Nature-based solutions for wastewater treatment and bioenergy recovery: a comparative Life Cycle Assessment

The aim of this study was to assess the environmental impacts of up-flow anaerobic sludge blanket (UASB) reactors coupled with high rate algal ponds (HRAPs) for wastewater treatment and bioenergy recovery using the Life Cycle Assessment (LCA) methodology. This solution was compared with the UASB reactor coupled with other consolidated technologies in rural areas of Brazil, such as trickling filters, polishing ponds and constructed wetlands. To this end, full-scale systems were designed based on experimental data obtained from pilot/demonstrative scale systems. The functional unit was 1 m3 of water. System boundaries comprised input and output flows of material and energy resources for system construction and operation. The LCA was performed with the software SimaPro®, using the ReCiPe midpoint method. The results showed that the HRAPs scenario was the most environmentally friendly alternative in 4 out of 8 impact categories (i.e. Global warming, Stratospheric Ozone Depletion, Terrestrial Ecotoxicity and Fossil resource scarcity). This was associated with the increase in biogas production by the co-digestion of microalgae and raw wastewater, leading to higher electricity and heat recovery. From an economic point of view, despite the HRAPs showed a higher capital cost, the operation and maintenance costs were completely offset by the revenue obtained from the electricity generated. Overall, the UASB reactor coupled with HRAPS showed to be a feasible nature-based solution to be used in small communities in Brazil, especially when microalgae biomass is valorised and used to increase biogas productivity.
The research was funded by the National Council for Scientific and Technological Development from Brazilian Ministry of Education – CNPq, the Reference Centre of Sustainable Sewage Treatment Plants - CR ETES, the Institute of Sustainable Sewage Treatment Plants - INCT ETEs, the Coordination for the Improvement of Higher Education Personnel – CAPES, the Foundation for Research of the State of Minas Gerais – FAPEMIG, and the CNPQ and to National Health Foundation – FUNASA from Brasil. Lucas Vassalle is grateful to the CNPQ (scholarship 204026/2018-0). Ivet Ferrer and Marianna Garfí are grateful to the Government of Catalonia (Consolidated Research Group 2017 SGR 1029), and Marianna Garfí to the Spanish Ministry of Economy and Competitiveness (RYC-2016 20059).
Peer Reviewed
Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant
Objectius de Desenvolupament Sostenible::6 - Aigua Neta i Sanejament
Postprint (author's final draft)