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

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

2. How Does the Calculator Work?

The calculator uses the SVI equation:

Where:

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

Explanation: The equation calculates the volume in milliliters occupied by one gram of sludge, providing insight into sludge settling properties.

3. Importance of SVI Calculation

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

4. Using the Calculator

Tips: Enter the settled volume in mL/L and MLSS concentration in g/L. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

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

Q2: How is settled volume measured?
A: Settled volume is measured by allowing a 1-liter sample of mixed liquor to settle for 30 minutes in a graduated cylinder and recording the volume of settled sludge.

Q3: What affects SVI values?
A: SVI is affected by factors like 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 sludge settling under low solids conditions.

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