A system includes a device disposed within a storage tank. The device includes a cyclonic separator and an electrostatic coalescer. The cyclonic separator is configured to receive and separate phases of a multi-phase fluid stream. The cyclonic separator is configured to induce cyclonic flow of the multi-phase fluid stream to separate the multi-phase fluid stream into a gas stream and a liquid stream. The liquid stream includes a first liquid phase and a second liquid phase. The cyclonic separator is configured to discharge at least a portion of the gas stream and at least a portion of the liquid stream. The electrostatic coalescer is downstream of and fluidically connected to the second outlet of the cyclonic separator. The electrostatic coalescer is configured to demulsify the liquid stream by causing coalescence of liquid droplets of one of the first or second liquid phases.