What is sludge, and where is it removed in a clarifier?

What is sludge, and where is it removed in a clarifier?

• A. Sludge is settled solids collected at the bottom of the basin; removed from the bottom.
• B. Sludge is floating scum on top; removed at the surface.
• C. Sludge is dissolved salts; removed through filtration
• D. Sludge is air bubbles; removed via vent.

Answer: (A)

Sludge is the settled solids that collect at the bottom of a clarifier. In this tank, heavier particles settle out of the water and form a sludge layer on the bottom. That sludge is then removed through the bottom of the tank by scraping or pumping to a sludge trough. The material at the top is scum and is removed at the surface, not as sludge. Dissolved salts aren’t sludge—they’re dissolved in the water and are dealt with by other treatment steps, not by bottom removal in a clarifier. Air bubbles are handled by vents or surface systems, not by bottom sludge removal.

Sludge is the settled solids that collect at the bottom of a clarifier. In this tank, heavier particles settle out of the water and form a sludge layer on the bottom. That sludge is then removed through the bottom of the tank by scraping or pumping to a sludge trough. The material at the top is scum and is removed at the surface, not as sludge. Dissolved salts aren’t sludge—they’re dissolved in the water and are dealt with by other treatment steps, not by bottom removal in a clarifier. Air bubbles are handled by vents or surface systems, not by bottom sludge removal.