| The primary objective of drinking water treatment is to provide microbially safe, aesthetically pleasing water at an affordable cost. Biological filtration effectively decreases the concentration of biodegradable substrate available for regrowth of microorganisms in distribution systems. Additionally, biofiltration removes a portion of the disinfection byproduct (DBP) precursor material and decreases chlorine demand, thus minimizing post-disinfection and associated chemical risks.; The overall objectives of this research were to provide baseline information on the microbial community structure of biofilters used for drinking water treatment, and to gain insight into the relationship between community structure and natural organic matter (NOM) removal. Additionally, the impact of operating conditions on biofilter performance and biomass profiles were systematically evaluated.; Phospholipid fatty acid (PLFA) profiles and the BIOLOG system for detecting the metabolism of sole carbon sources were found to be useful for characterizing the microbial communities in drinking water biofilters. Using the PLFA technique, it was found that ozonation, contact time, temperature, pH, and backwashing with water containing disinfectants each significantly impacted microbial community structure. The BIOLOG system differentiated communities based on ozonation, contact time, pH, and temperature. However, the results were not as highly reproducible as the PLFA technique. Source water differences were also observed among PLFA and BIOLOG profiles when data from all experiments were combined for statistical analysis.; Multiple linear regression models were used to relate removal of NOM constituents to PLFA profiles over all biofilters examined in this research. The multiple linear regression models gave good fits between groups of PLFAs, which are taxonomic markers for different types of microorganisms, and removal of dissolved organic carbon (DOC), biodegradable DOC, assimilable organic carbon, DBP precursors, and chlorine demand in the biofilters. Better fits were obtained when only the filters treating ozonated waters were analyzed, suggesting a strong association between changes in the NOM characteristics and the microbial communities growing in biofilters following ozonation.; The impact of the operational parameters evaluated in this research on biomass and biofilter performance was consistent with the findings of previous studies. Preozonation, contact time, and the presence of disinfectants in the backwash significantly impacted biofilter biomass and performance. Operating drinking water biofilters at {dollar}rm 5spcirc C{dollar} led to decreased removal of NOM and DBP precursors, and lower biofilter biomass. Varying source water pH did not significantly affect biomass concentrations, or removal of DOC, DBP precursors, or ozonation byproducts. |
