Quantifying microbial risk from drinking water production process under changing climate and socio-economic conditions

Consumption of drinking water containing pathogenic microorganisms may pose serious health risks from waterborne diseases. Quantifying such risks is essential for guiding interventions and policy decisions. Quantitative microbial risk assessment (QMRA) is a very useful method to estimate the public's risk of infection from disease-causing microorganisms in water sources. QMRA of drinking water production process is limited worldwide and so far no such QMRA study has been conducted in Bangladesh. Moreover, climate and socio-economic changes may impact waterborne pathogens and associated health risks, but to what extent remains unclear, because comprehensive QMRA by taking into account combined impact of climatic and socio-economic factors has never been done worldwide so far. In this study, the Swedish QMRA tool was applied to evaluate public health risk from drinking water production process in Dhaka, Bangladesh as a case study. At first, current risk was quantified, and then the potential future risk was projected by taking into account climate and socio-economic factors. The results revealed that the annual infection risks at the current (2020s) baseline condition were below the acceptable risk threshold 10^–4 infections per person per year (as proposed by several USEPA scientists) for all three pathogens Salmonella, norovirus and Giardia. However, after extreme events with sewer overflow and agricultural runoff, norovirus violates the acceptable risk thresholds, and the risks for Salmonella and Giardia are in borderline. The selected sustainable future scenario showed some improvement in terms of annual infection risks, while the uncontrolled scenario resulted in substantially higher infection risks both in the near and far future compared to the current scenarios. installment of a UV treatment step as an additional treatment barrier resulted in significant infection risk reduction. According to the sensitivity analysis results, socio-economic factors such as human population, livestock, and pathogen removal in wastewater were found to have greater influence on the infection risks, compared to climate change. The study can help policy makers and water managers to identify interventions to reduce the burden of disease on the population. The tool can be used to assess the health risk associated with drinking water production process in other areas of the world with similar characteristics.