Also, remember that during the first few hours/days, the ratio of
chemicals to water was much lower than it was after a week or two.

The point of the kits is to be used as soon as possible after disaster
before pollution can become an issue. By getting them right at the
beginning of a disaster, it allows for many individuals to shelter in
place and survive for several days until rescue can get around to them.
Many could have waited for a week on an unflooded second / third floor
while rescue concentrated on those that needed medical attention.

As a sad fact, I saw an image of someone who had painted 'Diabetes
Hear' on their roof. The use of 'Hear' instead of 'Here' was their
mistake, not mine.

Another way to get gasoline and diesel out of the water is to skim or
soak it up off the surface, use the sun to lightly heat the water and
evaporate the fuels off. If you need it immediately, a match or spark
will work as well.