Standard risk assessment methodology for quantifying potential risks in reusing wastewater treated by microalgae-based photorefinery

This work proposes a methodology for quantifying the potential risks to human health associated with reusing wastewater treated in a microalgae-based photorefinery. Microbial risks were quantified using Quantitative Microbial Risk Assessment, while physico-chemical risks were assessed through a combination of Failure Mode and Effects Analysis with World Health Organisation recommendations. Experimental data were obtained from a pilot-scale microalgae-based system set in Italy. Acceptable risk levels (Disability-Adjusted Life Years < 10^-6) were obtained for most parameters, demonstrating that wastewater reuse could be both technically and legally feasible. However, the strict Italian legal requirements on ammonium effluent concentrations complicated operations and reduced the amount of reclaimed water available for reuse. This study provides scientific evidence on the potential use of microalgae cultivation to produce reclaimed water, but improved control systems and safety measures should be implemented to mitigate the risks associated with pH, ammonium, and somatic coliphages.