Quantitative microbial risk assessment of wastewater and faecal sludge reuse in Ghana

The probabilistic health risks of rotavirus and Ascaris infections associated with different scenarios of diluted wastewater and faecal sludge agricultural reuse in Ghana were estimated based on the Quantitative Microbial Risk Assessment (QMRA) approach. The annual risks of rotavirus and Ascaris infections associated with diluted wastewater reuse scenarios were 10-2 and 10-3 to 10-4 respectively compared with the WHO tolerable health risk of 10-4 per person per year. The risk of Ascaris infection for the different scenarios of faecal sludge reuse ranged from 10-4 to 10-2 while it was <10-14 to 10-1 for rotavirus infections per single exposure. The treatment of faecal sludge significantly reduced the risk of rotavirus infections but had less effect on the reduction of Ascaris infections. It is stressed that the estimated risks of infection need to be validated against follow-up data obtained from epidemiological investigations coupled with studies on different health risk barriers.