Antibiotics in aquatic environments: A review of occurrence, fate, ecotoxicity and advanced removal technologies

Abstract

Antibiotics are among the most widely distributed contaminants of emerging concern in aquatic systems, entering water from hospital effluent, pharmaceutical manufacturing, livestock production, aquaculture and municipal sewage. Beyond direct ecotoxicity, residues at nanogram-per-litre concentrations exert sub-inhibitory selective pressure that enriches antibiotic resistance genes (ARGs). This review synthesises 120 publications on the occurrence, fate, ecotoxicity and removal of fluoroquinolones, tetracyclines, sulfonamides and β-lactams, comparing adsorption, oxidative degradation and biological treatment against a single criterion: whether each technology removes the resistance determinant as well as the parent compound. Measured concentrations span six orders of magnitude and are geographically uneven, with the highest values reported for parts of Asia and sub-Saharan Africa. Adsorbents reach capacities above 500 mg g −1 but transfer the contaminant to a solid phase; photocatalysts and persulfate systems remove 90–100% of target compounds, yet only 2 of 10 photocatalytic studies assessed intermediate toxicity. None of the 24 adsorption studies measured ARGs, whereas every constructed-wetland study did, with hybrid aerated wetlands removing 87.4–95.3% of antibiotics and 87.8–99.1% of ARGs. Evidence from chlorination, photocatalysis and activated sludge indicates that treatments which lyse cells can release extracellular ARGs, so parent-compound removal does not by itself measure the resistance hazard.