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

Hajar Aghili Dehnavi,Mohammad Mahdi Amin,Bijan Bina,Ali Fatehizadeh,Karim Ebrahimpour,Hossein Movahedian Attar

doi:10.34172/ehem.2021.24

Hajar Aghili Dehnavi, Mohammad Mahdi Amin + Show 4 more

Open Access

https://doi.org/10.34172/ehem.2021.24

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Abstract

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 8192:2007 procedure. In this method, the AS consortium (10-day age) was extracted from lab-scale 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 specific Nitrification inhibitor. Results: The obtained data showed that the height of oxygen uptake rate (OUR) profiles and amount of oxygen consumption reduced with increasing ERY dose. The half-maximal effective concentration (EC50) of ERY for heterotrophic and nitrifier microorganisms were 269.4 and 1243.1 mg/L, respectively. In Run 1, the kinetic coefficients bH, fA,H, YH, and µH were calculated as 2.61 d-1, 0.44, 0.4945 mg VSS/mg COD, and 0.047 d-1, respectively. Also, for maximum ERY concentration (1000 mg/L), the kinetic coefficients bH., fA,H, YH, and µH were calculated as 2.27 d-1, 0.3, 0.4983 mg VSS/mg COD, and 0.0049 d-1, respectively. Conclusion: The findings showed that the inhibitory impact of ERY was observed as a decrease in the amount of oxygen consumption by OUR profiles in rapid respirometric method (ISO 8192), 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.

Highlights

Antibiotics are one of the most important groups of pharmaceutical active compounds that have been widely used in medicine and veterinary medicine [1,2]
dissolved oxygen (DO) changes were analyzed in biodegradation of peptone-meat extract, the acute impact of ERY was evaluated by the calculation of oxygen uptake rate (OUR) reflected from the microbial system that was exposed to different ERY concentrations (0-1000 mg/L) for the first time as a nonbiodegradable substrate
According to experiment for both series, associated with biodegradation of peptone mixture in all runs (Table 1), the OUR level initially reached a peak value, followed by dropping to a stable endogenous respiration level with distinctly different rates corresponding to degradation of different chemical oxygen demand (COD) fractions in the substrate

Summary

Introduction

Antibiotics are one of the most important groups of pharmaceutical active compounds that have been widely used in medicine and veterinary medicine [1,2]. It should be noted that in most cases, wastewater treatment plants (WWTPs) are inadequate to remove the antibiotics discharged in them, which eventually enter the aquifer with effluent [5]. They may have the inhibitory or toxicity potential to the biomass in biological treatment systems, affecting their performance, and increasing bacterial resistance crisis [6,7]. For maximum ERY concentration (1000 mg/L), the kinetic coefficients bH., fA,H, YH, and μH were calculated as 2.27 d-1, 0.3, 0.4983 mg VSS/mg COD, and 0.0049 d-1, respectively. Assessment of toxicity and kinetic effects of erythromycin on activated sludge consortium by fast respirometry method.

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