## 1 Introduction  
Declining water quality is considered a global concern due to the rapid growth of the population and the expansion of industrial and agricultural activities [1]. Therefore, the scarcity of clean, safe and adequate fresh water is predicted to become worse and worse globally in the coming decades, not only in the arid regions, but also in regions presently considered water-rich [2]. Unfortunately, the surface water in lakes, rivers, streams, and reservoirs that are used as the main source of potable water is currently polluted by a combination of both anthropogenic and natural activities. This serious problem threatens the health and well-being of humans, plants, and animals, and is a cause of climate change. Natural organic matter (NOM) is one of the major compounds contained in surface or groundwater. NOM is considered a challenge in drinking water treatment since its presence in water results in several negative impacts on the performance of standard water treatment processes such as granular activated carbon filtration and membrane filtration [3]. Humic acid (HA), one of the major fractions of NOM in natural water, not only causes taste and odour issues and imparts a yellowish to brown color in natural water, but also poses serious problems for treatment systems. Through various transformation processes, HA can form different kinds of disinfection by-products (DBPs) which are very toxic and harmful for human health [4]. Typically, trihalomethanes (THMs), which are the result of a reaction between the chlorine used for disinfecting tap water and natural organic matter in the water, are associated with negative health effects such as cancer and adverse reproductive outcomes. Therefore, the removal of NOM from raw water before the disinfection process is necessary and considered a great health and environmental issue [5]. Pharmaceuticals and personal care products are currently recognized as a new class of emerging pollutants and have been the subject of increasing attention and scientific consideration [6; 7]. The occurrence of a huge number of pharmaceuticals in the aquatic environment has been gaining prominence because of their negative effects on human health. Although low concentrations can be currently detected in water bodies (just up to several \(\upmu\)g/L), the continuous discharge of pharmaceutical compounds into the environment from different sources makes them \"pseudo-persistent\" [8]. Among a large variety of pharmaceutical compounds, antibiotics are of special concern due to their widespread use in human and veterinary medicine [9]. Especially, tetracycline (TC) is one of the most commonly used antibiotics in agricultural applications such as husbandry, cattle, swine, poultry, and fishery production, with an extensive presence in surface waters. Unfortunately, the active components in most pharmaceuticals are transformed only partially in the human body and animal body and then a mixture of metabolites and bioactive forms are excreted into the sewage systems [10]. Constructed wetlands (CWs) have been proven to be a cost-effective ecological technology for the treatment of numerous kinds of contaminated waters, including for the treatment of domestic wastewater, industrial wastewater, agricultural wastewater, landfill leachate and stormwater runoff [11; 12]. A few years ago, these systems were also under study for their ability to remove emerging microcontaminants like pharmaceuticals [13]. Not only this, but the removal of NOM in water by using CWs was investigated by some researchers recently [14]. Such low-tech treatment systems are often more economical than energy-intensive engineered treatment plants, easier to operate and they provide numerous secondary benefits. The use of CWs has been successfully tested in pilot-scale and field-scale applications, contributing data on overall contaminant removal efficiency on the basis of either concentrations or loads [15; 16].