Mlvss Calculator

mg/L
Mixed Liquor Suspended Solids measured in the aeration basin.
Typically 0.7–0.85 for activated sludge.
Biology

Calculate Mixed Liquor Volatile Suspended Solids (MLVSS) from MLSS and the VSS/TSS ratio in a wastewater aeration basin.

Formula

MLVSS = MLSS × (VSS/TSS fraction)
  • MLVSS represents the active microbial fraction of the sludge.
  • VSS/TSS ratio is typically 0.70–0.85 for activated sludge systems.
  • Higher MLVSS indicates more active biomass for BOD removal.

3000 mg/L MLSS, 0.80 VSS/TSS

Inputs
  • MLSS Concentration: 3000 mg/L
  • VSS/TSS Ratio: 0.8

MLVSS = 3000 × 0.80 = 2,400 mg/L.

Frequently asked questions

What is the difference between MLSS and MLVSS?
MLSS includes all solids; MLVSS includes only volatile (organic, mostly microbial) solids.
What MLSS range is normal?
Conventional activated sludge: 1,500–3,000 mg/L. Extended aeration: 3,000–6,000 mg/L.