CT - Math Toolbox function returns the CT Required for Inactivation of Giardia Cysts for a given Disinfectant, Log Inactivation, Temperature, pH, and Disinfectant Residual from the EPA lookup tables.
CT(InactivationOf, Disinfectant, LogInactivation, Temp, pH, Cl2)
InactivationOf – Set 1 for Giardia or 2 for Viruses.
Disinfectant – Set to a number based on the following (i.e. set to 1 for Free Chlorine)
1 - Free Chlorine
2 - Chlorine Dioxide
3 - Chloramine
4 - Ozone
Log Inactivation - .5, 1, 1.5, 2, 2.5,3, or 4 (4 only applies to inactivation of Viruses)
Temperature – Water Temperature in Deg C
pH – pH of the water (only required for Inactivation of Giardia by Free Chlorine)
Cl2 – Chlorine Residual at end of disinfection segment in mg/L. Only used for Inactivation of Giardia by Free Chlorine, for all other lookups use -1 to indicate not used.
=CT(1,1,2,15,7.5,1) returns 60 from EPA CT Table C-4.
=CT(1,2,3,15,7.5,-1) returns 19 from EPA Table C-8. CT Required for 3 Log Inactivation of Giardia (1) by Chlorine Dioxide (2) at 15 Deg C with a pH between 6 and 9 (7.5).
Handling of Temperatures above 25:
Calculate the 0.5 log inactivation of Giardia Cysts by Ozone from EPA Table C-12 with a temperature of 30 Deg C. Option 1, set temperature to 25 and return the CT Required for 0.5 and temp of 25:
where V13105 is the Temperature in Deg C.
For Texas, based on rg-211 manual states "For temperatures above 25°C, CTrequired drops by a factor of two for each 10°C rise in temperature—that is, the CTrequired at 30°C is one-half the CTrequired at 20°C." This can be accomplished with the following equation. Note, the 0.08 is the CTrequired for 0.5 @ 25 Deg C.
where V13105 is the Temperature in Deg C
0.08 is the CTrequired for 0.5 @ 25 Deg C
SEE ALSO: CTR3LGC, CT Tables, Calculating CT in WIMS