Seasonal changes in removal of natural organic matter (NOM) by drinking water biofilters are often attributed to temperature differences. Bench-scale sand biofilters treating NOM isolated from a surface water source were operated in parallel at5,20, and 35℃ to isolate the effect of temperature from other water quality and operational parameters, which also vary seasonally. The biofilter operated at 5℃ achieved significantly lower removal of NOM and the NOM fraction that reacts withdisinfectants (disinfection byproduct precursors) compared to the filters operated at 20 and 35℃, which had similar performance levels. Viable biomass, measured as lipid phosphate, was significantly higher at the top and bottom of the filter operated at20℃. Phospholipid fatty acid (PLFA) profiles indicated an increasing gradient in markers for Gram-negative bacteria and microeukaryotes as biofilter operation temperature decreased, replacing general fatty acids and markers for Gram-positive bacteria and sulfate-reducing bacteria, which were observed in greatest abundance in the filter operated at 35℃. Principal components analysis differentiated the microbial PLFA profiles based on biofilter operation temperature and filter depth. These results werecorroborated by identifications of the dominant microbial colonies isolated on R2A agar.
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