Experimental study and modeling of denitrification in an MBBR reactor

A denitrification mathematical model was used to describe the nitrates and organic carbons use by the denitrify biomass in the Moving Bed Biofilm Reactor (MBBR). The model integrates the diffusive mass transfer mechanism as well as double substrates Monod kinetics. Preliminary experiments were realized in order to assess the operating conditions for growth of attached biomass, the determination of the optimal (COD/NO3-N) ratio, moreover the results of the previous study of the residence time distribution in this MBBR established the optimal hydrodynamic operating conditions with a dead volume of 22%. In this reactor, seeded with a mixed liquor from a purification station, kaldnesk1 were used as carriers. A total of 6 kinetic and stoichiometric constants under anoxic conditions were determined by batch-test pulsed respirometry; some parametric have been determined experimentally, such as YHD, YNO, μ ˆ HD ${\widehat{\mu }}_{\text{HD}}$ and KS, and with their values 0.4 mgCOD (mgCOD)−1, 0.6 mg COD (mgCOD)−1,0.864 d−1 and 12.48 mg COD L −1, respectively. The other constants were determined using the model fitting (using MATLAB), such as KNO3 and bHD with its values, 0.25 mg NO3-N. L−1 and 0.061 d−1, respectively. The model was used to simulated different operating condition and the results included the concentration profiles of NO3-N, COD and XBH, which showed good agreement with the experimental ones, mainly by using the effective volume determined experimentally in the hydrodynamic study (RTD test) and which can reach 62% of the total volume under some operating. Additionally, these findings demonstrate that moving bed reactor characterization may be accomplished using in situ pulsed respirometry (MBBR).

Modeling integrated fixed-film activated sludge and moving-bed biofilm reactor systems I: mathematical treatment and model development

A mathematical model for integrated fixed-film activated sludge (IFAS) and moving-bed biofilm reactor wastewater treatment processes was developed. The model is based on theoretical considerations that include simultaneous diffusion and Monod-type reaction kinetics inside the biofilm, competition between aerobic autotrophic nitrifiers, non-methanol-degrading facultative heterotrophs, methanol-degrading heterotrophs, slowly biodegradable chemical oxygen demand, and inert biomass for substrate (when appropriate) and space inside the biofilm; and biofilm and suspended biomass compartments, which compete for both the electron donor and electron acceptor. The model assumes identical reaction kinetics for bacteria within suspended biomass and biofilm. Analytical solutions to a 1-dimensional biofilm (assuming both zero- and first-order kinetics) applied to describe substrate flux across the biofilm surface are integrated with a revised and expanded matrix similar to that presented as the International Water Association (London, United Kingdom) Activated Sludge Model Number 2d (ASM2d) stoichiometric and kinetic matrix. The steady-state mathematical model describes a continuous-flow stirred-tank reactor.