Les bioprocédés environnementaux prennent une place de plus en plus importante dans le paysage industriel mondial. La complexité et la diversité des processus impliqués dans les réactions biologiques de dégradation des polluants limitent considérablement la compréhension et l’utilisation de ces procédés. De plus, les mesures disponibles pour le suivi de cette activité sont souvent hors-ligne et/ou indirectes. Dans ce cadre, les outils de modélisation phénoménologique permettent, via le choix d’hypothèses judicieuses, de lier les observations du système aux processus biologiques sous-jacents. Ces méthodes nécessitent néanmoins l’application d’une étude rigoureuse d’identifiabilité afin de pouvoir exploiter correctement les résultats obtenus. Les modèles ainsi développés permettent de capitaliser des connaissances sur la description des processus biologiques grâce aux mesures effectuées sur le système. Cette approche a été développé au travers de deux cas d’étude, correspondant à deux domaines d’application industrielle. La bioremédiation des sols contaminés aux hydrocarbures constitue la méthode la plus écologique de traitement des sols. Néanmoins, le processus de biodégradation peut être long, voire inexistant en fonction des conditions environnementales. Afin de mesurer l’efficacité de la dégradation, la mesure de la respiration en phase gaz apparaît comme étant l’observation la plus facile à mettre en œuvre. Le problème est que la simple mesure de la consommation d’oxygène est généralement insuffisante. Pour répondre à cette limite, un modèle capable d’expliquer les évolutions du quotient respiratoire apparent grâce aux différentes étapes de la biodégradation a été développé. Cette mesure pourrait alors donner une indication sur l’efficacité de la biodégradation. La seconde partie de ce travail, plus conséquente, s’intéresse à l’épuration des eaux usées par boues activées, elle reprend et amplifie l’approche méthodologique développée pour la biomédiation des sols. L’efficacité de ce traitement des eaux est grandement liée à la production de boues en excès, exprimée par le rendement hétérotrophe. Ce paramètre difficile à maitriser constitue une information primordiale pour la modélisation et la conduite des stations d’épurations. Il apparaît néanmoins que sa définition usuelle ne suffit pas à expliquer ses variations observées. Dans ce cadre, différents modèles phénoménologiques issus des travaux du groupe de travail ASM (Activated Sludge Modeling) ont été étudiés afin de décrire les variations de ce rendement apparent en introduisant les hypothèses réactionnelles liées au stockage du substrat. Une étude expérimentale en laboratoire a permis de confronter ces hypothèses à des mesures de dégradation de substrats purs par des boues activées en respiromètre. L’équilibre entre le stockage du substrat et la croissance bactérienne a ainsi été proposé comme source d’influence majeure sur la valeur du rendement. Ce travail a abouti à une clarification nécessaire de la définition du rendement hétérotrophe. / Environmental bioprocesses are gaining importance in the industrial landscape. Nevertheless, the complexity of mechanisms involved in biological reactions stays an issue for their implementation. Moreover, available measurements of biological activity are often off-tine and/or indirect. ln this context, phenomenological modeling tools are a solution to link observations of the system to underlying biological reactions, considering the right hypotheses. These methods require a rigorous sensitivity analysis in order to properly process the results. Thus, the models permit to obtain precise knowledge about biological systems thanks to indirect measurement. This approach was developed throughout two cases of study corresponding to two industrial fields of application. Bioremediation is the most ecological method for hydrocarbons contaminated soils remediation. Nevertheless, biodegradation can be long or absent depending on environmental conditions. In order to measure its efficiency, respiration measurement in the gas phase seems to be the easiest observation to implement. Oxygen measurement can be insufficient on its own, that is why a model able to describe the evolution of the apparent respiratory quotient has been developed considering the different steps of biodegradation. This observation alone could give insights on the efficiency of biodegradation. The second part of this work deals with activated sludge wastewater treatment using the theoretical approach developed for soil bioremediation. The eftïciency ofthe process depends on the excess production of sludge, which is linked to the heterotrophic yield of the reaction. This parameter is a key component for modeling and optimization of wastewater treatment plant. Most of the time, its common definition is not sufficient to explain its observed variations. In this context, several phenomenological models derived from the activated sludge models were studied to explain these variations, taking into account the substrate storage process. An experimental study was conducted in order to confront the reactional hypothesis of the models to actual measurements of single substrate degradations in respirometer. The balance between substrate storage and direct growth was proposed as a main component of the yield value. This study resulted in a necessary clarification of the heterotrophic yield definition.

The research part of the diploma thesis is focused on an issue of energy consumption in sludge treatment at wastewater treatment plants divided by the number of population equivalent. The aim of the practical part is to set indicators and propose evaluative criteria concerning energy performance of urban wastewater treatment plants. The verification of proposed criteria and energetic analysis result from data of the wastewater treatment plant in Novy Jicin.

Among all nanomaterials, which are intentionally manufactured and applied, nanosilver (nAg) is one of the most frequently applied nanomaterials. It is introduced into wastewater treatment plants (WWTPs) due to its use as antimicrobial resource in household and medical care products and hence concern raised regarding its impact on activated sludge organisms and their purification efficiency. Within this thesis, the effects of nAg on single species, simple food chains and communities related to activated sludge were investigated. Among all tested species in this thesis, the gammaproteobacteria R. planticola was the most sensitive organism regarding the tested nAg material, NM-300K. The environmental risk assessment (ERA), based on an assumed predicted environmental concentration derived from modeled concentrations of other types of nAg, revealed no risk for the activated sludge. This result should be interpreted with care, considering the tolerantly chosen safety factor for calculation of the predicted no effect concentration and the assumptions which were made concerning environmental concentrations. Differences in acute toxic effects of nAg on the ciliate P. tetraurelia were observed depending on the type of medium and the exposure pathway (via medium or via bacterial food). More detailed investigations are required to analyze the distribution, availability and uptake of nAg into ciliates in the respective tests. In chronic experiments concentration response was very steep in the range between the effect concentration determined in acute toxicity testing (resulting in 100% mortality) and a tenfold lower concentration (no effect observed) for both exposure pathways. Community experiments with activated sludge exposed to realistic and high concentrations of nAg revealed acute effects on the protozoan community at high nAg concentration using multivariate statistics for data analysis. In contrast, the sludge biotic index was not meaningful for data interpretation, as no differences were observed between the samples of different treatments. For chronic testing, more preliminary work is required to develop a protocol for artificial wastewater which serves the needs of activated sludge organisms over longer time periods and which retains a typical composition of the activated sludge community.