Volume 12, Number 4—April 2006
Research
Reducing Legionella Colonization of Water Systems with Monochloramine
Brendan Flannery*
, Lisa B. Gelling†, Duc J. Vugia‡, June M. Weintraub§, James J. Salerno¶, Michael J. Conroy¶, Valerie A. Stevens*, Charles E. Rose*, Matthew R. Moore*, Barry S. Fields*, and Richard E. Besser*
, Lisa B. Gelling†, Duc J. Vugia‡, June M. Weintraub§, James J. Salerno¶, Michael J. Conroy¶, Valerie A. Stevens*, Charles E. Rose*, Matthew R. Moore*, Barry S. Fields*, and Richard E. Besser*
Table 1
Characteristics of treated water in the city distribution system or in water heaters in 53 sampled buildings, San Francisco, California, stratified by year
| Measurement (unit)* | 2003, mean (range) | 2004,† mean (range) | Reference value‡ |
|---|---|---|---|
| Treated water | |||
| Total chlorine, ppm | 0.60 (0.01–2.20) | 1.97 (0.15–3.40) | 4.00 |
| Total trihalomethanes, ppb | 65.3 (16.0–143.0) | 34.8 (11.0–46.0) | 80.0 |
| Total haloacetic acids, ppb | 19.5 (6.0–55.0) | 20.3 (3.0–33.0) | 60.0 |
| Total organic carbon, ppb | 2.8 (2.4–3.3) | 2.9 (2.6–3.1) | NA |
| pH | 9.0 (7.4–9.9) | 8.8 (7.5–10.5) | NA |
| Lead, ppb§ | 6.7§ | 11.5 | 15.0 |
| Copper, ppb§ | 120§ | 90 | 1,300 |
| Water sampled from water heaters in 53 buildings¶ | |||
| Total chlorine, ppm | 0.13 (0–0.86) | 1.10 (0–2.20) | NA |
| Temperature, °C | 44.9 (17.8–87.8) | 45.1 (17.8–79.4) | NA |
| pH | 8.9 (7.5–10.5) | 8.7 (7.5–10.4) | NA |
*ppm, parts per million; ppb, parts per billion.
†Measurements were taken from March through December 2004, after conversion to chloramine for residual disinfection.
‡Maximum allowable levels for compliance with Environmental Protection Agency standards. NA, not applicable.
§Measurements for lead and copper are the 90th percentile for samples collected from point of use. Prechloramine samples were collected during 2001.
¶Water heater samples were collected on 3 occasions over a 10-month period. Mean and range were calculated for 159 samples.
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