Ph. D. offers

Aller à : navigation, rechercher

Optimization of wastewater resource recovery by high-rate algal pond

This thesis project focuses on wastewater resource recovery technologies using microalgae. A previous PhD conducted in the laboratory demonstrated the treatment performance and developed a numerical model of a high-rate algal pond (raceway pond).

This study is a continuation of this work. A pilot reactor is already present in the laboratory.

The use of processes combining microalgae and bacteria has a very interesting potential. Indeed, via photosynthesis, algae use sunlight to convert mineral carbon (CO2) and nutrients contained in water (nitrogen, phosphorus) into biomass and oxygen (O2). At the same time, bacteria use the oxygen produced by algae for their metabolism leading to the degradation of organic compounds and oxidation of ammoniacal nitrogen, while producing the nitrates and CO2 required by the algae.

This natural process does not require any additional energy input. In addition, the content of the microalgae produced, which is rich in nutrients and organic matter (especially lipids), can be used as biofuel, fertilizer, etc. The High-Rate Algal Pond (HRAP) is a process that uses this consortium of algae and bacteria. It consists of an open oblong channel with a depth of 0.2 to 1 m. The mixing is carried out via a paddle wheel ensuring a horizontal circulation speed of 0.15 to 0.3 m/s. Previous studies have shown that LHRAs can eliminate more than 90% of the Chemical Oxygen Demand (COD), 79% of total nitrogen, more than 90% of ammonia nitrogen and 57% of total phosphorus.

A first objective will be to develop and make the process more reliable in order to cope with variations in operating conditions: hydraulic residence time, light intensity, nutrient loading and the impact of nitrification, biomass recycling, etc. This will involve proposing strategies to maintain biomass stability within the reactor and performance. This requires a detailed understanding of the biological and chemical processes governing the dynamics of microalgae and bacteria present in the system: physico-chemical analyses, respirometric tests, strains identification, scenario analysis using the numerical model.

The second objective will be to study the potential for valorising the biomass produced according to different operating conditions. Various options will be investigated: methanisation, biodiesel production by transesterification, nutrients (N, P), high added-value compounds.

The PhD thesis will be directed by Julien LAURENT, Senior Lecturer at the Ecole Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES) and at the ICube laboratory. The doctoral student will be affiliated with the MecaFlu team of the laboratory.

Depending on the evolution of the work and the opportunities, collaborations will be considered with the University of Science and technology of Hanoi (USTH) for the application of the process in real conditions in a developing country as well as with the Institute of Molecular Plant Biology (IBMP) for the identification by mass spectrometry of potentially valuable compounds within the algae produced.

Contact: Julien LAURENT julien.laurent(at)icube.unistra.fr