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Figure 1. Ratio of treated to untreated wastewater reaching water bodies from 10 regions across the globe. More than 90% of the water is discharged untreated.
Water, is of utmost importance in our daily lives, hence, the need to improve and preserve its quality is growing continuously. Point and non-point sources are contaminating our valuable water resources. The main water pollution sources are from industrial, domestic and agricultural activities and other environmental and global changes. The surface and ground water in many places around the world is contaminated and not fit for drinking purposes. By 2020, the global population is supposed to reach up to 7.9 billion and because of this the world may experience the great scarcity of fresh water. More than 90% of the water untreated is discharged. The global demand for quality water, whether for purposes of drinking, sanitation, irrigation, and industrial use, has been on a continuous rise, and there has been overwhelming concern in recent years about water treatment and reuse requiring the strictest standards.
Figure 2. Water treatment process.
Wastewater treatment and reuse is an important issue and scientists are looking for inexpensive and suitable technologies. Water treatment technologies are used for three purposes i.e. water source reduction, wastewater treatment and recycling. At present, unit operations and processes are combined together to provide what is called primary, secondary and tertiary treatment. Primary treatment includes preliminary purification processes of a physical and chemical nature while secondary treatment deals with the biological treatment of wastewater. In tertiary treatment processes, wastewater (treated by primary and secondary processes) is converted into good quality water that can be used for different types of purpose, i.e. drinking, industrial, medicinal etc. supplies. In the tertiary process, up to 99% of the pollutants are removed and the water is converted into the safe quality for a specific use. In a complete water treatment plant, all these three processes are combined together for producing good quality and safe water.
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