Claire Albasi

Constructed wetlands (CWs) are nature-based solutions for wastewater treatment, yet their wide implementation remains limited due to constraints such as clogging. To mitigate it, ecological intensification through earthworm inoculation has been proposed, despite it could also promote hydraulic short-circuiting and ultimately impair treatment performance. This study investigated the effects of the inoculation of three earthworms’ species (Eisenia fetida, Eisenia andrei and Dendrobeana hortensis) on the hydrodynamics of CWs, based on the hypothesis that their burrowing activity could reduce clogging and promote a more homogeneous distribution of flow within the substrate. Outdoor experiments were conducted at mesocosm scale (0.2 m2), combining saturated hydraulic conductivity (Ks) monitoring and tracer tests. Complementary laboratory-scale experiments (0.01 m2) using artificial substrate and galleries were performed to compare the effects of different burrow structures. They revealed that only vertical percolating galleries significantly affected both Ks and hydraulic residence time distribution (RTD). In contrast at mesocosm-scale, the earthworms did not significantly change Ks or RTD curves but tended to increase the mean residence time and shift flow dynamics within the porous matrix towards more dispersive behavior, without generating preferential flow pathways. These findings are consistent with the ecological traits of these earthworm species, whose burrowing activity creates a network of multidirectional burrows near the substrate surface rather than preferential vertical flow pathways. Although no clogging occurred in these young mesocosms (< 2 years old), precluding conclusions on long-term effects, the selected earthworm species appeared promising for mitigating clogging in CWs while preserving their hydraulic functioning.

Wastewater discharge or reuse raises concerns about the dissemination of emerging contaminants such as pharmaceutical residues and other organic micropollutants, into the environment. Constructed wetlands (CWs) are nature-based solutions for wastewater treatment whose performance could potentially be enhanced through ecological intensification. This study investigated whether earthworms, as ecological engineers, can improve organic micropollutants removal, influence microbial communities and antibiotic resistance genes in CWs. Experiments were conducted on an experimental platform using mesocosm-scale (0.2 m²) CWs treating raw wastewater from a university campus building. EWs inoculation shifted substrate bacterial community structure and composition and slightly improved the removal of several pharmaceuticals and a human metabolite (e.g., atenolol, benzoylecgonine, citalopram, clarithromycin, diclofenac, irbesartan, metoprolol, sulfamethoxazole and trimethoprim). Earthworms also slightly reduced accumulation of spiked compounds (clarithromycin, diclofenac, metoprolol and trimethoprim), while substrate accumulation represented only a negligible fraction of their overall removal. A decrease in antibiotic resistance gene accumulation was also observed in the substrate. These effects coincided with an increased abundance of bacterial taxa involved in recalcitrant organic matter degradation. Overall, these findings highlight the potential of ecosystem engineers as a low-cost strategy for the ecological intensification of micropollutant removal in constructed wetlands, while further research is needed to confirm these effects with greater statistical power and assess their long-term persistence.

Wastewater discharge or reuse raises concerns about the dissemination of harmful substances, particularly emerging contaminants such as pharmaceutical residues and other organic micropollutants, which can pollute ecosystems and pose risks to human health. This study investigates earthworms-assisted constructed wetlands (EWs-assisted CWs) as a sustainable approach to remove pharmaceutical and other organic micropollutants residues from campus building wastewater. By leveraging earthworms (EWs), the aim is to improve the removal of targeted compounds, and reduce the spread of antibiotic resistance. Experiments were conducted on an experimental platform using mesocosm-scale (0.2 m²) and pilot-scale (5 m²) CWs treating raw wastewater from a university building. At the mesocosm scale, EWs inoculation led to shifts in bacterial community structure and composition and slightly improved removal of several pharmaceuticals and a human metabolite (e.g., atenolol, benzoylecgonine, clarithromycin, diclofenac, irbesartan, metoprolol, mycophenolic acid, and sulfamethoxazole). Additionally, earthworms slightly reduced accumulation of spiked compounds in the substrate. A decrease of antibiotic resistance gene accumulation was also observed in the substrate. These effects may be linked to an increased abundance of bacterial taxa involved in recalcitrant organic matter degradation. However at the pilot scale, no significant effects resulting from EWs inoculation were observed, likely due to unexpected spontaneous EWs colonization in control conditions and low worm biomass in EWs-assisted CWs. Therefore, results from the mesocosm experiment are still considered encouraging to keep investigating the full potential of EWs-assisted CWs.

Given the widespread presence of micropollutants in urban water systems, it is imperative to gain a comprehensive understanding of their degradation pathways. This paper focuses on sulfamethoxazole (SMX) as a model molecule due to its extensive study, aiming to elucidate its degradation pathways in biological (BIO) and oxidative (AOP) processes. Numerous reaction pathways are outlined in scientific papers. However, a significant deficiency in current methodologies has led to the development of a novel meta-analytical approach, seeking consensus among researchers by synthesizing data from studies characterized by their heterogeneity and contradictions. As an innovative alternative, probabilistic graphical models such as Bayesian networks (BNs) could illuminate the relationships and dependencies between various transformation products, providing a holistic view of the degradation process. Based on the analysis of an extensive bibliography gathering more than 45 articles for more than 140 molecules and 177 reaction pathways, this study proposes a meta-analysis methodology based on Bayesian networks.

Theoretical and functional ecology is a source of useful knowledge for ecological engineering. The better understanding of the natural service of water quality regulation is now inspiring for optimization of water resource management, restoration and bioremediation practices. This transfer with a biomimicry approach applies particularly well in the urban, rural and agricultural areas, but is yet underexplored for water quality purposes. This natural service intensely involves the benthic boundary layer as a biogeochemical hot spot with living communities. A selection of processes related to the bioturbation phenomena is explored because of their influence on properties of the aquatic environment. The applications are valuable in a range of fields, from water treatment technology to management of ecosystems such as constructed and natural wetlands, streams, rivers, lagoons and coastal ecosystems. This paper gathers the more obvious cases of potential applications of bioturbation research findings on the biomimicry of natural services to water practices. These include pollution pumping by bioturbated sediment, water column oxygen saving during early diagenesis of deposits under conveyors transport and conservation of macroporous as well as fine sediment. Some applications for constructed devices are also emerging, including infiltration optimization and sewage reduction based on cross-biological community involvement.

Membrane bioreactor technology has become relatively widespread as an advanced treatment for both industrial and municipal wastewaters. The main problem of these installations is that they do not operate at the maximum of their potential, mainly because of membrane fouling. Experimental research with this kind of installation requires resources and is time consuming. The use of a computer simulator, as in the present work, allows the fouling behaviour in a bench-scale submerged membrane bioreactor to be investigated over a wide range of operating parameters: average specific aeration intensity (0.041–0.277 L m⁻² s⁻¹), filtration flux (0.032–0.160 m³ m⁻² d⁻¹) and filtration and coarse bubble aeration cycles (filtration and aeration times: 60–1080 s, with/without ratio: 0.33/10). A quadratic optimization method applied to the energy consumption (EC) was first carried out: minimum values of 0.27 and 0.32 kW h m⁻³ were obtained for EC in the sequential and non-sequential operating modes, respectively. Using the optimal operating conditions and the most influent parameters found in the first part, the second part details their influence on both membrane fouling and EC for each operating mode. The mean filtration flux and the mean aeration intensity have opposite effects on fouling and EC, which implies that a more global, economic optimization, including chemical cleaning, is needed. The detailed study of filtration and coarse bubble aeration cycles showed that they had little influence for a with/without ratio superior to 1. Using the quadratic optimization method with in silico experiments gave reliable first approximation results.