Florida Wastewater Practice Test

What does a high sludge volume index (SVI) indicate about the sludge?

1. Good settleability

2. Poor settleability

3. Effective denitrification

4. High concentration of organic matter

The correct answer is: Poor settleability

A high sludge volume index (SVI) is an important indicator in wastewater treatment that reflects the behavior of the sludge during the settling process. Specifically, a high SVI signifies poor settleability of the sludge. This means that the sludge does not settle efficiently in the clarification process after biological treatment. When the SVI is high, it generally suggests that the floc structure is weak or bulky, and the sludge has a lower density, which makes it difficult to compact during settling. In contrast, good settleability would be indicated by a low SVI, where the sludge settles quickly and forms a dense sediment at the bottom of the tank. Considering this context, the options indicating good settleability or effective denitrification do not align with the implications of a high SVI, as these circumstances would typically correlate with a lower index. Moreover, while a high concentration of organic matter can influence sludge characteristics, it does not directly correlate with SVI measurements indicating settleability issues. Therefore, the understanding of SVI as a measure of settleability accurately supports this question's correct choice.