Search Results (3)

The eutrophication of surface waters is a natural process; however, anthropogenic activities significantly accelerate degradation processes. Most lakes in Poland and in the world belong to the poor and unsatisfactory water quality class. It is therefore necessary to limit negative anthropogenic impacts and introduce restoration methods, in particular those that are safe for the aquatic ecosystem. One of these is a pulverizing aeration Podsiadłowski method that uses only wind energy. The method allows for the moderate oxygenation of hypolimnion water, which maintains the oxygen conditions in the overlying water zone in the range of 0–1 mg O₂·dm^-1. The purpose of the work was to develop a new method of determining the efficiency of the aerator pulverization unit in the windy conditions of the lake. The method consists in determining the volumetric flow rates of water in the aerator pulverization unit, based on maximum hourly wind speeds. The pulverization efficiency in the conditions of Góreckie Lake was determined based on 6600 maximum hourly wind speeds in 2018. Based on the determined model, the theoretical performance of the machine was calculated, which in the conditions of Góreckie Lake in 2018 amounted to less than 79,000 m³ per year (nine months of the effective aerator operation). Full article

Nature-based solutions in lake restoration enable gradual ecosystem reconstruction without drastic and expensive intervention. Sustainable lake restoration involves limited external interference strong enough to initiate and maintain positive changes in the ecosystem. It was introduced in Lake Durowskie, an urban, flow-through lake situated in Western Poland, using hypolimnetic aeration, phosphorus precipitation with small doses of chemicals and biomanipulation in 2009, and is continued until today. Oxygen conditions in the lake hypolimnion after initial deterioration were gradually improved, and finally a shortening of the duration and range of oxygen deficits was observed. Nitrogen transformations were induced in the hypolimnion by water aeration as well, reducing ammonium N (30% during 2013–2017 in comparison to 2008) and increasing nitrates (90% in 2013–2017 in comparison to 2008). Phosphorus content was diminished (19% during 2015–2017 in relation to 2008 for SRP) due to effective iron-binding and a smaller amount of fresh organic matter being decomposed. Its reduction was related to lower phytoplankton biomass, expressed in a decrease of chlorophyll-a concentrations (55% reduction during 2013–2017 in comparison to 2008) and an increase in water transparency (two-fold during 2013–2017 in relation to 2008) throughout the nine years of treatment. A long-term restoration program, based on non-aggressive, multiple in-lake techniques was applied and, despite the lack of a reduction in total external loading, was able to suppress progressive eutrophication. Full article

The principal threat to lakes of the temperate zone is posed by factors accelerating their eutrophication and causing marked deoxygenation of the deeper layers of water, mainly the hypo- and metalimnion. Among their effects are frequent phytoplankton blooms, including those of blue-green algae, and general deterioration of water quality also affecting the abundance and health status of fish. The chief concern is a disturbed proportion between the quantity of complex chemical compounds, especially organic, and the oxygen content of lake waters. Natural processes of water oxygenation are not too intensive, because they are practically limited to the epilimnion layer, connected as they are with the activity of aquatic plants of the littoral and sublittoral zone (which tends to disappear in contaminated lakes) and wind energy (the effect of waving). In summer conditions, with a relatively great chemical activity of bottom deposits, the intensity of those processes is usually inadequate. Hence, in 1995 research was launched in the Institute of Agricultural Engineering of the Agricultural University in Poznań on an integrated lake restoration technology whose core was a self-powered aerator capable of oxygenating also the bottom layers of water (the hypolimnion) of deep lakes. The aerator uses energy obtained from a Savonius rotor mainly to diffuse gases: to release hydrogen sulphide, which usually saturates the hypolimnion water completely, and then to saturate this water with oxygen. Even early studies showed the constructed device to be highly efficient in improving oxygen conditions in the bottom zone. They also made it clear that it should be equipped with an autonomous system designed to inactivate phosphorus, one of the principal factors determining the rate of lake degradation. In 2003 the first wind-driven pulverizing aerator equipped with such a system was installed in Lake Urban in Chodzież. The aim of this work is to present the principles of operation of a wind-driven pulverizing aerator with a phosphorus inactivation system, as well as its general technical characteristics and preliminary results of a study of its performance. Full article