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Nitrogen Removal Calculator

Estimate ammonia nitrification, nitrate denitrification, oxygen demand, alkalinity effects, carbon demand, and preliminary anoxic-zone volume for an MBR or activated-sludge nitrogen-removal system.

Preliminary nitrogen balance: This tool is for screening and assumes the ammonia removed is nitrified and the nitrate above the selected target is denitrified. It excludes nitrogen assimilation, sidestream loads, recycle hydraulics, temperature and DO corrections, inhibition, and process-specific solids effects.

Input parameters
Enter average nitrogen concentrations and process assumptions.
m³/day
Nitrification targets
mg/L as NH4-N
mg/L as NH4-N
Denitrification targets and carbon
mg/L as NO3-N
mg/L as NO3-N
mg/L COD available to denitrification
kg COD per kg NO3-N; theoretical methanol-equivalent basis
Preliminary anoxic-zone sizing
mg/L MLVSS
g NO3-N/(g MLVSS·day); select from site-specific conditions
Integrated alkalinity and chemical screen
mg/L as CaCO3
mg/L as CaCO3; residual pH buffer target
fraction; 1.00 for dry chemical, 0.50 for a 50% solution
kg/L; use 1.00 for dry chemical output
Calculated results
All nitrogen quantities are reported as elemental N unless otherwise stated.

Enter values and select Calculate to view the nitrogen-removal estimate.

Equations used

The calculator applies stoichiometric nitrification factors of 4.57 kg O2/kg NH4-N and 7.14 kg as CaCO3/kg NH4-N. It applies denitrification credits of 2.86 kg O2/kg NO3-N and 3.57 kg as CaCO3/kg NO3-N. [1]

NH4-N nitrified = Q × (NH4,in − NH4,target) ÷ 1,000
NO3-N available = NO3,in + NH4-N nitrified concentration
NO3-N denitrified = Q × (NO3,available − NO3,target) ÷ 1,000
Nitrification O2 = NH4-N nitrified × 4.57
Nitrification alkalinity = NH4-N nitrified × 7.14
Denitrification COD demand = NO3-N denitrified × selected COD/N ratio
Anoxic volume = NO3-N denitrified × 1,000 ÷ (SDNR × MLVSS)

Scope and interpretation

Nitrogen removal depends on sufficient aerobic solids retention time, alkalinity, oxygen, anoxic conditions, available carbon, mixing, temperature, and inhibition control. The design calculations here do not replace a process model or pilot/plant data. NYS DEC nitrogen-removal training [1] EPA Nitrogen Control design manual [2]