### Occurrence, Fate and Transport of OMPs in WWTPs and Impact on Human and Environment  
Recent reports suggest the presence of numerous OMPs in increasing concentrations in polluted water environment (raw wastewater, surface and groundwater and drinking water), and that OMPs have become a global issue of great importance for environmental protection strategies [7; 13]. More recently, OMPs have generated increased concern among health authorities, industries and agricultural product manufacturers due to the associated risks to health of people and damage to the environment [8; 9; 10]. OMPs have been widely assessed in an environment (sediment, soils, atmosphere, sewage, surface, ground and drinking waters) and received increasing attention in recent years [7; 10; 14]. OMPs originate from either human activity, such as process effluents, discharges of treated effluents from sewage and hospital wastewater, agricultural runoff, septic tank or natural activities. Other anthropogenic sources include landfills, inappropriately disposed wastes, surface runoff, sewer offlow and leaking sewers [8; 9; 15] (Figure 1). Although OMPs are present in the environment at very low concentrations--only ranging from a few nanograms per liter (ng/L) to micrograms per liter (ug/L)--they may pose risks to humans and other living organisms [6; 9]. It has been reported that at 6.5 mg/L, the antibiotic ciprofloxacin had highest concentrations among more than 200 various pharmaceuticals detected in river waters all over the world. Single-compound  
Figure 1: Representative sources and routes of micropollutants in the environment [16]. Reproduced with permission from [16], Copyright Water Research, 2016.  
acute toxicity testing has found median sufficient levels (EC50s) for many OMPs to be \(<\) 1 mg/L [17]. For example, during spring and winter when infectious diseases spread rapidly, antibiotic consumption and discharge into aquatic environments increases. Those antibiotics accumulate in activated sludge; during summer, a peak concentration of around 9481.43 ng/g for the fluoroquinoline ofloxacin has been monitored in water bodies [18]. Nevertheless, accidental release of OMPs into the environment adversely affects several organisms such as flora and fauna, as well as human health [19; 20]. Such endocrine-disrupting compounds (EDC) include endogenic hormones, mycoestrogenes--the organic compounds produced by fungi, micropollutants polycyclic aromatic hydrocarbons (PAHs), surfactants, pesticides, halo-organic compounds including dioxins, furans [7] and steroid estrogens (SEs), such as estrone (E1), estradiol (E2) and ethinylestradioliol (EE2) [21]. A significant adverse effect on fish populations (_Pimephales promelas_) has been observed after exposure to 17-\(\alpha\)-Ethinyl estradiol (EE2) at a concentration of 5 ng/L in 7 years, due to estrogenic activity that affects hormones in animals even at very low 0.1 ng/L concentration [9; 22]. Findings suggest that some of industrial chemicals--nano/microplastics [23] and pesticides--pose some environmental and health concern. For instance, bisphenol A (BPA) is extensively used as a plastic additive and may pose health threats by entering the human body via different routes. There is increasing evidence that Bisphenol A (BPA) adversely affects reproduction and development systems, neural networks and cardiovascular, metabolic and immune systems [24]. Atrazine--one of the possible class-C carcinogens as detected by the United States-Environmental Protection Agency (US-EPA)--has also been found responsible for cancer in rats when exposed to high doses for extended periods [25]. The major point source for discharge of OMPs is from WWTPs. This can be attributed to the continuous presence of OMPs in the water bodies specifically close by urban dwellings [14; 26; 27]. More recently, OMPs have been identified in sewage and whole water bodies in North America, Europe, Asia and Africa [8]. [PERSON] et al. (2010) evaluated the fate and transport of OMPs in groundwater.