In designing the utilities of my tiny it was my intention to approach tiny house living in the simplest possible way even if it was primitive. If it didn't work out I could always upgrade. That I was actually able to buy a waste water tank on wheels was already a significant advance above anything I could improvise. These tanks were available from RV supply stores in several sizes. I chose the smallest 11 gallon tank which was already so heavy when full I could barely muscle it around.
So in the winter months I dragged the tank around the garden and emptied it at the base of trees. Little blankets of floating fat poured out too so when the rainy season was over I decided to filter the water before I poured it on plants. For this I made a bio filter from straw which I stuffed into a funnel that I place in the mouth of a five gallon water container. Then I made a ramp from a piece of plywood so I could get the tank up onto a pair of milk crates and let the water out while attempting to aim the stream into the filter. This actually worked to filter the solids out. But it took a while for the water to pass through the filter and I got tired of standing there so I thought I would try a filter inside.
All this might seem a bit much to do in day to day living, but when a friend told me how she spent all day getting a plumber in to clear a drain one Thanksgiving because she had put something she shouldn't have down the garbage disposal I felt fortunate I would never face such a job. I also will never have to have half the yard dug up to replace broken drain pipe at great expense. These are the worries that plague homeowners that are not even on my list of worries.
And best of all I get to re-use all my waste water on plants.