Comparing the Removal Efficiency of Four Widely Used Antibiotics from the Beta-Lactam Group in Two Municipal Wastewater Treatment Systems in Isfahan, Iran

In recent decades, there has been a growing concern about the presence of antibiotics in water resources. The presence of these micropollutants even in low concentrations has significant effects on the environment and human health, and their entry into the soil and especially receiving waters should be prevented as much as possible. As effluents from wastewater treatment plants (WWTPs) are significant sources of antibiotics in the environment, this study aimed to investigate the efficiency of antibiotics removal in municipal WWTPs.

In this study, Isfahan East WWTP with a combination of stabilization ponds and an aeration lagoon, and Isfahan South WWTP with conventional activated sludge treatment were selected as well as four antibiotics from the beta-lactam group including ampicillin, amoxicillin, cephalexin, and penicillin, and their removal efficiency was investigated in both WWTPs. Samples were collected from the influent and effluent of both WWTPs on 13 occasions and analyzed immediately after being transferred to the laboratory. The concentration of antibiotics was determined by high-performance liquid chromatography (HPLC).

In the Isfahan East WWTP, the average removal efficiency was 86.22 ± 19.84% for ampicillin, 34.35 ± 31.38% for amoxicillin, 78.75 ± 23.81% for cephalexin, and 89.80 ± 19.42% for penicillin. In the Isfahan South WWTP, the average removal efficiencies of amoxicillin, ampicillin, cephalexin, and penicillin were equal to 54.82 ± 33.29%, 66.85 ± 24.88%, 87.65 ± 21.76%, and 82.76 ± 21.85%, respectively.

The study's findings revealed that Isfahan municipal WWTPs were unable to fully eliminate antibiotics. According to statistical analysis, there were significant differences in the concentration of antibiotics in both WWTPs, and no critical correlation was observed between the removal efficiency of antibiotics and other principal wastewater parameters. Consequently, there is a need for stricter control over the discharge of effluent into the river or its use for agricultural irrigation.