Viral RNA reduction from wastewaters using microalgae-based treatments: Elucidating the effect of light and zero-valent iron nanoparticles

Microalgae-based systems can potentially inactivate E. coli and viruses. In this work, batch algal-bacterial photobioreactors were operated to elucidate the effect of zero-valent iron (ZVI) nanoparticles and light intensity on the reduction of viral RNA (MS2, Phi6 and Bovine coronavirus, BCoV) and uidA gene (E. coli) during secondary wastewater treatment. Biodegradation and abiotic control photoreactors were operated at high light intensity (1100 µE m^-2 s^-1), with and without ZVI-nanoparticles addition (HLNP and HL) and low light intensity (450 µE m^-2 s^-1), without nanoparticles (LL). After 72 h, HLNP matched or increased the reductions of at least 99.9 % for viruses and 99 % for uidA achieved within 192 h in HL and LL. Oxidative reactions in the presence of ZVI-nanoparticles seemed to mediate the decay of viral RNA and uidA. This work demonstrated for the first time the potential for enhanced reduction of viral RNA and E. coli by ZVI-nanoparticles during microalgae-based wastewater treatment.