In San Diego, California, USA where I live we have an initiative to build the worlds largest Desalination plant of its kind, yet are plagued by the state constantly forcing setbacks. Partially EPA related, partially playing card material for the Governor Jerry Brown.
China has a similar design going into effect right now and achieving an effective and profitable desalination design. Still, it comes down to two things:
1) Economy of scale in desalination (how much) There is currently a break point in efficiency/pollution whereby anything under 100 gallons/hr. can easily be cost efficient. Anything beyond that has to this point, cost more than importing it. San Diego's DeSal is attempting to create a new break point @ the high-end of production however (2 million gallons per hour) and it remains to be seen if it will work. Source
2) Supply & Demand When it rains, why spend money on desalination when you get it from the sky? As California's Jerry Brown once stated: "When it rains here in California, it might as well be raining money." Jerry Brown, 1982.
The biggest concerns from the EPA about Desalination technologies come down to what happens to the brine sludge byproducts and the cost to run. Well, San Diego's option is actually rather efficient and its cost only slightly higher than importing water. A cost we can live with, but the fight continues on another front! The sludge has become the new controversy that the EPA and PETA girls are all upset about.
Right now, most desal plants average about ~1 metric ton of sludge per ~12 million litres of fresh drinking water. So what happens to it?
- Australia, Africa, Saudi Arabia and the UK bury it.
- Ghana, Egypt, Nigeria and a few other African nations with Oil reserves are using it as part of their Oil extraction method
- USA, Japan and Greece currently use it for industrial use as soda ash and sodium bicarbinate
- Japan and Australia are currently looking to use it for cement compound, bricks and building materials
In summary, it certainly is NOT pumped back into the Ocean as much as it was even 5 years ago, but the EPA is still "concerned". We just cannot seem to win. Another technology being deployed RIGHT NOW will actually make use of it... ALL of it. WaterFX, a new company on the scene (relatively) has a solution to the amount of sludge that results in 93% of the water becoming palatable. With only 7% byproduct being "sludge salt", it is converted directly into Soda ash and Sodium Bicarbonate and used for: Fire extinguishers, Cooking, Neutralization of acids and bases, Medical uses, Personal hygiene, Cleaning agents, Biopesticides, Cattle feed supplements, Glass making, Pool chemicals, Water softeners, Laundry detergents and a ton of other uses.
None the less, we have to drudge through the political process to get anything done here in California, which unfortunately will take years.
