Longitudinal Removal of Bisphenol-A and Nonylphenols from Pretreated Domestic Wastewater by Tropical Horizontal Sub-Surface-Constructed Wetlands  
[PERSON]  
1 Grupo de Saneamiento Ambiental, Instituto Cinara, Universidad del Valle, Cali 100-00, Colombia; [EMAIL_ADDRESS]
2 Doctorado en Ciencias Ambientales, Universidad del Cauca, Popayan 190001, Colombia  
Escuela EIDENAR-Facultad de Ingenieria, Universidad del Valle, Cali 100-00, Colombia; [EMAIL_ADDRESS]  
3 UNESCO-IHE Institute for Water Education, 2611 AX Delft, The Netherlands; [EMAIL_ADDRESS] (H.G.-H.); [EMAIL_ADDRESS] (P.L.)  
Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968, USA; [EMAIL_ADDRESS]  
4  
[PERSON]  
3 Cavallo-Parra  
low concentrations (e.g., micrograms per liter, \(\mathrm{\mu g\cdot L^{-1}}\), or even nanograms per liter, \(\mathrm{ng\cdot L^{-1}}\)) have been identified to be present in the effluents of wastewater treatment plants (WWTPs) [2; 3]. Furthermore, due to their chemical and recalcitrant characteristics, some of these PPCP compounds pass through conventional wastewater treatment processes without undergoing any transformation, resulting in their direct discharge to the receiving waters [4; 5].  
Compounds such as Bisphenol A (BPA) are widely used in industrial processes as a primary raw material in the manufacturing of many products such as plastics for engineering applications (e.g., epoxy resins and polycarbonate plastics), electronic devices, food cans, bottles, and dental sealants [6]. There is evidence that relates BPA appearance directly to adverse reproductive and carcinogenic effects in mice with a dose of 25 \(\mathrm{ng\cdot kg^{-1}}\) per day and 1 \(\mathrm{\mu g\cdot kg^{-1}}\) per day, respectively [7]. Nonylphenols (NPs) are used in the manufacturing of anionic detergents, lubricants, agrochemicals, tanneries, and lubricant oil additives. The main source of NP in municipal wastewater is due to the intermediate degradation products of soaps and detergents. NPs are found to be endocrine disruptive compounds (EDCs), and have effects in the reproductive system of some mammals, including the reduction in testis and ovaries weight, and the appearance of an irregular estrous cycle [8].  
Different treatment systems for the reduction of EDCs from wastewater are being evaluated, such as membrane bioreactors, activated sludge systems, ozonation, photocatalysis, and sequencing batch reactors. Most of these processes require a high economic investment with high environmental costs related to their operation and maintenance which makes their implementation difficult in developing countries. Some studies focus on sustainable wastewater treatment by decreasing electricity consumption and mitigating its greenhouse gas footprint [9]. In this sense, constructed wetlands (CWs) are natural wastewater treatment systems that offer cost-effective treatment for small to medium-sized systems [10]. Recently, the removal of pharmaceuticals in horizontal and vertical subsurface flow constructed wetlandswas evaluated [9] with removal efficiencies for ibuprofen of 51-54% in winter and 85-96% in summer and for carbamazepine of 24-36% in winter and 48% in summer.  
The behavior of EDC removal in CW wastewater treatment systems is not fully understood. Data display a high variation in removal efficiency, ranging from 20% to 99%, depending on the chemical compound characteristics, plant type, flow conditions (regime), and geographic location [11]. Particularly under tropical climate conditions, some research has observedthat CW are capable of removing phenolic compounds in a range from 60% to 77% [12]. However, more research is required to understand the potential of CWs in the removal of EDCs, specifically regarding the effect of variables such as plant type and hydraulic retention time. Pilot-scale research is essential to enable extrapolation to full-scale CW design for effective removal of EDCs.