The use of copper and silver in carbon point-of-use filters for the suppression of Legionella throughput in domestic water systems
2008
Molloy, S.L. | Ives, R. | Hoyt, A. | Taylor, R. | Rose, J.B.
To evaluate throughput of seeded Legionella pneumophila bacteria in domestic point-of-use filters. The filters were challenged with tap water seeded with Leg. pneumophila. After multiple challenge events (4·25 x 10¹¹ CFU per filter), the levels of Legionella were lower in the effluent from the filter containing both copper and silver (mean 4·48 x 10³ CFU ml⁻¹) than in the effluent from the filter containing copper only (1·26 x 10⁴ CFU ml⁻¹; P < 0·001). After a single challenge event of approx. 5 x 10⁹ CFU L. pneumophila per filter, there was no significant difference between the levels of Legionella in the effluents from a carbon filter containing copper and a carbon filter with no metals (mean 6·87 x 10² and 6·89 x 10² CFU ml⁻¹, respectively; P = 0·985). Legionella was detected in filter effluent up to 6 weeks after being challenged, indicating that while filters may reduce the levels during an initial contamination event, the exposure is extended as the accumulated bacteria slough off over time. This study has provided an understanding of the response of Legionella to the use of silver and copper in domestic point-of-use carbon filters.
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