TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The solution containing soluble magnesium is treated with sodium hydroxide derived from the solution prior to precipitation of the magnesium hydroxide, where the solution containing soluble magnesium is treated to remove sodium chloride which is converted to sodium hydroxide for use in the precipitation of magnesium hydroxide (preferably the solution containing soluble magnesium is subjected to electrodialysis to remove sodium chloride, and the sodium chloride removed is electrolyzed to form sodium hydroxide). The precipitation of the magnesium hydroxide involves treatment of the solution containing soluble magnesium with at least one of sodium hydroxide, calcium oxide, calcium magnesium oxide and/or calcium hydroxide (preferably calcium oxide and/or calcium magnesium oxide to separately recover magnesium hydroxide and calcium hydroxide). The magnesium hydroxide and calcium hydroxide are recombined and calcined to form the oxide blend. A reductant is added to the oxide blend prior to reduction. An aluminum metal is added to the oxide blend before and/or during the reduction process. The oxide blend is reduced in a plasma direct current (DC) arc furnace at 1100-1700 degrees C to produce magnesium metal vapor. A portion of the magnesium hydroxide is converted to magnesium carbonate in a carbon dioxide sequestration process, by reacting the magnesium hydroxide with the carbon dioxide in a fluidized bed reactor. The process further involves recovering sodium chloride from the solution containing soluble magnesium and reporting the sodium chloride to a bioreactor housing microalgae for the production of biomass oil, in which the solution containing soluble magnesium is treated using electrodialysis to produce several streams having different salinity that are each fed to separate bioreactors, each housing microalgae; followed by reporting carbon dioxide produced during processing to the bioreactor. The process for the treatment of a waste stream emitted from a desalination plant involving steps (a1)-(c1) further involves reporting at least a portion of the sodium hydroxide back to the waste stream and/or to an outlet for the waste stream to modulate the pH of the water at the outlet for the waste stream. Preferred Components: The reductant is ferro silicon or aluminum oxide. EXAMPLE - No suitable example given.