Set the flow, peaking, tank count and peak surface overflow rate — get the total surface area,
tank length, hydraulic retention time, weir overflow rate and the TSS/BOD removal. The long-basin
alternative to the circular primary, common on constrained or retrofit sites.
1Duty & clarifier
Size by peak surface overflow rate (SOR 1.5–4.5 m/h peak). Rectangular basins run weir along both long sides; typical primary TSS removal 50–65 %, BOD 25–40 %.
Results — area & removal
Surface area
—m²
HRT
—h
Weir overflow
—m³/m·d
Item
Value
Basis
2Geometry & removal
One tank's footprint and the TSS/BOD the basin pulls out before the biology.
Item
Value
Basis
Operation envelope
Item
Value
Basis
Quote the clarifier instruments at factory price
A rectangular primary needs a sludge-level transmitter, RAS flowmeter and an influent TSS monitor —
all mappable to our catalogue and supplied at the manufacturer's ex-works price (margin from the export rebate only).
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Sources & parameter basis
[1]
METCALF & EDDY 5th ed. / TEN STATES — primary SOR peak 1.5–4.5 m/h, HRT 1.5–3 h (typical 2), depth 2.5–4.5 m, weir overflow ≤ 250–500 m³/m·d (straight), TSS removal 50–65 %, BOD 25–40 %.
Full derivation and worked example: Rectangular-Primary-Calculation-Sheet.md. The rectangular clarifier is the footprint-flexible alternative to the circular primary — run it, then carry Q & removals into the biological unit.
