Formation of disinfection by-products during ballast water treatment with ozone, chlorine, and peracetic acid: influence of water quality parameters

As ocean-going ships begin implementing chemical disinfection to treat ballast water, the potential formation of disinfection by-products (DBPs) is an important issue of concern. This is especially critical since ballast waters are often saline, and the information regarding DBP formation under these conditions is limited. This study exposed representative ballast waters (synthetically-made and natural freshwaters, brackish waters, and seawaters) to ozone, free chlorine, and peracetic acid (PAA) treatment where various water quality parameters and treatment conditions were varied to assess DBP formation. DBPs including bromate, trihalomethanes (THMs), and haloacetic acids (HAAs) were affected by changes in salinity (especially bromide concentration), dissolved organic matter (DOM) concentration/type, and oxidant type/dose. Temperature effects (22 +/- 2 degrees C or 4 +/- 2 degrees C) were limited for THMs and HAAs formation but were greater for bromate formation (only ozone) in waters containing high bromide levels. Interestingly, bromate formation during ozonation was rapid (complete formation in