*2.1.6 Flame retardants (FRs)*

Among all flame retardant compounds, organophosphate ester flame retardants (OPEFRs) class of phosphorus-containing flame retardants (FRs) and halogenated FRs such as polybrominated diphenyl ethers (PBDEs)) are known FR groups that decrease the flammability of industrial and consumer products. Organophosphate flame retardants (OPFRs) are used in furnishings, textiles, construction materials, electronics and as plasticizers in floor polishes and coatings. The discharge of OPFRs from wastewater treatment plants (WWTPs) into the surface water polluted marine environment causes toxicity. PBDEs are hydrophobic in nature and are mostly used as FRs in the manufacturing of carpets, computers, polyurethane foams, electronic cables, etc. [19].

## **2.2 Potential sources of emerging pollutants**

Emerging contaminants sources are the same as those of traditionally known contaminants and they are released to environment by agricultural, domestic, mining and industrial activities and hospitals. These sources are categorized as: point sources and non-point sources [20]. Contaminants from point sources are discharged from a particular site in high concentration and enter the ecological system in a spatially

distinctive way. Examples are discharges from industrial activities, mineral extraction and sewage treatment plants. While non-point sources also termed as diffuse sources release pollutants from indistinguishable disperse sources usually over large areas in low quantity. Examples are runoff of bio-solids or fertilizer applied to soils and rain overflow in urban or industrial areas (**Figure 2**) [21].

Water resources contamination by ECs from Wastewater is taking place all over the world particularly in those areas where wastewater treatment is not properly organized. Frequent use of drugs and personal care products lead to discharge of low quantity of different by-products. For example, triclosan, bisphenol-A and phthalates are significant industrial compounds integrated into several commercial household products. Their existence in water and environment affects their physical and chemical properties. PPCPs and other ECs metabolites are complex and hydrophobic in nature when released in water and settle at water surface. Thousands of these ECs and their metabolites have been discovered in the marine environment and are more noxious and harmful. Basically, wastewater treatment plants are not specifically designed for the effective removal of emerging contaminants [22].

## **2.3 Toxicological effects of emerging contaminants**

The adverse effects of ECs on living bodies have been widely reported which confirm that even small amount of ECs pose negative effects such as chronic toxicity and endocrine disruption in humans and animals. The major route of human contact with endocrine-disrupting chemicals (EDCs) is taking of foods and drinks connected to contaminated soil, water and microorganisms leading to bio magnification and

**Figure 2.** *Sources and their pathways of emerging contaminants.*

*Technologies for Removal of Emerging Contaminants from Wastewater DOI: http://dx.doi.org/10.5772/intechopen.104466*

**Figure 3.** *Harmful effects on human health.*

bioaccumulation in human body (**Figure 3**). Currently, researchers are focusing on ECs present in surface waters for many reasons: firstly, surface waters commonly contain high quantity and a diverse range of contaminants particularly when surface water is directly associated with industrial discharges and secondly it is easily monitored as compared to groundwater [23].

## **3. Traditional wastewater treatment methods**

Conventional techniques for the treatment of wastewater consist of physical, chemical and biological techniques for the removal of soluble and insoluble pollutants. Benefits and challenges of wastewater treatment technologies are given in **Table 1**. Biological treatment is of low cost and simple, but not effective for synthetic pollutants such as dyes as they are resistant to aerobic bio-degradation. Chemical treatments produce toxic by-products and are less efficient, while physical treatment is usually effective. Different phases included in wastewater treatment preliminary, primary, secondary and tertiary [24].


### **Table 1.**

*Benefits and challenges of wastewater treatment technologies.*

### **3.1 Preliminary treatment**

Preliminary treatment helps in the removal of suspended materials like dead animals, papers, oils, grease, etc., from wastewater. Different components such as screening, accumulation and floatation tanks and skimming reservoir are used in preliminary treatment. The accumulation tank is used for the elimination of sand and grit while oils and greases are removed by floatation units and skimming tanks.

### **3.2 Primary treatment**

In primary treatment, organic and inorganic components are removed by floatation and sedimentation processes. Throughout this treatment, untreated nitrogen, unrefined phosphorus, and heavy metals related with suspended impurities are drained off. This method reduces biochemical oxygen demand (BOD) ranges by 5–40%, 50–70% of entire floating particles and oil and grease up to 65% from wastewater. In various developed countries, primary treatment is required for the reuse of wastewater irrigation, i.e., for crops not used by humans.
