Treated domestic effluents for non-potable reuse: microbial risk assessment and economic viability

In this study, we applied quantitative microbial risk assessment and net present value methodologies to evaluate the economic viability and safety of wastewater treatment to produce water for reuse. We found payback periods of three to over 15 years for investment in the universalisation of sanitation services in the selected municipalities, wherein the most feasible scenarios were those in which water reuse was carried out at its maximum potential. Microbial risk was assessed in terms of reduced concentrations of Escherichia coli. Results show that reuse of wastewater treated by different plant configurations for crop irrigation, involving only secondary treatment processes, presented high risk of infection for both farmers and consumers (3.50E–02 ± 3.10E–03 and 5.80E 02 ± 3.30E–03, respectively). In the urban and industrial context, it did not pose any risk beyond the tolerable risk recommended by WHO, except for the worker’s droplet ingestion route of exposure (2.40E–03 ± 3.80E–03).