Figure 4.

(a) General strategy used to collect wastewater or sludge samples and detection of viral RNA using RT-PCR. (b) Digital droplet RT-PCR to detect signature SARS-CoV-2 mutations of variants (the figure was adapted from Heijnen et al. [36] with permission). (c) Concentrations of Norovirus genogroup II in combined decentralized wastewater collections were determined by qPCR and ddPCR (the figure was adapted from Jahne et al. [37] with permission).