Wastewater Treatment MCQ with answer and solution

Concept

Sludge Volume Index (SVI) Properties

Formula

SVI (mL/g) = [Settled Sludge Volume (mL/L) × 1,000] / MLSS (mg/L)

Step-by-step solution

1. Review the given question regarding the definition of Sludge Volume Index (SVI). 2. Recall the SVI formula and definition, which is the volume in mL occupied by 1 gram of sludge after settling for 30 minutes in a graduated cylinder. 3. Compare with the given choices and select Option (a) as the correct choice.

Explanation

Sludge Volume Index (SVI) is a standard test used in wastewater treatment to check how easily the activated sludge settles. It measures the volume in milliliters (mL) occupied by 1 gram of dry sludge solids after settling quietly for 30 minutes in a graduated cylinder. A lower SVI indicates good settling ability, while a high SVI indicates poor settling or bulking sludge.

Shortcut

To remember Sludge Volume Index (SVI), use the simple phrase "SVI = Volume per Gram in 30": - SVI: Settled Volume Index. - Volume per Gram: Measures the volume in mL occupied by 1 gram of sludge. - 30 Minutes: Measured after settling for 30 minutes in a graduated cylinder.

Common mistake

A common mistake is selecting Option C by confusing Sludge Volume Index (SVI) with Mixed Liquor Suspended Solids (MLSS), or selecting Option D by assuming SVI measures total sludge volume produced per unit of wastewater. SVI specifically measures the volume in milliliters occupied by 1 gram of dry sludge solids after settling for 30 minutes.