Modeling and simulation of a modified Ludzack-Ettinger wastewater treatment bioprocess based on the concept of multifunctional microbiota.

Abstract

This research investigates the behavior of key components within aerobic and anoxic bioreactors in Biological Nitrogen Removal (BNR) bioprocesses. A mathematical model based on the Modified Ludzack-Ettinger (MLE) configuration is proposed. The model comprises an ensemble of ten differential equations derived from mass balances in the MLE system, complemented with a set of biokinetic models. To reduce complexity and enhance applicability, the model treats all nitrogen and phosphorus compounds as atomic N and P, and aggregates carbon sources as Chemical Oxygen Demand (COD), eliminating the need for tuning complex compound-specific parameters. The model was calibrated and validated using analytical determinations of nitrogen, phosphorus, COD, dissolved oxygen, and biomass concentrations from experiments conducted with synthetic wastewater in aerobic and anoxic reactors. Complementing this, a metagenomic study characterized the diversity and relative abundance of taxonomic groups involved in nitrogen and phosphorus metabolism within the microbial communities. Utilizing biokinetic and stoichiometric parameters for the entire microbiota, the model can be solved for both transient and steady-state conditions across a range of operational variables. It enables the estimation of bioprocess resilience following disturbances and the subsequent recovery time to a new steady state. A one-at-a-time (OAT) sensitivity analysis identified the parameters most significantly affecting state variables. The experimental results confirm the model's validity and reliability in simulating BNR processes.