Using kinetics and modeling to predict denitrification fluxes in elemental‐sulfur‐based biofilms

Abstract

Elemental sulfur (S 0 ) can serve as an electron donor for water and wastewater denitrification, but few researchers have addressed the kinetics of S 0 -based reduction of nitrate (NO 3 − ), nitrite (NO 2 − ), and nitrous oxide (N 2 O). In addition, S 0based denitrifying biofilms are counter-diffusional. This is because the electron donor (S 0 ) is supplied from the biofilm attachment surface while the acceptor, for example, NO 3 − , is supplied from the bulk liquid. No existing mathematical model for S 0 -based denitrification considers this behavior. In this study, batch tests were used to determine the kinetic parameters for the reduction of NO 3 − , NO 2 − , and N 2 O.Additionally, a biofilm model was developed to explore the effects of counterdiffusion on overall fluxes, that is, the mass of NO 3 − or NO 2 − removed per unit biofilm support area per unit time. The maximum specific substrate utilization rates (q) for NO 3 − , NO 2 − , and N 2 O were 3.54, 1.98, and 6.28 g N g COD −1 ·d −1 , respectively. The maximum specific growth rates (μ) were 0.71, 1.21, and 1.67 d −1 for NO 3 − to NO 2 − , NO 2 − to N 2 O, and N 2 O to N 2 , respectively. Results suggest that the observed NO 2 − accumulation during S 0 -based denitrification results from a lowq for NO 2 − relative to that for NO 3 − . The highq for N 2 O, relative to that for NO 3 − and NO 2 − , suggest that little N 2 O accumulation occurs during denitrification. A counter-diffusional biofilm model was used to predict trends for NO 3 − fluxes, and confirmed NO 2 − accumulation in S 0 -based denitrification biofilms. It also explains the observed detrimental effects of biofilm thickness on denitrification fluxes. This study allows a more accurate prediction of NO 3 − , NO 2 − , and N 2 O transformations in S 0 -based denitrification.

Integrated experimental and modeling evaluation of removal efficiency and energy consumption for an autotrophic denitrifying biocathode

“…Biofilm growth/decay in the short and long term, and the impact of the biofilm thickness on denitrification efficiency and current demand should also be kept in consideration as substrate diffusion in the biofilm may greatly affect the denitrification process. 50,51 Perchlorate is often concomitant with NO 3 − in groundwater, has a similar reduction potential (0.75 for NO 3 − /N 2 and 0.87 for ClO 4 − /Cl), and may compete for electrons in biocathodic denitrification: 52 the presence of an additional TEA may strongly influence the denitrification kinetics also due to the different optimal pH for reduction Environmental Science: Water Research & Technology Paper overall denitrification process; similar findings were reported by Clauwaert et al 53 for denitrifying biocathodes in MFCs.…”

Improved Performance of Sulfur-Driven Autotrophic Denitrification Process by Regulating Sulfur-Based Electron Donors

“…The nucleophilic attack between sulfide (S 2− ) and S 0 under neutral or alkaline conditions results in the cleavage of S 8 0 rings and the formation of polysulfide (S n 2− ) as detailed in Equation ( 2) [20]. This chemical reaction has received much attention due to the higher solubility and bioavailability of S n 2− [20,28,29]. Therefore, the polysulfide-involved SADN (PiSADN) process (Equation (3)) might be an effective method for realizing high-rate NO 3 − removal.…”

Modelling the effect of SMP production and external carbon addition on S-driven autotrophic denitrification

“…In this framework, mathematical modelling is a useful tool to elucidate the competition among different microbial families and the performances in terms of nitrate removal and sulfate production occurring during the SdAD process. Indeed, previous mathematical models with elemental sulfur as electron donor have been mainly focused on evaluating the kinetics of the process in terms of nitrate removal 20 – 22 , nitrite accumulation 5 and N 2 O emission 23 , 24 . In addition, the co-occurrence of SdAD and heterotrophic denitrification 17 , 25 has been also modelled to investigate the same parameters.…”