PARVIRDIS · Enhancing natural wastewater treatment systems: the role of particles in sunlight-mediated virus inactivation

The processes by which viruses are inactivated in sunlight-exposed surface waters remains largely unknown. This lack of information severely limits our ability to predict the efficiency of and rationally design natural treatment systems that utilize sunlight-mediated inactivation (e.g., constructed wetlands). Viruses commonly associate with particles in surface waters, including photoreactive particles that can 1) adsorb viruses and 2) produce reactive oxygen species (ROS) when exposed to sunlight. Virus adsorption onto the surface of photoreactive particles exposes them to elevated ROS concentration and may increase inactivation compared to free viruses. The goal of this research is to characterize the adsorption and inactivation of particle-associated viruses in the dark and exposed to sunlight, with the aim of predicting the fate of viral pathogens within natural systems and using this information to improve their efficiency. We will quantify how different viral characteristics (e.g., isoelectric points, capsid size and composition, genome type) influence adsorption and inactivation, and which modes of inactivation are dominant (e.g., ROS damage to viral host binding sites, destruction of viral capsids by ROS or adsorption, and modification or destruction of genomic nucleic acids by ROS or nucleases). To aid in this study, a novel qPCR-based method for determining virus viability will be developed, a tool that will be of use for a variety of fields including environmental microbiology, public health and medicine. The detailed information gathered in this study will then guide the development of methods to improve the viral removal efficiency of a highly controllable constructed wetland. Different wetland configurations will be tested to promote virus adsorption onto iron-oxide coated sand and to maximize viral exposure to ROS. In so doing, this project will increase the efficacy of low-cost, effective systems for water and wastewater treatment.