We've probably been researching the same sites vis-a-vis LoDO brewing. Here's a link to the German LoDO brewers that I've found to be very useful:
http://www.********************/brewing-methods/the-basis-of-low-oxygen-methodology/
They suggest that Na Meta and K Meta are each useful in reducing D.O. in brewing water as a "home brewer's hack", but seem to favor Na Meta over the potassium version:
Potassium Metabisulfite – Several brewing science texts and papers, Narziss’ work in particular, point toward elevated levels of potassium being detrimental to certain enzymatic actions in the mash. Narziss specifies that keeping potassium levels under 10 ppm is optimal. This corresponds to ~30 ppm of KMeta. If this dose provides you with sufficient enough scavenging, then feel free to use KMeta. If not, you may want to consider NaMeta alone or in a “Trifecta” blend. Antioxin SBT utilizes KMeta in its blend.
Sodium Metabisulfite – When the original team members of the GBF first outlined the procedure for Low Oxygen brewing and specified the amounts of NaMeta one could use for active O2 protection, it came with the caveat that one would have to adjust the value as they developed their system improvements and “tightened” everything up. This is still valid, although it may be worth revisiting dose rates here:
100 ppm – This was the original “fullproof” dose rate. It assumed someone had made no system or process adjustments whatsoever, i.e. no capping, no reduction in agitation/stirring, etc. It is no longer recommended save for the brewers who have not made any other system or process alterations and require maximum active scavenging protection even so we still warn against using it.
50 ppm –This was the second dose recommended, but we feel this is still TOO HIGH. We recommend you start much lower, using too large of a dose may cause undesirable sulfur in the finished beer. The best suggestion we can offer is to use Sulfite testing strips to run “diagnostic” testing on your system. Once you know your consumption you can tailor your dose more specifically to your equipment. We would say it is essential not to exceed 50 ppm when brewing Ales, and ultimately, Ale brewers will most likely need to go much lower.
20-30 ppm –This should be the starting dosage. Once a brewer has implemented many of the steps shown below, i.e. mash capping, reduction in agitation, No-Sparge, etc., and has used either a DO meter or Sulfite testing strips to establish their system consumption, this value seems to be what most people are settling on. It also happens to be the stock dosing for Antioxin SBT and the most common “Trifecta” dosage for Meta. This is quickly becoming the most popular and most practical dose for those who have done diagnostics on their system and implemented a fair amount of the suggested changes. Ultimately this is going to be set using testing strips and/or sensory analysis. You want fresh malt flavors but not excess sulfur in the finished beer. Experiment with dosing in small increments until you find the sweet spot the target is ZERO after cooling the wort.
5-10 ppm – This was the original recommended dose for those who are sparging. This is a value that should ultimately be determined through diagnostics. You will most likely not have to exceed 5-10 ppm for sparging, as the residuals in the mash should be enough to protect you during the sparge.
“Trifecta” and other Blends – A popular method being utilized is a blend of known antioxidants such as Sodium and Potassium Metabisulfite, Ascorbic Acid and Gallotannins/BTB. There are some notable blends, Antioxin SBT in particular, that have fixed percentages but ultimately the brewer can use the combination to tailor the specific type of protection each chemical offers to their system. As a starting point, 45/45/10 can be used as percentages of Meta/AA/GT or BB respectively. Forum members have noted that certain “Dual” blends, like Meta/BTB or Meta/AA have worked well for them given specific beer styles, etc. There is quite a bit of latitude here but basing the blends around your Meta dose is a good idea. Be careful with the use of AA alone or without a metal chelating agent, it is a known super oxidizer though however. See our spreadsheet for a “trifecta” blending and dosing calculator (Standard or Metric). It is a good idea when using Antioxin SBT to add back a targeted amount of Brewtan B to the mash when you begin reducing the dose. Since the gallotannins in Antioxin SBT are a fixed percentage of the blend, by reducing the KMeta dosing you are also reducing your gallotannin dose. Custom “Trifecta” users need not worry about this, as they can set their Brewtan B dose accordingly.
Mods: sorry for the thread drift, but I think this is good and relevant info.
Brooo Brother