Fig. 1
SARS-CoV-2 RNA copy numbers detected using the IDT plasmid, and CODEX and EURM019 RNA standards from wastewater (a) and using IDT plasmid standard and EURM019 RNA (b). Wastewater samples collected from nine wastewater treatment plants in Finland. The number of samples per WWTP ranged from 12 to 20 (see Table 3). The IDT standard consistently yielded significantly higher copy numbers than the CODEX standard in all samples together (*p < 0.001, Wilcoxon signed-rank test). Similarly, the IDT standard consistently yielded significantly higher virus copy numbers than EURM019 standard (p < 0.001, Wilcoxon signed-rank test). Since small sample number of individual WWTP, we did not carryover statistical test for them. IDT, CODEX and EURM019 indicated in light green and light blue and orange boxes, respectively.
