Offer Description
Laboratory description:
LEESU (Laboratory for Water, Environment and Urban Systems, https://www.leesu.fr/) is a joint laboratory of the University of Paris-Est Créteil (UPEC) and the École Nationale des Ponts et Chaussées (ENPC). It conducts interdisciplinary research on water management in urban areas, with recognized expertise in the field of monitoring organic matter in aquatic environments and wastewater treatment plants.
Project summary:
Dissolved organic matter (DOM) is involved in a large number of biogeochemical processes and therefore plays an essential role in surface aquatic ecosystems. In particular, it plays a central role in the nature of the metabolism (heterotrophic or autotrophic) of river and therefore in the release of greenhouse gases into the atmosphere. In river ecosystems, biodegradable DOM can lead to eutrophication and depletion of dissolved oxygen in the environment (leading to fish mortality), as it increases the respiratory activity of the microorganisms that consume it. To better understand the various processes related to dissolved organic matter (DOM) and model river quality, it is necessary to better characterize its chemodiversity, its sources (which are strongly correlated with the hydroclimatic situation) and its transformations. Given the dynamics of the processes involving DOM, it is necessary to be able to characterize DOM at high frequency (several times per hour).
In addition to the biogeochemical issues mentioned above, there are significant operational challenges related to water purification and wastewater treatment. These two operational environments share the objective of removing DOM from the water to be treated for environmental and health reasons, respectively. To achieve this, high-performance technologies have been integrated into these treatment processes. However, their operation requires a high level of technical and scientific expertise and appropriate metrology. High-frequency characterization of the DOM present in the influents and effluents of the various treatment stages is one of the preferred methods for optimizing the control and operation of facilities in real time in order to improve treatment efficiency while saving energy and chemical reagents. There is therefore a very strong demand for the development of measurement technologies that can be implemented online or even in situ and enable high-frequency, real-time measurements.
LEESU, in collaboration with SIAAP (the public sanitation service for the Paris region), has developed a fluorescence probe (Fluocopée®) to characterize DOM in situ and at high frequency in aquatic environments. This probe was patented (EP4040139A1) in 2022. The advantage of this probe is that it allows in situ analysis of 29 different fluorophores in around ten minutes, compared with only 1 to 3 for commercially available fluorescence probes, and therefore better characterization of the chemical nature of DOM.
Five Fluocopée® probes are currently deployed in the Seine basin upstream and downstream of the Paris metropolitan area and constitute the MATOS observatory. The probes deployed in the MATOS observatory will provide insights into the biogeochemical processes taking place in the aquatic environments mentioned in the introduction. It will also make it possible to estimate the flows of organic matter from urban discharges in the Paris metropolitan area. The flows of dissolved organic carbon and its various biodegradable fractions passing through the estuary will also be quantified with a high degree of accuracy.
Main tasks and activities:
In collaboration with the LEESU’s “organic matter” thematic group, consisting of two researchers (Gilles Varrault (Professor) and Angélique Goffin (Assistant Professor)) and two to three PhD students, the postdoctoral researcher will work on the various tasks listed below.
Task 1: Optimization of post-processing of data acquired by the MATOS observatory and implementation of real-time visualization
The first objective of this task (task 1.1) is to improve and automate the post-processing of data acquired by high-frequency Fluocopée probes (four measurements per hour). The main objective of this task is to develop an automatic tool for evaluating data quality. The second objective of this task (task 1.2) will be to develop a graphical interface to enable real-time visualization of the data acquired by the MATOS observatory on the internet.
Task 2: Extension of the Matos observatory
The postdoctoral researcher recruited will be responsible for extending the MATOS observatory. He or she will participate in the selection of sites for the installation of Fluocopée probes, in collaboration with the SIAAP for installation at the outlet of STEU and storm water overflows, and in collaboration with the GIP Seine-Aval (which is piloting the Seine-Aval research programme, (https://www.seine-aval.fr)) for the extension towards the estuary and the sea. He or she will be responsible for installing the probes, monitoring them and interpreting the data obtained.
Task 3: Active management of bathing sites in the Seine and Marne rivers (Collaborations: SIAAP, City of Paris.)
In the summers of 2026 and 2027, the records of faecal indicator bacteria concentrations provided by Fluocopée probes (using the proxy developed in 2024) deployed in the Paris region will be compared with Escherichia coli measurements carried out using standard microbiological methods. This will validate the use of the Fluocopée probe as a tool for measuring faecal bacteria in rivers, paving the way for active management of river bathing sites and thus ensuring better health safety for bathers. If necessary, the statistical model already in place in 2024 will be improved to establish a more effective proxy for estimating microbiological contamination based on measurements taken by Fluocopée probes. The postdoctoral researcher recruited will be responsible for this action in collaboration with, in particular, the City of Paris and the SIAAP, which will be responsible for the microbiological analysis campaigns carried out during the summer period.
Task 4: Optimisation of water purification (Collaborations: SEDIF (Public Water Service))
The postdoctoral researcher will work on the link between the properties of the DOM contained in the resource and its treatability in terms of DOM removal in drinking water treatment plants. This treatability can then be assessed based on the quantities and chemical nature of the MO (biodegradability and solubility) in the resource, making it possible to link the fluorescence properties of the DOM to its treatability in drinking water treatment plants. This will enable managers to adapt the treatments applied to the resource in real time.
Where to apply
E-mail: varrault@u-pec.fr
Skills/Qualifications
Qualifications :
– Master’s degree in environmental physical chemistry
– PhD in environmental physical chemistry in the field of water, if possible related to organic matter
– Experience in spectrofluorescence analysis
– Very good command of Python and experience in managing data from high-frequency analysis
– Good command of statistical tools for data analysis
– Team spirit, rigour, organisational skills, adaptability, open-mindedness
– Autonomy, scientific curiosity
– Good oral and written communication skills (French or English)
Additional Information
Benefits
Contract duration:
from 1 December 2025 to 30 November 2027
Gross monthly salary:
€2,800, with room for negotiation depending on experience. Partial coverage of health insurance and commuting costs.
Selection process
How to apply:
Please send your CV (including a list of publications and the contact details of two scientific referees) and a cover letter to Gilles Varrault (varrault@u-pec.fr) before 1 October 2025
Website for additional job details: https://www.leesu.fr/
