Short-term performance of enhanced biological phosphorus removal (EBPR) system exposed to erythromycin (ERY) and oxytetracycline (OTC)

- P-removal efficiency decreased to 34.6% under the effect of ERY (10 mg/L).
- P-removal efficiency decreased to 0.0% under the effect of OTC (10 mg/L).
- Aerobic stage in EBPR system was more seriously inhibited than anaerobic stage.
- OTC showed more serious inhibitory effect on microorganism's oxygen utilization.
- Neither synergistic effect nor antagonistic effect was detected between ERY and OTC.

The effects of Erythromycin (ERY) and oxytetracycline (OTC), including individual and combinative effect, on enhanced biological phosphorus removal (EBPR) system within a short-term (24 h) were evaluated in this study. Results showed that the P-removal efficiency decreased to 34.6% and 0.0% under the effect of ERY (10 mg/L) and OTC (10 mg/L) for 24 h. OTC concentration higher than 5 mg/L was sufficient to cause serious adverse impact on the EBPR performance. While the performance of EBPR system will be impacted by ERY above 10 mg/L. OTC, due to its special antibacterial action to the gram-negative bacteria which most PAOs belong to, has more serious negative effect on the EBPR performance than ERY does. Moreover, in the combined antibiotics test, neither synergistic nor antagonistic effect was detected between ERY and OTC. Finally, ERY (10 mg/L) and OTC (10 mg/L) could inhibit the microorganisms' activity, while couldn't induce serious microorganisms death within 24 h.