Global stabilization of the chemostat with delayed and sampled measurements and control

International audienceThe classical model of the chemostat with one substrate, one species and a Haldane type growth rate function is considered. The input substrate concentration is supposed to be constant and the dilution rate is considered as the control. The problem of asymptotically stabilizing an equilibrium point of this system in the case where the measured concentrations are delayed and piecewise constant with a piecewise constant control is addressed

A method for the reconstruction of unknown non-monotonic growth functions in the chemostat

We propose an adaptive control law that allows one to identify unstable steady states of the open-loop system in the single-species chemostat model without the knowledge of the growth function. We then show how one can use this control law to trace out (reconstruct) the whole graph of the growth function. The process of tracing out the graph can be performed either continuously or step-wise. We present and compare both approaches. Even in the case of two species in competition, which is not directly accessible with our approach due to lack of controllability, feedback control improves identifiability of the non-dominant growth rate.Comment: expansion of ideas from proceedings paper (17 pages, 8 figures), proceedings paper is version v

A general chemostat model with second-order Poisson jumps: asymptotic properties and application to industrial waste-water treatment

A chemostat is a laboratory device (of the bioreactor type) in which organisms (bacteria, phytoplankton) develop in a controlled manner. This paper studies the asymptotic properties of a chemostat model with generalized interference function and Poisson noise. Due to the complexity of abrupt and erratic fluctuations, we consider the effect of the second order Itô-Lévy processes. The dynamics of our perturbed system are determined by the value of the threshold parameter $\mathfrak{C}^{\star}_0$. If $\mathfrak {C}^{\star}_0$ is strictly positive, the stationarity and ergodicity properties of our model are verified (practical scenario). If $\mathfrak {C}^{\star}_0$ is strictly negative, the considered and modeled microorganism will disappear in an exponential manner. This research provides a comprehensive overview of the chemostat interaction under general assumptions that can be applied to various models in biology and ecology. In order to verify the reliability of our results, we probe the case of industrial waste-water treatment. It is concluded that higher order jumps possess a negative influence on the long-term behavior of microorganisms in the sense that they lead to complete extinction

Nonlinear predictors for systems with bounded trajectories and delayed measurements

Novel nonlinear predictors are studied for nonlinear systems with delayed measurements without assuming globally Lipschitz conditions or a known predictor map but requiring instead bounded state trajectories. The delay is constant and known. These nonlinear predictors consists of a series of dynamic filters that generate estimates of the state vector (and its maximum magnitude) at different delayed time instants which differ from one another by a small fraction of the overall delay

Transient Electron Donor Concentration Experiments for the Determination of Dehalogenation Rate and Kinetic Parameter Shifts in an Anaerobic Microbial Culture

Trichloroethene (TCE) is a common groundwater contaminant. Bioremediation, or the enhancement of natural microbial processes for the transformation of toxic compounds in soil and groundwater, is an effective solution to this widespread problem. The organisms that transform TCE in the subsurface are sensitive to environmental conditions, especially to the presence of an electron donor, which is required in the form of hydrogen (H₂) for the microbial processes to occur. This study explored the effects of electron donor concentration on TCE transformation rates of the anaerobic bacteria, Dehalococcoides mccartyi. Degradation rates of TCE and its transformation products were monitored for nine months following an increase in electron donor concentration within reactors maintaining mixed cultures of D. mccartyi at Oregon State University. Kinetic parameters representative of microbial transformation abilities were also monitored to develop conclusions regarding the community dynamics within the reactors. Key Words: Trichloroethene, bioremediation, Dehalococcoides, electron dono

