introduction

Desalination goes back to the 1st century (150-249). Reverse-osmosis desalination was invented in California in the 1950s

Desalination is a process that takes away mineral components from saline water to produce fresh water. More generally desalination refers to the removal of salts and minerals from a target substance. Sea water is pumped into the desalination plant from the ocean and passes through pretreatment filtration to remove most large and small particles. Distillation occurs naturally through evaporation or through very simple methods such as boiling salted water and condensing the steam. There are two main methods that are used to produce desalinated water distillation and membrane processes. The membrane process is more recent and more widely used relies on a semipermeable membrane with pores so tiny that they separate the salt from water; this is reverse osmosis and it relies on natural processes and membranes. Drinking seawater straight is a bad idea because your body must expel the salt by urinating more water than it actually gains. Seawater contains roughly 130 grams of salt per gallon. Desalination can reduce salt levels below 2 grams per gallon which is the limit for human consumption

Desalination plants around the world consume more than 200 million kilowatt hours each day. Energy is the largest single expense for desalination plants, accounting for as much as half of the costs to make drinking water from the sea. Desalination takes only a quarter of the electricity to generate drinking water as it did in the 1980's because of more efficient pumps, membranes and energy-recovery devices. In order to supply 300,000 people the Carlsbad desalination plant will require the equivalent of 31.3 megawatt power.

Desalination often uses seawater, In California and other western states it has mostly been used to remove salt from brackish water which is saltier than freshwater but fresher than seawater. The top three desalination countries are Saudi Arabia with 17 percent of global output, the United Arab Emirates with 13.4 percent, and the United States with 13 percent. 80 percent of domestic water use in Israeli cities comes from desalinated water. As of 2013, Dubai was sourcing over 98 percent of its potable water supply from desalination. The Jebel Ali plant in the united Arab-Erimates can produce 564 million gallons of water a day from the sea. California has more than 60 years of experience with desalination ,and yet the process remains a minimal part of the state's water system,for a number of reasons,also Desalination plants operate in more than 100 countries.

The Sydney Desalination plant cost $2 billion although it hasn't produced water since 2012 because dam levels are above %70 it takes about 2 gallons (8 liters) of sea water to make 1 gallon (4 liters) of freshwater. Dianne Feinstein's proposed water bill which would reauthorize the desalination act of 1996 by providing $100 million in federal funds for research. Southern California water bond approved by voters in 2014 allocates $725 million to help local water agencies build water recycling and desalination plants.. Desalinated water typically uses 2,000 gallons of water roughly the amount of water a family of five uses a year. A thousand gallons of freshwater from a desalinated plant cost the average us consumer $ 2.50 to $5 for conventional freshwater. In 2013 the department of water of resources reported that the capacity for desalination in existing plants 140,000 acre feet (172.6 million meters from brackish sources. The purpose of my project was to seperate salt from water and make it fresh drinkable water.