## 4 Tertiary Water and Wastewater Pollutants  
### Contaminants of Emerging Concer  
Contaminants of emerging concern (CECs) are defined as chemicals or organisms whose concentrations are not regulated at present [44]. These contaminants could have adverse effects on humans or the environment. As mentioned previously, they were not a concern when wastewater treatment plants were initially designed, so they are not effectively removed by these plants.  
Endocrine-disrupting chemicals (EDCs) are a class of CECs that have been reported in drinking water in South Africa and other parts of the world [6; 45]. EDCs can be classified according to their use, with the main categories being oestrogens, pharmaceuticals, pesticides, perfluorinated carbons and personal care products [46]. The negative effects of ingesting these compounds include decreased fertility and abnormal reproductive capacity [47]. While EDC concentrations are not yet high enough to affect humans, the impact is visible in wildlife. This includes declining populations of some reptile, amphibian and fish species [48]. Wildlife is affected more because our discharge points are often located in their water supplies and aquatic habitants, causing them to experience high contaminant concentrations, prior to the rectifying effect of infinite dilution.  
The EDCs in each category may be further classified based on their persistence. While some EDCs decompose after being discharged, other EDCs act as persistent organic pollutants (POPs). POPs are problematic for water treatment plants, as their halogenated structure makes them stable and resistant to environmental degradation [49].  
Naturally, some EDC categories are more commonly found in water than others. During a study of the influents of three South African wastewater treatment plants, the three most common EDC categories were oestrogens, perfluorinated compounds (PFCs) and pharmaceuticals [46]. Of the three, oestrogens were the most commonly found and their concentration is rapidly increasing [50]. The primary source of these oestrogens in surface waters is E1 (oestrone) [51], a POP [46] excreted by both humans and animals.  
Pharmaceuticals were the most highly concentrated EDC group from the study (but not the most commonly found). The most persistent of these pharmaceuticals was carbamazepine (CBZ) [52]. This drug is used to treat epilepsy and bipolar disorder. CBZ is excreted by patients who make use of it, causing the drug to appear in the influent of wastewater plants [53]. Pharmaceuticals also enter wastewater plants when they are disposed of irresponsibly, such as when they are flushed down toilets or rinsed down basins. Furthermore, the concentration of CBZ in the plant effluent is sometimes higher than in the plant influent. This further reinforces the ineffectiveness of wastewater plants at removing EDCs. The presence of CBZ in water supplies is problematic because the unintentional consumption of it could lead to impaired red blood cell and platelet production [53].  
Perfluorinated compounds (PFCs), also referred to as perfluorinated alkyl substances (PFAss), were the third most commonly found EDC from the same study. They possess a strong carbon-fluorine bond that makes them highly stable and therefore persistent [54]. They are used in stain repellents for carpets and textiles, non-stick coatings for cooking utensils and in paints and adhesives [55]. One of the most widely studied of these PFCs is PFOS (perfluorinated octane sulphonate). Communities exposed to high PFC concentrations via their drinking water exhibited higher cases of kidney and testicular cancers [56]. Furthermore, children exposed to PFCs may develop hormonal issues and decreased immunity.