Assessment of selected physicochemical properties of restorated water of the Mogileriskie Lake

Excessive supply of nutrients contributes to gradual eutrophication of water. This process can happen fast, especially in shallow lakes which are more prone to degradation. This also causes deterioration of settlement conditions of many organisms and limits economic use of water. Eutrophication can lead to gradual shallowing and shrinking of water reservoirs and subsequently disappearance of lakes. Therefore, appropriate diagnosis and reduction of the amount of pollutantsflowing into lakes are crucial for the water quality improvement and prevention from further degradation. The Mogileńskie Lake, like many other town lakes was supplied with sewage. As a consequence, the reservoir stopped being an attractive urban element, and became an object cumbersomeaud dangerous to the residents health. For this reason the lake has been subjected to many protection and reclamation processes.The water samples were taken 10 times from 3 sampling points between September 2014 and June 2015. The contents of total phosphorus, phosphorates, total nitrogen, nitrates, nitrites, and ammonium nitrogen was measured in the tested water. The results obtained from the water analyzed for biogenic elements, and their compounds indicate low effectiveness of the carried out reclamation. According to many authors, the choice of artificial aeration as a reclamation process for the Mogileńskie Lake was a mistake.This cleaning method does not provide the expected results when used for shallow and polymictic lakes, especially in combination with an invasive method of dredging and the controversial deposing of the extracted residues in the direct proximity of the lake