[paul cotter (OP)]

This particular scam seems to be a recent occurrence. High concentrations of deuterium are harmful, the amount in regular water is insignificant. I have even seen one site offering super expensive "deuterium depleted water" with the claims (1) that it promotes longevity with an implication that deuterium is responsible for the ageing process and (2) that the absence of deuterium protects one's dna from the radiation that it would otherwise be exposed to!! My guess is they are selling tap water fraudulently.

[alancalverd]

It's a good way of getting rid of the waste product after you have extracted the valuable deuterium from tap water.

Much the same as corn flakes, made from the waste after extracting syrup, glue, and a dozen other valuable products from maize. Apparently the sludge is so useless and indigestible that they have to add sugar, salt, vitamins and minerals in order to sell it as a food.

As for Marmite.....but at least it tastes good.

[paul cotter (OP)]

 Yes, I know deuterium is stable. That's why I put two exclamation marks after that silly "claim".

[evan_au]

many organisms, from bacteria to eukaryotes, thrived perfectly well in up to 5% heavy water. However, many organisms did not survive water deuteration levels of 50 – 100%

https://medicine.yale.edu/lab/dmi/education/faqs/

Since the natural concentration of Deuterium is around 0.01%, one could say that this has minimal effect on living organisms, being 3 orders of magnitude lower than the levels causing visible biological impact.
https://en.wikipedia.org/wiki/Heavy_water#Effect_on_animals

[SeanB]

As for Marmite.....but at least it tastes good.

The factory that made the yeast extract used to be in the city, but finally they were offered enough money to make the move to a new place worthwhile. Guess the conference centre and Hilton finally got tired of the smell, but they could not complain, the warehouse and factory was there long before them.

[paul cotter (OP)]

In Ireland we once had a competitor for marmite called GYE, an acronym for "guinness yeast extract ". It had a similar to but stronger flavour than marmite. Gone a long time, unfortunately.

[Bored chemist]

The same process that concentrates the deuterium from water also concentrates tritium.
So, depending on the original water source, heavy water may contain enough tritium to be measurably (if not practically  significantly) radioactive.

By analogy, you can see how deuterium depleted water would also be tritium depleted.

So you would reduce the concentration of tritium from "unimportant" to "even less than that".

The only real  outcome is the transfer of money.

[alancalverd]

The UK Environment Agency treats tritium in waste water very seriously. At least, they nag me if I don't mention it in my reports.

[Bored chemist]

If memory serves, the concentration in heavy water is of the order of 1 to 10 Bg/litre.
Oops!
Bq/litre
I'm not going to lose sleep over that.

[alancalverd]

Billion grams (Bg) or Becquerels (Bq)?

I'd certainly lose sleep over that!

[evan_au]

the concentration in heavy water is of the order of 1 to 10 Bq/litre.

I am assuming that this is talking about the concentration of Tritium in heavy water (since deuterium is stable, and contributes 0 Bq)?

But it makes a big difference where you collect your heavy water:
- If you collect it from open ocean the concentration of Tritium is close to 0, since it has a short half-life (12 years), and almost no natural sources.
- If you collect your heavy water from a heavy water reactor, the level of tritium can be fairly high, since you are continually bombarding Deuterium with Neutrons, and sometimes they stick together (for a dozen years or so).

[Bored chemist]

But it makes a big difference where you collect your heavy water:

As I said.

depending on the original water source,

If you collect it from open ocean the concentration of Tritium is close to 0, since it has a short half-life (12 years), and almost no natural sources.

There's a natural source which is, in one sense, very big.
https://journals.aps.org/pr/abstract/10.1103/PhysRev.93.1337
"Contents ranging between 0.5 and 67 tritium atoms per 10^18 hydrogen atoms have been found. These correspond to an average cosmic-ray production rate of about 0.12 tritium atoms per cm^2 per second".
So ocean water has tritium in it.
If you get your water from deep boreholes where the water has been underground for centuries, there's not much tritium.
But it might have a fair bit of other radioactive stuff in it.