what do you guys do with the waste water after you wash the biodiesel. im sure just pouring it out on the ground isn't very safe. is there a safe clean way to discard it, or is there a way to reuse the water for something else?

The waste water is "supposed to be" pretty safe. Meaning, don't drink it, but not hugely toxic.
Some guys save the last wash water, use it for the first wash on the next batch. I just run it into the yard (pasture actually).
If you were really picky, measure the ph of it, add the correct amount of base? acid? to it to make it ph neutral. Then there is just some methanol in it.
Wags

im not picky, but if you're saying you just spray your yard with it i can do the same

I use NaOH which increases the sodium in the soil so I pour mine in my drive way. KOH puts potassium in the soil and is good for plants. There will be some methanol in the water, but it should be small and evaporate quickly.

Dido on the ph.

I use KOH. I just let it drain across an outdoor concrete floor to the ground.
Wags

I have a RV dump to the city sewer and just run mine into that. If I lived out of town, though, I would pour it in my driveway (I use NaOH) or anywhere else I would want to kill weeds.