Removal of pathogens at small-scale constructed wetlands under long-term operation

Constructed wetlands (CW) have been widely used as an economical and sustainable wastewater treatment technology. Although many studies have shown that CW can effectively reduce organic matter and nutrients, the long-term resilience for reducing pathogens at some level is still understudied. Therefore, this study aimed to evaluate the reduction of Escherichia coli, Rotavirus, Polyomavirus, Somatic Coliphage, and F-specific RNA bacteriophage by CW. We evaluated four configurations of CW, planted with Typha domingensis and fed with pre-treated municipal wastewater. Samples were collected at the inlet and outlet of each CW during different operational phases over almost 10 years, and the reduction of organic matter, nutrients, bacteria and enteric virus was determined. The reduction values varied between the CW and showed a downward trend throughout the operational phases studied. The HF module proved to be less stable than the other modules analyzed, which was corroborated by the results obtained for the physicochemical parameters. The results of the study suggest that the use of only one type of indicator microorganism may not be appropriate for evaluating pathogens removal in CW. In some cases, it was possible to achieve a reduction of between 3 and 4 logarithmic units, a value that corresponds to the minimum reduction required by the World Health Organization (WHO) for the safe reuse of wastewater in restricted irrigation situations. Water recycling might be facilitated using CW. Depending on the water use purpose and exposure scenarios, our results show that adopting reuse practices with no need to further chemical disinfection can be possible from a health risk perspective.