Ultrafiltration Harvesting of Microalgae Culture Cultivated in a WRRF: Long-Term Performance and Techno-Economic and Carbon Footprint Assessment

[EN] A cross-flow ultrafiltration harvesting system for a pre-concentrated microalgae culture was tested in an innovative anaerobic-based WRRF. The microalgae culture was cultivated in a membrane photobioreactor fed with effluent from an anaerobic membrane bioreactor treating sewage. These harvested microalgae biomasses were then anaerobically co-digested with primary and secondary sludge from the water line. Depending on the needs of this anaerobic co-digestion, the filtration harvesting process was evaluated intermittently over a period of 212 days for different operating conditions, mainly the total amount of microalgae biomass harvested and the desired final total solids concentration (up to 15.9 g center dot L-1 with an average of 9.7 g center dot L-1). Concentration ratios of 15-27 were obtained with average transmembrane fluxes ranging from 5 to 28 L center dot m-2 center dot h-1. Regarding membrane cleaning, both backflushing and chemical cleaning resulted in transmembrane flux recoveries that were, on average, 21% higher than those achieved with backflushing alone. The carbon footprint assessment shows promising results, as the GHG emissions associated with the cross-flow ultrafiltration harvesting process could be less than the emissions savings associated with the energy recovered from biogas production from the anaerobic valorisation of the harvested microalgae. This research work was supported by the Science and Innovation Spanish Ministry (Projects CTM2014-54980-C2-1-R/C2-2-R) and the European Regional Development Fund (ERDF). Generalitat Valenciana supported this study via fellowship APOTI/2016/56 to the first author. The Science and Innovation Spanish Ministry has also supported this study via a pre-doctoral FPU fellowship to the second author (FPU14/05082). The authors would also like to acknowledge the support received from the Universitat Politècnica de València via a pre-doctoral FPI fellowship for the third author, as well as the financial aid received from the European Climate KIC association for the MAB 2.0 Project (APIN0057_2015-3.6-230_P066-05). Mora-Sánchez, JF.; Gonzalez-Camejo, J.; Noriega-Hevia, G.; Seco, A.; Ruano, MV. (2024). Ultrafiltration Harvesting of Microalgae Culture Cultivated in a WRRF: Long-Term Performance and Techno-Economic and Carbon Footprint Assessment. Sustainability. 16(1). https://doi.org/10.3390/su16010369