Drinking Water 

CT Compliance Calculation Program

CT Compliance Software Available 2009

The Engineering Section has developed two software programs available to use for determining compliance with CT requirements of the Surface Water Treatment and Ground Water Rules.

The first is an older software program developed in the 1990’s to calculate the required CT value or the percent of the required CT value achieved from 0.5 to 3.0-log Giardia cyst inactivation for all approved disinfectants. It also calculates CT values from 2.0 to 4.0-log for virus inactivation using ozone, chlorine dioxide and chloramines. This program is in the form of an executable file (Ctcom.exe ). This is a stand-alone program that should be usable on operating systems ranging from DOS, Windows 3.11, Windows 95, 98, 2000 and XP. Windows Vista and Windows 7 users may experience problems running this program and are recommended to use the Excel program file below.

The current software program was developed in 2009 for the purposes of including all CT values up to 3.0-log Giardia Cyst and 4.0-log Virus inactivation for all approved disinfectants as well as up to 4.0-log Cryptosporidium Oocyst for Ozone and Chlorine Dioxide. It is more versatile and allows for multiple segments of a treatment plant to be used in the calculations. This program is available in the form of an (Office 2003) Excel spreadsheet file ( CT-TableCalc.xls ) and requires use of Microsoft Excel or other program capable of running *.XLS files.

Both programs use interpolated CT table data as published in the Surface Water Treatment Rule and Guidance Manual and do not use an empirical formula to estimate CT values. The data obtained with the programs should match data from manually checking the CT tables.

CT-TableCalc V1.xls