Dunia E. Santiago

This study addresses the management of sewage sludge (SS), a growing waste worldwide. In the case of the Canary Islands, Spain, 47.3% of the SS is disposed in landfills without further reuse. In this research, SS was used as a precursor to produce activated carbons (ACs), to remove pollutants from wastewater. The ACs were synthesized through chemical activation with phosphoric acid. The carbonization temperature and acid impregnation ratio were optimized, being 650 °C and 2 g H₃PO₄·g⁻¹ precursor, respectively. The methylene blue (MB) number of the optimized AC (AC-650–2) was 140, and that of a commercial AC used for comparison was 160. Additionally, magnetic activated carbons (MACs) were produced to facilitate material recovery and the regeneration of the adsorbent using an advanced oxidation technique (Fenton). AC-650–2 and MAC-3 adsorbed a maximum of 76.34 mg MB·g⁻¹ and 56.76 mg MB·g⁻¹, respectively, at 25 °C. The regeneration of the materials was investigated using conventional chemical methods and the Fenton reaction: NaOH washing (for AC-650–2 and MAC) and Fenton (for MAC) enabled recoveries higher than 50% after four cycles. The cost of producing AC-650–2 was estimated at 5.41 €·kg⁻¹. Graphical Abstract

A novel catalyst, composed of silver phosphate (Ag₃PO₄) deposited on a magnetic material containing titanium dioxide (TiO₂) and ferromagnetite (Fe₃O₄), was synthesized and tested with wastewater from the maintenance system of a swimming pool and from the secondary effluent of a wastewater treatment plant (WWTP). The magnetic material Ag₃PO₄@1-TiO₂-Fe₃O₄ presented a slightly lower photoactivity than bare Ag₃PO₄ but was able to remove over 64% COD from the secondary effluent of a WWTP and over 75% organic UV filters from a swimming pool wastewater. The material was easily recovered from the treated water with a magnet and could be reused at least four times. The efficiency loss after five reuses was 15%. The dissolution of silver after the photocatalytic reaction was over 80 mg·L⁻¹ for bare Ag₃PO₄ and less than 500 μg·L⁻¹ for the magnetic composites. The magnetic support prevents the dissolution of silver. The materials that contained Ag₃PO₄ showed antibacterial properties under dark conditions. The photocatalytic efficiency of Ag₃PO₄ and commercial TiO₂ was similar under sunlight, both for the removal of UV filters at µg·L⁻¹ concentrations from swimming pool wastewater, and for the removal of mild COD loads from a WWTP effluent (initial COD: 110 mg·L⁻¹).

This study deals with the effect of effluent recirculation (ER) on the pollutant removal efficacy of a full-scale, hybrid treatment system composed of a macrophyte pond and a horizontal flow constructed wetland. The average removals of 5-day biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, total N (TN), ammonium nitrogen (NH₄-N), total phosphorus (TP), sulfates, E. coli and Total coliforms (TC) for the years 2017–2018 (no recirculation), 2019 (50% recirculation) and 2021 (100% recirculation) were compared. Results show a general improvement of the effluent with ER. Removals for 0%, 50% and 100% ER, respectively, were: 59%, 61% and 66% for COD; 90%, 96% and 96% for BOD; 94%, 94% and 99% for TSS; 33%, 40% and 67% for TN; 22%, 30% and 55% for NH₄-N; 92%, 98% and 96% for sulfates; 99.6%, 99.7% and 99.9% for E. coli; and 99.5%, 99.7% and 9.9% for TC. No clear effect was observed on the removal of TP and dissolved PO₄-P, which were very low. 50% ER improved turbidity removal from 88% to 91%, but 100% ER provided worse results. The removal of NH₄-N and TN significantly improved with 100% ER. This indicates that ER can be a simple, economic, and feasible way to upgrade the performance of full-scale natural wastewater treatment systems.

This article analyzes whether the use of videos in flipped classrooms applied to lab practices in higher-education degrees improves the students’ performance. For this purpose, the flipped classroom methodology was used in the Sustainability and Environment Technologies subject, which is included in the curriculum of different engineering degrees. The results were evaluated by considering three different aspects: student satisfaction, student performance during the lab practice, and academic marks. The methodology of the study combines qualitative and quantitative approaches. The results show an improvement in student satisfaction, as well as in student performance during the lab practice. The academic marks of the test students in comparison to the control students also show some improvement. Overall, those who undertook the flipped classroom lab practice noted many benefits, including increased student engagement and satisfaction, as well as improvements in student skills and academic results. Novel aspects such as the qualitative and quantitative evaluations of the performance of the lab practice have been introduced in this research.