Removal of antimicrobials using advanced wastewater treatment

Insights into the Fate and Removal of Antibiotics in Engineered Biological Treatment Systems: A Critical Review

Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical-chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48-77%) in the removal of antibiotics. In this review, we systematically summarize the behavior and removal of different antibiotics in various biological treatment systems with discussion on their removal efficiency, removal mechanisms, critical bioreactor operating conditions affecting antibiotics removal, and recent innovative advancements. Besides, relevant background information including antibiotics classification, physical-chemical properties, and their occurrence in the environment from different sources is also briefly covered. This review aims to advance our understanding of the fate of various classes of antibiotics in engineered biological wastewater treatment systems and outlines future research directions.

Occurrence and Behavior of Macrolide Antibiotics in Municipal Wastewater Treatment: Possible Importance of Metabolites, Synthesis Byproducts, and Transformation Products

A one-year study on the occurrence and fate of macrolide antibiotics and their metabolites, synthesis byproducts, and transformation products (TPs) was performed in the wastewater treatment plant of the city of Zagreb (Croatia). The target compounds were found in all analyzed influent and effluent samples with the total concentrations of azithromycin-, clarithromycin-, and erythromycin-related compounds reaching up to 25, 12, and 0.25 μg/L, respectively. The most prominent individual constituents were the parent macrolides azithromycin and clarithromycin. However, a substantial contribution of their derivatives, formed by deglycolysation and microbial phosphorylation, was also detected. In addition, widespread presence of several linearized nontarget TPs was confirmed for the first time in real wastewater samples by suspect screening analysis. Complex characterization of macrolide-derived compounds enabled decoupling of industrial and therapeutic sources from the in situ transformations. Due to the high inputs and incomplete removal and/or formation of several TPs during the conventional wastewater treatment, the average mass load of azithromycin-related compounds in secondary effluents exceeded 3.0 g/day/1000 inhabitants. This is the first study to reveal the importance of metabolites, byproducts, and TPs for the overall mass balance of macrolide antibiotics in urban wastewater systems.

Chitosan-based sorbent for efficient removal and extraction of ciprofloxacin and norfloxacin from aqueous solutions

Nanosheets prepared from magnesium oxide, chitosan and graphene oxide (MgO/Chit/GO) were hydrothermally synthesized and used as a sorbent for removal of ciprofloxacin and norfloxacin from aqueous solutions. Residual antibiotics in sample were determined by HPLC/UV instrument. The sorbent was characterized by FTIR, XRD, BET, SEM, and TEM. Its high adsorption capacity is attributed to the high surface area (294 m².g^-1) as compared to bare MgO/chit or bare GO. The pore size of the mesoporous sorbent typically is 15 Å. The adsorption isotherms for the two model antibiotics studied (norfloxacin, ciprofloxacin) can be described with the Langmuir model, and the maximum adsorption capacities are 1111 and 1000 mg.g^-1 for ciprofloxacin and norfloxacin, respectively. The analysis of the kinetic data revealed that the synthesized sorbent followed pseudo-second-order kinetics and the maximum equilibrium was at over 120 and 150 min for ciprofloxacin and norfloxacin, respectively. Therefore, it is introduced as an economical, eco- friendly, and high-performance sorbent for removal of antibiotics from aqueous solutions. Graphical abstract Schematic presentation of dispersion of magnesium oxide/chitosan/graphene oxide (MgO/chit/GO) nanosheets in waste water for removal of ciprofloxacin and norfloxacin as water pollutants.