# Special Issue on Wastewater Treatment and Reuse Technologies
## 4 Removal of Trace Organic Contaminants  
In recent years, the occurrence of trace organic contaminants (TrOCs) such as pharmaceuticals, personal care products, pesticides, industrial chemicals and steroid hormones in raw and inadequately treated wastewater have raised significant concern [9, 10]. These TrOCs can adversely affect aquatic ecosystems and human health [11, 12, 13]. Conventional wastewater treatment plants cannot effectively remove TrOCs. In an article entitled \"_Degradation of Trace Organic Contaminants by a Membrane Distillation_--_Enzymatic bioreactor_\", [PERSON] et al. [14] developed an enzymatic membrane bioreactor for effective degradation of TrOCs. This study reported, for the first time, the additional benefits of coupling a 'high-retention' membrane compared to the micro and ultrafiltration membranes usually integrated with bioreactors. High retention membranes are expected to retain TrOCs effectively and thus remove them from the aqueous phase. However, [PERSON] et al. [14], demonstrated that coupling a high retention membrane (e.g., membrane distillation) also helps boost biodegradation of TrOCs, perhaps by ensuring close and prolonged contact between the enzyme and the TrOCs.  
Through their contribution, \"_Formulation of Lacase Nanobiocatalysts Based on Ionic and Covalent Interactions for the Enhanced Oxidation of Phenolic Compounds_\", [PERSON] et al. [15] demonstrated approaches to stabilize the xenobiotics removal performance of oxidative enzymes such as lacase. They compared several techniques of lacase immobilization on different superparamagnetic and non-magnetic nanoparticles based on ionic exchange and covalent bonding. A major advantage was that the immobilized lacase was magnetically recoverable from solution and, thus, could be reused in repeated cycles of phenol removal from wastewater. A particularly original aspect of the study was the assessment of the environmental impacts associated with the production of silica-coated magnetic nanoparticles. It was revealed that the use of energy and chemicals for the synthesis of laccase preparations were the major contributors of the environmental burden associated with the use of this technology.  
Reverse osmosis (RO) concentrate from wastewater reuse facilities contains concentrated emerging pollutants, such as pharmaceuticals [16]. In an article entitled \"_Removal of Croatuniton from Reverse Osmosis Concentrate by a TiO\({}_{2}\)/Zeolite Composite Sheet_\", [PERSON] et al. [17] assessed the removal of the antipruritie agent croatuniton from RO concentrate using a TiO\({}_{2}\)/zeolite composite sheet. The TiO\({}_{2}\)/zeolite composite sheet showed excellent performance for croatuniton adsorption without obvious inhibition by other components in the RO concentrate. With ultraviolet irradiation, croatuniton was simultaneously removed through adsorption and photocatalysis. The major degradation intermediates were also adsorbed by the composite sheet, i.e., the risk of secondary pollution caused by any harmful intermediates produced during advanced oxidation processes was mitigated.  
Constructed wetlands are a cost-effective wastewater treatment alternative due to their low operational cost, reduced energy consumption, and low sludge production [18]. [PERSON] et al. [19], in their study \"_Longitudinal Removal of Bisphenol-A and Nonylphenols from Pretreated Domestic Wastewater by Tropical Horizontal Sub-Surface Constructed Wetlands_\", assessed the removal of two endocrine disrupting TroCs, namely, Bisphenol A and nonylphenols, by an alternative wastewater treatment option: a constructed wetland. [PERSON] et al. [19] confirmed the significant removal of the target pollutants from wastewater by this process. Through a pilot study, they demonstrated that a native plant from the tropics could contribute to the enhanced removal of TroCs by constructed wetlands.