Abstract
A broad body of literature has been published regarding roof-harvested rainwater quality around the world. In particular, the presence of fecal indicator bacteria and pathogenic microorganisms has raised concerns regarding the acceptability of rainwater for potable and non-potable uses. As the use of molecular assays has improved understanding of the diverse microbial communities present in rainwater tanks and their role in providing benefits or harm to human health, a comprehensive review is needed to summarize the state of the science in this area. To provide a summary of microbial contaminants in rainwater tanks and contextual factors, a comprehensive review was conducted here to elucidate the uses of rainwater, factors affecting water quality, concentrations of fecal indicators and pathogens, the attribution of pathogens to host sources using microbial source tracking, microbial ecology, human health risks determined using epidemiological approaches and quantitative microbial risk assessment, and treatment approaches for mitigating risks. Research gaps were identified for pathogen concentration data, microbial source tracking approaches for identifying the sources of microbial contamination, limitations to current approaches for assessing viability, treatment, and maintenance practices. Frameworks should be developed to assess and prioritize these factors in order to optimize public health promotion for roof-harvested rainwater.
Highlights
Several studies reported that roof-harvested rainwater (RHRW) for drinking or domestic use has been associated with disease risks and outbreaks.[1–4]
A typical engineered RHRW collection system relies upon a sloped catchment system which drains via a gutter and attached pipe into a storage container.[10]
The variability in E. coli concentrations observed in the studies has been linked to meteorological factors,[33] catchment location, roof and/or storage container materials,[36] the presence of wildlife near the roof,[32] laboratory method used, and location and/or timing of the sampling event relative to the previous factors.[33]
Summary
Several studies reported that roof-harvested rainwater (RHRW) for drinking or domestic use has been associated with disease risks and outbreaks.[1–4] Rainwater harvesting is currently being practiced widely and is increasing as a result of a growing awareness of water conservation and stormwater runoff issues, desire for selfsufficiency, the proliferation of environmentally friendly housing developments, and incentives, subsidies, or mandates by government organizations.[5]. Given the variable nature of RHRW quality from different roof catchments, it can be challenging to designate appropriate uses in terms of water quality and safety Despite this limitation, it is important to identify contaminants and contributing factors for guiding rainwater treatment and use. E. coli are commonly found in the feces of warm-blooded animals in high numbers.[41] Their presence in a water source indicates the presence of fecal contamination and potential enteric pathogens. The variability in E. coli concentrations observed in the studies has been linked to meteorological factors,[33] catchment location, roof and/or storage container materials,[36] the presence of wildlife near the roof,[32] laboratory method used, and location and/or timing of the sampling event relative to the previous factors.[33]. The authors raised concerns regarding the E. coli contamination as the npj Clean Water (2019) 7
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