Air bubbles for water quality improvement

Thermal stratification in water supply reservoirs can result in a serious degradation in water quality. The techniques of artificial mixing and aeration, using air bubbles, have been applied in a number of impoundments to prevent the formation of the anaerobic conditions that lead to poor water quality. The first part of this report describes some of the aeration and mixing devices that have been used, and discusses the parameters used to compare their efficiency. The second part of the report presents measurements on the pumping and mixing performance of a destratification device that uses large (300 mm diameter) air bubbles. Experiments were conducted at laboratory and near-prototype scales. The experimental data is used to develop a design guide for large air bubble guns.