ANSWER is a French-Chinese collaborative project which focuses on the modelling and the simulation of eutrophic lake ecosystems to study the impact of anthropogenic environmental changes on the proliferation of cyanobacteria. Worldwide the current environmental situation is preoccupying: the water needs for humans increase while the quality of the available resources is deteriorating due to pollution of various kinds and to hydric stress. In particular, the eutrophication of lentic ecosystems due to excessive inputs of nutrients (phosphorus and nitrogen) has become a major problem because it promotes cyanobacteria blooms, which disrupt the functioning and the uses of the ecosystems. For 40 years, some measures of reduction of nutrient inputs, especially of phosphorus, have been applied in developed countries to fight against these blooms whereas a reverse tendency of increase of the nutrient loading is observed in other countries. At the same time, the temperature and the atmospheric CO2 concentration have been increasing with significant consequences on the dynamics of phytoplankton communities in lakes. All these local and global changes finally lead to significant modifications of the C/N/P ratio in ecosystems (i.e. the modification of the availability of the three major elements: C, N & P). The project ANSWER will evaluate the consequences that these variations can have on the dynamics of cyanobacterial blooms, by using modelling approaches and numerical simulations which will be based on existing and specific experiments and field data. To represent the complexity of the functioning of lentic ecosystems, the use of 3D dynamical models, obtained by coupling hydrodynamic and ecological models, is essential. Because the development, the calibration and the simulation of such models require a wide range of skills, researchers of various fields (computer science, applied mathematics, modelling, physical limnology and microbial ecology) will work together to develop an integrative platform for lake ecosystems modelling, which will include tools of data management and knowledge representation, models and statistical methods for model calibration and validation. The models will be used for: (1) the simulation of the short-term (weeks) impact of sudden changes of C/N/P ratio (due to weather events) on the initiation of blooms and the evolution of their spatial distribution; (2) comparative simulations of the dynamics and the composition of phytoplankton communities during an annual cycle following the observed trends for the C/N/P ratio in France and in China; (3) the test and optimization of control strategies whose combined impact with climate changes results in a modification of the C/N/P ratio. The processes of recycling of organic matter by bacteria in the water column and of release of nutrients from the sediments will be studied experimentally to improve the model ability. Indeed, although these processes are considered as essential for the dynamics of cyanobacteria, they are often ignored or poorly represented in existing models. One of the difficulties of the implementation of these modelling approaches often comes from the lack of data, or from their poor quality, which makes the validation and the calibration of the models difficult. Thanks to the diversity of the French and Chinese teams gathered in our consortium, we will have access to a rich database composed of good quality data acquired on diversified ecosystems (the large shallow Lake Taihu in China, the long and deep Villerest reservoir and the small and shallow urban Lake Champs-sur-Marne in France). The broad skills of our consortium, ranging from microbial ecology and limnology to modelling, will allow us to take into account in the construction, the validation and the analysis of the models, all the key processes involved in the ecosystem functioning.

Oxygenic photogranules (OPGs) could turn wastewater treatment in circular bioeconomy by capturing much of the energetic and chemical value of wastewater in their biomass. But essential knowledge on their formation and life cycle is still missing and needed for conducting a bioprocess based on OPGs. Omics (in particular metabolomics) are the best tools to understand photogranulation but still require a specific effort in statistical modelling to make full use of them. This project will tackle both challenges: the development of automatic and reproducible data analysis methods for metabolomics, the implementation of a longitudinal multi-omics data integration methodology and the use of these new approaches to investigate the life cycle of OPGs, mainly their switch from growth activity to storage of compounds which is one of the major remaining challenges for the industrial use of OPGs in depollution of wastewater.

The overall objective of the PHYCOVER project is to draw the scientific, technical and industrial contexts for an evolution of wastewater treatment plants, and urban wastewaters in particular. The project aims to identify an integrated and modular treatment process for the production of biogas while identifying opportunities to maximize the valorisation of residual material, the digestate. The method combines three modules. First, a high-rate algal pond is dedicated to the treatment of municipal wastewater. Then, an anaerobic digester capable of co- digesting biomass products (and others organic matter resources ) to significantly reduce biological and chemical contaminants while producing a sustainable energy as biogas is analysed. A final module aims to enhance the digestate valorisation to agricultural sectors (organic and mineral fertilizers) and cultures of high-value microalgae to aquaculture and green chemistry. Most recent studies indeed highlight the need to combine production of microalgae to liquid and gaseous effluents treatment, to decrease the cost and to limit the exogenous inputs of nitrogen, phosphorus and carbon. However, there is currently no technology optimized solution for combining water purification and production of microalgae, while complying with discharge standards. To further enlarge the potential of industrial applicability of this approach, it is important to control the fate of pathogens organisms in effluents and the project PHYCOVER will tackle these aspects. Finally, biotic and abiotic potential emissions to the atmosphere associated with the deployment of mass cultivation systems must be evaluated to enrich Life Cycle Analysis approaches. To assess the resource recovery from waste and wastewater using this innovative approach, the PHYCOVER project will work on a number of scientific and technological obstacles. First, the selection of algal communities demonstrating a strong effluent treatment capacity and resilience of productivity considering the environmental fluctuations will be performed in Task 1 and studied at pilot scale, representative of the industrial potential of sewage treatment and biogas production. The specific study of biotic and abiotic emissions to the atmosphere as well as the assessment of hygienisation of the integrated process will be the subject of the work done in Task 2. The management of organic matter through anaerobic digestion will addressed in Task 3. Management methods and opportunities for the valorisation of the digestate as agricultural fertilizer and microalgae nutriment for green chemistry will be studied in Task 4. The assessment and prediction of the overall performances in terms of environmental and energy outputs will be assessed in Task 5, together with the optimal process design. Finally, a techno-economical and environmental assessment of the sector as a whole will be given in Task 6. Overall, the project will lead to scientific, technical and economic achievements that will contribute to the establishment of a new and innovative chain for the treatment and valorization of urban waste and wastewater.

Plastic pollution might lead to the degradation of soils, with major environmental and economical costs for agriculture. Considering the multiple facets of plastic pollution (contaminant cocktails including additives and non-intentionally added substances NIAS, added alone in mulching or closely entangled with residual organic matter in amendments), this project will take a lead in assessing the extent of this threat and propose ways to remediate it. With a novel methodology based on a back and forth collaboration between polymer chemistry and soil ecology we will explore several exposure scenarios of soil organisms to custom-made plastics, deciphering their toxicity in different environmental compartments (rhizosphere, microorganisms, mesofauna, plastisphere), their impacts on soil functions and on biogeochemical cycles, their dynamics and that of plastic-associated microorganisms and the physico-chemical and microbial retroactions of soils on plastics.