Pharmaceuticals in Wastewater Treatment Plants: A Systematic Review on the Substances of Greatest Concern Responsible for the Development of Antimicrobial Resistance

Gabriele Frascaroli,Colin Hunter,Ania Escudero,Deborah Reid,Joanne Roberts,Karin Helwig,Janice Spencer

doi:10.3390/app11156670

Abstract

In recent years, there is a growing concern about the alarming spread of antimicrobial resistance (AMR) in different environments. Increasingly, many species of bacteria, fungi and viruses are becoming immune to the most commonly used pharmaceuticals. One of the causes of the development of the resistance is the persistence of these drugs, excreted by humans, in municipal and hospital wastewater (WW). Consequently, wastewater treatment plants (WWTPs) are a primary source of antimicrobial resistance genes as novel pollutants. This systematic review sought to examine the relevant literature on pharmaceutical residues (PRs) responsible for AMR in municipal and hospital WW in order to propose a classification of the PRs of greatest concern and provide an updated source for AMR management in WWTPs. Among 546 studies collected from four databases, 18 were included in the present review. The internal and external validity of each study was assessed, and the risk of bias was evaluated on a 20-parameter basis. Results were combined in a narrative synthesis discussing influent and effluent PR concentrations at 88 WWTPs, seasonal variations, differences between hospital and municipal WW, environmental risk assessment values of antimicrobial substances and treatment facilities removal efficiencies. Among the 45 PRs responsible for AMR evaluated in this study, the antibiotics ciprofloxacin, clarithromycin, erythromycin, metronidazole, ofloxacin, sulfamethoxazole and trimethoprim constitute a considerable risk in terms of ubiquitous distribution, worrying concentrations, risk quotient values and resistance to removal treatments. Gaps in knowledge, data and information reported in this review will provide a valuable source for managing AMR in WWTPs.

Highlights

The release of pharmaceutical residues (PRs) in the environment is arousing growing concern due to the significant risks posed towards humans, animals and microbial communities
More than 65% of the literature returned was published after 2015. This is likely to indicate that the problem related to the presence of PRs responsible for antimicrobial resistance (AMR) discharged in wastewater treatment plants (WWTPs) has come only recently to researchers’ attention
Out of the 45 antimicrobial substances detected amongst the target studies, ciprofloxacin, clarithromycin, erythromycin, metronidazole, ofloxacin, sulfamethoxazole and trimethoprim constitute a considerable risk in terms of ubiquitous distribution

Summary

Introduction

The release of pharmaceutical residues (PRs) in the environment is arousing growing concern due to the significant risks posed towards humans, animals and microbial communities. Pharmaceuticals can be only partly metabolised during therapeutic use, resulting in the excretion and release of residual fractions into the sewer [1]. Unchanged or in the form of metabolites or conjugates, PRs reach local municipal wastewater treatment plants (WWTPs) [2]. Many studies have shown that most drugs are significantly recalcitrant, and conventional treatment solutions for wastewater (WW) that involve the use of anaerobic/anoxic/oxic systems [4], oxidation ditches [5] or filters [6] are not designed to eliminate these compounds [7]. A consistent flow of pharmaceuticals and their metabolites reach the aquatic environment, disturbing the ecological balance of rivers, lakes and other habitats and polluting groundwater, surface water and drinking water [1,2,3,8,9]

Methods

Results

Discussion

Conclusion