The nitrogen content of solids was less variable than that of phosphorus. Across the focus period, the average biomass yield was 12.8 ± 0.7 kg TSS•(kg-N) -1 , corresponding to a solids nitrogen content of 7.8 ± 0.4% (average ± standard deviation; 5 th /50 th /95 th percentiles of 7.10%/7.82%/8.49%). Similar to phosphorus, nitrogen content of microalgae can vary, with reported nitrogen content ranging from 5.87% to 11.16% of total solids. N:P mass ratios across the focus period were 2.5 ± 0.6 (Figure ) but were notably higher prior to January 8, 2023 (3.3 ± 0.3, with phosphorus content of 2.4 ± 0.2%) than after (2.1 ± 0.2; with phosphorus content of 3.7 ± 0.4%). The nitrogen content remained relatively stable at 7.8 ± 0.5% to 7.9 ± 0.4% for the periods before and after January 8, 2023, respectively. Solids N:P ratio may vary with growth rate (linked to SRT) and influent N:P ratio through interspecific stoichiometric plasticity (especially under nutrient-limitation) or microbial community composition shifts in favor of species that have a competitive advantage in a given set of environmental conditions. The relationship between influent N:P and solids N:P was not significant (linear R 2 < 0.001, n = 12). However, solids N:P had a negative linear correlation with SRT (R 2 = 0.63, Figure ) during the period of superior performance (November 15, 2022 to February 14, 2023), varying from 2.1 to 4.2 days. In addition to SRT, the biomass N:P ratio may have also been influenced by the fate of recovered phosphorus, which varied between assimilation within the cells and highly localized precipitation on the cell surfaces or within the EPS during upstream coagulant use.