Abstract
Using a gas instantaneous water heater for heating below the boiling point, halogenated disinfection by-products as a whole and according to classes increased in some tap water samples but decreased in others with an increase in the temperature of the tap water. the tendency depends on the quality and quantity of halogenated by-products precursors in the tap water. Using a large-sized boiler or electric water warmer, total halogenated by-products and trihalomethanes and haloacetic acids increased, and volatile halogenated by-products as intermediate by-products decreased irrespective of its quality or quantity of by-products precursors.
Compared with heating below the boiling point using an instantaneous water heater, a large-sized boiler, or an electric water warmer, the heating temperature is higher, and the heating time is longer using an electric pot or a kettle. All volatile halogenated by-products except trihalomethanes disappeared after heat retention for 0-5 minutes following boiling at 100°C using an electric pot and after continuous boiling at 100°C for 0-5 minutes using a kettle. Trihalomethane disappeared after heat retention for 3-6 hours following boiling at 100°C using an electric pot and after continuous boiling at 100°C for 5-10 minutes using a kettle. After disappearance of trihalomethanes, only haloacetic acids remained among halogenated by-products. The remaining haloacetic acids was mainly dihaloacetic acid.
