Quantitative Microbial Risk Assessment (QMRA) of Campylobacter for Roof-Harvested Rainwater Domestic Use

The present study evaluated the microbiological risk for roof-harvested rainwater (RHRW), with Campylobacter as the pathogenic microorganism of reference, using a Quantitative Microbial Risk Assessment (QMRA). QMRA has been widely used as an alternative method for epidemiological assessment of human exposure to microorganisms that can cause diseases, through a four-step process: hazard identification, exposure assessment, dose–response assessment, and risk characterization. The results presented drinking as the water use with the highest median value for microbiological risk, with 3.4 × 10−4 disability-adjusted life years (DALYs) per person per year (pppy), and bathing, food washing, hose irrigation and toilet flushing with median values of 6.5 × 10−7, 4.0 × 10−7, 2.1 × 10−7 and 1.4 × 10−7 DALYs pppy, respectively. Therefore, drinking would be the only water use that would require preliminary treatment for its safe use, considering the acceptable risk standards set by the World Health Organization for drinking water. However, with the adoption of a sanitary barrier and a simple point-of-use treatment system, it was observed that drinking rainwater would have a median microbiological risk of 2 × 10−6 DALYs pppy, enough to meet the safety criteria considering developing countries.