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Occurrence of Legionella in Nonpotable Reclaimed Water

  • Author(s): Johnson, William J.; Jjemba, Patrick K.; Bukhari, Zia; LeChevallier, Mark W.
  • Publications: Journal - American Water Works Association
  • Issue Date: March 2018
  • Volume / Number: 110, Number 3
  • Page(s): 15-27
  • DOI:
  • Product Number: JAW_0085884
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Legionella was monitored in reclaimed water systems and were detected by culture in 50% of 115 samples, while 80% of the samples were positive by quantitative polymerase chain reaction (qPCR). The lowest level of Legionella was in a system that practiced biological nutrient removal and maintained an average 0.3 mg/L free chlorine residual. The difference between qPCR and ethidium monoazide treated samples was used as an indicator of viability, and the greatest difference was in a chloraminated system, where the molecular method indicated a 9% viability. Ninety-six percent of the species were L. pneumophila, and 87% were identified as L. pneumophila serotype 1. Total amoebae (summed as cysts or trophozoites) were detected in 100% of samples from all six systems, and were mostly (50-95%) in the active trophozoite phase. In the chloraminated system, 87% of the mesophilic amoebae and 66% of the thermophilic amoebae were in the cyst phase.

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