Removal efficiency of commonly prescribed antibiotics via tertiary wastewater treatment

Wastewater treatment plants (WWTPs) have been identified as "hot spots" of antibiotics release to the environment. Treatment operations at WWTPs may remove a significant proportion of antibiotics from influent wastewater; however, the effects of tertiary treatment processes on antibiotics removal are not well understood. The objective of this review is to summarize the current literature regarding antibiotics removal from common tertiary processes at full-scale municipal WWTPs and to reveal the research gaps and inform future research directions. Chlorination, ultraviolet (UV) irradiation, and sand filtration were reviewed due to their popularity of application in the USA. The majority of studies of antibiotics removal via tertiary wastewater treatment have been conducted in EU nations, the USA, Australia, and China. Chlorination significantly reduces antibiotics concentrations in wastewater effluents. In comparison, sand filtration and UV irradiation are less effective. However, a large discrepancy of removal efficiencies is apparent across different studies of these treatment processes. Increases in antibiotics concentration following tertiary treatment have also been observed. Possible reasons for the discrepancies, such as sorption to filtered particles, sampling strategies, specific operating parameters of wastewater treatment plants, and deconjugation, are discussed. It is concluded that the effects of tertiary treatment on antibiotic removal efficiency are still arguable, and caution must be taken when sampling wastewater in full-scale WWTPs for comparison of removal efficiencies of antibiotics.