No abstract

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.

No abstract

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.

No abstract

I n t e r n a t i o n a l J o u r n a l o f O c e a n o g r a p h y a n d H y d r o b i o l o g y AbstractThe study was conducted on Lake Długie, located in the city of Olsztyn, which for 20 years received raw domestic sewage (400 m 3 per day). After preliminary conservation operations, the lake was restored by artificial circulation and phosphorus inactivation methods. During artificial circulation, water temperature in the whole lake volume was equalized. The disconnection of the compressor stimulated the return to typical thermal parameters in the lake. Phosphorus inactivation did not affect the thermal regime in the lake. Artificial circulation caused an increase in the oxygen content in the whole lake, lowered the oxygen-depletion rate during stagnation, and shortened the duration of anaerobic conditions in the near-bottom waters. Phosphorus inactivation did not directly affect the content of oxygen. However, after the coagulant was added to the lake, the oxygenation of the water was further improved owing to the depressed photosynthesis caused by drastically reduced availability of phosphate for primary producers.

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.

The study was conducted on Długie Lake (area 26.8 ha, maximum depth 17.3 m), located in the town of Olsztyn, in north-eastern Poland (the Masurian Lake District). For 20 years starting in the 1950s, Długie Lake was used as a receiver of raw domestic and storm sewage in quantities oscillating between 350 and 400 m(3) day(-1). This led to complete degradation of the lake, known as saprotrophy. After some preliminary protective treatments in the catchment, the lake has been renewed by artificial aeration with thermal destratification and the phosphorus inactivation methods. Long-term reclamation of the reservoir has resulted in distinct and durable improvement of water quality. Before the restoration, the average phosphorus concentration in the surface water layer was 0.079 mg P L(-1) and in the over-bottom water it reached 2.277 mg P L(-1). The total phosphorus (TP) level also was very high, i.e. up to 3.5 mg P L(-1). After the restoration, these values have declined to 0.001-0.017 mg P L(-1) in the case of mineral P, and the current TP concentrations do not exceed 0.350 mg P L(-1).