I was taught in school that a preposition is always followed by a noun, pronoun or Gerund. But recently, I have encountered a case (Ielts writing test) in which I had to describe and write something like this: “The household trash is delivered to the trucks before dumped at a landfill site”.
I don’t know if it is grammatically right because the trash is an object so it should be dumped by people while V-ed is not supposed to follow “before”, a preposition.
So could you help me out with this question, I really appreciate it.