Descriptive statistics using uncensored and modeled left-censored values for concentrations of human enteric viruses in pre- and post-disinfection effluent, Ontario, Canada, 2014–2017
| . | Plants B, D, and E combined, n = 34 (providing secondary treatment) . | Plants A and C combined, n = 24 (providing tertiary treatment) . | Secondary vs. tertiary plant differences in LR means; p-value; 0.95 CI . | ||||
|---|---|---|---|---|---|---|---|
| Human enteric virus . | d (%) . | nd (%) . | mean (±SE) . | d (%) . | nd (%) . | mean (±SE) . | Welch two-sample t-test . |
| Enterovirus culture, MPN/L | |||||||
| Pre-disinfection | 27 (79) | 7 (21) | 8.3 × 10−1 (2.4 × 10−1) | 10 (42) | 14 (58) | 9.6 × 10−2 (3.2 × 10−2) | |
| Post-disinfection | 20 (59) | 14 (41) | 1.1 × 10−1 (2.5 × 10−2) | 12 (50) | 12 (50) | 5.3 × 10−2 (2.2 × 10−2) | |
| Mean LR | 0.9 (0.05) | 0.3 (0.03) | p < 0.001; 0.5–0.7 | ||||
| Enterovirus RT-PCR, GC/L | |||||||
| Pre-disinfection | 29 (85) | 5 (15) | 1.4 × 10+6 (5.1 × 10+5) | 13 (54) | 11 (46) | 4.3 × 10+5 (1.6 × 10+5) | |
| Post-disinfection | 20 (59) | 14 (41) | 7.2 × 10+5 (4.1 × 10+5) | 5 (21) | 19 (79) | 2.1 × 10+4 (1.3 × 10+4) | |
| Mean LR | 0.3 (0.03) | 1.3 (0.2) | p < 0.001; 0.7–1.3 | ||||
| Norovirus GI, GC/L | |||||||
| Pre-disinfection | 32 (94) | 2 (6) | 7.2 × 10+5 (2.2 × 10+5) | 17 (71) | 7 (29) | 1.4 × 10+5 (5.4 × 10+4) | |
| Post-disinfection | 28 (82) | 6 (18) | 2.5 × 10+5 (1.2 × 10+5) | 11 (46) | 13 (54) | 2.0 × 10+4 (1.4 × 10+4) | |
| Mean LR | 0.5 (0.05) | 0.8 (0.1) | p = 0.002; 0.2–0.6 | ||||
| Norovirus GII, GC/L | |||||||
| Pre-disinfection | 33 (97) | 1 (3) | 3.8 × 10+5 (1.8 × 10+5) | 15 (62) | 9 (38) | 3.0 × 10+4 (1.2 × 10+4) | |
| Post-disinfection | 30 (88) | 4 (12) | 1.1 × 10+5 (4.6 × 10+4) | 10 (42) | 14 (58) | 7.5 × 10+3 (5.0 × 10+3) | |
| Mean LR | 0.5 (0.1) | 0.6 (0.1) | p = 0.4 (NS); (–)0.1–0.2 | ||||
| Norovirus GI + GII, GC/L | |||||||
| Pre-disinfection | 34 (100) | 0 | 1.1 × 10+6 (3.3 × 10+5) | 17 (71) | 7 (29) | 1.7 × 10+5 (6.3 × 10+4) | |
| Post-disinfection | 31 (91) | 3 (9) | 3.6 × 10+5 (1.4 × 10+5) | 12 (50) | 12 (50) | 2.7 × 10+4 (1.9 × 10+4) | |
| Mean LR | 0.5 (0.04) | 0.8 (0.1) | p = 0.006; 0.1–0.5 | ||||
| . | Plants B, D, and E combined, n = 34 (providing secondary treatment) . | Plants A and C combined, n = 24 (providing tertiary treatment) . | Secondary vs. tertiary plant differences in LR means; p-value; 0.95 CI . | ||||
|---|---|---|---|---|---|---|---|
| Human enteric virus . | d (%) . | nd (%) . | mean (±SE) . | d (%) . | nd (%) . | mean (±SE) . | Welch two-sample t-test . |
| Enterovirus culture, MPN/L | |||||||
| Pre-disinfection | 27 (79) | 7 (21) | 8.3 × 10−1 (2.4 × 10−1) | 10 (42) | 14 (58) | 9.6 × 10−2 (3.2 × 10−2) | |
| Post-disinfection | 20 (59) | 14 (41) | 1.1 × 10−1 (2.5 × 10−2) | 12 (50) | 12 (50) | 5.3 × 10−2 (2.2 × 10−2) | |
| Mean LR | 0.9 (0.05) | 0.3 (0.03) | p < 0.001; 0.5–0.7 | ||||
| Enterovirus RT-PCR, GC/L | |||||||
| Pre-disinfection | 29 (85) | 5 (15) | 1.4 × 10+6 (5.1 × 10+5) | 13 (54) | 11 (46) | 4.3 × 10+5 (1.6 × 10+5) | |
| Post-disinfection | 20 (59) | 14 (41) | 7.2 × 10+5 (4.1 × 10+5) | 5 (21) | 19 (79) | 2.1 × 10+4 (1.3 × 10+4) | |
| Mean LR | 0.3 (0.03) | 1.3 (0.2) | p < 0.001; 0.7–1.3 | ||||
| Norovirus GI, GC/L | |||||||
| Pre-disinfection | 32 (94) | 2 (6) | 7.2 × 10+5 (2.2 × 10+5) | 17 (71) | 7 (29) | 1.4 × 10+5 (5.4 × 10+4) | |
| Post-disinfection | 28 (82) | 6 (18) | 2.5 × 10+5 (1.2 × 10+5) | 11 (46) | 13 (54) | 2.0 × 10+4 (1.4 × 10+4) | |
| Mean LR | 0.5 (0.05) | 0.8 (0.1) | p = 0.002; 0.2–0.6 | ||||
| Norovirus GII, GC/L | |||||||
| Pre-disinfection | 33 (97) | 1 (3) | 3.8 × 10+5 (1.8 × 10+5) | 15 (62) | 9 (38) | 3.0 × 10+4 (1.2 × 10+4) | |
| Post-disinfection | 30 (88) | 4 (12) | 1.1 × 10+5 (4.6 × 10+4) | 10 (42) | 14 (58) | 7.5 × 10+3 (5.0 × 10+3) | |
| Mean LR | 0.5 (0.1) | 0.6 (0.1) | p = 0.4 (NS); (–)0.1–0.2 | ||||
| Norovirus GI + GII, GC/L | |||||||
| Pre-disinfection | 34 (100) | 0 | 1.1 × 10+6 (3.3 × 10+5) | 17 (71) | 7 (29) | 1.7 × 10+5 (6.3 × 10+4) | |
| Post-disinfection | 31 (91) | 3 (9) | 3.6 × 10+5 (1.4 × 10+5) | 12 (50) | 12 (50) | 2.7 × 10+4 (1.9 × 10+4) | |
| Mean LR | 0.5 (0.04) | 0.8 (0.1) | p = 0.006; 0.1–0.5 | ||||
MPN, most probable number; GC, gene copies; n, number tested; d, number detected (percent); nd, number of non-detects (percent) that were modeled; SE, standard error; LR, log10 reduction; CI, confidence interval; NS, not significant (p > 0.05); counts are unadjusted for recovery – see the text.