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.

16Formulas

All levels Difficulty

Updated Oct 2026

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Fundamental

Wastewater Treatment Plant Peak Flow Factor

Peak Flow = Average Flow * Peaking Factor

Fundamental

Biodegradation Half-Life

t1/2 = ln(2) / k

Fundamental

Water Footprint of a Product

Water Footprint = Σ(Water used at each production stage)

Fundamental

Composting Carbon-to-Nitrogen (C:N) Ratio

C:N Ratio = Total Carbon (kg) / Total Nitrogen (kg)

Fundamental

Recycling Rate

Recycling Rate (%) = (Mass Recycled / Total Waste Generated) * 100

Fundamental

Municipal Solid Waste Generation per Capita

Waste per Capita = Total Waste Generated / Population

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