Trihalomethane precursor reactivity changes in drinking water treatment unit processes during a storm event

Area of Science:

• Environmental Science
• Water Chemistry
• Public Health

Background:

• Source water quality variations significantly affect water treatment efficacy.
• Existing models may not fully capture the impact of organic matter variability on treatment processes.
• Chlorinated and brominated trihalomethanes (THMs) are disinfection byproducts of concern.

Purpose of the Study:

• To investigate how source water quality variations impact water treatment unit processes.
• To understand the formation of THMs in response to treatment.
• To inform the development of improved water treatment models and operations.

Main Methods:

• Conducted a 72-hour field study during a storm event.
• Collected water samples along the treatment train.
• Analyzed water quality parameters including non-purgeable organic carbon (NPOC), UV absorbance, and THM concentrations.
• Performed chlorine spiking experiments.

Main Results:

• The remaining NPOC after treatment exhibited increased reactivity for THM formation.
• Brominated THMs formed more readily than chlorinated THMs in competitive reactions.
• THM formation potential changes significantly in response to treatment unit processes.

Conclusions:

• Both the quantity and reactivity of THM precursors are critical for maintaining drinking water standards.
• Model-assisted treatment operation and optimization should incorporate precursor reactivity.
• Advanced granular activated carbon (GAC) treatment may be necessary to manage precursor surges during storm events.