What percentage reduction in contaminants does a 1-Log, 2-Log, and 3-Log inactivation represent?

The concept of log inactivation is crucial in water treatment as it defines the effectiveness of a treatment process in reducing microbial contaminants. A 1-Log inactivation means that there is a 90% reduction in the number of organisms present, which means you are left with 10% of the original quantity. This aligns perfectly with the definition of 1-Log, which indicates that one order of magnitude (or ten times) is removed.

For 2-Log inactivation, the reduction is more significant, totaling a 99% decrease in contaminants. In this case, only 1% of the original organisms remain after treatment. This reduction is achieved by removing two orders of magnitude.

Lastly, 3-Log inactivation corresponds to a 99.9% reduction. After applying this level of inactivation, just 0.1% of the initial contaminants would still be present, effectively ensuring a very high level of treatment efficacy.

This systematic increase in reduction percentages—90%, 99%, and 99.9% for 1-Log, 2-Log, and 3-Log inactivation, respectively—provides a clear framework for evaluating the effectiveness of disinfection and treatment processes. Understanding this concept is essential