Sludge Production
Calculate the biological sludge production of a plant, P_x = Y × ΔS ÷ 1000 × Q, multiplying the cell yield coefficient (Y, kg VSS/kg BOD), the BOD removed (mg/L) and the flow (m³/day). The result, in kg/day, estimates the excess sludge mass generated by biomass growth, key to sizing wasting, thickening, dewatering and final disposal — a step that often drives much of a treatment plant's operating cost. Enter the yield Y, the BOD removed and the flow.
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Sludge production
Every biological treatment turns part of the organic matter it removes into new biomass — bacteria that grow and have to be drawn off periodically as waste sludge. Estimating how much sludge gets produced per day is fundamental, since sludge management (thickening, digestion, dewatering and final disposal) usually accounts for a large share of the operating cost of a wastewater treatment plant. The simplified form is P_x = Y × ΔS ÷ 1000 × Q: the cell yield coefficient Y (kg of volatile suspended solids generated per kg of BOD removed, typically 0.4–0.8) multiplies the BOD removed ΔS (mg/L, converted to kg/m³) and the flow rate Q (m³/day). The result, in kg/day, is the mass of biological sludge generated. Systems with a high sludge age (extended aeration, for instance) yield less sludge, since endogenous respiration consumes part of the biomass; high-rate systems yield more. This figure sets the size of the thickeners, the centrifuges or filter presses and the logistics of sludge destination. Enter the coefficient Y, the BOD removed and the flow rate.
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Oxygen Requirement (Aeration)
Calculate the oxygen requirement of an aerobic treatment system, O₂ = Q × ΔS ÷ 1000 × f, multiplying the flow (m³/day) by the BOD removed (mg/L) and an oxygen-demand factor (typically 1.0–1.5 kg O₂/kg BOD). The result, in kg O₂/day, sizes blowers and aerators in activated sludge and aerated lagoons, ensuring enough oxygen for the biological oxidation of organic matter. Enter the flow, the BOD removed and the oxygenation factor.
Sludge Recycle Ratio
Calculate the sludge recycle ratio (R) of an activated-sludge system by mass balance, R = X ÷ (X_r − X), from the mixed-liquor suspended solids (MLSS) and the return sludge concentration. The result (dimensionless, or ×100%) gives the fraction of influent flow that must be recycled from the secondary clarifier to keep the desired biomass in the reactor. Typical ratios range from 0.25 to 1.0. Enter the reactor MLSS and the return sludge concentration.
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Sludge Volume Index (SVI)
Calculate the sludge volume index (SVI), SVI = (V₃₀ × 1000) ÷ MLSS, from the 30-minute settled sludge volume (mL/L) and the mixed-liquor suspended solids concentration (mg/L). The result, in mL/g, measures activated-sludge settleability: values of 50–150 mL/g indicate well-settling sludge, while values above 150 signal filamentous bulking that impairs clarification. Enter the settled volume and the MLSS concentration.
Power by Admiralty Coefficient
Estimate a ship's propulsive power by the Admiralty formula, P = (∆^(2/3)·V³)/C, from the displacement (∆, t), the speed (V, knots) and the Admiralty coefficient (C), characteristic of similar hulls. It is a classic, fast method to predict the required power in the preliminary design stage, based on similarity with existing ships. The V³ dependence shows the high cost of speed. Enter the displacement, the speed and the coefficient C.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.