I'm not a water engineering expert, but I have toured first nation water plants and am currently working on several issues at Engage Canada.
My simple answer to the question would be that many of the water systems on first nations, the ones that service town and village sites, are simple chlorination systems that you would not see in other Canadian communities. There is no multi-barrier treatment, no use of ultraviolet light and other sorts of current membrane technology. Most first nations' systems are antiquated. That's in the town and village sites, but in a lot of communities, 60%, 70%, or 80% of the water used is in a rural context, so it comes from wells, cisterns, and trucking, all of which....
Take a look at the Kainai First Nation or Blood Tribe in southern Alberta. There are approximately 13,000 members there. It's one of the largest reserves in Canada. They have a small fleet of water trucks travels thousands of kilometres on unimproved roads to fill cisterns that are not adequately sized for the number of people who live in the homes.
That is a problem when it comes to regulation, funding, or guidelines—anything that touches on rural water use. The conversation nationally so far has been on anything that looks or feels like urban-based, centralized water treatment. And while that's a problem for first nations, the main challenge is servicing homes in rural settings.