Water pollution is the second most impactful type of global pollution. Water pollution covers the contamination of all water resources, from the smallest water sources to the oceans. One of the main sources of pollution at this point is wastewater, and wastewater contains a form of polluted water. Wastewater consists of various components and water and these components are basically called pollutants. Pollutants have negative effects on living things and nature in general. In this respect, wastewater treatment is important. There are various methods and tools for wastewater treatment. One of them is biological treatment of wastewater. The main principles of this method are reviewed in the chapter.
Top1. Introduction
Pollution is the introduction of substances or energy (such as light or heat) into the natural environment in quantities or concentrations that are harmful to humans, animals or plants (Owa, 2013). Today, pollution continues to be one of the most important global problems.
Pollution can arise and spread from various causes and sources. Accordingly, there are different categories of pollution. These mainly include air, water and soil pollution and each of them includes other types of pollution
Accordingly, plastic pollution, noise pollution, thermal pollution, radioactive pollution, oil pollution, etc. are sub-categories of these categories. In other words, they are the causes of the main 3 categories. For example, Oil pollution pollutes both the sea and land and indirectly the air.
Air pollution ranks first, while water and land pollution hold the second and third places, respectively. Logically, given that air is the main carrier, it is normal that its pollution is seen as a major global threat.
On the other hand, water pollution continues to spread as a major source of danger.
Water is considered polluted when certain substances or conditions are present to the extent that the water cannot be used for a specific purpose (Olaniran, 1995). Olaniran (1995) defined water pollution as the presence of hazards (pollutants) in excessive amounts in water that are unfit for drinking, bathing, cooking or other uses (Lin et al., 2022).
- •
In developing countries, 90% of wastewater is discharged directly into water bodies without treatment.
- •
The industry discharges about 300-400 megatons of waste into water bodies every year
- •
It is estimated that about one-third of global biodiversity loss is the result of degradation of freshwater ecosystems, mainly due to pollution of water resources and aquatic ecosystems
- •
Every day, 2 million tons of sewage and other wastewater flow into the world's waters
The above mentioned are some of the facts mentioned by UNESCO (Gupta, 2016) related to water quality. One of the main conclusions drawn from these facts is that water pollution exists as a global problem.
The poor quality of water, especially drinking water, has led to the emergence of water-borne diseases. According to a World Health Organization (WHO) survey, 80% of the world's diseases and 50% of child deaths are related to poor drinking water quality, and there are more than 50 diseases associated with poor drinking water quality (Tuser, 2021). Sources of water pollution come in two forms: Point source and Non-point source (Akpor et al., 2014). In general, the following can be mentioned as the main sources of pollution (Wang et al., 2009):
- •
Agriculture;
- •
Sewage and wastewater;
- •
Oil and oil products;
- •
Radioactive substances.