1. What is the Sludge Volume Index (SVI)?

The Sludge Volume Index (SVI) is a measurement used to characterize the settling properties of sludge in wastewater treatment processes. It indicates the volume occupied by 1 gram of activated sludge after 30 minutes of settling.

2. How Does the Calculator Work?

The calculator uses the SVI formula:

Where:

• \( Settled\ Volume \) — Volume of sludge settled after 30 minutes (mL/L)
• \( MLSS \) — Mixed Liquor Suspended Solids concentration (mg/L)

Explanation: The SVI provides a standardized way to compare sludge settling characteristics across different treatment plants.

3. Importance of SVI in Wastewater Treatment

Details: SVI is crucial for monitoring activated sludge processes. It helps operators assess sludge quality, predict clarifier performance, and identify potential bulking or pin floc problems.

4. Using the Calculator

Tips: Enter settled volume in mL/L and MLSS in mg/L. Both values must be positive numbers. Typical SVI values range from 50-150 mL/g.

5. Frequently Asked Questions (FAQ)

Q1: What is a good SVI value?
A: Generally, SVI between 50-150 mL/g indicates good settling sludge. Values above 150 may indicate bulking, while very low values may suggest old sludge.

Q2: How is settled volume measured?
A: A 1-liter sample of mixed liquor is allowed to settle for 30 minutes in a graduated cylinder, and the settled volume is recorded in mL/L.

Q3: What affects SVI values?
A: Factors include sludge age, food-to-microorganism ratio, dissolved oxygen levels, temperature, and the presence of filamentous organisms.

Q4: What's the difference between SVI and DSVI?
A: Diluted SVI (DSVI) is measured at a lower MLSS concentration (typically 1.5 g/L) to better assess bulking potential in high-MLSS systems.

Q5: How often should SVI be measured?
A: In most plants, SVI is measured daily as part of routine process control monitoring.