About MLSS (Mixed Liquor Suspended Solids)

MLSS is a measure of the concentration of suspended solids in the mixed liquor of an aeration tank during the activated sludge process. It's a key parameter for monitoring and controlling wastewater treatment plants.

Calculation Formula

The MLSS is calculated using the following formula:

MLSS = (A2 weight - A1 weight) × 1,000,000 / Sample Volume

Where:

• A1 weight: Initial weight of the Whatman filter paper (mg)
• A2 weight: Weight of the filter paper after filtering and drying (mg)
• Sample Volume: Volume of the sample filtered (ml)

Importance of MLSS

MLSS is crucial for:

• Determining the biomass concentration in the aeration tank
• Calculating the Food to Microorganism (F/M) ratio
• Determining sludge age
• Optimizing the activated sludge process

Typical MLSS Values

In conventional activated sludge processes, MLSS typically ranges between:

• 1,500 - 4,000 mg/L for conventional systems
• 4,000 - 10,000 mg/L for extended aeration systems