How to Calculate Sodium Acetate Dosage? Denitrification C/N Ratio and COD Equivalent

The dosage of external carbon source depends on the total nitrogen to be removed and the COD equivalent of the carbon source. Denitrification stoichiometry shows: removing 1 kg of total nitrogen (as NO3-N) requires about 2.86 kg COD (based on methanol).

Sodium acetate (as trihydrate CH3COONa·3H2O) has a COD equivalent of about 0.69~0.78 kgCOD/kg, giving a theoretical dosage of about 3.7~4.1 kg sodium acetate per kg TN removed; including system losses and assimilation by denitrifying bacteria, actual operation commonly uses an empirical range of 5~8 kg (trihydrate sodium acetate) per kg TN removed.

The final dosage should be determined by influent quality, C/N ratio and bench tests, and verified against the effluent TN target. Carbon source system design can refer to the relevant provisions on denitrification carbon source in the 'Outdoor Drainage Design Standard' GB 50014.