The article contains results of an investigation about nitrogen compounds in water of fish ponds fertilized with biologically treated municipal sewage. The object was fish ponds of “Komorowice” complex, which are located in north part of Bielsko-Biała city. Two ponds were chosen to investigation: Green and Stone, which are characterized with an individual inflow and outflow of water and dif-ferent technical parameters. Green pond is a shallow pond with an average depth about 1m, its surface about 4,2 ha, and a water capacity – 42 000 m3. Instead Stone pond is characterized with a smaller surface – 3,3 ha and is almost two times deeper then Green pond, its average depth about 1,7m, which gives water capacity 59 200 m3. Researches were conducted in vegetative season in 2007. In paper were qualify changes of total, ammonium, nitrite, nitrate and Kjeldahl nitrogen concentration. During of whole investigative season were ob-served lower against to biologically treated sewage values of analyzed nitrogen form in water outflow of ponds. During that time were observed that occurrence changes in concentration of analyzed nitrogen compounds in pond’s water were related with changes of its concentration in sewage, which fertilized ponds. Addi-tionally, were calculate basic statistical parameters of analyzed indicators such as: an average, minimum, maximum values, standard deviation, an interval and variance in biologically treated municipal sewage fertilized fish ponds. With use of t-Student test were qualify importance of differences between an average val-ues in biologically treated municipal sewage fertilized ponds and in outflow wa-ter of ponds. Statistical importance were following indicators: total, ammonium, nitrite and nitrate nitrogen at importance level α = 0,05.
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