Lakes and very large ponds ... aeration and filtration
Oxygenation and biofiltration .... John sent a question worth discussing today especially for those "farmers" amongst us. Here is the question ..... continue reading for my input and access to a great free report ... I am trying to aerate a 2 acre farm pond in a area of 6-8 feet in depth for the purpose of keeping a ice free area for ducks to be protected from predators during winter freezing times. The aerator will also be used in summer to improve my fishing habitat and fish growth. Do you have any info targeted for my needs? How to build, where to buy parts in the US? thanks. John Schultz
We tend to treat the visible symptoms of poor water quality such as, algae blooms, aquatic vegetation growth, odors, clogged sprinklers, valves and pumps rather than prevent them. Hopefully after reviewing this manual you will gain a better understanding of the causes of poor water quality and if necessary are able to 're-design' your approach to water quality management, allowing you to design an appropriate water quality management program that is preventative as opposed to fixative.
Treatment of these systems is beyond the scope of this website but they are helpful in understanding pond keeping anyway. I have therefore summarized a great white paper (see link below) produced by the US company Otterbine who make such large aeration systems
Summary Article
"Every Lake is a Unique Ecosystem" Imagine two lakes that are side by side, one is fresh, clean and healthy an asset to the property, while the other is dirty, weed-infested and creates odors (Figure 1).
By increasing your understanding you'll be able to develop a balanced management and prevention programs for your lakes.
We'll review the effects of poor water quality and the related costs to the property owner or manager, as well as focusing on crafting cause-oriented solutions, designing programs to put your lakes in ecological balance and preventing nuisance problems in the future.
Oligotrophic lakes are clear, cold lakes with low nutrient levels and few macrophytes or plants.
First, the littoral zone (Figure 2b) is the region of the pond sloping from the shore out to the area of open water.
It is the interface between the drainage basin and the open water, most generally the area where sunlight will penetrate to the bottom of the lake.
The littoral zone is the shoreline area where nutrients will runoff into the water.
The lack of dissolved oxygen sets in motion a series of chemical reactions that further reduce water quality: sulfide is converted to hydrogen sulfide, insoluble iron is converted to soluble forms, suspended solids increase and a severe decrease in the decomposition of waste materials on the pond bottom will occurs.
Shallow ponds less than 6ft/2m in depth tend to be very warm allowing for the entire water column to be productive with weed and algae growth.
The second essential factor in our lake management discussion is the impact of nutrients on the aquatic ecosystem.
In lake ecology the macro nutrients we specifically talk of are phosphorus and nitrogen.
As the nutrient level in the water increases so does aquatic plant and weed growth, this leads to severe problems from an environmental and aesthetic viewpoint.
The following chart shows the impact that nutrient levels can have on aquatic plants and algae.
Oxygen supports the food chain in a lake or pond, a healthy ecosystem in a lake contains a wide variety of plants and animals including a natural mechanism to biodegrade organic nutrients.
Aerobic digestion is a fast and efficient way of breaking down nutrients.
It is important that you understand the high cost of not acting, once a lake has lost its ecological balance and goes into crisis the costs of restoring the lake increase dramatically.
Many people view algae as the lake management problem but the true problem is poor water quality, Benthic or filamentous algae is a very difficult type of algae to control.
These plants grow from the bottom of the lake or benthic zone, break loose and float to the surface.
They will only grow in conditions where the depth and turbidity of the water allow sunlight to reach the lake bottom.
Increased nutrient/biomass levels in water causing sludge build-up Oxygen depletion issues such as odors and fish kills For the property manager the negative effects and costs of poor water quality are very real and can impact the property both in aesthetic and functional ways.
Clogged irrigation valves can create havoc on the turf while sediment build-up reduces storage capacity in water basins and aesthetic appeal is lost through odors, fish kills and algae.
Remember sediment increases the lake's oxygen demand and makes additional nutrients available for aquatic plant growth.
With the reduction in the basin's capability to store water, it has severe impact if the lake is an irrigation storage basin or a storm water retention pond.
Aeration, by definition, is the addition of oxygen into the water, the second component of aeration is circulation and destratification.
Aeration is a scientific discipline first used to treat wastewater during the industrial revoltion and continues to play an important role in the treatment of industrial and domestic waste.
Aeration can also make significant improvements to effluent waters that are being used for turf irrigation, similar to creating a mini-treatment plant in your lake.
Lastly, a properly sized aeration system will create circulation breaking down thermal stratification and lowering surface temperatures while adding dissolved oxygen to the lower regions of the lake (Figure 16).
This is due in part to mixing carbon dioxide enriched waters from the lake bottom up into the water column.
By pulling cool bottom water up to the surface, the surface layers are cooled and the growth of algae is slowed.
Air Diffusion Systems are the most unobtrusive aerators and are most effective in water that is 15ft or 5m deep or deeper.
At this time there is little or no university based data regarding ozone in our field and the International Ozone Association have no studies regarding ozone use for lake management of native fish and disrupt the food chain.
Also, by removing all of the aquatic plant growth in the pond a major source of oxygen is removed and odor and water quality problems can result.
Barley straw has also been receiving attention as a possible cure for algae blooms.
While there may be short term benefits in the long run the addition of more nutrient makes the lake more difficult to manage and creates additional biological imbalance.
A relatively new fad in water quality management is the burning of sulfur to treat irrigation water and lower the pH.
We stated that green and blue green algae have a two-week life, thus the use of a harvester for ongoing algae control would prove cost prohibitive.
Most aquatic algaecides and herbicides are copper-based products and are available in liquid (Figure 27a) or granular form (Figure 27b).
Chemicals may be applied by hand, however great care must be used to insure they are handled properly, in larger lakes they may be applied from a spray boat (Figure 27c).
This information has been summarized for benefit of subscribers from the
Integrated Pond & Lake Management Manual & Guide
published by Otterbine ... get full report at http://www.otterbine.com