How it works
- why a clarifier — Nearly every treatment train needs the bulk solids gone before anything clever happens downstream. A clarifier does it with no energy and no chemistry beyond the coagulant — just area and quiet. The cost is footprint, which is why the sizing question is always the same one.
- feedwell — Flow enters at the centre and is slowed inside the feedwell, which dissipates the inlet momentum. Get this wrong and the jet drives a current straight across the floor and out over the weir, carrying solids with it. The feedwell is the difference between a settling tank and an expensive pipe.
- settling zone — Water travels outward and upward toward the peripheral weir. A particle is captured if its settling velocity exceeds the rate at which water rises — the overflow rate, Q divided by surface area. Note what is absent: depth. Hazen showed capture depends on area, not on how deep the tank is.
- blanket & rake — Captured solids consolidate into a sludge blanket on the floor. A slow rake, typically two to three revolutions per hour, walks them to the centre hopper. Depth earns its keep here — it provides blanket storage and buffers a solids surge, even though it does not improve capture.
- what governs it — Drag the settling velocity down toward the overflow rate and watch capture collapse — that ratio is the whole design. Then check weir loading: too high and the approach velocity near the weir plucks settled floc back into the effluent, no matter how generous your area is.
Design parameters
The panel opposite runs the same correlations as the C-300 design sheet, so the animation and the calculator cannot disagree. Drag any of them and the picture responds.
- Feed flow — m³/h
- Influent SS — mg/L
- Tank diameter — m
- Side water depth — m
- Particle settling velocity — m/h
Open the full C-300 design sheet for the governing equations, the accepted design envelopes and the worked calculation.