Growth limiting conditions and denitrification govern extent and frequency of volume detachment of biofilms

This study aims at evaluating the mechanisms of biofilm detachment with regard of the physical properties of the biofilm. Biofilms were developed in Couette–Taylor reactor under controlled hydrodynamic conditions and under different environmental growth conditions. Five different conditions were tested and lead to the formation of two aerobic heterotrophic biofilms (aeHB1 and aeHB2), a mixed autotrophic and heterotrophic biofilm (MAHB) and two anoxic heterotrophic biofilms (anHB1 and anHB2). Biofilm detachment was evaluated by monitoring the size of the detached particles (using light-scattering) as well as the biofilm physical properties (using CCD camera and image analysis). Results indicate that volume erosion of large biofilm particles with size ranging from 50 to 500 lm dominated the biomass loss for all biofilms. Surface erosion of small particles with size lower than 20 lm dominates biofilm detachment in number. The extent of the volume detachment events was governed by the size of the biofilm surface heterogeneities (i.e., the absolute biofilm roughness) but never impacted more than 80% of the mean biofilm thickness due to the highly cohesive basal layer. Anoxic biofilms were smoother and thinner than aerobic biofilms and thus associated with the detachment of smaller particles. Our results contradict the simplifying assumption of surface detachment that is considered in many biofilm models and suggest that discrete volume events should be considered

Parameter and State Estimation of an Anaerobic Digestion of Organic Wastes Model with Addition of Stimulating Substances

New control inputs are introduced in the 5th order mass-balance non-linear model of the anaerobic digestion, which reflects the addition of stimulating substances (acetate and glucose). Laboratory experiments have been done with step-wise and pulse changes of these new inputs. On the basis of the step responses of the measured variables (biogas flow rate and acetate concentration in the bioreactor) and iterative methodology, involving non-linear optimisation and simulations, the model coefficients have been estimated. The model validity has been proved by another set of experiments. The observation part is built on a two-step structure. One estimator and two observers are designed on the basis of this process model. Their stability has been proved and their performances have been investigated with experimental data and simulations

Transcriptome and Proteome Exploration to Model Translation Efficiency and Protein Stability in Lactococcus lactis

This genome-scale study analysed the various parameters influencing protein levels in cells. To achieve this goal, the model bacterium Lactococcus lactis was grown at steady state in continuous cultures at different growth rates, and proteomic and transcriptomic data were thoroughly compared. Ratios of mRNA to protein were highly variable among proteins but also, for a given gene, between the different growth conditions. The modeling of cellular processes combined with a data fitting modeling approach allowed both translation efficiencies and degradation rates to be estimated for each protein in each growth condition. Estimated translational efficiencies and degradation rates strongly differed between proteins and were tested for their biological significance through statistical correlations with relevant parameters such as codon or amino acid bias. These efficiencies and degradation rates were not constant in all growth conditions and were inversely proportional to the growth rate, indicating a more efficient translation at low growth rate but an antagonistic higher rate of protein degradation. Estimated protein median half-lives ranged from 23 to 224 min, underlying the importance of protein degradation notably at low growth rates. The regulation of intracellular protein level was analysed through regulatory coefficient calculations, revealing a complex control depending on protein and growth conditions. The modeling approach enabled translational efficiencies and protein degradation rates to be estimated, two biological parameters extremely difficult to determine experimentally and generally lacking in bacteria. This method is generic and can now be extended to other environments and/or other micro-organisms

Automatisation d'un procede de fermentation semi-continu: optimisation et commande

SIGLEINIST T 74139 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Contribution à la commande de procédés biotechnologiques : application au traitement biologique de la pollution

In this document are presented our research activities since 1990 relative to modelling, parameter identification, state observation and control of biotechnological processes. Our main contributions in this domain are briefly explained with respect to the literature. The objective of the first chapter is to show the necessity of control of biological wastewater treatment processes, by defining the stakes, constraints and control problems. Following chapters concern process modelling, parameter identification tools and problems, process analysis and control. Conclusions and prospective complete this document by insisting of the main problem of such processes, i.e., lack of sensors, and propose some research directions to overcome this problem.Ce document présente nos activités de recherche depuis 1990 (fin du doctorat) dans le domaine de l'Automatique appliquée aux problèmes de modélisation, identification, observation et commande de procédés biotechnologiques. Nous présentons ici de façon synthétique nos principales contributions dans ce domaine, en replaçant nos travaux dans la littérature existante. Le premier chapitre a pour but de montrer la nécessité du contrôle des procédés biologiques de traitement de la pollution en définissant les enjeux, les contraintes et la problématique de commande. Dans les chapitres suivants sont successivement présentés les modèles que nous utilisons, les problèmes et outils pour l'identification des paramètres, les points clés de l'analyse de ces modèles et leur utilisation pour le contrôle des réactions biologiques. Nos conclusions et prospectives complètent le mémoire en insistant sur le problème majeur de ces procédés, l'absence d'instrumentation, et en proposant quelques pistes pour contourner ce problème

Simulation and control of denitrification biofilters described by PDEs

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Modelling and simulation of the steady-state of secondary settlers in wastewater treatment plants

This paper discusses the steady-state modelling of thickening in circular secondary settlers of activated sludge processes. The limitations of the solid flux theory basic models to represent steady-state operating conditions serve as a basis to introduce more sophisticated models derived from computational fluid dynamics. Parameter identification and sensitivity studies have been performed from lab-scale continuous experiments

Un tour d'horizon sur les techniques anti-windup pour les systèmes saturés

National audienceCet article traite de la synthèse anti-windup, technique de retouche d'un contrôleur qui permet de prendre en compte de manière explicite les phénomènes de saturation des actionneurs et de réduire leur impact négatif sur la dynamique d'un système commandé. Le procédé est décrit par un modèle d'état dynamique linéaire, de même que son contrôleur nominal construit a priori sans tenir compte des saturations. Les méthodes proposées s'appuient sur l'utilisation de conditions de secteurs afin d'encapsuler la fonction saturation et exploitent la stabilité de Lyapunov au travers de fonctions quadratiques permettant d'exprimer les conditions de stabilité et de performances par des inégalités matricielles linéaires

Process monitoring and control with artificial intelligence techniques

National audienc