Is it possible to do a day-trip from Xian to Hukou waterfalls?

From Xian East Bus Station, you can find direct buses to reach the water at 08:00 and 13:20 and the returning bus is at about 12:00 and 17:30. The single journey takes you about 5 hours.
Above all, you will be in a hurry if you want to finish visiting in one day, but you can still finish. If time is permitted, I suggest you to travel to that place in two days.