TABLE 1.
Numbers and percentages of positive samples and their geometric means determined by culture
| Treatment | No. of positive samples/total no. of samples (%) | χ2 value, P valuea | Geometric mean CFU liter−1 for positive samples (range) | F value, P valuea |
|---|---|---|---|---|
| Monochloramine | 4.131, NS | 1.963, NS | ||
| <2.0 mg liter−1 | 2/8 (25.0) | 2.0 × 103 (1.2 × 102–3.1 × 104) | ||
| 2.0–2.9 mg liter−1 | 4/29 (13.8) | 3.7 × 102 (25–5.7 × 103) | ||
| ≥3.0 mg liter−1 | 3/58 (5.2) | 25 (25) | ||
| Chlorine dioxide | 6.928, <0.05 | 2.058, NS | ||
| <0.30 mg liter−1 | 31/84 (36.9) | 4.0 × 102 (25–2.5 × 104) | ||
| 0.30–0.49 mg liter−1 | 18/54 (33.3) | 3.5 × 102 (25–4.1 × 104) | ||
| ≥0.50 mg liter−1 | 11/63 (17.5) | 1.0 × 102 (25–5.5 × 103) | ||
| Hydrogen peroxide | 10.339, <0.001 | 2.468, NS | ||
| <15.0 mg liter−1 | 46/91 (50.5) | 1.1 × 102 (25–1.4 × 103) | ||
| 15–19.9 mg liter−1 | 14/43 (32.6) | 2.6 × 102 (25–5.0 × 103) | ||
| ≥20.0 mg liter−1 | 20/74 (27.0) | 1.1 × 102 (25–2.3 × 103) | ||
| Hyperthermia | 33.31, <0.001 | 0.481, NS | ||
| 50–54.9°C | 19/21 (90.5) | 2.5 × 103 (25–1.2 × 104) | ||
| 55–59.9°C | 17/27 (63.0) | 1.2 × 103 (25–7.9 × 103) | ||
| ≥60°C | 0/18 (0) |
a
NS, not significant.