Fate of Coronaviruses during the Wastewater Coagulation with Ferric Chloride

Understanding the behavior of coronaviruses during wastewater treatment processes is imperative, but little is known about the fate of coronaviruses during the coagulation of municipal wastewater by ferric chloride. This study investigated the fate of two surrogate coronaviruses, i.e., feline infectious peritonitis virus (FIPV) and human coronavirus 229E (HCoV-229E), by measuring their infectivity in filtered and unfiltered raw wastewater subject to ferric coagulation. The dynamics of relevant wastewater parameters, including pH, COD (chemical oxygen demand), phosphate, sulfide, and iron species, were also profiled in parallel. In comparison to the natural decay of FIPV and HCoV-229E in filtered wastewater, the removal of both coronaviruses was significantly enhanced by the adsorption to solid particles in wastewater, including iron precipitates, coagulated solids, and original suspended solids (SSs). The entrapment of coronaviruses during the process of sweep coagulation, in combination with the electrostatic force between viruses and iron precipitates such as ferric phosphate and ferric oxyhydroxides, is believed to be responsible for the enhanced removal of viruses from the liquid phase of wastewater during ferric coagulation. These findings provide insight into the environmental fate of coronaviruses in wastewater treatment and raise awareness about the importance of safe disposal of wastewater sludge.