ABSTRACT
The current study had the objective to apply the tool of quantitative microbiological risk assessment (QMRA) to evaluate the reuse of greywater in order to define a range of maximum value allowed (MVA) to Escherichia coli by means of the concept of acceptable risk 10-3 and 10-6 per person per year (pppy), for the various purposes of reuse. For that, the following criteria were evaluated: the exposure, the dose-response and the probability of infection for different purposes of reuse. The Beta-Poisson model was used to assess the probability of infection. The input data for QMRA were evaluated from a systematic compilation of literature data. The greatest risks of infection resulted from food crops and balneability in mixed greywaters, resulting in MVA from 5.25 to 105 MPN/100 mL and from 3.95 to 39.5 MPN/100 mL respectively, to an acceptable risk of 10-3 and 0.00 to 0.10 NMP/100 mL and from 0.00 to 0.04 MPN/100 mL, simultaneously, to a risk of 10-6 pppy. Yet, the lowest risk of infection was due to the reuse of greywater from lavatories for washing floors, providing MVA from 21.4 × 101 to 2.14 × 103 MPN/100 mL to an acceptable risk of 10-3 and 0.71 to 14.3 MPN/100 mL, for a risk of 10-6 pppy. The QMRA with acceptable risk of 10-3 pppy has been a potential tool for the assessment of MVA in crude greywater aiming the reuse and the possibility of support in national policy decisions.
Keywords:
microbiological risk; greywater; Escherichia coli