The underground storage of treated drinking water results in the elimi
nation of trihalomethanes (THMs) and haloacetic acids (HAAs) produced
during treatment and in a decrease in the concentration of residual di
sinfection by-product (DBP) precursors. Removal of THMs is associated
with denitrifying conditions, whereas HAAs are removed under aerobic c
onditions. The findings are consistent with a biological mechanism for
DBP and DBP precursor removal.