1. What is Log Removal?

Log Removal Value (LRV) is a measure of the effectiveness of a treatment process in reducing the concentration of contaminants. It represents the logarithm (base 10) of the ratio of initial to final concentrations of a substance.

2. How Does the Calculator Work?

The calculator uses the Log Removal formula:

Where:

• \( C_0 \) — Initial concentration of contaminant (units/mL)
• \( C \) — Final concentration of contaminant (units/mL)
• \( LR \) — Log Removal Value (dimensionless)

Explanation: A 1-log reduction means 90% reduction (10 times less), 2-log means 99% reduction (100 times less), and so on.

3. Importance of Log Removal Calculation

Details: LRV is crucial in water treatment, sterilization processes, and air filtration to quantify the effectiveness of contaminant removal. It's commonly used in regulatory standards for water purification systems.

4. Using the Calculator

Tips: Enter both initial and final concentrations in the same units (typically CFU/mL for microorganisms). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What does a 4-log reduction mean?
A: A 4-log reduction means the concentration has been reduced by 99.99% (10,000 times less).

Q2: How is log removal different from percentage reduction?
A: Log removal provides a more intuitive understanding of the order of magnitude reduction, while percentage can be misleading for very high reductions.

Q3: What are typical log removal requirements for water treatment?
A: EPA requires 4-log (99.99%) removal of viruses and 3-log (99.9%) removal of Giardia in drinking water treatment.

Q4: Can log removal be negative?
A: No, if the final concentration is higher than initial, it indicates contamination rather than removal.

Q5: How precise should my concentration measurements be?
A: For accurate log removal values, measurements should be precise to at least 2 significant figures.