Which of the following factors does NOT affect disinfection byproduct formation?

The size of the water treatment facility does not influence the formation of disinfection byproducts (DBPs) directly. Disinfection byproduct formation is primarily governed by the chemical characteristics of the water being treated and the specific conditions during disinfection.

The concentration of chlorine added is crucial because higher chlorine levels can lead to increased reactions with organic matter, resulting in more DBPs. Similarly, turbidity and the type of natural organic matter (NOM) present in the water can significantly affect the reactions that produce DBPs; different types of NOM can react differently with disinfectants. Water temperature also plays a role, as higher temperatures can increase the rate of chemical reactions, potentially leading to higher DBP levels.

Therefore, the size of the water treatment facility does not inherently affect the chemical processes responsible for DBP formation, making it the correct choice for this question.