What is a necessary check when thick scummy dark tan foam is observed in the aeration tank?

When thick scummy dark tan foam is observed in the aeration tank, the appropriate response is to verify parameters such as Mixed Liquor Volatile Suspended Solids (MLVSS), Mean Cell Residence Time (MCRT), or a decreased Food-to-Microorganism ratio (F:M). Each of these factors can provide insights into the efficacy of biological treatment processes.

MLVSS is an important indicator of the concentration of active biomass in the aeration tank; a change here could signify issues with microbial health or growth. If MLVSS is too low, it may indicate that the microbial community is not thriving, potentially contributing to foaming issues. MCRT assesses how long microorganisms remain in the system, which influences their growth and stability. An inappropriate MCRT can lead to either washout of active biomass or accumulation of older, less active microorganisms, both of which can affect foam characteristics.

The F:M ratio indicates the balance between the organic substrate available and the microorganisms present to treat that substrate. A decreased F:M ratio suggests there may not be enough food for the microorganisms or that they're not effectively utilizing the available food, which can lead to growth of filamentous organisms that produce excessive foam. Evaluating these parameters will help determine the underlying