A sulfide online-monitoring system (S-OMS) was developed using a 3D-printed microfluidic platform to monitor sulfide in bioreactors. The S-OMS consisted of an electrochemical cell in which a microdevice was 3D-printed with co-polyester filaments and used an internal silver/silver sulfide (Ag/Ag₂S) working electrode and a commercial, external silver/silver chloride (Ag/AgCl) reference electrode. The analytical evaluation showed a wide linear range (1.5–30,400 mg L⁻¹) with repeatability and reproducibility presenting relative standard deviations of less than 5%. The S-OMS remained stable during working periods ranging from 16 h to 8 days, depending on the operation mode. Real samples from a sulfate-reducing bioreactor were used to validate the S-OMS, and the results were compared with those of a commercial sulfide ion-selective electrode (S²⁻-ISE), yielding a good linear correlation (R² = 0.92). Moreover, a t-test revealed no significant statistical difference between the two analytical methods. The bioreactor operation resulted in a high sulfate reduction rate and in the accumulation of total sulfide, as measured with the S-OMS, in the bioreactor. However, the H₂S inhibition was offset by an increase in pH and volatile suspended solids (VSS) throughout the operation. Overall, the S-OMS demonstrated robust analytical performance and operational suitability for online monitoring of sulfide in sulfide-producing bioreactors.

Surface-guided tram systems are increasingly being recognised not only as mobility instruments but also as agents of urban regeneration that reshape spatial and social dynamics. This study evaluates the configurational impact of the Trambesòs tram in Barcelona on accessibility, integration, and urban cohesion within the Levante del Besòs area. A Space Syntax analysis was conducted in UCL DepthmapX for axial map analysis and visual graph analysis within a 500 m radius around each station. Three typologies of intervention (site-specific, articulation axes, and saturation pieces) guided the assessment. This analysis shows that Avinguda Diagonal and Avinguda Meridiana are primary structural corridors, while stations Glòries, Ca l’Aranyó, and Pere IV recorded the highest accessibility and visual openness. The results indicate that targeted interventions have positive impacts on the Space Syntax metrics regardless of their spatial centrality, highlighting the critical role of this diverse intervention typology in shaping the study area’s spatial configuration and influencing a hierarchy of social appropriation and use. It is concluded that the Trambesòs tram and associated urban interventions have jointly enhanced centrality and permeability in key sectors, and specific peripheral enclaves have local functioning. These findings, focused on spatial and morphological patterns, may support future interventions in urban design and mobility planning. Although the analysis centres on spatial configuration, future research may integrate socioeconomic variables to broaden the understanding of regeneration processes.

Wastewater systems are high-energy consuming processes that discharge considerable amounts of pollutants into aquatic ecosystems, thus requiring appropriate optimization. Therefore, a full-scale activated sludge process was studied in this work through mathematical modeling of heterotrophic and nitrifying microorganisms. The airflow rate was introduced as the controlling parameter to accomplish the degradation of pollutants. Moreover, a sensitivity analysis was performed to determine the most sensible parameters that should be evaluated through further experiments, aiming to improve the model. The obtained results indicated that readily biological oxygen demand degradation and the oxidation of ammonia to nitrite could be achieved with an airflow rate of 35 m ³ air d ^-1. The sensitivity analysis showed that heterotrophic kinetic parameters and oxygen mass transfer coefficient through diffusers are the most sensitive to the system. These results also proved that the air-diffusing systems can work at 0.3% of their maximum capacity to accomplish degradation. Future studies should consider other oxygen-consuming variables.