A multi-part question here:
What makes long term stored water go "stale" or unuseable? Is it simply a loss of oxygen, or is there another composition change?

If it's treated sterile water and the problem is simply a loss of oxygen, why then could a barrel (or bottles) of LT stored water not be re-oxygenated?

Water is a molecule of 2 parts (2 atoms) hydrogen, 1 part (1 atom) oxygen, unless it undergoes electrolysis into elemental hydrogen and oxygen, it will remain H2O. Water can have dissolved oxygen (why fish can respire in water), but his does not affect the potablity of the water. Yes, it does affect the “taste”, which is why it is often recommended to pour boiled water from container to container, which will introduce dissolved oxygen and improve the taste. If the water is sterile and is maintained in a sterile sealed container, it cannot go “bad”. This additive, likely is, like adding hydrogen peroxide, in which a small amount of nascent or free oxygen is generated which has bacterialcidal properties.

Pete

So the need to "rotate your water" every few years, is more related to it's taste than it's purity.

Could an aquarium pump intoduce oxygen safely into 55 gallon drums of sterile water, and if so, would the water need to be retreated afterward?

The problem as I see it, would be to ensure the water in a 55 gal drum is truly sterile and is that sterility maintainable. Introduction of oxygen (aeration) is of little value until you go to drink the water (strictly for taste).

As to your question, even if the water was sterile to start with, the use an aquarium pump (assuming you can sterilize the internal workings of the pump) to aerate the water would likely result in contamination with airborne organisms.

I would look to long-term storage of water by treating the water with 2-3 times the normal bleach concentration, first ensuring the type of container will not be adversely affected by bleach and that your starting water quality (in term of organics, heavy metals, etc.) is in acceptable ranges. Most food grade 55 gal drums should be fine. I recently purchased two drums, one of each type from this Ebay seller. He has increased the prices quite a lot, since I purchased mine and you may want to check around before purchasing any from him/her. I have not used mine yet, but based upon the description, they are likely the best quality drums on the market.

Blue Light - Water Drums

Pete

Oxygen dissolved in water is also important for health, not only for taste.

AFAIK, people living in high mountainous areas and drinking only spring water (insuffisantly oxygenated - at high altitude, water has not get a chance to "absorb" enough oxygen, due to too short a travel) are more subject to goitre (A goitre is an enlarged thyroid gland) than the average population.

OTOH, drinking "de-oxygenated" (SP?) water for a short period, such as in an emergency situation, should not rise that kind of problem.

Sorry to have to strongly disagree with you, but a goiter is generally the result of iodine deficiency (why salt is commonly iodized). Lack of dissolved oxygen in water is (since we are not fish) strictly a taste issue.

From a search of Web MD:
“A goitre (or goiter) (Latin struma) is a swelling in the neck (just below adam's apple or larynx) due to an enlarged thyroid gland. The most common cause for goitre in the world is iodine deficiency. Other causes are:

1. Hashimoto's thyroiditis
2. Graves-Basedow disease
3. juvenile goitre
4. neoplasm of the thyroid
4. thyroiditis (acute, chronic)
5. side-effects of pharmacological therapy

Iodine is necessary for the synthesis of the thyroid hormones, triiodothyronine and thyroxine (T3 and T4). When iodine is not available these hormones cannot be made. In response to low thyroid hormones, the pituitary gland releases thyroid stimulating hormone (TSH).

Thyroid stimulating hormone acts to try and increase synthesis of T3 and T4, but also causes the thyroid gland to grow in size as a type of compensation.”

Pete

In addition, water is water, dissolved oxygen in no way changes water’s molecular structure. Dissolved oxygen is usually introduced into water through motion, i.e. precipitation, stream/river dynamics/agitation, poring water from one container to another. Water at higher elevations, may or may not (please site your source of this information) contain lower dissolved oxygen concentrations. However, since water absorption in the intestine, is by osmosis of the water molecule, what might be dissolved in the water is not necessarily transported across the intestinal mucosa, as each of these molecules would be absorbed/transported or not based upon their individual concentration in relationship to intercellular, interstitial and intervascular concentrations. The intestine is primary anaerobic (without oxygen), therefore I suspect oxygen concentrations in the area of the intestine where water is absorbed to be minimal at best. I think (do not know this for sure, but it is consistent with what chemistry and physiology I know) that any dissolved oxygen in consumed water would likely dissipate in the presence of stomach acids.

Pete

We already have two sterilized food grade 50 gallon drums. I'll fill them, treat the water and let them sit as stored treated water ....forever? If we need drinking water years from now we can pump portions of the water out of the drums and: 1. re-oxygenate via an aquarium pump with a charcoal filter or other sterile mechanical means and 2: re sterilize portions of the water to be consumed (just to be safe). Right?

Paramedic Pete: thank your for sharing your knowledge!

I smell a project....

Does anyone know what wavelength and intensity the UV water sterializer systems use? If they make an LED of that, run a sealed strip of them down the inside of the drum, and seal the points where the contracts enter with silicone. The LEDs run for, say 4 hours out of every 24. It would keep the water bug free for pretty much forever, depending on how well UV penetrates water. The cricuit would be easy enough, and the power draw would be minimial when on household, or even 12V.

I can answer this as an expert tomorrow, but I seem to remember 960 nanometers as the UV wavelength in question.

Your mileage may vary.

For storage, I'm relying on tap water hypochlorinated to 100ppm, checking it periodically (currently once a quarter), and re-chlorinating to a minimum of 5 ppm thereafter.