Effects of EBCT and water temperature on HAA removal using BAC

The effects of empty bed contact time (EBCT) and water temperature on the removal of haloacetic acids (HAAs) in biologically active carbon (BAC) filters were investigated. Experiments were conducted at four temperatures (4, 10, 20, and 30 degrees C) and four EBCTs (5, 10, 15, and 20 min). The results indicated that increasing EBCT or increasing water temperature increased the HAA removal in BAC columns. To achieve an HAA removal efficiency of 50% or higher in a BAC filter, the authors suggest a 10-min EBCT for 4 degrees C waters and a 5-min EBCT for waters at 10 degrees C or higher. The kinetic analysis suggested a first-order reaction model for HAA (except trichloroacetic acid) removal at 10 degrees C and a zero-order first-order reaction model for HAA removal at 4 degrees C. The pseudo-first-order reaction rate constants and half-lives were also calculated for HAA removal at 10 degrees C. The half-lives - ranging from 5.9 to 17.3 min - could be used to assist water utilities in designing and operating BAC filters for HAA removal.