Table 2.
Average concentration of Legionella spp. L. pneumophila and MAC (mean ± standard deviation copies/mL) measured at each sampling point of Distribution system 2 (DS2) using qPCR. Total monochloramine (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) | 1 | 40 | 54 | 137 | 54 | |
| Summer 27.3 °C (n = 10) | Monochloramine (mg/L) | 3.6 | 3.0 | 3.6 | 2.7 | <0.05 |
| Average Legionella spp. (copies/mL) | 444 ± 96 | 161 ± 19 | 134 ± 94 | 423 ± 399 | * 316,956 ± 169,8982 | |
| Average L. pneumophila (copies/mL) | 105 ± 8 | 712 ± 158 | 479 ± 177 | 12 ± 16 | 941 ± 154 | |
| Average MAC (copies/mL) | 9755 ± 7808 | 6910 ± 6128 | 2803 ± 584 | 1739 ± 539 | 5362 ± 1612 | |
| Autumn 14.7 °C (n = 13) | Monochloramine (mg/L) | 3.8 | 2.3 | 2.4 | 1.5 | <0.05 |
| Average Legionella spp. (copies/mL) | # 24,238 ± 2918 | 260 ± 10 | 24 ± 19 | 1597 ± 600 | 1094 ± 284 | |
| Average L. pneumophila (copies/mL) | 238 ± 232 | 87 ± 14 | 26 ± 40 | 666 ± 73 | 333 ± 86 | |
| Average MAC (copies/mL) | 542 ± 103 | 663 ± 325 | 4068 ± 1193 | 586 ± 0 | + 1424 ± 482 | |
| Winter 13.0 °C (n = 9) | Monochloramine (mg/L) | 3.6 | 3.7 | 2.3 | 0.8 | 0.2 |
| Average Legionella spp. (copies/mL) | 2016 ± 60 | 883 ± 143 | 303 ± 34 | 197 ± 99 | * 17,7727 ± 10,2437 | |
| Average L. pneumophila (copies/mL) | 248 ± 31 | 566 ± 220 | 573 ± 133 | 281 ± 185 | * 3176 ± 1950 | |
| Average MAC (copies/mL) | 367 ± 395 | 277 ± 144 | 4228 ± 3607 | 433 ± 271 | + 9526 ± 3271 | |
| Spring 21.2 °C (n = 10) | Monochloramine (mg/L) | 2.0 | 2.8 | 3.9 | 2.1 | <0.05 |
| Average Legionella spp. (copies/mL) | 913 ± 88 | 1780 ± 251 | 914 ± 48 | 1111 ± 1359 | * 128,9587 ± 53,042 | |
| Average L. pneumophila (copies/mL) | 10 ± 2 | 3 ± 0 | 4 ± 2 | 38 ± 31 | 19 ± 17 | |
| Average MAC (copies/mL) | 5184 ± 1464 | 2577 ± 483 | 2507 ± 1615 | 2039 ± 475 | 11,445 ± 3478 |
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. # magnitude higher, assumed to be due to biofilm fragment.