What is the typical range for a healthy MLSS concentration in a conventional activated sludge system?

In a conventional activated sludge system, a healthy Mixed Liquor Suspended Solids (MLSS) concentration typically falls within the range of 2,000 to 4,000 mg/L. This concentration is optimal for the biological processes occurring in the treatment system, where microorganisms are effectively breaking down organic matter in the wastewater. Having an MLSS concentration within this range ensures that there are enough microorganisms present to efficiently treat the incoming wastewater, while also maintaining good settling characteristics and preventing sludge washout from the system.

When the MLSS concentration is too low, it can lead to insufficient microbial population to effectively degrade pollutants, while higher concentrations beyond this range can lead to poor settling of solids and operational challenges. Maintaining the MLSS within the 2,000 to 4,000 mg/L range supports nutrient removal and enhances treatment efficiency, making it vital for effective wastewater management.