Dugout aeration study answers questions
   

For years there have been ongoing debates as to the most effective methods and devices for proper dugout aeration.

To answer some of these questions, PFRA staff in Peace River collected information that compares both different aeration devices and the differences between aerated and non-aerated dugouts. The three year study involved 18 dugouts located in the Falher, Alberta area, south of Peace River.

The main purpose of dugout aeration is to prevent the problem of black, smelly dugout water caused by decaying plant matter resulting from a lack of dissolved oxygen in the dugout water. PFRA studies have shown that unless a dugout is properly aerated, this problem can occur not only during winter, but also throughout the summer months.

Aeration is more than stirring

Many farmers felt that all aerating a dugout required was an air line into the dugout or something to stir the water, and their black water problems would end. Actually, this statement is only partially correct. What the study has shown is that devices that effectively diffuse air into water play an important part in improving dugout water quality.

Aeration through air injection circulates oxygen through the dugout water, but only to the depth of the injector. Water below the air injection point in the dugout actually became or remained closer to an anoxic state. To rectify this problem, the injection point must be located on the bottom of the dugout.

Thus, the amount of dissolved oxygen throughout the entire body of water is increased by water circulation and by the diffusion of the injected air into the water.

Diffusion type makes a difference

Findings have also shown that the type of air diffusion used can make an important difference. For instance, diffusers that produce smaller bubbles tend to create better circulation in the dugout and actually maintain higher levels of dissolved oxygen than open-end diffusion.

Although open-end diffusion may create an opening in ice during winter conditions, water that was injected with air through a small bubble diffuser tended to maintain higher dissolved oxygen levels, while maintaining a constant ice coverage during winter months.

In addition, maintaining oxygen saturation (using the same pump) in dugout water, required three to 10 times more air injection from open-end diffusion compared to the more efficient small bubble diffuser.

Surface aerators, although useful for other applications, tended to increase the temperature of the surface of the water during open water months and only seemed capable of making substantial differences in dissolved oxygen levels near the surface of the water. This left the deeper levels of the dugout with identifiably less dissolved oxygen.

Linear diffuser most consistent

As shown in Tables 2 and 3, the linear diffuser provides the most consistent levels of dissolved oxygen and temperature throughout the dugout depths.

In comparing temperature and oxygen profiles for dugouts under ice cover with different aeration methods, the linear diffuser consistently provided 10.6 mg/L of DO for all depths.

Therefore, the small bubble (linear) diffuser placed on the bottom of a dugout provides the most effective method of replenishing dissolved oxygen levels in dugout water during summer and winter months.


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