Table 1 Reactions and rate expressions considered in the model simulations. Rate symbols are defined in Table 2

Primary redox reactions-

(CH₂O) _x (NH₃) _y (H₃PO₄) _z + (x + 2y)O₂ + (y + 2z)HCO₃^- → (x + y + 2z)CO₂ + yNO₃^- + zHPO₄^2- + (x + 2y + 2z)H₂O

(CH₂O) _x (NH₃) _y (H₃PO₄) _z + ((4x + 3y)/5)NO₃^- → ((2x + 4y)/5)N₂ + ((x - 3y + 10x)/5)CO₂ + ((4x + 3y - 10z)/5)HCO₃^-+ zHPO₄^2- + ((3x + 6y + 10z)/5)H₂O

(CH₂O) _x (NH₃) _y (H₃PO₄) _z +(x/2)SO₄^2- + (y - 2z)CO₂ + (y - 2z)H₂O → (x/2)H₂S + (x + y - 2z)HCO₃^- + yNH₄⁺ + zHPO₄^2-

Secondary redox reactions-

NH₄⁺ + 2O₂ + 2HCO₃^- → NO₃^- + 2CO₂ + 3H₂O

H₂S + 2O₂ + 2HCO₃^- → SO₄^2- + 2CO₂ + 2H₂O

Acid-base reactions (equilibrium)-

CO₂ + H₂O → HCO₃^- + H⁺

HCO₃ ↔ CO₃^2- + H⁺

H₂S ↔ HS^- + H⁺

Adsorption reations (equilibrium)-

NH₄⁺(aq) ↔ NH₄⁺(ads)

Reaction rates-