What best describes how disinfection byproducts (DBPs) form and how they can be minimized?

• A. DBPs form when minerals are removed; minimize by adding minerals.
• B. DBPs form when disinfectants react with organic matter; they can be minimized by reducing precursor organics, optimizing disinfectant type, and controlling contact time and pH.
• C. DBPs form when water is boiled; minimize by turning off heat.
• D. DBPs form due to UV exposure; minimize by using chlorine.

Answer: (B)

Disinfection byproducts form when a disinfectant, such as chlorine, reacts with organic matter and other precursors already in the water. This reaction creates compounds like trihalomethanes and haloacetic acids that can raise health concerns if present at certain levels. The best way to minimize them is to attack the problem at its source and during treatment: remove as much precursor organic matter as possible before disinfection (through effective coagulation, settling, and filtration); choose and dose the disinfectant in a way that lowers DBP formation (selecting the appropriate disinfectant type and amount); and control factors that influence the reaction, specifically how long the water and disinfectant are in contact and the pH. The other ideas don’t address how DBPs form in the first place—minerals aren’t the key precursors, boiling isn’t how they’re generated, and UV exposure alone doesn’t explain the main formation pathway for chlorine-based DBPs.