About MLVSS (Mixed Liquor Volatile Suspended Solids)

MLVSS represents the volatile (organic) portion of the mixed liquor suspended solids in wastewater treatment systems. It's a critical parameter for assessing the active biomass concentration in the activated sludge process.

Calculation Formula

The MLVSS is calculated using the following formula:

MLVSS = (A3 weight) × 1,000,000 / Sample Volume

Where:

• A3 weight: Weight of the filter residue after burning at 550°C in a muffle furnace (mg)
• Sample Volume: Volume of the sample filtered (ml)

Importance of MLVSS

MLVSS is crucial for:

• Measuring the concentration of active microorganisms in the aeration tank
• Determining the organic content of the sludge
• Calculating the Food to Microorganism (F/M) ratio
• Monitoring process efficiency and biomass health
• Optimizing sludge wasting rates

Key Differences Between MLSS and MLVSS

• MLSS measures total suspended solids (both organic and inorganic)
• MLVSS measures only the volatile (organic) portion that can be oxidized
• The ratio of MLVSS/MLSS indicates the organic fraction of the sludge

Typical MLVSS Values

In conventional activated sludge processes, MLVSS typically ranges between:

• 1,000 - 3,000 mg/L for conventional systems
• 3,000 - 7,000 mg/L for extended aeration systems

Process Control Applications

MLVSS is used to:

• Determine sludge age (Mean Cell Residence Time)
• Calculate sludge volume index (SVI)
• Adjust aeration rates based on biomass concentration
• Optimize nutrient dosing for biological treatment