Water Treatment and Pathogen Control

The concept of multiple barriers is applied to both pathogens and chemicals, providing a robust treatment process to ensure public health protection.

Three barriers are typically used in drinking water treatment: coagulation/flocculation/sedimentation, filtration, and disinfection, which provide a 2 log virus removal, 2.5 log Giardia removal, and 2 log Cryptosporidium removal.

The Interim Enhanced Surface Water Treatment Rule (IESWTR) and Long Term 2 Enhanced Surface Water Treatment Rule (LT2) require multiple barriers for pathogen control, including coagulation/flocculation/sedimentation, filtration, and disinfection.

Potable reuse requires multiple barriers for pathogen reliability, including robustness, breadth, and toughness, to prevent failures and ensure public health protection.

A performance summary of barriers for pathogen control shows that different treatment processes, such as chlorine, ozone, microfiltration, reverse osmosis, and ultraviolet (UV) light, have varying levels of effectiveness against different pathogens like Giardia, Cryptosporidium, and viruses.

Multiple barriers provide robustness for "unknowns" and help address the diversity of chemicals and pathogens, minimizing the threat of unknowns.

The concept of multiple barriers is used in a broader context, including source protection, treatment, environment, distribution system, monitoring, and response.

Treatment train examples, such as Treatment Train #1, Treatment Train #2, and Treatment Train #3, demonstrate how multiple barriers can be used to remove pathogens and chemicals from wastewater.

California's Direct Potable Reuse regulations require at least 4 pathogen barriers providing 1-6 log reduction and at least 3 treatment mechanisms for each pathogen.

A treatment train typically includes physical degradation, oxidation, biological processes, adsorption, and inactivation mechanisms to remove pathogens and chemicals.

Chemicals are diverse, and the list continues to expand, with over 40,000 substances in the Toxic Substances Control Act (TSCA) inventory.

The performance summary of barriers for typical organic contaminants shows that different treatment processes have varying levels of effectiveness against different chemicals, highlighting the need for multiple barriers.