An Integrated, Sustainable Process for the Tertiary Treatment of Urban Wastewater using Microalgae in the Algarve region

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Biomass valorization via pyrolysis in microalgae-based wastewater treatment: challenges and opportunities for a circular bioeconomy

Publication . de Morais, Etiele Greque; da Silveira, Jéssica Teixeira; Schüler, Lisa Maylin; de Freitas, Barbara Catarina Bastos; Costa, Jorge Alberto Vieira; de Morais, Michele Greque; Ferrer, Ivet; Barreira, Luísa

Microalgae-based wastewater treatment technology is a sustainable and environmentally friendly alternative to conventional treatment systems. The biomass produced during microalgae-based wastewater treatment can be valorized via pyrolysis to generate multiple valuable products, such as biochar, bio-oil, and pyrolytic gas. This study summarizes the potential of pyrolysis for valorizing microalgal biomass produced from wastewater treatment. It shows how pyrolysis can provide a variety of valuable products, the composition of which is influenced by the type of microalgae used, the operating conditions of the pyrolysis process, and the presence of contaminants in the biomass. It also highlights the main challenges to be addressed before pyrolysis can be adopted to valorize microalgae biomass. These challenges include the high energy requirements of pyrolysis, the need for further research to optimize the process, and the potential for pyrolysis to produce harmful emissions. Despite this, pyrolysis appears as a promising technology with potential to contribute to the sustainable development of a circular economy. Future research should address these challenges and develop more efficient and environmentally friendly pyrolysis processes.

2023Journal article

Open Access

Tertiary urban wastewater treatment with microalgae natural consortia in novel pilot photobioreactors

Publication . Morais, Etiele; Amaro Marques, José Carlos; Cerqueira, Ricardo; Dimas, Cláudia; Sousa, Vânia Serrão; Gomes, Nuno; Ribau Teixeira, Margarida; Nunes, Luís; Varela, João; Barreira, Luísa

The 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.

2022Journal article

Open Access

Microalgal systems for wastewater treatment: technological trends and challenges towards waste recovery

Publication . Morais, Etiele; Cristofoli, N.L.; Maia, Inês Beatriz; Magina, Tânia; Cerqueira, Paulo R.; Teixeira, Margarida Ribau; Varela, João; Barreira, Luísa; Gouveia, Luisa

Wastewater (WW) treatment using microalgae has become a growing trend due the economic and environmental benefits of the process. As microalgae need CO₂, nitrogen, and phosphorus to grow, they remove these potential pollutants from wastewaters, making them able to replace energetically expensive treatment steps in conventional WW treatment. Unlike traditional sludge, biomass can be used to produce biofuels, biofertilizers, high value chemicals, and even next-generation growth media for “organically” grown microalgal biomass targeting zero-waste policies and contributing to a more sustainable circular bioeconomy. The main challenge in this technology is the techno-economic feasibility of the system. Alternatives such as the isolation of novel strains, the use of native consortia, and the design of new bioreactors have been studied to overcome this and aid the scale-up of microalgal systems. This review focuses on the treatment of urban, industrial, and agricultural wastewaters by microalgae and their ability to not only remove, but also promote the reuse, of those pollutants. Opportunities and future prospects are discussed, including the upgrading of the produced biomass into valuable compounds, mainly biofuels.

2021-12-03Journal article

Open Access

Biogas production from microalgal biomass produced in the tertiary treatment of urban wastewater: assessment of seasonal variations

Publication . Barros, Raúl; Raposo, Sara; Morais, Etiele; Rodrigues, Brígida; Lourenço Afonso, Valdemira; Gonçalves, Pedro; Marques, José; Cerqueira, Ricardo; Varela, João; Ribau Teixeira, Margarida; Barreira, Luísa

The 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.

2022-08-05Journal article

Open Access