Negative controls for dPCR were achieved using sterile water (DNA blanks) to confirm nonamplification. For positive process controls, 10 µL of TaqMan™ Universal DNA Spike in Control (Thermo Fisher) was spiked into the lysis step of the DNA extraction kit. Six extracts of the same wastewater sample were spiked to assess recovery efficiency of the extraction kit, giving an average recovery of 41 ± 12 % (figure ).