Insights of the Removal Mechanisms of Pharmaceutical and Personal Care Products in Constructed Wetlands

Abstract

Pharmaceutical and personal care products (PPCPs) are chemicals employed in human healthcare, veterinary, medical diagnosis, and cosmetics, which have increasingly polluted water sources. Extensive research has demonstrated constructed wetlands (CWs) technology as a low-cost but efficient approach for PPCPs removal. There has been a growing interest to better understand the degradation mechanisms of PPCPs in wetland cells. Data corroborated in this review show that these degradation mechanisms include photolytic degradation, adsorption, phytodegradation, and microbial degradation. Each of these degradation mechanisms performs differently in wetland cells. This review also highlights the lack of research works to quantify the contribution of these degradation mechanisms to the overall efficiency of CWs to remove PPCPs as a major bottleneck for further application of this technology. The ultimate goal is to apply and prioritize a suitable degradation mechanism for successfully eliminating corresponding PPCPs. This review, therefore, provides further insights to (i) elucidate the importance of these removal mechanisms, and (ii) quantify their contribution in overall PPCPs removal processes. This review aims to understand the importance and contribution of degradation mechanisms of PPCPs removal in constructed wetlands. The degradation mechanisms of PPCPs in constructed wetlands depended on various conditions; yet, which factors are preferred? Furthermore, the number of research works, related to quantifying the contribution of degradation mechanisms, is limited. The hydrophobic/hydrophilic character, reflecting as log Kow (or log Dow), is the most commonly used. The photolytic degradation is appropriate with low and moderate hydrophobic values (log Dow from − 2.3 to 3). The role of adsorption is moderate, while it is more efficient with the higher hydrophobic compounds. The media is important for plant growth and micro-organism community development. The plant uptake is better for PPCPs with higher hydrophobicity (log Kow from 1 to 4). However, it is difficult to quantify their contribution and the number of related studies is limited.