In a mixed liquor test, the MLSS is 2500 mg/L and a 1000 ml sample settles to 400 mls after 30 minutes. What is the SVI?

To determine the Sludge Volume Index (SVI), you need to use the formula:

[ \text{SVI} = \frac{\text{MLSS (mg/L)}}{\text{Settled Volume (mL) after a specific time (L)}} ]

In this scenario, you have a mixed liquor suspended solids (MLSS) concentration of 2500 mg/L. After settling a 1000 mL sample for 30 minutes, the volume of the sludge is reduced to 400 mL.

First, convert the MLSS concentration into a more appropriate unit for the SVI calculation. Since the MLSS is already given in mg/L, you can use it as is:

1. MLSS: 2500 mg/L

2. Settled Volume: 400 mL

Next, calculate the SVI:

[

\text{SVI} = \frac{2500 , \text{mg/L}}{0.4 , \text{L}} = \frac{2500}{0.4} = 6250 , \text{mg/L*mL}

]

However, since SVI should be expressed as mL/g, you need