Bubble Washing BiodieselBubble washing biodiesel is the most frequently used form of washing this fuel. This method is gentle enough that it deters emulsions - only mist washing is gentler.
In the wash tank there is a layer of water on the bottom, and the biodiesel on top. An aquarium stone sits on the bottom of the tank producing bubbles. These bubbles carry a bit of water with them as they rise through the biodiesel. The contaminants in the biodiesel hold on to the water. When the bubble reaches the top, it pops, and the water travels back down to the water layer taking more contaminants with it. After many hours of bubble washing biodiesel, the mixture is settled, the wastewater drained, and the process begins again until all contaminants are removed.
Wash tank Outlet to drain the wash water Aquarium bubbler with at least 3 watts of power 6-inch aquarium air stone (wood or ceramic will hold up well in biodiesel) Timer to turn off the bubbler (optional, but very convenient) pH strips to tell when the biodiesel is clean
Fill the wash tank 2/3 full of biodiesel and 1/3 of water. (When adding the water, add it very gently pouring it down the side of the tank to deter emulsions.) Secure the air pump to the tank above water level, drop the air stone in and bubble for a 6-8 hours. After 6-8 hours of bubbling, turn the bubbles off, let it sit for one or more hours while the water settles out. Drain the wash water through the water outlet. If there is an emulsion, drain that into a separate container and visit the emulsion page (coming soon) to see what to do with it. Add clean water (still 1/3 to 2/3 biodiesel) and repeat the process a few more times until the exiting wash water is clear and the same pH as when it entered. Bubble washing biodiesel uses less water than some of the other methods, is simple and effective, but it can take several days.
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