I know one must wash biodiesel to get methanol, glycerin and Sodium-hydroxide by products out. But to wash straight-up WVO?
There are two common ways to wash BioDiesel (which some people recommend for WVO as well):
- Mist washing
- Bubble washing
Both methods can cause emulsification of the water and oil (aka. salad dressing) so heating the water and oil is important to inhibit this behaviour. 50C will do fine if you're gentle - higher temperatures will be needed if you really agitate the two fluids.
I tried to wash 10L of my 10 micron filtered oil (my car fuel) with 10L of tap water in a small 30L glass aquarium. I bought an aquarium air pump, a 30cm wand bubbler (to make a bubble curtain), and a 150W aquarium heater. I hooked it all up, poured it all in and let it all go for 48 hours.
Result? No much changed in the colour or clarity of the oil. There isn't an other way to know if the quality improved without getting scientific testing equipment. The water got smokey - but that might just be oil suspended in the water. Plus I'd have to spend more time and mess dewatering now.
As it stands, I will not add any washing stage to my filtering operation until I can see more evidence.