Browsing by Author "Cerqueira, Ricardo"
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- Biogas production from microalgal biomass produced in the tertiary treatment of urban wastewater: assessment of seasonal variationsPublication . Barros, Raúl; Raposo, Sara; Morais, Etiele; Rodrigues, Brígida; Lourenço Afonso, Valdemira; Gonçalves, Pedro; Marques, José; Cerqueira, Ricardo; Varela, João; Ribau Teixeira, Margarida; Barreira, LuísaThe valorization of microalgal biomass produced during wastewater treatment has the potential to mitigate treatment costs. As contaminated biomass (e.g., with pharmaceuticals, toxic metals, etc.) is often generated, biogas production is considered an effective valorization option. The biomass was obtained from a pilot facility of photobioreactors for tertiary wastewater treatment. The pilots were run for one year with naturally formed microalgal consortia. The biogas was generated in 70 mL crimp-top vials at 35 °C, quantified with a manometer and the methane yield measured by gas chromatography. A maximum biogas production of 311 mL/g volatile solids (VS) with a methane yield of 252 mL/g VS was obtained with the spring samples. These rather low values were not improved using previous thermo-acidic hydrolysis, suggesting that the low intrinsic biodegradable organic matter content of the consortia might be the cause for low yield. Considering the total volume of wastewater treated by this plant and the average amount of methane produced in this study, the substitution of the current tertiary treatment with the one here proposed would reduce the energy consumption of the plant by 20% and create an energy surplus of 2.8%. The implementation of this system would therefore contribute towards meeting the ambitious decarbonization targets established by the EU.
- Impact of ocean acidification on the intestinal microbiota of the marine sea bream (Sparus aurata L.)Publication . Fonseca, Filomena; Cerqueira, Ricardo; Fuentes, JuanWithin a scenario of increasing atmospheric CO2 and ocean acidification (OA), it is highly relevant to investigate its impacts not only on fish performance but also on fish intestinal microbiome and how that reflects on host performance and health. The main objective of this study was to establish if the intestinal microbiota of the sea bream (Sparus aurata) was affected by high level of CO2 in line with the predictions for this century. The bacterial communities of the intestinal fluid were characterized in animals kept at the present-day level of CO2 (400 μatm) and in animals switched to high CO2 (1200 μatm) for 1 month. Bacterial taxa identification was based on molecular methods, using the DNA coding for the 16S ribosomal RNA and primers targeting the regions V1-V3. Amplicons obtained from DNA samples of animals in the same tank were combined, cloned to obtain a bacterial DNA library, and the clones were sequenced. No significant differences were found between the two treatments for alpha diversity. However, beta diversity analysis revealed distinct dysbiosis in response to hypercapnia, with phylum Firmicutes absent from the bacterial communities of fish exposed to 1200 μatm CO2, whereas Proteobacteria relative abundance was increased at elevated CO2, due to the presence of Gammaproteobacteria (Vibrionaceae and Alteromonadaceae), a class not present in the control samples. This study provides a first glimpse at the impact of OA in fish intestinal microbiota and highlights potential downstream effects to the general condition of fishes under hypercapnia.
- Tertiary urban wastewater treatment with microalgae natural consortia in novel pilot photobioreactorsPublication . Morais, Etiele; Amaro Marques, José Carlos; Cerqueira, Ricardo; Dimas, Cláudia; Sousa, Vânia Serrão; Gomes, Nuno; Ribau Teixeira, Margarida; Nunes, Luís; Varela, João; Barreira, LuísaThe aim of this work was to evaluate the efficiency of the new GreenDune photobioreactors for tertiary wastewater treatment, treated wastewater reuse and biomass application, using naturally occurring microalgae consortia. The study was conducted on a pilot installation in a wastewater treatment plant in Portugal and different operational conditions were tested. The system was capable to remove up to 95% of NH4+, the main pollutant in wastewater after secondary treatment using hydraulic retention times as low as 24 h. The application of a non-conservative scenario allowed the reuse of treated wastewater for seed production, and irrigation of naturally restricted use areas. The produced biomass was rich in proteins and carbohydrates with potential for biofuel production such as biogas or use as biofertilizers, closing the energy and nutrients cycle. Finally, the life cycle assessment of both the GreenDune and existing nitrification/denitrification systems were compared revealing that the operation of the GreenDune are more environmentally favourable than the existing system.