Patents: Desalination pre-treatments

Water containing dissolved salts, such as calcium sulfate, calcium chloride, magnesium sulfate, magnesium chloride, sodium carbonate, sodium chloride, sodium sulfate, calcium bicarbonate, and mixtures thereof, is treated to reduce the concentration of those salts. About 0.1 to about 60 g/L of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, calcium hydroxide, calcium carbonate, aluminum hydroxide, aluminum sulfate, aluminum potassium sulfate, and mixtures thereof is added to the water, whereby a precipitate forms in the water. The precipitate is separated from said water and the water is desalinated using reverse osmosis, flash evaporation, or another method. The process is preferably performed by first adding calcium oxide or calcium hydroxide, separating the precipitate that forms, then adding sodium hydroxide and sodium carbonate to form a second precipitate.

2003, patent number: 7198722

Apparatus for pretreatment of water using a bed of granular activated carbon

A water treatment plant includes a granulated activated carbon bed contactor used in pretreating influent water, including wastewater, prior to any filtration of the water in downstream stages of the plant. The contactor is operable either primarily for adsorption purposes or in a dual role for both adsorption and clarification or flocculation purposes to improve performance of downstream filters. In one embodiment, the carbon bed is partially fluidized and expanded by water flowing upwardly through the bed. This fluidization allows the passage of solids the bed and minimizes the plugging of the bed. The flow rate of water through the bed is adjustable and controllable to establish the degree of solids capture by the bed. Upwash and backwash carbon bed cleaning mechanisms are provided. Furthermore, the contactor has a countercurrent spent carbon removal and fresh carbon introduction system for rejuvenating the bed.

Patent number: 4659462