At pH levels associated with softening chemical precipitation, which component in the treated water may increase?

At pH levels associated with softening chemical precipitation, which component in the treated water may increase?

• A. Trihalomethane fraction; increase
• B. Alkalinity; increase
• C. Hardness; decrease
• D. pH; increase

Answer: (A)

When lime-based chemical precipitation is used to soften water, the treatment raises both pH and alkalinity. After softening, chlorine is typically used for disinfection, and disinfection byproducts form when chlorine reacts with natural organic matter present in the water. Higher pH conditions favor reaction pathways that lead to the formation of disinfection byproducts, particularly trihalomethanes. So, in treated water at the pH levels typical of chemical precipitation softening, the fraction of trihalomethanes can increase as chlorine reacts with organic precursors. The other changes you see with softening—hardness decreasing and alkalinity or pH rising—don’t directly indicate an increase in a measurable byproduct fraction in the same way, whereas THMs are specifically tied to the chlorination step and the elevated pH context.

When lime-based chemical precipitation is used to soften water, the treatment raises both pH and alkalinity. After softening, chlorine is typically used for disinfection, and disinfection byproducts form when chlorine reacts with natural organic matter present in the water. Higher pH conditions favor reaction pathways that lead to the formation of disinfection byproducts, particularly trihalomethanes. So, in treated water at the pH levels typical of chemical precipitation softening, the fraction of trihalomethanes can increase as chlorine reacts with organic precursors. The other changes you see with softening—hardness decreasing and alkalinity or pH rising—don’t directly indicate an increase in a measurable byproduct fraction in the same way, whereas THMs are specifically tied to the chlorination step and the elevated pH context.