Assessment of toxicity and kinetic effects of erythromycin on activated sludge consortium by fast respirometry method

Background: The present study aimed to assess the acute impact of erythromycin (ERY) as an inhibitor on peptone mixture utilization of activated sludge (AS) consortium. Methods: For this purpose, the inhibition of oxygen consumption was used based on the ISO ۸۱۹۲:۲۰۰۷ procedure. In this method, the AS consortium (۱۰-day age) was extracted from labscale membrane bioreactor, then, percentage inhibition for total, heterotrophic, and nitrifying microorganisms, in separate batch respirometric tests were calculated in the absence and presence of N-allylthiourea (ATU) as a specifc Nitrifcation inhibitor. Results: The obtained data showed that the height of oxygen uptake rate (OUR) profles and amount of oxygen consumption reduced with increasing ERY dose. The half-maximal effective concentration (EC ۵۰) of ERY for heterotrophic and nitrifer microorganisms were ۲۶۹.۴ and ۱۲۴۳.۱ mg/L, respectively. In Run ۱, the kinetic coeffcients bH, fA,H, YH, and µH were calculated as ۲.۶۱ d-۱, ۰.۴۴, ۰.۴۹۴۵ mg VSS/mg COD, and ۰.۰۴۷ d-۱, respectively. Also, for maximum ERY concentration (۱۰۰۰ mg/L), the kinetic coeffcients bH., fA,H, YH, and µH were calculated as ۲.۲۷ d-۱, ۰.۳, ۰.۴۹۸۳ mg VSS/mg COD, and ۰.۰۰۴۹ d-۱, respectively. Conclusion: The fndings showed that the inhibitory impact of ERY was observed as a decrease in the amount of oxygen consumption by OUR profles in rapid respirometric method (ISO ۸۱۹۲), which offered a novel insight for the acute inhibitory impact of this antibiotic. Also, chemical oxygen demand (COD) as an overall substrate parameter is most helpful in interpreting the behavior and the metabolic functions of AS systems.

کلیدواژه ها:

Toxicity ، Erythromycin ، Activated sludge ، Respirometry ، Kinetic coeffcients