Biological Treatment

Water, the main source of life for humans, constitutes a large part of the planet we live in. Although it makes up three-quarters of the world, the amount of water people can use to meet their needs is small, contrary to popular belief. The water that people need in order to survive in freshwater. These waters, the amount of which are low in the world, are in danger of extinction due to the increasing population, the increase in the usage rate due to the change and development of people’s understanding of cleanliness, the change and development of the areas where water is used day by day, and the increase in industrialization. Another factor that accelerates this process is the pollution of existing water resources for various reasons. The depletion of water is a situation that directly affects the life of living things. The decrease in water resources and the depletion of water is a situation that will endanger the life of living things. Especially the pollution of spring waters can be considered as the main source of this problem. Pollution in water occurs for various reasons. Fertilizers and pesticides used in agricultural fields mix with rainwater from the soil into spring waters, causing the pollution of natural spring waters. The increasing rate of urbanization due to the rapid population growth also increases water consumption, and when the wastewater from settlements is given to water resources without treatment, it is a situation that increases water pollution considerably. The increase in industrialization, the gradual development of industrial establishments, and the increase in production have also increased the wastewater coming out of these places, thus it has been a factor that negatively affects water pollution.

The water polluted by the increasing population, the increase of industrialization, the development, and the increase of industrial establishments endangers the existence of water and brings the importance of the treatment of wastewater to the agenda. The wastewater from here has now exceeded the amounts that nature can absorb, and started to damage the discharged places. In order not to disturb the ecological balance and to prevent contamination of existing water resources due to wastewater, it has become a current issue to treat these waters before being given to these areas. For this reason, wastewater systems have been developed and over time, wastewater treatment plants have improved according to wastewater content. Since wastewater can vary in content, the correct method must be used depending on the purpose of the treatment of wastewater. Because the water to be discharged to nature must adapt to the characteristics of the place where it is given and not disturb the balance.

The content of wastewater is among the factors that determine the method to be used in treatment. Most wastewater is water, and only a few are pollutants. These pollutants can be suspended in wastewater as solid waste or dissolved in water. The methods to be used to remove these pollutants from wastewater are changing. For example, the most effective method to be used to remove organic wastes from wastewater is biological treatment.

Biological treatment is the process of transforming dissolved or solid organic wastes in wastewater into biological flocs that can collapse as a result of the breakdown by bacteria and inorganic compounds that mix into the atmosphere in the gaseous state.

Control of bioflocculation and mineralization processes and destruction of organic wastes in nature constitute the basis of biological treatment. Biological treatment ensures a safe reaction of organic wastes in nature. It is classified as air (aerobic) and airless (anaerobic) depending on the presence of oxygen in the environment.

The purpose of biological treatment is to remove solids that do not settle in wastewater and to stabilize organic substances. In addition to organic substances in domestic wastewater, the treatment of substances such as nitrogen and phosphorus is also carried out with biological treatment. It is very important to treat nitrogen and phosphorus in wastewater returned from agricultural areas. The treatment of organic and inorganic wastes is also important in industrial treatment. Since these wastes have toxic effects, they may need to be pre-treated.

The amount of oxygen in the areas where the water is polluted for various reasons is supplied is very important for the life of the living in those places. The loss of oxygen in the environment occurs with biodegradable waste materials in the discharged water. These substances break down and change the content, causing the stored microbiological substances to reproduce due to pollution and naturally to more oxygen consumption. Organic substances in wastewater consume less oxygen. When wastes with high nitrogen and phosphorus content are given to the environments where wastewater is supplied, life in these environments is enriched and oxygen consumption increases. This causes the oxygen of the water to decrease gradually and to lose the oxygen of the environment over time. Biological treatment also reduces the biological oxygen need of environments with high oxygen consumption. The methods used in biological treatment systems are to reduce the energy level of the waste.


Activated sludge systems are the most commonly used technique in biological treatment in the presence of oxygen. Suspended microorganisms help remove organic pollution. It is a biological treatment process that is also used in the treatment of industrial wastewater. In this technique, trickle filters, aerated lagoons, biofilm systems, stabilization pools are used.


Various biological treatment techniques can be used when treating domestic and industrial wastewater. Since the content of the effluent is variable, it is the wastewater content that largely determines these methods. Because even in a residential area, the content of wastewater varies from house to house. Even the content changes according to the purpose of use and the amount of water consumption. The same is true for industrial establishments. The content of wastewater from different industrial establishments is naturally different from each other. Moreover, even different enterprises in the same sector may have different wastewater contents. Besides the wastewater content, another decisive factor is the region where the wastewater will be discharged or for what purpose the wastewater will be used.