Please have a look at this link and PDF attachments.

https://www.researchgate.net/post/How_to_remove_water_from_bio-diesel_after_water_washing

Please check the following link and PDF attachments also.

http://onlinelibrary.wiley.com/doi/10.1002/cjce.22279/abstract

Dear colleague

The removal of water content present in fuels such as biodiesel and diesel is quite important to adequate the fuel to standards for commercialization and to avoid corrosion of storage tanks and injection equipment in diesel engines. Hydrophilic hydrogels were employed to remove the water content in biodiesel and diesel fuel samples. The results showed that the hydrogels were capable of decreasing the free

water content and also the soluble water content present in the samples.

Regards 

The easiest and cost effective way is to treat biodiesel sample with anhydrous sodium sulfate; being inert to the FAMEs it will bind water molecules present and can be separated easily by filtration.

Small amounts can be dried using anhydrous sodium sulfate or even calcium chloride. In large quantities, heating under vacum.

depending on amounts, sodium sulphate and other salts are efficient to dry laboratory samples, azeotropic distillation works for laboratory and larger scale, vacuum drying seems to be the most cos ineffective

Good ans