Abstract: Light hydrocarbons are converted into heavier hydrocarbons by preparing a synthesis gas, converting the synthesis gas to heavier hydrocarbons. Heat generated while preparing and converting synthesis gas is removed by creating steam that is then used in a water treatment unit to treat a water stream to remove contaminants such as salt. A process for preparing heavier hydrocarbons from light hydrocarbons, electricity, and treated water uses the energy of the conversion process is used to power a electrical generator and the thermal energy is used to assist in treating the water. Systems to convert light hydrocarbons to heavier with water treatment and electrical production are also presented.