1. What is Log Removal?

Log Removal (LR) is a measure of the effectiveness of a disinfection or purification process in reducing the concentration of contaminants. It represents the logarithm (base 10) of the ratio of initial to final concentrations.

2. How Does the Calculator Work?

The calculator uses the Log Removal formula:

Where:

• \( LR \) — Log removal (dimensionless)
• \( C_0 \) — Initial concentration (units/mL)
• \( C \) — Final concentration (units/mL)

Explanation: A 1-log reduction means the concentration is reduced by 90%, 2-log by 99%, 3-log by 99.9%, and so on.

3. Importance of Log Removal Calculation

Details: Log removal values are critical in water treatment, food processing, and pharmaceutical manufacturing to ensure adequate pathogen reduction and regulatory compliance.

4. Using the Calculator

Tips: Enter both initial and final concentrations in the same units. Both values must be positive numbers, with initial concentration greater than final concentration.

5. Frequently Asked Questions (FAQ)

Q1: What does 4-log removal mean?
A: 4-log removal means a 99.99% reduction in contaminant concentration (10,000 times reduction).

Q2: How is log removal different from percentage reduction?
A: Log removal provides a more precise measurement of effectiveness, especially for very high reductions where percentages become less meaningful.

Q3: What are typical log removal requirements for water treatment?
A: US EPA requires 4-log removal of viruses and 3-log removal of Giardia and Cryptosporidium in drinking water treatment.

Q4: Can log removal be negative?
A: No, log removal should always be positive when calculated properly (C₀ > C). If C > C₀, it indicates concentration increase, not removal.

Q5: How is log removal verified in practice?
A: Through challenge testing with surrogate organisms or direct measurement of pathogen concentrations before and after treatment.