Question

The treated effluent from a wastewater treatment plant contains ammonium (NH4+) at 76.0 mg NH4+-N/L and nitrate at 22.0 mg NO3--N/L. Convert these concentrations to mg NH4+/L and mg NO3-/L.

Answer 1

We have (NH4+) at 76.0 mg NH4+-N/L and (NO3) at 22.0 mg NO3--N/L
The term NH4+-nitrogen (NH4+-N) refers to the weight of nitrogen atom within the NH4+ ion
Similarly, the term NO3--nitrogen (NO3--N) refers to the weight of nitrogen atom in the NO3- ion.

Molecular weight of nitrate ion(NO3-) = 62 g/mol
Ammonia(NH4+) ion weight = 18.04 g/mol

Therefore,

mg NH4+/L = (76.0 mg- N/L)(1 mol N/14g N) (1 mol NH4+/1 mol N) (18.04 g NH4+/mol NH4+)
       = 97.93 mg/L

mg NO3-/L = (22.0 mg- N/L)(1 mol N/14g N) (1 mol NO3-/1 mol N) (62 g NO3-/mol NO3-)
       = 97.43 mg/L