Artificial mixing and phosphorus inactivation methods using aluminum compounds are among the most popular lake restoration methods. Długie Lake (Olsztyńskie Lakeland, Poland) was restored using these two methods. Primarily, P precipitation and inactivation methods significantly increased the sorption properties of Długie Lake bottom sediment. Fifteen years after the termination of the restoration procedure, the alum-modified “active” sediment layer still has higher P adsorption abilities, which can limit P internal loading. Relatively low amounts of phosphates in the near-bottom water of Długie Lake, even in anoxia, as well as the fact that the assessed maximum sediment P sorption capacity is still higher than NH4Cl–P (labile P) and BD–P (Fe-bound P) sum (“native exchangeable P”), confirm that hypothesis. Among the tested P adsorption models for the sediment, the double Langmuir model showed the best fit to the experimental data (the highest R2 values). This may indicate that phosphorus adsorption by the tested sediments most likely occurs through phosphate binding at two types of active sorption sites. P adsorption by the studied lake sediment during experiments was significantly connected to aluminum content in sediment. The research into the adsorption properties of sediment can be used as a tool for the evaluation of lake restoration effects.

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The objective of this study was to evaluate the effect of lake restoration by the hypolimnetic withdrawal method on the intensity of ambient odour in the vicinity of the pipeline outlet. The study was carried out in [2012][2013] -N), total nitrogen (TN), dissolved nitrogen (DN), total particulate nitrogen (T-PN), total organic carbon (TOC), dissolved organic carbon (DOC) and total particulate organic carbon (T-POC). Water samples were also analysed to determine total bacterial abundance (TBA) and the counts of bacterial rods, cocci and spiral-shaped bacteria, and sulphate-reducing bacteria (SRB). Significant variations in odour intensity

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The study was conducted on Długie Lake in Olsztyn, which for 20 years since the mid-1950s served as a domestic and storm wastewater receiver, which led to its complete degradation. The discontinuation of wastewater inflow in 1976 caused a change in the trophic state from saprotrophic to hypertrophic. Evident improvement of water quality was possible only after the implementation of proper restoration techniques. Długie Lake was subjected to artificial aeration with thermal destratification (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000). After all opportunities to improve water quality in the lake by artificial aeration (low phosphorus sorption capacity of sediment) had been exhausted, it was decided that a phosphorus inactivation method using the coagulant PAX 18 be used (2001)(2002)(2003). Before restoration, the nutrient concentration in the near-bottom water layer of Długie Lake was very high at 22.9 mg TN L −1 and 3.50 mg TP L −1 . The average amount of chlorophyll a was ca. 200 μg L −1 , and the Secchi disc visibility did not exceed 1 m. In 2017, 14 years after termination of the lake restoration process, the total phosphorus concentration at the bottom was 0.21 mg P L −1 on average, and the total nitrogen was 1.5 mg N L −1 . The mean transparency of the water oscillated around approximately 5 m, and the amount of chlorophyll a was 1.86 μg L −1 . Studies have shown that the most important step in reclamation is to prevent pollutants from entering the lake to the maximum extent possible and to use a combination of several reclamation methods as a matter of good practice. Stable environmental conditions have developed in the lake, and the values of chlorophyll a and the Secchi disk visibility indicate that the lake has reached a mesotrophic state.

This study describes the impact of environmental factors on prokaryotic community structure and dominant bacterial groups in the monimolimnion of a meromictic lake. The

tandyRak R., PaRszuto k., GRochowska J., 2016. Water quality of Lake Ełk as a factor connected with tourism, leisure and recreation on an urban area. Quaestiones Geographicae 35(3), Bogucki Wydawnictwo Naukowe, Poznań, pp. 51-59, 4 figs, 3 tables. abstRact: Lake Ełk as an important element of the urban landscape is associated with tourism and active recreation and because of it with the economy of the town. Since 1999 the renovation method with the use of artificial aeration with simultaneous phosphorus inactivation and also as a biological filter -BIO-HYDRO structures were applied on the lake. This process was lasting 10 years and brought only a short-term improvement. At the same time, the shores of the lake were managed to develop of lake tourism: beach, swimming pool, tennis courts, a promenade, and two a water equipment rentals. The illuminated fountain, the road bridge and well -developed catering -accommodation base were made as well.