Since I'm still on-call this weekend and cannot enjoy the beautiful weather outdoors, I figured I would expand upon some of the pros and cons of desalinization since I constantly read comments (not on BPL) that Californians are idiots for not using this whole great big Pacific Ocean thing to the left of us to alleviate out water shortages.
(Maybe this post belongs on Chaff, but what the heck).
For reference, I'm using the plant being built in Carlsbad. Once operational in late 2015/early 2016, it will be the largest desal plant in the Western Hemisphere.
As I stated in my initial long post, desal is expensive (especially on a per acre foot basis) and energy intensive to operate. Initial plant cost is roughly 1 billion dollars. The plant will consume 38 MW of power a day, which is enough energy to power 28,500 houses. This will produce 48,000 acre feet a year (50 million gallons a day), enough to supply 7% of San Diego County's potable water needs.
Water will be sold to Carlsbad at $2,000 to $2,200 dollars per acre foot. Now, to put acre feet in perspective, picture an acre of land covered by a foot of water. That's an acre foot (326,700 gallons). It's roughly equivalent to what 2 American families of 5 use each year. Personally, I think that estimate is on the high side, especially compared to the average family of 5 in my water district. It's more like 4 families of 5 here.
Conservation costs ~$500 an acre foot. This includes replacing outdated fixtures, turf rebates, lawn replacement, switching to more efficient drip irrigation, etc.
Creating reservoirs to store recycled water costs ~$1,000 an acre foot to build.
Obviously the chief pro of desal is you have an abundant source of water to draw upon during drought years. Also, the construction process creates jobs, as does operating the plant. Estimates place the positive economic impact at 350 million dollars for the local economy. No small boost.
The 2 chief cons IMO is the power needed to operate the plant and the water cost, which will only increase in time (at least until solar power is a viable option).
Also, another con is the environmental impact. Desal intake pipes kill sea life, though I could find no definitive estimates. Then you must figure out how to dispose of the waste. Filtering sea water leaves behind very concentrated seawater (brine), the result of extracting the salt and trace amounts of water entering the filters. There are different proposals and methods already in use around the world. For the sake of keeping this post from becoming a novel, I will mention 2 methods I know are currently being utilized.
1) Diluting the brine at a 5:1 ratio with treated wastewater/agricultural waste/industrial waste, and dumping it back into the ocean.
2) Burying the outtake pipes under the seafloor, thus allowing the sand to act as a filter for the salt (expensive).
I'm trying not to inject too much of my own biases into the above paragraphs. I hope you find it interesting.
Cheers
