Table 2.

Initial simulation conditions for the aerobic case study: initial concentrations refer to the total (i.e., protonated and un-protonated forms) concentration of the chemical compounds; the CO₂ concentration presented in this table includes CO₂, H₂CO₃, ${\text{HCO}}_3^{-}$ and ${\text{CO}}_3^{2-}$ forms, while NH₃ refers to the total concentration of free ammonia (NH₃) and ammonium ion (${\text{NH}}_4^{+}$); both NO₂ and NO₃ terms incorporate the nitric/nitrous acid and their corresponding ion concentrations.

		Aerobic system
Simulation conditions		Simulation #
		1a	2a	3a	4a	5a
Concentration (mg/L)		Top boundary conditions
O2	9	Fixed	Fixed	Fixed	Fixed	Fixed
CO2	88	Fixed	Fixed	Fixed	Fixed	Fixed
NH3	30	Fixed	Variable	Fixed	Variable	Variable
NO2	0	Fixed	Variable	Fixed	Variable	Variable
NO3	0	Fixed	Variable	Fixed	Variable	Variable
Initial value		pH Control
pH	7.5	Constant	Constant	Free	Free	Buffered
		Simulation descriptor
		Fixed BC —constant pH	Dynamic BC —constant pH	Fixed BC —free pH	Dynamic BC —free pH	Dynamic BC —buffered pH