Water Treatment

Water treatment calculators and formulas for retention time, removal efficiency, and treatment design. Covers detention time, filtration rate, and dosage calculations for treatment plants.

11Formulas

All levels Difficulty

Updated Jul 2026

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Fundamental

Wastewater Treatment Plant Peak Flow Factor

Peak Flow = Average Flow * Peaking Factor

Fundamental

Water Quality Index (Simplified)

WQI = Σ(Wi * Qi) / ΣWi

Fundamental

Daily Per Capita Water Demand

Per Capita Demand = Total Daily Water Supplied / Population Served

Fundamental

Sludge Volume Index

SVI = (Settled Sludge Volume (mL/L) * 1000) / MLSS (mg/L)

Fundamental

Total Dissolved Solids from Electrical Conductivity

TDS (mg/L) = EC (µS/cm) * Conversion Factor

Fundamental

Rapid Sand Filtration Rate

Filtration Rate = Flow Rate / Filter Surface Area

Fundamental

Coagulant Dosage Scale-Up (Jar Test to Full Scale)

Full-Scale Dose (kg/day) = Jar Test Dose (mg/L) * Plant Flow (m3/day) / 1000

Fundamental

Water Hardness (as CaCO3)

Hardness (mg/L as CaCO3) = [Ca2+](mg/L)*2.5 + [Mg2+](mg/L)*4.1

Fundamental

Chlorine Dosage for Water Disinfection

Dose (kg/day) = Flow (m3/day) * Concentration (mg/L) / 1000

Fundamental

Pollutant Removal Efficiency

E = (C_in − C_out) / C_in × 100%

Fundamental

Hydraulic Retention Time

HRT = V / Q