This is a common question in meetings with consultants. Our answer is usually a question: “How can other aeration technologies be so energy in-effective?”

From an energy point of view - the energy you put in to a system decides the outcome and the inherent energy losses in a system determine the energy efficiency, or in-efficiency. But let’s start with a description of how water is oxygenated.

Surface area, molecular diffusion and elevation time

Oxygen molecules diffuse, i.e. move from air to water and from water to air according to the physics books and the laws of diffusion. This means that in the surface area where the air meets the water (bubble surface), an exchange of oxygen molecules happens. This means that oxygen molecules move both from the bubble, in to the water and vice versa. So, the larger the surface, the more oxygen will take the step from air to water. If you take one litre of air as a bubble, you have a relatively small surface for oxygen transfer. If you divide that bubble in to a million small bubbles, you will have an enormous surface for oxygen transfer!

The other important factor is called the elevation time. The longer it takes for a bubble to rise through the water, the more time it will have to release its oxygen. And small bubbles rise more slowly than large bubbles do. It is better to createsmall bubbles since they elevate slowly. Large bubbles elevate fast. It’s also better to generate the bubbles as deep down as possible, allowing them to travel upwards for as long as possible.

Conclusion - the most energy effective aeration technology is the one that creates small bubbles, deep down and with the least energy input!

Let’s look at how some common aeration technologies work and compare with Sorubin:

Suface Aerators

Surface aerators work in a similar way to fountains, at least in the respect that they send water up in to the air. Surface aerators are generally sturdy and require little maintenance. However, they are the most energy IN-efficient aerator type on the market.

Jet Aerators

This is a schematic jet aerator. It is submerged and only the chimney is seen above the surface. On the side is a submergible pump that pumps water through the horizontal pipe. Air is sucked in via the vertical pipe and mixed with the water. This results in a jet stream of water and bubbles that are sprayed in one direction. The water-in-the-pipe is accelerated just underneath the chimney. The acceleration creates suction through the chimney, resulting in atmospheric air being mixed in to the jet stream. Often, this kind of aerators is also used to direct water flow in a dam or basin.

Much of the energy you put in to a jet aerator is used to move water, and not to aerate. Thus the low energy effectiveness of this technical solution. Secondly, jet aerators don’t perform well in deep waters. Thirdly, they suffer from well-documented problems with clogging.