CWEA Advanced Water Treatment Practice Test

1-log removal corresponds to a reduction of 90% of a particular microorganism or contaminant. In water treatment, the term "log removal" is used to express how effective a treatment process is at reducing the number of pathogens in water. Each "log" represents a tenfold reduction in concentration. Therefore, a 1-log reduction means that the concentration of the pathogen is reduced by a factor of 10, which equates to 90% removal of the original amount.

This is crucial in water treatment processes where achieving high levels of pathogen removal is necessary for ensuring the safety and quality of drinking water. Higher log reductions correspond to increasingly stringent removal percentages: 2-log represents 99% removal, 3-log represents 99.9% removal, and so forth. Understanding these figures is essential for professionals in the field, as they guide the effectiveness of treatment methods used in various water treatment systems.