Water removal from the washed biodiesel. Found a site stating that it is possible to reduce water content of oil down to 10PPM.
I'm sure it is but for purposes of our process the water doesn't have to be that low. From testing I have found the average water content of well settled oil is around the 850ppm region. After glycerol pre-treating this reduces to around the 350ppm mark. This is more than good enough for our process.
Well washed biodiesel will be around the 1200ppm level just after the last wash, and will reduce to @ 1000ppm over the next day or two if just left to stand (depending on temperature)
In winter with cold nights some dissolved water in the bio turns into suspended water and will drop overnight, then if the temperature rises considerably during the day (as it can do with high pressure dominating) the bio may actually get to the point where it clears (suspended water goes back to being dissolved) even if it clears the water level will still be around the 1000ppm level.
This effect is noticeable with the bio layer on a 50/50 test. Depending where the jar is stood the bio will mist as the temperature falls and clear as the temperature rises.