Pond and Lagoon Aerators Information
Pond and lagoon aerators infuse dissolved oxygen into the water of the ponds and lagoons. Some aerators, such as fountain-style devices that circulate water from the bottom of a pool and spray it into the air, can also break up the thermal layers in the water. There are also aerators made especially for waste water treatment, since aerating the waste water is part of the treatment process. Sewage treatment lagoons usually use grid-style aerators, which are a network of pipes on the bottom of the lagoon that bubble air into the mix. The addition of dissolved oxygen to wastewater assists in breaking down harmful organic compounds in the waste matter. A fountain aerator also exposes the wastewater to sun, where the sunlight can further purify it.
The Role of Dissolved Oxygen
All ponds and bodies of water need to have good dissolved oxygen content for cleanliness and healthy aquatic life. One of the basic signs and measures of dirty polluted water is its low dissolved oxygen (DO) levels. This is usually due to the presence of pollutants such as human and animal waste, excess fertilizer and soil runoff from farms, and/or excess amounts of dead matter or algae in the water. Dissolved oxygen is not only the source of life for almost all living organisms in water, especially fish, but dissolved oxygen also oxidizes larger harmful chemical compounds, breaking them down into less-toxic or non-toxic chemical compounds.
Running water like that in shallow rivers doesn’t usually have a problem with dissolved oxygen levels, since the water flows over rapids and rocks and can absorb oxygen more easier because of its high surface area to volume ratio. But water in ponds and deep lagoons is usually stagnant and has a lower surface area to volume ratio. Stagnant water separates into layers due to temperature and not mix, so the water on the bottom of the pond will have less dissolved oxygen than the top layer, which can absorb oxygen from the air. Dissolved oxygen is also a function of water temperature, but it is the opposite of dissolved solids. As the water heats up, its capacity to hold dissolved oxygen decreases with higher temperature. But that is beyond the scope of this area since aerators are not water heating or cooling devices.
- Fixed fountain sprayer aerators are the oldest and most visible to the public
- Bottom fixed bubbler piped grid aerators
- Floating fountain aerators
- Floating paddle wheel sprayer types are ideal for destratification of the water layers due to mechanical action
- Flexible hose bubbler styles are less efficient but are a good short-term, easy to install solution
Aerator types (left to right): fountain style, aeration using a bottom-fixed grid aerator, floating paddle wheel.
Operation and Specifications
All aerators require some sort of power, usually the traditional 3 phase AC electric motor driven pumps. Carefully wiring and periodic maintenance is essential for use in water to avoid shorts and potentially fatal electrocution. Spray and paddle wheel styles of aerators increase the evaporation rate, which may increase the salinity of the water in a use such as a fish or shrimp pond. Evaporation is irrelevant, however, for wastewater treatment or a lake with some inflow.
Subsurface grids of fine bubble aerator pipes are ideal choices for cement-lined, purpose-built wastewater lagoons, since the air is delivered in fine bubbles at the bottom. This not only results in maximum dissolved oxygen transfer, but also keeps the lagoon layers destratified. This style also has the advantage of having the motor and compressor on shore for easier and safer use and maintenance. For fish or ornamental ponds, a less radical and expensive solution such as a floating paddle wheel or fountain aerator is suitable.
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