What wastewater component diminishes the effectiveness of UV treatment as its concentration increases?

Suspended solids diminish the effectiveness of UV treatment as their concentration increases because they can physically obstruct the path of UV light. This obstruction reduces the amount of UV radiation that can penetrate through the water to reach and inactivate microorganisms effectively. When a wastewater sample contains high levels of suspended solids, the UV light may not reach all of the pathogens present, reducing the overall disinfection efficiency.

In contrast, while organic matter can also impact UV treatment, it's primarily the suspended solids that provide a physical barrier. Nutrients do not significantly impede UV light penetration, and while microbial count is relevant for assessing treatment effectiveness, it is not a component that diminishes UV treatment directly. Thus, the presence of suspended solids is the critical factor adversely affecting the disinfection capabilities of UV processes.