Modeling N/S ratio and temperature effects in simultaneous biological denitrification and sulfide oxidation

Abstract

A model describing the simultaneous removal of NO3- and HS- by microorganisms is presented here. The oxidation of HS- (electron donor) can be controlled by the appropriate dosage of NO3-. The developed model, which includes variable process stoichiometry, attempts to predict the distribution of sulfur oxidation products. Stoichiometric coefficients are based on a 150 days experimental study of temperature (25-10 ?C) and N/S ratio (0.35-1.30) effects. The model can be used as a prediction tool for autotrophic denitrification with HS-. Elemental sulfur production is included in the mathematical model, however, its accumulation and release (as SO42-) with increasing feed N/S ratio (e.g. leading to higher effluent than feed total sulfur mass at N/S = 1.30) is not simulated. A conceptual model to account for biological accumulation and release of elemental sulfur is proposed here.