24 Sep 2014

Assessing dual water quality supply in domestic settings

We participated in a collaborative study that evaluated the quality of dual water supply in domestic settings.

The study examined the consequences of proposed alternative water supply systems, specifically looking at their technical feasibility, cost, health risks and public acceptance. For this project, we conducted an assessment of the health risks related to using low quality water (such as grey water or polluted ground water) for laundry and flushing toilets.

Microorganisms were considered the most likely threat to human safety in the proposed systems. As such, we used a quantitative microbial risk assessment (QMRA), with Norovirus as a model organism. Norovirus is the pathogen most likely to cause infection due to its:
  • potential presence in grey water and groundwater
  • relatively long lifespan
  • low sand filtration efficiency in the absence of coagulation
  • high concentration in the faeces of infected individuals
  • high contagion rate
We found that a grey water reuse system will need to include some kind of disinfection, such as ultraviolet (UV), to be safe. Alternatively, reuse could be restricted to laundry, with a systematic surveillance method in place to reduce the probability of cross-connections (cross contamination to the drinking water system).

Funded by the Danish Agency for Science, Technology and Innovation, we conducted this project in partnership with:
  • Technical University of Denmark’s Department of Environmental Engineering
  • HOFOR
  • Aalborg University’s Department of Development and Planning


Illustration of the four water supply options. © Elsevier