Ph.D position in Understanding clogging mechanisms and evaluating remediation methods for treatment wetland

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INRAE presentation

The French National Research Institute for Agriculture, Food, and Environment (INRAE) is a major player in research and innovation. It is a community of 12,000 people with 272 research, experimental research, and support units located in 18 regional centres throughout France. Internationally, INRAE is among the top research organisations in the agricultural and food sciences, plant and animal sciences, as well as in ecology and environmental science. It is the world’s leading research organisation specialising in agriculture, food and the environment. INRAE’s goal is to be a key player in the transitions necessary to address major global challenges. Faced with a growing world population, climate change, resource scarcity, and declining biodiversity, the Institute has a major role to play in building solutions and supporting the necessary acceleration of agricultural, food and environmental transitions.

Work environment, missions and activities

Work environment: the research unit you will be working in is REVERSAAL at the INRAE Lyon-Villeurbanne center. This research unit (UR) works on the treatment and valorization of wastewater (https://reversaal.Iyon-grenobIe.hub.inrae.fr/). As part of this research, REVERSAAL is particularly interested in monitoring wastewater treatment facilities, in rural or urban environments. This thesis will be co-supervised by INSA Lyon's DEEP laboratory as part of the activities of the RESEED joint research unit. You will be registered at PhD student at the Ecole Doctorale 206 " Chemistry, Process Engineering, Environment ".
Thesis background: Treatment wetlands for domestic wastewater is the most widespread technology for small communities (~20% of the number of wastewater treatment plants in France, i.e. around 6,000 installations, of which around 11% will be over 20 years old in 2024) in France. This technique is also widely used internationally. Adapted specifically for small communities, this sustainable and resilient vegetated system mimics the biological processes occurring in natural wetlands to treat effluent and, thanks to the associated ecosystem benefits, is classified as a "nature-based solution".
One of the current challenges associated with this technology is to understand the clogging mechanisms of filter media aggregates, which lead to filtration malfunction and end-of-life of the treatment plant. It is therefore necessary to develop strategies for rehabilitating these structures. Despite the considerable financial stakes involved, there is no knowledge or method for characterizing ageing structures, preventing and managing the accumulation of deposits in the filter media aggregates, nor any alternative to landfilling the materials, for example by promoting cleaning and reuse.
The aim of the proposed thesis, co-financed by the French Office for Biodiversity (OFB) and INRAE, is to characterize in detail the deposit forming in the filter media aggregates of vertical flow treatment wetlands, and then to develop one or more simple unclogging technique. Following a literature review, experimental work will be carried out under controlled conditions, on two scales: laboratory columns and semi-industrial-scale pilots (2 m²). These experiments will validate the technical feasibility and quantify the effectiveness of the methods in order to predict their performance. Various rehabilitation methods will be tested (among biological, chemical and mechanical solutions identified) to determine their performance and limitations.
The final outcome is to gain a better understanding of the clogging of treatment wetlands and to offer a first evaluation of several remediation techniques to field operators and funding agencies at national and international level.
In this thesis, you will be more specifically in charge of:
1.    Carry out a literature review on the mechanisms of clogging, the properties of the deposit and on the remediation technologies.
2.    Column and pilot testing of cleaning techniques and protocols identified in the literature to identify advantages/disadvantages, achievable cleaning performance and by-products generated.
3.    Test the ex-situ maturation of deposits on a dedicated platform.
4.    Seek alternative solutions to the current "excavate and landfill aggregates and rehabilitate with new materials" scenario in order to recover resources by reusing aggregates in-situ or ex-situ after cleaning the deposit.
5.    Promote scientific results at national/international conferences and in scientific journals.

Special operating conditions:
-    The experiments will take place either in the laboratories' experimental rooms, or in the Feyssine research hall (located 1.5 or 2 km from REVERSAAL’s offices).
-    Access to national and international bibliographic databases.

Training and skills

Recommended training: engineering or Master's 2 in process or bioprocess engineering, environmental chemistry or near-surface geo-chemistry.
Desired knowledge: wastewater treatment processes, characterization of organic matter, understanding of biological processes.
Experience appreciated: initial experience in the research field would be a plus.
Desired skills: strong taste for experimental work, team spirit, experimental rigor.

INRAE's life quality

By joining our teams, you benefit from (depending on the type of contract and its duration):

- up to 30 days of annual leave + 15 days "Reduction of Working Time" (for a full time);
- parenting support: CESU childcare, leisure services;
- skills development systems: training, career advise;
- social support: advice and listening, social assistance and loans;
- holiday and leisure services: holiday vouchers, accommodation at preferential rates;
- sports and cultural activities;
- collective catering.

How to apply

I send my CV and my motivation letter