Potable reuse, or the practice of treating wastewater for drinking water applications,  has become a critical component of many water resource portfolios. It is increasingly being used to overcome growing water shortages and to address practical demands.

However, stringent pathogen controls are needed to protect public health, particularly for viruses. It is therefore important to understand whether and how each unit process in advanced treatment trains achieves effective virus removal, and how to earn credits for the virus reductions achieved in these processes. Due to the high economic cost of typical reverse osmosis (RO)–based treatment, many communities opt for carbon-based advanced treatment (CBAT) trains as an alternative, underscoring the need to better understand how these non-RO processes contribute to virus removal and regulatory crediting. 

In a recent EPA-funded project, our team partnered with the Southern Nevada Water Authority, Trussell Technologies, Drexel University, and EOA to address a key challenge in potable reuse: how to reliably quantify virus removal in advanced treatment systems that do not rely on reverse osmosis. We focused on treatment processes that are widely used but currently lack established virus crediting guidance, including secondary biological wastewater treatment, coagulation, flocculation, and sedimentation upstream of ozone and biological activated carbon, as well as sub-residual ozone dosing. We synthesized extensive existing data from the literature on virus fate across these treatment processes and conducted targeted experiments to address critical knowledge gaps. Together, these efforts supported the development of log reduction crediting frameworks grounded in quantitative relationships between virus attenuation, operational conditions, and measurable surrogate parameters.

The findings of this study provide utilities and regulators with the scientific basis needed to confidently assess virus removal in carbon-based advanced treatment trains. Findings from this work will be published in 2025–2026.