Today, there are many studies about the problems that may be faced in the context of World Water Day. In this chapter, the structure, pollution, quality grading, and human health effects of water; possible pollution prevention measures; and water safety are discussed. It is expected that the world population, which is about 7 billion currently, will rise to 9 billion by 2050. Water consumption is expected to increase at a higher rate, which is a major problem for the environment. By 2025, it has been estimated that two-thirds of the world's population will deal with water shortage. The world is not as rich in water as once thought and, hence, is at high risk for water shortage. For these reasons, we must all fulfill our responsibility to leave a habitable world to future generations.
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A majority of the world when viewed from outer space is blue which represents to water (Cosgrove et al., 2014), (Kim et al., 2017). Approximately 70% of the Earth’s surface is covered with water (Cowan et al., 2014). However, 97% of this water is seawater, which is very difficult to use directly because of its salt content. (Das et al., 2014). Of the remaining 3%, a majority of two-third is sequestered in ice (Obbard et al., 2014). For this reason, only 1% of the world's water is available for human consumption (Hoekstra, 2014).
Water is a fundamental substance of great importance to all plants, animals (Weil et al., 2016). All living things being in the world need water to grow and maintain their existence (Black, 2016), as water comprises a large part of living things (De Asúa et al., 2017).
Water molecules are polar, leading to high solubility of salts in water (Snyder et al., 2014). In this regard, water creates a solution environment in which nutrients can be transported and biological reactions can occur in living cells (Tan, 2014). Many functions occur in our bodies. Owing to be a very good solvent water carries the nutrients necessary for our bodies to our cells and removes harmful substances from our cells (Hall, 2015). On the other hand, the fact that water is a very good solventthatcan cause to many deadly substances (Gschwend, 2016), harmful microorganisms, and water containing organic and inorganic chemicals unsuitable for human consumption (Priac et al., 2017) enter into human body. Water can be contaminated via (Spellman, 2017):
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The detergents we use and the kitchen dishwashing water, composed of dissolved organics, we discharge are polluting water resources. Many foods we use in our daily lives can have a dangerous effect when mixed with water. For example, if the sugar that we put in our tea mixes with a natural water source, it becomes a food source for the bacteria therein. Bacteria consume oxygen in the water along with the supplied nutrients, thus other aquatic organisms are prevented from consuming that oxygen and death may occur.
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Human and animal wastes, pesticides, and industrial plants that do not have wastewater treatment systems also damage water resources.
According to the water pollution control regulations set by the World Health Organization, waters are divided into four sections: high quality, less polluted, polluted, and heavily polluted (Zhang, 2017). Drinking water should be of high quality (Gazan et al., 2016). The water quality classes are based on physical, inorganic, organic, and bacteriological parameters (Gomes et al., 2014).
Some of the short-term effects to human health from dangerous substances in water include vomiting, fever, and dysentery. In the long run, death is a possibility (Raja, 2015). The highest number of deaths worldwide is due to consumption of unhealthy water (Blaikie et al., 2014).