|Chee Sanford, Joanne|
Submitted to: Journal of American Water Works Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2001
Publication Date: N/A
Citation: Interpretive Summary: Bromate can be formed as a disinfection by-product when bromide-containing water is treated with ozone, which is a process to remove residual organic compounds in water treatment systems. Ingestion of drinking water containing bromate can cause tumors. Biologically active carbon (BAC) filters are becoming more attractive in the U.S. for treatment of very low residual concentrations of toxic disinfectants and by-products, and depends on the activities of microorganisms associated with the filters. In this study, a BAC filter was shown to significantly remove bromate from water. This microbial activity was dependent on how much bromate was present and the community of microorganisms associated with the BAC filters was stable. The history of the BAC filter was important; for example, if transient disturbances such as high concentrations of oxygen, pH shifts, and fluctuating nutrient concentrations were present, there were adverse effects on bromate removal. The significance of this study was to demonstrate the feasibility of using BAC filters in a water treatment system to remove toxic bromate, but maintaining the critical factors affecting the microbial activities is crucial for the process to succeed.
Technical Abstract: This study examined the use of biologically active carbon (BAC) filters for microbial reduction of bromate to bromide. In these filters, abiotic reduction by the activated carbon did not play a significant role in bromate removal. Bromate removal in a BAC filter decreased by 30 percent after a system perturbation, suggesting that filter history affects bromate removal. While 2.5- and 5.1-cm (1- and 2-in.) inner-diameter BAC filters provided comparable bromate removals for the tested contact times, the larger filter exhibited nitrite production; system performance must be monitored to prevent such undesirable compounds from entering the water. The mass of bromate removed increased as the influent bromate concentration increased, while bromate removal did not change after backwashing. Experimental evidence indicated that increased regrowth would not be observed in the distribution system following BAC filtration with a low influent dissolved oxygen concentration (2 mg/L) in the tested water.