General Discussion

https://www.inforum.com/news/north-dakota/spirit-lake-nation-to-be-without-drinkable-tap-water-for-2-extra-weeks

Almost every article I could find online covered the public safety and political aspects of this, but no one seemed willing to speculate where the increase in Mn came from. Could be mine runoff, leaching, or illegal dumping -- all preventable and subject to regulation and legal penalties. They need to find out, so they can know if this will recur, or even become a permanent condition.

One particularly frightening possibility is that there has been acidification of local rainfall. Low pH can convert many Mn ores into soluble Mn salts. Mn(II) carbonate (a naturally occurring ore) and phosphate are more soluble than I expected, so Mn can't be precipitated from solution effectively with any of the common chemicals used for water treatment -- saturated solutions of either salt are near or in excess of the recommended safe exposure level.

Ash from coal-burning plants is another potential source that cannot be overlooked, especially if there are ash ponds upstream from the lake.