Which type, locations and time points of samples were measured from the study “Presence of SARS-Coronavirus-2 in sewage (Medema et al., 2020)”?

Wastewater treatment plants (WWTP) were selected that served 2 large and 3 medium sized cities and the main airport. The operators of the WWTP sampled a 24h flow-dependent composite sample of 250 mL that was stored at 4 °C during sampling. Samples were taken in 2020: on February 5, 6 and 7 (3 weeks before the first COVID-19 case was recognized by the health surveillance system in The Netherlands), on March 4 and 5 (38 resp. 82 reported COVID-19 cases in the Netherlands, total population 17.2 million), and March 15 and 16 (1135 resp. 1413 reported COVID-19 cases in the Netherlands). As the epidemic progressed, another WWTP (Tilburg, a medium-sized city in one of the most affected areas) was included in the sampling scheme.