How is the SVI of an aeration basin calculated if the settleable sample is 360 mL/L and mixed liquor suspended solids concentration is 4000 mg/L?

To calculate the Sludge Volume Index (SVI), the formula used is:

[ SVI = \frac{\text{Settleable Volume (mL/L) } \times 1000}{\text{Mixed Liquor Suspended Solids (MLSS) concentration (mg/L)}} ]

In this scenario, you have a settleable sample of 360 mL/L and a mixed liquor suspended solids concentration of 4000 mg/L.

Plugging the values into the formula:

[ SVI = \frac{360 \times 1000}{4000} ]

Calculating this gives:

[ SVI = \frac{360000}{4000} = 90 ]

This means that the SVI value, derived using the provided settleable sample and the MLSS concentration, correctly results in 90 mL/g.

Understanding SVI is crucial in wastewater treatment as it helps evaluate the settling characteristics of the sludge in the aeration basin. A lower SVI indicates good settling capabilities, while a higher SVI might indicate issues that could affect the treatment process.