C-300Circular Clarifier — Centre Feed

How it works

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. Centre feed — Water enters a flocculating well in the middle, drops, and travels outward to a peripheral weir. It is simple and forgiving, but the entering flow has to turn through 90 degrees and spread over the full radius, and it never quite does — real basins achieve about 85 per cent of ideal settling, which is the 0.85 in the model above.

Design parameters

The panel opposite runs the same correlations as the C-300 design sheet, so the animation and the calculator cannot disagree. Every parameter below is live — drag one and the picture responds.

Open the full C-300 design sheet for the other seven inputs, all twenty-five results with their envelopes, the seven equations printed beside the numbers they produce, and a calculation record you can export and put in a design file.