CDD Doctorat Infiltration d'eau usée traitée pour la recharge des nappes M/F

Organisation/Company CNRS Department Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols Research Field Geosciences Biological sciences Researcher Profile First Stage Researcher (R1) Application Deadline 23 Sep 2026 - 23:59 (UTC) Country France Type of Contract Temporary Job Status Full-time Hours Per Week 35 Offer Starting Date 2 Nov 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

Regular meetings will be scheduled

• Weekly meetings with the PhD supervisors
• monthly meetings with the project partners
• annual meeting with the RECHARGE project consortium

In the context of global changes, with increasing drought, heavy rainfall events and growing population, pressure on fresh water resources increases. Hence, exploring ways of enhancing groundwater recharge is crucial to maintain sustainable resources.

Natural Water Retention Measures (NWRMs) associated with non-conventional water resources (urban stormwater, rural runoff, treated wastewater) provide a range of promising solutions to improve groundwater recharge.

Nevertheless, scientific questions and societal hurdles to the implementation of NWRMs remain including the evaluation of their impact in quantity and quality on the groundwater resource, economical cost and ecosystemic value, up to societal perception and acceptability of such systems. In that context, there is an urgent need for more investigation on the opportunities and limits of NWRMs for the production of guidelines to raise users, stakeholders and policy‑makers' awareness on the potential for increasing groundwater recharge.

The RECHARGE project aims to investigate the NWRMs to enhance groundwater recharge through a truly interdisciplinary approach

Four scientific questions are addressed:

1. What is the ability of NWRMs to improve the recharge?
2. To which extent is the receiving ecosystem capable of removing chemical and microbiological pathogenic contaminants?
3. What are the appropriate monitoring indicators for these ecosystems?
4. What are the societal locks and drivers?

A pluri-disciplinary team of 20 researchers in Natural Sciences (Hydrogeology, Geochemistry, Microbiology, Modelling) and Human and Social Sciences (Social design, Environmental psychology, Economy) and Young researchers (4 PhD students and 2 Postdoc) will collaborate together to propose co‑constructed strategies to improve groundwater recharge.

DESCRIPTION OF THE PHD WORK

The PhD work will investigate a pilot SAT - Soil Aquifer Treatment in natural conditions to determine the fate of chemical and microbiological pathogenic contaminants, the associated processes and key factors.

Soil Aquifer Treatment (SAT) is proposed as a natural tertiary treatment for additional removal of micropollutants and pathogenic micro‑organisms (Amy and Drewes, 2007; Bekele et al., 2011; Laws et al., 2011), and even more for possible treated wastewater reuse (Salgot et al., 2018) contributing to increase the resilience of socio‑hydrosystems.

While 98% of the treated wastewater coming from Waste Water Treatment Plants (WWTPs) ends into the sea or rivers, SAT systems offer environmental benefits and greater social acceptability. However, taking into consideration the scale of these socio‑hydrosystems, little data has been gathered on the evolution of the water chemical and microbiological pathogenic fingerprints and on their appropriation by local stakeholders (water users, local residents, etc.). This dual data acquisition has to be fulfilled as the social and the hydrological systems are bound to evolve together over time. The overall impact of the SAT, downstream the discharges, as well as their in situ removal efficiency regarding emerging contaminants and microbiological pathogens (including specific genes), is currently poorly understood.

For chemical contaminants, the removal and fate of organic contaminants (TrOCs) and their metabolites are mainly controlled by sorption (Thiebault et al., 2016), dilution, the nature of the compounds (Hermes et al., 2019), and the biodegradation activity (Crampon et al., 2021) of the autochthonous microbial communities (Falås et al., 2016; Regnery et al., 2016).

For microbiological fecal pathogens, the removal capacity of SAT can be explained by the loss of viability or inactivation of bacteria, protozoa or viruses during the transfer in the unsaturated zone of effluents partially depurated by a reed bed (Regnery et al., 2015). This removal efficiency is difficult to estimate because it strongly depends on the effluent composition, the infiltration rate and the temperature (Foppen et al, 2006 ).

