Conventional fuel oil purification is usually done by a filter element combined with a coalescing device. The filter element usually has a pleated design to collect dirt on its surface or to trap contaminants through its depth. The coalescing device usually is made of some hydrophilic material, such as a cotton package in which micro-sized water droplets are absorbed by the highly hydrophilic cotton fibers to form a bigger water blob. The water blob is then separated from oil by a meshed Teflon screen cartridge (a separator). Often times, the processed fuel quality from conventional technology does not meet customer spec requirements and sometimes it fails far short due to stabilized emulsion. Fuel additives are commonly used in modern fuel to enhance engine performance. These additives are various types of surfactants, which will cause stabilized water-in-oil emulsion. The surfactant not only prevent the congregation of water droplets, but also changes the surface properties of a coalescer from hydrophilic to hydrophobic. This effect defeats the function of the coalescer that used to absorb the undissolved water in the fuel.