Biohazard identification: Profiling microalgal cultures growing on municipal wastewater and fertilizer medium in raceway photobioreactors

Abstract

Microalgae provide a promising way to combine wastewater treatment and biomass production. They are often used as pre-treatment to reduce pathogenic loads: however, a full characterisation of the risks is still needed to develop safety guidelines. Two raceways were inoculated with Scenedesmus, one in a fertilizer medium and one in wastewater. Biohazards were then explored in three ways: NGS analysis, commercial qPCR array and plate counts. Media and sampling locations contributed to shape bacterial and eukaryotic structures and pathogenic loads. Communities were variable across time with a higher diversity between inlets than between biomass and outlets. A lower presence of pathogens was seen in fertilizer, while wastewater showed a distinct reduction from inlet to outlet. The main pathogenic genera detected were Arcobacter and Elizabethkingia with an important presence of Aeromonas. The three analyses together identified the necessity of preventive and protection measures and of post-harvest treatments.