What does a high mixed liquor suspended solids (MLSS) indicate in an aeration basin?

What does a high mixed liquor suspended solids (MLSS) indicate in an aeration basin?

• A. Low biomass
• B. High dissolved oxygen
• C. High pH
• D. High concentration of microorganisms

Answer: (D)

In an aeration basin, MLSS represents how much suspended solid material is in the mixed liquor. Those solids are mainly the microorganisms—the active biomass that treats the wastewater. So a high MLSS indicates a high concentration of microorganisms. This tells you there’s more living microbial mass available to break down organics, though it doesn’t directly tell you the dissolved oxygen level or the pH. (High biomass can also make oxygen transfer less efficient, but the key point is that high MLSS reflects more microorganisms.)

In an aeration basin, MLSS represents how much suspended solid material is in the mixed liquor. Those solids are mainly the microorganisms—the active biomass that treats the wastewater. So a high MLSS indicates a high concentration of microorganisms. This tells you there’s more living microbial mass available to break down organics, though it doesn’t directly tell you the dissolved oxygen level or the pH. (High biomass can also make oxygen transfer less efficient, but the key point is that high MLSS reflects more microorganisms.)