I bought one of
these macerator pumps from amazon.
Hooks right to the discharge port on the trailer and will pump most anything through 100 feet of garden hose.
We park our camper at home, have 30 amp service and water, so the trailer gets used as a guest suite occasionally.
The pump makes dumping at home possible.
In your case, with just clean water, I would think watering the lawn and or garden would be acceptable, the cover for our discharge port has a garden hose fitting on it, they can also be had at amazon.
Good luck.
-Brian