| Popis: |
A quantitative microbial risk analysis of Ezousa (Cyprus) Managed Aquifer Recharge (MAR) site is presented herein to evaluate the health risks associated with the pathogenic fraction of three microorganisms: the bacterium Escherichia Coli (E. Coli), the Rotavirus and the protozoan Giardia duodenalis. At Ezousa, raw wastewater from the urban area is subject to wastewater treatment followed by soil-aquifer filtration prior reaching the end-users, who are mainly farmers. The removal efficiency standards of wastewater treatment processes are determined according to World Health Organization (WHO) reports, whereas two extreme end-user exposure scenarios are considered. The first scenario refers to a situation commonly encountered in industrialised countries, where farmers use tractors and associated farming equipment and are expected to wear protective gloves during their activities. The second scenario describes farming practices in developing countries, in which tractors and gloves are rarely used. The results suggest that all three pathogens are likely to infect individuals for both exposure scenarios. Regarding Scenario 1, around 25 % of the samples for E. Coli exceed the target values, whereas the highest health risks are found for Rotavirus and Giardia, in accordance with existing reports. As expected, the risk analysis for Scenario 2 provided much higher values for the health parameters compared to Scenario 1, suggesting that all pathogens possess a high risk for human health under the "worst-case" scenario. Finally, the Quantitative Microbial Risk Assessment (QMRA) was used to predict the required microbial removal after subsurface filtration of treated wastewater, in order to meet health-based targets. For E. Coli, the total performance requirement for Scenario 1 and Scenario 2 is found to be 5.5 〖log〗_10 and 7 〖log〗_10 units removal, respectively. These values are consistent with the findings of existing reports, suggesting that the removal efficiency of the soil-aquifer passage plays a crucial role under circumstances such as a heavy microbial load or technical failures. |
