relative permittivities of crude oil is generally between 2 and 4 independent of the density of the oil while that for water it is close to 80 the present electric field gradients induce forces which augment those from the applied electric fields for enhancing separation for such challenging emulsion systems electric field gradients may also impart compressive pressure on the enlarged water droplets and the separated water phase through electrohydrodynamic forces thereby enhancing oil water phase separation further as water emulsions and droplets enlarge due to coalescence under the influence of the oscillatory electric field the relative importance of dielectrophoretic and gravitational sedimentation forces increases leading to the acceleration of agglomeration of separated water however unless such macroscopic separated water is kept from the high electric field zones of the vessel the separated water which is generally conductive may cause energy loss and electrical shorting thus the electric field induced coalescence of emulsions and small water droplets are optimized along with the hydrodynamic and gravity induced sedimentation of enlarged water droplets and the separated water phase is removed from high electric field regions of the efis vessel the overall efficiency of efis separation process that is the amount of separation per electrical energy input depends both on the effectiveness of electric field and electric.