Will there be any "official" attempts at restoring or cleaning the water in the Water Sector? As that's where pretty much all of his brothers are, Don will have an immediate desire to shore up the sector as much as he can and would likely try and get involved in that.

If not, he'll likely want to at least try to get some sort of water filtration system in effect over there, even if it's just something for individual use, to at least avoid contamination from the dead things and whatever else might be wrong with it (particularly for swimmers or anyone needing some sort of contact with the canals for any reason). He would also look into ways to restore mineral content to the water, again, even if only on an individual basis (Want to protect your itty-bitty garden? Add this slightly-disgusting-looking mixture to your water supply! No, trust me, it's good for it! ...Why are you walking away!?)...but that would be only after he found out what was missing in the first place and found a way to restore it, which might not even be possible with his solo resources - but he'd try.

...Not sure if this is what you meant, but I thought I'd ask anyway?