Influence of different recultivation methods on durability of nitrogen compounds changes in the waters of an urban lake

The study was conducted on Dugie Lake, which was fed with raw domestic sewage for 20 years. After preliminary conservation operations, the lake was restored by the artificial circulation and phosphorus inactivation methods. Before the restoration of lake, average amount of ammonia in the bottom water layer achieved a value of 20.71mg/L, and Total nitrogen (TN) 22.89mg/L. Start up of artificial aeration caused a distinct change in the concentration of nitrogen compounds in the lake. The intensive nitrification processes occurred due to improving oxygenation of the lower layer and increasing the temperature. It resulted in an increase of nitrate nitrogen concentration to about 1.30mg/L. A tenfold decrease in ammonia and TN concentration has been achieved as a result of the artificial aeration. Concentrations of nitrogen compounds which were noted 8 years after termination of the lake recultivation were typical for reservoirs with moderate trophic status.