Table 1.
Average concentration of Legionella spp. L. pneumophila and MAC (mean ± standard deviation copies/mL) measured at each sampling point of Distribution system 1 (DS1) using qPCR. Total and free chlorine (mg/L) measured when samples were collected is also shown as well as the average water temperature for the month during which the sample was taken. The sampling points where a significant increase (p < 0.05) in the concentration of an organism compared to the concentration measured at sample point A within the same sampling period are also highlighted (*).
| Season Sampled and Average Water Temperature | Sample Point | A | B | C | D | E |
|---|---|---|---|---|---|---|
| Distance from treatment plant (km) | 5 | 7 | 10 | 18 | 22 | |
| Summer 4.3 °C (n = 8) | Total Chlorine (mg/L) | 1.4 | 0.7 | 1.1 | 0.4 | 0.4 |
| Free chlorine (mg/L) | 1.2 | 0.6 | 0.1 | 0.2 | 0.2 | |
| Average Legionella spp. (copies/mL) | 37 ± 53 | 9 ± 4 | 3 ± 0 | 187 ± 22 | + 1238 ± 47 | |
| Average L. pneumophila (copies/mL) | 10 ± 8 | 3 ± 0 | 3 ± 0 | 375 ± 305 | * 1981 ±298 | |
| Average MAC (copies/mL) | 36 ± 19 | 42 ± 19 | * 31,813 ± 17,017 | 116 ± 118 | + 4395 ± 2176 | |
| Autumn 18.6 °C (n = 8) | Total chlorine (mg/L) | 1.5 | N/A | 1.0 | 0.8 | 1.1 |
| Free chlorine (mg/L) | 1.3 | N/A | 0.8 | 0.6 | 0.9 | |
| Average Legionella spp. (copies/mL) | 5 ± 4 | N/A | 41 ± 21 | 47 ± 13 | 46 ± 17 | |
| Average L. pneumophila (copies/mL) | 3 ± 0 | N/A | 3 ± 0 | 46 ± 68 | + 487 ± 406 | |
| Average MAC (copies/mL) | 25 ± 0 | N/A | 25 ± 0 | 200 ± 157 | 25 ± 0 | |
| Winter 13.6 °C (n = 8) | Total chlorine (mg/L) | 1.2 | N/A | 1.3 | 0.4 | 0.7 |
| Free chlorine (mg/L) | 1.1 | N/A | 1.3 | 0.3 | 0.6 | |
| Average Legionella spp. (copies/mL) | 22 ± 31 | N/A | 3 ± 0 | 5 ± 1 | 3 ± 0 | |
| Average L. pneumophila (copies/mL) | 81 ± 134 | N/A | 3 ±1 | 3 ± 0 | 3 ± 0 | |
| Average MAC (copies/mL) | 25 ±0 | N/A | 25 ± 0 | 25 ± 0 | 25 ± 0 | |
| Spring 20.3 °C (n = 8) | Total chlorine (mg/L) | 1.0 | 0.7 | 0.3 | 0.4 | 0.7 |
| Free chlorine (mg/L) | 0.9 | 0.6 | 0.2 | 0.3 | 0.6 | |
| Average Legionella spp. (copies/mL) | 43 ± 69 | 120 ± 151 | 8 ± 3 | 93 ± 139 | 6 ± 6 | |
| Average L. pneumophila (copies/mL) | 36 ± 34 | 15 ± 12 | 9 ± 1 | 166 ± 122 | 3 ± 0 | |
| Average MAC (copies/mL) | 2468 ± 317 | 2224 ± 2342 | 1112 ± 328 | 294 ± 58 | 101 ± 69 |
N/A sample was not available to be collected at this time. * statistically significant increase. + an increase of concentration by an order of magnitude. The lack of statistical significance (p > 0.05) is possible due to the large variance in environmental samples shown by the standard deviation.