Impact of Emerging Contaminants and Biosolids Aging on Ecotoxicity in Soils

Approximately 50% of the biosolids generated in the U.S. are land applied. Still, little is known regarding the ecological impacts of emerging contaminants found in biosolids, especially antibacterial agents. In addition, current ecotoxicity studies rarely account for aging of the chemical with the biosolids throughout the treatment process, which could affect the bioavailability and ultimate toxicity of these chemicals. Experiments were set up to assess and compare the impacts of laboratory-generated biosolids aged and spiked with a common antibacterial agent, triclosan, on the function and community structure of soil denitrifiers. Biosolids were obtained using a bench-scale wastewater treatment sequencing batch reactors in series with anaerobic digesters receiving triclosan at concentrations commonly found entering wastewater treatment facilities. The resulting biosolids were amended into containers with soil at agronomic rates. Microbial community impacts were monitored over 84 days using restriction fragment length polymorphism (T-RLFP) and quantitative polymerase chain reaction (qPCR). Functional impacts were measured using the Denitrifying Enzyme Activity (DEA) assay. Inhibition was observed at triclosan concentrations greater than ten times lower than concentrations reported by other studies, which indicates a need to better understand triclosan bioavailability dynamics, and the role aging has on these effects.