Required RAS Rate
Estimates the return activated sludge (RAS) rate, expressed as a percent of the forward flow, needed to maintain a target mixed liquor suspended solids (MLSS) at a given RAS concentration. Use it to set RAS pump speed, stroke frequency, or a target RAS/MG ratio on the SCADA.
Required RAS Rate
Estimate the return activated sludge rate needed to maintain a target MLSS.
Enter all values above to calculate.
When you'd use this
Estimates the return activated sludge (RAS) rate, expressed as a percent of the forward flow, needed to maintain a target mixed liquor suspended solids (MLSS) at a given RAS concentration. Use it to set RAS pump speed, stroke frequency, or a target RAS/MG ratio on the SCADA.
Category
Activated Sludge Process ControlTarget mixed liquor suspended solids in the aeration basin.
Suspended solids concentration of the return activated sludge (commonly 8,000–15,000 mg/L for a well-settling sludge).
Run the math behind this reference.
Each calculator opens onto its own page with the formula, variable definitions, a worked example, and related operator math.
F/M Ratio
Compare the organic load entering the aeration basin to the biomass available to treat it.
MCRT (Sludge Age)
Calculate mean cell residence time from MLSS, wasting, and effluent solids data.
Solids Loading Rate
Check how many pounds of solids per day are applied per square foot of clarifier area.
Metcalf & Eddy, Wastewater Engineering — Activated Sludge Solids Inventory.
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