Biology & Life Science

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MLVSS Calculator.

Calculate mixed liquor volatile suspended solids from measured TSS concentration and an entered volatile fraction.

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MLVSS concentration: 2,100 mg/L

MLVSS concentration

2,100.00mg/L

Results update automatically as you type.

MLVSS concentration = TSS concentration × volatile fraction ÷ 100. Both values are measured or supplied by you. No crop, process, species, or regional factor is inferred.

Use Cases

Wastewater Treatment Process Control

Operators use MLVSS to monitor the biomass concentration in aeration tanks, helping to optimize the activated sludge process and ensure proper treatment efficiency.

Example: An operator inputs TSS = 2500 mg/L and volatile fraction = 75% to get MLVSS = 1875 mg/L.

Laboratory Analysis and Reporting

Lab technicians can quickly convert TSS and volatile fraction measurements into MLVSS for routine reporting and compliance documentation.

Example: A lab report requires MLVSS for a sample with TSS = 1800 mg/L and volatile fraction = 80%, yielding MLVSS = 1440 mg/L.

Frequently Asked Questions

What is MLVSS and why is it important?
MLVSS (mixed liquor volatile suspended solids) represents the organic or volatile portion of suspended solids in activated sludge. It is a key parameter for monitoring biological treatment processes, as it indicates the active biomass concentration. This calculator estimates MLVSS by multiplying the TSS concentration by the volatile fraction.
How is MLVSS calculated?
MLVSS is calculated by multiplying the TSS concentration (in mg/L) by the volatile fraction (expressed as a decimal). For example, if TSS is 3000 mg/L and volatile fraction is 70%, MLVSS = 3000 * 0.70 = 2100 mg/L.
What units does the MLVSS result use?
The result is given in mg/L, the same unit as the TSS concentration input. This is the standard unit for reporting MLVSS in wastewater treatment.

Tips & Common Mistakes

Tips

  • Ensure the volatile fraction is entered as a percentage (e.g., 70 for 70%), not as a decimal (0.70).
  • Use consistent units: TSS must be in mg/L for the MLVSS result to be in mg/L.
  • For accurate results, use representative samples and follow standard testing methods for TSS and volatile fraction.
  • MLVSS is an estimate; actual biomass may vary due to inert organic matter, so interpret results with context.

Common Mistakes to Avoid

  • Entering the volatile fraction as a decimal (e.g., 0.70) instead of a percentage (70), leading to a result 100 times too low.
  • Using TSS in units other than mg/L (e.g., g/L) without converting, causing incorrect MLVSS values.
  • Assuming MLVSS equals total biomass; it includes only the volatile portion, so non-volatile solids are excluded.

Last updated: August 13, 2026