine concentration percentage when both the first and second chloramine concentration percentages are utilized to control the chloramine concentration.

12. The method of claim 1 , wherein a feed rate of at least one of the chlorine and ammonia are determined by reservoir water volume and dwell time.

13. The method of claim 1 , wherein, if it is determined that the body of water has a residual chloramine concentration at or above the pre-determined residual chloramine concentration set-point after step b) or step d), the method further comprises:

e) determining residual chloramine concentration in a subsequent water sample obtained from the body of water; and

f) automatically engaging the supply of ammonia and the supply of chlorine to add both ammonia and chlorine to the body of water if:

i) the residual chloramine concentration in the subsequent water sample is determined to be below the pre-determined residual chloramine concentration set-point; or

ii) the residual chloramine concentration in the subsequent water sample is determined to be below a third chloramine concentration percentage of the pre-determined residual chloramine concentration set-point.

14. The method of claim 1 , wherein determining the residual chloramine concentration in the first and second water samples comprises measuring a total chlorine concentration in the first and second water samples.

15. A treatment delivery system for automatically controlling chloramine concentration in a body of water contained in a reservoir comprising:

a chemical dosing assembly at least partially submerged in the body of water;

a water sampling assembly configured to extract at least a first and second water sample from the body of water at different points in time;

an analyzer in fluid communication with the water sampling assembly and configured to determine residual chloramine concentration in the first and second water samples;

a controller in operable communication with the analyzer; and

one or more computer-readable storage mediums in operable communication with the controller and containing programming instructions that, when executed, cause the controller to:

a) determine whether the residual chloramine concentration in the first water sample obtained from the body of water is below a pre-determined residual chloramine concentration set-point or below a first chloramine concentration percentage of a pre-determined residual chloramine concentration set-point;

b) engage the chemical dosing assembly to add chlorine to the body of water when:

i) the residual chloramine concentration in the first water sample is determined to be below the pre-determined residual chloramine concentration set-point; or

ii) the residual chloramine concentration in the first water sample is determined to be below the first chloramine concentration percentage of the pre-determined residual chloramine concentration set-point;

c) determine whether the residual chloramine concentration in the second water sample obtained from the body of water after step b) is below the residual chloramine concentration in the first water sample or below a second chloramine concentration percentage of the pre-determined residual chloramine concentration set-point; and

d) engage a supply of chlorine and a supply of ammonia to add both ammonia and chlorine to the body of water if:

i) the residual chloramine concentration in the second water sample is determined to be below the residual chloramine concentration in the first water sample; or

ii) the residual chloramine concentration in the second water sample is determined to be below the second chloramine concentration percentage of the pre-determined residual chloramine concentration set-point,

wherein steps a) through d) form at least a portion of a first water treatment cycle, and wherein the one or more computer-readable storage mediums in operable communication with the controller contain additional programming instructions that, when executed, cause the controller to conduct a subsequent water treatment cycle that is different from the first water treatment cycle, and

wherein the programming instructions comprise algorithm X or algorithm XI for causing the controller to add chlorine and ammonia in the subsequent water treatment cycle:

Algorithm X: y′<x′=add chlorine and ammonia, where y′ is the residual chloramine concentration determined in the first water sample of the subsequent treatment cycle and x′ is the residual chloramine concentration set-point; or

Algorithm XI: y′<[(a′)(x′)]=add chlorine and ammonia, where y′ is the residual chloramine concentration determined in the first water sample of the subsequent treatment cycle, a′ is a percentage selected within a range of 99% to 80%, and x′ is the residual chloramine concentration set-point.

16. The system of claim 15 , wherein the water sampling assembly is a component of the chemical dosing assembly.

17. The system of claim 15 , wherein the analyzer comprises a total chlorine analyzer.

18. The system of claim 16 , wherein the chemical dosing assembly further comprises a water motive tube positioned below a release point of at least one chemical treatment flow tube.

19. The system of claim 18 , wherein the chemical dosing assembly further comprises a second chemical treatment flow tube and wherein the water motive tube is positioned below a release point of the second chemical treatment flow tube.

20. The system of claim 19 , wherein the first and second chemical treatment flow tubes are configured to deliver the chlorine and optionally the ammonia to an area above a release point of the water motive tube to form a high energy mixing zone.