What does an SVI of 250 or more indicate in a settleometer?

An SVI, or Sludge Volume Index, is a key measurement used in wastewater treatment to assess the settling characteristics of mixed liquor in a settleometer. An SVI of 250 or more indicates that the sludge is very young. This high value suggests that the biomass is predominantly made up of new microorganisms that have recently formed.

In wastewater treatment, young sludge typically has a larger volume due to the presence of active, healthy microorganisms that have not yet begun to break down or decompose significantly. As these organisms age, they tend to produce more extracellular polymeric substances (EPS) that can lead to improved settling characteristics, lowering the SVI value over time. Therefore, the observation of an SVI at 250 or higher indicates that the sludge has not yet reached a more mature state and implies that it may still be in the early stages of biological treatment.

Understanding the implications of different SVI levels helps operators manage and adjust operational practices to maintain optimal treatment conditions.