Aeration technology is applied in hundreds of Minnesota lakes and
reservoirs for at least three purposes: (a) to prevent winterkill of fish in
shallow lakes under ice cover, (b) to reduce nutrient release rates from the
sediments and (c) in aquaculture to provide aerated water to high-density
fish populations. A major uncertainty in the design, selection and application
of aeration systems is the often observed increase in oxygen demand after
aeration systems are installed and operated. As a result, the improvement in
dissolved oxygen is often less than anticipated, even zero.
In this study we have investigated this problem through a series of
carefully designed experiments. We have shown that sedimentary oxygen
demand (SOD), frequently the major oxygen consumer in lakes, increases
proportionally to the velocity with which the water above the sediments
moves. Aeration devices often and intentionally increase water velocity above
the sediments and thereby increase oxygen consumption in the lake. The
results given in this report allow a more realistic estimation of oxygen
demand in lakes for aerator selection. Recommendations for aerator
placement are also given.
Mackenthun, A. A.; Stefan, H. G..
Experimental Analysis of Sedimentary Oxygen Demand in Lakes; Dependence on Near-Bottom Flow Velocities and Implications for Aerator Design.
St. Anthony Falls Hydraulic Laboratory.
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