FAQ – Summer Destratifier

FAQ - Summer destratifier

How does the Limnetics Destratifier work to Improve water quality?
The anoxic bottom layer (hypolimneon) is recharged with oxygen-rich water from the surface layer (epilimneon). Oxygen keeps manganese, iron, and phosphorous bound in solid compounds in the sediment. Anoxic decomposition and hydrogen sulfide production are replaced by aerobic processes.

How much will it cost to operate the Limnetics Destratifier?

Typical electricity cost is $10 per day, or $300 per month for 24 hour per day operation of the 3HP motor.

What regular maintenance is needed for the Limnetics Destratifier?

Speed reducer oil changes are recommended every 2500 hours of operation.

Where should the Limnetics Destratifier be located?

For complete destratification, the unit must be located over the deepest part of the lake.

When should the Limnetics Destratifier be run?

Continuous 24 hour per day operation is recommended through the stratified season. This is typically from May through September.

When is the best time of year to start a new Limnetics Destratifier for the first time?

The first few weeks of operation may disrupt water quality by suspending sediment immediately below the unit. Late winter or early spring is the best time for this, as the lake is rich in oxygen and least susceptible to an upset.

Is it necessary to remove the Limnetics Destratifier from the lake at the end of the season?
Removal is not necessary on water bodies that get little or no freezing. Ice on large water bodies may shift enough to move anchors and damage the unit.

How is the Limnetics Destratifier installed?
The unit can be launched off a trailer on a boat ramp, or may be placed by crane.  It is held in place by three or four anchors weighing 400 – 700 lb each.  Anchors may be moved and lowered into position using the Limnetics Destratifier barge towed by a boat.  Power is delivered through a flexible cord resting on the lake bottom.

Why do lakes separate into upper and lower layers?
Water is heaviest at 38 degrees Fahrenheit. In summer, the coldest, heaviest water sinks. The lake becomes stratified. The upper epilimneon has light and oxygen to support plant and animal life. Temperature drops quickly down through the thin middle zone, or thermocline. Below is the cold, heavy, dark hypolimneon. Dead matter from above settles into the hypolimnion, consuming oxygen as it decomposes. Wind and waves mix near the surface, but may not affect lower water.

How is lake oxygen used up?
Oxygen is consumed by respiration of animals, including the aerobic microorganisms that decompose dead plants and animals.

How is lake oxygen replenished?
Oxygen molecules diffuse from the atmosphere to the water surface, particularly when wind and waves cause more water molecules to come in contact with air. Plants and algae also release oxygen during photosynthesis, in the presence of sunlight. Photosynthesis is the reason that lake oxygen is maximum in the afternoon.

Why are oxygen levels lower near the lake bottom?
Oxygen is replenished by (1) contact with the atmosphere, and (2) photosynthesis conversion of carbon dioxide to oxygen by plants. In a stratified lake, bottom water stays in the lower level (hypolimnion). It never comes in contact with the atmosphere, and gets little if any light needed for photosynthesis. Further, dead plant and animal matter settles to the bottom, where it consumes oxygen as it decomposes.

What harmful affects result from lake stratification?
If oxygen is depleted in the lower level (hypolimnion), game fish lose habitat. Algae-eating zooplankton also lose daytime refuge from predators. With oxygen absent at the bottom, phosphorous is released from the sediment into the water, promoting algae growth.  Manganese and iron in the sediment dissolve into the water column.   Hydrogen sulfide (sewer gas) is generated.

How does the Limnetics Destratifier affect lake stratification?
The more sheltered and stagnant a lake, the more likely it is to stratify. Whole-lake circulation by the Limnetics Destratifier prevents colder pockets of water from settling to the deepest part of the lake. This inhibits or prevents stratification.

How does the Limnetics Destratifier compare to a fountain in circulating water?
A fountain moves a small amount of water at high speed; water tends to recirculate back to the fountain, mixing small circular “cells” without much affect away from the fountain. The Limnetics Destratifier gently moves a much larger mass of water, with a fraction of the energy. The horizontal part of this flow creates long-distance currents that continuously circulate around large basins.

How does the Limnetics Destratifier compare to a diffused air bubbler system in circulating water?
A diffused air bubbler circulates water by “dragging” bottom water up along with rising bubbles. This requires more energy than the lift of a low-speed propeller. Like a fountain, a diffused air bubbler system also tends to recirculate water in small circular “cells”.

How can oxygen be transferred to water without bubbles?
Oxygen transfer occurs near the surface from (1) photosynthesis by phytoplankton and other plants, and (2) at the interface where air comes in contact with water. The larger the surface area of contact, the more oxygen is transferred. A thousand bubbles may have only one square foot of contact area, whereas a one acre water surface has 43,560 square feet, not counting waves. The key is to move a large volume of oxygen-poor water to the surface with minimum energy.