Constructed wetlands: a barrier against discharge of personal care products in water environment

In recent years, the issue of personal care products (PCPs) in wastewater has become a major concern as these substances can provide adverse effects to both human health and environment. Common wastewater treatments are not designed to deal with these compounds and data of their removal efficiencies are still scarce. Constructed wetlands (CWs) are very commonly used for treating domestic wastewaters all over the world. This study is an overview of the occurrence of a wide spectrum of PCPs in the influent and effluent of different types of CWs, including free water surface systems, as well as horizontal and vertical subsurface flow beds. CWs acting as primary, secondary or tertiary steps as well as CWs in hybrid systems were analysed and the corresponding removal efficiencies discussed. This study is based on about 40 peer reviewed papers referring to investigations carried out in Europe (64 %), America (28 %) and Asia (8 %). Included PCPs belong to the following classes: antioxidants, antiseptics, deodorants, flame retardants, insect repellents, plasticizers, sun screen products, fragrances and surfactants. PCP removal mechanisms (sorption, biodegradation, photodegradation and volatilization) were investigated as well as the influence on the removal efficiencies of the main CW design parameters (i.e. bed depth, filling material, presence of vegetation), operational (hydraulic load and retention time, feeding mode, redox conditions) and environmental conditions (temperature, rainfall). In secondary systems the highest average removal values were found for the hydrocinnamic acid (99 %) and methyl dihydrojasmonate (MDHJ, 95 %), in polishing ones for triclosan and some fragrances (> 70 %). A release was observed for a group of surfactants for which the formation, due to the degradation of others, is faster than their removal. An analysis of the effluent concentrations could provide, together with eco-toxicological data, an estimation of the impact that these compounds could have on the environment. CWs might represent a reliable and feasible treatment which is able to control and reduce the spread of PCPs in the aquatic environment (with limited operational costs) thanks to the different and simultaneous removal mechanisms occurring within these systems and their buffer capacity. These systems could be adequate for the treatment of wastewater in small communities that are not collected to the sewage network