More than 1.8 billion people live in countries where fresh water is scarce. In many arid regions, seawater or salty groundwater is plentiful but costly to desalinate. In addition, many industries pay high disposal costs for wastewater with high salt concentrations that cannot be treated using conventional technologies. Reverse osmosis, the most common desalination technology, requires greater and greater pressure as the salt content of water increases and cannot be used to treat water that is extremely salty, or hypersaline.
Hypersaline water, which can contain 10 times more salt than seawater, is an increasingly important challenge for many industries. Some oil and gas wells produce it in large volumes, for example, and it is a byproduct of many desalination technologies that produce both freshwater and concentrated brine. Increasing water consciousness across all industries is also a driver.
Industrial processes, in general, produce salty wastewater because the trend is to reuse water. Many industries are trying to have ‘closed loop’ water systems. Each time you recover freshwater, the salt in it becomes more concentrated. Eventually the wastewater becomes hypersaline and you either have to desalinate it or pay to dispose of it.
The cheese industry is a good example. The wastewater discharged by cheese manufacturing processes is highly saline. This waste is generated from whey demineralization, chromatography and clean-in-place processes. Salty effluent can be diluted with other effluents and discharged as trade waste but the high salinity can trigger penalties imposed by local water authorities. Alternatively, such waste can be sent to evaporation ponds, but in some areas of the world, environmental impacts regarding land degradation, odor and dust have prevented further pond construction. Similar concentrate and brine management issues are emerging in the seawater desalination and mining industries.
The oil and gas industry must also deal with saline water in the form of “produced water.” Produced water is a term used in the oil industry to describe water that is produced as a byproduct during the extraction of oil and natural gas. Produced water is a kind of brackish and saline waters from underground formation that are brought to the surface as a result of oil drilling. There is roughly six to eight barrels of produced water that comes with every barrel of oil brought to the surface.