The pilote site of Agon-Coutainville

Agon Coutainville is a coastal area in La Manche (50) where major social issues are: tourism, bathing and shellfish farming.

Since 2005, the treated effluent from the WWTP are infiltrated into on of the first SAT system. The treated effluent from the WWTP is discharged into reed beds, infiltrates and then flows in the sand aquifer to the sea (800 m).

Since 2016, this pilot site is monitored as part of BRGM/Sorbonne University studies (Picot‑Colbeaux et al., 2021, Guillemoto, 2022): piezometers allow to study groundwater. It is subject to anthropic (WWTP), climatic and tidal forcings (sea). The water in the SAT is a mixture of treated effluents from WWTPs containing TrOCs (including pharmaceutical residues), seawater (saline intrusion) and natural recharge, with different flow rates in the porous medium. An initial hydrogeological model has been developed (Picot‑Colbeaux et al., 2022; Guillemoto et al., 2023) and TrOCs sorption and degradation processes have been characterized (Crampon et al., 2021; Guillemoto et al., 2022).

Several piezometers (existing and to be installed within the project) provide direct access to the groundwater and the sediments (aquifer sands).

In this study, the PhD project will investigate the flow transect composed of 9 points equipped with specific probes (CTD diver) to record conductivity, temperature and water levels:

• 2 piezometers upstream of the infiltration give access to the upstream groundwater (non‑impacted by the treated wastewater)
• the outlet of the treatment plant
• the reef beds
• 4 piezometers downstream of the infiltration (impacted by the treated wastewaters)

AXIS 1: Analyse and synthesis of previous data (spatio temporal data since 2018)

1. Data of the plant (SAUR): chemical and microbiological quality of the effluent and the groundwater around the reef beds (time step ~1 month), effluent flow (time step 1h)
2. Data of previous campaigns:
3. About 10 campaigns from 2018 to 2025 on groundwater chemical data
4. 3 campaigns May 2024, Avril 2026 and July 2026 on groundwater and sediments: chemical and microbiological pathogens data
5. Time‑series of Water level, electrical conductivity and temperature along the flow transect (time step 10min, since 1 to 2 years depending on the points)

AXIS 2: New data acquisition

• Groundwater flow characterization: The water flows and residence time along the transect will be characterized in situ and in the lab by permeability experiments
• Chemical and microbiological pathogenic fingerprints: Six sampling campaigns will be scheduled, under contrasting hydro‑climatic and anthropogenic conditions. Samplings will be performed in waters (infiltrated water, reef bed water, and groundwater) and sediments.
• The PhD will measure: organic contaminants, major and trace ions, particulate and dissolved major nutrients (organic and mineral C, N, and P forms), fecal indicator bacteria (E. coli and intestinal enterococci) as well as pathogenic protozoa and virus (in collaboration with Eau de Paris lab).
• All the required methodologies and equipment are available and routinely implemented in both host laboratories of Sorbonne University and Rouen University

AXIS 3: Data interpretation and synthesis

• The whole data will be analyse to characterize the processes and the key factors of the SAT removal efficiency.
• Based on these results, a simple model of reactive transfer of chemical and microbiological contaminants will be proposed.
• Finally, a methodology and new hydrogeological, chemical and microbiological criteria‑indicators will be proposed to monitor the sustainability of managed infiltration and recharge.

SCIENTIF OBJECTIVES OF THE PHD WORK

Within this project, by following the pilot site, four major objectives will be addressed:

• the characterization of the chemical and microbiological pathogenic contaminants fingerprints within the receiving ecosystem downstream of WWTP discharges.
• the evaluation of the SAT removal efficiency for the chemical and microbiological pathogenic contaminants, by investigating associated processes and key factors.
• the modelisation of reactive transfers of chemical and microbiological pathogenic contaminants
• the proposal of a methodology and new hydrological, chemical and microbiological criteria‑indicators to monitor the sustainability of managed infiltration and recharge