What are typical indicators of poor settleability in a clarifier?

• A. Clear Effluent And Low Sludge Blanket
• B. Elevated Effluent Turbidity, High Sludge Blanket Depth, High SVI, And Visible Floating Solids
• C. Low SVI and Low Turbidity
• D. Rapid Settling and High Clarity

Answer: (B)

Poor settleability shows up when solids aren’t being effectively separated in the clarifier, leading to poorer treated water quality and a thicker settled solids layer. Elevated effluent turbidity means solids are still present in the water leaving the plant, rather than being removed. A high sludge blanket depth indicates a thick layer of suspended solids in the clarifier, which suggests solids aren’t settling out as they should. A high SVI means the sludge hasn’t compacted well and settles slowly, increasing the likelihood of solids remaining in suspension or being carried out with the effluent. Visible floating solids, such as scum or buoyant material, show that some solids aren’t being captured and held down by the clarifier’s physics.

In contrast, clear effluent with a low sludge blanket points to good separation; a low SVI with low turbidity indicates solids settle readily; and rapid settling with high clarity reflects efficient clarifier performance.