Modeling studies of biological gas desulfurization under haloalkaline conditions

Abstract Biogas, synthesis and natural gas streams often require treatment because of the presence of gaseous hydrogen sulphide (H2S). About 25 years ago, a biotechnological gas treatment process was developed as an alternative to the conventionally applied technologies. This process is known as the Thiopaq process and offers a number of advantages compared to the existing physical-chemical processes. Depending on the process conditions, H2S is oxidized to elemental bio-sulfur (90-94 mol%) and sulphate (6-10 mol%). In order to enable cost effective large scale applications, the selectivity for sulfur production should be increased to more than 97 mol%. Hence, a better understanding of the combined effect of abiotic and biological reaction kinetics and the relation to hydrodynamic characteristics is required. The first part of this PhD study focuses on biological reaction kinetics and biological pathways for sulphide oxidation that occur in the process at haloalkaline conditions. It was found that two different sulfide oxidizing enzyme systems are present in haloalkaline sulfide oxidizing bacteria. It has been hypothesized that the different enzymatic routes are determined by the process conditions. Both enzyme systems were taken into account to propose and validate a new physiological mathematical model that can handle multi-substrates and multi-products. In the second part of the thesis, this model was evaluated via a normalized sensitivity method and it was demonstrated that certain key parameters affect the activity of the biomass at different substrate levels. Furthermore, from CSTR simulations it has been demonstrated that non-linear effects are of importance when scaling up from lab-scale to full-scale industrial units. Finally, the developed kinetic models have been incorporated in a full-scale biodesulfurization model that includes the effects of turbulent flow regimes and mass transfer of oxygen. This enables us to better understand the overall process. Moreover, the model can also be used as a tool to design model-based control strategies which will lead to better overall process performance, i.e. maximize sulfur production and minimize chemical consumption rates.</p

生物学的亜硝酸酸化における可逆的および非可逆的阻害の動力学モデルに関する研究

本研究は、生物学的排水処理プロセスにおける微生物の増殖阻害について、その応答を阻害物質の濃度や曝露時間と関連付けて数学的に表現することを目的としたものである。北九州市立大

Instrumentation and control of anaerobic digestion processes: a review and some research challenges

The final publication is available at Springer via http://dx.doi.org/10.1007/s11157-015-9382-6[EN] To enhance energy production from methane or resource recovery from digestate, anaerobic digestion processes require advanced instrumentation and control tools. Over the years, research on these topics has evolved and followed the main fields of application of anaerobic digestion processes: from municipal sewage sludge to liquid mainly industrial then municipal organic fraction of solid waste and agricultural residues. Time constants of the processes have also changed with respect to the treated waste from minutes or hours to weeks or months. Since fast closed loop control is needed for short time constant processes, human operator is now included in the loop when taking decisions to optimize anaerobic digestion plants dealing with complex solid waste over a long retention time. Control objectives have also moved from the regulation of key variables measured online to the prediction of overall process perfor- mance based on global off-line measurements to optimize the feeding of the processes. Additionally, the need for more accurate prediction of methane production and organic matter biodegradation has impacted the complexity of instrumentation and should include a more detailed characterization of the waste (e.g., biochemical fractions like proteins, lipids and carbohydrates)andtheirbioaccessibility andbiodegradability characteristics. However, even if in the literature several methodologies have been developed to determine biodegradability based on organic matter characterization, only a few papers deal with bioaccessibility assessment. In this review, we emphasize the high potential of some promising techniques, such as spectral analysis, and we discuss issues that could appear in the near future concerning control of AD processes.The authors acknowledge the financial support of INRA (the French National Institute for Agricultural Research), the French National Research Agency (ANR) for the "Phycover" project (project ANR-14-CE04-0011) and ADEME for Inter-laboratory assay financial support.Jimenez, J.; Latrille, E.; Harmand, J.; Robles Martínez, Á.; Ferrer Polo, J.; Gaida, D.; Wolf, C.... (2015). Instrumentation and control of anaerobic digestion processes: a review and some research challenges. Reviews in Environmental Science and Biotechnology. 14(4):615-648. doi:10.1007/s11157-015-9382-6S615648144Aceves-Lara CA, Latrille E, Steyer JP (2010) Optimal control of hydrogen production in a continuous anaerobic fermentation bioreactor. 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