Pick an organism in each column. Physical removal bars show the log credit a filtration process earns. Disinfection rows show the CT (or UV dose) needed to hit your log target at the selected water temperature, and where that dose falls between practical and impractical.
BC's 4-3-2-1-0 objective
British Columbia's Ministry of Health sets one simple goal for drinking water drawn from lakes, rivers and creeks. Each number is one rule. The chart below checks the first two.
- 4
log of viruses
Kill 99.99% of viruses. This must be inactivation, by chlorine, UV or ozone. Filters can't be counted on to catch something this small.
Viruses column - 3
log of protozoa
Remove or kill 99.9% of Giardia and Cryptosporidium. Filtration, UV and ozone can all count toward it. Chlorine barely touches Cryptosporidium.
Protozoa column - 2
treatment processes
At least two separate barriers, such as filtration plus chlorine, or UV plus chlorine. If one fails, the other still protects people.
Pair processes - 1
NTU of turbidity
Treated water at 1 NTU or less, aiming for 0.1. Cloudy water shields pathogens from disinfection and hides failing filters.
Check your turbidimeter - 0
coliforms
No total coliforms and no E. coli in treated water samples. This is the result that shows the other four are working.
Check your lab results