Transmembrane chemical absorption (TMCS) is a promising technology to recover ammonia from high-strength wastewater and sustainably produce fertilizers for agricultural propose. In this study, the effect of ionic strength was analyzed by modelling and experiments, to establish the impact of the salinity of the treated effluent on the performance (ammonia recovery and water vapour transfer). The non-ideality of the solution is considered and the effect of pH, ionic strength and temperature is analyzed by a thermodynamic model approach using Phreeqc software. Results reveal that high ionic strength can play a positive or negative role in ammonia recovery efficiency, depending on the pH of the solution. The salinity also influences water vapour diffusion through the membrane which can negatively impact the process by diluting the ammonium salt produced. Results show that water vapour transfer is linearly correlated to ionic strength. It can occur in both directions from effluent to acid or inversely depending on difference of ionic strength. The impact of salinity of the effluent on ammonia and water vapour transfer through gas-permeable membranes was theoretically and experimentally assessed.

Anaerobic digestion, a renewable energy source, is the degradation of organic waste into biogas, mainly composed of CH4 and CO2. The sector is expanding rapidly due to its multiple environmental and economic benefits. This process is implemented industrially in concrete structures that are in direct contact with the biowaste being digested and the gas produced. Both phases can damage concrete through (i) the presence of volatile fatty acids, dissolved CO2, ammonium, and microbial biofilm in the liquid phase, and (ii) high concentrations of CO2 and various concentrations of H2S in the gas phase. In order to develop more sustainable concrete biogas units, long-term, in-situ experiments were carried out in a semi-industrial scale digester to provide new insights into the performance levels and deterioration mechanisms of various low-CO2 binders, including alkali-activated metakaolin (geopolymer), alkali-activated slag (AAS), and supersulfated cements (SSC), in comparison to calcium aluminate cement (CAC) and Portland cement based matrices. In the running conditions explored, carbonation of the cementitious matrices was predominant over other deterioration phenomena in both the digester liquid and the gas phases. Alkali-activated metakaolin and calcium aluminate cement performed better with few degradations observed. Supersulfated cements and alkali-activated slag showed an intermediate behaviour with good performance in the acidic liquid phase but low performance in the CO2-rich gas phase.

Biological methanation is a promising technology for gas and carbon valorisation. Therefore, process stability is required to allow its scale up and development. A pilot scale bubble column reactor was used for ex situ biological methanation with Mixed Microbial Culture (MMC). A 16S rRNA high throughput sequencing analysis revealed the MMC reached a stable composition with 50-60% Methanobacterium in closed liquid mode, a robust genus adapted to large scale constraints. Class MBA03 was identified as an indicator of process stability. Methanogenic genera moved toward 50% of Methanothermobacter when intensifying the process, and proteolytic activity was identified while 94% of H2/CO2 was converted into methane at 4NL.L-1.d-1. This study gives clarifications on the origin of volatile fatty acids (VFA) apparitions. Acetate and propionate accumulated when methanogenic activity weakened due to nutritive deficiency, and when PH2 reached 0.7 bar. The MMC withstood a storage period of 34d at room temperature indicating its suitability for industrial constraints.

Partial nitritation with anammox (PNA) process was achieved during 300 days to investigate the fate of N2O and NO. N2O emission factor increased from 0.4 +/- 0.1 % up to 6.1 +/- 0.3 % during intensification phase of 5 months and progressively stabilized at 2.0 +/- 0.1 % after 10 months without any significant emission of NO. The emission of N2O correlated with the ammonium consumption rate and the oxygen transfer rate. Experiment carried out in anoxic condition suggested that heterotrophic denitrification poorly contributed. Measurements of delta 15N, delta 18O and SP of N2O demonstrated that its production resulted from the reduction of nitrite. The stimulating effect of nitrite on N2O production was demonstrated with specific tests and observed during transient nitrite accumulation periods. This study highlighted the importance of nitrite and oxygen transfer rate control for future control strategies aiming to mitigate N2O emission in PNA system.

This study focuses on the hydrodynamic modelling of percolation and drainage cycles in the context of solid-state anaerobic digestion and fermentation (VFA platform) of household solid wastes (HSW) in leach bed reactors. Attention was given to the characterization of the water distribution and hydrodynamic properties of the beds. The experimental procedure enabled the measurement of water content in waste beds at different states of compaction during injection and drainage, and this for two types of HSW and for two other type of wastes. A numerical model, set up with experimental data from water content measurements, highlighted that a capillary-free dual-porosity model was not able to correctly reproduce all the hydrodynamic features and particularly the drainage dynamics. The model was improved by adding a reservoir water fraction to macroporosity which allowed to correctly simulate dynamics. This model, validated with data obtained from agricultural wastes, enabled to explain more precisely the water behaviour during percolation processes and these results should be useful for driving either solid-state anaerobic digestion or fermentation reactors. Indeed, this implies that the recirculation regime will impact the renewal of the immobile water fraction in macroporosity, inducing different concentration levels of fermentation products in the leachate.