Eutrophication in Water Resources: Definition, Types, Causes, Ecological Effects and Control Strategies

One of the most common problems is water quality management of seas and reservoirs around the world. About 30-40% of lakes and reservoirs worldwide are affected by abnormally high nutrients. Eutrophic phenomena are caused by an excess of nutrients in an aquatic system, especially by nitrogen and phosphorus, especially in lakes, estuaries and slow streams. Due to the excessive consumption of fertilizers and the discharge of untreated urban and industrial wastewater into water sources, the extent of eutrophication processes has increased significantly since the middle of the last century. One of the obvious signs of eutrophication is dense algal blooms, which cause high turbidity in water systems, decrease of oxygen and increase of hypoxia conditions in the inner parts of water bodies due to the sediments. In addition, extensive development of blue-green cyanobacteria, reduction of biodiversity, formation of hydrogen sulfide, increase in fish mortality, unpleasant odor, and increased phytoplankton and other aquatic plants, are other effects of eutrophication on the ecosystem. The main nutrients of interest are nitrogen and phosphorus, both of which are essential for algal growth, but the role of phosphorus is more critical because many cyanobacteria can obtain the nitrogen, they need from atmospheric nitrogen through nitrogen fixation. Therefore, most of the eutrophication control measures are directed towards reducing phosphorus. The purpose of this study is to investigate the types, causes, stages and factors, and finally solutions to control, modify and prevent the process of eutrophication.