Abstract: A method and a device for restoration of lakes by oxygen-enriching of the water. A lake having a depth exceeding 8-10 meters is oxygenated by air-treatment of the lower and colder hypolimnion layer only. Air is introduced into the hypolimnion and is prevented from rising and thereby reach the upper, warmer epilimnion layer by an air-entrapping bell-shaped housing which is located above the air introduction spot. The device comprises a vertical tube the upper end of which terminates within said housing and the lower end of which carries an air nozzle. The tube acts as an air-lift pump by which the water is circulated through the housing. The housing is provided with an air outlet at its uppermost part and water outlets at its lowermost part. To the water outlets there are connected ducts for distributing oxygenated water out over the lake. The outlet ducts are provided with air collecting chambers in which a secondary entrapping of air bubbles takes place.

Abstract: A method and a device for restoration of lakes by oxygenation of the water. A lake having a depth exceeding 8-10 meters is oxygenated by air-treatment of the lower and colder hypolimnion layer only. Air is introduced into the hypolimnion and is prevented from rising and thereby reaching the upper, warmer epilimnion layer by an air-entrapping bell-shaped housing which is located above the air introduction zone. The device comprises a vertical tube, the upper end of which terminates within said housing and the lower end of which is equipped with an air nozzle. The tube acts as an air-lift pump by which the water is circulated through the housing. The housing is provided with an air outlet at its uppermost part and water outlets at its lowermost part. Ducts for distributing oxygenated water over the lake are connected to the water outlets.