I try to give you more explanations.

When you careen a vessel on the land with a brush and a karcher for
example, you produce wastewater which contain solvant, antifouling,
metals...

This wastewater is very polluant for the marina sea.
So I would like to know if it exists systems to collect, treat this
wastewater before it flow in the sea or the river.
And where can we see examples of this systems which respect the
environment in the world ?

Best regards
Bruno