Inhibitory effects of sulfamethoxazole on denitrifying granule properties: Short- and long-term tests

- The effects of sulfamethoxazole on denitrifying granules were evaluated for the first time.
- The mathematical models used to quantify the performance fit the trial data well.
- Sulfamethoxazole changed the granule properties after long-term operation.
- The 100 mg L−1 sulfamethoxazole concentration had no adverse effects on the nitrogen removal performance.

The broad-spectrum antibiotic sulfamethoxazole (SMX) was chosen to assess its short- and long-term effects on denitrifying granules. The SMX concentration and pre-exposure time in batch testing influenced the denitrifying granule activity. In the continuous-flow experiments, no inhibitory effects on the upflow anaerobic sludge blanket performance were observed at SMX concentrations up to 100 mg L−1, probably because of functional redundancy and long-term acclimation. The specific denitrifying activity first decreased to a minimum of 49.3% and then recovered to a level comparable to the initial level as the SMX concentration increased. The changing trend of the extracellular polymer content was consistent with the specific denitrifying activity throughout the process, and relatively high EPS loss ratios (maximum loss of 61.8%) were observed. Additionally, the diameter of the denitrifying granules monophonically increased to a final value of 35.0%. This research provided the application of denitrifying granules to treat wastewater that contained antibiotic.