Impact of temperature on drinking water biofilter performance and microbial community structure

Seasonal changes in removal of natural organic matter (NOM) by drinking wat er biofilters are often attributed to temperature differences. Bench-scale sand biofilters treating NOM isolated from a surface water source were oper ated in parallel at 5, 20, and 35 degrees C to isolate the effect of temper ature from other water quality and operational parameters, which also vary seasonally. The biofilter operated at 5 degrees C achieved significantly lo wer removal of NOM and the NOM fraction that reacts with disinfectants (dis infection byproduct precursors) compared to the filters operated at 20 and 35 degrees C, which had similar performance levels. Viable biomass, measure d as lipid phosphate, was significantly higher at the top and bottom of the ! filter operated at 20 degrees C. Phospholipid fatty acid (PLFA) profiles indicated an increasing gradient in markers for Gram-negative bacteria and microeukaryotes as biofilter operation temperature decreased, replacing gen eral fatty acids and markers for Gram-positive bacteria and sulfate-reducin g bacteria, which were observed in greatest abundance in the filter operate d at 35 degrees C. Principal components analysis differentiated the microbi al PLFA profiles based an biofilter operation temperature and filter depth. These results were corroborated by identifications of the dominant microbi al colonies isolated on R2A agar.