Anoxic Filtration System: The secret of pond die-off with the lack of oxygen.

Saturday, June 29, 2013

The secret of pond die-off with the lack of oxygen.

Hear to help clarify some of the things that are said in this little article from the UK about stratification of ponds, lakes and rivers.

If you studied chemistry in high school or college, you may have this mystery solved already.

Okay, first we have many things at play here. Like atmospheric conditions that will effect the turnover of layers in a water body as too release carbon dioxide CO2 from the bottom of a pond or lake from organic matter decay, causing a die off or for those that don’t know, it will appear to look as if a lack of oxygen in the upper layers is depleted.

In most lakes and ponds CO2 escapes because the water is continually circulating, thanks to a process known as convection; Rain, cold weather, or even just wind blowing across the surface can cause the topmost layer of water to cool, making it denser and therefore heavier than the warmer layers below. The cool water sinks to the bottom and displacing the warmer water, -CO2-rich water- and pushing it high enough for the CO2 to come out of solution and into the atmosphere.

However, sometimes these processes are impeded and the convection processes breaks down. There is a physical limit as to how much CO2 water can absorb, and the waters mass or pressure that exist in all deep lakes and ponds can hold CO2 almost indefinitely. As the bottom layers become saturated, the CO2 eventually rises to a level where the pressure is low enough for it to start coming out of solution. At this point, any little disturbance can cause the CO2 to begin bubbling to the surface. So, when this happens you get a “chimney” effect, triggering a chain reaction that in one massive upheaval can cause the pond or lake to disgorge CO2 that has accumulated in its bottom layer.

CO2 is odorless, colorless, and non-toxic; to a point that is. What makes it a killer in certain circumstances is the fact it’s heavier than air: If enough escapes into the air above the waters mass at once, it displaces the air or oxygen on the waters surface, making the intersection topography of air, water, surface exchange vanish. A mixture of as little as 10% CO2 in the air can be fatal; even 5% can smother a flame… which explains why oxygen to a water body mass can easily be depleted of such and can’t easily be replenished. There are many instances of this happening throughout the world as I have explained. It is not that uncommon, as you would think.

In our ponds however, this is very unlikely because we artificially impregnate the water with air driven devises that churn our ponds water 24-hours a day, 7-days a week by the same chimney effect that I explain on top only with air bubbles, pumps and/or drains.

Now you know the secret of pond die-off with the lack of oxygen, the oxygen is still there only it can’t exchange with the surface of the water.