pipesI don't want to bother with the oxygen question, seems to me that is irrelevant with the process of blanching. It is however, in my humble opinion, best to begin your blanching process with the coldest possible water (and of course salt too, another "question" I don't care to bother with right now). WHY the coldest water?
Pipes, you know, those things that carry the water to your vessel.
some are copper, some PVC, some etc. etc.
Do pipes ever get clogged? (rhetorical question)
pipes are like arteries, they accumulate "stuff", and depending on whether they are metal or poly-, will do so to various degrees.
bottom line, heat (i.e. hot water) will tend to loosen debris and or metal pipe "residues" --thank god we don't live with lead that much these days.
anyway...COLD water tends to lessen this effect, AND helps prevent any unwanted "adulterants" that might disflavor your blanching product, and/or react with the salt.
So, Like stock, use cold water for blanching, bring it to a boil with some salt, and use iced water for shocking.
"Do not be careless with poor ingredients and do not depend on fine ingredients to do your work for you but work with everything with the same sincerity." --from the Tenzo Kyokun