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Log Removal Formula:
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Log Removal (LR) is a logarithmic measure of how effectively a process reduces the concentration of contaminants or microorganisms. It's commonly used in water treatment, sterilization processes, and microbiology to quantify the efficiency of removal or inactivation.
The calculator uses the Log Removal formula:
Where:
Explanation: A 1-log reduction means 90% reduction (10% remaining), 2-log means 99% reduction (1% remaining), and so on. The logarithmic scale helps express large reductions concisely.
Details: Log removal values are critical in water treatment regulations, sterilization validation, and microbial risk assessment. They provide a standardized way to compare the effectiveness of different treatment processes.
Tips: Enter both initial and final concentrations in the same units. Values must be positive numbers, with initial concentration greater than final concentration for meaningful results.
Q1: What does a 4-log reduction mean?
A: A 4-log reduction means 99.99% reduction - only 0.01% (or 1 in 10,000) of the original concentration remains.
Q2: Can log removal be negative?
A: No, log removal should always be positive when calculated properly (initial > final). A negative value would indicate an increase in concentration.
Q3: Why use logarithmic scale instead of percentages?
A: Logarithmic scales better represent the exponential nature of microbial growth and inactivation, and can more easily express very large reductions (like 99.9999% as 6-log).
Q4: Is log removal the same as percent removal?
A: They're related but different. Percent removal = 100 × (1 - 10-LR). For example, 2-log removal = 99% removal.
Q5: What are typical log removal requirements for water treatment?
A: Regulations often require 4-log removal of viruses and 3-log removal of Giardia and Cryptosporidium in drinking water treatment.