Simultaneous removal of sulfide, nitrate and acetate under denitrifying sulfide removal condition: modeling and experimental validation.

Simultaneous removal of sulfide (S(2-)), nitrate (NO3(-)) and acetate (Ac(-)) under denitrifying sulfide removal process (DSR) is a novel biological wastewater treatment process. This work developed a mathematical model to describe the kinetic behavior of sulfur-nitrogen-carbon and interactions between autotrophic denitrifiers and heterotrophic denitrifiers. The kinetic parameters of the model were estimated via data fitting considering the effects of initial S(2-) concentration, S(2-)/NO3(-)-N ratio and Ac(-)-C/NO3(-)-N ratio. Simulation supported that the heterotrophic denitratation step (NO3(-) reduction to NO2(-)) was inhibited by S(2-) compared with the denitritation step (NO2(-) reduction to N2). Also, the S(2-) oxidation by autotrophic denitrifiers was shown two times lower in rate with NO2(-) as electron acceptor than that with NO3(-) as electron acceptor. NO3(-) reduction by autotrophic denitrifiers occurs 3-10 times slower when S(0) participates as final electron donor compared to the S(2-)-driven pathway. Model simulation on continuous-flow DSR reactor suggested that the adjustment of hydraulic retention time is an efficient way to make the reactor tolerating high S(2-) loadings. The proposed model properly described the kinetic behaviors of DSR processes over wide parametric ranges and which can offer engineers with basis to optimize bioreactor operation to improve the treatment capacity.