Disinfection and particle removal by a nature-based Daphnia filtration system for wastewater treatment

Nature-based solutions (NBS) to treat wastewater are ecological treatments that work to mitigate the impact of conventional systems in wastewater treatment processes. In this study, the efficiency of an innovative wastewater tertiary treatment based on Daphnia filtration in removing suspended solids and E. coli is evaluated in combination with either vermifiltration or conventional secondary treatments. Daphnia filtration NBS was found to increase particle removal and E. coli inactivation over a wide range of water temperatures, solar radiation intensities, and hydraulic residence times. Moreover, two models to predict the quality of the treated wastewater, one that describes the removal of particles and another for E. coli inactivation, are developed and presented here. Both models depend on water temperature, the exposure to solar radiation and the hydraulic residence time in the reactor. The results using these models align with the experimental results in all cases. Hydraulic residence times above 24 h allowed suspended particle concentrations to be reduced by >75 % with water temperatures in the range of 10 °C to 27 °C and for E. coli to be inactivated by 1–3 log units in water temperature ranging from 8 °C to 27 °C. The developed models can also be used to provide information regarding the operating conditions (i.e. hydraulic residence times) required to obtain the desired regenerated water quality in accordance with reuse purposes and the regulations of different countries.