An apparatus for mixing and separating fluid phases, comprising: an inlet section comprising an inner inlet and an outer inlet for separately introducing the plurality of fluid phases of distinct specific gravity into the mixing section; a mixing section extending from the inlet section for mixing the plurality of fluid phases based on the difference of specific gravity and immiscibility associated the plurality of fluid phases, the mixing section comprising a first spiral section comprising a first plurality of spiral turns, each spiral turn of the first plurality of spiral turns having a helical channel followed by a counter-helical channel for enabling mixing of the plurality of fluid phases, the counter-helical channel changes the direction of flow of the plurality of fluid phases upon flow of the plurality of fluid phases from the helical channel to the counter-helical channel, wherein the mixing section comprises a plurality of baffles configured within one or more of the helical channel and counter-helical channel of the first plurality of spiral turns for enhancing mixing of the plurality of fluid phases, a separating section extending from the mixing section and capable of separating the plurality of fluid phases based on the specific gravity difference between said fluid phases, the separating section comprising a second spiral section extending from the mixing section and configured to receive a mixture of the plurality of fluid phases from the mixing section, the second spiral section comprising a second plurality of spiral turns for enabling separation of the plurality of fluid phases; and an outlet section configured at an end portion of the separating section, the outlet portion comprising an outer outlet and an inner outlet to facilitate separate withdrawal of the plurality of fluid phases of the mixture. an inlet section comprising an inner inlet and an outer inlet for separately introducing the plurality of fluid phases of distinct specific gravity into the mixing section; a mixing section extending from the inlet section for mixing the plurality of fluid phases based on the difference of specific gravity and immiscibility associated the plurality of fluid phases, the mixing section comprising a first spiral section comprising a first plurality of spiral turns, each spiral turn of the first plurality of spiral turns having a helical channel followed by a counter-helical channel for enabling mixing of the plurality of fluid phases, the counter-helical channel changes the direction of flow of the plurality of fluid phases upon flow of the plurality of fluid phases from the helical channel to the counter-helical channel, wherein the mixing section comprises a plurality of baffles configured within one or more of the helical channel and counter-helical channel of the first plurality of spiral turns for enhancing mixing of the plurality of fluid phases, a separating section extending from the mixing section and capable of separating the plurality of fluid phases based on the specific gravity difference between said fluid phases, the separating section comprising a second spiral section extending from the mixing section and configured to receive a mixture of the plurality of fluid phases from the mixing section, the second spiral section comprising a second plurality of spiral turns for enabling separation of the plurality of fluid phases; and an outlet section configured at an end portion of the separating section, the outlet portion comprising an outer outlet and an inner outlet to facilitate separate withdrawal of the plurality of fluid phases of the mixture.