As an airport owner in the USA
In USA anyways, the AVGAS supply chain is tightly controlled from source to airplane.
Obviously the stuff is manufactured in magical places, then stored regionally in huge large distribution tanks.
Then the fuel trucks carrying avfuel only carry avfuel, nothing else.
So nothing else gets mixed in during transport.
And they are periodically internally washed.
So the trucks are clean.
Our airport fuel tanks then have water detection starting 0.1 inches from the bottom of the tank. And the actual fuel takeoff is about 4 inches from the bottom.*
All remotely monitored and alarmed.
Each of our fuel dispensers then has its own $2,000 filter and housing at the connection to the hose. In addition to catching any solids, the filters are similar to VERY EXPENSIVE baby diapers: Like water filters used on boats they capture water. Should they get saturated by water they will block fuel flow before letting any water through. The dispenser will get slower and slower and then stop, but no water gets through. The housing also has sump drains IF water gets trapped. In many years I have never seen any. The fancy-schmancy filter housing also have sight gauges: If any water occurs it drools down to the bottom of the housing and the little white ball floating in blue fuel goes ..white.
Fueling out of a metal drum in the 3rd world probably a little different.
As most know, the more likely water hazard is condensation in un-filled tanks.
Also, blocked through-wing drains can allow the little 'swimming pools' around each fuel filler to fill with water, which can then drain past the caps.
I always carry 2ft pipe cleaners and drool a bit of fuel when refueling, to make sure the drains are clear. if not, out comes the pipe cleaner until they drool.
And then we have sumps.
You can now see why we don't handle autogas. Neither the supply chain nor the product are controlled, and the airport would be in the liability chain.
*I think auto gas station tanks also have about a 4 inch takeoff from the bottom of their tanks, below which accumulates all sorts of terrible things. Those terrible things get stirred each time a tanker refuels the tanks, which can take a while to settle back down into the abyss. Which is also why I try to avoid refueling cars if a gas station's are or have been recently refilled.
Possibly the original source of ethanol craziness - In the 3rd world gas stations, they quickly realized they could intentionally add water, reducing their cost per gallon, until cars quit. And they could blame the fuel. I am 99% sure someone said, "Hey, thats a great idea!" And then the environmental movement went "Ooo, ethanol is more natural!" And then the industry said, "Cool, higher price per gallon and less energy per $ = higher margin. EXCELLENTO!"
But I digress.
10300 Glen Way
Fort Washington, MD 20744