What is the primary purpose of the SV-30 test?

• A. Dissolved oxygen
• B. Temperature
• C. pH
• D. Sludge level and condition

Answer: (D)

The SV-30 test is a settleability check that looks at how much sludge settles out of mixed liquor in 30 minutes. Its main purpose is to gauge the sludge level in the clarifier and the physical condition of the solids—their compactness and ability to settle. When you take a sample, let it sit for half an hour and measure how much volume the settled sludge occupies. A small settled volume means the solids settle well and form a dense, easy-to-remove sludge blanket; a large settled volume suggests poor settling, fluffy or bulking sludge, or other issues that could cause poor clarifier performance. This information helps operators decide if adjustments are needed to sludge wasting, aeration, or chemical addition to restore proper settling. It’s not about measuring dissolved oxygen, temperature, or pH; those parameters are separate process measurements.