**2. Wastewater characteristics and their treatment**

Due to industrialization, population expansion and modern life style the wastewater generation is increasing day by day. The discharged of wastewater without proper treatment in to waterbodies are continuously overloading the fresh water bodies and minimizing their self-cleaning capacity. This overloading of waste into the freshwater bodies, disturbing the nutrient recycling process along with the disturbance in biogeochemical cycles i.e. nitrogen, carbon and water cycles through physical (evaporation, precipitation etc.), ecological (eutrophication, bio-magnification etc.) and biological process (photosynthesis, nitrogen fixation, respiration etc.). Availability of fresh water/irrigation water for fulfillment of daily requirement of the human society is also decreasing in the present changing environment [5]. To meet out the current demand of water for various anthropogenic activities, this is very necessary to increase the water reuse potential. This can be achieved through proper treatment of the wastewater generated during different activities. Wastewater is generally composed of water and wastes originate from commercial, industrial, home and institution activities. Wastewater at the point of origin contains high organic load, colorants, pesticides, heavy metals, hydrocarbons, numerous pathogens, toxic compounds and nutrients. The minimum treatment of this generated wastewater is required and recommended before disposing into the environment. The mechanistic understanding of the environmental effects, influencing factors, controls and effective utilization of the treatment process is essential to design the treatment process and its operation. There are three methods which are used to treat wastewater. These methods are physical, chemical and biological methods. The treatment of waste water is general divided into three systems of treatment i.e. primary, secondary and tertiary based on the capacity to remove the different contaminants. The general wastewater treatment process details are depicted in **Figure 1**.

**Figure 1.** *General wastewater treatment process.*
