چكيده لاتين
In recent years, water pollution caused by the widespread release of antibiotics through municipal, hospital, and industrial effluents has become a major environmental concern. Due to their relative persistence in aquatic environments and their ability to induce microbial resistance, antibiotics are considered emerging contaminants that pose serious threats to human health and ecosystems. Among them, ampicillin, one of the most commonly used β-lactam antibiotics, is frequently detected in wastewater and may adversely affect biological wastewater treatment processes, particularly aerobic denitrification. Therefore, the present study aimed to evaluate the effect of selective stress induced by ampicillin on the aerobic denitrification process using individual bacterial strains and a microbial consortium isolated from activated sludge.
To achieve this objective, seven bacterial strains were isolated and their abilities to remove nitrogenous compounds (nitrate, nitrite, and ammonium) were assessed in the presence of ampicillin. Moreover, the removal efficiency of ampicillin at different concentrations (10, 30, 50, and 70 mg/L) over 24, 48, 72, and 96 hours was measured using the microbial consortium.
The results showed that nitrate removal efficiency varied among the individual strains, ranging from 44.57% to 90.42%, while the consortium achieved a high efficiency of 88.96%. Similarly, nitrite removal by individual strains ranged from 54% to 99.79%, whereas the consortium reached a near-optimal efficiency of 97.62%. Ammonium removal varied between 69.88% and 90.47% in individual strains, with the consortium showing a moderate performance of 82.68%. Overall, these findings indicate that microbial consortia, due to metabolic complementarity and synergistic interactions among species, exhibited more stable and efficient performance in removing nitrogenous compounds compared with most individual strains.
Regarding ampicillin removal, the results demonstrated that the efficiency of the consortium was limited and strongly dependent on the initial antibiotic concentration. At lower concentrations (10 and 30 mg/L), only about 30–35% of the antibiotic was removed, with little variation over time. In contrast, at higher concentrations (50 and 70 mg/L), removal efficiency decreased sharply to approximately 29.16% and 18.13%, respectively. These findings suggest that while microorganisms can partially remove antibiotics through biodegradation and adsorption processes, high concentrations of ampicillin exert significant inhibitory effects, reducing overall treatment efficiency.
In conclusion, this study highlights the capability of microbial consortia to efficiently remove nitrogenous compounds under antibiotic stress, but also emphasizes the limitations of biological processes in fully eliminating antibiotics such as ampicillin. Therefore, the integration of biological treatment with complementary technologies (e.g., advanced oxidation, adsorption, or membrane processes) is necessary for the effective management of antibiotic-contaminated wastewater. The outcomes of this study provide valuable insights for the design of innovative treatment systems to address emerging contaminants in aquatic environments.
