Impact of Biosolids on Indigenous Soil Denitrifying Bacteria

A major drawback to land application of biosolids is the potential environmental release of nonregulated organic contaminants that accumulate in the biosolids during the wastewater treatment process. In particular, because some of the substances found in biosolids are designed to kill microorganisms (i.e., are disinfectants), there is a risk that these compounds could disrupt microbial ecology and negatively impact nutrient cycling, impacting soil and plant health in the long term. This study takes samples from four agricultural fields receiving liquid biosolids over a 150-day period, measures initial triclosan concentrations, and characterizes impacts by assessing changes in the denitrifying microbial community structure and function. Overall, a decrease in denitrification activity and denitrifier abundance is observed after 100 days following application. Although these data suggest that biosolids may affect denitrification, the effects cannot be attributed to biosolids application nor to the triclosan contained within the biosolids.