Pharmaceuticals' removal by constructed wetlands: a critical evaluation and meta-analysis on performance, risk reduction, and role of physicochemical properties on removal mechanisms.

Huma Ilyas,Eric D Van Hullebusch,Ilyas Masih

doi:10.2166/wh.2020.213

Abstract

This paper presents a comprehensive and critical analysis of the removal of pharmaceuticals (PhCs), the governing physicochemical properties, and removal mechanisms in constructed wetlands (CWs). The average removal efficiency of the most widely studied 34 PhCs ranges from 21% to 93%, with the exception of one PhC that exhibited negative removal. Moreover, CWs are effective in significantly reducing the environmental risk caused by many PhCs. Based on risk assessment, 12 PhCs were classified under high risk category (oxytetracycline > ofloxacin > sulfamethoxazole > erythromycin > sulfadiazine > gemfibrozil > ibuprofen > acetaminophen > salicylic acid > sulfamethazine > naproxen > clarithromycin), which could be considered for regular monitoring, water quality standard formulation and control purposes. Biodegradation (aerobic and anaerobic) is responsible for the removal of the majority of PhCs, often in conjunction with other mechanisms (e.g., adsorption/sorption, plant uptake, and photodegradation). The physicochemical properties of molecules play a pivotal role in the elimination processes, and could serve as important predictors of removal. The correlation and multiple linear regression analysis suggest that organic carbon sorption coefficient (Log Koc), octanol-water distribution coefficient (Log Dow), and molecular weight form a good predictive linear regression model for the removal efficiency of PhCs (R2 = 0.65, P-value <0.05).

Highlights

Pharmaceuticals (PhCs) are among the emerging organic contaminants (EOCs) that are discharged to water resources and the environment through various sources such as domestic wastewater, effluent discharge from wastewater treatment plants (WWTPs), hospital and PhCs’
The main objectives of this study are: (1) to conduct a comprehensive assessment of a large number of PhCs in wastewater and their removal by four types of constructed wetlands (CWs); (2) to critically evaluate and summarize the available evidence on major PhCs’ removal mechanisms in CWs; (3) to examine the impact of physicochemical properties of PhCs on their removal mechanisms; and (4) to assess the environmental risk posed by a large number of PhCs, and contribution of CWs in risk reduction
The large number of published studies provided the foundation of this comprehensive assessment, which is based on critical review of the literature and statistical analysis of data gathered from peer-reviewed studies

Summary

Introduction

Pharmaceuticals (PhCs) are among the emerging organic contaminants (EOCs) that are discharged to water resources and the environment through various sources such as domestic wastewater (excretion), effluent discharge from wastewater treatment plants (WWTPs), hospital and PhCs’. Several studies have indicated negative impacts of PhCs on aquatic and plant life (e.g., Caliman & Gavrilescu ; Carvalho et al )

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