We have tens of thousands of them on Shuswap Lake alone, from which people are drawing and treating their own water from the lake. I'm not aware of an effective decontamination process at this point, other than replacing water intake valves and screens and so on.
I was interested in the comment made earlier about using potash as a primary treatment method, but I have not come across its being used with any success as yet. I guess that's still in the research phase, if I understood you correctly.