Two-Year Evaluation ofLegionellain an Aging Residential Building: Assessment of Multiple Potable Water Remediation Approaches

Abstract

ABSTRACTLegionellais an opportunistic waterborne pathogen that is difficult to eradicate in colonized drinking water pipes.Legionellacontrol is further challenged by aging water infrastructure and lack of evidence-based guidance for building treatment. This study assessed multiple premise water remediation approaches designed to reduceLegionella pneumophila (Lp)within a residential building located in an aging, urban drinking water system over a two-year period. Samples (n=745) were collected from hot and cold-water lines and quantified via most probable number culture. Building-level treatment approaches included three single heat shocks (HS), three single chemical shocks (CS), and continuous low-level chemical disinfection (CCD) in the potable water system. The building was highly colonized withLpwith 71%Lppositivity. Single HS had a statistically significantLpreduction one day post treatment but no significantLpreduction one, two, and four weeks post treatment. The first two CS resulted in statistically significantLpreduction at two days and four weeks post treatment, but there was a significantLpincrease at four weeks following the third CS. CCD resulted in statistically significantLpreduction ten weeks post treatment implementation. This demonstrates that in a building highly colonized withLp, sustained remediation is best achieved using CCD.SYNOPSISLong-termLegionella control is difficult to maintain within aging premise plumbing. This study supports continuous low-level building treatment as an effective long-term remediation of a building highly colonized withLegionella.For Table of Contents Only