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It’s becoming more and more clear that a good water oxygen level is important for plants. Water that’s deep in the ground and is being pumped around doesn’t hold oxygen. Oxygen is needed for the removal of various matters from the water. Other gasses (such as CO2 and methane) do, however, are found in the deep ground water. Before we filter the pumped-up water, we first air it.  This is done to insert oxygen in the water and to blow gasses such as CO2 and methane from the water. The oxygen also makes sure that the iron in the water forms small flakes which are then easier to collect by all the filters.

Because iron reacts to oxygen, ventilation installations often look rusty due to the residue of a small part of the iron. Ventilating the day supply, clean water storage, dirt drain, etc. has big advantages.  Besides the fact that the 300 micron air outflows bring extra oxygen to the water, what keeps the water "alive", oxygen (o2) is also an oxidising substance and will contribute to a better water environment when there’s sufficient inflow.

Oxygen is the most important component of water. There’s no life without oxygen.

Oxygen: Air contains 20% oxygen. Contrary to what many people think, it’s relatively difficult to dissolve in water. Depending on the temperature, there’s up to 30 times as less oxygen in water than in air. Cold water can contain more oxygen than warm water. At 10 degrees that’s a maximum of 11 mg/l. and at 20 degrees a maximum of 9 mg/l.

In general it’s assumed that an oxygen saturation of 60% is entirely acceptable. This would come to an oxygen level of 6.5 mg/l. at 10 degrees and 5.5 mg/l. at 20 degrees.

Organisations within aquaculture, however, recommend a target value of 8 mg/l.

We can do better

Growers want only the very best conditions. Knowing how important oxygen is, there’s nothing else we can and should do than to aim for a full, 100%, oxygen saturation or our drip/rain water. Only then will we achieve the maximum from the potential and we’ll bypass critical situations of imminent oxygen deficiency resulting in sorts of nasty issues (fungal growth, dead hair roots etc.)

Diffusion

Diffusion is the process in which oxygen dissolves in water.  This takes place on the dividing line between air and water. The most important thing is the water surface. The more the water surface ripples – due to wind, for example – the more oxygen is dissolved in the water because of the larger intake capacity (surface enlargement) of the water. The conclusion here is that ventilation and water movement go hand in hand… One enhances the other.

An hour before sunrise the water reaches the highest CO2 reading and the lowest oxygen reading. That’s when the pH-reading is at its lowest as well. Ventilation should be on at all times.

Extra oxygen needed

Extra ventilation is also of importance if you have anticipated the water of fertilizers (salts). Salt water could contain less oxygen than fresh water, depending on the salt percentage you have added.  

Also consider that atmospheric disturbances, such as thunderstorms, extract enormous amounts of oxygen from the water due to drops in atmospheric pressure. That’s why, for example, you’ll find fish floating on their backs after a thunderstorm and heavy rain!

Oxygen is used/misused.

Most organisms that keep the processes in the reservoir water going use oxygen. Nitrifying bacteria, such as Nitrosomas and Nitrobacter which sustain the nitrogen cycle are the significant consumers here. And let’s not forget the rotting processes continuously going on in your reservoir. Decomposition of organic material, such as leaves, excrements and algae takes up a lot of oxygen. 

Adding oxygen

Probably the best way to enrich water with oxygen is to add pure oxygen. This is, however, an expensive undertaking and that’s why we’re leaving it at that for now...

The most common way is a good air pump with multiple air dividers.

Such an air pump with 300 micron air outflows has a pretty high yield when it comes to oxygen-enrichment, provided there are sufficient outflows. The air bubbles cannot go too fast and can certainly not be too big because that wouldn’t achieve anything – except for a lot of noise and a lot of air bubbles.

In this type of system – depending on the power of the air/water pump and the caused water movement - the yield is only 2 to 5%! This means that a minimum of 95% of the air brought in smashes back into the atmosphere. A further obstacle is that the air bubbles are mostly too big. The cast-iron rule is: the smaller the bubbles, the better the oxygen uptake.

That is why MelClean recommends air 300 micron outflows (without resistance).

A positive feature of air outflows is the water movement it causes. That is done in a fine curve which enables the draining of floating dirt in the water; up first and then with a curve down. The air outflows shoot CO2 from the water as well, which dissolves much easier in water than oxygen, by the way.CO2 and Methane gas advance bacteria growth.


MelClean is offering  an aeration set with a capacity of 15,000 liters air per hour distributed by 4 air vents. Through each air vent a flow of 3000 liters air per hour is generated with a diameter of 300 microns . The set is fully equipped, containing all the materials, the pump, hoses, and weighted air vents.

 

 

MelClean  Ron Vuijk