Hypolimnetic aerators: Predicting oxygen transfer and hydrodynamics

A simple model that predicts oxygen transfer in hypolimnetic aerators is described. The model accounts for cocurrent flow of air and water, variation of the saturated aqueous oxygen concentration with depth, and depletion of oxygen in the gas-phase. A correlation for water flow rate is developed from literature data, while existing correlation equations are used to estimate the mass transfer coefficient. Published experimental data for water flow rate and oxygen transfer are used for model validation with most of the observed data being predicted to within ±30%. Equations are provided for estimating the extent of the oxygenated zone-of-influence for an aerator operating in relatively stagnant water or a uniform underflow current. The potential deterioration in aerator performance due to short-circuiting of oxygenated water is briefly discussed. The model represents a substantial improvement in understanding of oxygen transfer in hypolimnetic aerators. It should be useful in the preliminary design and economic optimization of hypolimnetic aeration systems, and in determining spacing requirements for aerators in a lake or reservoir when more than one aerator is installed.