What is the sludge volume index if the 30-minute settleability percent solids was 17% and MLSS was 1,800 mg/L?

To determine the sludge volume index (SVI), you need to understand how it is calculated. SVI is a measure of the settleability of the sludge in wastewater treatment, and it helps in assessing the performance of the system. The formula for SVI is:

[ SVI = \frac{\text{MLSS}}{\text{settled sludge volume}} ]

In this scenario, the settled sludge volume is determined from the 30-minute settleability, which is given as 17%. This means that 17% of the total volume is settled sludge.

To find the volume of settled sludge (in mL) from a known MLSS concentration (in mg/L), we convert MLSS to grams per liter (since mg/L can be treated as g/L) and then use the percentage of settled sludge to find out how many liters settle:

1. MLSS: 1,800 mg/L translates to 1.8 g/L.

2. Settled Sludge Volume: At 17% settleability, if you have 1000 mL of mixed liquor, 17% of that would be 170 mL that settles.

Now using the SVI formula:

[ SVI = \frac