Table 3.
Summary of equivalent sample volumes (ESVs) and virus recoveries as a function of sample concentration method and target matrix. Sample concentration and analysis focused on liquid-phase viruses, except where solids are specified. The HFUF-Centricon method was applied to wastewater (10-L samples) and source/drinking water (10–20-L samples). All other methods were tested only with wastewater. ESVs indicate the volume of original sample reflected in each assay after accounting for sample concentration, sample processing, and molecular analyses.
| Primary Concentration | Secondary Concentration | Average ESV1 (mL) | Average ESV2 (mL) | BCoV Recovery (n = 3–4) | PMMoV Recovery (n = 2–4) |
|---|---|---|---|---|---|
| HFUF | None | 0.55 ± 0.05 | 0.11 ± 0.01 | 54% ± 11% | 4.0% ± 2.2% |
| HFUF | Centrifuge (Solids)3 | ∼12 | ∼2.4 | 0.18% ± 0.09% | 0.02% ± 0.01% |
| Centricon | None | 1.1 ± 0.78 | 0.22 ± 0.16 | 55% ± 38% | 1.3% ± 0.16% |
| PEG | None | 3.6 ± 0.07 | 0.72 ± 0.01 | 11% ± 8.4% | 0.28% ± 0.10% |
| HFUF | PEG | 53 ± 18 | 11 ± 3.6 | 0.34%5 | 0.01%5 |
| HFUF | Centricon | 11 ± 2.8 | 2.2 ± 0.57 | 2.1% ± 0.87% | 0.12% ± 0.05% |
| HFUF4 | Centricon | 500-1000 | N/A | N/A | N/A |
HFUF = hollow fiber ultrafiltration; PEG = polyethylene glycol; ESV = equivalent sample volume; BCoV = bovine coronavirus; PMMoV = pepper mild mottle virus; 1ESV for N1 and N2 assays (5 μL per reaction); 2ESV for E_Sarbeco, orf1a, BCoV, and PMMoV (1 μL per reaction); 3Recovery for solids may actually reflect low recovery and/or low virus partitioning to solids; 4Data for source/drinking water samples (only N1 and N2 assays and no recovery experiments performed in these matrices); 5Recovery evaluated in a single sample.