**Abstract**

Emerging contaminants (ECs) include both natural and man-made compounds that have recently been found to be present in wastewater and have a harmful effect on human health and aquatic environment. Several ECs such as pharmaceuticals, antibacterial, hormones, synthetic dyes, flame retardants are directly or indirectly discharged from hospitals, agricultural, industrial and other sources to the environment. Strategies have been developed to overcome the challenges faced by contaminated water treatment technologists. Advanced treatment technologies such as physical, chemical, and biological methods have been studied for ECs removal as well as for reduction of effluents levels in discharged water. Techniques such as membrane filtration, adsorption, coagulation-flocculation, solvent extraction, ion exchange, photodegradation, catalytic oxidation, electrochemical oxidation, ozonation and precipitation, etc., have been investigated. Based on past research, these techniques significantly remove one or more pollutants but are insufficient to remove most of the toxic contaminants efficiently from wastewater. Nanomaterial incorporated technologies may be a proficient approach for removing different contaminants from wastewater. These technologies are costly because of high-energy consumption during the treatment of wastewater for reuse on large scale. Consequently, comprehensive research for the improvement of wastewater treatment techniques is required to obtain complete and enhanced EC removal by wastewater treatment plants.

**Keywords:** wastewater treatment, membrane filtration, available technologies, effluents, emerging contaminants, nanotechnology, adsorption, personal care products, pharmaceuticals, aquatic environment

### **1. Introduction**

Wastewater is the water having surplus substances that may be dissolved or suspended solid particles or organic and inorganic substances or other impurities that critically influence its quality and make it unsuitable for use [1]. Wastewater

composition varies and is highly dependent on major sources of generation as industries, commercial and residential areas, agricultural sources, etc. [2]. In developing countries, the risk of consumption of contaminated water and its sanitation problem is increasing day by day.

Water covers about 70% of the earth's shells and is essential for all living organisms to survive and also for various manufacturing industries. About 3% of the total water on earth is fresh water of 0.01% is available for human use. The discharge of untreated contaminants from various industries directly to groundwater hinders the favorable use of water in normal operations of the ecosystem and causes water scarcity. Water deficiency is considered one of the most significant alarms for humanity and sustainable development [3]. According to the UNO report, about 1.2 billion people are affected by severe water scarcity due to the increasing world population and in future, 1.8 billion citizens are predicted to be affected by water insufficiency. Beyond water scarcity, water pollution also poses a greater threat to human health and aquatic life as well as the environment. Several new compounds recently detected in drinking, ground, and surface water have a major effect on water parameters. Water is a universal solvent and water quality is affected due to contamination by toxic substances dissolved in it which causes water pollution [4]. Water requirement is increasing due to adaptation in atmosphere, industrialization, increase in population, and obliteration of the surroundings [5]. The occurrence of organic and inorganic pollutants in wastewater is a major challenge to recycle water sources. To determine small amounts of unknown pollutants in the evaluation of emerging contaminants, the latest modern treatment techniques are still limited [6].

Currently, various analytical methods have been developed for different kinds of emerging pollutants. The separation of these toxic pollutants from water becomes important before the discharge of industrial wastewater into the aquatic environment. For this purpose, the development of proficient techniques has been a major area of environmental research. In general, traditional clean-up methods are classified as biological, physical, and chemical. Biological treatment is of low cost and simple, but not effective for synthetic dyes as they are resistant to aerobic biodegradation. Chemical treatments produce toxic by-products and are low efficient, while physical treatment is usually effective. For treating these organic pollutants present in water, several techniques such as membrane filtration, coagulation-flocculation, solvent extraction, ion exchange, catalytic oxidation, electrochemical oxidation, precipitation, etc. have been tested. However, these techniques are less effective, very expensive, and do not eliminate the contaminants from polluted water which makes this issue more challenging for the researchers. Besides these techniques, adsorption and photocatalytic degradation are considered the most potential approaches to removing wastewater contaminants [7].

The current chapter focuses on classification, potential sources, occurrence, prevention, control, and elimination of emerging contaminants. The major objective of this section is to study available technologies currently used for the removal of ECs from wastewater. This chapter also focuses on selecting the best available technology for removing emerging contaminants from wastewater. A schematic representation of treatment technologies, their principal advantages, performance efficiency, and limitations are discussed in the present study. Furthermore, future research opportunities are examined to provide more suitable and strategic recommendations for ECs removal from the aquatic environment.
