1 PhD position on Rheology and NIR, Towards a Whole Characterisation of Organic Complex Fluids in France | National Research Institute of Science and Technology for Environment and Agriculture

The aim of the PhD consists in defining a bunch of descriptors, easily and rapidly measurable, representative of sludge structure, composition and interactions between the compounds. These descriptors would form kind of “topological ball” defining sludge rheology: two sludge samples in the same ball would show the same rheological behaviour.

Scientific purposes

This PhD will lean on previous works developed by 2 Irstea teams (on the one hand on organic fluids characterisation based on electrical measurements and rheology and on the other hand on near infrared (NIR) spectroscopy on turbid fluids and soils). Its purpose consists in generating a matrix of data, representing sludge characterisation and from which it will be possible to link sludge macroscopic behaviour, microscopic structure and indicators of sludge composition.

In that way, NIR spectroscopy will be related to rheological and electrical analysis to understand how sludge evolves during treatment processes, e.g. anaerobic digestion.

Thus, at the end of this work, we intend to be able to characterise both the dynamic of evolution of the rheological behaviour (based on electrical measurements) and instantaneous pictures (based on NIR spectroscopy). The characterisation method that will be developed will allow us to analyse and optimise treatment processes via in-situ measurements.

Methods

On a methodological point of view, this PhD work will be divided into two parts. In a first time, focus will be done on NIR spectroscopy, including optics and mathematical analysis. The second part will be dedicated to rheology and electrical measurements, then simultaneous characterisation using NIR. First part will be realized in Montpellier (South of France) and second in Montoldre (Auvergne, Centre of France). This experimental work will start with the study of the state of the art.

Teams’ introduction

This PhD is a 3-years contract. The job is located in France.

This PhD will happen commonly within two Irstea teams: one located on the Centre of Montpellier, the other on the Centre of Clermont-Ferrand, on the site of Montoldre (Allier). The PhD subject being at the interface of the activities of these two teams, the applicant will be supervised by two researchers, Ryad Bendoula and Emilie Dieudé-Fauvel. The PhD direction will be done by Jean-Michel Roger and Jean-Christophe Baudez, both having an HDR (accreditation to supervise research).

The first team, located in Montpellier is well-known for its research in material characterisation and more precisely in near infra-red spectroscopy. It develops specific sensors and models for characterizing complex media like wastes, soils or turbid liquid (e.g. micro algae). It has developed a knowledge internationally recognised in NIR spectroscopy and chemometrics as shown by the chair of the 16th major international NIR conference in 2013 and of the 11th major international chemometrics conference in 2008. Original optical mountings have been set up for addressing turbid and complex matter and dedicated modelling techniques have been developed for overcoming the calibration robustness problems. These innovations are currently transferred to industrial partners e.g. in the context of waste sorting (TRI+ project) or of the micro algae monitoring (GreenStar project).

The second team, based in Auvergne (more precisely in Montoldre) is known for its pioneering work on sludge management and sludge rheology. Its experience in wastewater treatment domain will also allow us to keep in mind the professionals’ concerns. For the last 12 years, specific attention has been paid to biosolids characterisation (mainly talking about sewage sludge), using rheology, texturometry or electrical impedance spectroscopy. All those methods are dedicated to study complex materials behaviour. Such tools allowed us to develop the fields of application and many projects like the study of sewage sludge dewatering or biosolids transformation processes are realized. Many partnerships are developed in France and abroad: with industrials (Faure Equipements, Veolia, etc.), public institutions (ADEME, Water Agencies, Ministry in charge of the Ecology, etc.), and universities (Limoges (France), Liege (Belgium), Delaware (US), Melbourne (Australia)…).