Written by Industry Expert, Shannon Junior, Aquatic Ecologist and Territory Leader
As the regulatory climate in the United States regarding aquatic pesticides becomes more stringent, it is becoming increasingly important to find alternatives to algaecides and herbicides for our algae and nuisance vegetation management programs. The continual and repetitive release of pesticides into the environment for vegetation control is not sustainable or effective, and more environmentally-friendly methods have become necessary. Integrated Pest Management (IPM) is a comprehensive approach to pest management that includes the use of many alternative strategies prior to or in conjunction with the use of pesticides. The implementation of a long-term, proactive IPM Program for lake and pond management helps to reduce the use of treatment products, while still providing for a healthy and aesthetically pleasing waterbody.
One of the most commonly recommended Integrated Pest Management strategies for water quality restoration is the installation of an aeration or circulation system. Aeration improves the health of a waterbody by adding oxygen to the system, which facilitates the conversion of phosphorus to forms that are not usable by algae as food. It also alters pH and other related water quality parameters to favor the growth of healthy green phytoplankton at the base of the food chain rather than potentially toxic cyanobacteria species. The end result is a healthier lake or pond with fewer harmful algae blooms, and a reduction in the need for algaecide treatments.
The two most common types of aeration systems are submersed diffused air systems and surface aerators. While both types can be extremely effective, each type has certain features that would make it the appropriate choice depending on the characteristics of a particular waterbody.
Submersed diffused air aeration systems utilize pumped air to destratify the water column and to infuse oxygen into the pond. The typical configuration involves an air compressor that sits on the shore, which pushes air through subsurface tubing to one or more diffusers located on the bottom of the pond. The membrane on the diffuser breaks the air into tiny bubbles that are released into the pond. As the bubbles rise to the surface, they carry the hypoxic (low oxygen) bottom water upwards, where it is mixed with the oxygen rich surface water. This constant vertical mixing causes the water column to de-stratify and allows harmful gases to be released into the atmosphere. It also brings more of the water in the pond into contact with atmospheric oxygen, which increases the overall dissolved oxygen concentration in the water column.
Submersed diffused air aeration is most effective in lakes and larger ponds with depths greater than 6 feet. In very shallow water, the bubbles do not have enough depth to spread as they rise to the surface, so less of the water column is circulated. Diffused air aeration systems are less expensive and more energy efficient than surface aeration systems in large ponds, and also offer the advantage of no electric wires in the water. Additionally, these systems cause very little surface disturbance, which is attractive to people who like a smooth and natural looking lake or pond.
Surface aerators, such as floating fountains and high volume mixers, are floating on the surface of the pond. These units contain a float-mounted pump that sucks water from just below the surface and sprays it up into the air. Unlike submersed diffused air aerators, surface aerators are most effective in shallow lakes and ponds. The oxygenation from floating aerators occurs when the water that is sprayed into the air splashes back down onto the surface of the pond. This interaction allows for the venting of gases and the transfer of oxygen into the water. However, because all of the oxygen transfer occurs at the surface, very little benefit is gained in the lower depths near the sediment.
Surface aerators can also provide the benefit of an aesthetically pleasing spray pattern, with many different choices available. However, if the primary goal of installing the surface aerator is for functionality rather than aesthetics, it is important to select a spray pattern with a wide display to maximize the amount of turbulence at the pond’s surface. This turbulence is beneficial not only because it creates oxygen transfer, but also because it keeps the surface of the water clear of debris and biofilm.In most cases, a combination of subsurface and surface aeration would provide the greatest benefit, but it is important to consider the goals of the stakeholders, the size, depth and water quality of the lake or pond, and the installation and operating budgets of the facility when selecting the optimal aeration strategy. Whatever system is implemented, the long-term result will be a more balanced waterbody that requires fewer applications of algaecides to maintain it in a healthy and aesthetically pleasing state.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond and fisheries management needs.
Shannon Junior is an Aquatic Ecologist and Territory Leader with SOLitude Lake Management. Since 1998, SOLitude Lake Management has been committed to providing full service lake and pond management services that improve water quality, preserve natural resources, and reduce our environmental footprint. Lake, pond and fisheries management services, consulting, and aquatic products are available nationwide. Learn more about SOLitude Lake Management and purchase products at www.solitudelakemanagement.com.