Modeling of viral aggregation and its impact on chlorine disinfection efficacy

Viruses are persistent microbial contaminants in wastewater environments and pose a significant public health risk due to their frequent detection and low infectious doses. Although physical treatments remove some viral particles, this removal is often insufficient and highly variable, making chlorine disinfection a critical final process. However, virus susceptibility to chlorine varies depending on genetic and physicochemical properties, including aggregation state, as viruses may be released from infected hosts as aggregates. Consequently, disinfection conditions proposed in inactivation studies using dispersed viruses may not reflect real environmental conditions. This study developed a virus inactivation model incorporating an aggregation-dependent chlorine sensitivity parameter. The model was fitted using experimental data, and viral aggregation state was simulated using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and Population Balance Model (PBM) to evaluate its effects on disinfection efficacy across different environmental conditions. As the proportion of higher-order aggregates increased and primary particles decreased, the log reduction value declined by 0.2-0.3-log, regardless of the applied free chlorine dose. Simulations also revealed that higher ionic strength promoted viral aggregation, whereas greater zeta-potential magnitude prevented it, both potentially influencing disinfection efficiency. These findings highlight the importance of chlorine disinfection optimization and suggest the need of effective pretreatment steps for reliable virus removal in wastewater treatment.