Wastewater Treatment MCQ with answer and solution

Concept

SVI measures the physical settleability of activated sludge flocs in the aeration tank.

Formula

SVI = (Settled Sludge Volume in mL/L × 1000) / Suspended Solids in mg/L

Step-by-step solution

1. Understand the definition of Sludge Volume Index (SVI). 2. Note that SVI indicates the ability of biomass in the activated sludge process to settle and concentrate. 3. Relate settleability to option (B).

Explanation

The Sludge Volume Index (SVI) is defined as the volume in milliliters occupied by 1 gram of activated sludge after settling for 30 minutes in a 1000 mL graduated cylinder. It is a key parameter used to monitor the settling characteristics (settleability) of biological sludge in the activated sludge process.

Why the other options are wrong

A: Filtration rate relates to sand filters or membrane processes. C: Pathogen content is measured using coliform tests or microbiological assays. D: BOD value measures the biodegradable organic matter content.

Shortcut

SVI correlates directly with sludge settleability: low SVI means good settling, high SVI indicates bulking sludge.

Common mistake

Confusing SVI with filtration rate or BOD, which measure different characteristics of wastewater.