Biodegradation of biodiesel wash water from a biodiesel fuel production plant.

The objective of this research was the modification of our biodiesel fuel (BDF) production process to make higher quality BDF. The existing process which does not include a water washing process for raw BDF, has the advantage of no wash water discharge, but occasionally the resultant BDF is of lower grade due to residual ingredients. First, we attempted to integrate water washing into the existing process. After being neutralized and washed with H2SO4, the raw BDF was then washed with water equal to 20% of the raw BDF volume. A good separation of BDF and wash water was achieved, and the resultant wash water contained less than 2% methanol. Second, we evaluated biodegradation of the resultant wash water constituents, and 70% of the strains isolated from environmental samples removed 80 to 90% of total organic carbon. Among these, strain No. 20-68 removed both glycerol and methanol in the wash water within 7 days and was identified as Fusarium falciforme, a ubiquitous environmental microorganisms. These results suggest that if the wash water is released to the environments, the effects on environmental microorganisms will be minimal.