When
rainwater harvesting is utilized as an alternative water resource
in buildings, a combination of municipal water and rainwater is typically
required to meet water demands. Altering source water chemistry can
disrupt pipe scale and biofilm and negatively impact water quality
at the distribution level. Still, it is unknown if similar reactions
occur within building plumbing following a transition in source water
quality. The goal of this study was to investigate changes in water
chemistry and microbiology at a green building following a transition
between municipal water and rainwater. We monitored water chemistry
(metals, alkalinity, and disinfectant byproducts) and microbiology
(total cell counts, plate counts, and opportunistic pathogen gene
markers) throughout two source water transitions. Several constituents
including alkalinity and disinfectant byproducts served as indicators
of municipal water remaining in the system since the rainwater source
does not contain these constituents. In the treated rainwater, microbial
proliferation and Legionella spp. gene copy numbers
were often three logs higher than those in municipal water. Because
of differences in source water chemistry, rainwater and municipal
water uniquely interacted with building plumbing and generated distinctively
different drinking water chemical and microbial quality profiles.
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