Health concerns of using grey water to flush toilets

Water conservation is the main theme of discussion amongst future city planners and public utilities experts, and grey water is increasingly being put forward as a possible source of water for flushing toilets, as cities bid to reduce their overall water consumption. But, what is grey water and is it safe as a water source for flushing toilets?


Potable water is commonly used to flush toilets, but given the high cost of drinking water treatment, many people have proposed the alternative approach of using slightly contaminated water (i.e., grey water) for flushing toilets in an attempt to reduce water consumption. Specifically, grey water refers to not highly contaminated water such as rainwater collected from rooftops of buildings. But, is grey water a health concern in their presented use scenario for flushing toilets? The answer is a tentative yes.


Take, for example, rainwater, it contains significant amounts of airborne contaminants, including fungal and bacterial spores, not seen with the naked eye. In addition, rainwater is slightly acidic given the presence of pollutants such as sulphur dioxides and nitrogen oxides in air. Hence, long duration storage of rainwater for use in flushing toilets may introduce a health concern to households where there is none previously. Specifically, bacterial and fungal spores may germinate and grow within the flushing apparatus; thus, introducing hard to remove microorganisms into the household, which may impact on the health of the inhabitants.


Hence, while slightly contaminated water such as rainwater raises possible use as water for flushing toilets, their significant microbiological load in bacterial and fungal spores, put their use highly questionable as it introduces a microbiological hazard into households. Specifically, given the difficulty inherent in eradicating fungal contamination, rainwater from rooftops should not be collected and stored for use in flushing toilets.


Category: environment, environmental engineering, water treatment, environmental economics,

Tags: grey water, flush toilets, microbiological load, contaminant, bacteria, fungal spores,


Acknowledgement: Ng Wenfa thank Seah Kwi Shan for giving him the idea for this blog post.


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