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Some industrial processes,especially in the semiconductor and pharmaceutical industries, require large quantities of very pure water.In these cases, feed water is first treated to pure water and then further processed to produce ultrapure water.Another type of ultrapure water used in the pharmaceutical industry is called water for injection (WFI),and is typically produced by the multiple distillation or compression evaporation process of DI water or RO-DI water.It has a stricter bacterial requirement of 10 CFU per 100ml instead of 100 CFU per ml per USP.
Other uses 
Distilled or deionized water is commonly used to top up lead-acid batteries used in cars and trucks, among other applications.The presence of foreign ions commonly found in tap water can significantly shorten the life of a lead-acid battery.Distilled or deionized water is preferable to tap water in car cooling systems.Using deionized or distilled water in appliances that evaporate water, such as steam irons and humidifiers,can reduce the buildup of mineral scale that can shorten appliance life.Some appliance manufacturers say deionized water is no longer necessary.Purified water is used in freshwater and marine aquariums.Being free of impurities like copper and chlorine, it helps keep fish free from disease and avoids algal blooms on aquarium plants due to lack of phosphates and silicates.Deionized water should be remineralized before being used in an aquarium as it lacks many macro and micronutrients that plants and fish need.Water (sometimes mixed with methanol) has been used to improve the performance of aircraft engines.In piston engines, it delays the onset of engine knock.In a turbine engine,it allows more fuel flow and increases mass flow for a given turbine temperature limit.For example, it was used on early Boeing 707 models.Since then, advanced materials and engineering techniques have made such systems obsolete for new designs. However, spray cooling of the incoming air is still used to some extent for off-road turbocharged engines (road racing).
Deionized water is often used as an ingredient in many cosmetics and pharmaceuticals. "Aqua" is the standard name of water in the International Cosmetic Ingredient Nomenclature Standard,which is mandatory on product labels in some countries.Due to its high relative permittivity (~80), deionized water is also used as a high voltage dielectric (short duration, when resistive losses are acceptable) in many pulsed power applications, such as the Sandia National Laboratories Z machine.Distilled water can be used in PC water cooling system and laser marking system.The absence of impurities in the water means the system stays clean and prevents bacteria and algae from growing. Additionally, the low conductivity reduces the risk of electrical damage in the event of a leak.However, deionized water has been known to cause cracks in brass and copper fittings.When used as a rinse after washing cars, windows and similar applications, purified water dries without leaving spots caused by dissolved solutes.Deionized water is used in water mist fire suppression systems used in sensitive environments, such as where high voltage electrical and sensitive electronic equipment is used. "Sprinkler" nozzles use a finer spray jet than other systems and operate at pressures up to 35 MPa (350 bar; 5,000 psi).The extremely fine water mist produced quickly removes heat from the fire, and the fine water droplets are non-conductive (after deionization) and are less likely to damage sensitive equipment.However, deionized water is acidic in nature, and contaminants such as copper, dust, stainless and carbon steel, and many other common materials quickly provide ions that reionize the water.It is generally considered unacceptable to spray water on an energized circuit,and it is generally considered undesirable to use water in an electrical environment.Use distilled or purified water in humidors to prevent cigars from accumulating bacteria, mold, and contaminants, and to prevent residue from forming on humidifier materials.Window cleaners that use a water supply rod system also use purified water because it allows the windows to dry on their own without stains or smudges. Using purified water from the water supply pole also avoids the need to use ladders, thus ensuring compliance with UK working at heights legislation.
Mineral consumption
Distillation removes all minerals from water, while the membrane methods of reverse osmosis and nanofiltration remove most or nearly all minerals.This produces softened water, but it has not been proven to be healthier than drinking water.The World Health Organization investigated the health effects of demineralized water in 1980 and found that demineralized water increased diuresis and electrolyte elimination and decreased serum potassium
concentrations.Magnesium, calcium, and other nutrients in the water may help prevent nutrient deficiencies.The recommended minimum for magnesium is 10 mg/L, optimally 20–30 mg/L; for calcium, minimum 20 mg/L, optimally 40–80 mg/L, with a total water hardness (with added magnesium and calcium) of 2 -4 mmol/L.For fluoride, the recommended concentration for dental health is 0.5–1.0 mg/L, with a maximum guideline value of 1.5 mg/L to avoid dental fluorosis.
Municipal water supplies often have added or contained trace amounts of impurities at levels defined as safe to drink.Many of these additional impurities, such as volatile organic compounds, fluoride, and an estimated 75,000+ other compounds cannot be removed by conventional filtration; however, distillation and reverse osmosis eliminate nearly all of these impurities.
