1. What is Sludge Volume Index (SVI)?

Definition: SVI measures the settling characteristics of activated sludge in wastewater treatment processes.

Purpose: It helps wastewater treatment operators assess sludge quality and predict settling behavior in clarifiers.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( SVI \) — Sludge Volume Index (mL/g)
• \( SV \) — Settled Sludge Volume (mL/L)
• \( MLSS \) — Mixed Liquor Suspended Solids (mg/L)

Explanation: The formula calculates the volume occupied by 1 gram of sludge after 30 minutes of settling.

3. Importance of SVI in Wastewater Treatment

Details: SVI values indicate sludge quality:

• 50-150 mL/g: Good settling
• 150-250 mL/g: Fair settling
• >250 mL/g: Poor settling (bulking sludge)

4. Using the Calculator

Tips: Enter the 30-minute settled sludge volume (mL/L) and MLSS concentration (mg/L). Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical SVI value for good sludge?
A: Values between 50-150 mL/g indicate good settling characteristics.

Q2: What causes high SVI values?
A: Filamentous bacteria growth, nutrient deficiencies, or low dissolved oxygen can cause high SVI.

Q3: How is SV measured?
A: Fill a 1-liter graduated cylinder with mixed liquor, let settle for 30 minutes, and record the settled volume in mL/L.

Q4: What's the relationship between SVI and sludge age?
A: Generally, younger sludge has lower SVI, but extremely young sludge may have poor settling.

Q5: How often should SVI be measured?
A: Daily monitoring is recommended for most treatment plants to detect settling problems early.