Metabolic hazards of pharmaceuticals and personal care products (PPCPs) in sewers

The discharge of personal care products (PPCPs) to sewer systems increased due to the rapid expansion of cities, while PPCPs transformation in sewer and the potential threat to receiving water environments have been rarely revealed. In this study, six PPCPs (antibiotics, generic drugs and personal care products) were added continuously over a 90-day experimental period to investigate the effect of transformation in a pilot sewer. The results showed that the biological metabolism of carbon, nitrogen and phosphorus pollutants were restricted under the PPCPs stress condition. The genomic detection also confirmed that the diversity of microflora in sewer sediment were obviously decreased with the PPCPs transformation, and the total relative abundance of dominant phylum species (Firmicutes, Bacteroidetes and Proteobacteria) increased from 67.7% to 94.9%. In addition, principal coordinate analysis and metagenome showed that the two kinds of antibiotics were the most important inducement for the metabolic dysfunction in sewer systems, and led to the increase of functional gene of "Human Disease" (accounted for 0.97%) which could form more harmful metabolites to cause serious exposure hazards. Thus, this investigation provided the insights into the metabolic hazards of PPCPs bioconversions in sewers, which hoped to bring to the forefront of PPCPs emission to sewers by society.