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Perchlorate (ClOsub4/subsup-/sup) is a known endocrine disruptor that inhibits the normal function of thethyroid gland and is a possible carcinogen. Due to these health concerns and the presence ofperchlorate in drinking water sources, the California Department of Health Services set theaction level for perchlorate in drinking water at 4 ug/l. Biological treatment using fixed bedbiofilm reactors, such as Biological Activated Carbon (BAC) filters, has proven to be aneffective and economical method for the removal of perchlorate. By adding an electrondonor, such as acetate, an existing granular activated carbon (GAC) bed can be retrofittedto remove perchlorate to below 4 ug/l. Depending on raw water characteristics, it may evenbe possible to achieve perchlorate removal to below this level using the natural organicmatter (NOM) present in the raw water as the electron donor (Lin et al., 2002). BAC filterscontain biofilms that are growing attached to the surfaces of GAC. These biofilms consistof mixed communities, which contain mainly perchlorate reducing bacteria (PRB) andother heterotrophic bacteria. PRB are ubiquitous (Coates et al., 1999) and removeperchlorate using perchlorate reductase and chlorite dismutase enzymes as described byRikken et al (1996). When oxygen is present, most PRB use oxygen as their electronacceptor. They switch to using perchlorate as their electron acceptor when oxygen levelsare very low. Therefore, control of the dissolved oxygen (DO) concentration is important forthe successful reduction of perchlorate.Although the microbial aspects of biological perchlorate reduction have been relativelywell studied (Chaudhuri et al., 2002), no general design and operational criteria have beenestablished for BAC filters. The main objective of this paper is to provide a framework thatcan be used to predict the patterns of BAC reactor behavior under varying influent DOconcentrations and loading rates. This information can then be used to develop betterdesign and operational guidelines for BAC filters. Includes 9 references, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 7File Size: 1 file , 270 KB