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Volume 12, Number 4—April 2006

Research

Reducing Legionella Colonization of Water Systems with Monochloramine

Brendan Flannery*Comments to Author , 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*
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †California Emerging Infections Program, Oakland, California, USA; ‡California Department of Health Services, Richmond, California, USA; §City and County of San Francisco Department of Public Health, San Francisco, California, USA; ¶San Francisco Public Utilities Commission, Burlingame, California, USA

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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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