SEM-EDS was performed on a range of samples from the broader monitoring period (April 5, 2022 to February 13, 2023; SI Section S4.2, Table ), including samples with the highest and lowest phosphorus content, from periods with and without coagulant use, and start and end points of batch experiments. Of selected samples for SEM-EDS imaging, the February 13, 2023, sample had the greatest overall phosphorus content (5.1%). Phosphorus-rich granules were observed in biomass samples and appear to be within microalgal cells (Figures ), supporting the hypothesis that elevated phosphorus could be due to polyphosphate accumulation within cells.