Clarifier short-circuiting can be caused by differences in water density due to differences in what conditions?

• A. pH and alkalinity
• B. Temperature and velocity being too high
• C. Turbidity and color
• D. Dissolved oxygen and flow rate

Answer: (B)

Short-circuiting in a clarifier happens when density-driven currents form inside the tank, so part of the inflow takes a shortcut to the outlet instead of passing through the settled zone. The density differences that drive these currents mainly come from temperature: warmer water is less dense than cooler water, so streams at different temperatures don’t mix evenly and create vertical layers or intrusions that move more quickly than the bulk flow. When those temperature-related density contrasts occur together with high inflow velocity, strong internal jets develop and push water straight toward the effluent, reducing the time water spends in the clarifier. Other factors like pH/alkalinity, turbidity/color, or dissolved oxygen with flow rate don’t create the same density stratification, so they’re not the primary cause of this effect.