🚰 MLVSS Calculator
Convert measured mixed liquor suspended solids (MLSS/TSS) to volatile biomass concentration for activated sludge process control.
Fraction of MLSS that is volatile (organic) material.
How to Use This Calculator
Measure MLSS
Record mixed liquor suspended solids (mg/L) from lab analysis.
Determine volatile fraction
Use volatile suspended solids tests or historical plant data (often 0.7–0.8).
Calculate MLVSS
Multiply MLSS by the volatile fraction to estimate active biomass concentration.
Formula
MLVSS = MLSS × Volatile Fraction
Volatile fraction is the ratio of volatile suspended solids (VSS) to total suspended solids (TSS) in the mixed liquor sample.
Full Description
MLVSS represents the organic (biomass) component of mixed liquor, critical for calculating sludge age, food-to-microorganism ratio (F/M), and aeration requirements in activated sludge treatment plants.
Regularly comparing MLSS and MLVSS trends helps operators maintain healthy biological activity and respond to shock loads.
Frequently Asked Questions
What is a typical volatile fraction?
Activated sludge systems often range 0.70–0.80, but values depend on influent characteristics and sludge age.
How often should I measure VSS?
Perform at least weekly or whenever process conditions change significantly.
Can I estimate without lab data?
Use historical averages, but confirm with periodic VSS tests for accuracy.
Why is MLVSS lower than MLSS?
MLVSS excludes inorganic solids (grit, inert material) and reflects the biologically active fraction.