Work out clarifier surface loading instantly with clear inputs, formula shown and shareable results.
A secondary clarifier must satisfy three criteria: surface overflow rate for clarification, typically 16-32 m3/m2/day; solids loading rate for thickening, generally under 6 kg/m2/hour; and weir loading rate to avoid drawing solids over the weir. Solids loading uses the combined influent and return sludge flow.
Surface overflow rate
SOR = influent flow / clarifier area
Solids loading rate
SLR = (influent + return sludge) x MLSS / (area x 1000)
Solids loading in activated sludge plants with high MLSS, and surface overflow rate in water treatment or low-MLSS systems. Both must be checked at peak flow with the design return rate.
Bulking sludge with poor settleability, hydraulic overload, density currents from temperature or solids gradients, and inadequate sludge withdrawal causing a rising blanket.